; -*- fundamental -*- (asm-mode sucks) ; **************************************************************************** ; ; pxelinux.asm ; ; A program to boot Linux kernels off a TFTP server using the Intel PXE ; network booting API. It is based on the SYSLINUX boot loader for ; MS-DOS floppies. ; ; Copyright 1994-2009 H. Peter Anvin - All Rights Reserved ; Copyright 2009 Intel Corporation; author: 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 IS_PXELINUX 1 %include "head.inc" %include "pxe.inc" ; gPXE extensions support %define GPXE 1 ; ; Some semi-configurable constants... change on your own risk. ; my_id equ pxelinux_id NULLFILE equ 0 ; Zero byte == null file name NULLOFFSET equ 0 ; Position in which to look REBOOT_TIME equ 5*60 ; If failure, time until full reset %assign HIGHMEM_SLOP 128*1024 ; Avoid this much memory near the top TFTP_BLOCKSIZE_LG2 equ 9 ; log2(bytes/block) TFTP_BLOCKSIZE equ (1 << TFTP_BLOCKSIZE_LG2) SECTOR_SHIFT equ TFTP_BLOCKSIZE_LG2 SECTOR_SIZE equ TFTP_BLOCKSIZE ; ; The following structure is used for "virtual kernels"; i.e. LILO-style ; option labels. The options we permit here are `kernel' and `append ; Since there is no room in the bottom 64K for all of these, we ; stick them in high memory and copy them down before we need them. ; struc vkernel vk_vname: resb FILENAME_MAX ; Virtual name **MUST BE FIRST!** vk_rname: resb FILENAME_MAX ; Real name vk_ipappend: resb 1 ; "IPAPPEND" flag vk_type: resb 1 ; Type of file vk_appendlen: resw 1 alignb 4 vk_append: resb max_cmd_len+1 ; Command line alignb 4 vk_end: equ $ ; Should be <= vk_size endstruc ; --------------------------------------------------------------------------- ; BEGIN CODE ; --------------------------------------------------------------------------- ; ; Memory below this point is reserved for the BIOS and the MBR ; section .earlybss global trackbuf trackbufsize equ 8192 trackbuf resb trackbufsize ; Track buffer goes here ; ends at 2800h ; These fields save information from before the time ; .bss is zeroed... must be in .earlybss global InitStack InitStack resd 1 section .bss16 alignb FILENAME_MAX PXEStack resd 1 ; Saved stack during PXE call alignb 4 global DHCPMagic, RebootTime, APIVer RebootTime resd 1 ; Reboot timeout, if set by option StrucPtr resw 2 ; Pointer to PXENV+ or !PXE structure APIVer resw 1 ; PXE API version found LocalBootType resw 1 ; Local boot return code DHCPMagic resb 1 ; PXELINUX magic flags section .text16 StackBuf equ STACK_TOP-44 ; Base of stack if we use our own StackHome equ StackBuf ; PXE loads the whole file, but assume it can't be more ; than (384-31)K in size. MaxLMA equ 384*1024 ; ; Primary entry point. ; bootsec equ $ _start: jmp 0:_start1 ; Canonicalize the address and skip ; the patch header ; ; Patch area for adding hardwired DHCP options ; align 4 hcdhcp_magic dd 0x2983c8ac ; Magic number hcdhcp_len dd 7*4 ; Size of this structure hcdhcp_flags dd 0 ; Reserved for the future ; Parameters to be parsed before the ones from PXE bdhcp_offset dd 0 ; Offset (entered by patcher) bdhcp_len dd 0 ; Length (entered by patcher) ; Parameters to be parsed *after* the ones from PXE adhcp_offset dd 0 ; Offset (entered by patcher) adhcp_len dd 0 ; Length (entered by patcher) _start1: pushfd ; Paranoia... in case of return to PXE pushad ; ... save as much state as possible push ds push es push fs push gs cld ; Copy upwards xor ax,ax mov ds,ax mov es,ax %if 0 ; debugging code only... not intended for production use ; Clobber the stack segment, to test for specific pathologies mov di,STACK_BASE mov cx,STACK_LEN >> 1 mov ax,0xf4f4 rep stosw ; Clobber the tail of the 64K segment, too extern __bss1_end mov di,__bss1_end sub cx,di ; CX = 0 previously shr cx,1 rep stosw %endif ; That is all pushed onto the PXE stack. Save the pointer ; to it and switch to an internal stack. mov [InitStack],sp mov [InitStack+2],ss lss esp,[BaseStack] sti ; Stack set up and ready ; ; Move the hardwired DHCP options (if present) to a safe place... ; bdhcp_copy: mov cx,[bdhcp_len] mov ax,trackbufsize/2 jcxz .none cmp cx,ax jbe .oksize mov cx,ax mov [bdhcp_len],ax .oksize: mov eax,[bdhcp_offset] add eax,_start mov si,ax and si,000Fh shr eax,4 push ds mov ds,ax mov di,trackbuf add cx,3 shr cx,2 rep movsd pop ds .none: adhcp_copy: mov cx,[adhcp_len] mov ax,trackbufsize/2 jcxz .none cmp cx,ax jbe .oksize mov cx,ax mov [adhcp_len],ax .oksize: mov eax,[adhcp_offset] add eax,_start mov si,ax and si,000Fh shr eax,4 push ds mov ds,ax mov di,trackbuf+trackbufsize/2 add cx,3 shr cx,2 rep movsd pop ds .none: ; ; Initialize screen (if we're using one) ; %include "init.inc" ; ; Tell the user we got this far ; %ifdef VERBOSE_MESSAGES mov si,syslinux_banner call writestr_early mov si,copyright_str call writestr_early %endif ; ; do fs initialize ; mov eax,ROOT_FS_OPS xor ebp,ebp pm_call fs_init section .rodata alignz 4 ROOT_FS_OPS: extern pxe_fs_ops dd pxe_fs_ops dd 0 section .text16 ; ; Initialize the idle mechanism ; call reset_idle ; ; 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. ; ; ; Linux kernel loading code is common. However, we need to define ; a couple of helper macros... ; ; Unload PXE stack %define HAVE_UNLOAD_PREP %macro UNLOAD_PREP 0 pm_call unload_pxe %endmacro ; ; Load configuration file ; pm_call pm_load_config jz no_config_file ; ; Now we have the config file open. Parse the config file and ; run the user interface. ; %include "ui.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 %ifdef VERBOSE_MESSAGES mov si,localboot_msg call writestr_early %endif ; Restore the environment we were called with pm_call reset_pxe call cleanup_hardware lss sp,[InitStack] pop gs pop fs pop es pop ds popad mov ax,[cs:LocalBootType] cmp ax,-1 ; localboot -1 == INT 18h je .int18 popfd retf ; Return to PXE .int18: popfd int 18h jmp 0F000h:0FFF0h hlt ; ; kaboom: write a message and bail out. Wait for quite a while, ; or a user keypress, then do a hard reboot. ; ; Note: use BIOS_timer here; we may not have jiffies set up. ; global kaboom kaboom: RESET_STACK_AND_SEGS AX .patch: mov si,bailmsg call writestr_early ; 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 call do_idle 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 ; ; pxenv ; ; This is the main PXENV+/!PXE entry point, using the PXENV+ ; calling convention. This is a separate local routine so ; we can hook special things from it if necessary. In particular, ; some PXE stacks seem to not like being invoked from anything but ; the initial stack, so humour it. ; ; While we're at it, save and restore all registers. ; global pxenv pxenv: pushfd pushad ; We may be removing ourselves from memory cmp bx,0073h ; PXENV_RESTART_TFTP jz .disable_timer cmp bx,00E5h ; gPXE PXENV_FILE_EXEC jnz .store_stack .disable_timer: call timer_cleanup .store_stack: mov [cs:PXEStack],sp mov [cs:PXEStack+2],ss lss sp,[cs:InitStack] ; Pre-clear the Status field mov word [es:di],cs ; This works either for the PXENV+ or the !PXE calling ; convention, as long as we ignore CF (which is redundant ; with AX anyway.) push es push di push bx .jump: call 0:0 add sp,6 mov [cs:PXEStatus],ax lss sp,[cs:PXEStack] mov bp,sp and ax,ax setnz [bp+32] ; If AX != 0 set CF on return ; This clobbers the AX return, but we already saved it into ; the PXEStatus variable. popad ; If the call failed, it could return. cmp bx,0073h jz .enable_timer cmp bx,00E5h jnz .pop_flags .enable_timer: call timer_init .pop_flags: popfd ; Restore flags (incl. IF, DF) ret ; Must be after function def due to NASM bug global PXEEntry PXEEntry equ pxenv.jump+1 section .bss16 alignb 2 PXEStatus resb 2 section .text16 ; ; Invoke INT 1Ah on the PXE stack. This is used by the "Plan C" method ; for finding the PXE entry point. ; global pxe_int1a pxe_int1a: mov [cs:PXEStack],sp mov [cs:PXEStack+2],ss lss sp,[cs:InitStack] int 1Ah ; May trash registers lss sp,[cs:PXEStack] ret ; ; Special unload for gPXE: this switches the InitStack from ; gPXE to the ROM PXE stack. ; %if GPXE global gpxe_unload gpxe_unload: mov bx,PXENV_FILE_EXIT_HOOK mov di,pxe_file_exit_hook call pxenv jc .plain ; Now we actually need to exit back to gPXE, which will ; give control back to us on the *new* "original stack"... pushfd push ds push es mov [PXEStack],sp mov [PXEStack+2],ss lss sp,[InitStack] pop gs pop fs pop es pop ds popad popfd xor ax,ax retf .resume: cli ; gPXE will have a stack frame looking much like our ; InitStack, except it has a magic cookie at the top, ; and the segment registers are in reverse order. pop eax pop ax pop bx pop cx pop dx push ax push bx push cx push dx mov [cs:InitStack],sp mov [cs:InitStack+2],ss lss sp,[cs:PXEStack] pop es pop ds popfd .plain: ret section .data16 alignz 4 pxe_file_exit_hook: .status: dw 0 .offset: dw gpxe_unload.resume .seg: dw 0 %endif section .text16 ; ----------------------------------------------------------------------------- ; Common modules ; ----------------------------------------------------------------------------- %include "common.inc" ; Universal modules %include "writestr.inc" ; String output writestr_early equ writestr %include "writehex.inc" ; Hexadecimal output %include "rawcon.inc" ; Console I/O w/o using the console functions ; ----------------------------------------------------------------------------- ; Begin data section ; ----------------------------------------------------------------------------- section .data16 copyright_str db ' Copyright (C) 1994-' asciidec YEAR db ' H. Peter Anvin et al', 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 localboot_msg db 'Booting from local disk...', CR, LF, 0 syslinux_banner db CR, LF, MY_NAME, ' ', VERSION_STR, ' ', DATE_STR, ' ', 0 ; ; Config file keyword table ; %include "keywords.inc" ; ; Extensions to search for (in *forward* order). ; (.bs and .bss16 are disabled for PXELINUX, since they are not supported) ; alignz 4 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 ; ; Misc initialized (data) variables ; section .data16 global KeepPXE KeepPXE db 0 ; Should PXE be kept around? ; ; IP information. Note that the field are in the same order as the ; Linux kernel expects in the ip= option. ; section .bss16 alignb 4 global IPInfo IPInfo: .IPv4 resd 1 ; IPv4 information .MyIP resd 1 ; My IP address .ServerIP resd 1 .GatewayIP resd 1 .Netmask resd 1