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 : ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
117 0 : if (!ptep) {
118 0 : walk->action = ACTION_AGAIN;
119 0 : return 0;
120 : }
121 0 : for (; addr != end; ptep++, addr += PAGE_SIZE) {
122 0 : pte_t pte = ptep_get(ptep);
123 :
124 : /* We need to do cache lookup too for pte markers */
125 0 : if (pte_none_mostly(pte))
126 0 : __mincore_unmapped_range(addr, addr + PAGE_SIZE,
127 : vma, vec);
128 0 : else if (pte_present(pte))
129 0 : *vec = 1;
130 : else { /* pte is a swap entry */
131 0 : swp_entry_t entry = pte_to_swp_entry(pte);
132 :
133 0 : if (non_swap_entry(entry)) {
134 : /*
135 : * migration or hwpoison entries are always
136 : * uptodate
137 : */
138 0 : *vec = 1;
139 : } else {
140 : #ifdef CONFIG_SWAP
141 0 : *vec = mincore_page(swap_address_space(entry),
142 : swp_offset(entry));
143 : #else
144 : WARN_ON(1);
145 : *vec = 1;
146 : #endif
147 : }
148 : }
149 0 : vec++;
150 : }
151 0 : pte_unmap_unlock(ptep - 1, ptl);
152 : out:
153 0 : walk->private += nr;
154 0 : cond_resched();
155 0 : return 0;
156 : }
157 :
158 0 : static inline bool can_do_mincore(struct vm_area_struct *vma)
159 : {
160 0 : if (vma_is_anonymous(vma))
161 : return true;
162 0 : if (!vma->vm_file)
163 : return false;
164 : /*
165 : * Reveal pagecache information only for non-anonymous mappings that
166 : * correspond to the files the calling process could (if tried) open
167 : * for writing; otherwise we'd be including shared non-exclusive
168 : * mappings, which opens a side channel.
169 : */
170 0 : return inode_owner_or_capable(&nop_mnt_idmap,
171 0 : file_inode(vma->vm_file)) ||
172 0 : file_permission(vma->vm_file, MAY_WRITE) == 0;
173 : }
174 :
175 : static const struct mm_walk_ops mincore_walk_ops = {
176 : .pmd_entry = mincore_pte_range,
177 : .pte_hole = mincore_unmapped_range,
178 : .hugetlb_entry = mincore_hugetlb,
179 : };
180 :
181 : /*
182 : * Do a chunk of "sys_mincore()". We've already checked
183 : * all the arguments, we hold the mmap semaphore: we should
184 : * just return the amount of info we're asked for.
185 : */
186 0 : static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec)
187 : {
188 : struct vm_area_struct *vma;
189 : unsigned long end;
190 : int err;
191 :
192 0 : vma = vma_lookup(current->mm, addr);
193 0 : if (!vma)
194 : return -ENOMEM;
195 0 : end = min(vma->vm_end, addr + (pages << PAGE_SHIFT));
196 0 : if (!can_do_mincore(vma)) {
197 0 : unsigned long pages = DIV_ROUND_UP(end - addr, PAGE_SIZE);
198 0 : memset(vec, 1, pages);
199 0 : return pages;
200 : }
201 0 : err = walk_page_range(vma->vm_mm, addr, end, &mincore_walk_ops, vec);
202 0 : if (err < 0)
203 0 : return err;
204 0 : return (end - addr) >> PAGE_SHIFT;
205 : }
206 :
207 : /*
208 : * The mincore(2) system call.
209 : *
210 : * mincore() returns the memory residency status of the pages in the
211 : * current process's address space specified by [addr, addr + len).
212 : * The status is returned in a vector of bytes. The least significant
213 : * bit of each byte is 1 if the referenced page is in memory, otherwise
214 : * it is zero.
215 : *
216 : * Because the status of a page can change after mincore() checks it
217 : * but before it returns to the application, the returned vector may
218 : * contain stale information. Only locked pages are guaranteed to
219 : * remain in memory.
220 : *
221 : * return values:
222 : * zero - success
223 : * -EFAULT - vec points to an illegal address
224 : * -EINVAL - addr is not a multiple of PAGE_SIZE
225 : * -ENOMEM - Addresses in the range [addr, addr + len] are
226 : * invalid for the address space of this process, or
227 : * specify one or more pages which are not currently
228 : * mapped
229 : * -EAGAIN - A kernel resource was temporarily unavailable.
230 : */
231 0 : SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
232 : unsigned char __user *, vec)
233 : {
234 : long retval;
235 : unsigned long pages;
236 : unsigned char *tmp;
237 :
238 0 : start = untagged_addr(start);
239 :
240 : /* Check the start address: needs to be page-aligned.. */
241 0 : if (start & ~PAGE_MASK)
242 : return -EINVAL;
243 :
244 : /* ..and we need to be passed a valid user-space range */
245 0 : if (!access_ok((void __user *) start, len))
246 : return -ENOMEM;
247 :
248 : /* This also avoids any overflows on PAGE_ALIGN */
249 0 : pages = len >> PAGE_SHIFT;
250 0 : pages += (offset_in_page(len)) != 0;
251 :
252 0 : if (!access_ok(vec, pages))
253 : return -EFAULT;
254 :
255 0 : tmp = (void *) __get_free_page(GFP_USER);
256 0 : if (!tmp)
257 : return -EAGAIN;
258 :
259 : retval = 0;
260 0 : while (pages) {
261 : /*
262 : * Do at most PAGE_SIZE entries per iteration, due to
263 : * the temporary buffer size.
264 : */
265 0 : mmap_read_lock(current->mm);
266 0 : retval = do_mincore(start, min(pages, PAGE_SIZE), tmp);
267 0 : mmap_read_unlock(current->mm);
268 :
269 0 : if (retval <= 0)
270 : break;
271 0 : if (copy_to_user(vec, tmp, retval)) {
272 : retval = -EFAULT;
273 : break;
274 : }
275 0 : pages -= retval;
276 0 : vec += retval;
277 0 : start += retval << PAGE_SHIFT;
278 0 : retval = 0;
279 : }
280 0 : free_page((unsigned long) tmp);
281 0 : return retval;
282 : }
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