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