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_page_pmd_mm(walk->mm, addr, pmd);
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
146 if (pte)
147 err = walk->hugetlb_entry(pte, hmask, addr, next, walk);
148 else if (walk->pte_hole)
149 err = walk->pte_hole(addr, next, walk);
150
151 if (err)
152 break;
153 } while (addr = next, addr != end);
154
155 return err;
156 }
157
158 #else /* CONFIG_HUGETLB_PAGE */
159 static int walk_hugetlb_range(unsigned long addr, unsigned long end,
160 struct mm_walk *walk)
161 {
162 return 0;
163 }
164
165 #endif /* CONFIG_HUGETLB_PAGE */
166
167 /*
168 * Decide whether we really walk over the current vma on [@start, @end)
169 * or skip it via the returned value. Return 0 if we do walk over the
170 * current vma, and return 1 if we skip the vma. Negative values means
171 * error, where we abort the current walk.
172 */
173 static int walk_page_test(unsigned long start, unsigned long end,
174 struct mm_walk *walk)
175 {
176 struct vm_area_struct *vma = walk->vma;
177
178 if (walk->test_walk)
179 return walk->test_walk(start, end, walk);
180
181 /*
182 * vma(VM_PFNMAP) doesn't have any valid struct pages behind VM_PFNMAP
183 * range, so we don't walk over it as we do for normal vmas. However,
184 * Some callers are interested in handling hole range and they don't
185 * want to just ignore any single address range. Such users certainly
186 * define their ->pte_hole() callbacks, so let's delegate them to handle
187 * vma(VM_PFNMAP).
188 */
189 if (vma->vm_flags & VM_PFNMAP) {
190 int err = 1;
191 if (walk->pte_hole)
192 err = walk->pte_hole(start, end, walk);
193 return err ? err : 1;
194 }
195 return 0;
196 }
197
198 static int __walk_page_range(unsigned long start, unsigned long end,
199 struct mm_walk *walk)
200 {
201 int err = 0;
202 struct vm_area_struct *vma = walk->vma;
203
204 if (vma && is_vm_hugetlb_page(vma)) {
205 if (walk->hugetlb_entry)
206 err = walk_hugetlb_range(start, end, walk);
207 } else
208 err = walk_pgd_range(start, end, walk);
209
210 return err;
211 }
212
213 /**
214 * walk_page_range - walk page table with caller specific callbacks
215 *
216 * Recursively walk the page table tree of the process represented by @walk->mm
217 * within the virtual address range [@start, @end). During walking, we can do
218 * some caller-specific works for each entry, by setting up pmd_entry(),
219 * pte_entry(), and/or hugetlb_entry(). If you don't set up for some of these
220 * callbacks, the associated entries/pages are just ignored.
221 * The return values of these callbacks are commonly defined like below:
222 * - 0 : succeeded to handle the current entry, and if you don't reach the
223 * end address yet, continue to walk.
224 * - >0 : succeeded to handle the current entry, and return to the caller
225 * with caller specific value.
226 * - <0 : failed to handle the current entry, and return to the caller
227 * with error code.
228 *
229 * Before starting to walk page table, some callers want to check whether
230 * they really want to walk over the current vma, typically by checking
231 * its vm_flags. walk_page_test() and @walk->test_walk() are used for this
232 * purpose.
233 *
234 * struct mm_walk keeps current values of some common data like vma and pmd,
235 * which are useful for the access from callbacks. If you want to pass some
236 * caller-specific data to callbacks, @walk->private should be helpful.
237 *
238 * Locking:
239 * Callers of walk_page_range() and walk_page_vma() should hold
240 * @walk->mm->mmap_sem, because these function traverse vma list and/or
241 * access to vma's data.
242 */
243 int walk_page_range(unsigned long start, unsigned long end,
244 struct mm_walk *walk)
245 {
246 int err = 0;
247 unsigned long next;
248 struct vm_area_struct *vma;
249
250 if (start >= end)
251 return -EINVAL;
252
253 if (!walk->mm)
254 return -EINVAL;
255
256 VM_BUG_ON_MM(!rwsem_is_locked(&walk->mm->mmap_sem), walk->mm);
257
258 vma = find_vma(walk->mm, start);
259 do {
260 if (!vma) { /* after the last vma */
261 walk->vma = NULL;
262 next = end;
263 } else if (start < vma->vm_start) { /* outside vma */
264 walk->vma = NULL;
265 next = min(end, vma->vm_start);
266 } else { /* inside vma */
267 walk->vma = vma;
268 next = min(end, vma->vm_end);
269 vma = vma->vm_next;
270
271 err = walk_page_test(start, next, walk);
272 if (err > 0) {
273 /*
274 * positive return values are purely for
275 * controlling the pagewalk, so should never
276 * be passed to the callers.
277 */
278 err = 0;
279 continue;
280 }
281 if (err < 0)
282 break;
283 }
284 if (walk->vma || walk->pte_hole)
285 err = __walk_page_range(start, next, walk);
286 if (err)
287 break;
288 } while (start = next, start < end);
289 return err;
290 }
291
292 int walk_page_vma(struct vm_area_struct *vma, struct mm_walk *walk)
293 {
294 int err;
295
296 if (!walk->mm)
297 return -EINVAL;
298
299 VM_BUG_ON(!rwsem_is_locked(&walk->mm->mmap_sem));
300 VM_BUG_ON(!vma);
301 walk->vma = vma;
302 err = walk_page_test(vma->vm_start, vma->vm_end, walk);
303 if (err > 0)
304 return 0;
305 if (err < 0)
306 return err;
307 return __walk_page_range(vma->vm_start, vma->vm_end, walk);
308 }
309
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