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
mincore_hugetlb(pte_t * pte,unsigned long hmask,unsigned long addr,unsigned long end,struct mm_walk * walk)24 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 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 */
mincore_page(struct address_space * mapping,pgoff_t index)51 static unsigned char mincore_page(struct address_space *mapping, pgoff_t index)
52 {
53 unsigned char present = 0;
54 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 page = find_get_incore_page(mapping, index);
63 if (page) {
64 present = PageUptodate(page);
65 put_page(page);
66 }
67
68 return present;
69 }
70
__mincore_unmapped_range(unsigned long addr,unsigned long end,struct vm_area_struct * vma,unsigned char * vec)71 static int __mincore_unmapped_range(unsigned long addr, unsigned long end,
72 struct vm_area_struct *vma, unsigned char *vec)
73 {
74 unsigned long nr = (end - addr) >> PAGE_SHIFT;
75 int i;
76
77 if (vma->vm_file) {
78 pgoff_t pgoff;
79
80 pgoff = linear_page_index(vma, addr);
81 for (i = 0; i < nr; i++, pgoff++)
82 vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
83 } else {
84 for (i = 0; i < nr; i++)
85 vec[i] = 0;
86 }
87 return nr;
88 }
89
mincore_unmapped_range(unsigned long addr,unsigned long end,__always_unused int depth,struct mm_walk * walk)90 static int mincore_unmapped_range(unsigned long addr, unsigned long end,
91 __always_unused int depth,
92 struct mm_walk *walk)
93 {
94 walk->private += __mincore_unmapped_range(addr, end,
95 walk->vma, walk->private);
96 return 0;
97 }
98
mincore_pte_range(pmd_t * pmd,unsigned long addr,unsigned long end,struct mm_walk * walk)99 static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
100 struct mm_walk *walk)
101 {
102 spinlock_t *ptl;
103 struct vm_area_struct *vma = walk->vma;
104 pte_t *ptep;
105 unsigned char *vec = walk->private;
106 int nr = (end - addr) >> PAGE_SHIFT;
107
108 ptl = pmd_trans_huge_lock(pmd, vma);
109 if (ptl) {
110 memset(vec, 1, nr);
111 spin_unlock(ptl);
112 goto out;
113 }
114
115 if (pmd_trans_unstable(pmd)) {
116 __mincore_unmapped_range(addr, end, vma, vec);
117 goto out;
118 }
119
120 ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
121 for (; addr != end; ptep++, addr += PAGE_SIZE) {
122 pte_t pte = *ptep;
123
124 if (pte_none(pte))
125 __mincore_unmapped_range(addr, addr + PAGE_SIZE,
126 vma, vec);
127 else if (pte_present(pte))
128 *vec = 1;
129 else { /* pte is a swap entry */
130 swp_entry_t entry = pte_to_swp_entry(pte);
131
132 if (non_swap_entry(entry)) {
133 /*
134 * migration or hwpoison entries are always
135 * uptodate
136 */
137 *vec = 1;
138 } else {
139 #ifdef CONFIG_SWAP
140 *vec = mincore_page(swap_address_space(entry),
141 swp_offset(entry));
142 #else
143 WARN_ON(1);
144 *vec = 1;
145 #endif
146 }
147 }
148 vec++;
149 }
150 pte_unmap_unlock(ptep - 1, ptl);
151 out:
152 walk->private += nr;
153 cond_resched();
154 return 0;
155 }
156
can_do_mincore(struct vm_area_struct * vma)157 static inline bool can_do_mincore(struct vm_area_struct *vma)
158 {
159 if (vma_is_anonymous(vma))
160 return true;
161 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 return inode_owner_or_capable(file_inode(vma->vm_file)) ||
170 inode_permission(file_inode(vma->vm_file), MAY_WRITE) == 0;
171 }
172
173 static const struct mm_walk_ops mincore_walk_ops = {
174 .pmd_entry = mincore_pte_range,
175 .pte_hole = mincore_unmapped_range,
176 .hugetlb_entry = mincore_hugetlb,
177 };
178
179 /*
180 * Do a chunk of "sys_mincore()". We've already checked
181 * all the arguments, we hold the mmap semaphore: we should
182 * just return the amount of info we're asked for.
183 */
do_mincore(unsigned long addr,unsigned long pages,unsigned char * vec)184 static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec)
185 {
186 struct vm_area_struct *vma;
187 unsigned long end;
188 int err;
189
190 vma = find_vma(current->mm, addr);
191 if (!vma || addr < vma->vm_start)
192 return -ENOMEM;
193 end = min(vma->vm_end, addr + (pages << PAGE_SHIFT));
194 if (!can_do_mincore(vma)) {
195 unsigned long pages = DIV_ROUND_UP(end - addr, PAGE_SIZE);
196 memset(vec, 1, pages);
197 return pages;
198 }
199 err = walk_page_range(vma->vm_mm, addr, end, &mincore_walk_ops, vec);
200 if (err < 0)
201 return err;
202 return (end - addr) >> PAGE_SHIFT;
203 }
204
205 /*
206 * The mincore(2) system call.
207 *
208 * mincore() returns the memory residency status of the pages in the
209 * current process's address space specified by [addr, addr + len).
210 * The status is returned in a vector of bytes. The least significant
211 * bit of each byte is 1 if the referenced page is in memory, otherwise
212 * it is zero.
213 *
214 * Because the status of a page can change after mincore() checks it
215 * but before it returns to the application, the returned vector may
216 * contain stale information. Only locked pages are guaranteed to
217 * remain in memory.
218 *
219 * return values:
220 * zero - success
221 * -EFAULT - vec points to an illegal address
222 * -EINVAL - addr is not a multiple of PAGE_SIZE
223 * -ENOMEM - Addresses in the range [addr, addr + len] are
224 * invalid for the address space of this process, or
225 * specify one or more pages which are not currently
226 * mapped
227 * -EAGAIN - A kernel resource was temporarily unavailable.
228 */
SYSCALL_DEFINE3(mincore,unsigned long,start,size_t,len,unsigned char __user *,vec)229 SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
230 unsigned char __user *, vec)
231 {
232 long retval;
233 unsigned long pages;
234 unsigned char *tmp;
235
236 start = untagged_addr(start);
237
238 /* Check the start address: needs to be page-aligned.. */
239 if (start & ~PAGE_MASK)
240 return -EINVAL;
241
242 /* ..and we need to be passed a valid user-space range */
243 if (!access_ok((void __user *) start, len))
244 return -ENOMEM;
245
246 /* This also avoids any overflows on PAGE_ALIGN */
247 pages = len >> PAGE_SHIFT;
248 pages += (offset_in_page(len)) != 0;
249
250 if (!access_ok(vec, pages))
251 return -EFAULT;
252
253 tmp = (void *) __get_free_page(GFP_USER);
254 if (!tmp)
255 return -EAGAIN;
256
257 retval = 0;
258 while (pages) {
259 /*
260 * Do at most PAGE_SIZE entries per iteration, due to
261 * the temporary buffer size.
262 */
263 mmap_read_lock(current->mm);
264 retval = do_mincore(start, min(pages, PAGE_SIZE), tmp);
265 mmap_read_unlock(current->mm);
266
267 if (retval <= 0)
268 break;
269 if (copy_to_user(vec, tmp, retval)) {
270 retval = -EFAULT;
271 break;
272 }
273 pages -= retval;
274 vec += retval;
275 start += retval << PAGE_SHIFT;
276 retval = 0;
277 }
278 free_page((unsigned long) tmp);
279 return retval;
280 }
281
