1 /* 2 * Copyright (c) 2021-2025, Renesas Electronics Corporation. All rights reserved. 3 * 4 * SPDX-License-Identifier: BSD-3-Clause 5 */ 6 7 #include <stdint.h> 8 9 #include <arch_helpers.h> 10 #include <common/debug.h> 11 12 #define RANDOM_CANARY_VALUE ((u_register_t)0xDFF5FC8A720E205EULL) 13 14 u_register_t plat_get_stack_protector_canary(void) 15 { 16 uintptr_t val1 = (uintptr_t)__builtin_return_address(0U); 17 uintptr_t val2 = (uintptr_t)__builtin_frame_address(0U); 18 u_register_t cnt; 19 u_register_t seed; 20 u_register_t mul; 21 u_register_t ret; 22 23 cnt = read_cntpct_el0(); 24 seed = (cnt ^ RANDOM_CANARY_VALUE) & ULONG_MAX; 25 ret = seed; 26 27 INFO("seed value: 0x%16lx cnt: 0x%16lx\n", seed, cnt); 28 29 if ((ULONG_MAX / val1) > seed) { 30 mul = (u_register_t)(val1 * seed); 31 if ((ULONG_MAX - mul) > val2) { 32 ret = mul + val2; 33 } 34 } 35 36 INFO("canary value: 0x%lx cnt: 0x%16lx\n", ret, read_cntpct_el0()); 37 38 return ret; 39 } 40