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