Re: Res: [Qemu-devel] full dynamic instruction trace for MIPS target

[Vince Weaver <vince@csl.cornell.edu>]

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On Tue, 6 Apr 2010, Boris Cámara wrote:

>The aproach you are using on 
>http://www.csl.cornell.edu/~vince/projects/qemu-trace/ to get the PC dump 
>is similar to mine but as you dont disable the TB caches It is not a full 
>execution trace. 

I can assure you that it does in fact work.

> You only dump the PC when they are compiled and inserted 
> on the TB cache.

no, look closer.  My code at instrumentation time inserts a helper-op 
after each instruction.  This is like a virtual instruction that lives in 
the TB and calls my counting function.  So each time the TB is re-executed 
the calls happen again, as they are part of the TB instruction stream.

> Did you get correct values for your counters in bbvs[bb] ?

yes.  And the resuts match valgrind, pin, and hardware performance 
counters.

Vince



________________________________
De: Vince Weaver <vince@csl.cornell.edu>
Para: Boris Cámara <vesmar@rocketmail.com>
Cc: qemu-devel@nongnu.org
Enviadas: Segunda-feira, 5 de Abril de 2010 22:41:52
Assunto: Re: [Qemu-devel] full dynamic instruction trace for MIPS target


> I think the correct way to get the full instruction trace on a MIPS 
> emulated processor is:

the way you describe is slow because you are constantly re-generating the 
TBs.  The best way to do this is to add your instrumentation to the TBs.

I have code that does that for a recent version of Qemu here:
  http://www.csl.cornell.edu/~vince/projects/qemusim/

although it outputs Basic-Block vectors, not a full memory trace like you 
want.  It has been validated to match proper instruction counts using 
hardware performnce counters though.

I also have code creating full instruction/memory traces for Qemu MIPS 
that can be found here:
  http://www.csl.cornell.edu/~vince/projects/qemu-trace/

but it's against Qemu from 2007 pre-dating the TCG changeover so of 
limited use probably.  I hvae some code somewhere that updated this to 
work with TCG but I don't know what happened to it.

Vince


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