smiddy
Joined: 31 Oct 2004
Posts: 557
|
Greetings,
I have been working on loading my OS via CD and put together an alpha version that essentially allowed me to access the drive and traverse it. I was only reading one sector at a time. Now, when I want to load and run the OS, I load via the entire chunk (> 65,535 bytes; more than a segment). Everything I've read indicates I can load as many as 7Fh (127) sectors. But when I run in Virtual PC I get the error number 09h (over 64k boundary), though VirtualBox and Bochs both don't return this error. Every indication from Bochs is that it is trying to run too (which is weird in itself, no GPFs). Here's the latest code (not entirely ready for prime time, but you can get the idea):
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; ;;
;; Project : smiddyOS (CD-ROM Booter) ;;
;; Author : smiddy ;;
;; Website : ;;
;; Date : December 27, 2011 ;;
;; Quick Information: Compact Disc bootloader beta to load bootable software. ;;
;; Filename : cdboot2.asm ;;
;; Assembler Command: Using FASMW IDE ;;
;; ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; ;;
;; Useage: Using CDBOOT2.BIN as the boot loader from the created ISO from the ;;
;; CD-ROM creating CDROM.ASM from within FASMW IDE. ;;
;; ;;
;; See CDROM.ASM for further details. ;;
;; ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; ;;
;; v1.00 - Beta release; CD-ROM compatible booter, capable of booting bootable ;;
;; software, in this case SMIDDYOS.EXE. Change the file name to one you ;;
;; wish to load instead. The loader expects to be booted at 0060:0000 ;;
;; (600h linear) and the bootable software gets loaded at 0202:0000 ;;
;; (2020h linear). ;;
;; ;;
;; Limitations include that the boot file needs to be in the root ;;
;; directory and the root directory can not be longer than one CD sector ;;
;; (2048 bytes). ;;
;; ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
format binary as "bin" ; Tell FASM to make an BIN image
ORG 0
DEBUG_MESSAGES: ; Comment out to remove debugging messages
BootSector: ; Label in order to determine size of code for
; padding at the end.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Start Boot Procedure ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
Begin: ; Begining of instructions
CLI ; Turn off intterrupts
mov ax,0060h ; Boot Segment (no need to copy there)
mov ds,ax
mov es,ax
MOV [CDDriveNumber],DL ; Save boot drive, right away
MOV AX,7000h
MOV DS,AX ; Segment of saved variables for SmiddyOS
MOV BX,530h ; Offset of boot drive saved variable
MOV [DS:BX],DL ; Save the boot drive for SmiddyOS use later
MOV AX,60h
MOV DS,AX ; Reset segment
XOR AX,AX ; Zero out the stack segment
MOV SS,AX
MOV SP,5FEh ; 0000:05FE
MOV SP,AX
STI ; Turn interrupts back on
MOV SI,WelcomeMessage ; Tell everyone hello
CALL PrintString ; Print the welcome message
MOV SI,TheEndOfTheLine ; Go to the next line
CALL PrintString
MOV AL,[CDDriveNumber] ; Load drive number in for comparison
CMP AL,0 ; Compare to known BAD drive number for CD/DVD/BD
JE Failure ; If it is, it failed.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Get Status (Bootable CD-ROM)
;;
;; Call with: AX = 4B01H
;; DL = Drive number
;; DS:SI = Empty specification packet (needs to be 13h in size)
;;
;; Return: If Function Successful,
;; Carry Flag = Clear
;;
;; If Function Unsuccessful,
;; Carry Flag = Set
;; AX = Status code
;;
;; DS:SI = Specification packet filled
;; Offset Size Description
;; 00h db size of packet in bytes (13h)
;; 01h db boot media type
;; Bit(s) Description
;; 3-0 media type.
;; 0000 no emulation.
;; 0001 1.2M diskette.
;; 0010 1.44M diskette.
;; 0011 2.88M diskette.
;; 0100 hard disk
;; Other reserved
;; 5-4 reserved (0)
;; 6 image contains ATAPI driver
;; 7 image contains SCSI driver(s)
;; 02h db drive number
;; 00h floppy image
;; 80h bootable hard disk
;; 81h-FFh nonbootable or no emulation drive
;; 03h db CD-ROM controller number
;; 04h dd Logical Block Address (LBA) of disk image to emulate
;; 08h dw device specification (same as boot media type plus)
;; (IDE) bit 0: Drive is slave instead of master
;; (SCSI) bits 7-0: LUN and PUN
;; bits 15-8: Bus number
;; 0Ah dw segment of 3K buffer for caching CD-ROM reads
;; 0Ch dw load segment for initial boot image (if 0000h, load at segment 07C0h; only valid for INT 13h/AH=4Ch)
;; 0Eh dw number of 512-byte virtual sectors to load (only valid for INT 13h/AH=4Ch)
;; 10h db low byte of cylinder count (for INT 13/AH=08h)
;; 11h db sector count, high bits of cylinder count (for INT 13h/AH=08h)
;; 12h db head count (for INT 13h/AH=08h)
;;
;; Comments:
;;
;; The Function is used to get the status of the CD/DVD/BD. This function is called
;; first for "no emulation" booting of optical media. If the Function is successful,
;; the carry flag is clear, else carry flag is set and AX register returns status
;; code.
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
GetBootedCDStatus:
MOV DL,[CDDriveNumber] ; Prepare to read CD-ROM, load boot drive
MOV AH,4Bh ; Use function 4Bh
MOV AL,1
MOV SI,DiskResultsBuffer ; Results buffer to load
INT 13h ; Call Check Extensions Present?
JC Failure ; Need to engage the Failure Procedure
MOV AH,255 ; Load proposed error code (255 is our failure code for drive number miss detected)
MOV DL,[DiskResultsBuffer+2] ; Load resultant drive information
CMP [CDDriveNumber],DL ; Compare to see if they are the same (they should be)
JNE Failure ; If they are not, Failure
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; More information can be gathered here if needed later, not needed at this time.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Check INT 13h Extensions Present
;;
;; Call with: AH = 41H
;; DL = Drive number (80h - FFh; but we're interested in CDs for this exercise)
;; BX = 55AAh (Signature?)
;;
;; Return: If Function Successful,
;; Carry Flag = Clear
;; BX = AA55h if installed
;; AH = major version of extensions
;; 01h = 1.x
;; 20h = 2.0 / EDD-1.0
;; 21h = 2.1 / EDD-1.1
;; 30h = EDD-3.0
;; AL = internal use
;; CX = API subset support bitmap
;; 1 - Device Access using packet structure (INT 13h AH=42h-44h,47h,48h)
;; 2 - Drive Locking and Ejecting (INT 13h AH=45h,46h,48h,49h,INT 15h AH=52h)
;; 4 - Enhanced Disk Drive Support (INT 13h AH=48h,AH=4Eh)
;; DH = extension version (v2.0+ ??? -- not present in 1.x)
;;
;; If Function Unsuccessful,
;; Carry Flag = Set
;; AH = 01h (invalid function)
;;
;; Comments:
;;
;; The Function is used to see if INT 13h extensions are present (not really
;; needed if you can do the previous function, right?)
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
GetINT13hExtenstions:
MOV DL,[CDDriveNumber] ; Prepare to read CD-ROM, load boot drive
MOV AH,41h ; Use function 41h: Check Extensions Present
MOV BX,55AAh ; Signature?
INT 13h ; Call Check Extensions Present? (This makes no sense if you try INT 13h Function 4B01h, but details are
; provided upon return if CF isn't set)
JC Failure ; Nope, get out of here...
if defined DEBUG_MESSAGES
MOV [VersionEnhancedDiskDriveExtensions],AH
MOV [InternalUseEnhancedDiskDriveExtensions],AL
MOV [InterfaceSupportBitMask],CX
MOV AL,[VersionEnhancedDiskDriveExtensions]
MOV CL,8
CALL ToHex
MOV SI,HexBuffer
Call PrintString
MOV SI,AddTheHAtTheEnd
CALL PrintString
MOV SI,EnhancedDiskDriveVersionMessage
CALL PrintString
MOV AX,[InterfaceSupportBitMask]
MOV CL,16
CALL ToHex
MOV SI,HexBuffer
CALL PrintString
MOV SI,AddTheHAtTheEnd
CALL PrintString
MOV SI,IsEqualToTheCX
CALL PrintString
MOV SI,TheEndOfTheLine
call PrintString
end if
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Extended Read Function
;;
;; Call with AH=42h
;; DL = drive number
;; DS:SI = Disk Address Packet (DAP)
;; Offset Size Description
;; 00h db Size of packet (10h or 18h; we're using 10h here, see below)
;; 01h db Reserved (0)
;; 02h dw Number of sectors to read (max 007Fh for Phoenix EDD)
;; 04h dd Initial segment:offset where to load the read in sector(S)
;; 08h dq starting absolute sector number (for non-LBA devices, compute as (Cylinder*NumHeads + SelectedHead) * SectorPerTrack + SelectedSector - 1
;; 10h dq (EDD-3.0, optional) 64-bit flat address of transfer buffer; used if dd at 04h is FFFFh:FFFFh
;;
;; Return: If Function Successful,
;; Carry Flag = Clear
;; AH = 00h
;;
;; If Function Unsuccessful,
;; Carry Flag = Set
;; AH = Error code
;;
;; Error code:
;; 00h successful completion
;; 01h invalid function in AH or invalid parameter
;; 02h address mark not found
;; 03h disk write-protected
;; 04h sector not found/read error
;; 05h reset failed (hard disk)
;; 05h data did not verify correctly (TI Professional PC)
;; 06h disk changed (floppy)
;; 07h drive parameter activity failed (hard disk)
;; 08h DMA overrun
;; 09h data boundary error (attempted DMA across 64K boundary or >80h sectors)
;; 0Ah bad sector detected (hard disk)
;; 0Bh bad track detected (hard disk)
;; 0Ch unsupported track or invalid media
;; 0Dh invalid number of sectors on format (PS/2 hard disk)
;; 0Eh control data address mark detected (hard disk)
;; 0Fh DMA arbitration level out of range (hard disk)
;; 10h uncorrectable CRC or ECC error on read
;; 11h data ECC corrected (hard disk)
;; 20h controller failure
;; 31h no media in drive (IBM/MS INT 13 extensions)
;; 32h incorrect drive type stored in CMOS (Compaq)
;; 40h seek failed
;; 80h timeout (not ready)
;; AAh drive not ready (hard disk)
;; B0h volume not locked in drive (INT 13 extensions)
;; B1h volume locked in drive (INT 13 extensions)
;; B2h volume not removable (INT 13 extensions)
;; B3h volume in use (INT 13 extensions)
;; B4h lock count exceeded (INT 13 extensions)
;; B5h valid eject request failed (INT 13 extensions)
;; B6h volume present but read protected (INT 13 extensions)
;; BBh undefined error (hard disk)
;; CCh write fault (hard disk)
;; E0h status register error (hard disk)
;; FFh sense operation failed (hard disk)
;;
;; Initial DAP:
;;
;; db 10h - Initial Volume Descriptor, which has the important data we need
;; to get to the root directory where our OS is stored.
;; db 0 - Unused, should be zero
;; dw 1 - Number of sectors to read (initial one should be one for Volume Descriptor)
;; dd 0202:0000 - Initial segment:offset where to load the read in sector(S)
;; dq 16 - Starting sector to read in, then we need to get to the root directory
;;
;; Comments:
;;
;; This functions is called three times: Initially to get the Initial
;; Volume Descriptor so we can find the root directory; then it gets used
;; again to read in the root directory, so we can scan for SmiddyOS; finally
;; once we recognize SmiddyOS we load it and jump to it, if all goes as it
;; should "on a good day" as expected.
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
MOV DL,[CDDriveNumber] ; Set it up again
MOV AH,42h ; Read from drive function
MOV SI,DiskAddressPacket ; Load SI with address of the Disk Address Packet
INT 13h ; Call read sector from drive
JC Failure ; Nope, hosed, get out
MOV ES,[DiskAddressPacket.Segment]
MOV DI,[DiskAddressPacket.Offset]
MOV BX,40 ; Load BX with Volume Label offset (Check CDROM.ASM or ISO 9660)
VolumeLabelLoop:
MOV CL,[ES:DI+BX] ; Grab a letter
CMP CL,' ' ; Is it a space? (Assumes end of string is space, may run out)
JE .VolumeLabelDone ; Yes, we are done
MOV [VolumeLabel+BX-40],CL
INC BX
JMP VolumeLabelLoop ; Need to compare BX to length of Volume Label on CD (32?)
.VolumeLabelDone:
MOV byte [VolumeLabel+BX-40],0 ; End the string
MOV EAX,[ES:DI+158] ; LBA of root directory, where all things start.
MOV [DiskAddressPacket.End],EAX ; Load packet with new address on CD of the root directory
MOV DL,[CDDriveNumber] ; Set it up again
MOV AH,42h ; Read from drive function
MOV SI,DiskAddressPacket ; Load SI with address of the Disk Address
; Packet
INT 13h ; Call read sector from drive
JC Failure ; Nope, hosed, get out
CALL PrintDirectory
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Failure: Looks up error code and displays the error then waits for a key to ;;
;; reboot. ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
Failure:
mov AL,AH ; Put the error into lowest bits
mov cl,8 ; only 8 bits
call ToHex ; Get what is in the XX to display
MOV SI,FailureMessage ; reboot message
CALL PrintString
mov si,HexBuffer
CALL PrintString
MOV SI,AddTheHAtTheEnd
CALL PrintString
MOV SI,TheEndOfTheLine
CALL PrintString
mov SI,PressAnyKeyMessage
CALL PrintString
MOV AH,0 ; Reboot on error
INT 16h ; BIOS GetKey
INT 19h ; BIOS Reboot
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; PrintDirectory: Prints the root directory to the display.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
PrintDirectory:
MOV ES,[DiskAddressPacket.Segment]
MOV DI,[DiskAddressPacket.Offset]
MOV SI,DriveDisplayMessage
CALL PrintString
CMP byte [VolumeLabel],0
JE .NoLabel
MOV SI,VolumeLabel
CALL PrintString
JMP .LabelDone
.NoLabel:
MOV SI,HasNoLabel
CALL PrintString
.LabelDone:
MOV SI,TheEndOfTheLine
CALL PrintString
MOV SI,TheEndOfTheLine
CALL PrintString
.GrabDirectoryEntry:
MOV AL,[ES:DI] ; Length of the current directory entry
MOV [DirectoryEntrySize],AL
MOV EAX,[ES:DI+2] ; Starting sector of directory entry
MOV [FileSector],EAX
MOV EAX,[ES:DI+10] ; Size of directory entry on CD/DVD/BD
MOV [FileSize],EAX
MOV AL,[ES:DI+32] ; File's name length (see El Torito of ISO:9660 or CDROM.ASM)
MOV [FileNameLength],AL
XOR BX,BX ; Initialize BX
XOR CX,CX
MOV SI,DI
ADD SI,33
MOV BX,FileNameEntry
MOV AL,[FileNameLength]
CMP AL,1
JE .DotAndDotDotEntries
.LoopFileNameEntry:
MOV AL,[ES:SI]
MOV [DS:BX],AL
INC BX
INC CX
INC SI
XOR AX,AX
MOV AL,[FileNameLength]
CMP CX,AX
JB .LoopFileNameEntry
MOV byte [DS:BX],0
JMP .FileNameEntryDisplay
.DotAndDotDotEntries:
MOV AL,[FileEntryNumber]
CMP AL,0
JA .DoDotDotEntry
MOV word [FileNameEntry],'.' ; First directory entry
MOV byte [FileNameEntry+1],0 ; End the string with a termination
JMP .FileNameEntryDisplay
.DoDotDotEntry:
MOV word [FileNameEntry],'..' ; Second directory entry
MOV byte [FileNameEntry+2],0 ; End the string with a termination
.FileNameEntryDisplay:
MOV SI,FileNameEntry
CALL PrintString
MOV SI,FileNameEntry
PUSH DI
MOV DI,FileName
CALL StringCompare
POP DI
JC .EndOfTheLine
MOV SI,TheEndOfTheLine
CALL PrintString
MOV EAX,[FileSector]
MOV [DiskAddressPacket.End],EAX ; Save the starting sector into DAP
MOV EAX,[FileSize]
XOR EDX,EDX
MOV EBX,2048
DIV EBX
INC EAX
MOV [DiskAddressPacket.SectorsToRead],AX ; Save number of sectors to read
if defined DEBUG_MESSAGES
MOV CL,16
CALL ToHex
MOV SI,HexBuffer
Call PrintString
MOV SI,AddTheHAtTheEnd
CALL PrintString
MOV SI,TheEndOfTheLine
CALL PrintString
MOV EAX,[FileSector]
MOV CL,32
CALL ToHex
MOV SI,HexBuffer
CALL PrintString
MOV SI,AddTheHAtTheEnd
CALL PrintString
MOV SI,TheEndOfTheLine
call PrintString
end if
MOV DL,[CDDriveNumber] ; Set it up again
MOV AH,42h ; Read from drive function
MOV SI,DiskAddressPacket ; Load SI with address of the Disk Address Packet
INT 13h ; Call read sector from drive
JC Failure ; Nope, hosed, get out
MOV DL,[CDDriveNumber] ; Drive into DL for booting
PUSH WORD 0202h ; New Location
PUSH WORD 0000h ; CS:IP = 0202:0000
RETF ; Will pop our new CS:IP
.EndOfTheLine:
MOV SI,TheEndOfTheLine
CALL PrintString
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
XOR CX,CX ; Prepare CX to do math for DI
MOV CL,[DirectoryEntrySize] ; Get the size of the directory entry
ADD DI,CX ; Add that size to the DI to get to the next record
CMP byte [ES:DI],0 ; Is the next entry = 0?
JE .End ; If so, we're at the end of the directory, move on
XOR CX,CX
MOV BX,FileNameEntry
.ClearFileNameEntry:
MOV byte [DS:BX],0 ; Erase the begining of the
INC BX
INC CX
CMP CX,254
JB .ClearFileNameEntry
MOV byte [DS:BX],0
INC byte [FileEntryNumber]
JMP .GrabDirectoryEntry ; If not, we have more processing to do
.End:
RET
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; PrintString ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
PrintString:
PUSHA ; Save Registers
.Loop:
LODSB ; Load SI into AL, increment SI one byte
OR AL,AL ; AL = 0?
JZ .Done ; If yes, get out
MOV AH,0Eh
MOV BH,0
MOV BL,7 ; character attribute
INT 10h ; Display character in AL
JMP .Loop ; Do it again
.Done:
POPA ; Replace registers
RET
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; ToHex
;; Loads HexBuffer with ASCII corresponding to 8, 16, or 32 bit interger in
;; hex.
;; Requires interger in AL, AX, or EAX depending on bit size
;; Requires the number of bits in the CL
;; Returns a full buffer or an empty buffer on error
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
ToHex:
pusha
MOV BX,0x0000 ; Load BX with pointer offset
MOV [TheEAX],EAX ; Save the EAX
MOV [TheCL],CL ; Save the CL
CMP CL,0x08 ; Check for 8 bits
JNE .Check16
JMP .Loop1 ; Start loading the buffer
.Check16:
CMP CL,0x10 ; Check for 16 bits
JNE .Check32
JMP .Loop1 ; Start loading the buffer
.Check32:
CMP CL,0x20 ; Check for 32 bits
JNE .ErrorBits
.Loop1:
MOV EAX,[TheEAX] ; Reload EAX with the converter
SUB CL,0x04 ; Lower bit count by 4 bits
SHR EAX,CL
AND AL,0x0F
ADD AL,'0'
CMP AL,'9'
JBE .LoadBuff1
ADD AL,'A'-'0'-10 ; Convert to "A" to "F"
JMP .LoadBuff1
.Loop2:
MOV EAX,[TheEAX] ; Reload EAX again
SUB CL,4 ; Lower bit count by 8 bits
SHR EAX,CL
AND AL,0x0F
ADD AL,'0'
CMP AL,'9'
JBE .LoadBuff2
ADD AL,'A'-'0'-10 ; Convert A,B,C,D,E,F
JMP .LoadBuff2
.LoadBuff1:
MOV [HexBuffer+BX],AL ; Load buffer with AL
INC BX ; Increment buffer pointer
JMP .Loop2 ; Do next byte
.LoadBuff2:
MOV [HexBuffer+BX],AL ; Load buffer with AL
INC BX ; Increment buffer pointer
CMP CL,0 ; Check if we're done
JNE .Loop1 ; Do next Byte
.ErrorBits:
MOV AL,0
MOV [HexBuffer+BX],AL ; End the string with a zero
popa
RET
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; StringCompare ;;
;; ;;
;; Compares the equality of two strings, loaded in ESI and EDI. ;;
;; ;;
;; Sets the CF if not the same. ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
StringCompare:
PUSH SI ; Save ESI to be restored at the end
PUSH DI ; Save EDI to be restored at the end
.Loop:
MOV AL,[SI] ; Grab byte from ESI
MOV BL,[DI] ; Grab byte from EDI
CMP AL,BL ; Compare if they are equal
JNE .NotEqual ; They aren't equal
CMP AL,0 ; Both bytes are null
JE .Done
INC DI ; Increment EDI
INC SI ; Increment ESI
JMP .Loop ; Start looping
.NotEqual:
STC ; Set the carry flag to indicate failure
JMP .End
.Done:
CLC ; Clear the carry flag to indicate success
.End:
POP DI ; Restore EDI before returning to caller
POP SI ; Restore ESI before returning to caller
RET
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; StringLength ;;
;; ;;
;; Checks the length of the string in the ESI and returns it in the EAX. ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
StringLength:
XOR EAX,EAX
.Loop:
CMP byte [ESI+EAX],0
JE .End
INC EAX
JMP .Loop
.End:
RET
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Program Data ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
DirectoryEntrySize: db 0
FileSector: dd 0
FileSize: dd 0
FileNameLength: db 0
FileNameEntry: TIMES 255 db ' '
FileEntryNumber: db 0
DriveDisplayMessage: db 'Volume in drive: ',0 ; Get label from Primary Volume Descriptor (loaded first)
HasNoLabel: db 'no label',0
FileNamePointer: dw 0
DataSector: DW 0
CDDriveNumber: db 0
RootDirectorySector dd 0
absoluteSector: DB 0
absoluteHead: DB 0
absoluteTrack: DB 0
BootDotNumber: DB '1'
Cluster: DW 0
FileName: DB 'SMIDDYOS.EXE',0 ; FAT Filename, 8.3, or 11 characters
VersionEnhancedDiskDriveExtensions: db 0
InternalUseEnhancedDiskDriveExtensions: db 0
InterfaceSupportBitMask: dw 0
EnhancedDiskDriveVersionMessage: db ' - Enhanced Disk Drive Extensions Version Number.',13,10,0
DirectoryEntrySizeMessage: db ' - Directory entry size.',13,10,0
DiskResultsBufferMessage: db 'Disk Buffer on in here...',13,10,0
IsEqualToTheCX db ' = CX contents from INT 13h Function 41h.',13,10,0
IsEqualToTheEAX db ' = EAX contents is the sector of the root directory contents.',13,10,0
WelcomeMessage: DB 'smiddy OS CD boot v1.00',225,13,10,0 ; Version of CD-Boot
FailureMessage: db 'Failure: ',0
DriveNumberReported: db 'Drive number reported: ',0
PressAnyKeyMessage: db 'Press any key to reboot...',13,10,0
AddTheHAtTheEnd: db 'h',0
TheEndOfTheLine: db 13,10,0 ; Used to print the end of the line string
SizeOfPacketInBytes: db 'The size of packet in bytes: ',0
BootMediaType: db 'The boot media type: ',0
DriveNumberFromPacket: db 'Drive number from packet: ',0
VolumeLabel: TIMES 33 db 0 ; Where the volume label is stored
DiskAddressPacket: db 16,0
.SectorsToRead: dw 1 ; Number of sectors to read (read size of OS)
.Offset: dw 0 ; Offset :0000
.Segment: dw 0202h ; Segment 0202: currerntly, will change to 0202:0000 for loading SmiddyOS
.End: dq 16 ; Sector 16 or 10h on CD-ROM
DiskResultsBuffer: times 30 db 0 ; Return buffer from int 13h ah=48h
HexBuffer: DB 0,0,0,0,0,0,0,0,0 ; Buffer for hex text string
TheEAX: dd 0 ; Saves EAX
TheCL: db 0
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; 512 Byte Code Boot Signature ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
TIMES 2046-($-BootSector) DB 0
DW 0AA55h ; Bootloading sector signature (for CD/DVD/BD) I am not sure this is needed for optical media booting.
Should I put in a routine to load single sectors (2048 bytes per) and then increment the DAP segment:offset accordingly, then jump? That seems a bit in efficient.
Thoughts? |
Index
> OS Construction > CD/DVD/BD Loader: INT 13h, Function 42 help...
02 Jan 2012, 19:20
I could use the ATA code you put together, though in learning this...I'm figuring out the limitations of the INT13h stuff. I prefer to use no emulation too, so I can change the ISO image later on.
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