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 #endif 43 } 44 45 #endif /* _ASM_STACKPROTECTOR_H */ 46