linux/mm/gup.c
Peter Xu 607c63195d mm/gup: drop gup_fast_folio_allowed() in hugepd processing
Hugepd format for GUP is only used in PowerPC with hugetlbfs.  There are
some kernel usage of hugepd (can refer to hugepd_populate_kernel() for
PPC_8XX), however those pages are not candidates for GUP.

Commit a6e79df92e ("mm/gup: disallow FOLL_LONGTERM GUP-fast writing to
file-backed mappings") added a check to fail gup-fast if there's potential
risk of violating GUP over writeback file systems.  That should never
apply to hugepd.  Considering that hugepd is an old format (and even
software-only), there's no plan to extend hugepd into other file typed
memories that is prone to the same issue.

Drop that check, not only because it'll never be true for hugepd per any
known plan, but also it paves way for reusing the function outside
fast-gup.

To make sure we'll still remember this issue just in case hugepd will be
extended to support non-hugetlbfs memories, add a rich comment above
gup_huge_pd(), explaining the issue with proper references.

[akpm@linux-foundation.org: fix comment, per David]
Link: https://lkml.kernel.org/r/20240327152332.950956-7-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Tested-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrew Jones <andrew.jones@linux.dev>
Cc: Aneesh Kumar K.V (IBM) <aneesh.kumar@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: "Mike Rapoport (IBM)" <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-04-25 20:56:21 -07:00

3439 lines
97 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/spinlock.h>
#include <linux/mm.h>
#include <linux/memremap.h>
#include <linux/pagemap.h>
#include <linux/rmap.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/secretmem.h>
#include <linux/sched/signal.h>
#include <linux/rwsem.h>
#include <linux/hugetlb.h>
#include <linux/migrate.h>
#include <linux/mm_inline.h>
#include <linux/sched/mm.h>
#include <linux/shmem_fs.h>
#include <asm/mmu_context.h>
#include <asm/tlbflush.h>
#include "internal.h"
struct follow_page_context {
struct dev_pagemap *pgmap;
unsigned int page_mask;
};
static inline void sanity_check_pinned_pages(struct page **pages,
unsigned long npages)
{
if (!IS_ENABLED(CONFIG_DEBUG_VM))
return;
/*
* We only pin anonymous pages if they are exclusive. Once pinned, we
* can no longer turn them possibly shared and PageAnonExclusive() will
* stick around until the page is freed.
*
* We'd like to verify that our pinned anonymous pages are still mapped
* exclusively. The issue with anon THP is that we don't know how
* they are/were mapped when pinning them. However, for anon
* THP we can assume that either the given page (PTE-mapped THP) or
* the head page (PMD-mapped THP) should be PageAnonExclusive(). If
* neither is the case, there is certainly something wrong.
*/
for (; npages; npages--, pages++) {
struct page *page = *pages;
struct folio *folio = page_folio(page);
if (is_zero_page(page) ||
!folio_test_anon(folio))
continue;
if (!folio_test_large(folio) || folio_test_hugetlb(folio))
VM_BUG_ON_PAGE(!PageAnonExclusive(&folio->page), page);
else
/* Either a PTE-mapped or a PMD-mapped THP. */
VM_BUG_ON_PAGE(!PageAnonExclusive(&folio->page) &&
!PageAnonExclusive(page), page);
}
}
/*
* Return the folio with ref appropriately incremented,
* or NULL if that failed.
*/
static inline struct folio *try_get_folio(struct page *page, int refs)
{
struct folio *folio;
retry:
folio = page_folio(page);
if (WARN_ON_ONCE(folio_ref_count(folio) < 0))
return NULL;
if (unlikely(!folio_ref_try_add_rcu(folio, refs)))
return NULL;
/*
* At this point we have a stable reference to the folio; but it
* could be that between calling page_folio() and the refcount
* increment, the folio was split, in which case we'd end up
* holding a reference on a folio that has nothing to do with the page
* we were given anymore.
* So now that the folio is stable, recheck that the page still
* belongs to this folio.
*/
if (unlikely(page_folio(page) != folio)) {
if (!put_devmap_managed_page_refs(&folio->page, refs))
folio_put_refs(folio, refs);
goto retry;
}
return folio;
}
/**
* try_grab_folio() - Attempt to get or pin a folio.
* @page: pointer to page to be grabbed
* @refs: the value to (effectively) add to the folio's refcount
* @flags: gup flags: these are the FOLL_* flag values.
*
* "grab" names in this file mean, "look at flags to decide whether to use
* FOLL_PIN or FOLL_GET behavior, when incrementing the folio's refcount.
*
* Either FOLL_PIN or FOLL_GET (or neither) must be set, but not both at the
* same time. (That's true throughout the get_user_pages*() and
* pin_user_pages*() APIs.) Cases:
*
* FOLL_GET: folio's refcount will be incremented by @refs.
*
* FOLL_PIN on large folios: folio's refcount will be incremented by
* @refs, and its pincount will be incremented by @refs.
*
* FOLL_PIN on single-page folios: folio's refcount will be incremented by
* @refs * GUP_PIN_COUNTING_BIAS.
*
* Return: The folio containing @page (with refcount appropriately
* incremented) for success, or NULL upon failure. If neither FOLL_GET
* nor FOLL_PIN was set, that's considered failure, and furthermore,
* a likely bug in the caller, so a warning is also emitted.
*/
struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags)
{
struct folio *folio;
if (WARN_ON_ONCE((flags & (FOLL_GET | FOLL_PIN)) == 0))
return NULL;
if (unlikely(!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page)))
return NULL;
if (flags & FOLL_GET)
return try_get_folio(page, refs);
/* FOLL_PIN is set */
/*
* Don't take a pin on the zero page - it's not going anywhere
* and it is used in a *lot* of places.
*/
if (is_zero_page(page))
return page_folio(page);
folio = try_get_folio(page, refs);
if (!folio)
return NULL;
/*
* Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a
* right zone, so fail and let the caller fall back to the slow
* path.
*/
if (unlikely((flags & FOLL_LONGTERM) &&
!folio_is_longterm_pinnable(folio))) {
if (!put_devmap_managed_page_refs(&folio->page, refs))
folio_put_refs(folio, refs);
return NULL;
}
/*
* When pinning a large folio, use an exact count to track it.
*
* However, be sure to *also* increment the normal folio
* refcount field at least once, so that the folio really
* is pinned. That's why the refcount from the earlier
* try_get_folio() is left intact.
*/
if (folio_test_large(folio))
atomic_add(refs, &folio->_pincount);
else
folio_ref_add(folio,
refs * (GUP_PIN_COUNTING_BIAS - 1));
/*
* Adjust the pincount before re-checking the PTE for changes.
* This is essentially a smp_mb() and is paired with a memory
* barrier in folio_try_share_anon_rmap_*().
*/
smp_mb__after_atomic();
node_stat_mod_folio(folio, NR_FOLL_PIN_ACQUIRED, refs);
return folio;
}
static void gup_put_folio(struct folio *folio, int refs, unsigned int flags)
{
if (flags & FOLL_PIN) {
if (is_zero_folio(folio))
return;
node_stat_mod_folio(folio, NR_FOLL_PIN_RELEASED, refs);
if (folio_test_large(folio))
atomic_sub(refs, &folio->_pincount);
else
refs *= GUP_PIN_COUNTING_BIAS;
}
if (!put_devmap_managed_page_refs(&folio->page, refs))
folio_put_refs(folio, refs);
}
/**
* try_grab_page() - elevate a page's refcount by a flag-dependent amount
* @page: pointer to page to be grabbed
* @flags: gup flags: these are the FOLL_* flag values.
*
* This might not do anything at all, depending on the flags argument.
*
* "grab" names in this file mean, "look at flags to decide whether to use
* FOLL_PIN or FOLL_GET behavior, when incrementing the page's refcount.
*
* Either FOLL_PIN or FOLL_GET (or neither) may be set, but not both at the same
* time. Cases: please see the try_grab_folio() documentation, with
* "refs=1".
*
* Return: 0 for success, or if no action was required (if neither FOLL_PIN
* nor FOLL_GET was set, nothing is done). A negative error code for failure:
*
* -ENOMEM FOLL_GET or FOLL_PIN was set, but the page could not
* be grabbed.
*/
int __must_check try_grab_page(struct page *page, unsigned int flags)
{
struct folio *folio = page_folio(page);
if (WARN_ON_ONCE(folio_ref_count(folio) <= 0))
return -ENOMEM;
if (unlikely(!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page)))
return -EREMOTEIO;
if (flags & FOLL_GET)
folio_ref_inc(folio);
else if (flags & FOLL_PIN) {
/*
* Don't take a pin on the zero page - it's not going anywhere
* and it is used in a *lot* of places.
*/
if (is_zero_page(page))
return 0;
/*
* Similar to try_grab_folio(): be sure to *also*
* increment the normal page refcount field at least once,
* so that the page really is pinned.
*/
if (folio_test_large(folio)) {
folio_ref_add(folio, 1);
atomic_add(1, &folio->_pincount);
} else {
folio_ref_add(folio, GUP_PIN_COUNTING_BIAS);
}
node_stat_mod_folio(folio, NR_FOLL_PIN_ACQUIRED, 1);
}
return 0;
}
/**
* unpin_user_page() - release a dma-pinned page
* @page: pointer to page to be released
*
* Pages that were pinned via pin_user_pages*() must be released via either
* unpin_user_page(), or one of the unpin_user_pages*() routines. This is so
* that such pages can be separately tracked and uniquely handled. In
* particular, interactions with RDMA and filesystems need special handling.
*/
void unpin_user_page(struct page *page)
{
sanity_check_pinned_pages(&page, 1);
gup_put_folio(page_folio(page), 1, FOLL_PIN);
}
EXPORT_SYMBOL(unpin_user_page);
/**
* folio_add_pin - Try to get an additional pin on a pinned folio
* @folio: The folio to be pinned
*
* Get an additional pin on a folio we already have a pin on. Makes no change
* if the folio is a zero_page.
*/
void folio_add_pin(struct folio *folio)
{
if (is_zero_folio(folio))
return;
/*
* Similar to try_grab_folio(): be sure to *also* increment the normal
* page refcount field at least once, so that the page really is
* pinned.
*/
if (folio_test_large(folio)) {
WARN_ON_ONCE(atomic_read(&folio->_pincount) < 1);
folio_ref_inc(folio);
atomic_inc(&folio->_pincount);
} else {
WARN_ON_ONCE(folio_ref_count(folio) < GUP_PIN_COUNTING_BIAS);
folio_ref_add(folio, GUP_PIN_COUNTING_BIAS);
}
}
static inline struct folio *gup_folio_range_next(struct page *start,
unsigned long npages, unsigned long i, unsigned int *ntails)
{
struct page *next = nth_page(start, i);
struct folio *folio = page_folio(next);
unsigned int nr = 1;
if (folio_test_large(folio))
nr = min_t(unsigned int, npages - i,
folio_nr_pages(folio) - folio_page_idx(folio, next));
*ntails = nr;
return folio;
}
static inline struct folio *gup_folio_next(struct page **list,
unsigned long npages, unsigned long i, unsigned int *ntails)
{
struct folio *folio = page_folio(list[i]);
unsigned int nr;
for (nr = i + 1; nr < npages; nr++) {
if (page_folio(list[nr]) != folio)
break;
}
*ntails = nr - i;
return folio;
}
/**
* unpin_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages
* @pages: array of pages to be maybe marked dirty, and definitely released.
* @npages: number of pages in the @pages array.
* @make_dirty: whether to mark the pages dirty
*
* "gup-pinned page" refers to a page that has had one of the get_user_pages()
* variants called on that page.
*
* For each page in the @pages array, make that page (or its head page, if a
* compound page) dirty, if @make_dirty is true, and if the page was previously
* listed as clean. In any case, releases all pages using unpin_user_page(),
* possibly via unpin_user_pages(), for the non-dirty case.
*
* Please see the unpin_user_page() documentation for details.
*
* set_page_dirty_lock() is used internally. If instead, set_page_dirty() is
* required, then the caller should a) verify that this is really correct,
* because _lock() is usually required, and b) hand code it:
* set_page_dirty_lock(), unpin_user_page().
*
*/
void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages,
bool make_dirty)
{
unsigned long i;
struct folio *folio;
unsigned int nr;
if (!make_dirty) {
unpin_user_pages(pages, npages);
return;
}
sanity_check_pinned_pages(pages, npages);
for (i = 0; i < npages; i += nr) {
folio = gup_folio_next(pages, npages, i, &nr);
/*
* Checking PageDirty at this point may race with
* clear_page_dirty_for_io(), but that's OK. Two key
* cases:
*
* 1) This code sees the page as already dirty, so it
* skips the call to set_page_dirty(). That could happen
* because clear_page_dirty_for_io() called
* page_mkclean(), followed by set_page_dirty().
* However, now the page is going to get written back,
* which meets the original intention of setting it
* dirty, so all is well: clear_page_dirty_for_io() goes
* on to call TestClearPageDirty(), and write the page
* back.
*
* 2) This code sees the page as clean, so it calls
* set_page_dirty(). The page stays dirty, despite being
* written back, so it gets written back again in the
* next writeback cycle. This is harmless.
*/
if (!folio_test_dirty(folio)) {
folio_lock(folio);
folio_mark_dirty(folio);
folio_unlock(folio);
}
gup_put_folio(folio, nr, FOLL_PIN);
}
}
EXPORT_SYMBOL(unpin_user_pages_dirty_lock);
/**
* unpin_user_page_range_dirty_lock() - release and optionally dirty
* gup-pinned page range
*
* @page: the starting page of a range maybe marked dirty, and definitely released.
* @npages: number of consecutive pages to release.
* @make_dirty: whether to mark the pages dirty
*
* "gup-pinned page range" refers to a range of pages that has had one of the
* pin_user_pages() variants called on that page.
*
* For the page ranges defined by [page .. page+npages], make that range (or
* its head pages, if a compound page) dirty, if @make_dirty is true, and if the
* page range was previously listed as clean.
*
* set_page_dirty_lock() is used internally. If instead, set_page_dirty() is
* required, then the caller should a) verify that this is really correct,
* because _lock() is usually required, and b) hand code it:
* set_page_dirty_lock(), unpin_user_page().
*
*/
void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages,
bool make_dirty)
{
unsigned long i;
struct folio *folio;
unsigned int nr;
for (i = 0; i < npages; i += nr) {
folio = gup_folio_range_next(page, npages, i, &nr);
if (make_dirty && !folio_test_dirty(folio)) {
folio_lock(folio);
folio_mark_dirty(folio);
folio_unlock(folio);
}
gup_put_folio(folio, nr, FOLL_PIN);
}
}
EXPORT_SYMBOL(unpin_user_page_range_dirty_lock);
static void unpin_user_pages_lockless(struct page **pages, unsigned long npages)
{
unsigned long i;
struct folio *folio;
unsigned int nr;
/*
* Don't perform any sanity checks because we might have raced with
* fork() and some anonymous pages might now actually be shared --
* which is why we're unpinning after all.
*/
for (i = 0; i < npages; i += nr) {
folio = gup_folio_next(pages, npages, i, &nr);
gup_put_folio(folio, nr, FOLL_PIN);
}
}
/**
* unpin_user_pages() - release an array of gup-pinned pages.
* @pages: array of pages to be marked dirty and released.
* @npages: number of pages in the @pages array.
*
* For each page in the @pages array, release the page using unpin_user_page().
*
* Please see the unpin_user_page() documentation for details.
*/
void unpin_user_pages(struct page **pages, unsigned long npages)
{
unsigned long i;
struct folio *folio;
unsigned int nr;
/*
* If this WARN_ON() fires, then the system *might* be leaking pages (by
* leaving them pinned), but probably not. More likely, gup/pup returned
* a hard -ERRNO error to the caller, who erroneously passed it here.
*/
if (WARN_ON(IS_ERR_VALUE(npages)))
return;
sanity_check_pinned_pages(pages, npages);
for (i = 0; i < npages; i += nr) {
folio = gup_folio_next(pages, npages, i, &nr);
gup_put_folio(folio, nr, FOLL_PIN);
}
}
EXPORT_SYMBOL(unpin_user_pages);
/*
* Set the MMF_HAS_PINNED if not set yet; after set it'll be there for the mm's
* lifecycle. Avoid setting the bit unless necessary, or it might cause write
* cache bouncing on large SMP machines for concurrent pinned gups.
*/
static inline void mm_set_has_pinned_flag(unsigned long *mm_flags)
{
if (!test_bit(MMF_HAS_PINNED, mm_flags))
set_bit(MMF_HAS_PINNED, mm_flags);
}
#ifdef CONFIG_MMU
static struct page *no_page_table(struct vm_area_struct *vma,
unsigned int flags)
{
/*
* When core dumping an enormous anonymous area that nobody
* has touched so far, we don't want to allocate unnecessary pages or
* page tables. Return error instead of NULL to skip handle_mm_fault,
* then get_dump_page() will return NULL to leave a hole in the dump.
* But we can only make this optimization where a hole would surely
* be zero-filled if handle_mm_fault() actually did handle it.
*/
if ((flags & FOLL_DUMP) &&
(vma_is_anonymous(vma) || !vma->vm_ops->fault))
return ERR_PTR(-EFAULT);
return NULL;
}
static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
pte_t *pte, unsigned int flags)
{
if (flags & FOLL_TOUCH) {
pte_t orig_entry = ptep_get(pte);
pte_t entry = orig_entry;
if (flags & FOLL_WRITE)
entry = pte_mkdirty(entry);
entry = pte_mkyoung(entry);
if (!pte_same(orig_entry, entry)) {
set_pte_at(vma->vm_mm, address, pte, entry);
update_mmu_cache(vma, address, pte);
}
}
/* Proper page table entry exists, but no corresponding struct page */
return -EEXIST;
}
/* FOLL_FORCE can write to even unwritable PTEs in COW mappings. */
static inline bool can_follow_write_pte(pte_t pte, struct page *page,
struct vm_area_struct *vma,
unsigned int flags)
{
/* If the pte is writable, we can write to the page. */
if (pte_write(pte))
return true;
/* Maybe FOLL_FORCE is set to override it? */
if (!(flags & FOLL_FORCE))
return false;
/* But FOLL_FORCE has no effect on shared mappings */
if (vma->vm_flags & (VM_MAYSHARE | VM_SHARED))
return false;
/* ... or read-only private ones */
if (!(vma->vm_flags & VM_MAYWRITE))
return false;
/* ... or already writable ones that just need to take a write fault */
if (vma->vm_flags & VM_WRITE)
return false;
/*
* See can_change_pte_writable(): we broke COW and could map the page
* writable if we have an exclusive anonymous page ...
*/
if (!page || !PageAnon(page) || !PageAnonExclusive(page))
return false;
/* ... and a write-fault isn't required for other reasons. */
if (vma_soft_dirty_enabled(vma) && !pte_soft_dirty(pte))
return false;
return !userfaultfd_pte_wp(vma, pte);
}
static struct page *follow_page_pte(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmd, unsigned int flags,
struct dev_pagemap **pgmap)
{
struct mm_struct *mm = vma->vm_mm;
struct page *page;
spinlock_t *ptl;
pte_t *ptep, pte;
int ret;
/* FOLL_GET and FOLL_PIN are mutually exclusive. */
if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
(FOLL_PIN | FOLL_GET)))
return ERR_PTR(-EINVAL);
ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
if (!ptep)
return no_page_table(vma, flags);
pte = ptep_get(ptep);
if (!pte_present(pte))
goto no_page;
if (pte_protnone(pte) && !gup_can_follow_protnone(vma, flags))
goto no_page;
page = vm_normal_page(vma, address, pte);
/*
* We only care about anon pages in can_follow_write_pte() and don't
* have to worry about pte_devmap() because they are never anon.
*/
if ((flags & FOLL_WRITE) &&
!can_follow_write_pte(pte, page, vma, flags)) {
page = NULL;
goto out;
}
if (!page && pte_devmap(pte) && (flags & (FOLL_GET | FOLL_PIN))) {
/*
* Only return device mapping pages in the FOLL_GET or FOLL_PIN
* case since they are only valid while holding the pgmap
* reference.
*/
*pgmap = get_dev_pagemap(pte_pfn(pte), *pgmap);
if (*pgmap)
page = pte_page(pte);
else
goto no_page;
} else if (unlikely(!page)) {
if (flags & FOLL_DUMP) {
/* Avoid special (like zero) pages in core dumps */
page = ERR_PTR(-EFAULT);
goto out;
}
if (is_zero_pfn(pte_pfn(pte))) {
page = pte_page(pte);
} else {
ret = follow_pfn_pte(vma, address, ptep, flags);
page = ERR_PTR(ret);
goto out;
}
}
if (!pte_write(pte) && gup_must_unshare(vma, flags, page)) {
page = ERR_PTR(-EMLINK);
goto out;
}
VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) &&
!PageAnonExclusive(page), page);
/* try_grab_page() does nothing unless FOLL_GET or FOLL_PIN is set. */
ret = try_grab_page(page, flags);
if (unlikely(ret)) {
page = ERR_PTR(ret);
goto out;
}
/*
* We need to make the page accessible if and only if we are going
* to access its content (the FOLL_PIN case). Please see
* Documentation/core-api/pin_user_pages.rst for details.
*/
if (flags & FOLL_PIN) {
ret = arch_make_page_accessible(page);
if (ret) {
unpin_user_page(page);
page = ERR_PTR(ret);
goto out;
}
}
if (flags & FOLL_TOUCH) {
if ((flags & FOLL_WRITE) &&
!pte_dirty(pte) && !PageDirty(page))
set_page_dirty(page);
/*
* pte_mkyoung() would be more correct here, but atomic care
* is needed to avoid losing the dirty bit: it is easier to use
* mark_page_accessed().
*/
mark_page_accessed(page);
}
out:
pte_unmap_unlock(ptep, ptl);
return page;
no_page:
pte_unmap_unlock(ptep, ptl);
if (!pte_none(pte))
return NULL;
return no_page_table(vma, flags);
}
static struct page *follow_pmd_mask(struct vm_area_struct *vma,
unsigned long address, pud_t *pudp,
unsigned int flags,
struct follow_page_context *ctx)
{
pmd_t *pmd, pmdval;
spinlock_t *ptl;
struct page *page;
struct mm_struct *mm = vma->vm_mm;
pmd = pmd_offset(pudp, address);
pmdval = pmdp_get_lockless(pmd);
if (pmd_none(pmdval))
return no_page_table(vma, flags);
if (!pmd_present(pmdval))
return no_page_table(vma, flags);
if (pmd_devmap(pmdval)) {
ptl = pmd_lock(mm, pmd);
page = follow_devmap_pmd(vma, address, pmd, flags, &ctx->pgmap);
spin_unlock(ptl);
if (page)
return page;
return no_page_table(vma, flags);
}
if (likely(!pmd_trans_huge(pmdval)))
return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
if (pmd_protnone(pmdval) && !gup_can_follow_protnone(vma, flags))
return no_page_table(vma, flags);
ptl = pmd_lock(mm, pmd);
if (unlikely(!pmd_present(*pmd))) {
spin_unlock(ptl);
return no_page_table(vma, flags);
}
if (unlikely(!pmd_trans_huge(*pmd))) {
spin_unlock(ptl);
return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
}
if (flags & FOLL_SPLIT_PMD) {
spin_unlock(ptl);
split_huge_pmd(vma, pmd, address);
/* If pmd was left empty, stuff a page table in there quickly */
return pte_alloc(mm, pmd) ? ERR_PTR(-ENOMEM) :
follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
}
page = follow_trans_huge_pmd(vma, address, pmd, flags);
spin_unlock(ptl);
ctx->page_mask = HPAGE_PMD_NR - 1;
return page;
}
static struct page *follow_pud_mask(struct vm_area_struct *vma,
unsigned long address, p4d_t *p4dp,
unsigned int flags,
struct follow_page_context *ctx)
{
pud_t *pud;
spinlock_t *ptl;
struct page *page;
struct mm_struct *mm = vma->vm_mm;
pud = pud_offset(p4dp, address);
if (pud_none(*pud))
return no_page_table(vma, flags);
if (pud_devmap(*pud)) {
ptl = pud_lock(mm, pud);
page = follow_devmap_pud(vma, address, pud, flags, &ctx->pgmap);
spin_unlock(ptl);
if (page)
return page;
return no_page_table(vma, flags);
}
if (unlikely(pud_bad(*pud)))
return no_page_table(vma, flags);
return follow_pmd_mask(vma, address, pud, flags, ctx);
}
static struct page *follow_p4d_mask(struct vm_area_struct *vma,
unsigned long address, pgd_t *pgdp,
unsigned int flags,
struct follow_page_context *ctx)
{
p4d_t *p4dp, p4d;
p4dp = p4d_offset(pgdp, address);
p4d = READ_ONCE(*p4dp);
if (!p4d_present(p4d))
return no_page_table(vma, flags);
BUILD_BUG_ON(p4d_leaf(p4d));
if (unlikely(p4d_bad(p4d)))
return no_page_table(vma, flags);
return follow_pud_mask(vma, address, p4dp, flags, ctx);
}
/**
* follow_page_mask - look up a page descriptor from a user-virtual address
* @vma: vm_area_struct mapping @address
* @address: virtual address to look up
* @flags: flags modifying lookup behaviour
* @ctx: contains dev_pagemap for %ZONE_DEVICE memory pinning and a
* pointer to output page_mask
*
* @flags can have FOLL_ flags set, defined in <linux/mm.h>
*
* When getting pages from ZONE_DEVICE memory, the @ctx->pgmap caches
* the device's dev_pagemap metadata to avoid repeating expensive lookups.
*
* When getting an anonymous page and the caller has to trigger unsharing
* of a shared anonymous page first, -EMLINK is returned. The caller should
* trigger a fault with FAULT_FLAG_UNSHARE set. Note that unsharing is only
* relevant with FOLL_PIN and !FOLL_WRITE.
*
* On output, the @ctx->page_mask is set according to the size of the page.
*
* Return: the mapped (struct page *), %NULL if no mapping exists, or
* an error pointer if there is a mapping to something not represented
* by a page descriptor (see also vm_normal_page()).
*/
static struct page *follow_page_mask(struct vm_area_struct *vma,
unsigned long address, unsigned int flags,
struct follow_page_context *ctx)
{
pgd_t *pgd;
struct mm_struct *mm = vma->vm_mm;
ctx->page_mask = 0;
/*
* Call hugetlb_follow_page_mask for hugetlb vmas as it will use
* special hugetlb page table walking code. This eliminates the
* need to check for hugetlb entries in the general walking code.
*/
if (is_vm_hugetlb_page(vma))
return hugetlb_follow_page_mask(vma, address, flags,
&ctx->page_mask);
pgd = pgd_offset(mm, address);
if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
return no_page_table(vma, flags);
return follow_p4d_mask(vma, address, pgd, flags, ctx);
}
struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
unsigned int foll_flags)
{
struct follow_page_context ctx = { NULL };
struct page *page;
if (vma_is_secretmem(vma))
return NULL;
if (WARN_ON_ONCE(foll_flags & FOLL_PIN))
return NULL;
/*
* We never set FOLL_HONOR_NUMA_FAULT because callers don't expect
* to fail on PROT_NONE-mapped pages.
*/
page = follow_page_mask(vma, address, foll_flags, &ctx);
if (ctx.pgmap)
put_dev_pagemap(ctx.pgmap);
return page;
}
static int get_gate_page(struct mm_struct *mm, unsigned long address,
unsigned int gup_flags, struct vm_area_struct **vma,
struct page **page)
{
pgd_t *pgd;
p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
pte_t entry;
int ret = -EFAULT;
/* user gate pages are read-only */
if (gup_flags & FOLL_WRITE)
return -EFAULT;
if (address > TASK_SIZE)
pgd = pgd_offset_k(address);
else
pgd = pgd_offset_gate(mm, address);
if (pgd_none(*pgd))
return -EFAULT;
p4d = p4d_offset(pgd, address);
if (p4d_none(*p4d))
return -EFAULT;
pud = pud_offset(p4d, address);
if (pud_none(*pud))
return -EFAULT;
pmd = pmd_offset(pud, address);
if (!pmd_present(*pmd))
return -EFAULT;
pte = pte_offset_map(pmd, address);
if (!pte)
return -EFAULT;
entry = ptep_get(pte);
if (pte_none(entry))
goto unmap;
*vma = get_gate_vma(mm);
if (!page)
goto out;
*page = vm_normal_page(*vma, address, entry);
if (!*page) {
if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(entry)))
goto unmap;
*page = pte_page(entry);
}
ret = try_grab_page(*page, gup_flags);
if (unlikely(ret))
goto unmap;
out:
ret = 0;
unmap:
pte_unmap(pte);
return ret;
}
/*
* mmap_lock must be held on entry. If @flags has FOLL_UNLOCKABLE but not
* FOLL_NOWAIT, the mmap_lock may be released. If it is, *@locked will be set
* to 0 and -EBUSY returned.
*/
static int faultin_page(struct vm_area_struct *vma,
unsigned long address, unsigned int *flags, bool unshare,
int *locked)
{
unsigned int fault_flags = 0;
vm_fault_t ret;
if (*flags & FOLL_NOFAULT)
return -EFAULT;
if (*flags & FOLL_WRITE)
fault_flags |= FAULT_FLAG_WRITE;
if (*flags & FOLL_REMOTE)
fault_flags |= FAULT_FLAG_REMOTE;
if (*flags & FOLL_UNLOCKABLE) {
fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
/*
* FAULT_FLAG_INTERRUPTIBLE is opt-in. GUP callers must set
* FOLL_INTERRUPTIBLE to enable FAULT_FLAG_INTERRUPTIBLE.
* That's because some callers may not be prepared to
* handle early exits caused by non-fatal signals.
*/
if (*flags & FOLL_INTERRUPTIBLE)
fault_flags |= FAULT_FLAG_INTERRUPTIBLE;
}
if (*flags & FOLL_NOWAIT)
fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
if (*flags & FOLL_TRIED) {
/*
* Note: FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_TRIED
* can co-exist
*/
fault_flags |= FAULT_FLAG_TRIED;
}
if (unshare) {
fault_flags |= FAULT_FLAG_UNSHARE;
/* FAULT_FLAG_WRITE and FAULT_FLAG_UNSHARE are incompatible */
VM_BUG_ON(fault_flags & FAULT_FLAG_WRITE);
}
ret = handle_mm_fault(vma, address, fault_flags, NULL);
if (ret & VM_FAULT_COMPLETED) {
/*
* With FAULT_FLAG_RETRY_NOWAIT we'll never release the
* mmap lock in the page fault handler. Sanity check this.
*/
WARN_ON_ONCE(fault_flags & FAULT_FLAG_RETRY_NOWAIT);
*locked = 0;
/*
* We should do the same as VM_FAULT_RETRY, but let's not
* return -EBUSY since that's not reflecting the reality of
* what has happened - we've just fully completed a page
* fault, with the mmap lock released. Use -EAGAIN to show
* that we want to take the mmap lock _again_.
*/
return -EAGAIN;
}
if (ret & VM_FAULT_ERROR) {
int err = vm_fault_to_errno(ret, *flags);
if (err)
return err;
BUG();
}
if (ret & VM_FAULT_RETRY) {
if (!(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
*locked = 0;
return -EBUSY;
}
return 0;
}
/*
* Writing to file-backed mappings which require folio dirty tracking using GUP
* is a fundamentally broken operation, as kernel write access to GUP mappings
* do not adhere to the semantics expected by a file system.
*
* Consider the following scenario:-
*
* 1. A folio is written to via GUP which write-faults the memory, notifying
* the file system and dirtying the folio.
* 2. Later, writeback is triggered, resulting in the folio being cleaned and
* the PTE being marked read-only.
* 3. The GUP caller writes to the folio, as it is mapped read/write via the
* direct mapping.
* 4. The GUP caller, now done with the page, unpins it and sets it dirty
* (though it does not have to).
*
* This results in both data being written to a folio without writenotify, and
* the folio being dirtied unexpectedly (if the caller decides to do so).
*/
static bool writable_file_mapping_allowed(struct vm_area_struct *vma,
unsigned long gup_flags)
{
/*
* If we aren't pinning then no problematic write can occur. A long term
* pin is the most egregious case so this is the case we disallow.
*/
if ((gup_flags & (FOLL_PIN | FOLL_LONGTERM)) !=
(FOLL_PIN | FOLL_LONGTERM))
return true;
/*
* If the VMA does not require dirty tracking then no problematic write
* can occur either.
*/
return !vma_needs_dirty_tracking(vma);
}
static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
{
vm_flags_t vm_flags = vma->vm_flags;
int write = (gup_flags & FOLL_WRITE);
int foreign = (gup_flags & FOLL_REMOTE);
bool vma_anon = vma_is_anonymous(vma);
if (vm_flags & (VM_IO | VM_PFNMAP))
return -EFAULT;
if ((gup_flags & FOLL_ANON) && !vma_anon)
return -EFAULT;
if ((gup_flags & FOLL_LONGTERM) && vma_is_fsdax(vma))
return -EOPNOTSUPP;
if (vma_is_secretmem(vma))
return -EFAULT;
if (write) {
if (!vma_anon &&
!writable_file_mapping_allowed(vma, gup_flags))
return -EFAULT;
if (!(vm_flags & VM_WRITE) || (vm_flags & VM_SHADOW_STACK)) {
if (!(gup_flags & FOLL_FORCE))
return -EFAULT;
/* hugetlb does not support FOLL_FORCE|FOLL_WRITE. */
if (is_vm_hugetlb_page(vma))
return -EFAULT;
/*
* We used to let the write,force case do COW in a
* VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
* set a breakpoint in a read-only mapping of an
* executable, without corrupting the file (yet only
* when that file had been opened for writing!).
* Anon pages in shared mappings are surprising: now
* just reject it.
*/
if (!is_cow_mapping(vm_flags))
return -EFAULT;
}
} else if (!(vm_flags & VM_READ)) {
if (!(gup_flags & FOLL_FORCE))
return -EFAULT;
/*
* Is there actually any vma we can reach here which does not
* have VM_MAYREAD set?
*/
if (!(vm_flags & VM_MAYREAD))
return -EFAULT;
}
/*
* gups are always data accesses, not instruction
* fetches, so execute=false here
*/
if (!arch_vma_access_permitted(vma, write, false, foreign))
return -EFAULT;
return 0;
}
/*
* This is "vma_lookup()", but with a warning if we would have
* historically expanded the stack in the GUP code.
*/
static struct vm_area_struct *gup_vma_lookup(struct mm_struct *mm,
unsigned long addr)
{
#ifdef CONFIG_STACK_GROWSUP
return vma_lookup(mm, addr);
#else
static volatile unsigned long next_warn;
struct vm_area_struct *vma;
unsigned long now, next;
vma = find_vma(mm, addr);
if (!vma || (addr >= vma->vm_start))
return vma;
/* Only warn for half-way relevant accesses */
if (!(vma->vm_flags & VM_GROWSDOWN))
return NULL;
if (vma->vm_start - addr > 65536)
return NULL;
/* Let's not warn more than once an hour.. */
now = jiffies; next = next_warn;
if (next && time_before(now, next))
return NULL;
next_warn = now + 60*60*HZ;
/* Let people know things may have changed. */
pr_warn("GUP no longer grows the stack in %s (%d): %lx-%lx (%lx)\n",
current->comm, task_pid_nr(current),
vma->vm_start, vma->vm_end, addr);
dump_stack();
return NULL;
#endif
}
/**
* __get_user_pages() - pin user pages in memory
* @mm: mm_struct of target mm
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying pin behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long. Or NULL, if caller
* only intends to ensure the pages are faulted in.
* @locked: whether we're still with the mmap_lock held
*
* Returns either number of pages pinned (which may be less than the
* number requested), or an error. Details about the return value:
*
* -- If nr_pages is 0, returns 0.
* -- If nr_pages is >0, but no pages were pinned, returns -errno.
* -- If nr_pages is >0, and some pages were pinned, returns the number of
* pages pinned. Again, this may be less than nr_pages.
* -- 0 return value is possible when the fault would need to be retried.
*
* The caller is responsible for releasing returned @pages, via put_page().
*
* Must be called with mmap_lock held. It may be released. See below.
*
* __get_user_pages walks a process's page tables and takes a reference to
* each struct page that each user address corresponds to at a given
* instant. That is, it takes the page that would be accessed if a user
* thread accesses the given user virtual address at that instant.
*
* This does not guarantee that the page exists in the user mappings when
* __get_user_pages returns, and there may even be a completely different
* page there in some cases (eg. if mmapped pagecache has been invalidated
* and subsequently re-faulted). However it does guarantee that the page
* won't be freed completely. And mostly callers simply care that the page
* contains data that was valid *at some point in time*. Typically, an IO
* or similar operation cannot guarantee anything stronger anyway because
* locks can't be held over the syscall boundary.
*
* If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
* the page is written to, set_page_dirty (or set_page_dirty_lock, as
* appropriate) must be called after the page is finished with, and
* before put_page is called.
*
* If FOLL_UNLOCKABLE is set without FOLL_NOWAIT then the mmap_lock may
* be released. If this happens *@locked will be set to 0 on return.
*
* A caller using such a combination of @gup_flags must therefore hold the
* mmap_lock for reading only, and recognize when it's been released. Otherwise,
* it must be held for either reading or writing and will not be released.
*
* In most cases, get_user_pages or get_user_pages_fast should be used
* instead of __get_user_pages. __get_user_pages should be used only if
* you need some special @gup_flags.
*/
static long __get_user_pages(struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
int *locked)
{
long ret = 0, i = 0;
struct vm_area_struct *vma = NULL;
struct follow_page_context ctx = { NULL };
if (!nr_pages)
return 0;
start = untagged_addr_remote(mm, start);
VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN)));
do {
struct page *page;
unsigned int foll_flags = gup_flags;
unsigned int page_increm;
/* first iteration or cross vma bound */
if (!vma || start >= vma->vm_end) {
/*
* MADV_POPULATE_(READ|WRITE) wants to handle VMA
* lookups+error reporting differently.
*/
if (gup_flags & FOLL_MADV_POPULATE) {
vma = vma_lookup(mm, start);
if (!vma) {
ret = -ENOMEM;
goto out;
}
if (check_vma_flags(vma, gup_flags)) {
ret = -EINVAL;
goto out;
}
goto retry;
}
vma = gup_vma_lookup(mm, start);
if (!vma && in_gate_area(mm, start)) {
ret = get_gate_page(mm, start & PAGE_MASK,
gup_flags, &vma,
pages ? &page : NULL);
if (ret)
goto out;
ctx.page_mask = 0;
goto next_page;
}
if (!vma) {
ret = -EFAULT;
goto out;
}
ret = check_vma_flags(vma, gup_flags);
if (ret)
goto out;
}
retry:
/*
* If we have a pending SIGKILL, don't keep faulting pages and
* potentially allocating memory.
*/
if (fatal_signal_pending(current)) {
ret = -EINTR;
goto out;
}
cond_resched();
page = follow_page_mask(vma, start, foll_flags, &ctx);
if (!page || PTR_ERR(page) == -EMLINK) {
ret = faultin_page(vma, start, &foll_flags,
PTR_ERR(page) == -EMLINK, locked);
switch (ret) {
case 0:
goto retry;
case -EBUSY:
case -EAGAIN:
ret = 0;
fallthrough;
case -EFAULT:
case -ENOMEM:
case -EHWPOISON:
goto out;
}
BUG();
} else if (PTR_ERR(page) == -EEXIST) {
/*
* Proper page table entry exists, but no corresponding
* struct page. If the caller expects **pages to be
* filled in, bail out now, because that can't be done
* for this page.
*/
if (pages) {
ret = PTR_ERR(page);
goto out;
}
} else if (IS_ERR(page)) {
ret = PTR_ERR(page);
goto out;
}
next_page:
page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask);
if (page_increm > nr_pages)
page_increm = nr_pages;
if (pages) {
struct page *subpage;
unsigned int j;
/*
* This must be a large folio (and doesn't need to
* be the whole folio; it can be part of it), do
* the refcount work for all the subpages too.
*
* NOTE: here the page may not be the head page
* e.g. when start addr is not thp-size aligned.
* try_grab_folio() should have taken care of tail
* pages.
*/
if (page_increm > 1) {
struct folio *folio;
/*
* Since we already hold refcount on the
* large folio, this should never fail.
*/
folio = try_grab_folio(page, page_increm - 1,
foll_flags);
if (WARN_ON_ONCE(!folio)) {
/*
* Release the 1st page ref if the
* folio is problematic, fail hard.
*/
gup_put_folio(page_folio(page), 1,
foll_flags);
ret = -EFAULT;
goto out;
}
}
for (j = 0; j < page_increm; j++) {
subpage = nth_page(page, j);
pages[i + j] = subpage;
flush_anon_page(vma, subpage, start + j * PAGE_SIZE);
flush_dcache_page(subpage);
}
}
i += page_increm;
start += page_increm * PAGE_SIZE;
nr_pages -= page_increm;
} while (nr_pages);
out:
if (ctx.pgmap)
put_dev_pagemap(ctx.pgmap);
return i ? i : ret;
}
static bool vma_permits_fault(struct vm_area_struct *vma,
unsigned int fault_flags)
{
bool write = !!(fault_flags & FAULT_FLAG_WRITE);
bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
if (!(vm_flags & vma->vm_flags))
return false;
/*
* The architecture might have a hardware protection
* mechanism other than read/write that can deny access.
*
* gup always represents data access, not instruction
* fetches, so execute=false here:
*/
if (!arch_vma_access_permitted(vma, write, false, foreign))
return false;
return true;
}
/**
* fixup_user_fault() - manually resolve a user page fault
* @mm: mm_struct of target mm
* @address: user address
* @fault_flags:flags to pass down to handle_mm_fault()
* @unlocked: did we unlock the mmap_lock while retrying, maybe NULL if caller
* does not allow retry. If NULL, the caller must guarantee
* that fault_flags does not contain FAULT_FLAG_ALLOW_RETRY.
*
* This is meant to be called in the specific scenario where for locking reasons
* we try to access user memory in atomic context (within a pagefault_disable()
* section), this returns -EFAULT, and we want to resolve the user fault before
* trying again.
*
* Typically this is meant to be used by the futex code.
*
* The main difference with get_user_pages() is that this function will
* unconditionally call handle_mm_fault() which will in turn perform all the
* necessary SW fixup of the dirty and young bits in the PTE, while
* get_user_pages() only guarantees to update these in the struct page.
*
* This is important for some architectures where those bits also gate the
* access permission to the page because they are maintained in software. On
* such architectures, gup() will not be enough to make a subsequent access
* succeed.
*
* This function will not return with an unlocked mmap_lock. So it has not the
* same semantics wrt the @mm->mmap_lock as does filemap_fault().
*/
int fixup_user_fault(struct mm_struct *mm,
unsigned long address, unsigned int fault_flags,
bool *unlocked)
{
struct vm_area_struct *vma;
vm_fault_t ret;
address = untagged_addr_remote(mm, address);
if (unlocked)
fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
retry:
vma = gup_vma_lookup(mm, address);
if (!vma)
return -EFAULT;
if (!vma_permits_fault(vma, fault_flags))
return -EFAULT;
if ((fault_flags & FAULT_FLAG_KILLABLE) &&
fatal_signal_pending(current))
return -EINTR;
ret = handle_mm_fault(vma, address, fault_flags, NULL);
if (ret & VM_FAULT_COMPLETED) {
/*
* NOTE: it's a pity that we need to retake the lock here
* to pair with the unlock() in the callers. Ideally we
* could tell the callers so they do not need to unlock.
*/
mmap_read_lock(mm);
*unlocked = true;
return 0;
}
if (ret & VM_FAULT_ERROR) {
int err = vm_fault_to_errno(ret, 0);
if (err)
return err;
BUG();
}
if (ret & VM_FAULT_RETRY) {
mmap_read_lock(mm);
*unlocked = true;
fault_flags |= FAULT_FLAG_TRIED;
goto retry;
}
return 0;
}
EXPORT_SYMBOL_GPL(fixup_user_fault);
/*
* GUP always responds to fatal signals. When FOLL_INTERRUPTIBLE is
* specified, it'll also respond to generic signals. The caller of GUP
* that has FOLL_INTERRUPTIBLE should take care of the GUP interruption.
*/
static bool gup_signal_pending(unsigned int flags)
{
if (fatal_signal_pending(current))
return true;
if (!(flags & FOLL_INTERRUPTIBLE))
return false;
return signal_pending(current);
}
/*
* Locking: (*locked == 1) means that the mmap_lock has already been acquired by
* the caller. This function may drop the mmap_lock. If it does so, then it will
* set (*locked = 0).
*
* (*locked == 0) means that the caller expects this function to acquire and
* drop the mmap_lock. Therefore, the value of *locked will still be zero when
* the function returns, even though it may have changed temporarily during
* function execution.
*
* Please note that this function, unlike __get_user_pages(), will not return 0
* for nr_pages > 0, unless FOLL_NOWAIT is used.
*/
static __always_inline long __get_user_pages_locked(struct mm_struct *mm,
unsigned long start,
unsigned long nr_pages,
struct page **pages,
int *locked,
unsigned int flags)
{
long ret, pages_done;
bool must_unlock = false;
if (!nr_pages)
return 0;
/*
* The internal caller expects GUP to manage the lock internally and the
* lock must be released when this returns.
*/
if (!*locked) {
if (mmap_read_lock_killable(mm))
return -EAGAIN;
must_unlock = true;
*locked = 1;
}
else
mmap_assert_locked(mm);
if (flags & FOLL_PIN)
mm_set_has_pinned_flag(&mm->flags);
/*
* FOLL_PIN and FOLL_GET are mutually exclusive. Traditional behavior
* is to set FOLL_GET if the caller wants pages[] filled in (but has
* carelessly failed to specify FOLL_GET), so keep doing that, but only
* for FOLL_GET, not for the newer FOLL_PIN.
*
* FOLL_PIN always expects pages to be non-null, but no need to assert
* that here, as any failures will be obvious enough.
*/
if (pages && !(flags & FOLL_PIN))
flags |= FOLL_GET;
pages_done = 0;
for (;;) {
ret = __get_user_pages(mm, start, nr_pages, flags, pages,
locked);
if (!(flags & FOLL_UNLOCKABLE)) {
/* VM_FAULT_RETRY couldn't trigger, bypass */
pages_done = ret;
break;
}
/* VM_FAULT_RETRY or VM_FAULT_COMPLETED cannot return errors */
if (!*locked) {
BUG_ON(ret < 0);
BUG_ON(ret >= nr_pages);
}
if (ret > 0) {
nr_pages -= ret;
pages_done += ret;
if (!nr_pages)
break;
}
if (*locked) {
/*
* VM_FAULT_RETRY didn't trigger or it was a
* FOLL_NOWAIT.
*/
if (!pages_done)
pages_done = ret;
break;
}
/*
* VM_FAULT_RETRY triggered, so seek to the faulting offset.
* For the prefault case (!pages) we only update counts.
*/
if (likely(pages))
pages += ret;
start += ret << PAGE_SHIFT;
/* The lock was temporarily dropped, so we must unlock later */
must_unlock = true;
retry:
/*
* Repeat on the address that fired VM_FAULT_RETRY
* with both FAULT_FLAG_ALLOW_RETRY and
* FAULT_FLAG_TRIED. Note that GUP can be interrupted
* by fatal signals of even common signals, depending on
* the caller's request. So we need to check it before we
* start trying again otherwise it can loop forever.
*/
if (gup_signal_pending(flags)) {
if (!pages_done)
pages_done = -EINTR;
break;
}
ret = mmap_read_lock_killable(mm);
if (ret) {
BUG_ON(ret > 0);
if (!pages_done)
pages_done = ret;
break;
}
*locked = 1;
ret = __get_user_pages(mm, start, 1, flags | FOLL_TRIED,
pages, locked);
if (!*locked) {
/* Continue to retry until we succeeded */
BUG_ON(ret != 0);
goto retry;
}
if (ret != 1) {
BUG_ON(ret > 1);
if (!pages_done)
pages_done = ret;
break;
}
nr_pages--;
pages_done++;
if (!nr_pages)
break;
if (likely(pages))
pages++;
start += PAGE_SIZE;
}
if (must_unlock && *locked) {
/*
* We either temporarily dropped the lock, or the caller
* requested that we both acquire and drop the lock. Either way,
* we must now unlock, and notify the caller of that state.
*/
mmap_read_unlock(mm);
*locked = 0;
}
/*
* Failing to pin anything implies something has gone wrong (except when
* FOLL_NOWAIT is specified).
*/
if (WARN_ON_ONCE(pages_done == 0 && !(flags & FOLL_NOWAIT)))
return -EFAULT;
return pages_done;
}
/**
* populate_vma_page_range() - populate a range of pages in the vma.
* @vma: target vma
* @start: start address
* @end: end address
* @locked: whether the mmap_lock is still held
*
* This takes care of mlocking the pages too if VM_LOCKED is set.
*
* Return either number of pages pinned in the vma, or a negative error
* code on error.
*
* vma->vm_mm->mmap_lock must be held.
*
* If @locked is NULL, it may be held for read or write and will
* be unperturbed.
*
* If @locked is non-NULL, it must held for read only and may be
* released. If it's released, *@locked will be set to 0.
*/
long populate_vma_page_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end, int *locked)
{
struct mm_struct *mm = vma->vm_mm;
unsigned long nr_pages = (end - start) / PAGE_SIZE;
int local_locked = 1;
int gup_flags;
long ret;
VM_BUG_ON(!PAGE_ALIGNED(start));
VM_BUG_ON(!PAGE_ALIGNED(end));
VM_BUG_ON_VMA(start < vma->vm_start, vma);
VM_BUG_ON_VMA(end > vma->vm_end, vma);
mmap_assert_locked(mm);
/*
* Rightly or wrongly, the VM_LOCKONFAULT case has never used
* faultin_page() to break COW, so it has no work to do here.
*/
if (vma->vm_flags & VM_LOCKONFAULT)
return nr_pages;
/* ... similarly, we've never faulted in PROT_NONE pages */
if (!vma_is_accessible(vma))
return -EFAULT;
gup_flags = FOLL_TOUCH;
/*
* We want to touch writable mappings with a write fault in order
* to break COW, except for shared mappings because these don't COW
* and we would not want to dirty them for nothing.
*
* Otherwise, do a read fault, and use FOLL_FORCE in case it's not
* readable (ie write-only or executable).
*/
if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
gup_flags |= FOLL_WRITE;
else
gup_flags |= FOLL_FORCE;
if (locked)
gup_flags |= FOLL_UNLOCKABLE;
/*
* We made sure addr is within a VMA, so the following will
* not result in a stack expansion that recurses back here.
*/
ret = __get_user_pages(mm, start, nr_pages, gup_flags,
NULL, locked ? locked : &local_locked);
lru_add_drain();
return ret;
}
/*
* faultin_page_range() - populate (prefault) page tables inside the
* given range readable/writable
*
* This takes care of mlocking the pages, too, if VM_LOCKED is set.
*
* @mm: the mm to populate page tables in
* @start: start address
* @end: end address
* @write: whether to prefault readable or writable
* @locked: whether the mmap_lock is still held
*
* Returns either number of processed pages in the MM, or a negative error
* code on error (see __get_user_pages()). Note that this function reports
* errors related to VMAs, such as incompatible mappings, as expected by
* MADV_POPULATE_(READ|WRITE).
*
* The range must be page-aligned.
*
* mm->mmap_lock must be held. If it's released, *@locked will be set to 0.
*/
long faultin_page_range(struct mm_struct *mm, unsigned long start,
unsigned long end, bool write, int *locked)
{
unsigned long nr_pages = (end - start) / PAGE_SIZE;
int gup_flags;
long ret;
VM_BUG_ON(!PAGE_ALIGNED(start));
VM_BUG_ON(!PAGE_ALIGNED(end));
mmap_assert_locked(mm);
/*
* FOLL_TOUCH: Mark page accessed and thereby young; will also mark
* the page dirty with FOLL_WRITE -- which doesn't make a
* difference with !FOLL_FORCE, because the page is writable
* in the page table.
* FOLL_HWPOISON: Return -EHWPOISON instead of -EFAULT when we hit
* a poisoned page.
* !FOLL_FORCE: Require proper access permissions.
*/
gup_flags = FOLL_TOUCH | FOLL_HWPOISON | FOLL_UNLOCKABLE |
FOLL_MADV_POPULATE;
if (write)
gup_flags |= FOLL_WRITE;
ret = __get_user_pages_locked(mm, start, nr_pages, NULL, locked,
gup_flags);
lru_add_drain();
return ret;
}
/*
* __mm_populate - populate and/or mlock pages within a range of address space.
*
* This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
* flags. VMAs must be already marked with the desired vm_flags, and
* mmap_lock must not be held.
*/
int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
{
struct mm_struct *mm = current->mm;
unsigned long end, nstart, nend;
struct vm_area_struct *vma = NULL;
int locked = 0;
long ret = 0;
end = start + len;
for (nstart = start; nstart < end; nstart = nend) {
/*
* We want to fault in pages for [nstart; end) address range.
* Find first corresponding VMA.
*/
if (!locked) {
locked = 1;
mmap_read_lock(mm);
vma = find_vma_intersection(mm, nstart, end);
} else if (nstart >= vma->vm_end)
vma = find_vma_intersection(mm, vma->vm_end, end);
if (!vma)
break;
/*
* Set [nstart; nend) to intersection of desired address
* range with the first VMA. Also, skip undesirable VMA types.
*/
nend = min(end, vma->vm_end);
if (vma->vm_flags & (VM_IO | VM_PFNMAP))
continue;
if (nstart < vma->vm_start)
nstart = vma->vm_start;
/*
* Now fault in a range of pages. populate_vma_page_range()
* double checks the vma flags, so that it won't mlock pages
* if the vma was already munlocked.
*/
ret = populate_vma_page_range(vma, nstart, nend, &locked);
if (ret < 0) {
if (ignore_errors) {
ret = 0;
continue; /* continue at next VMA */
}
break;
}
nend = nstart + ret * PAGE_SIZE;
ret = 0;
}
if (locked)
mmap_read_unlock(mm);
return ret; /* 0 or negative error code */
}
#else /* CONFIG_MMU */
static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start,
unsigned long nr_pages, struct page **pages,
int *locked, unsigned int foll_flags)
{
struct vm_area_struct *vma;
bool must_unlock = false;
unsigned long vm_flags;
long i;
if (!nr_pages)
return 0;
/*
* The internal caller expects GUP to manage the lock internally and the
* lock must be released when this returns.
*/
if (!*locked) {
if (mmap_read_lock_killable(mm))
return -EAGAIN;
must_unlock = true;
*locked = 1;
}
/* calculate required read or write permissions.
* If FOLL_FORCE is set, we only require the "MAY" flags.
*/
vm_flags = (foll_flags & FOLL_WRITE) ?
(VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
vm_flags &= (foll_flags & FOLL_FORCE) ?
(VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
for (i = 0; i < nr_pages; i++) {
vma = find_vma(mm, start);
if (!vma)
break;
/* protect what we can, including chardevs */
if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
!(vm_flags & vma->vm_flags))
break;
if (pages) {
pages[i] = virt_to_page((void *)start);
if (pages[i])
get_page(pages[i]);
}
start = (start + PAGE_SIZE) & PAGE_MASK;
}
if (must_unlock && *locked) {
mmap_read_unlock(mm);
*locked = 0;
}
return i ? : -EFAULT;
}
#endif /* !CONFIG_MMU */
/**
* fault_in_writeable - fault in userspace address range for writing
* @uaddr: start of address range
* @size: size of address range
*
* Returns the number of bytes not faulted in (like copy_to_user() and
* copy_from_user()).
*/
size_t fault_in_writeable(char __user *uaddr, size_t size)
{
char __user *start = uaddr, *end;
if (unlikely(size == 0))
return 0;
if (!user_write_access_begin(uaddr, size))
return size;
if (!PAGE_ALIGNED(uaddr)) {
unsafe_put_user(0, uaddr, out);
uaddr = (char __user *)PAGE_ALIGN((unsigned long)uaddr);
}
end = (char __user *)PAGE_ALIGN((unsigned long)start + size);
if (unlikely(end < start))
end = NULL;
while (uaddr != end) {
unsafe_put_user(0, uaddr, out);
uaddr += PAGE_SIZE;
}
out:
user_write_access_end();
if (size > uaddr - start)
return size - (uaddr - start);
return 0;
}
EXPORT_SYMBOL(fault_in_writeable);
/**
* fault_in_subpage_writeable - fault in an address range for writing
* @uaddr: start of address range
* @size: size of address range
*
* Fault in a user address range for writing while checking for permissions at
* sub-page granularity (e.g. arm64 MTE). This function should be used when
* the caller cannot guarantee forward progress of a copy_to_user() loop.
*
* Returns the number of bytes not faulted in (like copy_to_user() and
* copy_from_user()).
*/
size_t fault_in_subpage_writeable(char __user *uaddr, size_t size)
{
size_t faulted_in;
/*
* Attempt faulting in at page granularity first for page table
* permission checking. The arch-specific probe_subpage_writeable()
* functions may not check for this.
*/
faulted_in = size - fault_in_writeable(uaddr, size);
if (faulted_in)
faulted_in -= probe_subpage_writeable(uaddr, faulted_in);
return size - faulted_in;
}
EXPORT_SYMBOL(fault_in_subpage_writeable);
/*
* fault_in_safe_writeable - fault in an address range for writing
* @uaddr: start of address range
* @size: length of address range
*
* Faults in an address range for writing. This is primarily useful when we
* already know that some or all of the pages in the address range aren't in
* memory.
*
* Unlike fault_in_writeable(), this function is non-destructive.
*
* Note that we don't pin or otherwise hold the pages referenced that we fault
* in. There's no guarantee that they'll stay in memory for any duration of
* time.
*
* Returns the number of bytes not faulted in, like copy_to_user() and
* copy_from_user().
*/
size_t fault_in_safe_writeable(const char __user *uaddr, size_t size)
{
unsigned long start = (unsigned long)uaddr, end;
struct mm_struct *mm = current->mm;
bool unlocked = false;
if (unlikely(size == 0))
return 0;
end = PAGE_ALIGN(start + size);
if (end < start)
end = 0;
mmap_read_lock(mm);
do {
if (fixup_user_fault(mm, start, FAULT_FLAG_WRITE, &unlocked))
break;
start = (start + PAGE_SIZE) & PAGE_MASK;
} while (start != end);
mmap_read_unlock(mm);
if (size > (unsigned long)uaddr - start)
return size - ((unsigned long)uaddr - start);
return 0;
}
EXPORT_SYMBOL(fault_in_safe_writeable);
/**
* fault_in_readable - fault in userspace address range for reading
* @uaddr: start of user address range
* @size: size of user address range
*
* Returns the number of bytes not faulted in (like copy_to_user() and
* copy_from_user()).
*/
size_t fault_in_readable(const char __user *uaddr, size_t size)
{
const char __user *start = uaddr, *end;
volatile char c;
if (unlikely(size == 0))
return 0;
if (!user_read_access_begin(uaddr, size))
return size;
if (!PAGE_ALIGNED(uaddr)) {
unsafe_get_user(c, uaddr, out);
uaddr = (const char __user *)PAGE_ALIGN((unsigned long)uaddr);
}
end = (const char __user *)PAGE_ALIGN((unsigned long)start + size);
if (unlikely(end < start))
end = NULL;
while (uaddr != end) {
unsafe_get_user(c, uaddr, out);
uaddr += PAGE_SIZE;
}
out:
user_read_access_end();
(void)c;
if (size > uaddr - start)
return size - (uaddr - start);
return 0;
}
EXPORT_SYMBOL(fault_in_readable);
/**
* get_dump_page() - pin user page in memory while writing it to core dump
* @addr: user address
*
* Returns struct page pointer of user page pinned for dump,
* to be freed afterwards by put_page().
*
* Returns NULL on any kind of failure - a hole must then be inserted into
* the corefile, to preserve alignment with its headers; and also returns
* NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
* allowing a hole to be left in the corefile to save disk space.
*
* Called without mmap_lock (takes and releases the mmap_lock by itself).
*/
#ifdef CONFIG_ELF_CORE
struct page *get_dump_page(unsigned long addr)
{
struct page *page;
int locked = 0;
int ret;
ret = __get_user_pages_locked(current->mm, addr, 1, &page, &locked,
FOLL_FORCE | FOLL_DUMP | FOLL_GET);
return (ret == 1) ? page : NULL;
}
#endif /* CONFIG_ELF_CORE */
#ifdef CONFIG_MIGRATION
/*
* Returns the number of collected pages. Return value is always >= 0.
*/
static unsigned long collect_longterm_unpinnable_pages(
struct list_head *movable_page_list,
unsigned long nr_pages,
struct page **pages)
{
unsigned long i, collected = 0;
struct folio *prev_folio = NULL;
bool drain_allow = true;
for (i = 0; i < nr_pages; i++) {
struct folio *folio = page_folio(pages[i]);
if (folio == prev_folio)
continue;
prev_folio = folio;
if (folio_is_longterm_pinnable(folio))
continue;
collected++;
if (folio_is_device_coherent(folio))
continue;
if (folio_test_hugetlb(folio)) {
isolate_hugetlb(folio, movable_page_list);
continue;
}
if (!folio_test_lru(folio) && drain_allow) {
lru_add_drain_all();
drain_allow = false;
}
if (!folio_isolate_lru(folio))
continue;
list_add_tail(&folio->lru, movable_page_list);
node_stat_mod_folio(folio,
NR_ISOLATED_ANON + folio_is_file_lru(folio),
folio_nr_pages(folio));
}
return collected;
}
/*
* Unpins all pages and migrates device coherent pages and movable_page_list.
* Returns -EAGAIN if all pages were successfully migrated or -errno for failure
* (or partial success).
*/
static int migrate_longterm_unpinnable_pages(
struct list_head *movable_page_list,
unsigned long nr_pages,
struct page **pages)
{
int ret;
unsigned long i;
for (i = 0; i < nr_pages; i++) {
struct folio *folio = page_folio(pages[i]);
if (folio_is_device_coherent(folio)) {
/*
* Migration will fail if the page is pinned, so convert
* the pin on the source page to a normal reference.
*/
pages[i] = NULL;
folio_get(folio);
gup_put_folio(folio, 1, FOLL_PIN);
if (migrate_device_coherent_page(&folio->page)) {
ret = -EBUSY;
goto err;
}
continue;
}
/*
* We can't migrate pages with unexpected references, so drop
* the reference obtained by __get_user_pages_locked().
* Migrating pages have been added to movable_page_list after
* calling folio_isolate_lru() which takes a reference so the
* page won't be freed if it's migrating.
*/
unpin_user_page(pages[i]);
pages[i] = NULL;
}
if (!list_empty(movable_page_list)) {
struct migration_target_control mtc = {
.nid = NUMA_NO_NODE,
.gfp_mask = GFP_USER | __GFP_NOWARN,
.reason = MR_LONGTERM_PIN,
};
if (migrate_pages(movable_page_list, alloc_migration_target,
NULL, (unsigned long)&mtc, MIGRATE_SYNC,
MR_LONGTERM_PIN, NULL)) {
ret = -ENOMEM;
goto err;
}
}
putback_movable_pages(movable_page_list);
return -EAGAIN;
err:
for (i = 0; i < nr_pages; i++)
if (pages[i])
unpin_user_page(pages[i]);
putback_movable_pages(movable_page_list);
return ret;
}
/*
* Check whether all pages are *allowed* to be pinned. Rather confusingly, all
* pages in the range are required to be pinned via FOLL_PIN, before calling
* this routine.
*
* If any pages in the range are not allowed to be pinned, then this routine
* will migrate those pages away, unpin all the pages in the range and return
* -EAGAIN. The caller should re-pin the entire range with FOLL_PIN and then
* call this routine again.
*
* If an error other than -EAGAIN occurs, this indicates a migration failure.
* The caller should give up, and propagate the error back up the call stack.
*
* If everything is OK and all pages in the range are allowed to be pinned, then
* this routine leaves all pages pinned and returns zero for success.
*/
static long check_and_migrate_movable_pages(unsigned long nr_pages,
struct page **pages)
{
unsigned long collected;
LIST_HEAD(movable_page_list);
collected = collect_longterm_unpinnable_pages(&movable_page_list,
nr_pages, pages);
if (!collected)
return 0;
return migrate_longterm_unpinnable_pages(&movable_page_list, nr_pages,
pages);
}
#else
static long check_and_migrate_movable_pages(unsigned long nr_pages,
struct page **pages)
{
return 0;
}
#endif /* CONFIG_MIGRATION */
/*
* __gup_longterm_locked() is a wrapper for __get_user_pages_locked which
* allows us to process the FOLL_LONGTERM flag.
*/
static long __gup_longterm_locked(struct mm_struct *mm,
unsigned long start,
unsigned long nr_pages,
struct page **pages,
int *locked,
unsigned int gup_flags)
{
unsigned int flags;
long rc, nr_pinned_pages;
if (!(gup_flags & FOLL_LONGTERM))
return __get_user_pages_locked(mm, start, nr_pages, pages,
locked, gup_flags);
flags = memalloc_pin_save();
do {
nr_pinned_pages = __get_user_pages_locked(mm, start, nr_pages,
pages, locked,
gup_flags);
if (nr_pinned_pages <= 0) {
rc = nr_pinned_pages;
break;
}
/* FOLL_LONGTERM implies FOLL_PIN */
rc = check_and_migrate_movable_pages(nr_pinned_pages, pages);
} while (rc == -EAGAIN);
memalloc_pin_restore(flags);
return rc ? rc : nr_pinned_pages;
}
/*
* Check that the given flags are valid for the exported gup/pup interface, and
* update them with the required flags that the caller must have set.
*/
static bool is_valid_gup_args(struct page **pages, int *locked,
unsigned int *gup_flags_p, unsigned int to_set)
{
unsigned int gup_flags = *gup_flags_p;
/*
* These flags not allowed to be specified externally to the gup
* interfaces:
* - FOLL_TOUCH/FOLL_PIN/FOLL_TRIED/FOLL_FAST_ONLY are internal only
* - FOLL_REMOTE is internal only and used on follow_page()
* - FOLL_UNLOCKABLE is internal only and used if locked is !NULL
*/
if (WARN_ON_ONCE(gup_flags & INTERNAL_GUP_FLAGS))
return false;
gup_flags |= to_set;
if (locked) {
/* At the external interface locked must be set */
if (WARN_ON_ONCE(*locked != 1))
return false;
gup_flags |= FOLL_UNLOCKABLE;
}
/* FOLL_GET and FOLL_PIN are mutually exclusive. */
if (WARN_ON_ONCE((gup_flags & (FOLL_PIN | FOLL_GET)) ==
(FOLL_PIN | FOLL_GET)))
return false;
/* LONGTERM can only be specified when pinning */
if (WARN_ON_ONCE(!(gup_flags & FOLL_PIN) && (gup_flags & FOLL_LONGTERM)))
return false;
/* Pages input must be given if using GET/PIN */
if (WARN_ON_ONCE((gup_flags & (FOLL_GET | FOLL_PIN)) && !pages))
return false;
/* We want to allow the pgmap to be hot-unplugged at all times */
if (WARN_ON_ONCE((gup_flags & FOLL_LONGTERM) &&
(gup_flags & FOLL_PCI_P2PDMA)))
return false;
*gup_flags_p = gup_flags;
return true;
}
#ifdef CONFIG_MMU
/**
* get_user_pages_remote() - pin user pages in memory
* @mm: mm_struct of target mm
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying lookup behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long. Or NULL, if caller
* only intends to ensure the pages are faulted in.
* @locked: pointer to lock flag indicating whether lock is held and
* subsequently whether VM_FAULT_RETRY functionality can be
* utilised. Lock must initially be held.
*
* Returns either number of pages pinned (which may be less than the
* number requested), or an error. Details about the return value:
*
* -- If nr_pages is 0, returns 0.
* -- If nr_pages is >0, but no pages were pinned, returns -errno.
* -- If nr_pages is >0, and some pages were pinned, returns the number of
* pages pinned. Again, this may be less than nr_pages.
*
* The caller is responsible for releasing returned @pages, via put_page().
*
* Must be called with mmap_lock held for read or write.
*
* get_user_pages_remote walks a process's page tables and takes a reference
* to each struct page that each user address corresponds to at a given
* instant. That is, it takes the page that would be accessed if a user
* thread accesses the given user virtual address at that instant.
*
* This does not guarantee that the page exists in the user mappings when
* get_user_pages_remote returns, and there may even be a completely different
* page there in some cases (eg. if mmapped pagecache has been invalidated
* and subsequently re-faulted). However it does guarantee that the page
* won't be freed completely. And mostly callers simply care that the page
* contains data that was valid *at some point in time*. Typically, an IO
* or similar operation cannot guarantee anything stronger anyway because
* locks can't be held over the syscall boundary.
*
* If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
* is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
* be called after the page is finished with, and before put_page is called.
*
* get_user_pages_remote is typically used for fewer-copy IO operations,
* to get a handle on the memory by some means other than accesses
* via the user virtual addresses. The pages may be submitted for
* DMA to devices or accessed via their kernel linear mapping (via the
* kmap APIs). Care should be taken to use the correct cache flushing APIs.
*
* See also get_user_pages_fast, for performance critical applications.
*
* get_user_pages_remote should be phased out in favor of
* get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
* should use get_user_pages_remote because it cannot pass
* FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
*/
long get_user_pages_remote(struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
int *locked)
{
int local_locked = 1;
if (!is_valid_gup_args(pages, locked, &gup_flags,
FOLL_TOUCH | FOLL_REMOTE))
return -EINVAL;
return __get_user_pages_locked(mm, start, nr_pages, pages,
locked ? locked : &local_locked,
gup_flags);
}
EXPORT_SYMBOL(get_user_pages_remote);
#else /* CONFIG_MMU */
long get_user_pages_remote(struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
int *locked)
{
return 0;
}
#endif /* !CONFIG_MMU */
/**
* get_user_pages() - pin user pages in memory
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying lookup behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long. Or NULL, if caller
* only intends to ensure the pages are faulted in.
*
* This is the same as get_user_pages_remote(), just with a less-flexible
* calling convention where we assume that the mm being operated on belongs to
* the current task, and doesn't allow passing of a locked parameter. We also
* obviously don't pass FOLL_REMOTE in here.
*/
long get_user_pages(unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages)
{
int locked = 1;
if (!is_valid_gup_args(pages, NULL, &gup_flags, FOLL_TOUCH))
return -EINVAL;
return __get_user_pages_locked(current->mm, start, nr_pages, pages,
&locked, gup_flags);
}
EXPORT_SYMBOL(get_user_pages);
/*
* get_user_pages_unlocked() is suitable to replace the form:
*
* mmap_read_lock(mm);
* get_user_pages(mm, ..., pages, NULL);
* mmap_read_unlock(mm);
*
* with:
*
* get_user_pages_unlocked(mm, ..., pages);
*
* It is functionally equivalent to get_user_pages_fast so
* get_user_pages_fast should be used instead if specific gup_flags
* (e.g. FOLL_FORCE) are not required.
*/
long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
struct page **pages, unsigned int gup_flags)
{
int locked = 0;
if (!is_valid_gup_args(pages, NULL, &gup_flags,
FOLL_TOUCH | FOLL_UNLOCKABLE))
return -EINVAL;
return __get_user_pages_locked(current->mm, start, nr_pages, pages,
&locked, gup_flags);
}
EXPORT_SYMBOL(get_user_pages_unlocked);
/*
* Fast GUP
*
* get_user_pages_fast attempts to pin user pages by walking the page
* tables directly and avoids taking locks. Thus the walker needs to be
* protected from page table pages being freed from under it, and should
* block any THP splits.
*
* One way to achieve this is to have the walker disable interrupts, and
* rely on IPIs from the TLB flushing code blocking before the page table
* pages are freed. This is unsuitable for architectures that do not need
* to broadcast an IPI when invalidating TLBs.
*
* Another way to achieve this is to batch up page table containing pages
* belonging to more than one mm_user, then rcu_sched a callback to free those
* pages. Disabling interrupts will allow the fast_gup walker to both block
* the rcu_sched callback, and an IPI that we broadcast for splitting THPs
* (which is a relatively rare event). The code below adopts this strategy.
*
* Before activating this code, please be aware that the following assumptions
* are currently made:
*
* *) Either MMU_GATHER_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to
* free pages containing page tables or TLB flushing requires IPI broadcast.
*
* *) ptes can be read atomically by the architecture.
*
* *) access_ok is sufficient to validate userspace address ranges.
*
* The last two assumptions can be relaxed by the addition of helper functions.
*
* This code is based heavily on the PowerPC implementation by Nick Piggin.
*/
#ifdef CONFIG_HAVE_FAST_GUP
/*
* Used in the GUP-fast path to determine whether GUP is permitted to work on
* a specific folio.
*
* This call assumes the caller has pinned the folio, that the lowest page table
* level still points to this folio, and that interrupts have been disabled.
*
* GUP-fast must reject all secretmem folios.
*
* Writing to pinned file-backed dirty tracked folios is inherently problematic
* (see comment describing the writable_file_mapping_allowed() function). We
* therefore try to avoid the most egregious case of a long-term mapping doing
* so.
*
* This function cannot be as thorough as that one as the VMA is not available
* in the fast path, so instead we whitelist known good cases and if in doubt,
* fall back to the slow path.
*/
static bool gup_fast_folio_allowed(struct folio *folio, unsigned int flags)
{
bool reject_file_backed = false;
struct address_space *mapping;
bool check_secretmem = false;
unsigned long mapping_flags;
/*
* If we aren't pinning then no problematic write can occur. A long term
* pin is the most egregious case so this is the one we disallow.
*/
if ((flags & (FOLL_PIN | FOLL_LONGTERM | FOLL_WRITE)) ==
(FOLL_PIN | FOLL_LONGTERM | FOLL_WRITE))
reject_file_backed = true;
/* We hold a folio reference, so we can safely access folio fields. */
/* secretmem folios are always order-0 folios. */
if (IS_ENABLED(CONFIG_SECRETMEM) && !folio_test_large(folio))
check_secretmem = true;
if (!reject_file_backed && !check_secretmem)
return true;
if (WARN_ON_ONCE(folio_test_slab(folio)))
return false;
/* hugetlb neither requires dirty-tracking nor can be secretmem. */
if (folio_test_hugetlb(folio))
return true;
/*
* GUP-fast disables IRQs. When IRQS are disabled, RCU grace periods
* cannot proceed, which means no actions performed under RCU can
* proceed either.
*
* inodes and thus their mappings are freed under RCU, which means the
* mapping cannot be freed beneath us and thus we can safely dereference
* it.
*/
lockdep_assert_irqs_disabled();
/*
* However, there may be operations which _alter_ the mapping, so ensure
* we read it once and only once.
*/
mapping = READ_ONCE(folio->mapping);
/*
* The mapping may have been truncated, in any case we cannot determine
* if this mapping is safe - fall back to slow path to determine how to
* proceed.
*/
if (!mapping)
return false;
/* Anonymous folios pose no problem. */
mapping_flags = (unsigned long)mapping & PAGE_MAPPING_FLAGS;
if (mapping_flags)
return mapping_flags & PAGE_MAPPING_ANON;
/*
* At this point, we know the mapping is non-null and points to an
* address_space object.
*/
if (check_secretmem && secretmem_mapping(mapping))
return false;
/* The only remaining allowed file system is shmem. */
return !reject_file_backed || shmem_mapping(mapping);
}
static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start,
unsigned int flags,
struct page **pages)
{
while ((*nr) - nr_start) {
struct page *page = pages[--(*nr)];
ClearPageReferenced(page);
if (flags & FOLL_PIN)
unpin_user_page(page);
else
put_page(page);
}
}
#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
/*
* Fast-gup relies on pte change detection to avoid concurrent pgtable
* operations.
*
* To pin the page, fast-gup needs to do below in order:
* (1) pin the page (by prefetching pte), then (2) check pte not changed.
*
* For the rest of pgtable operations where pgtable updates can be racy
* with fast-gup, we need to do (1) clear pte, then (2) check whether page
* is pinned.
*
* Above will work for all pte-level operations, including THP split.
*
* For THP collapse, it's a bit more complicated because fast-gup may be
* walking a pgtable page that is being freed (pte is still valid but pmd
* can be cleared already). To avoid race in such condition, we need to
* also check pmd here to make sure pmd doesn't change (corresponds to
* pmdp_collapse_flush() in the THP collapse code path).
*/
static int gup_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
struct dev_pagemap *pgmap = NULL;
int nr_start = *nr, ret = 0;
pte_t *ptep, *ptem;
ptem = ptep = pte_offset_map(&pmd, addr);
if (!ptep)
return 0;
do {
pte_t pte = ptep_get_lockless(ptep);
struct page *page;
struct folio *folio;
/*
* Always fallback to ordinary GUP on PROT_NONE-mapped pages:
* pte_access_permitted() better should reject these pages
* either way: otherwise, GUP-fast might succeed in
* cases where ordinary GUP would fail due to VMA access
* permissions.
*/
if (pte_protnone(pte))
goto pte_unmap;
if (!pte_access_permitted(pte, flags & FOLL_WRITE))
goto pte_unmap;
if (pte_devmap(pte)) {
if (unlikely(flags & FOLL_LONGTERM))
goto pte_unmap;
pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
if (unlikely(!pgmap)) {
undo_dev_pagemap(nr, nr_start, flags, pages);
goto pte_unmap;
}
} else if (pte_special(pte))
goto pte_unmap;
VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
page = pte_page(pte);
folio = try_grab_folio(page, 1, flags);
if (!folio)
goto pte_unmap;
if (unlikely(pmd_val(pmd) != pmd_val(*pmdp)) ||
unlikely(pte_val(pte) != pte_val(ptep_get(ptep)))) {
gup_put_folio(folio, 1, flags);
goto pte_unmap;
}
if (!gup_fast_folio_allowed(folio, flags)) {
gup_put_folio(folio, 1, flags);
goto pte_unmap;
}
if (!pte_write(pte) && gup_must_unshare(NULL, flags, page)) {
gup_put_folio(folio, 1, flags);
goto pte_unmap;
}
/*
* We need to make the page accessible if and only if we are
* going to access its content (the FOLL_PIN case). Please
* see Documentation/core-api/pin_user_pages.rst for
* details.
*/
if (flags & FOLL_PIN) {
ret = arch_make_page_accessible(page);
if (ret) {
gup_put_folio(folio, 1, flags);
goto pte_unmap;
}
}
folio_set_referenced(folio);
pages[*nr] = page;
(*nr)++;
} while (ptep++, addr += PAGE_SIZE, addr != end);
ret = 1;
pte_unmap:
if (pgmap)
put_dev_pagemap(pgmap);
pte_unmap(ptem);
return ret;
}
#else
/*
* If we can't determine whether or not a pte is special, then fail immediately
* for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
* to be special.
*
* For a futex to be placed on a THP tail page, get_futex_key requires a
* get_user_pages_fast_only implementation that can pin pages. Thus it's still
* useful to have gup_huge_pmd even if we can't operate on ptes.
*/
static int gup_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
return 0;
}
#endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
#if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
static int __gup_device_huge(unsigned long pfn, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
int nr_start = *nr;
struct dev_pagemap *pgmap = NULL;
do {
struct page *page = pfn_to_page(pfn);
pgmap = get_dev_pagemap(pfn, pgmap);
if (unlikely(!pgmap)) {
undo_dev_pagemap(nr, nr_start, flags, pages);
break;
}
if (!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page)) {
undo_dev_pagemap(nr, nr_start, flags, pages);
break;
}
SetPageReferenced(page);
pages[*nr] = page;
if (unlikely(try_grab_page(page, flags))) {
undo_dev_pagemap(nr, nr_start, flags, pages);
break;
}
(*nr)++;
pfn++;
} while (addr += PAGE_SIZE, addr != end);
put_dev_pagemap(pgmap);
return addr == end;
}
static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
unsigned long fault_pfn;
int nr_start = *nr;
fault_pfn = pmd_pfn(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr))
return 0;
if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
undo_dev_pagemap(nr, nr_start, flags, pages);
return 0;
}
return 1;
}
static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
unsigned long fault_pfn;
int nr_start = *nr;
fault_pfn = pud_pfn(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr))
return 0;
if (unlikely(pud_val(orig) != pud_val(*pudp))) {
undo_dev_pagemap(nr, nr_start, flags, pages);
return 0;
}
return 1;
}
#else
static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
BUILD_BUG();
return 0;
}
static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
BUILD_BUG();
return 0;
}
#endif
static int record_subpages(struct page *page, unsigned long addr,
unsigned long end, struct page **pages)
{
int nr;
for (nr = 0; addr != end; nr++, addr += PAGE_SIZE)
pages[nr] = nth_page(page, nr);
return nr;
}
#ifdef CONFIG_ARCH_HAS_HUGEPD
static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
unsigned long sz)
{
unsigned long __boundary = (addr + sz) & ~(sz-1);
return (__boundary - 1 < end - 1) ? __boundary : end;
}
static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
unsigned long pte_end;
struct page *page;
struct folio *folio;
pte_t pte;
int refs;
pte_end = (addr + sz) & ~(sz-1);
if (pte_end < end)
end = pte_end;
pte = huge_ptep_get(ptep);
if (!pte_access_permitted(pte, flags & FOLL_WRITE))
return 0;
/* hugepages are never "special" */
VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
page = nth_page(pte_page(pte), (addr & (sz - 1)) >> PAGE_SHIFT);
refs = record_subpages(page, addr, end, pages + *nr);
folio = try_grab_folio(page, refs, flags);
if (!folio)
return 0;
if (unlikely(pte_val(pte) != pte_val(ptep_get(ptep)))) {
gup_put_folio(folio, refs, flags);
return 0;
}
if (!pte_write(pte) && gup_must_unshare(NULL, flags, &folio->page)) {
gup_put_folio(folio, refs, flags);
return 0;
}
*nr += refs;
folio_set_referenced(folio);
return 1;
}
/*
* NOTE: currently GUP for a hugepd is only possible on hugetlbfs file
* systems on Power, which does not have issue with folio writeback against
* GUP updates. When hugepd will be extended to support non-hugetlbfs or
* even anonymous memory, we need to do extra check as what we do with most
* of the other folios. See writable_file_mapping_allowed() and
* gup_fast_folio_allowed() for more information.
*/
static int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
unsigned int pdshift, unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
pte_t *ptep;
unsigned long sz = 1UL << hugepd_shift(hugepd);
unsigned long next;
ptep = hugepte_offset(hugepd, addr, pdshift);
do {
next = hugepte_addr_end(addr, end, sz);
if (!gup_hugepte(ptep, sz, addr, end, flags, pages, nr))
return 0;
} while (ptep++, addr = next, addr != end);
return 1;
}
#else
static inline int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
unsigned int pdshift, unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
return 0;
}
#endif /* CONFIG_ARCH_HAS_HUGEPD */
static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
struct page *page;
struct folio *folio;
int refs;
if (!pmd_access_permitted(orig, flags & FOLL_WRITE))
return 0;
if (pmd_devmap(orig)) {
if (unlikely(flags & FOLL_LONGTERM))
return 0;
return __gup_device_huge_pmd(orig, pmdp, addr, end, flags,
pages, nr);
}
page = nth_page(pmd_page(orig), (addr & ~PMD_MASK) >> PAGE_SHIFT);
refs = record_subpages(page, addr, end, pages + *nr);
folio = try_grab_folio(page, refs, flags);
if (!folio)
return 0;
if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
gup_put_folio(folio, refs, flags);
return 0;
}
if (!gup_fast_folio_allowed(folio, flags)) {
gup_put_folio(folio, refs, flags);
return 0;
}
if (!pmd_write(orig) && gup_must_unshare(NULL, flags, &folio->page)) {
gup_put_folio(folio, refs, flags);
return 0;
}
*nr += refs;
folio_set_referenced(folio);
return 1;
}
static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
struct page *page;
struct folio *folio;
int refs;
if (!pud_access_permitted(orig, flags & FOLL_WRITE))
return 0;
if (pud_devmap(orig)) {
if (unlikely(flags & FOLL_LONGTERM))
return 0;
return __gup_device_huge_pud(orig, pudp, addr, end, flags,
pages, nr);
}
page = nth_page(pud_page(orig), (addr & ~PUD_MASK) >> PAGE_SHIFT);
refs = record_subpages(page, addr, end, pages + *nr);
folio = try_grab_folio(page, refs, flags);
if (!folio)
return 0;
if (unlikely(pud_val(orig) != pud_val(*pudp))) {
gup_put_folio(folio, refs, flags);
return 0;
}
if (!gup_fast_folio_allowed(folio, flags)) {
gup_put_folio(folio, refs, flags);
return 0;
}
if (!pud_write(orig) && gup_must_unshare(NULL, flags, &folio->page)) {
gup_put_folio(folio, refs, flags);
return 0;
}
*nr += refs;
folio_set_referenced(folio);
return 1;
}
static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
int refs;
struct page *page;
struct folio *folio;
if (!pgd_access_permitted(orig, flags & FOLL_WRITE))
return 0;
BUILD_BUG_ON(pgd_devmap(orig));
page = nth_page(pgd_page(orig), (addr & ~PGDIR_MASK) >> PAGE_SHIFT);
refs = record_subpages(page, addr, end, pages + *nr);
folio = try_grab_folio(page, refs, flags);
if (!folio)
return 0;
if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
gup_put_folio(folio, refs, flags);
return 0;
}
if (!pgd_write(orig) && gup_must_unshare(NULL, flags, &folio->page)) {
gup_put_folio(folio, refs, flags);
return 0;
}
if (!gup_fast_folio_allowed(folio, flags)) {
gup_put_folio(folio, refs, flags);
return 0;
}
*nr += refs;
folio_set_referenced(folio);
return 1;
}
static int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, unsigned long end,
unsigned int flags, struct page **pages, int *nr)
{
unsigned long next;
pmd_t *pmdp;
pmdp = pmd_offset_lockless(pudp, pud, addr);
do {
pmd_t pmd = pmdp_get_lockless(pmdp);
next = pmd_addr_end(addr, end);
if (!pmd_present(pmd))
return 0;
if (unlikely(pmd_leaf(pmd))) {
/* See gup_pte_range() */
if (pmd_protnone(pmd))
return 0;
if (!gup_huge_pmd(pmd, pmdp, addr, next, flags,
pages, nr))
return 0;
} else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
/*
* architecture have different format for hugetlbfs
* pmd format and THP pmd format
*/
if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
PMD_SHIFT, next, flags, pages, nr))
return 0;
} else if (!gup_pte_range(pmd, pmdp, addr, next, flags, pages, nr))
return 0;
} while (pmdp++, addr = next, addr != end);
return 1;
}
static int gup_pud_range(p4d_t *p4dp, p4d_t p4d, unsigned long addr, unsigned long end,
unsigned int flags, struct page **pages, int *nr)
{
unsigned long next;
pud_t *pudp;
pudp = pud_offset_lockless(p4dp, p4d, addr);
do {
pud_t pud = READ_ONCE(*pudp);
next = pud_addr_end(addr, end);
if (unlikely(!pud_present(pud)))
return 0;
if (unlikely(pud_leaf(pud))) {
if (!gup_huge_pud(pud, pudp, addr, next, flags,
pages, nr))
return 0;
} else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
PUD_SHIFT, next, flags, pages, nr))
return 0;
} else if (!gup_pmd_range(pudp, pud, addr, next, flags, pages, nr))
return 0;
} while (pudp++, addr = next, addr != end);
return 1;
}
static int gup_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr, unsigned long end,
unsigned int flags, struct page **pages, int *nr)
{
unsigned long next;
p4d_t *p4dp;
p4dp = p4d_offset_lockless(pgdp, pgd, addr);
do {
p4d_t p4d = READ_ONCE(*p4dp);
next = p4d_addr_end(addr, end);
if (!p4d_present(p4d))
return 0;
BUILD_BUG_ON(p4d_leaf(p4d));
if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {
if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
P4D_SHIFT, next, flags, pages, nr))
return 0;
} else if (!gup_pud_range(p4dp, p4d, addr, next, flags, pages, nr))
return 0;
} while (p4dp++, addr = next, addr != end);
return 1;
}
static void gup_pgd_range(unsigned long addr, unsigned long end,
unsigned int flags, struct page **pages, int *nr)
{
unsigned long next;
pgd_t *pgdp;
pgdp = pgd_offset(current->mm, addr);
do {
pgd_t pgd = READ_ONCE(*pgdp);
next = pgd_addr_end(addr, end);
if (pgd_none(pgd))
return;
if (unlikely(pgd_leaf(pgd))) {
if (!gup_huge_pgd(pgd, pgdp, addr, next, flags,
pages, nr))
return;
} else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
PGDIR_SHIFT, next, flags, pages, nr))
return;
} else if (!gup_p4d_range(pgdp, pgd, addr, next, flags, pages, nr))
return;
} while (pgdp++, addr = next, addr != end);
}
#else
static inline void gup_pgd_range(unsigned long addr, unsigned long end,
unsigned int flags, struct page **pages, int *nr)
{
}
#endif /* CONFIG_HAVE_FAST_GUP */
#ifndef gup_fast_permitted
/*
* Check if it's allowed to use get_user_pages_fast_only() for the range, or
* we need to fall back to the slow version:
*/
static bool gup_fast_permitted(unsigned long start, unsigned long end)
{
return true;
}
#endif
static unsigned long lockless_pages_from_mm(unsigned long start,
unsigned long end,
unsigned int gup_flags,
struct page **pages)
{
unsigned long flags;
int nr_pinned = 0;
unsigned seq;
if (!IS_ENABLED(CONFIG_HAVE_FAST_GUP) ||
!gup_fast_permitted(start, end))
return 0;
if (gup_flags & FOLL_PIN) {
seq = raw_read_seqcount(&current->mm->write_protect_seq);
if (seq & 1)
return 0;
}
/*
* Disable interrupts. The nested form is used, in order to allow full,
* general purpose use of this routine.
*
* With interrupts disabled, we block page table pages from being freed
* from under us. See struct mmu_table_batch comments in
* include/asm-generic/tlb.h for more details.
*
* We do not adopt an rcu_read_lock() here as we also want to block IPIs
* that come from THPs splitting.
*/
local_irq_save(flags);
gup_pgd_range(start, end, gup_flags, pages, &nr_pinned);
local_irq_restore(flags);
/*
* When pinning pages for DMA there could be a concurrent write protect
* from fork() via copy_page_range(), in this case always fail fast GUP.
*/
if (gup_flags & FOLL_PIN) {
if (read_seqcount_retry(&current->mm->write_protect_seq, seq)) {
unpin_user_pages_lockless(pages, nr_pinned);
return 0;
} else {
sanity_check_pinned_pages(pages, nr_pinned);
}
}
return nr_pinned;
}
static int internal_get_user_pages_fast(unsigned long start,
unsigned long nr_pages,
unsigned int gup_flags,
struct page **pages)
{
unsigned long len, end;
unsigned long nr_pinned;
int locked = 0;
int ret;
if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM |
FOLL_FORCE | FOLL_PIN | FOLL_GET |
FOLL_FAST_ONLY | FOLL_NOFAULT |
FOLL_PCI_P2PDMA | FOLL_HONOR_NUMA_FAULT)))
return -EINVAL;
if (gup_flags & FOLL_PIN)
mm_set_has_pinned_flag(&current->mm->flags);
if (!(gup_flags & FOLL_FAST_ONLY))
might_lock_read(&current->mm->mmap_lock);
start = untagged_addr(start) & PAGE_MASK;
len = nr_pages << PAGE_SHIFT;
if (check_add_overflow(start, len, &end))
return -EOVERFLOW;
if (end > TASK_SIZE_MAX)
return -EFAULT;
if (unlikely(!access_ok((void __user *)start, len)))
return -EFAULT;
nr_pinned = lockless_pages_from_mm(start, end, gup_flags, pages);
if (nr_pinned == nr_pages || gup_flags & FOLL_FAST_ONLY)
return nr_pinned;
/* Slow path: try to get the remaining pages with get_user_pages */
start += nr_pinned << PAGE_SHIFT;
pages += nr_pinned;
ret = __gup_longterm_locked(current->mm, start, nr_pages - nr_pinned,
pages, &locked,
gup_flags | FOLL_TOUCH | FOLL_UNLOCKABLE);
if (ret < 0) {
/*
* The caller has to unpin the pages we already pinned so
* returning -errno is not an option
*/
if (nr_pinned)
return nr_pinned;
return ret;
}
return ret + nr_pinned;
}
/**
* get_user_pages_fast_only() - pin user pages in memory
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying pin behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long.
*
* Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
* the regular GUP.
*
* If the architecture does not support this function, simply return with no
* pages pinned.
*
* Careful, careful! COW breaking can go either way, so a non-write
* access can get ambiguous page results. If you call this function without
* 'write' set, you'd better be sure that you're ok with that ambiguity.
*/
int get_user_pages_fast_only(unsigned long start, int nr_pages,
unsigned int gup_flags, struct page **pages)
{
/*
* Internally (within mm/gup.c), gup fast variants must set FOLL_GET,
* because gup fast is always a "pin with a +1 page refcount" request.
*
* FOLL_FAST_ONLY is required in order to match the API description of
* this routine: no fall back to regular ("slow") GUP.
*/
if (!is_valid_gup_args(pages, NULL, &gup_flags,
FOLL_GET | FOLL_FAST_ONLY))
return -EINVAL;
return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
}
EXPORT_SYMBOL_GPL(get_user_pages_fast_only);
/**
* get_user_pages_fast() - pin user pages in memory
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying pin behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long.
*
* Attempt to pin user pages in memory without taking mm->mmap_lock.
* If not successful, it will fall back to taking the lock and
* calling get_user_pages().
*
* Returns number of pages pinned. This may be fewer than the number requested.
* If nr_pages is 0 or negative, returns 0. If no pages were pinned, returns
* -errno.
*/
int get_user_pages_fast(unsigned long start, int nr_pages,
unsigned int gup_flags, struct page **pages)
{
/*
* The caller may or may not have explicitly set FOLL_GET; either way is
* OK. However, internally (within mm/gup.c), gup fast variants must set
* FOLL_GET, because gup fast is always a "pin with a +1 page refcount"
* request.
*/
if (!is_valid_gup_args(pages, NULL, &gup_flags, FOLL_GET))
return -EINVAL;
return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
}
EXPORT_SYMBOL_GPL(get_user_pages_fast);
/**
* pin_user_pages_fast() - pin user pages in memory without taking locks
*
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying pin behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long.
*
* Nearly the same as get_user_pages_fast(), except that FOLL_PIN is set. See
* get_user_pages_fast() for documentation on the function arguments, because
* the arguments here are identical.
*
* FOLL_PIN means that the pages must be released via unpin_user_page(). Please
* see Documentation/core-api/pin_user_pages.rst for further details.
*
* Note that if a zero_page is amongst the returned pages, it will not have
* pins in it and unpin_user_page() will not remove pins from it.
*/
int pin_user_pages_fast(unsigned long start, int nr_pages,
unsigned int gup_flags, struct page **pages)
{
if (!is_valid_gup_args(pages, NULL, &gup_flags, FOLL_PIN))
return -EINVAL;
return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
}
EXPORT_SYMBOL_GPL(pin_user_pages_fast);
/**
* pin_user_pages_remote() - pin pages of a remote process
*
* @mm: mm_struct of target mm
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying lookup behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long.
* @locked: pointer to lock flag indicating whether lock is held and
* subsequently whether VM_FAULT_RETRY functionality can be
* utilised. Lock must initially be held.
*
* Nearly the same as get_user_pages_remote(), except that FOLL_PIN is set. See
* get_user_pages_remote() for documentation on the function arguments, because
* the arguments here are identical.
*
* FOLL_PIN means that the pages must be released via unpin_user_page(). Please
* see Documentation/core-api/pin_user_pages.rst for details.
*
* Note that if a zero_page is amongst the returned pages, it will not have
* pins in it and unpin_user_page*() will not remove pins from it.
*/
long pin_user_pages_remote(struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
int *locked)
{
int local_locked = 1;
if (!is_valid_gup_args(pages, locked, &gup_flags,
FOLL_PIN | FOLL_TOUCH | FOLL_REMOTE))
return 0;
return __gup_longterm_locked(mm, start, nr_pages, pages,
locked ? locked : &local_locked,
gup_flags);
}
EXPORT_SYMBOL(pin_user_pages_remote);
/**
* pin_user_pages() - pin user pages in memory for use by other devices
*
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @gup_flags: flags modifying lookup behaviour
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long.
*
* Nearly the same as get_user_pages(), except that FOLL_TOUCH is not set, and
* FOLL_PIN is set.
*
* FOLL_PIN means that the pages must be released via unpin_user_page(). Please
* see Documentation/core-api/pin_user_pages.rst for details.
*
* Note that if a zero_page is amongst the returned pages, it will not have
* pins in it and unpin_user_page*() will not remove pins from it.
*/
long pin_user_pages(unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages)
{
int locked = 1;
if (!is_valid_gup_args(pages, NULL, &gup_flags, FOLL_PIN))
return 0;
return __gup_longterm_locked(current->mm, start, nr_pages,
pages, &locked, gup_flags);
}
EXPORT_SYMBOL(pin_user_pages);
/*
* pin_user_pages_unlocked() is the FOLL_PIN variant of
* get_user_pages_unlocked(). Behavior is the same, except that this one sets
* FOLL_PIN and rejects FOLL_GET.
*
* Note that if a zero_page is amongst the returned pages, it will not have
* pins in it and unpin_user_page*() will not remove pins from it.
*/
long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
struct page **pages, unsigned int gup_flags)
{
int locked = 0;
if (!is_valid_gup_args(pages, NULL, &gup_flags,
FOLL_PIN | FOLL_TOUCH | FOLL_UNLOCKABLE))
return 0;
return __gup_longterm_locked(current->mm, start, nr_pages, pages,
&locked, gup_flags);
}
EXPORT_SYMBOL(pin_user_pages_unlocked);