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Berserk wrote: I meant that i don't know what the hell Dynamically Loaded Librarys are.

Sorry, did a typo ::)

Pype.Clicker wrote: Hello, ...
there's something that troubles me a bit about shared dynamically-loaded libraries ...

Every process might have a different memory map, so how will the kernel ensure that - say - gui.dll (or libgui.so) will be mapped at the same virtual address in every process ?

If not mapped at the same address, the library will have to be relocated to its new location, no ? thus, breaking the 'sharability' (as every process will need a separate copy of the library with its own relocation entries written ...)

Now, there is the option of Position Independent Code: have a global register that keeps the address of a jump-table for the functions, so that when the library needs the address of function F (or the address for static variable X), it knows it is located at [ebx + <offset for x>] or [ebx + offset for F in the jump-table]

But locking one register to this still frustrate me ...
Why doesn't IA-32 have a [eip + offset] addressing mode

If not mapped at the same address, the library will have to be relocated to its new location, no ? thus, breaking the 'sharability' (as every process will need a separate copy of the library with its own relocation entries written ...)

--- dll.c
print_params p = { green_background | white_foreground, { 0, 0 } };

void ADllFunction(const char *str, void (*callback)(char, print_params*))
{
    while (*str != '\0')
    {
        callback(*str, &p);
        str++;
        p.x++;
    }
}

---- app.c
void print_function(char ch, print_params *p)
{
    // write to screen
}

int main(void)
{
    char str[] = "Hello, world!";
    ADllFunction(str, print_function);
}

• Calling a function in an EXE directly from a DLL won't work, because CS is different for each
• Passing data on the stack to a DLL won't work, because the compiler assumes DS == SS (which it won't be)
• Passing pointers from the DLL to the EXE (and vice versa) won't work, because a flat address space is assumed