pxelinux.asm

linux内核

		movzx ecx,word [4*0x1a+2]
		shl ecx,4
		add eax,ecx
		shr eax,10
		cmp ax,dx			; Not in range
		jae .ok
		cmp ax,[BIOS_fbm]
		jae .cant_free
		; inc bx

.ok:
		mov [BIOS_fbm],dx
.pop_ret:
		pop es
		pop ds
		ret
		
.cant_free:
		mov si,cant_free_msg
		call writestr
		push ax
		xchg bx,ax
		call writehex4
		mov al,'-'
		call writechr
		pop ax
		call writehex4
		mov al,'-'
		call writechr
		mov eax,[4*0x1a]
		call writehex8
		call crlf
		jmp .pop_ret

		; We want to keep PXE around, but still we should reset
		; it to the standard bootup configuration
reset_pxe:
		push es
		push cs
		pop es
		mov bx,PXENV_UDP_CLOSE
		mov di,pxe_udp_close_pkt
		call pxenv
		pop es
		ret

;
; gendotquad
;
; Take an IP address (in network byte order) in EAX and
; output a dotted quad string to ES:DI.
; DI points to terminal null at end of string on exit.
;
gendotquad:
		push eax
		push cx
		mov cx,4
.genchar:
		push eax
		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 [es:di],ah
		inc di

.lt100:
		aam 10
		; Now AH = 10-digit; AL = remainder
		add ah,'0'
		mov [es:di],ah		
		inc di

.lt10:
		add al,'0'
		stosb
		mov al,'.'
		stosb
		pop eax
		ror eax,8	; Move next char into LSB
		loop .genchar
		dec di
		mov [es:di], byte 0
		pop cx
		pop eax
		ret

;
; parse_dhcp
;
; Parse a DHCP packet.  This includes dealing with "overloaded"
; option fields (see RFC 2132, section 9.3)
;
; This should fill in the following global variables, if the
; information is present:
;
; MyIP		- client IP address
; ServerIP	- boot server IP address
; Netmask	- network mask
; Gateway	- default gateway router IP
; BootFile	- boot file name
; DNSServers	- DNS server IPs
; LocalDomain	- Local domain name
;
; This assumes the DHCP packet is in "trackbuf" and the length
; of the packet in in CX on entry.
;

parse_dhcp:
		mov byte [OverLoad],0		; Assume no overload
		mov eax, [trackbuf+bootp.yip]
		and eax, eax
		jz .noyip
		cmp al,224			; Class D or higher -> bad
		jae .noyip
		mov [MyIP], eax
.noyip:
		mov eax, [trackbuf+bootp.sip]
		and eax, eax
		jz .nosip
		cmp al,224			; Class D or higher -> bad
		jae .nosip
		mov [ServerIP], eax
.nosip:
		sub cx, bootp.options
		jbe .nooptions
		mov si, trackbuf+bootp.option_magic
		lodsd
		cmp eax, BOOTP_OPTION_MAGIC
		jne .nooptions
		call parse_dhcp_options
.nooptions:
		mov si, trackbuf+bootp.bootfile
		test byte [OverLoad],1
		jz .nofileoverload
		mov cx,128
		call parse_dhcp_options
		jmp short .parsed_file
.nofileoverload:
		cmp byte [si], 0
		jz .parsed_file			; No bootfile name
		mov di,BootFile
		mov cx,32
		rep movsd
		xor al,al
		stosb				; Null-terminate
.parsed_file:
		mov si, trackbuf+bootp.sname
		test byte [OverLoad],2
		jz .nosnameoverload
		mov cx,64
		call parse_dhcp_options
.nosnameoverload:
		ret

;
; Parse a sequence of DHCP options, pointed to by DS:SI; the field
; size is CX -- some DHCP servers leave option fields unterminated
; in violation of the spec.
;
; For parse_some_dhcp_options, DH contains the minimum value for
; the option to recognize -- this is used to restrict parsing to
; PXELINUX-specific options only.
;
parse_dhcp_options:
		xor dx,dx

parse_some_dhcp_options:
.loop:
		and cx,cx
		jz .done

		lodsb
		dec cx
		jz .done	; Last byte; must be PAD, END or malformed
		cmp al, 0	; PAD option
		je .loop
		cmp al,255	; END option
		je .done

		; Anything else will have a length field
		mov dl,al	; DL <- option number
		xor ax,ax
		lodsb		; AX <- option length
		dec cx
		sub cx,ax	; Decrement bytes left counter
		jb .done	; Malformed option: length > field size

		cmp dl,dh	; Is the option value valid?
		jb .opt_done

		cmp dl,1	; SUBNET MASK option
		jne .not_subnet
		mov ebx,[si]
		mov [Netmask],ebx
		jmp .opt_done
.not_subnet:

		cmp dl,3	; ROUTER option
		jne .not_router
		mov ebx,[si]
		mov [Gateway],ebx
		jmp .opt_done
.not_router:

		cmp dl,6	; DNS SERVERS option
		jne .not_dns
		pusha
		mov cx,ax
		shr cx,2
		cmp cl,DNS_MAX_SERVERS
		jna .oklen
		mov cl,DNS_MAX_SERVERS
.oklen:
		mov di,DNSServers
		rep movsd
		mov [LastDNSServer],di
		popa
		jmp .opt_done
.not_dns:

		cmp dl,15	; DNS LOCAL DOMAIN option
		jne .not_localdomain
		pusha
		mov bx,si
		add bx,ax
		xor ax,ax
		xchg [bx],al	; Zero-terminate option
		mov di,LocalDomain
		call dns_mangle	; Convert to DNS label set
		mov [bx],al	; Restore ending byte
		popa
		jmp .opt_done
.not_localdomain:

		cmp dl,43	; VENDOR ENCAPSULATED option
		jne .not_vendor
		pusha
		mov dh,208	; Only recognize PXELINUX options
		mov cx,ax	; Length of option = max bytes to parse
		call parse_some_dhcp_options	; Parse recursive structure
		popa
		jmp .opt_done
.not_vendor:

		cmp dl,52	; OPTION OVERLOAD option
		jne .not_overload
		mov bl,[si]
		mov [OverLoad],bl
		jmp .opt_done
.not_overload:

		cmp dl,67	; BOOTFILE NAME option
		jne .not_bootfile
		mov di,BootFile
		jmp short .copyoption
.done:
		ret		; This is here to make short jumps easier
.not_bootfile:

		cmp dl,208	; PXELINUX MAGIC option
		jne .not_pl_magic
		cmp al,4	; Must have length == 4
		jne .opt_done
		cmp dword [si], htonl(0xF100747E)	; Magic number
		jne .opt_done
		or byte [DHCPMagic], byte 1		; Found magic #
		jmp short .opt_done
.not_pl_magic:

		cmp dl,209	; PXELINUX CONFIGFILE option
		jne .not_pl_config
		mov di,ConfigName
		or byte [DHCPMagic], byte 2	; Got config file
		jmp short .copyoption
.not_pl_config:

		cmp dl,210	; PXELINUX PATHPREFIX option
		jne .not_pl_prefix
		mov di,PathPrefix
		or byte [DHCPMagic], byte 4	; Got path prefix
		jmp short .copyoption
.not_pl_prefix:

		cmp dl,211	; PXELINUX REBOOTTIME option
		jne .not_pl_timeout
		cmp al,4
		jne .opt_done
		mov ebx,[si]
		xchg bl,bh	; Convert to host byte order
		rol ebx,16
		xchg bl,bh
		mov [RebootTime],ebx
		or byte [DHCPMagic], byte 8	; Got RebootTime
		; jmp short .opt_done
.not_pl_timeout:

		; Unknown option.  Skip to the next one.
.opt_done:
		add si,ax
.opt_done_noskip:
		jmp .loop

		; Common code for copying an option verbatim
.copyoption:
		xchg cx,ax
		rep movsb
		xchg cx,ax	; Now ax == 0
		stosb		; Null-terminate
		jmp short .opt_done_noskip

;
; genipopt
;
; Generate an ip=<client-ip>:<boot-server-ip>:<gw-ip>:<netmask>
; option into IPOption based on a DHCP packet in trackbuf.
; Assumes CS == DS == ES.
;
genipopt:
		pushad
		mov di,IPOption
		mov eax,'ip='
		stosd
		dec di
		mov eax,[MyIP]
		call gendotquad
		mov al,':'
		stosb
		mov eax,[ServerIP]
		call gendotquad
		mov al,':'
		stosb
		mov eax,[Gateway]
		call gendotquad
		mov al,':'
		stosb
		mov eax,[Netmask]
		call gendotquad	; Zero-terminates its output
		sub di,IPOption
		mov [IPOptionLen],di
		popad
		ret

;
; Call the receive loop while idle.  This is done mostly so we can respond to
; ARP messages, but perhaps in the future this can be used to do network
; console.
;
; hpa sez: people using automatic control on the serial port get very
; unhappy if we poll for ARP too often (the PXE stack is pretty slow,
; typically.)  Therefore, only poll if at least 4 BIOS timer ticks have
; passed since the last poll, and reset this when a character is
; received (RESET_IDLE).
;
reset_idle:
		push ax
		mov ax,[cs:BIOS_timer]
		mov [cs:IdleTimer],ax
		pop ax
		ret

check_for_arp:
		push ax
		mov ax,[cs:BIOS_timer]
		sub ax,[cs:IdleTimer]
		cmp ax,4
		pop ax
		jae .need_poll
		ret
.need_poll:	pushad
		push ds
		push es
		mov ax,cs
		mov ds,ax
		mov es,ax
		mov di,packet_buf
		mov [pxe_udp_read_pkt.status],al	; 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 word [pxe_udp_read_pkt.lport],htons(9)	; discard port
		mov di,pxe_udp_read_pkt
		mov bx,PXENV_UDP_READ
		call pxenv
		; Ignore result...
		pop es
		pop ds
		popad
		RESET_IDLE
		ret

; -----------------------------------------------------------------------------
;  Common modules
; -----------------------------------------------------------------------------

%include "getc.inc"		; getc et al
%include "conio.inc"		; Console I/O
%include "writestr.inc"		; String output
writestr	equ cwritestr
%include "writehex.inc"		; Hexadecimal output
%include "parseconfig.inc"	; High-level config file handling
%include "parsecmd.inc"		; Low-level config file handling
%include "bcopy32.inc"		; 32-bit bcopy
%include "loadhigh.inc"		; Load a file into high memory
%include "font.inc"		; VGA font stuff
%include "graphics.inc"		; VGA graphics
%include "highmem.inc"		; High memory sizing
%include "strcpy.inc"		; strcpy()
%include "rawcon.inc"		; Console I/O w/o using the console functions
%include "dnsresolv.inc"	; DNS resolver

; -----------------------------------------------------------------------------
;  Begin data section
; -----------------------------------------------------------------------------

		section .data

hextbl_lower	db '0123456789abcdef'
copyright_str   db ' Copyright (C) 1994-', year, ' H. Peter Anvin'
		db CR, LF, 0
boot_prompt	db 'boot: ', 0
wipe_char	db BS, ' ', BS, 0
err_notfound	db 'Could not find kernel image: ',0
err_notkernel	db CR, LF, 'Invalid or corrupt kernel image.', CR, LF, 0
err_noram	db 'It appears your computer has less than '
		asciidec dosram_k
		db 'K of low ("DOS")'
		db CR, LF
		db 'RAM.  Linux needs at least this amount to boot.  If you get'
		db CR, LF
		db 'this message in error, hold down the Ctrl key while'
		db CR, LF
		db 'booting, and I will take your word for it.', CR, LF, 0
err_badcfg      db 'Unknown keyword in config file.', CR, LF, 0
err_noparm      db 'Missing parameter in config file.', CR, LF, 0
err_noinitrd    db CR, LF, 'Could not find ramdisk image: ', 0
err_nohighmem   db 'Not enough memory to load specified kernel.', CR, LF, 0
err_highload    db CR, LF, 'Kernel transfer failure.', CR, LF, 0
err_oldkernel   db 'Cannot load a ramdisk with an old kernel image.'
                db CR, LF, 0
err_notdos	db ': attempted DOS system call', CR, LF, 0
err_comlarge	db 'COMBOOT image too large.', CR, LF, 0
err_bssimage	db 'BSS images not supported.', CR, LF, 0
err_a20		db CR, LF, 'A20 gate not responding!', CR, LF, 0
err_bootfailed	db CR, LF, 'Boot failed: press a key to retry, or wait for reset...', CR, LF, 0
bailmsg		equ err_bootfailed
err_nopxe	db "No !PXE or PXENV+ API found; we're dead...", CR, LF, 0
err_pxefailed	db 'PXE API call failed, error ', 0
err_udpinit	db 'Failed to initialize UDP stack', CR, LF, 0
err_oldtftp	db 'TFTP server does not support the tsize option', CR, LF, 0
found_pxenv	db 'Found PXENV+ structure', CR, LF, 0
using_pxenv_msg db 'Old PXE API detected, using PXENV+ structure', CR, LF, 0
apiver_str	db 'PXE API version is ',0
pxeentry_msg	db 'PXE entry point found (we hope) at ', 0
pxenventry_msg	db 'PXENV entry point found (we hope) at ', 0
trymempxe_msg	db 'Scanning memory for !PXE structure... ', 0
trymempxenv_msg	db 'Scanning memory for PXENV+ structure... ', 0
undi_data_msg	  db 'UNDI data segment at:   ',0
undi_data_len_msg db 'UNDI data segment size: ',0 
undi_code_msg	  db 'UNDI code segment at:   ',0
undi_code_len_msg db 'UNDI code segment size: ',0 
cant_free_msg	db 'Failed to free base memory, error ', 0
notfound_msg	db 'not found', CR, LF, 0
myipaddr_msg	db 'My IP address seems to be ',0
tftpprefix_msg	db 'TFTP prefix: ', 0
localboot_msg	db 'Booting from local disk...', CR, LF, 0
cmdline_msg	db 'Command line: ', CR, LF, 0
ready_msg	db 'Ready.', CR, LF, 0
trying_msg	db 'Trying to load: ', 0
crlfloading_msg	db CR, LF			; Fall through
loading_msg     db 'Loading ', 0
dotdot_msg      db '.'
dot_msg         db '.', 0
fourbs_msg	db BS, BS, BS, BS, 0
aborted_msg	db ' aborted.'			; Fall through to crlf_msg!
crlf_msg	db CR, LF
null_msg	db 0
crff_msg	db CR, FF, 0
default_str	db 'default', 0
default_len	equ ($-default_str)
syslinux_banner	db CR, LF, 'PXELINUX ', version_str, ' ', date, ' ', 0
cfgprefix	db 'pxelinux.cfg/'		; No final null!
cfgprefix_len	equ ($-cfgprefix)

;
; Command line options we'd like to take a look at
;
; mem= and vga= are handled as normal 32-bit integer values
initrd_cmd	db 'initrd='
initrd_cmd_len	equ $-initrd_cmd

; This one we make ourselves
bootif_str	db 'BOOTIF='
bootif_str_len	equ $-bootif_str
;
; Config file keyword table
;
%include "keywords.inc"

;
; Extensions to search for (in *forward* order).
; (.bs and .bss are disabled for PXELINUX, since they are not supported)
;
		align 4, db 0
exten_table:	db '.cbt'		; COMBOOT (specific)
		db '.0', 0, 0		; PXE bootstrap program
		db '.com'		; COMBOOT (same as DOS)
		db '.c32'		; COM32
exten_table_end:
		dd 0, 0			; Need 8 null bytes here

;
; PXE unload sequences
;
new_api_unload:
		db PXENV_UDP_CLOSE
		db PXENV_UNDI_SHUTDOWN
		db PXENV_UNLOAD_STACK
		db PXENV_STOP_UNDI
		db 0
old_api_unload:
		db PXENV_UDP_CLOSE
		db PXENV_UNDI_SHUTDOWN
		db PXENV_UNLOAD_STACK
		db PXENV_UNDI_CLEANUP
		db 0

;
; PXE query packets partially filled in
;
pxe_bootp_query_pkt_2:
.status:	dw 0			; Status
.packettype:	dw 2			; DHCPACK packet
.buffersize:	dw trackbufsize		; Packet size
.buffer:	dw trackbuf, 0		; seg:off of buffer
.bufferlimit:	dw trackbufsize		; Unused

pxe_bootp_query_pkt_3:
.status:	dw 0			; Status
.packettype:	dw 3			; Boot server packet
.buffersize:	dw trackbufsize		; Packet size
.buffer:	dw trackbuf, 0		; seg:off of buffer
.bufferlimit:	dw trackbufsize		; Unused

pxe_bootp_size_query_pkt:
.status:	dw 0			; Status
.packettype:	dw 2			; DHCPACK packet
.buffersize:	dw 0			; Packet size
.buffer:	dw 0, 0			; seg:off of buffer
.bufferlimit:	dw 0			; Unused

pxe_udp_open_pkt:
.status:	dw 0			; Status
.sip:		dd 0			; Source (our) IP

pxe_udp_close_pkt:
.status:	dw 0			; Status

pxe_udp_write_pkt:
.status:	dw 0			; Status
.sip:		dd 0			; Server IP
.gip:		dd 0			; Gateway IP
.lport:		dw 0			; Local port
.rport:		dw 0			; Remote port
.buffersize:	dw 0			; Size of packet
.buffer:	dw 0, 0			; seg:off of buffer

pxe_udp_read_pkt:
.status:	dw 0			; Status
.sip:		dd 0			; Source IP
.dip:		dd 0			; Destination (our) IP
.rport:		dw 0			; Remote port
.lport:		dw 0			; Local port
.buffersize:	dw 0			; Max packet size
.buffer:	dw 0, 0			; seg:off of buffer

;
; Misc initialized (data) variables
;
		alignb 4, db 0
BaseStack	dd StackBuf		; ESP of base stack
		dw 0			; SS of base stack
NextSocket	dw 49152		; Counter for allocating socket numbers
KeepPXE		db 0			; Should PXE be kept around?

;
; TFTP commands
;
tftp_tail	db 'octet', 0				; Octet mode
tsize_str	db 'tsize' ,0				; Request size
tsize_len	equ ($-tsize_str)
		db '0', 0
blksize_str	db 'blksize', 0				; Request large blocks
blksize_len	equ ($-blksize_str)
		asciidec TFTP_LARGEBLK
		db 0
tftp_tail_len	equ ($-tftp_tail)

		alignb 2, db 0
;
; Options negotiation parsing table (string pointer, string len, offset
; into socket structure)
;
tftp_opt_table:
		dw tsize_str, tsize_len, tftp_filesize
		dw blksize_str, blksize_len, tftp_blksize
tftp_opts	equ ($-tftp_opt_table)/6

;
; Error packet to return on options negotiation error
;
tftp_opt_err	dw TFTP_ERROR				; ERROR packet
		dw TFTP_EOPTNEG				; ERROR 8: bad options
		db 'tsize option required', 0		; Error message
tftp_opt_err_len equ ($-tftp_opt_err)

		alignb 4, db 0
ack_packet_buf:	dw TFTP_ACK, 0				; TFTP ACK packet

;
; IP information (initialized to "unknown" values)
MyIP		dd 0			; My IP address
ServerIP	dd 0			; IP address of boot server
Netmask		dd 0			; Netmask of this subnet
Gateway		dd 0			; Default router
ServerPort	dw TFTP_PORT		; TFTP server port

;
; Variables that are uninitialized in SYSLINUX but initialized here
;
		alignb 4, db 0
BufSafe		dw trackbufsize/TFTP_BLOCKSIZE	; Clusters we can load into trackbuf
BufSafeSec	dw trackbufsize/512	; = how many sectors?
BufSafeBytes	dw trackbufsize		; = how many bytes?
EndOfGetCBuf	dw getcbuf+trackbufsize	; = getcbuf+BufSafeBytes
%ifndef DEPEND
%if ( trackbufsize % TFTP_BLOCKSIZE ) != 0
%error trackbufsize must be a multiple of TFTP_BLOCKSIZE
%endif
%endif
IPAppend	db 0			; Default IPAPPEND option
DHCPMagic	db 0			; DHCP site-specific option info