Re: [Valgrind-users] Using Valgrind for monitoring MMIO Access

[Nicholas N. <nj...@ca...>]

On Thu, 11 Sep 2003, Matthew Tippett wrote:

> Is it possible to configure valgrind to display reads and
> writes to memory locations if they can be determined?  For
> example, debugging a XFree86 driver by looking at what what
> is written to different parts of memory.
>
> Obviously with instrumentation this would appear to be possible,
> but I am wondering if there is a valgrind skin that allows you
> to do something like...
>
>    valgrind --skin=memwatch --region=000a0000-000c0000 X
>
> And consequently understand all the reads and writes (and
> possibly execution) of data and code in the BIOS.

No current skin can do that, but it would be easy to do.  Try modifying
Cachegrind (cachegrind/cg_main.c).  The SK_(instrument) function does the
instrumentation.  It's already setup to call one of several C functions on
every memory-accessing instruction.  Change it to call a different C
function that prints out (or whatever) the accesses in the given range.
Adding command-line options to skins is pretty easy, look at clo_I1_cache
for an example in Cachegrind.

There's a fair bit of stuff to know about when writing skins, but using
Cachegrind as a starting point will make it fairly easy, and provide a
good example.  Write back (me or the list) if you have problems.

N