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/*
* head.S: VMXAssist runtime start off.
*
* Leendert van Doorn, leendert@watson.ibm.com
* Copyright (c) 2005, International Business Machines Corporation.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope 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., 59 Temple
* Place - Suite 330, Boston, MA 02111-1307 USA.
*/
#include "vm86.h"
#include "machine.h"
/*
* When a partition tries to mask off the CR0_PE bit a world
* switch happens to the environment below. The magic indicates
* that this is a valid context.
*/
#ifdef TEST
.byte 0x55, 0xaa
.byte 0x80
.code16
jmp _start16
#else
jmp _start
#endif
.align 8
.long VMXASSIST_MAGIC
.long newctx /* new context */
.long oldctx /* old context */
#ifdef TEST
/*
* We are running in 16-bit. Get into the protected mode as soon as
* possible. We use our own (minimal) GDT to get started.
*
* ROM is a misnomer as this code isn't really rommable (although it
* only requires a few changes) but it does live in a BIOS ROM segment.
* This code allows me to debug vmxassists under (a modified version of)
* Bochs and load it as a "optromimage1".
*/
.code16
.globl _start16
_start16:
cli
/* load our own global descriptor table */
data32 addr32 lgdt %cs:(rom_gdtr - TEXTADDR)
/* go to protected mode */
movl %cr0, %eax
orl $(CR0_PE), %eax
movl %eax, %cr0
data32 ljmp $0x08, $1f
.align 32
.globl rom_gdt
rom_gdt:
.word 0, 0 /* 0x00: reserved */
.byte 0, 0, 0, 0
.word 0xFFFF, 0 /* 0x08: CS 32-bit */
.byte 0, 0x9A, 0xCF, 0
.word 0xFFFF, 0 /* 0x10: CS 32-bit */
.byte 0, 0x92, 0xCF, 0
rom_gdt_end:
.align 4
.globl rom_gdtr
rom_gdtr:
.word rom_gdt_end - rom_gdt - 1
.long rom_gdt
.code32
1:
/* welcome to the 32-bit world */
movw $0x10, %ax
movw %ax, %ds
movw %ax, %es
movw %ax, %ss
movw %ax, %fs
movw %ax, %gs
/* enable Bochs debug facilities */
movw $0x8A00, %dx
movw $0x8A00, %ax
outw %ax, (%dx)
jmp _start
#endif /* TEST */
/*
* This is the real start. Control was transfered to this point
* with CR0_PE set and executing in some 32-bit segment. We call
* main and setup our own environment.
*/
.globl _start
.code32
_start:
cli
/* save register parameters to C land */
#ifdef TEST
xorl %edx, %edx
#endif
/* clear bss */
cld
xorb %al, %al
movl $_bbss, %edi
movl $_ebss, %ecx
subl %edi, %ecx
rep stosb
movl %edx, booting_cpu
movl %ebx, booting_vector
/* make sure we are in a sane world */
clts
/* setup my own stack */
movl $stack_top - 4*4, %esp
movl %esp, %ebp
/* go ... */
call main
jmp halt
/*
* Something bad happened, print invoking %eip and loop forever
*/
.align 4
.globl halt
halt:
push $halt_msg
call printf
#ifdef TEST
movw $0x8A00, %dx
movw $0x8AE0, %ax
outw %ax, (%dx)
#endif
cli
jmp .
.data
halt_msg:
.asciz "Halt called from %%eip 0x%x\n"
/*
* Our stack
*/
.bss
.align 8
.globl stack, stack_top
stack:
.skip STACK_SIZE
stack_top:
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