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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/arch/x86/purgatory/entry64.S
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/* SPDX-License-Identifier: GPL-2.0-only */

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/*

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 * Copyright (C) 2003,2004  Eric Biederman ([email protected])

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 * Copyright (C) 2014  Red Hat Inc.

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 * Author(s): Vivek Goyal <[email protected]>

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 *

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 * This code has been taken from kexec-tools.

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 */

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#include <linux/linkage.h>

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	.text

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	.balign 16

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	.code64

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SYM_CODE_START(entry64)

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	/* Setup a gdt that should be preserved */

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	lgdt gdt(%rip)

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	/* load the data segments */

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	movl    $0x18, %eax     /* data segment */

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	movl    %eax, %ds

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	movl    %eax, %es

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	movl    %eax, %ss

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	movl    %eax, %fs

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	movl    %eax, %gs

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	/* Setup new stack */

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	leaq    stack_init(%rip), %rsp

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	pushq   $0x10 /* CS */

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	leaq    new_cs_exit(%rip), %rax

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	pushq   %rax

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	lretq

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new_cs_exit:

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	/* Load the registers */

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	movq	rax(%rip), %rax

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	movq	rbx(%rip), %rbx

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	movq	rcx(%rip), %rcx

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	movq	rdx(%rip), %rdx

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	movq	rsi(%rip), %rsi

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	movq	rdi(%rip), %rdi

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	movq    rsp(%rip), %rsp

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	movq	rbp(%rip), %rbp

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	movq	r8(%rip), %r8

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	movq	r9(%rip), %r9

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	movq	r10(%rip), %r10

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	movq	r11(%rip), %r11

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	movq	r12(%rip), %r12

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	movq	r13(%rip), %r13

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	movq	r14(%rip), %r14

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	movq	r15(%rip), %r15

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	/* Jump to the new code... */

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	jmpq	*rip(%rip)

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SYM_CODE_END(entry64)

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	.section ".rodata"

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	.balign 4

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SYM_DATA_START(entry64_regs)

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rax:	.quad 0x0

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rcx:	.quad 0x0

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rdx:	.quad 0x0

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rbx:	.quad 0x0

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rsp:	.quad 0x0

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rbp:	.quad 0x0

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rsi:	.quad 0x0

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rdi:	.quad 0x0

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r8:	.quad 0x0

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r9:	.quad 0x0

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r10:	.quad 0x0

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r11:	.quad 0x0

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r12:	.quad 0x0

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r13:	.quad 0x0

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r14:	.quad 0x0

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r15:	.quad 0x0

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rip:	.quad 0x0

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SYM_DATA_END(entry64_regs)

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	/* GDT */

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	.section ".rodata"

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	.balign 16

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SYM_DATA_START_LOCAL(gdt)

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	/*

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	 * 0x00 unusable segment

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	 * 0x08 unused

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	 * so use them as gdt ptr

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	 */

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	.word gdt_end - gdt - 1

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	.quad gdt

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	.word 0, 0, 0

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	/* 0x10 4GB flat code segment */

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	.word 0xFFFF, 0x0000, 0x9A00, 0x00AF

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	/* 0x18 4GB flat data segment */

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	.word 0xFFFF, 0x0000, 0x9200, 0x00CF

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SYM_DATA_END_LABEL(gdt, SYM_L_LOCAL, gdt_end)

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SYM_DATA_START_LOCAL(stack)

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	.quad   0, 0

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SYM_DATA_END_LABEL(stack, SYM_L_LOCAL, stack_init)

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