1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * Switch to non-secure mode
4 *
5 * Copyright (c) 2018 Heinrich Schuchardt
6 *
7 * This module contains the ARMv8 specific code required to adjust the exception
8 * level before booting an operating system.
9 */
10
11#include <common.h>
12#include <bootm.h>
13#include <cpu_func.h>
14#include <log.h>
15#include <asm/cache.h>
16#include <asm/setjmp.h>
17
18/**
19 * entry_non_secure() - entry point when switching to non-secure mode
20 *
21 * When switching to non-secure mode switch_to_non_secure_mode() calls this
22 * function passing a jump buffer. We use this jump buffer to restore the
23 * original stack and register state.
24 *
25 * @non_secure_jmp:	jump buffer for restoring stack and registers
26 */
27static void entry_non_secure(struct jmp_buf_data *non_secure_jmp)
28{
29	dcache_enable();
30	debug("Reached non-secure mode\n");
31
32	/* Restore stack and registers saved in switch_to_non_secure_mode() */
33	longjmp(non_secure_jmp, 1);
34}
35
36/**
37 * switch_to_non_secure_mode() - switch to non-secure mode
38 *
39 * Exception level EL3 is meant to be used by the secure monitor only (ARM
40 * trusted firmware being one embodiment). The operating system shall be
41 * started at exception level EL2. So here we check the exception level
42 * and switch it if necessary.
43 */
44void switch_to_non_secure_mode(void)
45{
46	struct jmp_buf_data non_secure_jmp;
47
48	/* On AArch64 we need to make sure we call our payload in < EL3 */
49	if (current_el() == 3) {
50		if (setjmp(&non_secure_jmp))
51			return;
52		dcache_disable();	/* flush cache before switch to EL2 */
53
54		/* Move into EL2 and keep running there */
55		armv8_switch_to_el2((uintptr_t)&non_secure_jmp, 0, 0, 0,
56				    (uintptr_t)entry_non_secure, ES_TO_AARCH64);
57	}
58}
59