; -*- 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) 1994-2001 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. ; ; **************************************************************************** ; ; Some semi-configurable constants... change on your own risk. Most are imposed ; by the kernel. ; max_cmd_len equ 255 ; Must be odd; 255 is the kernel limit retry_count equ 6 ; How patient are we with the disk? HIGHMEM_MAX equ 037FFFFFFh ; DEFAULT highest address for an initrd DEFAULT_BAUD equ 9600 ; Default baud rate for serial port BAUD_DIVISOR equ 115200 ; Serial port parameter ; ; Should be updated with every release to avoid bootsector/SYS file mismatch ; %define version_str VERSION ; Must be 4 characters long! %define date DATE_STR ; Defined from the Makefile %define year '2001' ; ; Debgging stuff ; ; %define debug 1 ; Uncomment to enable debugging ; ; ID for SYSLINUX (reported to kernel) ; syslinux_id equ 031h ; SYSLINUX (3) version 1.x (1) ; ; Segments used by Linux ; ; Note: the real_mode_seg is supposed to be 9000h, but some device drivers ; hog some of high memory. Therefore, we load it at 7000:0000h and copy ; it before starting the Linux kernel. ; real_mode_seg equ 7000h fake_setup_seg equ real_mode_seg+020h struc real_mode_seg_t resb 20h-($-$$) ; org 20h kern_cmd_magic resw 1 ; 0020 Magic # for command line kern_cmd_offset resw 1 ; 0022 Offset for kernel command line resb 497-($-$$) ; org 497d bs_setupsecs resb 1 ; 01F1 Sectors for setup code (0 -> 4) bs_rootflags resw 1 ; 01F2 Root readonly flag bs_syssize resw 1 ; 01F4 bs_swapdev resw 1 ; 01F6 Swap device (obsolete) bs_ramsize resw 1 ; 01F8 Ramdisk flags, formerly ramdisk size bs_vidmode resw 1 ; 01FA Video mode bs_rootdev resw 1 ; 01FC Root device bs_bootsign resw 1 ; 01FE Boot sector signature (0AA55h) su_jump resb 1 ; 0200 0EBh su_jump2 resb 1 ; 0201 Size of following header su_header resd 1 ; 0202 New setup code: header su_version resw 1 ; 0206 See linux/arch/i386/boot/setup.S su_switch resw 1 ; 0208 su_setupseg resw 1 ; 020A su_startsys resw 1 ; 020C su_kver resw 1 ; 020E Kernel version pointer su_loader resb 1 ; 0210 Loader ID su_loadflags resb 1 ; 0211 Load high flag su_movesize resw 1 ; 0212 su_code32start resd 1 ; 0214 Start of code loaded high su_ramdiskat resd 1 ; 0218 Start of initial ramdisk su_ramdisklen equ $ ; Length of initial ramdisk su_ramdisklen1 resw 1 ; 021C su_ramdisklen2 resw 1 ; 021E su_bsklugeoffs resw 1 ; 0220 su_bsklugeseg resw 1 ; 0222 su_heapend resw 1 ; 0224 su_pad1 resw 1 ; 0226 su_cmd_line_ptr resd 1 ; 0228 su_ramdisk_max resd 1 ; 022C resb (9000h-12)-($-$$) ; The setup is up to 32K long linux_stack equ $ ; 8FF4 linux_fdctab equ $ resb 9000h-($-$$) cmd_line_here equ $ ; 9000 Should be out of the way endstruc ; ; Kernel command line signature ; CMD_MAGIC equ 0A33Fh ; Command line magic ; ; Magic number of su_header field ; HEADER_ID equ 'HdrS' ; HdrS (in littleendian hex) ; ; Flags for the su_loadflags field ; LOAD_HIGH equ 01h ; Large kernel, load high CAN_USE_HEAP equ 80h ; Boot loader reports heap size ; ; 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 11 ; Virtual name **MUST BE FIRST!** vk_rname: resb 11 ; 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 %if (vk_end > vk_size) || (vk_size*max_vk > 65536) %error "Too many vkernels defined, reduce vk_power" %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) ; 7000h - real_mode_seg ; fat_seg equ 5000h ; 128K area for FAT (2x64K) vk_seg equ 4000h ; Virtual kernels xfer_buf_seg equ 3000h ; Bounce buffer for I/O to high mem comboot_seg equ 2000h ; COMBOOT image loading zone ; ; For our convenience: define macros for jump-over-unconditinal jumps ; %macro jmpz 1 jnz %%skip jmp %1 %%skip: %endmacro %macro jmpnz 1 jz %%skip jmp %1 %%skip: %endmacro %macro jmpe 1 jne %%skip jmp %1 %%skip: %endmacro %macro jmpne 1 je %%skip jmp %1 %%skip: %endmacro %macro jmpc 1 jnc %%skip jmp %1 %%skip: %endmacro %macro jmpnc 1 jc %%skip jmp %1 %%skip: %endmacro %macro jmpb 1 jnb %%skip jmp %1 %%skip: %endmacro %macro jmpnb 1 jb %%skip jmp %1 %%skip: %endmacro ; ; Macros similar to res[bwd], but which works in the code segment (after ; section .text) ; %macro zb 1 times %1 db 0 %endmacro %macro zw 1 times %1 dw 0 %endmacro %macro zd 1 times %1 dd 0 %endmacro ; --------------------------------------------------------------------------- ; BEGIN THE BIOS/CODE/DATA SEGMENT ; --------------------------------------------------------------------------- absolute 4*1Eh ; In the interrupt table fdctab equ $ fdctab1 resw 1 fdctab2 resw 1 absolute 0400h serial_base resw 4 ; Base addresses for 4 serial ports absolute 0484h BIOS_vidrows resb 1 ; Number of screen rows ; ; 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= 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 4 PartInfo resb 16 ; Partition table entry E820Buf resd 5 ; INT 15:E820 data buffer InitRDat resd 1 ; Load address (linear) for initrd 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) KernelName resb 12 ; Mangled name for kernel ; (note the spare byte after!) RootDir equ $ ; Location of root directory RootDir1 resw 1 RootDir2 resw 1 DataArea equ $ ; Location of data area DataArea1 resw 1 DataArea2 resw 1 FBytes equ $ ; Used by open/getc FBytes1 resw 1 FBytes2 resw 1 RootDirSize resw 1 ; Root dir size in sectors DirScanCtr resw 1 ; Used while searching directory DirBlocksLeft resw 1 ; Ditto EndofDirSec resw 1 ; = trackbuf+bsBytesPerSec-31 RunLinClust resw 1 ; Cluster # for LDLINUX.SYS ClustSize resw 1 ; Bytes/cluster SecPerClust resw 1 ; Same as bsSecPerClust, but a word NextCluster resw 1 ; Pointer to "nextcluster" routine 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 InitRDClust resw 1 ; Ramdisk size in clusters ClustPerMoby resw 1 ; Clusters per 64K 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 SavedSP resw 1 ; Our SP while running a COMBOOT image A20Test resw 1 ; Counter for testing status of A20 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 TextAttrBX equ $ TextAttribute resb 1 ; Text attribute for message file TextPage resb 1 ; Active display page 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 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 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 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 section .text org 7C00h StackBuf equ $ ; Start the stack here (grow down - 4K) ; ; 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... superblock equ $ bsBytesPerSec zw 1 bsSecPerClust zb 1 bsResSectors zw 1 bsFATs zb 1 bsRootDirEnts zw 1 bsSectors zw 1 bsMedia zb 1 bsFATsecs zw 1 bsSecPerTrack zw 1 bsHeads zw 1 bsHiddenSecs equ $ bsHidden1 zw 1 bsHidden2 zw 1 bsHugeSectors equ $ bsHugeSec1 zw 1 bsHugeSec2 zw 1 bsDriveNumber zb 1 bsReserved1 zb 1 bsBootSignature zb 1 ; 29h if the following fields exist bsVolumeID zd 1 bsVolumeLabel zb 11 bsFileSysType zb 8 ; Must be FAT12 for this version superblock_len equ $-superblock ; ; 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 cx,cx mov ss,cx mov sp,StackBuf ; Just below BSS mov es,cx ; ; DS:SI may contain a partition table entry. Preserve it for us. ; mov cl,8 ; Save partition info (CH == 0) mov di,PartInfo rep movsw ; ; 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 boot sector space with this code. ; ; This code no longer fits. Hope that noone really needs it anymore. ; (If so, it needs serious updating.) In fact, some indications is that ; this code does more harm than good with all the new kinds of drives and ; media. ; %ifdef SUPPORT_REALLY_BROKEN_BIOSES lds si,[ss:fdctab] ; DS:SI -> original push ds ; Save on stack in case push si ; we have to bail push bx mov cx,6 ; 12 bytes mov di,floppy_table push di cld rep movsw ; Faster to move words pop di mov ds,ax ; Now we can point DS to here, too mov cl,[bsSecPerTrack] ; Patch the sector count mov [di+4],cl mov [fdctab+2],ax ; Segment 0 mov [fdctab],di ; offset floppy_block %else mov ds,cx ; CX == 0 %endif ; ; Ready to enable interrupts, captain ; sti ; ; 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 ; mov [bsDriveNumber],dl test dl,80h ; If floppy disk (00-7F), assume no jz not_harddisk ; partition table test byte [di-16],7Fh ; Sanity check: "active flag" should jnz no_partition ; be 00 or 80 lea si,[di-8] ; Partition offset (dword) mov di,bsHidden1 mov cl,2 ; CH == 0 rep movsw 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 inc dh ; Contains # of heads - 1 mov [bsHeads],dh and cx,3fh mov [bsSecPerTrack],cx no_driveparm: not_harddisk: ; ; 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... ; debugentrypt: xor ax,ax ; INT 13:08 destroys ES mov es,ax mov al,[bsFATs] ; Number of FATs (AH == 0) mul word [bsFATsecs] ; Get the size of the FAT area add ax,[bsHidden1] ; Add hidden sectors adc dx,[bsHidden2] add ax,[bsResSectors] ; And reserved sectors adc dx,byte 0 mov [RootDir1],ax ; Location of root directory mov [RootDir2],dx mov [DataArea1],ax mov [DataArea2],dx push ax push dx mov ax,32 ; Size of a directory entry mul word [bsRootDirEnts] mov bx,[bsBytesPerSec] 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 [EndofDirSec],bx ; End of a single directory sector add [DataArea1],ax adc word [DataArea2],byte 0 pop dx ; Reload root directory starting point pop ax ; ; 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 ax push dx mov bx,trackbuf push bx call getonesec pop si sd_nextentry: cmp byte [si],0 ; Directory high water mark je kaboom test byte [si+11],18h ; Must be a file jnz sd_not_file mov di,ldlinux_name mov cx,11 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 dx pop ax add ax,byte 1 adc dx,byte 0 dec word [DirScanCtr] jnz sd_nextsec ; ; kaboom: write a message and bail out. ; kaboom: xor si,si mov ss,si mov sp,StackBuf ; Reset stack mov ds,si ; Reset data segment .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?) xor ax,ax mov al,[bsSecPerClust] mov bp,ax ; Load an entire cluster mov bx,[si+26] ; First cluster mov [RunLinClust],bx ; Save for later use dec bx ; First cluster is "cluster 2" dec bx mul bx add ax,[DataArea1] adc dx,[DataArea2] 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! ; ; 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:ldlinux_ent ; ; ; writestr: write a null-terminated string to the console ; writestr: wstr_1: lodsb and al,al jz return mov ah,0Eh ; Write to screen as TTY mov bx,0007h ; White on black, current page int 10h jmp short wstr_1 ; ; disk_error: decrement the retry count and bail if zero ; disk_error: dec si ; SI holds the disk retry counter jz kaboom pop bx ; pop cx ; pop dx ; pop ax ; (AH = 0) mov al,1 ; Once we fail, only transfer 1 sector jmp short disk_try_again return: ret ; ; 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 DX:AX 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. ; ; 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 si,[bsSecPerTrack] ; ; Dividing by sectors to get (track,sector): we may have ; up to 2^18 tracks, so we need to do this in two steps ; to produce a 32-bit quotient. ; xchg cx,ax ; CX <- LSW of LBA xchg ax,dx xor dx,dx ; DX:AX now == MSW of LBA div si ; Obtain MSW of track # xchg ax,cx ; Remainder -> MSW of new dividend ; LSW of LBA -> LSW of new dividend ; Quotient -> MSW of track # div si ; Obtain LSW of track #, remainder xchg cx,dx ; CX <- Sector index (0-based) ; DX <- MSW of track # div word [bsHeads] ; 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 __BEGIN_STUPID_PATCH_AREA: sub si,cx ; Sectors left on track cmp bp,si jna gls_lastchunk mov bp,si ; No more than a trackful, please! __END_STUPID_PATCH_AREA: gls_lastchunk: push ax ; Cylinder # push dx ; Head # push cx ; Sector # mov cl,6 ; Because IBM was STOOPID shl ah,cl ; 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 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: push ax ; Number of sectors we're transferring mov ah,02h ; READ DISK push dx ; push cx ; push bx ; push si ; int 13h pop si ; jc disk_error ; ; Disk access successful ; pop bx ; Buffer location pop ax ; No longer needed pop ax ; No longer needed pop di ; Sector transferred count pop cx ; Sector # mov ax,di ; 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 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 bs_checkpt_off equ ($-$$) %if bs_checkpt_off > 1EFh %error "Boot sector overflow" %endif zb 1EFh-($-$$) 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, 'SYSLINUX ', version_str, ' ', date, ' ', 0 db 0Dh, 0Ah, 1Ah ; EOF if we "type" this in DOS ldlinux_magic db 'LDLINUX SYS' dd HEXDATE dw 0AA55h align 4 ldlinux_ent: ; ; 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... ; mov dx,1 ; 64K xor ax,ax div word [bsBytesPerSec] ; sectors/64K mov si,ax push es mov bx,fat_seg ; Load into fat_seg:0000 mov es,bx mov ax,[bsHidden1] ; Hidden sectors mov dx,[bsHidden2] add ax,[bsResSectors] ; plus reserved sectors = FAT adc dx,byte 0 mov cx,[bsFATsecs] ; Sectors/FAT fat_load_loop: mov bp,cx 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 ax,bp ; Advance sector count adc dx,byte 0 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 di,[bsBytesPerSec] ; Used a lot below mov al,[bsSecPerClust] ; We do this in the boot xor ah,ah ; sector, too, but there mov [SecPerClust],ax ; wasn't space to save it mov si,ax ; Also used a lot... mul di mov [ClustSize],ax ; Bytes/cluster mov bx,ax mov ax,trackbufsize xor dx,dx div bx mov [BufSafe],ax ; # of cluster in trackbuf mul word [SecPerClust] 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... ; xor dx,dx xor cx,cx mov ax,[bsSectors] and ax,ax jnz have_secs mov ax,[bsHugeSectors] mov dx,[bsHugeSectors+2] have_secs: sub ax,[bsResSectors] sbb dx,byte 0 mov cl,[bsFATs] sec_fat_loop: sub ax,[bsFATsecs] sbb dx,byte 0 loop sec_fat_loop push ax push dx mov ax,[bsRootDirEnts] mov bx,32 ; Smaller than shift since we mul bx ; need the doubleword product add ax,di adc dx,byte 0 sub ax,byte 1 sbb dx,byte 0 div di mov bx,ax pop dx pop ax sub ax,bx sbb dx,byte 0 div si cmp ax,4086 ; Right value? mov ax,nextcluster_fat16 ja have_fat_type have_fat12: mov ax,nextcluster_fat12 have_fat_type: mov word [NextCluster],ax ; ; 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) ; ; 386 check getfssec: getfragment: xor bp,bp ; Fragment sector count mov ax,si ; Get sector address dec ax ; Convert to 0-based dec ax mul word [SecPerClust] add ax,[DataArea1] adc dx,[DataArea2] getseccnt: ; See if we can read > 1 clust add bp,[SecPerClust] dec cx ; Reduce clusters left to find mov di,si ; Predict next cluster inc di call [NextCluster] jc gfs_eof ; At EOF? jcxz endfragment ; Or was it the last we wanted? cmp si,di ; Is file continuous? jz getseccnt ; Yes, we can get endfragment: clc ; Not at EOF gfs_eof: pushf ; Remember EOF or not push si push cx gfs_getchunk: push ax push dx mov ax,es ; Check for 64K boundaries. mov cl,4 shl ax,cl add ax,bx xor dx,dx neg ax jnz gfs_partseg inc dx ; Full 64K segment gfs_partseg: div word [bsBytesPerSec] ; How many sectors fit? mov si,bp sub si,ax ; Compute remaining sectors jbe gfs_lastchunk mov bp,ax pop dx pop ax call getlinsecsr add ax,bp adc dx,byte 0 mov bp,si ; Remaining sector count jmp short gfs_getchunk gfs_lastchunk: pop dx pop ax call getlinsec pop cx pop si popf jcxz gfs_return ; If we hit the count limit jnc getfragment ; If we didn't hit EOF gfs_return: ret ; ; getlinsecsr: save registers, call getlinsec, restore registers ; getlinsecsr: push ax push dx push cx push bp push si push di call getlinsec pop di pop si pop bp pop cx pop dx pop ax ret ; ; nextcluster: Advance a cluster pointer in SI to the next cluster ; pointed at in the FAT tables (note: FAT12 assumed) ; Sets CF on return if end of file. ; ; The variable NextCluster gets set to the appropriate ; value here. ; nextcluster_fat12: push ax push ds mov ax,fat_seg mov ds,ax mov ax,si ; Multiply by 3/2 shr ax,1 pushf ; CF now set if odd add si,ax mov si,[si] popf jnc nc_even shr si,1 ; Needed for odd only shr si,1 shr si,1 shr si,1 nc_even: and si,0FFFh cmp si,0FF0h ; Clears CF if at end of file cmc ; But we want it SET... pop ds pop ax 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 cmc pop ds pop ax 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 ($-$$) %if rl_checkpt_off > 400h %error "Sector 1 overflow" %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 ; ; Check that no moron is trying to boot Linux on a 286 or so. According ; to Intel, the way to check is to see if the high 4 bits of the FLAGS ; register are either all stuck at 1 (8086/8088) or all stuck at 0 ; (286 in real mode), if not it is a 386 or higher. They didn't ; say how to check for a 186/188, so I *hope* it falls out as a 8086 ; or 286 in this test. ; ; Also, provide an escape route in case it doesn't work. ; check_escapes: mov ah,02h ; Check keyboard flags int 16h mov [KbdFlags],al ; Save for boot prompt check test al,04h ; Ctrl->skip 386 check jnz skip_checks test_8086: pushf ; Get flags pop ax and ax,0FFFh ; Clear top 4 bits push ax ; Load into FLAGS popf pushf ; And load back pop ax and ax,0F000h ; Get top 4 bits cmp ax,0F000h ; If set -> 8086/8088 je not_386 test_286: pushf ; Get flags pop ax or ax,0F000h ; Set top 4 bits push ax popf pushf pop ax and ax,0F000h ; Get top 4 bits jnz is_386 ; If not clear -> 386 not_386: mov si,err_not386 call writestr jmp kaboom is_386: ; Now we know it's a 386 or higher ; ; Now check that there is at least 512K of low (DOS) memory ; int 12h cmp ax,512 jae enough_ram mov si,err_noram call writestr jmp kaboom enough_ram: skip_checks: ; ; Check if we're 386 (as opposed to 486+); if so we need to blank out ; the WBINVD instruction ; ; We check for 486 by setting EFLAGS.AC ; pushfd ; Save the good flags pushfd pop eax mov ebx,eax xor eax,(1 << 18) ; AC bit push eax popfd pushfd pop eax popfd ; Restore the original flags xor eax,ebx jnz is_486 ; ; 386 - Looks like we better blot out the WBINVD instruction ; mov byte [try_wbinvd],0c3h ; Near RET is_486: ; ; Initialization that does not need to go into the any of the pre-load ; areas ; ; Now set up screen parameters call adjust_screen ; ; Now, everything is "up and running"... patch kaboom for more ; verbosity and using the full screen system ; mov byte [kaboom.patch],0e9h ; JMP NEAR mov word [kaboom.patch+1],kaboom2-(kaboom.patch+3) ; ; 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 ; ; Load configuration file ; mov di,syslinux_cfg call open jz near no_config_file parse_config: call getkeyword jc near end_config_file ; Config file loaded cmp ax,'de' ; DEfault je pc_default cmp ax,'ap' ; APpend je pc_append cmp ax,'ti' ; TImeout je near pc_timeout cmp ax,'pr' ; PRompt je near pc_prompt cmp ax,'fo' ; FOnt je near pc_font cmp ax,'kb' ; KBd je near pc_kbd cmp ax,'di' ; DIsplay je near pc_display cmp ax,'la' ; LAbel je near pc_label cmp ax,'ke' ; KErnel je pc_kernel cmp ax,'im' ; IMplicit je near pc_implicit cmp ax,'se' ; SErial je near pc_serial cmp al,'f' ; F-key jne parse_config jmp pc_fkey pc_default: mov di,default_cmd ; "default" command call getline xor al,al stosb ; null-terminate jmp short parse_config pc_append: cmp word [VKernelCtr],byte 0 ; "append" command ja pc_append_vk mov di,AppendBuf call getline sub di,AppendBuf pc_app1: mov [AppendLen],di jmp short parse_config pc_append_vk: mov di,VKernelBuf+vk_append ; "append" command (vkernel) call getline sub di,VKernelBuf+vk_append cmp di,byte 2 jne pc_app2 cmp byte [VKernelBuf+vk_append],'-' jne pc_app2 mov di,0 ; If "append -" -> null string pc_app2: mov [VKernelBuf+vk_appendlen],di jmp short parse_config_2 pc_kernel: cmp word [VKernelCtr],byte 0 ; "kernel" command je near parse_config ; ("label" section only) mov di,trackbuf push di call getline pop si mov di,VKernelBuf+vk_rname call mangle_name jmp short parse_config_2 pc_timeout: call getint ; "timeout" command jc parse_config_2 mov ax,0D215h ; There are approx 1.D215h mul bx ; clock ticks per 1/10 s add bx,dx mov [KbdTimeOut],bx jmp short parse_config_2 pc_display: call pc_getfile ; "display" command jz parse_config_2 ; File not found? call get_msg_file ; Load and display file parse_config_2: jmp parse_config pc_prompt: call getint ; "prompt" command jc parse_config_2 mov [ForcePrompt],bx jmp short parse_config_2 pc_implicit: call getint ; "implicit" command jc parse_config_2 mov [AllowImplicit],bx jmp short parse_config_2 pc_serial: call getint ; "serial" command jc parse_config_2 push bx ; Serial port # call skipspace jc parse_config_2 call ungetc call getint mov [FlowControl], word 0 ; Default to no flow control jc .nobaud .valid_baud: push ebx call skipspace jc .no_flow call ungetc call getint ; Hardware flow control? jnc .valid_flow .no_flow: xor bx,bx ; Default -> no flow control .valid_flow: and bh,0Fh ; FlowIgnore shl bh,4 mov [FlowIgnore],bh mov bh,bl and bx,0F003h ; Valid bits mov [FlowControl],bx pop ebx ; Baud rate jmp short .parse_baud .nobaud: mov ebx,DEFAULT_BAUD ; No baud rate given .parse_baud: pop di ; Serial port # cmp ebx,byte 75 jb parse_config_2 ; < 75 baud == bogus mov eax,BAUD_DIVISOR cdq div ebx push ax ; Baud rate divisor cmp di,3 ja .port_is_io ; If port > 3 then port is I/O addr shl di,1 mov di,[di+serial_base] ; Get the I/O port from the BIOS .port_is_io: mov [SerialPort],di lea dx,[di+3] ; DX -> LCR mov al,83h ; Enable DLAB call slow_out pop ax ; Divisor mov dx,di ; DX -> LS call slow_out inc dx ; DX -> MS mov al,ah call slow_out mov al,03h ; Disable DLAB add dx,byte 2 ; DX -> LCR call slow_out in al,dx ; Read back LCR (detect missing hw) cmp al,03h ; If nothing here we'll read 00 or FF jne .serial_port_bad ; Assume serial port busted sub dx,byte 2 ; DX -> IER xor al,al ; IRQ disable call slow_out add dx,byte 3 ; DX -> MCR in al,dx or al,[FlowOutput] ; Assert bits call slow_out ; Show some life mov si,syslinux_banner call write_serial_str mov si,copyright_str call write_serial_str jmp short parse_config_3 .serial_port_bad: mov [SerialPort], word 0 jmp short parse_config_3 pc_fkey: sub ah,'1' jnb pc_fkey1 mov ah,9 ; F10 pc_fkey1: xor cx,cx mov cl,ah push cx mov ax,1 shl ax,cl or [FKeyMap], ax ; Mark that we have this loaded mov di,trackbuf push di call getline ; Get filename to display pop si pop di shl di,4 ; Multiply number by 16 add di,FKeyName call mangle_name ; Mangle file name jmp short parse_config_3 pc_label: call commit_vk ; Commit any current vkernel mov di,trackbuf ; Get virtual filename push di call getline pop si mov di,VKernelBuf+vk_vname call mangle_name ; Mangle virtual name inc word [VKernelCtr] ; One more vkernel mov si,VKernelBuf+vk_vname ; By default, rname == vname mov di,VKernelBuf+vk_rname mov cx,11 rep movsb mov si,AppendBuf ; Default append==global append mov di,VKernelBuf+vk_append mov cx,[AppendLen] mov [VKernelBuf+vk_appendlen],cx rep movsb jmp near parse_config_3 pc_font: call pc_getfile ; "font" command jz parse_config_3 ; File not found? call loadfont ; Load and install font jmp short parse_config_3 pc_kbd: call pc_getfile ; "kbd" command jz parse_config_3 call loadkeys parse_config_3: jmp parse_config ; ; pc_getfile: For command line options that take file argument, this ; routine decodes the file argument and runs it through searchdir ; pc_getfile: mov di,trackbuf push di call getline pop si mov di,MNameBuf push di call mangle_name pop di jmp searchdir ; Tailcall ; ; commit_vk: Store the current VKernelBuf into buffer segment ; commit_vk: cmp word [VKernelCtr],byte 0 je cvk_ret ; No VKernel = return cmp word [VKernelCtr],max_vk ; Above limit? ja cvk_overflow mov di,[VKernelCtr] dec di shl di,vk_shift mov si,VKernelBuf mov cx,(vk_size >> 2) push es push word vk_seg pop es rep movsd ; Copy to buffer segment pop es cvk_ret: ret cvk_overflow: mov word [VKernelCtr],max_vk ; No more than max_vk, please ret ; ; End of configuration file ; end_config_file: call commit_vk ; Commit any current vkernel no_config_file: ; ; Check whether or not we are supposed to display the boot prompt. ; check_for_key: cmp word [ForcePrompt],byte 0 ; Force prompt? jnz enter_command test byte [KbdFlags],5Bh ; Caps, Scroll, Shift, Alt jz near auto_boot ; If neither, default boot enter_command: mov si,boot_prompt call cwritestr mov byte [FuncFlag],0 ; not pressed mov di,command_line ; ; get the very first character -- we can either time ; out, or receive a character press at this time. Some dorky BIOSes stuff ; a return in the buffer on bootup, so wipe the keyboard buffer first. ; clear_buffer: mov ah,1 ; Check for pending char int 16h jz get_char_time xor ax,ax ; Get char int 16h jmp short clear_buffer get_char_time: call vgashowcursor mov cx,[KbdTimeOut] and cx,cx jz get_char ; Timeout == 0 -> no timeout inc cx ; The first loop will happen ; immediately as we don't ; know the appropriate DX value time_loop: push cx tick_loop: push dx call pollchar jnz get_char_pop xor ax,ax int 1Ah ; Get time "of day" pop ax cmp dx,ax ; Has the timer advanced? je tick_loop pop cx loop time_loop ; If so, decrement counter call vgahidecursor jmp command_done ; Timeout! get_char_pop: pop eax ; Clear stack get_char: call vgashowcursor call getchar call vgahidecursor and al,al jz func_key got_ascii: cmp al,7Fh ; == je backspace cmp al,' ' ; ASCII? jb not_ascii ja enter_char cmp di,command_line ; Space must not be first je get_char enter_char: test byte [FuncFlag],1 jz .not_ctrl_f mov byte [FuncFlag],0 cmp al,'0' jb .not_ctrl_f je ctrl_f_0 cmp al,'9' jbe ctrl_f .not_ctrl_f: cmp di,max_cmd_len+command_line ; Check there's space jnb get_char stosb ; Save it call writechr ; Echo to screen get_char_2: jmp short get_char not_ascii: mov byte [FuncFlag],0 cmp al,0Dh ; Enter je command_done cmp al,06h ; je set_func_flag cmp al,08h ; Backspace jne get_char backspace: cmp di,command_line ; Make sure there is anything je get_char ; to erase dec di ; Unstore one character mov si,wipe_char ; and erase it from the screen call cwritestr jmp short get_char_2 set_func_flag: mov byte [FuncFlag],1 jmp short get_char_2 ctrl_f_0: add al,10 ; 0 == F10 ctrl_f: push di sub al,'1' xor ah,ah jmp short show_help func_key: push di cmp ah,68 ; F10 ja get_char_2 sub ah,59 ; F1 jb get_char_2 shr ax,8 show_help: ; AX = func key # (0 = F1, 9 = F10) mov cl,al shl ax,4 ; Convert to x16 mov bx,1 shl bx,cl and bx,[FKeyMap] jz get_char_2 ; Undefined F-key mov di,ax add di,FKeyName call searchdir jz fk_nofile push si call crlf pop si call get_msg_file jmp short fk_wrcmd fk_nofile: call crlf fk_wrcmd: mov si,boot_prompt call cwritestr pop di ; Command line write pointer push di mov byte [di],0 ; Null-terminate command line mov si,command_line call cwritestr ; Write command line so far pop di jmp short get_char_2 auto_boot: mov si,default_cmd mov di,command_line mov cx,(max_cmd_len+4) >> 2 rep movsd jmp short load_kernel command_done: call crlf cmp di,command_line ; Did we just hit return? je auto_boot xor al,al ; Store a final null stosb load_kernel: ; Load the kernel now ; ; First we need to mangle the kernel name the way DOS would... ; mov si,command_line mov di,KernelName push si push di call mangle_name pop di pop si ; ; Fast-forward to first option (we start over from the beginning, since ; mangle_name doesn't necessarily return a consistent ending state.) ; clin_non_wsp: lodsb cmp al,' ' ja clin_non_wsp clin_is_wsp: and al,al jz clin_opt_ptr lodsb cmp al,' ' jbe clin_is_wsp clin_opt_ptr: dec si ; Point to first nonblank mov [CmdOptPtr],si ; Save ptr to first option ; ; Now check if it is a "virtual kernel" ; mov cx,[VKernelCtr] push ds push word vk_seg pop ds cmp cx,byte 0 je not_vk xor si,si ; Point to first vkernel vk_check: pusha mov cx,11 repe cmpsb ; Is this it? je near vk_found popa add si,vk_size loop vk_check not_vk: pop ds ; ; Not a "virtual kernel" - check that's OK and construct the command line ; cmp word [AllowImplicit],byte 0 je bad_implicit push es push si push di mov di,real_mode_seg mov es,di mov si,AppendBuf mov di,cmd_line_here mov cx,[AppendLen] rep movsb mov [CmdLinePtr],di pop di pop si pop es mov bx,exten_count << 2 ; Alternates to try ; ; Find the kernel on disk ; get_kernel: mov byte [KernelName+11],0 ; Zero-terminate filename/extension mov eax,[KernelName+8] ; Save initial extension mov [OrigKernelExt],eax .search_loop: push bx mov di,KernelName ; Search on disk call searchdir pop bx jnz kernel_good mov eax,[exten_table+bx] ; Try a different extension mov [KernelName+8],eax sub bx,byte 4 jnb .search_loop bad_kernel: mov si,KernelName mov di,KernelCName push di call unmangle_name ; Get human form mov si,err_notfound ; Complain about missing kernel call cwritestr pop si ; KernelCName call cwritestr mov si,crlf_msg jmp abort_load ; Ask user for clue ; ; bad_implicit: The user entered a nonvirtual kernel name, with "implicit 0" ; bad_implicit: mov si,KernelName ; For the error message mov di,KernelCName call unmangle_name jmp short bad_kernel ; ; vk_found: We *are* using a "virtual kernel" ; vk_found: popa push di mov di,VKernelBuf mov cx,vk_size >> 2 rep movsd push es ; Restore old DS pop ds push es push word real_mode_seg pop es mov di,cmd_line_here mov si,VKernelBuf+vk_append mov cx,[VKernelBuf+vk_appendlen] rep movsb mov [CmdLinePtr],di ; Where to add rest of cmd pop es pop di ; DI -> KernelName push di mov si,VKernelBuf+vk_rname mov cx,11 ; We need ECX == CX later rep movsb pop di xor bx,bx ; Try only one version jmp get_kernel ; ; kernel_corrupt: Called if the kernel file does not seem healthy ; kernel_corrupt: mov si,err_notkernel jmp abort_load ; ; This is it! We have a name (and location on the disk)... let's load ; that sucker!! First we have to decide what kind of file this is; base ; that decision on the file extension. The following extensions are ; recognized: ; ; .COM - COMBOOT image ; .CBT - COMBOOT image ; .BS - Boot sector ; .BSS - Boot sector, but transfer over DOS superblock ; ; Anything else is assumed to be a Linux kernel. ; kernel_good: pusha mov si,KernelName mov di,KernelCName call unmangle_name ; Get human form sub di,KernelCName mov [KernelCNameLen],di popa mov ecx,[KernelName+8] ; Get (mangled) extension cmp ecx,'COM' je near is_comboot_image cmp ecx,'CBT' je near is_comboot_image cmp ecx,'BS ' je near is_bootsector cmp ecx,'BSS' je near is_bss_sector ; Otherwise Linux kernel ; ; A Linux kernel consists of three parts: boot sector, setup code, and ; kernel code. The boot sector is never executed when using an external ; booting utility, but it contains some status bytes that are necessary. ; The boot sector and setup code together form exactly 5 sectors that ; should be loaded at 9000:0. The subsequent code should be loaded ; at 1000:0. For simplicity, we load the whole thing at 0F60:0, and ; copy the latter stuff afterwards. ; ; NOTE: In the previous code I have avoided making any assumptions regarding ; the size of a sector, in case this concept ever gets extended to other ; media like CD-ROM (not that a CD-ROM would be bloody likely to use a FAT ; filesystem, of course). However, a "sector" when it comes to Linux booting ; stuff means 512 bytes *no matter what*, so here I am using that piece ; of knowledge. ; ; First check that our kernel is at least 1K and less than 8M (if it is ; more than 8M, we need to change the logic for loading it anyway...) ; ; We used to require the kernel to be 64K or larger, but it has gotten ; popular to use the Linux kernel format for other things, which may ; not be so large. ; is_linux_kernel: cmp dx,80h ; 8 megs ja kernel_corrupt and dx,dx jnz kernel_sane cmp ax,1024 ; Bootsect + 1 setup sect jb kernel_corrupt kernel_sane: push ax push dx push si mov si,loading_msg call cwritestr ; ; Now start transferring the kernel ; push word real_mode_seg pop es push ax push dx div word [ClustSize] ; # of clusters total and dx,dx ; Round up setnz dl movzx dx,dl add ax,dx mov [KernelClust],ax pop dx pop ax mov [KernelSize],ax mov [KernelSize+2],dx ; ; Now, if we transfer these straight, we'll hit 64K boundaries. Hence we ; have to see if we're loading more than 64K, and if so, load it step by ; step. ; mov dx,1 ; 10000h xor ax,ax div word [ClustSize] mov [ClustPerMoby],ax ; Clusters/64K ; ; Start by loading the bootsector/setup code, to see if we need to ; do something funky. It should fit in the first 32K (loading 64K won't ; work since we might have funny stuff up near the end of memory). ; If we have larger than 32K clusters, yes, we're hosed. ; call abort_check ; Check for abort key mov cx,[ClustPerMoby] shr cx,1 ; Half a moby cmp cx,[KernelClust] jna .normalkernel mov cx,[KernelClust] .normalkernel: sub [KernelClust],cx xor bx,bx pop si ; Cluster pointer on stack call getfssec cmp word [es:bs_bootsign],0AA55h jne near kernel_corrupt ; Boot sec signature missing ; ; Get the BIOS' idea of what the size of high memory is. ; push si ; Save our cluster pointer! ; ; First, try INT 15:E820 (get BIOS memory map) ; get_e820: push es xor ebx,ebx ; Start with first record mov es,bx ; Need ES = DS = 0 for now jmp short .do_e820 ; Skip "at end" check first time! .int_loop: and ebx,ebx ; If we're back at beginning... jz no_e820 ; ... bail; nothing found .do_e820: mov eax,0000E820h mov edx,534D4150h ; "SMAP" backwards mov ecx,20 mov di,E820Buf int 15h jc no_e820 cmp eax,534D4150h jne no_e820 ; ; Look for a memory block starting at <= 1 MB and continuing upward ; cmp dword [E820Buf+4], byte 0 ja .int_loop ; Start >= 4 GB? mov edx, (1 << 20) sub edx, [E820Buf] jb .int_loop ; Start >= 1 MB? mov eax, 0FFFFFFFFh cmp dword [E820Buf+12], byte 0 ja .huge ; Size >= 4 GB mov eax, [E820Buf+8] .huge: sub eax, edx ; Adjust size to start at 1 MB jbe .int_loop ; Completely below 1 MB? ; Now EAX contains the size of memory 1 MB...up cmp dword [E820Buf+16], byte 1 jne near err_nohighmem ; High memory isn't usable memory!!!! ; We're good! pop es jmp short got_highmem_add1mb ; Still need to add low 1 MB ; ; INT 15:E820 failed. Try INT 15:E801. ; no_e820: pop es mov ax,0e801h ; Query high memory (semi-recent) int 15h jc no_e801 cmp ax,3c00h ja no_e801 ; > 3C00h something's wrong with this call jb e801_hole ; If memory hole we can only use low part mov ax,bx shl eax,16 ; 64K chunks add eax,(16 << 20) ; Add first 16M jmp short got_highmem ; ; INT 15:E801 failed. Try INT 15:88. ; no_e801: mov ah,88h ; Query high memory (oldest) int 15h cmp ax,14*1024 ; Don't trust memory >15M jna e801_hole mov ax,14*1024 e801_hole: and eax,0ffffh shl eax,10 ; Convert from kilobytes got_highmem_add1mb: add eax,(1 << 20) ; First megabyte got_highmem: mov [HighMemSize],eax ; ; Construct the command line (append options have already been copied) ; mov di,[CmdLinePtr] mov si,boot_image ; BOOT_IMAGE= mov cx,boot_image_len rep movsb mov si,KernelCName ; Unmangled kernel name mov cx,[KernelCNameLen] rep movsb mov al,' ' ; Space stosb mov si,[CmdOptPtr] ; Options from user input mov cx,(kern_cmd_len+3) >> 2 rep movsd ; %ifdef debug push ds ; DEBUG DEBUG DEBUG push es pop ds mov si,cmd_line_here call cwritestr pop ds call crlf %endif ; ; Scan through the command line for anything that looks like we might be ; interested in. The original version of this code automatically assumed ; the first option was BOOT_IMAGE=, but that is no longer certain. ; mov si,cmd_line_here mov byte [initrd_flag],0 push es ; Set DS <- real_mode_seg pop ds get_next_opt: lodsb and al,al jz near cmdline_end cmp al,' ' jbe get_next_opt dec si mov eax,[si] cmp eax,'vga=' je is_vga_cmd cmp eax,'mem=' je is_mem_cmd push es ; Save ES -> real_mode_seg push ss pop es ; Set ES <- normal DS mov di,initrd_cmd mov cx,initrd_cmd_len repe cmpsb jne not_initrd mov di,InitRD push si ; mangle_dir mangles si call mangle_name ; Mangle ramdisk name pop si cmp byte [es:InitRD],' ' ; Null filename? seta byte [es:initrd_flag] ; Set flag if not not_initrd: pop es ; Restore ES -> real_mode_seg skip_this_opt: lodsb ; Load from command line cmp al,' ' ja skip_this_opt dec si jmp short get_next_opt is_vga_cmd: add si,byte 4 mov eax,[si] mov bx,-1 cmp eax, 'norm' ; vga=normal je vc0 and eax,0ffffffh ; 3 bytes mov bx,-2 cmp eax, 'ext' ; vga=ext je vc0 mov bx,-3 cmp eax, 'ask' ; vga=ask je vc0 call parseint ; vga= jc skip_this_opt ; Not an integer vc0: mov [bs_vidmode],bx ; Set video mode jmp short skip_this_opt is_mem_cmd: add si,byte 4 call parseint jc skip_this_opt ; Not an integer mov [cs:HighMemSize],ebx jmp short skip_this_opt cmdline_end: push cs ; Restore standard DS pop ds sub si,cmd_line_here mov [CmdLineLen],si ; Length including final null ; ; Now check if we have a large kernel, which needs to be loaded high ; mov dword [RamdiskMax], HIGHMEM_MAX ; Default initrd limit cmp dword [es:su_header],HEADER_ID ; New setup code ID jne near old_kernel ; Old kernel, load low cmp word [es:su_version],0200h ; Setup code version 2.0 jb near old_kernel ; Old kernel, load low cmp word [es:su_version],0201h ; Version 2.01+? jb new_kernel ; If 2.00, skip this step mov word [es:su_heapend],linux_stack ; Set up the heap or byte [es:su_loadflags],80h ; Let the kernel know we care cmp word [es:su_version],0203h ; Version 2.03+? jb new_kernel ; Not 2.03+ mov eax,[es:su_ramdisk_max] mov [RamdiskMax],eax ; Set the ramdisk limit ; ; We definitely have a new-style kernel. Let the kernel know who we are, ; and that we are clueful ; new_kernel: mov byte [es:su_loader],syslinux_id ; Show some ID movzx ax,byte [es:bs_setupsecs] ; Variable # of setup sectors mov [SetupSecs],ax ; ; Now see if we have an initial RAMdisk; if so, do requisite computation ; test byte [initrd_flag],1 jz nk_noinitrd push es ; ES->real_mode_seg push ds pop es ; We need ES==DS mov si,InitRD mov di,InitRDCName call unmangle_name ; Create human-readable name sub di,InitRDCName mov [InitRDCNameLen],di mov di,InitRD call searchdir ; Look for it in directory pop es jz initrd_notthere mov [initrd_ptr],si ; Save cluster pointer mov [es:su_ramdisklen1],ax ; Ram disk length mov [es:su_ramdisklen2],dx div word [ClustSize] and dx,dx ; Round up setnz dl movzx dx,dl add ax,dx mov [InitRDClust],ax ; Ramdisk clusters mov edx,[HighMemSize] ; End of memory dec edx mov eax,[RamdiskMax] ; Highest address allowed by kernel cmp edx,eax jna memsize_ok mov edx,eax ; Adjust to fit inside limit memsize_ok: inc edx xor dx,dx ; Round down to 64K boundary sub edx,[es:su_ramdisklen] ; Subtract size of ramdisk xor dx,dx ; Round down to 64K boundary mov [InitRDat],edx ; Load address call loadinitrd ; Load initial ramdisk jmp short initrd_end initrd_notthere: mov si,err_noinitrd call cwritestr mov si,InitRDCName call cwritestr mov si,crlf_msg jmp abort_load no_high_mem: mov si,err_nohighmem ; Error routine jmp abort_load ; ; About to load the kernel. This is a modern kernel, so use the boot flags ; we were provided. ; nk_noinitrd: initrd_end: mov al,[es:su_loadflags] mov [LoadFlags],al ; ; Load the kernel. We always load it at 100000h even if we're supposed to ; load it "low"; for a "low" load we copy it down to low memory right before ; jumping to it. ; read_kernel: mov si,KernelCName ; Print kernel name part of call cwritestr ; "Loading" message mov si,dotdot_msg ; Print dots call cwritestr mov eax,[HighMemSize] sub eax,100000h ; Load address cmp eax,[KernelSize] jb no_high_mem ; Not enough high memory ; ; Move the stuff beyond the setup code to high memory at 100000h ; movzx esi,word [SetupSecs] ; Setup sectors inc esi ; plus 1 boot sector shl esi,9 ; Convert to bytes mov ecx,108000h ; 108000h = 1M + 32K sub ecx,esi ; Adjust pointer to 2nd block mov [HiLoadAddr],ecx sub ecx,100000h ; Turn into a counter shr ecx,2 ; Convert to dwords add esi,(real_mode_seg << 4) ; Pointer to source mov edi,100000h ; Copy to address 100000h call bcopy ; Transfer to high memory push word xfer_buf_seg ; Transfer buffer segment pop es high_load_loop: mov si,dot_msg ; Progress report call cwritestr call abort_check mov cx,[KernelClust] and cx,cx jz high_load_done ; Zero left (tiny kernel?) cmp cx,[ClustPerMoby] jna high_last_moby mov cx,[ClustPerMoby] high_last_moby: sub [KernelClust],cx xor bx,bx ; Load at offset 0 pop si ; Restore cluster pointer call getfssec push si ; Save cluster pointer pushf ; Save EOF xor bx,bx mov esi,(xfer_buf_seg << 4) mov edi,[HiLoadAddr] ; Destination address mov ecx,4000h ; Cheating - transfer 64K call bcopy ; Transfer to high memory mov [HiLoadAddr],edi ; Point to next target area popf ; Restore EOF jc high_load_done ; If EOF we are done cmp word [KernelClust],byte 0 ; Are we done? jne high_load_loop ; Apparently not high_load_done: pop si ; No longer needed mov ax,real_mode_seg ; Set to real mode seg mov es,ax mov si,dot_msg call cwritestr ; ; Abandon hope, ye that enter here! We do no longer permit aborts. ; call abort_check ; Last chance!! mov si,ready_msg call cwritestr call vgaclearmode ; We can't trust ourselves after this ; ; Now, if we were supposed to load "low", copy the kernel down to 10000h ; and the real mode stuff to 90000h. We assume that all bzImage kernels are ; capable of starting their setup from a different address. ; mov bx,real_mode_seg ; Real mode segment mov fs,bx ; FS -> real_mode_seg ; ; Copy command line. Unfortunately, the kernel boot protocol requires ; the command line to exist in the 9xxxxh range even if the rest of the ; setup doesn't. ; cli ; In case of hooked interrupts test byte [LoadFlags],LOAD_HIGH jz need_high_cmdline cmp word [fs:su_version],0202h ; Support new cmdline protocol? jb need_high_cmdline ; New cmdline protocol ; Store 32-bit (flat) pointer to command line mov dword [fs:su_cmd_line_ptr],(real_mode_seg << 4) + cmd_line_here jmp short in_proper_place need_high_cmdline: ; ; Copy command line up to 90000h ; mov ax,9000h mov es,ax mov si,cmd_line_here mov di,si mov [fs:kern_cmd_magic],word CMD_MAGIC ; Store magic mov [fs:kern_cmd_offset],di ; Store pointer mov cx,[CmdLineLen] add cx,byte 3 shr cx,2 ; Convert to dwords fs rep movsd test byte [LoadFlags],LOAD_HIGH ; Note bx -> real_mode_seg still jnz in_proper_place ; If high load, we're done ; ; Loading low; we can't assume it's safe to run in place. ; ; Copy real_mode stuff up to 90000h ; mov ax,real_mode_seg mov fs,ax mov ax,9000h mov es,ax mov cx,[SetupSecs] inc cx ; Setup + boot sector shl cx,7 ; Sectors -> dwords xor si,si xor di,di fs rep movsd ; Copy setup + boot sector ; ; Some kernels in the 1.2 ballpark but pre-bzImage have more than 4 ; setup sectors, but the boot protocol had not yet been defined. They ; rely on a signature to figure out if they need to copy stuff from ; the "protected mode" kernel area. Unfortunately, we used that area ; as a transfer buffer, so it's going to find the signature there. ; Hence, zero the low 32K beyond the setup area. ; mov di,[SetupSecs] inc di ; Setup + boot sector mov cx,32768/512 ; Sectors/32K sub cx,di ; Remaining sectors shl di,9 ; Sectors -> bytes shl cx,7 ; Sectors -> dwords xor eax,eax rep stosd ; Clear region ; mov ecx,[KernelSize] add ecx,3 ; Round upwards shr ecx,2 ; Bytes -> dwords mov esi,100000h mov edi,10000h call bcopy mov bx,9000h ; Real mode segment ; ; Now everything is where it needs to be... ; in_proper_place: mov es,bx ; Real mode segment ; ; If the default root device is set to FLOPPY (0000h), change to ; /dev/fd0 (0200h) ; cmp word [es:bs_rootdev],byte 0 jne root_not_floppy mov word [es:bs_rootdev],0200h root_not_floppy: ; ; Copy the disk table to high memory, then re-initialize the floppy ; controller ; ; This needs to be moved before the copy ; %if 0 push ds push bx lds si,[fdctab] mov di,linux_fdctab mov cx,3 ; 12 bytes push di rep movsd pop di mov [fdctab1],di ; Save new floppy tab pos mov [fdctab2],es xor ax,ax xor dx,dx int 13h pop bx pop ds %endif ; ; Linux wants the floppy motor shut off before starting the kernel, ; at least bootsect.S seems to imply so ; kill_motor: mov dx,03F2h xor al,al call slow_out ; ; If we're debugging, wait for a keypress so we can read any debug messages ; %ifdef debug xor ax,ax int 16h %endif ; ; Set up segment registers and the Linux real-mode stack ; Note: bx == the real mode segment ; cli ; es is already == real mode segment mov ds,bx mov fs,bx mov gs,bx mov ss,bx mov sp,linux_stack ; ; We're done... now RUN THAT KERNEL!!!! ; Setup segment == real mode segment + 020h; we need to jump to offset ; zero in the real mode segment. ; add bx,020h push bx push word 0h retf ; ; Load an older kernel. Older kernels always have 4 setup sectors, can't have ; initrd, and are always loaded low. ; old_kernel: test byte [initrd_flag],1 ; Old kernel can't have initrd jz load_old_kernel mov si,err_oldkernel jmp abort_load load_old_kernel: mov word [SetupSecs],4 ; Always 4 setup sectors mov byte [LoadFlags],0 ; Always low jmp read_kernel ; ; Load a COMBOOT image. A COMBOOT image is basically a DOS .COM file, ; except that it may, of course, not contain any DOS system calls. We ; do, however, allow the execution of INT 20h to return to SYSLINUX. ; is_comboot_image: and dx,dx jnz comboot_too_large cmp ax,0ff00h ; Max size in bytes jae comboot_too_large ; ; Set up the DOS vectors in the IVT (INT 20h-3fh) ; mov dword [4*0x20],comboot_return ; INT 20h vector mov eax,comboot_bogus mov di,4*0x21 mov cx,31 ; All remaining DOS vectors rep stosd mov cx,comboot_seg mov es,cx mov bx,100h ; Load at :0100h mov cx,[ClustPerMoby] ; Absolute maximum # of clusters call getfssec xor di,di mov cx,64 ; 256 bytes (size of PSP) xor eax,eax ; Clear PSP rep stosd mov word [es:0], 020CDh ; INT 20h instruction ; First non-free paragraph mov word [es:02h], comboot_seg+1000h ; Copy the command line from high memory mov cx,125 ; Max cmdline len (minus space and CR) mov si,[CmdOptPtr] mov di,081h ; Offset in PSP for command line mov al,' ' ; DOS command lines begin with a space stosb comboot_cmd_cp: lodsb and al,al jz comboot_end_cmd stosb loop comboot_cmd_cp comboot_end_cmd: mov al,0Dh ; CR after last character stosb mov al,126 ; Include space but not CR sub al,cl mov [es:80h], al ; Store command line length call vgaclearmode ; Reset video mov ax,es mov ds,ax mov ss,ax xor sp,sp push word 0 ; Return to address 0 -> exit jmp comboot_seg:100h ; Run it ; Looks like a COMBOOT image but too large comboot_too_large: mov si,err_comlarge call cwritestr cb_enter: jmp enter_command ; Proper return vector comboot_return: cli ; Don't trust anyone xor ax,ax mov ss,ax mov sp,[ss:SavedSP] mov ds,ax mov es,ax sti cld jmp short cb_enter ; Attempted to execute DOS system call comboot_bogus: cli ; Don't trust anyone xor ax,ax mov ss,ax mov sp,[ss:SavedSP] mov ds,ax mov es,ax sti cld mov si,KernelCName call cwritestr mov si,err_notdos call cwritestr jmp short cb_enter ; ; Load a boot sector ; is_bootsector: ; Transfer zero bytes push word 0 jmp short load_bootsec is_bss_sector: ; Transfer the superblock push word superblock_len load_bootsec: and dx,dx jnz bad_bootsec mov bx,[bsBytesPerSec] cmp ax,bx jne bad_bootsec ; Make sure we don't test this uninitialized mov [bx+trackbuf-2],dx ; Note DX == 0 mov bx,trackbuf mov cx,1 ; 1 cluster >= 1 sector call getfssec mov bx,[bsBytesPerSec] mov ax,[bx+trackbuf-2] cmp ax,0AA55h ; Boot sector signature jne bad_bootsec mov si,superblock mov di,trackbuf+(superblock-bootsec) pop cx ; Transfer count rep movsb ; ; Okay, here we go... copy over our own boot sector and run the new one ; call vgaclearmode ; Reset video cli ; Point of no return mov dl,[bsDriveNumber] ; May not be in new bootsector! mov si,trackbuf mov di,bootsec mov cx,[bsBytesPerSec] rep movsb ; Copy the boot sector! mov si,PartInfo mov di,800h-18 ; Put partition info here push di mov cx,8 ; 16 bytes rep movsw pop si ; DS:SI points to partition info jmp bootsec bad_bootsec: mov si,err_bootsec call cwritestr jmp enter_command ; ; 32-bit bcopy routine for real mode ; ; We enter protected mode, set up a flat 32-bit environment, run rep movsd ; and then exit. IMPORTANT: This code assumes cs == ss == 0. ; ; This code is probably excessively anal-retentive in its handling of ; segments, but this stuff is painful enough as it is without having to rely ; on everything happening "as it ought to." ; align 4 bcopy_gdt: dw bcopy_gdt_size-1 ; Null descriptor - contains GDT dd bcopy_gdt ; pointer for LGDT instruction dw 0 dd 0000ffffh ; Code segment, use16, readable, dd 00009b00h ; present, dpl 0, cover 64K dd 0000ffffh ; Data segment, use16, read/write, dd 008f9300h ; present, dpl 0, cover all 4G dd 0000ffffh ; Data segment, use16, read/write, dd 00009300h ; present, dpl 0, cover 64K bcopy_gdt_size: equ $-bcopy_gdt bcopy: push eax pushf ; Saves, among others, the IF flag push gs push fs push ds push es cli call enable_a20 o32 lgdt [bcopy_gdt] mov eax,cr0 or al,1 mov cr0,eax ; Enter protected mode jmp 08h:.in_pm .in_pm: mov ax,10h ; Data segment selector mov es,ax mov ds,ax mov al,18h ; "Real-mode-like" data segment mov ss,ax mov fs,ax mov gs,ax a32 rep movsd ; Do our business mov es,ax ; Set to "real-mode-like" mov ds,ax mov eax,cr0 and al,~1 mov cr0,eax ; Disable protected mode jmp 0:.in_rm .in_rm: xor ax,ax ; Back in real mode mov ss,ax pop es pop ds pop fs pop gs call disable_a20 popf ; Re-enables interrupts pop eax ret ; ; Routines to enable and disable (yuck) A20. These routines are gathered ; from tips from a couple of sources, including the Linux kernel and ; http://www.x86.org/. The need for the delay to be as large as given here ; is indicated by Donnie Barnes of RedHat, the problematic system being an ; IBM ThinkPad 760EL. ; ; We typically toggle A20 twice for every 64K transferred. ; %define io_delay call _io_delay %define IO_DELAY_PORT 80h ; Invalid port (we hope!) %define disable_wait 32 ; How long to wait for a disable %define A20_DUNNO 0 ; A20 type unknown %define A20_NONE 1 ; A20 always on? %define A20_BIOS 2 ; A20 BIOS enable %define A20_KBC 3 ; A20 through KBC %define A20_FAST 4 ; A20 through port 92h slow_out: out dx, al ; Fall through _io_delay: out IO_DELAY_PORT,al out IO_DELAY_PORT,al ret enable_a20: pushad mov byte [cs:A20Tries],255 ; Times to try to make this work try_enable_a20: ; ; Flush the caches ; ; call try_wbinvd ; ; If the A20 type is known, jump straight to type ; mov bp,[cs:A20Type] add bp,bp ; Convert to word offset jmp word [cs:bp+A20List] ; ; First, see if we are on a system with no A20 gate ; a20_dunno: a20_none: mov byte [cs:A20Type], A20_NONE call a20_test jnz a20_done ; ; Next, try the BIOS (INT 15h AX=2401h) ; a20_bios: mov byte [cs:A20Type], A20_BIOS mov ax,2401h pushf ; Some BIOSes muck with IF int 15h popf call a20_test jnz a20_done ; ; Enable the keyboard controller A20 gate ; a20_kbc: mov dl, 1 ; Allow early exit call empty_8042 jnz a20_done ; A20 live, no need to use KBC mov byte [cs:A20Type], A20_KBC ; Starting KBC command sequence mov al,0D1h ; Command write out 064h, al call empty_8042_uncond mov al,0DFh ; A20 on out 060h, al call empty_8042_uncond ; Verify that A20 actually is enabled. Do that by ; observing a word in low memory and the same word in ; the HMA until they are no longer coherent. Note that ; we don't do the same check in the disable case, because ; we don't want to *require* A20 masking (SYSLINUX should ; work fine without it, if the BIOS does.) .kbc_wait: push cx xor cx,cx .kbc_wait_loop: call a20_test jnz a20_done_pop loop .kbc_wait_loop pop cx ; ; Running out of options here. Final attempt: enable the "fast A20 gate" ; a20_fast: mov byte [cs:A20Type], A20_FAST ; Haven't used the KBC yet in al, 092h or al,02h and al,~01h ; Don't accidentally reset the machine! out 092h, al .fast_wait: push cx xor cx,cx .fast_wait_loop: call a20_test jnz a20_done_pop loop .fast_wait_loop pop cx ; ; Oh bugger. A20 is not responding. Try frobbing it again; eventually give up ; and report failure to the user. ; dec byte [cs:A20Tries] jnz try_enable_a20 mov si, err_a20 jmp abort_load ; ; A20 unmasked, proceed... ; a20_done_pop: pop cx a20_done: popad ret ; ; This routine tests if A20 is enabled (ZF = 0). This routine ; must not destroy any register contents. ; a20_test: push es push cx push ax mov cx,0FFFFh ; HMA = segment 0FFFFh mov es,cx mov cx,32 ; Loop count mov ax,[cs:A20Test] .a20_wait: inc ax mov [cs:A20Test],ax io_delay ; Serialize, and fix delay cmp ax,[es:A20Test+10h] loopz .a20_wait .a20_done: pop ax pop cx pop es ret disable_a20: pushad ; ; Flush the caches ; ; call try_wbinvd mov bp,[cs:A20Type] add bp,bp ; Convert to word offset jmp word [cs:bp+A20DList] a20d_bios: mov ax,2400h pushf ; Some BIOSes muck with IF int 15h popf jmp short a20d_snooze ; ; Disable the "fast A20 gate" ; a20d_fast: in al, 092h and al,~03h out 092h, al jmp short a20d_snooze ; ; Disable the keyboard controller A20 gate ; a20d_kbc: call empty_8042_uncond mov al,0D1h out 064h, al ; Command write call empty_8042_uncond mov al,0DDh ; A20 off out 060h, al call empty_8042_uncond ; Wait a bit for it to take effect a20d_snooze: push cx mov cx, disable_wait .delayloop: call a20_test jz .disabled loop .delayloop .disabled: pop cx a20d_dunno: a20d_none: popad ret ; ; Routine to empty the 8042 KBC controller. If dl != 0 ; then we will test A20 in the loop and exit if A20 is ; suddenly enabled. ; empty_8042_uncond: xor dl,dl empty_8042: call a20_test jz .a20_on and dl,dl jnz .done .a20_on: io_delay in al, 064h ; Status port test al,1 jz .no_output io_delay in al, 060h ; Read input jmp short empty_8042 .no_output: test al,2 jnz empty_8042 io_delay .done: ret ; ; WBINVD instruction; gets auto-eliminated on 386 CPUs ; try_wbinvd: wbinvd ret ; ; Load RAM disk into high memory ; loadinitrd: push es ; Save ES on entry mov ax,real_mode_seg mov es,ax mov si,[initrd_ptr] mov edi,[InitRDat] ; initrd load address mov [es:su_ramdiskat],edi ; Offset for ram disk push si mov si,InitRDCName ; Write ramdisk name call cwritestr mov si,dotdot_msg ; Write dots call cwritestr rd_load_loop: mov si,dot_msg ; Progress report call cwritestr pop si ; Restore cluster pointer call abort_check mov cx,[InitRDClust] cmp cx,[ClustPerMoby] jna rd_last_moby mov cx,[ClustPerMoby] rd_last_moby: sub [InitRDClust],cx xor bx,bx ; Load at offset 0 push word xfer_buf_seg ; Bounce buffer segment pop es push cx call getfssec pop cx push si ; Save cluster pointer mov esi,(xfer_buf_seg << 4) mov edi,[InitRDat] mov ecx,4000h ; Copy 64K call bcopy ; Does not change flags!! jc rd_load_done ; EOF? add dword [InitRDat],10000h ; Point to next 64K cmp word [InitRDClust],byte 0 ; Are we done? jne rd_load_loop ; Apparently not rd_load_done: pop si ; Clean up the stack call crlf mov si,loading_msg ; Write new "Loading " for call cwritestr ; the benefit of the kernel pop es ; Restore original ES ret ; ; 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: mov ax,[bsRootDirEnts] mov [DirScanCtr],ax mov ax,[RootDirSize] mov [DirBlocksLeft],ax mov ax,[RootDir1] mov dx,[RootDir2] scan_group: mov bp,[DirBlocksLeft] and bp,bp jz dir_return cmp bp,[BufSafeSec] jna load_last mov bp,[BufSafeSec] load_last: sub [DirBlocksLeft],bp push ax push dx mov ax,[bsBytesPerSec] mul bp add ax,trackbuf-31 mov [EndofDirSec],ax ; End of loaded pop dx pop ax push bp ; Save number of sectors push ax ; Save present location push dx push di ; Save name mov bx,trackbuf call getlinsec pop di pop dx pop ax pop bp 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 ax,bp ; Increment linear sector number adc dx,byte 0 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: lf_ret: ret ; ; loadfont: Load a .psf font file and install it onto the VGA console ; (if we're not on a VGA screen then ignore.) It is called with ; SI and DX:AX set by routine searchdir ; loadfont: mov bx,trackbuf ; The trackbuf is >= 16K; the part mov cx,[BufSafe] ; of a PSF file we care about is no call getfssec ; more than 8K+4 bytes mov ax,[trackbuf] ; Magic number cmp ax,0436h jne lf_ret mov al,[trackbuf+2] ; File mode cmp al,5 ; Font modes 0-5 supported ja lf_ret mov bh,byte [trackbuf+3] ; Height of font cmp bh,2 ; VGA minimum jb lf_ret cmp bh,32 ; VGA maximum ja lf_ret ; Copy to font buffer mov si,trackbuf+4 ; Start of font data mov [VGAFontSize],bh mov di,vgafontbuf mov cx,(32*256) >> 2 ; Maximum size rep movsd mov [UserFont], byte 1 ; Set font flag ; Fall through to use_font ; ; use_font: ; This routine activates whatever font happens to be in the ; vgafontbuf, and updates the adjust_screen data. ; Must be called with CS = DS = ES ; use_font: test [UserFont], byte 1 ; Are we using a user-specified font? jz adjust_screen ; If not, just do the normal stuff mov bp,vgafontbuf mov bh,[VGAFontSize] xor bl,bl ; Needed by both INT 10h calls cmp [UsingVGA], byte 1 ; Are we in graphics mode? jne .text .graphics: xor cx,cx mov cl,bh ; CX = bytes/character mov ax,480 div cl ; Compute char rows per screen mov dl,al dec al mov [VidRows],al mov ax,1121h ; Set user character table int 10h mov [VidCols], byte 79 ; Always 80 bytes/line mov [TextPage], byte 0 ; Always page 0 ret ; No need to call adjust_screen .text: mov cx,256 xor dx,dx mov ax,1110h int 10h ; Load into VGA RAM xor bl,bl mov ax,1103h ; Select page 0 int 10h ; Fall through to adjust_screen ; ; adjust_screen: Set the internal variables associated with the screen size. ; This is a subroutine in case we're loading a custom font. ; adjust_screen: mov al,[BIOS_vidrows] and al,al jnz vidrows_is_ok mov al,24 ; No vidrows in BIOS, assume 25 ; (Remember: vidrows == rows-1) vidrows_is_ok: mov [VidRows],al mov ah,0fh int 10h ; Read video state mov [TextPage],bh dec ah ; Store count-1 (same as rows) mov [VidCols],ah ret ; ; loadkeys: Load a LILO-style keymap; SI and DX:AX set by searchdir ; loadkeys: and dx,dx ; Should be 256 bytes exactly jne loadkeys_ret cmp ax,256 jne loadkeys_ret mov bx,trackbuf mov cx,1 ; 1 cluster should be >= 256 bytes call getfssec mov si,trackbuf mov di,KbdMap mov cx,256 >> 2 rep movsd loadkeys_ret: ret ; ; get_msg_file: Load a text file and write its contents to the screen, ; interpreting color codes. Is called with SI and DX:AX ; set by routine searchdir ; get_msg_file: push es shl edx,16 ; EDX <- DX:AX (length of file) mov dx,ax mov ax,xfer_buf_seg ; Use for temporary storage mov es,ax mov byte [TextAttribute],07h ; Default grey on white mov byte [DisplayMask],07h ; Display text in all modes call msg_initvars get_msg_chunk: push edx ; EDX = length of file xor bx,bx ; == xbs_textbuf mov cx,[BufSafe] call getfssec pop edx push si ; Save current cluster xor si,si ; == xbs_textbuf mov cx,[BufSafeBytes] ; Number of bytes left in chunk print_msg_file: push cx push edx es lodsb cmp al,1Ah ; DOS EOF? je msg_done_pop push si mov cl,[UsingVGA] inc cl ; 01h = text mode, 02h = graphics call [NextCharJump] ; Do what shall be done pop si pop edx pop cx dec edx jz msg_done loop print_msg_file pop si jmp short get_msg_chunk msg_done_pop: add sp,byte 6 ; Drop pushed EDX, CX msg_done: pop si pop es ret msg_putchar: ; Normal character cmp al,0Fh ; ^O = color code follows je msg_ctrl_o cmp al,0Dh ; Ignore je msg_ignore cmp al,0Ah ; = newline je msg_newline cmp al,0Ch ; = clear screen je msg_formfeed cmp al,19h ; = return to text mode je near msg_novga cmp al,18h ; = VGA filename follows je near msg_vga jnb .not_modectl cmp al,10h ; 10h to 17h are mode controls jae near msg_modectl .not_modectl: msg_normal: call write_serial_displaymask ; Write to serial port test [DisplayMask],cl jz msg_ignore ; Not screen mov bx,[TextAttrBX] mov ah,09h ; Write character/attribute mov cx,1 ; One character only int 10h ; Write to screen mov al,[CursorCol] inc ax cmp al,[VidCols] ja msg_line_wrap ; Screen wraparound mov [CursorCol],al msg_gotoxy: mov bh,[TextPage] mov dx,[CursorDX] mov ah,02h ; Set cursor position int 10h msg_ignore: ret msg_ctrl_o: ; ^O = color code follows mov word [NextCharJump],msg_setbg ret msg_newline: ; Newline char or end of line mov si,crlf_msg call write_serial_str_displaymask msg_line_wrap: ; Screen wraparound test [DisplayMask],cl jz msg_ignore mov byte [CursorCol],0 mov al,[CursorRow] inc ax cmp al,[VidRows] ja msg_scroll mov [CursorRow],al jmp short msg_gotoxy msg_scroll: xor cx,cx ; Upper left hand corner mov dx,[ScreenSize] mov [CursorRow],dh ; New cursor at the bottom mov bh,[ScrollAttribute] mov ax,0601h ; Scroll up one line int 10h jmp short msg_gotoxy msg_formfeed: ; Form feed character mov si,crff_msg call write_serial_str_displaymask test [DisplayMask],cl jz msg_ignore xor cx,cx mov [CursorDX],cx ; Upper lefthand corner mov dx,[ScreenSize] mov bh,[TextAttribute] mov ax,0600h ; Clear screen region int 10h jmp short msg_gotoxy msg_setbg: ; Color background character call unhexchar jc msg_color_bad shl al,4 test [DisplayMask],cl jz .dontset mov [TextAttribute],al .dontset: mov word [NextCharJump],msg_setfg ret msg_setfg: ; Color foreground character call unhexchar jc msg_color_bad test [DisplayMask],cl jz .dontset or [TextAttribute],al ; setbg set foreground to 0 .dontset: jmp short msg_putcharnext msg_vga: mov word [NextCharJump],msg_filename mov di, VGAFileBuf jmp short msg_setvgafileptr msg_color_bad: mov byte [TextAttribute],07h ; Default attribute msg_putcharnext: mov word [NextCharJump],msg_putchar ret msg_filename: ; Getting VGA filename cmp al,0Ah ; = end of filename je msg_viewimage cmp al,' ' jbe msg_ret ; Ignore space/control char mov di,[VGAFilePtr] cmp di,VGAFileBufEnd jnb msg_ret mov [di],al ; Can't use stosb (DS:) inc di msg_setvgafileptr: mov [VGAFilePtr],di msg_ret: ret msg_novga: call vgaclearmode jmp short msg_initvars msg_viewimage: push es push ds pop es ; ES <- DS mov si,VGAFileBuf mov di,VGAFileMBuf push di call mangle_name pop di call searchdir pop es jz msg_putcharnext ; Not there call vgadisplayfile ; Fall through ; Subroutine to initialize variables, also needed ; after loading a graphics file msg_initvars: pusha mov bh,[TextPage] mov ah,03h ; Read cursor position int 10h mov [CursorDX],dx popa jmp short msg_putcharnext ; Initialize state machine msg_modectl: and al,07h mov [DisplayMask],al jmp short msg_putcharnext ; ; write_serial: If serial output is enabled, write character on serial port ; write_serial_displaymask: d:o, but ignore if DisplayMask & 04h == 0 ; write_serial_displaymask: test byte [DisplayMask], 04h jz write_serial.end write_serial: pushfd pushad mov bx,[SerialPort] and bx,bx je .noserial push ax mov ah,[FlowInput] .waitspace: ; Wait for space in transmit register lea dx,[bx+5] ; DX -> LSR in al,dx test al,20h jz .waitspace ; Wait for input flow control inc dx ; DX -> MSR in al,dx and al,ah cmp al,ah jne .waitspace .no_flow: xchg dx,bx ; DX -> THR pop ax call slow_out ; Send data .noserial: popad popfd .end: ret ; ; write_serial_str: write_serial for strings ; write_serial_str_displaymask: d:o, but ignore if DisplayMask & 04h == 0 ; write_serial_str_displaymask: test byte [DisplayMask], 04h jz write_serial_str.end write_serial_str: .loop lodsb and al,al jz .end call write_serial jmp short .loop .end: ret ; ; writechr: Write a single character in AL to the console without ; mangling any registers ; writechr: call write_serial ; write to serial port if needed pushfd pushad mov ah,0Eh mov bx,0007h ; white text on this page int 10h popad popfd ret ; ; crlf: Print a newline ; crlf: mov si,crlf_msg ; Fall through ; ; cwritestr: write a null-terminated string to the console, saving ; registers on entry. ; cwritestr: pushfd pushad .top: lodsb and al,al jz .end call writechr jmp short .top .end: popad popfd ret %ifdef debug ; ; writehex[248]: Write a hex number in (AL, AX, EAX) to the console ; writehex2: pushfd pushad rol eax,24 mov cx,2 jmp short writehex_common writehex4: pushfd pushad rol eax,16 mov cx,4 jmp short writehex_common writehex8: pushfd pushad mov cx,8 writehex_common: .loop: rol eax,4 push eax and al,0Fh cmp al,10 jae .high .low: add al,'0' jmp short .ischar .high: add al,'A'-10 .ischar: call writechr pop eax loop .loop popad popfd ret ; ; crlf: write CR LF ; crlf: push ax mov al, 13 call writechr mov al, 10 call writechr pop ax ret %endif ; ; pollchar: check if we have an input character pending (ZF = 0) ; pollchar: pushad mov ah,1 ; Poll keyboard int 16h jnz .done ; Keyboard response mov dx,[SerialPort] and dx,dx jz .done ; No serial port -> no input add dx,byte 5 ; DX -> LSR in al,dx test al,1 ; ZF = 0 if data pending jz .done inc dx ; DX -> MSR mov ah,[FlowIgnore] ; Required status bits in al,dx and al,ah cmp al,ah setne al dec al ; Set ZF = 0 if equal .done: popad ret ; ; getchar: Read a character from keyboard or serial port ; getchar: .again: mov ah,1 ; Poll keyboard int 16h jnz .kbd ; Keyboard input? mov bx,[SerialPort] and bx,bx jz .again lea dx,[bx+5] ; DX -> LSR in al,dx test al,1 jz .again inc dx ; DX -> MSR mov ah,[FlowIgnore] in al,dx and al,ah cmp al,ah jne .again .serial: xor ah,ah ; Avoid confusion xchg dx,bx ; Data port in al,dx ret .kbd: xor ax,ax ; Get keyboard input int 16h and al,al jz .func_key mov bx,KbdMap ; Convert character sets xlatb .func_key: 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 ; ; open,getc: Load a file a character at a time for parsing in a manner ; similar to the C library getc routine. Only one simultaneous ; use is supported. Note: "open" trashes the trackbuf. ; ; open: Input: mangled filename in DS:DI ; Output: ZF set on file not found or zero length ; ; getc: Output: CF set on end of file ; Character loaded in AL ; open: call searchdir jz open_return pushf mov [FBytes1],ax mov [FBytes2],dx add ax,[ClustSize] adc dx,byte 0 sub ax,byte 1 sbb dx,byte 0 div word [ClustSize] mov [FClust],ax ; Number of clusters mov [FNextClust],si ; Cluster pointer mov ax,[EndOfGetCBuf] ; Pointer at end of buffer -> mov [FPtr],ax ; nothing loaded yet popf ; Restore no ZF open_return: ret ; getc: stc ; If we exit here -> EOF mov ecx,[FBytes] jecxz getc_ret mov si,[FPtr] cmp si,[EndOfGetCBuf] jb getc_loaded ; Buffer empty -- load another set mov cx,[FClust] cmp cx,[BufSafe] jna getc_oksize mov cx,[BufSafe] getc_oksize: sub [FClust],cx ; Reduce remaining clusters mov si,[FNextClust] mov bx,getcbuf push bx push es ; ES may be != DS, save old ES push ds ; Trackbuf is in DS, not ES pop es call getfssec ; Load a trackbuf full of data mov [FNextClust],si ; Store new next pointer pop es ; Restore ES pop si ; SI -> newly loaded data getc_loaded: lodsb ; Load a byte mov [FPtr],si ; Update next byte pointer dec dword [FBytes] ; Update bytes left counter (CF = 1) clc ; Not EOF getc_ret: ret ; ; ungetc: Push a character (in AL) back into the getc buffer ; Note: if more than one byte is pushed back, this may cause ; bytes to be written below the getc buffer boundary. If there ; is a risk for this to occur, the getcbuf base address should ; be moved up. ; ungetc: mov si,[FPtr] dec si mov [si],al mov [FPtr],si inc dword [FBytes] ret ; ; skipspace: Skip leading whitespace using "getc". If we hit end-of-line ; or end-of-file, return with carry set; ZF = true of EOF ; ZF = false for EOLN; otherwise CF = ZF = 0. ; ; Otherwise AL = first character after whitespace ; skipspace: skipspace_loop: call getc jc skipspace_eof cmp al,1Ah ; DOS EOF je skipspace_eof cmp al,0Ah je skipspace_eoln cmp al,' ' jbe skipspace_loop ret ; CF = ZF = 0 skipspace_eof: cmp al,al ; Set ZF stc ; Set CF ret skipspace_eoln: add al,0FFh ; Set CF, clear ZF ret ; ; getkeyword: Get a keyword from the current "getc" file; only the two ; first characters are considered significant. ; ; Lines beginning with ASCII characters 33-47 are treated ; as comments and ignored; other lines are checked for ; validity by scanning through the keywd_table. ; ; The keyword and subsequent whitespace is skipped. ; ; On EOF, CF = 1; otherwise, CF = 0, AL:AH = lowercase char pair ; getkeyword: gkw_find: call skipspace jz gkw_eof ; end of file jc gkw_find ; end of line: try again cmp al,'0' jb gkw_skipline ; skip comment line push ax call getc pop bx jc gkw_eof mov bh,al ; Move character pair into BL:BH or bx,2020h ; Lower-case it mov si,keywd_table gkw_check: lodsw and ax,ax jz gkw_badline ; Bad keyword, write message cmp ax,bx jne gkw_check push ax gkw_skiprest: call getc jc gkw_eof_pop cmp al,'0' ja gkw_skiprest call ungetc call skipspace jz gkw_eof_pop jc gkw_missingpar ; Missing parameter after keyword call ungetc ; Return character to buffer clc ; Successful return gkw_eof_pop: pop ax gkw_eof: ret ; CF = 1 on all EOF conditions gkw_missingpar: pop ax mov si,err_noparm call cwritestr jmp gkw_find gkw_badline_pop: pop ax gkw_badline: mov si,err_badcfg call cwritestr jmp short gkw_find gkw_skipline: cmp al,10 ; Scan for LF je gkw_find call getc jc gkw_eof jmp short gkw_skipline ; ; getint: Load an integer from the getc file. ; Return CF if error; otherwise return integer in EBX ; getint: mov di,NumBuf gi_getnum: cmp di,NumBufEnd ; Last byte in NumBuf jae gi_loaded push di call getc pop di jc gi_loaded stosb cmp al,'-' jnb gi_getnum call ungetc ; Unget non-numeric gi_loaded: mov byte [di],0 mov si,NumBuf ; Fall through to parseint ; ; parseint: Convert an integer to a number in EBX ; Get characters from string in DS:SI ; Return CF on error ; DS:SI points to first character after number ; ; Syntaxes accepted: [-]dec, [-]0+oct, [-]0x+hex, val+K, val+M ; parseint: push eax push ecx push bp xor eax,eax ; Current digit (keep eax == al) mov ebx,eax ; Accumulator mov ecx,ebx ; Base xor bp,bp ; Used for negative flag pi_begin: lodsb cmp al,'-' jne pi_not_minus xor bp,1 ; Set unary minus flag jmp short pi_begin pi_not_minus: cmp al,'0' jb pi_err je pi_octhex cmp al,'9' ja pi_err mov cl,10 ; Base = decimal jmp short pi_foundbase pi_octhex: lodsb cmp al,'0' jb pi_km ; Value is zero or al,20h ; Downcase cmp al,'x' je pi_ishex cmp al,'7' ja pi_err mov cl,8 ; Base = octal jmp short pi_foundbase pi_ishex: mov al,'0' ; No numeric value accrued yet mov cl,16 ; Base = hex pi_foundbase: call unhexchar jc pi_km ; Not a (hex) digit cmp al,cl jae pi_km ; Invalid for base imul ebx,ecx ; Multiply accumulated by base add ebx,eax ; Add current digit lodsb jmp short pi_foundbase pi_km: dec si ; Back up to last non-numeric lodsb or al,20h cmp al,'k' je pi_isk cmp al,'m' je pi_ism dec si ; Back up pi_fini: and bp,bp jz pi_ret ; CF=0! neg ebx ; Value was negative pi_done: clc pi_ret: pop bp pop ecx pop eax ret pi_err: stc jmp short pi_ret pi_isk: shl ebx,10 ; x 2^10 jmp short pi_done pi_ism: shl ebx,20 ; x 2^20 jmp short pi_done ; ; unhexchar: Convert a hexadecimal digit in AL to the equivalent number; ; return CF=1 if not a hex digit ; unhexchar: cmp al,'0' jb uxc_ret ; If failure, CF == 1 already cmp al,'9' ja uxc_1 sub al,'0' ; CF <- 0 ret uxc_1: or al,20h ; upper case -> lower case cmp al,'a' jb uxc_ret ; If failure, CF == 1 already cmp al,'f' ja uxc_err sub al,'a'-10 ; CF <- 0 ret uxc_err: stc uxc_ret: ret ; ; ; getline: Get a command line, converting control characters to spaces ; and collapsing streches to one; a space is appended to the ; end of the string, unless the line is empty. ; The line is terminated by ^J, ^Z or EOF and is written ; to ES:DI. On return, DI points to first char after string. ; CF is set if we hit EOF. ; getline: call skipspace mov dl,1 ; Empty line -> empty string. jz gl_eof ; eof jc gl_eoln ; eoln call ungetc gl_fillloop: push dx push di call getc pop di pop dx jc gl_ret ; CF set! cmp al,' ' jna gl_ctrl xor dx,dx gl_store: stosb jmp short gl_fillloop gl_ctrl: cmp al,10 je gl_ret ; CF clear! cmp al,26 je gl_eof and dl,dl jnz gl_fillloop ; Ignore multiple spaces mov al,' ' ; Ctrl -> space inc dx jmp short gl_store gl_eoln: clc ; End of line is not end of file jmp short gl_ret gl_eof: stc gl_ret: pushf ; We want the last char to be space! and dl,dl jnz gl_xret mov al,' ' stosb gl_xret: popf ret ; ; 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 ; ---------------------------------------------------------------------------------- ; VGA splash screen code ; ---------------------------------------------------------------------------------- ; ; vgadisplayfile: ; Display a graphical splash screen. ; ; Input: ; ; SI = cluster/socket pointer ; vgadisplayfile: mov [VGACluster],si push es ; This is a cheap and easy way to make sure the screen is ; cleared in case we were in graphics mode already call vgaclearmode call vgasetmode jnz .error_nz .graphalready: mov ax,xfer_buf_seg ; Use as temporary storage mov es,ax mov fs,ax call vgagetchunk ; Get the first chunk ; The header WILL be in the first chunk. cmp dword [es:xbs_vgabuf],0x1413f33d ; Magic number .error_nz: jne near .error mov ax,[es:xbs_vgabuf+4] mov [GraphXSize],ax mov dx,xbs_vgabuf+8 ; Color map offset mov ax,1012h ; Set RGB registers xor bx,bx ; First register number mov cx,16 ; 16 registers int 10h .movecursor: mov ax,[es:xbs_vgabuf+6] ; Number of pixel rows mov dx,[VGAFontSize] add ax,dx dec ax div dl xor dx,dx ; Set column to 0 cmp al,[VidRows] jb .rowsok mov al,[VidRows] dec al .rowsok: mov dh,al mov ah,2 xor bx,bx int 10h ; Set cursor below image mov cx,[es:xbs_vgabuf+6] ; Number of graphics rows mov si,xbs_vgabuf+8+3*16 ; Beginning of pixel data mov word [VGAPos],0 .drawpixelrow: push cx mov cx,[GraphXSize] mov di,xbs_vgatmpbuf ; Row buffer call rledecode ; Decode one row push si mov si,xbs_vgatmpbuf mov di,si add di,[GraphXSize] mov cx,640/4 xor eax,eax rep stosd ; Clear rest of row mov di,0A000h ; VGA segment mov es,di mov di,[VGAPos] mov bp,640 call packedpixel2vga add word [VGAPos],byte 80 ; Advance to next pixel row push fs pop es pop si pop cx loop .drawpixelrow .error: pop es ret ; ; rledecode: ; Decode a pixel row in RLE16 format. ; ; FS:SI -> input ; CX -> pixel count ; ES:DI -> output (packed pixel) ; rledecode: shl esi,1 ; Nybble pointer xor dl,dl ; Last pixel .loop: call .getnybble cmp al,dl je .run ; Start of run sequence stosb mov dl,al dec cx jnz .loop .done: shr esi,1 adc si,byte 0 ret .run: xor bx,bx call .getnybble and al,al jz .longrun mov bl,al .dorun: push cx mov cx,bx mov al,dl rep stosb pop cx sub cx,bx ja .loop jmp short .done .longrun: call .getnybble mov ah,al call .getnybble shl al,4 or al,ah mov bl,al add bx,16 jmp short .dorun .getnybble: shr esi,1 fs lodsb jc .high dec si and al,0Fh stc rcl esi,1 ret .high: shr al,4 cmp si,xbs_vgabuf+trackbufsize ; Chunk overrun jb .nonewchunk call vgagetchunk mov si,xbs_vgabuf ; Start at beginning of buffer .nonewchunk: shl esi,1 ret ; ; vgagetchunk: ; Get a new trackbufsize chunk of VGA image data ; ; On input, ES is assumed to point to the buffer segment. ; vgagetchunk: pushad mov si,[VGACluster] and si,si jz .eof ; EOF overrun, not much to do... mov cx,[BufSafe] ; One trackbuf worth of data mov bx,xbs_vgabuf call getfssec jnc .noteof xor si,si .noteof: mov [VGACluster],si .eof: popad ret ; ; packedpixel2vga: ; Convert packed-pixel to VGA bitplanes ; ; FS:SI -> packed pixel string ; BP -> pixel count (multiple of 8) ; ES:DI -> output ; packedpixel2vga: mov dx,3C4h ; VGA Sequencer Register select port mov al,2 ; Sequencer mask out dx,al ; Select the sequencer mask inc dx ; VGA Sequencer Register data port mov al,1 mov bl,al .planeloop: pusha out dx,al .loop1: mov cx,8 .loop2: xchg cx,bx fs lodsb shr al,cl rcl ch,1 ; VGA is bigendian. Sigh. xchg cx,bx loop .loop2 mov al,bh stosb sub bp,byte 8 ja .loop1 popa inc bl shl al,1 cmp bl,4 jbe .planeloop ret ; ; vgasetmode: ; Enable VGA graphics, if possible; return ZF=1 on success ; DS must be set to the base segment; ES is set to DS. ; vgasetmode: push ds pop es mov ax,1A00h ; Get video card and monitor xor bx,bx int 10h cmp bl, 8 ; If not VGA card/VGA monitor, give up jne .error ; ZF=0 ; mov bx,TextColorReg ; mov dx,1009h ; Read color registers ; int 10h mov ax,0012h ; Set mode = 640x480 VGA 16 colors int 10h mov dx,linear_color mov ax,1002h ; Write color registers int 10h mov [UsingVGA], byte 1 call use_font ; Set graphics font/data mov byte [ScrollAttribute], 00h xor ax,ax ; Set ZF .error: ret ; ; vgaclearmode: ; Disable VGA graphics. It is not safe to assume any value ; for DS or ES. ; vgaclearmode: push ds push es pushad mov ax,cs mov ds,ax mov es,ax cmp [UsingVGA], byte 1 jne .done mov ax,0003h ; Return to normal video mode int 10h ; mov dx,TextColorReg ; Restore color registers ; mov ax,1002h ; int 10h mov [UsingVGA], byte 0 call use_font ; Restore text font/data mov byte [ScrollAttribute], 07h .done: popad pop es pop ds ret ; ; vgashowcursor/vgahidecursor: ; If VGA graphics is enabled, draw a cursor/clear a cursor ; vgashowcursor: pushad mov al,'_' jmp short vgacursorcommon vgahidecursor: pushad mov al,' ' vgacursorcommon: cmp [UsingVGA], byte 1 jne .done mov ah,09h mov bx,0007h mov cx,1 int 10h .done: popad ret ; Map colors to consecutive DAC registers linear_color db 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0 UsingVGA db 0 ; ---------------------------------------------------------------------------------- ; Begin data section ; ---------------------------------------------------------------------------------- CR equ 13 ; Carriage Return LF equ 10 ; Line Feed FF equ 12 ; Form Feed BS equ 8 ; Backspace ; ; 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_not386 db 'It appears your computer uses a 286 or lower CPU.' db CR, LF db 'You cannot run Linux unless you have a 386 or higher CPU' db CR, LF db 'in your machine. If you get this message in error, hold' db CR, LF db 'down the Ctrl key while booting, and I will take your' db CR, LF db 'word for it.', CR, LF, 0 err_noram db 'It appears your computer has less than 512K 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_bootsec db 'Invalid or corrupt boot sector image.', 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 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, 0 crff_msg db CR, FF, 0 syslinux_cfg db 'SYSLINUXCFG' ; ; 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 ; align 2 keywd_table db 'ap' ; append db 'de' ; default db 'ti' ; timeout db 'fo' ; font db 'kb' ; kbd db 'di' ; display db 'pr' ; prompt db 'la' ; label db 'im' ; implicit db 'ke' ; kernel db 'se' ; serial db 'f1' ; F1 db 'f2' ; F2 db 'f3' ; F3 db 'f4' ; F4 db 'f5' ; F5 db 'f6' ; F6 db 'f7' ; F7 db 'f8' ; F8 db 'f9' ; F9 db 'f0' ; F10 dw 0 ; ; Extensions to search for (in *reverse* order). Note that the last ; (lexically first) entry in the table is a placeholder for the original ; extension, needed for error messages. The exten_table is shifted so ; the table is 1-based; this is because a "loop" cx is used as index. ; exten_table: OrigKernelExt: dd 0 ; Original extension db 'COM',0 ; COMBOOT (same as DOS) db 'BS ',0 ; Boot Sector db 'BSS',0 ; Boot Sector (add superblock) db 'CBT',0 ; COMBOOT (specific) exten_count equ (($-exten_table) >> 2) - 1 ; Number of alternates ; ; 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 KbdTimeOut dw 0 ; Keyboard timeout (if any) FKeyMap dw 0 ; Bitmap for F-keys loaded 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 SerialPort dw 0 ; Serial port base (or 0 for no serial port) A20List dw a20_dunno, a20_none, a20_bios, a20_kbc, a20_fast A20DList dw a20d_dunno, a20d_none, a20d_bios, a20d_kbc, a20d_fast A20Type dw A20_DUNNO ; A20 type unknown 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 align 4, db 0 ; For the good of REP MOVSD command_line equ $ default_cmd equ $+(max_cmd_len+2) ldlinux_end equ default_cmd+(max_cmd_len+1) kern_cmd_len equ ldlinux_end-command_line ldlinux_len equ ldlinux_end-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 %if (getcbuf+trackbufsize) > vgafontbuf %error "Out of memory, better reorganize something..." %endif