returned value from custom interrupt

[i586coder]

Hello folks,

I have trouble with interrupts

i use this code in TC++3.1 to make custom interrupt

Code: Select all

void set_int( void far interrupt p() ,char intNo ){
     _AX=0;
     _ES=_AX;
     _AL=intNo;
     _BL=4;
     asm mul bl
     _BX=_AX;
     _SI=(int)p;
     asm{ mov es:[bx],si
          add bx,2
          mov ax,cs
          mov es:[bx],ax
     }
}

void interrupt myInterrupt(){
  switch(_AH){
    case 0x1: printf("subInt #00"); break;
    case 0x2: _DX+=2; break;
    case 0x3: _CX=_BH+_BL; break;
  }
}

main(){
 set_int(myInterrupt,0x88);
 int sum;
 asm{mov ah,3
       mov bh,2
       mov bl,4
       int 0x88
      mov word ptr[sum],cx
 }
 printf("%d",sum);}

result must be 2+4=6


my problem is
1) what is the best registers must use to pass parameter & the best to returne value
2) is it safe to use stack as parameter

ThAnKs

[System123]

The parameters are usually passed through the AX and DX registers. You can use all of them if you need but AX is the most common. Yes the stack can be used as long as you don't push or pop from it in between calling and executing the interrupt.

[i586coder]

Are GS,FS registers useful for my case,
and what is that registers anyway

[i586coder]

ok,if we talk about registers,anyone know some documents around Intel x86-64 registers

[AJ]

A very good link

and here

Cheers,
Adam

[pcmattman]

I would imagine the Intel manuals might be of assistance as well.

[i586coder]

links
thank you

[Combuster]

From what I recall, Turbo C normally compiles an interrupt call to preserve registers. That means you can
a) Not return anything directly
b) Those saved registers are most likely on the stack, so you can not easily pass anything that way.

Also Turbo C compiles for a 286 architecture. It can't do 32-bit code, let alone 64-bit code.
If you're serious about OS development you should grab a GCC Cross-Compiler instead.

[i586coder]

I tried DJGPP before, but I have a serious problem with
AT&T assembly syntax. since i am advanced coder with Intel syntax

[AJ]

Code: Select all

-masm=intel

This can be used directly with Combuster's suggestion of a cross compiler.

Cheers,
Adam

[Combuster]

You don't need to use GNU AS. Nasm, Yasm and Fasm are popular alternatives (and they all do intel syntax).

Still, AS in intel mode is awkward to use since it occasionally uses different names for opcodes compared to the intel manuals (especially the kernel-level instructions)

[inflater]

Nasm, Yasm and Fasm

No FASM if he wants to combine his code with any other compiler, let it be ASM, C, pascal or any other. (Well, if he wants to know the magic of hardcore hex-editing, file offsets and copying raw chunks of data, let him )

[i586coder]

All i need to know if there is any method to access assembly inside C (DJGPP)compiler instead of
use external assembler like NASM with Intel syntax

in TC i use

Code: Select all

asm{
    mov ebx, eax
}

and in DJGPP i will use

Code: Select all

asm("movl %eax, %ebx");

[Combuster]

http://www.google.com