1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3  * GCC stack protector support.
4  *
5  * (This is directly adopted from the ARM implementation)
6  *
7  * Stack protector works by putting predefined pattern at the start of
8  * the stack frame and verifying that it hasn't been overwritten when
9  * returning from the function.  The pattern is called stack canary
10  * and gcc expects it to be defined by a global variable called
11  * "__stack_chk_guard" on MIPS.  This unfortunately means that on SMP
12  * we cannot have a different canary value per task.
13  */
14 
15 #ifndef _ASM_STACKPROTECTOR_H
16 #define _ASM_STACKPROTECTOR_H 1
17 
18 #include <linux/random.h>
19 #include <linux/version.h>
20 
21 extern unsigned long __stack_chk_guard;
22 
23 /*
24  * Initialize the stackprotector canary value.
25  *
26  * NOTE: this must only be called from functions that never return,
27  * and it must always be inlined.
28  */
boot_init_stack_canary(void)29 static __always_inline void boot_init_stack_canary(void)
30 {
31 	unsigned long canary;
32 
33 	/* Try to get a semi random initial value. */
34 	get_random_bytes(&canary, sizeof(canary));
35 	canary ^= LINUX_VERSION_CODE;
36 
37 	current->stack_canary = canary;
38 	__stack_chk_guard = current->stack_canary;
39 }
40 
41 #endif	/* _ASM_STACKPROTECTOR_H */
42