1*ff6844c3SAntonio Nino Diaz /* 2*ff6844c3SAntonio Nino Diaz * Copyright (c) 2019, Arm Limited. All rights reserved. 3*ff6844c3SAntonio Nino Diaz * 4*ff6844c3SAntonio Nino Diaz * SPDX-License-Identifier: BSD-3-Clause 5*ff6844c3SAntonio Nino Diaz */ 6*ff6844c3SAntonio Nino Diaz 7*ff6844c3SAntonio Nino Diaz #include <cdefs.h> 8*ff6844c3SAntonio Nino Diaz #include <stdint.h> 9*ff6844c3SAntonio Nino Diaz 10*ff6844c3SAntonio Nino Diaz /* 11*ff6844c3SAntonio Nino Diaz * Instruction pointer authentication key A. The low 64-bit are at [0], and the 12*ff6844c3SAntonio Nino Diaz * high bits at [1]. They are run-time constants so they are placed in the 13*ff6844c3SAntonio Nino Diaz * rodata section. They are written before MMU is turned on and the permissions 14*ff6844c3SAntonio Nino Diaz * are effective. 15*ff6844c3SAntonio Nino Diaz */ 16*ff6844c3SAntonio Nino Diaz uint64_t plat_apiakey[2] __section("rodata.apiakey"); 17*ff6844c3SAntonio Nino Diaz 18*ff6844c3SAntonio Nino Diaz /* 19*ff6844c3SAntonio Nino Diaz * This is only a toy implementation to generate a seemingly random 128-bit key 20*ff6844c3SAntonio Nino Diaz * from sp and x30 values. A production system must re-implement this function 21*ff6844c3SAntonio Nino Diaz * to generate keys from a reliable randomness source. 22*ff6844c3SAntonio Nino Diaz */ 23*ff6844c3SAntonio Nino Diaz uint64_t *plat_init_apiakey(void) 24*ff6844c3SAntonio Nino Diaz { 25*ff6844c3SAntonio Nino Diaz uintptr_t return_addr = (uintptr_t)__builtin_return_address(0U); 26*ff6844c3SAntonio Nino Diaz uintptr_t frame_addr = (uintptr_t)__builtin_frame_address(0U); 27*ff6844c3SAntonio Nino Diaz 28*ff6844c3SAntonio Nino Diaz plat_apiakey[0] = (return_addr << 13) ^ frame_addr; 29*ff6844c3SAntonio Nino Diaz plat_apiakey[1] = (frame_addr << 15) ^ return_addr; 30*ff6844c3SAntonio Nino Diaz 31*ff6844c3SAntonio Nino Diaz return plat_apiakey; 32*ff6844c3SAntonio Nino Diaz } 33