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/*
* Copyright (C) 2012 Regents of the University of California
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation, version 2.
*
* This program is distributed in the hope that 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.
*/
#include <asm/thread_info.h>
#include <asm/asm-offsets.h>
#include <asm/asm.h>
#include <linux/init.h>
#include <linux/linkage.h>
#include <asm/thread_info.h>
#include <asm/page.h>
#include <asm/csr.h>
__INIT
ENTRY(_start)
/* Mask and clear all interrupts */
csrw sie, zero
csrw sip, zero
/* Load the global pointer */
.option push
.option norelax
la gp, __global_pointer$
.option pop
/*
* Disable FPU to detect illegal usage of
* floating point in kernel space
*/
li t0, SR_FS
csrc sstatus, t0
/* Pick one hart to run the main boot sequence */
la a3, hart_lottery
li a2, 1
amoadd.w a3, a2, (a3)
bnez a3, .Lsecondary_start
/* Clear BSS for flat non-ELF images */
la a3, __bss_start
la a4, __bss_stop
ble a4, a3, clear_bss_done
clear_bss:
REG_S zero, (a3)
add a3, a3, RISCV_SZPTR
blt a3, a4, clear_bss
clear_bss_done:
/* Save hart ID and DTB physical address */
mv s0, a0
mv s1, a1
la a2, boot_cpu_hartid
REG_S a0, (a2)
/* Initialize page tables and relocate to virtual addresses */
la sp, init_thread_union + THREAD_SIZE
call setup_vm
call relocate
/* Restore C environment */
la tp, init_task
sw zero, TASK_TI_CPU(tp)
la sp, init_thread_union + THREAD_SIZE
/* Start the kernel */
mv a0, s1
call parse_dtb
tail start_kernel
relocate:
/* Relocate return address */
li a1, PAGE_OFFSET
la a0, _start
sub a1, a1, a0
add ra, ra, a1
/* Point stvec to virtual address of intruction after satp write */
la a0, 1f
add a0, a0, a1
csrw stvec, a0
/* Compute satp for kernel page tables, but don't load it yet */
la a2, swapper_pg_dir
srl a2, a2, PAGE_SHIFT
li a1, SATP_MODE
or a2, a2, a1
/*
* Load trampoline page directory, which will cause us to trap to
* stvec if VA != PA, or simply fall through if VA == PA
*/
la a0, trampoline_pg_dir
srl a0, a0, PAGE_SHIFT
or a0, a0, a1
sfence.vma
csrw sptbr, a0
.align 2
1:
/* Set trap vector to spin forever to help debug */
la a0, .Lsecondary_park
csrw stvec, a0
/* Reload the global pointer */
.option push
.option norelax
la gp, __global_pointer$
.option pop
/* Switch to kernel page tables */
csrw sptbr, a2
ret
.Lsecondary_start:
#ifdef CONFIG_SMP
li a1, CONFIG_NR_CPUS
bgeu a0, a1, .Lsecondary_park
/* Set trap vector to spin forever to help debug */
la a3, .Lsecondary_park
csrw stvec, a3
slli a3, a0, LGREG
la a1, __cpu_up_stack_pointer
la a2, __cpu_up_task_pointer
add a1, a3, a1
add a2, a3, a2
/*
* This hart didn't win the lottery, so we wait for the winning hart to
* get far enough along the boot process that it should continue.
*/
.Lwait_for_cpu_up:
/* FIXME: We should WFI to save some energy here. */
REG_L sp, (a1)
REG_L tp, (a2)
beqz sp, .Lwait_for_cpu_up
beqz tp, .Lwait_for_cpu_up
fence
/* Enable virtual memory and relocate to virtual address */
call relocate
tail smp_callin
#endif
.align 2
.Lsecondary_park:
/* We lack SMP support or have too many harts, so park this hart */
wfi
j .Lsecondary_park
END(_start)
__PAGE_ALIGNED_BSS
/* Empty zero page */
.balign PAGE_SIZE
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