Atmosphere/exosphere/start.cold.s
2018-02-21 10:57:51 -08:00

101 lines
2.5 KiB
ArmAsm

.align 6
.section .text.cold.start, "ax", %progbits
.global __start_cold
__start_cold:
/* 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. */
/* mask all interrupts */
msr daifset, daif
/*
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 _set_lock_and_sp
mov x0, xzr
msr oslar_el1, x0
mov x0, #(1 << 63)
msr cpuactlr_el1, x0 /* disable regional clock gating */
isb
mov x0, #3
msr rmr_el3, x0
isb
dsb
/* Nintendo forgot to copy-paste the branch instruction below. */
_reset_wfi:
wfi
b _reset_wfi
.rept 65
nop /* guard against speculative excecution */
.endr
_set_lock_and_sp:
/* set the OS lock */
mov x0, #1
msr oslar_el1, x0
/* set SP = SP_EL0 (temporary stack) */
msr spsel, #0
ldr x20, =__cold_crt0_stack_top__
mov sp, x20
bl configure_memory
ldr x16, =__init_cold
br x16
.section .text.cold, "ax", %progbits
__init_cold:
/* set SP = SP_EL3 (exception stack) */
msr spsel, #1
ldr x20, =__main_stack_top__
mov sp, x20
/* set SP = SP_EL0 (temporary stack) */
msr spsel, #0
ldr x20, =__pk2_load_stack_top__
mov sp, x20
bl load_package2
ldr x20, =__cold_init_stack_top__
mov sp, x20
b coldboot_main
.global __set_sp_el0_and_jump_to_el1
.type __set_sp_el0_and_jump_to_el1, %function
__set_sp_el0_and_jump_to_el1:
/* the official handler does some weird stuff with SP_EL0 */
msr elr_el3, x1
mov sp, x2
mov x1, #0x3c5 /* EL1, all interrupts masked */
msr spsr_el3, x1
isb
eret