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/*
* kexec: Linux boots Linux
*
* Copyright (C) 2003,2004,2005 Eric Biederman (ebiederm@xmission.com)
*
* 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 of the License).
*
* 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.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
.equ MSR_K6_EFER, 0xC0000080
.equ EFER_LME, 0x00000100
.equ X86_CR4_PAE, 0x00000020
.equ CR0_PG, 0x80000000
.globl compat_x86_64, compat_x86_64_entry32
.text
.code64
.balign 16
compat_x86_64:
/* Setup a temporary gdt */
/* This also acts as a serializing instruction ensuring
* my self modifying code works.
*/
lgdt gdt(%rip)
/* Switch to 32bit compatiblity mode */
ljmp *lm_exit_addr(%rip)
lm_exit:
.code32
/* Disable paging */
movl %cr0, %eax
andl $~CR0_PG, %eax
movl %eax, %cr0
/* Disable long mode */
movl $MSR_K6_EFER, %ecx
rdmsr
andl $~EFER_LME, %eax
wrmsr
/* Disable PAE */
xorl %eax, %eax
movl %eax, %cr4
/* load the data segments */
movl $0x18, %eax /* data segment */
movl %eax, %ds
movl %eax, %es
movl %eax, %ss
movl %eax, %fs
movl %eax, %gs
/* set all of the registers to known values */
/* leave %esp alone */
xorl %eax, %eax
xorl %ebx, %ebx
xorl %ecx, %ecx
xorl %edx, %edx
xorl %esi, %esi
xorl %edi, %edi
xorl %ebp, %ebp
jmp *compat_x86_64_entry32
.section ".rodata"
.balign 16
gdt: /* 0x00 unusable segment
* 0x08 unused
* so use them as the gdt ptr
*/
.word gdt_end - gdt - 1
# A quad word pointer to the gdt with the high 32bits 0
.long gdt, 0
.word 0, 0, 0
/* 0x10 4GB flat code segment */
.word 0xFFFF, 0x0000, 0x9A00, 0x00CF
/* 0x18 4GB flat data segment */
.word 0xFFFF, 0x0000, 0x9200, 0x00CF
gdt_end:
lm_exit_addr:
.long lm_exit
.long 0x10
compat_x86_64_entry32:
.long 0
.size compat_x86_64_entry32, . - compat_x86_64_entry32
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