1 /*
2  * Copyright (c) 2019, Arm Limited. All rights reserved.
3  *
4  * SPDX-License-Identifier: BSD-3-Clause
5  */
6 
7 #include <arch_helpers.h>
8 #include <cdefs.h>
9 #include <stdint.h>
10 
11 /*
12  * This is only a toy implementation to generate a seemingly random
13  * 128-bit key from sp, x30 and cntpct_el0 values.
14  * A production system must re-implement this function to generate
15  * keys from a reliable randomness source.
16  */
plat_init_apkey(void)17 uint128_t plat_init_apkey(void)
18 {
19 	uint64_t return_addr = (uint64_t)__builtin_return_address(0U);
20 	uint64_t frame_addr = (uint64_t)__builtin_frame_address(0U);
21 	uint64_t cntpct = read_cntpct_el0();
22 
23 	/* Generate 128-bit key */
24 	uint64_t key_lo = (return_addr << 13) ^ frame_addr ^ cntpct;
25 	uint64_t key_hi = (frame_addr << 15) ^ return_addr ^ cntpct;
26 
27 	return ((uint128_t)(key_hi) << 64) | key_lo;
28 }
29