diff options
Diffstat (limited to 'mm/gup.c')
| -rw-r--r-- | mm/gup.c | 3402 |
1 files changed, 3402 insertions, 0 deletions
diff --git a/mm/gup.c b/mm/gup.c new file mode 100644 index 0000000000..2f8a2d89fd --- /dev/null +++ b/mm/gup.c @@ -0,0 +1,3402 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include <linux/kernel.h> +#include <linux/errno.h> +#include <linux/err.h> +#include <linux/spinlock.h> + +#include <linux/mm.h> +#include <linux/memremap.h> +#include <linux/pagemap.h> +#include <linux/rmap.h> +#include <linux/swap.h> +#include <linux/swapops.h> +#include <linux/secretmem.h> + +#include <linux/sched/signal.h> +#include <linux/rwsem.h> +#include <linux/hugetlb.h> +#include <linux/migrate.h> +#include <linux/mm_inline.h> +#include <linux/sched/mm.h> +#include <linux/shmem_fs.h> + +#include <asm/mmu_context.h> +#include <asm/tlbflush.h> + +#include "internal.h" + +struct follow_page_context { + struct dev_pagemap *pgmap; + unsigned int page_mask; +}; + +static inline void sanity_check_pinned_pages(struct page **pages, + unsigned long npages) +{ + if (!IS_ENABLED(CONFIG_DEBUG_VM)) + return; + + /* + * We only pin anonymous pages if they are exclusive. Once pinned, we + * can no longer turn them possibly shared and PageAnonExclusive() will + * stick around until the page is freed. + * + * We'd like to verify that our pinned anonymous pages are still mapped + * exclusively. The issue with anon THP is that we don't know how + * they are/were mapped when pinning them. However, for anon + * THP we can assume that either the given page (PTE-mapped THP) or + * the head page (PMD-mapped THP) should be PageAnonExclusive(). If + * neither is the case, there is certainly something wrong. + */ + for (; npages; npages--, pages++) { + struct page *page = *pages; + struct folio *folio = page_folio(page); + + if (is_zero_page(page) || + !folio_test_anon(folio)) + continue; + if (!folio_test_large(folio) || folio_test_hugetlb(folio)) + VM_BUG_ON_PAGE(!PageAnonExclusive(&folio->page), page); + else + /* Either a PTE-mapped or a PMD-mapped THP. */ + VM_BUG_ON_PAGE(!PageAnonExclusive(&folio->page) && + !PageAnonExclusive(page), page); + } +} + +/* + * Return the folio with ref appropriately incremented, + * or NULL if that failed. + */ +static inline struct folio *try_get_folio(struct page *page, int refs) +{ + struct folio *folio; + +retry: + folio = page_folio(page); + if (WARN_ON_ONCE(folio_ref_count(folio) < 0)) + return NULL; + if (unlikely(!folio_ref_try_add_rcu(folio, refs))) + return NULL; + + /* + * At this point we have a stable reference to the folio; but it + * could be that between calling page_folio() and the refcount + * increment, the folio was split, in which case we'd end up + * holding a reference on a folio that has nothing to do with the page + * we were given anymore. + * So now that the folio is stable, recheck that the page still + * belongs to this folio. + */ + if (unlikely(page_folio(page) != folio)) { + if (!put_devmap_managed_page_refs(&folio->page, refs)) + folio_put_refs(folio, refs); + goto retry; + } + + return folio; +} + +/** + * try_grab_folio() - Attempt to get or pin a folio. + * @page: pointer to page to be grabbed + * @refs: the value to (effectively) add to the folio's refcount + * @flags: gup flags: these are the FOLL_* flag values. + * + * "grab" names in this file mean, "look at flags to decide whether to use + * FOLL_PIN or FOLL_GET behavior, when incrementing the folio's refcount. + * + * Either FOLL_PIN or FOLL_GET (or neither) must be set, but not both at the + * same time. (That's true throughout the get_user_pages*() and + * pin_user_pages*() APIs.) Cases: + * + * FOLL_GET: folio's refcount will be incremented by @refs. + * + * FOLL_PIN on large folios: folio's refcount will be incremented by + * @refs, and its pincount will be incremented by @refs. + * + * FOLL_PIN on single-page folios: folio's refcount will be incremented by + * @refs * GUP_PIN_COUNTING_BIAS. + * + * Return: The folio containing @page (with refcount appropriately + * incremented) for success, or NULL upon failure. If neither FOLL_GET + * nor FOLL_PIN was set, that's considered failure, and furthermore, + * a likely bug in the caller, so a warning is also emitted. + */ +struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags) +{ + struct folio *folio; + + if (WARN_ON_ONCE((flags & (FOLL_GET | FOLL_PIN)) == 0)) + return NULL; + + if (unlikely(!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page))) + return NULL; + + if (flags & FOLL_GET) + return try_get_folio(page, refs); + + /* FOLL_PIN is set */ + + /* + * Don't take a pin on the zero page - it's not going anywhere + * and it is used in a *lot* of places. + */ + if (is_zero_page(page)) + return page_folio(page); + + folio = try_get_folio(page, refs); + if (!folio) + return NULL; + + /* + * Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a + * right zone, so fail and let the caller fall back to the slow + * path. + */ + if (unlikely((flags & FOLL_LONGTERM) && + !folio_is_longterm_pinnable(folio))) { + if (!put_devmap_managed_page_refs(&folio->page, refs)) + folio_put_refs(folio, refs); + return NULL; + } + + /* + * When pinning a large folio, use an exact count to track it. + * + * However, be sure to *also* increment the normal folio + * refcount field at least once, so that the folio really + * is pinned. That's why the refcount from the earlier + * try_get_folio() is left intact. + */ + if (folio_test_large(folio)) + atomic_add(refs, &folio->_pincount); + else + folio_ref_add(folio, + refs * (GUP_PIN_COUNTING_BIAS - 1)); + /* + * Adjust the pincount before re-checking the PTE for changes. + * This is essentially a smp_mb() and is paired with a memory + * barrier in page_try_share_anon_rmap(). + */ + smp_mb__after_atomic(); + + node_stat_mod_folio(folio, NR_FOLL_PIN_ACQUIRED, refs); + + return folio; +} + +static void gup_put_folio(struct folio *folio, int refs, unsigned int flags) +{ + if (flags & FOLL_PIN) { + if (is_zero_folio(folio)) + return; + node_stat_mod_folio(folio, NR_FOLL_PIN_RELEASED, refs); + if (folio_test_large(folio)) + atomic_sub(refs, &folio->_pincount); + else + refs *= GUP_PIN_COUNTING_BIAS; + } + + if (!put_devmap_managed_page_refs(&folio->page, refs)) + folio_put_refs(folio, refs); +} + +/** + * try_grab_page() - elevate a page's refcount by a flag-dependent amount + * @page: pointer to page to be grabbed + * @flags: gup flags: these are the FOLL_* flag values. + * + * This might not do anything at all, depending on the flags argument. + * + * "grab" names in this file mean, "look at flags to decide whether to use + * FOLL_PIN or FOLL_GET behavior, when incrementing the page's refcount. + * + * Either FOLL_PIN or FOLL_GET (or neither) may be set, but not both at the same + * time. Cases: please see the try_grab_folio() documentation, with + * "refs=1". + * + * Return: 0 for success, or if no action was required (if neither FOLL_PIN + * nor FOLL_GET was set, nothing is done). A negative error code for failure: + * + * -ENOMEM FOLL_GET or FOLL_PIN was set, but the page could not + * be grabbed. + */ +int __must_check try_grab_page(struct page *page, unsigned int flags) +{ + struct folio *folio = page_folio(page); + + if (WARN_ON_ONCE(folio_ref_count(folio) <= 0)) + return -ENOMEM; + + if (unlikely(!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page))) + return -EREMOTEIO; + + if (flags & FOLL_GET) + folio_ref_inc(folio); + else if (flags & FOLL_PIN) { + /* + * Don't take a pin on the zero page - it's not going anywhere + * and it is used in a *lot* of places. + */ + if (is_zero_page(page)) + return 0; + + /* + * Similar to try_grab_folio(): be sure to *also* + * increment the normal page refcount field at least once, + * so that the page really is pinned. + */ + if (folio_test_large(folio)) { + folio_ref_add(folio, 1); + atomic_add(1, &folio->_pincount); + } else { + folio_ref_add(folio, GUP_PIN_COUNTING_BIAS); + } + + node_stat_mod_folio(folio, NR_FOLL_PIN_ACQUIRED, 1); + } + + return 0; +} + +/** + * unpin_user_page() - release a dma-pinned page + * @page: pointer to page to be released + * + * Pages that were pinned via pin_user_pages*() must be released via either + * unpin_user_page(), or one of the unpin_user_pages*() routines. This is so + * that such pages can be separately tracked and uniquely handled. In + * particular, interactions with RDMA and filesystems need special handling. + */ +void unpin_user_page(struct page *page) +{ + sanity_check_pinned_pages(&page, 1); + gup_put_folio(page_folio(page), 1, FOLL_PIN); +} +EXPORT_SYMBOL(unpin_user_page); + +/** + * folio_add_pin - Try to get an additional pin on a pinned folio + * @folio: The folio to be pinned + * + * Get an additional pin on a folio we already have a pin on. Makes no change + * if the folio is a zero_page. + */ +void folio_add_pin(struct folio *folio) +{ + if (is_zero_folio(folio)) + return; + + /* + * Similar to try_grab_folio(): be sure to *also* increment the normal + * page refcount field at least once, so that the page really is + * pinned. + */ + if (folio_test_large(folio)) { + WARN_ON_ONCE(atomic_read(&folio->_pincount) < 1); + folio_ref_inc(folio); + atomic_inc(&folio->_pincount); + } else { + WARN_ON_ONCE(folio_ref_count(folio) < GUP_PIN_COUNTING_BIAS); + folio_ref_add(folio, GUP_PIN_COUNTING_BIAS); + } +} + +static inline struct folio *gup_folio_range_next(struct page *start, + unsigned long npages, unsigned long i, unsigned int *ntails) +{ + struct page *next = nth_page(start, i); + struct folio *folio = page_folio(next); + unsigned int nr = 1; + + if (folio_test_large(folio)) + nr = min_t(unsigned int, npages - i, + folio_nr_pages(folio) - folio_page_idx(folio, next)); + + *ntails = nr; + return folio; +} + +static inline struct folio *gup_folio_next(struct page **list, + unsigned long npages, unsigned long i, unsigned int *ntails) +{ + struct folio *folio = page_folio(list[i]); + unsigned int nr; + + for (nr = i + 1; nr < npages; nr++) { + if (page_folio(list[nr]) != folio) + break; + } + + *ntails = nr - i; + return folio; +} + +/** + * unpin_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages + * @pages: array of pages to be maybe marked dirty, and definitely released. + * @npages: number of pages in the @pages array. + * @make_dirty: whether to mark the pages dirty + * + * "gup-pinned page" refers to a page that has had one of the get_user_pages() + * variants called on that page. + * + * For each page in the @pages array, make that page (or its head page, if a + * compound page) dirty, if @make_dirty is true, and if the page was previously + * listed as clean. In any case, releases all pages using unpin_user_page(), + * possibly via unpin_user_pages(), for the non-dirty case. + * + * Please see the unpin_user_page() documentation for details. + * + * set_page_dirty_lock() is used internally. If instead, set_page_dirty() is + * required, then the caller should a) verify that this is really correct, + * because _lock() is usually required, and b) hand code it: + * set_page_dirty_lock(), unpin_user_page(). + * + */ +void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages, + bool make_dirty) +{ + unsigned long i; + struct folio *folio; + unsigned int nr; + + if (!make_dirty) { + unpin_user_pages(pages, npages); + return; + } + + sanity_check_pinned_pages(pages, npages); + for (i = 0; i < npages; i += nr) { + folio = gup_folio_next(pages, npages, i, &nr); + /* + * Checking PageDirty at this point may race with + * clear_page_dirty_for_io(), but that's OK. Two key + * cases: + * + * 1) This code sees the page as already dirty, so it + * skips the call to set_page_dirty(). That could happen + * because clear_page_dirty_for_io() called + * page_mkclean(), followed by set_page_dirty(). + * However, now the page is going to get written back, + * which meets the original intention of setting it + * dirty, so all is well: clear_page_dirty_for_io() goes + * on to call TestClearPageDirty(), and write the page + * back. + * + * 2) This code sees the page as clean, so it calls + * set_page_dirty(). The page stays dirty, despite being + * written back, so it gets written back again in the + * next writeback cycle. This is harmless. + */ + if (!folio_test_dirty(folio)) { + folio_lock(folio); + folio_mark_dirty(folio); + folio_unlock(folio); + } + gup_put_folio(folio, nr, FOLL_PIN); + } +} +EXPORT_SYMBOL(unpin_user_pages_dirty_lock); + +/** + * unpin_user_page_range_dirty_lock() - release and optionally dirty + * gup-pinned page range + * + * @page: the starting page of a range maybe marked dirty, and definitely released. + * @npages: number of consecutive pages to release. + * @make_dirty: whether to mark the pages dirty + * + * "gup-pinned page range" refers to a range of pages that has had one of the + * pin_user_pages() variants called on that page. + * + * For the page ranges defined by [page .. page+npages], make that range (or + * its head pages, if a compound page) dirty, if @make_dirty is true, and if the + * page range was previously listed as clean. + * + * set_page_dirty_lock() is used internally. If instead, set_page_dirty() is + * required, then the caller should a) verify that this is really correct, + * because _lock() is usually required, and b) hand code it: + * set_page_dirty_lock(), unpin_user_page(). + * + */ +void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages, + bool make_dirty) +{ + unsigned long i; + struct folio *folio; + unsigned int nr; + + for (i = 0; i < npages; i += nr) { + folio = gup_folio_range_next(page, npages, i, &nr); + if (make_dirty && !folio_test_dirty(folio)) { + folio_lock(folio); + folio_mark_dirty(folio); + folio_unlock(folio); + } + gup_put_folio(folio, nr, FOLL_PIN); + } +} +EXPORT_SYMBOL(unpin_user_page_range_dirty_lock); + +static void unpin_user_pages_lockless(struct page **pages, unsigned long npages) +{ + unsigned long i; + struct folio *folio; + unsigned int nr; + + /* + * Don't perform any sanity checks because we might have raced with + * fork() and some anonymous pages might now actually be shared -- + * which is why we're unpinning after all. + */ + for (i = 0; i < npages; i += nr) { + folio = gup_folio_next(pages, npages, i, &nr); + gup_put_folio(folio, nr, FOLL_PIN); + } +} + +/** + * unpin_user_pages() - release an array of gup-pinned pages. + * @pages: array of pages to be marked dirty and released. + * @npages: number of pages in the @pages array. + * + * For each page in the @pages array, release the page using unpin_user_page(). + * + * Please see the unpin_user_page() documentation for details. + */ +void unpin_user_pages(struct page **pages, unsigned long npages) +{ + unsigned long i; + struct folio *folio; + unsigned int nr; + + /* + * If this WARN_ON() fires, then the system *might* be leaking pages (by + * leaving them pinned), but probably not. More likely, gup/pup returned + * a hard -ERRNO error to the caller, who erroneously passed it here. + */ + if (WARN_ON(IS_ERR_VALUE(npages))) + return; + + sanity_check_pinned_pages(pages, npages); + for (i = 0; i < npages; i += nr) { + folio = gup_folio_next(pages, npages, i, &nr); + gup_put_folio(folio, nr, FOLL_PIN); + } +} +EXPORT_SYMBOL(unpin_user_pages); + +/* + * Set the MMF_HAS_PINNED if not set yet; after set it'll be there for the mm's + * lifecycle. Avoid setting the bit unless necessary, or it might cause write + * cache bouncing on large SMP machines for concurrent pinned gups. + */ +static inline void mm_set_has_pinned_flag(unsigned long *mm_flags) +{ + if (!test_bit(MMF_HAS_PINNED, mm_flags)) + set_bit(MMF_HAS_PINNED, mm_flags); +} + +#ifdef CONFIG_MMU +static struct page *no_page_table(struct vm_area_struct *vma, + unsigned int flags) +{ + /* + * When core dumping an enormous anonymous area that nobody + * has touched so far, we don't want to allocate unnecessary pages or + * page tables. Return error instead of NULL to skip handle_mm_fault, + * then get_dump_page() will return NULL to leave a hole in the dump. + * But we can only make this optimization where a hole would surely + * be zero-filled if handle_mm_fault() actually did handle it. + */ + if ((flags & FOLL_DUMP) && + (vma_is_anonymous(vma) || !vma->vm_ops->fault)) + return ERR_PTR(-EFAULT); + return NULL; +} + +static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address, + pte_t *pte, unsigned int flags) +{ + if (flags & FOLL_TOUCH) { + pte_t orig_entry = ptep_get(pte); + pte_t entry = orig_entry; + + if (flags & FOLL_WRITE) + entry = pte_mkdirty(entry); + entry = pte_mkyoung(entry); + + if (!pte_same(orig_entry, entry)) { + set_pte_at(vma->vm_mm, address, pte, entry); + update_mmu_cache(vma, address, pte); + } + } + + /* Proper page table entry exists, but no corresponding struct page */ + return -EEXIST; +} + +/* FOLL_FORCE can write to even unwritable PTEs in COW mappings. */ +static inline bool can_follow_write_pte(pte_t pte, struct page *page, + struct vm_area_struct *vma, + unsigned int flags) +{ + /* If the pte is writable, we can write to the page. */ + if (pte_write(pte)) + return true; + + /* Maybe FOLL_FORCE is set to override it? */ + if (!(flags & FOLL_FORCE)) + return false; + + /* But FOLL_FORCE has no effect on shared mappings */ + if (vma->vm_flags & (VM_MAYSHARE | VM_SHARED)) + return false; + + /* ... or read-only private ones */ + if (!(vma->vm_flags & VM_MAYWRITE)) + return false; + + /* ... or already writable ones that just need to take a write fault */ + if (vma->vm_flags & VM_WRITE) + return false; + + /* + * See can_change_pte_writable(): we broke COW and could map the page + * writable if we have an exclusive anonymous page ... + */ + if (!page || !PageAnon(page) || !PageAnonExclusive(page)) + return false; + + /* ... and a write-fault isn't required for other reasons. */ + if (vma_soft_dirty_enabled(vma) && !pte_soft_dirty(pte)) + return false; + return !userfaultfd_pte_wp(vma, pte); +} + +static struct page *follow_page_pte(struct vm_area_struct *vma, + unsigned long address, pmd_t *pmd, unsigned int flags, + struct dev_pagemap **pgmap) +{ + struct mm_struct *mm = vma->vm_mm; + struct page *page; + spinlock_t *ptl; + pte_t *ptep, pte; + int ret; + + /* FOLL_GET and FOLL_PIN are mutually exclusive. */ + if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == + (FOLL_PIN | FOLL_GET))) + return ERR_PTR(-EINVAL); + + ptep = pte_offset_map_lock(mm, pmd, address, &ptl); + if (!ptep) + return no_page_table(vma, flags); + pte = ptep_get(ptep); + if (!pte_present(pte)) + goto no_page; + if (pte_protnone(pte) && !gup_can_follow_protnone(vma, flags)) + goto no_page; + + page = vm_normal_page(vma, address, pte); + + /* + * We only care about anon pages in can_follow_write_pte() and don't + * have to worry about pte_devmap() because they are never anon. + */ + if ((flags & FOLL_WRITE) && + !can_follow_write_pte(pte, page, vma, flags)) { + page = NULL; + goto out; + } + + if (!page && pte_devmap(pte) && (flags & (FOLL_GET | FOLL_PIN))) { + /* + * Only return device mapping pages in the FOLL_GET or FOLL_PIN + * case since they are only valid while holding the pgmap + * reference. + */ + *pgmap = get_dev_pagemap(pte_pfn(pte), *pgmap); + if (*pgmap) + page = pte_page(pte); + else + goto no_page; + } else if (unlikely(!page)) { + if (flags & FOLL_DUMP) { + /* Avoid special (like zero) pages in core dumps */ + page = ERR_PTR(-EFAULT); + goto out; + } + + if (is_zero_pfn(pte_pfn(pte))) { + page = pte_page(pte); + } else { + ret = follow_pfn_pte(vma, address, ptep, flags); + page = ERR_PTR(ret); + goto out; + } + } + + if (!pte_write(pte) && gup_must_unshare(vma, flags, page)) { + page = ERR_PTR(-EMLINK); + goto out; + } + + VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) && + !PageAnonExclusive(page), page); + + /* try_grab_page() does nothing unless FOLL_GET or FOLL_PIN is set. */ + ret = try_grab_page(page, flags); + if (unlikely(ret)) { + page = ERR_PTR(ret); + goto out; + } + + /* + * We need to make the page accessible if and only if we are going + * to access its content (the FOLL_PIN case). Please see + * Documentation/core-api/pin_user_pages.rst for details. + */ + if (flags & FOLL_PIN) { + ret = arch_make_page_accessible(page); + if (ret) { + unpin_user_page(page); + page = ERR_PTR(ret); + goto out; + } + } + if (flags & FOLL_TOUCH) { + if ((flags & FOLL_WRITE) && + !pte_dirty(pte) && !PageDirty(page)) + set_page_dirty(page); + /* + * pte_mkyoung() would be more correct here, but atomic care + * is needed to avoid losing the dirty bit: it is easier to use + * mark_page_accessed(). + */ + mark_page_accessed(page); + } +out: + pte_unmap_unlock(ptep, ptl); + return page; +no_page: + pte_unmap_unlock(ptep, ptl); + if (!pte_none(pte)) + return NULL; + return no_page_table(vma, flags); +} + +static struct page *follow_pmd_mask(struct vm_area_struct *vma, + unsigned long address, pud_t *pudp, + unsigned int flags, + struct follow_page_context *ctx) +{ + pmd_t *pmd, pmdval; + spinlock_t *ptl; + struct page *page; + struct mm_struct *mm = vma->vm_mm; + + pmd = pmd_offset(pudp, address); + pmdval = pmdp_get_lockless(pmd); + if (pmd_none(pmdval)) + return no_page_table(vma, flags); + if (!pmd_present(pmdval)) + return no_page_table(vma, flags); + if (pmd_devmap(pmdval)) { + ptl = pmd_lock(mm, pmd); + page = follow_devmap_pmd(vma, address, pmd, flags, &ctx->pgmap); + spin_unlock(ptl); + if (page) + return page; + } + if (likely(!pmd_trans_huge(pmdval))) + return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); + + if (pmd_protnone(pmdval) && !gup_can_follow_protnone(vma, flags)) + return no_page_table(vma, flags); + + ptl = pmd_lock(mm, pmd); + if (unlikely(!pmd_present(*pmd))) { + spin_unlock(ptl); + return no_page_table(vma, flags); + } + if (unlikely(!pmd_trans_huge(*pmd))) { + spin_unlock(ptl); + return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); + } + if (flags & FOLL_SPLIT_PMD) { + spin_unlock(ptl); + split_huge_pmd(vma, pmd, address); + /* If pmd was left empty, stuff a page table in there quickly */ + return pte_alloc(mm, pmd) ? ERR_PTR(-ENOMEM) : + follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); + } + page = follow_trans_huge_pmd(vma, address, pmd, flags); + spin_unlock(ptl); + ctx->page_mask = HPAGE_PMD_NR - 1; + return page; +} + +static struct page *follow_pud_mask(struct vm_area_struct *vma, + unsigned long address, p4d_t *p4dp, + unsigned int flags, + struct follow_page_context *ctx) +{ + pud_t *pud; + spinlock_t *ptl; + struct page *page; + struct mm_struct *mm = vma->vm_mm; + + pud = pud_offset(p4dp, address); + if (pud_none(*pud)) + return no_page_table(vma, flags); + if (pud_devmap(*pud)) { + ptl = pud_lock(mm, pud); + page = follow_devmap_pud(vma, address, pud, flags, &ctx->pgmap); + spin_unlock(ptl); + if (page) + return page; + } + if (unlikely(pud_bad(*pud))) + return no_page_table(vma, flags); + + return follow_pmd_mask(vma, address, pud, flags, ctx); +} + +static struct page *follow_p4d_mask(struct vm_area_struct *vma, + unsigned long address, pgd_t *pgdp, + unsigned int flags, + struct follow_page_context *ctx) +{ + p4d_t *p4d; + + p4d = p4d_offset(pgdp, address); + if (p4d_none(*p4d)) + return no_page_table(vma, flags); + BUILD_BUG_ON(p4d_huge(*p4d)); + if (unlikely(p4d_bad(*p4d))) + return no_page_table(vma, flags); + + return follow_pud_mask(vma, address, p4d, flags, ctx); +} + +/** + * follow_page_mask - look up a page descriptor from a user-virtual address + * @vma: vm_area_struct mapping @address + * @address: virtual address to look up + * @flags: flags modifying lookup behaviour + * @ctx: contains dev_pagemap for %ZONE_DEVICE memory pinning and a + * pointer to output page_mask + * + * @flags can have FOLL_ flags set, defined in <linux/mm.h> + * + * When getting pages from ZONE_DEVICE memory, the @ctx->pgmap caches + * the device's dev_pagemap metadata to avoid repeating expensive lookups. + * + * When getting an anonymous page and the caller has to trigger unsharing + * of a shared anonymous page first, -EMLINK is returned. The caller should + * trigger a fault with FAULT_FLAG_UNSHARE set. Note that unsharing is only + * relevant with FOLL_PIN and !FOLL_WRITE. + * + * On output, the @ctx->page_mask is set according to the size of the page. + * + * Return: the mapped (struct page *), %NULL if no mapping exists, or + * an error pointer if there is a mapping to something not represented + * by a page descriptor (see also vm_normal_page()). + */ +static struct page *follow_page_mask(struct vm_area_struct *vma, + unsigned long address, unsigned int flags, + struct follow_page_context *ctx) +{ + pgd_t *pgd; + struct mm_struct *mm = vma->vm_mm; + + ctx->page_mask = 0; + + /* + * Call hugetlb_follow_page_mask for hugetlb vmas as it will use + * special hugetlb page table walking code. This eliminates the + * need to check for hugetlb entries in the general walking code. + */ + if (is_vm_hugetlb_page(vma)) + return hugetlb_follow_page_mask(vma, address, flags, + &ctx->page_mask); + + pgd = pgd_offset(mm, address); + + if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd))) + return no_page_table(vma, flags); + + return follow_p4d_mask(vma, address, pgd, flags, ctx); +} + +struct page *follow_page(struct vm_area_struct *vma, unsigned long address, + unsigned int foll_flags) +{ + struct follow_page_context ctx = { NULL }; + struct page *page; + + if (vma_is_secretmem(vma)) + return NULL; + + if (WARN_ON_ONCE(foll_flags & FOLL_PIN)) + return NULL; + + /* + * We never set FOLL_HONOR_NUMA_FAULT because callers don't expect + * to fail on PROT_NONE-mapped pages. + */ + page = follow_page_mask(vma, address, foll_flags, &ctx); + if (ctx.pgmap) + put_dev_pagemap(ctx.pgmap); + return page; +} + +static int get_gate_page(struct mm_struct *mm, unsigned long address, + unsigned int gup_flags, struct vm_area_struct **vma, + struct page **page) +{ + pgd_t *pgd; + p4d_t *p4d; + pud_t *pud; + pmd_t *pmd; + pte_t *pte; + pte_t entry; + int ret = -EFAULT; + + /* user gate pages are read-only */ + if (gup_flags & FOLL_WRITE) + return -EFAULT; + if (address > TASK_SIZE) + pgd = pgd_offset_k(address); + else + pgd = pgd_offset_gate(mm, address); + if (pgd_none(*pgd)) + return -EFAULT; + p4d = p4d_offset(pgd, address); + if (p4d_none(*p4d)) + return -EFAULT; + pud = pud_offset(p4d, address); + if (pud_none(*pud)) + return -EFAULT; + pmd = pmd_offset(pud, address); + if (!pmd_present(*pmd)) + return -EFAULT; + pte = pte_offset_map(pmd, address); + if (!pte) + return -EFAULT; + entry = ptep_get(pte); + if (pte_none(entry)) + goto unmap; + *vma = get_gate_vma(mm); + if (!page) + goto out; + *page = vm_normal_page(*vma, address, entry); + if (!*page) { + if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(entry))) + goto unmap; + *page = pte_page(entry); + } + ret = try_grab_page(*page, gup_flags); + if (unlikely(ret)) + goto unmap; +out: + ret = 0; +unmap: + pte_unmap(pte); + return ret; +} + +/* + * mmap_lock must be held on entry. If @flags has FOLL_UNLOCKABLE but not + * FOLL_NOWAIT, the mmap_lock may be released. If it is, *@locked will be set + * to 0 and -EBUSY returned. + */ +static int faultin_page(struct vm_area_struct *vma, + unsigned long address, unsigned int *flags, bool unshare, + int *locked) +{ + unsigned int fault_flags = 0; + vm_fault_t ret; + + if (*flags & FOLL_NOFAULT) + return -EFAULT; + if (*flags & FOLL_WRITE) + fault_flags |= FAULT_FLAG_WRITE; + if (*flags & FOLL_REMOTE) + fault_flags |= FAULT_FLAG_REMOTE; + if (*flags & FOLL_UNLOCKABLE) { + fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; + /* + * FAULT_FLAG_INTERRUPTIBLE is opt-in. GUP callers must set + * FOLL_INTERRUPTIBLE to enable FAULT_FLAG_INTERRUPTIBLE. + * That's because some callers may not be prepared to + * handle early exits caused by non-fatal signals. + */ + if (*flags & FOLL_INTERRUPTIBLE) + fault_flags |= FAULT_FLAG_INTERRUPTIBLE; + } + if (*flags & FOLL_NOWAIT) + fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT; + if (*flags & FOLL_TRIED) { + /* + * Note: FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_TRIED + * can co-exist + */ + fault_flags |= FAULT_FLAG_TRIED; + } + if (unshare) { + fault_flags |= FAULT_FLAG_UNSHARE; + /* FAULT_FLAG_WRITE and FAULT_FLAG_UNSHARE are incompatible */ + VM_BUG_ON(fault_flags & FAULT_FLAG_WRITE); + } + + ret = handle_mm_fault(vma, address, fault_flags, NULL); + + if (ret & VM_FAULT_COMPLETED) { + /* + * With FAULT_FLAG_RETRY_NOWAIT we'll never release the + * mmap lock in the page fault handler. Sanity check this. + */ + WARN_ON_ONCE(fault_flags & FAULT_FLAG_RETRY_NOWAIT); + *locked = 0; + + /* + * We should do the same as VM_FAULT_RETRY, but let's not + * return -EBUSY since that's not reflecting the reality of + * what has happened - we've just fully completed a page + * fault, with the mmap lock released. Use -EAGAIN to show + * that we want to take the mmap lock _again_. + */ + return -EAGAIN; + } + + if (ret & VM_FAULT_ERROR) { + int err = vm_fault_to_errno(ret, *flags); + + if (err) + return err; + BUG(); + } + + if (ret & VM_FAULT_RETRY) { + if (!(fault_flags & FAULT_FLAG_RETRY_NOWAIT)) + *locked = 0; + return -EBUSY; + } + + return 0; +} + +/* + * Writing to file-backed mappings which require folio dirty tracking using GUP + * is a fundamentally broken operation, as kernel write access to GUP mappings + * do not adhere to the semantics expected by a file system. + * + * Consider the following scenario:- + * + * 1. A folio is written to via GUP which write-faults the memory, notifying + * the file system and dirtying the folio. + * 2. Later, writeback is triggered, resulting in the folio being cleaned and + * the PTE being marked read-only. + * 3. The GUP caller writes to the folio, as it is mapped read/write via the + * direct mapping. + * 4. The GUP caller, now done with the page, unpins it and sets it dirty + * (though it does not have to). + * + * This results in both data being written to a folio without writenotify, and + * the folio being dirtied unexpectedly (if the caller decides to do so). + */ +static bool writable_file_mapping_allowed(struct vm_area_struct *vma, + unsigned long gup_flags) +{ + /* + * If we aren't pinning then no problematic write can occur. A long term + * pin is the most egregious case so this is the case we disallow. + */ + if ((gup_flags & (FOLL_PIN | FOLL_LONGTERM)) != + (FOLL_PIN | FOLL_LONGTERM)) + return true; + + /* + * If the VMA does not require dirty tracking then no problematic write + * can occur either. + */ + return !vma_needs_dirty_tracking(vma); +} + +static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) +{ + vm_flags_t vm_flags = vma->vm_flags; + int write = (gup_flags & FOLL_WRITE); + int foreign = (gup_flags & FOLL_REMOTE); + bool vma_anon = vma_is_anonymous(vma); + + if (vm_flags & (VM_IO | VM_PFNMAP)) + return -EFAULT; + + if ((gup_flags & FOLL_ANON) && !vma_anon) + return -EFAULT; + + if ((gup_flags & FOLL_LONGTERM) && vma_is_fsdax(vma)) + return -EOPNOTSUPP; + + if (vma_is_secretmem(vma)) + return -EFAULT; + + if (write) { + if (!vma_anon && + !writable_file_mapping_allowed(vma, gup_flags)) + return -EFAULT; + + if (!(vm_flags & VM_WRITE) || (vm_flags & VM_SHADOW_STACK)) { + if (!(gup_flags & FOLL_FORCE)) + return -EFAULT; + /* hugetlb does not support FOLL_FORCE|FOLL_WRITE. */ + if (is_vm_hugetlb_page(vma)) + return -EFAULT; + /* + * We used to let the write,force case do COW in a + * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could + * set a breakpoint in a read-only mapping of an + * executable, without corrupting the file (yet only + * when that file had been opened for writing!). + * Anon pages in shared mappings are surprising: now + * just reject it. + */ + if (!is_cow_mapping(vm_flags)) + return -EFAULT; + } + } else if (!(vm_flags & VM_READ)) { + if (!(gup_flags & FOLL_FORCE)) + return -EFAULT; + /* + * Is there actually any vma we can reach here which does not + * have VM_MAYREAD set? + */ + if (!(vm_flags & VM_MAYREAD)) + return -EFAULT; + } + /* + * gups are always data accesses, not instruction + * fetches, so execute=false here + */ + if (!arch_vma_access_permitted(vma, write, false, foreign)) + return -EFAULT; + return 0; +} + +/* + * This is "vma_lookup()", but with a warning if we would have + * historically expanded the stack in the GUP code. + */ +static struct vm_area_struct *gup_vma_lookup(struct mm_struct *mm, + unsigned long addr) +{ +#ifdef CONFIG_STACK_GROWSUP + return vma_lookup(mm, addr); +#else + static volatile unsigned long next_warn; + struct vm_area_struct *vma; + unsigned long now, next; + + vma = find_vma(mm, addr); + if (!vma || (addr >= vma->vm_start)) + return vma; + + /* Only warn for half-way relevant accesses */ + if (!(vma->vm_flags & VM_GROWSDOWN)) + return NULL; + if (vma->vm_start - addr > 65536) + return NULL; + + /* Let's not warn more than once an hour.. */ + now = jiffies; next = next_warn; + if (next && time_before(now, next)) + return NULL; + next_warn = now + 60*60*HZ; + + /* Let people know things may have changed. */ + pr_warn("GUP no longer grows the stack in %s (%d): %lx-%lx (%lx)\n", + current->comm, task_pid_nr(current), + vma->vm_start, vma->vm_end, addr); + dump_stack(); + return NULL; +#endif +} + +/** + * __get_user_pages() - pin user pages in memory + * @mm: mm_struct of target mm + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @gup_flags: flags modifying pin behaviour + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. Or NULL, if caller + * only intends to ensure the pages are faulted in. + * @locked: whether we're still with the mmap_lock held + * + * Returns either number of pages pinned (which may be less than the + * number requested), or an error. Details about the return value: + * + * -- If nr_pages is 0, returns 0. + * -- If nr_pages is >0, but no pages were pinned, returns -errno. + * -- If nr_pages is >0, and some pages were pinned, returns the number of + * pages pinned. Again, this may be less than nr_pages. + * -- 0 return value is possible when the fault would need to be retried. + * + * The caller is responsible for releasing returned @pages, via put_page(). + * + * Must be called with mmap_lock held. It may be released. See below. + * + * __get_user_pages walks a process's page tables and takes a reference to + * each struct page that each user address corresponds to at a given + * instant. That is, it takes the page that would be accessed if a user + * thread accesses the given user virtual address at that instant. + * + * This does not guarantee that the page exists in the user mappings when + * __get_user_pages returns, and there may even be a completely different + * page there in some cases (eg. if mmapped pagecache has been invalidated + * and subsequently re-faulted). However it does guarantee that the page + * won't be freed completely. And mostly callers simply care that the page + * contains data that was valid *at some point in time*. Typically, an IO + * or similar operation cannot guarantee anything stronger anyway because + * locks can't be held over the syscall boundary. + * + * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If + * the page is written to, set_page_dirty (or set_page_dirty_lock, as + * appropriate) must be called after the page is finished with, and + * before put_page is called. + * + * If FOLL_UNLOCKABLE is set without FOLL_NOWAIT then the mmap_lock may + * be released. If this happens *@locked will be set to 0 on return. + * + * A caller using such a combination of @gup_flags must therefore hold the + * mmap_lock for reading only, and recognize when it's been released. Otherwise, + * it must be held for either reading or writing and will not be released. + * + * In most cases, get_user_pages or get_user_pages_fast should be used + * instead of __get_user_pages. __get_user_pages should be used only if + * you need some special @gup_flags. + */ +static long __get_user_pages(struct mm_struct *mm, + unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + int *locked) +{ + long ret = 0, i = 0; + struct vm_area_struct *vma = NULL; + struct follow_page_context ctx = { NULL }; + + if (!nr_pages) + return 0; + + start = untagged_addr_remote(mm, start); + + VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN))); + + do { + struct page *page; + unsigned int foll_flags = gup_flags; + unsigned int page_increm; + + /* first iteration or cross vma bound */ + if (!vma || start >= vma->vm_end) { + 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; + + /* + * 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; + } + 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; + + 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. + */ + if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE) + gup_flags |= FOLL_WRITE; + + /* + * We want mlock to succeed for regions that have any permissions + * other than PROT_NONE. + */ + if (vma_is_accessible(vma)) + 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_vma_page_range() - populate (prefault) page tables inside the + * given VMA range readable/writable + * + * This takes care of mlocking the pages, too, if VM_LOCKED is set. + * + * @vma: target vma + * @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 vma, or a negative error + * code on error (see __get_user_pages()). + * + * vma->vm_mm->mmap_lock must be held. The range must be page-aligned and + * covered by the VMA. If it's released, *@locked will be set to 0. + */ +long faultin_vma_page_range(struct vm_area_struct *vma, unsigned long start, + unsigned long end, bool write, int *locked) +{ + struct mm_struct *mm = vma->vm_mm; + 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)); + VM_BUG_ON_VMA(start < vma->vm_start, vma); + VM_BUG_ON_VMA(end > vma->vm_end, vma); + 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; + if (write) + gup_flags |= FOLL_WRITE; + + /* + * We want to report -EINVAL instead of -EFAULT for any permission + * problems or incompatible mappings. + */ + if (check_vma_flags(vma, gup_flags)) + return -EINVAL; + + ret = __get_user_pages(mm, start, nr_pages, gup_flags, + NULL, locked); + 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, + }; + + 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_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 & (FOLL_PIN | FOLL_TRIED | FOLL_UNLOCKABLE | + FOLL_REMOTE | FOLL_FAST_ONLY))) + return false; + + gup_flags |= to_set; + if (locked) { + /* At the external interface locked must be set */ + if (WARN_ON_ONCE(*locked != 1)) + return false; + + gup_flags |= FOLL_UNLOCKABLE; + } + + /* FOLL_GET and FOLL_PIN are mutually exclusive. */ + if (WARN_ON_ONCE((gup_flags & (FOLL_PIN | FOLL_GET)) == + (FOLL_PIN | FOLL_GET))) + return false; + + /* LONGTERM can only be specified when pinning */ + if (WARN_ON_ONCE(!(gup_flags & FOLL_PIN) && (gup_flags & FOLL_LONGTERM))) + return false; + + /* Pages input must be given if using GET/PIN */ + if (WARN_ON_ONCE((gup_flags & (FOLL_GET | FOLL_PIN)) && !pages)) + return false; + + /* We want to allow the pgmap to be hot-unplugged at all times */ + if (WARN_ON_ONCE((gup_flags & FOLL_LONGTERM) && + (gup_flags & FOLL_PCI_P2PDMA))) + return false; + + *gup_flags_p = gup_flags; + return true; +} + +#ifdef CONFIG_MMU +/** + * get_user_pages_remote() - pin user pages in memory + * @mm: mm_struct of target mm + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @gup_flags: flags modifying lookup behaviour + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. Or NULL, if caller + * only intends to ensure the pages are faulted in. + * @locked: pointer to lock flag indicating whether lock is held and + * subsequently whether VM_FAULT_RETRY functionality can be + * utilised. Lock must initially be held. + * + * Returns either number of pages pinned (which may be less than the + * number requested), or an error. Details about the return value: + * + * -- If nr_pages is 0, returns 0. + * -- If nr_pages is >0, but no pages were pinned, returns -errno. + * -- If nr_pages is >0, and some pages were pinned, returns the number of + * pages pinned. Again, this may be less than nr_pages. + * + * The caller is responsible for releasing returned @pages, via put_page(). + * + * Must be called with mmap_lock held for read or write. + * + * get_user_pages_remote walks a process's page tables and takes a reference + * to each struct page that each user address corresponds to at a given + * instant. That is, it takes the page that would be accessed if a user + * thread accesses the given user virtual address at that instant. + * + * This does not guarantee that the page exists in the user mappings when + * get_user_pages_remote returns, and there may even be a completely different + * page there in some cases (eg. if mmapped pagecache has been invalidated + * and subsequently re-faulted). However it does guarantee that the page + * won't be freed completely. And mostly callers simply care that the page + * contains data that was valid *at some point in time*. Typically, an IO + * or similar operation cannot guarantee anything stronger anyway because + * locks can't be held over the syscall boundary. + * + * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page + * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must + * be called after the page is finished with, and before put_page is called. + * + * get_user_pages_remote is typically used for fewer-copy IO operations, + * to get a handle on the memory by some means other than accesses + * via the user virtual addresses. The pages may be submitted for + * DMA to devices or accessed via their kernel linear mapping (via the + * kmap APIs). Care should be taken to use the correct cache flushing APIs. + * + * See also get_user_pages_fast, for performance critical applications. + * + * get_user_pages_remote should be phased out in favor of + * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing + * should use get_user_pages_remote because it cannot pass + * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault. + */ +long get_user_pages_remote(struct mm_struct *mm, + unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + int *locked) +{ + int local_locked = 1; + + if (!is_valid_gup_args(pages, locked, &gup_flags, + FOLL_TOUCH | FOLL_REMOTE)) + return -EINVAL; + + return __get_user_pages_locked(mm, start, nr_pages, pages, + locked ? locked : &local_locked, + gup_flags); +} +EXPORT_SYMBOL(get_user_pages_remote); + +#else /* CONFIG_MMU */ +long get_user_pages_remote(struct mm_struct *mm, + unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + int *locked) +{ + return 0; +} +#endif /* !CONFIG_MMU */ + +/** + * get_user_pages() - pin user pages in memory + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @gup_flags: flags modifying lookup behaviour + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. Or NULL, if caller + * only intends to ensure the pages are faulted in. + * + * This is the same as get_user_pages_remote(), just with a less-flexible + * calling convention where we assume that the mm being operated on belongs to + * the current task, and doesn't allow passing of a locked parameter. We also + * obviously don't pass FOLL_REMOTE in here. + */ +long get_user_pages(unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages) +{ + int locked = 1; + + if (!is_valid_gup_args(pages, NULL, &gup_flags, FOLL_TOUCH)) + return -EINVAL; + + return __get_user_pages_locked(current->mm, start, nr_pages, pages, + &locked, gup_flags); +} +EXPORT_SYMBOL(get_user_pages); + +/* + * get_user_pages_unlocked() is suitable to replace the form: + * + * mmap_read_lock(mm); + * get_user_pages(mm, ..., pages, NULL); + * mmap_read_unlock(mm); + * + * with: + * + * get_user_pages_unlocked(mm, ..., pages); + * + * It is functionally equivalent to get_user_pages_fast so + * get_user_pages_fast should be used instead if specific gup_flags + * (e.g. FOLL_FORCE) are not required. + */ +long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages, + struct page **pages, unsigned int gup_flags) +{ + int locked = 0; + + if (!is_valid_gup_args(pages, NULL, &gup_flags, + FOLL_TOUCH | FOLL_UNLOCKABLE)) + return -EINVAL; + + return __get_user_pages_locked(current->mm, start, nr_pages, pages, + &locked, gup_flags); +} +EXPORT_SYMBOL(get_user_pages_unlocked); + +/* + * Fast GUP + * + * get_user_pages_fast attempts to pin user pages by walking the page + * tables directly and avoids taking locks. Thus the walker needs to be + * protected from page table pages being freed from under it, and should + * block any THP splits. + * + * One way to achieve this is to have the walker disable interrupts, and + * rely on IPIs from the TLB flushing code blocking before the page table + * pages are freed. This is unsuitable for architectures that do not need + * to broadcast an IPI when invalidating TLBs. + * + * Another way to achieve this is to batch up page table containing pages + * belonging to more than one mm_user, then rcu_sched a callback to free those + * pages. Disabling interrupts will allow the fast_gup walker to both block + * the rcu_sched callback, and an IPI that we broadcast for splitting THPs + * (which is a relatively rare event). The code below adopts this strategy. + * + * Before activating this code, please be aware that the following assumptions + * are currently made: + * + * *) Either MMU_GATHER_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to + * free pages containing page tables or TLB flushing requires IPI broadcast. + * + * *) ptes can be read atomically by the architecture. + * + * *) access_ok is sufficient to validate userspace address ranges. + * + * The last two assumptions can be relaxed by the addition of helper functions. + * + * This code is based heavily on the PowerPC implementation by Nick Piggin. + */ +#ifdef CONFIG_HAVE_FAST_GUP + +/* + * Used in the GUP-fast path to determine whether a pin is permitted for 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. + * + * 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 folio_fast_pin_allowed(struct folio *folio, unsigned int flags) +{ + struct address_space *mapping; + 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)) + return true; + + /* The folio is pinned, so we can safely access folio fields. */ + + if (WARN_ON_ONCE(folio_test_slab(folio))) + return false; + + /* hugetlb mappings do not require dirty-tracking. */ + 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. The only remaining whitelisted file system is + * shmem. + */ + return shmem_mapping(mapping); +} + +static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start, + unsigned int flags, + struct page **pages) +{ + while ((*nr) - nr_start) { + struct page *page = pages[--(*nr)]; + + ClearPageReferenced(page); + if (flags & FOLL_PIN) + unpin_user_page(page); + else + put_page(page); + } +} + +#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL +/* + * Fast-gup relies on pte change detection to avoid concurrent pgtable + * operations. + * + * To pin the page, fast-gup needs to do below in order: + * (1) pin the page (by prefetching pte), then (2) check pte not changed. + * + * For the rest of pgtable operations where pgtable updates can be racy + * with fast-gup, we need to do (1) clear pte, then (2) check whether page + * is pinned. + * + * Above will work for all pte-level operations, including THP split. + * + * For THP collapse, it's a bit more complicated because fast-gup may be + * walking a pgtable page that is being freed (pte is still valid but pmd + * can be cleared already). To avoid race in such condition, we need to + * also check pmd here to make sure pmd doesn't change (corresponds to + * pmdp_collapse_flush() in the THP collapse code path). + */ +static int gup_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr, + unsigned long end, unsigned int flags, + struct page **pages, int *nr) +{ + struct dev_pagemap *pgmap = NULL; + int nr_start = *nr, ret = 0; + pte_t *ptep, *ptem; + + ptem = ptep = pte_offset_map(&pmd, addr); + if (!ptep) + return 0; + do { + pte_t pte = ptep_get_lockless(ptep); + struct page *page; + struct folio *folio; + + /* + * Always fallback to ordinary GUP on PROT_NONE-mapped pages: + * pte_access_permitted() better should reject these pages + * either way: otherwise, GUP-fast might succeed in + * cases where ordinary GUP would fail due to VMA access + * permissions. + */ + if (pte_protnone(pte)) + goto pte_unmap; + + if (!pte_access_permitted(pte, flags & FOLL_WRITE)) + goto pte_unmap; + + if (pte_devmap(pte)) { + if (unlikely(flags & FOLL_LONGTERM)) + goto pte_unmap; + + pgmap = get_dev_pagemap(pte_pfn(pte), pgmap); + if (unlikely(!pgmap)) { + undo_dev_pagemap(nr, nr_start, flags, pages); + goto pte_unmap; + } + } else if (pte_special(pte)) + goto pte_unmap; + + VM_BUG_ON(!pfn_valid(pte_pfn(pte))); + page = pte_page(pte); + + folio = try_grab_folio(page, 1, flags); + if (!folio) + goto pte_unmap; + + if (unlikely(folio_is_secretmem(folio))) { + gup_put_folio(folio, 1, flags); + 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 (!folio_fast_pin_allowed(folio, flags)) { + gup_put_folio(folio, 1, flags); + goto pte_unmap; + } + + if (!pte_write(pte) && gup_must_unshare(NULL, flags, page)) { + gup_put_folio(folio, 1, flags); + goto pte_unmap; + } + + /* + * We need to make the page accessible if and only if we are + * going to access its content (the FOLL_PIN case). Please + * see Documentation/core-api/pin_user_pages.rst for + * details. + */ + if (flags & FOLL_PIN) { + ret = arch_make_page_accessible(page); + if (ret) { + gup_put_folio(folio, 1, flags); + goto pte_unmap; + } + } + folio_set_referenced(folio); + pages[*nr] = page; + (*nr)++; + } while (ptep++, addr += PAGE_SIZE, addr != end); + + ret = 1; + +pte_unmap: + if (pgmap) + put_dev_pagemap(pgmap); + pte_unmap(ptem); + return ret; +} +#else + +/* + * If we can't determine whether or not a pte is special, then fail immediately + * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not + * to be special. + * + * For a futex to be placed on a THP tail page, get_futex_key requires a + * get_user_pages_fast_only implementation that can pin pages. Thus it's still + * useful to have gup_huge_pmd even if we can't operate on ptes. + */ +static int gup_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr, + unsigned long end, unsigned int flags, + struct page **pages, int *nr) +{ + return 0; +} +#endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */ + +#if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE) +static int __gup_device_huge(unsigned long pfn, unsigned long addr, + unsigned long end, unsigned int flags, + struct page **pages, int *nr) +{ + int nr_start = *nr; + struct dev_pagemap *pgmap = NULL; + + do { + struct page *page = pfn_to_page(pfn); + + pgmap = get_dev_pagemap(pfn, pgmap); + if (unlikely(!pgmap)) { + undo_dev_pagemap(nr, nr_start, flags, pages); + break; + } + + if (!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page)) { + undo_dev_pagemap(nr, nr_start, flags, pages); + break; + } + + SetPageReferenced(page); + pages[*nr] = page; + if (unlikely(try_grab_page(page, flags))) { + undo_dev_pagemap(nr, nr_start, flags, pages); + break; + } + (*nr)++; + pfn++; + } while (addr += PAGE_SIZE, addr != end); + + put_dev_pagemap(pgmap); + return addr == end; +} + +static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, + unsigned long end, unsigned int flags, + struct page **pages, int *nr) +{ + unsigned long fault_pfn; + int nr_start = *nr; + + fault_pfn = pmd_pfn(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); + if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr)) + return 0; + + if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) { + undo_dev_pagemap(nr, nr_start, flags, pages); + return 0; + } + return 1; +} + +static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, + unsigned long end, unsigned int flags, + struct page **pages, int *nr) +{ + unsigned long fault_pfn; + int nr_start = *nr; + + fault_pfn = pud_pfn(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); + if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr)) + return 0; + + if (unlikely(pud_val(orig) != pud_val(*pudp))) { + undo_dev_pagemap(nr, nr_start, flags, pages); + return 0; + } + return 1; +} +#else +static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, + unsigned long end, unsigned int flags, + struct page **pages, int *nr) +{ + BUILD_BUG(); + return 0; +} + +static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr, + unsigned long end, unsigned int flags, + struct page **pages, int *nr) +{ + BUILD_BUG(); + return 0; +} +#endif + +static int record_subpages(struct page *page, unsigned long addr, + unsigned long end, struct page **pages) +{ + int nr; + + for (nr = 0; addr != end; nr++, addr += PAGE_SIZE) + pages[nr] = nth_page(page, nr); + + return nr; +} + +#ifdef CONFIG_ARCH_HAS_HUGEPD +static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end, + unsigned long sz) +{ + unsigned long __boundary = (addr + sz) & ~(sz-1); + return (__boundary - 1 < end - 1) ? __boundary : end; +} + +static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr, + unsigned long end, unsigned int flags, + struct page **pages, int *nr) +{ + unsigned long pte_end; + struct page *page; + struct folio *folio; + pte_t pte; + int refs; + + pte_end = (addr + sz) & ~(sz-1); + if (pte_end < end) + end = pte_end; + + pte = huge_ptep_get(ptep); + + if (!pte_access_permitted(pte, flags & FOLL_WRITE)) + return 0; + + /* hugepages are never "special" */ + VM_BUG_ON(!pfn_valid(pte_pfn(pte))); + + page = nth_page(pte_page(pte), (addr & (sz - 1)) >> PAGE_SHIFT); + refs = record_subpages(page, addr, end, pages + *nr); + + folio = try_grab_folio(page, refs, flags); + if (!folio) + return 0; + + if (unlikely(pte_val(pte) != pte_val(ptep_get(ptep)))) { + gup_put_folio(folio, refs, flags); + return 0; + } + + if (!folio_fast_pin_allowed(folio, flags)) { + gup_put_folio(folio, refs, flags); + return 0; + } + + if (!pte_write(pte) && gup_must_unshare(NULL, flags, &folio->page)) { + gup_put_folio(folio, refs, flags); + return 0; + } + + *nr += refs; + folio_set_referenced(folio); + return 1; +} + +static int gup_huge_pd(hugepd_t hugepd, unsigned long addr, + unsigned int pdshift, unsigned long end, unsigned int flags, + struct page **pages, int *nr) +{ + pte_t *ptep; + unsigned long sz = 1UL << hugepd_shift(hugepd); + unsigned long next; + + ptep = hugepte_offset(hugepd, addr, pdshift); + do { + next = hugepte_addr_end(addr, end, sz); + if (!gup_hugepte(ptep, sz, addr, end, flags, pages, nr)) + return 0; + } while (ptep++, addr = next, addr != end); + + return 1; +} +#else +static inline int gup_huge_pd(hugepd_t hugepd, unsigned long addr, + unsigned int pdshift, unsigned long end, unsigned int flags, + struct page **pages, int *nr) +{ + return 0; +} +#endif /* CONFIG_ARCH_HAS_HUGEPD */ + +static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, + unsigned long end, unsigned int flags, + struct page **pages, int *nr) +{ + struct page *page; + struct folio *folio; + int refs; + + if (!pmd_access_permitted(orig, flags & FOLL_WRITE)) + return 0; + + if (pmd_devmap(orig)) { + if (unlikely(flags & FOLL_LONGTERM)) + return 0; + return __gup_device_huge_pmd(orig, pmdp, addr, end, flags, + pages, nr); + } + + page = nth_page(pmd_page(orig), (addr & ~PMD_MASK) >> PAGE_SHIFT); + refs = record_subpages(page, addr, end, pages + *nr); + + folio = try_grab_folio(page, refs, flags); + if (!folio) + return 0; + + if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) { + gup_put_folio(folio, refs, flags); + return 0; + } + + if (!folio_fast_pin_allowed(folio, flags)) { + gup_put_folio(folio, refs, flags); + return 0; + } + if (!pmd_write(orig) && gup_must_unshare(NULL, flags, &folio->page)) { + gup_put_folio(folio, refs, flags); + return 0; + } + + *nr += refs; + folio_set_referenced(folio); + return 1; +} + +static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, + unsigned long end, unsigned int flags, + struct page **pages, int *nr) +{ + struct page *page; + struct folio *folio; + int refs; + + if (!pud_access_permitted(orig, flags & FOLL_WRITE)) + return 0; + + if (pud_devmap(orig)) { + if (unlikely(flags & FOLL_LONGTERM)) + return 0; + return __gup_device_huge_pud(orig, pudp, addr, end, flags, + pages, nr); + } + + page = nth_page(pud_page(orig), (addr & ~PUD_MASK) >> PAGE_SHIFT); + refs = record_subpages(page, addr, end, pages + *nr); + + folio = try_grab_folio(page, refs, flags); + if (!folio) + return 0; + + if (unlikely(pud_val(orig) != pud_val(*pudp))) { + gup_put_folio(folio, refs, flags); + return 0; + } + + if (!folio_fast_pin_allowed(folio, flags)) { + gup_put_folio(folio, refs, flags); + return 0; + } + + if (!pud_write(orig) && gup_must_unshare(NULL, flags, &folio->page)) { + gup_put_folio(folio, refs, flags); + return 0; + } + + *nr += refs; + folio_set_referenced(folio); + return 1; +} + +static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, + unsigned long end, unsigned int flags, + struct page **pages, int *nr) +{ + int refs; + struct page *page; + struct folio *folio; + + if (!pgd_access_permitted(orig, flags & FOLL_WRITE)) + return 0; + + BUILD_BUG_ON(pgd_devmap(orig)); + + page = nth_page(pgd_page(orig), (addr & ~PGDIR_MASK) >> PAGE_SHIFT); + refs = record_subpages(page, addr, end, pages + *nr); + + folio = try_grab_folio(page, refs, flags); + if (!folio) + return 0; + + if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) { + gup_put_folio(folio, refs, flags); + return 0; + } + + if (!pgd_write(orig) && gup_must_unshare(NULL, flags, &folio->page)) { + gup_put_folio(folio, refs, flags); + return 0; + } + + if (!folio_fast_pin_allowed(folio, flags)) { + gup_put_folio(folio, refs, flags); + return 0; + } + + *nr += refs; + folio_set_referenced(folio); + return 1; +} + +static int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, unsigned long end, + unsigned int flags, struct page **pages, int *nr) +{ + unsigned long next; + pmd_t *pmdp; + + pmdp = pmd_offset_lockless(pudp, pud, addr); + do { + pmd_t pmd = pmdp_get_lockless(pmdp); + + next = pmd_addr_end(addr, end); + if (!pmd_present(pmd)) + return 0; + + if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) || + pmd_devmap(pmd))) { + /* See gup_pte_range() */ + if (pmd_protnone(pmd)) + return 0; + + if (!gup_huge_pmd(pmd, pmdp, addr, next, flags, + pages, nr)) + return 0; + + } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) { + /* + * architecture have different format for hugetlbfs + * pmd format and THP pmd format + */ + if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr, + PMD_SHIFT, next, flags, pages, nr)) + return 0; + } else if (!gup_pte_range(pmd, pmdp, addr, next, flags, pages, nr)) + return 0; + } while (pmdp++, addr = next, addr != end); + + return 1; +} + +static int gup_pud_range(p4d_t *p4dp, p4d_t p4d, unsigned long addr, unsigned long end, + unsigned int flags, struct page **pages, int *nr) +{ + unsigned long next; + pud_t *pudp; + + pudp = pud_offset_lockless(p4dp, p4d, addr); + do { + pud_t pud = READ_ONCE(*pudp); + + next = pud_addr_end(addr, end); + if (unlikely(!pud_present(pud))) + return 0; + if (unlikely(pud_huge(pud) || pud_devmap(pud))) { + if (!gup_huge_pud(pud, pudp, addr, next, flags, + pages, nr)) + return 0; + } else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) { + if (!gup_huge_pd(__hugepd(pud_val(pud)), addr, + PUD_SHIFT, next, flags, pages, nr)) + return 0; + } else if (!gup_pmd_range(pudp, pud, addr, next, flags, pages, nr)) + return 0; + } while (pudp++, addr = next, addr != end); + + return 1; +} + +static int gup_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr, unsigned long end, + unsigned int flags, struct page **pages, int *nr) +{ + unsigned long next; + p4d_t *p4dp; + + p4dp = p4d_offset_lockless(pgdp, pgd, addr); + do { + p4d_t p4d = READ_ONCE(*p4dp); + + next = p4d_addr_end(addr, end); + if (p4d_none(p4d)) + return 0; + BUILD_BUG_ON(p4d_huge(p4d)); + if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) { + if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr, + P4D_SHIFT, next, flags, pages, nr)) + return 0; + } else if (!gup_pud_range(p4dp, p4d, addr, next, flags, pages, nr)) + return 0; + } while (p4dp++, addr = next, addr != end); + + return 1; +} + +static void gup_pgd_range(unsigned long addr, unsigned long end, + unsigned int flags, struct page **pages, int *nr) +{ + unsigned long next; + pgd_t *pgdp; + + pgdp = pgd_offset(current->mm, addr); + do { + pgd_t pgd = READ_ONCE(*pgdp); + + next = pgd_addr_end(addr, end); + if (pgd_none(pgd)) + return; + if (unlikely(pgd_huge(pgd))) { + if (!gup_huge_pgd(pgd, pgdp, addr, next, flags, + pages, nr)) + return; + } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) { + if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr, + PGDIR_SHIFT, next, flags, pages, nr)) + return; + } else if (!gup_p4d_range(pgdp, pgd, addr, next, flags, pages, nr)) + return; + } while (pgdp++, addr = next, addr != end); +} +#else +static inline void gup_pgd_range(unsigned long addr, unsigned long end, + unsigned int flags, struct page **pages, int *nr) +{ +} +#endif /* CONFIG_HAVE_FAST_GUP */ + +#ifndef gup_fast_permitted +/* + * Check if it's allowed to use get_user_pages_fast_only() for the range, or + * we need to fall back to the slow version: + */ +static bool gup_fast_permitted(unsigned long start, unsigned long end) +{ + return true; +} +#endif + +static unsigned long lockless_pages_from_mm(unsigned long start, + unsigned long end, + unsigned int gup_flags, + struct page **pages) +{ + unsigned long flags; + int nr_pinned = 0; + unsigned seq; + + if (!IS_ENABLED(CONFIG_HAVE_FAST_GUP) || + !gup_fast_permitted(start, end)) + return 0; + + if (gup_flags & FOLL_PIN) { + seq = raw_read_seqcount(¤t->mm->write_protect_seq); + if (seq & 1) + return 0; + } + + /* + * Disable interrupts. The nested form is used, in order to allow full, + * general purpose use of this routine. + * + * With interrupts disabled, we block page table pages from being freed + * from under us. See struct mmu_table_batch comments in + * include/asm-generic/tlb.h for more details. + * + * We do not adopt an rcu_read_lock() here as we also want to block IPIs + * that come from THPs splitting. + */ + local_irq_save(flags); + gup_pgd_range(start, end, gup_flags, pages, &nr_pinned); + local_irq_restore(flags); + + /* + * When pinning pages for DMA there could be a concurrent write protect + * from fork() via copy_page_range(), in this case always fail fast GUP. + */ + if (gup_flags & FOLL_PIN) { + if (read_seqcount_retry(¤t->mm->write_protect_seq, seq)) { + unpin_user_pages_lockless(pages, nr_pinned); + return 0; + } else { + sanity_check_pinned_pages(pages, nr_pinned); + } + } + return nr_pinned; +} + +static int internal_get_user_pages_fast(unsigned long start, + unsigned long nr_pages, + unsigned int gup_flags, + struct page **pages) +{ + unsigned long len, end; + unsigned long nr_pinned; + int locked = 0; + int ret; + + if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM | + FOLL_FORCE | FOLL_PIN | FOLL_GET | + FOLL_FAST_ONLY | FOLL_NOFAULT | + FOLL_PCI_P2PDMA | FOLL_HONOR_NUMA_FAULT))) + return -EINVAL; + + if (gup_flags & FOLL_PIN) + mm_set_has_pinned_flag(¤t->mm->flags); + + if (!(gup_flags & FOLL_FAST_ONLY)) + might_lock_read(¤t->mm->mmap_lock); + + start = untagged_addr(start) & PAGE_MASK; + len = nr_pages << PAGE_SHIFT; + if (check_add_overflow(start, len, &end)) + return -EOVERFLOW; + if (end > TASK_SIZE_MAX) + return -EFAULT; + if (unlikely(!access_ok((void __user *)start, len))) + return -EFAULT; + + nr_pinned = lockless_pages_from_mm(start, end, gup_flags, pages); + if (nr_pinned == nr_pages || gup_flags & FOLL_FAST_ONLY) + return nr_pinned; + + /* Slow path: try to get the remaining pages with get_user_pages */ + start += nr_pinned << PAGE_SHIFT; + pages += nr_pinned; + ret = __gup_longterm_locked(current->mm, start, nr_pages - nr_pinned, + pages, &locked, + gup_flags | FOLL_TOUCH | FOLL_UNLOCKABLE); + if (ret < 0) { + /* + * The caller has to unpin the pages we already pinned so + * returning -errno is not an option + */ + if (nr_pinned) + return nr_pinned; + return ret; + } + return ret + nr_pinned; +} + +/** + * get_user_pages_fast_only() - pin user pages in memory + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @gup_flags: flags modifying pin behaviour + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. + * + * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to + * the regular GUP. + * + * If the architecture does not support this function, simply return with no + * pages pinned. + * + * Careful, careful! COW breaking can go either way, so a non-write + * access can get ambiguous page results. If you call this function without + * 'write' set, you'd better be sure that you're ok with that ambiguity. + */ +int get_user_pages_fast_only(unsigned long start, int nr_pages, + unsigned int gup_flags, struct page **pages) +{ + /* + * Internally (within mm/gup.c), gup fast variants must set FOLL_GET, + * because gup fast is always a "pin with a +1 page refcount" request. + * + * FOLL_FAST_ONLY is required in order to match the API description of + * this routine: no fall back to regular ("slow") GUP. + */ + if (!is_valid_gup_args(pages, NULL, &gup_flags, + FOLL_GET | FOLL_FAST_ONLY)) + return -EINVAL; + + return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages); +} +EXPORT_SYMBOL_GPL(get_user_pages_fast_only); + +/** + * get_user_pages_fast() - pin user pages in memory + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @gup_flags: flags modifying pin behaviour + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. + * + * Attempt to pin user pages in memory without taking mm->mmap_lock. + * If not successful, it will fall back to taking the lock and + * calling get_user_pages(). + * + * Returns number of pages pinned. This may be fewer than the number requested. + * If nr_pages is 0 or negative, returns 0. If no pages were pinned, returns + * -errno. + */ +int get_user_pages_fast(unsigned long start, int nr_pages, + unsigned int gup_flags, struct page **pages) +{ + /* + * The caller may or may not have explicitly set FOLL_GET; either way is + * OK. However, internally (within mm/gup.c), gup fast variants must set + * FOLL_GET, because gup fast is always a "pin with a +1 page refcount" + * request. + */ + if (!is_valid_gup_args(pages, NULL, &gup_flags, FOLL_GET)) + return -EINVAL; + return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages); +} +EXPORT_SYMBOL_GPL(get_user_pages_fast); + +/** + * pin_user_pages_fast() - pin user pages in memory without taking locks + * + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @gup_flags: flags modifying pin behaviour + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. + * + * Nearly the same as get_user_pages_fast(), except that FOLL_PIN is set. See + * get_user_pages_fast() for documentation on the function arguments, because + * the arguments here are identical. + * + * FOLL_PIN means that the pages must be released via unpin_user_page(). Please + * see Documentation/core-api/pin_user_pages.rst for further details. + * + * Note that if a zero_page is amongst the returned pages, it will not have + * pins in it and unpin_user_page() will not remove pins from it. + */ +int pin_user_pages_fast(unsigned long start, int nr_pages, + unsigned int gup_flags, struct page **pages) +{ + if (!is_valid_gup_args(pages, NULL, &gup_flags, FOLL_PIN)) + return -EINVAL; + return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages); +} +EXPORT_SYMBOL_GPL(pin_user_pages_fast); + +/** + * pin_user_pages_remote() - pin pages of a remote process + * + * @mm: mm_struct of target mm + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @gup_flags: flags modifying lookup behaviour + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. + * @locked: pointer to lock flag indicating whether lock is held and + * subsequently whether VM_FAULT_RETRY functionality can be + * utilised. Lock must initially be held. + * + * Nearly the same as get_user_pages_remote(), except that FOLL_PIN is set. See + * get_user_pages_remote() for documentation on the function arguments, because + * the arguments here are identical. + * + * FOLL_PIN means that the pages must be released via unpin_user_page(). Please + * see Documentation/core-api/pin_user_pages.rst for details. + * + * Note that if a zero_page is amongst the returned pages, it will not have + * pins in it and unpin_user_page*() will not remove pins from it. + */ +long pin_user_pages_remote(struct mm_struct *mm, + unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + int *locked) +{ + int local_locked = 1; + + if (!is_valid_gup_args(pages, locked, &gup_flags, + FOLL_PIN | FOLL_TOUCH | FOLL_REMOTE)) + return 0; + return __gup_longterm_locked(mm, start, nr_pages, pages, + locked ? locked : &local_locked, + gup_flags); +} +EXPORT_SYMBOL(pin_user_pages_remote); + +/** + * pin_user_pages() - pin user pages in memory for use by other devices + * + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @gup_flags: flags modifying lookup behaviour + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. + * + * Nearly the same as get_user_pages(), except that FOLL_TOUCH is not set, and + * FOLL_PIN is set. + * + * FOLL_PIN means that the pages must be released via unpin_user_page(). Please + * see Documentation/core-api/pin_user_pages.rst for details. + * + * Note that if a zero_page is amongst the returned pages, it will not have + * pins in it and unpin_user_page*() will not remove pins from it. + */ +long pin_user_pages(unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages) +{ + int locked = 1; + + if (!is_valid_gup_args(pages, NULL, &gup_flags, FOLL_PIN)) + return 0; + return __gup_longterm_locked(current->mm, start, nr_pages, + pages, &locked, gup_flags); +} +EXPORT_SYMBOL(pin_user_pages); + +/* + * pin_user_pages_unlocked() is the FOLL_PIN variant of + * get_user_pages_unlocked(). Behavior is the same, except that this one sets + * FOLL_PIN and rejects FOLL_GET. + * + * Note that if a zero_page is amongst the returned pages, it will not have + * pins in it and unpin_user_page*() will not remove pins from it. + */ +long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages, + struct page **pages, unsigned int gup_flags) +{ + int locked = 0; + + if (!is_valid_gup_args(pages, NULL, &gup_flags, + FOLL_PIN | FOLL_TOUCH | FOLL_UNLOCKABLE)) + return 0; + + return __gup_longterm_locked(current->mm, start, nr_pages, pages, + &locked, gup_flags); +} +EXPORT_SYMBOL(pin_user_pages_unlocked); |