| #include <linux/kernel.h> |
| #include <linux/errno.h> |
| #include <linux/err.h> |
| #include <linux/spinlock.h> |
| |
| #include <linux/mm.h> |
| #include <linux/memremap.h> |
| #include <linux/pagemap.h> |
| #include <linux/rmap.h> |
| #include <linux/swap.h> |
| #include <linux/swapops.h> |
| |
| #include <linux/sched/signal.h> |
| #include <linux/rwsem.h> |
| #include <linux/hugetlb.h> |
| |
| #include <asm/mmu_context.h> |
| #include <asm/pgtable.h> |
| #include <asm/tlbflush.h> |
| |
| #include "internal.h" |
| |
| struct follow_page_context { |
| struct dev_pagemap *pgmap; |
| unsigned int page_mask; |
| }; |
| |
| 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->vm_ops || !vma->vm_ops->fault)) |
| return ERR_PTR(-EFAULT); |
| return NULL; |
| } |
| |
| static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address, |
| pte_t *pte, unsigned int flags) |
| { |
| /* No page to get reference */ |
| if (flags & FOLL_GET) |
| return -EFAULT; |
| |
| if (flags & FOLL_TOUCH) { |
| pte_t entry = *pte; |
| |
| if (flags & FOLL_WRITE) |
| entry = pte_mkdirty(entry); |
| entry = pte_mkyoung(entry); |
| |
| if (!pte_same(*pte, entry)) { |
| set_pte_at(vma->vm_mm, address, pte, entry); |
| update_mmu_cache(vma, address, pte); |
| } |
| } |
| |
| /* Proper page table entry exists, but no corresponding struct page */ |
| return -EEXIST; |
| } |
| |
| /* |
| * FOLL_FORCE can write to even unwritable pte's, but only |
| * after we've gone through a COW cycle and they are dirty. |
| */ |
| static inline bool can_follow_write_pte(pte_t pte, unsigned int flags) |
| { |
| return pte_write(pte) || |
| ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte)); |
| } |
| |
| static struct page *follow_page_pte(struct vm_area_struct *vma, |
| unsigned long address, pmd_t *pmd, unsigned int flags, |
| struct dev_pagemap **pgmap) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| struct page *page; |
| spinlock_t *ptl; |
| pte_t *ptep, pte; |
| |
| 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)) { |
| /* |
| * Only return device mapping pages in the FOLL_GET 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 { |
| int ret; |
| |
| ret = follow_pfn_pte(vma, address, ptep, flags); |
| page = ERR_PTR(ret); |
| goto out; |
| } |
| } |
| |
| if (flags & FOLL_SPLIT && PageTransCompound(page)) { |
| int ret; |
| get_page(page); |
| pte_unmap_unlock(ptep, ptl); |
| lock_page(page); |
| ret = split_huge_page(page); |
| unlock_page(page); |
| put_page(page); |
| if (ret) |
| return ERR_PTR(ret); |
| goto retry; |
| } |
| |
| if (flags & FOLL_GET) |
| get_page(page); |
| 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) && vma->vm_flags & VM_HUGETLB) { |
| 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_sem 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) { |
| 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 { |
| get_page(page); |
| spin_unlock(ptl); |
| lock_page(page); |
| ret = split_huge_page(page); |
| unlock_page(page); |
| put_page(page); |
| if (pmd_none(*pmd)) |
| return no_page_table(vma, flags); |
| } |
| |
| 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) && vma->vm_flags & VM_HUGETLB) { |
| 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()). |
| */ |
| 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)) { |
| BUG_ON(flags & FOLL_GET); |
| return page; |
| } |
| |
| pgd = pgd_offset(mm, address); |
| |
| if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd))) |
| return no_page_table(vma, flags); |
| |
| if (pgd_huge(*pgd)) { |
| page = follow_huge_pgd(mm, address, pgd, flags); |
| if (page) |
| return page; |
| return no_page_table(vma, flags); |
| } |
| if (is_hugepd(__hugepd(pgd_val(*pgd)))) { |
| page = follow_huge_pd(vma, address, |
| __hugepd(pgd_val(*pgd)), flags, |
| PGDIR_SHIFT); |
| if (page) |
| return page; |
| return no_page_table(vma, flags); |
| } |
| |
| return follow_p4d_mask(vma, address, pgd, flags, ctx); |
| } |
| |
| struct page *follow_page(struct vm_area_struct *vma, unsigned long address, |
| unsigned int foll_flags) |
| { |
| struct follow_page_context ctx = { NULL }; |
| struct page *page; |
| |
| page = follow_page_mask(vma, address, foll_flags, &ctx); |
| if (ctx.pgmap) |
| put_dev_pagemap(ctx.pgmap); |
| return page; |
| } |
| |
| static int get_gate_page(struct mm_struct *mm, unsigned long address, |
| unsigned int gup_flags, struct vm_area_struct **vma, |
| struct page **page) |
| { |
| pgd_t *pgd; |
| p4d_t *p4d; |
| pud_t *pud; |
| pmd_t *pmd; |
| pte_t *pte; |
| int ret = -EFAULT; |
| |
| /* user gate pages are read-only */ |
| if (gup_flags & FOLL_WRITE) |
| return -EFAULT; |
| if (address > TASK_SIZE) |
| pgd = pgd_offset_k(address); |
| else |
| pgd = pgd_offset_gate(mm, address); |
| BUG_ON(pgd_none(*pgd)); |
| p4d = p4d_offset(pgd, address); |
| BUG_ON(p4d_none(*p4d)); |
| pud = pud_offset(p4d, address); |
| BUG_ON(pud_none(*pud)); |
| 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); |
| |
| /* |
| * This should never happen (a device public page in the gate |
| * area). |
| */ |
| if (is_device_public_page(*page)) |
| goto unmap; |
| } |
| get_page(*page); |
| out: |
| ret = 0; |
| unmap: |
| pte_unmap(pte); |
| return ret; |
| } |
| |
| /* |
| * mmap_sem must be held on entry. If @nonblocking != NULL and |
| * *@flags does not include FOLL_NOWAIT, the mmap_sem may be released. |
| * If it is, *@nonblocking will be set to 0 and -EBUSY returned. |
| */ |
| static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma, |
| unsigned long address, unsigned int *flags, int *nonblocking) |
| { |
| unsigned int fault_flags = 0; |
| vm_fault_t ret; |
| |
| /* mlock all present pages, but do not fault in new pages */ |
| if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK) |
| return -ENOENT; |
| if (*flags & FOLL_WRITE) |
| fault_flags |= FAULT_FLAG_WRITE; |
| if (*flags & FOLL_REMOTE) |
| fault_flags |= FAULT_FLAG_REMOTE; |
| if (nonblocking) |
| fault_flags |= FAULT_FLAG_ALLOW_RETRY; |
| if (*flags & FOLL_NOWAIT) |
| fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT; |
| if (*flags & FOLL_TRIED) { |
| VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY); |
| fault_flags |= FAULT_FLAG_TRIED; |
| } |
| |
| ret = handle_mm_fault(vma, address, fault_flags); |
| if (ret & VM_FAULT_ERROR) { |
| int err = vm_fault_to_errno(ret, *flags); |
| |
| if (err) |
| return err; |
| BUG(); |
| } |
| |
| if (tsk) { |
| if (ret & VM_FAULT_MAJOR) |
| tsk->maj_flt++; |
| else |
| tsk->min_flt++; |
| } |
| |
| if (ret & VM_FAULT_RETRY) { |
| if (nonblocking && !(fault_flags & FAULT_FLAG_RETRY_NOWAIT)) |
| *nonblocking = 0; |
| return -EBUSY; |
| } |
| |
| /* |
| * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when |
| * necessary, even if maybe_mkwrite decided not to set pte_write. We |
| * can thus safely do subsequent page lookups as if they were reads. |
| * But only do so when looping for pte_write is futile: in some cases |
| * userspace may also be wanting to write to the gotten user page, |
| * which a read fault here might prevent (a readonly page might get |
| * reCOWed by userspace write). |
| */ |
| if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE)) |
| *flags |= FOLL_COW; |
| return 0; |
| } |
| |
| static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) |
| { |
| vm_flags_t vm_flags = vma->vm_flags; |
| int write = (gup_flags & FOLL_WRITE); |
| int foreign = (gup_flags & FOLL_REMOTE); |
| |
| if (vm_flags & (VM_IO | VM_PFNMAP)) |
| return -EFAULT; |
| |
| if (gup_flags & FOLL_ANON && !vma_is_anonymous(vma)) |
| return -EFAULT; |
| |
| if (write) { |
| if (!(vm_flags & VM_WRITE)) { |
| if (!(gup_flags & FOLL_FORCE)) |
| return -EFAULT; |
| /* |
| * We used to let the write,force case do COW in a |
| * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could |
| * set a breakpoint in a read-only mapping of an |
| * executable, without corrupting the file (yet only |
| * when that file had been opened for writing!). |
| * Anon pages in shared mappings are surprising: now |
| * just reject it. |
| */ |
| if (!is_cow_mapping(vm_flags)) |
| return -EFAULT; |
| } |
| } else if (!(vm_flags & VM_READ)) { |
| if (!(gup_flags & FOLL_FORCE)) |
| return -EFAULT; |
| /* |
| * Is there actually any vma we can reach here which does not |
| * have VM_MAYREAD set? |
| */ |
| if (!(vm_flags & VM_MAYREAD)) |
| return -EFAULT; |
| } |
| /* |
| * gups are always data accesses, not instruction |
| * fetches, so execute=false here |
| */ |
| if (!arch_vma_access_permitted(vma, write, false, foreign)) |
| return -EFAULT; |
| return 0; |
| } |
| |
| /** |
| * __get_user_pages() - pin user pages in memory |
| * @tsk: task_struct of target task |
| * @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. |
| * @nonblocking: whether waiting for disk IO or mmap_sem contention |
| * |
| * 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. Each page returned must be released |
| * with a put_page() call when it is finished with. vmas will only |
| * remain valid while mmap_sem is held. |
| * |
| * Must be called with mmap_sem 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 @nonblocking != NULL, __get_user_pages will not wait for disk IO |
| * or mmap_sem contention, and if waiting is needed to pin all pages, |
| * *@nonblocking will be set to 0. Further, if @gup_flags does not |
| * include FOLL_NOWAIT, the mmap_sem will be released via up_read() in |
| * this case. |
| * |
| * A caller using such a combination of @nonblocking and @gup_flags |
| * must therefore hold the mmap_sem 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 task_struct *tsk, struct mm_struct *mm, |
| unsigned long start, unsigned long nr_pages, |
| unsigned int gup_flags, struct page **pages, |
| struct vm_area_struct **vmas, int *nonblocking) |
| { |
| long ret = 0, i = 0; |
| struct vm_area_struct *vma = NULL; |
| struct follow_page_context ctx = { NULL }; |
| |
| if (!nr_pages) |
| return 0; |
| |
| VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET)); |
| |
| /* |
| * If FOLL_FORCE is set then do not force a full fault as the hinting |
| * fault information is unrelated to the reference behaviour of a task |
| * using the address space |
| */ |
| if (!(gup_flags & FOLL_FORCE)) |
| gup_flags |= FOLL_NUMA; |
| |
| do { |
| struct page *page; |
| unsigned int foll_flags = gup_flags; |
| unsigned int page_increm; |
| |
| /* first iteration or cross vma bound */ |
| if (!vma || start >= vma->vm_end) { |
| vma = find_extend_vma(mm, start); |
| if (!vma && in_gate_area(mm, start)) { |
| ret = get_gate_page(mm, start & PAGE_MASK, |
| gup_flags, &vma, |
| pages ? &pages[i] : NULL); |
| if (ret) |
| goto out; |
| ctx.page_mask = 0; |
| goto next_page; |
| } |
| |
| if (!vma || check_vma_flags(vma, gup_flags)) { |
| ret = -EFAULT; |
| goto out; |
| } |
| if (is_vm_hugetlb_page(vma)) { |
| i = follow_hugetlb_page(mm, vma, pages, vmas, |
| &start, &nr_pages, i, |
| gup_flags, nonblocking); |
| continue; |
| } |
| } |
| retry: |
| /* |
| * If we have a pending SIGKILL, don't keep faulting pages and |
| * potentially allocating memory. |
| */ |
| if (unlikely(fatal_signal_pending(current))) { |
| ret = -ERESTARTSYS; |
| goto out; |
| } |
| cond_resched(); |
| |
| page = follow_page_mask(vma, start, foll_flags, &ctx); |
| if (!page) { |
| ret = faultin_page(tsk, vma, start, &foll_flags, |
| nonblocking); |
| switch (ret) { |
| case 0: |
| goto retry; |
| case -EBUSY: |
| ret = 0; |
| /* FALLTHRU */ |
| 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 |
| * @tsk: the task_struct to use for page fault accounting, or |
| * NULL if faults are not to be recorded. |
| * @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_sem while retrying, maybe NULL if caller |
| * does not 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_sem. So it has not the |
| * same semantics wrt the @mm->mmap_sem as does filemap_fault(). |
| */ |
| int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm, |
| unsigned long address, unsigned int fault_flags, |
| bool *unlocked) |
| { |
| struct vm_area_struct *vma; |
| vm_fault_t ret, major = 0; |
| |
| if (unlocked) |
| fault_flags |= FAULT_FLAG_ALLOW_RETRY; |
| |
| retry: |
| vma = find_extend_vma(mm, address); |
| if (!vma || address < vma->vm_start) |
| return -EFAULT; |
| |
| if (!vma_permits_fault(vma, fault_flags)) |
| return -EFAULT; |
| |
| ret = handle_mm_fault(vma, address, fault_flags); |
| major |= ret & VM_FAULT_MAJOR; |
| if (ret & VM_FAULT_ERROR) { |
| int err = vm_fault_to_errno(ret, 0); |
| |
| if (err) |
| return err; |
| BUG(); |
| } |
| |
| if (ret & VM_FAULT_RETRY) { |
| down_read(&mm->mmap_sem); |
| if (!(fault_flags & FAULT_FLAG_TRIED)) { |
| *unlocked = true; |
| fault_flags &= ~FAULT_FLAG_ALLOW_RETRY; |
| fault_flags |= FAULT_FLAG_TRIED; |
| goto retry; |
| } |
| } |
| |
| if (tsk) { |
| if (major) |
| tsk->maj_flt++; |
| else |
| tsk->min_flt++; |
| } |
| return 0; |
| } |
| EXPORT_SYMBOL_GPL(fixup_user_fault); |
| |
| static __always_inline long __get_user_pages_locked(struct task_struct *tsk, |
| 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 (pages) |
| flags |= FOLL_GET; |
| |
| pages_done = 0; |
| lock_dropped = false; |
| for (;;) { |
| ret = __get_user_pages(tsk, 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 (!pages) |
| /* If it's a prefault don't insist harder */ |
| return ret; |
| |
| 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 */ |
| pages += ret; |
| start += ret << PAGE_SHIFT; |
| |
| /* |
| * Repeat on the address that fired VM_FAULT_RETRY |
| * without FAULT_FLAG_ALLOW_RETRY but with |
| * FAULT_FLAG_TRIED. |
| */ |
| *locked = 1; |
| lock_dropped = true; |
| down_read(&mm->mmap_sem); |
| ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED, |
| pages, NULL, NULL); |
| if (ret != 1) { |
| BUG_ON(ret > 1); |
| if (!pages_done) |
| pages_done = ret; |
| break; |
| } |
| nr_pages--; |
| pages_done++; |
| if (!nr_pages) |
| break; |
| 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. |
| */ |
| up_read(&mm->mmap_sem); |
| *locked = 0; |
| } |
| return pages_done; |
| } |
| |
| /* |
| * 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(). |
| * |
| * get_user_pages_locked() is suitable to replace the form: |
| * |
| * down_read(&mm->mmap_sem); |
| * do_something() |
| * get_user_pages(tsk, mm, ..., pages, NULL); |
| * up_read(&mm->mmap_sem); |
| * |
| * to: |
| * |
| * int locked = 1; |
| * down_read(&mm->mmap_sem); |
| * do_something() |
| * get_user_pages_locked(tsk, mm, ..., pages, &locked); |
| * if (locked) |
| * up_read(&mm->mmap_sem); |
| */ |
| long get_user_pages_locked(unsigned long start, unsigned long nr_pages, |
| unsigned int gup_flags, struct page **pages, |
| int *locked) |
| { |
| return __get_user_pages_locked(current, 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: |
| * |
| * down_read(&mm->mmap_sem); |
| * get_user_pages(tsk, mm, ..., pages, NULL); |
| * up_read(&mm->mmap_sem); |
| * |
| * with: |
| * |
| * get_user_pages_unlocked(tsk, 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; |
| |
| down_read(&mm->mmap_sem); |
| ret = __get_user_pages_locked(current, mm, start, nr_pages, pages, NULL, |
| &locked, gup_flags | FOLL_TOUCH); |
| if (locked) |
| up_read(&mm->mmap_sem); |
| return ret; |
| } |
| EXPORT_SYMBOL(get_user_pages_unlocked); |
| |
| /* |
| * get_user_pages_remote() - pin user pages in memory |
| * @tsk: the task_struct to use for page fault accounting, or |
| * NULL if faults are not to be recorded. |
| * @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 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. Each page returned must be released |
| * with a put_page() call when it is finished with. vmas will only |
| * remain valid while mmap_sem is held. |
| * |
| * Must be called with mmap_sem held for read or write. |
| * |
| * 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. |
| * |
| * get_user_pages 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 should be phased out in favor of |
| * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing |
| * should use get_user_pages because it cannot pass |
| * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault. |
| */ |
| long get_user_pages_remote(struct task_struct *tsk, 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 __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas, |
| locked, |
| gup_flags | FOLL_TOUCH | FOLL_REMOTE); |
| } |
| EXPORT_SYMBOL(get_user_pages_remote); |
| |
| /* |
| * This is the same as get_user_pages_remote(), just with a |
| * less-flexible calling convention where we assume that the task |
| * and mm being operated on are the current task's and don'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) |
| { |
| return __get_user_pages_locked(current, current->mm, start, nr_pages, |
| pages, vmas, NULL, |
| gup_flags | FOLL_TOUCH); |
| } |
| EXPORT_SYMBOL(get_user_pages); |
| |
| #ifdef CONFIG_FS_DAX |
| /* |
| * This is the same as get_user_pages() in that it assumes we are |
| * operating on the current task's mm, but it goes further to validate |
| * that the vmas associated with the address range are suitable for |
| * longterm elevated page reference counts. For example, filesystem-dax |
| * mappings are subject to the lifetime enforced by the filesystem and |
| * we need guarantees that longterm users like RDMA and V4L2 only |
| * establish mappings that have a kernel enforced revocation mechanism. |
| * |
| * "longterm" == userspace controlled elevated page count lifetime. |
| * Contrast this to iov_iter_get_pages() usages which are transient. |
| */ |
| long get_user_pages_longterm(unsigned long start, unsigned long nr_pages, |
| unsigned int gup_flags, struct page **pages, |
| struct vm_area_struct **vmas_arg) |
| { |
| struct vm_area_struct **vmas = vmas_arg; |
| struct vm_area_struct *vma_prev = NULL; |
| long rc, i; |
| |
| if (!pages) |
| return -EINVAL; |
| |
| if (!vmas) { |
| vmas = kcalloc(nr_pages, sizeof(struct vm_area_struct *), |
| GFP_KERNEL); |
| if (!vmas) |
| return -ENOMEM; |
| } |
| |
| rc = get_user_pages(start, nr_pages, gup_flags, pages, vmas); |
| |
| for (i = 0; i < rc; i++) { |
| struct vm_area_struct *vma = vmas[i]; |
| |
| if (vma == vma_prev) |
| continue; |
| |
| vma_prev = vma; |
| |
| if (vma_is_fsdax(vma)) |
| break; |
| } |
| |
| /* |
| * Either get_user_pages() failed, or the vma validation |
| * succeeded, in either case we don't need to put_page() before |
| * returning. |
| */ |
| if (i >= rc) |
| goto out; |
| |
| for (i = 0; i < rc; i++) |
| put_page(pages[i]); |
| rc = -EOPNOTSUPP; |
| out: |
| if (vmas != vmas_arg) |
| kfree(vmas); |
| return rc; |
| } |
| EXPORT_SYMBOL(get_user_pages_longterm); |
| #endif /* CONFIG_FS_DAX */ |
| |
| /** |
| * populate_vma_page_range() - populate a range of pages in the vma. |
| * @vma: target vma |
| * @start: start address |
| * @end: end address |
| * @nonblocking: |
| * |
| * This takes care of mlocking the pages too if VM_LOCKED is set. |
| * |
| * return 0 on success, negative error code on error. |
| * |
| * vma->vm_mm->mmap_sem must be held. |
| * |
| * If @nonblocking is NULL, it may be held for read or write and will |
| * be unperturbed. |
| * |
| * If @nonblocking is non-NULL, it must held for read only and may be |
| * released. If it's released, *@nonblocking will be set to 0. |
| */ |
| long populate_vma_page_range(struct vm_area_struct *vma, |
| unsigned long start, unsigned long end, int *nonblocking) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| unsigned long nr_pages = (end - start) / PAGE_SIZE; |
| int gup_flags; |
| |
| VM_BUG_ON(start & ~PAGE_MASK); |
| VM_BUG_ON(end & ~PAGE_MASK); |
| VM_BUG_ON_VMA(start < vma->vm_start, vma); |
| VM_BUG_ON_VMA(end > vma->vm_end, vma); |
| VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), 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->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) |
| 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(current, mm, start, nr_pages, gup_flags, |
| NULL, NULL, nonblocking); |
| } |
| |
| /* |
| * __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_sem 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; |
| down_read(&mm->mmap_sem); |
| 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) |
| up_read(&mm->mmap_sem); |
| return ret; /* 0 or negative error code */ |
| } |
| |
| /** |
| * get_dump_page() - pin user page in memory while writing it to core dump |
| * @addr: user address |
| * |
| * Returns struct page pointer of user page pinned for dump, |
| * to be freed afterwards by put_page(). |
| * |
| * Returns NULL on any kind of failure - a hole must then be inserted into |
| * the corefile, to preserve alignment with its headers; and also returns |
| * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found - |
| * allowing a hole to be left in the corefile to save diskspace. |
| * |
| * Called without mmap_sem, but after all other threads have been killed. |
| */ |
| #ifdef CONFIG_ELF_CORE |
| struct page *get_dump_page(unsigned long addr) |
| { |
| struct vm_area_struct *vma; |
| struct page *page; |
| |
| if (__get_user_pages(current, current->mm, addr, 1, |
| FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma, |
| NULL) < 1) |
| return NULL; |
| flush_cache_page(vma, addr, page_to_pfn(page)); |
| return page; |
| } |
| #endif /* CONFIG_ELF_CORE */ |
| |
| /* |
| * Generic 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 HAVE_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_GENERIC_GUP |
| |
| #ifndef gup_get_pte |
| /* |
| * We assume that the PTE can be read atomically. If this is not the case for |
| * your architecture, please provide the helper. |
| */ |
| static inline pte_t gup_get_pte(pte_t *ptep) |
| { |
| return READ_ONCE(*ptep); |
| } |
| #endif |
| |
| static void undo_dev_pagemap(int *nr, int nr_start, struct page **pages) |
| { |
| while ((*nr) - nr_start) { |
| struct page *page = pages[--(*nr)]; |
| |
| ClearPageReferenced(page); |
| put_page(page); |
| } |
| } |
| |
| #ifdef CONFIG_ARCH_HAS_PTE_SPECIAL |
| static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, |
| int write, struct page **pages, int *nr) |
| { |
| struct dev_pagemap *pgmap = NULL; |
| int nr_start = *nr, ret = 0; |
| pte_t *ptep, *ptem; |
| |
| ptem = ptep = pte_offset_map(&pmd, addr); |
| do { |
| pte_t pte = gup_get_pte(ptep); |
| struct page *head, *page; |
| |
| /* |
| * Similar to the PMD case below, NUMA hinting must take slow |
| * path using the pte_protnone check. |
| */ |
| if (pte_protnone(pte)) |
| goto pte_unmap; |
| |
| if (!pte_access_permitted(pte, write)) |
| goto pte_unmap; |
| |
| if (pte_devmap(pte)) { |
| pgmap = get_dev_pagemap(pte_pfn(pte), pgmap); |
| if (unlikely(!pgmap)) { |
| undo_dev_pagemap(nr, nr_start, 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 = compound_head(page); |
| |
| if (!page_cache_get_speculative(head)) |
| goto pte_unmap; |
| |
| if (unlikely(pte_val(pte) != pte_val(*ptep))) { |
| put_page(head); |
| goto pte_unmap; |
| } |
| |
| VM_BUG_ON_PAGE(compound_head(page) != head, page); |
| |
| 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 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, unsigned long addr, unsigned long end, |
| int write, struct page **pages, int *nr) |
| { |
| return 0; |
| } |
| #endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */ |
| |
| #if defined(__HAVE_ARCH_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE) |
| static int __gup_device_huge(unsigned long pfn, unsigned long addr, |
| unsigned long end, struct page **pages, int *nr) |
| { |
| int nr_start = *nr; |
| struct dev_pagemap *pgmap = NULL; |
| |
| do { |
| struct page *page = pfn_to_page(pfn); |
| |
| pgmap = get_dev_pagemap(pfn, pgmap); |
| if (unlikely(!pgmap)) { |
| undo_dev_pagemap(nr, nr_start, pages); |
| return 0; |
| } |
| SetPageReferenced(page); |
| pages[*nr] = page; |
| get_page(page); |
| (*nr)++; |
| pfn++; |
| } while (addr += PAGE_SIZE, addr != end); |
| |
| if (pgmap) |
| put_dev_pagemap(pgmap); |
| return 1; |
| } |
| |
| static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, |
| unsigned long end, 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, pages, nr)) |
| return 0; |
| |
| if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) { |
| undo_dev_pagemap(nr, nr_start, pages); |
| return 0; |
| } |
| return 1; |
| } |
| |
| static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, |
| unsigned long end, 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, pages, nr)) |
| return 0; |
| |
| if (unlikely(pud_val(orig) != pud_val(*pudp))) { |
| undo_dev_pagemap(nr, nr_start, pages); |
| return 0; |
| } |
| return 1; |
| } |
| #else |
| static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, |
| unsigned long end, 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, struct page **pages, int *nr) |
| { |
| BUILD_BUG(); |
| return 0; |
| } |
| #endif |
| |
| static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, |
| unsigned long end, int write, struct page **pages, int *nr) |
| { |
| struct page *head, *page; |
| int refs; |
| |
| if (!pmd_access_permitted(orig, write)) |
| return 0; |
| |
| if (pmd_devmap(orig)) |
| return __gup_device_huge_pmd(orig, pmdp, addr, end, pages, nr); |
| |
| refs = 0; |
| page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); |
| do { |
| pages[*nr] = page; |
| (*nr)++; |
| page++; |
| refs++; |
| } while (addr += PAGE_SIZE, addr != end); |
| |
| head = compound_head(pmd_page(orig)); |
| if (!page_cache_add_speculative(head, refs)) { |
| *nr -= refs; |
| return 0; |
| } |
| |
| if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) { |
| *nr -= refs; |
| while (refs--) |
| put_page(head); |
| return 0; |
| } |
| |
| SetPageReferenced(head); |
| return 1; |
| } |
| |
| static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, |
| unsigned long end, int write, struct page **pages, int *nr) |
| { |
| struct page *head, *page; |
| int refs; |
| |
| if (!pud_access_permitted(orig, write)) |
| return 0; |
| |
| if (pud_devmap(orig)) |
| return __gup_device_huge_pud(orig, pudp, addr, end, pages, nr); |
| |
| refs = 0; |
| page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); |
| do { |
| pages[*nr] = page; |
| (*nr)++; |
| page++; |
| refs++; |
| } while (addr += PAGE_SIZE, addr != end); |
| |
| head = compound_head(pud_page(orig)); |
| if (!page_cache_add_speculative(head, refs)) { |
| *nr -= refs; |
| return 0; |
| } |
| |
| if (unlikely(pud_val(orig) != pud_val(*pudp))) { |
| *nr -= refs; |
| while (refs--) |
| put_page(head); |
| return 0; |
| } |
| |
| SetPageReferenced(head); |
| return 1; |
| } |
| |
| static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, |
| unsigned long end, int write, |
| struct page **pages, int *nr) |
| { |
| int refs; |
| struct page *head, *page; |
| |
| if (!pgd_access_permitted(orig, write)) |
| return 0; |
| |
| BUILD_BUG_ON(pgd_devmap(orig)); |
| refs = 0; |
| page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); |
| do { |
| pages[*nr] = page; |
| (*nr)++; |
| page++; |
| refs++; |
| } while (addr += PAGE_SIZE, addr != end); |
| |
| head = compound_head(pgd_page(orig)); |
| if (!page_cache_add_speculative(head, refs)) { |
| *nr -= refs; |
| return 0; |
| } |
| |
| if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) { |
| *nr -= refs; |
| while (refs--) |
| put_page(head); |
| return 0; |
| } |
| |
| SetPageReferenced(head); |
| return 1; |
| } |
| |
| static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end, |
| int write, struct page **pages, int *nr) |
| { |
| unsigned long next; |
| pmd_t *pmdp; |
| |
| pmdp = pmd_offset(&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))) { |
| /* |
| * 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, write, |
| 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, write, pages, nr)) |
| return 0; |
| } else if (!gup_pte_range(pmd, addr, next, write, pages, nr)) |
| return 0; |
| } while (pmdp++, addr = next, addr != end); |
| |
| return 1; |
| } |
| |
| static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end, |
| int write, struct page **pages, int *nr) |
| { |
| unsigned long next; |
| pud_t *pudp; |
| |
| pudp = pud_offset(&p4d, addr); |
| do { |
| pud_t pud = READ_ONCE(*pudp); |
| |
| next = pud_addr_end(addr, end); |
| if (pud_none(pud)) |
| return 0; |
| if (unlikely(pud_huge(pud))) { |
| if (!gup_huge_pud(pud, pudp, addr, next, write, |
| 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, write, pages, nr)) |
| return 0; |
| } else if (!gup_pmd_range(pud, addr, next, write, pages, nr)) |
| return 0; |
| } while (pudp++, addr = next, addr != end); |
| |
| return 1; |
| } |
| |
| static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end, |
| int write, struct page **pages, int *nr) |
| { |
| unsigned long next; |
| p4d_t *p4dp; |
| |
| p4dp = p4d_offset(&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, write, pages, nr)) |
| return 0; |
| } else if (!gup_pud_range(p4d, addr, next, write, pages, nr)) |
| return 0; |
| } while (p4dp++, addr = next, addr != end); |
| |
| return 1; |
| } |
| |
| static void gup_pgd_range(unsigned long addr, unsigned long end, |
| int write, 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, write, |
| pages, nr)) |
| return; |
| } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) { |
| if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr, |
| PGDIR_SHIFT, next, write, pages, nr)) |
| return; |
| } else if (!gup_p4d_range(pgd, addr, next, write, pages, nr)) |
| return; |
| } while (pgdp++, addr = next, addr != end); |
| } |
| |
| #ifndef gup_fast_permitted |
| /* |
| * Check if it's allowed to use __get_user_pages_fast() for the range, or |
| * we need to fall back to the slow version: |
| */ |
| bool gup_fast_permitted(unsigned long start, int nr_pages, int write) |
| { |
| unsigned long len, end; |
| |
| len = (unsigned long) nr_pages << PAGE_SHIFT; |
| end = start + len; |
| return end >= start; |
| } |
| #endif |
| |
| /* |
| * 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. |
| */ |
| int __get_user_pages_fast(unsigned long start, int nr_pages, int write, |
| struct page **pages) |
| { |
| unsigned long len, end; |
| unsigned long flags; |
| int nr = 0; |
| |
| start &= PAGE_MASK; |
| len = (unsigned long) nr_pages << PAGE_SHIFT; |
| end = start + len; |
| |
| if (unlikely(!access_ok((void __user *)start, len))) |
| return 0; |
| |
| /* |
| * Disable interrupts. We use the nested form as we can already have |
| * interrupts disabled by get_futex_key. |
| * |
| * 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. |
| */ |
| |
| if (gup_fast_permitted(start, nr_pages, write)) { |
| local_irq_save(flags); |
| gup_pgd_range(start, end, write, pages, &nr); |
| local_irq_restore(flags); |
| } |
| |
| return nr; |
| } |
| |
| /** |
| * get_user_pages_fast() - pin user pages in memory |
| * @start: starting user address |
| * @nr_pages: number of pages from start to pin |
| * @write: whether pages will be written to |
| * @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_sem. |
| * 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, int write, |
| struct page **pages) |
| { |
| unsigned long addr, len, end; |
| int nr = 0, ret = 0; |
| |
| start &= PAGE_MASK; |
| addr = start; |
| len = (unsigned long) nr_pages << PAGE_SHIFT; |
| end = start + len; |
| |
| if (nr_pages <= 0) |
| return 0; |
| |
| if (unlikely(!access_ok((void __user *)start, len))) |
| return -EFAULT; |
| |
| if (gup_fast_permitted(start, nr_pages, write)) { |
| local_irq_disable(); |
| gup_pgd_range(addr, end, write, pages, &nr); |
| local_irq_enable(); |
| ret = nr; |
| } |
| |
| if (nr < nr_pages) { |
| /* Try to get the remaining pages with get_user_pages */ |
| start += nr << PAGE_SHIFT; |
| pages += nr; |
| |
| ret = get_user_pages_unlocked(start, nr_pages - nr, pages, |
| write ? FOLL_WRITE : 0); |
| |
| /* Have to be a bit careful with return values */ |
| if (nr > 0) { |
| if (ret < 0) |
| ret = nr; |
| else |
| ret += nr; |
| } |
| } |
| |
| return ret; |
| } |
| |
| #endif /* CONFIG_HAVE_GENERIC_GUP */ |