1 ; -*- fundamental -*- (asm-mode sucks)
2 ; ****************************************************************************
6 ; A program to boot Linux kernels off an MS-DOS formatted floppy disk. This
7 ; functionality is good to have for installation floppies, where it may
8 ; be hard to find a functional Linux system to run LILO off.
10 ; This program allows manipulation of the disk to take place entirely
11 ; from MS-LOSS, and can be especially useful in conjunction with the
14 ; Copyright (C) 1994-2007 H. Peter Anvin
16 ; This program is free software; you can redistribute it and/or modify
17 ; it under the terms of the GNU General Public License as published by
18 ; the Free Software Foundation, Inc., 53 Temple Place Ste 330,
19 ; Boston MA 02111-1307, USA; either version 2 of the License, or
20 ; (at your option) any later version; incorporated herein by reference.
22 ; ****************************************************************************
30 ; Some semi-configurable constants... change on your own risk.
33 FILENAME_MAX_LG2 equ 6 ; log2(Max filename size Including final null)
34 FILENAME_MAX equ (1<<FILENAME_MAX_LG2) ; Max mangled filename size
35 NULLFILE equ 0 ; First char space == null filename
36 NULLOFFSET equ 0 ; Position in which to look
37 retry_count equ 16 ; How patient are we with the disk?
38 %assign HIGHMEM_SLOP 0 ; Avoid this much memory near the top
39 LDLINUX_MAGIC equ 0x3eb202fe ; A random number to identify ourselves with
41 MAX_OPEN_LG2 equ 6 ; log2(Max number of open files)
42 MAX_OPEN equ (1 << MAX_OPEN_LG2)
45 SECTOR_SIZE equ (1 << SECTOR_SHIFT)
48 ; This is what we need to do when idle
58 ; The following structure is used for "virtual kernels"; i.e. LILO-style
59 ; option labels. The options we permit here are `kernel' and `append
60 ; Since there is no room in the bottom 64K for all of these, we
61 ; stick them at vk_seg:0000 and copy them down before we need them.
64 vk_vname: resb FILENAME_MAX ; Virtual name **MUST BE FIRST!**
65 vk_rname: resb FILENAME_MAX ; Real name
67 vk_type: resb 1 ; Type of file
69 vk_append: resb max_cmd_len+1 ; Command line
71 vk_end: equ $ ; Should be <= vk_size
75 ; Segment assignments in the bottom 640K
76 ; Stick to the low 512K in case we're using something like M-systems flash
77 ; which load a driver into low RAM (evil!!)
79 ; 0000h - main code/data segment (and BIOS segment)
81 real_mode_seg equ 4000h
82 cache_seg equ 3000h ; 64K area for metadata cache
83 vk_seg equ 2000h ; Virtual kernels
84 xfer_buf_seg equ 1000h ; Bounce buffer for I/O to high mem
85 comboot_seg equ real_mode_seg ; COMBOOT image loading zone
88 ; File structure. This holds the information for each currently open file.
91 file_sector resd 1 ; Sector pointer (0 = structure free)
92 file_left resd 1 ; Number of sectors left
96 %if (open_file_t_size & (open_file_t_size-1))
97 %error "open_file_t is not a power of 2"
101 ; ---------------------------------------------------------------------------
103 ; ---------------------------------------------------------------------------
106 ; Memory below this point is reserved for the BIOS and the MBR
109 trackbufsize equ 8192
110 trackbuf resb trackbufsize ; Track buffer goes here
111 getcbuf resb trackbufsize
117 ; Expanded superblock
119 resq 16 ; The first 16 bytes expanded 8 times
120 FAT resd 1 ; Location of (first) FAT
121 RootDirArea resd 1 ; Location of root directory area
122 RootDir resd 1 ; Location of root directory proper
123 DataArea resd 1 ; Location of data area
124 RootDirSize resd 1 ; Root dir size in sectors
125 TotalSectors resd 1 ; Total number of sectors
126 EndSector resd 1 ; Location of filesystem end
127 ClustSize resd 1 ; Bytes/cluster
128 ClustMask resd 1 ; Sectors/cluster - 1
129 CopySuper resb 1 ; Distinguish .bs versus .bss
130 DriveNumber resb 1 ; BIOS drive number
131 ClustShift resb 1 ; Shift count for sectors/cluster
132 ClustByteShift resb 1 ; Shift count for bytes/cluster
134 alignb open_file_t_size
135 Files resb MAX_OPEN*open_file_t_size
138 ; Constants for the xfer_buf_seg
140 ; The xfer_buf_seg is also used to store message file buffers. We
141 ; need two trackbuffers (text and graphics), plus a work buffer
142 ; for the graphics decompressor.
144 xbs_textbuf equ 0 ; Also hard-coded, do not change
145 xbs_vgabuf equ trackbufsize
146 xbs_vgatmpbuf equ 2*trackbufsize
151 ; Some of the things that have to be saved very early are saved
152 ; "close" to the initial stack pointer offset, in order to
153 ; reduce the code size...
155 StackBuf equ $-44-32 ; Start the stack here (grow down - 4K)
156 PartInfo equ StackBuf ; Saved partition table entry
157 FloppyTable equ PartInfo+16 ; Floppy info table (must follow PartInfo)
158 OrigFDCTabPtr equ StackBuf-4 ; The high dword on the stack
161 ; Primary entry point. Tempting as though it may be, we can't put the
162 ; initial "cli" here; the jmp opcode in the first byte is part of the
163 ; "magic number" (using the term very loosely) for the DOS superblock.
166 jmp short start ; 2 bytes
169 ; "Superblock" follows -- it's in the boot sector, so it's already
170 ; loaded and ready for us
172 bsOemName db 'SYSLINUX' ; The SYS command sets this, so...
174 ; These are the fields we actually care about. We end up expanding them
175 ; all to dword size early in the code, so generate labels for both
176 ; the expanded and unexpanded versions.
179 bx %+ %1 equ SuperInfo+($-superblock)*8+4
184 bx %+ %1 equ SuperInfo+($-superblock)*8
189 bx %+ %1 equ $ ; no expansion for dwords
204 superinfo_size equ ($-superblock)-1 ; How much to expand
208 ; This is as far as FAT12/16 and FAT32 are consistent
210 zb 54 ; FAT12/16 need 26 more bytes,
211 ; FAT32 need 54 more bytes
212 superblock_len equ $-superblock
214 SecPerClust equ bxSecPerClust
216 ; Note we don't check the constraints above now; we did that at install
220 cli ; No interrupts yet, please
227 mov sp,StackBuf ; Just below BSS
230 ; DS:SI may contain a partition table entry. Preserve it for us.
232 mov cx,8 ; Save partition info
236 mov ds,ax ; Now we can initialize DS...
239 ; Now sautee the BIOS floppy info block to that it will support decent-
240 ; size transfers; the floppy block is 11 bytes and is stored in the
241 ; INT 1Eh vector (brilliant waste of resources, eh?)
243 ; Of course, if BIOSes had been properly programmed, we wouldn't have
244 ; had to waste precious space with this code.
247 lfs si,[bx] ; FS:SI -> original fdctab
248 push fs ; Save on stack in case we need to bail
251 ; Save the old fdctab even if hard disk so the stack layout
252 ; is the same. The instructions above do not change the flags
253 mov [DriveNumber],dl ; Save drive number in DL
254 and dl,dl ; If floppy disk (00-7F), assume no
259 mov cl,6 ; 12 bytes (CX == 0)
260 ; es:di -> FloppyTable already
261 ; This should be safe to do now, interrupts are off...
262 mov [bx],di ; FloppyTable
263 mov [bx+2],ax ; Segment 0
264 fs rep movsw ; Faster to move words
265 mov cl,[bsSecPerTrack] ; Patch the sector count
268 int 13h ; Some BIOSes need this
270 jmp short not_harddisk
272 ; The drive number and possibly partition information was passed to us
273 ; by the BIOS or previous boot loader (MBR). Current "best practice" is to
274 ; trust that rather than what the superblock contains.
276 ; Would it be better to zero out bsHidden if we don't have a partition table?
278 ; Note: di points to beyond the end of PartInfo
281 test byte [di-16],7Fh ; Sanity check: "active flag" should
282 jnz no_partition ; be 00 or 80
283 mov eax,[di-8] ; Partition offset (dword)
287 ; Get disk drive parameters (don't trust the superblock.) Don't do this for
288 ; floppy drives -- INT 13:08 on floppy drives will (may?) return info about
289 ; what the *drive* supports, not about the *media*. Fortunately floppy disks
290 ; tend to have a fixed, well-defined geometry which is stored in the superblock.
292 ; DL == drive # still
299 inc dx ; Contains # of heads - 1
302 mov [bsSecPerTrack],cx
306 ; Ready to enable interrupts, captain
311 ; Do we have EBIOS (EDD)?
315 mov ah,41h ; EDD existence query
321 test cl,1 ; Extended disk access functionality set
324 ; We have EDD support...
326 mov byte [getlinsec.jmp+1],(getlinsec_ebios-(getlinsec.jmp+2))
330 ; Load the first sector of LDLINUX.SYS; this used to be all proper
331 ; with parsing the superblock and root directory; it doesn't fit
332 ; together with EBIOS support, unfortunately.
334 mov eax,[FirstSector] ; Sector start
335 mov bx,ldlinux_sys ; Where to load it
338 ; Some modicum of integrity checking
339 cmp dword [ldlinux_magic+4],LDLINUX_MAGIC^HEXDATE
346 ; getonesec: get one disk sector
349 mov bp,1 ; One sector
353 ; getlinsec: load a sequence of BP floppy sector given by the linear sector
354 ; number in EAX into the buffer at ES:BX. We try to optimize
355 ; by loading up to a whole track at a time, but the user
356 ; is responsible for not crossing a 64K boundary.
357 ; (Yes, BP is weird for a count, but it was available...)
359 ; On return, BX points to the first byte after the transferred
362 ; This routine assumes CS == DS, and trashes most registers.
364 ; Stylistic note: use "xchg" instead of "mov" when the source is a register
365 ; that is dead from that point; this saves space. However, please keep
366 ; the order to dst,src to keep things sane.
369 add eax,[bsHidden] ; Add partition offset
370 xor edx,edx ; Zero-extend LBA (eventually allow 64 bits)
372 .jmp: jmp strict short getlinsec_cbios
377 ; getlinsec implementation for EBIOS (EDD)
381 push bp ; Sectors left
383 call maxtrans ; Enforce maximum transfer size
384 movzx edi,bp ; Sectors we are about to read
401 mov ah,42h ; Extended Read
405 lea sp,[si+16] ; Remove DAPA
408 add eax,edi ; Advance sector pointer
409 sub bp,di ; Sectors left
410 shl di,SECTOR_SHIFT ; 512-byte sectors
411 add bx,di ; Advance buffer pointer
418 ; Some systems seem to get "stuck" in an error state when
419 ; using EBIOS. Doesn't happen when using CBIOS, which is
420 ; good, since some other systems get timeout failures
421 ; waiting for the floppy disk to spin up.
423 pushad ; Try resetting the device
428 loop .retry ; CX-- and jump if not zero
430 ;shr word [MaxTransfer],1 ; Reduce the transfer size
433 ; Total failure. Try falling back to CBIOS.
434 mov byte [getlinsec.jmp+1],(getlinsec_cbios-(getlinsec.jmp+2))
435 ;mov byte [MaxTransfer],63 ; Max possibe CBIOS transfer
438 ; ... fall through ...
443 ; getlinsec implementation for legacy CBIOS
452 movzx esi,word [bsSecPerTrack]
453 movzx edi,word [bsHeads]
455 ; Dividing by sectors to get (track,sector): we may have
456 ; up to 2^18 tracks, so we need to use 32-bit arithmetric.
460 xchg cx,dx ; CX <- sector index (0-based)
463 div edi ; Convert track to head/cyl
465 ; We should test this, but it doesn't fit...
470 ; Now we have AX = cyl, DX = head, CX = sector (0-based),
471 ; BP = sectors to transfer, SI = bsSecPerTrack,
472 ; ES:BX = data target
475 call maxtrans ; Enforce maximum transfer size
477 ; Must not cross track boundaries, so BP <= SI-CX
484 shl ah,6 ; Because IBM was STOOPID
485 ; and thought 8 bits were enough
486 ; then thought 10 bits were enough...
487 inc cx ; Sector numbers are 1-based, sigh
492 xchg ax,bp ; Sector to transfer count
493 mov ah,02h ; Read sectors
501 movzx ecx,al ; ECX <- sectors transferred
502 shl ax,SECTOR_SHIFT ; Convert sectors in AL to bytes in AX
517 xchg ax,bp ; Sectors transferred <- 0
518 shr word [MaxTransfer],1
520 ; Fall through to disk_error
523 ; kaboom: write a message and bail out.
529 mov sp,StackBuf-4 ; Reset stack
530 mov ds,si ; Reset data segment
531 pop dword [fdctab] ; Restore FDC table
532 .patch: ; When we have full code, intercept here
535 ; Write error message, this assumes screen page 0
539 mov ah,0Eh ; Write to screen as TTY
540 mov bx,0007h ; Attribute
545 int 16h ; Wait for keypress
546 int 19h ; And try once more to boot...
547 .norge: jmp short .norge ; If int 19h returned; this is the end
550 ; Truncate BP to MaxTransfer
559 ; Error message on failure
561 bailmsg: db 'Boot error', 0Dh, 0Ah, 0
563 ; This fails if the boot sector overflows
566 FirstSector dd 0xDEADBEEF ; Location of sector 1
567 MaxTransfer dw 0x007F ; Max transfer size
568 bootsignature dw 0AA55h
571 ; ===========================================================================
573 ; ===========================================================================
574 ; Start of LDLINUX.SYS
575 ; ===========================================================================
579 syslinux_banner db 0Dh, 0Ah
585 db version_str, ' ', date, ' ', 0
586 db 0Dh, 0Ah, 1Ah ; EOF if we "type" this in DOS
589 ldlinux_magic dd LDLINUX_MAGIC
590 dd LDLINUX_MAGIC^HEXDATE
593 ; This area is patched by the installer. It is found by looking for
594 ; LDLINUX_MAGIC, plus 8 bytes.
597 LDLDwords dw 0 ; Total dwords starting at ldlinux_sys
598 LDLSectors dw 0 ; Number of sectors - (bootsec+this sec)
599 CheckSum dd 0 ; Checksum starting at ldlinux_sys
600 ; value = LDLINUX_MAGIC - [sum of dwords]
602 ; Space for up to 64 sectors, the theoretical maximum
603 SectorPtrs times 64 dd 0
607 ; Note that some BIOSes are buggy and run the boot sector at 07C0:0000
608 ; instead of 0000:7C00 and the like. We don't want to add anything
609 ; more to the boot sector, so it is written to not assume a fixed
610 ; value in CS, but we don't want to deal with that anymore from now
617 ; Tell the user we got this far
619 mov si,syslinux_banner
623 ; Tell the user if we're using EBIOS or CBIOS
627 cmp byte [getlinsec.jmp+1],(getlinsec_ebios-(getlinsec.jmp+2))
635 %define HAVE_BIOSNAME 1
640 ; Now we read the rest of LDLINUX.SYS. Don't bother loading the first
641 ; sector again, though.
645 mov bx,7C00h+2*SECTOR_SIZE ; Where we start loading
651 lodsd ; First sector of this chunk
659 inc edx ; Next linear sector
660 cmp [si],edx ; Does it match
661 jnz .chunk_ready ; If not, this is it
662 add si,4 ; If so, add sector to chunk
663 jmp short .make_chunk
674 ; All loaded up, verify that we got what we needed.
675 ; Note: the checksum field is embedded in the checksum region, so
676 ; by the time we get to the end it should all cancel out.
681 mov edx,-LDLINUX_MAGIC
687 and edx,edx ; Should be zero
688 jz all_read ; We're cool, go for it!
691 ; Uh-oh, something went bad...
693 mov si,checksumerr_msg
698 ; -----------------------------------------------------------------------------
699 ; Subroutines that have to be in the first sector
700 ; -----------------------------------------------------------------------------
704 ; writestr: write a null-terminated string to the console
705 ; This assumes we're on page 0. This is only used for early
706 ; messages, so it should be OK.
712 mov ah,0Eh ; Write to screen as TTY
713 mov bx,0007h ; Attribute
719 ; getlinsecsr: save registers, call getlinsec, restore registers
727 ; Checksum error message
729 checksumerr_msg db ' Load error - ', 0 ; Boot failed appended
734 cbios_name db 'CBIOS', 0
735 ebios_name db 'EBIOS', 0
742 cmp word [Debug_Magic],0D00Dh
747 rl_checkpt equ $ ; Must be <= 8000h
749 rl_checkpt_off equ ($-$$)
751 %if rl_checkpt_off > 400h
752 %error "Sector 1 overflow"
756 ; ----------------------------------------------------------------------------
757 ; End of code and data that have to be in the first sector
758 ; ----------------------------------------------------------------------------
762 ; Let the user (and programmer!) know we got this far. This used to be
763 ; in Sector 1, but makes a lot more sense here.
770 ; Insane hack to expand the superblock to dwords
776 mov cx,superinfo_size
780 stosd ; Store expanded word
782 stosd ; Store expanded byte
786 ; Compute some information about this filesystem.
789 ; First, generate the map of regions
794 mov edx,[bsHugeSectors]
796 mov [TotalSectors],edx
801 mov eax,[bxResSectors]
802 mov [FAT],eax ; Beginning of FAT
806 mov edx,[bootsec+36] ; FAT32 BPB_FATsz32
810 mov [RootDirArea],eax ; Beginning of root directory
811 mov [RootDir],eax ; For FAT12/16 == root dir location
813 mov edx,[bxRootDirEnts]
814 add dx,SECTOR_SIZE/32-1
815 shr dx,SECTOR_SHIFT-5
816 mov [RootDirSize],edx
818 mov [DataArea],eax ; Beginning of data area
820 ; Next, generate a cluster size shift count and mask
821 mov eax,[bxSecPerClust]
826 mov [ClustByteShift],cl
835 ; FAT12, FAT16 or FAT28^H^H32? This computation is fscking ridiculous.
840 shr eax,cl ; cl == ClustShift
841 mov cl,nextcluster_fat12-(nextcluster+2)
842 cmp eax,4085 ; FAT12 limit
844 mov cl,nextcluster_fat16-(nextcluster+2)
845 cmp eax,65525 ; FAT16 limit
848 ; FAT32, root directory is a cluster chain
851 mov eax,[bootsec+44] ; Root directory cluster
856 mov cl,nextcluster_fat28-(nextcluster+2)
858 mov byte [nextcluster+1],cl
861 ; Common initialization code
863 %include "cpuinit.inc"
867 ; Clear Files structures
870 mov cx,(MAX_OPEN*open_file_t_size)/4
875 ; Initialize the metadata cache
880 ; Now, everything is "up and running"... patch kaboom for more
881 ; verbosity and using the full screen system
884 mov dword [kaboom.patch],0e9h+((kaboom2-(kaboom.patch+3)) << 8)
887 ; Now we're all set to start with our *real* business. First load the
888 ; configuration file (if any) and parse it.
890 ; In previous versions I avoided using 32-bit registers because of a
891 ; rumour some BIOSes clobbered the upper half of 32-bit registers at
892 ; random. I figure, though, that if there are any of those still left
893 ; they probably won't be trying to install Linux on them...
895 ; The code is still ripe with 16-bitisms, though. Not worth the hassle
896 ; to take'm out. In fact, we may want to put them back if we're going
897 ; to boot ELKS at some point.
901 ; Load configuration file
913 mov eax,[PrevDir] ; Make the directory with syslinux.cfg ...
914 mov [CurrentDir],eax ; ... the current directory
917 ; Now we have the config file open. Parse the config file and
918 ; run the user interface.
923 ; Linux kernel loading code is common.
925 %include "runkernel.inc"
928 ; COMBOOT-loading code
930 %include "comboot.inc"
932 %include "cmdline.inc"
935 ; Boot sector loading code
937 %include "bootsect.inc"
945 ; allocate_file: Allocate a file structure
958 .check: cmp dword [bx], byte 0
960 add bx,open_file_t_size ; ZF = 0
962 ; ZF = 0 if we fell out of the loop
968 ; Search a specific directory for a pre-mangled filename in
969 ; MangledBuf, in the directory starting in sector EAX.
971 ; NOTE: This file considers finding a zero-length file an
972 ; error. This is so we don't have to deal with that special
973 ; case elsewhere in the program (most loops have the test
976 ; Assumes DS == ES == CS.
981 ; EAX = file length (MAY BE ZERO!)
982 ; DL = file attributes
999 ; EAX <- directory sector to scan
1001 ; GS:SI now points to this sector
1003 mov cx,SECTOR_SIZE/32 ; 32 == directory entry size
1006 jz .failure ; Hit directory high water mark
1007 test byte [gs:si+11],8 ; Ignore volume labels and
1008 ; VFAT long filename entries
1025 jnc .scansector ; CF is set if we're at end
1027 ; If we get here, we failed
1034 xor eax,eax ; ZF <- 1
1037 mov eax,[gs:si+28] ; File size
1038 add eax,SECTOR_SIZE-1
1039 shr eax,SECTOR_SHIFT
1040 mov [bx+4],eax ; Sector count
1043 mov dx,[gs:si+20] ; High cluster word
1045 mov dx,[gs:si+26] ; Low cluster word
1049 mov [bx],edx ; Starting sector
1051 mov eax,[gs:si+28] ; File length again
1052 mov dl,[gs:si+11] ; File attribute
1053 mov si,bx ; File pointer...
1072 ; DX:AX or EAX = file length in bytes
1076 ; Assumes CS == DS == ES, and trashes BX and CX.
1079 mov eax,[CurrentDir]
1080 cmp byte [di],'/' ; Root directory?
1087 push eax ; <A> Current directory sector
1097 pop eax ; <A> Current directory sector
1099 mov [PrevDir],eax ; Remember last directory searched
1102 call mangle_dos_name ; MangledBuf <- component
1105 jz .notfound ; Pathname component missing
1107 cmp byte [di-1],'/' ; Do we expect a directory
1110 ; Otherwise, it should be a file
1112 test dl,18h ; Subdirectory|Volume Label
1113 jnz .badfile ; If not a file, it's a bad thing
1115 ; SI and EAX are already set
1117 shr edx,16 ; Old 16-bit remnant...
1118 and eax,eax ; EAX != 0
1122 ; If we expected a directory, it better be one...
1124 test dl,10h ; Subdirectory
1128 xchg eax,[si+file_sector] ; Get sector number and free file structure
1129 jmp .pathwalk ; Walk the next bit of the path
1133 mov [si],eax ; Free file structure
1142 CurrentDir resd 1 ; Current directory
1143 PrevDir resd 1 ; Last scanned directory
1149 ; kaboom2: once everything is loaded, replace the part of kaboom
1150 ; starting with "kaboom.patch" with this part
1153 mov si,err_bootfailed
1157 int 19h ; And try once more to boot...
1158 .norge: jmp short .norge ; If int 19h returned; this is the end
1161 ; mangle_name: Mangle a filename pointed to by DS:SI into a buffer pointed
1162 ; to by ES:DI; ends on encountering any whitespace.
1164 ; This verifies that a filename is < FILENAME_MAX characters,
1165 ; doesn't contain whitespace, zero-pads the output buffer,
1166 ; and removes trailing dots and redundant slashes, plus changes
1167 ; backslashes to forward slashes,
1168 ; so "repe cmpsb" can do a compare, and the path-searching routine
1169 ; gets a bit of an easier job.
1175 mov cx,FILENAME_MAX-1
1180 cmp al,' ' ; If control or space, end
1182 cmp al,'\' ; Backslash?
1184 mov al,'/' ; Change to forward slash
1186 cmp al,ah ; Repeated slash?
1193 .mn_skip: loop .mn_loop
1195 cmp bx,di ; At the beginning of the buffer?
1197 cmp byte [es:di-1],'.' ; Terminal dot?
1199 cmp byte [es:di-1],'/' ; Terminal slash?
1201 .mn_kill: dec di ; If so, remove it
1205 inc cx ; At least one null byte
1206 xor ax,ax ; Zero-fill name
1212 ; unmangle_name: Does the opposite of mangle_name; converts a DOS-mangled
1213 ; filename to the conventional representation. This is needed
1214 ; for the BOOT_IMAGE= parameter for the kernel.
1215 ; NOTE: A 13-byte buffer is mandatory, even if the string is
1216 ; known to be shorter.
1218 ; DS:SI -> input mangled file name
1219 ; ES:DI -> output buffer
1221 ; On return, DI points to the first byte after the output name,
1222 ; which is set to a null byte.
1224 unmangle_name: call strcpy
1225 dec di ; Point to final null byte
1230 ; Mangle a DOS filename component pointed to by DS:SI
1231 ; into [MangledBuf]; ends on encountering any whitespace or slash.
1232 ; Assumes CS == DS == ES.
1239 mov cx,11 ; # of bytes to write
1242 cmp al,' ' ; If control or space, end
1244 cmp al,'/' ; Slash, too
1246 cmp al,'.' ; Period -> space-fill
1253 jmp short .not_lower
1254 .is_period: mov al,' ' ; We need to space-fill
1255 .period_loop: cmp cx,3 ; If <= 3 characters left
1256 jbe .loop ; Just ignore it
1257 stosb ; Otherwise, write a period
1258 loop .period_loop ; Dec CX and (always) jump
1259 .not_uslower: cmp al,ucase_low
1263 mov bx,ucase_tab-ucase_low
1266 loop .loop ; Don't continue if too long
1268 mov al,' ' ; Space-fill name
1269 rep stosb ; Doesn't do anything if CX=0
1278 ; Case tables for extended characters; this is technically code page 865,
1279 ; but code page 437 users will probably not miss not being able to use the
1280 ; cent sign in kernel images too much :-)
1282 ; The table only covers the range 129 to 164; the rest we can deal with.
1288 ucase_tab db 154, 144, 'A', 142, 'A', 143, 128, 'EEEIII'
1289 db 142, 143, 144, 146, 146, 'O', 153, 'OUUY', 153, 154
1290 db 157, 156, 157, 158, 159, 'AIOU', 165
1294 ; getfssec_edx: Get multiple sectors from a file
1296 ; This routine makes sure the subtransfers do not cross a 64K boundary,
1297 ; and will correct the situation if it does, UNLESS *sectors* cross
1301 ; EDX -> Current sector number
1302 ; CX -> Sector count (0FFFFh = until end of file)
1303 ; Must not exceed the ES segment
1304 ; Returns EDX=0, CF=1 on EOF (not necessarily error)
1305 ; All arguments are advanced to reflect data read.
1311 xor ebp,ebp ; Fragment sector count
1312 push edx ; Starting sector pointer
1320 add ax,bx ; Now AX = how far into 64K block we are
1321 not ax ; Bytes left in 64K block
1323 shr eax,SECTOR_SHIFT ; Sectors left in 64K block
1325 jnb .do_read ; Unless there is at least 1 more sector room...
1326 mov eax,edx ; Current sector
1327 inc edx ; Predict it's the linearly next sector
1330 cmp edx,eax ; Did it match?
1333 pop eax ; Starting sector pointer
1335 lea eax,[eax+ebp-1] ; This is the last sector actually read
1337 add bx,bp ; Adjust buffer pointer
1353 ; getfssec: Get multiple sectors from a file
1355 ; Same as above, except SI is a pointer to a open_file_t
1358 ; DS:SI -> Pointer to open_file_t
1359 ; CX -> Sector count (0FFFFh = until end of file)
1360 ; Must not exceed the ES segment
1361 ; Returns CF=1 on EOF (not necessarily error)
1362 ; All arguments are advanced to reflect data read.
1380 ; nextcluster: Advance a cluster pointer in EDI to the next cluster
1381 ; pointed at in the FAT tables. CF=0 on return if end of file.
1384 jmp strict short nextcluster_fat28 ; This gets patched
1394 pushf ; Save the shifted-out LSB (=CF)
1423 ; FAT16 decoding routine.
1430 shr eax,SECTOR_SHIFT-1
1435 movzx edi,word [gs:si+bx]
1442 ; FAT28 ("FAT32") decoding routine.
1449 shr eax,SECTOR_SHIFT-2
1455 mov edi,dword [gs:si+bx]
1456 and edi,0FFFFFFFh ; 28 bits only
1464 ; nextsector: Given a sector in EAX on input, return the next sector
1465 ; of the same filesystem object, which may be the root
1466 ; directory or a cluster chain. Returns EOF.
1486 test edi,[ClustMask]
1489 ; It's not the final sector in a cluster
1494 push gs ; nextcluster trashes gs
1501 ; Now EDI contains the cluster number
1504 jc .exit ; There isn't anything else...
1506 ; New cluster number now in EDI
1508 shl edi,cl ; CF <- 0, unless something is very wrong
1519 ; getfatsector: Check for a particular sector (in EAX) in the FAT cache,
1520 ; and return a pointer in GS:SI, loading it if needed.
1525 add eax,[FAT] ; FAT starting address
1528 ; -----------------------------------------------------------------------------
1530 ; -----------------------------------------------------------------------------
1532 %include "getc.inc" ; getc et al
1533 %include "conio.inc" ; Console I/O
1534 %include "plaincon.inc" ; writechr
1535 %include "writestr.inc" ; String output
1536 %include "configinit.inc" ; Initialize configuration
1537 %include "parseconfig.inc" ; High-level config file handling
1538 %include "parsecmd.inc" ; Low-level config file handling
1539 %include "bcopy32.inc" ; 32-bit bcopy
1540 %include "loadhigh.inc" ; Load a file into high memory
1541 %include "font.inc" ; VGA font stuff
1542 %include "graphics.inc" ; VGA graphics
1543 %include "highmem.inc" ; High memory sizing
1544 %include "strcpy.inc" ; strcpy()
1545 %include "cache.inc" ; Metadata disk cache
1547 ; -----------------------------------------------------------------------------
1548 ; Begin data section
1549 ; -----------------------------------------------------------------------------
1552 copyright_str db ' Copyright (C) 1994-', year, ' H. Peter Anvin'
1554 boot_prompt db 'boot: ', 0
1555 wipe_char db BS, ' ', BS, 0
1556 err_notfound db 'Could not find kernel image: ',0
1557 err_notkernel db CR, LF, 'Invalid or corrupt kernel image.', CR, LF, 0
1558 err_noram db 'It appears your computer has less than '
1560 db 'K of low ("DOS")'
1562 db 'RAM. Linux needs at least this amount to boot. If you get'
1564 db 'this message in error, hold down the Ctrl key while'
1566 db 'booting, and I will take your word for it.', CR, LF, 0
1567 err_badcfg db 'Unknown keyword in syslinux.cfg.', CR, LF, 0
1568 err_noparm db 'Missing parameter in syslinux.cfg.', CR, LF, 0
1569 err_noinitrd db CR, LF, 'Could not find ramdisk image: ', 0
1570 err_nohighmem db 'Not enough memory to load specified kernel.', CR, LF, 0
1571 err_highload db CR, LF, 'Kernel transfer failure.', CR, LF, 0
1572 err_oldkernel db 'Cannot load a ramdisk with an old kernel image.'
1574 err_notdos db ': attempted DOS system call', CR, LF, 0
1575 err_comlarge db 'COMBOOT image too large.', CR, LF, 0
1576 err_a20 db CR, LF, 'A20 gate not responding!', CR, LF, 0
1577 err_bootfailed db CR, LF, 'Boot failed: please change disks and press '
1578 db 'a key to continue.', CR, LF, 0
1579 ready_msg db 'Ready.', CR, LF, 0
1580 crlfloading_msg db CR, LF
1581 loading_msg db 'Loading ', 0
1584 aborted_msg db ' aborted.' ; Fall through to crlf_msg!
1587 crff_msg db CR, FF, 0
1588 syslinux_cfg1 db '/boot' ; /boot/syslinux/syslinux.cfg
1589 syslinux_cfg2 db '/syslinux' ; /syslinux/syslinux.cfg
1590 syslinux_cfg3 db '/' ; /syslinux.cfg
1591 ConfigName db 'syslinux.cfg', 0 ; syslinux.cfg
1594 ; Command line options we'd like to take a look at
1596 ; mem= and vga= are handled as normal 32-bit integer values
1597 initrd_cmd db 'initrd='
1598 initrd_cmd_len equ 7
1601 ; Config file keyword table
1603 %include "keywords.inc"
1606 ; Extensions to search for (in *forward* order).
1608 exten_table: db 'CBT',0 ; COMBOOT (specific)
1609 db 'BSS',0 ; Boot Sector (add superblock)
1610 db 'BS ',0 ; Boot Sector
1611 db 'COM',0 ; COMBOOT (same as DOS)
1614 dd 0, 0 ; Need 8 null bytes here
1617 ; Misc initialized (data) variables
1619 %ifdef debug ; This code for debugging only
1620 debug_magic dw 0D00Dh ; Debug code sentinel
1624 BufSafe dw trackbufsize/SECTOR_SIZE ; Clusters we can load into trackbuf
1625 BufSafeSec dw trackbufsize/SECTOR_SIZE ; = how many sectors?
1626 BufSafeBytes dw trackbufsize ; = how many bytes?
1627 EndOfGetCBuf dw getcbuf+trackbufsize ; = getcbuf+BufSafeBytes
1629 %if ( trackbufsize % SECTOR_SIZE ) != 0
1630 %error trackbufsize must be a multiple of SECTOR_SIZE