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