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 :
24 0 : static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr,
25 : unsigned long end, struct mm_walk *walk)
26 : {
27 : #ifdef CONFIG_HUGETLB_PAGE
28 : unsigned char present;
29 : unsigned char *vec = walk->private;
30 :
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;
39 : #else
40 0 : BUG();
41 : #endif
42 : return 0;
43 : }
44 :
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 0 : static unsigned char mincore_page(struct address_space *mapping, pgoff_t index)
52 : {
53 0 : unsigned char present = 0;
54 0 : 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 0 : page = find_get_incore_page(mapping, index);
63 0 : if (page) {
64 0 : present = PageUptodate(page);
65 0 : put_page(page);
66 : }
67 :
68 0 : return present;
69 : }
70 :
71 0 : static int __mincore_unmapped_range(unsigned long addr, unsigned long end,
72 : struct vm_area_struct *vma, unsigned char *vec)
73 : {
74 0 : unsigned long nr = (end - addr) >> PAGE_SHIFT;
75 0 : int i;
76 :
77 0 : if (vma->vm_file) {
78 0 : pgoff_t pgoff;
79 :
80 0 : pgoff = linear_page_index(vma, addr);
81 0 : for (i = 0; i < nr; i++, pgoff++)
82 0 : vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
83 : } else {
84 0 : for (i = 0; i < nr; i++)
85 0 : vec[i] = 0;
86 : }
87 0 : return nr;
88 : }
89 :
90 0 : static int mincore_unmapped_range(unsigned long addr, unsigned long end,
91 : __always_unused int depth,
92 : struct mm_walk *walk)
93 : {
94 0 : walk->private += __mincore_unmapped_range(addr, end,
95 0 : walk->vma, walk->private);
96 0 : return 0;
97 : }
98 :
99 0 : static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
100 : struct mm_walk *walk)
101 : {
102 0 : spinlock_t *ptl;
103 0 : struct vm_area_struct *vma = walk->vma;
104 0 : pte_t *ptep;
105 0 : unsigned char *vec = walk->private;
106 0 : int nr = (end - addr) >> PAGE_SHIFT;
107 :
108 0 : ptl = pmd_trans_huge_lock(pmd, vma);
109 0 : if (ptl) {
110 0 : memset(vec, 1, nr);
111 0 : spin_unlock(ptl);
112 0 : goto out;
113 : }
114 :
115 0 : if (pmd_trans_unstable(pmd)) {
116 0 : __mincore_unmapped_range(addr, end, vma, vec);
117 0 : goto out;
118 : }
119 :
120 0 : ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
121 0 : for (; addr != end; ptep++, addr += PAGE_SIZE) {
122 0 : pte_t pte = *ptep;
123 :
124 0 : if (pte_none(pte))
125 0 : __mincore_unmapped_range(addr, addr + PAGE_SIZE,
126 : vma, vec);
127 0 : else if (pte_present(pte))
128 0 : *vec = 1;
129 : else { /* pte is a swap entry */
130 0 : swp_entry_t entry = pte_to_swp_entry(pte);
131 :
132 0 : if (non_swap_entry(entry)) {
133 : /*
134 : * migration or hwpoison entries are always
135 : * uptodate
136 : */
137 0 : *vec = 1;
138 : } else {
139 : #ifdef CONFIG_SWAP
140 : *vec = mincore_page(swap_address_space(entry),
141 : swp_offset(entry));
142 : #else
143 0 : WARN_ON(1);
144 0 : *vec = 1;
145 : #endif
146 : }
147 : }
148 0 : vec++;
149 : }
150 0 : pte_unmap_unlock(ptep - 1, ptl);
151 0 : out:
152 0 : walk->private += nr;
153 0 : cond_resched();
154 0 : return 0;
155 : }
156 :
157 0 : static inline bool can_do_mincore(struct vm_area_struct *vma)
158 : {
159 0 : if (vma_is_anonymous(vma))
160 : return true;
161 0 : if (!vma->vm_file)
162 : return false;
163 : /*
164 : * Reveal pagecache information only for non-anonymous mappings that
165 : * correspond to the files the calling process could (if tried) open
166 : * for writing; otherwise we'd be including shared non-exclusive
167 : * mappings, which opens a side channel.
168 : */
169 0 : return inode_owner_or_capable(&init_user_ns,
170 0 : file_inode(vma->vm_file)) ||
171 0 : file_permission(vma->vm_file, MAY_WRITE) == 0;
172 : }
173 :
174 : static const struct mm_walk_ops mincore_walk_ops = {
175 : .pmd_entry = mincore_pte_range,
176 : .pte_hole = mincore_unmapped_range,
177 : .hugetlb_entry = mincore_hugetlb,
178 : };
179 :
180 : /*
181 : * Do a chunk of "sys_mincore()". We've already checked
182 : * all the arguments, we hold the mmap semaphore: we should
183 : * just return the amount of info we're asked for.
184 : */
185 0 : static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec)
186 : {
187 0 : struct vm_area_struct *vma;
188 0 : unsigned long end;
189 0 : int err;
190 :
191 0 : vma = find_vma(current->mm, addr);
192 0 : if (!vma || addr < vma->vm_start)
193 : return -ENOMEM;
194 0 : end = min(vma->vm_end, addr + (pages << PAGE_SHIFT));
195 0 : if (!can_do_mincore(vma)) {
196 0 : unsigned long pages = DIV_ROUND_UP(end - addr, PAGE_SIZE);
197 0 : memset(vec, 1, pages);
198 0 : return pages;
199 : }
200 0 : err = walk_page_range(vma->vm_mm, addr, end, &mincore_walk_ops, vec);
201 0 : if (err < 0)
202 0 : return err;
203 0 : return (end - addr) >> PAGE_SHIFT;
204 : }
205 :
206 : /*
207 : * The mincore(2) system call.
208 : *
209 : * mincore() returns the memory residency status of the pages in the
210 : * current process's address space specified by [addr, addr + len).
211 : * The status is returned in a vector of bytes. The least significant
212 : * bit of each byte is 1 if the referenced page is in memory, otherwise
213 : * it is zero.
214 : *
215 : * Because the status of a page can change after mincore() checks it
216 : * but before it returns to the application, the returned vector may
217 : * contain stale information. Only locked pages are guaranteed to
218 : * remain in memory.
219 : *
220 : * return values:
221 : * zero - success
222 : * -EFAULT - vec points to an illegal address
223 : * -EINVAL - addr is not a multiple of PAGE_SIZE
224 : * -ENOMEM - Addresses in the range [addr, addr + len] are
225 : * invalid for the address space of this process, or
226 : * specify one or more pages which are not currently
227 : * mapped
228 : * -EAGAIN - A kernel resource was temporarily unavailable.
229 : */
230 0 : SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
231 : unsigned char __user *, vec)
232 : {
233 0 : long retval;
234 0 : unsigned long pages;
235 0 : unsigned char *tmp;
236 :
237 0 : start = untagged_addr(start);
238 :
239 : /* Check the start address: needs to be page-aligned.. */
240 0 : if (start & ~PAGE_MASK)
241 : return -EINVAL;
242 :
243 : /* ..and we need to be passed a valid user-space range */
244 0 : if (!access_ok((void __user *) start, len))
245 : return -ENOMEM;
246 :
247 : /* This also avoids any overflows on PAGE_ALIGN */
248 0 : pages = len >> PAGE_SHIFT;
249 0 : pages += (offset_in_page(len)) != 0;
250 :
251 0 : if (!access_ok(vec, pages))
252 : return -EFAULT;
253 :
254 0 : tmp = (void *) __get_free_page(GFP_USER);
255 0 : if (!tmp)
256 : return -EAGAIN;
257 :
258 : retval = 0;
259 0 : while (pages) {
260 : /*
261 : * Do at most PAGE_SIZE entries per iteration, due to
262 : * the temporary buffer size.
263 : */
264 0 : mmap_read_lock(current->mm);
265 0 : retval = do_mincore(start, min(pages, PAGE_SIZE), tmp);
266 0 : mmap_read_unlock(current->mm);
267 :
268 0 : if (retval <= 0)
269 : break;
270 0 : if (copy_to_user(vec, tmp, retval)) {
271 : retval = -EFAULT;
272 : break;
273 : }
274 0 : pages -= retval;
275 0 : vec += retval;
276 0 : start += retval << PAGE_SHIFT;
277 0 : retval = 0;
278 : }
279 0 : free_page((unsigned long) tmp);
280 0 : return retval;
281 : }
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