本教程是用的是 3.12.0 版本的 optee (opens new window)，运行环境为 QEMU 虚拟的 ARMv8 架构。
前面的文章介绍了使用 QEMU 运行 OP-TEE 所依赖 image 的编译以及启动过程。本文将开始介绍启动过程加载 bl1.bin 的流程。
调用 qemu-system-aarch64 启动 QEMU 时，会加载 $(BINARIES_PATH)--out/bin 目录的 bl1.bin 文件（本质上是 trusted-firmware-a/build/qemu/release/bl1.bin 的软链接）。bl1.bin 镜像的入口函数是 bl1_entrypoint (opens new window) 函数，由汇编代码编写，定义在 trusted-firmware-a/bl1/aarch64/bl1_entrypoint.S 文件如下
/*
* Copyright (c) 2013-2019, ARM Limited and Contributors. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <arch.h>
#include <el3_common_macros.S>
.globl bl1_entrypoint
/* -----------------------------------------------------
* bl1_entrypoint() is the entry point into the trusted
* firmware code when a cpu is released from warm or
* cold reset.
* -----------------------------------------------------
*/
func bl1_entrypoint
/* ---------------------------------------------------------------------
* If the reset address is programmable then bl1_entrypoint() is
* executed only on the cold boot path. Therefore, we can skip the warm
* boot mailbox mechanism.
* ---------------------------------------------------------------------
*/
el3_entrypoint_common \
_init_sctlr=1 \
_warm_boot_mailbox=!PROGRAMMABLE_RESET_ADDRESS \
_secondary_cold_boot=!COLD_BOOT_SINGLE_CPU \
_init_memory=1 \
_init_c_runtime=1 \
_exception_vectors=bl1_exceptions \
_pie_fixup_size=0
/* --------------------------------------------------------------------
* Perform BL1 setup
* --------------------------------------------------------------------
*/
bl bl1_setup
#if ENABLE_PAUTH
/* --------------------------------------------------------------------
* Program APIAKey_EL1 and enable pointer authentication.
* --------------------------------------------------------------------
*/
bl pauth_init_enable_el3
#endif /* ENABLE_PAUTH */
/* --------------------------------------------------------------------
* Initialize platform and jump to our c-entry point
* for this type of reset.
* --------------------------------------------------------------------
*/
bl bl1_main
#if ENABLE_PAUTH
/* --------------------------------------------------------------------
* Disable pointer authentication before jumping to next boot image.
* --------------------------------------------------------------------
*/
bl pauth_disable_el3
#endif /* ENABLE_PAUTH */
/* --------------------------------------------------
* Do the transition to next boot image.
* --------------------------------------------------
*/
b el3_exit
endfunc bl1_entrypoint
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