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
mincore_hugetlb(pte_t * pte,unsigned long hmask,unsigned long addr,unsigned long end,struct mm_walk * walk)25 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(huge_ptep_get(pte));
37 for (; addr != end; vec++, addr += PAGE_SIZE)
38 *vec = present;
39 walk->private = vec;
40 #else
41 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 */
mincore_page(struct address_space * mapping,pgoff_t index)52 static unsigned char mincore_page(struct address_space *mapping, pgoff_t index)
53 {
54 unsigned char present = 0;
55 struct page *page;
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 page = find_get_incore_page(mapping, index);
64 if (page) {
65 present = PageUptodate(page);
66 put_page(page);
67 }
68
69 return present;
70 }
71
__mincore_unmapped_range(unsigned long addr,unsigned long end,struct vm_area_struct * vma,unsigned char * vec)72 static int __mincore_unmapped_range(unsigned long addr, unsigned long end,
73 struct vm_area_struct *vma, unsigned char *vec)
74 {
75 unsigned long nr = (end - addr) >> PAGE_SHIFT;
76 int i;
77
78 if (vma->vm_file) {
79 pgoff_t pgoff;
80
81 pgoff = linear_page_index(vma, addr);
82 for (i = 0; i < nr; i++, pgoff++)
83 vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
84 } else {
85 for (i = 0; i < nr; i++)
86 vec[i] = 0;
87 }
88 return nr;
89 }
90
mincore_unmapped_range(unsigned long addr,unsigned long end,__always_unused int depth,struct mm_walk * walk)91 static int mincore_unmapped_range(unsigned long addr, unsigned long end,
92 __always_unused int depth,
93 struct mm_walk *walk)
94 {
95 walk->private += __mincore_unmapped_range(addr, end,
96 walk->vma, walk->private);
97 return 0;
98 }
99
mincore_pte_range(pmd_t * pmd,unsigned long addr,unsigned long end,struct mm_walk * walk)100 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 struct vm_area_struct *vma = walk->vma;
105 pte_t *ptep;
106 unsigned char *vec = walk->private;
107 int nr = (end - addr) >> PAGE_SHIFT;
108
109 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 if (pmd_trans_unstable(pmd)) {
117 __mincore_unmapped_range(addr, end, vma, vec);
118 goto out;
119 }
120
121 ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
122 for (; addr != end; ptep++, addr += PAGE_SIZE) {
123 pte_t pte = *ptep;
124
125 /* We need to do cache lookup too for pte markers */
126 if (pte_none_mostly(pte))
127 __mincore_unmapped_range(addr, addr + PAGE_SIZE,
128 vma, vec);
129 else if (pte_present(pte))
130 *vec = 1;
131 else { /* pte is a swap entry */
132 swp_entry_t entry = pte_to_swp_entry(pte);
133
134 if (non_swap_entry(entry)) {
135 /*
136 * migration or hwpoison entries are always
137 * uptodate
138 */
139 *vec = 1;
140 } else {
141 #ifdef CONFIG_SWAP
142 *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 vec++;
151 }
152 pte_unmap_unlock(ptep - 1, ptl);
153 out:
154 walk->private += nr;
155 cond_resched();
156 return 0;
157 }
158
can_do_mincore(struct vm_area_struct * vma)159 static inline bool can_do_mincore(struct vm_area_struct *vma)
160 {
161 if (vma_is_anonymous(vma))
162 return true;
163 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 return inode_owner_or_capable(&init_user_ns,
172 file_inode(vma->vm_file)) ||
173 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 */
do_mincore(unsigned long addr,unsigned long pages,unsigned char * vec)187 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 vma = find_vma(current->mm, addr);
194 if (!vma || addr < vma->vm_start)
195 return -ENOMEM;
196 end = min(vma->vm_end, addr + (pages << PAGE_SHIFT));
197 if (!can_do_mincore(vma)) {
198 unsigned long pages = DIV_ROUND_UP(end - addr, PAGE_SIZE);
199 memset(vec, 1, pages);
200 return pages;
201 }
202 err = walk_page_range(vma->vm_mm, addr, end, &mincore_walk_ops, vec);
203 if (err < 0)
204 return err;
205 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 */
SYSCALL_DEFINE3(mincore,unsigned long,start,size_t,len,unsigned char __user *,vec)232 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 start = untagged_addr(start);
240
241 /* Check the start address: needs to be page-aligned.. */
242 if (start & ~PAGE_MASK)
243 return -EINVAL;
244
245 /* ..and we need to be passed a valid user-space range */
246 if (!access_ok((void __user *) start, len))
247 return -ENOMEM;
248
249 /* This also avoids any overflows on PAGE_ALIGN */
250 pages = len >> PAGE_SHIFT;
251 pages += (offset_in_page(len)) != 0;
252
253 if (!access_ok(vec, pages))
254 return -EFAULT;
255
256 tmp = (void *) __get_free_page(GFP_USER);
257 if (!tmp)
258 return -EAGAIN;
259
260 retval = 0;
261 while (pages) {
262 /*
263 * Do at most PAGE_SIZE entries per iteration, due to
264 * the temporary buffer size.
265 */
266 mmap_read_lock(current->mm);
267 retval = do_mincore(start, min(pages, PAGE_SIZE), tmp);
268 mmap_read_unlock(current->mm);
269
270 if (retval <= 0)
271 break;
272 if (copy_to_user(vec, tmp, retval)) {
273 retval = -EFAULT;
274 break;
275 }
276 pages -= retval;
277 vec += retval;
278 start += retval << PAGE_SHIFT;
279 retval = 0;
280 }
281 free_page((unsigned long) tmp);
282 return retval;
283 }
284
