path: root/comboot.inc

;; -----------------------------------------------------------------------
;;
;;   Copyright 1994-2007 H. Peter Anvin - All Rights Reserved
;;
;;   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.
;;
;; -----------------------------------------------------------------------

;;
;; comboot.inc
;;
;; Common code for running a COMBOOT image
;;

		section .text

; Parameter registers definition; this is the definition
; of the stack frame used by INT 21h and INT 22h.
%define		P_FLAGS		word [bp+44]
%define		P_FLAGSL	byte [bp+44]
%define		P_FLAGSH	byte [bp+45]
%define		P_CS		word [bp+42]
%define		P_IP		word [bp+40]
%define		P_DS		word [bp+38]
%define		P_ES		word [bp+36]
%define		P_FS		word [bp+34]
%define		P_GS		word [bp+32]
%define		P_EAX		dword [bp+28]
%define		P_AX		word [bp+28]
%define		P_HAX		word [bp+30]
%define		P_AL		byte [bp+28]
%define		P_AH		byte [bp+29]
%define		P_ECX		dword [bp+24]
%define		P_CX		word [bp+24]
%define		P_HCX		word [bp+26]
%define		P_CL		byte [bp+24]
%define		P_CH		byte [bp+25]
%define		P_EDX		dword [bp+20]
%define		P_DX		word [bp+20]
%define		P_HDX		word [bp+22]
%define		P_DL		byte [bp+20]
%define		P_DH		byte [bp+21]
%define		P_EBX		dword [bp+16]
%define		P_BX		word [bp+16]
%define		P_HBX		word [bp+18]
%define		P_BL		byte [bp+16]
%define		P_BH		byte [bp+17]
%define		P_EBP		dword [bp+8]
%define		P_BP		word [bp+8]
%define		P_HBP		word [bp+10]
%define		P_ESI		dword [bp+4]
%define		P_SI		word [bp+4]
%define		P_HSI		word [bp+6]
%define		P_EDI		dword [bp]
%define		P_DI		word [bp]
%define		P_HDI		word [bp+2]

; Looks like a COMBOOT image but too large
comboot_too_large:
		mov si,err_comlarge
		call cwritestr
		jmp enter_command

;
; Load a COMBOOT image.  A COMBOOT image is basically a DOS .COM file,
; except that it may, of course, not contain any DOS system calls.  We
; do, however, allow the execution of INT 20h to return to SYSLINUX.
;
is_comboot_image:
		and dx,dx
		jnz comboot_too_large
		cmp ax,0ff00h		; Max size in bytes
		jae comboot_too_large

		push si			; Save file handle

		call make_plain_cmdline

		call comboot_setup_api

		mov cx,comboot_seg
		mov es,cx

		xor di,di
		mov cx,64		; 256 bytes (size of PSP)
		xor eax,eax		; Clear PSP
		rep stosd

		mov word [es:0], 020CDh	; INT 20h instruction
		; First non-free paragraph
		; This is valid because comboot_seg == real_mode_seg
		; == the highest segment used by all derivatives
		int 12h			; Get DOS memory size
		shl ax,6		; Kilobytes -> paragraphs
		mov word [es:02h],ax

%ifndef DEPEND
%if real_mode_seg != comboot_seg
%error "This code assumes real_mode_seg == comboot_seg"
%endif
%endif
		; Copy the command line from high memory
		mov si,cmd_line_here
		mov cx,125		; Max cmdline len (minus space and CR)
		mov di,081h		; Offset in PSP for command line
		mov al,' '		; DOS command lines begin with a space
		stosb

.loop:		es lodsb
		and al,al
		jz .done
		stosb
		loop .loop
.done:

		mov al,0Dh		; CR after last character
		stosb
		mov ax,di
		sub al,82h		; Include space but not CR
		mov [es:80h],al		; Store command line length

		; Now actually load the file...
		pop si			; File handle
		mov bx,100h		; Load at <seg>:0100h
		mov cx,0FF00h >> SECTOR_SHIFT
					; Absolute maximum # of sectors
		call getfssec

		; And invoke the program...
		mov ax,es
		mov ds,ax
		mov ss,ax
		xor sp,sp
		push word 0		; Return to address 0 -> exit

		jmp comboot_seg:100h	; Run it

; Proper return vector
comboot_return:	cli			; Don't trust anyone
		push enter_command	; Normal return to command prompt
		jmp comboot_exit

;
; Set up the COMBOOT API interrupt vectors.  This is also used
; by the COM32 code.
;
comboot_setup_api:
		mov di,4*0x20		; DOS interrupt vectors
		mov eax,comboot_return	; INT 20h = exit
		stosd
		mov ax,comboot_int21	; INT 21h = DOS-compatible syscalls
		stosd
		mov ax,comboot_int22	; INT 22h = proprietary syscalls
		stosd
		mov ax,comboot_bogus
		mov cx,29		; All remaining DOS vectors
		rep stosd
		ret

; INT 21h: generic DOS system call
comboot_int21:	cli
		push ds
		push es
		push fs
		push gs
		pushad
		cld
		mov bp,cs
		mov ds,bp
		mov es,bp
		mov bp,sp			; Set up stack frame

		call adjust_screen		; The COMBOOT program might have changed the screen

		mov cx,int21_count
		mov si,int21_table
.again:		lodsb
		cmp al,P_AH
		lodsw
		loopne .again
		; The last function in the list is the
		; "no such function" function
		clc
		call ax			; Call the invoked function
comboot_resume:
		mov bp,sp		; In case the function clobbers BP
		setc P_FLAGSL		; Propagate CF->error
		popad
		pop gs
		pop fs
		pop es
		pop ds
		iret

; Attempted to execute non-21h DOS system call
comboot_bogus:	cli			; Don't trust anyone
		mov cx,err_notdos
		push enter_command
		jmp comboot_exit_msg

;
; Generic COMBOOT return to command line code
;  stack -> where to go next
;     CX -> message (for _msg version)
;
comboot_exit:
		xor cx,cx
comboot_exit_msg:
		pop bx			; Return address
		RESET_STACK_AND_SEGS AX
		call adjust_screen	; The COMBOOT program might have changed the screen
		jcxz .nomsg
		mov si,KernelCName
		call cwritestr
		mov si,cx
		call cwritestr
.nomsg:
		jmp bx

;
; INT 21h system calls
;
comboot_getkey:				; 01 = get key with echo
		call vgashowcursor
		call comboot_getchar
		call vgahidecursor
		call writechr
		clc
		ret

comboot_writechr:			; 02 = writechr
		mov al,P_DL
		call writechr
		clc
		ret

comboot_writeserial:			; 04 = write serial port
		mov al,P_DL
		call write_serial
		clc
		ret

comboot_getkeynoecho:			; 08 = get key w/o echo
		call comboot_getchar
		clc
		ret

comboot_writestr:			; 09 = write DOS string
		mov es,P_DS
		mov si,P_DX
.loop:		es lodsb
		cmp al,'$'		; End string with $ - bizarre
		je .done
		call writechr
		jmp short .loop
.done:		clc
		ret

comboot_checkkey:			; 0B = check keyboard status
		cmp byte [APIKeyFlag],00h
		jnz .waiting
		call pollchar
.waiting:	setz al
		dec al			; AL = 0FFh if present, 0 if not
		mov P_AL,al
		clc
		ret

comboot_checkver:			; 30 = check DOS version
		; We return 0 in all DOS-compatible version registers,
		; but the high part of eax-ebx-ecx-edx spell "SYSLINUX"
		mov P_EAX,'SY' << 16
		mov P_EBX,'SL' << 16
		mov P_ECX,'IN' << 16
		mov P_EDX,'UX' << 16
		ret

comboot_getchar:
		cmp byte [APIKeyFlag],00h
		jne .queued
		call getchar		; If not queued get input
		and al,al		; Function key?  (CF <- 0)
		jnz .done
		mov [APIKeyWait],ah	; High part of key
		inc byte [APIKeyFlag]	; Set flag
.done:		mov P_AL,al
		ret
.queued:	mov al,[APIKeyWait]
		dec byte [APIKeyFlag]
		jmp .done

;
; INT 22h - SYSLINUX-specific system calls
;           System call number in ax
;
comboot_int22:
		cli
		push ds
		push es
		push fs
		push gs
		pushad
		cld
		mov bp,cs
		mov ds,bp
		mov es,bp
		mov bp,sp			; Set up stack frame

		call adjust_screen		; The COMBOOT program might have changed the screen

		cmp ax,int22_count
		jb .ok
		xor ax,ax			; Function 0 -> unimplemented
.ok:
		xchg ax,bx
		add bx,bx			; CF <- 0
		call [bx+int22_table]
		jmp comboot_resume		; On return

;
; INT 22h AX=0000h	Unimplemented call
;
comapi_err:
		stc
		ret

;
; INT 22h AX=0001h	Get SYSLINUX version
;
comapi_get_version:
		; Number of API functions supported
		mov P_AX,int22_count
		; SYSLINUX version
		mov P_CX,(VER_MAJOR << 8)+VER_MINOR
		; SYSLINUX derivative ID byte
		mov P_DX,my_id
		; For future use
		mov P_BX,cs	; cs == 0

		mov P_ES,ds
		; ES:SI -> version banner
		mov P_SI,syslinux_banner
		; ES:DI -> copyright string
		mov P_DI,copyright_str

comapi_nop:
		clc
		ret

;
; INT 22h AX=0002h	Write string
;
; Write null-terminated string in ES:BX
;
comapi_writestr:
		mov ds,P_ES
		mov si,P_BX
		call writestr
		clc
		ret

;
; INT 22h AX=0003h	Run command
;
; Terminates the COMBOOT program and executes the command line in
; ES:BX as if it had been entered by the user.
;
comapi_run:
		mov ds,P_ES
		mov si,P_BX
		mov di,command_line
		call strcpy
		push load_kernel		; Run a new kernel
		jmp comboot_exit		; Terminate task, clean up

;
; INT 22h AX=0004h	Run default command
;
; Terminates the COMBOOT program and executes the default command line
; as if a timeout had happened or the user pressed <Enter>.
;
comapi_run_default:
		push auto_boot
		jmp comboot_exit

;
; INT 22h AX=0005h	Force text mode
;
; Puts the video in standard text mode
;
comapi_textmode:
		call vgaclearmode
		clc
		ret

;
; INT 22h AX=0006h	Open file
;
comapi_open:
		push ds
		mov ds,P_ES
		mov si,P_SI
		mov di,InitRD
		call mangle_name
		pop ds
		call searchdir
		jz comapi_err
		mov P_AX,ax
		mov P_HAX,dx
		mov P_CX,SECTOR_SIZE
		mov P_SI,si
		clc
		ret

;
; INT 22h AX=0007h	Read file
;
comapi_read:
		mov es,P_ES
		mov bx,P_BX
		mov si,P_SI
		mov cx,P_CX
		call getfssec
		jnc .noteof
		xor si,si		; SI <- 0 on EOF, CF <- 0
.noteof:	mov P_SI,si
		ret

;
; INT 22h AX=0008h	Close file
;
comapi_close:
		mov si,P_SI
		call close_file
		clc
		ret

;
; INT 22h AX=0009h	Call PXE stack
;
%if IS_PXELINUX
comapi_pxecall:
		mov bx,P_BX
		mov es,P_ES
		mov di,P_DI
		call pxenv
		mov P_AX,ax
		clc
		ret
%else
comapi_pxecall	equ comapi_err			; Not available
%endif

;
; INT 22h AX=000Ah	Get Derivative-Specific Info
;
comapi_derinfo:
		mov P_AL,my_id
%if IS_PXELINUX
		mov ax,[APIVer]
		mov P_DX,ax
		mov ax,[StrucPtr]
		mov P_BX,ax
		mov ax,[StrucPtr+2]
		mov P_ES,ax
		mov ax,[InitStack]
		mov P_SI,ax
		mov ax,[InitStack+2]
		mov P_FS,ax
%else
		; Physical medium...

		mov P_CL,SECTOR_SHIFT
		mov al,[DriveNumber]
		mov P_DL,al
		mov P_FS,cs
		mov P_SI,OrigESDI
%if IS_SYSLINUX || IS_MDSLINUX || IS_EXTLINUX
		mov P_ES,cs
		mov P_BX,PartInfo
%elif IS_ISOLINUX
		mov P_ES,cs
		mov P_BX,spec_packet
%endif
%endif
		clc
		ret

;
; INT 22h AX=000Bh	Get Serial Console Configuration
;
comapi_serialcfg:
		mov ax,[SerialPort]
		mov P_DX,ax
		mov ax,[BaudDivisor]
		mov P_CX,ax
		mov ax,[FlowControl]
		or al,ah
		mov ah,[FlowIgnore]
		shr ah,4
		test byte [DisplayCon],01h
		jnz .normalconsole
		or ah,80h
.normalconsole:
		mov P_BX,ax
		clc
		ret

;
; INT 22h AX=000Ch	Perform final cleanup
;
comapi_cleanup:
%if IS_PXELINUX
		; Unload PXE if requested
		test dl,3
		setnz [KeepPXE]
		sub bp,sp		; unload_pxe may move the stack around
		call unload_pxe
		add bp,sp		; restore frame pointer...
%elif IS_SYSLINUX || IS_MDSLINUX || IS_EXTLINUX
		; Restore original FDC table
		mov eax,[OrigFDCTabPtr]
		mov [fdctab],eax
%endif
		; Reset the floppy disk subsystem
		xor ax,ax
		xor dx,dx
		int 13h
		clc
		ret

;
; INT 22h AX=000Dh	Clean up then replace bootstrap
;
comapi_chainboot:
		call comapi_cleanup
		mov eax,P_EDI
		mov [trackbuf+4],eax		; Copy from
		mov eax,P_ECX
		mov [trackbuf+8],eax		; Total bytes
		mov eax,7C00h
		mov [trackbuf],eax		; Copy to
		mov [EntryPoint],eax		; CS:IP entry point
		mov esi,P_ESI
		mov edx,P_EBX
		mov bx,P_DS
		jmp replace_bootstrap_one


;
; INT 22h AX=000Eh	Get configuration file name
;
comapi_configfile:
		mov P_ES,cs
		mov P_BX,ConfigName
		clc
		ret

;
; INT 22h AX=000Fh	Get IPAPPEND strings
;
%if IS_PXELINUX
comapi_ipappend:
		mov P_ES,cs
		mov P_CX,numIPAppends
		mov P_BX,IPAppends
		clc
		ret

		section .data
		alignb 2, db 0
IPAppends	dw IPOption
		dw BOOTIFStr
numIPAppends	equ ($-IPAppends)/2

%else
comapi_ipappend equ comapi_err
%endif

		section .text

;
; INT 22h AX=0010h	Resolve hostname
;
%if IS_PXELINUX
comapi_dnsresolv:
		mov ds,P_ES
		mov si,P_BX
		call dns_resolv
		mov P_EAX,eax
		clc
		ret
%else
comapi_dnsresolv equ comapi_err
%endif

		section .text

;
; INT 22h AX=0011h	Maximum number of shuffle descriptors
;
comapi_maxshuffle:
		mov P_CX,(2*trackbufsize)/12
		ret

;
; INT 22h AX=0012h	Cleanup, shuffle and boot
;
comapi_shuffle:
		cmp P_CX,(2*trackbufsize)/12
		ja .error

		call comapi_cleanup

		mov cx, P_CX
		push cx				; On stack: descriptor count

		lea cx,[ecx+ecx*2]		; CX *= 3

		mov fs,P_ES
		mov si,P_DI
		mov di,trackbuf
		push di				; On stack: descriptor list address
		fs rep movsd			; Copy the list

		mov eax,P_EBP
		mov [EntryPoint],eax		; CS:IP entry point
		mov esi,P_ESI
		mov edx,P_EBX
		mov bx,P_DS
		jmp replace_bootstrap
.error:
		stc
		ret

;
; INT 22h AX=0013h	Idle call
;
;
; *** FIX THIS ***
; The idle call seems to have detrimental effects on some machines when
; called from a COM32 context (WHY?) --  disable it for now.
;
%if 0 ; def HAVE_IDLE

comapi_idle:
		DO_IDLE
		clc
		ret

%else

comapi_idle	equ comapi_err

%endif

;
; INT 22h AX=0014h	Local boot
;
%if IS_PXELINUX || IS_ISOLINUX
comapi_localboot:
		mov ax,P_DX
		jmp local_boot
%else
comapi_localboot equ comapi_err
%endif

;
; INT 22h AX=0015h	Feature flags
;
comapi_features:
		mov P_ES,cs
		mov P_BX,feature_flags
		mov P_CX,feature_flags_len
		clc
		ret

;
; INT 22h AX=0016h	Run kernel image
;
comapi_runkernel:
		mov al,P_DL
		cmp al,VK_TYPES-1
		ja .error
		mov [KernelType],al
		push ds
		mov ds,P_DS
		mov si,P_SI
		mov di,KernelName
		call mangle_name
		pop ds
		call searchdir
		jz comapi_err

		; The kernel image was found, so we can load it...
		mov [Kernel_SI],si
		mov [Kernel_EAX],ax
		mov [Kernel_EAX+2],dx

		; It's not just possible, but quite likely, that ES:BX
		; points into real_mode_seg, so we need to exercise some
		; special care here... use xfer_buf_seg as an intermediary
		push ds
		push es
		mov ax,xfer_buf_seg
		mov ds,P_ES
		mov si,P_BX
		mov es,ax
		xor di,di
		call strcpy
		pop es
		pop ds

%if IS_PXELINUX
		mov al,P_CL
		mov [IPAppend],al
%endif

		call comboot_exit

.finish:
		; Copy the command line into its proper place
		push ds
		push es
		mov ax,xfer_buf_seg
		mov dx,real_mode_seg
		mov ds,ax
		mov es,dx
		xor si,si
		mov di,cmd_line_here
		call strcpy
		mov byte [es:di-1],' '		; Simulate APPEND
		pop es
		pop ds
		mov [CmdLinePtr],di
		mov word [CmdOptPtr],zero_string
		jmp kernel_good_saved

.error		equ comapi_shuffle.error

;
; INT 22h AX=0017h  Report video mode change
;
comapi_usingvga:
		mov ax,P_BX
		cmp ax,0Fh		; Unknown flags = failure
		ja .error
		mov [UsingVGA],al
		mov cx,P_CX
		mov dx,P_DX
		mov [GXPixCols],cx
		mov [GXPixRows],dx
		test al,08h
		jnz .notext
		call adjust_screen
.notext:
		clc
		ret
.error:
		stc
		ret

;
; INT 22h AX=0018h  Query custom font
;
comapi_userfont:
		mov al,[UserFont]
		and al,al
		jz .done
		mov al,[VGAFontSize]
		mov P_ES,ds
		mov P_BX,vgafontbuf

.done:		; CF=0 here
		mov P_AL,al
		ret

;
; INT 22h AX=0019h  Read disk
;
%if IS_SYSLINUX || IS_MDSLINUX || IS_ISOLINUX || IS_EXTLINUX
comapi_readdisk:
		mov esi,P_ESI		; Enforce ESI == EDI == 0, these
		or esi,P_EDI		; are reserved for future expansion
		jnz .err
		mov eax,P_EDX
		mov es,P_ES
		mov bx,P_BX
		mov bp,P_CX		; WE CANNOT use P_* after touching bp!
		call getlinsec
		clc
		ret
.err:
		stc
		ret
%else
comapi_readdisk	equ comapi_err
%endif

;
; INT 22h AX=001Ah	Cleanup, shuffle and boot to flat protected mode
;
comapi_shufflepm:
		cmp P_CX,(2*trackbufsize)/12
		ja .error

		call comapi_cleanup

		mov cx, P_CX
		push cx				; On stack: descriptor count

		lea cx,[ecx+ecx*2]		; CX *= 3

		mov fs,P_ES
		mov si,P_DI
		mov di,trackbuf
		push di				; On stack: descriptor list address
		fs rep movsd			; Copy the list

		mov fs,P_DS
		mov si,P_SI
		mov edi,TrampolineBuf
		mov al,0B8h			; MOV EAX opcode
		mov cl,9
.maketramp:
		stosb				; MOV opcode
		inc ax				; Next register opcode
		fs movsd			; immediate value
		loop .maketramp
		mov byte [di-5],0E9h		; Last opcode is JMP
		sub [di-4],edi			; Make JMP target relative

		mov dword [EntryPoint],trampoline_to_pm
		xor bx,bx			; DS on entry
		jmp replace_bootstrap
.error:
		stc
		ret

;
; INT 22h AX=001Bh	Cleanup, shuffle and boot with register setting
;
comapi_shufflerm:
		cmp P_CX,(2*trackbufsize)/12
		ja .error

		call comapi_cleanup

		mov cx, P_CX
		push cx				; On stack: descriptor count

		lea cx,[ecx+ecx*2]		; CX *= 3

		mov fs,P_ES
		mov si,P_DI
		mov di,trackbuf
		push di				; On stack: descriptor list address
		fs rep movsd			; Copy the list

		mov fs,P_DS
		mov si,P_SI
		mov di,TrampolineBuf

		; Generate segment-loading instructions
		mov bx,0C08Eh			; MOV ES,AX
		mov cl,6			; 6 segment registers (incl CS)
.segtramp:
		mov al,0B8h
		stosb				; MOV AX,imm16 opcode
		fs movsw			; imm16
		mov ax,bx
		add bh,8
		stosw				; MOV xS,AX
		loop .segtramp

		; Clobber the MOV CS,AX instruction.
		mov word [di-22], 9090h		; NOP NOP

		; Generate GPR-loading instructions
		mov ax,0B866h			; MOV EAX,imm32
		mov cl,8			; 8 GPRs
.gprtramp:
		stosw				; MOV ExX,imm32 opcode
		fs movsd			; imm32
		inc ah
		loop .gprtramp

		mov al,0EAh			; JMP FAR imm16:imm16 opcode
		stosb
		fs movsd			; CS:IP

		mov dword [EntryPoint],TrampolineBuf
		jmp replace_bootstrap
.error:
		stc
		ret

;
; INT 22h AX=001Ch	Get pointer to auxillary data vector
;
comapi_getadv:
		mov P_ES,ds
		mov P_BX,adv0.data
		mov P_CX,ADV_LEN
		ret

;
; INT 22h AX=001Dh	Write auxillary data vector
;
comapi_writeadv	equ adv_write

		section .data

%macro		int21 2
		db %1
		dw %2
%endmacro

int21_table:
		int21	00h, comboot_return
		int21	01h, comboot_getkey
		int21	02h, comboot_writechr
		int21	04h, comboot_writeserial
		int21	08h, comboot_getkeynoecho
		int21	09h, comboot_writestr
		int21	0Bh, comboot_checkkey
		int21	30h, comboot_checkver
		int21	4Ch, comboot_return
		int21	 -1, comboot_bogus
int21_count	equ ($-int21_table)/3

		align 2, db 0
int22_table:
		dw comapi_err		; 0000 unimplemented syscall
		dw comapi_get_version	; 0001 get SYSLINUX version
		dw comapi_writestr	; 0002 write string
		dw comapi_run		; 0003 run specified command
		dw comapi_run_default	; 0004 run default command
		dw comapi_textmode	; 0005 force text mode
		dw comapi_open		; 0006 open file
		dw comapi_read		; 0007 read file
		dw comapi_close		; 0008 close file
		dw comapi_pxecall	; 0009 call PXE stack
		dw comapi_derinfo	; 000A derivative-specific info
		dw comapi_serialcfg	; 000B get serial port config
		dw comapi_cleanup	; 000C perform final cleanup
		dw comapi_chainboot	; 000D clean up then bootstrap
		dw comapi_configfile	; 000E get name of config file
		dw comapi_ipappend	; 000F get ipappend strings
		dw comapi_dnsresolv	; 0010 resolve hostname
		dw comapi_maxshuffle	; 0011 maximum shuffle descriptors
		dw comapi_shuffle	; 0012 cleanup, shuffle and boot
		dw comapi_idle		; 0013 idle call
		dw comapi_localboot	; 0014 local boot
		dw comapi_features	; 0015 feature flags
		dw comapi_runkernel	; 0016 run kernel image
		dw comapi_usingvga	; 0017 report video mode change
		dw comapi_userfont	; 0018 query custom font
		dw comapi_readdisk	; 0019 read disk
		dw comapi_shufflepm	; 001A cleanup, shuffle and boot to pm
		dw comapi_shufflerm	; 001B cleanup, shuffle and boot to rm
		dw comapi_getadv	; 001C get pointer to ADV
		dw comapi_writeadv	; 001D write ADV to disk
int22_count	equ ($-int22_table)/2

APIKeyWait	db 0
APIKeyFlag	db 0

zero_string	db 0			; Empty, null-terminated string

;
; This is the feature flag array for INT 22h AX=0015h
feature_flags:
%if IS_PXELINUX
		db 1			; Have local boot, idle not noop
%elif IS_ISOLINUX
		db 3			; Have local boot, idle is noop
%else
		db 2			; No local boot, idle is noop
%endif
feature_flags_len equ ($-feature_flags)

err_notdos	db ': attempted DOS system call', CR, LF, 0
err_comlarge	db 'COMBOOT image too large.', CR, LF, 0

		section .bss1
ConfigName	resb	FILENAME_MAX