OSDev.org

I just recently incorporated TSS task-switching into my current OS, but I've got a rather annoying problem.

I can jump through tasks easily enough, and I can write an _intel_ syntax pre-emptive multitasker... but I'm having trouble with the GCC syntax...

asm("ljmp %0, $0"
    :
    : "r" (task->selector)
   );

Yields the following error message:
Error: suffix or operands invalid for `ljmp'

And yet I can hard-code asm("ljmp $0x28, $0") and it'll work.

I also tried something like this:
asm("pushw %0\n"
    "pushl $0\n"
    "ljmp (%%esp)\n"
    :
    : "r" (task->selector)
   );

But to no avail.

This seems like such a simple thing to get caught up on... maybe I should actually get some sleep

Anyway, I'm basically just looking for a jumpToTSS(long selectorNum) style function.

Cheers,
Jeff

I'm not an expert on the AT&T syntax, but IIRC, '%' is only used to prefix registers.

Yeah, but the %0 is, technically, a register.  Which, exact register, is up to GCC, but it will end up being a register.  I checked the syntax, and it's all right.

Oh well, no problem anyway, I just wrote the thing in nasm

; void jumpToTSS(short sel);
jumpToTSS:
        push    ebp
        mov     ebp, esp
        jmp far [ss:ebp+4]
        pop     ebp
        ret

I'm really not one of those people that hates AT&T syntax... I used to use it all the time, but man... Nasm always seems to work the way you want it to, eh?

Jeff