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1/*
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 PPC. 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
14
15#include <linux/random.h>
16#include <linux/version.h>
17#include <asm/reg.h>
18
19extern 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 */
27static __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 ^= mftb();
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 */