NetBSD-5.0.2/sys/arch/i386/stand/cdboot/cdboot.S
/* $NetBSD: cdboot.S,v 1.8 2008/05/03 13:07:31 ad Exp $ */
/*-
* Copyright (c) 2005 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Bang Jun-Young.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/*
* This is a primary boot loader that loads a secondary boot loader
* directly from CD without performing floppy/hard disk emulation as
* described by the El Torito specification.
*
* TODO:
* - Support for loading secondary boot loader > 64kB
*/
#include <machine/asm.h>
#include <sys/bootblock.h>
#define BOOT_ADDR 0x7c00
#define BLOCK_SIZE 2048 /* Default for ISO 9660 */
#define VD_LBA 16 /* LBA of Volume Descriptor (VD) */
#define PVD_ADDR 0x1000 /* Where Primary VD is loaded */
#define ROOTDIR_ADDR 0x1800 /* Where Root Directory is loaded */
#define LOADER_ADDR SECONDARY_LOAD_ADDRESS
#ifdef BOOT_FROM_FAT
#define MBR_AFTERBPB 90 /* BPB size in FAT32 partition BR */
#else
#define MBR_AFTERBPB 62 /* BPB size in floppy master BR */
#endif
/*
* See src/sys/sys/bootblock.h for details.
*/
#define MBR_PART_COUNT 4
#define MBR_PART_OFFSET 446
#define MBR_PART_SIZE 16 /* sizeof(struct mbr_partition) */
/*
* Disk error codes
*/
#define ERROR_TIMEOUT 0x80
/*
* Volume Descriptor types.
*/
#define VD_PRIMARY 1
#define VD_SUPPLEMENTARY 2
#define VD_TERMINATOR 255
/* Only actually used entries are listed below */
/*
* Format of Primary Volume Descriptor (8.4)
*/
#define PVD_ROOT_DR 156 /* Offset of Root Directory Record */
/*
* Format of Directory Record (9.1)
*/
#define DR_LEN 0
#define DR_EXTENT 2
#define DR_DATA_LEN 10
#define DR_NAME_LEN 32
#define DR_NAME 33
.text
.code16
ENTRY(start)
jmp start1
. = start + MBR_AFTERBPB /* skip BPB */
. = start + MBR_DSN_OFFSET
.long 0
/* mbr_bootsel_magic (not used here) */
. = start + MBR_BS_MAGIC_OFFSET
.word 0
. = start + MBR_PART_OFFSET
. = start + MBR_MAGIC_OFFSET
pbr_magic:
.word MBR_MAGIC
.fill 512 /* reserve space for disklabel */
start1:
jmp 1f
.balign 4
.long X86_BOOT_MAGIC_1 /* checked by installboot & pbr code */
boot_params: /* space for patchable variables */
.long 1f - boot_params /* length of this data area */
#include <boot_params.S>
. = start1 + 0x80 /* Space for patching unknown params */
1: xorw %ax, %ax
movw %ax, %ds
movw %ax, %es
movw %ax, %ss
movw $BOOT_ADDR, %sp
movw %sp, %si
movw $start, %di
movw $BLOCK_SIZE/2, %cx
rep
movsw
ljmp $0, $real_start
real_start:
movb %dl, boot_drive /* Save boot drive number */
#ifndef DISABLE_KEYPRESS
/*
* We can skip boot wait when:
* - there's no hard disk present.
* - there's no active partition in the MBR of the 1st hard disk.
*/
/*
* Check presence of hard disks.
*/
movw $0x475, %si
movb (%si), %al
testb %al, %al
jz boot_cdrom
/*
* Find the active partition from the MBR.
*/
movw $0x0201, %ax /* %al = number of sectors to read */
movw $BOOT_ADDR, %bx /* %es:%bx = data buffer */
movw $0x0001, %cx /* %ch = low 8 bits of cylinder no */
/* %cl = high 2 bits of cyl no & */
/* sector number */
movw $0x0080, %dx /* %dh = head number */
/* %dl = disk number */
int $0x13 /* Read MBR into memory */
jc boot_cdrom /* CF set on error */
movb $1, mbr_loaded
movb $MBR_PART_COUNT, %cl
movw $BOOT_ADDR+MBR_PART_OFFSET, %si
1:
movb (%si), %al
testb $0x80, %al
jnz found_active
addw $MBR_PART_SIZE, %si
decb %cl
testb %cl, %cl
jnz 1b /* If 0, no active partition found */
jmp boot_cdrom
found_active:
movw $str_press_key, %si
call message
next_second:
movw $str_dot, %si
call message
decb wait_count
jz boot_hard_disk
xorb %ah, %ah /* Get system time */
int $0x1a
movw %dx, %di /* %cx:%dx = number of clock ticks */
addw $19, %di /* 19 ~= 18.2 Hz */
wait_key:
movb $1, %ah /* Check for keystroke */
int $0x16
jz not_avail /* ZF clear if keystroke available */
xorb %ah, %ah /* Read key to flush keyboard buf */
int $0x16
jmp boot_cdrom
not_avail:
xorb %ah, %ah /* Get system time */
int $0x1a
cmpw %dx, %di /* Compare with saved time */
jnz wait_key
jmp next_second
boot_hard_disk:
movw $str_crlf, %si
call message
cmpb $1, mbr_loaded
jz 1f
movw $0x0201, %ax /* %al = number of sectors to read */
movw $BOOT_ADDR, %bx /* %es:%bx = data buffer */
movw $0x0001, %cx /* %ch = low 8 bits of cylinder no */
/* %cl = high 2 bits of cyl no & */
/* sector number */
movw $0x0080, %dx /* %dh = head number */
/* %dl = disk number */
int $0x13 /* Read MBR into memory */
jc panic /* CF set on error */
1:
movw %cs, %ax /* Restore initial state */
movw %ax, %ds
movw %ax, %es
movw $0x0080, %dx /* %dl = boot drive number */
jmp $0, $BOOT_ADDR /* Jump to MBR! */
jmp panic /* This should be never executed */
#endif /* !DISABLE_KEYPRESS */
boot_cdrom:
movw $str_banner, %si
call message
movl $VD_LBA, %eax
next_block:
movb $1, %dh /* Number of sectors to read */
movl $PVD_ADDR, %ebx
call read_sectors
cmpb $VD_PRIMARY, (%bx) /* Is it Primary Volume Descriptor? */
jz pvd_found
incl %eax
cmpb $VD_TERMINATOR, (%bx)
jnz next_block
movw $str_no_pvd, %si
call message
jmp panic
pvd_found:
movw $PVD_ADDR+PVD_ROOT_DR, %bx
movl DR_EXTENT(%bx), %eax /* LBA of the root directory */
movl DR_DATA_LEN(%bx), %edx
shrl $11, %edx /* Convert to number of sectors */
movb %dl, %dh /* ... and load it to %dh */
movl $ROOTDIR_ADDR, %ebx
call read_sectors
next_entry:
cmpb $0, DR_LEN(%bx)
jz last_entry
movw %bx, %si
addw $DR_NAME, %si
movb DR_NAME_LEN(%bx), %cl
movw $str_loader, %di
1:
movb (%si), %al
cmpb %al, (%di)
jnz fail
incw %si
incw %di
decb %cl
jnz 1b
jmp load_loader
fail:
addw DR_LEN(%bx), %bx
jmp next_entry
last_entry:
movw $str_no_loader, %si
call message
jmp panic
load_loader:
movl DR_EXTENT(%bx), %eax
movl DR_DATA_LEN(%bx), %edx
addl $(BLOCK_SIZE-1), %edx /* Convert file length to */
shrl $11, %edx /* ... number of sectors */
movb %dl, %dh
movl $LOADER_ADDR, %ebx
call read_sectors
movl $boot_params, %esi /* Provide boot_params */
xorl %edx, %edx
movb boot_drive, %dl
xorl %ebx, %ebx /* Zero sector number */
lcall $LOADER_ADDR/16, $0
/* fall through on load failure */
panic:
hlt
jmp panic
/*
* Read disk sector(s) into memory
*
* %eax = LBA of starting sector
* %ebx = buffer to store sectors
* %dh = number of sectors to read
*/
read_sectors:
pusha
movl %eax, edd_lba /* Convert LBA to segment */
shrl $4, %ebx
movw %bx, edd_segment
movb %dh, edd_nsecs
movb boot_drive, %dl
movw $edd_packet, %si
read_again:
movb $0x42, %ah
int $0x13
jc read_fail
popa
ret
read_fail:
cmpb $ERROR_TIMEOUT, %ah
jz read_again
movw $str_read_error, %si
call message
jmp panic
/*
* For debugging purpose
*/
put_char:
pusha
movb $0x0e, %ah
movw $0x0001, %bx
int $0x10
popa
ret
#include <message.S>
edd_packet:
edd_len: .word 16
edd_nsecs: .word 0 /* Number of sectors to transfer */
edd_offset: .word 0
edd_segment: .word 0
edd_lba: .quad 0
wait_count: .byte 6
boot_drive: .byte 0
mbr_loaded: .byte 0
str_banner: .ascii "\r\nNetBSD/x86 cd9660 Primary Bootstrap"
str_crlf: .asciz "\r\n"
str_press_key: .asciz "\r\nPress any key to boot from CD"
str_dot: .asciz "."
str_read_error: .asciz "Can't read CD"
str_no_pvd: .asciz "Can't find Primary Volume Descriptor"
str_no_loader: .asciz "Can't find /boot"
str_loader: .asciz "BOOT.;1"
/* Used to calculate free bytes */
free_space = end - .
. = start + BLOCK_SIZE
end: