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