Re: Is there a way to interrupt MMIO with kprobes/ltt/etc...

From: Vamsi Krishna S . (
Date: Fri Nov 08 2002 - 03:23:27 EST

On Fri, Nov 08, 2002 at 03:40:58AM +0000, Rusty Lynch wrote:
> I have been looking into the possible ways a fault injection tool could be
> implemented on the available tools/hooks in the 2.5 kernel. I can see how
> kprobes would help by allowing me to setup handlers when a specific address
> is executed, but what about when a specific memory mapped IO address is
> touched or looked at?
> I know there has been a lot of activity on kprobes, LTT, and others (isn't
> there something else?). Do any of these patches allow a handler to be
> called just before some MMIO is accessed? Messing with architecture
> specific debug registers seems problematic since it makes the solution
> architecture specific and the number of watch points is pretty limited.
You could do this with the interface provided by kwatchpoints patch [1]
without directly mucking with debug registers. The interface is simple:

int register_kwatch(unsigned long addr, u8 length, u8 type,
                kwatch_handler_t handler)

If you don't want to use debug registers or if they are not enough,
only other possibility I can think of is to find all code locations
where the MMIO space of interest is touched and put execution
probes there.

[1] You will need these two patches:


Vamsi Krishna S.
Linux Technology Center,
IBM Software Lab, Bangalore.
Ph: +91 80 5044959
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