Messages in this thread | | | Date | Wed, 12 Aug 1998 19:04:17 +1200 | From | Chris Wedgwood <> | Subject | Re: interrupt latency |
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On Wed, Aug 12, 1998 at 12:18:11AM +0000, Linus Torvalds wrote:
> Yes. Allowing user mode programs to simulate hardware interrupts > is a major security misfeature (imagine somebody fooling with the > system by simulating lots of timer interrupts), and as such Linux > doesn't allow it on the x86 even though the CPU itself would be > able to do it fairly transparently.
Fair 'nuf.
> (However, even if Linux _did_ allow it, you'd have to use > > asm("int $15+32"); > > to get IRQ15 - the kernel offsets the interrupts from 8592 by 32 to > make sure that they don't clash with the internally generated x86 > exceptions).
I tried it before in a module, with just plan int $15, and it didn't work.
With the offset of 32, things work as expected and I am able to `generate interrupts'. Cool bananas.
It means the guts of what I wanted to do will now have to be done in the module which means the interrupt times are going to be ring 0 -> ring 0 -> ring 0, instead of ring 3 -> ring 0 -> ring3, are the timings likely to be vastly different?
-cw
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