Calling From Nasm

[Tolga]

Hi.

In my C kernel, i want to call nasm functions from an assembly file. How can i do this? Show an example. ::)

( I don't want to use AT&T in C. Because i don't know it. ;D )

[Pype.Clicker]

export the name of your asm function, declare the function name in C and then invoke it. Function arguments will be on stack and return value should be placed in EAX before your function returns.

[Solar]

...and it's exactly the same in AT&T.

[Tolga]

Can somebody show an example? I'm new at C. A small example. ::)

[cenan]

[extern printf] ; c function

push 5 ; parameters are pushed from right to left
push msg
call printf
add esp,4 ; removing msg from stack
; this is same as printf("hodohodo %d", 5);
; now eax contains 8 (number of chars written)

[section .data]
msg db "hodohodo %d",0

[Ytinasni]

push 5 ; parameters are pushed from right to left
push msg
call printf
add esp,4 ; removing msg from stack

That'll need to be add esp, 8 if you're in protected-mode (which includes Windows, Linux, BSD, most of our hobby OS', etc...), as you need to remove both arguments ("%d", 5 ) from the stack.

[Schol-R-LEA]

This page ansd the ones it references might help.