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|
; "$Id: pxechain.asm,v 1.2 2007/12/16 08:15:39 jhutz Exp $"
; -*- fundamental -*- (asm-mode sucks) vim:noet:com=\:;
; ****************************************************************************
;
; pxechain.asm
;
; A comboot program to chain from PXELINUX to another PXE network
; bootstrap program (NBP). This improves on PXELINUX's built-in PXE
; chaining support by arranging for the server address and boot filename
; reported by the PXE stack to be those from which the new NBP was
; loaded, allowing PXELINUX to be used to select from multiple NBP's,
; such as gPXE, another PXELINUX(*), Windows RIS, and so on.
;
; (*) This seems unnecessary at first, but it is very helpful when
; selecting from among self-contained network boot images.
;
; Copyright (c) 2007 Carnegie Mellon University
; Copyright (C) 1994-2007 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 DEBUG
;%define NO_RUN
absolute 0
pspInt20: resw 1
pspNextP: resw 1
resb 124
pspCmdLen: resb 1
pspCmdArg: resb 127
section .text
org 0x100
%ifdef DEBUG
%macro MARK 1.nolist
mov ah,0x02
mov dl,%1&0xff
int 0x21
%if (%1 >> 8) & 0xff
mov dl,(%1 >> 8) & 0xff
int 0x21
%if (%1 >> 16) & 0xff
mov dl,(%1 >> 16) & 0xff
int 0x21
%if (%1 >> 24) & 0xff
mov dl,(%1 >> 24) & 0xff
int 0x21
%endif
%endif
%endif
mov dl,' '
int 0x21
%endmacro
%macro SHOWD 1.nolist
mov al,%1
call print_dec
mov ah,0x02
mov dl,' '
int 0x21
%endmacro
%macro SHOWX 1.nolist
mov bx,%1
call print_hex
mov ah,0x02
mov dl,' '
int 0x21
%endmacro
%else
%macro MARK 1.nolist
%endmacro
%macro SHOWD 1.nolist
%endmacro
%macro SHOWX 1.nolist
%endmacro
%endif
_start:
MARK 'INIT'
; There should be exactly one command-line argument, which is of the form
; [[ipaddress]::]tftp_filename, just like filenames given to PXELINUX.
; Too few or too many arguments is an error.
;
; This code is based on mangle_name in pxelinux.asm
parse_args:
cld
xor cx,cx
mov cl,[pspCmdLen]
dec cx
mov si,pspCmdArg+1
and cx,cx
je near usage ; no args is bad
add si,cx
dec si
std
.chomp: lodsb
cmp al,' '
loopz .chomp
inc cx
cld
mov [pspCmdLen],cl
mov si,pspCmdArg+1
cmp word [si],'::' ; Leading ::?
je near gotprefix
dec cx
jz noip
MARK 'SCAN'
.more:
inc si
cmp byte [si],' '
je near usage
cmp word [si],'::'
je near parse_ip
loop .more
noip:
MARK 'NOIP'
mov ax,0x0e ; get config file name
int 0x22
mov si,bx
%ifdef DEBUG
mov ah,0x02
mov dl,'['
int 0x21
mov ax,0x02
int 0x22
mov ah,0x02
mov dl,']'
int 0x21
mov dl,' '
int 0x21
%endif
push ds
push es
pop ds
pop es
push es
.find_prefix:
lodsb
and al,al
jnz .find_prefix
dec si
mov cx,si
sub cx,bx
MARK 'LEN'
SHOWD cl ; assume it's <256 for debugging
dec si
std
.find_slash:
lodsb
cmp al,'/'
je .slash
loop .find_slash
.slash:
cmp cx,127
cld
jna .copy_prefix
pop ds
jmp too_long
.copy_prefix:
SHOWD cl
MARK 'PFX'
mov si,bx
mov di,tftp_filename
mov bx,128
sub bx,cx
rep movsb
pop ds
mov cl,[pspCmdLen]
mov si,pspCmdArg+1
jmp prefix_done
usage:
xor cx,cx
mov si,msg_usage
jmp fail
too_long:
xor cx,cx
mov si,msg_too_long
jmp fail
parse_ip:
MARK 'PIP'
mov di,si
mov si,pspCmdArg+1
call parse_dotquad
jc .notdq
cmp si,di ; is it the same place?
jne .notdq
mov [tftp_siaddr],eax
jmp gotprefix
.notdq:
MARK 'NDQ'
mov si,di
mov bx,pspCmdArg+1
mov ax,0x0010 ; DNS resolve
int 0x22
and eax,eax
jz noip
mov [tftp_siaddr],eax
gotprefix:
MARK 'GOTP'
dec cx ; skip the ::
dec cx
inc si
inc si
mov di,tftp_filename
mov bx,128
prefix_done:
SHOWD bl
MARK 'LEFT'
; SI points at the filename, plus remaining arguments,
; CX contains their combined length.
; DI points to where the filename should be stored
; BX says how much space is left for the filename and NUL
and cx,cx
jz usage ; no args is bad
.copy_filename:
lodsb
%ifdef DEBUG
mov dl,al
mov ah,0x2
int 0x21
%endif
cmp al,' '
je usage
dec bx
jz too_long
stosb
loop .copy_filename
xor eax,eax
stosb
; get PXE cached data
MARK 'GCI'
mov ax,0x0009 ; call PXE stack
mov bx,0x0071 ; PXENV_GET_CACHED_INFO
mov di,PXECacheParms
int 0x22
and eax,eax
jz .fix_siaddr
mov cx,[gci_status]
mov si,msg_get_cache
jmp fail
.fix_siaddr:
mov bx,[gci_bufferseg]
mov es,bx
mov bx,[gci_buffer]
mov eax,[es:bx+12] ; save our address (ciaddr)
mov [open_ciaddr],eax ; ... in case we have to do UDP open
mov eax,[tftp_siaddr]
and eax,eax
jnz .replace_addr
MARK 'ADDR'
mov eax,[es:bx+20] ; siaddr
mov [tftp_siaddr],eax
jmp .addr_done
.replace_addr:
mov [es:bx+20],eax
.addr_done:
mov si,tftp_filename ; copy the new filename...
lea di,[es:bx+108] ; to the "cached DHCP response"
mov cx,128
rep movsb
mov bx,ds ; restore es before proceeding
mov es,bx
; print out what we are doing
%ifdef DEBUG
mov ah,0x02 ; write character
mov dl,0x0d ; print a CRLF first
int 0x21
mov dl,0x0a
int 0x21
%endif
mov ax,0x0002 ; write string
mov bx,msg_booting
int 0x22
mov ebx,[tftp_siaddr]
call print_dotquad
mov ah,0x02 ; write character
mov dl,' '
int 0x21
mov ax,0x0002 ; write string
mov bx,tftp_filename
int 0x22
mov ah,0x02 ; write character
mov dl,0x0d
int 0x21
mov dl,0x0a
int 0x21
%ifndef NO_RUN
mov ax,0x0009 ; call PXE stack
mov bx,0x0031 ; PXENV_UDP_CLOSE
mov di,PXECloseParms
int 0x22
mov cx,[close_status]
mov si,msg_udp_close
and ax,ax
jnz fail
mov ax,0x0009 ; call PXE stack
mov bx,0x0073 ; PXENV_RESTART_TFTP
mov di,PXERestartTFTPParms
int 0x22
mov cx,[tftp_status]
mov si,msg_rst_tftp
call fail
mov ax,0x0009 ; call PXE stack
mov bx,0x0030 ; PXENV_UDP_OPEN
mov di,PXEOpenParms
int 0x22
mov cx,[open_status]
mov si,msg_udp_open
and ax,ax
jnz fail
ret
%endif
fail:
MARK 'FAIL'
SHOWX cs
SHOWX ds
SHOWX es
SHOWX si
%ifdef DEBUG
mov ah,0x02 ; write character
mov dl,0x0d ; print a CRLF first
int 0x21
mov dl,0x0a
int 0x21
%endif
mov ax,0x0002 ; write string
mov bx,msg_progname ; print our name
int 0x22
mov bx,si ; ... the error message
int 0x22
mov ah,0x02 ; write character
jcxz .done
mov dl,' ' ; ... and the error code, in []
int 0x21
mov dl,'['
int 0x21
mov bx,cx
call print_hex
mov ah,0x02 ; write character
mov dl,']'
int 0x21
.done:
mov dl,0x0d ; and finally a CRLF
int 0x21
mov dl,0x0a
int 0x21
ret
; print_hex
;
; Take a 16-bit integer in BX and print it as 2 hex digits.
; Destroys AX and DL.
;
print_hex:
mov al,bh
aam 16
cmp ah,10
jb .lt_a000
add ah,'A'-'0'-10
.lt_a000: add ah,'0'
mov dl,ah
mov ah,0x02 ; write character
int 0x21
cmp al,10
jb .lt_a00
add al,'A'-'0'-10
.lt_a00: add al,'0'
mov dl,al
mov ah,0x02 ; write character
int 0x21
mov al,bl
aam 16
cmp ah,10
jb .lt_a0
add ah,'A'-'0'-10
.lt_a0: add ah,'0'
mov dl,ah
mov ah,0x02 ; write character
int 0x21
cmp al,10
jb .lt_a
add al,'A'-'0'-10
.lt_a: add al,'0'
mov dl,al
mov ah,0x02 ; write character
int 0x21
ret
; print_dec
;
; Take an 8-bit integer in AL and print it in decimal.
; Destroys AX and DL.
;
print_dec:
cmp al,10 ; < 10?
jb .lt10 ; If so, skip first 2 digits
cmp al,100 ; < 100
jb .lt100 ; If so, skip first digit
aam 100
; Now AH = 100-digit; AL = remainder
add ah,'0'
mov dl,ah
mov ah,0x02
int 0x21
.lt100:
aam 10
; Now AH = 10-digit; AL = remainder
add ah,'0'
mov dl,ah
mov ah,0x02
int 0x21
.lt10:
add al,'0'
mov dl,al
mov ah,0x02
int 0x21
ret
; print_dotquad
;
; Take an IP address (in network byte order) in EBX and print it
; as a dotted quad.
; Destroys EAX, EBX, ECX, EDX
;
print_dotquad:
mov cx,3
.octet:
mov al,bl
call print_dec
jcxz .done
mov ah,0x02
mov dl,'.'
int 0x21
ror ebx,8 ; Move next char into LSB
dec cx
jmp .octet
.done:
ret
; parse_dotquad:
; Read a dot-quad pathname in DS:SI and output an IP
; address in EAX, with SI pointing to the first
; nonmatching character.
;
; Return CF=1 on error.
;
; No segment assumptions permitted.
;
parse_dotquad:
push cx
mov cx,4
xor eax,eax
.parseloop:
mov ch,ah
mov ah,al
lodsb
sub al,'0'
jb .notnumeric
cmp al,9
ja .notnumeric
aad ; AL += 10 * AH; AH = 0;
xchg ah,ch
jmp .parseloop
.notnumeric:
cmp al,'.'-'0'
pushf
mov al,ah
mov ah,ch
xor ch,ch
ror eax,8
popf
jne .error
loop .parseloop
jmp .done
.error:
loop .realerror ; If CX := 1 then we're done
clc
jmp .done
.realerror:
stc
.done:
dec si ; CF unchanged!
pop cx
ret
section .data
msg_booting: db 'TFTP boot: ',0
msg_progname: db 'pxechain: ',0
msg_usage: db 'usage: pxechain.cbt [[ipaddress]::]filename',0dh,0ah,0
msg_too_long: db 'pxechain: filename is too long (max 127)',0dh,0ah,0
msg_get_cache: db 'PXENV_GET_CACHED_INFO',0
msg_rst_tftp: db 'PXENV_RESTART_TFTP',0
msg_udp_close: db 'PXENV_UDP_CLOSE',0
msg_udp_open: db 'PXENV_UDP_OPEN',0
PXECacheParms:
gci_status: dw 0
gci_packettype: dw 3 ; PXENV_PACKET_TYPE_CACHED_REPLY
gci_buffersize: dw 0
gci_buffer: dw 0
gci_bufferseg: dw 0
gci_bufferlim: dw 0
PXERestartTFTPParms:
tftp_status: dw 0
tftp_filename: times 128 db 0
tftp_bufsize: dd 0x00090000 ; available memory for NBP
tftp_bufaddr: dd 0x00007c00 ; PXE NBP load address
tftp_siaddr: dd 0
tftp_giaddr: dd 0
tftp_mcaddr: dd 0
tftp_mcport: dw 0
tftp_msport: dw 0
tftp_timeout: dw 0
tftp_reopendly: dw 0
PXECloseParms:
close_status: dw 0
PXEOpenParms:
open_status: dw 0
open_ciaddr: dd 0
section .bss
ipaddrbuf: resb 16
|