From f6c6df7ebc12fdaab252c5869732cef6fa48d864 Mon Sep 17 00:00:00 2001 From: Heinrich Schuchardt Date: Tue, 8 Jan 2019 18:13:06 +0100 Subject: efi_loader: refactor switch to non-secure mode Refactor the switch from supervisor to hypervisor to a new function called at the beginning of do_bootefi(). Signed-off-by: Heinrich Schuchardt Signed-off-by: Alexander Graf --- arch/arm/cpu/armv8/exception_level.c | 55 ++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) create mode 100644 arch/arm/cpu/armv8/exception_level.c (limited to 'arch/arm/cpu/armv8/exception_level.c') diff --git a/arch/arm/cpu/armv8/exception_level.c b/arch/arm/cpu/armv8/exception_level.c new file mode 100644 index 0000000000..57824eb2ac --- /dev/null +++ b/arch/arm/cpu/armv8/exception_level.c @@ -0,0 +1,55 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Switch to non-secure mode + * + * Copyright (c) 2018 Heinrich Schuchardt + * + * This module contains the ARMv8 specific code required to adjust the exception + * level before booting an operating system. + */ + +#include +#include +#include + +/** + * entry_non_secure() - entry point when switching to non-secure mode + * + * When switching to non-secure mode switch_to_non_secure_mode() calls this + * function passing a jump buffer. We use this jump buffer to restore the + * original stack and register state. + * + * @non_secure_jmp: jump buffer for restoring stack and registers + */ +static void entry_non_secure(struct jmp_buf_data *non_secure_jmp) +{ + dcache_enable(); + debug("Reached non-secure mode\n"); + + /* Restore stack and registers saved in switch_to_non_secure_mode() */ + longjmp(non_secure_jmp, 1); +} + +/** + * switch_to_non_secure_mode() - switch to non-secure mode + * + * Exception level EL3 is meant to be used by the secure monitor only (ARM + * trusted firmware being one embodiment). The operating system shall be + * started at exception level EL2. So here we check the exception level + * and switch it if necessary. + */ +void switch_to_non_secure_mode(void) +{ + struct jmp_buf_data non_secure_jmp; + + /* On AArch64 we need to make sure we call our payload in < EL3 */ + if (current_el() == 3) { + if (setjmp(&non_secure_jmp)) + return; + dcache_disable(); /* flush cache before switch to EL2 */ + + /* Move into EL2 and keep running there */ + armv8_switch_to_el2((uintptr_t)&non_secure_jmp, 0, 0, 0, + (uintptr_t)entry_non_secure, ES_TO_AARCH64); + } +} -- cgit v1.2.3