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 */
41