; -*- fundamental -*- (asm-mode sucks) ; $Id$ ; **************************************************************************** ; ; ldlinux.asm ; ; A program to boot Linux kernels off an MS-DOS formatted floppy disk. This ; functionality is good to have for installation floppies, where it may ; be hard to find a functional Linux system to run LILO off. ; ; This program allows manipulation of the disk to take place entirely ; from MS-LOSS, and can be especially useful in conjunction with the ; umsdos filesystem. ; ; This file is loaded in stages; first the boot sector at offset 7C00h, ; then the first sector (cluster, really, but we can only assume 1 sector) ; of LDLINUX.SYS at 7E00h and finally the remainder of LDLINUX.SYS at 8000h. ; ; Copyright (C) 1994-2004 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., 675 Mass Ave, Cambridge MA 02139, ; USA; either version 2 of the License, or (at your option) any later ; version; incorporated herein by reference. ; ; **************************************************************************** %ifndef IS_MDSLINUX %define IS_SYSLINUX 1 %endif %include "macros.inc" %include "config.inc" %include "kernel.inc" %include "bios.inc" %include "tracers.inc" ; ; Some semi-configurable constants... change on your own risk. ; my_id equ syslinux_id FILENAME_MAX_LG2 equ 4 ; log2(Max filename size Including final null) FILENAME_MAX equ 11 ; Max mangled filename size NULLFILE equ ' ' ; First char space == null filename retry_count equ 6 ; How patient are we with the disk? %assign HIGHMEM_SLOP 0 ; Avoid this much memory near the top ; ; This is what we need to do when idle ; %macro RESET_IDLE 0 ; Nothing %endmacro %macro DO_IDLE 0 ; Nothing %endmacro ; ; 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 at vk_seg:0000 and copy them down before we need them. ; ; Note: this structure can be added to, but it must ; %define vk_power 7 ; log2(max number of vkernels) %define max_vk (1 << vk_power) ; Maximum number of vkernels %define vk_shift (16-vk_power) ; Number of bits to shift %define vk_size (1 << vk_shift) ; Size of a vkernel buffer struc vkernel vk_vname: resb FILENAME_MAX ; Virtual name **MUST BE FIRST!** vk_rname: resb FILENAME_MAX ; Real name 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 %ifndef DEPEND %if (vk_end > vk_size) || (vk_size*max_vk > 65536) %error "Too many vkernels defined, reduce vk_power" %endif %endif ; ; Segment assignments in the bottom 640K ; Stick to the low 512K in case we're using something like M-systems flash ; which load a driver into low RAM (evil!!) ; ; 0000h - main code/data segment (and BIOS segment) ; real_mode_seg equ 5000h fat_seg equ 3000h ; 128K area for FAT (2x64K) vk_seg equ 2000h ; Virtual kernels xfer_buf_seg equ 1000h ; Bounce buffer for I/O to high mem comboot_seg equ real_mode_seg ; COMBOOT image loading zone ; --------------------------------------------------------------------------- ; BEGIN CODE ; --------------------------------------------------------------------------- ; ; Memory below this point is reserved for the BIOS and the MBR ; absolute 1000h trackbuf equ $ ; Track buffer goes here trackbufsize equ 16384 ; Safe size of track buffer ; trackbuf ends at 5000h ; ; Constants for the xfer_buf_seg ; ; The xfer_buf_seg is also used to store message file buffers. We ; need two trackbuffers (text and graphics), plus a work buffer ; for the graphics decompressor. ; xbs_textbuf equ 0 ; Also hard-coded, do not change xbs_vgabuf equ trackbufsize xbs_vgatmpbuf equ 2*trackbufsize absolute 5000h ; Here we keep our BSS stuff VKernelBuf: resb vk_size ; "Current" vkernel alignb 4 AppendBuf resb max_cmd_len+1 ; append= Ontimeout resb max_cmd_len+1 ; ontimeout Onerror resb max_cmd_len+1 ; onerror KbdMap resb 256 ; Keyboard map FKeyName resb 10*16 ; File names for F-key help NumBuf resb 15 ; Buffer to load number NumBufEnd resb 1 ; Last byte in NumBuf alignb 8 ; Expanded superblock SuperInfo equ $ resq 16 ; The first 16 bytes expanded 8 times ; ; These need to follow SuperInfo ; RootDir resd 1 ; Location of root directory DataArea resd 1 ; Location of data area RootDirSize resw 1 ; Root dir size in sectors DirScanCtr resw 1 ; Used while searching directory EndofDirSec resw 1 ; = trackbuf+bsBytesPerSec-31 alignb 4 E820Buf resd 5 ; INT 15:E820 data buffer E820Mem resd 1 ; Memory detected by E820 E820Max resd 1 ; Is E820 memory capped? HiLoadAddr resd 1 ; Address pointer for high load loop HighMemSize resd 1 ; End of memory pointer (bytes) RamdiskMax resd 1 ; Highest address for a ramdisk KernelSize resd 1 ; Size of kernel (bytes) SavedSSSP resd 1 ; Our SS:SP while running a COMBOOT image PMESP resd 1 ; Protected-mode ESP ClustPerMoby resd 1 ; Clusters per 64K ClustSize resd 1 ; Bytes/cluster KernelName resb 12 ; Mangled name for kernel ; (note the spare byte after!) OrigKernelExt resd 1 ; Original kernel extension FBytes equ $ ; Used by open/getc FBytes1 resw 1 FBytes2 resw 1 DirBlocksLeft resw 1 ; Ditto RunLinClust resw 1 ; Cluster # for LDLINUX.SYS BufSafe resw 1 ; Clusters we can load into trackbuf BufSafeSec resw 1 ; = how many sectors? BufSafeBytes resw 1 ; = how many bytes? EndOfGetCBuf resw 1 ; = getcbuf+BufSafeBytes KernelClust resw 1 ; Kernel size in clusters FClust resw 1 ; Number of clusters in open/getc file FNextClust resw 1 ; Pointer to next cluster in d:o FPtr resw 1 ; Pointer to next char in buffer CmdOptPtr resw 1 ; Pointer to first option on cmd line KernelCNameLen resw 1 ; Length of unmangled kernel name InitRDCNameLen resw 1 ; Length of unmangled initrd name NextCharJump resw 1 ; Routine to interpret next print char SetupSecs resw 1 ; Number of setup sectors A20Test resw 1 ; Counter for testing status of A20 A20Type resw 1 ; A20 type CmdLineLen resw 1 ; Length of command line including null GraphXSize resw 1 ; Width of splash screen file VGAPos resw 1 ; Pointer into VGA memory VGACluster resw 1 ; Cluster pointer for VGA image file VGAFilePtr resw 1 ; Pointer into VGAFileBuf Com32SysSP resw 1 ; SP saved during COM32 syscall CursorDX equ $ CursorCol resb 1 ; Cursor column for message file CursorRow resb 1 ; Cursor row for message file ScreenSize equ $ VidCols resb 1 ; Columns on screen-1 VidRows resb 1 ; Rows on screen-1 BaudDivisor resw 1 ; Baud rate divisor FlowControl equ $ FlowOutput resb 1 ; Outputs to assert for serial flow FlowInput resb 1 ; Input bits for serial flow FlowIgnore resb 1 ; Ignore input unless these bits set TextAttribute resb 1 ; Text attribute for message file RetryCount resb 1 ; Used for disk access retries KbdFlags resb 1 ; Check for keyboard escapes LoadFlags resb 1 ; Loadflags from kernel A20Tries resb 1 ; Times until giving up on A20 FuncFlag resb 1 ; Escape sequences received from keyboard DisplayMask resb 1 ; Display modes mask CopySuper resb 1 ; Distinguish .bs versus .bss MNameBuf resb 11 ; Generic mangled file name buffer InitRD resb 11 ; initrd= mangled name KernelCName resb 13 ; Unmangled kernel name InitRDCName resb 13 ; Unmangled initrd name TextColorReg resb 17 ; VGA color registers for text mode VGAFileBuf resb 13 ; Unmangled VGA image name VGAFileBufEnd equ $ VGAFileMBuf resb 11 ; Mangled VGA image name alignb 4 ; For the good of REP MOVSD command_line resb max_cmd_len+2 ; Command line buffer alignb 4 default_cmd resb max_cmd_len+1 ; "default" command line section .text org 7C00h ; ; Some of the things that have to be saved very early are saved ; "close" to the initial stack pointer offset, in order to ; reduce the code size... ; StackBuf equ $-44-32 ; Start the stack here (grow down - 4K) PartInfo equ StackBuf ; Saved partition table entry FloppyTable equ PartInfo+16 ; Floppy info table (must follow PartInfo) OrigFDCTabPtr equ StackBuf-4 ; The high dword on the stack ; ; Primary entry point. Tempting as though it may be, we can't put the ; initial "cli" here; the jmp opcode in the first byte is part of the ; "magic number" (using the term very loosely) for the DOS superblock. ; bootsec equ $ jmp short start ; 2 bytes nop ; 1 byte ; ; "Superblock" follows -- it's in the boot sector, so it's already ; loaded and ready for us ; bsOemName db 'SYSLINUX' ; The SYS command sets this, so... ; ; These are the fields we actually care about. We end up expanding them ; all to dword size early in the code, so generate labels for both ; the expanded and unexpanded versions. ;; %macro superb 1 bx %+ %1 equ SuperInfo+($-superblock)*8+4 bs %+ %1 equ $ zb 1 %endmacro %macro superw 1 bx %+ %1 equ SuperInfo+($-superblock)*8 bs %+ %1 equ $ zw 1 %endmacro %macro superd 1 bx %+ %1 equ $ ; no expansion for dwords bs %+ %1 equ $ zd 1 %endmacro superblock equ $ superw BytesPerSec superb SecPerClust superw ResSectors superb FATs superw RootDirEnts superw Sectors superb Media superw FATsecs superw SecPerTrack superw Heads superinfo_size equ ($-superblock)-1 ; How much to expand superd Hidden superd HugeSectors superb DriveNumber superb Reserved1 superb BootSignature ; 29h if the following fields exist superd VolumeID bsVolumeLabel zb 11 bsFileSysType zb 8 ; Must be FAT12 or FAT16 for this version superblock_len equ $-superblock SecPerClust equ bxSecPerClust ; ; Note we don't check the constraints above now; we did that at install ; time (we hope!) ; ;floppy_table equ $ ; No sense in wasting memory, overwrite start start: cli ; No interrupts yet, please cld ; Copy upwards ; ; Set up the stack ; xor ax,ax mov ss,ax mov sp,StackBuf ; Just below BSS mov es,ax ; ; DS:SI may contain a partition table entry. Preserve it for us. ; mov cx,8 ; Save partition info mov di,sp rep movsw mov ds,ax ; Now we can initialize DS... mov [di+bsDriveNumber-FloppyTable],dl ; ; Now sautee the BIOS floppy info block to that it will support decent- ; size transfers; the floppy block is 11 bytes and is stored in the ; INT 1Eh vector (brilliant waste of resources, eh?) ; ; Of course, if BIOSes had been properly programmed, we wouldn't have ; had to waste precious space with this code. ; mov bx,fdctab lfs si,[bx] ; FS:SI -> original fdctab push fs ; Save on stack in case we need to bail push si ; Save the old fdctab even if hard disk so the stack layout ; is the same. The instructions above do not change the flags and dl,dl ; If floppy disk (00-7F), assume no ; partition table js harddisk floppy: mov cl,6 ; 12 bytes (CX == 0) ; es:di -> FloppyTable already ; This should be safe to do now, interrupts are off... mov [bx],di ; FloppyTable mov [bx+2],ax ; Segment 0 fs rep movsw ; Faster to move words mov cl,[bsSecPerTrack] ; Patch the sector count mov [di-8],cl ; AX == 0 here int 13h ; Some BIOSes need this jmp short not_harddisk ; ; The drive number and possibly partition information was passed to us ; by the BIOS or previous boot loader (MBR). Current "best practice" is to ; trust that rather than what the superblock contains. ; ; Would it be better to zero out bsHidden if we don't have a partition table? ; ; Note: di points to beyond the end of PartInfo ; harddisk: test byte [di-16],7Fh ; Sanity check: "active flag" should jnz no_partition ; be 00 or 80 mov eax,[di-8] ; Partition offset (dword) mov [bsHidden],eax no_partition: ; ; Get disk drive parameters (don't trust the superblock.) Don't do this for ; floppy drives -- INT 13:08 on floppy drives will (may?) return info about ; what the *drive* supports, not about the *media*. Fortunately floppy disks ; tend to have a fixed, well-defined geometry which is stored in the superblock. ; ; DL == drive # still mov ah,08h int 13h jc no_driveparm and ah,ah jnz no_driveparm shr dx,8 inc dx ; Contains # of heads - 1 mov [bsHeads],dx and cx,3fh mov [bsSecPerTrack],cx no_driveparm: not_harddisk: ; ; Ready to enable interrupts, captain ; sti ; ; Insane hack to expand the superblock to dwords ; expand_super: xor eax,eax mov es,ax ; INT 13:08 destroys ES mov si,superblock mov di,SuperInfo mov cl,superinfo_size ; CH == 0 .loop: lodsw dec si stosd ; Store expanded word xor ah,ah stosd ; Store expanded byte loop .loop ; ; Now we have to do some arithmetric to figure out where things are located. ; If Micro$oft had had brains they would already have done this for us, ; and stored it in the superblock at format time, but here we go, ; wasting precious boot sector space again... ; %define Z di-superinfo_size*8-SuperInfo debugentrypt: mov ax,[bxFATs] ; Number of FATs (eax<31:16> == 0) mov edx,[Z+bxFATsecs] ; Sectors/FAT mul edx ; Get the size of the FAT area ; edx <- 0 add eax,[bxHidden] ; Add hidden sectors add eax,[Z+bxResSectors] ; And reserved sectors mov [RootDir],eax ; Location of root directory mov [DataArea],eax ; First data sector push eax mov eax,[Z+bxRootDirEnts] shl ax,5 ; Size of a directory entry mov bx,[Z+bxBytesPerSec] add ax,bx ; Round up, not down dec ax div bx ; Now we have the size of the root dir mov [RootDirSize],ax mov [DirScanCtr],ax add bx,trackbuf-31 mov [Z+EndofDirSec],bx ; End of a single directory sector add [Z+DataArea],eax pop eax ; Reload root directory starting point ; ; Now the fun begins. We have to search the root directory for ; LDLINUX.SYS and load the first sector, so we have a little more ; space to have fun with. Then we can go chasing through the FAT. ; Joy!! ; sd_nextsec: push eax mov bx,trackbuf push bx call getonesec pop si sd_nextentry: mov cx,11 cmp [si],ch ; Directory high water mark je kaboom ; This no longer fits... since we'd be dead anyway if there ; was a nonfile named LDLINUX.SYS on the disk, it shouldn't ; matter... ; test byte [si+11],18h ; Must be a file ; jnz sd_not_file mov di,ldlinux_name push si repe cmpsb pop si je found_it sd_not_file: add si,byte 32 ; Distance to next cmp si,[EndofDirSec] jb sd_nextentry pop eax inc eax dec word [DirScanCtr] jnz sd_nextsec ; ; kaboom: write a message and bail out. ; kaboom: xor si,si mov ss,si mov sp,StackBuf-4 ; Reset stack mov ds,si ; Reset data segment pop dword [fdctab] ; Restore FDC table .patch: mov si,bailmsg call writestr ; Returns with AL = 0 cbw ; AH <- 0 int 16h ; Wait for keypress int 19h ; And try once more to boot... .norge: jmp short .norge ; If int 19h returned; this is the end ; ; found_it: now we compute the location of the first sector, then ; load it and JUMP (since we're almost out of space) ; found_it: ; Note: we actually leave two words on the stack here ; (who cares?) mov eax,[bxSecPerClust] mov bp,ax ; Load an entire cluster movzx ebx,word [si+26] ; First cluster mov [RunLinClust],bx ; Save for later use dec bx ; First cluster is "cluster 2" dec bx mul ebx add eax,[DataArea] mov bx,ldlinux_sys call getlinsec mov si,bs_magic mov di,ldlinux_magic mov cx,magic_len repe cmpsb ; Make sure that the bootsector jne kaboom ; matches LDLINUX.SYS ; ; Done! Jump to the entry point! ; jmp ldlinux_ent ; ; ; writestr: write a null-terminated string to the console ; This assumes we're on page 0. This is only used for early ; messages, so it should be OK. ; writestr: .loop: lodsb and al,al jz .return mov ah,0Eh ; Write to screen as TTY mov bx,0007h ; Attribute int 10h jmp short .loop .return: ret ; ; disk_error: decrement the retry count and bail if zero. ; This gets patched once we have more space to try to ; optimize transfer sizes on broken machines. ; disk_error: dec si ; SI holds the disk retry counter jz kaboom ; End of patched "call" instruction! jmp short disk_try_again ; ; getonesec: like getlinsec, but pre-sets the count to 1 ; getonesec: mov bp,1 ; Fall through to getlinsec ; ; getlinsec: load a sequence of BP floppy sector given by the linear sector ; number in EAX into the buffer at ES:BX. We try to optimize ; by loading up to a whole track at a time, but the user ; is responsible for not crossing a 64K boundary. ; (Yes, BP is weird for a count, but it was available...) ; ; On return, BX points to the first byte after the transferred ; block. ; ; The "stupid patch area" gets replaced by the code ; mov bp,1 ; nop ... (BD 01 00 90 90...) when installing with ; the -s option. ; ; This routine assumes CS == DS. ; ; Stylistic note: use "xchg" instead of "mov" when the source is a register ; that is dead from that point; this saves space. However, please keep ; the order to dst,src to keep things sane. ; getlinsec: mov esi,[bxSecPerTrack] ; ; Dividing by sectors to get (track,sector): we may have ; up to 2^18 tracks, so we need to use 32-bit arithmetric. ; xor edx,edx ; Zero-extend LBA to 64 bits div esi xor cx,cx xchg cx,dx ; CX <- sector index (0-based) ; EDX <- 0 ; eax = track # div dword [bxHeads] ; Convert track to head/cyl ; ; Now we have AX = cyl, DX = head, CX = sector (0-based), ; BP = sectors to transfer, SI = bsSecPerTrack, ; ES:BX = data target ; gls_nextchunk: push si ; bsSecPerTrack push bp ; Sectors to transfer ; Important - this gets patched with a call. The call ; assumes cx, si and bp are set up, and can modify bp ; and destroy si. Until we have the space to do so, ; transfer one sector at a time. gls_set_size: __BEGIN_STUPID_PATCH_AREA: mov bp,1 ; 3 bytes, same as a call insn __END_STUPID_PATCH_AREA: push ax ; Cylinder # push dx ; Head # push cx ; Sector # shl ah,6 ; Because IBM was STOOPID ; and thought 8 bits were enough ; then thought 10 bits were enough... pop cx ; Sector # push cx ; Sector # inc cx ; Sector numbers are 1-based, sigh or cl,ah mov ch,al mov dh,dl mov dl,[bsDriveNumber] xchg ax,bp ; Sector to transfer count ; (xchg shorter than mov) mov si,retry_count ; # of times to retry a disk access ; ; Do the disk transfer... save the registers in case we fail :( ; disk_try_again: pusha ; mov ah,02h ; READ DISK int 13h popa ; jc disk_error ; ; Disk access successful ; pop cx ; Sector # mov di,ax ; Reduce sector left count mul word [bsBytesPerSec] ; Figure out how much to advance ptr add bx,ax ; Update buffer location pop dx ; Head # pop ax ; Cyl # pop bp ; Sectors left to transfer pop si ; Number of sectors/track sub bp,di ; Reduce with # of sectors just read jz writestr.return ; Done! add cx,di cmp cx,si jb gls_nextchunk inc dx ; Next track on cyl cmp dx,[bsHeads] ; Was this the last one? jb gls_nonewcyl inc ax ; If so, new cylinder xor dx,dx ; First head on new cylinder gls_nonewcyl: sub cx,si ; First sector on new track jmp short gls_nextchunk bailmsg: db 'Boot failed', 0Dh, 0Ah, 0 bs_checkpt equ $ ; Must be <= 7DEFh %if 1 bs_checkpt_off equ ($-$$) %ifndef DEPEND %if bs_checkpt_off > 1EFh %error "Boot sector overflow" %endif %endif zb 1EFh-($-$$) %endif bs_magic equ $ ; From here to the magic_len equ ; must match ldlinux_magic ldlinux_name: db 'LDLINUX SYS' ; Looks like this in the root dir dd HEXDATE ; Hopefully unique between compiles bootsignature dw 0AA55h magic_len equ $-bs_magic ; ; =========================================================================== ; End of boot sector ; =========================================================================== ; Start of LDLINUX.SYS ; =========================================================================== ldlinux_sys: syslinux_banner db 0Dh, 0Ah %if IS_MDSLINUX db 'MDSLINUX ' %else db 'SYSLINUX ' %endif db version_str, ' ', date, ' ', 0 db 0Dh, 0Ah, 1Ah ; EOF if we "type" this in DOS ldlinux_magic db 'LDLINUX SYS' dd HEXDATE dw 0AA55h ; ; This area is possibly patched by the installer. It is located ; immediately after the EOF + LDLINUX SYS + 4 bytes + 55 AA + alignment, ; so we can find it algorithmically. ; alignb 4, db 0 MaxTransfer dw 00FFh ; Absolutely maximum transfer size align 4 ldlinux_ent: ; ; Note that some BIOSes are buggy and run the boot sector at 07C0:0000 ; instead of 0000:7C00 and the like. We don't want to add anything ; more to the boot sector, so it is written to not assume a fixed ; value in CS, but we don't want to deal with that anymore from now ; on. ; jmp 0:.next .next: ; ; Tell the user we got this far ; mov si,syslinux_banner call writestr ; ; Remember, the boot sector loaded only the first cluster of LDLINUX.SYS. ; We can really only rely on a single sector having been loaded. Hence ; we should load the FAT into RAM and start chasing pointers... ; xor ax,ax cwd inc dx ; DX:AX <- 64K div word [bxBytesPerSec] ; sectors/64K mov si,ax push es mov bx,fat_seg ; Load into fat_seg:0000 mov es,bx mov eax,[bsHidden] ; Hidden sectors add edx,[bxResSectors] add eax,edx mov ecx,[bxFATsecs] ; Sectors/FAT fat_load_loop: mov ebp,ecx ; Make sure high EBP = 0 cmp bp,si jna fat_load mov bp,si ; A full 64K moby fat_load: xor bx,bx ; Offset 0 in the current ES call getlinsecsr sub cx,bp jz fat_load_done ; Last moby? add eax,ebp ; Advance sector count mov bx,es ; Next 64K moby add bx,1000h mov es,bx jmp short fat_load_loop fat_load_done: pop es ; ; Fine, now we have the FAT in memory. How big is a cluster, really? ; Also figure out how many clusters will fit in an 8K buffer, and how ; many sectors and bytes that is ; mov edi,[bxBytesPerSec] ; Used a lot below mov eax,[SecPerClust] mov si,ax ; Also used a lot mul di mov [ClustSize],eax ; Bytes/cluster mov bx,ax mov ax,trackbufsize ; High bit 0 cwd div bx mov [BufSafe],ax ; # of cluster in trackbuf mul si mov [BufSafeSec],ax mul di mov [BufSafeBytes],ax add ax,getcbuf ; Size of getcbuf is the same mov [EndOfGetCBuf],ax ; as for trackbuf ; ; FAT12 or FAT16? This computation is fscking ridiculous... ; mov eax,[bxSectors] and ax,ax jnz have_secs mov eax,[bsHugeSectors] have_secs: add eax,[bsHidden] ; These are not included sub eax,[RootDir] ; Start of root directory movzx ebx,word [RootDirSize] sub eax,ebx ; Subtract root directory size xor edx,edx div esi ; Convert to clusters cmp ax,4086 ; FAT12 limit jna is_fat12 ; Patch the jump mov byte [nextcluster+1],nextcluster_fat16-(nextcluster+2) is_fat12: ; ; Patch gls_set_size so we can transfer more than one sector at a time. ; mov byte [gls_set_size],0xe8 ; E8 = CALL NEAR mov word [gls_set_size+1],do_gls_set_size-(gls_set_size+3) mov byte [disk_error],0xe8 mov word [disk_error+1],do_disk_error-(disk_error+3) ; ; Now we read the rest of LDLINUX.SYS. Don't bother loading the first ; cluster again, though. ; load_rest: mov cx,[ClustSize] mov bx,ldlinux_sys add bx,cx mov si,[RunLinClust] call nextcluster xor dx,dx mov ax,ldlinux_len-1 ; To be on the safe side add ax,cx div cx ; the number of clusters dec ax ; We've already read one jz all_read_jmp mov cx,ax call getfssec ; ; All loaded up ; all_read_jmp: jmp all_read ; ; ----------------------------------------------------------------------------- ; Subroutines that have to be in the first sector ; ----------------------------------------------------------------------------- ; ; getfssec: Get multiple clusters from a file, given the starting cluster. ; ; This routine makes sure the subtransfers do not cross a 64K boundary, ; and will correct the situation if it does, UNLESS *sectors* cross ; 64K boundaries. ; ; ES:BX -> Buffer ; SI -> Starting cluster number (2-based) ; CX -> Cluster count (0FFFFh = until end of file) ; ; Returns CF=1 on EOF ; getfssec: .getfragment: xor ebp,ebp ; Fragment sector count lea eax,[si-2] ; Get 0-based sector address mul dword [SecPerClust] add eax,[DataArea] .getseccnt: ; See if we can read > 1 clust add bp,[SecPerClust] dec cx ; Reduce clusters left to find lea di,[si+1] call nextcluster cmc jc .eof ; At EOF? jcxz .endfragment ; Or was it the last we wanted? cmp si,di ; Is file continuous? je .getseccnt ; Yes, we can get .endfragment: clc ; Not at EOF .eof: pushf ; Remember EOF or not push si push cx .getchunk: push eax mov ax,es ; Check for 64K boundaries. shl ax,4 add ax,bx xor dx,dx neg ax setz dl ; DX <- 1 if full 64K segment div word [bsBytesPerSec] ; How many sectors fit? mov si,bp sub si,ax ; Compute remaining sectors jbe .lastchunk mov bp,ax pop eax call getlinsecsr add eax,ebp ; EBP<31:16> == 0 mov bp,si ; Remaining sector count jmp short .getchunk .lastchunk: pop eax call getlinsec pop cx pop si popf jcxz .return ; If we hit the count limit jnc .getfragment ; If we didn't hit EOF .return: ret ; ; getlinsecsr: save registers, call getlinsec, restore registers ; getlinsecsr: pushad call getlinsec popad ret ; ; nextcluster: Advance a cluster pointer in SI to the next cluster ; pointed at in the FAT tables. CF=0 on return if end of file. ; nextcluster: jmp short nextcluster_fat12 ; This gets patched nextcluster_fat12: push bx push ds mov bx,fat_seg mov ds,bx mov bx,si ; Multiply by 3/2 shr bx,1 ; CF now set if odd mov si,[si+bx] jnc nc_even shr si,4 ; Needed for odd only nc_even: and si,0FFFh cmp si,0FF0h ; Clears CF if at end of file pop ds pop bx nc_return: ret ; ; FAT16 decoding routine. Note that a 16-bit FAT can be up to 128K, ; so we have to decide if we're in the "low" or the "high" 64K-segment... ; nextcluster_fat16: push ax push ds mov ax,fat_seg shl si,1 jnc .seg0 mov ax,fat_seg+1000h .seg0: mov ds,ax mov si,[si] cmp si,0FFF0h pop ds pop ax ret ; ; Routine that controls how much we can transfer in one chunk. Called ; from gls_set_size in getlinsec. ; do_gls_set_size: sub si,cx ; Sectors left on track cmp bp,si jna .lastchunk mov bp,si ; No more than a trackful, please! .lastchunk: cmp bp,[MaxTransfer] ; Absolute maximum transfer size jna .oktransfer mov bp,[MaxTransfer] .oktransfer: ret ; ; This routine captures disk errors, and tries to decide if it is ; time to reduce the transfer size. ; do_disk_error: dec si ; Decrement the retry counter jz kaboom ; If expired, croak cmp si,2 ; If only 2 attempts left ja .nodanger mov al,1 ; Drop transfer size to 1 jmp short .setsize .nodanger: cmp si,retry_count-2 ja .again ; First time, just try again shr al,1 ; Otherwise, try to reduce adc al,0 ; the max transfer size, but not to 0 .setsize: mov [MaxTransfer],al .again: ret ; ; Debug routine ; %ifdef debug safedumpregs: cmp word [Debug_Magic],0D00Dh jnz nc_return jmp dumpregs %endif rl_checkpt equ $ ; Must be <= 8000h rl_checkpt_off equ ($-$$) %ifndef DEPEND %if rl_checkpt_off > 400h %error "Sector 1 overflow" %endif %endif ; ---------------------------------------------------------------------------- ; End of code and data that have to be in the first sector ; ---------------------------------------------------------------------------- all_read: ; ; Let the user (and programmer!) know we got this far. This used to be ; in Sector 1, but makes a lot more sense here. ; mov si,copyright_str call writestr ; ; Common initialization code ; %include "cpuinit.inc" ; ; Initialization that does not need to go into the any of the pre-load ; areas ; ; Now set up screen parameters call adjust_screen ; Wipe the F-key area mov al,NULLFILE mov di,FKeyName mov cx,10*(1 << FILENAME_MAX_LG2) rep stosb ; ; Now, everything is "up and running"... patch kaboom for more ; verbosity and using the full screen system ; ; E9 = JMP NEAR mov dword [kaboom.patch],0e9h+((kaboom2-(kaboom.patch+3)) << 8) ; ; Compute some parameters that depend on cluster size ; xor eax,eax cwd ; DX <- 0 inc dx ; DX:AX <- 64K div word [ClustSize] mov [ClustPerMoby],eax ; Clusters/64K ; ; 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 inc ch ; CX <- 256 mkkeymap: stosb inc al loop mkkeymap ; ; Load configuration file ; mov di,syslinux_cfg call open jz no_config_file ; ; 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. ; %include "runkernel.inc" ; ; COMBOOT-loading code ; %include "comboot.inc" %include "com32.inc" %include "cmdline.inc" ; ; Boot sector loading code ; %include "bootsect.inc" ; ; abort_check: let the user abort with or ; abort_check: call pollchar jz ac_ret1 pusha call getchar cmp al,27 ; je ac_kill cmp al,3 ; 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 cli mov sp,StackBuf-2*3 ; Reset stack mov ss,ax ; Just in case... 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 ; ; searchdir: Search the root directory for a pre-mangled filename in ; DS:DI. This routine is similar to the one in the boot ; sector, but is a little less Draconian when it comes to ; error handling, plus it reads the root directory in ; larger chunks than a sector at a time (which is probably ; a waste of coding effort, but I like to do things right). ; ; FIXME: usually we can load the entire root dir in memory, ; and files are usually at the beginning anyway. It probably ; would be worthwhile to remember if we have the first chunk ; in memory and skip the load if that (it would speed up online ; help, mainly.) ; ; NOTE: This file considers finding a zero-length file an ; error. This is so we don't have to deal with that special ; case elsewhere in the program (most loops have the test ; at the end). ; ; If successful: ; ZF clear ; SI = cluster # for the first cluster ; DX:AX = file length in bytes ; If unsuccessful ; ZF set ; searchdir: push bp mov ax,[bsRootDirEnts] mov [DirScanCtr],ax mov ax,[RootDirSize] mov [DirBlocksLeft],ax mov eax,[RootDir] scan_group: movzx ebp,word [DirBlocksLeft] and bp,bp jz dir_return cmp bp,[BufSafeSec] jna load_last mov bp,[BufSafeSec] load_last: sub [DirBlocksLeft],bp push eax mov ax,[bsBytesPerSec] mul bp add ax,trackbuf-31 mov [EndofDirSec],ax ; End of loaded pop eax mov bx,trackbuf call getlinsecsr mov si,trackbuf dir_test_name: cmp byte [si],0 ; Directory high water mark je dir_return ; Failed test byte [si+11],18h ; Check it really is a file jnz dir_not_this push di push si mov cx,11 ; Filename = 11 bytes repe cmpsb pop si pop di je dir_success dir_not_this: add si,byte 32 dec word [DirScanCtr] jz dir_return ; Out of it... cmp si,[EndofDirSec] jb dir_test_name add eax,ebp ; Increment linear sector number jmp short scan_group dir_success: mov ax,[si+28] ; Length of file mov dx,[si+30] mov si,[si+26] ; Cluster pointer mov bx,ax or bx,dx ; Sets ZF iff DX:AX is zero dir_return: pop bp ret ; ; writechr: Write a single character in AL to the console without ; mangling any registers; handle video pages correctly. ; writechr: call write_serial ; write to serial port if needed pushfd pushad mov ah,0Eh mov bl,07h ; attribute mov bh,[cs:BIOS_page] ; current page int 10h popad popfd ret ; ; ; kaboom2: once everything is loaded, replace the part of kaboom ; starting with "kaboom.patch" with this part kaboom2: mov si,err_bootfailed call cwritestr call getchar call vgaclearmode int 19h ; And try once more to boot... .norge: jmp short .norge ; If int 19h returned; this is the end ; ; mangle_name: Mangle a DOS filename pointed to by DS:SI into a buffer pointed ; to by ES:DI; ends on encountering any whitespace ; mangle_name: mov cx,11 ; # of bytes to write mn_loop: lodsb cmp al,' ' ; If control or space, end jna mn_end cmp al,'.' ; Period -> space-fill je mn_is_period cmp al,'a' jb mn_not_lower cmp al,'z' ja mn_not_uslower sub al,020h jmp short mn_not_lower mn_is_period: mov al,' ' ; We need to space-fill mn_period_loop: cmp cx,3 ; If <= 3 characters left jbe mn_loop ; Just ignore it stosb ; Otherwise, write a period loop mn_period_loop ; Dec CX and (always) jump mn_not_uslower: cmp al,ucase_low jb mn_not_lower cmp al,ucase_high ja mn_not_lower mov bx,ucase_tab-ucase_low cs xlatb mn_not_lower: stosb loop mn_loop ; Don't continue if too long mn_end: mov al,' ' ; Space-fill name rep stosb ; Doesn't do anything if CX=0 ret ; Done ; ; Upper-case table for extended characters; this is technically code page 865, ; but code page 437 users will probably not miss not being able to use the ; cent sign in kernel images too much :-) ; ; The table only covers the range 129 to 164; the rest we can deal with. ; ucase_low equ 129 ucase_high equ 164 ucase_tab db 154, 144, 'A', 142, 'A', 143, 128, 'EEEIII' db 142, 143, 144, 146, 146, 'O', 153, 'OUUY', 153, 154 db 157, 156, 157, 158, 159, 'AIOU', 165 ; ; unmangle_name: Does the opposite of mangle_name; converts a DOS-mangled ; filename to the conventional representation. This is needed ; for the BOOT_IMAGE= parameter for the kernel. ; NOTE: A 13-byte buffer is mandatory, even if the string is ; known to be shorter. ; ; DS:SI -> input mangled file name ; ES:DI -> output buffer ; ; On return, DI points to the first byte after the output name, ; which is set to a null byte. ; unmangle_name: push si ; Save pointer to original name mov cx,8 mov bp,di un_copy_body: lodsb call lower_case stosb cmp al,' ' jbe un_cb_space mov bp,di ; Position of last nonblank+1 un_cb_space: loop un_copy_body mov di,bp mov al,'.' ; Don't save stosb mov cx,3 un_copy_ext: lodsb call lower_case stosb cmp al,' ' jbe un_ce_space mov bp,di un_ce_space: loop un_copy_ext mov di,bp mov byte [es:di], 0 pop si ret ; ; lower_case: Lower case a character in AL ; lower_case: cmp al,'A' jb lc_ret cmp al,'Z' ja lc_1 or al,20h ret lc_1: cmp al,lcase_low jb lc_ret cmp al,lcase_high ja lc_ret push bx mov bx,lcase_tab-lcase_low cs xlatb pop bx lc_ret: ret ; ----------------------------------------------------------------------------- ; Common modules ; ----------------------------------------------------------------------------- %include "getc.inc" ; getc et al %include "conio.inc" ; Console I/O %include "writestr.inc" ; String 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() ; ----------------------------------------------------------------------------- ; Begin data section ; ----------------------------------------------------------------------------- ; ; Lower-case table for codepage 865 ; lcase_low equ 128 lcase_high equ 165 lcase_tab db 135, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138 db 139, 140, 141, 132, 134, 130, 145, 145, 147, 148, 149 db 150, 151, 152, 148, 129, 155, 156, 155, 158, 159, 160 db 161, 162, 163, 164, 164 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 syslinux.cfg.', CR, LF, 0 err_noparm db 'Missing parameter in syslinux.cfg.', 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_a20 db CR, LF, 'A20 gate not responding!', CR, LF, 0 err_bootfailed db CR, LF, 'Boot failed: please change disks and press ' db 'a key to continue.', CR, LF, 0 ready_msg db 'Ready.', CR, LF, 0 crlfloading_msg db CR, LF loading_msg db 'Loading ', 0 dotdot_msg db '.' dot_msg db '.', 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 syslinux_cfg db 'SYSLINUXCFG' ; Mangled form ConfigName db 'syslinux.cfg',0 ; Unmangled form %if IS_MDSLINUX manifest db 'MANIFEST ' %endif ; ; 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 7 ; ; Config file keyword table ; %include "keywords.inc" ; ; Extensions to search for (in *forward* order). ; exten_table: db 'CBT',0 ; COMBOOT (specific) db 'BSS',0 ; Boot Sector (add superblock) db 'BS ',0 ; Boot Sector db 'COM',0 ; COMBOOT (same as DOS) db 'C32',0 ; COM32 exten_table_end: dd 0, 0 ; Need 8 null bytes here ; ; Misc initialized (data) variables ; %ifdef debug ; This code for debugging only debug_magic dw 0D00Dh ; Debug code sentinel %endif AppendLen dw 0 ; Bytes in append= command OntimeoutLen dw 0 ; Bytes in ontimeout command OnerrorLen dw 0 ; Bytes in onerror command KbdTimeOut dw 0 ; Keyboard timeout (if any) CmdLinePtr dw cmd_line_here ; Command line advancing pointer initrd_flag equ $ initrd_ptr dw 0 ; Initial ramdisk pointer/flag VKernelCtr dw 0 ; Number of registered vkernels ForcePrompt dw 0 ; Force prompt AllowImplicit dw 1 ; Allow implicit kernels AllowOptions dw 1 ; User-specified options allowed SerialPort dw 0 ; Serial port base (or 0 for no serial port) VGAFontSize dw 16 ; Defaults to 16 byte font UserFont db 0 ; Using a user-specified font ScrollAttribute db 07h ; White on black (for text mode) ; ; Stuff for the command line; we do some trickery here with equ to avoid ; tons of zeros appended to our file and wasting space ; linuxauto_cmd db 'linux auto',0 linuxauto_len equ $-linuxauto_cmd boot_image db 'BOOT_IMAGE=' boot_image_len equ $-boot_image ldlinux_end equ $ ldlinux_len equ $-ldlinux_magic ; ; Put the getcbuf right after the code, aligned on a sector boundary ; end_of_code equ (ldlinux_end-bootsec)+7C00h getcbuf equ (end_of_code + 511) & 0FE00h ; VGA font buffer at the end of memory (so loading a font works even ; in graphics mode.) vgafontbuf equ 0E000h ; This is a compile-time assert that we didn't run out of space %ifndef DEPEND %if (getcbuf+trackbufsize) > vgafontbuf %error "Out of memory, better reorganize something..." %endif %endif