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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/mm/mincore.c
3 *
Linus Torvalds2f77d102006-12-16 09:44:32 -08004 * Copyright (C) 1994-2006 Linus Torvalds
Linus Torvalds1da177e2005-04-16 15:20:36 -07005 */
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>
Nick Piggin42da9cb2007-02-12 00:51:39 -080015#include <linux/swap.h>
16#include <linux/swapops.h>
Naoya Horiguchi4f16fc12009-12-14 17:59:58 -080017#include <linux/hugetlb.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070018
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 */
Nick Piggin42da9cb2007-02-12 00:51:39 -080028static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff)
Linus Torvalds1da177e2005-04-16 15:20:36 -070029{
30 unsigned char present = 0;
Nick Piggin42da9cb2007-02-12 00:51:39 -080031 struct page *page;
Linus Torvalds1da177e2005-04-16 15:20:36 -070032
Nick Piggin42da9cb2007-02-12 00:51:39 -080033 /*
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
Nick Piggin3c18ddd2008-04-28 02:12:10 -070037 * tmpfs's .fault). So swapped out tmpfs mappings are tested here.
Nick Piggin42da9cb2007-02-12 00:51:39 -080038 *
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);
Linus Torvalds1da177e2005-04-16 15:20:36 -070044 if (page) {
45 present = PageUptodate(page);
46 page_cache_release(page);
47 }
48
49 return present;
50}
51
Linus Torvalds2f77d102006-12-16 09:44:32 -080052/*
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 */
57static long do_mincore(unsigned long addr, unsigned char *vec, unsigned long pages)
Linus Torvalds1da177e2005-04-16 15:20:36 -070058{
Nick Piggin42da9cb2007-02-12 00:51:39 -080059 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;
Linus Torvalds2f77d102006-12-16 09:44:32 -080067 struct vm_area_struct *vma = find_vma(current->mm, addr);
Linus Torvalds1da177e2005-04-16 15:20:36 -070068
Linus Torvalds2f77d102006-12-16 09:44:32 -080069 /*
Linus Torvalds4fb23e42006-12-16 16:01:50 -080070 * find_vma() didn't find anything above us, or we're
71 * in an unmapped hole in the address space: ENOMEM.
Linus Torvalds2f77d102006-12-16 09:44:32 -080072 */
Linus Torvalds4fb23e42006-12-16 16:01:50 -080073 if (!vma || addr < vma->vm_start)
74 return -ENOMEM;
Linus Torvalds2f77d102006-12-16 09:44:32 -080075
Naoya Horiguchi4f16fc12009-12-14 17:59:58 -080076#ifdef CONFIG_HUGETLB_PAGE
77 if (is_vm_hugetlb_page(vma)) {
78 struct hstate *h;
79 unsigned long nr_huge;
80 unsigned char present;
81
82 i = 0;
83 nr = min(pages, (vma->vm_end - addr) >> PAGE_SHIFT);
84 h = hstate_vma(vma);
85 nr_huge = ((addr + pages * PAGE_SIZE - 1) >> huge_page_shift(h))
86 - (addr >> huge_page_shift(h)) + 1;
87 nr_huge = min(nr_huge,
88 (vma->vm_end - addr) >> huge_page_shift(h));
89 while (1) {
90 /* hugepage always in RAM for now,
91 * but generally it needs to be check */
92 ptep = huge_pte_offset(current->mm,
93 addr & huge_page_mask(h));
94 present = !!(ptep &&
95 !huge_pte_none(huge_ptep_get(ptep)));
96 while (1) {
97 vec[i++] = present;
98 addr += PAGE_SIZE;
99 /* reach buffer limit */
100 if (i == nr)
101 return nr;
102 /* check hugepage border */
103 if (!((addr & ~huge_page_mask(h))
104 >> PAGE_SHIFT))
105 break;
106 }
107 }
108 return nr;
109 }
110#endif
111
Linus Torvalds2f77d102006-12-16 09:44:32 -0800112 /*
Nick Piggin42da9cb2007-02-12 00:51:39 -0800113 * Calculate how many pages there are left in the last level of the
114 * PTE array for our address.
Linus Torvalds2f77d102006-12-16 09:44:32 -0800115 */
Nick Piggin42da9cb2007-02-12 00:51:39 -0800116 nr = PTRS_PER_PTE - ((addr >> PAGE_SHIFT) & (PTRS_PER_PTE-1));
Nick Piggine0a04cf2007-02-14 12:39:01 +0100117
118 /*
119 * Don't overrun this vma
120 */
121 nr = min(nr, (vma->vm_end - addr) >> PAGE_SHIFT);
122
123 /*
124 * Don't return more than the caller asked for
125 */
126 nr = min(nr, pages);
Linus Torvalds2f77d102006-12-16 09:44:32 -0800127
Nick Piggin42da9cb2007-02-12 00:51:39 -0800128 pgd = pgd_offset(vma->vm_mm, addr);
129 if (pgd_none_or_clear_bad(pgd))
130 goto none_mapped;
131 pud = pud_offset(pgd, addr);
132 if (pud_none_or_clear_bad(pud))
133 goto none_mapped;
134 pmd = pmd_offset(pud, addr);
135 if (pmd_none_or_clear_bad(pmd))
136 goto none_mapped;
Linus Torvalds2f77d102006-12-16 09:44:32 -0800137
Nick Piggin42da9cb2007-02-12 00:51:39 -0800138 ptep = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
139 for (i = 0; i < nr; i++, ptep++, addr += PAGE_SIZE) {
140 unsigned char present;
141 pte_t pte = *ptep;
142
143 if (pte_present(pte)) {
144 present = 1;
145
146 } else if (pte_none(pte)) {
147 if (vma->vm_file) {
148 pgoff = linear_page_index(vma, addr);
149 present = mincore_page(vma->vm_file->f_mapping,
150 pgoff);
151 } else
152 present = 0;
153
154 } else if (pte_file(pte)) {
155 pgoff = pte_to_pgoff(pte);
156 present = mincore_page(vma->vm_file->f_mapping, pgoff);
157
158 } else { /* pte is a swap entry */
159 swp_entry_t entry = pte_to_swp_entry(pte);
160 if (is_migration_entry(entry)) {
161 /* migration entries are always uptodate */
162 present = 1;
163 } else {
Nick Piggin30fcffe2007-02-14 12:35:02 +0100164#ifdef CONFIG_SWAP
Nick Piggin42da9cb2007-02-12 00:51:39 -0800165 pgoff = entry.val;
166 present = mincore_page(&swapper_space, pgoff);
Nick Piggin30fcffe2007-02-14 12:35:02 +0100167#else
168 WARN_ON(1);
169 present = 1;
170#endif
Nick Piggin42da9cb2007-02-12 00:51:39 -0800171 }
172 }
Nick Piggin4a76ef02007-02-14 12:36:32 +0100173
174 vec[i] = present;
Nick Piggin42da9cb2007-02-12 00:51:39 -0800175 }
176 pte_unmap_unlock(ptep-1, ptl);
177
178 return nr;
179
180none_mapped:
181 if (vma->vm_file) {
182 pgoff = linear_page_index(vma, addr);
183 for (i = 0; i < nr; i++, pgoff++)
184 vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
Nick Piggin4a76ef02007-02-14 12:36:32 +0100185 } else {
186 for (i = 0; i < nr; i++)
187 vec[i] = 0;
Nick Piggin42da9cb2007-02-12 00:51:39 -0800188 }
Linus Torvalds2f77d102006-12-16 09:44:32 -0800189
190 return nr;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700191}
192
193/*
194 * The mincore(2) system call.
195 *
196 * mincore() returns the memory residency status of the pages in the
197 * current process's address space specified by [addr, addr + len).
198 * The status is returned in a vector of bytes. The least significant
199 * bit of each byte is 1 if the referenced page is in memory, otherwise
200 * it is zero.
201 *
202 * Because the status of a page can change after mincore() checks it
203 * but before it returns to the application, the returned vector may
204 * contain stale information. Only locked pages are guaranteed to
205 * remain in memory.
206 *
207 * return values:
208 * zero - success
209 * -EFAULT - vec points to an illegal address
210 * -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE
211 * -ENOMEM - Addresses in the range [addr, addr + len] are
212 * invalid for the address space of this process, or
213 * specify one or more pages which are not currently
214 * mapped
215 * -EAGAIN - A kernel resource was temporarily unavailable.
216 */
Heiko Carstens3480b252009-01-14 14:14:16 +0100217SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
218 unsigned char __user *, vec)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700219{
Linus Torvalds2f77d102006-12-16 09:44:32 -0800220 long retval;
221 unsigned long pages;
222 unsigned char *tmp;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700223
Linus Torvalds2f77d102006-12-16 09:44:32 -0800224 /* Check the start address: needs to be page-aligned.. */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700225 if (start & ~PAGE_CACHE_MASK)
Linus Torvalds2f77d102006-12-16 09:44:32 -0800226 return -EINVAL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700227
Linus Torvalds2f77d102006-12-16 09:44:32 -0800228 /* ..and we need to be passed a valid user-space range */
229 if (!access_ok(VERIFY_READ, (void __user *) start, len))
230 return -ENOMEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700231
Linus Torvalds2f77d102006-12-16 09:44:32 -0800232 /* This also avoids any overflows on PAGE_CACHE_ALIGN */
233 pages = len >> PAGE_SHIFT;
234 pages += (len & ~PAGE_MASK) != 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700235
Linus Torvalds2f77d102006-12-16 09:44:32 -0800236 if (!access_ok(VERIFY_WRITE, vec, pages))
237 return -EFAULT;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700238
Linus Torvalds2f77d102006-12-16 09:44:32 -0800239 tmp = (void *) __get_free_page(GFP_USER);
240 if (!tmp)
Linus Torvalds4fb23e42006-12-16 16:01:50 -0800241 return -EAGAIN;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700242
Linus Torvalds2f77d102006-12-16 09:44:32 -0800243 retval = 0;
244 while (pages) {
245 /*
246 * Do at most PAGE_SIZE entries per iteration, due to
247 * the temporary buffer size.
248 */
249 down_read(&current->mm->mmap_sem);
Oleg Nesterov825020c2006-12-17 18:52:47 +0300250 retval = do_mincore(start, tmp, min(pages, PAGE_SIZE));
Linus Torvalds2f77d102006-12-16 09:44:32 -0800251 up_read(&current->mm->mmap_sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700252
Linus Torvalds2f77d102006-12-16 09:44:32 -0800253 if (retval <= 0)
254 break;
255 if (copy_to_user(vec, tmp, retval)) {
256 retval = -EFAULT;
257 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700258 }
Linus Torvalds2f77d102006-12-16 09:44:32 -0800259 pages -= retval;
260 vec += retval;
261 start += retval << PAGE_SHIFT;
262 retval = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700263 }
Linus Torvalds2f77d102006-12-16 09:44:32 -0800264 free_page((unsigned long) tmp);
265 return retval;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700266}