diff options
Diffstat (limited to 'contrib/syslinux-4.02/core/isolinux.asm')
| -rw-r--r-- | contrib/syslinux-4.02/core/isolinux.asm | 1383 |
1 files changed, 1383 insertions, 0 deletions
diff --git a/contrib/syslinux-4.02/core/isolinux.asm b/contrib/syslinux-4.02/core/isolinux.asm new file mode 100644 index 0000000..1ef68d8 --- /dev/null +++ b/contrib/syslinux-4.02/core/isolinux.asm @@ -0,0 +1,1383 @@ +; -*- fundamental -*- (asm-mode sucks) +; **************************************************************************** +; +; isolinux.asm +; +; A program to boot Linux kernels off a CD-ROM using the El Torito +; boot standard in "no emulation" mode, making the entire filesystem +; available. It is based on the SYSLINUX boot loader for MS-DOS +; floppies. +; +; Copyright 1994-2009 H. Peter Anvin - All Rights Reserved +; Copyright 2009 Intel Corporation; author: H. Peter Anvin +; +; This program is free software; you can redistribute it and/or modify +; it under the terms of the GNU General Public License as published by +; the Free Software Foundation, Inc., 53 Temple Place Ste 330, +; Boston MA 02111-1307, USA; either version 2 of the License, or +; (at your option) any later version; incorporated herein by reference. +; +; **************************************************************************** + +%define IS_ISOLINUX 1 +%include "head.inc" + +; +; Some semi-configurable constants... change on your own risk. +; +my_id equ isolinux_id +NULLFILE equ 0 ; Zero byte == null file name +NULLOFFSET equ 0 ; Position in which to look +retry_count equ 6 ; How patient are we with the BIOS? +%assign HIGHMEM_SLOP 128*1024 ; Avoid this much memory near the top +SECTOR_SHIFT equ 11 ; 2048 bytes/sector (El Torito requirement) +SECTOR_SIZE equ (1 << SECTOR_SHIFT) + +ROOT_DIR_WORD equ 0x002F + +; +; The following structure is used for "virtual kernels"; i.e. LILO-style +; option labels. The options we permit here are `kernel' and `append +; Since there is no room in the bottom 64K for all of these, we +; stick them in high memory and copy them down before we need them. +; + struc vkernel +vk_vname: resb FILENAME_MAX ; Virtual name **MUST BE FIRST!** +vk_rname: resb FILENAME_MAX ; Real name +vk_appendlen: resw 1 +vk_type: resb 1 ; Type of file + alignb 4 +vk_append: resb max_cmd_len+1 ; Command line + alignb 4 +vk_end: equ $ ; Should be <= vk_size + endstruc + +; +; File structure. This holds the information for each currently open file. +; + struc open_file_t +file_sector resd 1 ; Sector pointer (0 = structure free) +file_bytesleft resd 1 ; Number of bytes left +file_left resd 1 ; Number of sectors left + resd 1 ; Unused + endstruc + +%ifndef DEPEND +%if (open_file_t_size & (open_file_t_size-1)) +%error "open_file_t is not a power of 2" +%endif +%endif + +; --------------------------------------------------------------------------- +; BEGIN CODE +; --------------------------------------------------------------------------- + +; +; Memory below this point is reserved for the BIOS and the MBR +; + section .earlybss + global trackbuf +trackbufsize equ 8192 +trackbuf resb trackbufsize ; Track buffer goes here +; ends at 2800h + + ; Some of these are touched before the whole image + ; is loaded. DO NOT move this to .bss16/.uibss. + section .earlybss + alignb 4 +FirstSecSum resd 1 ; Checksum of bytes 64-2048 +ImageDwords resd 1 ; isolinux.bin size, dwords +InitStack resd 1 ; Initial stack pointer (SS:SP) +DiskSys resw 1 ; Last INT 13h call +ImageSectors resw 1 ; isolinux.bin size, sectors +; These following two are accessed as a single dword... +GetlinsecPtr resw 1 ; The sector-read pointer +BIOSName resw 1 ; Display string for BIOS type +%define HAVE_BIOSNAME 1 +BIOSType resw 1 +DiskError resb 1 ; Error code for disk I/O +DriveNumber resb 1 ; CD-ROM BIOS drive number +ISOFlags resb 1 ; Flags for ISO directory search +RetryCount resb 1 ; Used for disk access retries + + alignb 8 +Hidden resq 1 ; Used in hybrid mode +bsSecPerTrack resw 1 ; Used in hybrid mode +bsHeads resw 1 ; Used in hybrid mode + + +; +; El Torito spec packet +; + + alignb 8 +_spec_start equ $ +spec_packet: resb 1 ; Size of packet +sp_media: resb 1 ; Media type +sp_drive: resb 1 ; Drive number +sp_controller: resb 1 ; Controller index +sp_lba: resd 1 ; LBA for emulated disk image +sp_devspec: resw 1 ; IDE/SCSI information +sp_buffer: resw 1 ; User-provided buffer +sp_loadseg: resw 1 ; Load segment +sp_sectors: resw 1 ; Sector count +sp_chs: resb 3 ; Simulated CHS geometry +sp_dummy: resb 1 ; Scratch, safe to overwrite + +; +; EBIOS drive parameter packet +; + alignb 8 +drive_params: resw 1 ; Buffer size +dp_flags: resw 1 ; Information flags +dp_cyl: resd 1 ; Physical cylinders +dp_head: resd 1 ; Physical heads +dp_sec: resd 1 ; Physical sectors/track +dp_totalsec: resd 2 ; Total sectors +dp_secsize: resw 1 ; Bytes per sector +dp_dpte: resd 1 ; Device Parameter Table +dp_dpi_key: resw 1 ; 0BEDDh if rest valid +dp_dpi_len: resb 1 ; DPI len + resb 1 + resw 1 +dp_bus: resb 4 ; Host bus type +dp_interface: resb 8 ; Interface type +db_i_path: resd 2 ; Interface path +db_d_path: resd 2 ; Device path + resb 1 +db_dpi_csum: resb 1 ; Checksum for DPI info + +; +; EBIOS disk address packet +; + alignb 8 +dapa: resw 1 ; Packet size +.count: resw 1 ; Block count +.off: resw 1 ; Offset of buffer +.seg: resw 1 ; Segment of buffer +.lba: resd 2 ; LBA (LSW, MSW) + +; +; Spec packet for disk image emulation +; + alignb 8 +dspec_packet: resb 1 ; Size of packet +dsp_media: resb 1 ; Media type +dsp_drive: resb 1 ; Drive number +dsp_controller: resb 1 ; Controller index +dsp_lba: resd 1 ; LBA for emulated disk image +dsp_devspec: resw 1 ; IDE/SCSI information +dsp_buffer: resw 1 ; User-provided buffer +dsp_loadseg: resw 1 ; Load segment +dsp_sectors: resw 1 ; Sector count +dsp_chs: resb 3 ; Simulated CHS geometry +dsp_dummy: resb 1 ; Scratch, safe to overwrite + + alignb 4 +_spec_end equ $ +_spec_len equ _spec_end - _spec_start + + section .init +;; +;; Primary entry point. Because BIOSes are buggy, we only load the first +;; CD-ROM sector (2K) of the file, so the number one priority is actually +;; loading the rest. +;; +StackBuf equ STACK_TOP-44 ; 44 bytes needed for + ; the bootsector chainloading + ; code! +OrigESDI equ StackBuf-4 ; The high dword on the stack +StackHome equ OrigESDI + +bootsec equ $ + +_start: ; Far jump makes sure we canonicalize the address + cli + jmp 0:_start1 + times 8-($-$$) nop ; Pad to file offset 8 + + ; This table hopefully gets filled in by mkisofs using the + ; -boot-info-table option. If not, the values in this + ; table are default values that we can use to get us what + ; we need, at least under a certain set of assumptions. + global iso_boot_info +iso_boot_info: +bi_pvd: dd 16 ; LBA of primary volume descriptor +bi_file: dd 0 ; LBA of boot file +bi_length: dd 0xdeadbeef ; Length of boot file +bi_csum: dd 0xdeadbeef ; Checksum of boot file +bi_reserved: times 10 dd 0xdeadbeef ; Reserved +bi_end: + + ; Custom entry point for the hybrid-mode disk. + ; The following values will have been pushed onto the + ; entry stack: + ; - partition offset (qword) + ; - ES + ; - DI + ; - DX (including drive number) + ; - CBIOS Heads + ; - CBIOS Sectors + ; - EBIOS flag + ; (top of stack) + ; + ; If we had an old isohybrid, the partition offset will + ; be missing; we can check for that with sp >= 0x7c00. + ; Serious hack alert. +%ifndef DEBUG_MESSAGES +_hybrid_signature: + dd 0x7078c0fb ; An arbitrary number... + +_start_hybrid: + pop cx ; EBIOS flag + pop word [cs:bsSecPerTrack] + pop word [cs:bsHeads] + pop dx + pop di + pop es + xor eax,eax + xor ebx,ebx + cmp sp,7C00h + jae .nooffset + pop eax + pop ebx +.nooffset: + mov si,bios_cbios + jcxz _start_common + mov si,bios_ebios + jmp _start_common +%endif + +_start1: + mov si,bios_cdrom + xor eax,eax + xor ebx,ebx +_start_common: + mov [cs:InitStack],sp ; Save initial stack pointer + mov [cs:InitStack+2],ss + xor cx,cx + mov ss,cx + mov sp,StackBuf ; Set up stack + push es ; Save initial ES:DI -> $PnP pointer + push di + mov ds,cx + mov es,cx + mov fs,cx + mov gs,cx + sti + cld + + mov [Hidden],eax + mov [Hidden+4],ebx + + mov [BIOSType],si + mov eax,[si] + mov [GetlinsecPtr],eax + + ; Show signs of life + mov si,syslinux_banner + call writestr_early +%ifdef DEBUG_MESSAGES + mov si,copyright_str +%else + mov si,[BIOSName] +%endif + call writestr_early + + ; + ; Before modifying any memory, get the checksum of bytes + ; 64-2048 + ; +initial_csum: xor edi,edi + mov si,bi_end + mov cx,(SECTOR_SIZE-64) >> 2 +.loop: lodsd + add edi,eax + loop .loop + mov [FirstSecSum],edi + + mov [DriveNumber],dl +%ifdef DEBUG_MESSAGES + mov si,startup_msg + call writemsg + mov al,dl + call writehex2 + call crlf +%endif + ; + ; Initialize spec packet buffers + ; + mov di,_spec_start + mov cx,_spec_len >> 2 + xor eax,eax + rep stosd + + ; Initialize length field of the various packets + mov byte [spec_packet],13h + mov byte [drive_params],30 + mov byte [dapa],16 + mov byte [dspec_packet],13h + + ; Other nonzero fields + inc word [dsp_sectors] + + ; Are we just pretending to be a CD-ROM? + cmp word [BIOSType],bios_cdrom + jne found_drive ; If so, no spec packet... + + ; Now figure out what we're actually doing + ; Note: use passed-in DL value rather than 7Fh because + ; at least some BIOSes will get the wrong value otherwise + mov ax,4B01h ; Get disk emulation status + mov dl,[DriveNumber] + mov si,spec_packet + call int13 + jc award_hack ; changed for BrokenAwardHack + mov dl,[DriveNumber] + cmp [sp_drive],dl ; Should contain the drive number + jne spec_query_failed + +%ifdef DEBUG_MESSAGES + mov si,spec_ok_msg + call writemsg + mov al,byte [sp_drive] + call writehex2 + call crlf +%endif + +found_drive: + ; Alright, we have found the drive. Now, try to find the + ; boot file itself. If we have a boot info table, life is + ; good; if not, we have to make some assumptions, and try + ; to figure things out ourselves. In particular, the + ; assumptions we have to make are: + ; - single session only + ; - only one boot entry (no menu or other alternatives) + + cmp dword [bi_file],0 ; Address of code to load + jne found_file ; Boot info table present :) + +%ifdef DEBUG_MESSAGES + mov si,noinfotable_msg + call writemsg +%endif + + ; No such luck. See if the spec packet contained one. + mov eax,[sp_lba] + and eax,eax + jz set_file ; Good enough + +%ifdef DEBUG_MESSAGES + mov si,noinfoinspec_msg + call writemsg +%endif + + ; No such luck. Get the Boot Record Volume, assuming single + ; session disk, and that we're the first entry in the chain. + mov eax,17 ; Assumed address of BRV + mov bx,trackbuf + call getonesec + + mov eax,[trackbuf+47h] ; Get boot catalog address + mov bx,trackbuf + call getonesec ; Get boot catalog + + mov eax,[trackbuf+28h] ; First boot entry + ; And hope and pray this is us... + + ; Some BIOSes apparently have limitations on the size + ; that may be loaded (despite the El Torito spec being very + ; clear on the fact that it must all be loaded.) Therefore, + ; we load it ourselves, and *bleep* the BIOS. + +set_file: + mov [bi_file],eax + +found_file: + ; Set up boot file sizes + mov eax,[bi_length] + sub eax,SECTOR_SIZE-3 ; ... minus sector loaded + shr eax,2 ; bytes->dwords + mov [ImageDwords],eax ; boot file dwords + add eax,((SECTOR_SIZE-1) >> 2) + shr eax,SECTOR_SHIFT-2 ; dwords->sectors + mov [ImageSectors],ax ; boot file sectors + + mov eax,[bi_file] ; Address of code to load + inc eax ; Don't reload bootstrap code +%ifdef DEBUG_MESSAGES + mov si,offset_msg + call writemsg + call writehex8 + call crlf +%endif + + ; Load the rest of the file. However, just in case there + ; are still BIOSes with 64K wraparound problems, we have to + ; take some extra precautions. Since the normal load + ; address (TEXT_START) is *not* 2K-sector-aligned, we round + ; the target address upward to a sector boundary, + ; and then move the entire thing down as a unit. +MaxLMA equ 384*1024 ; Reasonable limit (384K) + + mov bx,((TEXT_START+2*SECTOR_SIZE-1) & ~(SECTOR_SIZE-1)) >> 4 + mov bp,[ImageSectors] + push bx ; Load segment address + +.more: + push bx ; Segment address + push bp ; Sector count + mov es,bx + mov cx,0xfff + and bx,cx + inc cx + sub cx,bx + shr cx,SECTOR_SHIFT - 4 + jnz .notaligned + mov cx,0x10000 >> SECTOR_SHIFT ; Full 64K segment possible +.notaligned: + cmp bp,cx + jbe .ok + mov bp,cx +.ok: + xor bx,bx + push bp + call getlinsec + pop cx + mov dx,cx + pop bp + pop bx + + shl cx,SECTOR_SHIFT - 4 + add bx,cx + sub bp,dx + jnz .more + + ; Move the image into place, and also verify the + ; checksum + pop ax ; Load segment address + mov bx,(TEXT_START + SECTOR_SIZE) >> 4 + mov ecx,[ImageDwords] + mov edi,[FirstSecSum] ; First sector checksum + xor si,si + +move_verify_image: +.setseg: + mov ds,ax + mov es,bx +.loop: + mov edx,[si] + add edi,edx + dec ecx + mov [es:si],edx + jz .done + add si,4 + jnz .loop + add ax,1000h + add bx,1000h + jmp .setseg +.done: + mov ax,cs + mov ds,ax + mov es,ax + + ; Verify the checksum on the loaded image. + cmp [bi_csum],edi + je integrity_ok + + mov si,checkerr_msg + call writemsg + jmp kaboom + +integrity_ok: +%ifdef DEBUG_MESSAGES + mov si,allread_msg + call writemsg +%endif + jmp all_read ; Jump to main code + +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; +;; Start of BrokenAwardHack --- 10-nov-2002 Knut_Petersen@t-online.de +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; +;; +;; There is a problem with certain versions of the AWARD BIOS ... +;; the boot sector will be loaded and executed correctly, but, because the +;; int 13 vector points to the wrong code in the BIOS, every attempt to +;; load the spec packet will fail. We scan for the equivalent of +;; +;; mov ax,0201h +;; mov bx,7c00h +;; mov cx,0006h +;; mov dx,0180h +;; pushf +;; call <direct far> +;; +;; and use <direct far> as the new vector for int 13. The code above is +;; used to load the boot code into ram, and there should be no reason +;; for anybody to change it now or in the future. There are no opcodes +;; that use encodings relativ to IP, so scanning is easy. If we find the +;; code above in the BIOS code we can be pretty sure to run on a machine +;; with an broken AWARD BIOS ... +;; +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; + ;; +%ifdef DEBUG_MESSAGES ;; + ;; +award_notice db "Trying BrokenAwardHack first ...",CR,LF,0 ;; +award_not_orig db "BAH: Original Int 13 vector : ",0 ;; +award_not_new db "BAH: Int 13 vector changed to : ",0 ;; +award_not_succ db "BAH: SUCCESS",CR,LF,0 ;; +award_not_fail db "BAH: FAILURE" ;; +award_not_crlf db CR,LF,0 ;; + ;; +%endif ;; + ;; +award_oldint13 dd 0 ;; +award_string db 0b8h,1,2,0bbh,0,7ch,0b9h,6,0,0bah,80h,1,09ch,09ah ;; + ;; + ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; +award_hack: mov si,spec_err_msg ; Moved to this place from + call writemsg ; spec_query_faild + ; +%ifdef DEBUG_MESSAGES ; + ; + mov si,award_notice ; display our plan + call writemsg ; + mov si,award_not_orig ; display original int 13 + call writemsg ; vector +%endif ; + mov eax,[13h*4] ; + mov [award_oldint13],eax ; + ; +%ifdef DEBUG_MESSAGES ; + ; + call writehex8 ; + mov si,award_not_crlf ; + call writestr_early ; +%endif ; + push es ; save ES + mov ax,0f000h ; ES = BIOS Seg + mov es,ax ; + cld ; + xor di,di ; start at ES:DI = f000:0 +award_loop: push di ; save DI + mov si,award_string ; scan for award_string + mov cx,7 ; length of award_string = 7dw + repz cmpsw ; compare + pop di ; restore DI + jcxz award_found ; jmp if found + inc di ; not found, inc di + jno award_loop ; + ; +award_failed: pop es ; No, not this way :-(( +award_fail2: ; + ; +%ifdef DEBUG_MESSAGES ; + ; + mov si,award_not_fail ; display failure ... + call writemsg ; +%endif ; + mov eax,[award_oldint13] ; restore the original int + or eax,eax ; 13 vector if there is one + jz spec_query_failed ; and try other workarounds + mov [13h*4],eax ; + jmp spec_query_failed ; + ; +award_found: mov eax,[es:di+0eh] ; load possible int 13 addr + pop es ; restore ES + ; + cmp eax,[award_oldint13] ; give up if this is the + jz award_failed ; active int 13 vector, + mov [13h*4],eax ; otherwise change 0:13h*4 + ; + ; +%ifdef DEBUG_MESSAGES ; + ; + push eax ; display message and + mov si,award_not_new ; new vector address + call writemsg ; + pop eax ; + call writehex8 ; + mov si,award_not_crlf ; + call writestr_early ; +%endif ; + mov ax,4B01h ; try to read the spec packet + mov dl,[DriveNumber] ; now ... it should not fail + mov si,spec_packet ; any longer + int 13h ; + jc award_fail2 ; + ; +%ifdef DEBUG_MESSAGES ; + ; + mov si,award_not_succ ; display our SUCCESS + call writemsg ; +%endif ; + jmp found_drive ; and leave error recovery code + ; +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; +;; End of BrokenAwardHack ---- 10-nov-2002 Knut_Petersen@t-online.de +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; + + + ; INT 13h, AX=4B01h, DL=<passed in value> failed. + ; Try to scan the entire 80h-FFh from the end. + +spec_query_failed: + + ; some code moved to BrokenAwardHack + + mov dl,0FFh +.test_loop: pusha + mov ax,4B01h + mov si,spec_packet + mov byte [si],13h ; Size of buffer + call int13 + popa + jc .still_broken + + mov si,maybe_msg + call writemsg + mov al,dl + call writehex2 + call crlf + + cmp byte [sp_drive],dl + jne .maybe_broken + + ; Okay, good enough... + mov si,alright_msg + call writemsg +.found_drive0: mov [DriveNumber],dl +.found_drive: jmp found_drive + + ; Award BIOS 4.51 apparently passes garbage in sp_drive, + ; but if this was the drive number originally passed in + ; DL then consider it "good enough" +.maybe_broken: + mov al,[DriveNumber] + cmp al,dl + je .found_drive + + ; Intel Classic R+ computer with Adaptec 1542CP BIOS 1.02 + ; passes garbage in sp_drive, and the drive number originally + ; passed in DL does not have 80h bit set. + or al,80h + cmp al,dl + je .found_drive0 + +.still_broken: dec dx + cmp dl, 80h + jnb .test_loop + + ; No spec packet anywhere. Some particularly pathetic + ; BIOSes apparently don't even implement function + ; 4B01h, so we can't query a spec packet no matter + ; what. If we got a drive number in DL, then try to + ; use it, and if it works, then well... + mov dl,[DriveNumber] + cmp dl,81h ; Should be 81-FF at least + jb fatal_error ; If not, it's hopeless + + ; Write a warning to indicate we're on *very* thin ice now + mov si,nospec_msg + call writemsg + mov al,dl + call writehex2 + call crlf + mov si,trysbm_msg + call writemsg + jmp .found_drive ; Pray that this works... + +fatal_error: + mov si,nothing_msg + call writemsg + +.norge: jmp short .norge + + ; Information message (DS:SI) output + ; Prefix with "isolinux: " + ; +writemsg: push ax + push si + mov si,isolinux_str + call writestr_early + pop si + call writestr_early + pop ax + ret + +; +; Write a character to the screen. There is a more "sophisticated" +; version of this in the subsequent code, so we patch the pointer +; when appropriate. +; + +writechr: +.simple: + pushfd + pushad + mov ah,0Eh + xor bx,bx + int 10h + popad + popfd + ret + +; +; int13: save all the segment registers and call INT 13h. +; Some CD-ROM BIOSes have been found to corrupt segment registers +; and/or disable interrupts. +; +int13: + pushf + push bp + push ds + push es + push fs + push gs + int 13h + mov bp,sp + setc [bp+10] ; Propagate CF to the caller + pop gs + pop fs + pop es + pop ds + pop bp + popf + ret + +; +; Get one sector. Convenience entry point. +; +getonesec: + mov bp,1 + ; Fall through to getlinsec + +; +; Get linear sectors - EBIOS LBA addressing, 2048-byte sectors. +; +; Input: +; EAX - Linear sector number +; ES:BX - Target buffer +; BP - Sector count +; + global getlinsec +getlinsec: jmp word [cs:GetlinsecPtr] + +%ifndef DEBUG_MESSAGES + +; +; First, the variants that we use when actually loading off a disk +; (hybrid mode.) These are adapted versions of the equivalent routines +; in ldlinux.asm. +; + +; +; getlinsec_ebios: +; +; getlinsec implementation for floppy/HDD EBIOS (EDD) +; +getlinsec_ebios: + xor edx,edx + shld edx,eax,2 + shl eax,2 ; Convert to HDD sectors + add eax,[Hidden] + adc edx,[Hidden+4] + shl bp,2 + +.loop: + push bp ; Sectors left +.retry2: + call maxtrans ; Enforce maximum transfer size + movzx edi,bp ; Sectors we are about to read + mov cx,retry_count +.retry: + + ; Form DAPA on stack + push edx + push eax + push es + push bx + push di + push word 16 + mov si,sp + pushad + mov dl,[DriveNumber] + push ds + push ss + pop ds ; DS <- SS + mov ah,42h ; Extended Read + call int13 + pop ds + popad + lea sp,[si+16] ; Remove DAPA + jc .error + pop bp + add eax,edi ; Advance sector pointer + adc edx,0 + sub bp,di ; Sectors left + shl di,9 ; 512-byte sectors + add bx,di ; Advance buffer pointer + and bp,bp + jnz .loop + + ret + +.error: + ; Some systems seem to get "stuck" in an error state when + ; using EBIOS. Doesn't happen when using CBIOS, which is + ; good, since some other systems get timeout failures + ; waiting for the floppy disk to spin up. + + pushad ; Try resetting the device + xor ax,ax + mov dl,[DriveNumber] + call int13 + popad + loop .retry ; CX-- and jump if not zero + + ;shr word [MaxTransfer],1 ; Reduce the transfer size + ;jnz .retry2 + + ; Total failure. Try falling back to CBIOS. + mov word [GetlinsecPtr], getlinsec_cbios + ;mov byte [MaxTransfer],63 ; Max possibe CBIOS transfer + + pop bp + jmp getlinsec_cbios.loop + +; +; getlinsec_cbios: +; +; getlinsec implementation for legacy CBIOS +; +getlinsec_cbios: + xor edx,edx + shl eax,2 ; Convert to HDD sectors + add eax,[Hidden] + shl bp,2 + +.loop: + push edx + push eax + push bp + push bx + + movzx esi,word [bsSecPerTrack] + movzx edi,word [bsHeads] + ; + ; Dividing by sectors to get (track,sector): we may have + ; up to 2^18 tracks, so we need to use 32-bit arithmetric. + ; + div esi + xor cx,cx + xchg cx,dx ; CX <- sector index (0-based) + ; EDX <- 0 + ; eax = track # + div edi ; Convert track to head/cyl + + ; We should test this, but it doesn't fit... + ; cmp eax,1023 + ; ja .error + + ; + ; Now we have AX = cyl, DX = head, CX = sector (0-based), + ; BP = sectors to transfer, SI = bsSecPerTrack, + ; ES:BX = data target + ; + + call maxtrans ; Enforce maximum transfer size + + ; Must not cross track boundaries, so BP <= SI-CX + sub si,cx + cmp bp,si + jna .bp_ok + mov bp,si +.bp_ok: + + shl ah,6 ; Because IBM was STOOPID + ; and thought 8 bits were enough + ; then thought 10 bits were enough... + inc cx ; Sector numbers are 1-based, sigh + or cl,ah + mov ch,al + mov dh,dl + mov dl,[DriveNumber] + xchg ax,bp ; Sector to transfer count + mov ah,02h ; Read sectors + mov bp,retry_count +.retry: + pushad + call int13 + popad + jc .error +.resume: + movzx ecx,al ; ECX <- sectors transferred + shl ax,9 ; Convert sectors in AL to bytes in AX + pop bx + add bx,ax + pop bp + pop eax + pop edx + add eax,ecx + sub bp,cx + jnz .loop + ret + +.error: + dec bp + jnz .retry + + xchg ax,bp ; Sectors transferred <- 0 + shr word [MaxTransfer],1 + jnz .resume + jmp disk_error + +; +; Truncate BP to MaxTransfer +; +maxtrans: + cmp bp,[MaxTransfer] + jna .ok + mov bp,[MaxTransfer] +.ok: ret + +%endif + +; +; This is the variant we use for real CD-ROMs: +; LBA, 2K sectors, some special error handling. +; +getlinsec_cdrom: + mov si,dapa ; Load up the DAPA + mov [si+4],bx + mov [si+6],es + mov [si+8],eax +.loop: + push bp ; Sectors left + cmp bp,[MaxTransferCD] + jbe .bp_ok + mov bp,[MaxTransferCD] +.bp_ok: + mov [si+2],bp + push si + mov dl,[DriveNumber] + mov ah,42h ; Extended Read + call xint13 + pop si + pop bp + movzx eax,word [si+2] ; Sectors we read + add [si+8],eax ; Advance sector pointer + sub bp,ax ; Sectors left + shl ax,SECTOR_SHIFT-4 ; 2048-byte sectors -> segment + add [si+6],ax ; Advance buffer pointer + and bp,bp + jnz .loop + mov eax,[si+8] ; Next sector + ret + + ; INT 13h with retry +xint13: mov byte [RetryCount],retry_count +.try: pushad + call int13 + jc .error + add sp,byte 8*4 ; Clean up stack + ret +.error: + mov [DiskError],ah ; Save error code + popad + mov [DiskSys],ax ; Save system call number + dec byte [RetryCount] + jz .real_error + push ax + mov al,[RetryCount] + mov ah,[dapa+2] ; Sector transfer count + cmp al,2 ; Only 2 attempts left + ja .nodanger + mov ah,1 ; Drop transfer size to 1 + jmp short .setsize +.nodanger: + cmp al,retry_count-2 + ja .again ; First time, just try again + shr ah,1 ; Otherwise, try to reduce + adc ah,0 ; the max transfer size, but not to 0 +.setsize: + mov [MaxTransferCD],ah + mov [dapa+2],ah +.again: + pop ax + jmp .try + +.real_error: mov si,diskerr_msg + call writemsg + mov al,[DiskError] + call writehex2 + mov si,oncall_str + call writestr_early + mov ax,[DiskSys] + call writehex4 + mov si,ondrive_str + call writestr_early + mov al,dl + call writehex2 + call crlf + ; Fall through to kaboom + +; +; kaboom: write a message and bail out. Wait for a user keypress, +; then do a hard reboot. +; + global kaboom +disk_error: +kaboom: + RESET_STACK_AND_SEGS AX + mov si,err_bootfailed + call writestr + call getchar + cli + mov word [BIOS_magic],0 ; Cold reboot + jmp 0F000h:0FFF0h ; Reset vector address + +; ----------------------------------------------------------------------------- +; Common modules needed in the first sector +; ----------------------------------------------------------------------------- + +%include "writestr.inc" ; String output +writestr_early equ writestr +%include "writehex.inc" ; Hexadecimal output + +; ----------------------------------------------------------------------------- +; Data that needs to be in the first sector +; ----------------------------------------------------------------------------- + +syslinux_banner db CR, LF, MY_NAME, ' ', VERSION_STR, ' ', DATE_STR, ' ', 0 +copyright_str db ' Copyright (C) 1994-' + asciidec YEAR + db ' H. Peter Anvin et al', CR, LF, 0 +isolinux_str db 'isolinux: ', 0 +%ifdef DEBUG_MESSAGES +startup_msg: db 'Starting up, DL = ', 0 +spec_ok_msg: db 'Loaded spec packet OK, drive = ', 0 +secsize_msg: db 'Sector size ', 0 +offset_msg: db 'Main image LBA = ', 0 +verify_msg: db 'Image checksum verified.', CR, LF, 0 +allread_msg db 'Main image read, jumping to main code...', CR, LF, 0 +%endif +noinfotable_msg db 'No boot info table, assuming single session disk...', CR, LF, 0 +noinfoinspec_msg db 'Spec packet missing LBA information, trying to wing it...', CR, LF, 0 +spec_err_msg: db 'Loading spec packet failed, trying to wing it...', CR, LF, 0 +maybe_msg: db 'Found something at drive = ', 0 +alright_msg: db 'Looks reasonable, continuing...', CR, LF, 0 +nospec_msg db 'Extremely broken BIOS detected, last attempt with drive = ', 0 +nothing_msg: db 'Failed to locate CD-ROM device; boot failed.', CR, LF +trysbm_msg db 'See http://syslinux.zytor.com/sbm for more information.', CR, LF, 0 +diskerr_msg: db 'Disk error ', 0 +oncall_str: db ', AX = ',0 +ondrive_str: db ', drive ', 0 +checkerr_msg: db 'Image checksum error, sorry...', CR, LF, 0 + +err_bootfailed db CR, LF, 'Boot failed: press a key to retry...' +bailmsg equ err_bootfailed +crlf_msg db CR, LF +null_msg db 0 + +bios_cdrom_str db 'ETCD', 0 +%ifndef DEBUG_MESSAGES +bios_cbios_str db 'CHDD', 0 +bios_ebios_str db 'EHDD' ,0 +%endif + + alignz 4 +bios_cdrom: dw getlinsec_cdrom, bios_cdrom_str +%ifndef DEBUG_MESSAGES +bios_cbios: dw getlinsec_cbios, bios_cbios_str +bios_ebios: dw getlinsec_ebios, bios_ebios_str +%endif + +; Maximum transfer size +MaxTransfer dw 127 ; Hard disk modes +MaxTransferCD dw 32 ; CD mode + +rl_checkpt equ $ ; Must be <= 800h + + ; This pads to the end of sector 0 and errors out on + ; overflow. + times 2048-($-$$) db 0 + +; ---------------------------------------------------------------------------- +; End of code and data that have to be in the first sector +; ---------------------------------------------------------------------------- + + section .text16 + +all_read: + +; Test tracers + TRACER 'T' + TRACER '>' + +; +; Common initialization code +; +%include "init.inc" + + ; Patch the writechr routine to point to the full code + mov di,writechr + mov al,0e9h + stosb + mov ax,writechr_full-2 + sub ax,di + stosw + +; Tell the user we got this far... +%ifndef DEBUG_MESSAGES ; Gets messy with debugging on + mov si,copyright_str + call writestr_early +%endif + +; +; Now we're all set to start with our *real* business. First load the +; configuration file (if any) and parse it. +; +; In previous versions I avoided using 32-bit registers because of a +; rumour some BIOSes clobbered the upper half of 32-bit registers at +; random. I figure, though, that if there are any of those still left +; they probably won't be trying to install Linux on them... +; +; The code is still ripe with 16-bitisms, though. Not worth the hassle +; to take'm out. In fact, we may want to put them back if we're going +; to boot ELKS at some point. +; + +; +; Now, we need to sniff out the actual filesystem data structures. +; mkisofs gave us a pointer to the primary volume descriptor +; (which will be at 16 only for a single-session disk!); from the PVD +; we should be able to find the rest of what we need to know. +; +init_fs: + pushad + mov eax,ROOT_FS_OPS + mov dl,[DriveNumber] + cmp word [BIOSType],bios_cdrom + sete dh ; 1 for cdrom, 0 for hybrid mode + jne .hybrid + movzx ebp,word [MaxTransferCD] + jmp .common +.hybrid: + movzx ebp,word [MaxTransfer] +.common: + mov ecx,[Hidden] + mov ebx,[Hidden+4] + mov si,[bsHeads] + mov di,[bsSecPerTrack] + pm_call fs_init + popad + + section .rodata + alignz 4 +ROOT_FS_OPS: + extern iso_fs_ops + dd iso_fs_ops + dd 0 + + section .text16 + +; +; Locate the configuration file +; + pm_call load_config + +; +; Now we have the config file open. Parse the config file and +; run the user interface. +; +%include "ui.inc" + +; +; Enable disk emulation. The kind of disk we emulate is dependent on the +; size of the file: 1200K, 1440K or 2880K floppy, otherwise harddisk. +; +is_disk_image: + TRACER CR + TRACER LF + TRACER 'D' + TRACER ':' + + mov edx,eax ; File size + mov di,img_table + mov cx,img_table_count + mov eax,[si+file_sector] ; Starting LBA of file + mov [dsp_lba],eax ; Location of file + mov byte [dsp_drive], 0 ; 00h floppy, 80h hard disk +.search_table: + TRACER 't' + mov eax,[di+4] + cmp edx,[di] + je .type_found + add di,8 + loop .search_table + + ; Hard disk image. Need to examine the partition table + ; in order to deduce the C/H/S geometry. Sigh. +.hard_disk_image: + TRACER 'h' + cmp edx,512 + jb .bad_image + + mov bx,trackbuf + mov cx,1 ; Load 1 sector + pm_call getfssec + + cmp word [trackbuf+510],0aa55h ; Boot signature + jne .bad_image ; Image not bootable + + mov cx,4 ; 4 partition entries + mov di,trackbuf+446 ; Start of partition table + + xor ax,ax ; Highest sector(al) head(ah) + +.part_scan: + cmp byte [di+4], 0 + jz .part_loop + lea si,[di+1] + call .hs_check + add si,byte 4 + call .hs_check +.part_loop: + add di,byte 16 + loop .part_scan + + push eax ; H/S + push edx ; File size + mov bl,ah + xor bh,bh + inc bx ; # of heads in BX + xor ah,ah ; # of sectors in AX + cwde ; EAX[31:16] <- 0 + mul bx + shl eax,9 ; Convert to bytes + ; Now eax contains the number of bytes per cylinder + pop ebx ; File size + xor edx,edx + div ebx + and edx,edx + jz .no_remainder + inc eax ; Fractional cylinder... + ; Now (e)ax contains the number of cylinders +.no_remainder: cmp eax,1024 + jna .ok_cyl + mov ax,1024 ; Max possible # +.ok_cyl: dec ax ; Convert to max cylinder no + pop ebx ; S(bl) H(bh) + shl ah,6 + or bl,ah + xchg ax,bx + shl eax,16 + mov ah,bl + mov al,4 ; Hard disk boot + mov byte [dsp_drive], 80h ; Drive 80h = hard disk + +.type_found: + TRACER 'T' + mov bl,[sp_media] + and bl,0F0h ; Copy controller info bits + or al,bl + mov [dsp_media],al ; Emulation type + shr eax,8 + mov [dsp_chs],eax ; C/H/S geometry + mov ax,[sp_devspec] ; Copy device spec + mov [dsp_devspec],ax + mov al,[sp_controller] ; Copy controller index + mov [dsp_controller],al + + TRACER 'V' + call vgaclearmode ; Reset video + + mov ax,4C00h ; Enable emulation and boot + mov si,dspec_packet + mov dl,[DriveNumber] + lss sp,[InitStack] + TRACER 'X' + + call int13 + + ; If this returns, we have problems +.bad_image: + mov si,err_disk_image + call writestr + jmp enter_command + +; +; Look for the highest seen H/S geometry +; We compute cylinders separately +; +.hs_check: + mov bl,[si] ; Head # + cmp bl,ah + jna .done_track + mov ah,bl ; New highest head # +.done_track: mov bl,[si+1] + and bl,3Fh ; Sector # + cmp bl,al + jna .done_sector + mov al,bl +.done_sector: ret + + + +; ----------------------------------------------------------------------------- +; Common modules +; ----------------------------------------------------------------------------- + +%include "common.inc" ; Universal modules +%include "rawcon.inc" ; Console I/O w/o using the console functions +%include "localboot.inc" ; Disk-based local boot + +; ----------------------------------------------------------------------------- +; Begin data section +; ----------------------------------------------------------------------------- + + section .data16 +err_disk_image db 'Cannot load disk image (invalid file)?', CR, LF, 0 + +; +; Config file keyword table +; +%include "keywords.inc" + +; +; Extensions to search for (in *forward* order). +; + alignz 4 +exten_table: db '.cbt' ; COMBOOT (specific) + db '.img' ; Disk image + db '.bin' ; CD boot sector + db '.com' ; COMBOOT (same as DOS) + db '.c32' ; COM32 +exten_table_end: + dd 0, 0 ; Need 8 null bytes here + +; +; Floppy image table +; + alignz 4 +img_table_count equ 3 +img_table: + dd 1200*1024 ; 1200K floppy + db 1 ; Emulation type + db 80-1 ; Max cylinder + db 15 ; Max sector + db 2-1 ; Max head + + dd 1440*1024 ; 1440K floppy + db 2 ; Emulation type + db 80-1 ; Max cylinder + db 18 ; Max sector + db 2-1 ; Max head + + dd 2880*1024 ; 2880K floppy + db 3 ; Emulation type + db 80-1 ; Max cylinder + db 36 ; Max sector + db 2-1 ; Max head |