pxelinux.asm

Windows上的精简Linux系统

		call writehex4
		call crlf
		mov si,undi_code_msg
		call writestr
		mov ax,[es:bx+32h]
		call writehex8
		call crlf
		mov si,undi_code_len_msg
		call writestr
		mov ax,[es:bx+36h]
		call writehex4
		call crlf

		; Compute base memory size from !PXE structure
		xor esi,esi
		mov eax,[es:bx+2Ah]
		cmp eax,[es:bx+32h]
		ja .use_data
		mov eax,[es:bx+32h]
		mov si,[es:bx+36h]
		jmp short .combine
.use_data:
		mov si,[es:bx+2Eh]
.combine:
		add eax,esi
		shr eax,10
		mov [RealBaseMem],ax

		mov si,pxeentry_msg
		call writestr
		mov ax,[PXEEntry+2]
		call writehex4
		mov al,':'
		call writechr
		mov ax,[PXEEntry]
		call writehex4
		call crlf

have_entrypoint:

;
; Clear Sockets structures
;
clear_sockets:
		mov ax,ds	; Set ES <- DS
		mov es,ax

		mov di,Sockets
		mov cx,(MAX_SOCKETS*tftp_port_t_size)/4
		xor eax,eax
		push di
		rep stosd
		pop di		; di <- Sockets
		mov cx,MAX_SOCKETS
.setbufptr:
		mov [di+tftp_pktbuf],ax
		add di,tftp_port_t_size
		add ax,PKTBUF_SIZE
		loop .setbufptr

;
; Now attempt to get the BOOTP/DHCP packet that brought us life (and an IP
; address).  This lives in the DHCPACK packet (query info 2).
;
query_bootp:
		mov di,pxe_bootp_query_pkt_2
		mov bx,PXENV_GET_CACHED_INFO

		call pxenv
		push word [pxe_bootp_query_pkt_2.status]
		jc .pxe_err1
		cmp ax,byte 0
		je .pxe_ok
.pxe_err1:
		mov di,pxe_bootp_size_query_pkt
		mov bx,PXENV_GET_CACHED_INFO

		call pxenv
		jc .pxe_err
.pxe_size:
		mov ax,[pxe_bootp_size_query_pkt.buffersize]
		call writehex4
		call crlf

.pxe_err:
		mov si,err_pxefailed
		call writestr
		call writehex4
		mov al, ' '
		call writechr
		pop ax				; Status
		call writehex4
		call crlf
		jmp kaboom			; We're dead

.pxe_ok:
		pop cx				; Forget status
		mov cx,[pxe_bootp_query_pkt_2.buffersize]
		call parse_dhcp			; Parse DHCP packet
;
; Save away MAC address (assume this is in query info 2.  If this
; turns out to be problematic it might be better getting it from
; the query info 1 packet.)
;
.save_mac:
		movzx cx,byte [trackbuf+bootp.hardlen]
		mov [MACLen],cl
		mov al,[trackbuf+bootp.hardware]
		mov [MACType],al
		mov si,trackbuf+bootp.macaddr
		mov di,MAC
		push cx
		rep movsb
		mov cx,MAC+16
		sub cx,di
		xor ax,ax
		rep stosb
		pop cx
		
		mov si,MACType
		mov di,MACStr
		inc cx
		mov bx,hextbl_lower
.hexify_mac:
		lodsb
		mov ah,al
		shr al,4
		xlatb
		stosb
		mov al,ah
		and al,0Fh
		xlatb
		stosb
		mov al,'-'
		stosb
		loop .hexify_mac
		mov [di-1],byte 0		; Null-terminate and strip final colon

;
; Now, get the boot file and other info.  This lives in the CACHED_REPLY
; packet (query info 3).
;
		mov [pxe_bootp_size_query_pkt.packettype], byte 3

		mov di,pxe_bootp_query_pkt_3
		mov bx,PXENV_GET_CACHED_INFO

		call pxenv
		push word [pxe_bootp_query_pkt_3.status]
		jc .pxe_err1
		cmp ax,byte 0
		jne .pxe_err1

		; Packet loaded OK...
		pop cx				; Forget status
		mov cx,[pxe_bootp_query_pkt_3.buffersize]
		call parse_dhcp			; Parse DHCP packet
;
; Generate ip= option
;
		call genipopt

;
; Print IP address
;
		mov eax,[MyIP]
		mov di,DotQuadBuf
		push di
		call gendotquad			; This takes network byte order input

		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 "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.
;
		mov si,linuxauto_cmd		; Default command: "linux auto"
		mov di,default_cmd
                mov cx,linuxauto_len
		rep movsb

		mov di,KbdMap			; Default keymap 1:1
		xor al,al
		mov cx,256
mkkeymap:	stosb
		inc al
		loop mkkeymap


;
; 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
		lea cx,[di-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:
		mov di,trackbuf
		mov si,cfgprefix
		mov cx,cfgprefix_len
		rep movsb
;
; Begin looking for configuration file
;
config_scan:
		test byte [DHCPMagic], 02h
		jz .no_option

		; We got a DHCP option, try it first
		push di
		mov si,trying_msg
		call writestr
		mov di,ConfigName
		mov si,di
		call writestr
		call crlf
		call open
		pop di
		jnz .success

.no_option:	; Have to guess config file name
		; Try loading by MAC address
		push di
		mov si,MACStr
		mov cx,(3*17+1)/2
		rep movsw
		mov si,trying_msg
		call writestr
		mov di,trackbuf
		mov si,di
		call writestr
		call crlf
		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,trackbuf
		mov si,di
		call writestr
		call crlf
		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,bootif_str
		mov cx,bootif_str_len
		rep movsb
		mov si,MACStr
		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:
		mov si,cs
		mov ds,si			; Restore DI
		lss esp,[BaseStack]
		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_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
		lss esp,[BaseStack]
		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


;
; 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.