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 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 
18 extern 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  */
26 static __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 */
39