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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 | ||
22 | /* | |
23 | * Later we can get more picky about what "in core" means precisely. | |
24 | * For now, simply check to see if the page is in the page cache, | |
25 | * and is up to date; i.e. that no page-in operation would be required | |
26 | * at this time if an application were to map and access this page. | |
27 | */ | |
42da9cbd | 28 | static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff) |
1da177e4 LT |
29 | { |
30 | unsigned char present = 0; | |
42da9cbd | 31 | struct page *page; |
1da177e4 | 32 | |
42da9cbd NP |
33 | /* |
34 | * When tmpfs swaps out a page from a file, any process mapping that | |
35 | * file will not get a swp_entry_t in its pte, but rather it is like | |
36 | * any other file mapping (ie. marked !present and faulted in with | |
3c18ddd1 | 37 | * tmpfs's .fault). So swapped out tmpfs mappings are tested here. |
42da9cbd NP |
38 | * |
39 | * However when tmpfs moves the page from pagecache and into swapcache, | |
40 | * it is still in core, but the find_get_page below won't find it. | |
41 | * No big deal, but make a note of it. | |
42 | */ | |
43 | page = find_get_page(mapping, pgoff); | |
1da177e4 LT |
44 | if (page) { |
45 | present = PageUptodate(page); | |
46 | page_cache_release(page); | |
47 | } | |
48 | ||
49 | return present; | |
50 | } | |
51 | ||
2f77d107 LT |
52 | /* |
53 | * Do a chunk of "sys_mincore()". We've already checked | |
54 | * all the arguments, we hold the mmap semaphore: we should | |
55 | * just return the amount of info we're asked for. | |
56 | */ | |
6a60f1b3 | 57 | static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec) |
1da177e4 | 58 | { |
42da9cbd NP |
59 | pgd_t *pgd; |
60 | pud_t *pud; | |
61 | pmd_t *pmd; | |
62 | pte_t *ptep; | |
63 | spinlock_t *ptl; | |
64 | unsigned long nr; | |
65 | int i; | |
66 | pgoff_t pgoff; | |
6a60f1b3 | 67 | struct vm_area_struct *vma; |
1da177e4 | 68 | |
6a60f1b3 | 69 | vma = find_vma(current->mm, addr); |
4fb23e43 LT |
70 | if (!vma || addr < vma->vm_start) |
71 | return -ENOMEM; | |
1da177e4 | 72 | |
6a60f1b3 JW |
73 | nr = min(pages, (vma->vm_end - addr) >> PAGE_SHIFT); |
74 | ||
4f16fc10 NH |
75 | #ifdef CONFIG_HUGETLB_PAGE |
76 | if (is_vm_hugetlb_page(vma)) { | |
77 | struct hstate *h; | |
4f16fc10 NH |
78 | |
79 | i = 0; | |
4f16fc10 | 80 | h = hstate_vma(vma); |
4f16fc10 | 81 | while (1) { |
6a60f1b3 JW |
82 | unsigned char present; |
83 | /* | |
84 | * Huge pages are always in RAM for now, but | |
85 | * theoretically it needs to be checked. | |
86 | */ | |
4f16fc10 NH |
87 | ptep = huge_pte_offset(current->mm, |
88 | addr & huge_page_mask(h)); | |
6a60f1b3 | 89 | present = ptep && !huge_pte_none(huge_ptep_get(ptep)); |
4f16fc10 NH |
90 | while (1) { |
91 | vec[i++] = present; | |
92 | addr += PAGE_SIZE; | |
93 | /* reach buffer limit */ | |
94 | if (i == nr) | |
95 | return nr; | |
96 | /* check hugepage border */ | |
6a60f1b3 | 97 | if (!(addr & ~huge_page_mask(h))) |
4f16fc10 NH |
98 | break; |
99 | } | |
100 | } | |
101 | return nr; | |
102 | } | |
103 | #endif | |
104 | ||
2f77d107 | 105 | /* |
42da9cbd NP |
106 | * Calculate how many pages there are left in the last level of the |
107 | * PTE array for our address. | |
2f77d107 | 108 | */ |
6a60f1b3 | 109 | nr = min(nr, PTRS_PER_PTE - ((addr >> PAGE_SHIFT) & (PTRS_PER_PTE-1))); |
1da177e4 | 110 | |
42da9cbd NP |
111 | pgd = pgd_offset(vma->vm_mm, addr); |
112 | if (pgd_none_or_clear_bad(pgd)) | |
113 | goto none_mapped; | |
114 | pud = pud_offset(pgd, addr); | |
115 | if (pud_none_or_clear_bad(pud)) | |
116 | goto none_mapped; | |
117 | pmd = pmd_offset(pud, addr); | |
118 | if (pmd_none_or_clear_bad(pmd)) | |
119 | goto none_mapped; | |
120 | ||
121 | ptep = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); | |
122 | for (i = 0; i < nr; i++, ptep++, addr += PAGE_SIZE) { | |
42da9cbd | 123 | pte_t pte = *ptep; |
1da177e4 | 124 | |
6a60f1b3 | 125 | if (pte_none(pte)) { |
42da9cbd NP |
126 | if (vma->vm_file) { |
127 | pgoff = linear_page_index(vma, addr); | |
6a60f1b3 JW |
128 | vec[i] = mincore_page(vma->vm_file->f_mapping, |
129 | pgoff); | |
42da9cbd | 130 | } else |
6a60f1b3 JW |
131 | vec[i] = 0; |
132 | } else if (pte_present(pte)) | |
133 | vec[i] = 1; | |
134 | else if (pte_file(pte)) { | |
42da9cbd | 135 | pgoff = pte_to_pgoff(pte); |
6a60f1b3 | 136 | vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff); |
42da9cbd NP |
137 | } else { /* pte is a swap entry */ |
138 | swp_entry_t entry = pte_to_swp_entry(pte); | |
6a60f1b3 | 139 | |
42da9cbd NP |
140 | if (is_migration_entry(entry)) { |
141 | /* migration entries are always uptodate */ | |
6a60f1b3 | 142 | vec[i] = 1; |
42da9cbd | 143 | } else { |
30fcffed | 144 | #ifdef CONFIG_SWAP |
42da9cbd | 145 | pgoff = entry.val; |
6a60f1b3 | 146 | vec[i] = mincore_page(&swapper_space, pgoff); |
30fcffed NP |
147 | #else |
148 | WARN_ON(1); | |
6a60f1b3 | 149 | vec[i] = 1; |
30fcffed | 150 | #endif |
42da9cbd NP |
151 | } |
152 | } | |
153 | } | |
6a60f1b3 | 154 | pte_unmap_unlock(ptep - 1, ptl); |
42da9cbd NP |
155 | |
156 | return nr; | |
157 | ||
158 | none_mapped: | |
159 | if (vma->vm_file) { | |
160 | pgoff = linear_page_index(vma, addr); | |
161 | for (i = 0; i < nr; i++, pgoff++) | |
162 | vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff); | |
4a76ef03 NP |
163 | } else { |
164 | for (i = 0; i < nr; i++) | |
165 | vec[i] = 0; | |
42da9cbd | 166 | } |
1da177e4 | 167 | |
2f77d107 | 168 | return nr; |
1da177e4 LT |
169 | } |
170 | ||
171 | /* | |
172 | * The mincore(2) system call. | |
173 | * | |
174 | * mincore() returns the memory residency status of the pages in the | |
175 | * current process's address space specified by [addr, addr + len). | |
176 | * The status is returned in a vector of bytes. The least significant | |
177 | * bit of each byte is 1 if the referenced page is in memory, otherwise | |
178 | * it is zero. | |
179 | * | |
180 | * Because the status of a page can change after mincore() checks it | |
181 | * but before it returns to the application, the returned vector may | |
182 | * contain stale information. Only locked pages are guaranteed to | |
183 | * remain in memory. | |
184 | * | |
185 | * return values: | |
186 | * zero - success | |
187 | * -EFAULT - vec points to an illegal address | |
188 | * -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE | |
189 | * -ENOMEM - Addresses in the range [addr, addr + len] are | |
190 | * invalid for the address space of this process, or | |
191 | * specify one or more pages which are not currently | |
192 | * mapped | |
193 | * -EAGAIN - A kernel resource was temporarily unavailable. | |
194 | */ | |
3480b257 HC |
195 | SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, |
196 | unsigned char __user *, vec) | |
1da177e4 | 197 | { |
2f77d107 LT |
198 | long retval; |
199 | unsigned long pages; | |
200 | unsigned char *tmp; | |
1da177e4 | 201 | |
2f77d107 LT |
202 | /* Check the start address: needs to be page-aligned.. */ |
203 | if (start & ~PAGE_CACHE_MASK) | |
204 | return -EINVAL; | |
1da177e4 | 205 | |
2f77d107 LT |
206 | /* ..and we need to be passed a valid user-space range */ |
207 | if (!access_ok(VERIFY_READ, (void __user *) start, len)) | |
208 | return -ENOMEM; | |
1da177e4 | 209 | |
2f77d107 LT |
210 | /* This also avoids any overflows on PAGE_CACHE_ALIGN */ |
211 | pages = len >> PAGE_SHIFT; | |
212 | pages += (len & ~PAGE_MASK) != 0; | |
1da177e4 | 213 | |
2f77d107 LT |
214 | if (!access_ok(VERIFY_WRITE, vec, pages)) |
215 | return -EFAULT; | |
1da177e4 | 216 | |
2f77d107 LT |
217 | tmp = (void *) __get_free_page(GFP_USER); |
218 | if (!tmp) | |
4fb23e43 | 219 | return -EAGAIN; |
2f77d107 LT |
220 | |
221 | retval = 0; | |
222 | while (pages) { | |
223 | /* | |
224 | * Do at most PAGE_SIZE entries per iteration, due to | |
225 | * the temporary buffer size. | |
226 | */ | |
227 | down_read(¤t->mm->mmap_sem); | |
6a60f1b3 | 228 | retval = do_mincore(start, min(pages, PAGE_SIZE), tmp); |
2f77d107 LT |
229 | up_read(¤t->mm->mmap_sem); |
230 | ||
231 | if (retval <= 0) | |
232 | break; | |
233 | if (copy_to_user(vec, tmp, retval)) { | |
234 | retval = -EFAULT; | |
235 | break; | |
1da177e4 | 236 | } |
2f77d107 LT |
237 | pages -= retval; |
238 | vec += retval; | |
239 | start += retval << PAGE_SHIFT; | |
240 | retval = 0; | |
1da177e4 | 241 | } |
2f77d107 LT |
242 | free_page((unsigned long) tmp); |
243 | return retval; | |
1da177e4 | 244 | } |