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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/pagemap.h>
11 #include <linux/gfp.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 #include <linux/shmem_fs.h>
18 #include <linux/hugetlb.h>
19
20 #include <linux/uaccess.h>
21 #include <asm/pgtable.h>
22
23 static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr,
24 unsigned long end, struct mm_walk *walk)
25 {
26 #ifdef CONFIG_HUGETLB_PAGE
27 unsigned char present;
28 unsigned char *vec = walk->private;
29
30 /*
31 * Hugepages under user process are always in RAM and never
32 * swapped out, but theoretically it needs to be checked.
33 */
34 present = pte && !huge_pte_none(huge_ptep_get(pte));
35 for (; addr != end; vec++, addr += PAGE_SIZE)
36 *vec = present;
37 walk->private = vec;
38 #else
39 BUG();
40 #endif
41 return 0;
42 }
43
44 /*
45 * Later we can get more picky about what "in core" means precisely.
46 * For now, simply check to see if the page is in the page cache,
47 * and is up to date; i.e. that no page-in operation would be required
48 * at this time if an application were to map and access this page.
49 */
50 static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff)
51 {
52 unsigned char present = 0;
53 struct page *page;
54
55 /*
56 * When tmpfs swaps out a page from a file, any process mapping that
57 * file will not get a swp_entry_t in its pte, but rather it is like
58 * any other file mapping (ie. marked !present and faulted in with
59 * tmpfs's .fault). So swapped out tmpfs mappings are tested here.
60 */
61 #ifdef CONFIG_SWAP
62 if (shmem_mapping(mapping)) {
63 page = find_get_entry(mapping, pgoff);
64 /*
65 * shmem/tmpfs may return swap: account for swapcache
66 * page too.
67 */
68 if (radix_tree_exceptional_entry(page)) {
69 swp_entry_t swp = radix_to_swp_entry(page);
70 page = find_get_page(swap_address_space(swp),
71 swp_offset(swp));
72 }
73 } else
74 page = find_get_page(mapping, pgoff);
75 #else
76 page = find_get_page(mapping, pgoff);
77 #endif
78 if (page) {
79 present = PageUptodate(page);
80 put_page(page);
81 }
82
83 return present;
84 }
85
86 static int __mincore_unmapped_range(unsigned long addr, unsigned long end,
87 struct vm_area_struct *vma, unsigned char *vec)
88 {
89 unsigned long nr = (end - addr) >> PAGE_SHIFT;
90 int i;
91
92 if (vma->vm_file) {
93 pgoff_t pgoff;
94
95 pgoff = linear_page_index(vma, addr);
96 for (i = 0; i < nr; i++, pgoff++)
97 vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
98 } else {
99 for (i = 0; i < nr; i++)
100 vec[i] = 0;
101 }
102 return nr;
103 }
104
105 static int mincore_unmapped_range(unsigned long addr, unsigned long end,
106 struct mm_walk *walk)
107 {
108 walk->private += __mincore_unmapped_range(addr, end,
109 walk->vma, walk->private);
110 return 0;
111 }
112
113 static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
114 struct mm_walk *walk)
115 {
116 spinlock_t *ptl;
117 struct vm_area_struct *vma = walk->vma;
118 pte_t *ptep;
119 unsigned char *vec = walk->private;
120 int nr = (end - addr) >> PAGE_SHIFT;
121
122 ptl = pmd_trans_huge_lock(pmd, vma);
123 if (ptl) {
124 memset(vec, 1, nr);
125 spin_unlock(ptl);
126 goto out;
127 }
128
129 if (pmd_trans_unstable(pmd)) {
130 __mincore_unmapped_range(addr, end, vma, vec);
131 goto out;
132 }
133
134 ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
135 for (; addr != end; ptep++, addr += PAGE_SIZE) {
136 pte_t pte = *ptep;
137
138 if (pte_none(pte))
139 __mincore_unmapped_range(addr, addr + PAGE_SIZE,
140 vma, vec);
141 else if (pte_present(pte))
142 *vec = 1;
143 else { /* pte is a swap entry */
144 swp_entry_t entry = pte_to_swp_entry(pte);
145
146 if (non_swap_entry(entry)) {
147 /*
148 * migration or hwpoison entries are always
149 * uptodate
150 */
151 *vec = 1;
152 } else {
153 #ifdef CONFIG_SWAP
154 *vec = mincore_page(swap_address_space(entry),
155 swp_offset(entry));
156 #else
157 WARN_ON(1);
158 *vec = 1;
159 #endif
160 }
161 }
162 vec++;
163 }
164 pte_unmap_unlock(ptep - 1, ptl);
165 out:
166 walk->private += nr;
167 cond_resched();
168 return 0;
169 }
170
171 /*
172 * Do a chunk of "sys_mincore()". We've already checked
173 * all the arguments, we hold the mmap semaphore: we should
174 * just return the amount of info we're asked for.
175 */
176 static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec)
177 {
178 struct vm_area_struct *vma;
179 unsigned long end;
180 int err;
181 struct mm_walk mincore_walk = {
182 .pmd_entry = mincore_pte_range,
183 .pte_hole = mincore_unmapped_range,
184 .hugetlb_entry = mincore_hugetlb,
185 .private = vec,
186 };
187
188 vma = find_vma(current->mm, addr);
189 if (!vma || addr < vma->vm_start)
190 return -ENOMEM;
191 mincore_walk.mm = vma->vm_mm;
192 end = min(vma->vm_end, addr + (pages << PAGE_SHIFT));
193 err = walk_page_range(addr, end, &mincore_walk);
194 if (err < 0)
195 return err;
196 return (end - addr) >> PAGE_SHIFT;
197 }
198
199 /*
200 * The mincore(2) system call.
201 *
202 * mincore() returns the memory residency status of the pages in the
203 * current process's address space specified by [addr, addr + len).
204 * The status is returned in a vector of bytes. The least significant
205 * bit of each byte is 1 if the referenced page is in memory, otherwise
206 * it is zero.
207 *
208 * Because the status of a page can change after mincore() checks it
209 * but before it returns to the application, the returned vector may
210 * contain stale information. Only locked pages are guaranteed to
211 * remain in memory.
212 *
213 * return values:
214 * zero - success
215 * -EFAULT - vec points to an illegal address
216 * -EINVAL - addr is not a multiple of PAGE_SIZE
217 * -ENOMEM - Addresses in the range [addr, addr + len] are
218 * invalid for the address space of this process, or
219 * specify one or more pages which are not currently
220 * mapped
221 * -EAGAIN - A kernel resource was temporarily unavailable.
222 */
223 SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
224 unsigned char __user *, vec)
225 {
226 long retval;
227 unsigned long pages;
228 unsigned char *tmp;
229
230 /* Check the start address: needs to be page-aligned.. */
231 if (start & ~PAGE_MASK)
232 return -EINVAL;
233
234 /* ..and we need to be passed a valid user-space range */
235 if (!access_ok(VERIFY_READ, (void __user *) start, len))
236 return -ENOMEM;
237
238 /* This also avoids any overflows on PAGE_ALIGN */
239 pages = len >> PAGE_SHIFT;
240 pages += (offset_in_page(len)) != 0;
241
242 if (!access_ok(VERIFY_WRITE, vec, pages))
243 return -EFAULT;
244
245 tmp = (void *) __get_free_page(GFP_USER);
246 if (!tmp)
247 return -EAGAIN;
248
249 retval = 0;
250 while (pages) {
251 /*
252 * Do at most PAGE_SIZE entries per iteration, due to
253 * the temporary buffer size.
254 */
255 down_read(&current->mm->mmap_sem);
256 retval = do_mincore(start, min(pages, PAGE_SIZE), tmp);
257 up_read(&current->mm->mmap_sem);
258
259 if (retval <= 0)
260 break;
261 if (copy_to_user(vec, tmp, retval)) {
262 retval = -EFAULT;
263 break;
264 }
265 pages -= retval;
266 vec += retval;
267 start += retval << PAGE_SHIFT;
268 retval = 0;
269 }
270 free_page((unsigned long) tmp);
271 return retval;
272 }