; ****************************************************************************
; Note: The Makefile builds one version with DEBUG_MESSAGES automatically.
-; %define DEBUG_TRACERS ; Uncomment to get debugging tracers
+%define DEBUG_TRACERS ; Uncomment to get debugging tracers
; %define DEBUG_MESSAGES ; Uncomment to get debugging messages
%ifdef DEBUG_TRACERS
; El Torito spec packet
;
align 8, db 0
-spec_packet: db 13 ; Size of packet
+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_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
+
+;
+; 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
;
; EBIOS drive parameter packet
;
; .com - COMBOOT image
; .cbt - COMBOOT image
-; .bs - Boot sector
-; .bss - Boot sector, but transfer over DOS superblock
-;
-; Boot sectors are currently not supported by PXELINUX.
+; .bs - Boot sector (SYSLINUX only)
+; .bss - DOS boot sector (SYSLINUX only)
+; .img - Disk image (ISOLINUX only)
;
; Anything else is assumed to be a Linux kernel.
;
pop ax
pop di
+;
+; At this point, DX:AX contains the size of the kernel, and SI contains
+; the file handle/cluster pointer.
+;
or ecx,20202000h ; Force lower case
cmp ecx,'.com'
je near is_comboot_image
cmp ecx,'.cbt'
je near is_comboot_image
+ cmp ecx,'.img'
+ je near is_disk_image
cmp ecx,'.bss'
je near is_bss_sector
and ecx, 00ffffffh
.badness: jmp short .badness
;
+; 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 near .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 near .bad_image
+
+ mov bx,trackbuf
+ mov cx,1 ; Load 1 sector
+ call getfssec
+
+ cmp word [trackbuf+510],0aa55h ; Boot signature
+ jne near .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.")
;
default_len equ ($-default_str)
isolinux_dir db '/isolinux', 0
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
;
align 4, db 0
exten_table: db '.cbt' ; COMBOOT (specific)
- db '.bss' ; Boot Sector (add superblock)
- db '.bs', 0 ; Boot Sector
+ db '.img' ; Disk image
db '.com' ; COMBOOT (same as DOS)
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
;
AppendLen dw 0 ; Bytes in append= command
debugging messages enabled. If you are having problems with ISOLINUX,
I would greatly appreciate if you could try out the debugging version
(isolinux-debug.bin) and let me know what it reports.
+
+
+ ++++ BOOTING DOS (OR OTHER SIMILAR OPERATING SYSTEMS) ++++
+
+To boot DOS, or other real-mode operating systems (protected-mode
+operating systems may or may not work correctly), using ISOLINUX, you
+need to prepare a disk image (usually a floppy image, but a hard disk
+image can be used on *most* systems) with the relevant operating
+system. This file should be included on the CD-ROM in the /isolinux
+directory, and have a .img extension. The ".img" extension does not
+have to be specified on the command line, but has to be explicitly
+specified if used in a "kernel" statement in isolinux.cfg.
+
+For a floppy image, the size of the image should be exactly one of the
+following:
+
+ 1,228,800 bytes - For a 1200K floppy image
+ 1,474,560 bytes - For a 1440K floppy image
+ 2,949,120 bytes - For a 2880K floppy image
+
+Any other size is assumed to be a hard disk image. In order to work
+on as many systems as possible, a hard disk image should have exactly
+one partition, marked active, that covers the entire size of the disk
+image file. Even so, hard disk images are not supported on all
+BIOSes.
+
+
projects / platform / upstream / syslinux.git / commitdiff