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 */ boot_init_stack_canary(void)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