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Re: Build IDs for finding packages
- From: Arnaldo Carvalho de Melo <acme at ghostprotocols dot net>
- To: elfutils-devel at lists dot fedorahosted dot org
- Date: Thu, 31 Jan 2013 08:53:54 -0300
- Subject: Re: Build IDs for finding packages
Em Thu, Jan 31, 2013 at 11:22:40AM +0100, Mark Wielaard escreveu:
> On Wed, 2013-01-30 at 14:50 -0300, Arnaldo Carvalho de Melo wrote:
> > Right now we have to, at the end of the 'perf record' session,
> > traverse the generated perf.data files looking for DSOs that had
> > samples, and then generating a header with the build-ids.
> > This has issues with long running sessions where updates can take
> > place and also there is this overhead at the end of the session, so
> > one item in the 'perf' TODO list is to add the build-id to the
> > PERF_RECORD_MMAP event to fix this.
> This would also be useful for systemtap which currently does this at
> runtime itself when it is running in kernel mode. At translation time it
> records the build-ids for the code it is expecting to place probes in
> and for which it has symbol/unwind tables available. Then at runtime it
> checks them against the vmas mapped in. See _stp_build_id_check in
> runtime/sym.c. Having some mechanism in the kernel to easily catch vmas
> that are mapped in associated with a particular build-id and/or not
> having to grovel through memory by hand to get at the build-id
> associated with a vma would be nice. Do you already have some
> design/patch for this?
Nope, its just a TODO entry stating a problem we have.