1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3  * GCC stack protector support.
4  *
5  * Stack protector works by putting predefined pattern at the start of
6  * the stack frame and verifying that it hasn't been overwritten when
7  * returning from the function.  The pattern is called stack canary
8  * and gcc expects it to be defined by a global variable called
9  * "__stack_chk_guard" on ARM.  This prevents SMP systems from using a
10  * different value for each task unless we enable a GCC plugin that
11  * replaces these symbol references with references to each task's own
12  * value.
13  */
14 
15 #ifndef _ASM_STACKPROTECTOR_H
16 #define _ASM_STACKPROTECTOR_H 1
17 
18 #include <asm/thread_info.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 = get_random_canary();
31 
32 	current->stack_canary = canary;
33 #ifndef CONFIG_STACKPROTECTOR_PER_TASK
34 	__stack_chk_guard = current->stack_canary;
35 #endif
36 }
37 
38 #endif	/* _ASM_STACKPROTECTOR_H */
39