1*91f16700Schasinglulu /* 2*91f16700Schasinglulu * Copyright (c) 2017-2019, ARM Limited and Contributors. All rights reserved. 3*91f16700Schasinglulu * 4*91f16700Schasinglulu * SPDX-License-Identifier: BSD-3-Clause 5*91f16700Schasinglulu */ 6*91f16700Schasinglulu 7*91f16700Schasinglulu #include <stdint.h> 8*91f16700Schasinglulu 9*91f16700Schasinglulu #include <lib/utils.h> 10*91f16700Schasinglulu #include <lib/utils_def.h> 11*91f16700Schasinglulu 12*91f16700Schasinglulu #include <drivers/rpi3/rng/rpi3_rng.h> 13*91f16700Schasinglulu 14*91f16700Schasinglulu /* Get 128 bits of entropy and fuse the values together to form the canary. */ 15*91f16700Schasinglulu #define TRNG_NBYTES 16U 16*91f16700Schasinglulu 17*91f16700Schasinglulu u_register_t plat_get_stack_protector_canary(void) 18*91f16700Schasinglulu { 19*91f16700Schasinglulu size_t i; 20*91f16700Schasinglulu u_register_t buf[TRNG_NBYTES / sizeof(u_register_t)]; 21*91f16700Schasinglulu u_register_t ret = 0U; 22*91f16700Schasinglulu 23*91f16700Schasinglulu rpi3_rng_read(buf, sizeof(buf)); 24*91f16700Schasinglulu 25*91f16700Schasinglulu for (i = 0U; i < ARRAY_SIZE(buf); i++) 26*91f16700Schasinglulu ret ^= buf[i]; 27*91f16700Schasinglulu 28*91f16700Schasinglulu return ret; 29*91f16700Schasinglulu } 30