1 /* 2 * GCC stack protector support. 3 * 4 * (This is directly adopted from the ARM implementation) 5 * 6 * Stack protector works by putting predefined pattern at the start of 7 * the stack frame and verifying that it hasn't been overwritten when 8 * returning from the function. The pattern is called stack canary 9 * and gcc expects it to be defined by a global variable called 10 * "__stack_chk_guard" on Xtensa. This unfortunately means that on SMP 11 * we cannot have a different canary value per task. 12 */ 13 14 #ifndef _ASM_STACKPROTECTOR_H 15 #define _ASM_STACKPROTECTOR_H 1 16 17 #include <linux/random.h> 18 #include <linux/version.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; 31 32 /* Try to get a semi random initial value. */ 33 get_random_bytes(&canary, sizeof(canary)); 34 canary ^= LINUX_VERSION_CODE; 35 36 current->stack_canary = canary; 37 __stack_chk_guard = current->stack_canary; 38 } 39 40 #endif /* _ASM_STACKPROTECTOR_H */ 41