// SPDX-License-Identifier: GPL-2.0 #include <linux/pagewalk.h> #include <linux/highmem.h> #include <linux/sched.h> #include <linux/hugetlb.h> /* * 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 = pte_offset_map(pmd, addr); err = walk_pte_range_inner(pte, addr, end, walk); pte_unmap(pte); } else { pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); err = walk_pte_range_inner(pte, addr, end, walk); pte_unmap_unlock(pte, ptl); } 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) || (!walk->vma && !walk->no_vma)) { 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); if (pmd_trans_unstable(pmd)) goto again; } err = walk_pte_range(pmd, addr, next, walk); if (err) break; } 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) || (!walk->vma && !walk->no_vma)) { 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; do { next = hugetlb_entry_end(h, addr, end); pte = huge_pte_offset(walk->mm, 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); 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 (vma && ops->pre_vma) { err = ops->pre_vma(start, end, walk); if (err) return err; } if (vma && 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 (vma && ops->post_vma) ops->post_vma(walk); return err; } /** * 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_sem, * 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; lockdep_assert_held(&walk.mm->mmap_sem); vma = find_vma(walk.mm, start); do { if (!vma) { /* after the last vma */ walk.vma = NULL; next = end; } else if (start < vma->vm_start) { /* outside vma */ walk.vma = NULL; next = min(end, vma->vm_start); } else { /* inside vma */ walk.vma = vma; next = min(end, vma->vm_end); vma = vma->vm_next; 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; } if (walk.vma || walk.ops->pte_hole) err = __walk_page_range(start, next, &walk); if (err) break; } while (start = next, start < end); return err; } /* * 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. */ 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; lockdep_assert_held(&walk.mm->mmap_sem); 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, }; int err; if (!walk.mm) return -EINVAL; lockdep_assert_held(&walk.mm->mmap_sem); err = walk_page_test(vma->vm_start, vma->vm_end, &walk); if (err > 0) return 0; if (err < 0) return err; 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_sem 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_sem 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; }