1 /*
2 * Access kernel memory without faulting.
3 */
4 #include <linux/export.h>
5 #include <linux/mm.h>
6 #include <linux/uaccess.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
18 long __weak probe_kernel_read(void *dst, const void *src, size_t size)
19 __attribute__((alias("__probe_kernel_read")));
20
__probe_kernel_read(void * dst,const void * src,size_t size)21 long __probe_kernel_read(void *dst, const 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 }
35 EXPORT_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 */
46 long __weak probe_kernel_write(void *dst, const void *src, size_t size)
47 __attribute__((alias("__probe_kernel_write")));
48
__probe_kernel_write(void * dst,const void * src,size_t size)49 long __probe_kernel_write(void *dst, const 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 }
62 EXPORT_SYMBOL_GPL(probe_kernel_write);
63