Thread: What's the best way to provide a hookable interface?

If have a "panic" function in my kernel, during VERY early boot it just prints to video memory. I want to have a way to hook it at run time. What's the best way to do that?

Currently, I have a little abstraction. So that when I make the switch from compile time hookable to run time hookable, it will have no effect on code that uses panic.

Here is panic.h:

Code:

#ifndef PANIC_H_INCLUDED
#define PANIC_H_INCLUDED

extern void panic(char *function, char *message);

#endif /* PANIC_H_INCLUDED */

panic.c

Code:

void print(char *message)
{
    int i;
    static int j;
    char* video_mem = (char*)0xb8000;
    for(i = 0;message[i] != 0;i++)
    {
        if(j >= 0x1000)
            j = 0;
        video_mem[j*2] = message[i];
        video_mem[(j*2) + 1] = 7;
        j++;
    }
}

void panic(char *function, char *message)
{
    print("panic: ");
    print(function);
    print(" : ");
    print(message);
}

Is there a way to do this w/o resorting to making a pointer to hold the location of the hook and calling the pointer(with panic as a wrapper to call the real function that hooked it)?

I don't have anything against function pointers. I just thought it looked like a hack, something not good to include in what will hopefully be lasting code. The way I implement function pointers was probably the root of my misconception. Before seeing the code Salem posted, I'd have done it in a messier way.

Thanks.