pxelinux.asm

linux内核

		xchg ah,al			; Convert to host byte order
		ror eax,16			; (BSWAP doesn't work on 386)
		xchg ah,al

		mov si,myipaddr_msg
		call writestr
		call writehex8
		mov al,' '
		call writechr
		pop si				; DotQuadBuf
		call writestr
		call crlf

		mov si,IPOption
		call writestr
		call crlf

;
; Check to see if we got any PXELINUX-specific DHCP options; in particular,
; if we didn't get the magic enable, do not recognize any other options.
;
check_dhcp_magic:
		test byte [DHCPMagic], 1	; If we didn't get the magic enable...
		jnz .got_magic
		mov byte [DHCPMagic], 0		; If not, kill all other options
.got_magic:
	

;
; Initialize UDP stack
;
udp_init:
		mov eax,[MyIP]
		mov [pxe_udp_open_pkt.sip],eax
		mov di,pxe_udp_open_pkt
		mov bx,PXENV_UDP_OPEN
		call pxenv
		jc .failed
		cmp word [pxe_udp_open_pkt.status], byte 0
		je .success
.failed:	mov si,err_udpinit
		call writestr
		jmp kaboom
.success:

;
; 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.
;

;
; Store standard filename prefix
;
prefix:		test byte [DHCPMagic], 04h	; Did we get a path prefix option
		jnz .got_prefix
		mov si,BootFile
		mov di,PathPrefix
		cld
		call strcpy
		mov cx,di
		sub cx,PathPrefix+1
		std
		lea si,[di-2]			; Skip final null!
.find_alnum:	lodsb
		or al,20h
		cmp al,'.'			; Count . or - as alphanum
		je .alnum
		cmp al,'-'
		je .alnum
		cmp al,'0'
		jb .notalnum
		cmp al,'9'
		jbe .alnum
		cmp al,'a'
		jb .notalnum
		cmp al,'z'
		ja .notalnum
.alnum:		loop .find_alnum
		dec si
.notalnum:	mov byte [si+2],0		; Zero-terminate after delimiter
		cld
.got_prefix:
		mov si,tftpprefix_msg
		call writestr
		mov si,PathPrefix
		call writestr
		call crlf

;
; Load configuration file
;
find_config:

;
; Begin looking for configuration file
;
config_scan:
		mov di,ConfigServer
		xor eax,eax
		stosd				; The config file is always from the server

		test byte [DHCPMagic], 02h
		jz .no_option

		; We got a DHCP option, try it first
		mov si,trying_msg
		call writestr
		; mov di,ConfigName		; - already the case
		mov si,di
		call writestr
		call crlf
		mov di,ConfigServer
		call open
		jnz .success

.no_option:
		mov di,ConfigName
		mov si,cfgprefix
		mov cx,cfgprefix_len
		rep movsb

		; Try loading by MAC address
		; Have to guess config file name
		push di
		mov si,MACStr
		mov cx,(3*17+1)/2
		rep movsw
		mov si,trying_msg
		call writestr
		mov di,ConfigName
		mov si,di
		call writestr
		call crlf
		mov di,ConfigServer
		call open
		pop di
		jnz .success

.scan_ip:
		mov cx,8
		mov eax,[MyIP]
		xchg ah,al			; Convert to host byte order
		ror eax,16
		xchg ah,al
.hexify_loop:	rol eax,4
		push eax
		and al,0Fh
		cmp al,10
		jae .high
.low:		add al,'0'
		jmp short .char
.high:		add al,'A'-10
.char:		stosb
		pop eax
		loop .hexify_loop

		mov cx,9			; Up to 9 attempts

.tryagain:	mov byte [di],0
		cmp cx,byte 1
		jne .not_default
		pusha
		mov si,default_str
		mov cx,default_len
		rep movsb			; Copy "default" string
		popa
.not_default:	pusha
		mov si,trying_msg
		call writestr
		mov di,ConfigName
		mov si,di
		call writestr
		call crlf
		mov di,ConfigServer
		call open
		popa
		jnz .success
		dec di
		loop .tryagain

		jmp no_config_file

.success:

;
; 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.  However, we need to define
; a couple of helper macros...
;

; Handle "ipappend" option
%define HAVE_SPECIAL_APPEND
%macro	SPECIAL_APPEND 0
		test byte [IPAppend],01h	; ip=
		jz .noipappend1
		mov si,IPOption
		mov cx,[IPOptionLen]
		rep movsb
		mov al,' '
		stosb
.noipappend1:
		test byte [IPAppend],02h
		jz .noipappend2
		mov si,BOOTIFStr
		call strcpy
		mov byte [es:di-1],' '		; Replace null with space
.noipappend2:
%endmacro

; Unload PXE stack
%define HAVE_UNLOAD_PREP
%macro	UNLOAD_PREP 0
		call unload_pxe
%endmacro

%include "runkernel.inc"

;
; COMBOOT-loading code
;
%include "comboot.inc"
%include "com32.inc"
%include "cmdline.inc"

;
; Boot sector loading code
;
%include "bootsect.inc"

;
; Boot to the local disk by returning the appropriate PXE magic.
; AX contains the appropriate return code.
;
local_boot:
		push cs
		pop ds
		mov [LocalBootType],ax
		call vgaclearmode
		mov si,localboot_msg
		call writestr
		; Restore the environment we were called with
		lss sp,[InitStack]
		pop gs
		pop fs
		pop es
		pop ds
		popad
		mov ax,[cs:LocalBootType]
		popfd
		retf				; Return to PXE

;
; Abort loading code
;
%include "abort.inc"

;
; kaboom: write a message and bail out.  Wait for quite a while,
;	  or a user keypress, then do a hard reboot.
;
kaboom:
		mov ax,cs
		mov es,ax
		mov ds,ax
		lss esp,[BaseStack]
		sti
.patch:		mov si,bailmsg
		call writestr		; Returns with AL = 0
.drain:		call pollchar
		jz .drained
		call getchar
		jmp short .drain
.drained:
		mov edi,[RebootTime]
		mov al,[DHCPMagic]
		and al,09h		; Magic+Timeout
		cmp al,09h
		je .time_set
		mov edi,REBOOT_TIME
.time_set:
		mov cx,18
.wait1:		push cx
		mov ecx,edi
.wait2:		mov dx,[BIOS_timer]
.wait3:		call pollchar
		jnz .keypress
		cmp dx,[BIOS_timer]
		je .wait3
		loop .wait2,ecx
		mov al,'.'
		call writechr
		pop cx
		loop .wait1
.keypress:
		call crlf
		mov word [BIOS_magic],0	; Cold reboot
		jmp 0F000h:0FFF0h	; Reset vector address

;
; memory_scan_for_pxe_struct:
;
;	If none of the standard methods find the !PXE structure, look for it
;	by scanning memory.
;
;	On exit, if found:
;		CF = 0, ES:BX -> !PXE structure
;	Otherwise CF = 1, all registers saved
;	
memory_scan_for_pxe_struct:
		push ds
		pusha
		mov ax,cs
		mov ds,ax
		mov si,trymempxe_msg
		call writestr
		mov ax,[BIOS_fbm]	; Starting segment
		shl ax,(10-4)		; Kilobytes -> paragraphs
;		mov ax,01000h		; Start to look here
		dec ax			; To skip inc ax
.mismatch:
		inc ax
		cmp ax,0A000h		; End of memory
		jae .not_found
		call writehex4
		mov si,fourbs_msg
		call writestr
		mov es,ax
		mov edx,[es:0]
		cmp edx,'!PXE'
		jne .mismatch
		movzx cx,byte [es:4]	; Length of structure
		cmp cl,08h		; Minimum length
		jb .mismatch
		push ax
		xor ax,ax
		xor si,si
.checksum:	es lodsb
		add ah,al
		loop .checksum
		pop ax
		jnz .mismatch		; Checksum must == 0
.found:		mov bp,sp
		xor bx,bx
		mov [bp+8],bx		; Save BX into stack frame (will be == 0)
		mov ax,es
		call writehex4
		call crlf
		popa
		pop ds
		clc
		ret
.not_found:	mov si,notfound_msg
		call writestr
		popa
		pop ds
		stc
		ret

;
; memory_scan_for_pxenv_struct:
;
;	If none of the standard methods find the PXENV+ structure, look for it
;	by scanning memory.
;
;	On exit, if found:
;		CF = 0, ES:BX -> PXENV+ structure
;	Otherwise CF = 1, all registers saved
;	
memory_scan_for_pxenv_struct:
		pusha
		mov si,trymempxenv_msg
		call writestr
;		mov ax,[BIOS_fbm]	; Starting segment
;		shl ax,(10-4)		; Kilobytes -> paragraphs
		mov ax,01000h		; Start to look here
		dec ax			; To skip inc ax
.mismatch:
		inc ax
		cmp ax,0A000h		; End of memory
		jae .not_found
		mov es,ax
		mov edx,[es:0]
		cmp edx,'PXEN'
		jne .mismatch
		mov dx,[es:4]
		cmp dx,'V+'
		jne .mismatch
		movzx cx,byte [es:8]	; Length of structure
		cmp cl,26h		; Minimum length
		jb .mismatch
		xor ax,ax
		xor si,si
.checksum:	es lodsb
		add ah,al
		loop .checksum
		and ah,ah
		jnz .mismatch		; Checksum must == 0
.found:		mov bp,sp
		mov [bp+8],bx		; Save BX into stack frame
		mov ax,bx
		call writehex4
		call crlf
		clc
		ret
.not_found:	mov si,notfound_msg
		call writestr
		popad
		stc
		ret

;
; searchdir:
;
;	Open a TFTP connection to the server 
;
;	     On entry:
;		DS:DI	= mangled filename
;	     If successful:
;		ZF clear
;		SI	= socket pointer
;		DX:AX	= file length in bytes
;	     If unsuccessful
;		ZF set
;

searchdir:
		push es
		push bx
		push cx
		mov ax,ds
		mov es,ax
		mov si,di
		push bp
		mov bp,sp

		call allocate_socket
		jz .ret

		mov ax,PKT_RETRY	; Retry counter
		mov word [PktTimeout],PKT_TIMEOUT	; Initial timeout
	
.sendreq:	push ax			; [bp-2]  - Retry counter
		push si			; [bp-4]  - File name 

		mov di,packet_buf
		mov [pxe_udp_write_pkt.buffer],di

		mov ax,TFTP_RRQ		; TFTP opcode
		stosw

		lodsd			; EAX <- server override (if any)
		and eax,eax
		jnz .noprefix		; No prefix, and we have the server

		push si			; Add common prefix
		mov si,PathPrefix
		call strcpy
		dec di
		pop si

		mov eax,[ServerIP]	; Get default server

.noprefix:
		call strcpy		; Filename

		mov [bx+tftp_remoteip],eax

		push bx			; [bp-6]  - TFTP block
		mov bx,[bx]
		push bx			; [bp-8]  - TID (local port no)

		mov [pxe_udp_write_pkt.status],byte 0
		mov [pxe_udp_write_pkt.sip],eax
		; Now figure out the gateway
		xor eax,[MyIP]
		and eax,[Netmask]
		jz .nogwneeded
		mov eax,[Gateway]
.nogwneeded:
		mov [pxe_udp_write_pkt.gip],eax
		mov [pxe_udp_write_pkt.lport],bx
		mov ax,[ServerPort]
		mov [pxe_udp_write_pkt.rport],ax
		mov si,tftp_tail
		mov cx,tftp_tail_len
		rep movsb
		sub di,packet_buf	; Get packet size
		mov [pxe_udp_write_pkt.buffersize],di

		mov di,pxe_udp_write_pkt
		mov bx,PXENV_UDP_WRITE
		call pxenv
		jc .failure
		cmp word [pxe_udp_write_pkt.status],byte 0
		jne .failure

		;
		; Danger, Will Robinson!  We need to support timeout
		; and retry lest we just lost a packet...
		;

		; Packet transmitted OK, now we need to receive
.getpacket:	push word [PktTimeout]	; [bp-10]
		push word [BIOS_timer]	; [bp-12]

.pkt_loop:	mov bx,[bp-8]		; TID
		mov di,packet_buf
		mov word [pxe_udp_read_pkt.status],0
		mov [pxe_udp_read_pkt.buffer],di
		mov [pxe_udp_read_pkt.buffer+2],ds
		mov word [pxe_udp_read_pkt.buffersize],packet_buf_size
		mov eax,[MyIP]
		mov [pxe_udp_read_pkt.dip],eax
		mov [pxe_udp_read_pkt.lport],bx
		mov di,pxe_udp_read_pkt
		mov bx,PXENV_UDP_READ
		call pxenv
		and ax,ax
		jz .got_packet			; Wait for packet
.no_packet:
		mov dx,[BIOS_timer]
		cmp dx,[bp-12]
		je .pkt_loop
		mov [bp-12],dx
		dec word [bp-10]		; Timeout
		jnz .pkt_loop
		pop ax	; Adjust stack
		pop ax
		shl word [PktTimeout],1		; Exponential backoff
		jmp .failure
		
.got_packet:
		mov si,[bp-6]			; TFTP pointer
		mov bx,[bp-8]			; TID

		mov eax,[si+tftp_remoteip]
		cmp [pxe_udp_read_pkt.sip],eax	; This is technically not to the TFTP spec?
		jne .no_packet

		; Got packet - reset timeout
		mov word [PktTimeout],PKT_TIMEOUT

		pop ax	; Adjust stack
		pop ax

		mov ax,[pxe_udp_read_pkt.rport]
		mov [si+tftp_remoteport],ax

		; filesize <- -1 == unknown
		mov dword [si+tftp_filesize], -1
		; Default blksize unless blksize option negotiated
		mov word [si+tftp_blksize], TFTP_BLOCKSIZE

		mov cx,[pxe_udp_read_pkt.buffersize]
		sub cx,2		; CX <- bytes after opcode
		jb .failure		; Garbled reply

		mov si,packet_buf
		lodsw

		cmp ax, TFTP_ERROR
		je .bailnow		; ERROR reply: don't try again

		cmp ax, TFTP_OACK
		jne .no_tsize

		; Now we need to parse the OACK packet to get the transfer
		; size.  SI -> first byte of options; CX -> byte count
.parse_oack:
		jcxz .no_tsize			; No options acked
.get_opt_name:
		mov di,si
		mov bx,si
.opt_name_loop:	lodsb
		and al,al
		jz .got_opt_name
		or al,20h			; Convert to lowercase
		stosb
		loop .opt_name_loop
		; We ran out, and no final null
		jmp .err_reply
.got_opt_name:	; si -> option value
		dec cx				; bytes left in pkt
		jz .err_reply			; Option w/o value

		; Parse option pointed to by bx; guaranteed to be
		; null-terminated.
		push cx
		push si
		mov si,bx			; -> option name
		mov bx,tftp_opt_table
		mov cx,tftp_opts
.opt_loop:
		push cx
		push si
		mov di,[bx]			; Option pointer
		mov cx,[bx+2]			; Option len
		repe cmpsb
		pop si
		pop cx
		je .get_value			; OK, known option
		add bx,6
		loop .opt_loop

		pop si
		pop cx
		jmp .err_reply			; Non-negotiated option returned

.get_value:	pop si				; si -> option value
		pop cx				; cx -> bytes left in pkt
		mov bx,[bx+4]			; Pointer to data target
		add bx,[bp-6]			; TFTP socket pointer
		xor eax,eax
		xor edx,edx
.value_loop:	lodsb
		and al,al
		jz .got_value
		sub al,'0'
		cmp al, 9
		ja .err_reply			; Not a decimal digit
		imul edx,10
		add edx,eax
		mov [bx],edx
		loop .value_loop
		; Ran out before final null, accept anyway
		jmp short .done_pkt

.got_value:
		dec cx