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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; ;;
;; 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.
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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.
)