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-rw-r--r--mm/pagewalk.c563
1 files changed, 563 insertions, 0 deletions
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
new file mode 100644
index 000000000..371ec21a1
--- /dev/null
+++ b/mm/pagewalk.c
@@ -0,0 +1,563 @@
+// 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)) {
+ 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)) {
+ 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 (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;
+}
+
+/**
+ * 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;
+
+ mmap_assert_locked(walk.mm);
+
+ 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 */
+ 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;
+ 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;
+
+ mmap_assert_write_locked(walk.mm);
+
+ return walk_pgd_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;
+
+ mmap_assert_locked(walk.mm);
+
+ 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_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;
+}
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