| Morten Borup Petersen | 406ac20 | 2020-01-29 16:44:17 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2020, 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 | static uint32_t plat_generate_random_number(void) |
| 13 | { |
| 14 | uintptr_t return_addr = (uintptr_t)__builtin_return_address(0U); |
| 15 | uintptr_t frame_addr = (uintptr_t)__builtin_frame_address(0U); |
| 16 | uint64_t cntpct = read_cntpct_el0(); |
| 17 | |
| 18 | /* Generate 32-bit pattern: saving the 2 least significant bytes |
| 19 | * in random_lo and random_hi |
| 20 | */ |
| 21 | uint16_t random_lo = (uint16_t)( |
| 22 | (((uint64_t)return_addr) << 13) ^ frame_addr ^ cntpct |
| 23 | ); |
| 24 | |
| 25 | uint16_t random_hi = (uint16_t)( |
| 26 | (((uint64_t)frame_addr) << 15) ^ return_addr ^ cntpct |
| 27 | ); |
| 28 | |
| 29 | return (((uint32_t)random_hi) << 16) | random_lo; |
| 30 | } |
| 31 | |
| 32 | u_register_t plat_get_stack_protector_canary(void) |
| 33 | { |
| 34 | return plat_generate_random_number(); /* a 32-bit pattern is returned */ |
| 35 | } |