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