boot_init_stack_canary
[Author: Bo Shen <[email protected]>]
[Linux kernel: git: 0c0bd34]
<arch/arm/include/asm/stackprotector.h>
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 */
这代码具体做何用处还不知道，暂时不表。