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

["Vamsi Krishna S ." <vamsi@in.ibm.com>]

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:
http://marc.theaimsgroup.com/?l=linux-kernel&m=103528454215523&w=2
http://marc.theaimsgroup.com/?l=linux-kernel&m=103528454015520&w=2

Cheers,
Vamsi.
-- 
Vamsi Krishna S.
Linux Technology Center,
IBM Software Lab, Bangalore.
Ph: +91 80 5044959
Internet: vamsi@in.ibm.com