linux-kernel - Re: [RFC] perf record: missing buildid for callstack modules

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Message-ID: <20160111173036.GA6344@twins.programming.kicks-ass.net>
Date:	Mon, 11 Jan 2016 18:30:36 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Stephane Eranian <eranian@...gle.com>,
	Namhyung Kim <namhyung@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Jiri Olsa <jolsa@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>
Subject: Re: [RFC] perf record: missing buildid for callstack modules

On Fri, Jan 08, 2016 at 03:19:42PM -0300, Arnaldo Carvalho de Melo wrote:
> We already discussed how to solve it, and it involves extending once
> more PERF_RECORD_MMAP, so that, when we load a DSO we stash its build-id
> in a per-DSO data structure in the kernel, then, when generating
> PERF_RECORD_MMAP3 we put the buildid there, this way if any of those
> binaries gets replaced while we're recording samples, we would notice,
> i.e. we wouldn't care that much about the pathname, looking everything
> by the content based buildid instead.

Does the kernel even know about the buildid crap? AFAIK the binfmt stuff
doesn't know or care about things like that. Heck, we support binfmts
that do not even have a buildid.