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Nicolas Pitrec743f382010-05-24 23:55:42 -04001/*
2 * GCC stack protector support.
3 *
4 * Stack protector works by putting predefined pattern at the start of
5 * the stack frame and verifying that it hasn't been overwritten when
6 * returning from the function. The pattern is called stack canary
7 * and gcc expects it to be defined by a global variable called
8 * "__stack_chk_guard" on ARM. This unfortunately means that on SMP
9 * we cannot have a different canary value per task.
10 */
11
12#ifndef _ASM_STACKPROTECTOR_H
13#define _ASM_STACKPROTECTOR_H 1
14
15#include <linux/random.h>
16#include <linux/version.h>
17
18extern unsigned long __stack_chk_guard;
19
20/*
21 * Initialize the stackprotector canary value.
22 *
23 * NOTE: this must only be called from functions that never return,
24 * and it must always be inlined.
25 */
26static __always_inline void boot_init_stack_canary(void)
27{
28 unsigned long canary;
29
30 /* Try to get a semi random initial value. */
31 get_random_bytes(&canary, sizeof(canary));
32 canary ^= LINUX_VERSION_CODE;
33
34 current->stack_canary = canary;
35 __stack_chk_guard = current->stack_canary;
36}
37
38#endif /* _ASM_STACKPROTECTOR_H */