1b2441318SGreg Kroah-Hartman /* SPDX-License-Identifier: GPL-2.0 */ 2c0c264aeSLaura Abbott /* 3c0c264aeSLaura Abbott * GCC stack protector support. 4c0c264aeSLaura Abbott * 5c0c264aeSLaura Abbott * Stack protector works by putting predefined pattern at the start of 6c0c264aeSLaura Abbott * the stack frame and verifying that it hasn't been overwritten when 7c0c264aeSLaura Abbott * returning from the function. The pattern is called stack canary 8c0c264aeSLaura Abbott * and gcc expects it to be defined by a global variable called 9c0c264aeSLaura Abbott * "__stack_chk_guard" on ARM. This unfortunately means that on SMP 10c0c264aeSLaura Abbott * we cannot have a different canary value per task. 11c0c264aeSLaura Abbott */ 12c0c264aeSLaura Abbott 13c0c264aeSLaura Abbott #ifndef __ASM_STACKPROTECTOR_H 14c0c264aeSLaura Abbott #define __ASM_STACKPROTECTOR_H 15c0c264aeSLaura Abbott 16c0c264aeSLaura Abbott #include <linux/random.h> 17c0c264aeSLaura Abbott #include <linux/version.h> 18c0c264aeSLaura Abbott 19c0c264aeSLaura Abbott extern unsigned long __stack_chk_guard; 20c0c264aeSLaura Abbott 21c0c264aeSLaura Abbott /* 22c0c264aeSLaura Abbott * Initialize the stackprotector canary value. 23c0c264aeSLaura Abbott * 24c0c264aeSLaura Abbott * NOTE: this must only be called from functions that never return, 25c0c264aeSLaura Abbott * and it must always be inlined. 26c0c264aeSLaura Abbott */ 27c0c264aeSLaura Abbott static __always_inline void boot_init_stack_canary(void) 28c0c264aeSLaura Abbott { 29c0c264aeSLaura Abbott unsigned long canary; 30c0c264aeSLaura Abbott 31c0c264aeSLaura Abbott /* Try to get a semi random initial value. */ 32c0c264aeSLaura Abbott get_random_bytes(&canary, sizeof(canary)); 33c0c264aeSLaura Abbott canary ^= LINUX_VERSION_CODE; 34d21f5498SRik van Riel canary &= CANARY_MASK; 35c0c264aeSLaura Abbott 36c0c264aeSLaura Abbott current->stack_canary = canary; 37*0a1213faSArd Biesheuvel if (!IS_ENABLED(CONFIG_STACKPROTECTOR_PER_TASK)) 38c0c264aeSLaura Abbott __stack_chk_guard = current->stack_canary; 39c0c264aeSLaura Abbott } 40c0c264aeSLaura Abbott 41c0c264aeSLaura Abbott #endif /* _ASM_STACKPROTECTOR_H */ 42