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git.proxmox.com Git - mirror_ubuntu-zesty-kernel.git/blob - mm/mincore.c
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>
16 #include <asm/uaccess.h>
17 #include <asm/pgtable.h>
20 * Later we can get more picky about what "in core" means precisely.
21 * For now, simply check to see if the page is in the page cache,
22 * and is up to date; i.e. that no page-in operation would be required
23 * at this time if an application were to map and access this page.
25 static unsigned char mincore_page(struct vm_area_struct
* vma
,
28 unsigned char present
= 0;
29 struct address_space
* as
= vma
->vm_file
->f_mapping
;
32 page
= find_get_page(as
, pgoff
);
34 present
= PageUptodate(page
);
35 page_cache_release(page
);
42 * Do a chunk of "sys_mincore()". We've already checked
43 * all the arguments, we hold the mmap semaphore: we should
44 * just return the amount of info we're asked for.
46 static long do_mincore(unsigned long addr
, unsigned char *vec
, unsigned long pages
)
48 unsigned long i
, nr
, pgoff
;
49 struct vm_area_struct
*vma
= find_vma(current
->mm
, addr
);
52 * find_vma() didn't find anything above us, or we're
53 * in an unmapped hole in the address space: ENOMEM.
55 if (!vma
|| addr
< vma
->vm_start
)
59 * Ok, got it. But check whether it's a segment we support
60 * mincore() on. Right now, we don't do any anonymous mappings.
62 * FIXME: This is just stupid. And returning ENOMEM is
63 * stupid too. We should just look at the page tables. But
64 * this is what we've traditionally done, so we'll just
71 * Calculate how many pages there are left in the vma, and
72 * what the pgoff is for our address.
74 nr
= (vma
->vm_end
- addr
) >> PAGE_SHIFT
;
78 pgoff
= (addr
- vma
->vm_start
) >> PAGE_SHIFT
;
79 pgoff
+= vma
->vm_pgoff
;
81 /* And then we just fill the sucker in.. */
82 for (i
= 0 ; i
< nr
; i
++, pgoff
++)
83 vec
[i
] = mincore_page(vma
, pgoff
);
89 * The mincore(2) system call.
91 * mincore() returns the memory residency status of the pages in the
92 * current process's address space specified by [addr, addr + len).
93 * The status is returned in a vector of bytes. The least significant
94 * bit of each byte is 1 if the referenced page is in memory, otherwise
97 * Because the status of a page can change after mincore() checks it
98 * but before it returns to the application, the returned vector may
99 * contain stale information. Only locked pages are guaranteed to
104 * -EFAULT - vec points to an illegal address
105 * -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE
106 * -ENOMEM - Addresses in the range [addr, addr + len] are
107 * invalid for the address space of this process, or
108 * specify one or more pages which are not currently
110 * -EAGAIN - A kernel resource was temporarily unavailable.
112 asmlinkage
long sys_mincore(unsigned long start
, size_t len
,
113 unsigned char __user
* vec
)
119 /* Check the start address: needs to be page-aligned.. */
120 if (start
& ~PAGE_CACHE_MASK
)
123 /* ..and we need to be passed a valid user-space range */
124 if (!access_ok(VERIFY_READ
, (void __user
*) start
, len
))
127 /* This also avoids any overflows on PAGE_CACHE_ALIGN */
128 pages
= len
>> PAGE_SHIFT
;
129 pages
+= (len
& ~PAGE_MASK
) != 0;
131 if (!access_ok(VERIFY_WRITE
, vec
, pages
))
134 tmp
= (void *) __get_free_page(GFP_USER
);
141 * Do at most PAGE_SIZE entries per iteration, due to
142 * the temporary buffer size.
144 down_read(¤t
->mm
->mmap_sem
);
145 retval
= do_mincore(start
, tmp
, min(pages
, PAGE_SIZE
));
146 up_read(¤t
->mm
->mmap_sem
);
150 if (copy_to_user(vec
, tmp
, retval
)) {
156 start
+= retval
<< PAGE_SHIFT
;
159 free_page((unsigned long) tmp
);