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) 1994-2005 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 16 ; 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
315 ; Do we have EBIOS (EDD)?
319 mov ah,41h ; EDD existence query
325 test cl,1 ; Extended disk access functionality set
328 ; We have EDD support...
331 mov word [getlinsec_cbios],((getlinsec_ebios-(getlinsec_cbios+2)) << 8) + 0xeb
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+4],LDLINUX_MAGIC^HEXDATE
351 ; getonesec: get one disk sector
354 mov bp,1 ; One sector
358 ; getlinsec: load a sequence of BP floppy sector given by the linear sector
359 ; number in EAX into the buffer at ES:BX. We try to optimize
360 ; by loading up to a whole track at a time, but the user
361 ; is responsible for not crossing a 64K boundary.
362 ; (Yes, BP is weird for a count, but it was available...)
364 ; On return, BX points to the first byte after the transferred
367 ; This routine assumes CS == DS, and trashes most registers.
369 ; Stylistic note: use "xchg" instead of "mov" when the source is a register
370 ; that is dead from that point; this saves space. However, please keep
371 ; the order to dst,src to keep things sane.
374 add eax,[bsHidden] ; Add partition offset
375 xor edx,edx ; Zero-extend LBA (eventually allow 64 bits)
377 ; Fall through. In the case of EBIOS, we patch over the first instruction.
381 ; getlinsec implementation for legacy CBIOS
390 movzx esi,word [bsSecPerTrack]
391 movzx edi,word [bsHeads]
393 ; Dividing by sectors to get (track,sector): we may have
394 ; up to 2^18 tracks, so we need to use 32-bit arithmetric.
398 xchg cx,dx ; CX <- sector index (0-based)
401 div edi ; Convert track to head/cyl
403 ; We should test this, but it doesn't fit...
408 ; Now we have AX = cyl, DX = head, CX = sector (0-based),
409 ; BP = sectors to transfer, SI = bsSecPerTrack,
410 ; ES:BX = data target
413 call maxtrans ; Enforce maximum transfer size
415 ; Must not cross track boundaries, so BP <= SI-CX
422 shl ah,6 ; Because IBM was STOOPID
423 ; and thought 8 bits were enough
424 ; then thought 10 bits were enough...
425 inc cx ; Sector numbers are 1-based, sigh
430 xchg ax,bp ; Sector to transfer count
431 mov ah,02h ; Read sectors
439 movzx ecx,al ; ECX <- sectors transferred
440 shl ax,SECTOR_SHIFT ; Convert sectors in AL to bytes in AX
455 xor ax,ax ; Sectors transferred <- 0
456 shr word [MaxTransfer],1
463 ; getlinsec implementation for EBIOS (EDD)
467 push bp ; Sectors left
469 call maxtrans ; Enforce maximum transfer size
470 movzx edi,bp ; Sectors we are about to read
483 mov ah,42h ; Extended Read
491 lea sp,[si+16] ; Remove DAPA
494 add eax,edi ; Advance sector pointer
495 sub bp,di ; Sectors left
496 shl di,SECTOR_SHIFT ; 512-byte sectors
497 add bx,di ; Advance buffer pointer
504 ; Some systems seem to get "stuck" in an error state when
505 ; using EBIOS. Doesn't happen when using CBIOS, which is
506 ; good, since some other systems get timeout failures
507 ; waiting for the floppy disk to spin up.
509 pushad ; Try resetting the device
513 loop .retry ; CX-- and jump if not zero
515 shr word [MaxTransfer],1 ; Reduce the transfer size
518 ; Fall back to CBIOS here?
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
560 ; Error message on failure
562 bailmsg: db 'Boot failed', 0Dh, 0Ah, 0
565 bs_checkpt_off equ ($-$$)
567 %if bs_checkpt_off > 1F8h
568 %error "Boot sector overflow"
574 FirstSector dd 0xDEADBEEF ; Location of sector 1
575 MaxTransfer dw 0x007F ; Max transfer size
576 bootsignature dw 0AA55h
579 ; ===========================================================================
581 ; ===========================================================================
582 ; Start of LDLINUX.SYS
583 ; ===========================================================================
587 syslinux_banner db 0Dh, 0Ah
593 db version_str, ' ', date, ' ', 0
594 db 0Dh, 0Ah, 1Ah ; EOF if we "type" this in DOS
597 ldlinux_magic dd LDLINUX_MAGIC
598 dd LDLINUX_MAGIC^HEXDATE
601 ; This area is patched by the installer. It is found by looking for
602 ; LDLINUX_MAGIC, plus 8 bytes.
605 LDLDwords dw 0 ; Total dwords starting at ldlinux_sys
606 LDLSectors dw 0 ; Number of sectors - (bootsec+this sec)
607 CheckSum dd 0 ; Checksum starting at ldlinux_sys
608 ; value = LDLINUX_MAGIC - [sum of dwords]
610 ; Space for up to 64 sectors, the theoretical maximum
611 SectorPtrs times 64 dd 0
615 ; Note that some BIOSes are buggy and run the boot sector at 07C0:0000
616 ; instead of 0000:7C00 and the like. We don't want to add anything
617 ; more to the boot sector, so it is written to not assume a fixed
618 ; value in CS, but we don't want to deal with that anymore from now
625 ; Tell the user we got this far
627 mov si,syslinux_banner
631 ; Now we read the rest of LDLINUX.SYS. Don't bother loading the first
632 ; sector again, though.
636 mov bx,7C00h+2*SECTOR_SIZE ; Where we start loading
642 lodsd ; First sector of this chunk
650 inc edx ; Next linear sector
651 cmp [esi],edx ; Does it match
652 jnz .chunk_ready ; If not, this is it
653 add esi,4 ; If so, add sector to chunk
654 jmp short .make_chunk
665 ; All loaded up, verify that we got what we needed.
666 ; Note: the checksum field is embedded in the checksum region, so
667 ; by the time we get to the end it should all cancel out.
672 mov edx,-LDLINUX_MAGIC
678 and edx,edx ; Should be zero
679 jz all_read ; We're cool, go for it!
682 ; Uh-oh, something went bad...
684 mov si,checksumerr_msg
689 ; -----------------------------------------------------------------------------
690 ; Subroutines that have to be in the first sector
691 ; -----------------------------------------------------------------------------
695 ; writestr: write a null-terminated string to the console
696 ; This assumes we're on page 0. This is only used for early
697 ; messages, so it should be OK.
703 mov ah,0Eh ; Write to screen as TTY
704 mov bx,0007h ; Attribute
710 ; getlinsecsr: save registers, call getlinsec, restore registers
718 ; Checksum error message
720 checksumerr_msg db 'Load error - ', 0 ; Boot failed appended
727 cmp word [Debug_Magic],0D00Dh
732 rl_checkpt equ $ ; Must be <= 8000h
734 rl_checkpt_off equ ($-$$)
736 %if rl_checkpt_off > 400h
737 %error "Sector 1 overflow"
741 ; ----------------------------------------------------------------------------
742 ; End of code and data that have to be in the first sector
743 ; ----------------------------------------------------------------------------
747 ; Let the user (and programmer!) know we got this far. This used to be
748 ; in Sector 1, but makes a lot more sense here.
755 ; Insane hack to expand the superblock to dwords
761 mov cx,superinfo_size
765 stosd ; Store expanded word
767 stosd ; Store expanded byte
771 ; Compute some information about this filesystem.
774 ; First, generate the map of regions
779 mov edx,[bsHugeSectors]
781 mov [TotalSectors],edx
786 mov eax,[bxResSectors]
787 mov [FAT],eax ; Beginning of FAT
791 mov edx,[bootsec+36] ; FAT32 BPB_FATsz32
795 mov [RootDirArea],eax ; Beginning of root directory
796 mov [RootDir],eax ; For FAT12/16 == root dir location
798 mov edx,[bxRootDirEnts]
799 add dx,SECTOR_SIZE/32-1
800 shr dx,SECTOR_SHIFT-5
801 mov [RootDirSize],edx
803 mov [DataArea],eax ; Beginning of data area
805 ; Next, generate a cluster size shift count and mask
806 mov eax,[bxSecPerClust]
811 mov [ClustByteShift],cl
820 ; FAT12, FAT16 or FAT28^H^H32? This computation is fscking ridiculous.
825 shr eax,cl ; cl == ClustShift
826 mov cl,nextcluster_fat12-(nextcluster+2)
827 cmp eax,4085 ; FAT12 limit
829 mov cl,nextcluster_fat16-(nextcluster+2)
830 cmp eax,65525 ; FAT16 limit
833 ; FAT32, root directory is a cluster chain
836 mov eax,[bootsec+44] ; Root directory cluster
841 mov cl,nextcluster_fat28-(nextcluster+2)
843 mov byte [nextcluster+1],cl
846 ; Common initialization code
848 %include "cpuinit.inc"
852 ; Clear Files structures
855 mov cx,(MAX_OPEN*open_file_t_size)/4
860 ; Initialize the metadata cache
865 ; Now, everything is "up and running"... patch kaboom for more
866 ; verbosity and using the full screen system
869 mov dword [kaboom.patch],0e9h+((kaboom2-(kaboom.patch+3)) << 8)
872 ; Now we're all set to start with our *real* business. First load the
873 ; configuration file (if any) and parse it.
875 ; In previous versions I avoided using 32-bit registers because of a
876 ; rumour some BIOSes clobbered the upper half of 32-bit registers at
877 ; random. I figure, though, that if there are any of those still left
878 ; they probably won't be trying to install Linux on them...
880 ; The code is still ripe with 16-bitisms, though. Not worth the hassle
881 ; to take'm out. In fact, we may want to put them back if we're going
882 ; to boot ELKS at some point.
886 ; Load configuration file
893 ; Now we have the config file open. Parse the config file and
894 ; run the user interface.
899 ; Linux kernel loading code is common.
901 %include "runkernel.inc"
904 ; COMBOOT-loading code
906 %include "comboot.inc"
908 %include "cmdline.inc"
911 ; Boot sector loading code
913 %include "bootsect.inc"
916 ; abort_check: let the user abort with <ESC> or <Ctrl-C>
927 ac_kill: mov si,aborted_msg
930 ; abort_load: Called by various routines which wants to print a fatal
931 ; error message and return to the command prompt. Since this
932 ; may happen at just about any stage of the boot process, assume
933 ; our state is messed up, and just reset the segment registers
934 ; and the stack forcibly.
936 ; SI = offset (in _text) of error message to print
939 mov ax,cs ; Restore CS = DS = ES
943 mov sp,StackBuf-2*3 ; Reset stack
944 mov ss,ax ; Just in case...
946 call cwritestr ; Expects SI -> error msg
947 al_ok: jmp enter_command ; Return to command prompt
955 ; allocate_file: Allocate a file structure
968 .check: cmp dword [bx], byte 0
970 add bx,open_file_t_size ; ZF = 0
972 ; ZF = 0 if we fell out of the loop
978 ; Search the root directory for a pre-mangled filename in DS:DI.
980 ; NOTE: This file considers finding a zero-length file an
981 ; error. This is so we don't have to deal with that special
982 ; case elsewhere in the program (most loops have the test
988 ; DX:AX = file length in bytes
1002 mov eax,[RootDir] ; First root directory sector
1006 ; GS:SI now points to this sector
1008 mov cx,SECTOR_SIZE/32 ; 32 == directory entry size
1011 jz .failure ; Hit directory high water mark
1025 jnc .scansector ; CF is set if we're at end
1027 ; If we get here, we failed
1035 mov eax,[gs:si+28] ; File size
1036 add eax,SECTOR_SIZE-1
1037 shr eax,SECTOR_SHIFT
1038 jz .failure ; Zero-length file
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 dx,[gs:si+30] ; 16-bitism, sigh
1053 and eax,eax ; ZF <- 0
1060 ; writechr: Write a single character in AL to the console without
1061 ; mangling any registers; handle video pages correctly.
1064 call write_serial ; write to serial port if needed
1066 test byte [cs:DisplayCon], 01h
1070 mov bl,07h ; attribute
1071 mov bh,[cs:BIOS_page] ; current page
1080 ; kaboom2: once everything is loaded, replace the part of kaboom
1081 ; starting with "kaboom.patch" with this part
1084 mov si,err_bootfailed
1088 int 19h ; And try once more to boot...
1089 .norge: jmp short .norge ; If int 19h returned; this is the end
1092 ; mangle_name: Mangle a DOS filename pointed to by DS:SI into a buffer pointed
1093 ; to by ES:DI; ends on encountering any whitespace
1097 mov cx,11 ; # of bytes to write
1100 cmp al,' ' ; If control or space, end
1102 cmp al,'.' ; Period -> space-fill
1109 jmp short mn_not_lower
1110 mn_is_period: mov al,' ' ; We need to space-fill
1111 mn_period_loop: cmp cx,3 ; If <= 3 characters left
1112 jbe mn_loop ; Just ignore it
1113 stosb ; Otherwise, write a period
1114 loop mn_period_loop ; Dec CX and (always) jump
1115 mn_not_uslower: cmp al,ucase_low
1119 mov bx,ucase_tab-ucase_low
1122 loop mn_loop ; Don't continue if too long
1124 mov al,' ' ; Space-fill name
1125 rep stosb ; Doesn't do anything if CX=0
1129 ; Upper-case table for extended characters; this is technically code page 865,
1130 ; but code page 437 users will probably not miss not being able to use the
1131 ; cent sign in kernel images too much :-)
1133 ; The table only covers the range 129 to 164; the rest we can deal with.
1137 ucase_tab db 154, 144, 'A', 142, 'A', 143, 128, 'EEEIII'
1138 db 142, 143, 144, 146, 146, 'O', 153, 'OUUY', 153, 154
1139 db 157, 156, 157, 158, 159, 'AIOU', 165
1142 ; unmangle_name: Does the opposite of mangle_name; converts a DOS-mangled
1143 ; filename to the conventional representation. This is needed
1144 ; for the BOOT_IMAGE= parameter for the kernel.
1145 ; NOTE: A 13-byte buffer is mandatory, even if the string is
1146 ; known to be shorter.
1148 ; DS:SI -> input mangled file name
1149 ; ES:DI -> output buffer
1151 ; On return, DI points to the first byte after the output name,
1152 ; which is set to a null byte.
1155 push si ; Save pointer to original name
1163 mov bp,di ; Position of last nonblank+1
1164 un_cb_space: loop un_copy_body
1166 mov al,'.' ; Don't save
1175 un_ce_space: loop un_copy_ext
1182 ; lower_case: Lower case a character in AL
1191 lc_1: cmp al,lcase_low
1196 mov bx,lcase_tab-lcase_low
1202 ; getfssec_edx: Get multiple sectors from a file
1204 ; This routine makes sure the subtransfers do not cross a 64K boundary,
1205 ; and will correct the situation if it does, UNLESS *sectors* cross
1209 ; EDX -> Current sector number
1210 ; CX -> Sector count (0FFFFh = until end of file)
1211 ; Must not exceed the ES segment
1212 ; Returns EDX=0, CF=1 on EOF (not necessarily error)
1213 ; All arguments are advanced to reflect data read.
1219 xor ebp,ebp ; Fragment sector count
1220 push edx ; Starting sector pointer
1228 add ax,bx ; Now AX = how far into 64K block we are
1229 not ax ; Bytes left in 64K block
1231 shr eax,SECTOR_SHIFT ; Sectors left in 64K block
1233 jnb .do_read ; Unless there is at least 1 more sector room...
1234 mov eax,edx ; Current sector
1235 inc edx ; Predict it's the linearly next sector
1238 cmp edx,eax ; Did it match?
1241 pop eax ; Starting sector pointer
1243 lea eax,[eax+ebp-1] ; This is the last sector actually read
1245 add bx,bp ; Adjust buffer pointer
1261 ; getfssec: Get multiple sectors from a file
1263 ; Same as above, except SI is a pointer to a open_file_t
1266 ; DS:SI -> Pointer to open_file_t
1267 ; CX -> Sector count (0FFFFh = until end of file)
1268 ; Must not exceed the ES segment
1269 ; Returns CF=1 on EOF (not necessarily error)
1270 ; All arguments are advanced to reflect data read.
1288 ; nextcluster: Advance a cluster pointer in EDI to the next cluster
1289 ; pointed at in the FAT tables. CF=0 on return if end of file.
1292 jmp strict short nextcluster_fat28 ; This gets patched
1302 pushf ; Save the shifted-out LSB (=CF)
1331 ; FAT16 decoding routine.
1338 shr eax,SECTOR_SHIFT-1
1343 movzx edi,word [gs:si+bx]
1350 ; FAT28 ("FAT32") decoding routine.
1357 shr eax,SECTOR_SHIFT-2
1363 mov edi,dword [gs:si+bx]
1364 and edi,0FFFFFFFh ; 28 bits only
1372 ; nextsector: Given a sector in EAX on input, return the next sector
1373 ; of the same filesystem object, which may be the root
1374 ; directory or a cluster chain. Returns EOF.
1394 test edi,[ClustMask]
1397 ; It's not the final sector in a cluster
1402 push gs ; nextcluster trashes gs
1409 ; Now EDI contains the cluster number
1412 jc .exit ; There isn't anything else...
1414 ; New cluster number now in EDI
1416 shl edi,cl ; CF <- 0, unless something is very wrong
1427 ; getfatsector: Check for a particular sector (in EAX) in the FAT cache,
1428 ; and return a pointer in GS:SI, loading it if needed.
1433 add eax,[FAT] ; FAT starting address
1436 ; -----------------------------------------------------------------------------
1438 ; -----------------------------------------------------------------------------
1440 %include "getc.inc" ; getc et al
1441 %include "conio.inc" ; Console I/O
1442 %include "writestr.inc" ; String output
1443 %include "parseconfig.inc" ; High-level config file handling
1444 %include "parsecmd.inc" ; Low-level config file handling
1445 %include "bcopy32.inc" ; 32-bit bcopy
1446 %include "loadhigh.inc" ; Load a file into high memory
1447 %include "font.inc" ; VGA font stuff
1448 %include "graphics.inc" ; VGA graphics
1449 %include "highmem.inc" ; High memory sizing
1450 %include "strcpy.inc" ; strcpy()
1451 %include "cache.inc" ; Metadata disk cache
1453 ; -----------------------------------------------------------------------------
1454 ; Begin data section
1455 ; -----------------------------------------------------------------------------
1459 ; Lower-case table for codepage 865
1463 lcase_tab db 135, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138
1464 db 139, 140, 141, 132, 134, 130, 145, 145, 147, 148, 149
1465 db 150, 151, 152, 148, 129, 155, 156, 155, 158, 159, 160
1466 db 161, 162, 163, 164, 164
1468 copyright_str db ' Copyright (C) 1994-', year, ' H. Peter Anvin'
1470 boot_prompt db 'boot: ', 0
1471 wipe_char db BS, ' ', BS, 0
1472 err_notfound db 'Could not find kernel image: ',0
1473 err_notkernel db CR, LF, 'Invalid or corrupt kernel image.', CR, LF, 0
1474 err_noram db 'It appears your computer has less than '
1476 db 'K of low ("DOS")'
1478 db 'RAM. Linux needs at least this amount to boot. If you get'
1480 db 'this message in error, hold down the Ctrl key while'
1482 db 'booting, and I will take your word for it.', CR, LF, 0
1483 err_badcfg db 'Unknown keyword in syslinux.cfg.', CR, LF, 0
1484 err_noparm db 'Missing parameter in syslinux.cfg.', CR, LF, 0
1485 err_noinitrd db CR, LF, 'Could not find ramdisk image: ', 0
1486 err_nohighmem db 'Not enough memory to load specified kernel.', CR, LF, 0
1487 err_highload db CR, LF, 'Kernel transfer failure.', CR, LF, 0
1488 err_oldkernel db 'Cannot load a ramdisk with an old kernel image.'
1490 err_notdos db ': attempted DOS system call', CR, LF, 0
1491 err_comlarge db 'COMBOOT image too large.', CR, LF, 0
1492 err_a20 db CR, LF, 'A20 gate not responding!', CR, LF, 0
1493 err_bootfailed db CR, LF, 'Boot failed: please change disks and press '
1494 db 'a key to continue.', CR, LF, 0
1495 ready_msg db 'Ready.', CR, LF, 0
1496 crlfloading_msg db CR, LF
1497 loading_msg db 'Loading ', 0
1500 aborted_msg db ' aborted.' ; Fall through to crlf_msg!
1503 crff_msg db CR, FF, 0
1504 syslinux_cfg db 'SYSLINUXCFG' ; Mangled form
1505 ConfigName db 'syslinux.cfg',0 ; Unmangled form
1507 manifest db 'MANIFEST '
1510 ; Command line options we'd like to take a look at
1512 ; mem= and vga= are handled as normal 32-bit integer values
1513 initrd_cmd db 'initrd='
1514 initrd_cmd_len equ 7
1517 ; Config file keyword table
1519 %include "keywords.inc"
1522 ; Extensions to search for (in *forward* order).
1524 exten_table: db 'CBT',0 ; COMBOOT (specific)
1525 db 'BSS',0 ; Boot Sector (add superblock)
1526 db 'BS ',0 ; Boot Sector
1527 db 'COM',0 ; COMBOOT (same as DOS)
1530 dd 0, 0 ; Need 8 null bytes here
1533 ; Misc initialized (data) variables
1535 %ifdef debug ; This code for debugging only
1536 debug_magic dw 0D00Dh ; Debug code sentinel
1540 BufSafe dw trackbufsize/SECTOR_SIZE ; Clusters we can load into trackbuf
1541 BufSafeSec dw trackbufsize/SECTOR_SIZE ; = how many sectors?
1542 BufSafeBytes dw trackbufsize ; = how many bytes?
1543 EndOfGetCBuf dw getcbuf+trackbufsize ; = getcbuf+BufSafeBytes
1545 %if ( trackbufsize % SECTOR_SIZE ) != 0
1546 %error trackbufsize must be a multiple of SECTOR_SIZE