Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | * linux/mm/mincore.c | |
3 | * | |
2f77d107 | 4 | * Copyright (C) 1994-2006 Linus Torvalds |
1da177e4 LT |
5 | */ |
6 | ||
7 | /* | |
8 | * The mincore() system call. | |
9 | */ | |
1da177e4 | 10 | #include <linux/pagemap.h> |
5a0e3ad6 | 11 | #include <linux/gfp.h> |
1da177e4 LT |
12 | #include <linux/mm.h> |
13 | #include <linux/mman.h> | |
14 | #include <linux/syscalls.h> | |
42da9cbd NP |
15 | #include <linux/swap.h> |
16 | #include <linux/swapops.h> | |
4f16fc10 | 17 | #include <linux/hugetlb.h> |
1da177e4 LT |
18 | |
19 | #include <asm/uaccess.h> | |
20 | #include <asm/pgtable.h> | |
21 | ||
f4884010 JW |
22 | static void mincore_hugetlb_page_range(struct vm_area_struct *vma, |
23 | unsigned long addr, unsigned long nr, | |
24 | unsigned char *vec) | |
25 | { | |
26 | #ifdef CONFIG_HUGETLB_PAGE | |
27 | struct hstate *h; | |
28 | int i; | |
29 | ||
30 | i = 0; | |
31 | h = hstate_vma(vma); | |
32 | while (1) { | |
33 | unsigned char present; | |
34 | pte_t *ptep; | |
35 | /* | |
36 | * Huge pages are always in RAM for now, but | |
37 | * theoretically it needs to be checked. | |
38 | */ | |
39 | ptep = huge_pte_offset(current->mm, | |
40 | addr & huge_page_mask(h)); | |
41 | present = ptep && !huge_pte_none(huge_ptep_get(ptep)); | |
42 | while (1) { | |
43 | vec[i++] = present; | |
44 | addr += PAGE_SIZE; | |
45 | /* reach buffer limit */ | |
46 | if (i == nr) | |
47 | return; | |
48 | /* check hugepage border */ | |
49 | if (!(addr & ~huge_page_mask(h))) | |
50 | break; | |
51 | } | |
52 | } | |
53 | #else | |
54 | BUG(); | |
55 | #endif | |
56 | } | |
57 | ||
1da177e4 LT |
58 | /* |
59 | * Later we can get more picky about what "in core" means precisely. | |
60 | * For now, simply check to see if the page is in the page cache, | |
61 | * and is up to date; i.e. that no page-in operation would be required | |
62 | * at this time if an application were to map and access this page. | |
63 | */ | |
42da9cbd | 64 | static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff) |
1da177e4 LT |
65 | { |
66 | unsigned char present = 0; | |
42da9cbd | 67 | struct page *page; |
1da177e4 | 68 | |
42da9cbd NP |
69 | /* |
70 | * When tmpfs swaps out a page from a file, any process mapping that | |
71 | * file will not get a swp_entry_t in its pte, but rather it is like | |
72 | * any other file mapping (ie. marked !present and faulted in with | |
3c18ddd1 | 73 | * tmpfs's .fault). So swapped out tmpfs mappings are tested here. |
42da9cbd NP |
74 | * |
75 | * However when tmpfs moves the page from pagecache and into swapcache, | |
76 | * it is still in core, but the find_get_page below won't find it. | |
77 | * No big deal, but make a note of it. | |
78 | */ | |
79 | page = find_get_page(mapping, pgoff); | |
1da177e4 LT |
80 | if (page) { |
81 | present = PageUptodate(page); | |
82 | page_cache_release(page); | |
83 | } | |
84 | ||
85 | return present; | |
86 | } | |
87 | ||
f4884010 JW |
88 | static void mincore_unmapped_range(struct vm_area_struct *vma, |
89 | unsigned long addr, unsigned long nr, | |
90 | unsigned char *vec) | |
91 | { | |
92 | int i; | |
93 | ||
94 | if (vma->vm_file) { | |
95 | pgoff_t pgoff; | |
96 | ||
97 | pgoff = linear_page_index(vma, addr); | |
98 | for (i = 0; i < nr; i++, pgoff++) | |
99 | vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff); | |
100 | } else { | |
101 | for (i = 0; i < nr; i++) | |
102 | vec[i] = 0; | |
103 | } | |
104 | } | |
105 | ||
106 | static void mincore_pte_range(struct vm_area_struct *vma, pmd_t *pmd, | |
107 | unsigned long addr, unsigned long nr, | |
108 | unsigned char *vec) | |
109 | { | |
110 | spinlock_t *ptl; | |
111 | pte_t *ptep; | |
112 | int i; | |
113 | ||
114 | ptep = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); | |
115 | for (i = 0; i < nr; i++, ptep++, addr += PAGE_SIZE) { | |
116 | pte_t pte = *ptep; | |
117 | pgoff_t pgoff; | |
118 | ||
119 | if (pte_none(pte)) | |
120 | mincore_unmapped_range(vma, addr, 1, vec); | |
121 | else if (pte_present(pte)) | |
122 | vec[i] = 1; | |
123 | else if (pte_file(pte)) { | |
124 | pgoff = pte_to_pgoff(pte); | |
125 | vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff); | |
126 | } else { /* pte is a swap entry */ | |
127 | swp_entry_t entry = pte_to_swp_entry(pte); | |
128 | ||
129 | if (is_migration_entry(entry)) { | |
130 | /* migration entries are always uptodate */ | |
131 | vec[i] = 1; | |
132 | } else { | |
133 | #ifdef CONFIG_SWAP | |
134 | pgoff = entry.val; | |
135 | vec[i] = mincore_page(&swapper_space, pgoff); | |
136 | #else | |
137 | WARN_ON(1); | |
138 | vec[i] = 1; | |
139 | #endif | |
140 | } | |
141 | } | |
142 | } | |
143 | pte_unmap_unlock(ptep - 1, ptl); | |
144 | } | |
145 | ||
2f77d107 LT |
146 | /* |
147 | * Do a chunk of "sys_mincore()". We've already checked | |
148 | * all the arguments, we hold the mmap semaphore: we should | |
149 | * just return the amount of info we're asked for. | |
150 | */ | |
6a60f1b3 | 151 | static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec) |
1da177e4 | 152 | { |
42da9cbd NP |
153 | pgd_t *pgd; |
154 | pud_t *pud; | |
155 | pmd_t *pmd; | |
42da9cbd | 156 | unsigned long nr; |
6a60f1b3 | 157 | struct vm_area_struct *vma; |
1da177e4 | 158 | |
6a60f1b3 | 159 | vma = find_vma(current->mm, addr); |
4fb23e43 LT |
160 | if (!vma || addr < vma->vm_start) |
161 | return -ENOMEM; | |
1da177e4 | 162 | |
6a60f1b3 JW |
163 | nr = min(pages, (vma->vm_end - addr) >> PAGE_SHIFT); |
164 | ||
4f16fc10 | 165 | if (is_vm_hugetlb_page(vma)) { |
f4884010 | 166 | mincore_hugetlb_page_range(vma, addr, nr, vec); |
4f16fc10 NH |
167 | return nr; |
168 | } | |
4f16fc10 | 169 | |
2f77d107 | 170 | /* |
42da9cbd NP |
171 | * Calculate how many pages there are left in the last level of the |
172 | * PTE array for our address. | |
2f77d107 | 173 | */ |
6a60f1b3 | 174 | nr = min(nr, PTRS_PER_PTE - ((addr >> PAGE_SHIFT) & (PTRS_PER_PTE-1))); |
1da177e4 | 175 | |
42da9cbd NP |
176 | pgd = pgd_offset(vma->vm_mm, addr); |
177 | if (pgd_none_or_clear_bad(pgd)) | |
178 | goto none_mapped; | |
179 | pud = pud_offset(pgd, addr); | |
180 | if (pud_none_or_clear_bad(pud)) | |
181 | goto none_mapped; | |
182 | pmd = pmd_offset(pud, addr); | |
183 | if (pmd_none_or_clear_bad(pmd)) | |
184 | goto none_mapped; | |
185 | ||
f4884010 | 186 | mincore_pte_range(vma, pmd, addr, nr, vec); |
42da9cbd NP |
187 | return nr; |
188 | ||
189 | none_mapped: | |
f4884010 | 190 | mincore_unmapped_range(vma, addr, nr, vec); |
2f77d107 | 191 | return nr; |
1da177e4 LT |
192 | } |
193 | ||
194 | /* | |
195 | * The mincore(2) system call. | |
196 | * | |
197 | * mincore() returns the memory residency status of the pages in the | |
198 | * current process's address space specified by [addr, addr + len). | |
199 | * The status is returned in a vector of bytes. The least significant | |
200 | * bit of each byte is 1 if the referenced page is in memory, otherwise | |
201 | * it is zero. | |
202 | * | |
203 | * Because the status of a page can change after mincore() checks it | |
204 | * but before it returns to the application, the returned vector may | |
205 | * contain stale information. Only locked pages are guaranteed to | |
206 | * remain in memory. | |
207 | * | |
208 | * return values: | |
209 | * zero - success | |
210 | * -EFAULT - vec points to an illegal address | |
211 | * -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE | |
212 | * -ENOMEM - Addresses in the range [addr, addr + len] are | |
213 | * invalid for the address space of this process, or | |
214 | * specify one or more pages which are not currently | |
215 | * mapped | |
216 | * -EAGAIN - A kernel resource was temporarily unavailable. | |
217 | */ | |
3480b257 HC |
218 | SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, |
219 | unsigned char __user *, vec) | |
1da177e4 | 220 | { |
2f77d107 LT |
221 | long retval; |
222 | unsigned long pages; | |
223 | unsigned char *tmp; | |
1da177e4 | 224 | |
2f77d107 LT |
225 | /* Check the start address: needs to be page-aligned.. */ |
226 | if (start & ~PAGE_CACHE_MASK) | |
227 | return -EINVAL; | |
1da177e4 | 228 | |
2f77d107 LT |
229 | /* ..and we need to be passed a valid user-space range */ |
230 | if (!access_ok(VERIFY_READ, (void __user *) start, len)) | |
231 | return -ENOMEM; | |
1da177e4 | 232 | |
2f77d107 LT |
233 | /* This also avoids any overflows on PAGE_CACHE_ALIGN */ |
234 | pages = len >> PAGE_SHIFT; | |
235 | pages += (len & ~PAGE_MASK) != 0; | |
1da177e4 | 236 | |
2f77d107 LT |
237 | if (!access_ok(VERIFY_WRITE, vec, pages)) |
238 | return -EFAULT; | |
1da177e4 | 239 | |
2f77d107 LT |
240 | tmp = (void *) __get_free_page(GFP_USER); |
241 | if (!tmp) | |
4fb23e43 | 242 | return -EAGAIN; |
2f77d107 LT |
243 | |
244 | retval = 0; | |
245 | while (pages) { | |
246 | /* | |
247 | * Do at most PAGE_SIZE entries per iteration, due to | |
248 | * the temporary buffer size. | |
249 | */ | |
250 | down_read(¤t->mm->mmap_sem); | |
6a60f1b3 | 251 | retval = do_mincore(start, min(pages, PAGE_SIZE), tmp); |
2f77d107 LT |
252 | up_read(¤t->mm->mmap_sem); |
253 | ||
254 | if (retval <= 0) | |
255 | break; | |
256 | if (copy_to_user(vec, tmp, retval)) { | |
257 | retval = -EFAULT; | |
258 | break; | |
1da177e4 | 259 | } |
2f77d107 LT |
260 | pages -= retval; |
261 | vec += retval; | |
262 | start += retval << PAGE_SHIFT; | |
263 | retval = 0; | |
1da177e4 | 264 | } |
2f77d107 LT |
265 | free_page((unsigned long) tmp); |
266 | return retval; | |
1da177e4 | 267 | } |