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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
1da177e4 LT |
2 | /* |
3 | * linux/mm/mincore.c | |
4 | * | |
2f77d107 | 5 | * Copyright (C) 1994-2006 Linus Torvalds |
1da177e4 LT |
6 | */ |
7 | ||
8 | /* | |
9 | * The mincore() system call. | |
10 | */ | |
1da177e4 | 11 | #include <linux/pagemap.h> |
5a0e3ad6 | 12 | #include <linux/gfp.h> |
a520110e | 13 | #include <linux/pagewalk.h> |
1da177e4 LT |
14 | #include <linux/mman.h> |
15 | #include <linux/syscalls.h> | |
42da9cbd NP |
16 | #include <linux/swap.h> |
17 | #include <linux/swapops.h> | |
3a4f8a0b | 18 | #include <linux/shmem_fs.h> |
4f16fc10 | 19 | #include <linux/hugetlb.h> |
65fddcfc | 20 | #include <linux/pgtable.h> |
1da177e4 | 21 | |
7c0f6ba6 | 22 | #include <linux/uaccess.h> |
1da177e4 | 23 | |
1e25a271 NH |
24 | static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr, |
25 | unsigned long end, struct mm_walk *walk) | |
f4884010 JW |
26 | { |
27 | #ifdef CONFIG_HUGETLB_PAGE | |
1e25a271 NH |
28 | unsigned char present; |
29 | unsigned char *vec = walk->private; | |
f4884010 | 30 | |
1e25a271 NH |
31 | /* |
32 | * Hugepages under user process are always in RAM and never | |
33 | * swapped out, but theoretically it needs to be checked. | |
34 | */ | |
35 | present = pte && !huge_pte_none(huge_ptep_get(pte)); | |
36 | for (; addr != end; vec++, addr += PAGE_SIZE) | |
37 | *vec = present; | |
38 | walk->private = vec; | |
f4884010 JW |
39 | #else |
40 | BUG(); | |
41 | #endif | |
1e25a271 | 42 | return 0; |
f4884010 JW |
43 | } |
44 | ||
30bac164 LT |
45 | /* |
46 | * Later we can get more picky about what "in core" means precisely. | |
47 | * For now, simply check to see if the page is in the page cache, | |
48 | * and is up to date; i.e. that no page-in operation would be required | |
49 | * at this time if an application were to map and access this page. | |
50 | */ | |
51 | static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff) | |
52 | { | |
53 | unsigned char present = 0; | |
54 | struct page *page; | |
55 | ||
56 | /* | |
57 | * When tmpfs swaps out a page from a file, any process mapping that | |
58 | * file will not get a swp_entry_t in its pte, but rather it is like | |
59 | * any other file mapping (ie. marked !present and faulted in with | |
60 | * tmpfs's .fault). So swapped out tmpfs mappings are tested here. | |
61 | */ | |
62 | #ifdef CONFIG_SWAP | |
63 | if (shmem_mapping(mapping)) { | |
64 | page = find_get_entry(mapping, pgoff); | |
65 | /* | |
66 | * shmem/tmpfs may return swap: account for swapcache | |
67 | * page too. | |
68 | */ | |
69 | if (xa_is_value(page)) { | |
70 | swp_entry_t swp = radix_to_swp_entry(page); | |
aeb309b8 HY |
71 | struct swap_info_struct *si; |
72 | ||
73 | /* Prevent swap device to being swapoff under us */ | |
74 | si = get_swap_device(swp); | |
75 | if (si) { | |
76 | page = find_get_page(swap_address_space(swp), | |
77 | swp_offset(swp)); | |
78 | put_swap_device(si); | |
79 | } else | |
80 | page = NULL; | |
30bac164 LT |
81 | } |
82 | } else | |
83 | page = find_get_page(mapping, pgoff); | |
84 | #else | |
85 | page = find_get_page(mapping, pgoff); | |
86 | #endif | |
87 | if (page) { | |
88 | present = PageUptodate(page); | |
89 | put_page(page); | |
90 | } | |
91 | ||
92 | return present; | |
93 | } | |
94 | ||
95 | static int __mincore_unmapped_range(unsigned long addr, unsigned long end, | |
96 | struct vm_area_struct *vma, unsigned char *vec) | |
1e25a271 | 97 | { |
574823bf | 98 | unsigned long nr = (end - addr) >> PAGE_SHIFT; |
30bac164 | 99 | int i; |
574823bf | 100 | |
30bac164 LT |
101 | if (vma->vm_file) { |
102 | pgoff_t pgoff; | |
103 | ||
104 | pgoff = linear_page_index(vma, addr); | |
105 | for (i = 0; i < nr; i++, pgoff++) | |
106 | vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff); | |
107 | } else { | |
108 | for (i = 0; i < nr; i++) | |
109 | vec[i] = 0; | |
110 | } | |
111 | return nr; | |
112 | } | |
113 | ||
114 | static int mincore_unmapped_range(unsigned long addr, unsigned long end, | |
b7a16c7a | 115 | __always_unused int depth, |
30bac164 LT |
116 | struct mm_walk *walk) |
117 | { | |
118 | walk->private += __mincore_unmapped_range(addr, end, | |
119 | walk->vma, walk->private); | |
1e25a271 | 120 | return 0; |
f4884010 JW |
121 | } |
122 | ||
1e25a271 NH |
123 | static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, |
124 | struct mm_walk *walk) | |
f4884010 JW |
125 | { |
126 | spinlock_t *ptl; | |
1e25a271 | 127 | struct vm_area_struct *vma = walk->vma; |
f4884010 | 128 | pte_t *ptep; |
1e25a271 NH |
129 | unsigned char *vec = walk->private; |
130 | int nr = (end - addr) >> PAGE_SHIFT; | |
131 | ||
b6ec57f4 KS |
132 | ptl = pmd_trans_huge_lock(pmd, vma); |
133 | if (ptl) { | |
1e25a271 NH |
134 | memset(vec, 1, nr); |
135 | spin_unlock(ptl); | |
136 | goto out; | |
137 | } | |
f4884010 | 138 | |
1e25a271 | 139 | if (pmd_trans_unstable(pmd)) { |
30bac164 | 140 | __mincore_unmapped_range(addr, end, vma, vec); |
1e25a271 NH |
141 | goto out; |
142 | } | |
143 | ||
144 | ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); | |
145 | for (; addr != end; ptep++, addr += PAGE_SIZE) { | |
f4884010 | 146 | pte_t pte = *ptep; |
f4884010 JW |
147 | |
148 | if (pte_none(pte)) | |
30bac164 LT |
149 | __mincore_unmapped_range(addr, addr + PAGE_SIZE, |
150 | vma, vec); | |
f4884010 | 151 | else if (pte_present(pte)) |
25ef0e50 | 152 | *vec = 1; |
0661a336 | 153 | else { /* pte is a swap entry */ |
f4884010 JW |
154 | swp_entry_t entry = pte_to_swp_entry(pte); |
155 | ||
30bac164 LT |
156 | if (non_swap_entry(entry)) { |
157 | /* | |
158 | * migration or hwpoison entries are always | |
159 | * uptodate | |
160 | */ | |
161 | *vec = 1; | |
162 | } else { | |
163 | #ifdef CONFIG_SWAP | |
164 | *vec = mincore_page(swap_address_space(entry), | |
165 | swp_offset(entry)); | |
166 | #else | |
167 | WARN_ON(1); | |
168 | *vec = 1; | |
169 | #endif | |
170 | } | |
f4884010 | 171 | } |
25ef0e50 | 172 | vec++; |
1e25a271 | 173 | } |
f4884010 | 174 | pte_unmap_unlock(ptep - 1, ptl); |
1e25a271 NH |
175 | out: |
176 | walk->private += nr; | |
177 | cond_resched(); | |
178 | return 0; | |
e48293fd JW |
179 | } |
180 | ||
134fca90 JK |
181 | static inline bool can_do_mincore(struct vm_area_struct *vma) |
182 | { | |
183 | if (vma_is_anonymous(vma)) | |
184 | return true; | |
185 | if (!vma->vm_file) | |
186 | return false; | |
187 | /* | |
188 | * Reveal pagecache information only for non-anonymous mappings that | |
189 | * correspond to the files the calling process could (if tried) open | |
190 | * for writing; otherwise we'd be including shared non-exclusive | |
191 | * mappings, which opens a side channel. | |
192 | */ | |
193 | return inode_owner_or_capable(file_inode(vma->vm_file)) || | |
194 | inode_permission(file_inode(vma->vm_file), MAY_WRITE) == 0; | |
195 | } | |
196 | ||
7b86ac33 CH |
197 | static const struct mm_walk_ops mincore_walk_ops = { |
198 | .pmd_entry = mincore_pte_range, | |
199 | .pte_hole = mincore_unmapped_range, | |
200 | .hugetlb_entry = mincore_hugetlb, | |
201 | }; | |
202 | ||
2f77d107 LT |
203 | /* |
204 | * Do a chunk of "sys_mincore()". We've already checked | |
205 | * all the arguments, we hold the mmap semaphore: we should | |
206 | * just return the amount of info we're asked for. | |
207 | */ | |
6a60f1b3 | 208 | static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec) |
1da177e4 | 209 | { |
6a60f1b3 | 210 | struct vm_area_struct *vma; |
25ef0e50 | 211 | unsigned long end; |
1e25a271 | 212 | int err; |
1da177e4 | 213 | |
6a60f1b3 | 214 | vma = find_vma(current->mm, addr); |
4fb23e43 LT |
215 | if (!vma || addr < vma->vm_start) |
216 | return -ENOMEM; | |
25ef0e50 | 217 | end = min(vma->vm_end, addr + (pages << PAGE_SHIFT)); |
134fca90 JK |
218 | if (!can_do_mincore(vma)) { |
219 | unsigned long pages = DIV_ROUND_UP(end - addr, PAGE_SIZE); | |
220 | memset(vec, 1, pages); | |
221 | return pages; | |
222 | } | |
7b86ac33 | 223 | err = walk_page_range(vma->vm_mm, addr, end, &mincore_walk_ops, vec); |
1e25a271 NH |
224 | if (err < 0) |
225 | return err; | |
25ef0e50 | 226 | return (end - addr) >> PAGE_SHIFT; |
1da177e4 LT |
227 | } |
228 | ||
229 | /* | |
230 | * The mincore(2) system call. | |
231 | * | |
232 | * mincore() returns the memory residency status of the pages in the | |
233 | * current process's address space specified by [addr, addr + len). | |
234 | * The status is returned in a vector of bytes. The least significant | |
235 | * bit of each byte is 1 if the referenced page is in memory, otherwise | |
236 | * it is zero. | |
237 | * | |
238 | * Because the status of a page can change after mincore() checks it | |
239 | * but before it returns to the application, the returned vector may | |
240 | * contain stale information. Only locked pages are guaranteed to | |
241 | * remain in memory. | |
242 | * | |
243 | * return values: | |
244 | * zero - success | |
245 | * -EFAULT - vec points to an illegal address | |
ea1754a0 | 246 | * -EINVAL - addr is not a multiple of PAGE_SIZE |
1da177e4 LT |
247 | * -ENOMEM - Addresses in the range [addr, addr + len] are |
248 | * invalid for the address space of this process, or | |
249 | * specify one or more pages which are not currently | |
250 | * mapped | |
251 | * -EAGAIN - A kernel resource was temporarily unavailable. | |
252 | */ | |
3480b257 HC |
253 | SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, |
254 | unsigned char __user *, vec) | |
1da177e4 | 255 | { |
2f77d107 LT |
256 | long retval; |
257 | unsigned long pages; | |
258 | unsigned char *tmp; | |
1da177e4 | 259 | |
057d3389 AK |
260 | start = untagged_addr(start); |
261 | ||
2f77d107 | 262 | /* Check the start address: needs to be page-aligned.. */ |
09cbfeaf | 263 | if (start & ~PAGE_MASK) |
2f77d107 | 264 | return -EINVAL; |
1da177e4 | 265 | |
2f77d107 | 266 | /* ..and we need to be passed a valid user-space range */ |
96d4f267 | 267 | if (!access_ok((void __user *) start, len)) |
2f77d107 | 268 | return -ENOMEM; |
1da177e4 | 269 | |
ea1754a0 | 270 | /* This also avoids any overflows on PAGE_ALIGN */ |
2f77d107 | 271 | pages = len >> PAGE_SHIFT; |
e7bbdd07 | 272 | pages += (offset_in_page(len)) != 0; |
1da177e4 | 273 | |
96d4f267 | 274 | if (!access_ok(vec, pages)) |
2f77d107 | 275 | return -EFAULT; |
1da177e4 | 276 | |
2f77d107 LT |
277 | tmp = (void *) __get_free_page(GFP_USER); |
278 | if (!tmp) | |
4fb23e43 | 279 | return -EAGAIN; |
2f77d107 LT |
280 | |
281 | retval = 0; | |
282 | while (pages) { | |
283 | /* | |
284 | * Do at most PAGE_SIZE entries per iteration, due to | |
285 | * the temporary buffer size. | |
286 | */ | |
287 | down_read(¤t->mm->mmap_sem); | |
6a60f1b3 | 288 | retval = do_mincore(start, min(pages, PAGE_SIZE), tmp); |
2f77d107 LT |
289 | up_read(¤t->mm->mmap_sem); |
290 | ||
291 | if (retval <= 0) | |
292 | break; | |
293 | if (copy_to_user(vec, tmp, retval)) { | |
294 | retval = -EFAULT; | |
295 | break; | |
1da177e4 | 296 | } |
2f77d107 LT |
297 | pages -= retval; |
298 | vec += retval; | |
299 | start += retval << PAGE_SHIFT; | |
300 | retval = 0; | |
1da177e4 | 301 | } |
2f77d107 LT |
302 | free_page((unsigned long) tmp); |
303 | return retval; | |
1da177e4 | 304 | } |