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 */
probe_kernel_read(void * dst,void * src,size_t size)17 long probe_kernel_read(void *dst, void *src, size_t size)
18 {
19 long ret;
20 mm_segment_t old_fs = get_fs();
21
22 set_fs(KERNEL_DS);
23 pagefault_disable();
24 ret = __copy_from_user_inatomic(dst,
25 (__force const void __user *)src, size);
26 pagefault_enable();
27 set_fs(old_fs);
28
29 return ret ? -EFAULT : 0;
30 }
31 EXPORT_SYMBOL_GPL(probe_kernel_read);
32
33 /**
34 * probe_kernel_write(): safely attempt to write to a location
35 * @dst: address to write to
36 * @src: pointer to the data that shall be written
37 * @size: size of the data chunk
38 *
39 * Safely write to address @dst from the buffer at @src. If a kernel fault
40 * happens, handle that and return -EFAULT.
41 */
probe_kernel_write(void * dst,void * src,size_t size)42 long probe_kernel_write(void *dst, void *src, size_t size)
43 {
44 long ret;
45 mm_segment_t old_fs = get_fs();
46
47 set_fs(KERNEL_DS);
48 pagefault_disable();
49 ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
50 pagefault_enable();
51 set_fs(old_fs);
52
53 return ret ? -EFAULT : 0;
54 }
55 EXPORT_SYMBOL_GPL(probe_kernel_write);
56