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From: Ian Rogers <irogers@google.com>
Date: Wed, 20 Mar 2024 09:36:19 -0700
Message-ID: <CAP-5=fUVtGgaLgVhoSa3SZdSceifFWs_v1rMnEANj3N=VdpC_A@mail.gmail.com>
Subject: Re: [PATCH v1] perf build: Pretend scandirat is missing with msan
To: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>, 
	Arnaldo Carvalho de Melo <acme@kernel.org>, Namhyung Kim <namhyung@kernel.org>, 
	Mark Rutland <mark.rutland@arm.com>, 
	Alexander Shishkin <alexander.shishkin@linux.intel.com>, Jiri Olsa <jolsa@kernel.org>, 
	Ian Rogers <irogers@google.com>, Adrian Hunter <adrian.hunter@intel.com>, 
	linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
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On Wed, Mar 20, 2024 at 9:32=E2=80=AFAM Ian Rogers <irogers@google.com> wro=
te:
>
> 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=3D/tmp/perf DEBUG=3D1 EXTRA_CFLAGS=3D"-O0 -g
-fno-omit-frame-pointer -fsanitize=3Dmemory
-fsanitize-memory-track-origins" CC=3Dclang CXX=3Dclang++ HOSTCC=3Dclang
NO_LIBTRACEEVENT=3D1 NO_LIBELF=3D1 BUILD_BPF_SKEL=3D0 NO_LIBPFM=3D1
```
oh, I disabled libbpf here as the bpf system call also lacks msan intercept=
ors.

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 ($(feature-scandirat), 1)
> -  CFLAGS +=3D -DHAVE_SCANDIRAT_SUPPORT
> +  # Ignore having scandirat with memory sanitizer that lacks an intercep=
tor.
> +  ifeq ($(filter s% -fsanitize=3Dmemory%,$(EXTRA_CFLAGS),),)
> +    CFLAGS +=3D -DHAVE_SCANDIRAT_SUPPORT
> +  endif
>  endif
>
>  ifeq ($(feature-sched_getcpu), 1)
> --
> 2.44.0.291.gc1ea87d7ee-goog
>