2 * Access kernel memory without faulting.
4 #include <linux/export.h>
6 #include <linux/uaccess.h>
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
14 * Safely read from address @src to the buffer at @dst. If a kernel fault
15 * happens, handle that and return -EFAULT.
18 long __weak probe_kernel_read(void *dst, const void *src, size_t size)
19 __attribute__((alias("__probe_kernel_read")));
21 long __probe_kernel_read(void *dst, const void *src, size_t size)
24 mm_segment_t old_fs = get_fs();
28 ret = __copy_from_user_inatomic(dst,
29 (__force const void __user *)src, size);
33 return ret ? -EFAULT : 0;
35 EXPORT_SYMBOL_GPL(probe_kernel_read);
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
43 * Safely write to address @dst from the buffer at @src. If a kernel fault
44 * happens, handle that and return -EFAULT.
46 long __weak probe_kernel_write(void *dst, const void *src, size_t size)
47 __attribute__((alias("__probe_kernel_write")));
49 long __probe_kernel_write(void *dst, const void *src, size_t size)
52 mm_segment_t old_fs = get_fs();
56 ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
60 return ret ? -EFAULT : 0;
62 EXPORT_SYMBOL_GPL(probe_kernel_write);
65 * strncpy_from_unsafe: - Copy a NUL terminated string from unsafe address.
66 * @dst: Destination address, in kernel space. This buffer must be at
67 * least @count bytes long.
68 * @src: Unsafe address.
69 * @count: Maximum number of bytes to copy, including the trailing NUL.
71 * Copies a NUL-terminated string from unsafe address to kernel buffer.
73 * On success, returns the length of the string INCLUDING the trailing NUL.
75 * If access fails, returns -EFAULT (some data may have been copied
76 * and the trailing NUL added).
78 * If @count is smaller than the length of the string, copies @count-1 bytes,
79 * sets the last byte of @dst buffer to NUL and returns @count.
81 long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count)
83 mm_segment_t old_fs = get_fs();
84 const void *src = unsafe_addr;
87 if (unlikely(count <= 0))
94 ret = __copy_from_user_inatomic(dst++,
95 (const void __user __force *)src++, 1);
96 } while (dst[-1] && ret == 0 && src - unsafe_addr < count);
102 return ret < 0 ? ret : src - unsafe_addr;