1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * GCC stack protector support.
4 *
5 * (This is directly adopted from the ARM implementation)
6 *
7 * Stack protector works by putting predefined pattern at the start of
8 * the stack frame and verifying that it hasn't been overwritten when
9 * returning from the function. The pattern is called stack canary
10 * and gcc expects it to be defined by a global variable called
11 * "__stack_chk_guard" on MIPS. This unfortunately means that on SMP
12 * we cannot have a different canary value per task.
13 */
14
15 #ifndef _ASM_STACKPROTECTOR_H
16 #define _ASM_STACKPROTECTOR_H 1
17
18 #include <linux/random.h>
19 #include <linux/version.h>
20
21 extern unsigned long __stack_chk_guard;
22
23 /*
24 * Initialize the stackprotector canary value.
25 *
26 * NOTE: this must only be called from functions that never return,
27 * and it must always be inlined.
28 */
29 static __always_inline void boot_init_stack_canary(void)
30 {
31 unsigned long canary;
32
33 /* Try to get a semi random initial value. */
34 get_random_bytes(&canary, sizeof(canary));
35 canary ^= LINUX_VERSION_CODE;
36
37 current->stack_canary = canary;
38 __stack_chk_guard = current->stack_canary;
39 }
40
41 #endif /* _ASM_STACKPROTECTOR_H */