diff options
Diffstat (limited to 'mm/gup.c')
| -rw-r--r-- | mm/gup.c | 3040 |
1 files changed, 3040 insertions, 0 deletions
diff --git a/mm/gup.c b/mm/gup.c new file mode 100644 index 000000000..11307a8b2 --- /dev/null +++ b/mm/gup.c @@ -0,0 +1,3040 @@ +// 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/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 <asm/mmu_context.h> +#include <asm/tlbflush.h> + +#include "internal.h" + +struct follow_page_context { + struct dev_pagemap *pgmap; + unsigned int page_mask; +}; + +static void hpage_pincount_add(struct page *page, int refs) +{ + VM_BUG_ON_PAGE(!hpage_pincount_available(page), page); + VM_BUG_ON_PAGE(page != compound_head(page), page); + + atomic_add(refs, compound_pincount_ptr(page)); +} + +static void hpage_pincount_sub(struct page *page, int refs) +{ + VM_BUG_ON_PAGE(!hpage_pincount_available(page), page); + VM_BUG_ON_PAGE(page != compound_head(page), page); + + atomic_sub(refs, compound_pincount_ptr(page)); +} + +/* Equivalent to calling put_page() @refs times. */ +static void put_page_refs(struct page *page, int refs) +{ +#ifdef CONFIG_DEBUG_VM + if (VM_WARN_ON_ONCE_PAGE(page_ref_count(page) < refs, page)) + return; +#endif + + /* + * Calling put_page() for each ref is unnecessarily slow. Only the last + * ref needs a put_page(). + */ + if (refs > 1) + page_ref_sub(page, refs - 1); + put_page(page); +} + +/* + * Return the compound head page with ref appropriately incremented, + * or NULL if that failed. + */ +static inline struct page *try_get_compound_head(struct page *page, int refs) +{ + struct page *head = compound_head(page); + + if (WARN_ON_ONCE(page_ref_count(head) < 0)) + return NULL; + if (unlikely(!page_cache_add_speculative(head, refs))) + return NULL; + + /* + * At this point we have a stable reference to the head page; but it + * could be that between the compound_head() lookup and the refcount + * increment, the compound page was split, in which case we'd end up + * holding a reference on a page that has nothing to do with the page + * we were given anymore. + * So now that the head page is stable, recheck that the pages still + * belong together. + */ + if (unlikely(compound_head(page) != head)) { + put_page_refs(head, refs); + return NULL; + } + + return head; +} + +/* + * try_grab_compound_head() - attempt to elevate a page's refcount, by a + * flags-dependent amount. + * + * "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) 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: page's refcount will be incremented by 1. + * FOLL_PIN: page's refcount will be incremented by GUP_PIN_COUNTING_BIAS. + * + * Return: head 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. + */ +static __maybe_unused struct page *try_grab_compound_head(struct page *page, + int refs, + unsigned int flags) +{ + if (flags & FOLL_GET) + return try_get_compound_head(page, refs); + else if (flags & FOLL_PIN) { + int orig_refs = refs; + + /* + * Can't do FOLL_LONGTERM + FOLL_PIN with CMA in the gup fast + * path, so fail and let the caller fall back to the slow path. + */ + if (unlikely(flags & FOLL_LONGTERM) && + is_migrate_cma_page(page)) + return NULL; + + /* + * CAUTION: Don't use compound_head() on the page before this + * point, the result won't be stable. + */ + page = try_get_compound_head(page, refs); + if (!page) + return NULL; + + /* + * When pinning a compound page of order > 1 (which is what + * hpage_pincount_available() checks for), use an exact count to + * track it, via hpage_pincount_add/_sub(). + * + * However, be sure to *also* increment the normal page refcount + * field at least once, so that the page really is pinned. + */ + if (hpage_pincount_available(page)) + hpage_pincount_add(page, refs); + else + page_ref_add(page, refs * (GUP_PIN_COUNTING_BIAS - 1)); + + mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_ACQUIRED, + orig_refs); + + return page; + } + + WARN_ON_ONCE(1); + return NULL; +} + +static void put_compound_head(struct page *page, int refs, unsigned int flags) +{ + if (flags & FOLL_PIN) { + mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED, + refs); + + if (hpage_pincount_available(page)) + hpage_pincount_sub(page, refs); + else + refs *= GUP_PIN_COUNTING_BIAS; + } + + put_page_refs(page, refs); +} + +/** + * try_grab_page() - elevate a page's refcount by a flag-dependent amount + * + * 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. + * + * @page: pointer to page to be grabbed + * @flags: gup flags: these are the FOLL_* flag values. + * + * Either FOLL_PIN or FOLL_GET (or neither) may be set, but not both at the same + * time. Cases: + * + * FOLL_GET: page's refcount will be incremented by 1. + * FOLL_PIN: page's refcount will be incremented by GUP_PIN_COUNTING_BIAS. + * + * Return: true for success, or if no action was required (if neither FOLL_PIN + * nor FOLL_GET was set, nothing is done). False for failure: FOLL_GET or + * FOLL_PIN was set, but the page could not be grabbed. + */ +bool __must_check try_grab_page(struct page *page, unsigned int flags) +{ + WARN_ON_ONCE((flags & (FOLL_GET | FOLL_PIN)) == (FOLL_GET | FOLL_PIN)); + + if (flags & FOLL_GET) + return try_get_page(page); + else if (flags & FOLL_PIN) { + int refs = 1; + + page = compound_head(page); + + if (WARN_ON_ONCE(page_ref_count(page) <= 0)) + return false; + + if (hpage_pincount_available(page)) + hpage_pincount_add(page, 1); + else + refs = GUP_PIN_COUNTING_BIAS; + + /* + * Similar to try_grab_compound_head(): even if using the + * hpage_pincount_add/_sub() routines, be sure to + * *also* increment the normal page refcount field at least + * once, so that the page really is pinned. + */ + page_ref_add(page, refs); + + mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_ACQUIRED, 1); + } + + return true; +} + +/** + * 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) +{ + put_compound_head(compound_head(page), 1, FOLL_PIN); +} +EXPORT_SYMBOL(unpin_user_page); + +/** + * 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 index; + + /* + * TODO: this can be optimized for huge pages: if a series of pages is + * physically contiguous and part of the same compound page, then a + * single operation to the head page should suffice. + */ + + if (!make_dirty) { + unpin_user_pages(pages, npages); + return; + } + + for (index = 0; index < npages; index++) { + struct page *page = compound_head(pages[index]); + /* + * 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 (!PageDirty(page)) + set_page_dirty_lock(page); + unpin_user_page(page); + } +} +EXPORT_SYMBOL(unpin_user_pages_dirty_lock); + +/** + * 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 index; + + /* + * 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; + /* + * TODO: this can be optimized for huge pages: if a series of pages is + * physically contiguous and part of the same compound page, then a + * single operation to the head page should suffice. + */ + for (index = 0; index < npages; index++) + unpin_user_page(pages[index]); +} +EXPORT_SYMBOL(unpin_user_pages); + +#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) +{ + /* No page to get reference */ + if (flags & FOLL_GET) + return -EFAULT; + + if (flags & FOLL_TOUCH) { + pte_t entry = *pte; + + if (flags & FOLL_WRITE) + entry = pte_mkdirty(entry); + entry = pte_mkyoung(entry); + + if (!pte_same(*pte, 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 pte's, but only + * after we've gone through a COW cycle and they are dirty. + */ +static inline bool can_follow_write_pte(pte_t pte, unsigned int flags) +{ + return pte_write(pte) || + ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(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); + + /* + * Considering PTE level hugetlb, like continuous-PTE hugetlb on + * ARM64 architecture. + */ + if (is_vm_hugetlb_page(vma)) { + page = follow_huge_pmd_pte(vma, address, flags); + if (page) + return page; + return no_page_table(vma, flags); + } + +retry: + if (unlikely(pmd_bad(*pmd))) + return no_page_table(vma, flags); + + ptep = pte_offset_map_lock(mm, pmd, address, &ptl); + pte = *ptep; + if (!pte_present(pte)) { + swp_entry_t entry; + /* + * KSM's break_ksm() relies upon recognizing a ksm page + * even while it is being migrated, so for that case we + * need migration_entry_wait(). + */ + if (likely(!(flags & FOLL_MIGRATION))) + goto no_page; + if (pte_none(pte)) + goto no_page; + entry = pte_to_swp_entry(pte); + if (!is_migration_entry(entry)) + goto no_page; + pte_unmap_unlock(ptep, ptl); + migration_entry_wait(mm, pmd, address); + goto retry; + } + if ((flags & FOLL_NUMA) && pte_protnone(pte)) + goto no_page; + if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) { + pte_unmap_unlock(ptep, ptl); + return NULL; + } + + page = vm_normal_page(vma, address, pte); + 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 (flags & FOLL_SPLIT && PageTransCompound(page)) { + get_page(page); + pte_unmap_unlock(ptep, ptl); + lock_page(page); + ret = split_huge_page(page); + unlock_page(page); + put_page(page); + if (ret) + return ERR_PTR(ret); + goto retry; + } + + /* try_grab_page() does nothing unless FOLL_GET or FOLL_PIN is set. */ + if (unlikely(!try_grab_page(page, flags))) { + page = ERR_PTR(-ENOMEM); + 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); + } + if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { + /* Do not mlock pte-mapped THP */ + if (PageTransCompound(page)) + goto out; + + /* + * The preliminary mapping check is mainly to avoid the + * pointless overhead of lock_page on the ZERO_PAGE + * which might bounce very badly if there is contention. + * + * If the page is already locked, we don't need to + * handle it now - vmscan will handle it later if and + * when it attempts to reclaim the page. + */ + if (page->mapping && trylock_page(page)) { + lru_add_drain(); /* push cached pages to LRU */ + /* + * Because we lock page here, and migration is + * blocked by the pte's page reference, and we + * know the page is still mapped, we don't even + * need to check for file-cache page truncation. + */ + mlock_vma_page(page); + unlock_page(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); + /* + * The READ_ONCE() will stabilize the pmdval in a register or + * on the stack so that it will stop changing under the code. + */ + pmdval = READ_ONCE(*pmd); + if (pmd_none(pmdval)) + return no_page_table(vma, flags); + if (pmd_huge(pmdval) && is_vm_hugetlb_page(vma)) { + page = follow_huge_pmd_pte(vma, address, flags); + if (page) + return page; + return no_page_table(vma, flags); + } + if (is_hugepd(__hugepd(pmd_val(pmdval)))) { + page = follow_huge_pd(vma, address, + __hugepd(pmd_val(pmdval)), flags, + PMD_SHIFT); + if (page) + return page; + return no_page_table(vma, flags); + } +retry: + if (!pmd_present(pmdval)) { + if (likely(!(flags & FOLL_MIGRATION))) + return no_page_table(vma, flags); + VM_BUG_ON(thp_migration_supported() && + !is_pmd_migration_entry(pmdval)); + if (is_pmd_migration_entry(pmdval)) + pmd_migration_entry_wait(mm, pmd); + pmdval = READ_ONCE(*pmd); + /* + * MADV_DONTNEED may convert the pmd to null because + * mmap_lock is held in read mode + */ + if (pmd_none(pmdval)) + return no_page_table(vma, flags); + goto retry; + } + 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 ((flags & FOLL_NUMA) && pmd_protnone(pmdval)) + return no_page_table(vma, flags); + +retry_locked: + ptl = pmd_lock(mm, pmd); + if (unlikely(pmd_none(*pmd))) { + spin_unlock(ptl); + return no_page_table(vma, flags); + } + if (unlikely(!pmd_present(*pmd))) { + spin_unlock(ptl); + if (likely(!(flags & FOLL_MIGRATION))) + return no_page_table(vma, flags); + pmd_migration_entry_wait(mm, pmd); + goto retry_locked; + } + if (unlikely(!pmd_trans_huge(*pmd))) { + spin_unlock(ptl); + return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); + } + if (flags & (FOLL_SPLIT | FOLL_SPLIT_PMD)) { + int ret; + page = pmd_page(*pmd); + if (is_huge_zero_page(page)) { + spin_unlock(ptl); + ret = 0; + split_huge_pmd(vma, pmd, address); + if (pmd_trans_unstable(pmd)) + ret = -EBUSY; + } else if (flags & FOLL_SPLIT) { + if (unlikely(!try_get_page(page))) { + spin_unlock(ptl); + return ERR_PTR(-ENOMEM); + } + spin_unlock(ptl); + lock_page(page); + ret = split_huge_page(page); + unlock_page(page); + put_page(page); + if (pmd_none(*pmd)) + return no_page_table(vma, flags); + } else { /* flags & FOLL_SPLIT_PMD */ + spin_unlock(ptl); + split_huge_pmd(vma, pmd, address); + ret = pte_alloc(mm, pmd) ? -ENOMEM : 0; + } + + return ret ? ERR_PTR(ret) : + 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_huge(*pud) && is_vm_hugetlb_page(vma)) { + page = follow_huge_pud(mm, address, pud, flags); + if (page) + return page; + return no_page_table(vma, flags); + } + if (is_hugepd(__hugepd(pud_val(*pud)))) { + page = follow_huge_pd(vma, address, + __hugepd(pud_val(*pud)), flags, + PUD_SHIFT); + if (page) + return page; + 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; + struct page *page; + + 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); + + if (is_hugepd(__hugepd(p4d_val(*p4d)))) { + page = follow_huge_pd(vma, address, + __hugepd(p4d_val(*p4d)), flags, + P4D_SHIFT); + if (page) + return page; + 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. + * + * 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 page *page; + struct mm_struct *mm = vma->vm_mm; + + ctx->page_mask = 0; + + /* make this handle hugepd */ + page = follow_huge_addr(mm, address, flags & FOLL_WRITE); + if (!IS_ERR(page)) { + WARN_ON_ONCE(flags & (FOLL_GET | FOLL_PIN)); + return page; + } + + pgd = pgd_offset(mm, address); + + if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd))) + return no_page_table(vma, flags); + + if (pgd_huge(*pgd)) { + page = follow_huge_pgd(mm, address, pgd, flags); + if (page) + return page; + return no_page_table(vma, flags); + } + if (is_hugepd(__hugepd(pgd_val(*pgd)))) { + page = follow_huge_pd(vma, address, + __hugepd(pgd_val(*pgd)), flags, + PGDIR_SHIFT); + if (page) + return page; + 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; + + 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; + 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; + VM_BUG_ON(pmd_trans_huge(*pmd)); + pte = pte_offset_map(pmd, address); + if (pte_none(*pte)) + goto unmap; + *vma = get_gate_vma(mm); + if (!page) + goto out; + *page = vm_normal_page(*vma, address, *pte); + if (!*page) { + if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte))) + goto unmap; + *page = pte_page(*pte); + } + if (unlikely(!try_grab_page(*page, gup_flags))) { + ret = -ENOMEM; + goto unmap; + } +out: + ret = 0; +unmap: + pte_unmap(pte); + return ret; +} + +/* + * mmap_lock must be held on entry. If @locked != NULL and *@flags + * does not include 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, int *locked) +{ + unsigned int fault_flags = 0; + vm_fault_t ret; + + /* mlock all present pages, but do not fault in new pages */ + if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK) + return -ENOENT; + if (*flags & FOLL_WRITE) + fault_flags |= FAULT_FLAG_WRITE; + if (*flags & FOLL_REMOTE) + fault_flags |= FAULT_FLAG_REMOTE; + if (locked) + fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; + 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; + } + + ret = handle_mm_fault(vma, address, fault_flags, NULL); + if (ret & VM_FAULT_ERROR) { + int err = vm_fault_to_errno(ret, *flags); + + if (err) + return err; + BUG(); + } + + if (ret & VM_FAULT_RETRY) { + if (locked && !(fault_flags & FAULT_FLAG_RETRY_NOWAIT)) + *locked = 0; + return -EBUSY; + } + + /* + * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when + * necessary, even if maybe_mkwrite decided not to set pte_write. We + * can thus safely do subsequent page lookups as if they were reads. + * But only do so when looping for pte_write is futile: in some cases + * userspace may also be wanting to write to the gotten user page, + * which a read fault here might prevent (a readonly page might get + * reCOWed by userspace write). + */ + if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE)) + *flags |= FOLL_COW; + return 0; +} + +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); + + if (vm_flags & (VM_IO | VM_PFNMAP)) + return -EFAULT; + + if (gup_flags & FOLL_ANON && !vma_is_anonymous(vma)) + return -EFAULT; + + if (write) { + if (!(vm_flags & VM_WRITE)) { + if (!(gup_flags & FOLL_FORCE)) + 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; +} + +/** + * __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. + * @vmas: array of pointers to vmas corresponding to each page. + * Or NULL if the caller does not require them. + * @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(). + * + * @vmas are valid only as long as mmap_lock is held. + * + * 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 @locked != NULL, *@locked will be set to 0 when mmap_lock is + * released by an up_read(). That can happen if @gup_flags does not + * have FOLL_NOWAIT. + * + * A caller using such a combination of @locked and @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, + struct vm_area_struct **vmas, 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(start); + + VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN))); + + /* + * If FOLL_FORCE is set then do not force a full fault as the hinting + * fault information is unrelated to the reference behaviour of a task + * using the address space + */ + if (!(gup_flags & FOLL_FORCE)) + gup_flags |= FOLL_NUMA; + + 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 = find_extend_vma(mm, start); + if (!vma && in_gate_area(mm, start)) { + ret = get_gate_page(mm, start & PAGE_MASK, + gup_flags, &vma, + pages ? &pages[i] : NULL); + if (ret) + goto out; + ctx.page_mask = 0; + goto next_page; + } + + if (!vma || check_vma_flags(vma, gup_flags)) { + ret = -EFAULT; + goto out; + } + if (is_vm_hugetlb_page(vma)) { + i = follow_hugetlb_page(mm, vma, pages, vmas, + &start, &nr_pages, i, + gup_flags, locked); + if (locked && *locked == 0) { + /* + * We've got a VM_FAULT_RETRY + * and we've lost mmap_lock. + * We must stop here. + */ + BUG_ON(gup_flags & FOLL_NOWAIT); + BUG_ON(ret != 0); + goto out; + } + continue; + } + } +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) { + ret = faultin_page(vma, start, &foll_flags, locked); + switch (ret) { + case 0: + goto retry; + case -EBUSY: + ret = 0; + fallthrough; + case -EFAULT: + case -ENOMEM: + case -EHWPOISON: + goto out; + case -ENOENT: + goto next_page; + } + BUG(); + } else if (PTR_ERR(page) == -EEXIST) { + /* + * Proper page table entry exists, but no corresponding + * struct page. + */ + goto next_page; + } else if (IS_ERR(page)) { + ret = PTR_ERR(page); + goto out; + } + if (pages) { + pages[i] = page; + flush_anon_page(vma, page, start); + flush_dcache_page(page); + ctx.page_mask = 0; + } +next_page: + if (vmas) { + vmas[i] = vma; + ctx.page_mask = 0; + } + page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask); + if (page_increm > nr_pages) + page_increm = nr_pages; + 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, major = 0; + + address = untagged_addr(address); + + if (unlocked) + fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; + +retry: + vma = find_extend_vma(mm, address); + if (!vma || address < vma->vm_start) + 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); + major |= ret & VM_FAULT_MAJOR; + 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); + +/* + * Please note that this function, unlike __get_user_pages will not + * return 0 for nr_pages > 0 without FOLL_NOWAIT + */ +static __always_inline long __get_user_pages_locked(struct mm_struct *mm, + unsigned long start, + unsigned long nr_pages, + struct page **pages, + struct vm_area_struct **vmas, + int *locked, + unsigned int flags) +{ + long ret, pages_done; + bool lock_dropped; + + if (locked) { + /* if VM_FAULT_RETRY can be returned, vmas become invalid */ + BUG_ON(vmas); + /* check caller initialized locked */ + BUG_ON(*locked != 1); + } + + if (flags & FOLL_PIN) + atomic_set(&mm->has_pinned, 1); + + /* + * 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; + lock_dropped = false; + for (;;) { + ret = __get_user_pages(mm, start, nr_pages, flags, pages, + vmas, locked); + if (!locked) + /* VM_FAULT_RETRY couldn't trigger, bypass */ + return ret; + + /* VM_FAULT_RETRY 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; + lock_dropped = 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, so we need to check it before we + * start trying again otherwise it can loop forever. + */ + + if (fatal_signal_pending(current)) { + 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, NULL, 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 (lock_dropped && *locked) { + /* + * We must let the caller know we temporarily dropped the lock + * and so the critical section protected by it was lost. + */ + 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 gup_flags; + + VM_BUG_ON(start & ~PAGE_MASK); + VM_BUG_ON(end & ~PAGE_MASK); + VM_BUG_ON_VMA(start < vma->vm_start, vma); + VM_BUG_ON_VMA(end > vma->vm_end, vma); + mmap_assert_locked(mm); + + gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK; + if (vma->vm_flags & VM_LOCKONFAULT) + gup_flags &= ~FOLL_POPULATE; + /* + * 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; + + /* + * We made sure addr is within a VMA, so the following will + * not result in a stack expansion that recurses back here. + */ + return __get_user_pages(mm, start, nr_pages, gup_flags, + NULL, NULL, locked); +} + +/* + * __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(mm, nstart); + } else if (nstart >= vma->vm_end) + vma = vma->vm_next; + if (!vma || vma->vm_start >= end) + 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, + struct vm_area_struct **vmas, int *locked, + unsigned int foll_flags) +{ + struct vm_area_struct *vma; + unsigned long vm_flags; + int i; + + /* 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) + goto finish_or_fault; + + /* protect what we can, including chardevs */ + if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) || + !(vm_flags & vma->vm_flags)) + goto finish_or_fault; + + if (pages) { + pages[i] = virt_to_page(start); + if (pages[i]) + get_page(pages[i]); + } + if (vmas) + vmas[i] = vma; + start = (start + PAGE_SIZE) & PAGE_MASK; + } + + return i; + +finish_or_fault: + return i ? : -EFAULT; +} +#endif /* !CONFIG_MMU */ + +/** + * 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 diskspace. + * + * 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 mm_struct *mm = current->mm; + struct page *page; + int locked = 1; + int ret; + + if (mmap_read_lock_killable(mm)) + return NULL; + ret = __get_user_pages_locked(mm, addr, 1, &page, NULL, &locked, + FOLL_FORCE | FOLL_DUMP | FOLL_GET); + if (locked) + mmap_read_unlock(mm); + return (ret == 1) ? page : NULL; +} +#endif /* CONFIG_ELF_CORE */ + +#if defined(CONFIG_FS_DAX) || defined (CONFIG_CMA) +static bool check_dax_vmas(struct vm_area_struct **vmas, long nr_pages) +{ + long i; + struct vm_area_struct *vma_prev = NULL; + + for (i = 0; i < nr_pages; i++) { + struct vm_area_struct *vma = vmas[i]; + + if (vma == vma_prev) + continue; + + vma_prev = vma; + + if (vma_is_fsdax(vma)) + return true; + } + return false; +} + +#ifdef CONFIG_CMA +static long check_and_migrate_cma_pages(struct mm_struct *mm, + unsigned long start, + unsigned long nr_pages, + struct page **pages, + struct vm_area_struct **vmas, + unsigned int gup_flags) +{ + unsigned long i, isolation_error_count; + bool drain_allow; + LIST_HEAD(cma_page_list); + long ret = nr_pages; + struct page *prev_head, *head; + struct migration_target_control mtc = { + .nid = NUMA_NO_NODE, + .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_NOWARN, + }; + +check_again: + prev_head = NULL; + isolation_error_count = 0; + drain_allow = true; + for (i = 0; i < nr_pages; i++) { + head = compound_head(pages[i]); + if (head == prev_head) + continue; + prev_head = head; + /* + * If we get a page from the CMA zone, since we are going to + * be pinning these entries, we might as well move them out + * of the CMA zone if possible. + */ + if (is_migrate_cma_page(head)) { + if (PageHuge(head)) { + if (isolate_hugetlb(head, &cma_page_list)) + isolation_error_count++; + } else { + if (!PageLRU(head) && drain_allow) { + lru_add_drain_all(); + drain_allow = false; + } + + if (isolate_lru_page(head)) { + isolation_error_count++; + continue; + } + list_add_tail(&head->lru, &cma_page_list); + mod_node_page_state(page_pgdat(head), + NR_ISOLATED_ANON + + page_is_file_lru(head), + thp_nr_pages(head)); + } + } + } + + /* + * If list is empty, and no isolation errors, means that all pages are + * in the correct zone. + */ + if (list_empty(&cma_page_list) && !isolation_error_count) + return ret; + + if (!list_empty(&cma_page_list)) { + /* + * drop the above get_user_pages reference. + */ + if (gup_flags & FOLL_PIN) + unpin_user_pages(pages, nr_pages); + else + for (i = 0; i < nr_pages; i++) + put_page(pages[i]); + + ret = migrate_pages(&cma_page_list, alloc_migration_target, + NULL, (unsigned long)&mtc, MIGRATE_SYNC, + MR_CONTIG_RANGE); + if (ret) { + if (!list_empty(&cma_page_list)) + putback_movable_pages(&cma_page_list); + return ret > 0 ? -ENOMEM : ret; + } + + /* We unpinned pages before migration, pin them again */ + ret = __get_user_pages_locked(mm, start, nr_pages, pages, vmas, + NULL, gup_flags); + if (ret <= 0) + return ret; + nr_pages = ret; + } + + /* + * check again because pages were unpinned, and we also might have + * had isolation errors and need more pages to migrate. + */ + goto check_again; +} +#else +static long check_and_migrate_cma_pages(struct mm_struct *mm, + unsigned long start, + unsigned long nr_pages, + struct page **pages, + struct vm_area_struct **vmas, + unsigned int gup_flags) +{ + return nr_pages; +} +#endif /* CONFIG_CMA */ + +/* + * __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, + struct vm_area_struct **vmas, + unsigned int gup_flags) +{ + struct vm_area_struct **vmas_tmp = vmas; + unsigned long flags = 0; + long rc, i; + + if (gup_flags & FOLL_LONGTERM) { + if (!pages) + return -EINVAL; + + if (!vmas_tmp) { + vmas_tmp = kcalloc(nr_pages, + sizeof(struct vm_area_struct *), + GFP_KERNEL); + if (!vmas_tmp) + return -ENOMEM; + } + flags = memalloc_nocma_save(); + } + + rc = __get_user_pages_locked(mm, start, nr_pages, pages, + vmas_tmp, NULL, gup_flags); + + if (gup_flags & FOLL_LONGTERM) { + if (rc < 0) + goto out; + + if (check_dax_vmas(vmas_tmp, rc)) { + if (gup_flags & FOLL_PIN) + unpin_user_pages(pages, rc); + else + for (i = 0; i < rc; i++) + put_page(pages[i]); + rc = -EOPNOTSUPP; + goto out; + } + + rc = check_and_migrate_cma_pages(mm, start, rc, pages, + vmas_tmp, gup_flags); +out: + memalloc_nocma_restore(flags); + } + + if (vmas_tmp != vmas) + kfree(vmas_tmp); + return rc; +} +#else /* !CONFIG_FS_DAX && !CONFIG_CMA */ +static __always_inline long __gup_longterm_locked(struct mm_struct *mm, + unsigned long start, + unsigned long nr_pages, + struct page **pages, + struct vm_area_struct **vmas, + unsigned int flags) +{ + return __get_user_pages_locked(mm, start, nr_pages, pages, vmas, + NULL, flags); +} +#endif /* CONFIG_FS_DAX || CONFIG_CMA */ + +static bool is_valid_gup_flags(unsigned int gup_flags) +{ + /* + * FOLL_PIN must only be set internally by the pin_user_pages*() APIs, + * never directly by the caller, so enforce that with an assertion: + */ + if (WARN_ON_ONCE(gup_flags & FOLL_PIN)) + return false; + /* + * FOLL_PIN is a prerequisite to FOLL_LONGTERM. Another way of saying + * that is, FOLL_LONGTERM is a specific case, more restrictive case of + * FOLL_PIN. + */ + if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM)) + return false; + + return true; +} + +#ifdef CONFIG_MMU +static long __get_user_pages_remote(struct mm_struct *mm, + unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + struct vm_area_struct **vmas, int *locked) +{ + /* + * Parts of FOLL_LONGTERM behavior are incompatible with + * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on + * vmas. However, this only comes up if locked is set, and there are + * callers that do request FOLL_LONGTERM, but do not set locked. So, + * allow what we can. + */ + if (gup_flags & FOLL_LONGTERM) { + if (WARN_ON_ONCE(locked)) + return -EINVAL; + /* + * This will check the vmas (even if our vmas arg is NULL) + * and return -ENOTSUPP if DAX isn't allowed in this case: + */ + return __gup_longterm_locked(mm, start, nr_pages, pages, + vmas, gup_flags | FOLL_TOUCH | + FOLL_REMOTE); + } + + return __get_user_pages_locked(mm, start, nr_pages, pages, vmas, + locked, + gup_flags | FOLL_TOUCH | FOLL_REMOTE); +} + +/** + * 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. + * @vmas: array of pointers to vmas corresponding to each page. + * Or NULL if the caller does not require them. + * @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(). + * + * @vmas are valid only as long as mmap_lock is held. + * + * 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, + struct vm_area_struct **vmas, int *locked) +{ + if (!is_valid_gup_flags(gup_flags)) + return -EINVAL; + + return __get_user_pages_remote(mm, start, nr_pages, gup_flags, + pages, vmas, locked); +} +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, + struct vm_area_struct **vmas, int *locked) +{ + return 0; +} + +static long __get_user_pages_remote(struct mm_struct *mm, + unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + struct vm_area_struct **vmas, 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. + * @vmas: array of pointers to vmas corresponding to each page. + * Or NULL if the caller does not require them. + * + * 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, + struct vm_area_struct **vmas) +{ + if (!is_valid_gup_flags(gup_flags)) + return -EINVAL; + + return __gup_longterm_locked(current->mm, start, nr_pages, + pages, vmas, gup_flags | FOLL_TOUCH); +} +EXPORT_SYMBOL(get_user_pages); + +/** + * get_user_pages_locked() is suitable to replace the form: + * + * mmap_read_lock(mm); + * do_something() + * get_user_pages(mm, ..., pages, NULL); + * mmap_read_unlock(mm); + * + * to: + * + * int locked = 1; + * mmap_read_lock(mm); + * do_something() + * get_user_pages_locked(mm, ..., pages, &locked); + * if (locked) + * mmap_read_unlock(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. + * + * We can leverage the VM_FAULT_RETRY functionality in the page fault + * paths better by using either get_user_pages_locked() or + * get_user_pages_unlocked(). + * + */ +long get_user_pages_locked(unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + int *locked) +{ + /* + * FIXME: Current FOLL_LONGTERM behavior is incompatible with + * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on + * vmas. As there are no users of this flag in this call we simply + * disallow this option for now. + */ + if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM)) + return -EINVAL; + /* + * FOLL_PIN must only be set internally by the pin_user_pages*() APIs, + * never directly by the caller, so enforce that: + */ + if (WARN_ON_ONCE(gup_flags & FOLL_PIN)) + return -EINVAL; + + return __get_user_pages_locked(current->mm, start, nr_pages, + pages, NULL, locked, + gup_flags | FOLL_TOUCH); +} +EXPORT_SYMBOL(get_user_pages_locked); + +/* + * 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) +{ + struct mm_struct *mm = current->mm; + int locked = 1; + long ret; + + /* + * FIXME: Current FOLL_LONGTERM behavior is incompatible with + * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on + * vmas. As there are no users of this flag in this call we simply + * disallow this option for now. + */ + if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM)) + return -EINVAL; + + mmap_read_lock(mm); + ret = __get_user_pages_locked(mm, start, nr_pages, pages, NULL, + &locked, gup_flags | FOLL_TOUCH); + if (locked) + mmap_read_unlock(mm); + return ret; +} +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 +#ifdef CONFIG_GUP_GET_PTE_LOW_HIGH + +/* + * WARNING: only to be used in the get_user_pages_fast() implementation. + * + * With get_user_pages_fast(), we walk down the pagetables without taking any + * locks. For this we would like to load the pointers atomically, but sometimes + * that is not possible (e.g. without expensive cmpxchg8b on x86_32 PAE). What + * we do have is the guarantee that a PTE will only either go from not present + * to present, or present to not present or both -- it will not switch to a + * completely different present page without a TLB flush in between; something + * that we are blocking by holding interrupts off. + * + * Setting ptes from not present to present goes: + * + * ptep->pte_high = h; + * smp_wmb(); + * ptep->pte_low = l; + * + * And present to not present goes: + * + * ptep->pte_low = 0; + * smp_wmb(); + * ptep->pte_high = 0; + * + * We must ensure here that the load of pte_low sees 'l' IFF pte_high sees 'h'. + * We load pte_high *after* loading pte_low, which ensures we don't see an older + * value of pte_high. *Then* we recheck pte_low, which ensures that we haven't + * picked up a changed pte high. We might have gotten rubbish values from + * pte_low and pte_high, but we are guaranteed that pte_low will not have the + * present bit set *unless* it is 'l'. Because get_user_pages_fast() only + * operates on present ptes we're safe. + */ +static inline pte_t gup_get_pte(pte_t *ptep) +{ + pte_t pte; + + do { + pte.pte_low = ptep->pte_low; + smp_rmb(); + pte.pte_high = ptep->pte_high; + smp_rmb(); + } while (unlikely(pte.pte_low != ptep->pte_low)); + + return pte; +} +#else /* CONFIG_GUP_GET_PTE_LOW_HIGH */ +/* + * We require that the PTE can be read atomically. + */ +static inline pte_t gup_get_pte(pte_t *ptep) +{ + return ptep_get(ptep); +} +#endif /* CONFIG_GUP_GET_PTE_LOW_HIGH */ + +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); + do { + pte_t pte = gup_get_pte(ptep); + struct page *head, *page; + + /* + * Similar to the PMD case below, NUMA hinting must take slow + * path using the pte_protnone check. + */ + 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); + + head = try_grab_compound_head(page, 1, flags); + if (!head) + goto pte_unmap; + + if (unlikely(pmd_val(pmd) != pmd_val(*pmdp)) || + unlikely(pte_val(pte) != pte_val(*ptep))) { + put_compound_head(head, 1, flags); + goto pte_unmap; + } + + VM_BUG_ON_PAGE(compound_head(page) != head, page); + + /* + * 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); + goto pte_unmap; + } + } + SetPageReferenced(page); + 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); + return 0; + } + SetPageReferenced(page); + pages[*nr] = page; + if (unlikely(!try_grab_page(page, flags))) { + undo_dev_pagemap(nr, nr_start, flags, pages); + return 0; + } + (*nr)++; + pfn++; + } while (addr += PAGE_SIZE, addr != end); + + if (pgmap) + put_dev_pagemap(pgmap); + return 1; +} + +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; addr += PAGE_SIZE) + pages[nr++] = page++; + + 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 *head, *page; + 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))); + + head = pte_page(pte); + page = head + ((addr & (sz-1)) >> PAGE_SHIFT); + refs = record_subpages(page, addr, end, pages + *nr); + + head = try_grab_compound_head(head, refs, flags); + if (!head) + return 0; + + if (unlikely(pte_val(pte) != pte_val(*ptep))) { + put_compound_head(head, refs, flags); + return 0; + } + + *nr += refs; + SetPageReferenced(head); + 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 *head, *page; + 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 = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); + refs = record_subpages(page, addr, end, pages + *nr); + + head = try_grab_compound_head(pmd_page(orig), refs, flags); + if (!head) + return 0; + + if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) { + put_compound_head(head, refs, flags); + return 0; + } + + *nr += refs; + SetPageReferenced(head); + 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 *head, *page; + 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 = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); + refs = record_subpages(page, addr, end, pages + *nr); + + head = try_grab_compound_head(pud_page(orig), refs, flags); + if (!head) + return 0; + + if (unlikely(pud_val(orig) != pud_val(*pudp))) { + put_compound_head(head, refs, flags); + return 0; + } + + *nr += refs; + SetPageReferenced(head); + 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 *head, *page; + + if (!pgd_access_permitted(orig, flags & FOLL_WRITE)) + return 0; + + BUILD_BUG_ON(pgd_devmap(orig)); + + page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); + refs = record_subpages(page, addr, end, pages + *nr); + + head = try_grab_compound_head(pgd_page(orig), refs, flags); + if (!head) + return 0; + + if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) { + put_compound_head(head, refs, flags); + return 0; + } + + *nr += refs; + SetPageReferenced(head); + 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 = READ_ONCE(*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))) { + /* + * NUMA hinting faults need to be handled in the GUP + * slowpath for accounting purposes and so that they + * can be serialised against THP migration. + */ + 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 int __gup_longterm_unlocked(unsigned long start, int nr_pages, + unsigned int gup_flags, struct page **pages) +{ + int ret; + + /* + * FIXME: FOLL_LONGTERM does not work with + * get_user_pages_unlocked() (see comments in that function) + */ + if (gup_flags & FOLL_LONGTERM) { + mmap_read_lock(current->mm); + ret = __gup_longterm_locked(current->mm, + start, nr_pages, + pages, NULL, gup_flags); + mmap_read_unlock(current->mm); + } else { + ret = get_user_pages_unlocked(start, nr_pages, + pages, gup_flags); + } + + return ret; +} + +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(pages, nr_pinned); + return 0; + } + } + 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 ret; + + if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM | + FOLL_FORCE | FOLL_PIN | FOLL_GET | + FOLL_FAST_ONLY))) + return -EINVAL; + + if (gup_flags & FOLL_PIN) + atomic_set(¤t->mm->has_pinned, 1); + + 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 0; + 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_unlocked(start, nr_pages - nr_pinned, gup_flags, + pages); + 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. + * Note a difference with get_user_pages_fast: this always returns the + * number of pages pinned, 0 if no pages were pinned. + * + * 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) +{ + int nr_pinned; + /* + * 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. + */ + gup_flags |= FOLL_GET | FOLL_FAST_ONLY; + + nr_pinned = internal_get_user_pages_fast(start, nr_pages, gup_flags, + pages); + + /* + * As specified in the API description above, this routine is not + * allowed to return negative values. However, the common core + * routine internal_get_user_pages_fast() *can* return -errno. + * Therefore, correct for that here: + */ + if (nr_pinned < 0) + nr_pinned = 0; + + return nr_pinned; +} +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) +{ + if (!is_valid_gup_flags(gup_flags)) + return -EINVAL; + + /* + * 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. + */ + gup_flags |= FOLL_GET; + 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. + */ +int pin_user_pages_fast(unsigned long start, int nr_pages, + unsigned int gup_flags, struct page **pages) +{ + /* FOLL_GET and FOLL_PIN are mutually exclusive. */ + if (WARN_ON_ONCE(gup_flags & FOLL_GET)) + return -EINVAL; + + gup_flags |= FOLL_PIN; + return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages); +} +EXPORT_SYMBOL_GPL(pin_user_pages_fast); + +/* + * This is the FOLL_PIN equivalent of get_user_pages_fast_only(). Behavior + * is the same, except that this one sets FOLL_PIN instead of FOLL_GET. + * + * The API rules are the same, too: no negative values may be returned. + */ +int pin_user_pages_fast_only(unsigned long start, int nr_pages, + unsigned int gup_flags, struct page **pages) +{ + int nr_pinned; + + /* + * FOLL_GET and FOLL_PIN are mutually exclusive. Note that the API + * rules require returning 0, rather than -errno: + */ + if (WARN_ON_ONCE(gup_flags & FOLL_GET)) + return 0; + /* + * FOLL_FAST_ONLY is required in order to match the API description of + * this routine: no fall back to regular ("slow") GUP. + */ + gup_flags |= (FOLL_PIN | FOLL_FAST_ONLY); + nr_pinned = internal_get_user_pages_fast(start, nr_pages, gup_flags, + pages); + /* + * This routine is not allowed to return negative values. However, + * internal_get_user_pages_fast() *can* return -errno. Therefore, + * correct for that here: + */ + if (nr_pinned < 0) + nr_pinned = 0; + + return nr_pinned; +} +EXPORT_SYMBOL_GPL(pin_user_pages_fast_only); + +/** + * 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. Or NULL, if caller + * only intends to ensure the pages are faulted in. + * @vmas: array of pointers to vmas corresponding to each page. + * Or NULL if the caller does not require them. + * @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. + */ +long pin_user_pages_remote(struct mm_struct *mm, + unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + struct vm_area_struct **vmas, int *locked) +{ + /* FOLL_GET and FOLL_PIN are mutually exclusive. */ + if (WARN_ON_ONCE(gup_flags & FOLL_GET)) + return -EINVAL; + + gup_flags |= FOLL_PIN; + return __get_user_pages_remote(mm, start, nr_pages, gup_flags, + pages, vmas, locked); +} +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. Or NULL, if caller + * only intends to ensure the pages are faulted in. + * @vmas: array of pointers to vmas corresponding to each page. + * Or NULL if the caller does not require them. + * + * 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. + */ +long pin_user_pages(unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + struct vm_area_struct **vmas) +{ + /* FOLL_GET and FOLL_PIN are mutually exclusive. */ + if (WARN_ON_ONCE(gup_flags & FOLL_GET)) + return -EINVAL; + + gup_flags |= FOLL_PIN; + return __gup_longterm_locked(current->mm, start, nr_pages, + pages, vmas, 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. + */ +long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages, + struct page **pages, unsigned int gup_flags) +{ + /* FOLL_GET and FOLL_PIN are mutually exclusive. */ + if (WARN_ON_ONCE(gup_flags & FOLL_GET)) + return -EINVAL; + + gup_flags |= FOLL_PIN; + return get_user_pages_unlocked(start, nr_pages, pages, gup_flags); +} +EXPORT_SYMBOL(pin_user_pages_unlocked); + +/* + * pin_user_pages_locked() is the FOLL_PIN variant of get_user_pages_locked(). + * Behavior is the same, except that this one sets FOLL_PIN and rejects + * FOLL_GET. + */ +long pin_user_pages_locked(unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + int *locked) +{ + /* + * FIXME: Current FOLL_LONGTERM behavior is incompatible with + * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on + * vmas. As there are no users of this flag in this call we simply + * disallow this option for now. + */ + if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM)) + return -EINVAL; + + /* FOLL_GET and FOLL_PIN are mutually exclusive. */ + if (WARN_ON_ONCE(gup_flags & FOLL_GET)) + return -EINVAL; + + gup_flags |= FOLL_PIN; + return __get_user_pages_locked(current->mm, start, nr_pages, + pages, NULL, locked, + gup_flags | FOLL_TOUCH); +} +EXPORT_SYMBOL(pin_user_pages_locked); |