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[mirror_ubuntu-bionic-kernel.git] / mm / pagewalk.c
1 #include <linux/mm.h>
2 #include <linux/highmem.h>
3 #include <linux/sched.h>
4 #include <linux/hugetlb.h>
5
6 static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
7 struct mm_walk *walk)
8 {
9 pte_t *pte;
10 int err = 0;
11
12 pte = pte_offset_map(pmd, addr);
13 for (;;) {
14 err = walk->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
15 if (err)
16 break;
17 addr += PAGE_SIZE;
18 if (addr == end)
19 break;
20 pte++;
21 }
22
23 pte_unmap(pte);
24 return err;
25 }
26
27 static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
28 struct mm_walk *walk)
29 {
30 pmd_t *pmd;
31 unsigned long next;
32 int err = 0;
33
34 pmd = pmd_offset(pud, addr);
35 do {
36 again:
37 next = pmd_addr_end(addr, end);
38 if (pmd_none(*pmd) || !walk->vma) {
39 if (walk->pte_hole)
40 err = walk->pte_hole(addr, next, walk);
41 if (err)
42 break;
43 continue;
44 }
45 /*
46 * This implies that each ->pmd_entry() handler
47 * needs to know about pmd_trans_huge() pmds
48 */
49 if (walk->pmd_entry)
50 err = walk->pmd_entry(pmd, addr, next, walk);
51 if (err)
52 break;
53
54 /*
55 * Check this here so we only break down trans_huge
56 * pages when we _need_ to
57 */
58 if (!walk->pte_entry)
59 continue;
60
61 split_huge_pmd(walk->vma, pmd, addr);
62 if (pmd_trans_unstable(pmd))
63 goto again;
64 err = walk_pte_range(pmd, addr, next, walk);
65 if (err)
66 break;
67 } while (pmd++, addr = next, addr != end);
68
69 return err;
70 }
71
72 static int walk_pud_range(pgd_t *pgd, unsigned long addr, unsigned long end,
73 struct mm_walk *walk)
74 {
75 pud_t *pud;
76 unsigned long next;
77 int err = 0;
78
79 pud = pud_offset(pgd, addr);
80 do {
81 next = pud_addr_end(addr, end);
82 if (pud_none_or_clear_bad(pud)) {
83 if (walk->pte_hole)
84 err = walk->pte_hole(addr, next, walk);
85 if (err)
86 break;
87 continue;
88 }
89 if (walk->pmd_entry || walk->pte_entry)
90 err = walk_pmd_range(pud, addr, next, walk);
91 if (err)
92 break;
93 } while (pud++, addr = next, addr != end);
94
95 return err;
96 }
97
98 static int walk_pgd_range(unsigned long addr, unsigned long end,
99 struct mm_walk *walk)
100 {
101 pgd_t *pgd;
102 unsigned long next;
103 int err = 0;
104
105 pgd = pgd_offset(walk->mm, addr);
106 do {
107 next = pgd_addr_end(addr, end);
108 if (pgd_none_or_clear_bad(pgd)) {
109 if (walk->pte_hole)
110 err = walk->pte_hole(addr, next, walk);
111 if (err)
112 break;
113 continue;
114 }
115 if (walk->pmd_entry || walk->pte_entry)
116 err = walk_pud_range(pgd, addr, next, walk);
117 if (err)
118 break;
119 } while (pgd++, addr = next, addr != end);
120
121 return err;
122 }
123
124 #ifdef CONFIG_HUGETLB_PAGE
125 static unsigned long hugetlb_entry_end(struct hstate *h, unsigned long addr,
126 unsigned long end)
127 {
128 unsigned long boundary = (addr & huge_page_mask(h)) + huge_page_size(h);
129 return boundary < end ? boundary : end;
130 }
131
132 static int walk_hugetlb_range(unsigned long addr, unsigned long end,
133 struct mm_walk *walk)
134 {
135 struct vm_area_struct *vma = walk->vma;
136 struct hstate *h = hstate_vma(vma);
137 unsigned long next;
138 unsigned long hmask = huge_page_mask(h);
139 pte_t *pte;
140 int err = 0;
141
142 do {
143 next = hugetlb_entry_end(h, addr, end);
144 pte = huge_pte_offset(walk->mm, addr & hmask);
145 if (pte && walk->hugetlb_entry)
146 err = walk->hugetlb_entry(pte, hmask, addr, next, walk);
147 if (err)
148 break;
149 } while (addr = next, addr != end);
150
151 return err;
152 }
153
154 #else /* CONFIG_HUGETLB_PAGE */
155 static int walk_hugetlb_range(unsigned long addr, unsigned long end,
156 struct mm_walk *walk)
157 {
158 return 0;
159 }
160
161 #endif /* CONFIG_HUGETLB_PAGE */
162
163 /*
164 * Decide whether we really walk over the current vma on [@start, @end)
165 * or skip it via the returned value. Return 0 if we do walk over the
166 * current vma, and return 1 if we skip the vma. Negative values means
167 * error, where we abort the current walk.
168 */
169 static int walk_page_test(unsigned long start, unsigned long end,
170 struct mm_walk *walk)
171 {
172 struct vm_area_struct *vma = walk->vma;
173
174 if (walk->test_walk)
175 return walk->test_walk(start, end, walk);
176
177 /*
178 * vma(VM_PFNMAP) doesn't have any valid struct pages behind VM_PFNMAP
179 * range, so we don't walk over it as we do for normal vmas. However,
180 * Some callers are interested in handling hole range and they don't
181 * want to just ignore any single address range. Such users certainly
182 * define their ->pte_hole() callbacks, so let's delegate them to handle
183 * vma(VM_PFNMAP).
184 */
185 if (vma->vm_flags & VM_PFNMAP) {
186 int err = 1;
187 if (walk->pte_hole)
188 err = walk->pte_hole(start, end, walk);
189 return err ? err : 1;
190 }
191 return 0;
192 }
193
194 static int __walk_page_range(unsigned long start, unsigned long end,
195 struct mm_walk *walk)
196 {
197 int err = 0;
198 struct vm_area_struct *vma = walk->vma;
199
200 if (vma && is_vm_hugetlb_page(vma)) {
201 if (walk->hugetlb_entry)
202 err = walk_hugetlb_range(start, end, walk);
203 } else
204 err = walk_pgd_range(start, end, walk);
205
206 return err;
207 }
208
209 /**
210 * walk_page_range - walk page table with caller specific callbacks
211 *
212 * Recursively walk the page table tree of the process represented by @walk->mm
213 * within the virtual address range [@start, @end). During walking, we can do
214 * some caller-specific works for each entry, by setting up pmd_entry(),
215 * pte_entry(), and/or hugetlb_entry(). If you don't set up for some of these
216 * callbacks, the associated entries/pages are just ignored.
217 * The return values of these callbacks are commonly defined like below:
218 * - 0 : succeeded to handle the current entry, and if you don't reach the
219 * end address yet, continue to walk.
220 * - >0 : succeeded to handle the current entry, and return to the caller
221 * with caller specific value.
222 * - <0 : failed to handle the current entry, and return to the caller
223 * with error code.
224 *
225 * Before starting to walk page table, some callers want to check whether
226 * they really want to walk over the current vma, typically by checking
227 * its vm_flags. walk_page_test() and @walk->test_walk() are used for this
228 * purpose.
229 *
230 * struct mm_walk keeps current values of some common data like vma and pmd,
231 * which are useful for the access from callbacks. If you want to pass some
232 * caller-specific data to callbacks, @walk->private should be helpful.
233 *
234 * Locking:
235 * Callers of walk_page_range() and walk_page_vma() should hold
236 * @walk->mm->mmap_sem, because these function traverse vma list and/or
237 * access to vma's data.
238 */
239 int walk_page_range(unsigned long start, unsigned long end,
240 struct mm_walk *walk)
241 {
242 int err = 0;
243 unsigned long next;
244 struct vm_area_struct *vma;
245
246 if (start >= end)
247 return -EINVAL;
248
249 if (!walk->mm)
250 return -EINVAL;
251
252 VM_BUG_ON_MM(!rwsem_is_locked(&walk->mm->mmap_sem), walk->mm);
253
254 vma = find_vma(walk->mm, start);
255 do {
256 if (!vma) { /* after the last vma */
257 walk->vma = NULL;
258 next = end;
259 } else if (start < vma->vm_start) { /* outside vma */
260 walk->vma = NULL;
261 next = min(end, vma->vm_start);
262 } else { /* inside vma */
263 walk->vma = vma;
264 next = min(end, vma->vm_end);
265 vma = vma->vm_next;
266
267 err = walk_page_test(start, next, walk);
268 if (err > 0) {
269 /*
270 * positive return values are purely for
271 * controlling the pagewalk, so should never
272 * be passed to the callers.
273 */
274 err = 0;
275 continue;
276 }
277 if (err < 0)
278 break;
279 }
280 if (walk->vma || walk->pte_hole)
281 err = __walk_page_range(start, next, walk);
282 if (err)
283 break;
284 } while (start = next, start < end);
285 return err;
286 }
287
288 int walk_page_vma(struct vm_area_struct *vma, struct mm_walk *walk)
289 {
290 int err;
291
292 if (!walk->mm)
293 return -EINVAL;
294
295 VM_BUG_ON(!rwsem_is_locked(&walk->mm->mmap_sem));
296 VM_BUG_ON(!vma);
297 walk->vma = vma;
298 err = walk_page_test(vma->vm_start, vma->vm_end, walk);
299 if (err > 0)
300 return 0;
301 if (err < 0)
302 return err;
303 return __walk_page_range(vma->vm_start, vma->vm_end, walk);
304 }