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 <linux/random.h>
19 #include <linux/version.h>
20
21 #include <asm/thread_info.h>
22
23 extern unsigned long __stack_chk_guard;
24
25 /*
26 * Initialize the stackprotector canary value.
27 *
28 * NOTE: this must only be called from functions that never return,
29 * and it must always be inlined.
30 */
31 static __always_inline void boot_init_stack_canary(void)
32 {
33 unsigned long canary;
34
35 /* Try to get a semi random initial value. */
36 get_random_bytes(&canary, sizeof(canary));
37 canary ^= LINUX_VERSION_CODE;
38
39 current->stack_canary = canary;
40 #ifndef CONFIG_STACKPROTECTOR_PER_TASK
41 __stack_chk_guard = current->stack_canary;
42 #else
43 current_thread_info()->stack_canary = current->stack_canary;
44 #endif
45 }
46
47 #endif /* _ASM_STACKPROTECTOR_H */