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 unfortunately means that on SMP 10 * we cannot have a different canary value per task. 11 */ 12 13 #ifndef __ASM_STACKPROTECTOR_H 14 #define __ASM_STACKPROTECTOR_H 15 16 #include <linux/random.h> 17 #include <linux/version.h> 18 19 extern unsigned long __stack_chk_guard; 20 21 /* 22 * Initialize the stackprotector canary value. 23 * 24 * NOTE: this must only be called from functions that never return, 25 * and it must always be inlined. 26 */ 27 static __always_inline void boot_init_stack_canary(void) 28 { 29 unsigned long canary; 30 31 /* Try to get a semi random initial value. */ 32 get_random_bytes(&canary, sizeof(canary)); 33 canary ^= LINUX_VERSION_CODE; 34 canary &= CANARY_MASK; 35 36 current->stack_canary = canary; 37 if (!IS_ENABLED(CONFIG_STACKPROTECTOR_PER_TASK)) 38 __stack_chk_guard = current->stack_canary; 39 } 40 41 #endif /* _ASM_STACKPROTECTOR_H */ 42