perf build: Pretend scandirat is missing with msan

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.

Additional notes from Ian on running in this mode:

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.

Signed-off-by: Ian Rogers <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

1 files changed, 4 insertions, 1 deletions

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 7783479de691..7f1e016a9253 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -496,7 +496,10 @@ 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)