1 ; -*- fundamental -*- (asm-mode sucks)
3 ; ****************************************************************************
7 ; A program to boot Linux kernels off an MS-DOS formatted floppy disk. This
8 ; functionality is good to have for installation floppies, where it may
9 ; be hard to find a functional Linux system to run LILO off.
11 ; This program allows manipulation of the disk to take place entirely
12 ; from MS-LOSS, and can be especially useful in conjunction with the
15 ; Copyright (C) 1994-2004 H. Peter Anvin
17 ; This program is free software; you can redistribute it and/or modify
18 ; it under the terms of the GNU General Public License as published by
19 ; the Free Software Foundation, Inc., 53 Temple Place Ste 330,
20 ; Boston MA 02111-1307, USA; either version 2 of the License, or
21 ; (at your option) any later version; incorporated herein by reference.
23 ; ****************************************************************************
32 %include "tracers.inc"
35 ; Some semi-configurable constants... change on your own risk.
38 FILENAME_MAX_LG2 equ 4 ; log2(Max filename size Including final null)
39 FILENAME_MAX equ 11 ; Max mangled filename size
40 NULLFILE equ ' ' ; First char space == null filename
41 NULLOFFSET equ 0 ; Position in which to look
42 retry_count equ 6 ; How patient are we with the disk?
43 %assign HIGHMEM_SLOP 0 ; Avoid this much memory near the top
44 LDLINUX_MAGIC equ 0x3eb202fe ; A random number to identify ourselves with
46 MAX_OPEN_LG2 equ 6 ; log2(Max number of open files)
47 MAX_OPEN equ (1 << MAX_OPEN_LG2)
50 SECTOR_SIZE equ (1 << SECTOR_SHIFT)
53 ; This is what we need to do when idle
63 ; The following structure is used for "virtual kernels"; i.e. LILO-style
64 ; option labels. The options we permit here are `kernel' and `append
65 ; Since there is no room in the bottom 64K for all of these, we
66 ; stick them at vk_seg:0000 and copy them down before we need them.
69 vk_vname: resb FILENAME_MAX ; Virtual name **MUST BE FIRST!**
70 vk_rname: resb FILENAME_MAX ; Real name
73 vk_append: resb max_cmd_len+1 ; Command line
75 vk_end: equ $ ; Should be <= vk_size
79 ; Segment assignments in the bottom 640K
80 ; Stick to the low 512K in case we're using something like M-systems flash
81 ; which load a driver into low RAM (evil!!)
83 ; 0000h - main code/data segment (and BIOS segment)
85 real_mode_seg equ 4000h
86 cache_seg equ 3000h ; 64K area for metadata cache
87 vk_seg equ 2000h ; Virtual kernels
88 xfer_buf_seg equ 1000h ; Bounce buffer for I/O to high mem
89 comboot_seg equ real_mode_seg ; COMBOOT image loading zone
92 ; File structure. This holds the information for each currently open file.
95 file_sector resd 1 ; Sector pointer (0 = structure free)
96 file_left resd 1 ; Number of sectors left
100 %if (open_file_t_size & (open_file_t_size-1))
101 %error "open_file_t is not a power of 2"
105 ; ---------------------------------------------------------------------------
107 ; ---------------------------------------------------------------------------
110 ; Memory below this point is reserved for the BIOS and the MBR
113 trackbufsize equ 8192
114 trackbuf resb trackbufsize ; Track buffer goes here
115 getcbuf resb trackbufsize
121 ; Expanded superblock
123 resq 16 ; The first 16 bytes expanded 8 times
124 FAT resd 1 ; Location of (first) FAT
125 RootDirArea resd 1 ; Location of root directory area
126 RootDir resd 1 ; Location of root directory proper
127 DataArea resd 1 ; Location of data area
128 RootDirSize resd 1 ; Root dir size in sectors
129 TotalSectors resd 1 ; Total number of sectors
130 EndSector resd 1 ; Location of filesystem end
131 ClustSize resd 1 ; Bytes/cluster
132 ClustMask resd 1 ; Sectors/cluster - 1
133 CopySuper resb 1 ; Distinguish .bs versus .bss
134 DriveNumber resb 1 ; BIOS drive number
135 ClustShift resb 1 ; Shift count for sectors/cluster
136 ClustByteShift resb 1 ; Shift count for bytes/cluster
138 alignb open_file_t_size
139 Files resb MAX_OPEN*open_file_t_size
142 ; Constants for the xfer_buf_seg
144 ; The xfer_buf_seg is also used to store message file buffers. We
145 ; need two trackbuffers (text and graphics), plus a work buffer
146 ; for the graphics decompressor.
148 xbs_textbuf equ 0 ; Also hard-coded, do not change
149 xbs_vgabuf equ trackbufsize
150 xbs_vgatmpbuf equ 2*trackbufsize
155 ; Some of the things that have to be saved very early are saved
156 ; "close" to the initial stack pointer offset, in order to
157 ; reduce the code size...
159 StackBuf equ $-44-32 ; Start the stack here (grow down - 4K)
160 PartInfo equ StackBuf ; Saved partition table entry
161 FloppyTable equ PartInfo+16 ; Floppy info table (must follow PartInfo)
162 OrigFDCTabPtr equ StackBuf-4 ; The high dword on the stack
165 ; Primary entry point. Tempting as though it may be, we can't put the
166 ; initial "cli" here; the jmp opcode in the first byte is part of the
167 ; "magic number" (using the term very loosely) for the DOS superblock.
170 jmp short start ; 2 bytes
173 ; "Superblock" follows -- it's in the boot sector, so it's already
174 ; loaded and ready for us
176 bsOemName db 'SYSLINUX' ; The SYS command sets this, so...
178 ; These are the fields we actually care about. We end up expanding them
179 ; all to dword size early in the code, so generate labels for both
180 ; the expanded and unexpanded versions.
183 bx %+ %1 equ SuperInfo+($-superblock)*8+4
188 bx %+ %1 equ SuperInfo+($-superblock)*8
193 bx %+ %1 equ $ ; no expansion for dwords
208 superinfo_size equ ($-superblock)-1 ; How much to expand
212 ; This is as far as FAT12/16 and FAT32 are consistent
214 zb 54 ; FAT12/16 need 26 more bytes,
215 ; FAT32 need 54 more bytes
216 superblock_len equ $-superblock
218 SecPerClust equ bxSecPerClust
220 ; Note we don't check the constraints above now; we did that at install
224 cli ; No interrupts yet, please
231 mov sp,StackBuf ; Just below BSS
234 ; DS:SI may contain a partition table entry. Preserve it for us.
236 mov cx,8 ; Save partition info
240 mov ds,ax ; Now we can initialize DS...
243 ; Now sautee the BIOS floppy info block to that it will support decent-
244 ; size transfers; the floppy block is 11 bytes and is stored in the
245 ; INT 1Eh vector (brilliant waste of resources, eh?)
247 ; Of course, if BIOSes had been properly programmed, we wouldn't have
248 ; had to waste precious space with this code.
251 lfs si,[bx] ; FS:SI -> original fdctab
252 push fs ; Save on stack in case we need to bail
255 ; Save the old fdctab even if hard disk so the stack layout
256 ; is the same. The instructions above do not change the flags
257 mov [DriveNumber],dl ; Save drive number in DL
258 and dl,dl ; If floppy disk (00-7F), assume no
263 mov cl,6 ; 12 bytes (CX == 0)
264 ; es:di -> FloppyTable already
265 ; This should be safe to do now, interrupts are off...
266 mov [bx],di ; FloppyTable
267 mov [bx+2],ax ; Segment 0
268 fs rep movsw ; Faster to move words
269 mov cl,[bsSecPerTrack] ; Patch the sector count
272 int 13h ; Some BIOSes need this
274 jmp short not_harddisk
276 ; The drive number and possibly partition information was passed to us
277 ; by the BIOS or previous boot loader (MBR). Current "best practice" is to
278 ; trust that rather than what the superblock contains.
280 ; Would it be better to zero out bsHidden if we don't have a partition table?
282 ; Note: di points to beyond the end of PartInfo
285 test byte [di-16],7Fh ; Sanity check: "active flag" should
286 jnz no_partition ; be 00 or 80
287 mov eax,[di-8] ; Partition offset (dword)
291 ; Get disk drive parameters (don't trust the superblock.) Don't do this for
292 ; floppy drives -- INT 13:08 on floppy drives will (may?) return info about
293 ; what the *drive* supports, not about the *media*. Fortunately floppy disks
294 ; tend to have a fixed, well-defined geometry which is stored in the superblock.
296 ; DL == drive # still
303 inc dx ; Contains # of heads - 1
306 mov [bsSecPerTrack],cx
310 ; Ready to enable interrupts, captain
316 ; Do we have EBIOS (EDD)?
320 mov ah,41h ; EDD existence query
326 test cl,1 ; Extended disk access functionality set
329 ; We have EDD support...
331 mov byte [getlinsec.jmp+1],getlinsec_ebios-(getlinsec.jmp+2)
335 ; Load the first sector of LDLINUX.SYS; this used to be all proper
336 ; with parsing the superblock and root directory; it doesn't fit
337 ; together with EBIOS support, unfortunately.
339 mov eax,[FirstSector] ; Sector start
340 mov bx,ldlinux_sys ; Where to load it
343 ; Some modicum of integrity checking
344 cmp dword [ldlinux_magic],LDLINUX_MAGIC
346 cmp dword [ldlinux_magic+4],HEXDATE
353 ; kaboom: write a message and bail out.
358 mov sp,StackBuf-4 ; Reset stack
359 mov ds,si ; Reset data segment
360 pop dword [fdctab] ; Restore FDC table
361 .patch: mov si,bailmsg
362 call writestr ; Returns with AL = 0
364 int 16h ; Wait for keypress
365 int 19h ; And try once more to boot...
366 .norge: jmp short .norge ; If int 19h returned; this is the end
370 ; writestr: write a null-terminated string to the console
371 ; This assumes we're on page 0. This is only used for early
372 ; messages, so it should be OK.
378 mov ah,0Eh ; Write to screen as TTY
379 mov bx,0007h ; Attribute
385 ; xint13: wrapper for int 13h which will retry 6 times and then die,
386 ; AND save all registers except BP
398 jmp strict near kaboom ; Patched
402 ; getonesec: get one disk sector
405 mov bp,1 ; One sector
409 ; getlinsec: load a sequence of BP floppy sector given by the linear sector
410 ; number in EAX into the buffer at ES:BX. We try to optimize
411 ; by loading up to a whole track at a time, but the user
412 ; is responsible for not crossing a 64K boundary.
413 ; (Yes, BP is weird for a count, but it was available...)
415 ; On return, BX points to the first byte after the transferred
418 ; This routine assumes CS == DS, and trashes most registers.
420 ; Stylistic note: use "xchg" instead of "mov" when the source is a register
421 ; that is dead from that point; this saves space. However, please keep
422 ; the order to dst,src to keep things sane.
425 add eax,[bsHidden] ; Add partition offset
426 .jmp: jmp strict short getlinsec_cbios ; This is patched
431 ; getlinsec implementation for EBIOS (EDD)
435 push bp ; Sectors left
436 call maxtrans ; Enforce maximum transfer size
437 movzx ecx,bp ; Sectors we are about to read
448 mov ah,42h ; Extended Read
455 add sp,16 ; Remove DAPA
457 add eax,ecx ; Advance sector pointer
458 sub bp,cx ; Sectors left
459 shl cx,9 ; 512-byte sectors
460 add bx,cx ; Advance buffer pointer
469 ; getlinsec implementation for legacy CBIOS
477 movzx esi,word [bsSecPerTrack]
478 movzx edi,word [bsHeads]
480 ; Dividing by sectors to get (track,sector): we may have
481 ; up to 2^18 tracks, so we need to use 32-bit arithmetric.
483 xor edx,edx ; Zero-extend LBA to 64 bits
486 xchg cx,dx ; CX <- sector index (0-based)
489 div edi ; Convert track to head/cyl
491 ; Now we have AX = cyl, DX = head, CX = sector (0-based),
492 ; BP = sectors to transfer, SI = bsSecPerTrack,
493 ; ES:BX = data target
496 call maxtrans ; Enforce maximum transfer size
498 ; Must not cross track boundaries, so BP <= SI-CX
505 shl ah,6 ; Because IBM was STOOPID
506 ; and thought 8 bits were enough
507 ; then thought 10 bits were enough...
508 inc cx ; Sector numbers are 1-based, sigh
513 xchg ax,bp ; Sector to transfer count
514 mov ah,02h ; Read sectors
517 shl ax,9 ; Convert sectors in AL to bytes in AX
528 ; Truncate BP to MaxTransfer
537 ; Error message on failure
539 bailmsg: db 'Boot failed', 0Dh, 0Ah, 0
542 bs_checkpt_off equ ($-$$)
544 %if bs_checkpt_off > 1F8h
545 %error "Boot sector overflow"
551 FirstSector dd 0xDEADBEEF ; Location of sector 1
552 MaxTransfer dw 0x007F ; Max transfer size
553 bootsignature dw 0AA55h
556 ; ===========================================================================
558 ; ===========================================================================
559 ; Start of LDLINUX.SYS
560 ; ===========================================================================
564 syslinux_banner db 0Dh, 0Ah
570 db version_str, ' ', date, ' ', 0
571 db 0Dh, 0Ah, 1Ah ; EOF if we "type" this in DOS
574 ldlinux_magic dd LDLINUX_MAGIC
578 ; This area is patched by the installer. It is found by looking for
579 ; LDLINUX_MAGIC, plus 8 bytes.
582 LDLDwords dw 0 ; Total dwords starting at ldlinux_sys
583 LDLSectors dw 0 ; Number of sectors - (bootsec+this sec)
584 CheckSum dd 0 ; Checksum starting at ldlinux_sys
585 ; value = LDLINUX_MAGIC - [sum of dwords]
587 ; Space for up to 64 sectors, the theoretical maximum
588 SectorPtrs times 64 dd 0
592 ; Note that some BIOSes are buggy and run the boot sector at 07C0:0000
593 ; instead of 0000:7C00 and the like. We don't want to add anything
594 ; more to the boot sector, so it is written to not assume a fixed
595 ; value in CS, but we don't want to deal with that anymore from now
602 ; Tell the user we got this far
604 mov si,syslinux_banner
608 ; Patch disk error handling
610 mov word [xint13.disk_error+1],do_disk_error-(xint13.disk_error+3)
613 ; Now we read the rest of LDLINUX.SYS. Don't bother loading the first
614 ; sector again, though.
618 mov bx,7C00h+2*SECTOR_SIZE ; Where we start loading
624 lodsd ; First sector of this chunk
632 inc edx ; Next linear sector
633 cmp [esi],edx ; Does it match
634 jnz .chunk_ready ; If not, this is it
635 add esi,4 ; If so, add sector to chunk
636 jmp short .make_chunk
647 ; All loaded up, verify that we got what we needed.
648 ; Note: the checksum field is embedded in the checksum region, so
649 ; by the time we get to the end it should all cancel out.
654 mov edx,-LDLINUX_MAGIC
660 and edx,edx ; Should be zero
661 jz all_read ; We're cool, go for it!
664 ; Uh-oh, something went bad...
666 mov si,checksumerr_msg
671 ; -----------------------------------------------------------------------------
672 ; Subroutines that have to be in the first sector
673 ; -----------------------------------------------------------------------------
676 ; getlinsecsr: save registers, call getlinsec, restore registers
684 ; This routine captures disk errors, and tries to decide if it is
685 ; time to reduce the transfer size.
690 shr al,1 ; Try reducing the transfer size
692 jz kaboom ; If we can't, we're dead...
693 jmp xint13 ; Try again
704 ; Checksum error message
706 checksumerr_msg db 'Load error - ', 0 ; Boot failed appended
713 cmp word [Debug_Magic],0D00Dh
718 rl_checkpt equ $ ; Must be <= 8000h
720 rl_checkpt_off equ ($-$$)
722 %if rl_checkpt_off > 400h
723 %error "Sector 1 overflow"
727 ; ----------------------------------------------------------------------------
728 ; End of code and data that have to be in the first sector
729 ; ----------------------------------------------------------------------------
733 ; Let the user (and programmer!) know we got this far. This used to be
734 ; in Sector 1, but makes a lot more sense here.
741 ; Insane hack to expand the superblock to dwords
747 mov cx,superinfo_size
751 stosd ; Store expanded word
753 stosd ; Store expanded byte
757 ; Compute some information about this filesystem.
760 ; First, generate the map of regions
765 mov edx,[bsHugeSectors]
767 mov [TotalSectors],edx
772 mov eax,[bxResSectors]
773 mov [FAT],eax ; Beginning of FAT
777 mov edx,[bootsec+36] ; FAT32 BPB_FATsz32
781 mov [RootDirArea],eax ; Beginning of root directory
782 mov [RootDir],eax ; For FAT12/16 == root dir location
784 mov edx,[bxRootDirEnts]
785 add dx,SECTOR_SIZE/32-1
786 shr dx,SECTOR_SHIFT-5
787 mov [RootDirSize],edx
789 mov [DataArea],eax ; Beginning of data area
791 ; Next, generate a cluster size shift count and mask
792 mov eax,[bxSecPerClust]
797 mov [ClustByteShift],cl
806 ; FAT12, FAT16 or FAT28^H^H32? This computation is fscking ridiculous.
811 shr eax,cl ; cl == ClustShift
812 mov cl,nextcluster_fat12-(nextcluster+2)
813 cmp eax,4085 ; FAT12 limit
815 mov cl,nextcluster_fat16-(nextcluster+2)
816 cmp eax,65525 ; FAT16 limit
819 ; FAT32, root directory is a cluster chain
822 mov eax,[bootsec+44] ; Root directory cluster
827 mov cl,nextcluster_fat28-(nextcluster+2)
829 mov byte [nextcluster+1],cl
832 ; Common initialization code
834 %include "cpuinit.inc"
838 ; Clear Files structures
841 mov cx,(MAX_OPEN*open_file_t_size)/4
846 ; Initialize the metadata cache
851 ; Now, everything is "up and running"... patch kaboom for more
852 ; verbosity and using the full screen system
855 mov dword [kaboom.patch],0e9h+((kaboom2-(kaboom.patch+3)) << 8)
858 ; Now we're all set to start with our *real* business. First load the
859 ; configuration file (if any) and parse it.
861 ; In previous versions I avoided using 32-bit registers because of a
862 ; rumour some BIOSes clobbered the upper half of 32-bit registers at
863 ; random. I figure, though, that if there are any of those still left
864 ; they probably won't be trying to install Linux on them...
866 ; The code is still ripe with 16-bitisms, though. Not worth the hassle
867 ; to take'm out. In fact, we may want to put them back if we're going
868 ; to boot ELKS at some point.
872 ; Load configuration file
879 ; Now we have the config file open. Parse the config file and
880 ; run the user interface.
885 ; Linux kernel loading code is common.
887 %include "runkernel.inc"
890 ; COMBOOT-loading code
892 %include "comboot.inc"
894 %include "cmdline.inc"
897 ; Boot sector loading code
899 %include "bootsect.inc"
902 ; abort_check: let the user abort with <ESC> or <Ctrl-C>
913 ac_kill: mov si,aborted_msg
916 ; abort_load: Called by various routines which wants to print a fatal
917 ; error message and return to the command prompt. Since this
918 ; may happen at just about any stage of the boot process, assume
919 ; our state is messed up, and just reset the segment registers
920 ; and the stack forcibly.
922 ; SI = offset (in _text) of error message to print
925 mov ax,cs ; Restore CS = DS = ES
929 mov sp,StackBuf-2*3 ; Reset stack
930 mov ss,ax ; Just in case...
932 call cwritestr ; Expects SI -> error msg
933 al_ok: jmp enter_command ; Return to command prompt
941 ; allocate_file: Allocate a file structure
954 .check: cmp dword [bx], byte 0
956 add bx,open_file_t_size ; ZF = 0
958 ; ZF = 0 if we fell out of the loop
964 ; Search the root directory for a pre-mangled filename in DS:DI.
966 ; NOTE: This file considers finding a zero-length file an
967 ; error. This is so we don't have to deal with that special
968 ; case elsewhere in the program (most loops have the test
974 ; DX:AX = file length in bytes
988 mov eax,[RootDir] ; First root directory sector
992 ; GS:SI now points to this sector
994 mov cx,SECTOR_SIZE/32 ; 32 == directory entry size
997 jz .failure ; Hit directory high water mark
1011 jnc .scansector ; CF is set if we're at end
1013 ; If we get here, we failed
1021 mov eax,[gs:si+28] ; File size
1022 add eax,SECTOR_SIZE-1
1023 shr eax,SECTOR_SHIFT
1024 jz .failure ; Zero-length file
1028 mov dx,[gs:si+20] ; High cluster word
1030 mov dx,[gs:si+26] ; Low cluster word
1034 mov [bx],edx ; Starting sector
1036 mov eax,[gs:si+28] ; File length again
1037 mov dx,[gs:si+30] ; 16-bitism, sigh
1039 and eax,eax ; ZF <- 0
1046 ; writechr: Write a single character in AL to the console without
1047 ; mangling any registers; handle video pages correctly.
1050 call write_serial ; write to serial port if needed
1052 test byte [cs:DisplayCon], 01h
1056 mov bl,07h ; attribute
1057 mov bh,[cs:BIOS_page] ; current page
1066 ; kaboom2: once everything is loaded, replace the part of kaboom
1067 ; starting with "kaboom.patch" with this part
1070 mov si,err_bootfailed
1074 int 19h ; And try once more to boot...
1075 .norge: jmp short .norge ; If int 19h returned; this is the end
1078 ; mangle_name: Mangle a DOS filename pointed to by DS:SI into a buffer pointed
1079 ; to by ES:DI; ends on encountering any whitespace
1083 mov cx,11 ; # of bytes to write
1086 cmp al,' ' ; If control or space, end
1088 cmp al,'.' ; Period -> space-fill
1095 jmp short mn_not_lower
1096 mn_is_period: mov al,' ' ; We need to space-fill
1097 mn_period_loop: cmp cx,3 ; If <= 3 characters left
1098 jbe mn_loop ; Just ignore it
1099 stosb ; Otherwise, write a period
1100 loop mn_period_loop ; Dec CX and (always) jump
1101 mn_not_uslower: cmp al,ucase_low
1105 mov bx,ucase_tab-ucase_low
1108 loop mn_loop ; Don't continue if too long
1110 mov al,' ' ; Space-fill name
1111 rep stosb ; Doesn't do anything if CX=0
1115 ; Upper-case table for extended characters; this is technically code page 865,
1116 ; but code page 437 users will probably not miss not being able to use the
1117 ; cent sign in kernel images too much :-)
1119 ; The table only covers the range 129 to 164; the rest we can deal with.
1123 ucase_tab db 154, 144, 'A', 142, 'A', 143, 128, 'EEEIII'
1124 db 142, 143, 144, 146, 146, 'O', 153, 'OUUY', 153, 154
1125 db 157, 156, 157, 158, 159, 'AIOU', 165
1128 ; unmangle_name: Does the opposite of mangle_name; converts a DOS-mangled
1129 ; filename to the conventional representation. This is needed
1130 ; for the BOOT_IMAGE= parameter for the kernel.
1131 ; NOTE: A 13-byte buffer is mandatory, even if the string is
1132 ; known to be shorter.
1134 ; DS:SI -> input mangled file name
1135 ; ES:DI -> output buffer
1137 ; On return, DI points to the first byte after the output name,
1138 ; which is set to a null byte.
1141 push si ; Save pointer to original name
1149 mov bp,di ; Position of last nonblank+1
1150 un_cb_space: loop un_copy_body
1152 mov al,'.' ; Don't save
1161 un_ce_space: loop un_copy_ext
1168 ; lower_case: Lower case a character in AL
1177 lc_1: cmp al,lcase_low
1182 mov bx,lcase_tab-lcase_low
1188 ; getfssec_edx: Get multiple sectors from a file
1190 ; This routine makes sure the subtransfers do not cross a 64K boundary,
1191 ; and will correct the situation if it does, UNLESS *sectors* cross
1195 ; EDX -> Current sector number
1196 ; CX -> Sector count (0FFFFh = until end of file)
1197 ; Must not exceed the ES segment
1198 ; Returns EDX=0, CF=1 on EOF (not necessarily error)
1199 ; All arguments are advanced to reflect data read.
1205 xor ebp,ebp ; Fragment sector count
1206 push edx ; Starting sector pointer
1214 add ax,bx ; Now AX = how far into 64K block we are
1215 not ax ; Bytes left in 64K block
1217 shr eax,SECTOR_SHIFT ; Sectors left in 64K block
1219 jnb .do_read ; Unless there is at least 1 more sector room...
1220 mov eax,edx ; Current sector
1221 inc edx ; Predict it's the linearly next sector
1224 cmp edx,eax ; Did it match?
1227 pop eax ; Starting sector pointer
1229 lea eax,[eax+ebp-1] ; This is the last sector actually read
1231 add bx,bp ; Adjust buffer pointer
1247 ; getfssec: Get multiple sectors from a file
1249 ; Same as above, except SI is a pointer to a open_file_t
1252 ; DS:SI -> Pointer to open_file_t
1253 ; CX -> Sector count (0FFFFh = until end of file)
1254 ; Must not exceed the ES segment
1255 ; Returns CF=1 on EOF (not necessarily error)
1256 ; All arguments are advanced to reflect data read.
1274 ; nextcluster: Advance a cluster pointer in EDI to the next cluster
1275 ; pointed at in the FAT tables. CF=0 on return if end of file.
1278 jmp strict short nextcluster_fat28 ; This gets patched
1288 pushf ; Save the shifted-out LSB (=CF)
1317 ; FAT16 decoding routine.
1324 shr eax,SECTOR_SHIFT-1
1329 movzx edi,word [gs:si+bx]
1336 ; FAT28 ("FAT32") decoding routine.
1343 shr eax,SECTOR_SHIFT-2
1349 mov edi,dword [gs:si+bx]
1350 and edi,0FFFFFFFh ; 28 bits only
1358 ; nextsector: Given a sector in EAX on input, return the next sector
1359 ; of the same filesystem object, which may be the root
1360 ; directory or a cluster chain. Returns EOF.
1380 test edi,[ClustMask]
1383 ; It's not the final sector in a cluster
1388 push gs ; nextcluster trashes gs
1395 ; Now EDI contains the cluster number
1398 jc .exit ; There isn't anything else...
1400 ; New cluster number now in EDI
1402 shl edi,cl ; CF <- 0, unless something is very wrong
1413 ; getfatsector: Check for a particular sector (in EAX) in the FAT cache,
1414 ; and return a pointer in GS:SI, loading it if needed.
1419 add eax,[FAT] ; FAT starting address
1422 ; -----------------------------------------------------------------------------
1424 ; -----------------------------------------------------------------------------
1426 %include "getc.inc" ; getc et al
1427 %include "conio.inc" ; Console I/O
1428 %include "writestr.inc" ; String output
1429 %include "parseconfig.inc" ; High-level config file handling
1430 %include "parsecmd.inc" ; Low-level config file handling
1431 %include "bcopy32.inc" ; 32-bit bcopy
1432 %include "loadhigh.inc" ; Load a file into high memory
1433 %include "font.inc" ; VGA font stuff
1434 %include "graphics.inc" ; VGA graphics
1435 %include "highmem.inc" ; High memory sizing
1436 %include "strcpy.inc" ; strcpy()
1437 %include "cache.inc" ; Metadata disk cache
1439 ; -----------------------------------------------------------------------------
1440 ; Begin data section
1441 ; -----------------------------------------------------------------------------
1445 ; Lower-case table for codepage 865
1449 lcase_tab db 135, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138
1450 db 139, 140, 141, 132, 134, 130, 145, 145, 147, 148, 149
1451 db 150, 151, 152, 148, 129, 155, 156, 155, 158, 159, 160
1452 db 161, 162, 163, 164, 164
1454 copyright_str db ' Copyright (C) 1994-', year, ' H. Peter Anvin'
1456 boot_prompt db 'boot: ', 0
1457 wipe_char db BS, ' ', BS, 0
1458 err_notfound db 'Could not find kernel image: ',0
1459 err_notkernel db CR, LF, 'Invalid or corrupt kernel image.', CR, LF, 0
1460 err_noram db 'It appears your computer has less than '
1462 db 'K of low ("DOS")'
1464 db 'RAM. Linux needs at least this amount to boot. If you get'
1466 db 'this message in error, hold down the Ctrl key while'
1468 db 'booting, and I will take your word for it.', CR, LF, 0
1469 err_badcfg db 'Unknown keyword in syslinux.cfg.', CR, LF, 0
1470 err_noparm db 'Missing parameter in syslinux.cfg.', CR, LF, 0
1471 err_noinitrd db CR, LF, 'Could not find ramdisk image: ', 0
1472 err_nohighmem db 'Not enough memory to load specified kernel.', CR, LF, 0
1473 err_highload db CR, LF, 'Kernel transfer failure.', CR, LF, 0
1474 err_oldkernel db 'Cannot load a ramdisk with an old kernel image.'
1476 err_notdos db ': attempted DOS system call', CR, LF, 0
1477 err_comlarge db 'COMBOOT image too large.', CR, LF, 0
1478 err_a20 db CR, LF, 'A20 gate not responding!', CR, LF, 0
1479 err_bootfailed db CR, LF, 'Boot failed: please change disks and press '
1480 db 'a key to continue.', CR, LF, 0
1481 ready_msg db 'Ready.', CR, LF, 0
1482 crlfloading_msg db CR, LF
1483 loading_msg db 'Loading ', 0
1486 aborted_msg db ' aborted.' ; Fall through to crlf_msg!
1489 crff_msg db CR, FF, 0
1490 syslinux_cfg db 'SYSLINUXCFG' ; Mangled form
1491 ConfigName db 'syslinux.cfg',0 ; Unmangled form
1493 manifest db 'MANIFEST '
1496 ; Command line options we'd like to take a look at
1498 ; mem= and vga= are handled as normal 32-bit integer values
1499 initrd_cmd db 'initrd='
1500 initrd_cmd_len equ 7
1503 ; Config file keyword table
1505 %include "keywords.inc"
1508 ; Extensions to search for (in *forward* order).
1510 exten_table: db 'CBT',0 ; COMBOOT (specific)
1511 db 'BSS',0 ; Boot Sector (add superblock)
1512 db 'BS ',0 ; Boot Sector
1513 db 'COM',0 ; COMBOOT (same as DOS)
1516 dd 0, 0 ; Need 8 null bytes here
1519 ; Misc initialized (data) variables
1521 %ifdef debug ; This code for debugging only
1522 debug_magic dw 0D00Dh ; Debug code sentinel
1526 BufSafe dw trackbufsize/SECTOR_SIZE ; Clusters we can load into trackbuf
1527 BufSafeSec dw trackbufsize/SECTOR_SIZE ; = how many sectors?
1528 BufSafeBytes dw trackbufsize ; = how many bytes?
1529 EndOfGetCBuf dw getcbuf+trackbufsize ; = getcbuf+BufSafeBytes
1531 %if ( trackbufsize % SECTOR_SIZE ) != 0
1532 %error trackbufsize must be a multiple of SECTOR_SIZE