1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_PAGEWALK_H
3 #define _LINUX_PAGEWALK_H
4
5 #include <linux/mm.h>
6
7 struct mm_walk;
8
9 /* Locking requirement during a page walk. */
10 enum page_walk_lock {
11 /* mmap_lock should be locked for read to stabilize the vma tree */
12 PGWALK_RDLOCK = 0,
13 /* vma will be write-locked during the walk */
14 PGWALK_WRLOCK = 1,
15 /* vma is expected to be already write-locked during the walk */
16 PGWALK_WRLOCK_VERIFY = 2,
17 };
18
19 /**
20 * struct mm_walk_ops - callbacks for walk_page_range
21 * @pgd_entry: if set, called for each non-empty PGD (top-level) entry
22 * @p4d_entry: if set, called for each non-empty P4D entry
23 * @pud_entry: if set, called for each non-empty PUD entry
24 * @pmd_entry: if set, called for each non-empty PMD entry
25 * this handler is required to be able to handle
26 * pmd_trans_huge() pmds. They may simply choose to
27 * split_huge_page() instead of handling it explicitly.
28 * @pte_entry: if set, called for each PTE (lowest-level) entry,
29 * including empty ones
30 * @pte_hole: if set, called for each hole at all levels,
31 * depth is -1 if not known, 0:PGD, 1:P4D, 2:PUD, 3:PMD.
32 * Any folded depths (where PTRS_PER_P?D is equal to 1)
33 * are skipped.
34 * @hugetlb_entry: if set, called for each hugetlb entry. This hook
35 * function is called with the vma lock held, in order to
36 * protect against a concurrent freeing of the pte_t* or
37 * the ptl. In some cases, the hook function needs to drop
38 * and retake the vma lock in order to avoid deadlocks
39 * while calling other functions. In such cases the hook
40 * function must either refrain from accessing the pte or
41 * ptl after dropping the vma lock, or else revalidate
42 * those items after re-acquiring the vma lock and before
43 * accessing them.
44 * @test_walk: caller specific callback function to determine whether
45 * we walk over the current vma or not. Returning 0 means
46 * "do page table walk over the current vma", returning
47 * a negative value means "abort current page table walk
48 * right now" and returning 1 means "skip the current vma"
49 * Note that this callback is not called when the caller
50 * passes in a single VMA as for walk_page_vma().
51 * @pre_vma: if set, called before starting walk on a non-null vma.
52 * @post_vma: if set, called after a walk on a non-null vma, provided
53 * that @pre_vma and the vma walk succeeded.
54 *
55 * p?d_entry callbacks are called even if those levels are folded on a
56 * particular architecture/configuration.
57 */
58 struct mm_walk_ops {
59 int (*pgd_entry)(pgd_t *pgd, unsigned long addr,
60 unsigned long next, struct mm_walk *walk);
61 int (*p4d_entry)(p4d_t *p4d, unsigned long addr,
62 unsigned long next, struct mm_walk *walk);
63 int (*pud_entry)(pud_t *pud, unsigned long addr,
64 unsigned long next, struct mm_walk *walk);
65 int (*pmd_entry)(pmd_t *pmd, unsigned long addr,
66 unsigned long next, struct mm_walk *walk);
67 int (*pte_entry)(pte_t *pte, unsigned long addr,
68 unsigned long next, struct mm_walk *walk);
69 int (*pte_hole)(unsigned long addr, unsigned long next,
70 int depth, struct mm_walk *walk);
71 int (*hugetlb_entry)(pte_t *pte, unsigned long hmask,
72 unsigned long addr, unsigned long next,
73 struct mm_walk *walk);
74 int (*test_walk)(unsigned long addr, unsigned long next,
75 struct mm_walk *walk);
76 int (*pre_vma)(unsigned long start, unsigned long end,
77 struct mm_walk *walk);
78 void (*post_vma)(struct mm_walk *walk);
79 enum page_walk_lock walk_lock;
80 };
81
82 /*
83 * Action for pud_entry / pmd_entry callbacks.
84 * ACTION_SUBTREE is the default
85 */
86 enum page_walk_action {
87 /* Descend to next level, splitting huge pages if needed and possible */
88 ACTION_SUBTREE = 0,
89 /* Continue to next entry at this level (ignoring any subtree) */
90 ACTION_CONTINUE = 1,
91 /* Call again for this entry */
92 ACTION_AGAIN = 2
93 };
94
95 /**
96 * struct mm_walk - walk_page_range data
97 * @ops: operation to call during the walk
98 * @mm: mm_struct representing the target process of page table walk
99 * @pgd: pointer to PGD; only valid with no_vma (otherwise set to NULL)
100 * @vma: vma currently walked (NULL if walking outside vmas)
101 * @action: next action to perform (see enum page_walk_action)
102 * @no_vma: walk ignoring vmas (vma will always be NULL)
103 * @private: private data for callbacks' usage
104 *
105 * (see the comment on walk_page_range() for more details)
106 */
107 struct mm_walk {
108 const struct mm_walk_ops *ops;
109 struct mm_struct *mm;
110 pgd_t *pgd;
111 struct vm_area_struct *vma;
112 enum page_walk_action action;
113 bool no_vma;
114 void *private;
115 };
116
117 int walk_page_range(struct mm_struct *mm, unsigned long start,
118 unsigned long end, const struct mm_walk_ops *ops,
119 void *private);
120 int walk_page_range_novma(struct mm_struct *mm, unsigned long start,
121 unsigned long end, const struct mm_walk_ops *ops,
122 pgd_t *pgd,
123 void *private);
124 int walk_page_range_vma(struct vm_area_struct *vma, unsigned long start,
125 unsigned long end, const struct mm_walk_ops *ops,
126 void *private);
127 int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
128 void *private);
129 int walk_page_mapping(struct address_space *mapping, pgoff_t first_index,
130 pgoff_t nr, const struct mm_walk_ops *ops,
131 void *private);
132
133 #endif /* _LINUX_PAGEWALK_H */
134
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