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4 * Copyright (C) 1994-2006 Linus Torvalds
8 * The mincore() system call.
10 #include <linux/slab.h>
11 #include <linux/pagemap.h>
13 #include <linux/mman.h>
14 #include <linux/syscalls.h>
15 #include <linux/swap.h>
16 #include <linux/swapops.h>
18 #include <asm/uaccess.h>
19 #include <asm/pgtable.h>
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.
27 static unsigned char mincore_page(struct address_space
*mapping
, pgoff_t pgoff
)
29 unsigned char present
= 0;
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.
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.
42 page
= find_get_page(mapping
, pgoff
);
44 present
= PageUptodate(page
);
45 page_cache_release(page
);
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.
56 static long do_mincore(unsigned long addr
, unsigned char *vec
, unsigned long pages
)
66 struct vm_area_struct
*vma
= find_vma(current
->mm
, addr
);
69 * find_vma() didn't find anything above us, or we're
70 * in an unmapped hole in the address space: ENOMEM.
72 if (!vma
|| addr
< vma
->vm_start
)
76 * Calculate how many pages there are left in the last level of the
77 * PTE array for our address.
79 nr
= PTRS_PER_PTE
- ((addr
>> PAGE_SHIFT
) & (PTRS_PER_PTE
-1));
83 pgd
= pgd_offset(vma
->vm_mm
, addr
);
84 if (pgd_none_or_clear_bad(pgd
))
86 pud
= pud_offset(pgd
, addr
);
87 if (pud_none_or_clear_bad(pud
))
89 pmd
= pmd_offset(pud
, addr
);
90 if (pmd_none_or_clear_bad(pmd
))
93 ptep
= pte_offset_map_lock(vma
->vm_mm
, pmd
, addr
, &ptl
);
94 for (i
= 0; i
< nr
; i
++, ptep
++, addr
+= PAGE_SIZE
) {
95 unsigned char present
;
98 if (pte_present(pte
)) {
101 } else if (pte_none(pte
)) {
103 pgoff
= linear_page_index(vma
, addr
);
104 present
= mincore_page(vma
->vm_file
->f_mapping
,
109 } else if (pte_file(pte
)) {
110 pgoff
= pte_to_pgoff(pte
);
111 present
= mincore_page(vma
->vm_file
->f_mapping
, pgoff
);
113 } else { /* pte is a swap entry */
114 swp_entry_t entry
= pte_to_swp_entry(pte
);
115 if (is_migration_entry(entry
)) {
116 /* migration entries are always uptodate */
120 present
= mincore_page(&swapper_space
, pgoff
);
124 pte_unmap_unlock(ptep
-1, ptl
);
130 pgoff
= linear_page_index(vma
, addr
);
131 for (i
= 0; i
< nr
; i
++, pgoff
++)
132 vec
[i
] = mincore_page(vma
->vm_file
->f_mapping
, pgoff
);
139 * The mincore(2) system call.
141 * mincore() returns the memory residency status of the pages in the
142 * current process's address space specified by [addr, addr + len).
143 * The status is returned in a vector of bytes. The least significant
144 * bit of each byte is 1 if the referenced page is in memory, otherwise
147 * Because the status of a page can change after mincore() checks it
148 * but before it returns to the application, the returned vector may
149 * contain stale information. Only locked pages are guaranteed to
154 * -EFAULT - vec points to an illegal address
155 * -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE
156 * -ENOMEM - Addresses in the range [addr, addr + len] are
157 * invalid for the address space of this process, or
158 * specify one or more pages which are not currently
160 * -EAGAIN - A kernel resource was temporarily unavailable.
162 asmlinkage
long sys_mincore(unsigned long start
, size_t len
,
163 unsigned char __user
* vec
)
169 /* Check the start address: needs to be page-aligned.. */
170 if (start
& ~PAGE_CACHE_MASK
)
173 /* ..and we need to be passed a valid user-space range */
174 if (!access_ok(VERIFY_READ
, (void __user
*) start
, len
))
177 /* This also avoids any overflows on PAGE_CACHE_ALIGN */
178 pages
= len
>> PAGE_SHIFT
;
179 pages
+= (len
& ~PAGE_MASK
) != 0;
181 if (!access_ok(VERIFY_WRITE
, vec
, pages
))
184 tmp
= (void *) __get_free_page(GFP_USER
);
191 * Do at most PAGE_SIZE entries per iteration, due to
192 * the temporary buffer size.
194 down_read(¤t
->mm
->mmap_sem
);
195 retval
= do_mincore(start
, tmp
, min(pages
, PAGE_SIZE
));
196 up_read(¤t
->mm
->mmap_sem
);
200 if (copy_to_user(vec
, tmp
, retval
)) {
206 start
+= retval
<< PAGE_SHIFT
;
209 free_page((unsigned long) tmp
);