[ros-diffs] [sedwards] 64: added freeldr isoboot code as well as openfirmware boot code. Added freeldr debugger by Brian Palmer

added freeldr isoboot code as well as openfirmware boot code. Added
freeldr debugger by Brian Palmer
Added: trunk/reactos/boot/freeldr/bootsect/
Added: trunk/reactos/boot/freeldr/bootsect/isoboot.asm
Added: trunk/reactos/boot/freeldr/bootsect/ofwboot.s
Added: trunk/reactos/boot/freeldr/fdebug/
Added: trunk/reactos/boot/freeldr/fdebug/De.rc
Added: trunk/reactos/boot/freeldr/fdebug/En.rc
Added: trunk/reactos/boot/freeldr/fdebug/Hu.rc
Added: trunk/reactos/boot/freeldr/fdebug/Ja.rc
Added: trunk/reactos/boot/freeldr/fdebug/Pl.rc
Added: trunk/reactos/boot/freeldr/fdebug/Tr.rc
Added: trunk/reactos/boot/freeldr/fdebug/fdebug.c
Added: trunk/reactos/boot/freeldr/fdebug/fdebug.ico
Added: trunk/reactos/boot/freeldr/fdebug/fdebug.rc
Added: trunk/reactos/boot/freeldr/fdebug/resource.h
Added: trunk/reactos/boot/freeldr/fdebug/rs232.c
Added: trunk/reactos/boot/freeldr/fdebug/rs232.h
  _____  

Added: trunk/reactos/boot/freeldr/bootsect/isoboot.asm
--- trunk/reactos/boot/freeldr/bootsect/isoboot.asm	2006-01-31
07:37:05 UTC (rev 63)
+++ trunk/reactos/boot/freeldr/bootsect/isoboot.asm	2006-01-31
18:58:49 UTC (rev 64)
@@ -0,0 +1,1015 @@

+;
************************************************************************
****
+;
+;  isolinux.asm
+;
+;  A program to boot Linux kernels off a CD-ROM using the El Torito
+;  boot standard in "no emulation" mode, making the entire filesystem
+;  available.  It is based on the SYSLINUX boot loader for MS-DOS
+;  floppies.
+;
+;   Copyright (C) 1994-2001  H. Peter Anvin
+;
+;  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, Inc., 675 Mass Ave, Cambridge MA
02139,
+;  USA; either version 2 of the License, or (at your option) any later
+;  version; incorporated herein by reference.
+; 
+;
************************************************************************
****
+;
+; THIS FILE IS A MODIFIED VERSION OF ISOLINUX.ASM
+; MODIFICATION DONE BY MICHAEL K TER LOUW
+; LAST UPDATED 3-9-2002
+; SEE "COPYING" FOR INFORMATION ABOUT THE LICENSE THAT APPLIES TO THIS
RELEASE
+;
+;
************************************************************************
****
+;
+; This file is a modified version of ISOLINUX.ASM.
+; Modification done by Eric Kohl
+; Last update 04-25-2002
+;
+;
************************************************************************
****
+
+; Note: The Makefile builds one version with DEBUG_MESSAGES
automatically.
+;%define DEBUG_MESSAGES                ; Uncomment to get debugging
messages
+
+%define WAIT_FOR_KEY
+
+
+;
------------------------------------------------------------------------
---
+;   BEGIN THE BIOS/CODE/DATA SEGMENT
+;
------------------------------------------------------------------------
---
+
+		absolute 0400h
+serial_base	resw 4			; Base addresses for 4 serial
ports
+		absolute 0413h
+BIOS_fbm	resw 1			; Free Base Memory (kilobytes)
+		absolute 046Ch
+BIOS_timer	resw 1			; Timer ticks
+		absolute 0472h
+BIOS_magic	resw 1			; BIOS reset magic
+		absolute 0484h
+BIOS_vidrows	resb 1			; Number of screen rows
+
+;
+; Memory below this point is reserved for the BIOS and the MBR
+;
+		absolute 1000h
+trackbuf	resb 8192		; Track buffer goes here
+trackbufsize	equ $-trackbuf
+;		trackbuf ends at 3000h
+
+		struc open_file_t
+file_sector	resd 1			; Sector pointer (0 = structure
free)
+file_left	resd 1			; Number of sectors left
+		endstruc
+
+		struc dir_t
+dir_lba		resd 1			; Directory start (LBA)
+dir_len		resd 1			; Length in bytes
+dir_clust	resd 1			; Length in clusters
+		endstruc
+
+
+MAX_OPEN_LG2	equ 2			; log2(Max number of open files)
+MAX_OPEN	equ (1 << MAX_OPEN_LG2)
+SECTORSIZE_LG2	equ 11			; 2048 bytes/sector (El Torito
requirement)
+SECTORSIZE	equ (1 << SECTORSIZE_LG2)
+CR		equ 13			; Carriage Return
+LF		equ 10			; Line Feed
+retry_count	equ 6			; How patient are we with the
BIOS?
+
+
+
+	absolute 5000h				; Here we keep our BSS
stuff
+
+DriveNo		resb 1			; CD-ROM BIOS drive
number
+DiskError	resb 1			; Error code for disk I/O
+RetryCount	resb 1			; Used for disk access retries
+TimeoutCount	resb 1			; Timeout counter
+ISOFlags	resb 1			; Flags for ISO directory search
+RootDir		resb dir_t_size		; Root directory
+CurDir		resb dir_t_size		; Current directory
+ISOFileName	resb 64			; ISO filename canonicalization
buffer
+ISOFileNameEnd	equ $
+
+
+		alignb open_file_t_size
+Files		resb MAX_OPEN*open_file_t_size
+
+
+
+	section .text
+	org 7000h
+
+start:
+	cli					; Disable interrupts
+	xor	ax, ax				; ax = segment zero
+	mov	ss, ax				; Initialize stack
segment
+	mov	sp, start			; Set up stack
+	mov	ds, ax				; Initialize other
segment registers
+	mov	es, ax
+	mov	fs, ax
+	mov	gs, ax
+	sti					; Enable interrupts
+	cld					; Increment pointers
+
+	mov	cx, 2048 >> 2			; Copy the bootsector
+	mov	si, 0x7C00			; from 0000:7C00
+	mov	di, 0x7000			; to 0000:7000
+	rep	movsd				; copy the program
+	jmp	0:relocate			; jump into relocated
code
+
+relocate:
+	; Display the banner and copyright
+%ifdef DEBUG_MESSAGES
+	mov	si, isolinux_banner		; si points to hello
message
+	call	writestr			; display the message
+	mov	si,copyright_str
+	call	writestr
+%endif
+
+
+	; Make sure the keyboard buffer is empty
+%ifdef WAIT_FOR_KEY
+.kbd_buffer_test:
+	call	pollchar
+	jz	.kbd_buffer_empty
+	call	getchar
+	jmp	.kbd_buffer_test
+.kbd_buffer_empty:
+
+	; Check if there is harddisk
+	pusha
+	mov	ax, 0800h
+	mov	dx, 0080h
+	int	13h
+	popa
+	jc	.boot_cdrom
+
+	; Display the 'Press key' message and wait for a maximum of 5
seconds
+	call	crlf
+	mov	si, presskey_msg		; si points to 'Press
key' message
+	call	writestr			; display the message
+
+	mov	byte [TimeoutCount], 5
+.next_second:
+	mov	eax, [BIOS_timer]		; load current tick
counter
+	add	eax, 19				; 
+
+.poll_again:
+	call	pollchar
+	jnz	.boot_cdrom
+
+	mov	ebx, [BIOS_timer]
+	cmp	eax, ebx
+	jnz	.poll_again
+
+	mov	si, dot_msg			; print '.'
+	call	writestr
+	dec	byte [TimeoutCount]		; decrement timeout
counter
+	jz	.boot_harddisk
+	jmp	.next_second
+
+.boot_harddisk:
+	call	crlf
+
+	; Boot first harddisk (drive 0x80)
+	mov	ax, 0201h
+	mov	dx, 0080h
+	mov	cx, 0001h
+	mov	bx, 7C00h
+	int	13h
+	jnc	.go_hd
+	jmp	kaboom
+.go_hd:
+	mov	ax, cs
+	mov	ds, ax
+	mov	es, ax
+	mov	fs, ax
+	mov	gs, ax
+	mov	dx, 0080h
+
+	jmp	0:0x7C00
+%endif
+
+.boot_cdrom:
+%ifdef WAIT_FOR_KEY
+	call	crlf
+	call	crlf
+%endif
+
+	; Save and display the boot drive number
+	mov	[DriveNo], dl
+%ifdef DEBUG_MESSAGES
+	mov	si, startup_msg
+	call	writemsg
+	mov	al, dl
+	call	writehex2
+	call	crlf
+%endif
+
+	; Now figure out what we're actually doing
+	; Note: use passed-in DL value rather than 7Fh because
+	; at least some BIOSes will get the wrong value otherwise
+	mov	ax, 4B01h			; Get disk emulation
status
+	mov	dl, [DriveNo]
+	mov	si, spec_packet
+	int	13h
+	jc	near spec_query_failed		; Shouldn't happen (BIOS
bug)
+	mov	dl, [DriveNo]
+	cmp	[sp_drive], dl			; Should contain the
drive number
+	jne	near spec_query_failed
+
+%ifdef DEBUG_MESSAGES
+	mov	si, spec_ok_msg
+	call	writemsg
+	mov	al, byte [sp_drive]
+	call	writehex2
+	call	crlf
+%endif
+
+found_drive:
+	; Get drive information
+	mov	ah, 48h
+	mov	dl, [DriveNo]
+	mov	si, drive_params
+	int	13h
+	jnc	params_ok
+
+	; mov	si, nosecsize_msg	No use in reporting this
+	; call	writemsg
+
+params_ok:
+	; Check for the sector size (should be 2048, but
+	; some BIOSes apparently think we're 512-byte media)
+	;
+	; FIX: We need to check what the proper behaviour
+	; is for getlinsec when the BIOS thinks the sector
+	; size is 512!!!  For that, we need such a BIOS, though...
+%ifdef DEBUG_MESSAGES
+	mov	si, secsize_msg
+	call	writemsg
+	mov	ax, [dp_secsize]
+	call	writehex4
+	call	crlf
+%endif
+
+
+	;
+	; Clear Files structures
+	;
+	mov	di, Files
+	mov	cx, (MAX_OPEN*open_file_t_size)/4
+	xor	eax, eax
+	rep	stosd
+
+	;
+	; Now, we need to sniff out the actual filesystem data
structures.
+	; mkisofs gave us a pointer to the primary volume descriptor
+	; (which will be at 16 only for a single-session disk!); from
the PVD
+	; we should be able to find the rest of what we need to know.
+	;
+get_fs_structures:
+	mov	eax, 16			; Primary Volume Descriptor
(sector 16)
+	mov	bx, trackbuf
+	call	getonesec
+
+	mov	eax, [trackbuf+156+2]
+	mov	[RootDir+dir_lba],eax
+	mov	[CurDir+dir_lba],eax
+%ifdef DEBUG_MESSAGES
+	mov	si, rootloc_msg
+	call	writemsg
+	call	writehex8
+	call	crlf
+%endif
+
+	mov	eax,[trackbuf+156+10]
+	mov	[RootDir+dir_len],eax
+	mov	[CurDir+dir_len],eax
+%ifdef DEBUG_MESSAGES
+	mov	si, rootlen_msg
+	call	writemsg
+	call	writehex8
+	call	crlf
+%endif
+	add	eax,SECTORSIZE-1
+	shr	eax,SECTORSIZE_LG2
+	mov	[RootDir+dir_clust],eax
+	mov	[CurDir+dir_clust],eax
+%ifdef DEBUG_MESSAGES
+	mov	si, rootsect_msg
+	call	writemsg
+	call	writehex8
+	call	crlf
+%endif
+
+	; Look for the "REACTOS" directory, and if found,
+	; make it the current directory instead of the root
+	; directory.
+	mov	di,isolinux_dir
+	mov	al,02h				; Search for a directory
+	call	searchdir_iso
+	jnz	.dir_found
+	mov	si,no_dir_msg
+	call	writemsg
+	jmp	kaboom
+
+.dir_found:
+	mov	[CurDir+dir_len],eax
+	mov	eax,[si+file_left]
+	mov	[CurDir+dir_clust],eax
+	xor	eax,eax				; Free this file pointer
entry
+	xchg	eax,[si+file_sector]
+	mov	[CurDir+dir_lba],eax
+
+
+	mov	di, isolinux_bin		; di points to Isolinux
filename
+	call	searchdir			; look for the file
+	jnz	.isolinux_opened		; got the file
+	mov	si, no_isolinux_msg		; si points to error
message
+	call	writemsg			; display the message
+	jmp	kaboom				; fail boot
+
+.isolinux_opened:
+	mov	di, si				; save file pointer
+
+%ifdef DEBUG_MESSAGES
+	mov	si, filelen_msg
+	call	writemsg
+	call	writehex8
+	call	crlf
+%endif
+
+	mov ecx, eax			; calculate sector count
+	shr ecx, 11
+	test eax, 0x7FF
+	jz .full_sector
+	inc ecx
+.full_sector:
+
+%ifdef DEBUG_MESSAGES
+	mov eax, ecx
+	mov	si, filesect_msg
+	call	writemsg
+	call	writehex8
+	call	crlf
+%endif
+
+	mov	bx, 0x8000			; bx = load address
+	mov	si, di				; restore file pointer
+	mov	cx, 0xFFFF			; load the whole file
+	call	getfssec			; get the whole file
+
+%ifdef DEBUG_MESSAGES
+	mov	si, startldr_msg
+	call	writemsg
+	call	crlf
+%endif
+
+	mov	dl, [DriveNo]			; dl = boot drive
+	mov dh, 0					; dh = boot
partition
+	jmp	0:0x8000			; jump into OSLoader
+
+
+
+;
+; searchdir:
+;
+; Open a file
+;
+;  On entry:
+;	DS:DI	= filename
+;  If successful:
+;	ZF clear
+;	SI		= file pointer
+;	DX:AX or EAX	= file length in bytes
+;  If unsuccessful
+;	ZF set
+;
+
+;
+; searchdir_iso is a special entry point for ISOLINUX only.  In
addition
+; to the above, searchdir_iso passes a file flag mask in AL.  This is
useful
+; for searching for directories.
+;
+alloc_failure:
+	xor	ax,ax				; ZF <- 1
+	ret
+
+searchdir:
+	xor	al,al
+searchdir_iso:
+	mov	[ISOFlags],al
+	call	allocate_file			; Temporary file
structure for directory
+	jnz	alloc_failure
+	push	es
+	push	ds
+	pop	es				; ES = DS
+	mov	si,CurDir
+	cmp	byte [di],'\'			; If filename begins
with slash
+	jne	.not_rooted
+	inc	di				; Skip leading slash
+	mov	si,RootDir			; Reference root
directory instead
+.not_rooted:
+	mov	eax,[si+dir_clust]
+	mov	[bx+file_left],eax
+	mov	eax,[si+dir_lba]
+	mov	[bx+file_sector],eax
+	mov	edx,[si+dir_len]
+
+.look_for_slash:
+	mov	ax,di
+.scan:
+	mov	cl,[di]
+	inc	di
+	and	cl,cl
+	jz	.isfile
+	cmp	cl,'\'
+	jne	.scan
+	mov	[di-1],byte 0			; Terminate at directory
name
+	mov	cl,02h				; Search for directory
+	xchg	cl,[ISOFlags]
+	push	di
+	push	cx
+	push	word .resume			; Where to "return" to
+	push	es
+.isfile:
+	xchg	ax,di
+
+.getsome:
+	; Get a chunk of the directory
+	mov	si,trackbuf
+	pushad
+	xchg	bx,si
+	mov	cx,1				; load one sector
+	call	getfssec
+	popad
+
+.compare:
+	movzx	eax, byte [si]			; Length of directory
entry
+	cmp	al, 33
+	jb	.next_sector
+	mov	cl, [si+25]
+	xor	cl, [ISOFlags]
+	test	cl, byte 8Eh			; Unwanted file
attributes!
+	jnz	.not_file
+	pusha
+	movzx	cx, byte [si+32]		; File identifier length
+	add	si, byte 33			; File identifier offset
+	call	iso_compare_names
+	popa
+	je	.success
+.not_file:
+	sub	edx, eax			; Decrease bytes left
+	jbe	.failure
+	add	si, ax				; Advance pointer
+
+.check_overrun:
+	; Did we finish the buffer?
+	cmp	si, trackbuf+trackbufsize
+	jb	.compare			; No, keep going
+
+	jmp	short .getsome			; Get some more
directory
+
+.next_sector:
+	; Advance to the beginning of next sector
+	lea	ax, [si+SECTORSIZE-1]
+	and	ax, ~(SECTORSIZE-1)
+	sub	ax, si
+	jmp	short .not_file			; We still need to do
length checks
+
+.failure:
+%ifdef DEBUG_MESSAGES
+	mov	si, findfail_msg
+	call	writemsg
+	call	crlf
+%endif
+	xor	eax, eax			; ZF = 1
+	mov	[bx+file_sector], eax
+	pop	es
+	ret
+
+.success:
+	mov	eax, [si+2]			; Location of extent
+	mov	[bx+file_sector], eax
+	mov	eax, [si+10]			; Data length
+	push	eax
+	add	eax, SECTORSIZE-1
+	shr	eax, SECTORSIZE_LG2
+	mov	[bx+file_left], eax
+	pop	eax
+	mov	edx, eax
+	shr	edx, 16
+	and	bx, bx				; ZF = 0
+	mov	si, bx
+	pop	es
+	ret
+
+.resume:
+	; We get here if we were only doing part of a lookup
+	; This relies on the fact that .success returns bx == si
+	xchg	edx, eax			; Directory length in
edx
+	pop	cx				; Old ISOFlags
+	pop	di				; Next filename pointer
+
+	mov	byte [di-1], '\'		; restore the backslash
in the filename
+
+	mov	[ISOFlags], cl			; Restore the flags
+	jz	.failure			; Did we fail?  If so
fail for real!
+	jmp	.look_for_slash			; Otherwise, next level
+
+;
+; allocate_file: Allocate a file structure
+;
+;		If successful:
+;		  ZF set
+;		  BX = file pointer
+;		In unsuccessful:
+;		  ZF clear
+;
+allocate_file:
+	push	cx
+	mov	bx, Files
+	mov	cx, MAX_OPEN
+.check:
+	cmp	dword [bx], byte 0
+	je	.found
+	add	bx, open_file_t_size		; ZF = 0
+	loop	.check
+	; ZF = 0 if we fell out of the loop
+.found:
+	pop	cx
+	ret
+
+;
+; iso_compare_names:
+;	Compare the names DS:SI and DS:DI and report if they are
+;	equal from an ISO 9660 perspective.  SI is the name from
+;	the filesystem; CX indicates its length, and ';' terminates.
+;	DI is expected to end with a null.
+;
+;	Note: clobbers AX, CX, SI, DI; assumes DS == ES == base segment
+;
+iso_compare_names:
+	; First, terminate and canonicalize input filename
+	push	di
+	mov	di, ISOFileName
+.canon_loop:
+	jcxz	.canon_end
+	lodsb
+	dec	cx
+	cmp	al, ';'
+	je	.canon_end
+	and	al, al
+	je	.canon_end
+	stosb
+	cmp	di, ISOFileNameEnd-1		; Guard against buffer
overrun
+	jb	.canon_loop
+.canon_end:
+	cmp	di, ISOFileName
+	jbe	.canon_done
+	cmp	byte [di-1], '.'		; Remove terminal dots
+	jne	.canon_done
+	dec	di
+	jmp	short .canon_end
+.canon_done:
+	mov	[di], byte 0			; Null-terminate string
+	pop	di
+	mov	si, ISOFileName
+.compare:
+	lodsb
+	mov	ah, [di]
+	inc	di
+	and	ax, ax
+	jz	.success			; End of string for both
+	and	al, al				; Is either one end of
string?
+	jz	.failure			; If so, failure
+	and	ah, ah
+	jz	.failure
+	or	ax, 2020h			; Convert to lower case
+	cmp	al, ah
+	je	.compare
+.failure:
+	and	ax, ax				; ZF = 0 (at least one
will be nonzero)
+.success:
+	ret
+
+
+
+
+
+
+
+;
+; getfssec: Get multiple clusters from a file, given the file pointer.
+;
+;  On entry:
+;	ES:BX	-> Buffer
+;	SI	-> File pointer
+;	CX	-> Cluster count; 0FFFFh = until end of file
+;  On exit:
+;	SI	-> File pointer (or 0 on EOF)
+;	CF = 1	-> Hit EOF
+;
+getfssec:
+	cmp	cx, [si+file_left]
+	jna	.ok_size
+	mov	cx, [si+file_left]
+
+.ok_size:
+	mov	bp, cx
+	push	cx
+	push	si
+	mov	eax, [si+file_sector]
+	call	getlinsec
+	xor	ecx, ecx
+	pop	si
+	pop	cx
+
+	add	[si+file_sector], ecx
+	sub	[si+file_left], ecx
+	ja	.not_eof			; CF = 0
+
+	xor	ecx, ecx
+	mov	[si+file_sector], ecx		; Mark as unused
+	xor	si,si
+	stc
+
+.not_eof:
+	ret
+
+
+
+; INT 13h, AX=4B01h, DL=<passed in value> failed.
+; Try to scan the entire 80h-FFh from the end.
+spec_query_failed:
+	mov	si,spec_err_msg
+	call	writemsg
+
+	mov	dl, 0FFh
+.test_loop:
+	pusha
+	mov	ax, 4B01h
+	mov	si, spec_packet
+	mov	byte [si], 13			; Size of buffer
+	int	13h
+	popa
+	jc	.still_broken
+
+	mov	si, maybe_msg
+	call	writemsg
+	mov	al, dl
+	call	writehex2
+	call	crlf
+
+	cmp	byte [sp_drive], dl
+	jne	.maybe_broken
+
+	; Okay, good enough...
+	mov	si, alright_msg
+	call	writemsg
+	mov	[DriveNo], dl
+.found_drive:
+	jmp	found_drive
+
+	; Award BIOS 4.51 apparently passes garbage in sp_drive,
+	; but if this was the drive number originally passed in
+	; DL then consider it "good enough"
+.maybe_broken:
+	cmp	byte [DriveNo], dl
+	je	.found_drive
+
+.still_broken:
+	dec dx
+	cmp	dl, 80h
+	jnb	.test_loop
+
+fatal_error:
+	mov	si, nothing_msg
+	call	writemsg
+
+.norge:
+	jmp	short .norge
+
+
+
+	; Information message (DS:SI) output
+	; Prefix with "isolinux: "
+	;
+writemsg:
+	push	ax
+	push	si
+	mov	si, isolinux_str
+	call	writestr
+	pop	si
+	call	writestr
+	pop	ax
+	ret
+
+;
+; crlf: Print a newline
+;
+crlf:
+	mov	si, crlf_msg
+	; Fall through
+
+;
+; writestr: write a null-terminated string to the console, saving
+;           registers on entry.
+;
+writestr:
+	pushfd
+	pushad
+.top:
+	lodsb
+	and	al, al
+	jz	.end
+	call	writechr
+	jmp	short .top
+.end:
+	popad
+	popfd
+	ret
+
+
+;
+; writehex[248]: Write a hex number in (AL, AX, EAX) to the console
+;
+writehex2:
+	pushfd
+	pushad
+	shl	eax, 24
+	mov	cx, 2
+	jmp	short writehex_common
+writehex4:
+	pushfd
+	pushad
+	shl	eax, 16
+	mov	cx, 4
+	jmp	short writehex_common
+writehex8:
+	pushfd
+	pushad
+	mov	cx, 8
+writehex_common:
+.loop:
+	rol	eax, 4
+	push	eax
+	and	al, 0Fh
+	cmp	al, 10
+	jae	.high
+.low:
+	add	al, '0'
+	jmp	short .ischar
+.high:
+	add	al, 'A'-10
+.ischar:
+	call	writechr
+	pop	eax
+	loop	.loop
+	popad
+	popfd
+	ret
+
+;
+; Write a character to the screen.  There is a more "sophisticated"
+; version of this in the subsequent code, so we patch the pointer
+; when appropriate.
+;
+
+writechr:
+	pushfd
+	pushad
+	mov	ah, 0Eh
+	xor	bx, bx
+	int	10h
+	popad
+	popfd
+	ret
+
+;
+; Get one sector.  Convenience entry point.
+;
+getonesec:
+	mov	bp, 1
+	; Fall through to getlinsec
+
+;
+; Get linear sectors - EBIOS LBA addressing, 2048-byte sectors.
+;
+; Note that we can't always do this as a single request, because at
least
+; Phoenix BIOSes has a 127-sector limit.  To be on the safe side, stick
+; to 32 sectors (64K) per request.
+;
+; Input:
+;	EAX	- Linear sector number
+;	ES:BX	- Target buffer
+;	BP	- Sector count
+;
+getlinsec:
+	mov si,dapa			; Load up the DAPA
+	mov [si+4],bx
+	mov bx,es
+	mov [si+6],bx
+	mov [si+8],eax
+.loop2:
+	push bp				; Sectors left
+	cmp bp,[MaxTransfer]
+	jbe .bp_ok
+	mov bp,[MaxTransfer]
+.bp_ok:
+	mov [si+2],bp
+	push si
+	mov dl,[DriveNo]
+	mov ah,42h			; Extended Read
+	call xint13
+	pop si
+	pop bp
+	movzx eax,word [si+2]		; Sectors we read
+	add [si+8],eax			; Advance sector pointer
+	sub bp,ax			; Sectors left
+	shl ax,SECTORSIZE_LG2-4		; 2048-byte sectors -> segment
+	add [si+6],ax			; Advance buffer pointer
+	and bp,bp
+	jnz .loop2
+	mov eax,[si+8]			; Next sector
+	ret
+
+	; INT 13h with retry
+xint13:
+	mov	byte [RetryCount], retry_count
+.try:
+	pushad
+	int	13h
+	jc	.error
+	add	sp, byte 8*4			; Clean up stack
+	ret
+.error:
+	mov	[DiskError], ah		; Save error code
+	popad
+	dec byte [RetryCount]
+	jz .real_error
+	push ax
+	mov al,[RetryCount]
+	mov ah,[dapa+2]			; Sector transfer count
+	cmp al,2			; Only 2 attempts left
+	ja .nodanger
+	mov ah,1			; Drop transfer size to 1
+	jmp short .setsize
+.nodanger:
+	cmp al,retry_count-2
+	ja .again			; First time, just try again
+	shr ah,1			; Otherwise, try to reduce
+	adc ah,0			; the max transfer size, but not
to 0
+.setsize:
+	mov [MaxTransfer],ah
+	mov [dapa+2],ah
+.again:
+	pop ax
+	jmp .try
+
+.real_error:
+	mov	si, diskerr_msg
+	call	writemsg
+	mov	al, [DiskError]
+	call	writehex2
+	mov	si, ondrive_str
+	call	writestr
+	mov	al, dl
+	call	writehex2
+	call	crlf
+	; Fall through to kaboom
+
+;
+; kaboom: write a message and bail out.  Wait for a user keypress,
+;	  then do a hard reboot.
+;
+kaboom:
+	mov	ax, cs
+	mov	ds, ax
+	mov	es, ax
+	mov	fs, ax
+	mov	gs, ax
+	sti
+	mov	si, err_bootfailed
+	call	writestr
+	call	getchar
+	cli
+	mov	word [BIOS_magic], 0	; Cold reboot
+	jmp	0F000h:0FFF0h		; Reset vector address
+
+getchar:
+.again:
+	mov	ah, 1		; Poll keyboard
+	int	16h
+	jz	.again
+.kbd:
+	xor	ax, ax		; Get keyboard input
+	int	16h
+.func_key:
+	ret
+
+
+;
+; pollchar: check if we have an input character pending (ZF = 0)
+;
+pollchar:
+	pushad
+	mov ah,1		; Poll keyboard
+	int 16h
+	popad
+	ret
+
+
+
+isolinux_banner	db CR, LF, 'Loading IsoBoot...', CR, LF, 0
+copyright_str	db ' Copyright (C) 1994-2002 H. Peter Anvin', CR, LF, 0
+presskey_msg	db 'Press any key to boot from CD', 0
+dot_msg		db '.',0
+
+%ifdef DEBUG_MESSAGES
+startup_msg:	db 'Starting up, DL = ', 0
+spec_ok_msg:	db 'Loaded spec packet OK, drive = ', 0
+secsize_msg:	db 'Sector size appears to be ', 0
+rootloc_msg:	db 'Root directory location: ', 0
+rootlen_msg:	db 'Root directory length: ', 0
+rootsect_msg:	db 'Root directory length(sectors): ', 0
+fileloc_msg:	db 'SETUPLDR.SYS location: ', 0
+filelen_msg:	db 'SETUPLDR.SYS length: ', 0
+filesect_msg:	db 'SETUPLDR.SYS length(sectors): ', 0
+findfail_msg:	db 'Failed to find file!', 0
+startldr_msg:	db 'Starting SETUPLDR.SYS', 0
+%endif
+
+nosecsize_msg:	db 'Failed to get sector size, assuming 0800', CR, LF, 0
+spec_err_msg:	db 'Loading spec packet failed, trying to wing it...',
CR, LF, 0
+maybe_msg:	db 'Found something at drive = ', 0
+alright_msg:	db 'Looks like it might be right, continuing...', CR,
LF, 0
+nothing_msg:	db 'Failed to locate CD-ROM device; boot failed.', CR,
LF, 0
+isolinux_str	db 'IsoBoot: ', 0
+crlf_msg	db CR, LF, 0
+diskerr_msg:	db 'Disk error ', 0
+ondrive_str:	db ', drive ', 0
+err_bootfailed	db CR, LF, 'Boot failed: press a key to retry...'
+isolinux_dir	db '\LOADER', 0
+no_dir_msg	db 'Could not find the LOADER directory.', CR, LF, 0
+isolinux_bin	db 'SETUPLDR.SYS', 0
+no_isolinux_msg	db 'Could not find SETUPLDR.SYS.', CR, LF, 0
+
+;
+; El Torito spec packet
+;
+		align 8, db 0
+spec_packet:	db 13h				; Size of packet
+sp_media:	db 0				; Media type
+sp_drive:	db 0				; Drive number
+sp_controller:	db 0				; Controller index
+sp_lba:		dd 0				; LBA for
emulated disk image
+sp_devspec:	dw 0				; IDE/SCSI information
+sp_buffer:	dw 0				; User-provided buffer
+sp_loadseg:	dw 0				; Load segment
+sp_sectors:	dw 0				; Sector count
+sp_chs:		db 0,0,0			; Simulated CHS
geometry
+sp_dummy:	db 0				; Scratch, safe to
overwrite
+
+;
+; EBIOS drive parameter packet
+;
+		align 8, db 0
+drive_params:	dw 30				; Buffer size
+dp_flags:	dw 0				; Information flags
+dp_cyl:		dd 0				; Physical
cylinders
+dp_head:	dd 0				; Physical heads
+dp_sec:		dd 0				; Physical
sectors/track
+dp_totalsec:	dd 0,0				; Total sectors
+dp_secsize:	dw 0				; Bytes per sector
+dp_dpte:	dd 0				; Device Parameter Table
+dp_dpi_key:	dw 0				; 0BEDDh if rest valid
+dp_dpi_len:	db 0				; DPI len
+		db 0
+		dw 0
+dp_bus:		times 4 db 0			; Host bus type
+dp_interface:	times 8 db 0			; Interface type
+db_i_path:	dd 0,0				; Interface path
[truncated at 1000 lines; 3426 more skipped]