Re: [Nasm-users] calling 'C' functions

[zak100 <zul...@ya...>]

Hi,

The changes for jump code lies here:

GiveControlToOS: ; PROC

        LEA AX,[szDone]
        Call PrintMessage
        CALL GetKey
        
;        db 0e9h        ;Far JMP op code.
;        dw 512         ;JMP 512 bytes ahead
    ;jmp 0:7E00h;-----------------------------------At this point we are
going to Kernel code; for including C prog:test_kernel2.asm

        ;jmp 7D0h:100h
         jmp 0:7D00h
;       POP AX         ;//Another why to make 
                       ;the CPU jump to a new place.
;       POP AX
;       Push 7E0h      ;Push New CS address.
;       Push 0          ;Push New IP address.
               ;The address that comes out is 7E00:0000. 
; comment does not match code!


               ;(512 bytes Higher from were BIOS Put us.)
       retf
; you'd want "retf" here.
        
;GiveControlToOS EndP 

The changes for ..start lie here

..start:
extern _K_main
;--- test kernel.bin---

;    push cs
;    push cs
;    pop ds
;    pop es
    mov ax, 7E0H
    mov ds,ax
    mov es,ax
    mov si, msg

    mov ah, 0Eh
    mov bx, 7
top:
    lodsb
    cmp al, 0
    jz blackhole
    int 10h
    jmp short top

blackhole:
    
    mov cx,1000
    Delay: Loop Delay
    call _K_main; this is in main.c
    hlt
    jmp blackhole

msg db 'Welcome to the Kernel!', 0

times 0x200-($-$$) db 0

Kindly help me with this.


Zulfi.
        
Frank Kotler-3 wrote:
> 
> zak100 wrote:
>> Hi,
>> I am able to make the binary using alink. partcopy was giving prob but it
>> was handled as done previously.
>> 
>> The steps are provided below:
>> D:\nasm prog>nasm -f bin -o boot.bin BLKernelT.asm
>> 
>> D:\NASMPR~1>nasm -f bin -o writeit.com writeit.asm
>> 
>> D:\NASMPR~1>writeit
>> 
>> D:\NASMPR~1>del test_kernel2.onj
>> Could Not Find D:\NASMPR~1\test_kernel2.onj
>> 
>> D:\NASMPR~1>del test_kernel2.obj
>> 
>> D:\NASMPR~1>nasm -f obj test_kernel2.asm
>> 
>> D:\NASMPR~1>dir t*.obj
>>  Volume in drive D is New Volume
>>  Volume Serial Number is 70FD-1D2C
>> 
>>  Directory of D:\NASMPR~1
>> 
>> 07/10/2009  10:55 AM               642 test_kernel2.obj
>>                1 File(s)            642 bytes
>>                0 Dir(s)  22,656,360,448 bytes free
>> 
>> D:\NASMPR~1>alink -o kernel.bin test_kernel2.obj main1.o
>> ALINK v1.6 (C) Copyright 1998-9 Anthony A.J. Williams.
>> All Rights Reserved
>> 
>> Loading file test_kernel2.obj
>> Loading file main1.o
>> matched Externs
>> matched ComDefs
>> Warning, no entry point specified
> 
> You can fix this by adding a "..start:" label where you want your 
> entrypoint.
> 
>> Warning - no stack
> 
> segment stack stack
> resb ???? ; how big do you want? C uses a lot of stack, I understand.
> 
> The first "stack" is just a name - could be anything. The second "stack" 
> is necessary to let Nasm know what we want. I've been ignoring the 
> warning, and "let the OS take care of the stack". We set up a stack in 
> the bootsector which should be "okay for now". When you get to task 
> switching/multitasking, you'll want to swap stacks for each process (I 
> imagine).
> 
>> D:\NASMPR~1>alink -o kernel.exe test_kernel2.obj main1.o
>> ALINK v1.6 (C) Copyright 1998-9 Anthony A.J. Williams.
>> All Rights Reserved
>> 
>> Loading file test_kernel2.obj
>> Loading file main1.o
>> matched Externs
>> matched ComDefs
>> Warning, no entry point specified
>> Warning - no stack
>> 
>> D:\NASMPR~1>del kernel.bin
>> 
>> D:\NASMPR~1>exe2bin kernel.exe kernel.bin
> 
> Good. This produces a .com file (no matter what we call it) which 
> expects to be loaded at 100h into... whatever segment.
> 
>> D:\NASMPR~1>partcopy kernel.bin 0 200 -f0 200
>> Failed to read source at offset 144
>> D:\NASMPR~1>partcopy kernel.bin 0 144 -f0 200
>> 
>> D:\NASMPR~1>
>> -----------------------------------
>> 
>> But when I rebooted , I got boot sector statment but I am not seeing the
>> "welcome....." kernel message.
>> Can somebody plz guide me??
> 
> Try jumping to 7D0h:100h (assuming that you're writing this to 7E00h).
> 
> I haven't done anything further with this. I've downloaded source (in 
> assembly) for an exe2bin clone, thinking we might be able to modify it 
> to produce a binary at "org 0", or perhaps create a loader for MZ to be 
> included in our code. Only just begun to look at it.
> 
> Tyler mentioned using bochs for testing. That would speed up development 
> a *lot* (especially for me, since I don't like rebooting). I've 
> downloaded bochs a couple of times, but never tried it. I've seen too 
> many posts about "my bootsector works in bochs, but not in a real 
> machine" (or vise versa), and "bochs is giving me this error message, 
> what the heck does it mean?"... suggesting that bochs doesn't accurately 
> reflect "real hardware" (can't match *all* of 'em, of course), and has a 
> "learning curve" to it...
> 
> Any tips, Tyler? Is bochs going to insist on seeing a full 1.44M image 
> before it'll boot from a "fake floppy"? Well, I'll figure it out (or 
> not), if and when I get around to trying it...
> 
> Best,
> Frank
> 
> 
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