1 /*
2 * Copyright (c) 2024, ARM Limited and Contributors. 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 <plat/common/platform.h>
11
12 #define RANDOM_CANARY_VALUE ((u_register_t) 3288484550995823360ULL)
13
plat_get_stack_protector_canary(void)14 u_register_t plat_get_stack_protector_canary(void)
15 {
16 /*
17 * On the Total Compute platform, it can generate RNG via MHU channel
18 * and communicate with RSE. But the stack protector canary function
19 * is needed prior to MHU channel gets ready.
20 *
21 * Since now MHU module cannot distinguish if MHU channel has been
22 * initialized or not, if it arbitrarily tries to send message, it will
23 * cause panic. For this reason, this function cannot rollback to
24 * dummy random number based on the MHU failure.
25 *
26 * For above reasons, simply return a value of the combination of a
27 * timer's value and a compile-time constant.
28 */
29 return RANDOM_CANARY_VALUE ^ read_cntpct_el0();
30 }
31