linux-kernel - [PATCH 3/3] perf test: Initialize memory in dwarf-unwind

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Date:   Sat, 30 May 2020 01:20:15 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Quentin Monnet <quentin@...valent.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Cc:     Stephane Eranian <eranian@...gle.com>,
        Ian Rogers <irogers@...gle.com>
Subject: [PATCH 3/3] perf test: Initialize memory in dwarf-unwind

Avoid a false positive caused by assembly code in arch/x86.
In tests, zero the perf_event to avoid uninitialized memory uses.
Warnings were caught using clang with -fsanitize=memory.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/arch/x86/tests/dwarf-unwind.c | 8 ++++++++
 tools/perf/tests/dwarf-unwind.c          | 1 +
 2 files changed, 9 insertions(+)

diff --git a/tools/perf/arch/x86/tests/dwarf-unwind.c b/tools/perf/arch/x86/tests/dwarf-unwind.c
index ef43be9b6ec2..4e40402a4f81 100644
--- a/tools/perf/arch/x86/tests/dwarf-unwind.c
+++ b/tools/perf/arch/x86/tests/dwarf-unwind.c
@@ -55,6 +55,14 @@ int test__arch_unwind_sample(struct perf_sample *sample,
 		return -1;
 	}
 
+#ifdef MEMORY_SANITIZER
+	/*
+	 * Assignments to buf in the assembly function perf_regs_load aren't
+	 * seen by memory sanitizer. Zero the memory to convince memory
+	 * sanitizer the memory is initialized.
+	 */
+	memset(buf, 0, sizeof(u64) * PERF_REGS_MAX);
+#endif
 	perf_regs_load(buf);
 	regs->abi  = PERF_SAMPLE_REGS_ABI;
 	regs->regs = buf;
diff --git a/tools/perf/tests/dwarf-unwind.c b/tools/perf/tests/dwarf-unwind.c
index 2a0dac81f44c..2491d167bf76 100644
--- a/tools/perf/tests/dwarf-unwind.c
+++ b/tools/perf/tests/dwarf-unwind.c
@@ -37,6 +37,7 @@ static int init_live_machine(struct machine *machine)
 	union perf_event event;
 	pid_t pid = getpid();
 
+	memset(&event, 0, sizeof(event));
 	return perf_event__synthesize_mmap_events(NULL, &event, pid, pid,
 						  mmap_handler, machine, true);
 }
-- 
2.27.0.rc2.251.g90737beb825-goog