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