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