| // 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_folio_refs(folio, 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_folio_refs(folio, 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_folio_refs(folio, 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 gup_fast_unpin_user_pages(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 |
| |
| #if defined(CONFIG_ARCH_HAS_HUGEPD) || defined(CONFIG_HAVE_GUP_FAST) |
| static int record_subpages(struct page *page, unsigned long sz, |
| unsigned long addr, unsigned long end, |
| struct page **pages) |
| { |
| struct page *start_page; |
| int nr; |
| |
| start_page = nth_page(page, (addr & (sz - 1)) >> PAGE_SHIFT); |
| for (nr = 0; addr != end; nr++, addr += PAGE_SIZE) |
| pages[nr] = nth_page(start_page, nr); |
| |
| return nr; |
| } |
| #endif /* CONFIG_ARCH_HAS_HUGEPD || CONFIG_HAVE_GUP_FAST */ |
| |
| #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; |
| } |
| |
| /* |
| * Returns 1 if succeeded, 0 if failed, -EMLINK if unshare needed. |
| * |
| * NOTE: for the same entry, gup-fast and gup-slow can return different |
| * results (0 v.s. -EMLINK) depending on whether vma is available. This is |
| * the expected behavior, where we simply want gup-fast to fallback to |
| * gup-slow to take the vma reference first. |
| */ |
| static int gup_hugepte(struct vm_area_struct *vma, 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 = pte_page(pte); |
| refs = record_subpages(page, sz, 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(vma, flags, &folio->page)) { |
| gup_put_folio(folio, refs, flags); |
| return -EMLINK; |
| } |
| |
| *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_hugepd(struct vm_area_struct *vma, 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; |
| int ret; |
| |
| ptep = hugepte_offset(hugepd, addr, pdshift); |
| do { |
| next = hugepte_addr_end(addr, end, sz); |
| ret = gup_hugepte(vma, ptep, sz, addr, end, flags, pages, nr); |
| if (ret != 1) |
| return ret; |
| } while (ptep++, addr = next, addr != end); |
| |
| return 1; |
| } |
| |
| static struct page *follow_hugepd(struct vm_area_struct *vma, hugepd_t hugepd, |
| unsigned long addr, unsigned int pdshift, |
| unsigned int flags, |
| struct follow_page_context *ctx) |
| { |
| struct page *page; |
| struct hstate *h; |
| spinlock_t *ptl; |
| int nr = 0, ret; |
| pte_t *ptep; |
| |
| /* Only hugetlb supports hugepd */ |
| if (WARN_ON_ONCE(!is_vm_hugetlb_page(vma))) |
| return ERR_PTR(-EFAULT); |
| |
| h = hstate_vma(vma); |
| ptep = hugepte_offset(hugepd, addr, pdshift); |
| ptl = huge_pte_lock(h, vma->vm_mm, ptep); |
| ret = gup_hugepd(vma, hugepd, addr, pdshift, addr + PAGE_SIZE, |
| flags, &page, &nr); |
| spin_unlock(ptl); |
| |
| if (ret == 1) { |
| /* GUP succeeded */ |
| WARN_ON_ONCE(nr != 1); |
| ctx->page_mask = (1U << huge_page_order(h)) - 1; |
| return page; |
| } |
| |
| /* ret can be either 0 (translates to NULL) or negative */ |
| return ERR_PTR(ret); |
| } |
| #else /* CONFIG_ARCH_HAS_HUGEPD */ |
| static inline int gup_hugepd(struct vm_area_struct *vma, hugepd_t hugepd, |
| unsigned long addr, unsigned int pdshift, |
| unsigned long end, unsigned int flags, |
| struct page **pages, int *nr) |
| { |
| return 0; |
| } |
| |
| static struct page *follow_hugepd(struct vm_area_struct *vma, hugepd_t hugepd, |
| unsigned long addr, unsigned int pdshift, |
| unsigned int flags, |
| struct follow_page_context *ctx) |
| { |
| return NULL; |
| } |
| #endif /* CONFIG_ARCH_HAS_HUGEPD */ |
| |
| |
| static struct page *no_page_table(struct vm_area_struct *vma, |
| unsigned int flags, unsigned long address) |
| { |
| if (!(flags & FOLL_DUMP)) |
| return NULL; |
| |
| /* |
| * When core dumping, 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 (is_vm_hugetlb_page(vma)) { |
| struct hstate *h = hstate_vma(vma); |
| |
| if (!hugetlbfs_pagecache_present(h, vma, address)) |
| return ERR_PTR(-EFAULT); |
| } else if ((vma_is_anonymous(vma) || !vma->vm_ops->fault)) { |
| return ERR_PTR(-EFAULT); |
| } |
| |
| return NULL; |
| } |
| |
| #ifdef CONFIG_PGTABLE_HAS_HUGE_LEAVES |
| static struct page *follow_huge_pud(struct vm_area_struct *vma, |
| unsigned long addr, pud_t *pudp, |
| int flags, struct follow_page_context *ctx) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| struct page *page; |
| pud_t pud = *pudp; |
| unsigned long pfn = pud_pfn(pud); |
| int ret; |
| |
| assert_spin_locked(pud_lockptr(mm, pudp)); |
| |
| if ((flags & FOLL_WRITE) && !pud_write(pud)) |
| return NULL; |
| |
| if (!pud_present(pud)) |
| return NULL; |
| |
| pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT; |
| |
| if (IS_ENABLED(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) && |
| pud_devmap(pud)) { |
| /* |
| * device mapped pages can only be returned if the caller |
| * will manage the page reference count. |
| * |
| * At least one of FOLL_GET | FOLL_PIN must be set, so |
| * assert that here: |
| */ |
| if (!(flags & (FOLL_GET | FOLL_PIN))) |
| return ERR_PTR(-EEXIST); |
| |
| if (flags & FOLL_TOUCH) |
| touch_pud(vma, addr, pudp, flags & FOLL_WRITE); |
| |
| ctx->pgmap = get_dev_pagemap(pfn, ctx->pgmap); |
| if (!ctx->pgmap) |
| return ERR_PTR(-EFAULT); |
| } |
| |
| page = pfn_to_page(pfn); |
| |
| if (!pud_devmap(pud) && !pud_write(pud) && |
| gup_must_unshare(vma, flags, page)) |
| return ERR_PTR(-EMLINK); |
| |
| ret = try_grab_page(page, flags); |
| if (ret) |
| page = ERR_PTR(ret); |
| else |
| ctx->page_mask = HPAGE_PUD_NR - 1; |
| |
| return page; |
| } |
| |
| /* FOLL_FORCE can write to even unwritable PMDs in COW mappings. */ |
| static inline bool can_follow_write_pmd(pmd_t pmd, struct page *page, |
| struct vm_area_struct *vma, |
| unsigned int flags) |
| { |
| /* If the pmd is writable, we can write to the page. */ |
| if (pmd_write(pmd)) |
| 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) && !pmd_soft_dirty(pmd)) |
| return false; |
| return !userfaultfd_huge_pmd_wp(vma, pmd); |
| } |
| |
| static struct page *follow_huge_pmd(struct vm_area_struct *vma, |
| unsigned long addr, pmd_t *pmd, |
| unsigned int flags, |
| struct follow_page_context *ctx) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| pmd_t pmdval = *pmd; |
| struct page *page; |
| int ret; |
| |
| assert_spin_locked(pmd_lockptr(mm, pmd)); |
| |
| page = pmd_page(pmdval); |
| if ((flags & FOLL_WRITE) && |
| !can_follow_write_pmd(pmdval, page, vma, flags)) |
| return NULL; |
| |
| /* Avoid dumping huge zero page */ |
| if ((flags & FOLL_DUMP) && is_huge_zero_pmd(pmdval)) |
| return ERR_PTR(-EFAULT); |
| |
| if (pmd_protnone(*pmd) && !gup_can_follow_protnone(vma, flags)) |
| return NULL; |
| |
| if (!pmd_write(pmdval) && gup_must_unshare(vma, flags, page)) |
| return ERR_PTR(-EMLINK); |
| |
| VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) && |
| !PageAnonExclusive(page), page); |
| |
| ret = try_grab_page(page, flags); |
| if (ret) |
| return ERR_PTR(ret); |
| |
| #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
| if (pmd_trans_huge(pmdval) && (flags & FOLL_TOUCH)) |
| touch_pmd(vma, addr, pmd, flags & FOLL_WRITE); |
| #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ |
| |
| page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; |
| ctx->page_mask = HPAGE_PMD_NR - 1; |
| |
| return page; |
| } |
| |
| #else /* CONFIG_PGTABLE_HAS_HUGE_LEAVES */ |
| static struct page *follow_huge_pud(struct vm_area_struct *vma, |
| unsigned long addr, pud_t *pudp, |
| int flags, struct follow_page_context *ctx) |
| { |
| return NULL; |
| } |
| |
| static struct page *follow_huge_pmd(struct vm_area_struct *vma, |
| unsigned long addr, pmd_t *pmd, |
| unsigned int flags, |
| struct follow_page_context *ctx) |
| { |
| return NULL; |
| } |
| #endif /* CONFIG_PGTABLE_HAS_HUGE_LEAVES */ |
| |
| 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, address); |
| 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, address); |
| } |
| |
| 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, address); |
| if (!pmd_present(pmdval)) |
| return no_page_table(vma, flags, address); |
| if (unlikely(is_hugepd(__hugepd(pmd_val(pmdval))))) |
| return follow_hugepd(vma, __hugepd(pmd_val(pmdval)), |
| address, PMD_SHIFT, flags, ctx); |
| 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, address); |
| } |
| if (likely(!pmd_leaf(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, address); |
| |
| ptl = pmd_lock(mm, pmd); |
| pmdval = *pmd; |
| if (unlikely(!pmd_present(pmdval))) { |
| spin_unlock(ptl); |
| return no_page_table(vma, flags, address); |
| } |
| if (unlikely(!pmd_leaf(pmdval))) { |
| spin_unlock(ptl); |
| return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); |
| } |
| if (pmd_trans_huge(pmdval) && (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_huge_pmd(vma, address, pmd, flags, ctx); |
| spin_unlock(ptl); |
| 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 *pudp, pud; |
| spinlock_t *ptl; |
| struct page *page; |
| struct mm_struct *mm = vma->vm_mm; |
| |
| pudp = pud_offset(p4dp, address); |
| pud = READ_ONCE(*pudp); |
| if (!pud_present(pud)) |
| return no_page_table(vma, flags, address); |
| if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) |
| return follow_hugepd(vma, __hugepd(pud_val(pud)), |
| address, PUD_SHIFT, flags, ctx); |
| if (pud_leaf(pud)) { |
| ptl = pud_lock(mm, pudp); |
| page = follow_huge_pud(vma, address, pudp, flags, ctx); |
| spin_unlock(ptl); |
| if (page) |
| return page; |
| return no_page_table(vma, flags, address); |
| } |
| if (unlikely(pud_bad(pud))) |
| return no_page_table(vma, flags, address); |
| |
| return follow_pmd_mask(vma, address, pudp, 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); |
| BUILD_BUG_ON(p4d_leaf(p4d)); |
| |
| if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) |
| return follow_hugepd(vma, __hugepd(p4d_val(p4d)), |
| address, P4D_SHIFT, flags, ctx); |
| |
| if (!p4d_present(p4d) || p4d_bad(p4d)) |
| return no_page_table(vma, flags, address); |
| |
| 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; |
| struct page *page; |
| |
| vma_pgtable_walk_begin(vma); |
| |
| ctx->page_mask = 0; |
| pgd = pgd_offset(mm, address); |
| |
| if (unlikely(is_hugepd(__hugepd(pgd_val(*pgd))))) |
| page = follow_hugepd(vma, __hugepd(pgd_val(*pgd)), |
| address, PGDIR_SHIFT, flags, ctx); |
| else if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd))) |
| page = no_page_table(vma, flags, address); |
| else |
| page = follow_p4d_mask(vma, address, pgd, flags, ctx); |
| |
| vma_pgtable_walk_end(vma); |
| |
| return page; |
| } |
| |
| 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); |
| |
| /* |
| * GUP-fast |
| * |
| * 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 gup_fast() 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_GUP_FAST |
| |
| /* |
| * 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 gup_fast_undo_dev_pagemap(int *nr, int nr_start, |
| unsigned int flags, struct page **pages) |
| { |
| while ((*nr) - nr_start) { |
| struct folio *folio = page_folio(pages[--(*nr)]); |
| |
| folio_clear_referenced(folio); |
| gup_put_folio(folio, 1, flags); |
| } |
| } |
| |
| #ifdef CONFIG_ARCH_HAS_PTE_SPECIAL |
| /* |
| * GUP-fast relies on pte change detection to avoid concurrent pgtable |
| * operations. |
| * |
| * To pin the page, GUP-fast 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 GUP-fast, 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 GUP-fast 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_fast_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)) { |
| gup_fast_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_fast_pmd_leaf even if we can't operate on ptes. |
| */ |
| static int gup_fast_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_fast_devmap_leaf(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 folio *folio; |
| struct page *page = pfn_to_page(pfn); |
| |
| pgmap = get_dev_pagemap(pfn, pgmap); |
| if (unlikely(!pgmap)) { |
| gup_fast_undo_dev_pagemap(nr, nr_start, flags, pages); |
| break; |
| } |
| |
| if (!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page)) { |
| gup_fast_undo_dev_pagemap(nr, nr_start, flags, pages); |
| break; |
| } |
| |
| folio = try_grab_folio(page, 1, flags); |
| if (!folio) { |
| gup_fast_undo_dev_pagemap(nr, nr_start, flags, pages); |
| break; |
| } |
| folio_set_referenced(folio); |
| pages[*nr] = page; |
| (*nr)++; |
| pfn++; |
| } while (addr += PAGE_SIZE, addr != end); |
| |
| put_dev_pagemap(pgmap); |
| return addr == end; |
| } |
| |
| static int gup_fast_devmap_pmd_leaf(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_fast_devmap_leaf(fault_pfn, addr, end, flags, pages, nr)) |
| return 0; |
| |
| if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) { |
| gup_fast_undo_dev_pagemap(nr, nr_start, flags, pages); |
| return 0; |
| } |
| return 1; |
| } |
| |
| static int gup_fast_devmap_pud_leaf(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_fast_devmap_leaf(fault_pfn, addr, end, flags, pages, nr)) |
| return 0; |
| |
| if (unlikely(pud_val(orig) != pud_val(*pudp))) { |
| gup_fast_undo_dev_pagemap(nr, nr_start, flags, pages); |
| return 0; |
| } |
| return 1; |
| } |
| #else |
| static int gup_fast_devmap_pmd_leaf(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_fast_devmap_pud_leaf(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 gup_fast_pmd_leaf(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_fast_devmap_pmd_leaf(orig, pmdp, addr, end, flags, |
| pages, nr); |
| } |
| |
| page = pmd_page(orig); |
| refs = record_subpages(page, PMD_SIZE, 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_fast_pud_leaf(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_fast_devmap_pud_leaf(orig, pudp, addr, end, flags, |
| pages, nr); |
| } |
| |
| page = pud_page(orig); |
| refs = record_subpages(page, PUD_SIZE, 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_fast_pgd_leaf(pgd_t orig, pgd_t *pgdp, unsigned long addr, |
| unsigned long end, unsigned int flags, struct page **pages, |
| int *nr) |
| { |
|