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I have problem with handling interrupts. Those work fine as good as come the 'iret' instruction. Then it just stops there. I have read and done as in some tutorials, but it isn't working fine.
00004739770i[CPU ] fetch_raw_descriptor: GDT: index > limit
This says exactly what happened: Somehow, a (bad) segment selector got loaded into a segment register, that is outside the gdt. And this is probably due to a messed up stack, because the code segment gets reloaded during IRET with a value from the stack that is pushed on interrupt. Which interrupt is this exactly? Remember that faults also push a fault code on the stack, that has to be popped manually before you can do IRET.
extern void Do_int_call();
//code here
Do_int_call();
I had done something to registers that I should not. I forgot that it's not maybe good to touch some registers before saving them when we are calling an assembly function from C code. I think thats the reason why it didn't worked.
Okay. I have a new problem. Interrupts are working quite good expect numbers 8,10,11,12,13 and 14 which should put some kind of error code to the stack. For some reason those don't seem to do so.
That code doesn't work correctly because the error code isn't put to the stack automaticly. I that interrupt code working by adding another push instruction there. What's wrong? Everything should be okay. I use 'asm("int $0x08")' in my code to test that interrupt code.
beware: when generated from the CPU, some exceptions do have an error code on the stack (and that's the case for e.g. exception #13). When you instead use "int 0xD", no such error code is pushed, so you're not in the right conditions to test your handler.
You should find more info about this in the 'interrupts' chapter of the intel manual which i advice you to print out and review with glowpen and pencil at hand (oh, a cup of tea and some cookies could be welcome too, of course).
OK. So if use 'int' instruction to call to ints #8, #10, #11, #12 , #13 and #14 the processor doesn't push error code. So I should somehow mess the things in my code to cause those interrupts. Then it would work properly.
Maybe I should read more those Intel manuals like Pype.Clicker suggested.
;; use a valid, flat enough segment
mov dword [ds:0xdeadbeef],0 ;; will raise PF with CR2 == 0xdeadbeef
Testing stack fault is much more complicated since you need the stack to recover it. I usually suggest you use a task gate and a failure-recovery TSS for stack fault, double fault and invalid TSS errors.
OK. I thinks my interrups are working fine, but I have little problem with IRQ1. The timer interrupt works fine, but IRQ1 doesn't. I can get only one keyboard interrupt. The interrupt routine puts just things to stack, calls IRQ handler which only prints IRQ number. Then the handler pops things form stack and sends 0x20 to port 0x20 (PIC 1). I just doesn't seem to work with IRQ1. Should I read something from keyboard ports before the 'iret' instruction or do something else like send something to some ports?
Mike wrote:
Yes. Read a byte from port 0x60 - the keyboard data port. It can only hold one byte, and the interrupt is triggered when there is a byte to read.
actually, this is the case for most IRQs: they're here to notify the CPU of something to be done, and unless that thing is done, the device remains "stalled", unable to deliver more interrupts. Same will occur with the mouse, the network card, the disks, etc.
