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/mm.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 | |
21 | #include <linux/uaccess.h> |
22 | #include <asm/pgtable.h> |
23 | |
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 | */ |
51 | static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff) |
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 | #ifdef CONFIG_SWAP |
63 | if (shmem_mapping(mapping)) { |
64 | page = find_get_entry(mapping, pgoff); |
65 | /* |
66 | * shmem/tmpfs may return swap: account for swapcache |
67 | * page too. |
68 | */ |
69 | if (xa_is_value(page)) { |
70 | swp_entry_t swp = radix_to_swp_entry(page); |
71 | page = find_get_page(swap_address_space(swp), |
72 | swp_offset(swp)); |
73 | } |
74 | } else |
75 | page = find_get_page(mapping, pgoff); |
76 | #else |
77 | page = find_get_page(mapping, pgoff); |
78 | #endif |
79 | if (page) { |
80 | present = PageUptodate(page); |
81 | put_page(page); |
82 | } |
83 | |
84 | return present; |
85 | } |
86 | |
87 | static int __mincore_unmapped_range(unsigned long addr, unsigned long end, |
88 | struct vm_area_struct *vma, unsigned char *vec) |
89 | { |
90 | unsigned long nr = (end - addr) >> PAGE_SHIFT; |
91 | int i; |
92 | |
93 | if (vma->vm_file) { |
94 | pgoff_t pgoff; |
95 | |
96 | pgoff = linear_page_index(vma, addr); |
97 | for (i = 0; i < nr; i++, pgoff++) |
98 | vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff); |
99 | } else { |
100 | for (i = 0; i < nr; i++) |
101 | vec[i] = 0; |
102 | } |
103 | return nr; |
104 | } |
105 | |
106 | static int mincore_unmapped_range(unsigned long addr, unsigned long end, |
107 | struct mm_walk *walk) |
108 | { |
109 | walk->private += __mincore_unmapped_range(addr, end, |
110 | walk->vma, walk->private); |
111 | return 0; |
112 | } |
113 | |
114 | static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, |
115 | struct mm_walk *walk) |
116 | { |
117 | spinlock_t *ptl; |
118 | struct vm_area_struct *vma = walk->vma; |
119 | pte_t *ptep; |
120 | unsigned char *vec = walk->private; |
121 | int nr = (end - addr) >> PAGE_SHIFT; |
122 | |
123 | ptl = pmd_trans_huge_lock(pmd, vma); |
124 | if (ptl) { |
125 | memset(vec, 1, nr); |
126 | spin_unlock(ptl); |
127 | goto out; |
128 | } |
129 | |
130 | if (pmd_trans_unstable(pmd)) { |
131 | __mincore_unmapped_range(addr, end, vma, vec); |
132 | goto out; |
133 | } |
134 | |
135 | ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); |
136 | for (; addr != end; ptep++, addr += PAGE_SIZE) { |
137 | pte_t pte = *ptep; |
138 | |
139 | if (pte_none(pte)) |
140 | __mincore_unmapped_range(addr, addr + PAGE_SIZE, |
141 | vma, vec); |
142 | else if (pte_present(pte)) |
143 | *vec = 1; |
144 | else { /* pte is a swap entry */ |
145 | swp_entry_t entry = pte_to_swp_entry(pte); |
146 | |
147 | if (non_swap_entry(entry)) { |
148 | /* |
149 | * migration or hwpoison entries are always |
150 | * uptodate |
151 | */ |
152 | *vec = 1; |
153 | } else { |
154 | #ifdef CONFIG_SWAP |
155 | *vec = mincore_page(swap_address_space(entry), |
156 | swp_offset(entry)); |
157 | #else |
158 | WARN_ON(1); |
159 | *vec = 1; |
160 | #endif |
161 | } |
162 | } |
163 | vec++; |
164 | } |
165 | pte_unmap_unlock(ptep - 1, ptl); |
166 | out: |
167 | walk->private += nr; |
168 | cond_resched(); |
169 | return 0; |
170 | } |
171 | |
172 | /* |
173 | * Do a chunk of "sys_mincore()". We've already checked |
174 | * all the arguments, we hold the mmap semaphore: we should |
175 | * just return the amount of info we're asked for. |
176 | */ |
177 | static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec) |
178 | { |
179 | struct vm_area_struct *vma; |
180 | unsigned long end; |
181 | int err; |
182 | struct mm_walk mincore_walk = { |
183 | .pmd_entry = mincore_pte_range, |
184 | .pte_hole = mincore_unmapped_range, |
185 | .hugetlb_entry = mincore_hugetlb, |
186 | .private = vec, |
187 | }; |
188 | |
189 | vma = find_vma(current->mm, addr); |
190 | if (!vma || addr < vma->vm_start) |
191 | return -ENOMEM; |
192 | mincore_walk.mm = vma->vm_mm; |
193 | end = min(vma->vm_end, addr + (pages << PAGE_SHIFT)); |
194 | err = walk_page_range(addr, end, &mincore_walk); |
195 | if (err < 0) |
196 | return err; |
197 | return (end - addr) >> PAGE_SHIFT; |
198 | } |
199 | |
200 | /* |
201 | * The mincore(2) system call. |
202 | * |
203 | * mincore() returns the memory residency status of the pages in the |
204 | * current process's address space specified by [addr, addr + len). |
205 | * The status is returned in a vector of bytes. The least significant |
206 | * bit of each byte is 1 if the referenced page is in memory, otherwise |
207 | * it is zero. |
208 | * |
209 | * Because the status of a page can change after mincore() checks it |
210 | * but before it returns to the application, the returned vector may |
211 | * contain stale information. Only locked pages are guaranteed to |
212 | * remain in memory. |
213 | * |
214 | * return values: |
215 | * zero - success |
216 | * -EFAULT - vec points to an illegal address |
217 | * -EINVAL - addr is not a multiple of PAGE_SIZE |
218 | * -ENOMEM - Addresses in the range [addr, addr + len] are |
219 | * invalid for the address space of this process, or |
220 | * specify one or more pages which are not currently |
221 | * mapped |
222 | * -EAGAIN - A kernel resource was temporarily unavailable. |
223 | */ |
224 | SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, |
225 | unsigned char __user *, vec) |
226 | { |
227 | long retval; |
228 | unsigned long pages; |
229 | unsigned char *tmp; |
230 | |
231 | /* Check the start address: needs to be page-aligned.. */ |
232 | if (start & ~PAGE_MASK) |
233 | return -EINVAL; |
234 | |
235 | /* ..and we need to be passed a valid user-space range */ |
236 | if (!access_ok((void __user *) start, len)) |
237 | return -ENOMEM; |
238 | |
239 | /* This also avoids any overflows on PAGE_ALIGN */ |
240 | pages = len >> PAGE_SHIFT; |
241 | pages += (offset_in_page(len)) != 0; |
242 | |
243 | if (!access_ok(vec, pages)) |
244 | return -EFAULT; |
245 | |
246 | tmp = (void *) __get_free_page(GFP_USER); |
247 | if (!tmp) |
248 | return -EAGAIN; |
249 | |
250 | retval = 0; |
251 | while (pages) { |
252 | /* |
253 | * Do at most PAGE_SIZE entries per iteration, due to |
254 | * the temporary buffer size. |
255 | */ |
256 | down_read(¤t->mm->mmap_sem); |
257 | retval = do_mincore(start, min(pages, PAGE_SIZE), tmp); |
258 | up_read(¤t->mm->mmap_sem); |
259 | |
260 | if (retval <= 0) |
261 | break; |
262 | if (copy_to_user(vec, tmp, retval)) { |
263 | retval = -EFAULT; |
264 | break; |
265 | } |
266 | pages -= retval; |
267 | vec += retval; |
268 | start += retval << PAGE_SHIFT; |
269 | retval = 0; |
270 | } |
271 | free_page((unsigned long) tmp); |
272 | return retval; |
273 | } |
274 | |