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Atmosphere/exosphere2/loader_stub/source/start.s

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/*
* Copyright (c) 2018-2020 Atmosphère-NX
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/* For some reason GAS doesn't know about it, even with .cpu cortex-a57 */
#define cpuactlr_el1 s3_1_c15_c2_0
#define cpuectlr_el1 s3_1_c15_c2_1
.macro RESET_CORE
mov x0, #(1 << 63)
msr cpuactlr_el1, x0 /* disable regional clock gating */
isb
mov x0, #3
msr rmr_el3, x0
isb
dsb sy
/* Nintendo forgot to copy-paste the branch instruction below. */
1:
wfi
b 1b
.endm
.macro ERRATUM_INVALIDATE_BTB_AT_BOOT
/* Nintendo copy-pasted https://github.com/ARM-software/arm-trusted-firmware/blob/master/plat/nvidia/tegra/common/aarch64/tegra_helpers.S#L312 */
/*
* Copyright (c) 2015-2017, ARM Limited and Contributors. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
/* The following comments are mine. */
/*
Enable invalidates of branch target buffer, then flush
the entire instruction cache at the local level, and
with the reg change, the branch target buffer, then disable
invalidates of the branch target buffer again.
*/
mrs x0, cpuactlr_el1
orr x0, x0, #1
msr cpuactlr_el1, x0
dsb sy
isb
ic iallu
dsb sy
isb
mrs x0, cpuactlr_el1
bic x0, x0, #1
msr cpuactlr_el1, x0
.rept 7
nop /* wait long enough for the write to cpuactlr_el1 to have completed */
.endr
/* if the OS lock is set, disable it and request a warm reset */
mrs x0, oslsr_el1
ands x0, x0, #2
b.eq 2f
mov x0, xzr
msr oslar_el1, x0
RESET_CORE
.rept 65
nop /* guard against speculative excecution */
.endr
2:
/* set the OS lock */
mov x0, #1
msr oslar_el1, x0
.endm
.section .crt0.text.start, "ax", %progbits
.align 6
.global _start
_start:
/* mask all interrupts */
msr daifset, #0xF
/* Fixup hardware erratum */
ERRATUM_INVALIDATE_BTB_AT_BOOT
/* Set the stack pointer to a temporary location. */
ldr x20, =0x7C020000
mov sp, x20
/* Call our init array functions. */
bl __libc_init_array
/* Uncompress the program and iram boot code images. */
b _ZN3ams6secmon6loader20UncompressAndExecuteEv