201 lines
4.3 KiB
ArmAsm
201 lines
4.3 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2012 Regents of the University of California
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*/
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#include <asm/thread_info.h>
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#include <asm/asm-offsets.h>
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#include <asm/asm.h>
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#include <linux/init.h>
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#include <linux/linkage.h>
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#include <asm/thread_info.h>
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#include <asm/page.h>
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#include <asm/csr.h>
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#include <asm/image.h>
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__INIT
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ENTRY(_start)
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/*
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* Image header expected by Linux boot-loaders. The image header data
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* structure is described in asm/image.h.
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* Do not modify it without modifying the structure and all bootloaders
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* that expects this header format!!
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*/
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/* jump to start kernel */
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j _start_kernel
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/* reserved */
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.word 0
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.balign 8
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#if __riscv_xlen == 64
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/* Image load offset(2MB) from start of RAM */
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.dword 0x200000
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#else
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/* Image load offset(4MB) from start of RAM */
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.dword 0x400000
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#endif
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/* Effective size of kernel image */
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.dword _end - _start
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.dword __HEAD_FLAGS
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.word RISCV_HEADER_VERSION
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.word 0
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.dword 0
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.ascii RISCV_IMAGE_MAGIC
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.balign 4
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.ascii RISCV_IMAGE_MAGIC2
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.word 0
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.global _start_kernel
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_start_kernel:
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/* Mask all interrupts */
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csrw CSR_SIE, zero
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csrw CSR_SIP, zero
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/* Load the global pointer */
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.option push
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.option norelax
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la gp, __global_pointer$
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.option pop
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/*
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* Disable FPU to detect illegal usage of
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* floating point in kernel space
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*/
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li t0, SR_FS
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csrc CSR_SSTATUS, t0
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#ifdef CONFIG_SMP
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li t0, CONFIG_NR_CPUS
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bgeu a0, t0, .Lsecondary_park
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#endif
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/* Pick one hart to run the main boot sequence */
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la a3, hart_lottery
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li a2, 1
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amoadd.w a3, a2, (a3)
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bnez a3, .Lsecondary_start
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/* Clear BSS for flat non-ELF images */
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la a3, __bss_start
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la a4, __bss_stop
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ble a4, a3, clear_bss_done
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clear_bss:
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REG_S zero, (a3)
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add a3, a3, RISCV_SZPTR
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blt a3, a4, clear_bss
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clear_bss_done:
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/* Save hart ID and DTB physical address */
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mv s0, a0
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mv s1, a1
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la a2, boot_cpu_hartid
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REG_S a0, (a2)
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/* Initialize page tables and relocate to virtual addresses */
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la sp, init_thread_union + THREAD_SIZE
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mv a0, s1
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call setup_vm
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la a0, early_pg_dir
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call relocate
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/* Restore C environment */
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la tp, init_task
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sw zero, TASK_TI_CPU(tp)
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la sp, init_thread_union + THREAD_SIZE
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/* Start the kernel */
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call parse_dtb
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tail start_kernel
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relocate:
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/* Relocate return address */
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li a1, PAGE_OFFSET
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la a2, _start
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sub a1, a1, a2
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add ra, ra, a1
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/* Point stvec to virtual address of intruction after satp write */
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la a2, 1f
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add a2, a2, a1
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csrw CSR_STVEC, a2
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/* Compute satp for kernel page tables, but don't load it yet */
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srl a2, a0, PAGE_SHIFT
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li a1, SATP_MODE
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or a2, a2, a1
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/*
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* Load trampoline page directory, which will cause us to trap to
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* stvec if VA != PA, or simply fall through if VA == PA. We need a
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* full fence here because setup_vm() just wrote these PTEs and we need
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* to ensure the new translations are in use.
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*/
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la a0, trampoline_pg_dir
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srl a0, a0, PAGE_SHIFT
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or a0, a0, a1
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sfence.vma
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csrw CSR_SATP, a0
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.align 2
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1:
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/* Set trap vector to spin forever to help debug */
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la a0, .Lsecondary_park
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csrw CSR_STVEC, a0
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/* Reload the global pointer */
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.option push
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.option norelax
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la gp, __global_pointer$
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.option pop
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/*
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* Switch to kernel page tables. A full fence is necessary in order to
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* avoid using the trampoline translations, which are only correct for
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* the first superpage. Fetching the fence is guarnteed to work
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* because that first superpage is translated the same way.
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*/
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csrw CSR_SATP, a2
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sfence.vma
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ret
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.Lsecondary_start:
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#ifdef CONFIG_SMP
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/* Set trap vector to spin forever to help debug */
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la a3, .Lsecondary_park
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csrw CSR_STVEC, a3
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slli a3, a0, LGREG
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la a1, __cpu_up_stack_pointer
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la a2, __cpu_up_task_pointer
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add a1, a3, a1
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add a2, a3, a2
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/*
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* This hart didn't win the lottery, so we wait for the winning hart to
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* get far enough along the boot process that it should continue.
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*/
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.Lwait_for_cpu_up:
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/* FIXME: We should WFI to save some energy here. */
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REG_L sp, (a1)
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REG_L tp, (a2)
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beqz sp, .Lwait_for_cpu_up
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beqz tp, .Lwait_for_cpu_up
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fence
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/* Enable virtual memory and relocate to virtual address */
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la a0, swapper_pg_dir
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call relocate
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tail smp_callin
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#endif
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.align 2
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.Lsecondary_park:
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/* We lack SMP support or have too many harts, so park this hart */
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wfi
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j .Lsecondary_park
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END(_start)
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__PAGE_ALIGNED_BSS
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/* Empty zero page */
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.balign PAGE_SIZE
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