// SPDX-License-Identifier: GPL-2.0 #include #include #include #include #include #include /* * We want to know the real level where a entry is located ignoring any * folding of levels which may be happening. For example if p4d is folded then * a missing entry found at level 1 (p4d) is actually at level 0 (pgd). */ static int real_depth(int depth) { if (depth == 3 && PTRS_PER_PMD == 1) depth = 2; if (depth == 2 && PTRS_PER_PUD == 1) depth = 1; if (depth == 1 && PTRS_PER_P4D == 1) depth = 0; return depth; } static int walk_pte_range_inner(pte_t *pte, unsigned long addr, unsigned long end, struct mm_walk *walk) { const struct mm_walk_ops *ops = walk->ops; int err = 0; for (;;) { err = ops->pte_entry(pte, addr, addr + PAGE_SIZE, walk); if (err) break; if (addr >= end - PAGE_SIZE) break; addr += PAGE_SIZE; pte++; } return err; } static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, struct mm_walk *walk) { pte_t *pte; int err = 0; spinlock_t *ptl; if (walk->no_vma) { /* * pte_offset_map() might apply user-specific validation. * Indeed, on x86_64 the pmd entries set up by init_espfix_ap() * fit its pmd_bad() check (_PAGE_NX set and _PAGE_RW clear), * and CONFIG_EFI_PGT_DUMP efi_mm goes so far as to walk them. */ if (walk->mm == &init_mm || addr >= TASK_SIZE) pte = pte_offset_kernel(pmd, addr); else pte = pte_offset_map(pmd, addr); if (pte) { err = walk_pte_range_inner(pte, addr, end, walk); if (walk->mm != &init_mm && addr < TASK_SIZE) pte_unmap(pte); } } else { pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); if (pte) { err = walk_pte_range_inner(pte, addr, end, walk); pte_unmap_unlock(pte, ptl); } } if (!pte) walk->action = ACTION_AGAIN; return err; } static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end, struct mm_walk *walk) { pmd_t *pmd; unsigned long next; const struct mm_walk_ops *ops = walk->ops; int err = 0; int depth = real_depth(3); pmd = pmd_offset(pud, addr); do { again: next = pmd_addr_end(addr, end); if (pmd_none(*pmd)) { if (ops->pte_hole) err = ops->pte_hole(addr, next, depth, walk); if (err) break; continue; } walk->action = ACTION_SUBTREE; /* * This implies that each ->pmd_entry() handler * needs to know about pmd_trans_huge() pmds */ if (ops->pmd_entry) err = ops->pmd_entry(pmd, addr, next, walk); if (err) break; if (walk->action == ACTION_AGAIN) goto again; /* * Check this here so we only break down trans_huge * pages when we _need_ to */ if ((!walk->vma && (pmd_leaf(*pmd) || !pmd_present(*pmd))) || walk->action == ACTION_CONTINUE || !(ops->pte_entry)) continue; if (walk->vma) split_huge_pmd(walk->vma, pmd, addr); err = walk_pte_range(pmd, addr, next, walk); if (err) break; if (walk->action == ACTION_AGAIN) goto again; } while (pmd++, addr = next, addr != end); return err; } static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end, struct mm_walk *walk) { pud_t *pud; unsigned long next; const struct mm_walk_ops *ops = walk->ops; int err = 0; int depth = real_depth(2); pud = pud_offset(p4d, addr); do { again: next = pud_addr_end(addr, end); if (pud_none(*pud)) { if (ops->pte_hole) err = ops->pte_hole(addr, next, depth, walk); if (err) break; continue; } walk->action = ACTION_SUBTREE; if (ops->pud_entry) err = ops->pud_entry(pud, addr, next, walk); if (err) break; if (walk->action == ACTION_AGAIN) goto again; if ((!walk->vma && (pud_leaf(*pud) || !pud_present(*pud))) || walk->action == ACTION_CONTINUE || !(ops->pmd_entry || ops->pte_entry)) continue; if (walk->vma) split_huge_pud(walk->vma, pud, addr); if (pud_none(*pud)) goto again; err = walk_pmd_range(pud, addr, next, walk); if (err) break; } while (pud++, addr = next, addr != end); return err; } static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end, struct mm_walk *walk) { p4d_t *p4d; unsigned long next; const struct mm_walk_ops *ops = walk->ops; int err = 0; int depth = real_depth(1); p4d = p4d_offset(pgd, addr); do { next = p4d_addr_end(addr, end); if (p4d_none_or_clear_bad(p4d)) { if (ops->pte_hole) err = ops->pte_hole(addr, next, depth, walk); if (err) break; continue; } if (ops->p4d_entry) { err = ops->p4d_entry(p4d, addr, next, walk); if (err) break; } if (ops->pud_entry || ops->pmd_entry || ops->pte_entry) err = walk_pud_range(p4d, addr, next, walk); if (err) break; } while (p4d++, addr = next, addr != end); return err; } static int walk_pgd_range(unsigned long addr, unsigned long end, struct mm_walk *walk) { pgd_t *pgd; unsigned long next; const struct mm_walk_ops *ops = walk->ops; int err = 0; if (walk->pgd) pgd = walk->pgd + pgd_index(addr); else pgd = pgd_offset(walk->mm, addr); do { next = pgd_addr_end(addr, end); if (pgd_none_or_clear_bad(pgd)) { if (ops->pte_hole) err = ops->pte_hole(addr, next, 0, walk); if (err) break; continue; } if (ops->pgd_entry) { err = ops->pgd_entry(pgd, addr, next, walk); if (err) break; } if (ops->p4d_entry || ops->pud_entry || ops->pmd_entry || ops->pte_entry) err = walk_p4d_range(pgd, addr, next, walk); if (err) break; } while (pgd++, addr = next, addr != end); return err; } #ifdef CONFIG_HUGETLB_PAGE static unsigned long hugetlb_entry_end(struct hstate *h, unsigned long addr, unsigned long end) { unsigned long boundary = (addr & huge_page_mask(h)) + huge_page_size(h); return boundary < end ? boundary : end; } static int walk_hugetlb_range(unsigned long addr, unsigned long end, struct mm_walk *walk) { struct vm_area_struct *vma = walk->vma; struct hstate *h = hstate_vma(vma); unsigned long next; unsigned long hmask = huge_page_mask(h); unsigned long sz = huge_page_size(h); pte_t *pte; const struct mm_walk_ops *ops = walk->ops; int err = 0; hugetlb_vma_lock_read(vma); do { next = hugetlb_entry_end(h, addr, end); pte = hugetlb_walk(vma, addr & hmask, sz); if (pte) err = ops->hugetlb_entry(pte, hmask, addr, next, walk); else if (ops->pte_hole) err = ops->pte_hole(addr, next, -1, walk); if (err) break; } while (addr = next, addr != end); hugetlb_vma_unlock_read(vma); return err; } #else /* CONFIG_HUGETLB_PAGE */ static int walk_hugetlb_range(unsigned long addr, unsigned long end, struct mm_walk *walk) { return 0; } #endif /* CONFIG_HUGETLB_PAGE */ /* * Decide whether we really walk over the current vma on [@start, @end) * or skip it via the returned value. Return 0 if we do walk over the * current vma, and return 1 if we skip the vma. Negative values means * error, where we abort the current walk. */ static int walk_page_test(unsigned long start, unsigned long end, struct mm_walk *walk) { struct vm_area_struct *vma = walk->vma; const struct mm_walk_ops *ops = walk->ops; if (ops->test_walk) return ops->test_walk(start, end, walk); /* * vma(VM_PFNMAP) doesn't have any valid struct pages behind VM_PFNMAP * range, so we don't walk over it as we do for normal vmas. However, * Some callers are interested in handling hole range and they don't * want to just ignore any single address range. Such users certainly * define their ->pte_hole() callbacks, so let's delegate them to handle * vma(VM_PFNMAP). */ if (vma->vm_flags & VM_PFNMAP) { int err = 1; if (ops->pte_hole) err = ops->pte_hole(start, end, -1, walk); return err ? err : 1; } return 0; } static int __walk_page_range(unsigned long start, unsigned long end, struct mm_walk *walk) { int err = 0; struct vm_area_struct *vma = walk->vma; const struct mm_walk_ops *ops = walk->ops; if (ops->pre_vma) { err = ops->pre_vma(start, end, walk); if (err) return err; } if (is_vm_hugetlb_page(vma)) { if (ops->hugetlb_entry) err = walk_hugetlb_range(start, end, walk); } else err = walk_pgd_range(start, end, walk); if (ops->post_vma) ops->post_vma(walk); return err; } static inline void process_mm_walk_lock(struct mm_struct *mm, enum page_walk_lock walk_lock) { if (walk_lock == PGWALK_RDLOCK) mmap_assert_locked(mm); else mmap_assert_write_locked(mm); } static inline void process_vma_walk_lock(struct vm_area_struct *vma, enum page_walk_lock walk_lock) { #ifdef CONFIG_PER_VMA_LOCK switch (walk_lock) { case PGWALK_WRLOCK: vma_start_write(vma); break; case PGWALK_WRLOCK_VERIFY: vma_assert_write_locked(vma); break; case PGWALK_RDLOCK: /* PGWALK_RDLOCK is handled by process_mm_walk_lock */ break; } #endif } /** * walk_page_range - walk page table with caller specific callbacks * @mm: mm_struct representing the target process of page table walk * @start: start address of the virtual address range * @end: end address of the virtual address range * @ops: operation to call during the walk * @private: private data for callbacks' usage * * Recursively walk the page table tree of the process represented by @mm * within the virtual address range [@start, @end). During walking, we can do * some caller-specific works for each entry, by setting up pmd_entry(), * pte_entry(), and/or hugetlb_entry(). If you don't set up for some of these * callbacks, the associated entries/pages are just ignored. * The return values of these callbacks are commonly defined like below: * * - 0 : succeeded to handle the current entry, and if you don't reach the * end address yet, continue to walk. * - >0 : succeeded to handle the current entry, and return to the caller * with caller specific value. * - <0 : failed to handle the current entry, and return to the caller * with error code. * * Before starting to walk page table, some callers want to check whether * they really want to walk over the current vma, typically by checking * its vm_flags. walk_page_test() and @ops->test_walk() are used for this * purpose. * * If operations need to be staged before and committed after a vma is walked, * there are two callbacks, pre_vma() and post_vma(). Note that post_vma(), * since it is intended to handle commit-type operations, can't return any * errors. * * struct mm_walk keeps current values of some common data like vma and pmd, * which are useful for the access from callbacks. If you want to pass some * caller-specific data to callbacks, @private should be helpful. * * Locking: * Callers of walk_page_range() and walk_page_vma() should hold @mm->mmap_lock, * because these function traverse vma list and/or access to vma's data. */ int walk_page_range(struct mm_struct *mm, unsigned long start, unsigned long end, const struct mm_walk_ops *ops, void *private) { int err = 0; unsigned long next; struct vm_area_struct *vma; struct mm_walk walk = { .ops = ops, .mm = mm, .private = private, }; if (start >= end) return -EINVAL; if (!walk.mm) return -EINVAL; process_mm_walk_lock(walk.mm, ops->walk_lock); vma = find_vma(walk.mm, start); do { if (!vma) { /* after the last vma */ walk.vma = NULL; next = end; if (ops->pte_hole) err = ops->pte_hole(start, next, -1, &walk); } else if (start < vma->vm_start) { /* outside vma */ walk.vma = NULL; next = min(end, vma->vm_start); if (ops->pte_hole) err = ops->pte_hole(start, next, -1, &walk); } else { /* inside vma */ process_vma_walk_lock(vma, ops->walk_lock); walk.vma = vma; next = min(end, vma->vm_end); vma = find_vma(mm, vma->vm_end); err = walk_page_test(start, next, &walk); if (err > 0) { /* * positive return values are purely for * controlling the pagewalk, so should never * be passed to the callers. */ err = 0; continue; } if (err < 0) break; err = __walk_page_range(start, next, &walk); } if (err) break; } while (start = next, start < end); return err; } /** * walk_page_range_novma - walk a range of pagetables not backed by a vma * @mm: mm_struct representing the target process of page table walk * @start: start address of the virtual address range * @end: end address of the virtual address range * @ops: operation to call during the walk * @pgd: pgd to walk if different from mm->pgd * @private: private data for callbacks' usage * * Similar to walk_page_range() but can walk any page tables even if they are * not backed by VMAs. Because 'unusual' entries may be walked this function * will also not lock the PTEs for the pte_entry() callback. This is useful for * walking the kernel pages tables or page tables for firmware. * * Note: Be careful to walk the kernel pages tables, the caller may be need to * take other effective approache (mmap lock may be insufficient) to prevent * the intermediate kernel page tables belonging to the specified address range * from being freed (e.g. memory hot-remove). */ int walk_page_range_novma(struct mm_struct *mm, unsigned long start, unsigned long end, const struct mm_walk_ops *ops, pgd_t *pgd, void *private) { struct mm_walk walk = { .ops = ops, .mm = mm, .pgd = pgd, .private = private, .no_vma = true }; if (start >= end || !walk.mm) return -EINVAL; /* * 1) For walking the user virtual address space: * * The mmap lock protects the page walker from changes to the page * tables during the walk. However a read lock is insufficient to * protect those areas which don't have a VMA as munmap() detaches * the VMAs before downgrading to a read lock and actually tearing * down PTEs/page tables. In which case, the mmap write lock should * be hold. * * 2) For walking the kernel virtual address space: * * The kernel intermediate page tables usually do not be freed, so * the mmap map read lock is sufficient. But there are some exceptions. * E.g. memory hot-remove. In which case, the mmap lock is insufficient * to prevent the intermediate kernel pages tables belonging to the * specified address range from being freed. The caller should take * other actions to prevent this race. */ if (mm == &init_mm) mmap_assert_locked(walk.mm); else mmap_assert_write_locked(walk.mm); return walk_pgd_range(start, end, &walk); } int walk_page_range_vma(struct vm_area_struct *vma, unsigned long start, unsigned long end, const struct mm_walk_ops *ops, void *private) { struct mm_walk walk = { .ops = ops, .mm = vma->vm_mm, .vma = vma, .private = private, }; if (start >= end || !walk.mm) return -EINVAL; if (start < vma->vm_start || end > vma->vm_end) return -EINVAL; process_mm_walk_lock(walk.mm, ops->walk_lock); process_vma_walk_lock(vma, ops->walk_lock); return __walk_page_range(start, end, &walk); } int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops, void *private) { struct mm_walk walk = { .ops = ops, .mm = vma->vm_mm, .vma = vma, .private = private, }; if (!walk.mm) return -EINVAL; process_mm_walk_lock(walk.mm, ops->walk_lock); process_vma_walk_lock(vma, ops->walk_lock); return __walk_page_range(vma->vm_start, vma->vm_end, &walk); } /** * walk_page_mapping - walk all memory areas mapped into a struct address_space. * @mapping: Pointer to the struct address_space * @first_index: First page offset in the address_space * @nr: Number of incremental page offsets to cover * @ops: operation to call during the walk * @private: private data for callbacks' usage * * This function walks all memory areas mapped into a struct address_space. * The walk is limited to only the given page-size index range, but if * the index boundaries cross a huge page-table entry, that entry will be * included. * * Also see walk_page_range() for additional information. * * Locking: * This function can't require that the struct mm_struct::mmap_lock is held, * since @mapping may be mapped by multiple processes. Instead * @mapping->i_mmap_rwsem must be held. This might have implications in the * callbacks, and it's up tho the caller to ensure that the * struct mm_struct::mmap_lock is not needed. * * Also this means that a caller can't rely on the struct * vm_area_struct::vm_flags to be constant across a call, * except for immutable flags. Callers requiring this shouldn't use * this function. * * Return: 0 on success, negative error code on failure, positive number on * caller defined premature termination. */ int walk_page_mapping(struct address_space *mapping, pgoff_t first_index, pgoff_t nr, const struct mm_walk_ops *ops, void *private) { struct mm_walk walk = { .ops = ops, .private = private, }; struct vm_area_struct *vma; pgoff_t vba, vea, cba, cea; unsigned long start_addr, end_addr; int err = 0; lockdep_assert_held(&mapping->i_mmap_rwsem); vma_interval_tree_foreach(vma, &mapping->i_mmap, first_index, first_index + nr - 1) { /* Clip to the vma */ vba = vma->vm_pgoff; vea = vba + vma_pages(vma); cba = first_index; cba = max(cba, vba); cea = first_index + nr; cea = min(cea, vea); start_addr = ((cba - vba) << PAGE_SHIFT) + vma->vm_start; end_addr = ((cea - vba) << PAGE_SHIFT) + vma->vm_start; if (start_addr >= end_addr) continue; walk.vma = vma; walk.mm = vma->vm_mm; err = walk_page_test(vma->vm_start, vma->vm_end, &walk); if (err > 0) { err = 0; break; } else if (err < 0) break; err = __walk_page_range(start_addr, end_addr, &walk); if (err) break; } return err; } /** * folio_walk_start - walk the page tables to a folio * @fw: filled with information on success. * @vma: the VMA. * @addr: the virtual address to use for the page table walk. * @flags: flags modifying which folios to walk to. * * Walk the page tables using @addr in a given @vma to a mapped folio and * return the folio, making sure that the page table entry referenced by * @addr cannot change until folio_walk_end() was called. * * As default, this function returns only folios that are not special (e.g., not * the zeropage) and never returns folios that are supposed to be ignored by the * VM as documented by vm_normal_page(). If requested, zeropages will be * returned as well. * * As default, this function only considers present page table entries. * If requested, it will also consider migration entries. * * If this function returns NULL it might either indicate "there is nothing" or * "there is nothing suitable". * * On success, @fw is filled and the function returns the folio while the PTL * is still held and folio_walk_end() must be called to clean up, * releasing any held locks. The returned folio must *not* be used after the * call to folio_walk_end(), unless a short-term folio reference is taken before * that call. * * @fw->page will correspond to the page that is effectively referenced by * @addr. However, for migration entries and shared zeropages @fw->page is * set to NULL. Note that large folios might be mapped by multiple page table * entries, and this function will always only lookup a single entry as * specified by @addr, which might or might not cover more than a single page of * the returned folio. * * This function must *not* be used as a naive replacement for * get_user_pages() / pin_user_pages(), especially not to perform DMA or * to carelessly modify page content. This function may *only* be used to grab * short-term folio references, never to grab long-term folio references. * * Using the page table entry pointers in @fw for reading or modifying the * entry should be avoided where possible: however, there might be valid * use cases. * * WARNING: Modifying page table entries in hugetlb VMAs requires a lot of care. * For example, PMD page table sharing might require prior unsharing. Also, * logical hugetlb entries might span multiple physical page table entries, * which *must* be modified in a single operation (set_huge_pte_at(), * huge_ptep_set_*, ...). Note that the page table entry stored in @fw might * not correspond to the first physical entry of a logical hugetlb entry. * * The mmap lock must be held in read mode. * * Return: folio pointer on success, otherwise NULL. */ struct folio *folio_walk_start(struct folio_walk *fw, struct vm_area_struct *vma, unsigned long addr, folio_walk_flags_t flags) { unsigned long entry_size; bool expose_page = true; struct page *page; pud_t *pudp, pud; pmd_t *pmdp, pmd; pte_t *ptep, pte; spinlock_t *ptl; pgd_t *pgdp; p4d_t *p4dp; mmap_assert_locked(vma->vm_mm); vma_pgtable_walk_begin(vma); if (WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end)) goto not_found; pgdp = pgd_offset(vma->vm_mm, addr); if (pgd_none_or_clear_bad(pgdp)) goto not_found; p4dp = p4d_offset(pgdp, addr); if (p4d_none_or_clear_bad(p4dp)) goto not_found; pudp = pud_offset(p4dp, addr); pud = pudp_get(pudp); if (pud_none(pud)) goto not_found; if (IS_ENABLED(CONFIG_PGTABLE_HAS_HUGE_LEAVES) && pud_leaf(pud)) { ptl = pud_lock(vma->vm_mm, pudp); pud = pudp_get(pudp); entry_size = PUD_SIZE; fw->level = FW_LEVEL_PUD; fw->pudp = pudp; fw->pud = pud; if (!pud_present(pud) || pud_devmap(pud) || pud_special(pud)) { spin_unlock(ptl); goto not_found; } else if (!pud_leaf(pud)) { spin_unlock(ptl); goto pmd_table; } /* * TODO: vm_normal_page_pud() will be handy once we want to * support PUD mappings in VM_PFNMAP|VM_MIXEDMAP VMAs. */ page = pud_page(pud); goto found; } pmd_table: VM_WARN_ON_ONCE(pud_leaf(*pudp)); pmdp = pmd_offset(pudp, addr); pmd = pmdp_get_lockless(pmdp); if (pmd_none(pmd)) goto not_found; if (IS_ENABLED(CONFIG_PGTABLE_HAS_HUGE_LEAVES) && pmd_leaf(pmd)) { ptl = pmd_lock(vma->vm_mm, pmdp); pmd = pmdp_get(pmdp); entry_size = PMD_SIZE; fw->level = FW_LEVEL_PMD; fw->pmdp = pmdp; fw->pmd = pmd; if (pmd_none(pmd)) { spin_unlock(ptl); goto not_found; } else if (!pmd_leaf(pmd)) { spin_unlock(ptl); goto pte_table; } else if (pmd_present(pmd)) { page = vm_normal_page_pmd(vma, addr, pmd); if (page) { goto found; } else if ((flags & FW_ZEROPAGE) && is_huge_zero_pmd(pmd)) { page = pfn_to_page(pmd_pfn(pmd)); expose_page = false; goto found; } } else if ((flags & FW_MIGRATION) && is_pmd_migration_entry(pmd)) { swp_entry_t entry = pmd_to_swp_entry(pmd); page = pfn_swap_entry_to_page(entry); expose_page = false; goto found; } spin_unlock(ptl); goto not_found; } pte_table: VM_WARN_ON_ONCE(pmd_leaf(pmdp_get_lockless(pmdp))); ptep = pte_offset_map_lock(vma->vm_mm, pmdp, addr, &ptl); if (!ptep) goto not_found; pte = ptep_get(ptep); entry_size = PAGE_SIZE; fw->level = FW_LEVEL_PTE; fw->ptep = ptep; fw->pte = pte; if (pte_present(pte)) { page = vm_normal_page(vma, addr, pte); if (page) goto found; if ((flags & FW_ZEROPAGE) && is_zero_pfn(pte_pfn(pte))) { page = pfn_to_page(pte_pfn(pte)); expose_page = false; goto found; } } else if (!pte_none(pte)) { swp_entry_t entry = pte_to_swp_entry(pte); if ((flags & FW_MIGRATION) && is_migration_entry(entry)) { page = pfn_swap_entry_to_page(entry); expose_page = false; goto found; } } pte_unmap_unlock(ptep, ptl); not_found: vma_pgtable_walk_end(vma); return NULL; found: if (expose_page) /* Note: Offset from the mapped page, not the folio start. */ fw->page = nth_page(page, (addr & (entry_size - 1)) >> PAGE_SHIFT); else fw->page = NULL; fw->ptl = ptl; return page_folio(page); }