I'm studying x86 and Real Time Systems, and I have a question, that is:
Which steps x86 follows to handle any interrupt ?
+1
A:
Start here with the Interrupt Descriptor Table. Basically, when an interrupt occurs, flow control jumps to this table and then on to whatever is in this table. Also, I believe all registers are pushed as soon as the interrupt occurs, but I'm not 100% certain of this as it's been a long, long time since I've dealt with this.
Michael Dorgan
2010-05-24 15:04:44
All the registers and the flags ar pushed before the interrupt occurs and are popped after the interrupt-handling code is over.
nc3b
2010-05-24 15:05:55
Yep, kinda what I thought. On some of the stuff I've worked on, you've had to do the pushing and popping yourself. Was pretty sure that x86 did this for you.
Michael Dorgan
2010-05-24 15:09:46
The processor flags are pushed automatically, but the other registers aren't; when it's dispatched, the ISR should explicitly preserve any/all registers which it intends to alter.
ChrisW
2010-05-24 15:16:59
+2
A:
When an interrupt occurs, the CPU does the following:
- Push the current address (contents of the Instruction Pointer) onto the stack; also, push the processor flags (but not all the other processor registers)
- Jump to the address of the ISR (Interrupt Service Routine), which is specified in the Interrupt Descriptor Table.
The ISR should do the following:
- Push any registers which it intends to alter (or, push all registers)
- Handle the interrupt
- Reenable interrupts
- Pop any registers which it pushed
- Use the IRET instructions, which pops the CPU flags and Instruction Pointer value from the stack (and thus returns to whatever was executing when the interrupt occured).
ChrisW
2010-05-24 15:15:19