aboutsummaryrefslogtreecommitdiffstats
path: root/mm/mincore.c
blob: 07833dc5829df353b4d3cbab0c8c0af668b4f7d7 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
/*
 *	linux/mm/mincore.c
 *
 * Copyright (C) 1994-1999  Linus Torvalds
 */

/*
 * The mincore() system call.
 */
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/syscalls.h>

#include <asm/uaccess.h>
#include <asm/pgtable.h>

/*
 * Later we can get more picky about what "in core" means precisely.
 * For now, simply check to see if the page is in the page cache,
 * and is up to date; i.e. that no page-in operation would be required
 * at this time if an application were to map and access this page.
 */
static unsigned char mincore_page(struct vm_area_struct * vma,
	unsigned long pgoff)
{
	unsigned char present = 0;
	struct address_space * as = vma->vm_file->f_mapping;
	struct page * page;

	page = find_get_page(as, pgoff);
	if (page) {
		present = PageUptodate(page);
		page_cache_release(page);
	}

	return present;
}

static long mincore_vma(struct vm_area_struct * vma,
	unsigned long start, unsigned long end, unsigned char __user * vec)
{
	long error, i, remaining;
	unsigned char * tmp;

	error = -ENOMEM;
	if (!vma->vm_file)
		return error;

	start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
	if (end > vma->vm_end)
		end = vma->vm_end;
	end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;

	error = -EAGAIN;
	tmp = (unsigned char *) __get_free_page(GFP_KERNEL);
	if (!tmp)
		return error;

	/* (end - start) is # of pages, and also # of bytes in "vec */
	remaining = (end - start),

	error = 0;
	for (i = 0; remaining > 0; remaining -= PAGE_SIZE, i++) {
		int j = 0;
		long thispiece = (remaining < PAGE_SIZE) ?
						remaining : PAGE_SIZE;

		while (j < thispiece)
			tmp[j++] = mincore_page(vma, start++);

		if (copy_to_user(vec + PAGE_SIZE * i, tmp, thispiece)) {
			error = -EFAULT;
			break;
		}
	}

	free_page((unsigned long) tmp);
	return error;
}

/*
 * The mincore(2) system call.
 *
 * mincore() returns the memory residency status of the pages in the
 * current process's address space specified by [addr, addr + len).
 * The status is returned in a vector of bytes.  The least significant
 * bit of each byte is 1 if the referenced page is in memory, otherwise
 * it is zero.
 *
 * Because the status of a page can change after mincore() checks it
 * but before it returns to the application, the returned vector may
 * contain stale information.  Only locked pages are guaranteed to
 * remain in memory.
 *
 * return values:
 *  zero    - success
 *  -EFAULT - vec points to an illegal address
 *  -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE
 *  -ENOMEM - Addresses in the range [addr, addr + len] are
 *		invalid for the address space of this process, or
 *		specify one or more pages which are not currently
 *		mapped
 *  -EAGAIN - A kernel resource was temporarily unavailable.
 */
asmlinkage long sys_mincore(unsigned long start, size_t len,
	unsigned char __user * vec)
{
	int index = 0;
	unsigned long end, limit;
	struct vm_area_struct * vma;
	size_t max;
	int unmapped_error = 0;
	long error;

	/* check the arguments */
 	if (start & ~PAGE_CACHE_MASK)
		goto einval;

	if (start < FIRST_USER_PGD_NR * PGDIR_SIZE)
		goto enomem;

	limit = TASK_SIZE;
	if (start >= limit)
		goto enomem;

	if (!len)
		return 0;

	max = limit - start;
	len = PAGE_CACHE_ALIGN(len);
	if (len > max || !len)
		goto enomem;

	end = start + len;

	/* check the output buffer whilst holding the lock */
	error = -EFAULT;
	down_read(&current->mm->mmap_sem);

	if (!access_ok(VERIFY_WRITE, vec, len >> PAGE_SHIFT))
		goto out;

	/*
	 * If the interval [start,end) covers some unmapped address
	 * ranges, just ignore them, but return -ENOMEM at the end.
	 */
	error = 0;

	vma = find_vma(current->mm, start);
	while (vma) {
		/* Here start < vma->vm_end. */
		if (start < vma->vm_start) {
			unmapped_error = -ENOMEM;
			start = vma->vm_start;
		}

		/* Here vma->vm_start <= start < vma->vm_end. */
		if (end <= vma->vm_end) {
			if (start < end) {
				error = mincore_vma(vma, start, end,
							&vec[index]);
				if (error)
					goto out;
			}
			error = unmapped_error;
			goto out;
		}

		/* Here vma->vm_start <= start < vma->vm_end < end. */
		error = mincore_vma(vma, start, vma->vm_end, &vec[index]);
		if (error)
			goto out;
		index += (vma->vm_end - start) >> PAGE_CACHE_SHIFT;
		start = vma->vm_end;
		vma = vma->vm_next;
	}

	/* we found a hole in the area queried if we arrive here */
	error = -ENOMEM;

out:
	up_read(&current->mm->mmap_sem);
	return error;

einval:
	return -EINVAL;
enomem:
	return -ENOMEM;
}