| // 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 <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. |
| * |
| * Even though the name includes "compound_head", this function is still |
| * appropriate for callers that have a non-compound @page to get. |
| * |
| * @page: pointer to page to be grabbed |
| * @refs: the value to (effectively) add to the page'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 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 @refs. |
| * |
| * FOLL_PIN on compound pages that are > two pages long: page's refcount will |
| * be incremented by @refs, and page[2].hpage_pinned_refcount will be |
| * incremented by @refs * GUP_PIN_COUNTING_BIAS. |
| * |
| * FOLL_PIN on normal pages, or compound pages that are two pages long: |
| * page's refcount will be incremented by @refs * 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. |
| */ |
| __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) { |
| /* |
| * 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) && |
| !is_pinnable_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. |
| * That's why the refcount from the earlier |
| * try_get_compound_head() is left intact. |
| */ |
| 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, |
| 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: please see the try_grab_compound_head() documentation, with |
| * "refs=1". |
| * |
| * 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); |
| |
| static inline void compound_range_next(unsigned long i, unsigned long npages, |
| struct page **list, struct page **head, |
| unsigned int *ntails) |
| { |
| struct page *next, *page; |
| unsigned int nr = 1; |
| |
| if (i >= npages) |
| return; |
| |
| next = *list + i; |
| page = compound_head(next); |
| if (PageCompound(page) && compound_order(page) >= 1) |
| nr = min_t(unsigned int, |
| page + compound_nr(page) - next, npages - i); |
| |
| *head = page; |
| *ntails = nr; |
| } |
| |
| #define for_each_compound_range(__i, __list, __npages, __head, __ntails) \ |
| for (__i = 0, \ |
| compound_range_next(__i, __npages, __list, &(__head), &(__ntails)); \ |
| __i < __npages; __i += __ntails, \ |
| compound_range_next(__i, __npages, __list, &(__head), &(__ntails))) |
| |
| static inline void compound_next(unsigned long i, unsigned long npages, |
| struct page **list, struct page **head, |
| unsigned int *ntails) |
| { |
| struct page *page; |
| unsigned int nr; |
| |
| if (i >= npages) |
| return; |
| |
| page = compound_head(list[i]); |
| for (nr = i + 1; nr < npages; nr++) { |
| if (compound_head(list[nr]) != page) |
| break; |
| } |
| |
| *head = page; |
| *ntails = nr - i; |
| } |
| |
| #define for_each_compound_head(__i, __list, __npages, __head, __ntails) \ |
| for (__i = 0, \ |
| compound_next(__i, __npages, __list, &(__head), &(__ntails)); \ |
| __i < __npages; __i += __ntails, \ |
| compound_next(__i, __npages, __list, &(__head), &(__ntails))) |
| |
| /** |
| * 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; |
| struct page *head; |
| unsigned int ntails; |
| |
| if (!make_dirty) { |
| unpin_user_pages(pages, npages); |
| return; |
| } |
| |
| for_each_compound_head(index, pages, npages, head, ntails) { |
| /* |
| * 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(head)) |
| set_page_dirty_lock(head); |
| put_compound_head(head, ntails, 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 index; |
| struct page *head; |
| unsigned int ntails; |
| |
| for_each_compound_range(index, &page, npages, head, ntails) { |
| if (make_dirty && !PageDirty(head)) |
| set_page_dirty_lock(head); |
| put_compound_head(head, ntails, FOLL_PIN); |
| } |
| } |
| EXPORT_SYMBOL(unpin_user_page_range_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; |
| struct page *head; |
| unsigned int ntails; |
| |
| /* |
| * 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; |
| |
| for_each_compound_head(index, pages, npages, head, ntails) |
| put_compound_head(head, ntails, 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) |
| { |
| /* No page to get reference */ |
| if (flags & (FOLL_GET | FOLL_PIN)) |
| 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); |
| 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; |
| } |
| } |
| |
| /* 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(mm, address, pmd, 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_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 { |
| 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; |
| |
| if (vma_is_secretmem(vma)) |
| return NULL; |
| |
| 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_NOFAULT) |
| return -EFAULT; |
| 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 ((gup_flags & FOLL_LONGTERM) && vma_is_fsdax(vma)) |
| return -EOPNOTSUPP; |
| |
| if (vma_is_secretmem(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) { |
| ret = -EFAULT; |
| goto out; |
| } |
| ret = check_vma_flags(vma, gup_flags); |
| if (ret) |
| 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); |
| 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; |
| |
| 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); |
| 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) |
| 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; |
| 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(!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); |
| |
| 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); |
| } |
| |
| /* |
| * 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 @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 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; |
| |
| 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_POPULATE: Always populate memory with VM_LOCKONFAULT. |
| * !FOLL_FORCE: Require proper access permissions. |
| */ |
| gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK | FOLL_HWPOISON; |
| 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; |
| |
| 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; |
| long 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 */ |
| |
| /** |
| * 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 (!PAGE_ALIGNED(uaddr)) { |
| if (unlikely(__put_user(0, uaddr) != 0)) |
| return size; |
| 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) { |
| if (unlikely(__put_user(0, uaddr) != 0)) |
| goto out; |
| uaddr += PAGE_SIZE; |
| } |
| |
| out: |
| if (size > uaddr - start) |
| return size - (uaddr - start); |
| return 0; |
| } |
| EXPORT_SYMBOL(fault_in_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 (!PAGE_ALIGNED(uaddr)) { |
| if (unlikely(__get_user(c, uaddr) != 0)) |
| return size; |
| 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) { |
| if (unlikely(__get_user(c, uaddr) != 0)) |
| goto out; |
| uaddr += PAGE_SIZE; |
| } |
| |
| out: |
| (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 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 */ |
| |
| #ifdef CONFIG_MIGRATION |
| /* |
| * Check whether all pages are pinnable, if so return number of pages. If some |
| * pages are not pinnable, migrate them, and unpin all pages. Return zero if |
| * pages were migrated, or if some pages were not successfully isolated. |
| * Return negative error if migration fails. |
| */ |
| static long check_and_migrate_movable_pages(unsigned long nr_pages, |
| struct page **pages, |
| unsigned int gup_flags) |
| { |
| unsigned long i; |
| unsigned long isolation_error_count = 0; |
| bool drain_allow = true; |
| LIST_HEAD(movable_page_list); |
| long ret = 0; |
| struct page *prev_head = NULL; |
| struct page *head; |
| struct migration_target_control mtc = { |
| .nid = NUMA_NO_NODE, |
| .gfp_mask = GFP_USER | __GFP_NOWARN, |
| }; |
| |
| for (i = 0; i < nr_pages; i++) { |
| head = compound_head(pages[i]); |
| if (head == prev_head) |
| continue; |
| prev_head = head; |
| /* |
| * If we get a movable page, since we are going to be pinning |
| * these entries, try to move them out if possible. |
| */ |
| if (!is_pinnable_page(head)) { |
| if (PageHuge(head)) { |
| if (!isolate_huge_page(head, &movable_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, &movable_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(&movable_page_list) && !isolation_error_count) |
| return nr_pages; |
| |
| if (gup_flags & FOLL_PIN) { |
| unpin_user_pages(pages, nr_pages); |
| } else { |
| for (i = 0; i < nr_pages; i++) |
| put_page(pages[i]); |
| } |
| if (!list_empty(&movable_page_list)) { |
| ret = migrate_pages(&movable_page_list, alloc_migration_target, |
| NULL, (unsigned long)&mtc, MIGRATE_SYNC, |
| MR_LONGTERM_PIN, NULL); |
| if (ret && !list_empty(&movable_page_list)) |
| putback_movable_pages(&movable_page_list); |
| } |
| |
| return ret > 0 ? -ENOMEM : ret; |
| } |
| #else |
| static long check_and_migrate_movable_pages(unsigned long nr_pages, |
| struct page **pages, |
| unsigned int gup_flags) |
| { |
| return nr_pages; |
| } |
| #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, |
| struct vm_area_struct **vmas, |
| unsigned int gup_flags) |
| { |
| unsigned int flags; |
| long rc; |
| |
| if (!(gup_flags & FOLL_LONGTERM)) |
| return __get_user_pages_locked(mm, start, nr_pages, pages, vmas, |
| NULL, gup_flags); |
| flags = memalloc_pin_save(); |
| do { |
| rc = __get_user_pages_locked(mm, start, nr_pages, pages, vmas, |
| NULL, gup_flags); |
| if (rc <= 0) |
| break; |
| rc = check_and_migrate_movable_pages(rc, pages, gup_flags); |
| } while (!rc); |
| memalloc_pin_restore(flags); |
| |
| return rc; |
| } |
| |
| 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() - variant of get_user_pages() |
| * |
| * @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. |
| * |
| * It 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); |
| * |
| * 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 |
| |
| 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 = ptep_get_lockless(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(page_is_secretmem(page))) { |
| put_compound_head(head, 1, flags); |
| 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; |
| int ret = 1; |
| |
| 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); |
| ret = 0; |
| break; |
| } |
| SetPageReferenced(page); |
| pages[*nr] = page; |
| if (unlikely(!try_grab_page(page, flags))) { |
| undo_dev_pagemap(nr, nr_start, flags, pages); |
| ret = 0; |
| break; |
| } |
| (*nr)++; |
| pfn++; |
| } while (addr += PAGE_SIZE, addr != end); |
| |
| put_dev_pagemap(pgmap); |
| return ret; |
| } |
| |
| 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))) { |
| 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 | FOLL_NOFAULT))) |
| 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 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); |