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v4.6
 
   1#include <linux/kernel.h>
   2#include <linux/errno.h>
   3#include <linux/err.h>
   4#include <linux/spinlock.h>
   5
   6#include <linux/mm.h>
   7#include <linux/memremap.h>
   8#include <linux/pagemap.h>
   9#include <linux/rmap.h>
  10#include <linux/swap.h>
  11#include <linux/swapops.h>
 
  12
  13#include <linux/sched.h>
  14#include <linux/rwsem.h>
  15#include <linux/hugetlb.h>
 
 
 
 
  16
  17#include <asm/mmu_context.h>
  18#include <asm/pgtable.h>
  19#include <asm/tlbflush.h>
  20
  21#include "internal.h"
  22
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  23static struct page *no_page_table(struct vm_area_struct *vma,
  24		unsigned int flags)
  25{
  26	/*
  27	 * When core dumping an enormous anonymous area that nobody
  28	 * has touched so far, we don't want to allocate unnecessary pages or
  29	 * page tables.  Return error instead of NULL to skip handle_mm_fault,
  30	 * then get_dump_page() will return NULL to leave a hole in the dump.
  31	 * But we can only make this optimization where a hole would surely
  32	 * be zero-filled if handle_mm_fault() actually did handle it.
  33	 */
  34	if ((flags & FOLL_DUMP) && (!vma->vm_ops || !vma->vm_ops->fault))
 
  35		return ERR_PTR(-EFAULT);
  36	return NULL;
  37}
  38
  39static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
  40		pte_t *pte, unsigned int flags)
  41{
  42	/* No page to get reference */
  43	if (flags & FOLL_GET)
  44		return -EFAULT;
  45
  46	if (flags & FOLL_TOUCH) {
  47		pte_t entry = *pte;
 
  48
  49		if (flags & FOLL_WRITE)
  50			entry = pte_mkdirty(entry);
  51		entry = pte_mkyoung(entry);
  52
  53		if (!pte_same(*pte, entry)) {
  54			set_pte_at(vma->vm_mm, address, pte, entry);
  55			update_mmu_cache(vma, address, pte);
  56		}
  57	}
  58
  59	/* Proper page table entry exists, but no corresponding struct page */
  60	return -EEXIST;
  61}
  62
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  63static struct page *follow_page_pte(struct vm_area_struct *vma,
  64		unsigned long address, pmd_t *pmd, unsigned int flags)
 
  65{
  66	struct mm_struct *mm = vma->vm_mm;
  67	struct dev_pagemap *pgmap = NULL;
  68	struct page *page;
  69	spinlock_t *ptl;
  70	pte_t *ptep, pte;
 
  71
  72retry:
  73	if (unlikely(pmd_bad(*pmd)))
  74		return no_page_table(vma, flags);
 
  75
  76	ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
  77	pte = *ptep;
  78	if (!pte_present(pte)) {
  79		swp_entry_t entry;
  80		/*
  81		 * KSM's break_ksm() relies upon recognizing a ksm page
  82		 * even while it is being migrated, so for that case we
  83		 * need migration_entry_wait().
  84		 */
  85		if (likely(!(flags & FOLL_MIGRATION)))
  86			goto no_page;
  87		if (pte_none(pte))
  88			goto no_page;
  89		entry = pte_to_swp_entry(pte);
  90		if (!is_migration_entry(entry))
  91			goto no_page;
  92		pte_unmap_unlock(ptep, ptl);
  93		migration_entry_wait(mm, pmd, address);
  94		goto retry;
  95	}
  96	if ((flags & FOLL_NUMA) && pte_protnone(pte))
  97		goto no_page;
  98	if ((flags & FOLL_WRITE) && !pte_write(pte)) {
  99		pte_unmap_unlock(ptep, ptl);
 100		return NULL;
 101	}
 102
 103	page = vm_normal_page(vma, address, pte);
 104	if (!page && pte_devmap(pte) && (flags & FOLL_GET)) {
 
 
 
 
 
 
 
 
 
 
 
 105		/*
 106		 * Only return device mapping pages in the FOLL_GET case since
 107		 * they are only valid while holding the pgmap reference.
 
 108		 */
 109		pgmap = get_dev_pagemap(pte_pfn(pte), NULL);
 110		if (pgmap)
 111			page = pte_page(pte);
 112		else
 113			goto no_page;
 114	} else if (unlikely(!page)) {
 115		if (flags & FOLL_DUMP) {
 116			/* Avoid special (like zero) pages in core dumps */
 117			page = ERR_PTR(-EFAULT);
 118			goto out;
 119		}
 120
 121		if (is_zero_pfn(pte_pfn(pte))) {
 122			page = pte_page(pte);
 123		} else {
 124			int ret;
 125
 126			ret = follow_pfn_pte(vma, address, ptep, flags);
 127			page = ERR_PTR(ret);
 128			goto out;
 129		}
 130	}
 131
 132	if (flags & FOLL_SPLIT && PageTransCompound(page)) {
 133		int ret;
 134		get_page(page);
 135		pte_unmap_unlock(ptep, ptl);
 136		lock_page(page);
 137		ret = split_huge_page(page);
 138		unlock_page(page);
 139		put_page(page);
 140		if (ret)
 141			return ERR_PTR(ret);
 142		goto retry;
 143	}
 144
 145	if (flags & FOLL_GET) {
 146		get_page(page);
 
 
 
 
 
 
 
 147
 148		/* drop the pgmap reference now that we hold the page */
 149		if (pgmap) {
 150			put_dev_pagemap(pgmap);
 151			pgmap = NULL;
 
 
 
 
 
 
 
 152		}
 153	}
 154	if (flags & FOLL_TOUCH) {
 155		if ((flags & FOLL_WRITE) &&
 156		    !pte_dirty(pte) && !PageDirty(page))
 157			set_page_dirty(page);
 158		/*
 159		 * pte_mkyoung() would be more correct here, but atomic care
 160		 * is needed to avoid losing the dirty bit: it is easier to use
 161		 * mark_page_accessed().
 162		 */
 163		mark_page_accessed(page);
 164	}
 165	if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
 166		/* Do not mlock pte-mapped THP */
 167		if (PageTransCompound(page))
 168			goto out;
 169
 170		/*
 171		 * The preliminary mapping check is mainly to avoid the
 172		 * pointless overhead of lock_page on the ZERO_PAGE
 173		 * which might bounce very badly if there is contention.
 174		 *
 175		 * If the page is already locked, we don't need to
 176		 * handle it now - vmscan will handle it later if and
 177		 * when it attempts to reclaim the page.
 178		 */
 179		if (page->mapping && trylock_page(page)) {
 180			lru_add_drain();  /* push cached pages to LRU */
 181			/*
 182			 * Because we lock page here, and migration is
 183			 * blocked by the pte's page reference, and we
 184			 * know the page is still mapped, we don't even
 185			 * need to check for file-cache page truncation.
 186			 */
 187			mlock_vma_page(page);
 188			unlock_page(page);
 189		}
 190	}
 191out:
 192	pte_unmap_unlock(ptep, ptl);
 193	return page;
 194no_page:
 195	pte_unmap_unlock(ptep, ptl);
 196	if (!pte_none(pte))
 197		return NULL;
 198	return no_page_table(vma, flags);
 199}
 200
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 201/**
 202 * follow_page_mask - look up a page descriptor from a user-virtual address
 203 * @vma: vm_area_struct mapping @address
 204 * @address: virtual address to look up
 205 * @flags: flags modifying lookup behaviour
 206 * @page_mask: on output, *page_mask is set according to the size of the page
 
 207 *
 208 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
 209 *
 210 * Returns the mapped (struct page *), %NULL if no mapping exists, or
 
 
 
 
 
 
 
 
 
 
 211 * an error pointer if there is a mapping to something not represented
 212 * by a page descriptor (see also vm_normal_page()).
 213 */
 214struct page *follow_page_mask(struct vm_area_struct *vma,
 215			      unsigned long address, unsigned int flags,
 216			      unsigned int *page_mask)
 217{
 218	pgd_t *pgd;
 219	pud_t *pud;
 220	pmd_t *pmd;
 221	spinlock_t *ptl;
 222	struct page *page;
 223	struct mm_struct *mm = vma->vm_mm;
 224
 225	*page_mask = 0;
 226
 227	page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
 228	if (!IS_ERR(page)) {
 229		BUG_ON(flags & FOLL_GET);
 230		return page;
 231	}
 
 
 
 232
 233	pgd = pgd_offset(mm, address);
 
 234	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
 235		return no_page_table(vma, flags);
 236
 237	pud = pud_offset(pgd, address);
 238	if (pud_none(*pud))
 239		return no_page_table(vma, flags);
 240	if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
 241		page = follow_huge_pud(mm, address, pud, flags);
 242		if (page)
 243			return page;
 244		return no_page_table(vma, flags);
 245	}
 246	if (unlikely(pud_bad(*pud)))
 247		return no_page_table(vma, flags);
 248
 249	pmd = pmd_offset(pud, address);
 250	if (pmd_none(*pmd))
 251		return no_page_table(vma, flags);
 252	if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
 253		page = follow_huge_pmd(mm, address, pmd, flags);
 254		if (page)
 255			return page;
 256		return no_page_table(vma, flags);
 257	}
 258	if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
 259		return no_page_table(vma, flags);
 260	if (pmd_devmap(*pmd)) {
 261		ptl = pmd_lock(mm, pmd);
 262		page = follow_devmap_pmd(vma, address, pmd, flags);
 263		spin_unlock(ptl);
 264		if (page)
 265			return page;
 266	}
 267	if (likely(!pmd_trans_huge(*pmd)))
 268		return follow_page_pte(vma, address, pmd, flags);
 269
 270	ptl = pmd_lock(mm, pmd);
 271	if (unlikely(!pmd_trans_huge(*pmd))) {
 272		spin_unlock(ptl);
 273		return follow_page_pte(vma, address, pmd, flags);
 274	}
 275	if (flags & FOLL_SPLIT) {
 276		int ret;
 277		page = pmd_page(*pmd);
 278		if (is_huge_zero_page(page)) {
 279			spin_unlock(ptl);
 280			ret = 0;
 281			split_huge_pmd(vma, pmd, address);
 282		} else {
 283			get_page(page);
 284			spin_unlock(ptl);
 285			lock_page(page);
 286			ret = split_huge_page(page);
 287			unlock_page(page);
 288			put_page(page);
 289		}
 290
 291		return ret ? ERR_PTR(ret) :
 292			follow_page_pte(vma, address, pmd, flags);
 293	}
 294
 295	page = follow_trans_huge_pmd(vma, address, pmd, flags);
 296	spin_unlock(ptl);
 297	*page_mask = HPAGE_PMD_NR - 1;
 
 
 
 
 298	return page;
 299}
 300
 301static int get_gate_page(struct mm_struct *mm, unsigned long address,
 302		unsigned int gup_flags, struct vm_area_struct **vma,
 303		struct page **page)
 304{
 305	pgd_t *pgd;
 
 306	pud_t *pud;
 307	pmd_t *pmd;
 308	pte_t *pte;
 
 309	int ret = -EFAULT;
 310
 311	/* user gate pages are read-only */
 312	if (gup_flags & FOLL_WRITE)
 313		return -EFAULT;
 314	if (address > TASK_SIZE)
 315		pgd = pgd_offset_k(address);
 316	else
 317		pgd = pgd_offset_gate(mm, address);
 318	BUG_ON(pgd_none(*pgd));
 319	pud = pud_offset(pgd, address);
 320	BUG_ON(pud_none(*pud));
 
 
 
 
 
 321	pmd = pmd_offset(pud, address);
 322	if (pmd_none(*pmd))
 323		return -EFAULT;
 324	VM_BUG_ON(pmd_trans_huge(*pmd));
 325	pte = pte_offset_map(pmd, address);
 326	if (pte_none(*pte))
 
 
 
 327		goto unmap;
 328	*vma = get_gate_vma(mm);
 329	if (!page)
 330		goto out;
 331	*page = vm_normal_page(*vma, address, *pte);
 332	if (!*page) {
 333		if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
 334			goto unmap;
 335		*page = pte_page(*pte);
 336	}
 337	get_page(*page);
 
 
 338out:
 339	ret = 0;
 340unmap:
 341	pte_unmap(pte);
 342	return ret;
 343}
 344
 345/*
 346 * mmap_sem must be held on entry.  If @nonblocking != NULL and
 347 * *@flags does not include FOLL_NOWAIT, the mmap_sem may be released.
 348 * If it is, *@nonblocking will be set to 0 and -EBUSY returned.
 349 */
 350static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
 351		unsigned long address, unsigned int *flags, int *nonblocking)
 
 352{
 353	struct mm_struct *mm = vma->vm_mm;
 354	unsigned int fault_flags = 0;
 355	int ret;
 356
 357	/* mlock all present pages, but do not fault in new pages */
 358	if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
 359		return -ENOENT;
 360	/* For mm_populate(), just skip the stack guard page. */
 361	if ((*flags & FOLL_POPULATE) &&
 362			(stack_guard_page_start(vma, address) ||
 363			 stack_guard_page_end(vma, address + PAGE_SIZE)))
 364		return -ENOENT;
 365	if (*flags & FOLL_WRITE)
 366		fault_flags |= FAULT_FLAG_WRITE;
 367	if (*flags & FOLL_REMOTE)
 368		fault_flags |= FAULT_FLAG_REMOTE;
 369	if (nonblocking)
 370		fault_flags |= FAULT_FLAG_ALLOW_RETRY;
 
 
 
 
 
 
 
 
 
 371	if (*flags & FOLL_NOWAIT)
 372		fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
 373	if (*flags & FOLL_TRIED) {
 374		VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY);
 
 
 
 375		fault_flags |= FAULT_FLAG_TRIED;
 376	}
 
 
 
 
 
 377
 378	ret = handle_mm_fault(mm, vma, address, fault_flags);
 379	if (ret & VM_FAULT_ERROR) {
 380		if (ret & VM_FAULT_OOM)
 381			return -ENOMEM;
 382		if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
 383			return *flags & FOLL_HWPOISON ? -EHWPOISON : -EFAULT;
 384		if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
 385			return -EFAULT;
 386		BUG();
 
 
 
 
 
 
 
 
 
 387	}
 388
 389	if (tsk) {
 390		if (ret & VM_FAULT_MAJOR)
 391			tsk->maj_flt++;
 392		else
 393			tsk->min_flt++;
 
 394	}
 395
 396	if (ret & VM_FAULT_RETRY) {
 397		if (nonblocking)
 398			*nonblocking = 0;
 399		return -EBUSY;
 400	}
 401
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 402	/*
 403	 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
 404	 * necessary, even if maybe_mkwrite decided not to set pte_write. We
 405	 * can thus safely do subsequent page lookups as if they were reads.
 406	 * But only do so when looping for pte_write is futile: in some cases
 407	 * userspace may also be wanting to write to the gotten user page,
 408	 * which a read fault here might prevent (a readonly page might get
 409	 * reCOWed by userspace write).
 410	 */
 411	if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
 412		*flags &= ~FOLL_WRITE;
 413	return 0;
 
 
 
 
 
 
 414}
 415
 416static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
 417{
 418	vm_flags_t vm_flags = vma->vm_flags;
 419	int write = (gup_flags & FOLL_WRITE);
 420	int foreign = (gup_flags & FOLL_REMOTE);
 
 421
 422	if (vm_flags & (VM_IO | VM_PFNMAP))
 423		return -EFAULT;
 424
 
 
 
 
 
 
 
 
 
 425	if (write) {
 426		if (!(vm_flags & VM_WRITE)) {
 
 
 
 
 427			if (!(gup_flags & FOLL_FORCE))
 428				return -EFAULT;
 
 
 
 429			/*
 430			 * We used to let the write,force case do COW in a
 431			 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
 432			 * set a breakpoint in a read-only mapping of an
 433			 * executable, without corrupting the file (yet only
 434			 * when that file had been opened for writing!).
 435			 * Anon pages in shared mappings are surprising: now
 436			 * just reject it.
 437			 */
 438			if (!is_cow_mapping(vm_flags))
 439				return -EFAULT;
 440		}
 441	} else if (!(vm_flags & VM_READ)) {
 442		if (!(gup_flags & FOLL_FORCE))
 443			return -EFAULT;
 444		/*
 445		 * Is there actually any vma we can reach here which does not
 446		 * have VM_MAYREAD set?
 447		 */
 448		if (!(vm_flags & VM_MAYREAD))
 449			return -EFAULT;
 450	}
 451	/*
 452	 * gups are always data accesses, not instruction
 453	 * fetches, so execute=false here
 454	 */
 455	if (!arch_vma_access_permitted(vma, write, false, foreign))
 456		return -EFAULT;
 457	return 0;
 458}
 459
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 460/**
 461 * __get_user_pages() - pin user pages in memory
 462 * @tsk:	task_struct of target task
 463 * @mm:		mm_struct of target mm
 464 * @start:	starting user address
 465 * @nr_pages:	number of pages from start to pin
 466 * @gup_flags:	flags modifying pin behaviour
 467 * @pages:	array that receives pointers to the pages pinned.
 468 *		Should be at least nr_pages long. Or NULL, if caller
 469 *		only intends to ensure the pages are faulted in.
 470 * @vmas:	array of pointers to vmas corresponding to each page.
 471 *		Or NULL if the caller does not require them.
 472 * @nonblocking: whether waiting for disk IO or mmap_sem contention
 473 *
 474 * Returns number of pages pinned. This may be fewer than the number
 475 * requested. If nr_pages is 0 or negative, returns 0. If no pages
 476 * were pinned, returns -errno. Each page returned must be released
 477 * with a put_page() call when it is finished with. vmas will only
 478 * remain valid while mmap_sem is held.
 479 *
 480 * Must be called with mmap_sem held.  It may be released.  See below.
 
 
 
 
 
 
 
 
 481 *
 482 * __get_user_pages walks a process's page tables and takes a reference to
 483 * each struct page that each user address corresponds to at a given
 484 * instant. That is, it takes the page that would be accessed if a user
 485 * thread accesses the given user virtual address at that instant.
 486 *
 487 * This does not guarantee that the page exists in the user mappings when
 488 * __get_user_pages returns, and there may even be a completely different
 489 * page there in some cases (eg. if mmapped pagecache has been invalidated
 490 * and subsequently re faulted). However it does guarantee that the page
 491 * won't be freed completely. And mostly callers simply care that the page
 492 * contains data that was valid *at some point in time*. Typically, an IO
 493 * or similar operation cannot guarantee anything stronger anyway because
 494 * locks can't be held over the syscall boundary.
 495 *
 496 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
 497 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
 498 * appropriate) must be called after the page is finished with, and
 499 * before put_page is called.
 500 *
 501 * If @nonblocking != NULL, __get_user_pages will not wait for disk IO
 502 * or mmap_sem contention, and if waiting is needed to pin all pages,
 503 * *@nonblocking will be set to 0.  Further, if @gup_flags does not
 504 * include FOLL_NOWAIT, the mmap_sem will be released via up_read() in
 505 * this case.
 506 *
 507 * A caller using such a combination of @nonblocking and @gup_flags
 508 * must therefore hold the mmap_sem for reading only, and recognize
 509 * when it's been released.  Otherwise, it must be held for either
 510 * reading or writing and will not be released.
 511 *
 512 * In most cases, get_user_pages or get_user_pages_fast should be used
 513 * instead of __get_user_pages. __get_user_pages should be used only if
 514 * you need some special @gup_flags.
 515 */
 516long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 517		unsigned long start, unsigned long nr_pages,
 518		unsigned int gup_flags, struct page **pages,
 519		struct vm_area_struct **vmas, int *nonblocking)
 520{
 521	long i = 0;
 522	unsigned int page_mask;
 523	struct vm_area_struct *vma = NULL;
 
 524
 525	if (!nr_pages)
 526		return 0;
 527
 528	VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
 529
 530	/*
 531	 * If FOLL_FORCE is set then do not force a full fault as the hinting
 532	 * fault information is unrelated to the reference behaviour of a task
 533	 * using the address space
 534	 */
 535	if (!(gup_flags & FOLL_FORCE))
 536		gup_flags |= FOLL_NUMA;
 537
 538	do {
 539		struct page *page;
 540		unsigned int foll_flags = gup_flags;
 541		unsigned int page_increm;
 542
 543		/* first iteration or cross vma bound */
 544		if (!vma || start >= vma->vm_end) {
 545			vma = find_extend_vma(mm, start);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 546			if (!vma && in_gate_area(mm, start)) {
 547				int ret;
 548				ret = get_gate_page(mm, start & PAGE_MASK,
 549						gup_flags, &vma,
 550						pages ? &pages[i] : NULL);
 551				if (ret)
 552					return i ? : ret;
 553				page_mask = 0;
 554				goto next_page;
 555			}
 556
 557			if (!vma || check_vma_flags(vma, gup_flags))
 558				return i ? : -EFAULT;
 559			if (is_vm_hugetlb_page(vma)) {
 560				i = follow_hugetlb_page(mm, vma, pages, vmas,
 561						&start, &nr_pages, i,
 562						gup_flags);
 563				continue;
 564			}
 
 
 
 565		}
 566retry:
 567		/*
 568		 * If we have a pending SIGKILL, don't keep faulting pages and
 569		 * potentially allocating memory.
 570		 */
 571		if (unlikely(fatal_signal_pending(current)))
 572			return i ? i : -ERESTARTSYS;
 
 
 573		cond_resched();
 574		page = follow_page_mask(vma, start, foll_flags, &page_mask);
 575		if (!page) {
 576			int ret;
 577			ret = faultin_page(tsk, vma, start, &foll_flags,
 578					nonblocking);
 579			switch (ret) {
 580			case 0:
 581				goto retry;
 
 
 
 
 582			case -EFAULT:
 583			case -ENOMEM:
 584			case -EHWPOISON:
 585				return i ? i : ret;
 586			case -EBUSY:
 587				return i;
 588			case -ENOENT:
 589				goto next_page;
 590			}
 591			BUG();
 592		} else if (PTR_ERR(page) == -EEXIST) {
 593			/*
 594			 * Proper page table entry exists, but no corresponding
 595			 * struct page.
 
 
 596			 */
 597			goto next_page;
 
 
 
 598		} else if (IS_ERR(page)) {
 599			return i ? i : PTR_ERR(page);
 600		}
 601		if (pages) {
 602			pages[i] = page;
 603			flush_anon_page(vma, page, start);
 604			flush_dcache_page(page);
 605			page_mask = 0;
 606		}
 607next_page:
 608		if (vmas) {
 609			vmas[i] = vma;
 610			page_mask = 0;
 611		}
 612		page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
 613		if (page_increm > nr_pages)
 614			page_increm = nr_pages;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 615		i += page_increm;
 616		start += page_increm * PAGE_SIZE;
 617		nr_pages -= page_increm;
 618	} while (nr_pages);
 619	return i;
 
 
 
 620}
 621EXPORT_SYMBOL(__get_user_pages);
 622
 623bool vma_permits_fault(struct vm_area_struct *vma, unsigned int fault_flags)
 
 624{
 625	bool write   = !!(fault_flags & FAULT_FLAG_WRITE);
 626	bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
 627	vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
 628
 629	if (!(vm_flags & vma->vm_flags))
 630		return false;
 631
 632	/*
 633	 * The architecture might have a hardware protection
 634	 * mechanism other than read/write that can deny access.
 635	 *
 636	 * gup always represents data access, not instruction
 637	 * fetches, so execute=false here:
 638	 */
 639	if (!arch_vma_access_permitted(vma, write, false, foreign))
 640		return false;
 641
 642	return true;
 643}
 644
 645/*
 646 * fixup_user_fault() - manually resolve a user page fault
 647 * @tsk:	the task_struct to use for page fault accounting, or
 648 *		NULL if faults are not to be recorded.
 649 * @mm:		mm_struct of target mm
 650 * @address:	user address
 651 * @fault_flags:flags to pass down to handle_mm_fault()
 652 * @unlocked:	did we unlock the mmap_sem while retrying, maybe NULL if caller
 653 *		does not allow retry
 
 654 *
 655 * This is meant to be called in the specific scenario where for locking reasons
 656 * we try to access user memory in atomic context (within a pagefault_disable()
 657 * section), this returns -EFAULT, and we want to resolve the user fault before
 658 * trying again.
 659 *
 660 * Typically this is meant to be used by the futex code.
 661 *
 662 * The main difference with get_user_pages() is that this function will
 663 * unconditionally call handle_mm_fault() which will in turn perform all the
 664 * necessary SW fixup of the dirty and young bits in the PTE, while
 665 * get_user_pages() only guarantees to update these in the struct page.
 666 *
 667 * This is important for some architectures where those bits also gate the
 668 * access permission to the page because they are maintained in software.  On
 669 * such architectures, gup() will not be enough to make a subsequent access
 670 * succeed.
 671 *
 672 * This function will not return with an unlocked mmap_sem. So it has not the
 673 * same semantics wrt the @mm->mmap_sem as does filemap_fault().
 674 */
 675int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
 676		     unsigned long address, unsigned int fault_flags,
 677		     bool *unlocked)
 678{
 679	struct vm_area_struct *vma;
 680	int ret, major = 0;
 
 
 681
 682	if (unlocked)
 683		fault_flags |= FAULT_FLAG_ALLOW_RETRY;
 684
 685retry:
 686	vma = find_extend_vma(mm, address);
 687	if (!vma || address < vma->vm_start)
 688		return -EFAULT;
 689
 690	if (!vma_permits_fault(vma, fault_flags))
 691		return -EFAULT;
 692
 693	ret = handle_mm_fault(mm, vma, address, fault_flags);
 694	major |= ret & VM_FAULT_MAJOR;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 695	if (ret & VM_FAULT_ERROR) {
 696		if (ret & VM_FAULT_OOM)
 697			return -ENOMEM;
 698		if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
 699			return -EHWPOISON;
 700		if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
 701			return -EFAULT;
 702		BUG();
 703	}
 704
 705	if (ret & VM_FAULT_RETRY) {
 706		down_read(&mm->mmap_sem);
 707		if (!(fault_flags & FAULT_FLAG_TRIED)) {
 708			*unlocked = true;
 709			fault_flags &= ~FAULT_FLAG_ALLOW_RETRY;
 710			fault_flags |= FAULT_FLAG_TRIED;
 711			goto retry;
 712		}
 713	}
 714
 715	if (tsk) {
 716		if (major)
 717			tsk->maj_flt++;
 718		else
 719			tsk->min_flt++;
 720	}
 721	return 0;
 722}
 
 
 
 
 
 
 
 
 
 
 
 723
 724static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
 725						struct mm_struct *mm,
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 726						unsigned long start,
 727						unsigned long nr_pages,
 728						int write, int force,
 729						struct page **pages,
 730						struct vm_area_struct **vmas,
 731						int *locked, bool notify_drop,
 732						unsigned int flags)
 733{
 734	long ret, pages_done;
 735	bool lock_dropped;
 736
 737	if (locked) {
 738		/* if VM_FAULT_RETRY can be returned, vmas become invalid */
 739		BUG_ON(vmas);
 740		/* check caller initialized locked */
 741		BUG_ON(*locked != 1);
 
 
 
 
 
 
 
 742	}
 
 
 743
 744	if (pages)
 
 
 
 
 
 
 
 
 
 
 
 
 745		flags |= FOLL_GET;
 746	if (write)
 747		flags |= FOLL_WRITE;
 748	if (force)
 749		flags |= FOLL_FORCE;
 750
 751	pages_done = 0;
 752	lock_dropped = false;
 753	for (;;) {
 754		ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages,
 755				       vmas, locked);
 756		if (!locked)
 757			/* VM_FAULT_RETRY couldn't trigger, bypass */
 758			return ret;
 
 
 759
 760		/* VM_FAULT_RETRY cannot return errors */
 761		if (!*locked) {
 762			BUG_ON(ret < 0);
 763			BUG_ON(ret >= nr_pages);
 764		}
 765
 766		if (!pages)
 767			/* If it's a prefault don't insist harder */
 768			return ret;
 769
 770		if (ret > 0) {
 771			nr_pages -= ret;
 772			pages_done += ret;
 773			if (!nr_pages)
 774				break;
 775		}
 776		if (*locked) {
 777			/* VM_FAULT_RETRY didn't trigger */
 
 
 
 778			if (!pages_done)
 779				pages_done = ret;
 780			break;
 781		}
 782		/* VM_FAULT_RETRY triggered, so seek to the faulting offset */
 783		pages += ret;
 
 
 
 
 784		start += ret << PAGE_SHIFT;
 785
 
 
 
 
 786		/*
 787		 * Repeat on the address that fired VM_FAULT_RETRY
 788		 * without FAULT_FLAG_ALLOW_RETRY but with
 789		 * FAULT_FLAG_TRIED.
 
 
 
 790		 */
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 791		*locked = 1;
 792		lock_dropped = true;
 793		down_read(&mm->mmap_sem);
 794		ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED,
 795				       pages, NULL, NULL);
 
 
 
 796		if (ret != 1) {
 797			BUG_ON(ret > 1);
 798			if (!pages_done)
 799				pages_done = ret;
 800			break;
 801		}
 802		nr_pages--;
 803		pages_done++;
 804		if (!nr_pages)
 805			break;
 806		pages++;
 
 807		start += PAGE_SIZE;
 808	}
 809	if (notify_drop && lock_dropped && *locked) {
 810		/*
 811		 * We must let the caller know we temporarily dropped the lock
 812		 * and so the critical section protected by it was lost.
 
 813		 */
 814		up_read(&mm->mmap_sem);
 815		*locked = 0;
 816	}
 817	return pages_done;
 818}
 819
 820/*
 821 * We can leverage the VM_FAULT_RETRY functionality in the page fault
 822 * paths better by using either get_user_pages_locked() or
 823 * get_user_pages_unlocked().
 824 *
 825 * get_user_pages_locked() is suitable to replace the form:
 826 *
 827 *      down_read(&mm->mmap_sem);
 828 *      do_something()
 829 *      get_user_pages(tsk, mm, ..., pages, NULL);
 830 *      up_read(&mm->mmap_sem);
 831 *
 832 *  to:
 833 *
 834 *      int locked = 1;
 835 *      down_read(&mm->mmap_sem);
 836 *      do_something()
 837 *      get_user_pages_locked(tsk, mm, ..., pages, &locked);
 838 *      if (locked)
 839 *          up_read(&mm->mmap_sem);
 840 */
 841long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
 842			   int write, int force, struct page **pages,
 843			   int *locked)
 844{
 845	return __get_user_pages_locked(current, current->mm, start, nr_pages,
 846				       write, force, pages, NULL, locked, true,
 847				       FOLL_TOUCH);
 848}
 849EXPORT_SYMBOL(get_user_pages_locked);
 850
 851/*
 852 * Same as get_user_pages_unlocked(...., FOLL_TOUCH) but it allows to
 853 * pass additional gup_flags as last parameter (like FOLL_HWPOISON).
 854 *
 855 * NOTE: here FOLL_TOUCH is not set implicitly and must be set by the
 856 * caller if required (just like with __get_user_pages). "FOLL_GET",
 857 * "FOLL_WRITE" and "FOLL_FORCE" are set implicitly as needed
 858 * according to the parameters "pages", "write", "force"
 859 * respectively.
 860 */
 861__always_inline long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
 862					       unsigned long start, unsigned long nr_pages,
 863					       int write, int force, struct page **pages,
 864					       unsigned int gup_flags)
 865{
 866	long ret;
 867	int locked = 1;
 868	down_read(&mm->mmap_sem);
 869	ret = __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
 870				      pages, NULL, &locked, false, gup_flags);
 871	if (locked)
 872		up_read(&mm->mmap_sem);
 873	return ret;
 874}
 875EXPORT_SYMBOL(__get_user_pages_unlocked);
 876
 877/*
 878 * get_user_pages_unlocked() is suitable to replace the form:
 879 *
 880 *      down_read(&mm->mmap_sem);
 881 *      get_user_pages(tsk, mm, ..., pages, NULL);
 882 *      up_read(&mm->mmap_sem);
 883 *
 884 *  with:
 885 *
 886 *      get_user_pages_unlocked(tsk, mm, ..., pages);
 887 *
 888 * It is functionally equivalent to get_user_pages_fast so
 889 * get_user_pages_fast should be used instead, if the two parameters
 890 * "tsk" and "mm" are respectively equal to current and current->mm,
 891 * or if "force" shall be set to 1 (get_user_pages_fast misses the
 892 * "force" parameter).
 893 */
 894long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
 895			     int write, int force, struct page **pages)
 896{
 897	return __get_user_pages_unlocked(current, current->mm, start, nr_pages,
 898					 write, force, pages, FOLL_TOUCH);
 899}
 900EXPORT_SYMBOL(get_user_pages_unlocked);
 901
 902/*
 903 * get_user_pages_remote() - pin user pages in memory
 904 * @tsk:	the task_struct to use for page fault accounting, or
 905 *		NULL if faults are not to be recorded.
 906 * @mm:		mm_struct of target mm
 907 * @start:	starting user address
 908 * @nr_pages:	number of pages from start to pin
 909 * @write:	whether pages will be written to by the caller
 910 * @force:	whether to force access even when user mapping is currently
 911 *		protected (but never forces write access to shared mapping).
 912 * @pages:	array that receives pointers to the pages pinned.
 913 *		Should be at least nr_pages long. Or NULL, if caller
 914 *		only intends to ensure the pages are faulted in.
 915 * @vmas:	array of pointers to vmas corresponding to each page.
 916 *		Or NULL if the caller does not require them.
 917 *
 918 * Returns number of pages pinned. This may be fewer than the number
 919 * requested. If nr_pages is 0 or negative, returns 0. If no pages
 920 * were pinned, returns -errno. Each page returned must be released
 921 * with a put_page() call when it is finished with. vmas will only
 922 * remain valid while mmap_sem is held.
 923 *
 924 * Must be called with mmap_sem held for read or write.
 925 *
 926 * get_user_pages walks a process's page tables and takes a reference to
 927 * each struct page that each user address corresponds to at a given
 928 * instant. That is, it takes the page that would be accessed if a user
 929 * thread accesses the given user virtual address at that instant.
 930 *
 931 * This does not guarantee that the page exists in the user mappings when
 932 * get_user_pages returns, and there may even be a completely different
 933 * page there in some cases (eg. if mmapped pagecache has been invalidated
 934 * and subsequently re faulted). However it does guarantee that the page
 935 * won't be freed completely. And mostly callers simply care that the page
 936 * contains data that was valid *at some point in time*. Typically, an IO
 937 * or similar operation cannot guarantee anything stronger anyway because
 938 * locks can't be held over the syscall boundary.
 939 *
 940 * If write=0, the page must not be written to. If the page is written to,
 941 * set_page_dirty (or set_page_dirty_lock, as appropriate) must be called
 942 * after the page is finished with, and before put_page is called.
 943 *
 944 * get_user_pages is typically used for fewer-copy IO operations, to get a
 945 * handle on the memory by some means other than accesses via the user virtual
 946 * addresses. The pages may be submitted for DMA to devices or accessed via
 947 * their kernel linear mapping (via the kmap APIs). Care should be taken to
 948 * use the correct cache flushing APIs.
 949 *
 950 * See also get_user_pages_fast, for performance critical applications.
 951 *
 952 * get_user_pages should be phased out in favor of
 953 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
 954 * should use get_user_pages because it cannot pass
 955 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
 956 */
 957long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
 958		unsigned long start, unsigned long nr_pages,
 959		int write, int force, struct page **pages,
 960		struct vm_area_struct **vmas)
 961{
 962	return __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
 963				       pages, vmas, NULL, false,
 964				       FOLL_TOUCH | FOLL_REMOTE);
 965}
 966EXPORT_SYMBOL(get_user_pages_remote);
 967
 968/*
 969 * This is the same as get_user_pages_remote(), just with a
 970 * less-flexible calling convention where we assume that the task
 971 * and mm being operated on are the current task's.  We also
 972 * obviously don't pass FOLL_REMOTE in here.
 973 */
 974long get_user_pages(unsigned long start, unsigned long nr_pages,
 975		int write, int force, struct page **pages,
 976		struct vm_area_struct **vmas)
 977{
 978	return __get_user_pages_locked(current, current->mm, start, nr_pages,
 979				       write, force, pages, vmas, NULL, false,
 980				       FOLL_TOUCH);
 981}
 982EXPORT_SYMBOL(get_user_pages);
 983
 984/**
 985 * populate_vma_page_range() -  populate a range of pages in the vma.
 986 * @vma:   target vma
 987 * @start: start address
 988 * @end:   end address
 989 * @nonblocking:
 990 *
 991 * This takes care of mlocking the pages too if VM_LOCKED is set.
 992 *
 993 * return 0 on success, negative error code on error.
 
 994 *
 995 * vma->vm_mm->mmap_sem must be held.
 996 *
 997 * If @nonblocking is NULL, it may be held for read or write and will
 998 * be unperturbed.
 999 *
1000 * If @nonblocking is non-NULL, it must held for read only and may be
1001 * released.  If it's released, *@nonblocking will be set to 0.
1002 */
1003long populate_vma_page_range(struct vm_area_struct *vma,
1004		unsigned long start, unsigned long end, int *nonblocking)
1005{
1006	struct mm_struct *mm = vma->vm_mm;
1007	unsigned long nr_pages = (end - start) / PAGE_SIZE;
 
1008	int gup_flags;
 
1009
1010	VM_BUG_ON(start & ~PAGE_MASK);
1011	VM_BUG_ON(end   & ~PAGE_MASK);
1012	VM_BUG_ON_VMA(start < vma->vm_start, vma);
1013	VM_BUG_ON_VMA(end   > vma->vm_end, vma);
1014	VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
1015
1016	gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
 
 
 
1017	if (vma->vm_flags & VM_LOCKONFAULT)
1018		gup_flags &= ~FOLL_POPULATE;
 
 
 
 
 
 
1019	/*
1020	 * We want to touch writable mappings with a write fault in order
1021	 * to break COW, except for shared mappings because these don't COW
1022	 * and we would not want to dirty them for nothing.
 
 
 
1023	 */
1024	if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
1025		gup_flags |= FOLL_WRITE;
1026
1027	/*
1028	 * We want mlock to succeed for regions that have any permissions
1029	 * other than PROT_NONE.
1030	 */
1031	if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
1032		gup_flags |= FOLL_FORCE;
1033
 
 
 
1034	/*
1035	 * We made sure addr is within a VMA, so the following will
1036	 * not result in a stack expansion that recurses back here.
1037	 */
1038	return __get_user_pages(current, mm, start, nr_pages, gup_flags,
1039				NULL, NULL, nonblocking);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1040}
1041
1042/*
1043 * __mm_populate - populate and/or mlock pages within a range of address space.
1044 *
1045 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1046 * flags. VMAs must be already marked with the desired vm_flags, and
1047 * mmap_sem must not be held.
1048 */
1049int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
1050{
1051	struct mm_struct *mm = current->mm;
1052	unsigned long end, nstart, nend;
1053	struct vm_area_struct *vma = NULL;
1054	int locked = 0;
1055	long ret = 0;
1056
1057	VM_BUG_ON(start & ~PAGE_MASK);
1058	VM_BUG_ON(len != PAGE_ALIGN(len));
1059	end = start + len;
1060
1061	for (nstart = start; nstart < end; nstart = nend) {
1062		/*
1063		 * We want to fault in pages for [nstart; end) address range.
1064		 * Find first corresponding VMA.
1065		 */
1066		if (!locked) {
1067			locked = 1;
1068			down_read(&mm->mmap_sem);
1069			vma = find_vma(mm, nstart);
1070		} else if (nstart >= vma->vm_end)
1071			vma = vma->vm_next;
1072		if (!vma || vma->vm_start >= end)
 
1073			break;
1074		/*
1075		 * Set [nstart; nend) to intersection of desired address
1076		 * range with the first VMA. Also, skip undesirable VMA types.
1077		 */
1078		nend = min(end, vma->vm_end);
1079		if (vma->vm_flags & (VM_IO | VM_PFNMAP))
1080			continue;
1081		if (nstart < vma->vm_start)
1082			nstart = vma->vm_start;
1083		/*
1084		 * Now fault in a range of pages. populate_vma_page_range()
1085		 * double checks the vma flags, so that it won't mlock pages
1086		 * if the vma was already munlocked.
1087		 */
1088		ret = populate_vma_page_range(vma, nstart, nend, &locked);
1089		if (ret < 0) {
1090			if (ignore_errors) {
1091				ret = 0;
1092				continue;	/* continue at next VMA */
1093			}
1094			break;
1095		}
1096		nend = nstart + ret * PAGE_SIZE;
1097		ret = 0;
1098	}
1099	if (locked)
1100		up_read(&mm->mmap_sem);
1101	return ret;	/* 0 or negative error code */
1102}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1103
1104/**
1105 * get_dump_page() - pin user page in memory while writing it to core dump
1106 * @addr: user address
1107 *
1108 * Returns struct page pointer of user page pinned for dump,
1109 * to be freed afterwards by put_page().
1110 *
1111 * Returns NULL on any kind of failure - a hole must then be inserted into
1112 * the corefile, to preserve alignment with its headers; and also returns
1113 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1114 * allowing a hole to be left in the corefile to save diskspace.
1115 *
1116 * Called without mmap_sem, but after all other threads have been killed.
1117 */
1118#ifdef CONFIG_ELF_CORE
1119struct page *get_dump_page(unsigned long addr)
1120{
1121	struct vm_area_struct *vma;
1122	struct page *page;
 
 
1123
1124	if (__get_user_pages(current, current->mm, addr, 1,
1125			     FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
1126			     NULL) < 1)
1127		return NULL;
1128	flush_cache_page(vma, addr, page_to_pfn(page));
1129	return page;
1130}
1131#endif /* CONFIG_ELF_CORE */
1132
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1133/*
1134 * Generic RCU Fast GUP
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1135 *
1136 * get_user_pages_fast attempts to pin user pages by walking the page
1137 * tables directly and avoids taking locks. Thus the walker needs to be
1138 * protected from page table pages being freed from under it, and should
1139 * block any THP splits.
1140 *
1141 * One way to achieve this is to have the walker disable interrupts, and
1142 * rely on IPIs from the TLB flushing code blocking before the page table
1143 * pages are freed. This is unsuitable for architectures that do not need
1144 * to broadcast an IPI when invalidating TLBs.
1145 *
1146 * Another way to achieve this is to batch up page table containing pages
1147 * belonging to more than one mm_user, then rcu_sched a callback to free those
1148 * pages. Disabling interrupts will allow the fast_gup walker to both block
1149 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
1150 * (which is a relatively rare event). The code below adopts this strategy.
1151 *
1152 * Before activating this code, please be aware that the following assumptions
1153 * are currently made:
1154 *
1155 *  *) HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table is used to free
1156 *      pages containing page tables.
1157 *
1158 *  *) ptes can be read atomically by the architecture.
1159 *
1160 *  *) access_ok is sufficient to validate userspace address ranges.
1161 *
1162 * The last two assumptions can be relaxed by the addition of helper functions.
1163 *
1164 * This code is based heavily on the PowerPC implementation by Nick Piggin.
1165 */
1166#ifdef CONFIG_HAVE_GENERIC_RCU_GUP
1167
1168#ifdef __HAVE_ARCH_PTE_SPECIAL
1169static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1170			 int write, struct page **pages, int *nr)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1171{
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1172	pte_t *ptep, *ptem;
1173	int ret = 0;
1174
1175	ptem = ptep = pte_offset_map(&pmd, addr);
 
 
1176	do {
1177		/*
1178		 * In the line below we are assuming that the pte can be read
1179		 * atomically. If this is not the case for your architecture,
1180		 * please wrap this in a helper function!
1181		 *
1182		 * for an example see gup_get_pte in arch/x86/mm/gup.c
1183		 */
1184		pte_t pte = READ_ONCE(*ptep);
1185		struct page *head, *page;
1186
1187		/*
1188		 * Similar to the PMD case below, NUMA hinting must take slow
1189		 * path using the pte_protnone check.
 
 
 
1190		 */
1191		if (!pte_present(pte) || pte_special(pte) ||
1192			pte_protnone(pte) || (write && !pte_write(pte)))
1193			goto pte_unmap;
1194
1195		if (!arch_pte_access_permitted(pte, write))
 
 
 
 
 
 
 
 
 
 
 
 
1196			goto pte_unmap;
1197
1198		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
1199		page = pte_page(pte);
1200		head = compound_head(page);
1201
1202		if (!page_cache_get_speculative(head))
 
 
 
 
 
1203			goto pte_unmap;
 
1204
1205		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
1206			put_page(head);
 
1207			goto pte_unmap;
1208		}
1209
1210		VM_BUG_ON_PAGE(compound_head(page) != head, page);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1211		pages[*nr] = page;
1212		(*nr)++;
1213
1214	} while (ptep++, addr += PAGE_SIZE, addr != end);
1215
1216	ret = 1;
1217
1218pte_unmap:
 
 
1219	pte_unmap(ptem);
1220	return ret;
1221}
1222#else
1223
1224/*
1225 * If we can't determine whether or not a pte is special, then fail immediately
1226 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
1227 * to be special.
1228 *
1229 * For a futex to be placed on a THP tail page, get_futex_key requires a
1230 * __get_user_pages_fast implementation that can pin pages. Thus it's still
1231 * useful to have gup_huge_pmd even if we can't operate on ptes.
1232 */
1233static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1234			 int write, struct page **pages, int *nr)
 
1235{
1236	return 0;
1237}
1238#endif /* __HAVE_ARCH_PTE_SPECIAL */
1239
1240static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
1241		unsigned long end, int write, struct page **pages, int *nr)
 
 
1242{
1243	struct page *head, *page;
1244	int refs;
1245
1246	if (write && !pmd_write(orig))
1247		return 0;
1248
1249	refs = 0;
1250	head = pmd_page(orig);
1251	page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
1252	do {
1253		VM_BUG_ON_PAGE(compound_head(page) != head, page);
 
 
 
 
 
 
 
 
 
 
 
 
 
1254		pages[*nr] = page;
 
 
 
 
1255		(*nr)++;
1256		page++;
1257		refs++;
1258	} while (addr += PAGE_SIZE, addr != end);
1259
1260	if (!page_cache_add_speculative(head, refs)) {
1261		*nr -= refs;
 
 
 
 
 
 
 
 
 
 
 
1262		return 0;
1263	}
1264
1265	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
1266		*nr -= refs;
1267		while (refs--)
1268			put_page(head);
1269		return 0;
1270	}
 
 
 
 
 
 
 
 
 
 
 
 
 
1271
 
 
 
 
1272	return 1;
1273}
 
 
 
 
 
 
 
 
1274
1275static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
1276		unsigned long end, int write, struct page **pages, int *nr)
 
1277{
1278	struct page *head, *page;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1279	int refs;
1280
1281	if (write && !pud_write(orig))
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1282		return 0;
1283
1284	refs = 0;
1285	head = pud_page(orig);
1286	page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1287	do {
1288		VM_BUG_ON_PAGE(compound_head(page) != head, page);
1289		pages[*nr] = page;
1290		(*nr)++;
1291		page++;
1292		refs++;
1293	} while (addr += PAGE_SIZE, addr != end);
1294
1295	if (!page_cache_add_speculative(head, refs)) {
1296		*nr -= refs;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1297		return 0;
1298	}
1299
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1300	if (unlikely(pud_val(orig) != pud_val(*pudp))) {
1301		*nr -= refs;
1302		while (refs--)
1303			put_page(head);
 
 
 
 
 
 
 
 
1304		return 0;
1305	}
1306
 
 
1307	return 1;
1308}
1309
1310static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
1311			unsigned long end, int write,
1312			struct page **pages, int *nr)
1313{
1314	int refs;
1315	struct page *head, *page;
 
1316
1317	if (write && !pgd_write(orig))
1318		return 0;
1319
1320	refs = 0;
1321	head = pgd_page(orig);
1322	page = head + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
1323	do {
1324		VM_BUG_ON_PAGE(compound_head(page) != head, page);
1325		pages[*nr] = page;
1326		(*nr)++;
1327		page++;
1328		refs++;
1329	} while (addr += PAGE_SIZE, addr != end);
1330
1331	if (!page_cache_add_speculative(head, refs)) {
1332		*nr -= refs;
1333		return 0;
1334	}
1335
1336	if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
1337		*nr -= refs;
1338		while (refs--)
1339			put_page(head);
1340		return 0;
1341	}
1342
 
 
 
 
 
 
 
 
 
 
 
 
1343	return 1;
1344}
1345
1346static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
1347		int write, struct page **pages, int *nr)
1348{
1349	unsigned long next;
1350	pmd_t *pmdp;
1351
1352	pmdp = pmd_offset(&pud, addr);
1353	do {
1354		pmd_t pmd = READ_ONCE(*pmdp);
1355
1356		next = pmd_addr_end(addr, end);
1357		if (pmd_none(pmd))
1358			return 0;
1359
1360		if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd))) {
1361			/*
1362			 * NUMA hinting faults need to be handled in the GUP
1363			 * slowpath for accounting purposes and so that they
1364			 * can be serialised against THP migration.
1365			 */
1366			if (pmd_protnone(pmd))
1367				return 0;
1368
1369			if (!gup_huge_pmd(pmd, pmdp, addr, next, write,
1370				pages, nr))
1371				return 0;
1372
1373		} else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
1374			/*
1375			 * architecture have different format for hugetlbfs
1376			 * pmd format and THP pmd format
1377			 */
1378			if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
1379					 PMD_SHIFT, next, write, pages, nr))
1380				return 0;
1381		} else if (!gup_pte_range(pmd, addr, next, write, pages, nr))
1382				return 0;
 
 
1383	} while (pmdp++, addr = next, addr != end);
1384
1385	return 1;
1386}
1387
1388static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
1389			 int write, struct page **pages, int *nr)
1390{
1391	unsigned long next;
1392	pud_t *pudp;
1393
1394	pudp = pud_offset(&pgd, addr);
1395	do {
1396		pud_t pud = READ_ONCE(*pudp);
1397
1398		next = pud_addr_end(addr, end);
1399		if (pud_none(pud))
1400			return 0;
1401		if (unlikely(pud_huge(pud))) {
1402			if (!gup_huge_pud(pud, pudp, addr, next, write,
1403					  pages, nr))
1404				return 0;
1405		} else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
1406			if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
1407					 PUD_SHIFT, next, write, pages, nr))
1408				return 0;
1409		} else if (!gup_pmd_range(pud, addr, next, write, pages, nr))
1410			return 0;
1411	} while (pudp++, addr = next, addr != end);
1412
1413	return 1;
1414}
1415
1416/*
1417 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
1418 * the regular GUP. It will only return non-negative values.
1419 */
1420int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
1421			  struct page **pages)
1422{
1423	struct mm_struct *mm = current->mm;
1424	unsigned long addr, len, end;
1425	unsigned long next, flags;
1426	pgd_t *pgdp;
1427	int nr = 0;
1428
1429	start &= PAGE_MASK;
1430	addr = start;
1431	len = (unsigned long) nr_pages << PAGE_SHIFT;
1432	end = start + len;
1433
1434	if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
1435					start, len)))
1436		return 0;
 
 
 
 
 
 
 
 
1437
1438	/*
1439	 * Disable interrupts.  We use the nested form as we can already have
1440	 * interrupts disabled by get_futex_key.
1441	 *
1442	 * With interrupts disabled, we block page table pages from being
1443	 * freed from under us. See mmu_gather_tlb in asm-generic/tlb.h
1444	 * for more details.
1445	 *
1446	 * We do not adopt an rcu_read_lock(.) here as we also want to
1447	 * block IPIs that come from THPs splitting.
1448	 */
1449
1450	local_irq_save(flags);
1451	pgdp = pgd_offset(mm, addr);
 
 
 
 
 
1452	do {
1453		pgd_t pgd = READ_ONCE(*pgdp);
1454
1455		next = pgd_addr_end(addr, end);
1456		if (pgd_none(pgd))
1457			break;
1458		if (unlikely(pgd_huge(pgd))) {
1459			if (!gup_huge_pgd(pgd, pgdp, addr, next, write,
1460					  pages, &nr))
1461				break;
1462		} else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
1463			if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
1464					 PGDIR_SHIFT, next, write, pages, &nr))
1465				break;
1466		} else if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
1467			break;
1468	} while (pgdp++, addr = next, addr != end);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1469	local_irq_restore(flags);
1470
1471	return nr;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1472}
1473
1474/**
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1475 * get_user_pages_fast() - pin user pages in memory
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1476 * @start:	starting user address
1477 * @nr_pages:	number of pages from start to pin
1478 * @write:	whether pages will be written to
1479 * @pages:	array that receives pointers to the pages pinned.
1480 *		Should be at least nr_pages long.
 
 
 
 
 
 
 
1481 *
1482 * Attempt to pin user pages in memory without taking mm->mmap_sem.
1483 * If not successful, it will fall back to taking the lock and
1484 * calling get_user_pages().
1485 *
1486 * Returns number of pages pinned. This may be fewer than the number
1487 * requested. If nr_pages is 0 or negative, returns 0. If no pages
1488 * were pinned, returns -errno.
1489 */
1490int get_user_pages_fast(unsigned long start, int nr_pages, int write,
1491			struct page **pages)
1492{
1493	int nr, ret;
1494
1495	start &= PAGE_MASK;
1496	nr = __get_user_pages_fast(start, nr_pages, write, pages);
1497	ret = nr;
1498
1499	if (nr < nr_pages) {
1500		/* Try to get the remaining pages with get_user_pages */
1501		start += nr << PAGE_SHIFT;
1502		pages += nr;
1503
1504		ret = get_user_pages_unlocked(start, nr_pages - nr, write, 0, pages);
1505
1506		/* Have to be a bit careful with return values */
1507		if (nr > 0) {
1508			if (ret < 0)
1509				ret = nr;
1510			else
1511				ret += nr;
1512		}
1513	}
1514
1515	return ret;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1516}
 
1517
1518#endif /* CONFIG_HAVE_GENERIC_RCU_GUP */
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
v6.9.4
   1// SPDX-License-Identifier: GPL-2.0-only
   2#include <linux/kernel.h>
   3#include <linux/errno.h>
   4#include <linux/err.h>
   5#include <linux/spinlock.h>
   6
   7#include <linux/mm.h>
   8#include <linux/memremap.h>
   9#include <linux/pagemap.h>
  10#include <linux/rmap.h>
  11#include <linux/swap.h>
  12#include <linux/swapops.h>
  13#include <linux/secretmem.h>
  14
  15#include <linux/sched/signal.h>
  16#include <linux/rwsem.h>
  17#include <linux/hugetlb.h>
  18#include <linux/migrate.h>
  19#include <linux/mm_inline.h>
  20#include <linux/sched/mm.h>
  21#include <linux/shmem_fs.h>
  22
  23#include <asm/mmu_context.h>
 
  24#include <asm/tlbflush.h>
  25
  26#include "internal.h"
  27
  28struct follow_page_context {
  29	struct dev_pagemap *pgmap;
  30	unsigned int page_mask;
  31};
  32
  33static inline void sanity_check_pinned_pages(struct page **pages,
  34					     unsigned long npages)
  35{
  36	if (!IS_ENABLED(CONFIG_DEBUG_VM))
  37		return;
  38
  39	/*
  40	 * We only pin anonymous pages if they are exclusive. Once pinned, we
  41	 * can no longer turn them possibly shared and PageAnonExclusive() will
  42	 * stick around until the page is freed.
  43	 *
  44	 * We'd like to verify that our pinned anonymous pages are still mapped
  45	 * exclusively. The issue with anon THP is that we don't know how
  46	 * they are/were mapped when pinning them. However, for anon
  47	 * THP we can assume that either the given page (PTE-mapped THP) or
  48	 * the head page (PMD-mapped THP) should be PageAnonExclusive(). If
  49	 * neither is the case, there is certainly something wrong.
  50	 */
  51	for (; npages; npages--, pages++) {
  52		struct page *page = *pages;
  53		struct folio *folio = page_folio(page);
  54
  55		if (is_zero_page(page) ||
  56		    !folio_test_anon(folio))
  57			continue;
  58		if (!folio_test_large(folio) || folio_test_hugetlb(folio))
  59			VM_BUG_ON_PAGE(!PageAnonExclusive(&folio->page), page);
  60		else
  61			/* Either a PTE-mapped or a PMD-mapped THP. */
  62			VM_BUG_ON_PAGE(!PageAnonExclusive(&folio->page) &&
  63				       !PageAnonExclusive(page), page);
  64	}
  65}
  66
  67/*
  68 * Return the folio with ref appropriately incremented,
  69 * or NULL if that failed.
  70 */
  71static inline struct folio *try_get_folio(struct page *page, int refs)
  72{
  73	struct folio *folio;
  74
  75retry:
  76	folio = page_folio(page);
  77	if (WARN_ON_ONCE(folio_ref_count(folio) < 0))
  78		return NULL;
  79	if (unlikely(!folio_ref_try_add_rcu(folio, refs)))
  80		return NULL;
  81
  82	/*
  83	 * At this point we have a stable reference to the folio; but it
  84	 * could be that between calling page_folio() and the refcount
  85	 * increment, the folio was split, in which case we'd end up
  86	 * holding a reference on a folio that has nothing to do with the page
  87	 * we were given anymore.
  88	 * So now that the folio is stable, recheck that the page still
  89	 * belongs to this folio.
  90	 */
  91	if (unlikely(page_folio(page) != folio)) {
  92		if (!put_devmap_managed_page_refs(&folio->page, refs))
  93			folio_put_refs(folio, refs);
  94		goto retry;
  95	}
  96
  97	return folio;
  98}
  99
 100/**
 101 * try_grab_folio() - Attempt to get or pin a folio.
 102 * @page:  pointer to page to be grabbed
 103 * @refs:  the value to (effectively) add to the folio's refcount
 104 * @flags: gup flags: these are the FOLL_* flag values.
 105 *
 106 * "grab" names in this file mean, "look at flags to decide whether to use
 107 * FOLL_PIN or FOLL_GET behavior, when incrementing the folio's refcount.
 108 *
 109 * Either FOLL_PIN or FOLL_GET (or neither) must be set, but not both at the
 110 * same time. (That's true throughout the get_user_pages*() and
 111 * pin_user_pages*() APIs.) Cases:
 112 *
 113 *    FOLL_GET: folio's refcount will be incremented by @refs.
 114 *
 115 *    FOLL_PIN on large folios: folio's refcount will be incremented by
 116 *    @refs, and its pincount will be incremented by @refs.
 117 *
 118 *    FOLL_PIN on single-page folios: folio's refcount will be incremented by
 119 *    @refs * GUP_PIN_COUNTING_BIAS.
 120 *
 121 * Return: The folio containing @page (with refcount appropriately
 122 * incremented) for success, or NULL upon failure. If neither FOLL_GET
 123 * nor FOLL_PIN was set, that's considered failure, and furthermore,
 124 * a likely bug in the caller, so a warning is also emitted.
 125 */
 126struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags)
 127{
 128	struct folio *folio;
 129
 130	if (WARN_ON_ONCE((flags & (FOLL_GET | FOLL_PIN)) == 0))
 131		return NULL;
 132
 133	if (unlikely(!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page)))
 134		return NULL;
 135
 136	if (flags & FOLL_GET)
 137		return try_get_folio(page, refs);
 138
 139	/* FOLL_PIN is set */
 140
 141	/*
 142	 * Don't take a pin on the zero page - it's not going anywhere
 143	 * and it is used in a *lot* of places.
 144	 */
 145	if (is_zero_page(page))
 146		return page_folio(page);
 147
 148	folio = try_get_folio(page, refs);
 149	if (!folio)
 150		return NULL;
 151
 152	/*
 153	 * Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a
 154	 * right zone, so fail and let the caller fall back to the slow
 155	 * path.
 156	 */
 157	if (unlikely((flags & FOLL_LONGTERM) &&
 158		     !folio_is_longterm_pinnable(folio))) {
 159		if (!put_devmap_managed_page_refs(&folio->page, refs))
 160			folio_put_refs(folio, refs);
 161		return NULL;
 162	}
 163
 164	/*
 165	 * When pinning a large folio, use an exact count to track it.
 166	 *
 167	 * However, be sure to *also* increment the normal folio
 168	 * refcount field at least once, so that the folio really
 169	 * is pinned.  That's why the refcount from the earlier
 170	 * try_get_folio() is left intact.
 171	 */
 172	if (folio_test_large(folio))
 173		atomic_add(refs, &folio->_pincount);
 174	else
 175		folio_ref_add(folio,
 176				refs * (GUP_PIN_COUNTING_BIAS - 1));
 177	/*
 178	 * Adjust the pincount before re-checking the PTE for changes.
 179	 * This is essentially a smp_mb() and is paired with a memory
 180	 * barrier in folio_try_share_anon_rmap_*().
 181	 */
 182	smp_mb__after_atomic();
 183
 184	node_stat_mod_folio(folio, NR_FOLL_PIN_ACQUIRED, refs);
 185
 186	return folio;
 187}
 188
 189static void gup_put_folio(struct folio *folio, int refs, unsigned int flags)
 190{
 191	if (flags & FOLL_PIN) {
 192		if (is_zero_folio(folio))
 193			return;
 194		node_stat_mod_folio(folio, NR_FOLL_PIN_RELEASED, refs);
 195		if (folio_test_large(folio))
 196			atomic_sub(refs, &folio->_pincount);
 197		else
 198			refs *= GUP_PIN_COUNTING_BIAS;
 199	}
 200
 201	if (!put_devmap_managed_page_refs(&folio->page, refs))
 202		folio_put_refs(folio, refs);
 203}
 204
 205/**
 206 * try_grab_page() - elevate a page's refcount by a flag-dependent amount
 207 * @page:    pointer to page to be grabbed
 208 * @flags:   gup flags: these are the FOLL_* flag values.
 209 *
 210 * This might not do anything at all, depending on the flags argument.
 211 *
 212 * "grab" names in this file mean, "look at flags to decide whether to use
 213 * FOLL_PIN or FOLL_GET behavior, when incrementing the page's refcount.
 214 *
 215 * Either FOLL_PIN or FOLL_GET (or neither) may be set, but not both at the same
 216 * time. Cases: please see the try_grab_folio() documentation, with
 217 * "refs=1".
 218 *
 219 * Return: 0 for success, or if no action was required (if neither FOLL_PIN
 220 * nor FOLL_GET was set, nothing is done). A negative error code for failure:
 221 *
 222 *   -ENOMEM		FOLL_GET or FOLL_PIN was set, but the page could not
 223 *			be grabbed.
 224 */
 225int __must_check try_grab_page(struct page *page, unsigned int flags)
 226{
 227	struct folio *folio = page_folio(page);
 228
 229	if (WARN_ON_ONCE(folio_ref_count(folio) <= 0))
 230		return -ENOMEM;
 231
 232	if (unlikely(!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page)))
 233		return -EREMOTEIO;
 234
 235	if (flags & FOLL_GET)
 236		folio_ref_inc(folio);
 237	else if (flags & FOLL_PIN) {
 238		/*
 239		 * Don't take a pin on the zero page - it's not going anywhere
 240		 * and it is used in a *lot* of places.
 241		 */
 242		if (is_zero_page(page))
 243			return 0;
 244
 245		/*
 246		 * Similar to try_grab_folio(): be sure to *also*
 247		 * increment the normal page refcount field at least once,
 248		 * so that the page really is pinned.
 249		 */
 250		if (folio_test_large(folio)) {
 251			folio_ref_add(folio, 1);
 252			atomic_add(1, &folio->_pincount);
 253		} else {
 254			folio_ref_add(folio, GUP_PIN_COUNTING_BIAS);
 255		}
 256
 257		node_stat_mod_folio(folio, NR_FOLL_PIN_ACQUIRED, 1);
 258	}
 259
 260	return 0;
 261}
 262
 263/**
 264 * unpin_user_page() - release a dma-pinned page
 265 * @page:            pointer to page to be released
 266 *
 267 * Pages that were pinned via pin_user_pages*() must be released via either
 268 * unpin_user_page(), or one of the unpin_user_pages*() routines. This is so
 269 * that such pages can be separately tracked and uniquely handled. In
 270 * particular, interactions with RDMA and filesystems need special handling.
 271 */
 272void unpin_user_page(struct page *page)
 273{
 274	sanity_check_pinned_pages(&page, 1);
 275	gup_put_folio(page_folio(page), 1, FOLL_PIN);
 276}
 277EXPORT_SYMBOL(unpin_user_page);
 278
 279/**
 280 * folio_add_pin - Try to get an additional pin on a pinned folio
 281 * @folio: The folio to be pinned
 282 *
 283 * Get an additional pin on a folio we already have a pin on.  Makes no change
 284 * if the folio is a zero_page.
 285 */
 286void folio_add_pin(struct folio *folio)
 287{
 288	if (is_zero_folio(folio))
 289		return;
 290
 291	/*
 292	 * Similar to try_grab_folio(): be sure to *also* increment the normal
 293	 * page refcount field at least once, so that the page really is
 294	 * pinned.
 295	 */
 296	if (folio_test_large(folio)) {
 297		WARN_ON_ONCE(atomic_read(&folio->_pincount) < 1);
 298		folio_ref_inc(folio);
 299		atomic_inc(&folio->_pincount);
 300	} else {
 301		WARN_ON_ONCE(folio_ref_count(folio) < GUP_PIN_COUNTING_BIAS);
 302		folio_ref_add(folio, GUP_PIN_COUNTING_BIAS);
 303	}
 304}
 305
 306static inline struct folio *gup_folio_range_next(struct page *start,
 307		unsigned long npages, unsigned long i, unsigned int *ntails)
 308{
 309	struct page *next = nth_page(start, i);
 310	struct folio *folio = page_folio(next);
 311	unsigned int nr = 1;
 312
 313	if (folio_test_large(folio))
 314		nr = min_t(unsigned int, npages - i,
 315			   folio_nr_pages(folio) - folio_page_idx(folio, next));
 316
 317	*ntails = nr;
 318	return folio;
 319}
 320
 321static inline struct folio *gup_folio_next(struct page **list,
 322		unsigned long npages, unsigned long i, unsigned int *ntails)
 323{
 324	struct folio *folio = page_folio(list[i]);
 325	unsigned int nr;
 326
 327	for (nr = i + 1; nr < npages; nr++) {
 328		if (page_folio(list[nr]) != folio)
 329			break;
 330	}
 331
 332	*ntails = nr - i;
 333	return folio;
 334}
 335
 336/**
 337 * unpin_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages
 338 * @pages:  array of pages to be maybe marked dirty, and definitely released.
 339 * @npages: number of pages in the @pages array.
 340 * @make_dirty: whether to mark the pages dirty
 341 *
 342 * "gup-pinned page" refers to a page that has had one of the get_user_pages()
 343 * variants called on that page.
 344 *
 345 * For each page in the @pages array, make that page (or its head page, if a
 346 * compound page) dirty, if @make_dirty is true, and if the page was previously
 347 * listed as clean. In any case, releases all pages using unpin_user_page(),
 348 * possibly via unpin_user_pages(), for the non-dirty case.
 349 *
 350 * Please see the unpin_user_page() documentation for details.
 351 *
 352 * set_page_dirty_lock() is used internally. If instead, set_page_dirty() is
 353 * required, then the caller should a) verify that this is really correct,
 354 * because _lock() is usually required, and b) hand code it:
 355 * set_page_dirty_lock(), unpin_user_page().
 356 *
 357 */
 358void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages,
 359				 bool make_dirty)
 360{
 361	unsigned long i;
 362	struct folio *folio;
 363	unsigned int nr;
 364
 365	if (!make_dirty) {
 366		unpin_user_pages(pages, npages);
 367		return;
 368	}
 369
 370	sanity_check_pinned_pages(pages, npages);
 371	for (i = 0; i < npages; i += nr) {
 372		folio = gup_folio_next(pages, npages, i, &nr);
 373		/*
 374		 * Checking PageDirty at this point may race with
 375		 * clear_page_dirty_for_io(), but that's OK. Two key
 376		 * cases:
 377		 *
 378		 * 1) This code sees the page as already dirty, so it
 379		 * skips the call to set_page_dirty(). That could happen
 380		 * because clear_page_dirty_for_io() called
 381		 * page_mkclean(), followed by set_page_dirty().
 382		 * However, now the page is going to get written back,
 383		 * which meets the original intention of setting it
 384		 * dirty, so all is well: clear_page_dirty_for_io() goes
 385		 * on to call TestClearPageDirty(), and write the page
 386		 * back.
 387		 *
 388		 * 2) This code sees the page as clean, so it calls
 389		 * set_page_dirty(). The page stays dirty, despite being
 390		 * written back, so it gets written back again in the
 391		 * next writeback cycle. This is harmless.
 392		 */
 393		if (!folio_test_dirty(folio)) {
 394			folio_lock(folio);
 395			folio_mark_dirty(folio);
 396			folio_unlock(folio);
 397		}
 398		gup_put_folio(folio, nr, FOLL_PIN);
 399	}
 400}
 401EXPORT_SYMBOL(unpin_user_pages_dirty_lock);
 402
 403/**
 404 * unpin_user_page_range_dirty_lock() - release and optionally dirty
 405 * gup-pinned page range
 406 *
 407 * @page:  the starting page of a range maybe marked dirty, and definitely released.
 408 * @npages: number of consecutive pages to release.
 409 * @make_dirty: whether to mark the pages dirty
 410 *
 411 * "gup-pinned page range" refers to a range of pages that has had one of the
 412 * pin_user_pages() variants called on that page.
 413 *
 414 * For the page ranges defined by [page .. page+npages], make that range (or
 415 * its head pages, if a compound page) dirty, if @make_dirty is true, and if the
 416 * page range was previously listed as clean.
 417 *
 418 * set_page_dirty_lock() is used internally. If instead, set_page_dirty() is
 419 * required, then the caller should a) verify that this is really correct,
 420 * because _lock() is usually required, and b) hand code it:
 421 * set_page_dirty_lock(), unpin_user_page().
 422 *
 423 */
 424void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages,
 425				      bool make_dirty)
 426{
 427	unsigned long i;
 428	struct folio *folio;
 429	unsigned int nr;
 430
 431	for (i = 0; i < npages; i += nr) {
 432		folio = gup_folio_range_next(page, npages, i, &nr);
 433		if (make_dirty && !folio_test_dirty(folio)) {
 434			folio_lock(folio);
 435			folio_mark_dirty(folio);
 436			folio_unlock(folio);
 437		}
 438		gup_put_folio(folio, nr, FOLL_PIN);
 439	}
 440}
 441EXPORT_SYMBOL(unpin_user_page_range_dirty_lock);
 442
 443static void unpin_user_pages_lockless(struct page **pages, unsigned long npages)
 444{
 445	unsigned long i;
 446	struct folio *folio;
 447	unsigned int nr;
 448
 449	/*
 450	 * Don't perform any sanity checks because we might have raced with
 451	 * fork() and some anonymous pages might now actually be shared --
 452	 * which is why we're unpinning after all.
 453	 */
 454	for (i = 0; i < npages; i += nr) {
 455		folio = gup_folio_next(pages, npages, i, &nr);
 456		gup_put_folio(folio, nr, FOLL_PIN);
 457	}
 458}
 459
 460/**
 461 * unpin_user_pages() - release an array of gup-pinned pages.
 462 * @pages:  array of pages to be marked dirty and released.
 463 * @npages: number of pages in the @pages array.
 464 *
 465 * For each page in the @pages array, release the page using unpin_user_page().
 466 *
 467 * Please see the unpin_user_page() documentation for details.
 468 */
 469void unpin_user_pages(struct page **pages, unsigned long npages)
 470{
 471	unsigned long i;
 472	struct folio *folio;
 473	unsigned int nr;
 474
 475	/*
 476	 * If this WARN_ON() fires, then the system *might* be leaking pages (by
 477	 * leaving them pinned), but probably not. More likely, gup/pup returned
 478	 * a hard -ERRNO error to the caller, who erroneously passed it here.
 479	 */
 480	if (WARN_ON(IS_ERR_VALUE(npages)))
 481		return;
 482
 483	sanity_check_pinned_pages(pages, npages);
 484	for (i = 0; i < npages; i += nr) {
 485		folio = gup_folio_next(pages, npages, i, &nr);
 486		gup_put_folio(folio, nr, FOLL_PIN);
 487	}
 488}
 489EXPORT_SYMBOL(unpin_user_pages);
 490
 491/*
 492 * Set the MMF_HAS_PINNED if not set yet; after set it'll be there for the mm's
 493 * lifecycle.  Avoid setting the bit unless necessary, or it might cause write
 494 * cache bouncing on large SMP machines for concurrent pinned gups.
 495 */
 496static inline void mm_set_has_pinned_flag(unsigned long *mm_flags)
 497{
 498	if (!test_bit(MMF_HAS_PINNED, mm_flags))
 499		set_bit(MMF_HAS_PINNED, mm_flags);
 500}
 501
 502#ifdef CONFIG_MMU
 503static struct page *no_page_table(struct vm_area_struct *vma,
 504		unsigned int flags)
 505{
 506	/*
 507	 * When core dumping an enormous anonymous area that nobody
 508	 * has touched so far, we don't want to allocate unnecessary pages or
 509	 * page tables.  Return error instead of NULL to skip handle_mm_fault,
 510	 * then get_dump_page() will return NULL to leave a hole in the dump.
 511	 * But we can only make this optimization where a hole would surely
 512	 * be zero-filled if handle_mm_fault() actually did handle it.
 513	 */
 514	if ((flags & FOLL_DUMP) &&
 515			(vma_is_anonymous(vma) || !vma->vm_ops->fault))
 516		return ERR_PTR(-EFAULT);
 517	return NULL;
 518}
 519
 520static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
 521		pte_t *pte, unsigned int flags)
 522{
 
 
 
 
 523	if (flags & FOLL_TOUCH) {
 524		pte_t orig_entry = ptep_get(pte);
 525		pte_t entry = orig_entry;
 526
 527		if (flags & FOLL_WRITE)
 528			entry = pte_mkdirty(entry);
 529		entry = pte_mkyoung(entry);
 530
 531		if (!pte_same(orig_entry, entry)) {
 532			set_pte_at(vma->vm_mm, address, pte, entry);
 533			update_mmu_cache(vma, address, pte);
 534		}
 535	}
 536
 537	/* Proper page table entry exists, but no corresponding struct page */
 538	return -EEXIST;
 539}
 540
 541/* FOLL_FORCE can write to even unwritable PTEs in COW mappings. */
 542static inline bool can_follow_write_pte(pte_t pte, struct page *page,
 543					struct vm_area_struct *vma,
 544					unsigned int flags)
 545{
 546	/* If the pte is writable, we can write to the page. */
 547	if (pte_write(pte))
 548		return true;
 549
 550	/* Maybe FOLL_FORCE is set to override it? */
 551	if (!(flags & FOLL_FORCE))
 552		return false;
 553
 554	/* But FOLL_FORCE has no effect on shared mappings */
 555	if (vma->vm_flags & (VM_MAYSHARE | VM_SHARED))
 556		return false;
 557
 558	/* ... or read-only private ones */
 559	if (!(vma->vm_flags & VM_MAYWRITE))
 560		return false;
 561
 562	/* ... or already writable ones that just need to take a write fault */
 563	if (vma->vm_flags & VM_WRITE)
 564		return false;
 565
 566	/*
 567	 * See can_change_pte_writable(): we broke COW and could map the page
 568	 * writable if we have an exclusive anonymous page ...
 569	 */
 570	if (!page || !PageAnon(page) || !PageAnonExclusive(page))
 571		return false;
 572
 573	/* ... and a write-fault isn't required for other reasons. */
 574	if (vma_soft_dirty_enabled(vma) && !pte_soft_dirty(pte))
 575		return false;
 576	return !userfaultfd_pte_wp(vma, pte);
 577}
 578
 579static struct page *follow_page_pte(struct vm_area_struct *vma,
 580		unsigned long address, pmd_t *pmd, unsigned int flags,
 581		struct dev_pagemap **pgmap)
 582{
 583	struct mm_struct *mm = vma->vm_mm;
 
 584	struct page *page;
 585	spinlock_t *ptl;
 586	pte_t *ptep, pte;
 587	int ret;
 588
 589	/* FOLL_GET and FOLL_PIN are mutually exclusive. */
 590	if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
 591			 (FOLL_PIN | FOLL_GET)))
 592		return ERR_PTR(-EINVAL);
 593
 594	ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
 595	if (!ptep)
 596		return no_page_table(vma, flags);
 597	pte = ptep_get(ptep);
 598	if (!pte_present(pte))
 599		goto no_page;
 600	if (pte_protnone(pte) && !gup_can_follow_protnone(vma, flags))
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 601		goto no_page;
 
 
 
 
 602
 603	page = vm_normal_page(vma, address, pte);
 604
 605	/*
 606	 * We only care about anon pages in can_follow_write_pte() and don't
 607	 * have to worry about pte_devmap() because they are never anon.
 608	 */
 609	if ((flags & FOLL_WRITE) &&
 610	    !can_follow_write_pte(pte, page, vma, flags)) {
 611		page = NULL;
 612		goto out;
 613	}
 614
 615	if (!page && pte_devmap(pte) && (flags & (FOLL_GET | FOLL_PIN))) {
 616		/*
 617		 * Only return device mapping pages in the FOLL_GET or FOLL_PIN
 618		 * case since they are only valid while holding the pgmap
 619		 * reference.
 620		 */
 621		*pgmap = get_dev_pagemap(pte_pfn(pte), *pgmap);
 622		if (*pgmap)
 623			page = pte_page(pte);
 624		else
 625			goto no_page;
 626	} else if (unlikely(!page)) {
 627		if (flags & FOLL_DUMP) {
 628			/* Avoid special (like zero) pages in core dumps */
 629			page = ERR_PTR(-EFAULT);
 630			goto out;
 631		}
 632
 633		if (is_zero_pfn(pte_pfn(pte))) {
 634			page = pte_page(pte);
 635		} else {
 
 
 636			ret = follow_pfn_pte(vma, address, ptep, flags);
 637			page = ERR_PTR(ret);
 638			goto out;
 639		}
 640	}
 641
 642	if (!pte_write(pte) && gup_must_unshare(vma, flags, page)) {
 643		page = ERR_PTR(-EMLINK);
 644		goto out;
 
 
 
 
 
 
 
 
 645	}
 646
 647	VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) &&
 648		       !PageAnonExclusive(page), page);
 649
 650	/* try_grab_page() does nothing unless FOLL_GET or FOLL_PIN is set. */
 651	ret = try_grab_page(page, flags);
 652	if (unlikely(ret)) {
 653		page = ERR_PTR(ret);
 654		goto out;
 655	}
 656
 657	/*
 658	 * We need to make the page accessible if and only if we are going
 659	 * to access its content (the FOLL_PIN case).  Please see
 660	 * Documentation/core-api/pin_user_pages.rst for details.
 661	 */
 662	if (flags & FOLL_PIN) {
 663		ret = arch_make_page_accessible(page);
 664		if (ret) {
 665			unpin_user_page(page);
 666			page = ERR_PTR(ret);
 667			goto out;
 668		}
 669	}
 670	if (flags & FOLL_TOUCH) {
 671		if ((flags & FOLL_WRITE) &&
 672		    !pte_dirty(pte) && !PageDirty(page))
 673			set_page_dirty(page);
 674		/*
 675		 * pte_mkyoung() would be more correct here, but atomic care
 676		 * is needed to avoid losing the dirty bit: it is easier to use
 677		 * mark_page_accessed().
 678		 */
 679		mark_page_accessed(page);
 680	}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 681out:
 682	pte_unmap_unlock(ptep, ptl);
 683	return page;
 684no_page:
 685	pte_unmap_unlock(ptep, ptl);
 686	if (!pte_none(pte))
 687		return NULL;
 688	return no_page_table(vma, flags);
 689}
 690
 691static struct page *follow_pmd_mask(struct vm_area_struct *vma,
 692				    unsigned long address, pud_t *pudp,
 693				    unsigned int flags,
 694				    struct follow_page_context *ctx)
 695{
 696	pmd_t *pmd, pmdval;
 697	spinlock_t *ptl;
 698	struct page *page;
 699	struct mm_struct *mm = vma->vm_mm;
 700
 701	pmd = pmd_offset(pudp, address);
 702	pmdval = pmdp_get_lockless(pmd);
 703	if (pmd_none(pmdval))
 704		return no_page_table(vma, flags);
 705	if (!pmd_present(pmdval))
 706		return no_page_table(vma, flags);
 707	if (pmd_devmap(pmdval)) {
 708		ptl = pmd_lock(mm, pmd);
 709		page = follow_devmap_pmd(vma, address, pmd, flags, &ctx->pgmap);
 710		spin_unlock(ptl);
 711		if (page)
 712			return page;
 713		return no_page_table(vma, flags);
 714	}
 715	if (likely(!pmd_trans_huge(pmdval)))
 716		return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
 717
 718	if (pmd_protnone(pmdval) && !gup_can_follow_protnone(vma, flags))
 719		return no_page_table(vma, flags);
 720
 721	ptl = pmd_lock(mm, pmd);
 722	if (unlikely(!pmd_present(*pmd))) {
 723		spin_unlock(ptl);
 724		return no_page_table(vma, flags);
 725	}
 726	if (unlikely(!pmd_trans_huge(*pmd))) {
 727		spin_unlock(ptl);
 728		return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
 729	}
 730	if (flags & FOLL_SPLIT_PMD) {
 731		spin_unlock(ptl);
 732		split_huge_pmd(vma, pmd, address);
 733		/* If pmd was left empty, stuff a page table in there quickly */
 734		return pte_alloc(mm, pmd) ? ERR_PTR(-ENOMEM) :
 735			follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
 736	}
 737	page = follow_trans_huge_pmd(vma, address, pmd, flags);
 738	spin_unlock(ptl);
 739	ctx->page_mask = HPAGE_PMD_NR - 1;
 740	return page;
 741}
 742
 743static struct page *follow_pud_mask(struct vm_area_struct *vma,
 744				    unsigned long address, p4d_t *p4dp,
 745				    unsigned int flags,
 746				    struct follow_page_context *ctx)
 747{
 748	pud_t *pud;
 749	spinlock_t *ptl;
 750	struct page *page;
 751	struct mm_struct *mm = vma->vm_mm;
 752
 753	pud = pud_offset(p4dp, address);
 754	if (pud_none(*pud))
 755		return no_page_table(vma, flags);
 756	if (pud_devmap(*pud)) {
 757		ptl = pud_lock(mm, pud);
 758		page = follow_devmap_pud(vma, address, pud, flags, &ctx->pgmap);
 759		spin_unlock(ptl);
 760		if (page)
 761			return page;
 762		return no_page_table(vma, flags);
 763	}
 764	if (unlikely(pud_bad(*pud)))
 765		return no_page_table(vma, flags);
 766
 767	return follow_pmd_mask(vma, address, pud, flags, ctx);
 768}
 769
 770static struct page *follow_p4d_mask(struct vm_area_struct *vma,
 771				    unsigned long address, pgd_t *pgdp,
 772				    unsigned int flags,
 773				    struct follow_page_context *ctx)
 774{
 775	p4d_t *p4d;
 776
 777	p4d = p4d_offset(pgdp, address);
 778	if (p4d_none(*p4d))
 779		return no_page_table(vma, flags);
 780	BUILD_BUG_ON(p4d_huge(*p4d));
 781	if (unlikely(p4d_bad(*p4d)))
 782		return no_page_table(vma, flags);
 783
 784	return follow_pud_mask(vma, address, p4d, flags, ctx);
 785}
 786
 787/**
 788 * follow_page_mask - look up a page descriptor from a user-virtual address
 789 * @vma: vm_area_struct mapping @address
 790 * @address: virtual address to look up
 791 * @flags: flags modifying lookup behaviour
 792 * @ctx: contains dev_pagemap for %ZONE_DEVICE memory pinning and a
 793 *       pointer to output page_mask
 794 *
 795 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
 796 *
 797 * When getting pages from ZONE_DEVICE memory, the @ctx->pgmap caches
 798 * the device's dev_pagemap metadata to avoid repeating expensive lookups.
 799 *
 800 * When getting an anonymous page and the caller has to trigger unsharing
 801 * of a shared anonymous page first, -EMLINK is returned. The caller should
 802 * trigger a fault with FAULT_FLAG_UNSHARE set. Note that unsharing is only
 803 * relevant with FOLL_PIN and !FOLL_WRITE.
 804 *
 805 * On output, the @ctx->page_mask is set according to the size of the page.
 806 *
 807 * Return: the mapped (struct page *), %NULL if no mapping exists, or
 808 * an error pointer if there is a mapping to something not represented
 809 * by a page descriptor (see also vm_normal_page()).
 810 */
 811static struct page *follow_page_mask(struct vm_area_struct *vma,
 812			      unsigned long address, unsigned int flags,
 813			      struct follow_page_context *ctx)
 814{
 815	pgd_t *pgd;
 
 
 
 
 816	struct mm_struct *mm = vma->vm_mm;
 817
 818	ctx->page_mask = 0;
 819
 820	/*
 821	 * Call hugetlb_follow_page_mask for hugetlb vmas as it will use
 822	 * special hugetlb page table walking code.  This eliminates the
 823	 * need to check for hugetlb entries in the general walking code.
 824	 */
 825	if (is_vm_hugetlb_page(vma))
 826		return hugetlb_follow_page_mask(vma, address, flags,
 827						&ctx->page_mask);
 828
 829	pgd = pgd_offset(mm, address);
 830
 831	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
 832		return no_page_table(vma, flags);
 833
 834	return follow_p4d_mask(vma, address, pgd, flags, ctx);
 835}
 
 
 
 
 
 
 
 
 
 836
 837struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
 838			 unsigned int foll_flags)
 839{
 840	struct follow_page_context ctx = { NULL };
 841	struct page *page;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 842
 843	if (vma_is_secretmem(vma))
 844		return NULL;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 845
 846	if (WARN_ON_ONCE(foll_flags & FOLL_PIN))
 847		return NULL;
 
 848
 849	/*
 850	 * We never set FOLL_HONOR_NUMA_FAULT because callers don't expect
 851	 * to fail on PROT_NONE-mapped pages.
 852	 */
 853	page = follow_page_mask(vma, address, foll_flags, &ctx);
 854	if (ctx.pgmap)
 855		put_dev_pagemap(ctx.pgmap);
 856	return page;
 857}
 858
 859static int get_gate_page(struct mm_struct *mm, unsigned long address,
 860		unsigned int gup_flags, struct vm_area_struct **vma,
 861		struct page **page)
 862{
 863	pgd_t *pgd;
 864	p4d_t *p4d;
 865	pud_t *pud;
 866	pmd_t *pmd;
 867	pte_t *pte;
 868	pte_t entry;
 869	int ret = -EFAULT;
 870
 871	/* user gate pages are read-only */
 872	if (gup_flags & FOLL_WRITE)
 873		return -EFAULT;
 874	if (address > TASK_SIZE)
 875		pgd = pgd_offset_k(address);
 876	else
 877		pgd = pgd_offset_gate(mm, address);
 878	if (pgd_none(*pgd))
 879		return -EFAULT;
 880	p4d = p4d_offset(pgd, address);
 881	if (p4d_none(*p4d))
 882		return -EFAULT;
 883	pud = pud_offset(p4d, address);
 884	if (pud_none(*pud))
 885		return -EFAULT;
 886	pmd = pmd_offset(pud, address);
 887	if (!pmd_present(*pmd))
 888		return -EFAULT;
 
 889	pte = pte_offset_map(pmd, address);
 890	if (!pte)
 891		return -EFAULT;
 892	entry = ptep_get(pte);
 893	if (pte_none(entry))
 894		goto unmap;
 895	*vma = get_gate_vma(mm);
 896	if (!page)
 897		goto out;
 898	*page = vm_normal_page(*vma, address, entry);
 899	if (!*page) {
 900		if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(entry)))
 901			goto unmap;
 902		*page = pte_page(entry);
 903	}
 904	ret = try_grab_page(*page, gup_flags);
 905	if (unlikely(ret))
 906		goto unmap;
 907out:
 908	ret = 0;
 909unmap:
 910	pte_unmap(pte);
 911	return ret;
 912}
 913
 914/*
 915 * mmap_lock must be held on entry.  If @flags has FOLL_UNLOCKABLE but not
 916 * FOLL_NOWAIT, the mmap_lock may be released.  If it is, *@locked will be set
 917 * to 0 and -EBUSY returned.
 918 */
 919static int faultin_page(struct vm_area_struct *vma,
 920		unsigned long address, unsigned int *flags, bool unshare,
 921		int *locked)
 922{
 
 923	unsigned int fault_flags = 0;
 924	vm_fault_t ret;
 925
 926	if (*flags & FOLL_NOFAULT)
 927		return -EFAULT;
 
 
 
 
 
 
 928	if (*flags & FOLL_WRITE)
 929		fault_flags |= FAULT_FLAG_WRITE;
 930	if (*flags & FOLL_REMOTE)
 931		fault_flags |= FAULT_FLAG_REMOTE;
 932	if (*flags & FOLL_UNLOCKABLE) {
 933		fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 934		/*
 935		 * FAULT_FLAG_INTERRUPTIBLE is opt-in. GUP callers must set
 936		 * FOLL_INTERRUPTIBLE to enable FAULT_FLAG_INTERRUPTIBLE.
 937		 * That's because some callers may not be prepared to
 938		 * handle early exits caused by non-fatal signals.
 939		 */
 940		if (*flags & FOLL_INTERRUPTIBLE)
 941			fault_flags |= FAULT_FLAG_INTERRUPTIBLE;
 942	}
 943	if (*flags & FOLL_NOWAIT)
 944		fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
 945	if (*flags & FOLL_TRIED) {
 946		/*
 947		 * Note: FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_TRIED
 948		 * can co-exist
 949		 */
 950		fault_flags |= FAULT_FLAG_TRIED;
 951	}
 952	if (unshare) {
 953		fault_flags |= FAULT_FLAG_UNSHARE;
 954		/* FAULT_FLAG_WRITE and FAULT_FLAG_UNSHARE are incompatible */
 955		VM_BUG_ON(fault_flags & FAULT_FLAG_WRITE);
 956	}
 957
 958	ret = handle_mm_fault(vma, address, fault_flags, NULL);
 959
 960	if (ret & VM_FAULT_COMPLETED) {
 961		/*
 962		 * With FAULT_FLAG_RETRY_NOWAIT we'll never release the
 963		 * mmap lock in the page fault handler. Sanity check this.
 964		 */
 965		WARN_ON_ONCE(fault_flags & FAULT_FLAG_RETRY_NOWAIT);
 966		*locked = 0;
 967
 968		/*
 969		 * We should do the same as VM_FAULT_RETRY, but let's not
 970		 * return -EBUSY since that's not reflecting the reality of
 971		 * what has happened - we've just fully completed a page
 972		 * fault, with the mmap lock released.  Use -EAGAIN to show
 973		 * that we want to take the mmap lock _again_.
 974		 */
 975		return -EAGAIN;
 976	}
 977
 978	if (ret & VM_FAULT_ERROR) {
 979		int err = vm_fault_to_errno(ret, *flags);
 980
 981		if (err)
 982			return err;
 983		BUG();
 984	}
 985
 986	if (ret & VM_FAULT_RETRY) {
 987		if (!(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
 988			*locked = 0;
 989		return -EBUSY;
 990	}
 991
 992	return 0;
 993}
 994
 995/*
 996 * Writing to file-backed mappings which require folio dirty tracking using GUP
 997 * is a fundamentally broken operation, as kernel write access to GUP mappings
 998 * do not adhere to the semantics expected by a file system.
 999 *
1000 * Consider the following scenario:-
1001 *
1002 * 1. A folio is written to via GUP which write-faults the memory, notifying
1003 *    the file system and dirtying the folio.
1004 * 2. Later, writeback is triggered, resulting in the folio being cleaned and
1005 *    the PTE being marked read-only.
1006 * 3. The GUP caller writes to the folio, as it is mapped read/write via the
1007 *    direct mapping.
1008 * 4. The GUP caller, now done with the page, unpins it and sets it dirty
1009 *    (though it does not have to).
1010 *
1011 * This results in both data being written to a folio without writenotify, and
1012 * the folio being dirtied unexpectedly (if the caller decides to do so).
1013 */
1014static bool writable_file_mapping_allowed(struct vm_area_struct *vma,
1015					  unsigned long gup_flags)
1016{
1017	/*
1018	 * If we aren't pinning then no problematic write can occur. A long term
1019	 * pin is the most egregious case so this is the case we disallow.
 
 
 
 
 
1020	 */
1021	if ((gup_flags & (FOLL_PIN | FOLL_LONGTERM)) !=
1022	    (FOLL_PIN | FOLL_LONGTERM))
1023		return true;
1024
1025	/*
1026	 * If the VMA does not require dirty tracking then no problematic write
1027	 * can occur either.
1028	 */
1029	return !vma_needs_dirty_tracking(vma);
1030}
1031
1032static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
1033{
1034	vm_flags_t vm_flags = vma->vm_flags;
1035	int write = (gup_flags & FOLL_WRITE);
1036	int foreign = (gup_flags & FOLL_REMOTE);
1037	bool vma_anon = vma_is_anonymous(vma);
1038
1039	if (vm_flags & (VM_IO | VM_PFNMAP))
1040		return -EFAULT;
1041
1042	if ((gup_flags & FOLL_ANON) && !vma_anon)
1043		return -EFAULT;
1044
1045	if ((gup_flags & FOLL_LONGTERM) && vma_is_fsdax(vma))
1046		return -EOPNOTSUPP;
1047
1048	if (vma_is_secretmem(vma))
1049		return -EFAULT;
1050
1051	if (write) {
1052		if (!vma_anon &&
1053		    !writable_file_mapping_allowed(vma, gup_flags))
1054			return -EFAULT;
1055
1056		if (!(vm_flags & VM_WRITE) || (vm_flags & VM_SHADOW_STACK)) {
1057			if (!(gup_flags & FOLL_FORCE))
1058				return -EFAULT;
1059			/* hugetlb does not support FOLL_FORCE|FOLL_WRITE. */
1060			if (is_vm_hugetlb_page(vma))
1061				return -EFAULT;
1062			/*
1063			 * We used to let the write,force case do COW in a
1064			 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
1065			 * set a breakpoint in a read-only mapping of an
1066			 * executable, without corrupting the file (yet only
1067			 * when that file had been opened for writing!).
1068			 * Anon pages in shared mappings are surprising: now
1069			 * just reject it.
1070			 */
1071			if (!is_cow_mapping(vm_flags))
1072				return -EFAULT;
1073		}
1074	} else if (!(vm_flags & VM_READ)) {
1075		if (!(gup_flags & FOLL_FORCE))
1076			return -EFAULT;
1077		/*
1078		 * Is there actually any vma we can reach here which does not
1079		 * have VM_MAYREAD set?
1080		 */
1081		if (!(vm_flags & VM_MAYREAD))
1082			return -EFAULT;
1083	}
1084	/*
1085	 * gups are always data accesses, not instruction
1086	 * fetches, so execute=false here
1087	 */
1088	if (!arch_vma_access_permitted(vma, write, false, foreign))
1089		return -EFAULT;
1090	return 0;
1091}
1092
1093/*
1094 * This is "vma_lookup()", but with a warning if we would have
1095 * historically expanded the stack in the GUP code.
1096 */
1097static struct vm_area_struct *gup_vma_lookup(struct mm_struct *mm,
1098	 unsigned long addr)
1099{
1100#ifdef CONFIG_STACK_GROWSUP
1101	return vma_lookup(mm, addr);
1102#else
1103	static volatile unsigned long next_warn;
1104	struct vm_area_struct *vma;
1105	unsigned long now, next;
1106
1107	vma = find_vma(mm, addr);
1108	if (!vma || (addr >= vma->vm_start))
1109		return vma;
1110
1111	/* Only warn for half-way relevant accesses */
1112	if (!(vma->vm_flags & VM_GROWSDOWN))
1113		return NULL;
1114	if (vma->vm_start - addr > 65536)
1115		return NULL;
1116
1117	/* Let's not warn more than once an hour.. */
1118	now = jiffies; next = next_warn;
1119	if (next && time_before(now, next))
1120		return NULL;
1121	next_warn = now + 60*60*HZ;
1122
1123	/* Let people know things may have changed. */
1124	pr_warn("GUP no longer grows the stack in %s (%d): %lx-%lx (%lx)\n",
1125		current->comm, task_pid_nr(current),
1126		vma->vm_start, vma->vm_end, addr);
1127	dump_stack();
1128	return NULL;
1129#endif
1130}
1131
1132/**
1133 * __get_user_pages() - pin user pages in memory
 
1134 * @mm:		mm_struct of target mm
1135 * @start:	starting user address
1136 * @nr_pages:	number of pages from start to pin
1137 * @gup_flags:	flags modifying pin behaviour
1138 * @pages:	array that receives pointers to the pages pinned.
1139 *		Should be at least nr_pages long. Or NULL, if caller
1140 *		only intends to ensure the pages are faulted in.
1141 * @locked:     whether we're still with the mmap_lock held
1142 *
1143 * Returns either number of pages pinned (which may be less than the
1144 * number requested), or an error. Details about the return value:
 
 
 
 
 
1145 *
1146 * -- If nr_pages is 0, returns 0.
1147 * -- If nr_pages is >0, but no pages were pinned, returns -errno.
1148 * -- If nr_pages is >0, and some pages were pinned, returns the number of
1149 *    pages pinned. Again, this may be less than nr_pages.
1150 * -- 0 return value is possible when the fault would need to be retried.
1151 *
1152 * The caller is responsible for releasing returned @pages, via put_page().
1153 *
1154 * Must be called with mmap_lock held.  It may be released.  See below.
1155 *
1156 * __get_user_pages walks a process's page tables and takes a reference to
1157 * each struct page that each user address corresponds to at a given
1158 * instant. That is, it takes the page that would be accessed if a user
1159 * thread accesses the given user virtual address at that instant.
1160 *
1161 * This does not guarantee that the page exists in the user mappings when
1162 * __get_user_pages returns, and there may even be a completely different
1163 * page there in some cases (eg. if mmapped pagecache has been invalidated
1164 * and subsequently re-faulted). However it does guarantee that the page
1165 * won't be freed completely. And mostly callers simply care that the page
1166 * contains data that was valid *at some point in time*. Typically, an IO
1167 * or similar operation cannot guarantee anything stronger anyway because
1168 * locks can't be held over the syscall boundary.
1169 *
1170 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
1171 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
1172 * appropriate) must be called after the page is finished with, and
1173 * before put_page is called.
1174 *
1175 * If FOLL_UNLOCKABLE is set without FOLL_NOWAIT then the mmap_lock may
1176 * be released. If this happens *@locked will be set to 0 on return.
1177 *
1178 * A caller using such a combination of @gup_flags must therefore hold the
1179 * mmap_lock for reading only, and recognize when it's been released. Otherwise,
1180 * it must be held for either reading or writing and will not be released.
 
 
 
 
1181 *
1182 * In most cases, get_user_pages or get_user_pages_fast should be used
1183 * instead of __get_user_pages. __get_user_pages should be used only if
1184 * you need some special @gup_flags.
1185 */
1186static long __get_user_pages(struct mm_struct *mm,
1187		unsigned long start, unsigned long nr_pages,
1188		unsigned int gup_flags, struct page **pages,
1189		int *locked)
1190{
1191	long ret = 0, i = 0;
 
1192	struct vm_area_struct *vma = NULL;
1193	struct follow_page_context ctx = { NULL };
1194
1195	if (!nr_pages)
1196		return 0;
1197
1198	start = untagged_addr_remote(mm, start);
1199
1200	VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN)));
 
 
 
 
 
 
1201
1202	do {
1203		struct page *page;
1204		unsigned int foll_flags = gup_flags;
1205		unsigned int page_increm;
1206
1207		/* first iteration or cross vma bound */
1208		if (!vma || start >= vma->vm_end) {
1209			/*
1210			 * MADV_POPULATE_(READ|WRITE) wants to handle VMA
1211			 * lookups+error reporting differently.
1212			 */
1213			if (gup_flags & FOLL_MADV_POPULATE) {
1214				vma = vma_lookup(mm, start);
1215				if (!vma) {
1216					ret = -ENOMEM;
1217					goto out;
1218				}
1219				if (check_vma_flags(vma, gup_flags)) {
1220					ret = -EINVAL;
1221					goto out;
1222				}
1223				goto retry;
1224			}
1225			vma = gup_vma_lookup(mm, start);
1226			if (!vma && in_gate_area(mm, start)) {
 
1227				ret = get_gate_page(mm, start & PAGE_MASK,
1228						gup_flags, &vma,
1229						pages ? &page : NULL);
1230				if (ret)
1231					goto out;
1232				ctx.page_mask = 0;
1233				goto next_page;
1234			}
1235
1236			if (!vma) {
1237				ret = -EFAULT;
1238				goto out;
 
 
 
 
1239			}
1240			ret = check_vma_flags(vma, gup_flags);
1241			if (ret)
1242				goto out;
1243		}
1244retry:
1245		/*
1246		 * If we have a pending SIGKILL, don't keep faulting pages and
1247		 * potentially allocating memory.
1248		 */
1249		if (fatal_signal_pending(current)) {
1250			ret = -EINTR;
1251			goto out;
1252		}
1253		cond_resched();
1254
1255		page = follow_page_mask(vma, start, foll_flags, &ctx);
1256		if (!page || PTR_ERR(page) == -EMLINK) {
1257			ret = faultin_page(vma, start, &foll_flags,
1258					   PTR_ERR(page) == -EMLINK, locked);
1259			switch (ret) {
1260			case 0:
1261				goto retry;
1262			case -EBUSY:
1263			case -EAGAIN:
1264				ret = 0;
1265				fallthrough;
1266			case -EFAULT:
1267			case -ENOMEM:
1268			case -EHWPOISON:
1269				goto out;
 
 
 
 
1270			}
1271			BUG();
1272		} else if (PTR_ERR(page) == -EEXIST) {
1273			/*
1274			 * Proper page table entry exists, but no corresponding
1275			 * struct page. If the caller expects **pages to be
1276			 * filled in, bail out now, because that can't be done
1277			 * for this page.
1278			 */
1279			if (pages) {
1280				ret = PTR_ERR(page);
1281				goto out;
1282			}
1283		} else if (IS_ERR(page)) {
1284			ret = PTR_ERR(page);
1285			goto out;
 
 
 
 
 
1286		}
1287next_page:
1288		page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask);
 
 
 
 
1289		if (page_increm > nr_pages)
1290			page_increm = nr_pages;
1291
1292		if (pages) {
1293			struct page *subpage;
1294			unsigned int j;
1295
1296			/*
1297			 * This must be a large folio (and doesn't need to
1298			 * be the whole folio; it can be part of it), do
1299			 * the refcount work for all the subpages too.
1300			 *
1301			 * NOTE: here the page may not be the head page
1302			 * e.g. when start addr is not thp-size aligned.
1303			 * try_grab_folio() should have taken care of tail
1304			 * pages.
1305			 */
1306			if (page_increm > 1) {
1307				struct folio *folio;
1308
1309				/*
1310				 * Since we already hold refcount on the
1311				 * large folio, this should never fail.
1312				 */
1313				folio = try_grab_folio(page, page_increm - 1,
1314						       foll_flags);
1315				if (WARN_ON_ONCE(!folio)) {
1316					/*
1317					 * Release the 1st page ref if the
1318					 * folio is problematic, fail hard.
1319					 */
1320					gup_put_folio(page_folio(page), 1,
1321						      foll_flags);
1322					ret = -EFAULT;
1323					goto out;
1324				}
1325			}
1326
1327			for (j = 0; j < page_increm; j++) {
1328				subpage = nth_page(page, j);
1329				pages[i + j] = subpage;
1330				flush_anon_page(vma, subpage, start + j * PAGE_SIZE);
1331				flush_dcache_page(subpage);
1332			}
1333		}
1334
1335		i += page_increm;
1336		start += page_increm * PAGE_SIZE;
1337		nr_pages -= page_increm;
1338	} while (nr_pages);
1339out:
1340	if (ctx.pgmap)
1341		put_dev_pagemap(ctx.pgmap);
1342	return i ? i : ret;
1343}
 
1344
1345static bool vma_permits_fault(struct vm_area_struct *vma,
1346			      unsigned int fault_flags)
1347{
1348	bool write   = !!(fault_flags & FAULT_FLAG_WRITE);
1349	bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
1350	vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
1351
1352	if (!(vm_flags & vma->vm_flags))
1353		return false;
1354
1355	/*
1356	 * The architecture might have a hardware protection
1357	 * mechanism other than read/write that can deny access.
1358	 *
1359	 * gup always represents data access, not instruction
1360	 * fetches, so execute=false here:
1361	 */
1362	if (!arch_vma_access_permitted(vma, write, false, foreign))
1363		return false;
1364
1365	return true;
1366}
1367
1368/**
1369 * fixup_user_fault() - manually resolve a user page fault
 
 
1370 * @mm:		mm_struct of target mm
1371 * @address:	user address
1372 * @fault_flags:flags to pass down to handle_mm_fault()
1373 * @unlocked:	did we unlock the mmap_lock while retrying, maybe NULL if caller
1374 *		does not allow retry. If NULL, the caller must guarantee
1375 *		that fault_flags does not contain FAULT_FLAG_ALLOW_RETRY.
1376 *
1377 * This is meant to be called in the specific scenario where for locking reasons
1378 * we try to access user memory in atomic context (within a pagefault_disable()
1379 * section), this returns -EFAULT, and we want to resolve the user fault before
1380 * trying again.
1381 *
1382 * Typically this is meant to be used by the futex code.
1383 *
1384 * The main difference with get_user_pages() is that this function will
1385 * unconditionally call handle_mm_fault() which will in turn perform all the
1386 * necessary SW fixup of the dirty and young bits in the PTE, while
1387 * get_user_pages() only guarantees to update these in the struct page.
1388 *
1389 * This is important for some architectures where those bits also gate the
1390 * access permission to the page because they are maintained in software.  On
1391 * such architectures, gup() will not be enough to make a subsequent access
1392 * succeed.
1393 *
1394 * This function will not return with an unlocked mmap_lock. So it has not the
1395 * same semantics wrt the @mm->mmap_lock as does filemap_fault().
1396 */
1397int fixup_user_fault(struct mm_struct *mm,
1398		     unsigned long address, unsigned int fault_flags,
1399		     bool *unlocked)
1400{
1401	struct vm_area_struct *vma;
1402	vm_fault_t ret;
1403
1404	address = untagged_addr_remote(mm, address);
1405
1406	if (unlocked)
1407		fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
1408
1409retry:
1410	vma = gup_vma_lookup(mm, address);
1411	if (!vma)
1412		return -EFAULT;
1413
1414	if (!vma_permits_fault(vma, fault_flags))
1415		return -EFAULT;
1416
1417	if ((fault_flags & FAULT_FLAG_KILLABLE) &&
1418	    fatal_signal_pending(current))
1419		return -EINTR;
1420
1421	ret = handle_mm_fault(vma, address, fault_flags, NULL);
1422
1423	if (ret & VM_FAULT_COMPLETED) {
1424		/*
1425		 * NOTE: it's a pity that we need to retake the lock here
1426		 * to pair with the unlock() in the callers. Ideally we
1427		 * could tell the callers so they do not need to unlock.
1428		 */
1429		mmap_read_lock(mm);
1430		*unlocked = true;
1431		return 0;
1432	}
1433
1434	if (ret & VM_FAULT_ERROR) {
1435		int err = vm_fault_to_errno(ret, 0);
1436
1437		if (err)
1438			return err;
 
 
1439		BUG();
1440	}
1441
1442	if (ret & VM_FAULT_RETRY) {
1443		mmap_read_lock(mm);
1444		*unlocked = true;
1445		fault_flags |= FAULT_FLAG_TRIED;
1446		goto retry;
 
 
 
1447	}
1448
 
 
 
 
 
 
1449	return 0;
1450}
1451EXPORT_SYMBOL_GPL(fixup_user_fault);
1452
1453/*
1454 * GUP always responds to fatal signals.  When FOLL_INTERRUPTIBLE is
1455 * specified, it'll also respond to generic signals.  The caller of GUP
1456 * that has FOLL_INTERRUPTIBLE should take care of the GUP interruption.
1457 */
1458static bool gup_signal_pending(unsigned int flags)
1459{
1460	if (fatal_signal_pending(current))
1461		return true;
1462
1463	if (!(flags & FOLL_INTERRUPTIBLE))
1464		return false;
1465
1466	return signal_pending(current);
1467}
1468
1469/*
1470 * Locking: (*locked == 1) means that the mmap_lock has already been acquired by
1471 * the caller. This function may drop the mmap_lock. If it does so, then it will
1472 * set (*locked = 0).
1473 *
1474 * (*locked == 0) means that the caller expects this function to acquire and
1475 * drop the mmap_lock. Therefore, the value of *locked will still be zero when
1476 * the function returns, even though it may have changed temporarily during
1477 * function execution.
1478 *
1479 * Please note that this function, unlike __get_user_pages(), will not return 0
1480 * for nr_pages > 0, unless FOLL_NOWAIT is used.
1481 */
1482static __always_inline long __get_user_pages_locked(struct mm_struct *mm,
1483						unsigned long start,
1484						unsigned long nr_pages,
 
1485						struct page **pages,
1486						int *locked,
 
1487						unsigned int flags)
1488{
1489	long ret, pages_done;
1490	bool must_unlock = false;
1491
1492	if (!nr_pages)
1493		return 0;
1494
1495	/*
1496	 * The internal caller expects GUP to manage the lock internally and the
1497	 * lock must be released when this returns.
1498	 */
1499	if (!*locked) {
1500		if (mmap_read_lock_killable(mm))
1501			return -EAGAIN;
1502		must_unlock = true;
1503		*locked = 1;
1504	}
1505	else
1506		mmap_assert_locked(mm);
1507
1508	if (flags & FOLL_PIN)
1509		mm_set_has_pinned_flag(&mm->flags);
1510
1511	/*
1512	 * FOLL_PIN and FOLL_GET are mutually exclusive. Traditional behavior
1513	 * is to set FOLL_GET if the caller wants pages[] filled in (but has
1514	 * carelessly failed to specify FOLL_GET), so keep doing that, but only
1515	 * for FOLL_GET, not for the newer FOLL_PIN.
1516	 *
1517	 * FOLL_PIN always expects pages to be non-null, but no need to assert
1518	 * that here, as any failures will be obvious enough.
1519	 */
1520	if (pages && !(flags & FOLL_PIN))
1521		flags |= FOLL_GET;
 
 
 
 
1522
1523	pages_done = 0;
 
1524	for (;;) {
1525		ret = __get_user_pages(mm, start, nr_pages, flags, pages,
1526				       locked);
1527		if (!(flags & FOLL_UNLOCKABLE)) {
1528			/* VM_FAULT_RETRY couldn't trigger, bypass */
1529			pages_done = ret;
1530			break;
1531		}
1532
1533		/* VM_FAULT_RETRY or VM_FAULT_COMPLETED cannot return errors */
1534		if (!*locked) {
1535			BUG_ON(ret < 0);
1536			BUG_ON(ret >= nr_pages);
1537		}
1538
 
 
 
 
1539		if (ret > 0) {
1540			nr_pages -= ret;
1541			pages_done += ret;
1542			if (!nr_pages)
1543				break;
1544		}
1545		if (*locked) {
1546			/*
1547			 * VM_FAULT_RETRY didn't trigger or it was a
1548			 * FOLL_NOWAIT.
1549			 */
1550			if (!pages_done)
1551				pages_done = ret;
1552			break;
1553		}
1554		/*
1555		 * VM_FAULT_RETRY triggered, so seek to the faulting offset.
1556		 * For the prefault case (!pages) we only update counts.
1557		 */
1558		if (likely(pages))
1559			pages += ret;
1560		start += ret << PAGE_SHIFT;
1561
1562		/* The lock was temporarily dropped, so we must unlock later */
1563		must_unlock = true;
1564
1565retry:
1566		/*
1567		 * Repeat on the address that fired VM_FAULT_RETRY
1568		 * with both FAULT_FLAG_ALLOW_RETRY and
1569		 * FAULT_FLAG_TRIED.  Note that GUP can be interrupted
1570		 * by fatal signals of even common signals, depending on
1571		 * the caller's request. So we need to check it before we
1572		 * start trying again otherwise it can loop forever.
1573		 */
1574		if (gup_signal_pending(flags)) {
1575			if (!pages_done)
1576				pages_done = -EINTR;
1577			break;
1578		}
1579
1580		ret = mmap_read_lock_killable(mm);
1581		if (ret) {
1582			BUG_ON(ret > 0);
1583			if (!pages_done)
1584				pages_done = ret;
1585			break;
1586		}
1587
1588		*locked = 1;
1589		ret = __get_user_pages(mm, start, 1, flags | FOLL_TRIED,
1590				       pages, locked);
1591		if (!*locked) {
1592			/* Continue to retry until we succeeded */
1593			BUG_ON(ret != 0);
1594			goto retry;
1595		}
1596		if (ret != 1) {
1597			BUG_ON(ret > 1);
1598			if (!pages_done)
1599				pages_done = ret;
1600			break;
1601		}
1602		nr_pages--;
1603		pages_done++;
1604		if (!nr_pages)
1605			break;
1606		if (likely(pages))
1607			pages++;
1608		start += PAGE_SIZE;
1609	}
1610	if (must_unlock && *locked) {
1611		/*
1612		 * We either temporarily dropped the lock, or the caller
1613		 * requested that we both acquire and drop the lock. Either way,
1614		 * we must now unlock, and notify the caller of that state.
1615		 */
1616		mmap_read_unlock(mm);
1617		*locked = 0;
1618	}
 
 
1619
1620	/*
1621	 * Failing to pin anything implies something has gone wrong (except when
1622	 * FOLL_NOWAIT is specified).
1623	 */
1624	if (WARN_ON_ONCE(pages_done == 0 && !(flags & FOLL_NOWAIT)))
1625		return -EFAULT;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1626
1627	return pages_done;
 
 
 
 
 
 
 
 
 
 
 
 
1628}
 
1629
1630/**
1631 * populate_vma_page_range() -  populate a range of pages in the vma.
1632 * @vma:   target vma
1633 * @start: start address
1634 * @end:   end address
1635 * @locked: whether the mmap_lock is still held
1636 *
1637 * This takes care of mlocking the pages too if VM_LOCKED is set.
1638 *
1639 * Return either number of pages pinned in the vma, or a negative error
1640 * code on error.
1641 *
1642 * vma->vm_mm->mmap_lock must be held.
1643 *
1644 * If @locked is NULL, it may be held for read or write and will
1645 * be unperturbed.
1646 *
1647 * If @locked is non-NULL, it must held for read only and may be
1648 * released.  If it's released, *@locked will be set to 0.
1649 */
1650long populate_vma_page_range(struct vm_area_struct *vma,
1651		unsigned long start, unsigned long end, int *locked)
1652{
1653	struct mm_struct *mm = vma->vm_mm;
1654	unsigned long nr_pages = (end - start) / PAGE_SIZE;
1655	int local_locked = 1;
1656	int gup_flags;
1657	long ret;
1658
1659	VM_BUG_ON(!PAGE_ALIGNED(start));
1660	VM_BUG_ON(!PAGE_ALIGNED(end));
1661	VM_BUG_ON_VMA(start < vma->vm_start, vma);
1662	VM_BUG_ON_VMA(end   > vma->vm_end, vma);
1663	mmap_assert_locked(mm);
1664
1665	/*
1666	 * Rightly or wrongly, the VM_LOCKONFAULT case has never used
1667	 * faultin_page() to break COW, so it has no work to do here.
1668	 */
1669	if (vma->vm_flags & VM_LOCKONFAULT)
1670		return nr_pages;
1671
1672	/* ... similarly, we've never faulted in PROT_NONE pages */
1673	if (!vma_is_accessible(vma))
1674		return -EFAULT;
1675
1676	gup_flags = FOLL_TOUCH;
1677	/*
1678	 * We want to touch writable mappings with a write fault in order
1679	 * to break COW, except for shared mappings because these don't COW
1680	 * and we would not want to dirty them for nothing.
1681	 *
1682	 * Otherwise, do a read fault, and use FOLL_FORCE in case it's not
1683	 * readable (ie write-only or executable).
1684	 */
1685	if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
1686		gup_flags |= FOLL_WRITE;
1687	else
 
 
 
 
 
1688		gup_flags |= FOLL_FORCE;
1689
1690	if (locked)
1691		gup_flags |= FOLL_UNLOCKABLE;
1692
1693	/*
1694	 * We made sure addr is within a VMA, so the following will
1695	 * not result in a stack expansion that recurses back here.
1696	 */
1697	ret = __get_user_pages(mm, start, nr_pages, gup_flags,
1698			       NULL, locked ? locked : &local_locked);
1699	lru_add_drain();
1700	return ret;
1701}
1702
1703/*
1704 * faultin_page_range() - populate (prefault) page tables inside the
1705 *			  given range readable/writable
1706 *
1707 * This takes care of mlocking the pages, too, if VM_LOCKED is set.
1708 *
1709 * @mm: the mm to populate page tables in
1710 * @start: start address
1711 * @end: end address
1712 * @write: whether to prefault readable or writable
1713 * @locked: whether the mmap_lock is still held
1714 *
1715 * Returns either number of processed pages in the MM, or a negative error
1716 * code on error (see __get_user_pages()). Note that this function reports
1717 * errors related to VMAs, such as incompatible mappings, as expected by
1718 * MADV_POPULATE_(READ|WRITE).
1719 *
1720 * The range must be page-aligned.
1721 *
1722 * mm->mmap_lock must be held. If it's released, *@locked will be set to 0.
1723 */
1724long faultin_page_range(struct mm_struct *mm, unsigned long start,
1725			unsigned long end, bool write, int *locked)
1726{
1727	unsigned long nr_pages = (end - start) / PAGE_SIZE;
1728	int gup_flags;
1729	long ret;
1730
1731	VM_BUG_ON(!PAGE_ALIGNED(start));
1732	VM_BUG_ON(!PAGE_ALIGNED(end));
1733	mmap_assert_locked(mm);
1734
1735	/*
1736	 * FOLL_TOUCH: Mark page accessed and thereby young; will also mark
1737	 *	       the page dirty with FOLL_WRITE -- which doesn't make a
1738	 *	       difference with !FOLL_FORCE, because the page is writable
1739	 *	       in the page table.
1740	 * FOLL_HWPOISON: Return -EHWPOISON instead of -EFAULT when we hit
1741	 *		  a poisoned page.
1742	 * !FOLL_FORCE: Require proper access permissions.
1743	 */
1744	gup_flags = FOLL_TOUCH | FOLL_HWPOISON | FOLL_UNLOCKABLE |
1745		    FOLL_MADV_POPULATE;
1746	if (write)
1747		gup_flags |= FOLL_WRITE;
1748
1749	ret = __get_user_pages_locked(mm, start, nr_pages, NULL, locked,
1750				      gup_flags);
1751	lru_add_drain();
1752	return ret;
1753}
1754
1755/*
1756 * __mm_populate - populate and/or mlock pages within a range of address space.
1757 *
1758 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1759 * flags. VMAs must be already marked with the desired vm_flags, and
1760 * mmap_lock must not be held.
1761 */
1762int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
1763{
1764	struct mm_struct *mm = current->mm;
1765	unsigned long end, nstart, nend;
1766	struct vm_area_struct *vma = NULL;
1767	int locked = 0;
1768	long ret = 0;
1769
 
 
1770	end = start + len;
1771
1772	for (nstart = start; nstart < end; nstart = nend) {
1773		/*
1774		 * We want to fault in pages for [nstart; end) address range.
1775		 * Find first corresponding VMA.
1776		 */
1777		if (!locked) {
1778			locked = 1;
1779			mmap_read_lock(mm);
1780			vma = find_vma_intersection(mm, nstart, end);
1781		} else if (nstart >= vma->vm_end)
1782			vma = find_vma_intersection(mm, vma->vm_end, end);
1783
1784		if (!vma)
1785			break;
1786		/*
1787		 * Set [nstart; nend) to intersection of desired address
1788		 * range with the first VMA. Also, skip undesirable VMA types.
1789		 */
1790		nend = min(end, vma->vm_end);
1791		if (vma->vm_flags & (VM_IO | VM_PFNMAP))
1792			continue;
1793		if (nstart < vma->vm_start)
1794			nstart = vma->vm_start;
1795		/*
1796		 * Now fault in a range of pages. populate_vma_page_range()
1797		 * double checks the vma flags, so that it won't mlock pages
1798		 * if the vma was already munlocked.
1799		 */
1800		ret = populate_vma_page_range(vma, nstart, nend, &locked);
1801		if (ret < 0) {
1802			if (ignore_errors) {
1803				ret = 0;
1804				continue;	/* continue at next VMA */
1805			}
1806			break;
1807		}
1808		nend = nstart + ret * PAGE_SIZE;
1809		ret = 0;
1810	}
1811	if (locked)
1812		mmap_read_unlock(mm);
1813	return ret;	/* 0 or negative error code */
1814}
1815#else /* CONFIG_MMU */
1816static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start,
1817		unsigned long nr_pages, struct page **pages,
1818		int *locked, unsigned int foll_flags)
1819{
1820	struct vm_area_struct *vma;
1821	bool must_unlock = false;
1822	unsigned long vm_flags;
1823	long i;
1824
1825	if (!nr_pages)
1826		return 0;
1827
1828	/*
1829	 * The internal caller expects GUP to manage the lock internally and the
1830	 * lock must be released when this returns.
1831	 */
1832	if (!*locked) {
1833		if (mmap_read_lock_killable(mm))
1834			return -EAGAIN;
1835		must_unlock = true;
1836		*locked = 1;
1837	}
1838
1839	/* calculate required read or write permissions.
1840	 * If FOLL_FORCE is set, we only require the "MAY" flags.
1841	 */
1842	vm_flags  = (foll_flags & FOLL_WRITE) ?
1843			(VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
1844	vm_flags &= (foll_flags & FOLL_FORCE) ?
1845			(VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
1846
1847	for (i = 0; i < nr_pages; i++) {
1848		vma = find_vma(mm, start);
1849		if (!vma)
1850			break;
1851
1852		/* protect what we can, including chardevs */
1853		if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
1854		    !(vm_flags & vma->vm_flags))
1855			break;
1856
1857		if (pages) {
1858			pages[i] = virt_to_page((void *)start);
1859			if (pages[i])
1860				get_page(pages[i]);
1861		}
1862
1863		start = (start + PAGE_SIZE) & PAGE_MASK;
1864	}
1865
1866	if (must_unlock && *locked) {
1867		mmap_read_unlock(mm);
1868		*locked = 0;
1869	}
1870
1871	return i ? : -EFAULT;
1872}
1873#endif /* !CONFIG_MMU */
1874
1875/**
1876 * fault_in_writeable - fault in userspace address range for writing
1877 * @uaddr: start of address range
1878 * @size: size of address range
1879 *
1880 * Returns the number of bytes not faulted in (like copy_to_user() and
1881 * copy_from_user()).
1882 */
1883size_t fault_in_writeable(char __user *uaddr, size_t size)
1884{
1885	char __user *start = uaddr, *end;
1886
1887	if (unlikely(size == 0))
1888		return 0;
1889	if (!user_write_access_begin(uaddr, size))
1890		return size;
1891	if (!PAGE_ALIGNED(uaddr)) {
1892		unsafe_put_user(0, uaddr, out);
1893		uaddr = (char __user *)PAGE_ALIGN((unsigned long)uaddr);
1894	}
1895	end = (char __user *)PAGE_ALIGN((unsigned long)start + size);
1896	if (unlikely(end < start))
1897		end = NULL;
1898	while (uaddr != end) {
1899		unsafe_put_user(0, uaddr, out);
1900		uaddr += PAGE_SIZE;
1901	}
1902
1903out:
1904	user_write_access_end();
1905	if (size > uaddr - start)
1906		return size - (uaddr - start);
1907	return 0;
1908}
1909EXPORT_SYMBOL(fault_in_writeable);
1910
1911/**
1912 * fault_in_subpage_writeable - fault in an address range for writing
1913 * @uaddr: start of address range
1914 * @size: size of address range
1915 *
1916 * Fault in a user address range for writing while checking for permissions at
1917 * sub-page granularity (e.g. arm64 MTE). This function should be used when
1918 * the caller cannot guarantee forward progress of a copy_to_user() loop.
1919 *
1920 * Returns the number of bytes not faulted in (like copy_to_user() and
1921 * copy_from_user()).
1922 */
1923size_t fault_in_subpage_writeable(char __user *uaddr, size_t size)
1924{
1925	size_t faulted_in;
1926
1927	/*
1928	 * Attempt faulting in at page granularity first for page table
1929	 * permission checking. The arch-specific probe_subpage_writeable()
1930	 * functions may not check for this.
1931	 */
1932	faulted_in = size - fault_in_writeable(uaddr, size);
1933	if (faulted_in)
1934		faulted_in -= probe_subpage_writeable(uaddr, faulted_in);
1935
1936	return size - faulted_in;
1937}
1938EXPORT_SYMBOL(fault_in_subpage_writeable);
1939
1940/*
1941 * fault_in_safe_writeable - fault in an address range for writing
1942 * @uaddr: start of address range
1943 * @size: length of address range
1944 *
1945 * Faults in an address range for writing.  This is primarily useful when we
1946 * already know that some or all of the pages in the address range aren't in
1947 * memory.
1948 *
1949 * Unlike fault_in_writeable(), this function is non-destructive.
1950 *
1951 * Note that we don't pin or otherwise hold the pages referenced that we fault
1952 * in.  There's no guarantee that they'll stay in memory for any duration of
1953 * time.
1954 *
1955 * Returns the number of bytes not faulted in, like copy_to_user() and
1956 * copy_from_user().
1957 */
1958size_t fault_in_safe_writeable(const char __user *uaddr, size_t size)
1959{
1960	unsigned long start = (unsigned long)uaddr, end;
1961	struct mm_struct *mm = current->mm;
1962	bool unlocked = false;
1963
1964	if (unlikely(size == 0))
1965		return 0;
1966	end = PAGE_ALIGN(start + size);
1967	if (end < start)
1968		end = 0;
1969
1970	mmap_read_lock(mm);
1971	do {
1972		if (fixup_user_fault(mm, start, FAULT_FLAG_WRITE, &unlocked))
1973			break;
1974		start = (start + PAGE_SIZE) & PAGE_MASK;
1975	} while (start != end);
1976	mmap_read_unlock(mm);
1977
1978	if (size > (unsigned long)uaddr - start)
1979		return size - ((unsigned long)uaddr - start);
1980	return 0;
1981}
1982EXPORT_SYMBOL(fault_in_safe_writeable);
1983
1984/**
1985 * fault_in_readable - fault in userspace address range for reading
1986 * @uaddr: start of user address range
1987 * @size: size of user address range
1988 *
1989 * Returns the number of bytes not faulted in (like copy_to_user() and
1990 * copy_from_user()).
1991 */
1992size_t fault_in_readable(const char __user *uaddr, size_t size)
1993{
1994	const char __user *start = uaddr, *end;
1995	volatile char c;
1996
1997	if (unlikely(size == 0))
1998		return 0;
1999	if (!user_read_access_begin(uaddr, size))
2000		return size;
2001	if (!PAGE_ALIGNED(uaddr)) {
2002		unsafe_get_user(c, uaddr, out);
2003		uaddr = (const char __user *)PAGE_ALIGN((unsigned long)uaddr);
2004	}
2005	end = (const char __user *)PAGE_ALIGN((unsigned long)start + size);
2006	if (unlikely(end < start))
2007		end = NULL;
2008	while (uaddr != end) {
2009		unsafe_get_user(c, uaddr, out);
2010		uaddr += PAGE_SIZE;
2011	}
2012
2013out:
2014	user_read_access_end();
2015	(void)c;
2016	if (size > uaddr - start)
2017		return size - (uaddr - start);
2018	return 0;
2019}
2020EXPORT_SYMBOL(fault_in_readable);
2021
2022/**
2023 * get_dump_page() - pin user page in memory while writing it to core dump
2024 * @addr: user address
2025 *
2026 * Returns struct page pointer of user page pinned for dump,
2027 * to be freed afterwards by put_page().
2028 *
2029 * Returns NULL on any kind of failure - a hole must then be inserted into
2030 * the corefile, to preserve alignment with its headers; and also returns
2031 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
2032 * allowing a hole to be left in the corefile to save disk space.
2033 *
2034 * Called without mmap_lock (takes and releases the mmap_lock by itself).
2035 */
2036#ifdef CONFIG_ELF_CORE
2037struct page *get_dump_page(unsigned long addr)
2038{
 
2039	struct page *page;
2040	int locked = 0;
2041	int ret;
2042
2043	ret = __get_user_pages_locked(current->mm, addr, 1, &page, &locked,
2044				      FOLL_FORCE | FOLL_DUMP | FOLL_GET);
2045	return (ret == 1) ? page : NULL;
 
 
 
2046}
2047#endif /* CONFIG_ELF_CORE */
2048
2049#ifdef CONFIG_MIGRATION
2050/*
2051 * Returns the number of collected pages. Return value is always >= 0.
2052 */
2053static unsigned long collect_longterm_unpinnable_pages(
2054					struct list_head *movable_page_list,
2055					unsigned long nr_pages,
2056					struct page **pages)
2057{
2058	unsigned long i, collected = 0;
2059	struct folio *prev_folio = NULL;
2060	bool drain_allow = true;
2061
2062	for (i = 0; i < nr_pages; i++) {
2063		struct folio *folio = page_folio(pages[i]);
2064
2065		if (folio == prev_folio)
2066			continue;
2067		prev_folio = folio;
2068
2069		if (folio_is_longterm_pinnable(folio))
2070			continue;
2071
2072		collected++;
2073
2074		if (folio_is_device_coherent(folio))
2075			continue;
2076
2077		if (folio_test_hugetlb(folio)) {
2078			isolate_hugetlb(folio, movable_page_list);
2079			continue;
2080		}
2081
2082		if (!folio_test_lru(folio) && drain_allow) {
2083			lru_add_drain_all();
2084			drain_allow = false;
2085		}
2086
2087		if (!folio_isolate_lru(folio))
2088			continue;
2089
2090		list_add_tail(&folio->lru, movable_page_list);
2091		node_stat_mod_folio(folio,
2092				    NR_ISOLATED_ANON + folio_is_file_lru(folio),
2093				    folio_nr_pages(folio));
2094	}
2095
2096	return collected;
2097}
2098
2099/*
2100 * Unpins all pages and migrates device coherent pages and movable_page_list.
2101 * Returns -EAGAIN if all pages were successfully migrated or -errno for failure
2102 * (or partial success).
2103 */
2104static int migrate_longterm_unpinnable_pages(
2105					struct list_head *movable_page_list,
2106					unsigned long nr_pages,
2107					struct page **pages)
2108{
2109	int ret;
2110	unsigned long i;
2111
2112	for (i = 0; i < nr_pages; i++) {
2113		struct folio *folio = page_folio(pages[i]);
2114
2115		if (folio_is_device_coherent(folio)) {
2116			/*
2117			 * Migration will fail if the page is pinned, so convert
2118			 * the pin on the source page to a normal reference.
2119			 */
2120			pages[i] = NULL;
2121			folio_get(folio);
2122			gup_put_folio(folio, 1, FOLL_PIN);
2123
2124			if (migrate_device_coherent_page(&folio->page)) {
2125				ret = -EBUSY;
2126				goto err;
2127			}
2128
2129			continue;
2130		}
2131
2132		/*
2133		 * We can't migrate pages with unexpected references, so drop
2134		 * the reference obtained by __get_user_pages_locked().
2135		 * Migrating pages have been added to movable_page_list after
2136		 * calling folio_isolate_lru() which takes a reference so the
2137		 * page won't be freed if it's migrating.
2138		 */
2139		unpin_user_page(pages[i]);
2140		pages[i] = NULL;
2141	}
2142
2143	if (!list_empty(movable_page_list)) {
2144		struct migration_target_control mtc = {
2145			.nid = NUMA_NO_NODE,
2146			.gfp_mask = GFP_USER | __GFP_NOWARN,
2147		};
2148
2149		if (migrate_pages(movable_page_list, alloc_migration_target,
2150				  NULL, (unsigned long)&mtc, MIGRATE_SYNC,
2151				  MR_LONGTERM_PIN, NULL)) {
2152			ret = -ENOMEM;
2153			goto err;
2154		}
2155	}
2156
2157	putback_movable_pages(movable_page_list);
2158
2159	return -EAGAIN;
2160
2161err:
2162	for (i = 0; i < nr_pages; i++)
2163		if (pages[i])
2164			unpin_user_page(pages[i]);
2165	putback_movable_pages(movable_page_list);
2166
2167	return ret;
2168}
2169
2170/*
2171 * Check whether all pages are *allowed* to be pinned. Rather confusingly, all
2172 * pages in the range are required to be pinned via FOLL_PIN, before calling
2173 * this routine.
2174 *
2175 * If any pages in the range are not allowed to be pinned, then this routine
2176 * will migrate those pages away, unpin all the pages in the range and return
2177 * -EAGAIN. The caller should re-pin the entire range with FOLL_PIN and then
2178 * call this routine again.
2179 *
2180 * If an error other than -EAGAIN occurs, this indicates a migration failure.
2181 * The caller should give up, and propagate the error back up the call stack.
2182 *
2183 * If everything is OK and all pages in the range are allowed to be pinned, then
2184 * this routine leaves all pages pinned and returns zero for success.
2185 */
2186static long check_and_migrate_movable_pages(unsigned long nr_pages,
2187					    struct page **pages)
2188{
2189	unsigned long collected;
2190	LIST_HEAD(movable_page_list);
2191
2192	collected = collect_longterm_unpinnable_pages(&movable_page_list,
2193						nr_pages, pages);
2194	if (!collected)
2195		return 0;
2196
2197	return migrate_longterm_unpinnable_pages(&movable_page_list, nr_pages,
2198						pages);
2199}
2200#else
2201static long check_and_migrate_movable_pages(unsigned long nr_pages,
2202					    struct page **pages)
2203{
2204	return 0;
2205}
2206#endif /* CONFIG_MIGRATION */
2207
2208/*
2209 * __gup_longterm_locked() is a wrapper for __get_user_pages_locked which
2210 * allows us to process the FOLL_LONGTERM flag.
2211 */
2212static long __gup_longterm_locked(struct mm_struct *mm,
2213				  unsigned long start,
2214				  unsigned long nr_pages,
2215				  struct page **pages,
2216				  int *locked,
2217				  unsigned int gup_flags)
2218{
2219	unsigned int flags;
2220	long rc, nr_pinned_pages;
2221
2222	if (!(gup_flags & FOLL_LONGTERM))
2223		return __get_user_pages_locked(mm, start, nr_pages, pages,
2224					       locked, gup_flags);
2225
2226	flags = memalloc_pin_save();
2227	do {
2228		nr_pinned_pages = __get_user_pages_locked(mm, start, nr_pages,
2229							  pages, locked,
2230							  gup_flags);
2231		if (nr_pinned_pages <= 0) {
2232			rc = nr_pinned_pages;
2233			break;
2234		}
2235
2236		/* FOLL_LONGTERM implies FOLL_PIN */
2237		rc = check_and_migrate_movable_pages(nr_pinned_pages, pages);
2238	} while (rc == -EAGAIN);
2239	memalloc_pin_restore(flags);
2240	return rc ? rc : nr_pinned_pages;
2241}
2242
2243/*
2244 * Check that the given flags are valid for the exported gup/pup interface, and
2245 * update them with the required flags that the caller must have set.
2246 */
2247static bool is_valid_gup_args(struct page **pages, int *locked,
2248			      unsigned int *gup_flags_p, unsigned int to_set)
2249{
2250	unsigned int gup_flags = *gup_flags_p;
2251
2252	/*
2253	 * These flags not allowed to be specified externally to the gup
2254	 * interfaces:
2255	 * - FOLL_TOUCH/FOLL_PIN/FOLL_TRIED/FOLL_FAST_ONLY are internal only
2256	 * - FOLL_REMOTE is internal only and used on follow_page()
2257	 * - FOLL_UNLOCKABLE is internal only and used if locked is !NULL
2258	 */
2259	if (WARN_ON_ONCE(gup_flags & INTERNAL_GUP_FLAGS))
2260		return false;
2261
2262	gup_flags |= to_set;
2263	if (locked) {
2264		/* At the external interface locked must be set */
2265		if (WARN_ON_ONCE(*locked != 1))
2266			return false;
2267
2268		gup_flags |= FOLL_UNLOCKABLE;
2269	}
2270
2271	/* FOLL_GET and FOLL_PIN are mutually exclusive. */
2272	if (WARN_ON_ONCE((gup_flags & (FOLL_PIN | FOLL_GET)) ==
2273			 (FOLL_PIN | FOLL_GET)))
2274		return false;
2275
2276	/* LONGTERM can only be specified when pinning */
2277	if (WARN_ON_ONCE(!(gup_flags & FOLL_PIN) && (gup_flags & FOLL_LONGTERM)))
2278		return false;
2279
2280	/* Pages input must be given if using GET/PIN */
2281	if (WARN_ON_ONCE((gup_flags & (FOLL_GET | FOLL_PIN)) && !pages))
2282		return false;
2283
2284	/* We want to allow the pgmap to be hot-unplugged at all times */
2285	if (WARN_ON_ONCE((gup_flags & FOLL_LONGTERM) &&
2286			 (gup_flags & FOLL_PCI_P2PDMA)))
2287		return false;
2288
2289	*gup_flags_p = gup_flags;
2290	return true;
2291}
2292
2293#ifdef CONFIG_MMU
2294/**
2295 * get_user_pages_remote() - pin user pages in memory
2296 * @mm:		mm_struct of target mm
2297 * @start:	starting user address
2298 * @nr_pages:	number of pages from start to pin
2299 * @gup_flags:	flags modifying lookup behaviour
2300 * @pages:	array that receives pointers to the pages pinned.
2301 *		Should be at least nr_pages long. Or NULL, if caller
2302 *		only intends to ensure the pages are faulted in.
2303 * @locked:	pointer to lock flag indicating whether lock is held and
2304 *		subsequently whether VM_FAULT_RETRY functionality can be
2305 *		utilised. Lock must initially be held.
2306 *
2307 * Returns either number of pages pinned (which may be less than the
2308 * number requested), or an error. Details about the return value:
2309 *
2310 * -- If nr_pages is 0, returns 0.
2311 * -- If nr_pages is >0, but no pages were pinned, returns -errno.
2312 * -- If nr_pages is >0, and some pages were pinned, returns the number of
2313 *    pages pinned. Again, this may be less than nr_pages.
2314 *
2315 * The caller is responsible for releasing returned @pages, via put_page().
2316 *
2317 * Must be called with mmap_lock held for read or write.
2318 *
2319 * get_user_pages_remote walks a process's page tables and takes a reference
2320 * to each struct page that each user address corresponds to at a given
2321 * instant. That is, it takes the page that would be accessed if a user
2322 * thread accesses the given user virtual address at that instant.
2323 *
2324 * This does not guarantee that the page exists in the user mappings when
2325 * get_user_pages_remote returns, and there may even be a completely different
2326 * page there in some cases (eg. if mmapped pagecache has been invalidated
2327 * and subsequently re-faulted). However it does guarantee that the page
2328 * won't be freed completely. And mostly callers simply care that the page
2329 * contains data that was valid *at some point in time*. Typically, an IO
2330 * or similar operation cannot guarantee anything stronger anyway because
2331 * locks can't be held over the syscall boundary.
2332 *
2333 * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
2334 * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
2335 * be called after the page is finished with, and before put_page is called.
2336 *
2337 * get_user_pages_remote is typically used for fewer-copy IO operations,
2338 * to get a handle on the memory by some means other than accesses
2339 * via the user virtual addresses. The pages may be submitted for
2340 * DMA to devices or accessed via their kernel linear mapping (via the
2341 * kmap APIs). Care should be taken to use the correct cache flushing APIs.
2342 *
2343 * See also get_user_pages_fast, for performance critical applications.
2344 *
2345 * get_user_pages_remote should be phased out in favor of
2346 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
2347 * should use get_user_pages_remote because it cannot pass
2348 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
2349 */
2350long get_user_pages_remote(struct mm_struct *mm,
2351		unsigned long start, unsigned long nr_pages,
2352		unsigned int gup_flags, struct page **pages,
2353		int *locked)
2354{
2355	int local_locked = 1;
2356
2357	if (!is_valid_gup_args(pages, locked, &gup_flags,
2358			       FOLL_TOUCH | FOLL_REMOTE))
2359		return -EINVAL;
2360
2361	return __get_user_pages_locked(mm, start, nr_pages, pages,
2362				       locked ? locked : &local_locked,
2363				       gup_flags);
2364}
2365EXPORT_SYMBOL(get_user_pages_remote);
2366
2367#else /* CONFIG_MMU */
2368long get_user_pages_remote(struct mm_struct *mm,
2369			   unsigned long start, unsigned long nr_pages,
2370			   unsigned int gup_flags, struct page **pages,
2371			   int *locked)
2372{
2373	return 0;
2374}
2375#endif /* !CONFIG_MMU */
2376
2377/**
2378 * get_user_pages() - pin user pages in memory
2379 * @start:      starting user address
2380 * @nr_pages:   number of pages from start to pin
2381 * @gup_flags:  flags modifying lookup behaviour
2382 * @pages:      array that receives pointers to the pages pinned.
2383 *              Should be at least nr_pages long. Or NULL, if caller
2384 *              only intends to ensure the pages are faulted in.
2385 *
2386 * This is the same as get_user_pages_remote(), just with a less-flexible
2387 * calling convention where we assume that the mm being operated on belongs to
2388 * the current task, and doesn't allow passing of a locked parameter.  We also
2389 * obviously don't pass FOLL_REMOTE in here.
2390 */
2391long get_user_pages(unsigned long start, unsigned long nr_pages,
2392		    unsigned int gup_flags, struct page **pages)
2393{
2394	int locked = 1;
2395
2396	if (!is_valid_gup_args(pages, NULL, &gup_flags, FOLL_TOUCH))
2397		return -EINVAL;
2398
2399	return __get_user_pages_locked(current->mm, start, nr_pages, pages,
2400				       &locked, gup_flags);
2401}
2402EXPORT_SYMBOL(get_user_pages);
2403
2404/*
2405 * get_user_pages_unlocked() is suitable to replace the form:
2406 *
2407 *      mmap_read_lock(mm);
2408 *      get_user_pages(mm, ..., pages, NULL);
2409 *      mmap_read_unlock(mm);
2410 *
2411 *  with:
2412 *
2413 *      get_user_pages_unlocked(mm, ..., pages);
2414 *
2415 * It is functionally equivalent to get_user_pages_fast so
2416 * get_user_pages_fast should be used instead if specific gup_flags
2417 * (e.g. FOLL_FORCE) are not required.
2418 */
2419long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
2420			     struct page **pages, unsigned int gup_flags)
2421{
2422	int locked = 0;
2423
2424	if (!is_valid_gup_args(pages, NULL, &gup_flags,
2425			       FOLL_TOUCH | FOLL_UNLOCKABLE))
2426		return -EINVAL;
2427
2428	return __get_user_pages_locked(current->mm, start, nr_pages, pages,
2429				       &locked, gup_flags);
2430}
2431EXPORT_SYMBOL(get_user_pages_unlocked);
2432
2433/*
2434 * Fast GUP
2435 *
2436 * get_user_pages_fast attempts to pin user pages by walking the page
2437 * tables directly and avoids taking locks. Thus the walker needs to be
2438 * protected from page table pages being freed from under it, and should
2439 * block any THP splits.
2440 *
2441 * One way to achieve this is to have the walker disable interrupts, and
2442 * rely on IPIs from the TLB flushing code blocking before the page table
2443 * pages are freed. This is unsuitable for architectures that do not need
2444 * to broadcast an IPI when invalidating TLBs.
2445 *
2446 * Another way to achieve this is to batch up page table containing pages
2447 * belonging to more than one mm_user, then rcu_sched a callback to free those
2448 * pages. Disabling interrupts will allow the fast_gup walker to both block
2449 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
2450 * (which is a relatively rare event). The code below adopts this strategy.
2451 *
2452 * Before activating this code, please be aware that the following assumptions
2453 * are currently made:
2454 *
2455 *  *) Either MMU_GATHER_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to
2456 *  free pages containing page tables or TLB flushing requires IPI broadcast.
2457 *
2458 *  *) ptes can be read atomically by the architecture.
2459 *
2460 *  *) access_ok is sufficient to validate userspace address ranges.
2461 *
2462 * The last two assumptions can be relaxed by the addition of helper functions.
2463 *
2464 * This code is based heavily on the PowerPC implementation by Nick Piggin.
2465 */
2466#ifdef CONFIG_HAVE_FAST_GUP
2467
2468/*
2469 * Used in the GUP-fast path to determine whether a pin is permitted for a
2470 * specific folio.
2471 *
2472 * This call assumes the caller has pinned the folio, that the lowest page table
2473 * level still points to this folio, and that interrupts have been disabled.
2474 *
2475 * Writing to pinned file-backed dirty tracked folios is inherently problematic
2476 * (see comment describing the writable_file_mapping_allowed() function). We
2477 * therefore try to avoid the most egregious case of a long-term mapping doing
2478 * so.
2479 *
2480 * This function cannot be as thorough as that one as the VMA is not available
2481 * in the fast path, so instead we whitelist known good cases and if in doubt,
2482 * fall back to the slow path.
2483 */
2484static bool folio_fast_pin_allowed(struct folio *folio, unsigned int flags)
2485{
2486	struct address_space *mapping;
2487	unsigned long mapping_flags;
2488
2489	/*
2490	 * If we aren't pinning then no problematic write can occur. A long term
2491	 * pin is the most egregious case so this is the one we disallow.
2492	 */
2493	if ((flags & (FOLL_PIN | FOLL_LONGTERM | FOLL_WRITE)) !=
2494	    (FOLL_PIN | FOLL_LONGTERM | FOLL_WRITE))
2495		return true;
2496
2497	/* The folio is pinned, so we can safely access folio fields. */
2498
2499	if (WARN_ON_ONCE(folio_test_slab(folio)))
2500		return false;
2501
2502	/* hugetlb mappings do not require dirty-tracking. */
2503	if (folio_test_hugetlb(folio))
2504		return true;
2505
2506	/*
2507	 * GUP-fast disables IRQs. When IRQS are disabled, RCU grace periods
2508	 * cannot proceed, which means no actions performed under RCU can
2509	 * proceed either.
2510	 *
2511	 * inodes and thus their mappings are freed under RCU, which means the
2512	 * mapping cannot be freed beneath us and thus we can safely dereference
2513	 * it.
2514	 */
2515	lockdep_assert_irqs_disabled();
2516
2517	/*
2518	 * However, there may be operations which _alter_ the mapping, so ensure
2519	 * we read it once and only once.
2520	 */
2521	mapping = READ_ONCE(folio->mapping);
2522
2523	/*
2524	 * The mapping may have been truncated, in any case we cannot determine
2525	 * if this mapping is safe - fall back to slow path to determine how to
2526	 * proceed.
2527	 */
2528	if (!mapping)
2529		return false;
2530
2531	/* Anonymous folios pose no problem. */
2532	mapping_flags = (unsigned long)mapping & PAGE_MAPPING_FLAGS;
2533	if (mapping_flags)
2534		return mapping_flags & PAGE_MAPPING_ANON;
2535
2536	/*
2537	 * At this point, we know the mapping is non-null and points to an
2538	 * address_space object. The only remaining whitelisted file system is
2539	 * shmem.
2540	 */
2541	return shmem_mapping(mapping);
2542}
2543
2544static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start,
2545					    unsigned int flags,
2546					    struct page **pages)
2547{
2548	while ((*nr) - nr_start) {
2549		struct page *page = pages[--(*nr)];
2550
2551		ClearPageReferenced(page);
2552		if (flags & FOLL_PIN)
2553			unpin_user_page(page);
2554		else
2555			put_page(page);
2556	}
2557}
2558
2559#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
2560/*
2561 * Fast-gup relies on pte change detection to avoid concurrent pgtable
2562 * operations.
2563 *
2564 * To pin the page, fast-gup needs to do below in order:
2565 * (1) pin the page (by prefetching pte), then (2) check pte not changed.
2566 *
2567 * For the rest of pgtable operations where pgtable updates can be racy
2568 * with fast-gup, we need to do (1) clear pte, then (2) check whether page
2569 * is pinned.
2570 *
2571 * Above will work for all pte-level operations, including THP split.
2572 *
2573 * For THP collapse, it's a bit more complicated because fast-gup may be
2574 * walking a pgtable page that is being freed (pte is still valid but pmd
2575 * can be cleared already).  To avoid race in such condition, we need to
2576 * also check pmd here to make sure pmd doesn't change (corresponds to
2577 * pmdp_collapse_flush() in the THP collapse code path).
2578 */
2579static int gup_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
2580			 unsigned long end, unsigned int flags,
2581			 struct page **pages, int *nr)
2582{
2583	struct dev_pagemap *pgmap = NULL;
2584	int nr_start = *nr, ret = 0;
2585	pte_t *ptep, *ptem;
 
2586
2587	ptem = ptep = pte_offset_map(&pmd, addr);
2588	if (!ptep)
2589		return 0;
2590	do {
2591		pte_t pte = ptep_get_lockless(ptep);
2592		struct page *page;
2593		struct folio *folio;
 
 
 
 
 
 
2594
2595		/*
2596		 * Always fallback to ordinary GUP on PROT_NONE-mapped pages:
2597		 * pte_access_permitted() better should reject these pages
2598		 * either way: otherwise, GUP-fast might succeed in
2599		 * cases where ordinary GUP would fail due to VMA access
2600		 * permissions.
2601		 */
2602		if (pte_protnone(pte))
 
2603			goto pte_unmap;
2604
2605		if (!pte_access_permitted(pte, flags & FOLL_WRITE))
2606			goto pte_unmap;
2607
2608		if (pte_devmap(pte)) {
2609			if (unlikely(flags & FOLL_LONGTERM))
2610				goto pte_unmap;
2611
2612			pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
2613			if (unlikely(!pgmap)) {
2614				undo_dev_pagemap(nr, nr_start, flags, pages);
2615				goto pte_unmap;
2616			}
2617		} else if (pte_special(pte))
2618			goto pte_unmap;
2619
2620		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
2621		page = pte_page(pte);
 
2622
2623		folio = try_grab_folio(page, 1, flags);
2624		if (!folio)
2625			goto pte_unmap;
2626
2627		if (unlikely(folio_is_secretmem(folio))) {
2628			gup_put_folio(folio, 1, flags);
2629			goto pte_unmap;
2630		}
2631
2632		if (unlikely(pmd_val(pmd) != pmd_val(*pmdp)) ||
2633		    unlikely(pte_val(pte) != pte_val(ptep_get(ptep)))) {
2634			gup_put_folio(folio, 1, flags);
2635			goto pte_unmap;
2636		}
2637
2638		if (!folio_fast_pin_allowed(folio, flags)) {
2639			gup_put_folio(folio, 1, flags);
2640			goto pte_unmap;
2641		}
2642
2643		if (!pte_write(pte) && gup_must_unshare(NULL, flags, page)) {
2644			gup_put_folio(folio, 1, flags);
2645			goto pte_unmap;
2646		}
2647
2648		/*
2649		 * We need to make the page accessible if and only if we are
2650		 * going to access its content (the FOLL_PIN case).  Please
2651		 * see Documentation/core-api/pin_user_pages.rst for
2652		 * details.
2653		 */
2654		if (flags & FOLL_PIN) {
2655			ret = arch_make_page_accessible(page);
2656			if (ret) {
2657				gup_put_folio(folio, 1, flags);
2658				goto pte_unmap;
2659			}
2660		}
2661		folio_set_referenced(folio);
2662		pages[*nr] = page;
2663		(*nr)++;
 
2664	} while (ptep++, addr += PAGE_SIZE, addr != end);
2665
2666	ret = 1;
2667
2668pte_unmap:
2669	if (pgmap)
2670		put_dev_pagemap(pgmap);
2671	pte_unmap(ptem);
2672	return ret;
2673}
2674#else
2675
2676/*
2677 * If we can't determine whether or not a pte is special, then fail immediately
2678 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
2679 * to be special.
2680 *
2681 * For a futex to be placed on a THP tail page, get_futex_key requires a
2682 * get_user_pages_fast_only implementation that can pin pages. Thus it's still
2683 * useful to have gup_huge_pmd even if we can't operate on ptes.
2684 */
2685static int gup_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
2686			 unsigned long end, unsigned int flags,
2687			 struct page **pages, int *nr)
2688{
2689	return 0;
2690}
2691#endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
2692
2693#if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
2694static int __gup_device_huge(unsigned long pfn, unsigned long addr,
2695			     unsigned long end, unsigned int flags,
2696			     struct page **pages, int *nr)
2697{
2698	int nr_start = *nr;
2699	struct dev_pagemap *pgmap = NULL;
 
 
 
2700
 
 
 
2701	do {
2702		struct page *page = pfn_to_page(pfn);
2703
2704		pgmap = get_dev_pagemap(pfn, pgmap);
2705		if (unlikely(!pgmap)) {
2706			undo_dev_pagemap(nr, nr_start, flags, pages);
2707			break;
2708		}
2709
2710		if (!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page)) {
2711			undo_dev_pagemap(nr, nr_start, flags, pages);
2712			break;
2713		}
2714
2715		SetPageReferenced(page);
2716		pages[*nr] = page;
2717		if (unlikely(try_grab_page(page, flags))) {
2718			undo_dev_pagemap(nr, nr_start, flags, pages);
2719			break;
2720		}
2721		(*nr)++;
2722		pfn++;
 
2723	} while (addr += PAGE_SIZE, addr != end);
2724
2725	put_dev_pagemap(pgmap);
2726	return addr == end;
2727}
2728
2729static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2730				 unsigned long end, unsigned int flags,
2731				 struct page **pages, int *nr)
2732{
2733	unsigned long fault_pfn;
2734	int nr_start = *nr;
2735
2736	fault_pfn = pmd_pfn(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
2737	if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr))
2738		return 0;
 
2739
2740	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
2741		undo_dev_pagemap(nr, nr_start, flags, pages);
 
 
2742		return 0;
2743	}
2744	return 1;
2745}
2746
2747static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
2748				 unsigned long end, unsigned int flags,
2749				 struct page **pages, int *nr)
2750{
2751	unsigned long fault_pfn;
2752	int nr_start = *nr;
2753
2754	fault_pfn = pud_pfn(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
2755	if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr))
2756		return 0;
2757
2758	if (unlikely(pud_val(orig) != pud_val(*pudp))) {
2759		undo_dev_pagemap(nr, nr_start, flags, pages);
2760		return 0;
2761	}
2762	return 1;
2763}
2764#else
2765static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2766				 unsigned long end, unsigned int flags,
2767				 struct page **pages, int *nr)
2768{
2769	BUILD_BUG();
2770	return 0;
2771}
2772
2773static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
2774				 unsigned long end, unsigned int flags,
2775				 struct page **pages, int *nr)
2776{
2777	BUILD_BUG();
2778	return 0;
2779}
2780#endif
2781
2782static int record_subpages(struct page *page, unsigned long addr,
2783			   unsigned long end, struct page **pages)
2784{
2785	int nr;
2786
2787	for (nr = 0; addr != end; nr++, addr += PAGE_SIZE)
2788		pages[nr] = nth_page(page, nr);
2789
2790	return nr;
2791}
2792
2793#ifdef CONFIG_ARCH_HAS_HUGEPD
2794static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
2795				      unsigned long sz)
2796{
2797	unsigned long __boundary = (addr + sz) & ~(sz-1);
2798	return (__boundary - 1 < end - 1) ? __boundary : end;
2799}
2800
2801static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
2802		       unsigned long end, unsigned int flags,
2803		       struct page **pages, int *nr)
2804{
2805	unsigned long pte_end;
2806	struct page *page;
2807	struct folio *folio;
2808	pte_t pte;
2809	int refs;
2810
2811	pte_end = (addr + sz) & ~(sz-1);
2812	if (pte_end < end)
2813		end = pte_end;
2814
2815	pte = huge_ptep_get(ptep);
2816
2817	if (!pte_access_permitted(pte, flags & FOLL_WRITE))
2818		return 0;
2819
2820	/* hugepages are never "special" */
2821	VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
2822
2823	page = nth_page(pte_page(pte), (addr & (sz - 1)) >> PAGE_SHIFT);
2824	refs = record_subpages(page, addr, end, pages + *nr);
2825
2826	folio = try_grab_folio(page, refs, flags);
2827	if (!folio)
2828		return 0;
2829
2830	if (unlikely(pte_val(pte) != pte_val(ptep_get(ptep)))) {
2831		gup_put_folio(folio, refs, flags);
2832		return 0;
2833	}
2834
2835	if (!folio_fast_pin_allowed(folio, flags)) {
2836		gup_put_folio(folio, refs, flags);
2837		return 0;
2838	}
2839
2840	if (!pte_write(pte) && gup_must_unshare(NULL, flags, &folio->page)) {
2841		gup_put_folio(folio, refs, flags);
2842		return 0;
2843	}
2844
2845	*nr += refs;
2846	folio_set_referenced(folio);
2847	return 1;
2848}
2849
2850static int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
2851		unsigned int pdshift, unsigned long end, unsigned int flags,
2852		struct page **pages, int *nr)
2853{
2854	pte_t *ptep;
2855	unsigned long sz = 1UL << hugepd_shift(hugepd);
2856	unsigned long next;
2857
2858	ptep = hugepte_offset(hugepd, addr, pdshift);
2859	do {
2860		next = hugepte_addr_end(addr, end, sz);
2861		if (!gup_hugepte(ptep, sz, addr, end, flags, pages, nr))
2862			return 0;
2863	} while (ptep++, addr = next, addr != end);
 
 
2864
2865	return 1;
2866}
2867#else
2868static inline int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
2869		unsigned int pdshift, unsigned long end, unsigned int flags,
2870		struct page **pages, int *nr)
2871{
2872	return 0;
2873}
2874#endif /* CONFIG_ARCH_HAS_HUGEPD */
2875
2876static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2877			unsigned long end, unsigned int flags,
2878			struct page **pages, int *nr)
2879{
2880	struct page *page;
2881	struct folio *folio;
2882	int refs;
2883
2884	if (!pmd_access_permitted(orig, flags & FOLL_WRITE))
2885		return 0;
2886
2887	if (pmd_devmap(orig)) {
2888		if (unlikely(flags & FOLL_LONGTERM))
2889			return 0;
2890		return __gup_device_huge_pmd(orig, pmdp, addr, end, flags,
2891					     pages, nr);
2892	}
2893
2894	page = nth_page(pmd_page(orig), (addr & ~PMD_MASK) >> PAGE_SHIFT);
2895	refs = record_subpages(page, addr, end, pages + *nr);
2896
2897	folio = try_grab_folio(page, refs, flags);
2898	if (!folio)
2899		return 0;
2900
2901	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
2902		gup_put_folio(folio, refs, flags);
2903		return 0;
2904	}
2905
2906	if (!folio_fast_pin_allowed(folio, flags)) {
2907		gup_put_folio(folio, refs, flags);
2908		return 0;
2909	}
2910	if (!pmd_write(orig) && gup_must_unshare(NULL, flags, &folio->page)) {
2911		gup_put_folio(folio, refs, flags);
2912		return 0;
2913	}
2914
2915	*nr += refs;
2916	folio_set_referenced(folio);
2917	return 1;
2918}
2919
2920static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
2921			unsigned long end, unsigned int flags,
2922			struct page **pages, int *nr)
2923{
2924	struct page *page;
2925	struct folio *folio;
2926	int refs;
2927
2928	if (!pud_access_permitted(orig, flags & FOLL_WRITE))
2929		return 0;
2930
2931	if (pud_devmap(orig)) {
2932		if (unlikely(flags & FOLL_LONGTERM))
2933			return 0;
2934		return __gup_device_huge_pud(orig, pudp, addr, end, flags,
2935					     pages, nr);
2936	}
2937
2938	page = nth_page(pud_page(orig), (addr & ~PUD_MASK) >> PAGE_SHIFT);
2939	refs = record_subpages(page, addr, end, pages + *nr);
2940
2941	folio = try_grab_folio(page, refs, flags);
2942	if (!folio)
2943		return 0;
2944
2945	if (unlikely(pud_val(orig) != pud_val(*pudp))) {
2946		gup_put_folio(folio, refs, flags);
2947		return 0;
2948	}
2949
2950	if (!folio_fast_pin_allowed(folio, flags)) {
2951		gup_put_folio(folio, refs, flags);
2952		return 0;
2953	}
2954
2955	if (!pud_write(orig) && gup_must_unshare(NULL, flags, &folio->page)) {
2956		gup_put_folio(folio, refs, flags);
2957		return 0;
2958	}
2959
2960	*nr += refs;
2961	folio_set_referenced(folio);
2962	return 1;
2963}
2964
2965static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
2966			unsigned long end, unsigned int flags,
2967			struct page **pages, int *nr)
2968{
2969	int refs;
2970	struct page *page;
2971	struct folio *folio;
2972
2973	if (!pgd_access_permitted(orig, flags & FOLL_WRITE))
2974		return 0;
2975
2976	BUILD_BUG_ON(pgd_devmap(orig));
2977
2978	page = nth_page(pgd_page(orig), (addr & ~PGDIR_MASK) >> PAGE_SHIFT);
2979	refs = record_subpages(page, addr, end, pages + *nr);
 
 
 
 
 
 
2980
2981	folio = try_grab_folio(page, refs, flags);
2982	if (!folio)
2983		return 0;
 
2984
2985	if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
2986		gup_put_folio(folio, refs, flags);
 
 
2987		return 0;
2988	}
2989
2990	if (!pgd_write(orig) && gup_must_unshare(NULL, flags, &folio->page)) {
2991		gup_put_folio(folio, refs, flags);
2992		return 0;
2993	}
2994
2995	if (!folio_fast_pin_allowed(folio, flags)) {
2996		gup_put_folio(folio, refs, flags);
2997		return 0;
2998	}
2999
3000	*nr += refs;
3001	folio_set_referenced(folio);
3002	return 1;
3003}
3004
3005static int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, unsigned long end,
3006		unsigned int flags, struct page **pages, int *nr)
3007{
3008	unsigned long next;
3009	pmd_t *pmdp;
3010
3011	pmdp = pmd_offset_lockless(pudp, pud, addr);
3012	do {
3013		pmd_t pmd = pmdp_get_lockless(pmdp);
3014
3015		next = pmd_addr_end(addr, end);
3016		if (!pmd_present(pmd))
3017			return 0;
3018
3019		if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) ||
3020			     pmd_devmap(pmd))) {
3021			/* See gup_pte_range() */
 
 
 
3022			if (pmd_protnone(pmd))
3023				return 0;
3024
3025			if (!gup_huge_pmd(pmd, pmdp, addr, next, flags,
3026				pages, nr))
3027				return 0;
3028
3029		} else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
3030			/*
3031			 * architecture have different format for hugetlbfs
3032			 * pmd format and THP pmd format
3033			 */
3034			if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
3035					 PMD_SHIFT, next, flags, pages, nr))
 
 
3036				return 0;
3037		} else if (!gup_pte_range(pmd, pmdp, addr, next, flags, pages, nr))
3038			return 0;
3039	} while (pmdp++, addr = next, addr != end);
3040
3041	return 1;
3042}
3043
3044static int gup_pud_range(p4d_t *p4dp, p4d_t p4d, unsigned long addr, unsigned long end,
3045			 unsigned int flags, struct page **pages, int *nr)
3046{
3047	unsigned long next;
3048	pud_t *pudp;
3049
3050	pudp = pud_offset_lockless(p4dp, p4d, addr);
3051	do {
3052		pud_t pud = READ_ONCE(*pudp);
3053
3054		next = pud_addr_end(addr, end);
3055		if (unlikely(!pud_present(pud)))
3056			return 0;
3057		if (unlikely(pud_huge(pud) || pud_devmap(pud))) {
3058			if (!gup_huge_pud(pud, pudp, addr, next, flags,
3059					  pages, nr))
3060				return 0;
3061		} else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
3062			if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
3063					 PUD_SHIFT, next, flags, pages, nr))
3064				return 0;
3065		} else if (!gup_pmd_range(pudp, pud, addr, next, flags, pages, nr))
3066			return 0;
3067	} while (pudp++, addr = next, addr != end);
3068
3069	return 1;
3070}
3071
3072static int gup_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr, unsigned long end,
3073			 unsigned int flags, struct page **pages, int *nr)
 
 
 
 
3074{
3075	unsigned long next;
3076	p4d_t *p4dp;
 
 
 
3077
3078	p4dp = p4d_offset_lockless(pgdp, pgd, addr);
3079	do {
3080		p4d_t p4d = READ_ONCE(*p4dp);
 
3081
3082		next = p4d_addr_end(addr, end);
3083		if (p4d_none(p4d))
3084			return 0;
3085		BUILD_BUG_ON(p4d_huge(p4d));
3086		if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {
3087			if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
3088					 P4D_SHIFT, next, flags, pages, nr))
3089				return 0;
3090		} else if (!gup_pud_range(p4dp, p4d, addr, next, flags, pages, nr))
3091			return 0;
3092	} while (p4dp++, addr = next, addr != end);
3093
3094	return 1;
3095}
 
 
 
 
 
 
 
 
 
3096
3097static void gup_pgd_range(unsigned long addr, unsigned long end,
3098		unsigned int flags, struct page **pages, int *nr)
3099{
3100	unsigned long next;
3101	pgd_t *pgdp;
3102
3103	pgdp = pgd_offset(current->mm, addr);
3104	do {
3105		pgd_t pgd = READ_ONCE(*pgdp);
3106
3107		next = pgd_addr_end(addr, end);
3108		if (pgd_none(pgd))
3109			return;
3110		if (unlikely(pgd_huge(pgd))) {
3111			if (!gup_huge_pgd(pgd, pgdp, addr, next, flags,
3112					  pages, nr))
3113				return;
3114		} else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
3115			if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
3116					 PGDIR_SHIFT, next, flags, pages, nr))
3117				return;
3118		} else if (!gup_p4d_range(pgdp, pgd, addr, next, flags, pages, nr))
3119			return;
3120	} while (pgdp++, addr = next, addr != end);
3121}
3122#else
3123static inline void gup_pgd_range(unsigned long addr, unsigned long end,
3124		unsigned int flags, struct page **pages, int *nr)
3125{
3126}
3127#endif /* CONFIG_HAVE_FAST_GUP */
3128
3129#ifndef gup_fast_permitted
3130/*
3131 * Check if it's allowed to use get_user_pages_fast_only() for the range, or
3132 * we need to fall back to the slow version:
3133 */
3134static bool gup_fast_permitted(unsigned long start, unsigned long end)
3135{
3136	return true;
3137}
3138#endif
3139
3140static unsigned long lockless_pages_from_mm(unsigned long start,
3141					    unsigned long end,
3142					    unsigned int gup_flags,
3143					    struct page **pages)
3144{
3145	unsigned long flags;
3146	int nr_pinned = 0;
3147	unsigned seq;
3148
3149	if (!IS_ENABLED(CONFIG_HAVE_FAST_GUP) ||
3150	    !gup_fast_permitted(start, end))
3151		return 0;
3152
3153	if (gup_flags & FOLL_PIN) {
3154		seq = raw_read_seqcount(&current->mm->write_protect_seq);
3155		if (seq & 1)
3156			return 0;
3157	}
3158
3159	/*
3160	 * Disable interrupts. The nested form is used, in order to allow full,
3161	 * general purpose use of this routine.
3162	 *
3163	 * With interrupts disabled, we block page table pages from being freed
3164	 * from under us. See struct mmu_table_batch comments in
3165	 * include/asm-generic/tlb.h for more details.
3166	 *
3167	 * We do not adopt an rcu_read_lock() here as we also want to block IPIs
3168	 * that come from THPs splitting.
3169	 */
3170	local_irq_save(flags);
3171	gup_pgd_range(start, end, gup_flags, pages, &nr_pinned);
3172	local_irq_restore(flags);
3173
3174	/*
3175	 * When pinning pages for DMA there could be a concurrent write protect
3176	 * from fork() via copy_page_range(), in this case always fail fast GUP.
3177	 */
3178	if (gup_flags & FOLL_PIN) {
3179		if (read_seqcount_retry(&current->mm->write_protect_seq, seq)) {
3180			unpin_user_pages_lockless(pages, nr_pinned);
3181			return 0;
3182		} else {
3183			sanity_check_pinned_pages(pages, nr_pinned);
3184		}
3185	}
3186	return nr_pinned;
3187}
3188
3189static int internal_get_user_pages_fast(unsigned long start,
3190					unsigned long nr_pages,
3191					unsigned int gup_flags,
3192					struct page **pages)
3193{
3194	unsigned long len, end;
3195	unsigned long nr_pinned;
3196	int locked = 0;
3197	int ret;
3198
3199	if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM |
3200				       FOLL_FORCE | FOLL_PIN | FOLL_GET |
3201				       FOLL_FAST_ONLY | FOLL_NOFAULT |
3202				       FOLL_PCI_P2PDMA | FOLL_HONOR_NUMA_FAULT)))
3203		return -EINVAL;
3204
3205	if (gup_flags & FOLL_PIN)
3206		mm_set_has_pinned_flag(&current->mm->flags);
3207
3208	if (!(gup_flags & FOLL_FAST_ONLY))
3209		might_lock_read(&current->mm->mmap_lock);
3210
3211	start = untagged_addr(start) & PAGE_MASK;
3212	len = nr_pages << PAGE_SHIFT;
3213	if (check_add_overflow(start, len, &end))
3214		return -EOVERFLOW;
3215	if (end > TASK_SIZE_MAX)
3216		return -EFAULT;
3217	if (unlikely(!access_ok((void __user *)start, len)))
3218		return -EFAULT;
3219
3220	nr_pinned = lockless_pages_from_mm(start, end, gup_flags, pages);
3221	if (nr_pinned == nr_pages || gup_flags & FOLL_FAST_ONLY)
3222		return nr_pinned;
3223
3224	/* Slow path: try to get the remaining pages with get_user_pages */
3225	start += nr_pinned << PAGE_SHIFT;
3226	pages += nr_pinned;
3227	ret = __gup_longterm_locked(current->mm, start, nr_pages - nr_pinned,
3228				    pages, &locked,
3229				    gup_flags | FOLL_TOUCH | FOLL_UNLOCKABLE);
3230	if (ret < 0) {
3231		/*
3232		 * The caller has to unpin the pages we already pinned so
3233		 * returning -errno is not an option
3234		 */
3235		if (nr_pinned)
3236			return nr_pinned;
3237		return ret;
3238	}
3239	return ret + nr_pinned;
3240}
3241
3242/**
3243 * get_user_pages_fast_only() - pin user pages in memory
3244 * @start:      starting user address
3245 * @nr_pages:   number of pages from start to pin
3246 * @gup_flags:  flags modifying pin behaviour
3247 * @pages:      array that receives pointers to the pages pinned.
3248 *              Should be at least nr_pages long.
3249 *
3250 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
3251 * the regular GUP.
3252 *
3253 * If the architecture does not support this function, simply return with no
3254 * pages pinned.
3255 *
3256 * Careful, careful! COW breaking can go either way, so a non-write
3257 * access can get ambiguous page results. If you call this function without
3258 * 'write' set, you'd better be sure that you're ok with that ambiguity.
3259 */
3260int get_user_pages_fast_only(unsigned long start, int nr_pages,
3261			     unsigned int gup_flags, struct page **pages)
3262{
3263	/*
3264	 * Internally (within mm/gup.c), gup fast variants must set FOLL_GET,
3265	 * because gup fast is always a "pin with a +1 page refcount" request.
3266	 *
3267	 * FOLL_FAST_ONLY is required in order to match the API description of
3268	 * this routine: no fall back to regular ("slow") GUP.
3269	 */
3270	if (!is_valid_gup_args(pages, NULL, &gup_flags,
3271			       FOLL_GET | FOLL_FAST_ONLY))
3272		return -EINVAL;
3273
3274	return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
3275}
3276EXPORT_SYMBOL_GPL(get_user_pages_fast_only);
3277
3278/**
3279 * get_user_pages_fast() - pin user pages in memory
3280 * @start:      starting user address
3281 * @nr_pages:   number of pages from start to pin
3282 * @gup_flags:  flags modifying pin behaviour
3283 * @pages:      array that receives pointers to the pages pinned.
3284 *              Should be at least nr_pages long.
3285 *
3286 * Attempt to pin user pages in memory without taking mm->mmap_lock.
3287 * If not successful, it will fall back to taking the lock and
3288 * calling get_user_pages().
3289 *
3290 * Returns number of pages pinned. This may be fewer than the number requested.
3291 * If nr_pages is 0 or negative, returns 0. If no pages were pinned, returns
3292 * -errno.
3293 */
3294int get_user_pages_fast(unsigned long start, int nr_pages,
3295			unsigned int gup_flags, struct page **pages)
3296{
3297	/*
3298	 * The caller may or may not have explicitly set FOLL_GET; either way is
3299	 * OK. However, internally (within mm/gup.c), gup fast variants must set
3300	 * FOLL_GET, because gup fast is always a "pin with a +1 page refcount"
3301	 * request.
3302	 */
3303	if (!is_valid_gup_args(pages, NULL, &gup_flags, FOLL_GET))
3304		return -EINVAL;
3305	return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
3306}
3307EXPORT_SYMBOL_GPL(get_user_pages_fast);
3308
3309/**
3310 * pin_user_pages_fast() - pin user pages in memory without taking locks
3311 *
3312 * @start:      starting user address
3313 * @nr_pages:   number of pages from start to pin
3314 * @gup_flags:  flags modifying pin behaviour
3315 * @pages:      array that receives pointers to the pages pinned.
3316 *              Should be at least nr_pages long.
3317 *
3318 * Nearly the same as get_user_pages_fast(), except that FOLL_PIN is set. See
3319 * get_user_pages_fast() for documentation on the function arguments, because
3320 * the arguments here are identical.
3321 *
3322 * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
3323 * see Documentation/core-api/pin_user_pages.rst for further details.
3324 *
3325 * Note that if a zero_page is amongst the returned pages, it will not have
3326 * pins in it and unpin_user_page() will not remove pins from it.
3327 */
3328int pin_user_pages_fast(unsigned long start, int nr_pages,
3329			unsigned int gup_flags, struct page **pages)
3330{
3331	if (!is_valid_gup_args(pages, NULL, &gup_flags, FOLL_PIN))
3332		return -EINVAL;
3333	return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
3334}
3335EXPORT_SYMBOL_GPL(pin_user_pages_fast);
3336
3337/**
3338 * pin_user_pages_remote() - pin pages of a remote process
3339 *
3340 * @mm:		mm_struct of target mm
3341 * @start:	starting user address
3342 * @nr_pages:	number of pages from start to pin
3343 * @gup_flags:	flags modifying lookup behaviour
3344 * @pages:	array that receives pointers to the pages pinned.
3345 *		Should be at least nr_pages long.
3346 * @locked:	pointer to lock flag indicating whether lock is held and
3347 *		subsequently whether VM_FAULT_RETRY functionality can be
3348 *		utilised. Lock must initially be held.
3349 *
3350 * Nearly the same as get_user_pages_remote(), except that FOLL_PIN is set. See
3351 * get_user_pages_remote() for documentation on the function arguments, because
3352 * the arguments here are identical.
3353 *
3354 * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
3355 * see Documentation/core-api/pin_user_pages.rst for details.
 
3356 *
3357 * Note that if a zero_page is amongst the returned pages, it will not have
3358 * pins in it and unpin_user_page*() will not remove pins from it.
3359 */
3360long pin_user_pages_remote(struct mm_struct *mm,
3361			   unsigned long start, unsigned long nr_pages,
3362			   unsigned int gup_flags, struct page **pages,
3363			   int *locked)
3364{
3365	int local_locked = 1;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3366
3367	if (!is_valid_gup_args(pages, locked, &gup_flags,
3368			       FOLL_PIN | FOLL_TOUCH | FOLL_REMOTE))
3369		return 0;
3370	return __gup_longterm_locked(mm, start, nr_pages, pages,
3371				     locked ? locked : &local_locked,
3372				     gup_flags);
3373}
3374EXPORT_SYMBOL(pin_user_pages_remote);
3375
3376/**
3377 * pin_user_pages() - pin user pages in memory for use by other devices
3378 *
3379 * @start:	starting user address
3380 * @nr_pages:	number of pages from start to pin
3381 * @gup_flags:	flags modifying lookup behaviour
3382 * @pages:	array that receives pointers to the pages pinned.
3383 *		Should be at least nr_pages long.
3384 *
3385 * Nearly the same as get_user_pages(), except that FOLL_TOUCH is not set, and
3386 * FOLL_PIN is set.
3387 *
3388 * FOLL_PIN means that the pages must be released via unpin_user_page(). Please
3389 * see Documentation/core-api/pin_user_pages.rst for details.
3390 *
3391 * Note that if a zero_page is amongst the returned pages, it will not have
3392 * pins in it and unpin_user_page*() will not remove pins from it.
3393 */
3394long pin_user_pages(unsigned long start, unsigned long nr_pages,
3395		    unsigned int gup_flags, struct page **pages)
3396{
3397	int locked = 1;
3398
3399	if (!is_valid_gup_args(pages, NULL, &gup_flags, FOLL_PIN))
3400		return 0;
3401	return __gup_longterm_locked(current->mm, start, nr_pages,
3402				     pages, &locked, gup_flags);
3403}
3404EXPORT_SYMBOL(pin_user_pages);
3405
3406/*
3407 * pin_user_pages_unlocked() is the FOLL_PIN variant of
3408 * get_user_pages_unlocked(). Behavior is the same, except that this one sets
3409 * FOLL_PIN and rejects FOLL_GET.
3410 *
3411 * Note that if a zero_page is amongst the returned pages, it will not have
3412 * pins in it and unpin_user_page*() will not remove pins from it.
3413 */
3414long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
3415			     struct page **pages, unsigned int gup_flags)
3416{
3417	int locked = 0;
3418
3419	if (!is_valid_gup_args(pages, NULL, &gup_flags,
3420			       FOLL_PIN | FOLL_TOUCH | FOLL_UNLOCKABLE))
3421		return 0;
3422
3423	return __gup_longterm_locked(current->mm, start, nr_pages, pages,
3424				     &locked, gup_flags);
3425}
3426EXPORT_SYMBOL(pin_user_pages_unlocked);