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/*
* Copyright (C) 2011 Michael Brown <mbrown@fensystems.co.uk>.
*
* 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; either version 2 of the
* License, or any later version.
*
* 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., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*
*/
FILE_LICENCE ( GPL2_OR_LATER )
/* Initial temporary stack size */
#define EXE_STACK_SIZE 0x400
/* Temporary decompression area (avoid DOS high memory area) */
#define EXE_DECOMPRESS_ADDRESS 0x110000
/* Fields within the Program Segment Prefix */
#define PSP_CMDLINE_LEN 0x80
#define PSP_CMDLINE_START 0x81
.text
.arch i386
.org 0
.code16
.section ".prefix", "awx", @progbits
signature:
/* "MZ" signature */
.ascii "MZ"
last_block:
/* Number of bytes in last block that are really used */
.word 0
blocks:
/* Number of 512-byte blocks */
.word 0
.section ".zinfo.fixup", "a", @progbits /* Compressor fixups */
.ascii "ADDW"
.long blocks
.long 512
.long 0
.previous
num_reloc:
/* Number of relocation entries stored after the header */
.word 0
header_pgh:
/* Number of paragraphs in the header */
.word ( ( _exe_start - signature ) / 16 )
min_bss_pgh:
/* Minimum number of paragraphs of additional (BSS) memory */
.word ( EXE_STACK_SIZE / 16 )
max_bss_pgh:
/* Maximum number of paragraphs of additional (BSS) memory */
.word ( EXE_STACK_SIZE / 16 )
init_ss:
/* Initial stack segment (relative to start of executable) */
.word -( ( _exe_start - signature ) / 16 )
.section ".zinfo.fixup", "a", @progbits /* Compressor fixups */
.ascii "ADDW"
.long init_ss
.long 16
.long 0
.previous
init_sp:
/* Initial stack pointer */
.word EXE_STACK_SIZE
checksum:
/* Checksum (ignored) */
.word 0
init_ip:
/* Initial instruction pointer */
.word _exe_start
init_cs:
/* Initial code segment (relative to start of executable) */
.word -( ( _exe_start - signature ) / 16 )
reloc_table:
/* Relocation table offset */
.word 0
overlay:
/* Overlay number */
.word 0
.align 16, 0
.globl _exe_start
_exe_start:
/* Install iPXE. Use a fixed temporary decompression area to
* avoid trashing the DOS high memory area.
*/
call alloc_basemem
xorl %esi, %esi
movl $EXE_DECOMPRESS_ADDRESS, %edi
orl $0xffffffff, %ebp /* Allow arbitrary relocation */
call install_prealloc
/* Set up real-mode stack */
movw %bx, %ss
movw $_estack16, %sp
/* Jump to .text16 segment */
pushw %ax
pushw $1f
lret
.section ".text16", "awx", @progbits
1:
/* Terminate command line with a NUL */
movzbw PSP_CMDLINE_LEN, %si
movb $0, PSP_CMDLINE_START(%si)
/* Calculate command line physical address */
xorl %esi, %esi
movw %ds, %si
shll $4, %esi
addl $PSP_CMDLINE_START, %esi
/* Set up %ds for access to .data16 */
movw %bx, %ds
/* Record command line address */
movl %esi, cmdline_phys
/* Run iPXE */
pushl $main
pushw %cs
call prot_call
popl %ecx /* discard */
/* Uninstall iPXE */
call uninstall
/* Exit back to DOS. This is very unlikely to work */
movw $0x4c00, %ax
int $0x21
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