Root/mm/maccess.c

1/*
2 * Access kernel memory without faulting.
3 */
4#include <linux/uaccess.h>
5#include <linux/module.h>
6#include <linux/mm.h>
7
8/**
9 * probe_kernel_read(): safely attempt to read from a location
10 * @dst: pointer to the buffer that shall take the data
11 * @src: address to read from
12 * @size: size of the data chunk
13 *
14 * Safely read from address @src to the buffer at @dst. If a kernel fault
15 * happens, handle that and return -EFAULT.
16 */
17
18long __weak probe_kernel_read(void *dst, void *src, size_t size)
19    __attribute__((alias("__probe_kernel_read")));
20
21long __probe_kernel_read(void *dst, void *src, size_t size)
22{
23    long ret;
24    mm_segment_t old_fs = get_fs();
25
26    set_fs(KERNEL_DS);
27    pagefault_disable();
28    ret = __copy_from_user_inatomic(dst,
29            (__force const void __user *)src, size);
30    pagefault_enable();
31    set_fs(old_fs);
32
33    return ret ? -EFAULT : 0;
34}
35EXPORT_SYMBOL_GPL(probe_kernel_read);
36
37/**
38 * probe_kernel_write(): safely attempt to write to a location
39 * @dst: address to write to
40 * @src: pointer to the data that shall be written
41 * @size: size of the data chunk
42 *
43 * Safely write to address @dst from the buffer at @src. If a kernel fault
44 * happens, handle that and return -EFAULT.
45 */
46long __weak probe_kernel_write(void *dst, void *src, size_t size)
47    __attribute__((alias("__probe_kernel_write")));
48
49long __probe_kernel_write(void *dst, void *src, size_t size)
50{
51    long ret;
52    mm_segment_t old_fs = get_fs();
53
54    set_fs(KERNEL_DS);
55    pagefault_disable();
56    ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
57    pagefault_enable();
58    set_fs(old_fs);
59
60    return ret ? -EFAULT : 0;
61}
62EXPORT_SYMBOL_GPL(probe_kernel_write);
63

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