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
68 vk_append: resb max_cmd_len+1 ; Command line
70 vk_end: equ $ ; Should be <= vk_size
74 ; Segment assignments in the bottom 640K
75 ; Stick to the low 512K in case we're using something like M-systems flash
76 ; which load a driver into low RAM (evil!!)
78 ; 0000h - main code/data segment (and BIOS segment)
80 real_mode_seg equ 4000h
81 cache_seg equ 3000h ; 64K area for metadata cache
82 vk_seg equ 2000h ; Virtual kernels
83 xfer_buf_seg equ 1000h ; Bounce buffer for I/O to high mem
84 comboot_seg equ real_mode_seg ; COMBOOT image loading zone
87 ; File structure. This holds the information for each currently open file.
90 file_sector resd 1 ; Sector pointer (0 = structure free)
91 file_left resd 1 ; Number of sectors left
95 %if (open_file_t_size & (open_file_t_size-1))
96 %error "open_file_t is not a power of 2"
100 ; ---------------------------------------------------------------------------
102 ; ---------------------------------------------------------------------------
105 ; Memory below this point is reserved for the BIOS and the MBR
108 trackbufsize equ 8192
109 trackbuf resb trackbufsize ; Track buffer goes here
110 getcbuf resb trackbufsize
116 ; Expanded superblock
118 resq 16 ; The first 16 bytes expanded 8 times
119 FAT resd 1 ; Location of (first) FAT
120 RootDirArea resd 1 ; Location of root directory area
121 RootDir resd 1 ; Location of root directory proper
122 DataArea resd 1 ; Location of data area
123 RootDirSize resd 1 ; Root dir size in sectors
124 TotalSectors resd 1 ; Total number of sectors
125 EndSector resd 1 ; Location of filesystem end
126 ClustSize resd 1 ; Bytes/cluster
127 ClustMask resd 1 ; Sectors/cluster - 1
128 CopySuper resb 1 ; Distinguish .bs versus .bss
129 DriveNumber resb 1 ; BIOS drive number
130 ClustShift resb 1 ; Shift count for sectors/cluster
131 ClustByteShift resb 1 ; Shift count for bytes/cluster
133 alignb open_file_t_size
134 Files resb MAX_OPEN*open_file_t_size
137 ; Constants for the xfer_buf_seg
139 ; The xfer_buf_seg is also used to store message file buffers. We
140 ; need two trackbuffers (text and graphics), plus a work buffer
141 ; for the graphics decompressor.
143 xbs_textbuf equ 0 ; Also hard-coded, do not change
144 xbs_vgabuf equ trackbufsize
145 xbs_vgatmpbuf equ 2*trackbufsize
150 ; Some of the things that have to be saved very early are saved
151 ; "close" to the initial stack pointer offset, in order to
152 ; reduce the code size...
154 StackBuf equ $-44-32 ; Start the stack here (grow down - 4K)
155 PartInfo equ StackBuf ; Saved partition table entry
156 FloppyTable equ PartInfo+16 ; Floppy info table (must follow PartInfo)
157 OrigFDCTabPtr equ StackBuf-4 ; The high dword on the stack
160 ; Primary entry point. Tempting as though it may be, we can't put the
161 ; initial "cli" here; the jmp opcode in the first byte is part of the
162 ; "magic number" (using the term very loosely) for the DOS superblock.
165 jmp short start ; 2 bytes
168 ; "Superblock" follows -- it's in the boot sector, so it's already
169 ; loaded and ready for us
171 bsOemName db 'SYSLINUX' ; The SYS command sets this, so...
173 ; These are the fields we actually care about. We end up expanding them
174 ; all to dword size early in the code, so generate labels for both
175 ; the expanded and unexpanded versions.
178 bx %+ %1 equ SuperInfo+($-superblock)*8+4
183 bx %+ %1 equ SuperInfo+($-superblock)*8
188 bx %+ %1 equ $ ; no expansion for dwords
203 superinfo_size equ ($-superblock)-1 ; How much to expand
207 ; This is as far as FAT12/16 and FAT32 are consistent
209 zb 54 ; FAT12/16 need 26 more bytes,
210 ; FAT32 need 54 more bytes
211 superblock_len equ $-superblock
213 SecPerClust equ bxSecPerClust
215 ; Note we don't check the constraints above now; we did that at install
219 cli ; No interrupts yet, please
226 mov sp,StackBuf ; Just below BSS
229 ; DS:SI may contain a partition table entry. Preserve it for us.
231 mov cx,8 ; Save partition info
235 mov ds,ax ; Now we can initialize DS...
238 ; Now sautee the BIOS floppy info block to that it will support decent-
239 ; size transfers; the floppy block is 11 bytes and is stored in the
240 ; INT 1Eh vector (brilliant waste of resources, eh?)
242 ; Of course, if BIOSes had been properly programmed, we wouldn't have
243 ; had to waste precious space with this code.
246 lfs si,[bx] ; FS:SI -> original fdctab
247 push fs ; Save on stack in case we need to bail
250 ; Save the old fdctab even if hard disk so the stack layout
251 ; is the same. The instructions above do not change the flags
252 mov [DriveNumber],dl ; Save drive number in DL
253 and dl,dl ; If floppy disk (00-7F), assume no
258 mov cl,6 ; 12 bytes (CX == 0)
259 ; es:di -> FloppyTable already
260 ; This should be safe to do now, interrupts are off...
261 mov [bx],di ; FloppyTable
262 mov [bx+2],ax ; Segment 0
263 fs rep movsw ; Faster to move words
264 mov cl,[bsSecPerTrack] ; Patch the sector count
267 int 13h ; Some BIOSes need this
269 jmp short not_harddisk
271 ; The drive number and possibly partition information was passed to us
272 ; by the BIOS or previous boot loader (MBR). Current "best practice" is to
273 ; trust that rather than what the superblock contains.
275 ; Would it be better to zero out bsHidden if we don't have a partition table?
277 ; Note: di points to beyond the end of PartInfo
280 test byte [di-16],7Fh ; Sanity check: "active flag" should
281 jnz no_partition ; be 00 or 80
282 mov eax,[di-8] ; Partition offset (dword)
286 ; Get disk drive parameters (don't trust the superblock.) Don't do this for
287 ; floppy drives -- INT 13:08 on floppy drives will (may?) return info about
288 ; what the *drive* supports, not about the *media*. Fortunately floppy disks
289 ; tend to have a fixed, well-defined geometry which is stored in the superblock.
291 ; DL == drive # still
298 inc dx ; Contains # of heads - 1
301 mov [bsSecPerTrack],cx
305 ; Ready to enable interrupts, captain
310 ; Do we have EBIOS (EDD)?
314 mov ah,41h ; EDD existence query
320 test cl,1 ; Extended disk access functionality set
323 ; We have EDD support...
325 mov byte [getlinsec.jmp+1],(getlinsec_ebios-(getlinsec.jmp+2))
329 ; Load the first sector of LDLINUX.SYS; this used to be all proper
330 ; with parsing the superblock and root directory; it doesn't fit
331 ; together with EBIOS support, unfortunately.
333 mov eax,[FirstSector] ; Sector start
334 mov bx,ldlinux_sys ; Where to load it
337 ; Some modicum of integrity checking
338 cmp dword [ldlinux_magic+4],LDLINUX_MAGIC^HEXDATE
345 ; getonesec: get one disk sector
348 mov bp,1 ; One sector
352 ; getlinsec: load a sequence of BP floppy sector given by the linear sector
353 ; number in EAX into the buffer at ES:BX. We try to optimize
354 ; by loading up to a whole track at a time, but the user
355 ; is responsible for not crossing a 64K boundary.
356 ; (Yes, BP is weird for a count, but it was available...)
358 ; On return, BX points to the first byte after the transferred
361 ; This routine assumes CS == DS, and trashes most registers.
363 ; Stylistic note: use "xchg" instead of "mov" when the source is a register
364 ; that is dead from that point; this saves space. However, please keep
365 ; the order to dst,src to keep things sane.
368 add eax,[bsHidden] ; Add partition offset
369 xor edx,edx ; Zero-extend LBA (eventually allow 64 bits)
371 .jmp: jmp strict short getlinsec_cbios
376 ; getlinsec implementation for EBIOS (EDD)
380 push bp ; Sectors left
382 call maxtrans ; Enforce maximum transfer size
383 movzx edi,bp ; Sectors we are about to read
400 mov ah,42h ; Extended Read
404 lea sp,[si+16] ; Remove DAPA
407 add eax,edi ; Advance sector pointer
408 sub bp,di ; Sectors left
409 shl di,SECTOR_SHIFT ; 512-byte sectors
410 add bx,di ; Advance buffer pointer
417 ; Some systems seem to get "stuck" in an error state when
418 ; using EBIOS. Doesn't happen when using CBIOS, which is
419 ; good, since some other systems get timeout failures
420 ; waiting for the floppy disk to spin up.
422 pushad ; Try resetting the device
427 loop .retry ; CX-- and jump if not zero
429 ;shr word [MaxTransfer],1 ; Reduce the transfer size
432 ; Total failure. Try falling back to CBIOS.
433 mov byte [getlinsec.jmp+1],(getlinsec_cbios-(getlinsec.jmp+2))
434 ;mov byte [MaxTransfer],63 ; Max possibe CBIOS transfer
437 ; ... fall through ...
442 ; getlinsec implementation for legacy CBIOS
451 movzx esi,word [bsSecPerTrack]
452 movzx edi,word [bsHeads]
454 ; Dividing by sectors to get (track,sector): we may have
455 ; up to 2^18 tracks, so we need to use 32-bit arithmetric.
459 xchg cx,dx ; CX <- sector index (0-based)
462 div edi ; Convert track to head/cyl
464 ; We should test this, but it doesn't fit...
469 ; Now we have AX = cyl, DX = head, CX = sector (0-based),
470 ; BP = sectors to transfer, SI = bsSecPerTrack,
471 ; ES:BX = data target
474 call maxtrans ; Enforce maximum transfer size
476 ; Must not cross track boundaries, so BP <= SI-CX
483 shl ah,6 ; Because IBM was STOOPID
484 ; and thought 8 bits were enough
485 ; then thought 10 bits were enough...
486 inc cx ; Sector numbers are 1-based, sigh
491 xchg ax,bp ; Sector to transfer count
492 mov ah,02h ; Read sectors
500 movzx ecx,al ; ECX <- sectors transferred
501 shl ax,SECTOR_SHIFT ; Convert sectors in AL to bytes in AX
516 xchg ax,bp ; Sectors transferred <- 0
517 shr word [MaxTransfer],1
519 ; Fall through to disk_error
522 ; kaboom: write a message and bail out.
528 mov sp,StackBuf-4 ; Reset stack
529 mov ds,si ; Reset data segment
530 pop dword [fdctab] ; Restore FDC table
531 .patch: ; When we have full code, intercept here
534 ; Write error message, this assumes screen page 0
538 mov ah,0Eh ; Write to screen as TTY
539 mov bx,0007h ; Attribute
544 int 16h ; Wait for keypress
545 int 19h ; And try once more to boot...
546 .norge: jmp short .norge ; If int 19h returned; this is the end
549 ; Truncate BP to MaxTransfer
558 ; Error message on failure
560 bailmsg: db 'Boot error', 0Dh, 0Ah, 0
562 ; This fails if the boot sector overflows
565 FirstSector dd 0xDEADBEEF ; Location of sector 1
566 MaxTransfer dw 0x007F ; Max transfer size
567 bootsignature dw 0AA55h
570 ; ===========================================================================
572 ; ===========================================================================
573 ; Start of LDLINUX.SYS
574 ; ===========================================================================
578 syslinux_banner db 0Dh, 0Ah
584 db version_str, ' ', date, ' ', 0
585 db 0Dh, 0Ah, 1Ah ; EOF if we "type" this in DOS
588 ldlinux_magic dd LDLINUX_MAGIC
589 dd LDLINUX_MAGIC^HEXDATE
592 ; This area is patched by the installer. It is found by looking for
593 ; LDLINUX_MAGIC, plus 8 bytes.
596 LDLDwords dw 0 ; Total dwords starting at ldlinux_sys
597 LDLSectors dw 0 ; Number of sectors - (bootsec+this sec)
598 CheckSum dd 0 ; Checksum starting at ldlinux_sys
599 ; value = LDLINUX_MAGIC - [sum of dwords]
601 ; Space for up to 64 sectors, the theoretical maximum
602 SectorPtrs times 64 dd 0
606 ; Note that some BIOSes are buggy and run the boot sector at 07C0:0000
607 ; instead of 0000:7C00 and the like. We don't want to add anything
608 ; more to the boot sector, so it is written to not assume a fixed
609 ; value in CS, but we don't want to deal with that anymore from now
616 ; Tell the user we got this far
618 mov si,syslinux_banner
622 ; Tell the user if we're using EBIOS or CBIOS
626 cmp byte [getlinsec.jmp+1],(getlinsec_ebios-(getlinsec.jmp+2))
634 %define HAVE_BIOSNAME 1
639 ; Now we read the rest of LDLINUX.SYS. Don't bother loading the first
640 ; sector again, though.
644 mov bx,7C00h+2*SECTOR_SIZE ; Where we start loading
650 lodsd ; First sector of this chunk
658 inc edx ; Next linear sector
659 cmp [si],edx ; Does it match
660 jnz .chunk_ready ; If not, this is it
661 add si,4 ; If so, add sector to chunk
662 jmp short .make_chunk
673 ; All loaded up, verify that we got what we needed.
674 ; Note: the checksum field is embedded in the checksum region, so
675 ; by the time we get to the end it should all cancel out.
680 mov edx,-LDLINUX_MAGIC
686 and edx,edx ; Should be zero
687 jz all_read ; We're cool, go for it!
690 ; Uh-oh, something went bad...
692 mov si,checksumerr_msg
697 ; -----------------------------------------------------------------------------
698 ; Subroutines that have to be in the first sector
699 ; -----------------------------------------------------------------------------
703 ; writestr: write a null-terminated string to the console
704 ; This assumes we're on page 0. This is only used for early
705 ; messages, so it should be OK.
711 mov ah,0Eh ; Write to screen as TTY
712 mov bx,0007h ; Attribute
718 ; getlinsecsr: save registers, call getlinsec, restore registers
726 ; Checksum error message
728 checksumerr_msg db ' Load error - ', 0 ; Boot failed appended
733 cbios_name db 'CBIOS', 0
734 ebios_name db 'EBIOS', 0
741 cmp word [Debug_Magic],0D00Dh
746 rl_checkpt equ $ ; Must be <= 8000h
748 rl_checkpt_off equ ($-$$)
750 %if rl_checkpt_off > 400h
751 %error "Sector 1 overflow"
755 ; ----------------------------------------------------------------------------
756 ; End of code and data that have to be in the first sector
757 ; ----------------------------------------------------------------------------
761 ; Let the user (and programmer!) know we got this far. This used to be
762 ; in Sector 1, but makes a lot more sense here.
769 ; Insane hack to expand the superblock to dwords
775 mov cx,superinfo_size
779 stosd ; Store expanded word
781 stosd ; Store expanded byte
785 ; Compute some information about this filesystem.
788 ; First, generate the map of regions
793 mov edx,[bsHugeSectors]
795 mov [TotalSectors],edx
800 mov eax,[bxResSectors]
801 mov [FAT],eax ; Beginning of FAT
805 mov edx,[bootsec+36] ; FAT32 BPB_FATsz32
809 mov [RootDirArea],eax ; Beginning of root directory
810 mov [RootDir],eax ; For FAT12/16 == root dir location
812 mov edx,[bxRootDirEnts]
813 add dx,SECTOR_SIZE/32-1
814 shr dx,SECTOR_SHIFT-5
815 mov [RootDirSize],edx
817 mov [DataArea],eax ; Beginning of data area
819 ; Next, generate a cluster size shift count and mask
820 mov eax,[bxSecPerClust]
825 mov [ClustByteShift],cl
834 ; FAT12, FAT16 or FAT28^H^H32? This computation is fscking ridiculous.
839 shr eax,cl ; cl == ClustShift
840 mov cl,nextcluster_fat12-(nextcluster+2)
841 cmp eax,4085 ; FAT12 limit
843 mov cl,nextcluster_fat16-(nextcluster+2)
844 cmp eax,65525 ; FAT16 limit
847 ; FAT32, root directory is a cluster chain
850 mov eax,[bootsec+44] ; Root directory cluster
855 mov cl,nextcluster_fat28-(nextcluster+2)
857 mov byte [nextcluster+1],cl
860 ; Common initialization code
862 %include "cpuinit.inc"
866 ; Clear Files structures
869 mov cx,(MAX_OPEN*open_file_t_size)/4
874 ; Initialize the metadata cache
879 ; Now, everything is "up and running"... patch kaboom for more
880 ; verbosity and using the full screen system
883 mov dword [kaboom.patch],0e9h+((kaboom2-(kaboom.patch+3)) << 8)
886 ; Now we're all set to start with our *real* business. First load the
887 ; configuration file (if any) and parse it.
889 ; In previous versions I avoided using 32-bit registers because of a
890 ; rumour some BIOSes clobbered the upper half of 32-bit registers at
891 ; random. I figure, though, that if there are any of those still left
892 ; they probably won't be trying to install Linux on them...
894 ; The code is still ripe with 16-bitisms, though. Not worth the hassle
895 ; to take'm out. In fact, we may want to put them back if we're going
896 ; to boot ELKS at some point.
900 ; Load configuration file
912 mov eax,[PrevDir] ; Make the directory with syslinux.cfg ...
913 mov [CurrentDir],eax ; ... the current directory
916 ; Now we have the config file open. Parse the config file and
917 ; run the user interface.
922 ; Linux kernel loading code is common.
924 %include "runkernel.inc"
927 ; COMBOOT-loading code
929 %include "comboot.inc"
931 %include "cmdline.inc"
934 ; Boot sector loading code
936 %include "bootsect.inc"
944 ; allocate_file: Allocate a file structure
957 .check: cmp dword [bx], byte 0
959 add bx,open_file_t_size ; ZF = 0
961 ; ZF = 0 if we fell out of the loop
967 ; Search a specific directory for a pre-mangled filename in
968 ; MangledBuf, in the directory starting in sector EAX.
970 ; NOTE: This file considers finding a zero-length file an
971 ; error. This is so we don't have to deal with that special
972 ; case elsewhere in the program (most loops have the test
975 ; Assumes DS == ES == CS.
980 ; EAX = file length (MAY BE ZERO!)
981 ; DL = file attributes
998 ; EAX <- directory sector to scan
1000 ; GS:SI now points to this sector
1002 mov cx,SECTOR_SIZE/32 ; 32 == directory entry size
1005 jz .failure ; Hit directory high water mark
1006 test byte [gs:si+11],8 ; Ignore volume labels and
1007 ; VFAT long filename entries
1024 jnc .scansector ; CF is set if we're at end
1026 ; If we get here, we failed
1033 xor eax,eax ; ZF <- 1
1036 mov eax,[gs:si+28] ; File size
1037 add eax,SECTOR_SIZE-1
1038 shr eax,SECTOR_SHIFT
1039 mov [bx+4],eax ; Sector count
1042 mov dx,[gs:si+20] ; High cluster word
1044 mov dx,[gs:si+26] ; Low cluster word
1048 mov [bx],edx ; Starting sector
1050 mov eax,[gs:si+28] ; File length again
1051 mov dl,[gs:si+11] ; File attribute
1052 mov si,bx ; File pointer...
1071 ; DX:AX or EAX = file length in bytes
1075 ; Assumes CS == DS == ES, and trashes BX and CX.
1078 mov eax,[CurrentDir]
1079 cmp byte [di],'/' ; Root directory?
1086 push eax ; <A> Current directory sector
1096 pop eax ; <A> Current directory sector
1098 mov [PrevDir],eax ; Remember last directory searched
1101 call mangle_dos_name ; MangledBuf <- component
1104 jz .notfound ; Pathname component missing
1106 cmp byte [di-1],'/' ; Do we expect a directory
1109 ; Otherwise, it should be a file
1111 test dl,18h ; Subdirectory|Volume Label
1112 jnz .badfile ; If not a file, it's a bad thing
1114 ; SI and EAX are already set
1116 shr edx,16 ; Old 16-bit remnant...
1117 and eax,eax ; EAX != 0
1121 ; If we expected a directory, it better be one...
1123 test dl,10h ; Subdirectory
1127 xchg eax,[si+file_sector] ; Get sector number and free file structure
1128 jmp .pathwalk ; Walk the next bit of the path
1132 mov [si],eax ; Free file structure
1141 CurrentDir resd 1 ; Current directory
1142 PrevDir resd 1 ; Last scanned directory
1148 ; kaboom2: once everything is loaded, replace the part of kaboom
1149 ; starting with "kaboom.patch" with this part
1152 mov si,err_bootfailed
1156 int 19h ; And try once more to boot...
1157 .norge: jmp short .norge ; If int 19h returned; this is the end
1160 ; mangle_name: Mangle a filename pointed to by DS:SI into a buffer pointed
1161 ; to by ES:DI; ends on encountering any whitespace.
1163 ; This verifies that a filename is < FILENAME_MAX characters,
1164 ; doesn't contain whitespace, zero-pads the output buffer,
1165 ; and removes trailing dots and redundant slashes, plus changes
1166 ; backslashes to forward slashes,
1167 ; so "repe cmpsb" can do a compare, and the path-searching routine
1168 ; gets a bit of an easier job.
1174 mov cx,FILENAME_MAX-1
1179 cmp al,' ' ; If control or space, end
1181 cmp al,'\' ; Backslash?
1183 mov al,'/' ; Change to forward slash
1185 cmp al,ah ; Repeated slash?
1192 .mn_skip: loop .mn_loop
1194 cmp bx,di ; At the beginning of the buffer?
1196 cmp byte [es:di-1],'.' ; Terminal dot?
1198 cmp byte [es:di-1],'/' ; Terminal slash?
1200 .mn_kill: dec di ; If so, remove it
1204 inc cx ; At least one null byte
1205 xor ax,ax ; Zero-fill name
1211 ; unmangle_name: Does the opposite of mangle_name; converts a DOS-mangled
1212 ; filename to the conventional representation. This is needed
1213 ; for the BOOT_IMAGE= parameter for the kernel.
1214 ; NOTE: A 13-byte buffer is mandatory, even if the string is
1215 ; known to be shorter.
1217 ; DS:SI -> input mangled file name
1218 ; ES:DI -> output buffer
1220 ; On return, DI points to the first byte after the output name,
1221 ; which is set to a null byte.
1223 unmangle_name: call strcpy
1224 dec di ; Point to final null byte
1229 ; Mangle a DOS filename component pointed to by DS:SI
1230 ; into [MangledBuf]; ends on encountering any whitespace or slash.
1231 ; Assumes CS == DS == ES.
1238 mov cx,11 ; # of bytes to write
1241 cmp al,' ' ; If control or space, end
1243 cmp al,'/' ; Slash, too
1245 cmp al,'.' ; Period -> space-fill
1252 jmp short .not_lower
1253 .is_period: mov al,' ' ; We need to space-fill
1254 .period_loop: cmp cx,3 ; If <= 3 characters left
1255 jbe .loop ; Just ignore it
1256 stosb ; Otherwise, write a period
1257 loop .period_loop ; Dec CX and (always) jump
1258 .not_uslower: cmp al,ucase_low
1262 mov bx,ucase_tab-ucase_low
1265 loop .loop ; Don't continue if too long
1267 mov al,' ' ; Space-fill name
1268 rep stosb ; Doesn't do anything if CX=0
1277 ; Case tables for extended characters; this is technically code page 865,
1278 ; but code page 437 users will probably not miss not being able to use the
1279 ; cent sign in kernel images too much :-)
1281 ; The table only covers the range 129 to 164; the rest we can deal with.
1287 ucase_tab db 154, 144, 'A', 142, 'A', 143, 128, 'EEEIII'
1288 db 142, 143, 144, 146, 146, 'O', 153, 'OUUY', 153, 154
1289 db 157, 156, 157, 158, 159, 'AIOU', 165
1293 ; getfssec_edx: Get multiple sectors from a file
1295 ; This routine makes sure the subtransfers do not cross a 64K boundary,
1296 ; and will correct the situation if it does, UNLESS *sectors* cross
1300 ; EDX -> Current sector number
1301 ; CX -> Sector count (0FFFFh = until end of file)
1302 ; Must not exceed the ES segment
1303 ; Returns EDX=0, CF=1 on EOF (not necessarily error)
1304 ; All arguments are advanced to reflect data read.
1310 xor ebp,ebp ; Fragment sector count
1311 push edx ; Starting sector pointer
1319 add ax,bx ; Now AX = how far into 64K block we are
1320 not ax ; Bytes left in 64K block
1322 shr eax,SECTOR_SHIFT ; Sectors left in 64K block
1324 jnb .do_read ; Unless there is at least 1 more sector room...
1325 mov eax,edx ; Current sector
1326 inc edx ; Predict it's the linearly next sector
1329 cmp edx,eax ; Did it match?
1332 pop eax ; Starting sector pointer
1334 lea eax,[eax+ebp-1] ; This is the last sector actually read
1336 add bx,bp ; Adjust buffer pointer
1352 ; getfssec: Get multiple sectors from a file
1354 ; Same as above, except SI is a pointer to a open_file_t
1357 ; DS:SI -> Pointer to open_file_t
1358 ; CX -> Sector count (0FFFFh = until end of file)
1359 ; Must not exceed the ES segment
1360 ; Returns CF=1 on EOF (not necessarily error)
1361 ; All arguments are advanced to reflect data read.
1379 ; nextcluster: Advance a cluster pointer in EDI to the next cluster
1380 ; pointed at in the FAT tables. CF=0 on return if end of file.
1383 jmp strict short nextcluster_fat28 ; This gets patched
1393 pushf ; Save the shifted-out LSB (=CF)
1422 ; FAT16 decoding routine.
1429 shr eax,SECTOR_SHIFT-1
1434 movzx edi,word [gs:si+bx]
1441 ; FAT28 ("FAT32") decoding routine.
1448 shr eax,SECTOR_SHIFT-2
1454 mov edi,dword [gs:si+bx]
1455 and edi,0FFFFFFFh ; 28 bits only
1463 ; nextsector: Given a sector in EAX on input, return the next sector
1464 ; of the same filesystem object, which may be the root
1465 ; directory or a cluster chain. Returns EOF.
1485 test edi,[ClustMask]
1488 ; It's not the final sector in a cluster
1493 push gs ; nextcluster trashes gs
1500 ; Now EDI contains the cluster number
1503 jc .exit ; There isn't anything else...
1505 ; New cluster number now in EDI
1507 shl edi,cl ; CF <- 0, unless something is very wrong
1518 ; getfatsector: Check for a particular sector (in EAX) in the FAT cache,
1519 ; and return a pointer in GS:SI, loading it if needed.
1524 add eax,[FAT] ; FAT starting address
1527 ; -----------------------------------------------------------------------------
1529 ; -----------------------------------------------------------------------------
1531 %include "getc.inc" ; getc et al
1532 %include "conio.inc" ; Console I/O
1533 %include "plaincon.inc" ; writechr
1534 %include "writestr.inc" ; String output
1535 %include "parseconfig.inc" ; High-level config file handling
1536 %include "parsecmd.inc" ; Low-level config file handling
1537 %include "bcopy32.inc" ; 32-bit bcopy
1538 %include "loadhigh.inc" ; Load a file into high memory
1539 %include "font.inc" ; VGA font stuff
1540 %include "graphics.inc" ; VGA graphics
1541 %include "highmem.inc" ; High memory sizing
1542 %include "strcpy.inc" ; strcpy()
1543 %include "cache.inc" ; Metadata disk cache
1545 ; -----------------------------------------------------------------------------
1546 ; Begin data section
1547 ; -----------------------------------------------------------------------------
1550 copyright_str db ' Copyright (C) 1994-', year, ' H. Peter Anvin'
1552 boot_prompt db 'boot: ', 0
1553 wipe_char db BS, ' ', BS, 0
1554 err_notfound db 'Could not find kernel image: ',0
1555 err_notkernel db CR, LF, 'Invalid or corrupt kernel image.', CR, LF, 0
1556 err_noram db 'It appears your computer has less than '
1558 db 'K of low ("DOS")'
1560 db 'RAM. Linux needs at least this amount to boot. If you get'
1562 db 'this message in error, hold down the Ctrl key while'
1564 db 'booting, and I will take your word for it.', CR, LF, 0
1565 err_badcfg db 'Unknown keyword in syslinux.cfg.', CR, LF, 0
1566 err_noparm db 'Missing parameter in syslinux.cfg.', CR, LF, 0
1567 err_noinitrd db CR, LF, 'Could not find ramdisk image: ', 0
1568 err_nohighmem db 'Not enough memory to load specified kernel.', CR, LF, 0
1569 err_highload db CR, LF, 'Kernel transfer failure.', CR, LF, 0
1570 err_oldkernel db 'Cannot load a ramdisk with an old kernel image.'
1572 err_notdos db ': attempted DOS system call', CR, LF, 0
1573 err_comlarge db 'COMBOOT image too large.', CR, LF, 0
1574 err_a20 db CR, LF, 'A20 gate not responding!', CR, LF, 0
1575 err_bootfailed db CR, LF, 'Boot failed: please change disks and press '
1576 db 'a key to continue.', CR, LF, 0
1577 ready_msg db 'Ready.', CR, LF, 0
1578 crlfloading_msg db CR, LF
1579 loading_msg db 'Loading ', 0
1582 aborted_msg db ' aborted.' ; Fall through to crlf_msg!
1585 crff_msg db CR, FF, 0
1586 syslinux_cfg1 db '/boot' ; /boot/syslinux/syslinux.cfg
1587 syslinux_cfg2 db '/syslinux' ; /syslinux/syslinux.cfg
1588 syslinux_cfg3 db '/' ; /syslinux.cfg
1589 ConfigName db 'syslinux.cfg', 0 ; syslinux.cfg
1592 ; Command line options we'd like to take a look at
1594 ; mem= and vga= are handled as normal 32-bit integer values
1595 initrd_cmd db 'initrd='
1596 initrd_cmd_len equ 7
1599 ; Config file keyword table
1601 %include "keywords.inc"
1604 ; Extensions to search for (in *forward* order).
1606 exten_table: db 'CBT',0 ; COMBOOT (specific)
1607 db 'BSS',0 ; Boot Sector (add superblock)
1608 db 'BS ',0 ; Boot Sector
1609 db 'COM',0 ; COMBOOT (same as DOS)
1612 dd 0, 0 ; Need 8 null bytes here
1615 ; Misc initialized (data) variables
1617 %ifdef debug ; This code for debugging only
1618 debug_magic dw 0D00Dh ; Debug code sentinel
1622 BufSafe dw trackbufsize/SECTOR_SIZE ; Clusters we can load into trackbuf
1623 BufSafeSec dw trackbufsize/SECTOR_SIZE ; = how many sectors?
1624 BufSafeBytes dw trackbufsize ; = how many bytes?
1625 EndOfGetCBuf dw getcbuf+trackbufsize ; = getcbuf+BufSafeBytes
1627 %if ( trackbufsize % SECTOR_SIZE ) != 0
1628 %error trackbufsize must be a multiple of SECTOR_SIZE