1b2441318SGreg Kroah-Hartman /* SPDX-License-Identifier: GPL-2.0 */ 2c743f380SNicolas Pitre /* 3c743f380SNicolas Pitre * GCC stack protector support. 4c743f380SNicolas Pitre * 5c743f380SNicolas Pitre * Stack protector works by putting predefined pattern at the start of 6c743f380SNicolas Pitre * the stack frame and verifying that it hasn't been overwritten when 7c743f380SNicolas Pitre * returning from the function. The pattern is called stack canary 8c743f380SNicolas Pitre * and gcc expects it to be defined by a global variable called 9*189af465SArd Biesheuvel * "__stack_chk_guard" on ARM. This prevents SMP systems from using a 10*189af465SArd Biesheuvel * different value for each task unless we enable a GCC plugin that 11*189af465SArd Biesheuvel * replaces these symbol references with references to each task's own 12*189af465SArd Biesheuvel * value. 13c743f380SNicolas Pitre */ 14c743f380SNicolas Pitre 15c743f380SNicolas Pitre #ifndef _ASM_STACKPROTECTOR_H 16c743f380SNicolas Pitre #define _ASM_STACKPROTECTOR_H 1 17c743f380SNicolas Pitre 18c743f380SNicolas Pitre #include <linux/random.h> 19c743f380SNicolas Pitre #include <linux/version.h> 20c743f380SNicolas Pitre 21*189af465SArd Biesheuvel #include <asm/thread_info.h> 22*189af465SArd Biesheuvel 23c743f380SNicolas Pitre extern unsigned long __stack_chk_guard; 24c743f380SNicolas Pitre 25c743f380SNicolas Pitre /* 26c743f380SNicolas Pitre * Initialize the stackprotector canary value. 27c743f380SNicolas Pitre * 28c743f380SNicolas Pitre * NOTE: this must only be called from functions that never return, 29c743f380SNicolas Pitre * and it must always be inlined. 30c743f380SNicolas Pitre */ 31c743f380SNicolas Pitre static __always_inline void boot_init_stack_canary(void) 32c743f380SNicolas Pitre { 33c743f380SNicolas Pitre unsigned long canary; 34c743f380SNicolas Pitre 35c743f380SNicolas Pitre /* Try to get a semi random initial value. */ 36c743f380SNicolas Pitre get_random_bytes(&canary, sizeof(canary)); 37c743f380SNicolas Pitre canary ^= LINUX_VERSION_CODE; 38c743f380SNicolas Pitre 39c743f380SNicolas Pitre current->stack_canary = canary; 40*189af465SArd Biesheuvel #ifndef CONFIG_STACKPROTECTOR_PER_TASK 41c743f380SNicolas Pitre __stack_chk_guard = current->stack_canary; 42*189af465SArd Biesheuvel #else 43*189af465SArd Biesheuvel current_thread_info()->stack_canary = current->stack_canary; 44*189af465SArd Biesheuvel #endif 45c743f380SNicolas Pitre } 46c743f380SNicolas Pitre 47c743f380SNicolas Pitre #endif /* _ASM_STACKPROTECTOR_H */ 48