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