Andreas Färber writes: > Am 02.07.2011 um 10:32 schrieb Stefan Hajnoczi: >> On Fri, Jul 1, 2011 at 8:32 PM, Blue Swirl <blauwir...@gmail.com> wrote: >>> 2011/6/27 Ben Vogler <bvog...@toyotatech.com.au>: >>>> - Are there any inbuilt data tracing features? For example, >>>> hardware signal tracing, register monitoring etc. >>> >>> Tracing is quite new addition, so far it's only used for development >>> or debugging QEMU point of view I think. >> >> I think you are referring to hardware model debugging and logging. >> The QEMU "tracing" mechanism that Blue Swirl mentioned is a >> DTrace/SystemTap style tool for observing QEMU internals and not what >> you are looking for.
> I believe Lluís (cc'ed) has worked on using/extending the trace framework to > instrument guests. Yes, the idea is to have a set of generic guest events (e.g., information during instruction fetch, privilege-level change, control flow instructions, etc.) that are target agnostic. This is coupled with the possibility to statically instrument tracing points with user-provided code, so that almost anything can be done with these few basic pieces, ranging from code instrumentation tools a-la PIN, information flow tracking analysis or even cycle-accurate simulations driven by QEMU as the target emulation component. All with a target-agnostic interface that is common to both system-wide and user application functional simulation. I've also modified the timing infrasructure to have a more accurate guest cycle counter that is able to handle a per-vCPU CPI (cycles per instruction), as the current approach in QEMU is not adecuate for cycle-accurate simulations. I've been developing all these changes in small self-contained patches, as my intention is to work towards having these generic pieces integrated into QEMU proper, so that everybody can benefit from that work, as well as avoid having a separate project that will otherwise quickly fall behind QEMU's codebase. What I still haven't decided is whether this generic interface should provide the user with a way to modify the behaviour of the guest, like skipping the execution of QEMU-generated code and instead execute user-provided code to change the semantics of certain instructions without having to hack directly into QEMU. Lluis -- "And it's much the same thing with knowledge, for whenever you learn something new, the whole world becomes that much richer." -- The Princess of Pure Reason, as told by Norton Juster in The Phantom Tollbooth
