; Boot sector for GeekOS
; Copyright (c) 2001,2004 David H. Hovemeyer <daveho@cs.umd.edu>
; Copyright (c) 2003, Jeffrey K. Hollingsworth <hollings@cs.umd.edu>
-; $Revision: 1.2 $
+; Copyright (c) 2008, Jack Lange <jarusl@cs.northwestern.edu
+; Copyright (c) 2008, Peter Dinda <pdinda@northwestern.edu
+; $Revision: 1.8 $
; This is free software. You are permitted to use,
; redistribute, and modify it as specified in the file "COPYING".
[ORG 0x0]
BeginText: ; needed to calculate padding bytes to fill the sector
-
; Copy the boot sector into INITSEG.
mov ax, BOOTSEG
mov ds, ax ; source segment for string copy
after_move:
; Now we're executing in INITSEG
+
; We want the data segment to refer to INITSEG
; (since we've defined variables in the same place as the code)
mov ds, ax ; ax still contains INITSEG
mov ss, ax
mov sp, (BOOTSEG << 4) + 512 - 2
+
load_setup:
; Load the setup code.
mov ax, word [setupStart]
cmp word [sec_count], bx
jl .again
+
+
load_kernel:
; Load the kernel image from sectors KERN_START_SEC..n of the
; floppy into memory at KERNSEG. Note that there are 128 sectors
; equivalent to dividing by 128).
; Figure out start sector and max sector
+
mov ax, word [kernelStart]
- mov word [sec_count], ax
+ mov word [sec_count], aX
add ax, word [kernelSize]
mov word [max_sector], ax
-.again:
+
+
+.again2:
+
mov ax, [sec_count] ; logical sector on the floppy
push ax ; 1st param to ReadSector (log sec num)
- sub ax, [kernelStart] ; convert to 0-indexed
- mov cx, ax ; save in cx
- shr ax, 7 ; divide by 128
- shl ax, 12 ; ...and multiply by 0x1000
- add ax, KERNSEG ; ...to get base relative to KERNSEG
+
+; mov dx, ax
+; call PrintHex
+; call PrintNL
+
+ mov ax, VMSEG ; ...to get base relative to VMSEG
push ax ; 2nd param to ReadSector (seg base)
- and cx, 0x7f ; mod sector by 128
- shl cx, 9 ; ...and multiply by 512
- push cx ; to get offset in segment (3rd parm)
+
+; mov dx, ax ;
+; call PrintHex
+; call PrintNL
+
+ mov ax, 2000h ; Always write at the start of the segment
+ push ax ; 3rd parameter
+
+; mov dx, ax
+; call PrintHex
+; call PrintNL
; read the sector from the floppy
call ReadSector
add sp, 6 ; clear 3 word params
+ push VMSEG
+ pop es
+
+; mov dx, word [es:2000h] ;
+; call PrintHex
+; call PrintNL
+
+
+
+; execute bios call
+
+ push cx
+ push si
+ push bx
+ push es ;
+
+ push cs
+ pop es
+ mov si, bootsect_gdt
+ mov ah, 87h
+
+ mov cx, 100h
+
+ int 0x15
+
+ adc ax, 0
+
+; mov dx, ax
+; call PrintHex
+; call PrintNL
+
+
+
+ pop es ;
+ pop bx
+ pop si
+ pop cx
+
; on to next sector
inc word [sec_count]
+
+ ; update the low->high copy table for the bios
+; mov ax, word [bootsect_src_base] ;
+; add ax, 512
+; mov dx,ax;
+; call PrintHex
+; adc byte [bootsect_src_base+2], 0
+; mov word [bootsect_src_base],ax
+
+ mov ax, word [bootsect_dst_base] ;
+ add ax, 512
+ adc byte [bootsect_dst_base+2], 0
+ mov word [bootsect_dst_base],ax
+
; have we loaded all of the sectors?
+
mov bx, word [max_sector]
cmp word [sec_count], bx
- jl .again
+
+.stall
+; jmp .skip
+ jl .again2
+
+.skip
; Now we've loaded the setup code and the kernel image.
; Jump to setup code.
jmp SETUPSEG:0
xor dl, dl ; hard code drive=0
mov bx, [bp+4] ; offset goes in bx
; (es:bx points to buffer)
-
; Call the BIOS Read Diskette Sectors service
int 0x13
-
+
; If the carry flag is NOT set, then there was no error
; and we're done.
jnc .done
pop bp ; leave stack frame
ret
-; Include utility routines
-%include "util.asm"
+; Include utility routines:
+;%include "util.asm"
+; REPLACED WITH FOLLOWING WHICH MUST BE COMPILED 16 FOR USE IN THIS CODE
+PrintHex:
+ pusha
+ mov cx, 4 ; 4 hex digits
+.PrintDigit:
+ rol dx, 4 ; rotate so that lowest 4 bits are used
+ mov ax, 0E0Fh ; ah = request, al = mask for nybble
+ and al, dl
+ add al, 90h ; convert al to ascii hex (four instructions)
+ daa ; I've spent 1 hour to understand how it works..
+ adc al, 40h
+ daa
+ int 10h
+ loop .PrintDigit
+ popa
+ ret
+
+; Print a newline.
+PrintNL: ; print CR and NL
+ push ax
+ mov ax, 0E0Dh ; CR
+ int 10h
+ mov al, 0Ah ; LF
+ int 10h
+ pop ax
+ ret
+
+
; ----------------------------------------------------------------------
; Variables
sec_count: dw 0
max_sector: dw 0
+
+
+
+bootsect_gdt:
+ dw 0,0,0,0
+ dw 0,0,0,0
+bootsect_src:
+ dw 0xffff
+bootsect_src_base:
+ db 0,0x20,0x08 ; ! base = 0x082000
+ db 0x93 ; ! typbyte
+ dw 0 ; ! limit16,base24 =0
+bootsect_dst:
+ dw 0xffff
+bootsect_dst_base:
+ db 0,0,0x10 ; ! base = 0x100000
+ db 0x93 ; ! typbyte
+ dw 0 ; ! limit16,base24 =0
+ dw 0,0,0,0 ; ! BIOS CS
+ dw 0,0,0,0 ; ! BIOS DS
+
+
; Padding to make the PFAT Boot Record sit just before the BIOS signature.
-Pad_From_Symbol PFAT_BOOT_RECORD_OFFSET, BeginText
+;Pad_From_Symbol PFAT_BOOT_RECORD_OFFSET, BeginText
; PFAT boot record
; Describes how to load the setup program and kernel.
;; part of pfat boot record
kernelSize:
- dw NUM_KERN_SECTORS+NUM_VM_KERNEL_SECTORS
+ dw NUM_KERN_SECTORS
+
+
-; Finish by writing the BIOS signature to mark this as
+ ; Finish by writing the BIOS signature to mark this as
; a valid boot sector.
Pad_From_Symbol BIOS_SIGNATURE_OFFSET, BeginText
Signature dw 0xAA55 ; BIOS controls this to ensure this is a boot sector
