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; -*- fundamental -*- (asm-mode sucks)
; $Id$
; ****************************************************************************
;
; 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) 1994-2004 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., 53 Temple Place Ste 330,
; Boston MA 02111-1307, USA; either version 2 of the License, or
; (at your option) any later version; incorporated herein by reference.
;
; ****************************************************************************
%define IS_ISOLINUX 1
%include "macros.inc"
%include "config.inc"
%include "kernel.inc"
%include "bios.inc"
%include "tracers.inc"
%include "layout.inc"
;
; Some semi-configurable constants... change on your own risk.
;
my_id equ isolinux_id
FILENAME_MAX_LG2 equ 8 ; log2(Max filename size Including final null)
FILENAME_MAX equ (1 << FILENAME_MAX_LG2)
NULLFILE equ 0 ; Zero byte == null file name
NULLOFFSET equ 0 ; Position in which to look
retry_count equ 6 ; How patient are we with the BIOS?
%assign HIGHMEM_SLOP 128*1024 ; Avoid this much memory near the top
MAX_OPEN_LG2 equ 6 ; log2(Max number of open files)
MAX_OPEN equ (1 << MAX_OPEN_LG2)
SECTOR_SHIFT equ 11 ; 2048 bytes/sector (El Torito requirement)
SECTOR_SIZE equ (1 << SECTOR_SHIFT)
;
; This is what we need to do when idle
;
%macro RESET_IDLE 0
; Nothing
%endmacro
%macro DO_IDLE 0
; Nothing
%endmacro
;
; The following structure is used for "virtual kernels"; i.e. LILO-style
; option labels. The options we permit here are `kernel' and `append
; Since there is no room in the bottom 64K for all of these, we
; stick them at vk_seg:0000 and copy them down before we need them.
;
struc vkernel
vk_vname: resb FILENAME_MAX ; Virtual name **MUST BE FIRST!**
vk_rname: resb FILENAME_MAX ; Real name
vk_appendlen: resw 1
alignb 4
vk_append: resb max_cmd_len+1 ; Command line
alignb 4
vk_end: equ $ ; Should be <= vk_size
endstruc
;
; Segment assignments in the bottom 640K
; 0000h - main code/data segment (and BIOS segment)
;
real_mode_seg equ 3000h
vk_seg equ 2000h ; Virtual kernels
xfer_buf_seg equ 1000h ; Bounce buffer for I/O to high mem
comboot_seg equ real_mode_seg ; COMBOOT image loading zone
;
; File structure. This holds the information for each currently open file.
;
struc open_file_t
file_sector resd 1 ; Sector pointer (0 = structure free)
file_left resd 1 ; Number of sectors left
endstruc
%ifndef DEPEND
%if (open_file_t_size & (open_file_t_size-1))
%error "open_file_t is not a power of 2"
%endif
%endif
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
; ---------------------------------------------------------------------------
; BEGIN CODE
; ---------------------------------------------------------------------------
;
; Memory below this point is reserved for the BIOS and the MBR
;
section .earlybss
trackbufsize equ 8192
trackbuf resb trackbufsize ; Track buffer goes here
getcbuf resb trackbufsize
; ends at 4800h
section .bss
alignb 4
ISOFileName resb 64 ; ISO filename canonicalization buffer
ISOFileNameEnd equ $
CurDir resb dir_t_size ; Current directory
RootDir resb dir_t_size ; Root directory
FirstSecSum resd 1 ; Checksum of bytes 64-2048
ImageDwords resd 1 ; isolinux.bin size, dwords
InitStack resd 1 ; Initial stack pointer (SS:SP)
DiskSys resw 1 ; Last INT 13h call
ImageSectors resw 1 ; isolinux.bin size, sectors
DiskError resb 1 ; Error code for disk I/O
DriveNo resb 1 ; CD-ROM BIOS drive number
ISOFlags resb 1 ; Flags for ISO directory search
RetryCount resb 1 ; Used for disk access retries
alignb open_file_t_size
Files resb MAX_OPEN*open_file_t_size
;
; Constants for the xfer_buf_seg
;
; The xfer_buf_seg is also used to store message file buffers. We
; need two trackbuffers (text and graphics), plus a work buffer
; for the graphics decompressor.
;
xbs_textbuf equ 0 ; Also hard-coded, do not change
xbs_vgabuf equ trackbufsize
xbs_vgatmpbuf equ 2*trackbufsize
section .text
;;
;; Primary entry point. Because BIOSes are buggy, we only load the first
;; CD-ROM sector (2K) of the file, so the number one priority is actually
;; loading the rest.
;;
bootsec equ $
StackBuf equ $-44
_start: ; Far jump makes sure we canonicalize the address
cli
jmp 0:_start1
times 8-($-$$) nop ; Pad to file offset 8
; This table hopefully gets filled in by mkisofs using the
; -boot-info-table option. If not, the values in this
; table are default values that we can use to get us what
; we need, at least under a certain set of assumptions.
bi_pvd: dd 16 ; LBA of primary volume descriptor
bi_file: dd 0 ; LBA of boot file
bi_length: dd 0xdeadbeef ; Length of boot file
bi_csum: dd 0xdeadbeef ; Checksum of boot file
bi_reserved: times 10 dd 0xdeadbeef ; Reserved
_start1: mov [cs:InitStack],sp ; Save initial stack pointer
mov [cs:InitStack+2],ss
xor ax,ax
mov ss,ax
mov sp,StackBuf ; Set up stack
mov ds,ax
mov es,ax
mov fs,ax
mov gs,ax
sti
cld
; Show signs of life
mov si,syslinux_banner
call writestr
%ifdef DEBUG_MESSAGES
mov si,copyright_str
call writestr
%endif
;
; Before modifying any memory, get the checksum of bytes
; 64-2048
;
initial_csum: xor edi,edi
mov si,_start1
mov cx,(SECTOR_SIZE-64) >> 2
.loop: lodsd
add edi,eax
loop .loop
mov [FirstSecSum],edi
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 award_hack ; changed for BrokenAwardHack
mov dl,[DriveNo]
cmp [sp_drive],dl ; Should contain the drive number
jne 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:
; Alright, we have found the drive. Now, try to find the
; boot file itself. If we have a boot info table, life is
; good; if not, we have to make some assumptions, and try
; to figure things out ourselves. In particular, the
; assumptions we have to make are:
; - single session only
; - only one boot entry (no menu or other alternatives)
cmp dword [bi_file],0 ; Address of code to load
jne found_file ; Boot info table present :)
%ifdef DEBUG_MESSAGES
mov si,noinfotable_msg
call writemsg
%endif
; No such luck. See if the the spec packet contained one.
mov eax,[sp_lba]
and eax,eax
jz set_file ; Good enough
%ifdef DEBUG_MESSAGES
mov si,noinfoinspec_msg
call writemsg
%endif
; No such luck. Get the Boot Record Volume, assuming single
; session disk, and that we're the first entry in the chain
mov eax,17 ; Assumed address of BRV
mov bx,trackbuf
call getonesec
mov eax,[trackbuf+47h] ; Get boot catalog address
mov bx,trackbuf
call getonesec ; Get boot catalog
mov eax,[trackbuf+28h] ; First boot entry
; And hope and pray this is us...
; Some BIOSes apparently have limitations on the size
; that may be loaded (despite the El Torito spec being very
; clear on the fact that it must all be loaded.) Therefore,
; we load it ourselves, and *bleep* the BIOS.
set_file:
mov [bi_file],eax
found_file:
; Set up boot file sizes
mov eax,[bi_length]
sub eax,SECTOR_SIZE-3
shr eax,2 ; bytes->dwords
mov [ImageDwords],eax ; boot file dwords
add eax,(2047 >> 2)
shr eax,9 ; dwords->sectors
mov [ImageSectors],ax ; boot file sectors
mov eax,[bi_file] ; Address of code to load
inc eax ; Don't reload bootstrap code
%ifdef DEBUG_MESSAGES
mov si,offset_msg
call writemsg
call writehex8
call crlf
%endif
; Just in case some BIOSes have problems with
; segment wraparound, use the normalized address
mov bx,((7C00h+2048) >> 4)
mov es,bx
xor bx,bx
mov bp,[ImageSectors]
%ifdef DEBUG_MESSAGES
push ax
mov si,size_msg
call writemsg
mov ax,bp
call writehex4
call crlf
pop ax
%endif
call getlinsec
push ds
pop es
%ifdef DEBUG_MESSAGES
mov si,loaded_msg
call writemsg
%endif
; Verify the checksum on the loaded image.
verify_image:
mov si,7C00h+2048
mov bx,es
mov ecx,[ImageDwords]
mov edi,[FirstSecSum] ; First sector checksum
.loop es lodsd
add edi,eax
dec ecx
jz .done
and si,si
jnz .loop
; SI wrapped around, advance ES
add bx,1000h
mov es,bx
jmp short .loop
.done: mov ax,ds
mov es,ax
cmp [bi_csum],edi
je integrity_ok
mov si,checkerr_msg
call writemsg
jmp kaboom
integrity_ok:
%ifdef DEBUG_MESSAGES
mov si,allread_msg
call writemsg
%endif
jmp all_read ; Jump to main code
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Start of BrokenAwardHack --- 10-nov-2002 Knut_Petersen@t-online.de
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; There is a problem with certain versions of the AWARD BIOS ...
;; the boot sector will be loaded and executed correctly, but, because the
;; int 13 vector points to the wrong code in the BIOS, every attempt to
;; load the spec packet will fail. We scan for the equivalent of
;;
;; mov ax,0201h
;; mov bx,7c00h
;; mov cx,0006h
;; mov dx,0180h
;; pushf
;; call <direct far>
;;
;; and use <direct far> as the new vector for int 13. The code above is
;; used to load the boot code into ram, and there should be no reason
;; for anybody to change it now or in the future. There are no opcodes
;; that use encodings relativ to IP, so scanning is easy. If we find the
;; code above in the BIOS code we can be pretty sure to run on a machine
;; with an broken AWARD BIOS ...
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
%ifdef DEBUG_MESSAGES ;;
;;
award_notice db "Trying BrokenAwardHack first ...",CR,LF,0 ;;
award_not_orig db "BAH: Original Int 13 vector : ",0 ;;
award_not_new db "BAH: Int 13 vector changed to : ",0 ;;
award_not_succ db "BAH: SUCCESS",CR,LF,0 ;;
award_not_fail db "BAH: FAILURE" ;;
award_not_crlf db CR,LF,0 ;;
;;
%endif ;;
;;
award_oldint13 dd 0 ;;
award_string db 0b8h,1,2,0bbh,0,7ch,0b9h,6,0,0bah,80h,1,09ch,09ah ;;
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
award_hack: mov si,spec_err_msg ; Moved to this place from
call writemsg ; spec_query_faild
;
%ifdef DEBUG_MESSAGES ;
;
mov si,award_notice ; display our plan
call writemsg ;
mov si,award_not_orig ; display original int 13
call writemsg ; vector
%endif ;
mov eax,[13h*4] ;
mov [award_oldint13],eax ;
;
%ifdef DEBUG_MESSAGES ;
;
call writehex8 ;
mov si,award_not_crlf ;
call writestr ;
%endif ;
push es ; save ES
mov ax,0f000h ; ES = BIOS Seg
mov es,ax ;
cld ;
xor di,di ; start at ES:DI = f000:0
award_loop: push di ; save DI
mov si,award_string ; scan for award_string
mov cx,7 ; length of award_string = 7dw
repz cmpsw ; compare
pop di ; restore DI
jcxz award_found ; jmp if found
inc di ; not found, inc di
jno award_loop ;
;
award_failed: pop es ; No, not this way :-((
award_fail2: ;
;
%ifdef DEBUG_MESSAGES ;
;
mov si,award_not_fail ; display failure ...
call writemsg ;
%endif ;
mov eax,[award_oldint13] ; restore the original int
or eax,eax ; 13 vector if there is one
jz spec_query_failed ; and try other workarounds
mov [13h*4],eax ;
jmp spec_query_failed ;
;
award_found: mov eax,[es:di+0eh] ; load possible int 13 addr
pop es ; restore ES
;
cmp eax,[award_oldint13] ; give up if this is the
jz award_failed ; active int 13 vector,
mov [13h*4],eax ; otherwise change 0:13h*4
;
;
%ifdef DEBUG_MESSAGES ;
;
push eax ; display message and
mov si,award_not_new ; new vector address
call writemsg ;
pop eax ;
call writehex8 ;
mov si,award_not_crlf ;
call writestr ;
%endif ;
mov ax,4B01h ; try to read the spec packet
mov dl,[DriveNo] ; now ... it should not fail
mov si,spec_packet ; any longer
int 13h ;
jc award_fail2 ;
;
%ifdef DEBUG_MESSAGES ;
;
mov si,award_not_succ ; display our SUCCESS
call writemsg ;
%endif ;
jmp found_drive ; and leave error recovery code
;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; End of BrokenAwardHack ---- 10-nov-2002 Knut_Petersen@t-online.de
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; INT 13h, AX=4B01h, DL=<passed in value> failed.
; Try to scan the entire 80h-FFh from the end.
spec_query_failed:
; some code moved to BrokenAwardHack
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
; No spec packet anywhere. Some particularly pathetic
; BIOSes apparently don't even implement function
; 4B01h, so we can't query a spec packet no matter
; what. If we got a drive number in DL, then try to
; use it, and if it works, then well...
mov dl,[DriveNo]
cmp dl,81h ; Should be 81-FF at least
jb fatal_error ; If not, it's hopeless
; Write a warning to indicate we're on *very* thin ice now
mov si,nospec_msg
call writemsg
mov al,dl
call writehex2
call crlf
jmp .found_drive ; Pray that this works...
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
;
; 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:
jmp near writechr_simple ; 3-byte jump
writechr_simple:
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
.loop:
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,SECTOR_SHIFT-4 ; 2048-byte sectors -> segment
add [si+6],ax ; Advance buffer pointer
and bp,bp
jnz .loop
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
mov [DiskSys],ax ; Save system call number
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,oncall_str
call writestr
mov ax,[DiskSys]
call writehex4
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:
lss sp,[cs:Stack]
mov ax,cs
mov ds,ax
mov es,ax
mov fs,ax
mov gs,ax
sti
mov si,err_bootfailed
call cwritestr
call getchar
cli
mov word [BIOS_magic],0 ; Cold reboot
jmp 0F000h:0FFF0h ; Reset vector address
; -----------------------------------------------------------------------------
; Common modules needed in the first sector
; -----------------------------------------------------------------------------
%include "writestr.inc" ; String output
writestr equ cwritestr
%include "writehex.inc" ; Hexadecimal output
; -----------------------------------------------------------------------------
; Data that needs to be in the first sector
; -----------------------------------------------------------------------------
syslinux_banner db CR, LF, 'ISOLINUX ', version_str, ' ', date, ' ', 0
copyright_str db ' Copyright (C) 1994-', year, ' H. Peter Anvin'
db CR, LF, 0
isolinux_str db 'isolinux: ', 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
offset_msg: db 'Loading main image from LBA = ', 0
size_msg: db 'Sectors to load = ', 0
loaded_msg: db 'Loaded boot image, verifying...', CR, LF, 0
verify_msg: db 'Image checksum verified.', CR, LF, 0
allread_msg db 'Main image read, jumping to main code...', CR, LF, 0
%endif
noinfotable_msg db 'No boot info table, assuming single session disk...', CR, LF, 0
noinfoinspec_msg db 'Spec packet missing LBA information, trying to wing it...', 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
nospec_msg db 'Extremely broken BIOS detected, last ditch attempt with drive = ', 0
nosecsize_msg: db 'Failed to get sector size, assuming 0800', CR, LF, 0
diskerr_msg: db 'Disk error ', 0
oncall_str: db ', AX = ',0
ondrive_str: db ', drive ', 0
nothing_msg: db 'Failed to locate CD-ROM device; boot failed.', CR, LF, 0
checkerr_msg: db 'Image checksum error, sorry...', CR, LF, 0
err_bootfailed db CR, LF, 'Boot failed: press a key to retry...'
bailmsg equ err_bootfailed
crlf_msg db CR, LF
null_msg db 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
db_d_path: dd 0,0 ; Device path
db 0
db_dpi_csum: db 0 ; Checksum for DPI info
;
; EBIOS disk address packet
;
align 8, db 0
dapa: dw 16 ; Packet size
.count: dw 0 ; Block count
.off: dw 0 ; Offset of buffer
.seg: dw 0 ; Segment of buffer
.lba: dd 0 ; LBA (LSW)
dd 0 ; LBA (MSW)
alignb 4, db 0
Stack dw _start, 0 ; SS:SP for stack reset
MaxTransfer dw 32 ; Max sectors per transfer
rl_checkpt equ $ ; Must be <= 800h
rl_checkpt_off equ ($-$$)
%ifndef DEPEND
%if rl_checkpt_off > 0x800
%error "Sector 0 overflow"
%endif
%endif
; ----------------------------------------------------------------------------
; End of code and data that have to be in the first sector
; ----------------------------------------------------------------------------
all_read:
;
; Initialize screen (if we're using one)
;
; Now set up screen parameters
call adjust_screen
; Wipe the F-key area
mov al,NULLFILE
mov di,FKeyName
mov cx,10*(1 << FILENAME_MAX_LG2)
rep stosb
; Patch the writechr routine to point to the full code
mov word [writechr+1], writechr_full-(writechr+3)
; Tell the user we got this far...
%ifndef DEBUG_MESSAGES ; Gets messy with debugging on
mov si,copyright_str
call writestr
%endif
; Test tracers
TRACER 'T'
TRACER '>'
;
; Common initialization code
;
%include "init.inc"
%include "cpuinit.inc"
;
; Now we're all set to start with our *real* business. First load the
; configuration file (if any) and parse it.
;
; In previous versions I avoided using 32-bit registers because of a
; rumour some BIOSes clobbered the upper half of 32-bit registers at
; random. I figure, though, that if there are any of those still left
; they probably won't be trying to install Linux on them...
;
; The code is still ripe with 16-bitisms, though. Not worth the hassle
; to take'm out. In fact, we may want to put them back if we're going
; to boot ELKS at some point.
;
;
; 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,[bi_pvd]
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,dbg_rootdir_msg
call writemsg
call writehex8
call crlf
%endif
mov eax,[trackbuf+156+10]
mov [RootDir+dir_len],eax
mov [CurDir+dir_len],eax
add eax,SECTOR_SIZE-1
shr eax,SECTOR_SHIFT
mov [RootDir+dir_clust],eax
mov [CurDir+dir_clust],eax
; Look for an isolinux directory, and if found,
; make it the current directory instead of the root
; directory.
mov di,boot_dir ; Search for /boot/isolinux
mov al,02h
call searchdir_iso
jnz .found_dir
mov di,isolinux_dir
mov al,02h ; Search for /isolinux
call searchdir_iso
jz .no_isolinux_dir
.found_dir:
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
%ifdef DEBUG_MESSAGES
push si
mov si,dbg_isodir_msg
call writemsg
pop si
call writehex8
call crlf
%endif
.no_isolinux_dir:
;
; Locate the configuration file
;
load_config:
%ifdef DEBUG_MESSAGES
mov si,dbg_config_msg
call writemsg
%endif
mov di,isolinux_cfg
call open
jz no_config_file ; Not found or empty
%ifdef DEBUG_MESSAGES
mov si,dbg_configok_msg
call writemsg
%endif
;
; Now we have the config file open. Parse the config file and
; run the user interface.
;
%include "ui.inc"
;
; Linux kernel loading code is common.
;
%include "runkernel.inc"
;
; COMBOOT-loading code
;
%include "comboot.inc"
%include "com32.inc"
%include "cmdline.inc"
;
; Boot sector loading code
;
%include "bootsect.inc"
;
; Enable disk emulation. The kind of disk we emulate is dependent on the size of
; the file: 1200K, 1440K or 2880K floppy, otherwise harddisk.
;
is_disk_image:
TRACER CR
TRACER LF
TRACER 'D'
TRACER ':'
shl edx,16
mov dx,ax ; Set EDX <- file size
mov di,img_table
mov cx,img_table_count
mov eax,[si+file_sector] ; Starting LBA of file
mov [dsp_lba],eax ; Location of file
mov byte [dsp_drive], 0 ; 00h floppy, 80h hard disk
.search_table:
TRACER 't'
mov eax,[di+4]
cmp edx,[di]
je .type_found
add di,8
loop .search_table
; Hard disk image. Need to examine the partition table
; in order to deduce the C/H/S geometry. Sigh.
.hard_disk_image:
TRACER 'h'
cmp edx,512
jb .bad_image
mov bx,trackbuf
mov cx,1 ; Load 1 sector
call getfssec
cmp word [trackbuf+510],0aa55h ; Boot signature
jne .bad_image ; Image not bootable
mov cx,4 ; 4 partition entries
mov di,trackbuf+446 ; Start of partition table
xor ax,ax ; Highest sector(al) head(ah)
.part_scan:
cmp byte [di+4], 0
jz .part_loop
lea si,[di+1]
call .hs_check
add si,byte 4
call .hs_check
.part_loop:
add di,byte 16
loop .part_scan
push eax ; H/S
push edx ; File size
mov bl,ah
xor bh,bh
inc bx ; # of heads in BX
xor ah,ah ; # of sectors in AX
cwde ; EAX[31:16] <- 0
mul bx
shl eax,9 ; Convert to bytes
; Now eax contains the number of bytes per cylinder
pop ebx ; File size
xor edx,edx
div ebx
and edx,edx
jz .no_remainder
inc eax ; Fractional cylinder...
; Now (e)ax contains the number of cylinders
.no_remainder: cmp eax,1024
jna .ok_cyl
mov ax,1024 ; Max possible #
.ok_cyl: dec ax ; Convert to max cylinder no
pop ebx ; S(bl) H(bh)
shl ah,6
or bl,ah
xchg ax,bx
shl eax,16
mov ah,bl
mov al,4 ; Hard disk boot
mov byte [dsp_drive], 80h ; Drive 80h = hard disk
.type_found:
TRACER 'T'
mov bl,[sp_media]
and bl,0F0h ; Copy controller info bits
or al,bl
mov [dsp_media],al ; Emulation type
shr eax,8
mov [dsp_chs],eax ; C/H/S geometry
mov ax,[sp_devspec] ; Copy device spec
mov [dsp_devspec],ax
mov al,[sp_controller] ; Copy controller index
mov [dsp_controller],al
TRACER 'V'
call vgaclearmode ; Reset video
mov ax,4C00h ; Enable emulation and boot
mov si,dspec_packet
mov dl,[DriveNo]
lss sp,[InitStack]
TRACER 'X'
int 13h
; If this returns, we have problems
.bad_image:
mov si,err_disk_image
call cwritestr
jmp enter_command
;
; Look for the highest seen H/S geometry
; We compute cylinders separately
;
.hs_check:
mov bl,[si] ; Head #
cmp bl,ah
jna .done_track
mov ah,bl ; New highest head #
.done_track: mov bl,[si+1]
and bl,3Fh ; Sector #
cmp bl,al
jna .done_sector
mov al,bl
.done_sector: ret
;
; Boot a specified local disk. AX specifies the BIOS disk number; or
; 0xFFFF in case we should execute INT 18h ("next device.")
;
local_boot:
call vgaclearmode
lss sp,[cs:Stack] ; Restore stack pointer
xor dx,dx
mov ds,dx
mov es,dx
mov fs,dx
mov gs,dx
mov si,localboot_msg
call writestr
cmp ax,-1
je .int18
; Load boot sector from the specified BIOS device and jump to it.
mov dl,al
xor dh,dh
push dx
xor ax,ax ; Reset drive
call xint13
mov ax,0201h ; Read one sector
mov cx,0001h ; C/H/S = 0/0/1 (first sector)
mov bx,trackbuf
call xint13
pop dx
cli ; Abandon hope, ye who enter here
mov si,trackbuf
mov di,07C00h
mov cx,512 ; Probably overkill, but should be safe
rep movsd
lss sp,[cs:InitStack]
jmp 0:07C00h ; Jump to new boot sector
.int18:
int 18h ; Hope this does the right thing...
jmp kaboom ; If we returned, oh boy...
;
; abort_check: let the user abort with <ESC> or <Ctrl-C>
;
abort_check:
call pollchar
jz ac_ret1
pusha
call getchar
cmp al,27 ; <ESC>
je ac_kill
cmp al,3 ; <Ctrl-C>
jne ac_ret2
ac_kill: mov si,aborted_msg
;
; abort_load: Called by various routines which wants to print a fatal
; error message and return to the command prompt. Since this
; may happen at just about any stage of the boot process, assume
; our state is messed up, and just reset the segment registers
; and the stack forcibly.
;
; SI = offset (in _text) of error message to print
;
abort_load:
mov ax,cs ; Restore CS = DS = ES
mov ds,ax
mov es,ax
cli
lss sp,[cs:Stack] ; Reset the stack
sti
call cwritestr ; Expects SI -> error msg
al_ok: jmp enter_command ; Return to command prompt
;
; End of abort_check
;
ac_ret2: popa
ac_ret1: ret
;
; 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
TRACER 'S'
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 ; Save these...
push cx
; Create recursion stack frame...
push word .resume ; Where to "return" to
push es
.isfile: xchg ax,di
.getsome:
; Get a chunk of the directory
; This relies on the fact that ISOLINUX doesn't change SI
mov si,trackbuf
TRACER 'g'
pushad
xchg bx,si
mov cx,[BufSafe]
call getfssec
popad
.compare:
movzx eax,byte [si] ; Length of directory entry
cmp al,33
jb .next_sector
TRACER 'c'
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
TRACER 'i'
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+SECTOR_SIZE-1]
and ax,~(SECTOR_SIZE-1)
sub ax,si
jmp short .not_file ; We still need to do length checks
.failure: 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,SECTOR_SIZE-1
shr eax,SECTOR_SHIFT
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 slash
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:
TRACER 'a'
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
;
; mangle_name: Mangle a filename pointed to by DS:SI into a buffer pointed
; to by ES:DI; ends on encountering any whitespace.
;
; This verifies that a filename is < FILENAME_MAX characters,
; doesn't contain whitespace, zero-pads the output buffer,
; and removes trailing dots and redundant slashes,
; so "repe cmpsb" can do a compare, and the
; path-searching routine gets a bit of an easier job.
;
mangle_name:
push bx
xor ax,ax
mov cx,FILENAME_MAX-1
mov bx,di
.mn_loop:
lodsb
cmp al,' ' ; If control or space, end
jna .mn_end
cmp al,ah ; Repeated slash?
je .mn_skip
xor ah,ah
cmp al,'/'
jne .mn_ok
mov ah,al
.mn_ok stosb
.mn_skip: loop .mn_loop
.mn_end:
cmp bx,di ; At the beginning of the buffer?
jbe .mn_zero
cmp byte [di-1],'.' ; Terminal dot?
je .mn_kill
cmp byte [di-1],'/' ; Terminal slash?
jne .mn_zero
.mn_kill: dec di ; If so, remove it
inc cx
jmp short .mn_end
.mn_zero:
inc cx ; At least one null byte
xor ax,ax ; Zero-fill name
rep stosb
pop bx
ret ; Done
;
; unmangle_name: Does the opposite of mangle_name; converts a DOS-mangled
; filename to the conventional representation. This is needed
; for the BOOT_IMAGE= parameter for the kernel.
; NOTE: A 13-byte buffer is mandatory, even if the string is
; known to be shorter.
;
; DS:SI -> input mangled file name
; ES:DI -> output buffer
;
; On return, DI points to the first byte after the output name,
; which is set to a null byte.
;
unmangle_name: call strcpy
dec di ; Point to final null byte
ret
;
; getfssec: Get multiple clusters from a file, given the file pointer.
;
; On entry:
; ES:BX -> Buffer
; SI -> File pointer
; CX -> Cluster count
; On exit:
; SI -> File pointer (or 0 on EOF)
; CF = 1 -> Hit EOF
;
getfssec:
TRACER 'F'
push ds
push cs
pop ds ; DS <- CS
movzx ecx,cx
cmp ecx,[si+file_left]
jna .ok_size
mov ecx,[si+file_left]
.ok_size:
mov bp,cx
push cx
push si
mov eax,[si+file_sector]
TRACER 'l'
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:
pop ds
TRACER 'f'
ret
; -----------------------------------------------------------------------------
; Common modules
; -----------------------------------------------------------------------------
%include "getc.inc" ; getc et al
%include "conio.inc" ; Console I/O
%include "parseconfig.inc" ; High-level config file handling
%include "parsecmd.inc" ; Low-level config file handling
%include "bcopy32.inc" ; 32-bit bcopy
%include "loadhigh.inc" ; Load a file into high memory
%include "font.inc" ; VGA font stuff
%include "graphics.inc" ; VGA graphics
%include "highmem.inc" ; High memory sizing
%include "strcpy.inc" ; strcpy()
%include "rawcon.inc" ; Console I/O w/o using the console functions
; -----------------------------------------------------------------------------
; Begin data section
; -----------------------------------------------------------------------------
section .data
boot_prompt db 'boot: ', 0
wipe_char db BS, ' ', BS, 0
err_notfound db 'Could not find kernel image: ',0
err_notkernel db CR, LF, 'Invalid or corrupt kernel image.', CR, LF, 0
err_noram db 'It appears your computer has less than '
asciidec dosram_k
db 'K of low ("DOS")'
db CR, LF
db 'RAM. Linux needs at least this amount to boot. If you get'
db CR, LF
db 'this message in error, hold down the Ctrl key while'
db CR, LF
db 'booting, and I will take your word for it.', CR, LF, 0
err_badcfg db 'Unknown keyword in config file.', CR, LF, 0
err_noparm db 'Missing parameter in config file.', CR, LF, 0
err_noinitrd db CR, LF, 'Could not find ramdisk image: ', 0
err_nohighmem db 'Not enough memory to load specified kernel.', CR, LF, 0
err_highload db CR, LF, 'Kernel transfer failure.', CR, LF, 0
err_oldkernel db 'Cannot load a ramdisk with an old kernel image.'
db CR, LF, 0
err_notdos db ': attempted DOS system call', CR, LF, 0
err_comlarge db 'COMBOOT image too large.', CR, LF, 0
err_bssimage db 'BSS images not supported.', CR, LF, 0
err_a20 db CR, LF, 'A20 gate not responding!', CR, LF, 0
notfound_msg db 'not found', CR, LF, 0
localboot_msg db 'Booting from local disk...', CR, LF, 0
cmdline_msg db 'Command line: ', CR, LF, 0
ready_msg db 'Ready.', CR, LF, 0
trying_msg db 'Trying to load: ', 0
crlfloading_msg db CR, LF ; Fall through
loading_msg db 'Loading ', 0
dotdot_msg db '.'
dot_msg db '.', 0
fourbs_msg db BS, BS, BS, BS, 0
aborted_msg db ' aborted.', CR, LF, 0
crff_msg db CR, FF, 0
default_str db 'default', 0
default_len equ ($-default_str)
boot_dir db '/boot' ; /boot/isolinux
isolinux_dir db '/isolinux', 0
ConfigName equ $
isolinux_cfg db 'isolinux.cfg', 0
err_disk_image db 'Cannot load disk image (invalid file)?', CR, LF, 0
%ifdef DEBUG_MESSAGES
dbg_rootdir_msg db 'Root directory at LBA = ', 0
dbg_isodir_msg db 'isolinux directory at LBA = ', 0
dbg_config_msg db 'About to load config file...', CR, LF, 0
dbg_configok_msg db 'Configuration file opened...', CR, LF, 0
%endif
;
; Command line options we'd like to take a look at
;
; mem= and vga= are handled as normal 32-bit integer values
initrd_cmd db 'initrd='
initrd_cmd_len equ 7
;
; Config file keyword table
;
%include "keywords.inc"
;
; Extensions to search for (in *forward* order).
;
align 4, db 0
exten_table: db '.cbt' ; COMBOOT (specific)
db '.img' ; Disk image
db '.bin' ; CD boot sector
db '.com' ; COMBOOT (same as DOS)
db '.c32' ; COM32
exten_table_end:
dd 0, 0 ; Need 8 null bytes here
;
; Floppy image table
;
align 4, db 0
img_table_count equ 3
img_table:
dd 1200*1024 ; 1200K floppy
db 1 ; Emulation type
db 80-1 ; Max cylinder
db 15 ; Max sector
db 2-1 ; Max head
dd 1440*1024 ; 1440K floppy
db 2 ; Emulation type
db 80-1 ; Max cylinder
db 18 ; Max sector
db 2-1 ; Max head
dd 2880*1024 ; 2880K floppy
db 3 ; Emulation type
db 80-1 ; Max cylinder
db 36 ; Max sector
db 2-1 ; Max head
;
; Misc initialized (data) variables
;
;
; Spec packet for disk image emulation
;
align 8, db 0
dspec_packet: db 13h ; Size of packet
dsp_media: db 0 ; Media type
dsp_drive: db 0 ; Drive number
dsp_controller: db 0 ; Controller index
dsp_lba: dd 0 ; LBA for emulated disk image
dsp_devspec: dw 0 ; IDE/SCSI information
dsp_buffer: dw 0 ; User-provided buffer
dsp_loadseg: dw 0 ; Load segment
dsp_sectors: dw 1 ; Sector count
dsp_chs: db 0,0,0 ; Simulated CHS geometry
dsp_dummy: db 0 ; Scratch, safe to overwrite
;
; Variables that are uninitialized in SYSLINUX but initialized here
;
; **** ISOLINUX:: We may have to make this flexible, based on what the
; **** BIOS expects our "sector size" to be.
;
alignb 4, db 0
BufSafe dw trackbufsize/SECTOR_SIZE ; Clusters we can load into trackbuf
BufSafeSec dw trackbufsize/SECTOR_SIZE ; = how many sectors?
BufSafeBytes dw trackbufsize ; = how many bytes?
EndOfGetCBuf dw getcbuf+trackbufsize ; = getcbuf+BufSafeBytes
%ifndef DEPEND
%if ( trackbufsize % SECTOR_SIZE ) != 0
%error trackbufsize must be a multiple of SECTOR_SIZE
%endif
%endif