862 lines
27 KiB
NASM
862 lines
27 KiB
NASM
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;++
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;
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;Copyright (c) 1995 Compaq Computer Corporation
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;
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;Module Name:
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;
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; etfsboot.asm
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;
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;Abstract:
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;
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; The ROM in the IBM PC starts the boot process by performing a hardware
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; initialization and a verification of all external devices. If an El
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; Torito CD-ROM with no-emulation support is detected, it will then load
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; the "image" pointed to in the Boot Catalog. This "image" is placed at
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; the physical address specified in the Boot Catalog (which should be 07C00h).
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;
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; The code in this "image" is responsible for locating NTLDR, loading the
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; first sector of NTLDR into memory at 2000:0000, and branching to it.
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;
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; There are only two errors possible during execution of this code.
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; 1 - NTLDR does not exist
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; 2 - BIOS read error
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;
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; In both cases, a short message is printed, and the user is prompted to
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; reboot the system.
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;
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;
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;Author:
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;
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; Steve Collins (stevec) 25-Oct-1995
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;
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;Environment:
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;
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; Image has been loaded at 7C0:0000 by BIOS. (or 0000:7C00 to support some broken BIOSes)
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; Real mode
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; ISO 9660 El Torito no-emulation CD-ROM Boot support
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; DL = El Torito drive number we booted from
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;
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;Revision History:
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;
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; Calin Negreanu (calinn) 25-May-1998 - added safety check at the beginning of the code
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; - added code for loading and executing BOOTFIX.BIN
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; - modified error path
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;--
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page ,132
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title boot - NTLDR ETFS loader
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name etfsboot
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EtfsCodeSize EQU 2048
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BootSeg segment at 07c0h
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BootSeg ends
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DirSeg segment at 1000h
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DirSeg ends
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LoadSeg segment at 2000h
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LoadSeg ends
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BootCode segment ;would like to use BootSeg here, but LINK flips its lid
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ASSUME CS:BootCode,DS:NOTHING,ES:NOTHING,SS:NOTHING
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public ETFSBOOT
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ETFSBOOT proc far
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cli
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;WARNING!!! DO NOT CHANGE THE STACK SETUP. BOOTFIX NEEDS THIS TO BE HERE.
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xor ax,ax ; Setup the stack to a known good spot
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mov ss,ax ; Stack is set to 0000:7c00, which is just below this code
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mov sp,7c00h
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sti
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mov ax,cs ; Set DS to our code segment (should be 07C0h)
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mov ds,ax
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assume DS:BootCode
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;
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; Save the Drive Number for later use
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;
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push dx
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;
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; Let's do some safety checks here. We are going to check for three things:
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; 1. We are loaded at 07c0:0000 or 0000:7C00
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; 2. Boot Drive Number looks good (80h-FFh)
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; 3. Our code was completely loaded by the BIOS
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;
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call NextInstr
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NextInstr:
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pop si ; Get IP from the stack
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sub si,OFFSET NextInstr ; See if we run with ORIGIN 0
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jz NormalCase ; Yes
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cmp si,7C00h ; See if, at least we run with ORIGIN 7C00H
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jne BootErr$wof1 ; If not, try to display some message
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mov ax,cs ; If offset is 7C00H, segment should be 0
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cmp ax,0000h
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jne BootErr$wof2 ; If not, try to display some message
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; We are loaded at 0000:7C00 instead of 07C0:0000. This could mess up
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; some stuff so we are going to fix it.
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; hack to execute JMP 07c0:BootOK
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db 0eah
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dw OFFSET BootOK
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dw BootSeg
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NormalCase:
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mov MSG_BAD_BIOS_CODE, '3'
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mov ax,cs ; See if segment is 07C0H
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cmp ax,07c0h
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jne BootErr$wnb ; If not, try to display some message
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BootOK:
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;
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; Reset ds in case we needed to change code segment
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;
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mov ax,cs
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mov ds,ax
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;
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; OK so far. Let's try to see if drive letter looks good (80h-FFh)
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;
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mov MSG_BAD_BIOS_CODE, '4'
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cmp dl,80h
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jb BootErr$wnb
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;
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; OK so far. Let's try to see if all our code was loaded.
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; We look for our signature at the end of the code.
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;
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mov MSG_BAD_BIOS_CODE, '5'
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mov bx, EtfsCodeSize - 2
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mov ax, WORD PTR DS:[bx]
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cmp ax, 0AA55h
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jne BootErr$wnb
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;
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; Finally, everything looks good.
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;
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;
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; Save the Drive Number for later use - right now drive number is pushed on the stack
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;
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pop dx
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mov DriveNum,dl
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;
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; Let's try to load and run BOOTFIX.BIN
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;
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.386
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push OFFSET BOOTFIXNAME
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push 11
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push LoadSeg
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call LoadFile
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jc FindSetupLdr
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;
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; We have BOOTFIX.BIN loaded. We call that code to see if we should boot from CD. If we shouldn't
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; we'll not come back here.
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;
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.286
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pusha
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push ds
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push es
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;
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; BOOTFIX requires:
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; DL = INT 13 drive number we booted from
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;
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mov dl, DriveNum ; DL = CD drive number
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;hack to execute CALL LoadSeg:0000
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db 9Ah
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dw 0000h
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dw LoadSeg
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pop es
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pop ds
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popa
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.8086
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FindSetupldr:
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;
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; Scan for the presence of SETUPLDR.BIN
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;
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.386
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push OFFSET LOADERNAME
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push 12
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push LoadSeg
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call LoadFile
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jc BootErr$bnf
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;
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; SETUPLDR requires:
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; DL = INT 13 drive number we booted from
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;
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mov dl, DriveNum ; DL = CD drive number
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xor ax,ax
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.386
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push LoadSeg
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push ax
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retf ; "return" to NTLDR (LoadSeg:0000h). Will not come back here.
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ETFSBOOT endp
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;
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; BootErr - print error message and hang the system.
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;
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BootErr proc
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BootErr$wof1: ; we were loaded at a wrong address - Code 1
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PUSH SI
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MOV BX, SI
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ADD BX, OFFSET MSG_BAD_BIOS_CODE
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MOV BYTE PTR DS:[BX], '1'
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ADD SI, OFFSET MSG_BAD_BIOS
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JMP BootErr2
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BootErr$wof2: ; we were loaded at a wrong address - Code 2
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PUSH SI
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MOV BX, SI
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ADD BX, OFFSET MSG_BAD_BIOS_CODE
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MOV BYTE PTR DS:[BX], '2'
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ADD SI, OFFSET MSG_BAD_BIOS
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JMP BootErr2
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BootErr$wnb: ; some other BIOS problem
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PUSH 0
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MOV SI, OFFSET MSG_BAD_BIOS
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JMP BootErr2
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BootErr$bnf: ; NTLDR not found
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PUSH 0
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MOV SI, OFFSET MSG_NO_NTLDR
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JMP BootErr2
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BootErr$mof: ; memory overflow
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PUSH 0
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MOV SI, OFFSET MSG_MEM_OVERFLOW
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JMP BootErr2
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BootErr2:
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CALL BootErrPrint
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POP SI
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JMP BootFromHD
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BootErrPrint:
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LODSB ; Get next character
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OR AL, AL
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JZ BEdone
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MOV AH, 14 ; Write teletype
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MOV BX, 7 ; Attribute
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INT 10H ; Print it
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JMP BootErrPrint
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BEdone:
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RET
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BootErr endp
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;
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; we are trying to boot from HD. We need to move ourself out of
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; this area because we are going to load MBR here
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;
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BootFromHD:
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;
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; let's wait here for two seconds, so the user gets a chance to see the message
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;
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;
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; hook INT08
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;
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MOV [SI+TicksCount], 24H ; two seconds delay
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CLI
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PUSH ES
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XOR AX, AX
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MOV ES, AX
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MOV BX, 0020H
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MOV AX, ES:[BX]
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MOV WORD PTR [SI+OldInt08], AX
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MOV AX, ES:[BX+2]
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MOV WORD PTR [SI+OldInt08+2], AX
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MOV ES:[BX], SI
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ADD ES:[BX], OFFSET NewInt08
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MOV ES:[BX+2], CS
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POP ES
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STI
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;
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; now let's actively wait for TicksCount to become zero
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;
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Delay:
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CMP [SI+TicksCount], 0
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JNE Delay
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;
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; unhook INT08
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;
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cli
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push es
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xor ax,ax
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mov es,ax
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mov bx,08h * 4
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mov ax,WORD PTR [SI+OldInt08]
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mov es:[bx],ax
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mov ax,WORD PTR [SI+OldInt08+2]
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mov es:[bx+2],ax
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pop es
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sti
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;
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; now let's move ourselves away from here because we are going to load MBR here
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;
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MoveCode:
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push ds
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push es
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mov ax, LoadSeg
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mov es, ax
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mov ax, cs
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mov ds, ax
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;si is already set
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xor di, di
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mov cx, EtfsCodeSize
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rep movsb
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pop es
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pop ds
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;hack to execute JMP LoadSeg:AfterMoveLabel
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db 0eah
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dw OFFSET AfterMoveLabel
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dw LoadSeg
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AfterMoveLabel:
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;
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; finally load MBR
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;
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push es
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mov ax, BootSeg
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mov es, ax
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mov bx, 0000h
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mov ax, 0201h ;read function, one sector
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mov cx, 0001h
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mov dx, 0080h
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int 13h
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jnc MbrOk
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;
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; there was an error, nothing else to do
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;
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jmp $
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MbrOk:
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pop es
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;
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; now let's return into MBR code
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;
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mov dl,80h
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;hack to execute JMP 0000:7C00
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db 0eah
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dw 7c00h
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dw 0000h
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;
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; We rely on the fact that SI is not changed when this INT occurs
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; This is a pretty good assumption since this code is active only
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; within the tight loop near Delay label. The odds are that some
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; other IRQ occures, enables interrupts, changes SI and then INT08
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; occures. This should not happen.
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;
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NewInt08:
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PUSHF
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CLI
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CMP CS:[SI+TicksCount], 0
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JE Default08
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DEC WORD PTR CS:[SI+TicksCount]
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Default08:
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POPF
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PUSH WORD PTR CS:[SI+OldInt08+2]
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PUSH WORD PTR CS:[SI+OldInt08]
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RETF
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include etfsboot.inc ; message text
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;
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; ScanForEntry - Scan for an entry in a directory
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;
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; Entry:
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; ES:0 points to the beginning of the directory to search
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; Directory length in bytes is in ExtentLen1 and Extend_Len_0
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;
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; Exit:
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; CF set on error, clear on success.
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; ES:BX points to record containing entry if match is found
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;
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ScanForEntry proc near
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mov ScanIncCount, 0
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mov cx,ExtentLen0 ; CX = length of root directory in bytes (low word only)
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cld ; Work up for string compares
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xor bx,bx
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xor dx,dx
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ScanLoop:
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mov si, EntryToFind
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mov dl,byte ptr es:[bx] ; directory record length -> DL
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cmp dl,0
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jz Skip00 ; if the "record length" assume it is "system use" and skip it
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mov ax,bx
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add ax,021h ; file identifier is at offset 21h in directory record
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mov di,ax ; ES:DI now points to file identifier
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push cx
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xor cx,cx
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mov cl,EntryLen ; compare bytes
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repe cmpsb
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pop cx
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jz ScanEnd ; do we have a match?
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CheckCountUnderFlow:
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|
|
; 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?
|
||
|
|
jne ResetContinue
|
||
|
|
stc ; We overran the end of the directory - corrupt/invalid directory
|
||
|
|
ret
|
||
|
|
ResetContinue:
|
||
|
|
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
|
||
|
|
|
||
|
|
clc
|
||
|
|
ret
|
||
|
|
ScanForEntry 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
|
||
|
|
|
||
|
|
LoadFile proc near
|
||
|
|
push bp
|
||
|
|
mov bp, sp
|
||
|
|
;
|
||
|
|
; First thing, 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
|
||
|
|
jc EntryNotFound
|
||
|
|
;
|
||
|
|
; 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 the file that we need
|
||
|
|
; ES points to directory segment
|
||
|
|
;
|
||
|
|
|
||
|
|
mov ax, DirSeg
|
||
|
|
mov es, ax
|
||
|
|
mov ax, [bp][8]
|
||
|
|
mov EntryToFind, ax
|
||
|
|
mov al, [bp][6]
|
||
|
|
mov EntryLen, al
|
||
|
|
mov IsDir,0
|
||
|
|
call ScanForEntry
|
||
|
|
jc EntryNotFound
|
||
|
|
;
|
||
|
|
; We found the needed file, so now get its extent location (offset -31 from filename ID)
|
||
|
|
; ES:[BX] still points to the directory record for that code
|
||
|
|
;
|
||
|
|
call GetExtentInfo
|
||
|
|
|
||
|
|
;
|
||
|
|
; Now, go read the file
|
||
|
|
;
|
||
|
|
.286
|
||
|
|
push [bp][4] ; Segment used for transfer
|
||
|
|
.8086
|
||
|
|
call ReadExtent
|
||
|
|
add sp,2 ; Clean 1 argument off the stack
|
||
|
|
|
||
|
|
EntryNotFound:
|
||
|
|
pop bp
|
||
|
|
ret
|
||
|
|
|
||
|
|
LoadFile endp
|
||
|
|
|
||
|
|
|
||
|
|
OldInt08 DD ? ; Default Int08 vector
|
||
|
|
TicksCount dw 24H ; two seconds
|
||
|
|
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"
|
||
|
|
BOOTFIXNAME db "BOOTFIX.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 ? ; Boolean indicating if we need to add 1 to Count after adjustment in ScanForEntry
|
||
|
|
|
||
|
|
.errnz ($-ETFSBOOT) GT (EtfsCodeSize - 2) ; FATAL PROBLEM: boot sector is too large
|
||
|
|
|
||
|
|
org (EtfsCodeSize - 2)
|
||
|
|
db 55h,0aah
|
||
|
|
|
||
|
|
BootSectorEnd label dword
|
||
|
|
|
||
|
|
BootCode ends
|
||
|
|
|
||
|
|
|
||
|
|
END ETFSBOOT
|
||
|
|
|