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1// SPDX-License-Identifier: GPL-2.0
2#include <linux/mm.h>
3#include <linux/highmem.h>
4#include <linux/sched.h>
5#include <linux/hugetlb.h>
6
7static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
8 struct mm_walk *walk)
9{
10 pte_t *pte;
11 int err = 0;
12
13 pte = pte_offset_map(pmd, addr);
14 for (;;) {
15 err = walk->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
16 if (err)
17 break;
18 addr += PAGE_SIZE;
19 if (addr == end)
20 break;
21 pte++;
22 }
23
24 pte_unmap(pte);
25 return err;
26}
27
28static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
29 struct mm_walk *walk)
30{
31 pmd_t *pmd;
32 unsigned long next;
33 int err = 0;
34
35 pmd = pmd_offset(pud, addr);
36 do {
37again:
38 next = pmd_addr_end(addr, end);
39 if (pmd_none(*pmd) || !walk->vma) {
40 if (walk->pte_hole)
41 err = walk->pte_hole(addr, next, walk);
42 if (err)
43 break;
44 continue;
45 }
46 /*
47 * This implies that each ->pmd_entry() handler
48 * needs to know about pmd_trans_huge() pmds
49 */
50 if (walk->pmd_entry)
51 err = walk->pmd_entry(pmd, addr, next, walk);
52 if (err)
53 break;
54
55 /*
56 * Check this here so we only break down trans_huge
57 * pages when we _need_ to
58 */
59 if (!walk->pte_entry)
60 continue;
61
62 split_huge_pmd(walk->vma, pmd, addr);
63 if (pmd_trans_unstable(pmd))
64 goto again;
65 err = walk_pte_range(pmd, addr, next, walk);
66 if (err)
67 break;
68 } while (pmd++, addr = next, addr != end);
69
70 return err;
71}
72
73static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
74 struct mm_walk *walk)
75{
76 pud_t *pud;
77 unsigned long next;
78 int err = 0;
79
80 pud = pud_offset(p4d, addr);
81 do {
82 again:
83 next = pud_addr_end(addr, end);
84 if (pud_none(*pud) || !walk->vma) {
85 if (walk->pte_hole)
86 err = walk->pte_hole(addr, next, walk);
87 if (err)
88 break;
89 continue;
90 }
91
92 if (walk->pud_entry) {
93 spinlock_t *ptl = pud_trans_huge_lock(pud, walk->vma);
94
95 if (ptl) {
96 err = walk->pud_entry(pud, addr, next, walk);
97 spin_unlock(ptl);
98 if (err)
99 break;
100 continue;
101 }
102 }
103
104 split_huge_pud(walk->vma, pud, addr);
105 if (pud_none(*pud))
106 goto again;
107
108 if (walk->pmd_entry || walk->pte_entry)
109 err = walk_pmd_range(pud, addr, next, walk);
110 if (err)
111 break;
112 } while (pud++, addr = next, addr != end);
113
114 return err;
115}
116
117static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
118 struct mm_walk *walk)
119{
120 p4d_t *p4d;
121 unsigned long next;
122 int err = 0;
123
124 p4d = p4d_offset(pgd, addr);
125 do {
126 next = p4d_addr_end(addr, end);
127 if (p4d_none_or_clear_bad(p4d)) {
128 if (walk->pte_hole)
129 err = walk->pte_hole(addr, next, walk);
130 if (err)
131 break;
132 continue;
133 }
134 if (walk->pmd_entry || walk->pte_entry)
135 err = walk_pud_range(p4d, addr, next, walk);
136 if (err)
137 break;
138 } while (p4d++, addr = next, addr != end);
139
140 return err;
141}
142
143static int walk_pgd_range(unsigned long addr, unsigned long end,
144 struct mm_walk *walk)
145{
146 pgd_t *pgd;
147 unsigned long next;
148 int err = 0;
149
150 pgd = pgd_offset(walk->mm, addr);
151 do {
152 next = pgd_addr_end(addr, end);
153 if (pgd_none_or_clear_bad(pgd)) {
154 if (walk->pte_hole)
155 err = walk->pte_hole(addr, next, walk);
156 if (err)
157 break;
158 continue;
159 }
160 if (walk->pmd_entry || walk->pte_entry)
161 err = walk_p4d_range(pgd, addr, next, walk);
162 if (err)
163 break;
164 } while (pgd++, addr = next, addr != end);
165
166 return err;
167}
168
169#ifdef CONFIG_HUGETLB_PAGE
170static unsigned long hugetlb_entry_end(struct hstate *h, unsigned long addr,
171 unsigned long end)
172{
173 unsigned long boundary = (addr & huge_page_mask(h)) + huge_page_size(h);
174 return boundary < end ? boundary : end;
175}
176
177static int walk_hugetlb_range(unsigned long addr, unsigned long end,
178 struct mm_walk *walk)
179{
180 struct vm_area_struct *vma = walk->vma;
181 struct hstate *h = hstate_vma(vma);
182 unsigned long next;
183 unsigned long hmask = huge_page_mask(h);
184 unsigned long sz = huge_page_size(h);
185 pte_t *pte;
186 int err = 0;
187
188 do {
189 next = hugetlb_entry_end(h, addr, end);
190 pte = huge_pte_offset(walk->mm, addr & hmask, sz);
191
192 if (pte)
193 err = walk->hugetlb_entry(pte, hmask, addr, next, walk);
194 else if (walk->pte_hole)
195 err = walk->pte_hole(addr, next, walk);
196
197 if (err)
198 break;
199 } while (addr = next, addr != end);
200
201 return err;
202}
203
204#else /* CONFIG_HUGETLB_PAGE */
205static int walk_hugetlb_range(unsigned long addr, unsigned long end,
206 struct mm_walk *walk)
207{
208 return 0;
209}
210
211#endif /* CONFIG_HUGETLB_PAGE */
212
213/*
214 * Decide whether we really walk over the current vma on [@start, @end)
215 * or skip it via the returned value. Return 0 if we do walk over the
216 * current vma, and return 1 if we skip the vma. Negative values means
217 * error, where we abort the current walk.
218 */
219static int walk_page_test(unsigned long start, unsigned long end,
220 struct mm_walk *walk)
221{
222 struct vm_area_struct *vma = walk->vma;
223
224 if (walk->test_walk)
225 return walk->test_walk(start, end, walk);
226
227 /*
228 * vma(VM_PFNMAP) doesn't have any valid struct pages behind VM_PFNMAP
229 * range, so we don't walk over it as we do for normal vmas. However,
230 * Some callers are interested in handling hole range and they don't
231 * want to just ignore any single address range. Such users certainly
232 * define their ->pte_hole() callbacks, so let's delegate them to handle
233 * vma(VM_PFNMAP).
234 */
235 if (vma->vm_flags & VM_PFNMAP) {
236 int err = 1;
237 if (walk->pte_hole)
238 err = walk->pte_hole(start, end, walk);
239 return err ? err : 1;
240 }
241 return 0;
242}
243
244static int __walk_page_range(unsigned long start, unsigned long end,
245 struct mm_walk *walk)
246{
247 int err = 0;
248 struct vm_area_struct *vma = walk->vma;
249
250 if (vma && is_vm_hugetlb_page(vma)) {
251 if (walk->hugetlb_entry)
252 err = walk_hugetlb_range(start, end, walk);
253 } else
254 err = walk_pgd_range(start, end, walk);
255
256 return err;
257}
258
259/**
260 * walk_page_range - walk page table with caller specific callbacks
261 * @start: start address of the virtual address range
262 * @end: end address of the virtual address range
263 * @walk: mm_walk structure defining the callbacks and the target address space
264 *
265 * Recursively walk the page table tree of the process represented by @walk->mm
266 * within the virtual address range [@start, @end). During walking, we can do
267 * some caller-specific works for each entry, by setting up pmd_entry(),
268 * pte_entry(), and/or hugetlb_entry(). If you don't set up for some of these
269 * callbacks, the associated entries/pages are just ignored.
270 * The return values of these callbacks are commonly defined like below:
271 *
272 * - 0 : succeeded to handle the current entry, and if you don't reach the
273 * end address yet, continue to walk.
274 * - >0 : succeeded to handle the current entry, and return to the caller
275 * with caller specific value.
276 * - <0 : failed to handle the current entry, and return to the caller
277 * with error code.
278 *
279 * Before starting to walk page table, some callers want to check whether
280 * they really want to walk over the current vma, typically by checking
281 * its vm_flags. walk_page_test() and @walk->test_walk() are used for this
282 * purpose.
283 *
284 * struct mm_walk keeps current values of some common data like vma and pmd,
285 * which are useful for the access from callbacks. If you want to pass some
286 * caller-specific data to callbacks, @walk->private should be helpful.
287 *
288 * Locking:
289 * Callers of walk_page_range() and walk_page_vma() should hold
290 * @walk->mm->mmap_sem, because these function traverse vma list and/or
291 * access to vma's data.
292 */
293int walk_page_range(unsigned long start, unsigned long end,
294 struct mm_walk *walk)
295{
296 int err = 0;
297 unsigned long next;
298 struct vm_area_struct *vma;
299
300 if (start >= end)
301 return -EINVAL;
302
303 if (!walk->mm)
304 return -EINVAL;
305
306 VM_BUG_ON_MM(!rwsem_is_locked(&walk->mm->mmap_sem), walk->mm);
307
308 vma = find_vma(walk->mm, start);
309 do {
310 if (!vma) { /* after the last vma */
311 walk->vma = NULL;
312 next = end;
313 } else if (start < vma->vm_start) { /* outside vma */
314 walk->vma = NULL;
315 next = min(end, vma->vm_start);
316 } else { /* inside vma */
317 walk->vma = vma;
318 next = min(end, vma->vm_end);
319 vma = vma->vm_next;
320
321 err = walk_page_test(start, next, walk);
322 if (err > 0) {
323 /*
324 * positive return values are purely for
325 * controlling the pagewalk, so should never
326 * be passed to the callers.
327 */
328 err = 0;
329 continue;
330 }
331 if (err < 0)
332 break;
333 }
334 if (walk->vma || walk->pte_hole)
335 err = __walk_page_range(start, next, walk);
336 if (err)
337 break;
338 } while (start = next, start < end);
339 return err;
340}
341
342int walk_page_vma(struct vm_area_struct *vma, struct mm_walk *walk)
343{
344 int err;
345
346 if (!walk->mm)
347 return -EINVAL;
348
349 VM_BUG_ON(!rwsem_is_locked(&walk->mm->mmap_sem));
350 VM_BUG_ON(!vma);
351 walk->vma = vma;
352 err = walk_page_test(vma->vm_start, vma->vm_end, walk);
353 if (err > 0)
354 return 0;
355 if (err < 0)
356 return err;
357 return __walk_page_range(vma->vm_start, vma->vm_end, walk);
358}
1// SPDX-License-Identifier: GPL-2.0
2#include <linux/pagewalk.h>
3#include <linux/highmem.h>
4#include <linux/sched.h>
5#include <linux/hugetlb.h>
6#include <linux/mmu_context.h>
7#include <linux/swap.h>
8#include <linux/swapops.h>
9
10#include <asm/tlbflush.h>
11
12#include "internal.h"
13
14/*
15 * We want to know the real level where a entry is located ignoring any
16 * folding of levels which may be happening. For example if p4d is folded then
17 * a missing entry found at level 1 (p4d) is actually at level 0 (pgd).
18 */
19static int real_depth(int depth)
20{
21 if (depth == 3 && PTRS_PER_PMD == 1)
22 depth = 2;
23 if (depth == 2 && PTRS_PER_PUD == 1)
24 depth = 1;
25 if (depth == 1 && PTRS_PER_P4D == 1)
26 depth = 0;
27 return depth;
28}
29
30static int walk_pte_range_inner(pte_t *pte, unsigned long addr,
31 unsigned long end, struct mm_walk *walk)
32{
33 const struct mm_walk_ops *ops = walk->ops;
34 int err = 0;
35
36 for (;;) {
37 if (ops->install_pte && pte_none(ptep_get(pte))) {
38 pte_t new_pte;
39
40 err = ops->install_pte(addr, addr + PAGE_SIZE, &new_pte,
41 walk);
42 if (err)
43 break;
44
45 set_pte_at(walk->mm, addr, pte, new_pte);
46 /* Non-present before, so for arches that need it. */
47 if (!WARN_ON_ONCE(walk->no_vma))
48 update_mmu_cache(walk->vma, addr, pte);
49 } else {
50 err = ops->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
51 if (err)
52 break;
53 }
54 if (addr >= end - PAGE_SIZE)
55 break;
56 addr += PAGE_SIZE;
57 pte++;
58 }
59 return err;
60}
61
62static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
63 struct mm_walk *walk)
64{
65 pte_t *pte;
66 int err = 0;
67 spinlock_t *ptl;
68
69 if (walk->no_vma) {
70 /*
71 * pte_offset_map() might apply user-specific validation.
72 * Indeed, on x86_64 the pmd entries set up by init_espfix_ap()
73 * fit its pmd_bad() check (_PAGE_NX set and _PAGE_RW clear),
74 * and CONFIG_EFI_PGT_DUMP efi_mm goes so far as to walk them.
75 */
76 if (walk->mm == &init_mm || addr >= TASK_SIZE)
77 pte = pte_offset_kernel(pmd, addr);
78 else
79 pte = pte_offset_map(pmd, addr);
80 if (pte) {
81 err = walk_pte_range_inner(pte, addr, end, walk);
82 if (walk->mm != &init_mm && addr < TASK_SIZE)
83 pte_unmap(pte);
84 }
85 } else {
86 pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
87 if (pte) {
88 err = walk_pte_range_inner(pte, addr, end, walk);
89 pte_unmap_unlock(pte, ptl);
90 }
91 }
92 if (!pte)
93 walk->action = ACTION_AGAIN;
94 return err;
95}
96
97static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
98 struct mm_walk *walk)
99{
100 pmd_t *pmd;
101 unsigned long next;
102 const struct mm_walk_ops *ops = walk->ops;
103 bool has_handler = ops->pte_entry;
104 bool has_install = ops->install_pte;
105 int err = 0;
106 int depth = real_depth(3);
107
108 pmd = pmd_offset(pud, addr);
109 do {
110again:
111 next = pmd_addr_end(addr, end);
112 if (pmd_none(*pmd)) {
113 if (has_install)
114 err = __pte_alloc(walk->mm, pmd);
115 else if (ops->pte_hole)
116 err = ops->pte_hole(addr, next, depth, walk);
117 if (err)
118 break;
119 if (!has_install)
120 continue;
121 }
122
123 walk->action = ACTION_SUBTREE;
124
125 /*
126 * This implies that each ->pmd_entry() handler
127 * needs to know about pmd_trans_huge() pmds
128 */
129 if (ops->pmd_entry)
130 err = ops->pmd_entry(pmd, addr, next, walk);
131 if (err)
132 break;
133
134 if (walk->action == ACTION_AGAIN)
135 goto again;
136 if (walk->action == ACTION_CONTINUE)
137 continue;
138
139 if (!has_handler) { /* No handlers for lower page tables. */
140 if (!has_install)
141 continue; /* Nothing to do. */
142 /*
143 * We are ONLY installing, so avoid unnecessarily
144 * splitting a present huge page.
145 */
146 if (pmd_present(*pmd) &&
147 (pmd_trans_huge(*pmd) || pmd_devmap(*pmd)))
148 continue;
149 }
150
151 if (walk->vma)
152 split_huge_pmd(walk->vma, pmd, addr);
153 else if (pmd_leaf(*pmd) || !pmd_present(*pmd))
154 continue; /* Nothing to do. */
155
156 err = walk_pte_range(pmd, addr, next, walk);
157 if (err)
158 break;
159
160 if (walk->action == ACTION_AGAIN)
161 goto again;
162
163 } while (pmd++, addr = next, addr != end);
164
165 return err;
166}
167
168static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
169 struct mm_walk *walk)
170{
171 pud_t *pud;
172 unsigned long next;
173 const struct mm_walk_ops *ops = walk->ops;
174 bool has_handler = ops->pmd_entry || ops->pte_entry;
175 bool has_install = ops->install_pte;
176 int err = 0;
177 int depth = real_depth(2);
178
179 pud = pud_offset(p4d, addr);
180 do {
181 again:
182 next = pud_addr_end(addr, end);
183 if (pud_none(*pud)) {
184 if (has_install)
185 err = __pmd_alloc(walk->mm, pud, addr);
186 else if (ops->pte_hole)
187 err = ops->pte_hole(addr, next, depth, walk);
188 if (err)
189 break;
190 if (!has_install)
191 continue;
192 }
193
194 walk->action = ACTION_SUBTREE;
195
196 if (ops->pud_entry)
197 err = ops->pud_entry(pud, addr, next, walk);
198 if (err)
199 break;
200
201 if (walk->action == ACTION_AGAIN)
202 goto again;
203 if (walk->action == ACTION_CONTINUE)
204 continue;
205
206 if (!has_handler) { /* No handlers for lower page tables. */
207 if (!has_install)
208 continue; /* Nothing to do. */
209 /*
210 * We are ONLY installing, so avoid unnecessarily
211 * splitting a present huge page.
212 */
213 if (pud_present(*pud) &&
214 (pud_trans_huge(*pud) || pud_devmap(*pud)))
215 continue;
216 }
217
218 if (walk->vma)
219 split_huge_pud(walk->vma, pud, addr);
220 else if (pud_leaf(*pud) || !pud_present(*pud))
221 continue; /* Nothing to do. */
222
223 if (pud_none(*pud))
224 goto again;
225
226 err = walk_pmd_range(pud, addr, next, walk);
227 if (err)
228 break;
229 } while (pud++, addr = next, addr != end);
230
231 return err;
232}
233
234static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
235 struct mm_walk *walk)
236{
237 p4d_t *p4d;
238 unsigned long next;
239 const struct mm_walk_ops *ops = walk->ops;
240 bool has_handler = ops->pud_entry || ops->pmd_entry || ops->pte_entry;
241 bool has_install = ops->install_pte;
242 int err = 0;
243 int depth = real_depth(1);
244
245 p4d = p4d_offset(pgd, addr);
246 do {
247 next = p4d_addr_end(addr, end);
248 if (p4d_none_or_clear_bad(p4d)) {
249 if (has_install)
250 err = __pud_alloc(walk->mm, p4d, addr);
251 else if (ops->pte_hole)
252 err = ops->pte_hole(addr, next, depth, walk);
253 if (err)
254 break;
255 if (!has_install)
256 continue;
257 }
258 if (ops->p4d_entry) {
259 err = ops->p4d_entry(p4d, addr, next, walk);
260 if (err)
261 break;
262 }
263 if (has_handler || has_install)
264 err = walk_pud_range(p4d, addr, next, walk);
265 if (err)
266 break;
267 } while (p4d++, addr = next, addr != end);
268
269 return err;
270}
271
272static int walk_pgd_range(unsigned long addr, unsigned long end,
273 struct mm_walk *walk)
274{
275 pgd_t *pgd;
276 unsigned long next;
277 const struct mm_walk_ops *ops = walk->ops;
278 bool has_handler = ops->p4d_entry || ops->pud_entry || ops->pmd_entry ||
279 ops->pte_entry;
280 bool has_install = ops->install_pte;
281 int err = 0;
282
283 if (walk->pgd)
284 pgd = walk->pgd + pgd_index(addr);
285 else
286 pgd = pgd_offset(walk->mm, addr);
287 do {
288 next = pgd_addr_end(addr, end);
289 if (pgd_none_or_clear_bad(pgd)) {
290 if (has_install)
291 err = __p4d_alloc(walk->mm, pgd, addr);
292 else if (ops->pte_hole)
293 err = ops->pte_hole(addr, next, 0, walk);
294 if (err)
295 break;
296 if (!has_install)
297 continue;
298 }
299 if (ops->pgd_entry) {
300 err = ops->pgd_entry(pgd, addr, next, walk);
301 if (err)
302 break;
303 }
304 if (has_handler || has_install)
305 err = walk_p4d_range(pgd, addr, next, walk);
306 if (err)
307 break;
308 } while (pgd++, addr = next, addr != end);
309
310 return err;
311}
312
313#ifdef CONFIG_HUGETLB_PAGE
314static unsigned long hugetlb_entry_end(struct hstate *h, unsigned long addr,
315 unsigned long end)
316{
317 unsigned long boundary = (addr & huge_page_mask(h)) + huge_page_size(h);
318 return boundary < end ? boundary : end;
319}
320
321static int walk_hugetlb_range(unsigned long addr, unsigned long end,
322 struct mm_walk *walk)
323{
324 struct vm_area_struct *vma = walk->vma;
325 struct hstate *h = hstate_vma(vma);
326 unsigned long next;
327 unsigned long hmask = huge_page_mask(h);
328 unsigned long sz = huge_page_size(h);
329 pte_t *pte;
330 const struct mm_walk_ops *ops = walk->ops;
331 int err = 0;
332
333 hugetlb_vma_lock_read(vma);
334 do {
335 next = hugetlb_entry_end(h, addr, end);
336 pte = hugetlb_walk(vma, addr & hmask, sz);
337 if (pte)
338 err = ops->hugetlb_entry(pte, hmask, addr, next, walk);
339 else if (ops->pte_hole)
340 err = ops->pte_hole(addr, next, -1, walk);
341 if (err)
342 break;
343 } while (addr = next, addr != end);
344 hugetlb_vma_unlock_read(vma);
345
346 return err;
347}
348
349#else /* CONFIG_HUGETLB_PAGE */
350static int walk_hugetlb_range(unsigned long addr, unsigned long end,
351 struct mm_walk *walk)
352{
353 return 0;
354}
355
356#endif /* CONFIG_HUGETLB_PAGE */
357
358/*
359 * Decide whether we really walk over the current vma on [@start, @end)
360 * or skip it via the returned value. Return 0 if we do walk over the
361 * current vma, and return 1 if we skip the vma. Negative values means
362 * error, where we abort the current walk.
363 */
364static int walk_page_test(unsigned long start, unsigned long end,
365 struct mm_walk *walk)
366{
367 struct vm_area_struct *vma = walk->vma;
368 const struct mm_walk_ops *ops = walk->ops;
369
370 if (ops->test_walk)
371 return ops->test_walk(start, end, walk);
372
373 /*
374 * vma(VM_PFNMAP) doesn't have any valid struct pages behind VM_PFNMAP
375 * range, so we don't walk over it as we do for normal vmas. However,
376 * Some callers are interested in handling hole range and they don't
377 * want to just ignore any single address range. Such users certainly
378 * define their ->pte_hole() callbacks, so let's delegate them to handle
379 * vma(VM_PFNMAP).
380 */
381 if (vma->vm_flags & VM_PFNMAP) {
382 int err = 1;
383 if (ops->pte_hole)
384 err = ops->pte_hole(start, end, -1, walk);
385 return err ? err : 1;
386 }
387 return 0;
388}
389
390static int __walk_page_range(unsigned long start, unsigned long end,
391 struct mm_walk *walk)
392{
393 int err = 0;
394 struct vm_area_struct *vma = walk->vma;
395 const struct mm_walk_ops *ops = walk->ops;
396 bool is_hugetlb = is_vm_hugetlb_page(vma);
397
398 /* We do not support hugetlb PTE installation. */
399 if (ops->install_pte && is_hugetlb)
400 return -EINVAL;
401
402 if (ops->pre_vma) {
403 err = ops->pre_vma(start, end, walk);
404 if (err)
405 return err;
406 }
407
408 if (is_hugetlb) {
409 if (ops->hugetlb_entry)
410 err = walk_hugetlb_range(start, end, walk);
411 } else
412 err = walk_pgd_range(start, end, walk);
413
414 if (ops->post_vma)
415 ops->post_vma(walk);
416
417 return err;
418}
419
420static inline void process_mm_walk_lock(struct mm_struct *mm,
421 enum page_walk_lock walk_lock)
422{
423 if (walk_lock == PGWALK_RDLOCK)
424 mmap_assert_locked(mm);
425 else
426 mmap_assert_write_locked(mm);
427}
428
429static inline void process_vma_walk_lock(struct vm_area_struct *vma,
430 enum page_walk_lock walk_lock)
431{
432#ifdef CONFIG_PER_VMA_LOCK
433 switch (walk_lock) {
434 case PGWALK_WRLOCK:
435 vma_start_write(vma);
436 break;
437 case PGWALK_WRLOCK_VERIFY:
438 vma_assert_write_locked(vma);
439 break;
440 case PGWALK_RDLOCK:
441 /* PGWALK_RDLOCK is handled by process_mm_walk_lock */
442 break;
443 }
444#endif
445}
446
447/*
448 * See the comment for walk_page_range(), this performs the heavy lifting of the
449 * operation, only sets no restrictions on how the walk proceeds.
450 *
451 * We usually restrict the ability to install PTEs, but this functionality is
452 * available to internal memory management code and provided in mm/internal.h.
453 */
454int walk_page_range_mm(struct mm_struct *mm, unsigned long start,
455 unsigned long end, const struct mm_walk_ops *ops,
456 void *private)
457{
458 int err = 0;
459 unsigned long next;
460 struct vm_area_struct *vma;
461 struct mm_walk walk = {
462 .ops = ops,
463 .mm = mm,
464 .private = private,
465 };
466
467 if (start >= end)
468 return -EINVAL;
469
470 if (!walk.mm)
471 return -EINVAL;
472
473 process_mm_walk_lock(walk.mm, ops->walk_lock);
474
475 vma = find_vma(walk.mm, start);
476 do {
477 if (!vma) { /* after the last vma */
478 walk.vma = NULL;
479 next = end;
480 if (ops->pte_hole)
481 err = ops->pte_hole(start, next, -1, &walk);
482 } else if (start < vma->vm_start) { /* outside vma */
483 walk.vma = NULL;
484 next = min(end, vma->vm_start);
485 if (ops->pte_hole)
486 err = ops->pte_hole(start, next, -1, &walk);
487 } else { /* inside vma */
488 process_vma_walk_lock(vma, ops->walk_lock);
489 walk.vma = vma;
490 next = min(end, vma->vm_end);
491 vma = find_vma(mm, vma->vm_end);
492
493 err = walk_page_test(start, next, &walk);
494 if (err > 0) {
495 /*
496 * positive return values are purely for
497 * controlling the pagewalk, so should never
498 * be passed to the callers.
499 */
500 err = 0;
501 continue;
502 }
503 if (err < 0)
504 break;
505 err = __walk_page_range(start, next, &walk);
506 }
507 if (err)
508 break;
509 } while (start = next, start < end);
510 return err;
511}
512
513/*
514 * Determine if the walk operations specified are permitted to be used for a
515 * page table walk.
516 *
517 * This check is performed on all functions which are parameterised by walk
518 * operations and exposed in include/linux/pagewalk.h.
519 *
520 * Internal memory management code can use the walk_page_range_mm() function to
521 * be able to use all page walking operations.
522 */
523static bool check_ops_valid(const struct mm_walk_ops *ops)
524{
525 /*
526 * The installation of PTEs is solely under the control of memory
527 * management logic and subject to many subtle locking, security and
528 * cache considerations so we cannot permit other users to do so, and
529 * certainly not for exported symbols.
530 */
531 if (ops->install_pte)
532 return false;
533
534 return true;
535}
536
537/**
538 * walk_page_range - walk page table with caller specific callbacks
539 * @mm: mm_struct representing the target process of page table walk
540 * @start: start address of the virtual address range
541 * @end: end address of the virtual address range
542 * @ops: operation to call during the walk
543 * @private: private data for callbacks' usage
544 *
545 * Recursively walk the page table tree of the process represented by @mm
546 * within the virtual address range [@start, @end). During walking, we can do
547 * some caller-specific works for each entry, by setting up pmd_entry(),
548 * pte_entry(), and/or hugetlb_entry(). If you don't set up for some of these
549 * callbacks, the associated entries/pages are just ignored.
550 * The return values of these callbacks are commonly defined like below:
551 *
552 * - 0 : succeeded to handle the current entry, and if you don't reach the
553 * end address yet, continue to walk.
554 * - >0 : succeeded to handle the current entry, and return to the caller
555 * with caller specific value.
556 * - <0 : failed to handle the current entry, and return to the caller
557 * with error code.
558 *
559 * Before starting to walk page table, some callers want to check whether
560 * they really want to walk over the current vma, typically by checking
561 * its vm_flags. walk_page_test() and @ops->test_walk() are used for this
562 * purpose.
563 *
564 * If operations need to be staged before and committed after a vma is walked,
565 * there are two callbacks, pre_vma() and post_vma(). Note that post_vma(),
566 * since it is intended to handle commit-type operations, can't return any
567 * errors.
568 *
569 * struct mm_walk keeps current values of some common data like vma and pmd,
570 * which are useful for the access from callbacks. If you want to pass some
571 * caller-specific data to callbacks, @private should be helpful.
572 *
573 * Locking:
574 * Callers of walk_page_range() and walk_page_vma() should hold @mm->mmap_lock,
575 * because these function traverse vma list and/or access to vma's data.
576 */
577int walk_page_range(struct mm_struct *mm, unsigned long start,
578 unsigned long end, const struct mm_walk_ops *ops,
579 void *private)
580{
581 if (!check_ops_valid(ops))
582 return -EINVAL;
583
584 return walk_page_range_mm(mm, start, end, ops, private);
585}
586
587/**
588 * walk_page_range_novma - walk a range of pagetables not backed by a vma
589 * @mm: mm_struct representing the target process of page table walk
590 * @start: start address of the virtual address range
591 * @end: end address of the virtual address range
592 * @ops: operation to call during the walk
593 * @pgd: pgd to walk if different from mm->pgd
594 * @private: private data for callbacks' usage
595 *
596 * Similar to walk_page_range() but can walk any page tables even if they are
597 * not backed by VMAs. Because 'unusual' entries may be walked this function
598 * will also not lock the PTEs for the pte_entry() callback. This is useful for
599 * walking the kernel pages tables or page tables for firmware.
600 *
601 * Note: Be careful to walk the kernel pages tables, the caller may be need to
602 * take other effective approaches (mmap lock may be insufficient) to prevent
603 * the intermediate kernel page tables belonging to the specified address range
604 * from being freed (e.g. memory hot-remove).
605 */
606int walk_page_range_novma(struct mm_struct *mm, unsigned long start,
607 unsigned long end, const struct mm_walk_ops *ops,
608 pgd_t *pgd,
609 void *private)
610{
611 struct mm_walk walk = {
612 .ops = ops,
613 .mm = mm,
614 .pgd = pgd,
615 .private = private,
616 .no_vma = true
617 };
618
619 if (start >= end || !walk.mm)
620 return -EINVAL;
621 if (!check_ops_valid(ops))
622 return -EINVAL;
623
624 /*
625 * 1) For walking the user virtual address space:
626 *
627 * The mmap lock protects the page walker from changes to the page
628 * tables during the walk. However a read lock is insufficient to
629 * protect those areas which don't have a VMA as munmap() detaches
630 * the VMAs before downgrading to a read lock and actually tearing
631 * down PTEs/page tables. In which case, the mmap write lock should
632 * be hold.
633 *
634 * 2) For walking the kernel virtual address space:
635 *
636 * The kernel intermediate page tables usually do not be freed, so
637 * the mmap map read lock is sufficient. But there are some exceptions.
638 * E.g. memory hot-remove. In which case, the mmap lock is insufficient
639 * to prevent the intermediate kernel pages tables belonging to the
640 * specified address range from being freed. The caller should take
641 * other actions to prevent this race.
642 */
643 if (mm == &init_mm)
644 mmap_assert_locked(walk.mm);
645 else
646 mmap_assert_write_locked(walk.mm);
647
648 return walk_pgd_range(start, end, &walk);
649}
650
651int walk_page_range_vma(struct vm_area_struct *vma, unsigned long start,
652 unsigned long end, const struct mm_walk_ops *ops,
653 void *private)
654{
655 struct mm_walk walk = {
656 .ops = ops,
657 .mm = vma->vm_mm,
658 .vma = vma,
659 .private = private,
660 };
661
662 if (start >= end || !walk.mm)
663 return -EINVAL;
664 if (start < vma->vm_start || end > vma->vm_end)
665 return -EINVAL;
666 if (!check_ops_valid(ops))
667 return -EINVAL;
668
669 process_mm_walk_lock(walk.mm, ops->walk_lock);
670 process_vma_walk_lock(vma, ops->walk_lock);
671 return __walk_page_range(start, end, &walk);
672}
673
674int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
675 void *private)
676{
677 struct mm_walk walk = {
678 .ops = ops,
679 .mm = vma->vm_mm,
680 .vma = vma,
681 .private = private,
682 };
683
684 if (!walk.mm)
685 return -EINVAL;
686 if (!check_ops_valid(ops))
687 return -EINVAL;
688
689 process_mm_walk_lock(walk.mm, ops->walk_lock);
690 process_vma_walk_lock(vma, ops->walk_lock);
691 return __walk_page_range(vma->vm_start, vma->vm_end, &walk);
692}
693
694/**
695 * walk_page_mapping - walk all memory areas mapped into a struct address_space.
696 * @mapping: Pointer to the struct address_space
697 * @first_index: First page offset in the address_space
698 * @nr: Number of incremental page offsets to cover
699 * @ops: operation to call during the walk
700 * @private: private data for callbacks' usage
701 *
702 * This function walks all memory areas mapped into a struct address_space.
703 * The walk is limited to only the given page-size index range, but if
704 * the index boundaries cross a huge page-table entry, that entry will be
705 * included.
706 *
707 * Also see walk_page_range() for additional information.
708 *
709 * Locking:
710 * This function can't require that the struct mm_struct::mmap_lock is held,
711 * since @mapping may be mapped by multiple processes. Instead
712 * @mapping->i_mmap_rwsem must be held. This might have implications in the
713 * callbacks, and it's up tho the caller to ensure that the
714 * struct mm_struct::mmap_lock is not needed.
715 *
716 * Also this means that a caller can't rely on the struct
717 * vm_area_struct::vm_flags to be constant across a call,
718 * except for immutable flags. Callers requiring this shouldn't use
719 * this function.
720 *
721 * Return: 0 on success, negative error code on failure, positive number on
722 * caller defined premature termination.
723 */
724int walk_page_mapping(struct address_space *mapping, pgoff_t first_index,
725 pgoff_t nr, const struct mm_walk_ops *ops,
726 void *private)
727{
728 struct mm_walk walk = {
729 .ops = ops,
730 .private = private,
731 };
732 struct vm_area_struct *vma;
733 pgoff_t vba, vea, cba, cea;
734 unsigned long start_addr, end_addr;
735 int err = 0;
736
737 if (!check_ops_valid(ops))
738 return -EINVAL;
739
740 lockdep_assert_held(&mapping->i_mmap_rwsem);
741 vma_interval_tree_foreach(vma, &mapping->i_mmap, first_index,
742 first_index + nr - 1) {
743 /* Clip to the vma */
744 vba = vma->vm_pgoff;
745 vea = vba + vma_pages(vma);
746 cba = first_index;
747 cba = max(cba, vba);
748 cea = first_index + nr;
749 cea = min(cea, vea);
750
751 start_addr = ((cba - vba) << PAGE_SHIFT) + vma->vm_start;
752 end_addr = ((cea - vba) << PAGE_SHIFT) + vma->vm_start;
753 if (start_addr >= end_addr)
754 continue;
755
756 walk.vma = vma;
757 walk.mm = vma->vm_mm;
758
759 err = walk_page_test(vma->vm_start, vma->vm_end, &walk);
760 if (err > 0) {
761 err = 0;
762 break;
763 } else if (err < 0)
764 break;
765
766 err = __walk_page_range(start_addr, end_addr, &walk);
767 if (err)
768 break;
769 }
770
771 return err;
772}
773
774/**
775 * folio_walk_start - walk the page tables to a folio
776 * @fw: filled with information on success.
777 * @vma: the VMA.
778 * @addr: the virtual address to use for the page table walk.
779 * @flags: flags modifying which folios to walk to.
780 *
781 * Walk the page tables using @addr in a given @vma to a mapped folio and
782 * return the folio, making sure that the page table entry referenced by
783 * @addr cannot change until folio_walk_end() was called.
784 *
785 * As default, this function returns only folios that are not special (e.g., not
786 * the zeropage) and never returns folios that are supposed to be ignored by the
787 * VM as documented by vm_normal_page(). If requested, zeropages will be
788 * returned as well.
789 *
790 * As default, this function only considers present page table entries.
791 * If requested, it will also consider migration entries.
792 *
793 * If this function returns NULL it might either indicate "there is nothing" or
794 * "there is nothing suitable".
795 *
796 * On success, @fw is filled and the function returns the folio while the PTL
797 * is still held and folio_walk_end() must be called to clean up,
798 * releasing any held locks. The returned folio must *not* be used after the
799 * call to folio_walk_end(), unless a short-term folio reference is taken before
800 * that call.
801 *
802 * @fw->page will correspond to the page that is effectively referenced by
803 * @addr. However, for migration entries and shared zeropages @fw->page is
804 * set to NULL. Note that large folios might be mapped by multiple page table
805 * entries, and this function will always only lookup a single entry as
806 * specified by @addr, which might or might not cover more than a single page of
807 * the returned folio.
808 *
809 * This function must *not* be used as a naive replacement for
810 * get_user_pages() / pin_user_pages(), especially not to perform DMA or
811 * to carelessly modify page content. This function may *only* be used to grab
812 * short-term folio references, never to grab long-term folio references.
813 *
814 * Using the page table entry pointers in @fw for reading or modifying the
815 * entry should be avoided where possible: however, there might be valid
816 * use cases.
817 *
818 * WARNING: Modifying page table entries in hugetlb VMAs requires a lot of care.
819 * For example, PMD page table sharing might require prior unsharing. Also,
820 * logical hugetlb entries might span multiple physical page table entries,
821 * which *must* be modified in a single operation (set_huge_pte_at(),
822 * huge_ptep_set_*, ...). Note that the page table entry stored in @fw might
823 * not correspond to the first physical entry of a logical hugetlb entry.
824 *
825 * The mmap lock must be held in read mode.
826 *
827 * Return: folio pointer on success, otherwise NULL.
828 */
829struct folio *folio_walk_start(struct folio_walk *fw,
830 struct vm_area_struct *vma, unsigned long addr,
831 folio_walk_flags_t flags)
832{
833 unsigned long entry_size;
834 bool expose_page = true;
835 struct page *page;
836 pud_t *pudp, pud;
837 pmd_t *pmdp, pmd;
838 pte_t *ptep, pte;
839 spinlock_t *ptl;
840 pgd_t *pgdp;
841 p4d_t *p4dp;
842
843 mmap_assert_locked(vma->vm_mm);
844 vma_pgtable_walk_begin(vma);
845
846 if (WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end))
847 goto not_found;
848
849 pgdp = pgd_offset(vma->vm_mm, addr);
850 if (pgd_none_or_clear_bad(pgdp))
851 goto not_found;
852
853 p4dp = p4d_offset(pgdp, addr);
854 if (p4d_none_or_clear_bad(p4dp))
855 goto not_found;
856
857 pudp = pud_offset(p4dp, addr);
858 pud = pudp_get(pudp);
859 if (pud_none(pud))
860 goto not_found;
861 if (IS_ENABLED(CONFIG_PGTABLE_HAS_HUGE_LEAVES) &&
862 (!pud_present(pud) || pud_leaf(pud))) {
863 ptl = pud_lock(vma->vm_mm, pudp);
864 pud = pudp_get(pudp);
865
866 entry_size = PUD_SIZE;
867 fw->level = FW_LEVEL_PUD;
868 fw->pudp = pudp;
869 fw->pud = pud;
870
871 /*
872 * TODO: FW_MIGRATION support for PUD migration entries
873 * once there are relevant users.
874 */
875 if (!pud_present(pud) || pud_devmap(pud) || pud_special(pud)) {
876 spin_unlock(ptl);
877 goto not_found;
878 } else if (!pud_leaf(pud)) {
879 spin_unlock(ptl);
880 goto pmd_table;
881 }
882 /*
883 * TODO: vm_normal_page_pud() will be handy once we want to
884 * support PUD mappings in VM_PFNMAP|VM_MIXEDMAP VMAs.
885 */
886 page = pud_page(pud);
887 goto found;
888 }
889
890pmd_table:
891 VM_WARN_ON_ONCE(!pud_present(pud) || pud_leaf(pud));
892 pmdp = pmd_offset(pudp, addr);
893 pmd = pmdp_get_lockless(pmdp);
894 if (pmd_none(pmd))
895 goto not_found;
896 if (IS_ENABLED(CONFIG_PGTABLE_HAS_HUGE_LEAVES) &&
897 (!pmd_present(pmd) || pmd_leaf(pmd))) {
898 ptl = pmd_lock(vma->vm_mm, pmdp);
899 pmd = pmdp_get(pmdp);
900
901 entry_size = PMD_SIZE;
902 fw->level = FW_LEVEL_PMD;
903 fw->pmdp = pmdp;
904 fw->pmd = pmd;
905
906 if (pmd_none(pmd)) {
907 spin_unlock(ptl);
908 goto not_found;
909 } else if (pmd_present(pmd) && !pmd_leaf(pmd)) {
910 spin_unlock(ptl);
911 goto pte_table;
912 } else if (pmd_present(pmd)) {
913 page = vm_normal_page_pmd(vma, addr, pmd);
914 if (page) {
915 goto found;
916 } else if ((flags & FW_ZEROPAGE) &&
917 is_huge_zero_pmd(pmd)) {
918 page = pfn_to_page(pmd_pfn(pmd));
919 expose_page = false;
920 goto found;
921 }
922 } else if ((flags & FW_MIGRATION) &&
923 is_pmd_migration_entry(pmd)) {
924 swp_entry_t entry = pmd_to_swp_entry(pmd);
925
926 page = pfn_swap_entry_to_page(entry);
927 expose_page = false;
928 goto found;
929 }
930 spin_unlock(ptl);
931 goto not_found;
932 }
933
934pte_table:
935 VM_WARN_ON_ONCE(!pmd_present(pmd) || pmd_leaf(pmd));
936 ptep = pte_offset_map_lock(vma->vm_mm, pmdp, addr, &ptl);
937 if (!ptep)
938 goto not_found;
939 pte = ptep_get(ptep);
940
941 entry_size = PAGE_SIZE;
942 fw->level = FW_LEVEL_PTE;
943 fw->ptep = ptep;
944 fw->pte = pte;
945
946 if (pte_present(pte)) {
947 page = vm_normal_page(vma, addr, pte);
948 if (page)
949 goto found;
950 if ((flags & FW_ZEROPAGE) &&
951 is_zero_pfn(pte_pfn(pte))) {
952 page = pfn_to_page(pte_pfn(pte));
953 expose_page = false;
954 goto found;
955 }
956 } else if (!pte_none(pte)) {
957 swp_entry_t entry = pte_to_swp_entry(pte);
958
959 if ((flags & FW_MIGRATION) &&
960 is_migration_entry(entry)) {
961 page = pfn_swap_entry_to_page(entry);
962 expose_page = false;
963 goto found;
964 }
965 }
966 pte_unmap_unlock(ptep, ptl);
967not_found:
968 vma_pgtable_walk_end(vma);
969 return NULL;
970found:
971 if (expose_page)
972 /* Note: Offset from the mapped page, not the folio start. */
973 fw->page = nth_page(page, (addr & (entry_size - 1)) >> PAGE_SHIFT);
974 else
975 fw->page = NULL;
976 fw->ptl = ptl;
977 return page_folio(page);
978}