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
  14#include <linux/sched/signal.h>
  15#include <linux/rwsem.h>
  16#include <linux/hugetlb.h>
  17#include <linux/migrate.h>
  18#include <linux/mm_inline.h>
  19#include <linux/sched/mm.h>
  20
  21#include <asm/mmu_context.h>
  22#include <asm/pgtable.h>
  23#include <asm/tlbflush.h>
  24
  25#include "internal.h"
  26
  27struct follow_page_context {
  28	struct dev_pagemap *pgmap;
  29	unsigned int page_mask;
  30};
  31
  32/**
  33 * put_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages
  34 * @pages:  array of pages to be maybe marked dirty, and definitely released.
  35 * @npages: number of pages in the @pages array.
  36 * @make_dirty: whether to mark the pages dirty
  37 *
  38 * "gup-pinned page" refers to a page that has had one of the get_user_pages()
  39 * variants called on that page.
  40 *
  41 * For each page in the @pages array, make that page (or its head page, if a
  42 * compound page) dirty, if @make_dirty is true, and if the page was previously
  43 * listed as clean. In any case, releases all pages using put_user_page(),
  44 * possibly via put_user_pages(), for the non-dirty case.
  45 *
  46 * Please see the put_user_page() documentation for details.
  47 *
  48 * set_page_dirty_lock() is used internally. If instead, set_page_dirty() is
  49 * required, then the caller should a) verify that this is really correct,
  50 * because _lock() is usually required, and b) hand code it:
  51 * set_page_dirty_lock(), put_user_page().
  52 *
  53 */
  54void put_user_pages_dirty_lock(struct page **pages, unsigned long npages,
  55			       bool make_dirty)
  56{
  57	unsigned long index;
  58
  59	/*
  60	 * TODO: this can be optimized for huge pages: if a series of pages is
  61	 * physically contiguous and part of the same compound page, then a
  62	 * single operation to the head page should suffice.
  63	 */
  64
  65	if (!make_dirty) {
  66		put_user_pages(pages, npages);
  67		return;
  68	}
  69
  70	for (index = 0; index < npages; index++) {
  71		struct page *page = compound_head(pages[index]);
  72		/*
  73		 * Checking PageDirty at this point may race with
  74		 * clear_page_dirty_for_io(), but that's OK. Two key
  75		 * cases:
  76		 *
  77		 * 1) This code sees the page as already dirty, so it
  78		 * skips the call to set_page_dirty(). That could happen
  79		 * because clear_page_dirty_for_io() called
  80		 * page_mkclean(), followed by set_page_dirty().
  81		 * However, now the page is going to get written back,
  82		 * which meets the original intention of setting it
  83		 * dirty, so all is well: clear_page_dirty_for_io() goes
  84		 * on to call TestClearPageDirty(), and write the page
  85		 * back.
  86		 *
  87		 * 2) This code sees the page as clean, so it calls
  88		 * set_page_dirty(). The page stays dirty, despite being
  89		 * written back, so it gets written back again in the
  90		 * next writeback cycle. This is harmless.
  91		 */
  92		if (!PageDirty(page))
  93			set_page_dirty_lock(page);
  94		put_user_page(page);
  95	}
  96}
  97EXPORT_SYMBOL(put_user_pages_dirty_lock);
  98
  99/**
 100 * put_user_pages() - release an array of gup-pinned pages.
 101 * @pages:  array of pages to be marked dirty and released.
 102 * @npages: number of pages in the @pages array.
 103 *
 104 * For each page in the @pages array, release the page using put_user_page().
 105 *
 106 * Please see the put_user_page() documentation for details.
 107 */
 108void put_user_pages(struct page **pages, unsigned long npages)
 109{
 110	unsigned long index;
 111
 112	/*
 113	 * TODO: this can be optimized for huge pages: if a series of pages is
 114	 * physically contiguous and part of the same compound page, then a
 115	 * single operation to the head page should suffice.
 116	 */
 117	for (index = 0; index < npages; index++)
 118		put_user_page(pages[index]);
 119}
 120EXPORT_SYMBOL(put_user_pages);
 121
 122#ifdef CONFIG_MMU
 123static struct page *no_page_table(struct vm_area_struct *vma,
 124		unsigned int flags)
 125{
 126	/*
 127	 * When core dumping an enormous anonymous area that nobody
 128	 * has touched so far, we don't want to allocate unnecessary pages or
 129	 * page tables.  Return error instead of NULL to skip handle_mm_fault,
 130	 * then get_dump_page() will return NULL to leave a hole in the dump.
 131	 * But we can only make this optimization where a hole would surely
 132	 * be zero-filled if handle_mm_fault() actually did handle it.
 133	 */
 134	if ((flags & FOLL_DUMP) && (!vma->vm_ops || !vma->vm_ops->fault))
 135		return ERR_PTR(-EFAULT);
 136	return NULL;
 137}
 138
 139static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
 140		pte_t *pte, unsigned int flags)
 141{
 142	/* No page to get reference */
 143	if (flags & FOLL_GET)
 144		return -EFAULT;
 145
 146	if (flags & FOLL_TOUCH) {
 147		pte_t entry = *pte;
 148
 149		if (flags & FOLL_WRITE)
 150			entry = pte_mkdirty(entry);
 151		entry = pte_mkyoung(entry);
 152
 153		if (!pte_same(*pte, entry)) {
 154			set_pte_at(vma->vm_mm, address, pte, entry);
 155			update_mmu_cache(vma, address, pte);
 156		}
 157	}
 158
 159	/* Proper page table entry exists, but no corresponding struct page */
 160	return -EEXIST;
 161}
 162
 163/*
 164 * FOLL_FORCE can write to even unwritable pte's, but only
 165 * after we've gone through a COW cycle and they are dirty.
 166 */
 167static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
 168{
 169	return pte_write(pte) ||
 170		((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
 171}
 172
 173static struct page *follow_page_pte(struct vm_area_struct *vma,
 174		unsigned long address, pmd_t *pmd, unsigned int flags,
 175		struct dev_pagemap **pgmap)
 176{
 177	struct mm_struct *mm = vma->vm_mm;
 
 178	struct page *page;
 179	spinlock_t *ptl;
 180	pte_t *ptep, pte;
 181
 182retry:
 183	if (unlikely(pmd_bad(*pmd)))
 184		return no_page_table(vma, flags);
 185
 186	ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
 187	pte = *ptep;
 188	if (!pte_present(pte)) {
 189		swp_entry_t entry;
 190		/*
 191		 * KSM's break_ksm() relies upon recognizing a ksm page
 192		 * even while it is being migrated, so for that case we
 193		 * need migration_entry_wait().
 194		 */
 195		if (likely(!(flags & FOLL_MIGRATION)))
 196			goto no_page;
 197		if (pte_none(pte))
 198			goto no_page;
 199		entry = pte_to_swp_entry(pte);
 200		if (!is_migration_entry(entry))
 201			goto no_page;
 202		pte_unmap_unlock(ptep, ptl);
 203		migration_entry_wait(mm, pmd, address);
 204		goto retry;
 205	}
 206	if ((flags & FOLL_NUMA) && pte_protnone(pte))
 207		goto no_page;
 208	if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) {
 209		pte_unmap_unlock(ptep, ptl);
 210		return NULL;
 211	}
 212
 213	page = vm_normal_page(vma, address, pte);
 214	if (!page && pte_devmap(pte) && (flags & FOLL_GET)) {
 215		/*
 216		 * Only return device mapping pages in the FOLL_GET case since
 217		 * they are only valid while holding the pgmap reference.
 218		 */
 219		*pgmap = get_dev_pagemap(pte_pfn(pte), *pgmap);
 220		if (*pgmap)
 221			page = pte_page(pte);
 222		else
 223			goto no_page;
 224	} else if (unlikely(!page)) {
 225		if (flags & FOLL_DUMP) {
 226			/* Avoid special (like zero) pages in core dumps */
 227			page = ERR_PTR(-EFAULT);
 228			goto out;
 229		}
 230
 231		if (is_zero_pfn(pte_pfn(pte))) {
 232			page = pte_page(pte);
 233		} else {
 234			int ret;
 235
 236			ret = follow_pfn_pte(vma, address, ptep, flags);
 237			page = ERR_PTR(ret);
 238			goto out;
 239		}
 240	}
 241
 242	if (flags & FOLL_SPLIT && PageTransCompound(page)) {
 243		int ret;
 244		get_page(page);
 245		pte_unmap_unlock(ptep, ptl);
 246		lock_page(page);
 247		ret = split_huge_page(page);
 248		unlock_page(page);
 249		put_page(page);
 250		if (ret)
 251			return ERR_PTR(ret);
 252		goto retry;
 253	}
 254
 255	if (flags & FOLL_GET) {
 256		if (unlikely(!try_get_page(page))) {
 257			page = ERR_PTR(-ENOMEM);
 258			goto out;
 
 
 
 259		}
 260	}
 261	if (flags & FOLL_TOUCH) {
 262		if ((flags & FOLL_WRITE) &&
 263		    !pte_dirty(pte) && !PageDirty(page))
 264			set_page_dirty(page);
 265		/*
 266		 * pte_mkyoung() would be more correct here, but atomic care
 267		 * is needed to avoid losing the dirty bit: it is easier to use
 268		 * mark_page_accessed().
 269		 */
 270		mark_page_accessed(page);
 271	}
 272	if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
 273		/* Do not mlock pte-mapped THP */
 274		if (PageTransCompound(page))
 275			goto out;
 276
 277		/*
 278		 * The preliminary mapping check is mainly to avoid the
 279		 * pointless overhead of lock_page on the ZERO_PAGE
 280		 * which might bounce very badly if there is contention.
 281		 *
 282		 * If the page is already locked, we don't need to
 283		 * handle it now - vmscan will handle it later if and
 284		 * when it attempts to reclaim the page.
 285		 */
 286		if (page->mapping && trylock_page(page)) {
 287			lru_add_drain();  /* push cached pages to LRU */
 288			/*
 289			 * Because we lock page here, and migration is
 290			 * blocked by the pte's page reference, and we
 291			 * know the page is still mapped, we don't even
 292			 * need to check for file-cache page truncation.
 293			 */
 294			mlock_vma_page(page);
 295			unlock_page(page);
 296		}
 297	}
 298out:
 299	pte_unmap_unlock(ptep, ptl);
 300	return page;
 301no_page:
 302	pte_unmap_unlock(ptep, ptl);
 303	if (!pte_none(pte))
 304		return NULL;
 305	return no_page_table(vma, flags);
 306}
 307
 308static struct page *follow_pmd_mask(struct vm_area_struct *vma,
 309				    unsigned long address, pud_t *pudp,
 310				    unsigned int flags,
 311				    struct follow_page_context *ctx)
 
 
 
 
 
 
 
 
 
 
 
 
 312{
 313	pmd_t *pmd, pmdval;
 
 
 314	spinlock_t *ptl;
 315	struct page *page;
 316	struct mm_struct *mm = vma->vm_mm;
 317
 318	pmd = pmd_offset(pudp, address);
 319	/*
 320	 * The READ_ONCE() will stabilize the pmdval in a register or
 321	 * on the stack so that it will stop changing under the code.
 322	 */
 323	pmdval = READ_ONCE(*pmd);
 324	if (pmd_none(pmdval))
 
 
 
 325		return no_page_table(vma, flags);
 326	if (pmd_huge(pmdval) && vma->vm_flags & VM_HUGETLB) {
 327		page = follow_huge_pmd(mm, address, pmd, flags);
 
 
 
 
 328		if (page)
 329			return page;
 330		return no_page_table(vma, flags);
 331	}
 332	if (is_hugepd(__hugepd(pmd_val(pmdval)))) {
 333		page = follow_huge_pd(vma, address,
 334				      __hugepd(pmd_val(pmdval)), flags,
 335				      PMD_SHIFT);
 
 
 
 
 336		if (page)
 337			return page;
 338		return no_page_table(vma, flags);
 339	}
 340retry:
 341	if (!pmd_present(pmdval)) {
 342		if (likely(!(flags & FOLL_MIGRATION)))
 343			return no_page_table(vma, flags);
 344		VM_BUG_ON(thp_migration_supported() &&
 345				  !is_pmd_migration_entry(pmdval));
 346		if (is_pmd_migration_entry(pmdval))
 347			pmd_migration_entry_wait(mm, pmd);
 348		pmdval = READ_ONCE(*pmd);
 349		/*
 350		 * MADV_DONTNEED may convert the pmd to null because
 351		 * mmap_sem is held in read mode
 352		 */
 353		if (pmd_none(pmdval))
 354			return no_page_table(vma, flags);
 355		goto retry;
 356	}
 357	if (pmd_devmap(pmdval)) {
 358		ptl = pmd_lock(mm, pmd);
 359		page = follow_devmap_pmd(vma, address, pmd, flags, &ctx->pgmap);
 360		spin_unlock(ptl);
 361		if (page)
 362			return page;
 363	}
 364	if (likely(!pmd_trans_huge(pmdval)))
 365		return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
 366
 367	if ((flags & FOLL_NUMA) && pmd_protnone(pmdval))
 368		return no_page_table(vma, flags);
 369
 370retry_locked:
 371	ptl = pmd_lock(mm, pmd);
 372	if (unlikely(pmd_none(*pmd))) {
 373		spin_unlock(ptl);
 374		return no_page_table(vma, flags);
 375	}
 376	if (unlikely(!pmd_present(*pmd))) {
 377		spin_unlock(ptl);
 378		if (likely(!(flags & FOLL_MIGRATION)))
 379			return no_page_table(vma, flags);
 380		pmd_migration_entry_wait(mm, pmd);
 381		goto retry_locked;
 382	}
 383	if (unlikely(!pmd_trans_huge(*pmd))) {
 384		spin_unlock(ptl);
 385		return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
 386	}
 387	if (flags & (FOLL_SPLIT | FOLL_SPLIT_PMD)) {
 388		int ret;
 389		page = pmd_page(*pmd);
 390		if (is_huge_zero_page(page)) {
 391			spin_unlock(ptl);
 392			ret = 0;
 393			split_huge_pmd(vma, pmd, address);
 394			if (pmd_trans_unstable(pmd))
 395				ret = -EBUSY;
 396		} else if (flags & FOLL_SPLIT) {
 397			if (unlikely(!try_get_page(page))) {
 398				spin_unlock(ptl);
 399				return ERR_PTR(-ENOMEM);
 400			}
 401			spin_unlock(ptl);
 402			lock_page(page);
 403			ret = split_huge_page(page);
 404			unlock_page(page);
 405			put_page(page);
 406			if (pmd_none(*pmd))
 407				return no_page_table(vma, flags);
 408		} else {  /* flags & FOLL_SPLIT_PMD */
 409			spin_unlock(ptl);
 410			split_huge_pmd(vma, pmd, address);
 411			ret = pte_alloc(mm, pmd) ? -ENOMEM : 0;
 412		}
 413
 414		return ret ? ERR_PTR(ret) :
 415			follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
 416	}
 
 417	page = follow_trans_huge_pmd(vma, address, pmd, flags);
 418	spin_unlock(ptl);
 419	ctx->page_mask = HPAGE_PMD_NR - 1;
 420	return page;
 421}
 422
 423static struct page *follow_pud_mask(struct vm_area_struct *vma,
 424				    unsigned long address, p4d_t *p4dp,
 425				    unsigned int flags,
 426				    struct follow_page_context *ctx)
 427{
 428	pud_t *pud;
 429	spinlock_t *ptl;
 430	struct page *page;
 431	struct mm_struct *mm = vma->vm_mm;
 432
 433	pud = pud_offset(p4dp, address);
 434	if (pud_none(*pud))
 435		return no_page_table(vma, flags);
 436	if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
 437		page = follow_huge_pud(mm, address, pud, flags);
 438		if (page)
 439			return page;
 440		return no_page_table(vma, flags);
 441	}
 442	if (is_hugepd(__hugepd(pud_val(*pud)))) {
 443		page = follow_huge_pd(vma, address,
 444				      __hugepd(pud_val(*pud)), flags,
 445				      PUD_SHIFT);
 446		if (page)
 447			return page;
 448		return no_page_table(vma, flags);
 449	}
 450	if (pud_devmap(*pud)) {
 451		ptl = pud_lock(mm, pud);
 452		page = follow_devmap_pud(vma, address, pud, flags, &ctx->pgmap);
 453		spin_unlock(ptl);
 454		if (page)
 455			return page;
 456	}
 457	if (unlikely(pud_bad(*pud)))
 458		return no_page_table(vma, flags);
 459
 460	return follow_pmd_mask(vma, address, pud, flags, ctx);
 461}
 462
 463static struct page *follow_p4d_mask(struct vm_area_struct *vma,
 464				    unsigned long address, pgd_t *pgdp,
 465				    unsigned int flags,
 466				    struct follow_page_context *ctx)
 467{
 468	p4d_t *p4d;
 469	struct page *page;
 470
 471	p4d = p4d_offset(pgdp, address);
 472	if (p4d_none(*p4d))
 473		return no_page_table(vma, flags);
 474	BUILD_BUG_ON(p4d_huge(*p4d));
 475	if (unlikely(p4d_bad(*p4d)))
 476		return no_page_table(vma, flags);
 477
 478	if (is_hugepd(__hugepd(p4d_val(*p4d)))) {
 479		page = follow_huge_pd(vma, address,
 480				      __hugepd(p4d_val(*p4d)), flags,
 481				      P4D_SHIFT);
 482		if (page)
 483			return page;
 484		return no_page_table(vma, flags);
 485	}
 486	return follow_pud_mask(vma, address, p4d, flags, ctx);
 487}
 488
 489/**
 490 * follow_page_mask - look up a page descriptor from a user-virtual address
 491 * @vma: vm_area_struct mapping @address
 492 * @address: virtual address to look up
 493 * @flags: flags modifying lookup behaviour
 494 * @ctx: contains dev_pagemap for %ZONE_DEVICE memory pinning and a
 495 *       pointer to output page_mask
 496 *
 497 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
 498 *
 499 * When getting pages from ZONE_DEVICE memory, the @ctx->pgmap caches
 500 * the device's dev_pagemap metadata to avoid repeating expensive lookups.
 501 *
 502 * On output, the @ctx->page_mask is set according to the size of the page.
 503 *
 504 * Return: the mapped (struct page *), %NULL if no mapping exists, or
 505 * an error pointer if there is a mapping to something not represented
 506 * by a page descriptor (see also vm_normal_page()).
 507 */
 508static struct page *follow_page_mask(struct vm_area_struct *vma,
 509			      unsigned long address, unsigned int flags,
 510			      struct follow_page_context *ctx)
 511{
 512	pgd_t *pgd;
 513	struct page *page;
 514	struct mm_struct *mm = vma->vm_mm;
 515
 516	ctx->page_mask = 0;
 517
 518	/* make this handle hugepd */
 519	page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
 520	if (!IS_ERR(page)) {
 521		BUG_ON(flags & FOLL_GET);
 522		return page;
 523	}
 524
 525	pgd = pgd_offset(mm, address);
 526
 527	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
 528		return no_page_table(vma, flags);
 529
 530	if (pgd_huge(*pgd)) {
 531		page = follow_huge_pgd(mm, address, pgd, flags);
 532		if (page)
 533			return page;
 534		return no_page_table(vma, flags);
 535	}
 536	if (is_hugepd(__hugepd(pgd_val(*pgd)))) {
 537		page = follow_huge_pd(vma, address,
 538				      __hugepd(pgd_val(*pgd)), flags,
 539				      PGDIR_SHIFT);
 540		if (page)
 541			return page;
 542		return no_page_table(vma, flags);
 543	}
 544
 545	return follow_p4d_mask(vma, address, pgd, flags, ctx);
 546}
 547
 548struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
 549			 unsigned int foll_flags)
 550{
 551	struct follow_page_context ctx = { NULL };
 552	struct page *page;
 553
 554	page = follow_page_mask(vma, address, foll_flags, &ctx);
 555	if (ctx.pgmap)
 556		put_dev_pagemap(ctx.pgmap);
 557	return page;
 558}
 559
 560static int get_gate_page(struct mm_struct *mm, unsigned long address,
 561		unsigned int gup_flags, struct vm_area_struct **vma,
 562		struct page **page)
 563{
 564	pgd_t *pgd;
 565	p4d_t *p4d;
 566	pud_t *pud;
 567	pmd_t *pmd;
 568	pte_t *pte;
 569	int ret = -EFAULT;
 570
 571	/* user gate pages are read-only */
 572	if (gup_flags & FOLL_WRITE)
 573		return -EFAULT;
 574	if (address > TASK_SIZE)
 575		pgd = pgd_offset_k(address);
 576	else
 577		pgd = pgd_offset_gate(mm, address);
 578	if (pgd_none(*pgd))
 579		return -EFAULT;
 580	p4d = p4d_offset(pgd, address);
 581	if (p4d_none(*p4d))
 582		return -EFAULT;
 583	pud = pud_offset(p4d, address);
 584	if (pud_none(*pud))
 585		return -EFAULT;
 586	pmd = pmd_offset(pud, address);
 587	if (!pmd_present(*pmd))
 588		return -EFAULT;
 589	VM_BUG_ON(pmd_trans_huge(*pmd));
 590	pte = pte_offset_map(pmd, address);
 591	if (pte_none(*pte))
 592		goto unmap;
 593	*vma = get_gate_vma(mm);
 594	if (!page)
 595		goto out;
 596	*page = vm_normal_page(*vma, address, *pte);
 597	if (!*page) {
 598		if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
 599			goto unmap;
 600		*page = pte_page(*pte);
 601	}
 602	if (unlikely(!try_get_page(*page))) {
 603		ret = -ENOMEM;
 604		goto unmap;
 605	}
 606out:
 607	ret = 0;
 608unmap:
 609	pte_unmap(pte);
 610	return ret;
 611}
 612
 613/*
 614 * mmap_sem must be held on entry.  If @nonblocking != NULL and
 615 * *@flags does not include FOLL_NOWAIT, the mmap_sem may be released.
 616 * If it is, *@nonblocking will be set to 0 and -EBUSY returned.
 617 */
 618static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
 619		unsigned long address, unsigned int *flags, int *nonblocking)
 620{
 
 621	unsigned int fault_flags = 0;
 622	vm_fault_t ret;
 623
 624	/* mlock all present pages, but do not fault in new pages */
 625	if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
 626		return -ENOENT;
 
 
 
 
 
 627	if (*flags & FOLL_WRITE)
 628		fault_flags |= FAULT_FLAG_WRITE;
 629	if (*flags & FOLL_REMOTE)
 630		fault_flags |= FAULT_FLAG_REMOTE;
 631	if (nonblocking)
 632		fault_flags |= FAULT_FLAG_ALLOW_RETRY;
 633	if (*flags & FOLL_NOWAIT)
 634		fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
 635	if (*flags & FOLL_TRIED) {
 636		VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY);
 637		fault_flags |= FAULT_FLAG_TRIED;
 638	}
 639
 640	ret = handle_mm_fault(vma, address, fault_flags);
 641	if (ret & VM_FAULT_ERROR) {
 642		int err = vm_fault_to_errno(ret, *flags);
 643
 644		if (err)
 645			return err;
 
 
 646		BUG();
 647	}
 648
 649	if (tsk) {
 650		if (ret & VM_FAULT_MAJOR)
 651			tsk->maj_flt++;
 652		else
 653			tsk->min_flt++;
 654	}
 655
 656	if (ret & VM_FAULT_RETRY) {
 657		if (nonblocking && !(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
 658			*nonblocking = 0;
 659		return -EBUSY;
 660	}
 661
 662	/*
 663	 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
 664	 * necessary, even if maybe_mkwrite decided not to set pte_write. We
 665	 * can thus safely do subsequent page lookups as if they were reads.
 666	 * But only do so when looping for pte_write is futile: in some cases
 667	 * userspace may also be wanting to write to the gotten user page,
 668	 * which a read fault here might prevent (a readonly page might get
 669	 * reCOWed by userspace write).
 670	 */
 671	if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
 672		*flags |= FOLL_COW;
 673	return 0;
 674}
 675
 676static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
 677{
 678	vm_flags_t vm_flags = vma->vm_flags;
 679	int write = (gup_flags & FOLL_WRITE);
 680	int foreign = (gup_flags & FOLL_REMOTE);
 681
 682	if (vm_flags & (VM_IO | VM_PFNMAP))
 683		return -EFAULT;
 684
 685	if (gup_flags & FOLL_ANON && !vma_is_anonymous(vma))
 686		return -EFAULT;
 687
 688	if (write) {
 689		if (!(vm_flags & VM_WRITE)) {
 690			if (!(gup_flags & FOLL_FORCE))
 691				return -EFAULT;
 692			/*
 693			 * We used to let the write,force case do COW in a
 694			 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
 695			 * set a breakpoint in a read-only mapping of an
 696			 * executable, without corrupting the file (yet only
 697			 * when that file had been opened for writing!).
 698			 * Anon pages in shared mappings are surprising: now
 699			 * just reject it.
 700			 */
 701			if (!is_cow_mapping(vm_flags))
 702				return -EFAULT;
 703		}
 704	} else if (!(vm_flags & VM_READ)) {
 705		if (!(gup_flags & FOLL_FORCE))
 706			return -EFAULT;
 707		/*
 708		 * Is there actually any vma we can reach here which does not
 709		 * have VM_MAYREAD set?
 710		 */
 711		if (!(vm_flags & VM_MAYREAD))
 712			return -EFAULT;
 713	}
 714	/*
 715	 * gups are always data accesses, not instruction
 716	 * fetches, so execute=false here
 717	 */
 718	if (!arch_vma_access_permitted(vma, write, false, foreign))
 719		return -EFAULT;
 720	return 0;
 721}
 722
 723/**
 724 * __get_user_pages() - pin user pages in memory
 725 * @tsk:	task_struct of target task
 726 * @mm:		mm_struct of target mm
 727 * @start:	starting user address
 728 * @nr_pages:	number of pages from start to pin
 729 * @gup_flags:	flags modifying pin behaviour
 730 * @pages:	array that receives pointers to the pages pinned.
 731 *		Should be at least nr_pages long. Or NULL, if caller
 732 *		only intends to ensure the pages are faulted in.
 733 * @vmas:	array of pointers to vmas corresponding to each page.
 734 *		Or NULL if the caller does not require them.
 735 * @nonblocking: whether waiting for disk IO or mmap_sem contention
 736 *
 737 * Returns number of pages pinned. This may be fewer than the number
 738 * requested. If nr_pages is 0 or negative, returns 0. If no pages
 739 * were pinned, returns -errno. Each page returned must be released
 740 * with a put_page() call when it is finished with. vmas will only
 741 * remain valid while mmap_sem is held.
 742 *
 743 * Must be called with mmap_sem held.  It may be released.  See below.
 744 *
 745 * __get_user_pages walks a process's page tables and takes a reference to
 746 * each struct page that each user address corresponds to at a given
 747 * instant. That is, it takes the page that would be accessed if a user
 748 * thread accesses the given user virtual address at that instant.
 749 *
 750 * This does not guarantee that the page exists in the user mappings when
 751 * __get_user_pages returns, and there may even be a completely different
 752 * page there in some cases (eg. if mmapped pagecache has been invalidated
 753 * and subsequently re faulted). However it does guarantee that the page
 754 * won't be freed completely. And mostly callers simply care that the page
 755 * contains data that was valid *at some point in time*. Typically, an IO
 756 * or similar operation cannot guarantee anything stronger anyway because
 757 * locks can't be held over the syscall boundary.
 758 *
 759 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
 760 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
 761 * appropriate) must be called after the page is finished with, and
 762 * before put_page is called.
 763 *
 764 * If @nonblocking != NULL, __get_user_pages will not wait for disk IO
 765 * or mmap_sem contention, and if waiting is needed to pin all pages,
 766 * *@nonblocking will be set to 0.  Further, if @gup_flags does not
 767 * include FOLL_NOWAIT, the mmap_sem will be released via up_read() in
 768 * this case.
 769 *
 770 * A caller using such a combination of @nonblocking and @gup_flags
 771 * must therefore hold the mmap_sem for reading only, and recognize
 772 * when it's been released.  Otherwise, it must be held for either
 773 * reading or writing and will not be released.
 774 *
 775 * In most cases, get_user_pages or get_user_pages_fast should be used
 776 * instead of __get_user_pages. __get_user_pages should be used only if
 777 * you need some special @gup_flags.
 778 */
 779static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 780		unsigned long start, unsigned long nr_pages,
 781		unsigned int gup_flags, struct page **pages,
 782		struct vm_area_struct **vmas, int *nonblocking)
 783{
 784	long ret = 0, i = 0;
 
 785	struct vm_area_struct *vma = NULL;
 786	struct follow_page_context ctx = { NULL };
 787
 788	if (!nr_pages)
 789		return 0;
 790
 791	start = untagged_addr(start);
 792
 793	VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
 794
 795	/*
 796	 * If FOLL_FORCE is set then do not force a full fault as the hinting
 797	 * fault information is unrelated to the reference behaviour of a task
 798	 * using the address space
 799	 */
 800	if (!(gup_flags & FOLL_FORCE))
 801		gup_flags |= FOLL_NUMA;
 802
 803	do {
 804		struct page *page;
 805		unsigned int foll_flags = gup_flags;
 806		unsigned int page_increm;
 807
 808		/* first iteration or cross vma bound */
 809		if (!vma || start >= vma->vm_end) {
 810			vma = find_extend_vma(mm, start);
 811			if (!vma && in_gate_area(mm, start)) {
 
 812				ret = get_gate_page(mm, start & PAGE_MASK,
 813						gup_flags, &vma,
 814						pages ? &pages[i] : NULL);
 815				if (ret)
 816					goto out;
 817				ctx.page_mask = 0;
 818				goto next_page;
 819			}
 820
 821			if (!vma || check_vma_flags(vma, gup_flags)) {
 822				ret = -EFAULT;
 823				goto out;
 824			}
 825			if (is_vm_hugetlb_page(vma)) {
 826				i = follow_hugetlb_page(mm, vma, pages, vmas,
 827						&start, &nr_pages, i,
 828						gup_flags, nonblocking);
 829				continue;
 830			}
 831		}
 832retry:
 833		/*
 834		 * If we have a pending SIGKILL, don't keep faulting pages and
 835		 * potentially allocating memory.
 836		 */
 837		if (fatal_signal_pending(current)) {
 838			ret = -ERESTARTSYS;
 839			goto out;
 840		}
 841		cond_resched();
 842
 843		page = follow_page_mask(vma, start, foll_flags, &ctx);
 844		if (!page) {
 
 845			ret = faultin_page(tsk, vma, start, &foll_flags,
 846					nonblocking);
 847			switch (ret) {
 848			case 0:
 849				goto retry;
 850			case -EBUSY:
 851				ret = 0;
 852				/* FALLTHRU */
 853			case -EFAULT:
 854			case -ENOMEM:
 855			case -EHWPOISON:
 856				goto out;
 
 
 857			case -ENOENT:
 858				goto next_page;
 859			}
 860			BUG();
 861		} else if (PTR_ERR(page) == -EEXIST) {
 862			/*
 863			 * Proper page table entry exists, but no corresponding
 864			 * struct page.
 865			 */
 866			goto next_page;
 867		} else if (IS_ERR(page)) {
 868			ret = PTR_ERR(page);
 869			goto out;
 870		}
 871		if (pages) {
 872			pages[i] = page;
 873			flush_anon_page(vma, page, start);
 874			flush_dcache_page(page);
 875			ctx.page_mask = 0;
 876		}
 877next_page:
 878		if (vmas) {
 879			vmas[i] = vma;
 880			ctx.page_mask = 0;
 881		}
 882		page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask);
 883		if (page_increm > nr_pages)
 884			page_increm = nr_pages;
 885		i += page_increm;
 886		start += page_increm * PAGE_SIZE;
 887		nr_pages -= page_increm;
 888	} while (nr_pages);
 889out:
 890	if (ctx.pgmap)
 891		put_dev_pagemap(ctx.pgmap);
 892	return i ? i : ret;
 893}
 
 894
 895static bool vma_permits_fault(struct vm_area_struct *vma,
 896			      unsigned int fault_flags)
 897{
 898	bool write   = !!(fault_flags & FAULT_FLAG_WRITE);
 899	bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
 900	vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
 901
 902	if (!(vm_flags & vma->vm_flags))
 903		return false;
 904
 905	/*
 906	 * The architecture might have a hardware protection
 907	 * mechanism other than read/write that can deny access.
 908	 *
 909	 * gup always represents data access, not instruction
 910	 * fetches, so execute=false here:
 911	 */
 912	if (!arch_vma_access_permitted(vma, write, false, foreign))
 913		return false;
 914
 915	return true;
 916}
 917
 918/*
 919 * fixup_user_fault() - manually resolve a user page fault
 920 * @tsk:	the task_struct to use for page fault accounting, or
 921 *		NULL if faults are not to be recorded.
 922 * @mm:		mm_struct of target mm
 923 * @address:	user address
 924 * @fault_flags:flags to pass down to handle_mm_fault()
 925 * @unlocked:	did we unlock the mmap_sem while retrying, maybe NULL if caller
 926 *		does not allow retry
 927 *
 928 * This is meant to be called in the specific scenario where for locking reasons
 929 * we try to access user memory in atomic context (within a pagefault_disable()
 930 * section), this returns -EFAULT, and we want to resolve the user fault before
 931 * trying again.
 932 *
 933 * Typically this is meant to be used by the futex code.
 934 *
 935 * The main difference with get_user_pages() is that this function will
 936 * unconditionally call handle_mm_fault() which will in turn perform all the
 937 * necessary SW fixup of the dirty and young bits in the PTE, while
 938 * get_user_pages() only guarantees to update these in the struct page.
 939 *
 940 * This is important for some architectures where those bits also gate the
 941 * access permission to the page because they are maintained in software.  On
 942 * such architectures, gup() will not be enough to make a subsequent access
 943 * succeed.
 944 *
 945 * This function will not return with an unlocked mmap_sem. So it has not the
 946 * same semantics wrt the @mm->mmap_sem as does filemap_fault().
 947 */
 948int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
 949		     unsigned long address, unsigned int fault_flags,
 950		     bool *unlocked)
 951{
 952	struct vm_area_struct *vma;
 953	vm_fault_t ret, major = 0;
 954
 955	address = untagged_addr(address);
 956
 957	if (unlocked)
 958		fault_flags |= FAULT_FLAG_ALLOW_RETRY;
 959
 960retry:
 961	vma = find_extend_vma(mm, address);
 962	if (!vma || address < vma->vm_start)
 963		return -EFAULT;
 964
 965	if (!vma_permits_fault(vma, fault_flags))
 966		return -EFAULT;
 967
 968	ret = handle_mm_fault(vma, address, fault_flags);
 969	major |= ret & VM_FAULT_MAJOR;
 970	if (ret & VM_FAULT_ERROR) {
 971		int err = vm_fault_to_errno(ret, 0);
 972
 973		if (err)
 974			return err;
 
 
 975		BUG();
 976	}
 977
 978	if (ret & VM_FAULT_RETRY) {
 979		down_read(&mm->mmap_sem);
 980		if (!(fault_flags & FAULT_FLAG_TRIED)) {
 981			*unlocked = true;
 982			fault_flags &= ~FAULT_FLAG_ALLOW_RETRY;
 983			fault_flags |= FAULT_FLAG_TRIED;
 984			goto retry;
 985		}
 986	}
 987
 988	if (tsk) {
 989		if (major)
 990			tsk->maj_flt++;
 991		else
 992			tsk->min_flt++;
 993	}
 994	return 0;
 995}
 996EXPORT_SYMBOL_GPL(fixup_user_fault);
 997
 998static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
 999						struct mm_struct *mm,
1000						unsigned long start,
1001						unsigned long nr_pages,
 
1002						struct page **pages,
1003						struct vm_area_struct **vmas,
1004						int *locked,
1005						unsigned int flags)
1006{
1007	long ret, pages_done;
1008	bool lock_dropped;
1009
1010	if (locked) {
1011		/* if VM_FAULT_RETRY can be returned, vmas become invalid */
1012		BUG_ON(vmas);
1013		/* check caller initialized locked */
1014		BUG_ON(*locked != 1);
1015	}
1016
1017	if (pages)
1018		flags |= FOLL_GET;
 
 
 
 
1019
1020	pages_done = 0;
1021	lock_dropped = false;
1022	for (;;) {
1023		ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages,
1024				       vmas, locked);
1025		if (!locked)
1026			/* VM_FAULT_RETRY couldn't trigger, bypass */
1027			return ret;
1028
1029		/* VM_FAULT_RETRY cannot return errors */
1030		if (!*locked) {
1031			BUG_ON(ret < 0);
1032			BUG_ON(ret >= nr_pages);
1033		}
1034
 
 
 
 
1035		if (ret > 0) {
1036			nr_pages -= ret;
1037			pages_done += ret;
1038			if (!nr_pages)
1039				break;
1040		}
1041		if (*locked) {
1042			/*
1043			 * VM_FAULT_RETRY didn't trigger or it was a
1044			 * FOLL_NOWAIT.
1045			 */
1046			if (!pages_done)
1047				pages_done = ret;
1048			break;
1049		}
1050		/*
1051		 * VM_FAULT_RETRY triggered, so seek to the faulting offset.
1052		 * For the prefault case (!pages) we only update counts.
1053		 */
1054		if (likely(pages))
1055			pages += ret;
1056		start += ret << PAGE_SHIFT;
1057
1058		/*
1059		 * Repeat on the address that fired VM_FAULT_RETRY
1060		 * without FAULT_FLAG_ALLOW_RETRY but with
1061		 * FAULT_FLAG_TRIED.
1062		 */
1063		*locked = 1;
1064		lock_dropped = true;
1065		down_read(&mm->mmap_sem);
1066		ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED,
1067				       pages, NULL, NULL);
1068		if (ret != 1) {
1069			BUG_ON(ret > 1);
1070			if (!pages_done)
1071				pages_done = ret;
1072			break;
1073		}
1074		nr_pages--;
1075		pages_done++;
1076		if (!nr_pages)
1077			break;
1078		if (likely(pages))
1079			pages++;
1080		start += PAGE_SIZE;
1081	}
1082	if (lock_dropped && *locked) {
1083		/*
1084		 * We must let the caller know we temporarily dropped the lock
1085		 * and so the critical section protected by it was lost.
1086		 */
1087		up_read(&mm->mmap_sem);
1088		*locked = 0;
1089	}
1090	return pages_done;
1091}
1092
1093/*
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1094 * get_user_pages_remote() - pin user pages in memory
1095 * @tsk:	the task_struct to use for page fault accounting, or
1096 *		NULL if faults are not to be recorded.
1097 * @mm:		mm_struct of target mm
1098 * @start:	starting user address
1099 * @nr_pages:	number of pages from start to pin
1100 * @gup_flags:	flags modifying lookup behaviour
 
 
1101 * @pages:	array that receives pointers to the pages pinned.
1102 *		Should be at least nr_pages long. Or NULL, if caller
1103 *		only intends to ensure the pages are faulted in.
1104 * @vmas:	array of pointers to vmas corresponding to each page.
1105 *		Or NULL if the caller does not require them.
1106 * @locked:	pointer to lock flag indicating whether lock is held and
1107 *		subsequently whether VM_FAULT_RETRY functionality can be
1108 *		utilised. Lock must initially be held.
1109 *
1110 * Returns number of pages pinned. This may be fewer than the number
1111 * requested. If nr_pages is 0 or negative, returns 0. If no pages
1112 * were pinned, returns -errno. Each page returned must be released
1113 * with a put_page() call when it is finished with. vmas will only
1114 * remain valid while mmap_sem is held.
1115 *
1116 * Must be called with mmap_sem held for read or write.
1117 *
1118 * get_user_pages walks a process's page tables and takes a reference to
1119 * each struct page that each user address corresponds to at a given
1120 * instant. That is, it takes the page that would be accessed if a user
1121 * thread accesses the given user virtual address at that instant.
1122 *
1123 * This does not guarantee that the page exists in the user mappings when
1124 * get_user_pages returns, and there may even be a completely different
1125 * page there in some cases (eg. if mmapped pagecache has been invalidated
1126 * and subsequently re faulted). However it does guarantee that the page
1127 * won't be freed completely. And mostly callers simply care that the page
1128 * contains data that was valid *at some point in time*. Typically, an IO
1129 * or similar operation cannot guarantee anything stronger anyway because
1130 * locks can't be held over the syscall boundary.
1131 *
1132 * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
1133 * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
1134 * be called after the page is finished with, and before put_page is called.
1135 *
1136 * get_user_pages is typically used for fewer-copy IO operations, to get a
1137 * handle on the memory by some means other than accesses via the user virtual
1138 * addresses. The pages may be submitted for DMA to devices or accessed via
1139 * their kernel linear mapping (via the kmap APIs). Care should be taken to
1140 * use the correct cache flushing APIs.
1141 *
1142 * See also get_user_pages_fast, for performance critical applications.
1143 *
1144 * get_user_pages should be phased out in favor of
1145 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
1146 * should use get_user_pages because it cannot pass
1147 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
1148 */
1149long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
1150		unsigned long start, unsigned long nr_pages,
1151		unsigned int gup_flags, struct page **pages,
1152		struct vm_area_struct **vmas, int *locked)
1153{
1154	/*
1155	 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
1156	 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
1157	 * vmas.  As there are no users of this flag in this call we simply
1158	 * disallow this option for now.
1159	 */
1160	if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
1161		return -EINVAL;
1162
1163	return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
1164				       locked,
1165				       gup_flags | FOLL_TOUCH | FOLL_REMOTE);
1166}
1167EXPORT_SYMBOL(get_user_pages_remote);
1168
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1169/**
1170 * populate_vma_page_range() -  populate a range of pages in the vma.
1171 * @vma:   target vma
1172 * @start: start address
1173 * @end:   end address
1174 * @nonblocking:
1175 *
1176 * This takes care of mlocking the pages too if VM_LOCKED is set.
1177 *
1178 * return 0 on success, negative error code on error.
1179 *
1180 * vma->vm_mm->mmap_sem must be held.
1181 *
1182 * If @nonblocking is NULL, it may be held for read or write and will
1183 * be unperturbed.
1184 *
1185 * If @nonblocking is non-NULL, it must held for read only and may be
1186 * released.  If it's released, *@nonblocking will be set to 0.
1187 */
1188long populate_vma_page_range(struct vm_area_struct *vma,
1189		unsigned long start, unsigned long end, int *nonblocking)
1190{
1191	struct mm_struct *mm = vma->vm_mm;
1192	unsigned long nr_pages = (end - start) / PAGE_SIZE;
1193	int gup_flags;
1194
1195	VM_BUG_ON(start & ~PAGE_MASK);
1196	VM_BUG_ON(end   & ~PAGE_MASK);
1197	VM_BUG_ON_VMA(start < vma->vm_start, vma);
1198	VM_BUG_ON_VMA(end   > vma->vm_end, vma);
1199	VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
1200
1201	gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
1202	if (vma->vm_flags & VM_LOCKONFAULT)
1203		gup_flags &= ~FOLL_POPULATE;
1204	/*
1205	 * We want to touch writable mappings with a write fault in order
1206	 * to break COW, except for shared mappings because these don't COW
1207	 * and we would not want to dirty them for nothing.
1208	 */
1209	if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
1210		gup_flags |= FOLL_WRITE;
1211
1212	/*
1213	 * We want mlock to succeed for regions that have any permissions
1214	 * other than PROT_NONE.
1215	 */
1216	if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
1217		gup_flags |= FOLL_FORCE;
1218
1219	/*
1220	 * We made sure addr is within a VMA, so the following will
1221	 * not result in a stack expansion that recurses back here.
1222	 */
1223	return __get_user_pages(current, mm, start, nr_pages, gup_flags,
1224				NULL, NULL, nonblocking);
1225}
1226
1227/*
1228 * __mm_populate - populate and/or mlock pages within a range of address space.
1229 *
1230 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
1231 * flags. VMAs must be already marked with the desired vm_flags, and
1232 * mmap_sem must not be held.
1233 */
1234int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
1235{
1236	struct mm_struct *mm = current->mm;
1237	unsigned long end, nstart, nend;
1238	struct vm_area_struct *vma = NULL;
1239	int locked = 0;
1240	long ret = 0;
1241
 
 
1242	end = start + len;
1243
1244	for (nstart = start; nstart < end; nstart = nend) {
1245		/*
1246		 * We want to fault in pages for [nstart; end) address range.
1247		 * Find first corresponding VMA.
1248		 */
1249		if (!locked) {
1250			locked = 1;
1251			down_read(&mm->mmap_sem);
1252			vma = find_vma(mm, nstart);
1253		} else if (nstart >= vma->vm_end)
1254			vma = vma->vm_next;
1255		if (!vma || vma->vm_start >= end)
1256			break;
1257		/*
1258		 * Set [nstart; nend) to intersection of desired address
1259		 * range with the first VMA. Also, skip undesirable VMA types.
1260		 */
1261		nend = min(end, vma->vm_end);
1262		if (vma->vm_flags & (VM_IO | VM_PFNMAP))
1263			continue;
1264		if (nstart < vma->vm_start)
1265			nstart = vma->vm_start;
1266		/*
1267		 * Now fault in a range of pages. populate_vma_page_range()
1268		 * double checks the vma flags, so that it won't mlock pages
1269		 * if the vma was already munlocked.
1270		 */
1271		ret = populate_vma_page_range(vma, nstart, nend, &locked);
1272		if (ret < 0) {
1273			if (ignore_errors) {
1274				ret = 0;
1275				continue;	/* continue at next VMA */
1276			}
1277			break;
1278		}
1279		nend = nstart + ret * PAGE_SIZE;
1280		ret = 0;
1281	}
1282	if (locked)
1283		up_read(&mm->mmap_sem);
1284	return ret;	/* 0 or negative error code */
1285}
1286
1287/**
1288 * get_dump_page() - pin user page in memory while writing it to core dump
1289 * @addr: user address
1290 *
1291 * Returns struct page pointer of user page pinned for dump,
1292 * to be freed afterwards by put_page().
1293 *
1294 * Returns NULL on any kind of failure - a hole must then be inserted into
1295 * the corefile, to preserve alignment with its headers; and also returns
1296 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1297 * allowing a hole to be left in the corefile to save diskspace.
1298 *
1299 * Called without mmap_sem, but after all other threads have been killed.
1300 */
1301#ifdef CONFIG_ELF_CORE
1302struct page *get_dump_page(unsigned long addr)
1303{
1304	struct vm_area_struct *vma;
1305	struct page *page;
1306
1307	if (__get_user_pages(current, current->mm, addr, 1,
1308			     FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
1309			     NULL) < 1)
1310		return NULL;
1311	flush_cache_page(vma, addr, page_to_pfn(page));
1312	return page;
1313}
1314#endif /* CONFIG_ELF_CORE */
1315#else /* CONFIG_MMU */
1316static long __get_user_pages_locked(struct task_struct *tsk,
1317		struct mm_struct *mm, unsigned long start,
1318		unsigned long nr_pages, struct page **pages,
1319		struct vm_area_struct **vmas, int *locked,
1320		unsigned int foll_flags)
1321{
1322	struct vm_area_struct *vma;
1323	unsigned long vm_flags;
1324	int i;
1325
1326	/* calculate required read or write permissions.
1327	 * If FOLL_FORCE is set, we only require the "MAY" flags.
1328	 */
1329	vm_flags  = (foll_flags & FOLL_WRITE) ?
1330			(VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
1331	vm_flags &= (foll_flags & FOLL_FORCE) ?
1332			(VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
1333
1334	for (i = 0; i < nr_pages; i++) {
1335		vma = find_vma(mm, start);
1336		if (!vma)
1337			goto finish_or_fault;
1338
1339		/* protect what we can, including chardevs */
1340		if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
1341		    !(vm_flags & vma->vm_flags))
1342			goto finish_or_fault;
1343
1344		if (pages) {
1345			pages[i] = virt_to_page(start);
1346			if (pages[i])
1347				get_page(pages[i]);
1348		}
1349		if (vmas)
1350			vmas[i] = vma;
1351		start = (start + PAGE_SIZE) & PAGE_MASK;
1352	}
1353
1354	return i;
1355
1356finish_or_fault:
1357	return i ? : -EFAULT;
1358}
1359#endif /* !CONFIG_MMU */
1360
1361#if defined(CONFIG_FS_DAX) || defined (CONFIG_CMA)
1362static bool check_dax_vmas(struct vm_area_struct **vmas, long nr_pages)
1363{
1364	long i;
1365	struct vm_area_struct *vma_prev = NULL;
1366
1367	for (i = 0; i < nr_pages; i++) {
1368		struct vm_area_struct *vma = vmas[i];
1369
1370		if (vma == vma_prev)
1371			continue;
1372
1373		vma_prev = vma;
1374
1375		if (vma_is_fsdax(vma))
1376			return true;
1377	}
1378	return false;
1379}
1380
1381#ifdef CONFIG_CMA
1382static struct page *new_non_cma_page(struct page *page, unsigned long private)
1383{
1384	/*
1385	 * We want to make sure we allocate the new page from the same node
1386	 * as the source page.
1387	 */
1388	int nid = page_to_nid(page);
1389	/*
1390	 * Trying to allocate a page for migration. Ignore allocation
1391	 * failure warnings. We don't force __GFP_THISNODE here because
1392	 * this node here is the node where we have CMA reservation and
1393	 * in some case these nodes will have really less non movable
1394	 * allocation memory.
1395	 */
1396	gfp_t gfp_mask = GFP_USER | __GFP_NOWARN;
1397
1398	if (PageHighMem(page))
1399		gfp_mask |= __GFP_HIGHMEM;
1400
1401#ifdef CONFIG_HUGETLB_PAGE
1402	if (PageHuge(page)) {
1403		struct hstate *h = page_hstate(page);
1404		/*
1405		 * We don't want to dequeue from the pool because pool pages will
1406		 * mostly be from the CMA region.
1407		 */
1408		return alloc_migrate_huge_page(h, gfp_mask, nid, NULL);
1409	}
1410#endif
1411	if (PageTransHuge(page)) {
1412		struct page *thp;
1413		/*
1414		 * ignore allocation failure warnings
1415		 */
1416		gfp_t thp_gfpmask = GFP_TRANSHUGE | __GFP_NOWARN;
1417
1418		/*
1419		 * Remove the movable mask so that we don't allocate from
1420		 * CMA area again.
1421		 */
1422		thp_gfpmask &= ~__GFP_MOVABLE;
1423		thp = __alloc_pages_node(nid, thp_gfpmask, HPAGE_PMD_ORDER);
1424		if (!thp)
1425			return NULL;
1426		prep_transhuge_page(thp);
1427		return thp;
1428	}
1429
1430	return __alloc_pages_node(nid, gfp_mask, 0);
1431}
1432
1433static long check_and_migrate_cma_pages(struct task_struct *tsk,
1434					struct mm_struct *mm,
1435					unsigned long start,
1436					unsigned long nr_pages,
1437					struct page **pages,
1438					struct vm_area_struct **vmas,
1439					unsigned int gup_flags)
1440{
1441	unsigned long i;
1442	unsigned long step;
1443	bool drain_allow = true;
1444	bool migrate_allow = true;
1445	LIST_HEAD(cma_page_list);
1446
1447check_again:
1448	for (i = 0; i < nr_pages;) {
1449
1450		struct page *head = compound_head(pages[i]);
1451
1452		/*
1453		 * gup may start from a tail page. Advance step by the left
1454		 * part.
1455		 */
1456		step = compound_nr(head) - (pages[i] - head);
1457		/*
1458		 * If we get a page from the CMA zone, since we are going to
1459		 * be pinning these entries, we might as well move them out
1460		 * of the CMA zone if possible.
1461		 */
1462		if (is_migrate_cma_page(head)) {
1463			if (PageHuge(head))
1464				isolate_huge_page(head, &cma_page_list);
1465			else {
1466				if (!PageLRU(head) && drain_allow) {
1467					lru_add_drain_all();
1468					drain_allow = false;
1469				}
1470
1471				if (!isolate_lru_page(head)) {
1472					list_add_tail(&head->lru, &cma_page_list);
1473					mod_node_page_state(page_pgdat(head),
1474							    NR_ISOLATED_ANON +
1475							    page_is_file_cache(head),
1476							    hpage_nr_pages(head));
1477				}
1478			}
1479		}
1480
1481		i += step;
1482	}
1483
1484	if (!list_empty(&cma_page_list)) {
1485		/*
1486		 * drop the above get_user_pages reference.
1487		 */
1488		for (i = 0; i < nr_pages; i++)
1489			put_page(pages[i]);
1490
1491		if (migrate_pages(&cma_page_list, new_non_cma_page,
1492				  NULL, 0, MIGRATE_SYNC, MR_CONTIG_RANGE)) {
1493			/*
1494			 * some of the pages failed migration. Do get_user_pages
1495			 * without migration.
1496			 */
1497			migrate_allow = false;
1498
1499			if (!list_empty(&cma_page_list))
1500				putback_movable_pages(&cma_page_list);
1501		}
1502		/*
1503		 * We did migrate all the pages, Try to get the page references
1504		 * again migrating any new CMA pages which we failed to isolate
1505		 * earlier.
1506		 */
1507		nr_pages = __get_user_pages_locked(tsk, mm, start, nr_pages,
1508						   pages, vmas, NULL,
1509						   gup_flags);
1510
1511		if ((nr_pages > 0) && migrate_allow) {
1512			drain_allow = true;
1513			goto check_again;
1514		}
1515	}
1516
1517	return nr_pages;
1518}
1519#else
1520static long check_and_migrate_cma_pages(struct task_struct *tsk,
1521					struct mm_struct *mm,
1522					unsigned long start,
1523					unsigned long nr_pages,
1524					struct page **pages,
1525					struct vm_area_struct **vmas,
1526					unsigned int gup_flags)
1527{
1528	return nr_pages;
1529}
1530#endif /* CONFIG_CMA */
1531
1532/*
1533 * __gup_longterm_locked() is a wrapper for __get_user_pages_locked which
1534 * allows us to process the FOLL_LONGTERM flag.
1535 */
1536static long __gup_longterm_locked(struct task_struct *tsk,
1537				  struct mm_struct *mm,
1538				  unsigned long start,
1539				  unsigned long nr_pages,
1540				  struct page **pages,
1541				  struct vm_area_struct **vmas,
1542				  unsigned int gup_flags)
1543{
1544	struct vm_area_struct **vmas_tmp = vmas;
1545	unsigned long flags = 0;
1546	long rc, i;
1547
1548	if (gup_flags & FOLL_LONGTERM) {
1549		if (!pages)
1550			return -EINVAL;
1551
1552		if (!vmas_tmp) {
1553			vmas_tmp = kcalloc(nr_pages,
1554					   sizeof(struct vm_area_struct *),
1555					   GFP_KERNEL);
1556			if (!vmas_tmp)
1557				return -ENOMEM;
1558		}
1559		flags = memalloc_nocma_save();
1560	}
1561
1562	rc = __get_user_pages_locked(tsk, mm, start, nr_pages, pages,
1563				     vmas_tmp, NULL, gup_flags);
1564
1565	if (gup_flags & FOLL_LONGTERM) {
1566		memalloc_nocma_restore(flags);
1567		if (rc < 0)
1568			goto out;
1569
1570		if (check_dax_vmas(vmas_tmp, rc)) {
1571			for (i = 0; i < rc; i++)
1572				put_page(pages[i]);
1573			rc = -EOPNOTSUPP;
1574			goto out;
1575		}
1576
1577		rc = check_and_migrate_cma_pages(tsk, mm, start, rc, pages,
1578						 vmas_tmp, gup_flags);
1579	}
1580
1581out:
1582	if (vmas_tmp != vmas)
1583		kfree(vmas_tmp);
1584	return rc;
1585}
1586#else /* !CONFIG_FS_DAX && !CONFIG_CMA */
1587static __always_inline long __gup_longterm_locked(struct task_struct *tsk,
1588						  struct mm_struct *mm,
1589						  unsigned long start,
1590						  unsigned long nr_pages,
1591						  struct page **pages,
1592						  struct vm_area_struct **vmas,
1593						  unsigned int flags)
1594{
1595	return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
1596				       NULL, flags);
1597}
1598#endif /* CONFIG_FS_DAX || CONFIG_CMA */
1599
1600/*
1601 * This is the same as get_user_pages_remote(), just with a
1602 * less-flexible calling convention where we assume that the task
1603 * and mm being operated on are the current task's and don't allow
1604 * passing of a locked parameter.  We also obviously don't pass
1605 * FOLL_REMOTE in here.
1606 */
1607long get_user_pages(unsigned long start, unsigned long nr_pages,
1608		unsigned int gup_flags, struct page **pages,
1609		struct vm_area_struct **vmas)
1610{
1611	return __gup_longterm_locked(current, current->mm, start, nr_pages,
1612				     pages, vmas, gup_flags | FOLL_TOUCH);
1613}
1614EXPORT_SYMBOL(get_user_pages);
1615
1616/*
1617 * We can leverage the VM_FAULT_RETRY functionality in the page fault
1618 * paths better by using either get_user_pages_locked() or
1619 * get_user_pages_unlocked().
1620 *
1621 * get_user_pages_locked() is suitable to replace the form:
1622 *
1623 *      down_read(&mm->mmap_sem);
1624 *      do_something()
1625 *      get_user_pages(tsk, mm, ..., pages, NULL);
1626 *      up_read(&mm->mmap_sem);
1627 *
1628 *  to:
1629 *
1630 *      int locked = 1;
1631 *      down_read(&mm->mmap_sem);
1632 *      do_something()
1633 *      get_user_pages_locked(tsk, mm, ..., pages, &locked);
1634 *      if (locked)
1635 *          up_read(&mm->mmap_sem);
1636 */
1637long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
1638			   unsigned int gup_flags, struct page **pages,
1639			   int *locked)
1640{
1641	/*
1642	 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
1643	 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
1644	 * vmas.  As there are no users of this flag in this call we simply
1645	 * disallow this option for now.
1646	 */
1647	if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
1648		return -EINVAL;
1649
1650	return __get_user_pages_locked(current, current->mm, start, nr_pages,
1651				       pages, NULL, locked,
1652				       gup_flags | FOLL_TOUCH);
1653}
1654EXPORT_SYMBOL(get_user_pages_locked);
1655
1656/*
1657 * get_user_pages_unlocked() is suitable to replace the form:
1658 *
1659 *      down_read(&mm->mmap_sem);
1660 *      get_user_pages(tsk, mm, ..., pages, NULL);
1661 *      up_read(&mm->mmap_sem);
1662 *
1663 *  with:
1664 *
1665 *      get_user_pages_unlocked(tsk, mm, ..., pages);
1666 *
1667 * It is functionally equivalent to get_user_pages_fast so
1668 * get_user_pages_fast should be used instead if specific gup_flags
1669 * (e.g. FOLL_FORCE) are not required.
1670 */
1671long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
1672			     struct page **pages, unsigned int gup_flags)
1673{
1674	struct mm_struct *mm = current->mm;
1675	int locked = 1;
1676	long ret;
1677
1678	/*
1679	 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
1680	 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
1681	 * vmas.  As there are no users of this flag in this call we simply
1682	 * disallow this option for now.
1683	 */
1684	if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
1685		return -EINVAL;
1686
1687	down_read(&mm->mmap_sem);
1688	ret = __get_user_pages_locked(current, mm, start, nr_pages, pages, NULL,
1689				      &locked, gup_flags | FOLL_TOUCH);
1690	if (locked)
1691		up_read(&mm->mmap_sem);
1692	return ret;
1693}
1694EXPORT_SYMBOL(get_user_pages_unlocked);
1695
1696/*
1697 * Fast GUP
1698 *
1699 * get_user_pages_fast attempts to pin user pages by walking the page
1700 * tables directly and avoids taking locks. Thus the walker needs to be
1701 * protected from page table pages being freed from under it, and should
1702 * block any THP splits.
1703 *
1704 * One way to achieve this is to have the walker disable interrupts, and
1705 * rely on IPIs from the TLB flushing code blocking before the page table
1706 * pages are freed. This is unsuitable for architectures that do not need
1707 * to broadcast an IPI when invalidating TLBs.
1708 *
1709 * Another way to achieve this is to batch up page table containing pages
1710 * belonging to more than one mm_user, then rcu_sched a callback to free those
1711 * pages. Disabling interrupts will allow the fast_gup walker to both block
1712 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
1713 * (which is a relatively rare event). The code below adopts this strategy.
1714 *
1715 * Before activating this code, please be aware that the following assumptions
1716 * are currently made:
1717 *
1718 *  *) Either HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to
1719 *  free pages containing page tables or TLB flushing requires IPI broadcast.
1720 *
1721 *  *) ptes can be read atomically by the architecture.
1722 *
1723 *  *) access_ok is sufficient to validate userspace address ranges.
1724 *
1725 * The last two assumptions can be relaxed by the addition of helper functions.
1726 *
1727 * This code is based heavily on the PowerPC implementation by Nick Piggin.
1728 */
1729#ifdef CONFIG_HAVE_FAST_GUP
1730#ifdef CONFIG_GUP_GET_PTE_LOW_HIGH
1731/*
1732 * WARNING: only to be used in the get_user_pages_fast() implementation.
1733 *
1734 * With get_user_pages_fast(), we walk down the pagetables without taking any
1735 * locks.  For this we would like to load the pointers atomically, but sometimes
1736 * that is not possible (e.g. without expensive cmpxchg8b on x86_32 PAE).  What
1737 * we do have is the guarantee that a PTE will only either go from not present
1738 * to present, or present to not present or both -- it will not switch to a
1739 * completely different present page without a TLB flush in between; something
1740 * that we are blocking by holding interrupts off.
1741 *
1742 * Setting ptes from not present to present goes:
1743 *
1744 *   ptep->pte_high = h;
1745 *   smp_wmb();
1746 *   ptep->pte_low = l;
1747 *
1748 * And present to not present goes:
1749 *
1750 *   ptep->pte_low = 0;
1751 *   smp_wmb();
1752 *   ptep->pte_high = 0;
1753 *
1754 * We must ensure here that the load of pte_low sees 'l' IFF pte_high sees 'h'.
1755 * We load pte_high *after* loading pte_low, which ensures we don't see an older
1756 * value of pte_high.  *Then* we recheck pte_low, which ensures that we haven't
1757 * picked up a changed pte high. We might have gotten rubbish values from
1758 * pte_low and pte_high, but we are guaranteed that pte_low will not have the
1759 * present bit set *unless* it is 'l'. Because get_user_pages_fast() only
1760 * operates on present ptes we're safe.
1761 */
1762static inline pte_t gup_get_pte(pte_t *ptep)
1763{
1764	pte_t pte;
1765
1766	do {
1767		pte.pte_low = ptep->pte_low;
1768		smp_rmb();
1769		pte.pte_high = ptep->pte_high;
1770		smp_rmb();
1771	} while (unlikely(pte.pte_low != ptep->pte_low));
1772
1773	return pte;
1774}
1775#else /* CONFIG_GUP_GET_PTE_LOW_HIGH */
1776/*
1777 * We require that the PTE can be read atomically.
1778 */
1779static inline pte_t gup_get_pte(pte_t *ptep)
1780{
1781	return READ_ONCE(*ptep);
1782}
1783#endif /* CONFIG_GUP_GET_PTE_LOW_HIGH */
1784
1785static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start,
1786					    struct page **pages)
1787{
1788	while ((*nr) - nr_start) {
1789		struct page *page = pages[--(*nr)];
1790
1791		ClearPageReferenced(page);
1792		put_page(page);
1793	}
1794}
1795
1796/*
1797 * Return the compund head page with ref appropriately incremented,
1798 * or NULL if that failed.
1799 */
1800static inline struct page *try_get_compound_head(struct page *page, int refs)
1801{
1802	struct page *head = compound_head(page);
1803	if (WARN_ON_ONCE(page_ref_count(head) < 0))
1804		return NULL;
1805	if (unlikely(!page_cache_add_speculative(head, refs)))
1806		return NULL;
1807	return head;
1808}
1809
1810#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
1811static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1812			 unsigned int flags, struct page **pages, int *nr)
1813{
1814	struct dev_pagemap *pgmap = NULL;
1815	int nr_start = *nr, ret = 0;
1816	pte_t *ptep, *ptem;
 
1817
1818	ptem = ptep = pte_offset_map(&pmd, addr);
1819	do {
1820		pte_t pte = gup_get_pte(ptep);
 
 
 
 
 
 
 
1821		struct page *head, *page;
1822
1823		/*
1824		 * Similar to the PMD case below, NUMA hinting must take slow
1825		 * path using the pte_protnone check.
1826		 */
1827		if (pte_protnone(pte))
 
1828			goto pte_unmap;
1829
1830		if (!pte_access_permitted(pte, flags & FOLL_WRITE))
1831			goto pte_unmap;
1832
1833		if (pte_devmap(pte)) {
1834			if (unlikely(flags & FOLL_LONGTERM))
1835				goto pte_unmap;
1836
1837			pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
1838			if (unlikely(!pgmap)) {
1839				undo_dev_pagemap(nr, nr_start, pages);
1840				goto pte_unmap;
1841			}
1842		} else if (pte_special(pte))
1843			goto pte_unmap;
1844
1845		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
1846		page = pte_page(pte);
 
1847
1848		head = try_get_compound_head(page, 1);
1849		if (!head)
1850			goto pte_unmap;
1851
1852		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
1853			put_page(head);
1854			goto pte_unmap;
1855		}
1856
1857		VM_BUG_ON_PAGE(compound_head(page) != head, page);
1858
1859		SetPageReferenced(page);
1860		pages[*nr] = page;
1861		(*nr)++;
1862
1863	} while (ptep++, addr += PAGE_SIZE, addr != end);
1864
1865	ret = 1;
1866
1867pte_unmap:
1868	if (pgmap)
1869		put_dev_pagemap(pgmap);
1870	pte_unmap(ptem);
1871	return ret;
1872}
1873#else
1874
1875/*
1876 * If we can't determine whether or not a pte is special, then fail immediately
1877 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
1878 * to be special.
1879 *
1880 * For a futex to be placed on a THP tail page, get_futex_key requires a
1881 * __get_user_pages_fast implementation that can pin pages. Thus it's still
1882 * useful to have gup_huge_pmd even if we can't operate on ptes.
1883 */
1884static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1885			 unsigned int flags, struct page **pages, int *nr)
1886{
1887	return 0;
1888}
1889#endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
1890
1891#if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
1892static int __gup_device_huge(unsigned long pfn, unsigned long addr,
1893		unsigned long end, struct page **pages, int *nr)
1894{
1895	int nr_start = *nr;
1896	struct dev_pagemap *pgmap = NULL;
1897
1898	do {
1899		struct page *page = pfn_to_page(pfn);
1900
1901		pgmap = get_dev_pagemap(pfn, pgmap);
1902		if (unlikely(!pgmap)) {
1903			undo_dev_pagemap(nr, nr_start, pages);
1904			return 0;
1905		}
1906		SetPageReferenced(page);
1907		pages[*nr] = page;
1908		get_page(page);
1909		(*nr)++;
1910		pfn++;
1911	} while (addr += PAGE_SIZE, addr != end);
1912
1913	if (pgmap)
1914		put_dev_pagemap(pgmap);
1915	return 1;
1916}
1917
1918static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
1919		unsigned long end, struct page **pages, int *nr)
1920{
1921	unsigned long fault_pfn;
1922	int nr_start = *nr;
1923
1924	fault_pfn = pmd_pfn(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
1925	if (!__gup_device_huge(fault_pfn, addr, end, pages, nr))
1926		return 0;
1927
1928	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
1929		undo_dev_pagemap(nr, nr_start, pages);
1930		return 0;
1931	}
1932	return 1;
1933}
1934
1935static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
1936		unsigned long end, struct page **pages, int *nr)
1937{
1938	unsigned long fault_pfn;
1939	int nr_start = *nr;
1940
1941	fault_pfn = pud_pfn(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
1942	if (!__gup_device_huge(fault_pfn, addr, end, pages, nr))
1943		return 0;
1944
1945	if (unlikely(pud_val(orig) != pud_val(*pudp))) {
1946		undo_dev_pagemap(nr, nr_start, pages);
1947		return 0;
1948	}
1949	return 1;
1950}
1951#else
1952static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
1953		unsigned long end, struct page **pages, int *nr)
1954{
1955	BUILD_BUG();
1956	return 0;
1957}
1958
1959static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
1960		unsigned long end, struct page **pages, int *nr)
1961{
1962	BUILD_BUG();
1963	return 0;
1964}
1965#endif
1966
1967#ifdef CONFIG_ARCH_HAS_HUGEPD
1968static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
1969				      unsigned long sz)
1970{
1971	unsigned long __boundary = (addr + sz) & ~(sz-1);
1972	return (__boundary - 1 < end - 1) ? __boundary : end;
1973}
1974
1975static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
1976		       unsigned long end, unsigned int flags,
1977		       struct page **pages, int *nr)
1978{
1979	unsigned long pte_end;
1980	struct page *head, *page;
1981	pte_t pte;
1982	int refs;
1983
1984	pte_end = (addr + sz) & ~(sz-1);
1985	if (pte_end < end)
1986		end = pte_end;
1987
1988	pte = READ_ONCE(*ptep);
1989
1990	if (!pte_access_permitted(pte, flags & FOLL_WRITE))
1991		return 0;
1992
1993	/* hugepages are never "special" */
1994	VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
1995
1996	refs = 0;
1997	head = pte_page(pte);
1998
1999	page = head + ((addr & (sz-1)) >> PAGE_SHIFT);
2000	do {
2001		VM_BUG_ON(compound_head(page) != head);
2002		pages[*nr] = page;
2003		(*nr)++;
2004		page++;
2005		refs++;
2006	} while (addr += PAGE_SIZE, addr != end);
2007
2008	head = try_get_compound_head(head, refs);
2009	if (!head) {
2010		*nr -= refs;
2011		return 0;
2012	}
2013
2014	if (unlikely(pte_val(pte) != pte_val(*ptep))) {
2015		/* Could be optimized better */
2016		*nr -= refs;
2017		while (refs--)
2018			put_page(head);
2019		return 0;
2020	}
2021
2022	SetPageReferenced(head);
2023	return 1;
2024}
2025
2026static int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
2027		unsigned int pdshift, unsigned long end, unsigned int flags,
2028		struct page **pages, int *nr)
2029{
2030	pte_t *ptep;
2031	unsigned long sz = 1UL << hugepd_shift(hugepd);
2032	unsigned long next;
2033
2034	ptep = hugepte_offset(hugepd, addr, pdshift);
2035	do {
2036		next = hugepte_addr_end(addr, end, sz);
2037		if (!gup_hugepte(ptep, sz, addr, end, flags, pages, nr))
2038			return 0;
2039	} while (ptep++, addr = next, addr != end);
2040
2041	return 1;
2042}
2043#else
2044static inline int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
2045		unsigned int pdshift, unsigned long end, unsigned int flags,
2046		struct page **pages, int *nr)
2047{
2048	return 0;
2049}
2050#endif /* CONFIG_ARCH_HAS_HUGEPD */
2051
2052static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2053			unsigned long end, unsigned int flags,
2054			struct page **pages, int *nr)
2055{
2056	struct page *head, *page;
2057	int refs;
2058
2059	if (!pmd_access_permitted(orig, flags & FOLL_WRITE))
2060		return 0;
2061
2062	if (pmd_devmap(orig)) {
2063		if (unlikely(flags & FOLL_LONGTERM))
2064			return 0;
2065		return __gup_device_huge_pmd(orig, pmdp, addr, end, pages, nr);
2066	}
2067
2068	refs = 0;
2069	page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
 
2070	do {
 
2071		pages[*nr] = page;
2072		(*nr)++;
2073		page++;
2074		refs++;
2075	} while (addr += PAGE_SIZE, addr != end);
2076
2077	head = try_get_compound_head(pmd_page(orig), refs);
2078	if (!head) {
2079		*nr -= refs;
2080		return 0;
2081	}
2082
2083	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
2084		*nr -= refs;
2085		while (refs--)
2086			put_page(head);
2087		return 0;
2088	}
2089
2090	SetPageReferenced(head);
2091	return 1;
2092}
2093
2094static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
2095		unsigned long end, unsigned int flags, struct page **pages, int *nr)
2096{
2097	struct page *head, *page;
2098	int refs;
2099
2100	if (!pud_access_permitted(orig, flags & FOLL_WRITE))
2101		return 0;
2102
2103	if (pud_devmap(orig)) {
2104		if (unlikely(flags & FOLL_LONGTERM))
2105			return 0;
2106		return __gup_device_huge_pud(orig, pudp, addr, end, pages, nr);
2107	}
2108
2109	refs = 0;
2110	page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
 
2111	do {
 
2112		pages[*nr] = page;
2113		(*nr)++;
2114		page++;
2115		refs++;
2116	} while (addr += PAGE_SIZE, addr != end);
2117
2118	head = try_get_compound_head(pud_page(orig), refs);
2119	if (!head) {
2120		*nr -= refs;
2121		return 0;
2122	}
2123
2124	if (unlikely(pud_val(orig) != pud_val(*pudp))) {
2125		*nr -= refs;
2126		while (refs--)
2127			put_page(head);
2128		return 0;
2129	}
2130
2131	SetPageReferenced(head);
2132	return 1;
2133}
2134
2135static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
2136			unsigned long end, unsigned int flags,
2137			struct page **pages, int *nr)
2138{
2139	int refs;
2140	struct page *head, *page;
2141
2142	if (!pgd_access_permitted(orig, flags & FOLL_WRITE))
2143		return 0;
2144
2145	BUILD_BUG_ON(pgd_devmap(orig));
2146	refs = 0;
2147	page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
 
2148	do {
 
2149		pages[*nr] = page;
2150		(*nr)++;
2151		page++;
2152		refs++;
2153	} while (addr += PAGE_SIZE, addr != end);
2154
2155	head = try_get_compound_head(pgd_page(orig), refs);
2156	if (!head) {
2157		*nr -= refs;
2158		return 0;
2159	}
2160
2161	if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
2162		*nr -= refs;
2163		while (refs--)
2164			put_page(head);
2165		return 0;
2166	}
2167
2168	SetPageReferenced(head);
2169	return 1;
2170}
2171
2172static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
2173		unsigned int flags, struct page **pages, int *nr)
2174{
2175	unsigned long next;
2176	pmd_t *pmdp;
2177
2178	pmdp = pmd_offset(&pud, addr);
2179	do {
2180		pmd_t pmd = READ_ONCE(*pmdp);
2181
2182		next = pmd_addr_end(addr, end);
2183		if (!pmd_present(pmd))
2184			return 0;
2185
2186		if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) ||
2187			     pmd_devmap(pmd))) {
2188			/*
2189			 * NUMA hinting faults need to be handled in the GUP
2190			 * slowpath for accounting purposes and so that they
2191			 * can be serialised against THP migration.
2192			 */
2193			if (pmd_protnone(pmd))
2194				return 0;
2195
2196			if (!gup_huge_pmd(pmd, pmdp, addr, next, flags,
2197				pages, nr))
2198				return 0;
2199
2200		} else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
2201			/*
2202			 * architecture have different format for hugetlbfs
2203			 * pmd format and THP pmd format
2204			 */
2205			if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
2206					 PMD_SHIFT, next, flags, pages, nr))
 
 
2207				return 0;
2208		} else if (!gup_pte_range(pmd, addr, next, flags, pages, nr))
2209			return 0;
2210	} while (pmdp++, addr = next, addr != end);
2211
2212	return 1;
2213}
2214
2215static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
2216			 unsigned int flags, struct page **pages, int *nr)
2217{
2218	unsigned long next;
2219	pud_t *pudp;
2220
2221	pudp = pud_offset(&p4d, addr);
2222	do {
2223		pud_t pud = READ_ONCE(*pudp);
2224
2225		next = pud_addr_end(addr, end);
2226		if (pud_none(pud))
2227			return 0;
2228		if (unlikely(pud_huge(pud))) {
2229			if (!gup_huge_pud(pud, pudp, addr, next, flags,
2230					  pages, nr))
2231				return 0;
2232		} else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
2233			if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
2234					 PUD_SHIFT, next, flags, pages, nr))
2235				return 0;
2236		} else if (!gup_pmd_range(pud, addr, next, flags, pages, nr))
2237			return 0;
2238	} while (pudp++, addr = next, addr != end);
2239
2240	return 1;
2241}
2242
2243static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end,
2244			 unsigned int flags, struct page **pages, int *nr)
2245{
2246	unsigned long next;
2247	p4d_t *p4dp;
2248
2249	p4dp = p4d_offset(&pgd, addr);
2250	do {
2251		p4d_t p4d = READ_ONCE(*p4dp);
2252
2253		next = p4d_addr_end(addr, end);
2254		if (p4d_none(p4d))
2255			return 0;
2256		BUILD_BUG_ON(p4d_huge(p4d));
2257		if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {
2258			if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
2259					 P4D_SHIFT, next, flags, pages, nr))
2260				return 0;
2261		} else if (!gup_pud_range(p4d, addr, next, flags, pages, nr))
2262			return 0;
2263	} while (p4dp++, addr = next, addr != end);
2264
2265	return 1;
2266}
2267
2268static void gup_pgd_range(unsigned long addr, unsigned long end,
2269		unsigned int flags, struct page **pages, int *nr)
2270{
2271	unsigned long next;
2272	pgd_t *pgdp;
2273
2274	pgdp = pgd_offset(current->mm, addr);
2275	do {
2276		pgd_t pgd = READ_ONCE(*pgdp);
2277
2278		next = pgd_addr_end(addr, end);
2279		if (pgd_none(pgd))
2280			return;
2281		if (unlikely(pgd_huge(pgd))) {
2282			if (!gup_huge_pgd(pgd, pgdp, addr, next, flags,
2283					  pages, nr))
2284				return;
2285		} else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
2286			if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
2287					 PGDIR_SHIFT, next, flags, pages, nr))
2288				return;
2289		} else if (!gup_p4d_range(pgd, addr, next, flags, pages, nr))
2290			return;
2291	} while (pgdp++, addr = next, addr != end);
2292}
2293#else
2294static inline void gup_pgd_range(unsigned long addr, unsigned long end,
2295		unsigned int flags, struct page **pages, int *nr)
2296{
2297}
2298#endif /* CONFIG_HAVE_FAST_GUP */
2299
2300#ifndef gup_fast_permitted
2301/*
2302 * Check if it's allowed to use __get_user_pages_fast() for the range, or
2303 * we need to fall back to the slow version:
2304 */
2305static bool gup_fast_permitted(unsigned long start, unsigned long end)
2306{
2307	return true;
2308}
2309#endif
2310
2311/*
2312 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
2313 * the regular GUP.
2314 * Note a difference with get_user_pages_fast: this always returns the
2315 * number of pages pinned, 0 if no pages were pinned.
2316 *
2317 * If the architecture does not support this function, simply return with no
2318 * pages pinned.
2319 */
2320int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
2321			  struct page **pages)
2322{
2323	unsigned long len, end;
2324	unsigned long flags;
 
 
2325	int nr = 0;
2326
2327	start = untagged_addr(start) & PAGE_MASK;
 
2328	len = (unsigned long) nr_pages << PAGE_SHIFT;
2329	end = start + len;
2330
2331	if (end <= start)
2332		return 0;
2333	if (unlikely(!access_ok((void __user *)start, len)))
2334		return 0;
2335
2336	/*
2337	 * Disable interrupts.  We use the nested form as we can already have
2338	 * interrupts disabled by get_futex_key.
2339	 *
2340	 * With interrupts disabled, we block page table pages from being
2341	 * freed from under us. See struct mmu_table_batch comments in
2342	 * include/asm-generic/tlb.h for more details.
2343	 *
2344	 * We do not adopt an rcu_read_lock(.) here as we also want to
2345	 * block IPIs that come from THPs splitting.
2346	 */
2347
2348	if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) &&
2349	    gup_fast_permitted(start, end)) {
2350		local_irq_save(flags);
2351		gup_pgd_range(start, end, write ? FOLL_WRITE : 0, pages, &nr);
2352		local_irq_restore(flags);
2353	}
2354
2355	return nr;
2356}
2357EXPORT_SYMBOL_GPL(__get_user_pages_fast);
2358
2359static int __gup_longterm_unlocked(unsigned long start, int nr_pages,
2360				   unsigned int gup_flags, struct page **pages)
2361{
2362	int ret;
2363
2364	/*
2365	 * FIXME: FOLL_LONGTERM does not work with
2366	 * get_user_pages_unlocked() (see comments in that function)
2367	 */
2368	if (gup_flags & FOLL_LONGTERM) {
2369		down_read(&current->mm->mmap_sem);
2370		ret = __gup_longterm_locked(current, current->mm,
2371					    start, nr_pages,
2372					    pages, NULL, gup_flags);
2373		up_read(&current->mm->mmap_sem);
2374	} else {
2375		ret = get_user_pages_unlocked(start, nr_pages,
2376					      pages, gup_flags);
2377	}
 
2378
2379	return ret;
2380}
2381
2382/**
2383 * get_user_pages_fast() - pin user pages in memory
2384 * @start:	starting user address
2385 * @nr_pages:	number of pages from start to pin
2386 * @gup_flags:	flags modifying pin behaviour
2387 * @pages:	array that receives pointers to the pages pinned.
2388 *		Should be at least nr_pages long.
2389 *
2390 * Attempt to pin user pages in memory without taking mm->mmap_sem.
2391 * If not successful, it will fall back to taking the lock and
2392 * calling get_user_pages().
2393 *
2394 * Returns number of pages pinned. This may be fewer than the number
2395 * requested. If nr_pages is 0 or negative, returns 0. If no pages
2396 * were pinned, returns -errno.
2397 */
2398int get_user_pages_fast(unsigned long start, int nr_pages,
2399			unsigned int gup_flags, struct page **pages)
2400{
2401	unsigned long addr, len, end;
2402	int nr = 0, ret = 0;
2403
2404	if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM)))
2405		return -EINVAL;
2406
2407	start = untagged_addr(start) & PAGE_MASK;
2408	addr = start;
2409	len = (unsigned long) nr_pages << PAGE_SHIFT;
2410	end = start + len;
2411
2412	if (end <= start)
2413		return 0;
2414	if (unlikely(!access_ok((void __user *)start, len)))
2415		return -EFAULT;
2416
2417	if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) &&
2418	    gup_fast_permitted(start, end)) {
2419		local_irq_disable();
2420		gup_pgd_range(addr, end, gup_flags, pages, &nr);
2421		local_irq_enable();
2422		ret = nr;
2423	}
2424
2425	if (nr < nr_pages) {
2426		/* Try to get the remaining pages with get_user_pages */
2427		start += nr << PAGE_SHIFT;
2428		pages += nr;
2429
2430		ret = __gup_longterm_unlocked(start, nr_pages - nr,
2431					      gup_flags, pages);
2432
2433		/* Have to be a bit careful with return values */
2434		if (nr > 0) {
2435			if (ret < 0)
2436				ret = nr;
2437			else
2438				ret += nr;
2439		}
2440	}
2441
2442	return ret;
2443}
2444EXPORT_SYMBOL_GPL(get_user_pages_fast);