Protected mode exception keeps reoccuring

[helino]

Hi,

I've just started to get my IDT working (works great for IRQ and INT instructions).
However, in order to test that it was working for protected mode exceptions, I wrote the following assembly code:

Code: Select all

mov edx, 0
div edx

in order to generate a divide error (#DE).

My interrupt handler gets called, but the problem is, it gets called multiple times.
I'm using a trap gate in the IDT and I don't disable interrupts in my handler, therefore other interrupts can happen at the same time.

Should protected mode exceptions keep reoccurring, or have I done something wrong (most likely )?
Do I need to acknowledge that I've handled the exception somehow?

Thanks!

[Combuster]

If you return to the faulting code without fixing the problem it will obviously reoccur.

[Velko]

If you simply "return" from exception handler, it is perfectly normal.

• Instruction generates #DE
• Exception handler is called
• Exception handler returns
• CPU tries to execute the same instruction again
• Instruction generates #DE again
• ...

In real system you should do something else, like sending a signal to process, killing it, or something like that, but return to same instruction.

When handling #PF it may be acceptable, though. If you adjust Page Tables accordingly before returning.

[helino]

Aah, now I see, of course!

Thanks for your great answers, Combuster and Velko, I really appreciate it!