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 <asm/thread_info.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 = get_random_canary(); 31 32 current->stack_canary = canary; 33 #ifndef CONFIG_STACKPROTECTOR_PER_TASK 34 __stack_chk_guard = current->stack_canary; 35 #endif 36 } 37 38 #endif /* _ASM_STACKPROTECTOR_H */ 39