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 MIPS.  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
20extern 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 */
28static __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 */