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Date: Thu, 25 Apr 2024 15:47:32 -0300
From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Ian Rogers <irogers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@kernel.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1] perf build: Pretend scandirat is missing with msan
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References: <20240320163244.1287780-1-irogers@google.com>
 <CAP-5=fUVtGgaLgVhoSa3SZdSceifFWs_v1rMnEANj3N=VdpC_A@mail.gmail.com>
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On Wed, Mar 20, 2024 at 09:36:19AM -0700, Ian Rogers wrote:
> On Wed, Mar 20, 2024 at 9:32 AM Ian Rogers <irogers@google.com> wrote:
> >
> > Memory sanitizer lacks an interceptor for scandirat, reporting all
> > memory it allocates as uninitialized. Memory sanitizer has a scandir
> > interceptor so use the fallback function in this case. This allows
> > perf test to run under memory sanitizer.
> >
> > Signed-off-by: Ian Rogers <irogers@google.com>
> 
> Note, as msan needs to instrument memory allocations libraries need to
> be compiled with it. I lacked the msan built libraries and so built
> with:
> ```
> $ make -C tools/perf O=/tmp/perf DEBUG=1 EXTRA_CFLAGS="-O0 -g
> -fno-omit-frame-pointer -fsanitize=memory
> -fsanitize-memory-track-origins" CC=clang CXX=clang++ HOSTCC=clang
> NO_LIBTRACEEVENT=1 NO_LIBELF=1 BUILD_BPF_SKEL=0 NO_LIBPFM=1
> ```
> oh, I disabled libbpf here as the bpf system call also lacks msan interceptors.

I added the above notes to the cset message.

- Arnaldo
 
> Thanks,
> Ian
> 
> > ---
> >  tools/perf/Makefile.config | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> > index 1fe8df97fe88..74e0b17050b5 100644
> > --- a/tools/perf/Makefile.config
> > +++ b/tools/perf/Makefile.config
> > @@ -486,7 +486,10 @@ ifdef NO_DWARF
> >  endif
> >
> >  ifeq ($(feature-scandirat), 1)
> > -  CFLAGS += -DHAVE_SCANDIRAT_SUPPORT
> > +  # Ignore having scandirat with memory sanitizer that lacks an interceptor.
> > +  ifeq ($(filter s% -fsanitize=memory%,$(EXTRA_CFLAGS),),)
> > +    CFLAGS += -DHAVE_SCANDIRAT_SUPPORT
> > +  endif
> >  endif
> >
> >  ifeq ($(feature-sched_getcpu), 1)
> > --
> > 2.44.0.291.gc1ea87d7ee-goog
> >