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Diffstat (limited to 'private/ntos/boot/bootcode/etfs/i386/etfsboot.asm')
| -rw-r--r-- | private/ntos/boot/bootcode/etfs/i386/etfsboot.asm | 584 |
1 files changed, 584 insertions, 0 deletions
diff --git a/private/ntos/boot/bootcode/etfs/i386/etfsboot.asm b/private/ntos/boot/bootcode/etfs/i386/etfsboot.asm new file mode 100644 index 000000000..15d2d4a85 --- /dev/null +++ b/private/ntos/boot/bootcode/etfs/i386/etfsboot.asm @@ -0,0 +1,584 @@ +;++ +; +;Copyright (c) 1995 Compaq Computer Corporation +; +;Module Name: +; +; etfsboot.asm +; +;Abstract: +; +; The ROM in the IBM PC starts the boot process by performing a hardware +; initialization and a verification of all external devices. If an El +; Torito CD-ROM with no-emulation support is detected, it will then load +; the "image" pointed to in the Boot Catalog. This "image" is placed at +; the physical address specified in the Boot Catalog (which should be 07C00h). +; +; The code in this "image" is responsible for locating NTLDR, loading the +; first sector of NTLDR into memory at 2000:0000, and branching to it. +; +; There are only two errors possible during execution of this code. +; 1 - NTLDR does not exist +; 2 - BIOS read error +; +; In both cases, a short message is printed, and the user is prompted to +; reboot the system. +; +; +;Author: +; +; Steve Collins (stevec) 25-Oct-1995 +; +;Environment: +; +; Image has been loaded at 7C0:0000 by BIOS. +; Real mode +; ISO 9660 El Torito no-emulation CD-ROM Boot support +; DL = El Torito drive number we booted from +; +;Revision History: +; +;-- + page ,132 + title boot - NTLDR ETFS loader + name etfsboot + + +BootSeg segment at 07c0h +BootSeg ends + +DirSeg segment at 1000h +DirSeg ends + +NtLdrSeg segment at 2000h +NtLdrSeg ends + +BootCode segment ;would like to use BootSeg here, but LINK flips its lid + ASSUME CS:BootCode,DS:NOTHING,ES:NOTHING,SS:NOTHING + + public ETFSBOOT +ETFSBOOT proc far + + xor ax,ax ; Setup the stack to a known good spot + mov ss,ax ; Stack is set to 0000:7c00, which is just below this code + mov sp,7c00h + + mov ax,BootSeg ; Set DS to our code/data segment (07C0h) + mov ds,ax +assume DS:BootCode + +; +; Save the Drive Number for later use + mov DriveNum,dl + +; +; The system is now prepared for us to begin reading. First, we need to +; read in the Primary Volume Descriptor so we can locate the root directory +; +.286 + push 01h ; Word 0 (low word) of Transfer size = 1 block (2048 bytes) + push 0h ; Word 1 (high word) of Transfer size = 0 + push DirSeg ; Segment of Transfer buffer = DirSeg + push 010h ; Word 0 (low word) of Starting absolute block number = 10h + push 0h ; Word 1 of Starting absolute block number = 0 +.8086 + call ExtRead + add sp,10 ; Clean 5 arguments off the stack + +; +; Determine the root directory location LBN -> ExtentLoc1:ExtentLoc0 +; determine the root directory data length in bytes -> ExtentLen1:ExtentLen0 +; + mov ax,DirSeg ; ES is set to segment used for storing PVD and directories + mov es,ax +ASSUME ES:DirSeg + mov ax,es:[09eh] ; 32-bit LBN of extent at offset 158 in Primary Volume Descriptor + mov ExtentLoc0,ax ; store low word + mov ax,es:[0a0h] + mov ExtentLoc1,ax ; store high word + mov ax,es:[0a6h] ; 32-bit Root directory data length in bytes at offset 166 in Primary Volume Descriptor + mov ExtentLen0,ax ; store low word + mov ax,es:[0a8h] + mov ExtentLen1,ax ; store high word + +; +; Now read in the root directory +; +.286 + push DirSeg ; Segment used for transfer = DirSeg +.8086 + call ReadExtent + add sp,2 ; Clean 1 argument off the stack + +; +; Scan for the presence of the I386 directory +; ES points to directory segment +; + mov EntryToFind, offset I386DIRNAME + mov EntryLen,4 + mov IsDir,1 + call ScanForEntry + +; +; We found the I386 directory entry, so now get its extent location (offset -31 from filename ID) +; ES:[BX] still points to the directory record for the I386 directory +; + call GetExtentInfo + +; +; Now read in the I386 directory +; +.286 + push DirSeg ; Segment used for transfer = DirSeg +.8086 + call ReadExtent + add sp,2 ; Clean 1 argument off the stack + +; +; Scan for the presence of SETUPLDR.BIN +; ES points to directory segment +; + mov ax,DirSeg + mov es,ax + mov EntryToFind, offset LOADERNAME + mov EntryLen,12 + mov IsDir,0 + call ScanForEntry + +; +; We found the loader entry, so now get its extent location (offset -31 from filename ID) +; ES:[BX] still points to the directory record for the LOADER +; + call GetExtentInfo + +; +; Now, go read the file +; +.286 + push NtLdrSeg ; Segment used for transfer = NtLdrSeg +.8086 + call ReadExtent + add sp,2 ; Clean 1 argument off the stack + +; +; NTLDR requires: +; DL = INT 13 drive number we booted from +; + mov dl, DriveNum ; DL = CD drive number - this isn't really necessary since DirveNum is already in dl + xor ax,ax +.386 + push NtLdrSeg + push ax + retf ; "return" to NTLDR. + +ETFSBOOT endp + + +; +; ScanForEntry - Scan for an entry in a directory +; +; Entry: +; ES:0 points to the beginning of the directory to search +; Directory length in bytes is in ExtentLen1 and Extend_Len_0 +; +; Exit: +; ES:BX points to record containing entry if match is found +; Otherwise, we jump to error routine +; +ScanForEntry proc near + mov cx,ExtentLen0 ; CX = length of root directory in bytes (low word only) + cld ; Work up for string compares + xor bx,bx + xor dx,dx +ScanLoop: + mov si, EntryToFind + mov dl,byte ptr es:[bx] ; directory record length -> DL + cmp dl,0 + jz Skip00 ; if the "record length" assume it is "system use" and skip it + mov ax,bx + add ax,021h ; file identifier is at offset 21h in directory record + mov di,ax ; ES:DI now points to file identifier + push cx + xor cx,cx + mov cl,EntryLen ; compare bytes + repe cmpsb + pop cx + jz ScanEnd ; do we have a match? + +CheckCountUnderFlow: + ; If CX is about to underflow or be 0 we need to reset CX, ES and BX if ExtentLen1 is non-0 + cmp dx,cx + jae ResetCount0 + + sub cx,dx ; update CX to contain number of bytes left in directory + cmp ScanIncCount, 1 + je ScanAdd1ToCount + +AdjustScanPtr: ; Adjust ES:BX to point to next record + add dx,bx + mov bx,dx + and bx,0fh + push cx + mov cl,4 + shr dx,cl + pop cx + mov ax,es + add ax,dx + mov es,ax + jmp ScanLoop + +Skip00: + mov dx,1 ; Skip past this byte + jmp CheckCountUnderFlow + +ScanAdd1ToCount: + inc cx + mov ScanIncCount,0 + jmp AdjustScanPtr + +S0: + mov ScanIncCount,1 ; We'll need to increment Count next time we get a chance + jmp SetNewCount + +ResetCount0: + cmp ExtentLen1,0 ; Do we still have at least 64K bytes left to scan? + je BootErr$bnf ; We overran the end of the directory - corrupt/invalid directory + sub ExtentLen1,1 + + add bx,dx ; Adjust ES:BX to point to next record - we cross seg boundary here + push bx + push cx + mov cl,4 + shr bx,cl + pop cx + mov ax,es + add ax,bx + mov es,ax + pop bx + and bx,0fh + + sub dx,cx ; Get overflow amount + je S0 ; If we ended right on the boundary we need to make special adjustments + dec dx +SetNewCount: + mov ax,0ffffh + sub ax,dx ; and subtract it from 10000h + mov cx,ax ; - this is the new count + jmp ScanLoop + +ScanEnd: + cmp IsDir,1 + je CheckDir + + test byte ptr es:[bx][25],2 ; Is this a file? + jnz CheckCountUnderFlow ; No - go to next record + jmp CheckLen + +CheckDir: + test byte ptr es:[bx][25],2 ; Is this a directory? + jz CheckCountUnderFlow ; No - go to next record + +CheckLen: + mov al,EntryLen + cmp byte ptr es:[bx][32],al ; Is the identifier length correct? + jnz CheckCountUnderFlow ; No - go to next record + + ret +ScanForEntry endp + +; +; BootErr - print error message and hang the system. +; +BootErr proc +BootErr$bnf: + MOV SI,OFFSET MSG_NO_NTLDR + jmp short BootErr2 +BootErr$mof: + MOV SI,OFFSET MSG_MEM_OVERFLOW + jmp short BootErr2 +BootErr2: + call BootErrPrint + MOV SI,OFFSET MSG_REBOOT_ERROR + call BootErrPrint + sti + jmp $ ;Wait forever + +BootErrPrint: + LODSB ; Get next character + or al,al + jz BEdone + + MOV AH,14 ; Write teletype + MOV BX,7 ; Attribute + INT 10H ; Print it + jmp BootErrPrint +BEdone: + + ret +BootErr endp + +; +; ExtRead - Do an INT 13h extended read +; NOTE: I force the offset of the Transfer buffer address to be 0 +; I force the high 2 words of the Starting absolute block number to be 0 +; - This allows for a max 4 GB medium - a safe assumption for now +; +; Entry: +; Arg1 - word 0 (low word) of Number of 2048-byte blocks to transfer +; Arg2 - word 1 (high word) of Number of 2048-byte blocks to transfer +; Arg3 - segment of Transfer buffer address +; Arg4 - word 0 (low word) of Starting absolute block number +; Arg5 - word 1 of Starting absolute block number +; +; Exit +; The following are modified: +; Count0 +; Count1 +; Dest +; Source0 +; Source1 +; PartialRead +; NumBlocks +; Disk Address Packet [DiskAddPack] +; +ExtRead proc near + push bp ; set up stack frame so we can get args + mov bp,sp + + push bx ; Save registers used during this routine + push si + push dx + push ax + + mov bx,offset DiskAddPack ; Use BX as base to index into Disk Address Packet + + ; Set up constant fields + mov [bx][0],byte ptr 010h ; Offset 0: Packet size = 16 bytes + mov [bx][1],byte ptr 0h ; Offset 1: Reserved (must be 0) + mov [bx][3],byte ptr 0h ; Offset 3: Reserved (must be 0) + mov [bx][4],word ptr 0h ; Offset 4: Offset of Transfer buffer address (force 0) + mov [bx][12],word ptr 0h ; Offset 12: Word 2 of Starting absolute block number (force 0) + mov [bx][14],word ptr 0h ; Offset 14: Word 3 (high word) of Starting absolute block number (force 0) + +; +; Initialize loop variables +; + mov ax,[bp][12] ; set COUNT to number of blocks to transfer + mov Count0,ax + mov ax,[bp][10] + mov Count1,ax + + mov ax,[bp][8] ; set DEST to destination segment + mov Dest,ax + + mov ax,[bp][6] ; set SOURCE to source lbn + mov Source0,ax + mov ax,[bp][4] + mov Source1,ax + +ExtReadLoop: +; +; First check if COUNT <= 32 +; + cmp Count1,word ptr 0h ; Is upper word 0? + jne SetupPartialRead ; No - we're trying to read at least 64K blocks (128 MB) + cmp Count0,word ptr 20h ; Is lower word greater than 32? + jg SetupPartialRead ; Yes - only read in 32-block increments + + mov PartialRead,0 ; Clear flag to indicate we are doing a full read + + mov ax,Count0 ; NUMBLOCKS = COUNT + mov NumBlocks,al ; Since Count0 < 32 we're OK just using low byte + + jmp DoExtRead ; Do read + +SetupPartialRead: +; +; Since COUNT > 32, +; Set flag indicating we are only doing a partial read +; + mov PartialRead,1 + + mov NumBlocks,20h ; NUMBYTES = 32 + +DoExtRead: +; +; Perform Extended Read +; + mov al,NumBlocks ; Offset 2: Number of 2048-byte blocks to transfer + mov [bx][2],al + mov ax,Dest ; Offset 6: Segment of Transfer buffer address + mov [bx][6],ax + mov ax,Source0 ; Offset 8: Word 0 (low word) of Starting absolute block number + mov [bx][8],ax + mov ax,Source1 ; Offset 10: Word 1 of Starting absolute block number + mov [bx][10],ax + + mov si,offset DiskAddPack ; Disk Address Packet in DS:SI + mov ah,042h ; Function = Extended Read + mov dl,DriveNum ; CD-ROM drive number + int 13h + +; +; Determine if we are done reading +; + cmp PartialRead,1 ; Did we just do a partial read? + jne ExtReadDone ; No - we're done + +ReadjustValues: +; +; We're not done reading yet, so +; COUNT = COUNT - 32 +; + sub Count0,020h ; Subtract low-order words + sbb Count1,0h ; Subtract high-order words + +; +; Just read 32 blocks and have more to read +; Increment DEST to next 64K segment (this equates to adding 1000h to the segment) +; + add Dest,1000h + jc BootErr$mof ; Error if we overflowed + +; +; SOURCE = SOURCE + 32 blocks +; + add Source0,word ptr 020h ; Add low order words + adc Source1,word ptr 0h ; Add high order words + ; NOTE - I don't account for overflow - probably OK now since we already account for 4 GB medium + +; +; jump back to top of loop to do another read +; + jmp ExtReadLoop + +ExtReadDone: + + pop ax ; Restore registers used during this routine + pop dx + pop si + pop bx + + mov sp,bp ; restore BP and SP + pop bp + + ret +ExtRead endp + +; +; ReadExtent - Read in an extent +; +; Arg1 - segment to transfer extent to +; +; Entry: +; ExtentLen0 = word 0 (low word) of extent length in bytes +; ExtentLen1 = word 1 (high word) of extent length in bytes +; ExtentLoc0 = word 0 (low word) of starting absolute block number of extent +; ExtentLoc1 = word 1 of starting absolute block number of extent +; +; Exit: +; ExtRead exit mods +; +ReadExtent proc near + push bp ; set up stack frame so we can get args + mov bp,sp + + push cx ; Save registers used during this routine + push bx + push ax + + mov cl,11 ; Convert length in bytes to 2048-byte blocks + mov bx,ExtentLen1 ; Directory length = BX:AX + mov ax,ExtentLen0 + +.386 + shrd ax,bx,cl ; Shift AX, filling with BX +.8086 + shr bx,cl ; BX:AX = number of blocks (rounded down) + test ExtentLen0,07ffh ; If any of the low-order 11 bits are set we need to round up + jz ReadExtentNoRoundUp + add ax,1 ; We need to round up by incrementing AX, and + adc bx,0 ; adding the carry to BX +ReadExtentNoRoundUp: + + push ax ; Word 0 (low word) of Transfer size = AX + push bx ; Word 1 (high word) of Transfer size = BX +.286 + push [bp][4] ; Segment used to transfer extent +.8086 + push ExtentLoc0 ; Word 0 (low word) of Starting absolute block number + push ExtentLoc1 ; Word 1 of Starting absolute block number + call ExtRead + add sp,10 ; Clean 5 arguments off the stack + + pop ax ; Restore registers used during this routine + pop bx + pop cx + + mov sp,bp ; restore BP and SP + pop bp + + ret +ReadExtent endp + +; +; GetExtentInfo - Get extent location +; +; Entry: +; ES:BX points to record +; Exit: +; Location -> ExtentLoc1 and ExtentLoc0 +; Length -> ExtentLen1 and ExtentLen0 +; +GetExtentInfo proc near + push ax ; Save registers used during this routine + + mov ax,es:[bx][2] ; 32-bit LBN of extent + mov ExtentLoc0,ax ; store low word + mov ax,es:[bx][4] + mov ExtentLoc1,ax ; store high word + mov ax,es:[bx][10] ; 32-bit file length in bytes + mov ExtentLen0,ax ; store low word + mov ax,es:[bx][12] + mov ExtentLen1,ax ; store high word + + pop ax ; Restore registers used during this routine + + ret +GetExtentInfo endp + + +include etfsboot.inc ; message text + +DiskAddPack db 16 dup (?) ; Disk Address Packet +PartialRead db 0 ; Boolean indicating whether or not we are doing a partial read +LOADERNAME db "SETUPLDR.BIN" +I386DIRNAME db "I386" +DriveNum db (?) ; Drive number used for INT 13h extended reads +ExtentLoc0 dw (?) ; Loader LBN - low word +ExtentLoc1 dw (?) ; Loader LBN - high word +ExtentLen0 dw (?) ; Loader Length - low word +ExtentLen1 dw (?) ; Loader Length - high word +Count0 dw (?) ; Read Count - low word +Count1 dw (?) ; Read Count - high word +Dest dw (?) ; Read Destination segment +Source0 dw (?) ; Read Source - word 0 (low word) +Source1 dw (?) ; Read Source - word 1 +NumBlocks db (?) ; Number of blocks to Read +EntryToFind dw (?) ; Offset of string trying to match in ScanForEntry +EntryLen db (?) ; Length in bytes of entry to match in ScanForEntry +IsDir db (?) ; Boolean indicating whether or not entry to match in ScanForEntry is a directory +ScanIncCount db 0 ; Boolean indicating if we need to add 1 to Count after adjustment in ScanForEntry + + .errnz ($-ETFSBOOT) GT 2046 ; FATAL PROBLEM: boot sector is too large + + org 2046 + db 55h,0aah + +BootSectorEnd label dword + +BootCode ends + + + END ETFSBOOT + |