Merge "simpleperf: add warning for `--call-graph fp` option on arm."

3 files changed, 25 insertions, 0 deletions

diff --git a/simpleperf/README.md b/simpleperf/README.md
index 5412f906..5700c8aa 100644
--- a/simpleperf/README.md
+++ b/simpleperf/README.md
@@ -582,6 +582,12 @@ but not well on arm).
     angler:/data/data/com.example.sudogame $./simpleperf record -p 10324 --call-graph fp --symfs . --duration 30
     simpleperf I 01-01 10:03:58 11267 11267 cmd_record.cpp:341] Samples recorded: 56736. Samples lost: 0.
 
+**Recording stack frame based call graph doesn't work well on arm architecture,**
+**even if compiled using -O0 -g -fno-omit-frame-pointer options. It is because**
+**the kernel can't unwind user stack containing both arm/thumb code. So please**
+**consider using dwarf based call graph on arm architecture, or profiling in**
+**aarch64 environment.**
+
 #### Report call graph
 Report accumulated period. In the table below, the first column is “Children”,
 it is the cpu cycle percentage of a function and functions called by that
diff --git a/simpleperf/cmd_record.cpp b/simpleperf/cmd_record.cpp
index 1cbb86cd..f1bf7aad 100644
--- a/simpleperf/cmd_record.cpp
+++ b/simpleperf/cmd_record.cpp
@@ -559,6 +559,13 @@ bool RecordCommand::ParseOptions(const std::vector<std::string>& args,
     }
   }
 
+  if (fp_callchain_sampling_) {
+    if (GetBuildArch() == ARCH_ARM) {
+      LOG(WARNING) << "`--callgraph fp` option doesn't work well on arm architecture, "
+                   << "consider using `-g` option or profiling on aarch64 architecture.";
+    }
+  }
+
   if (system_wide_collection_ && event_selection_set_.HasMonitoredTarget()) {
     LOG(ERROR) << "Record system wide and existing processes/threads can't be "
                   "used at the same time.";
diff --git a/simpleperf/cmd_record_test.cpp b/simpleperf/cmd_record_test.cpp
index 3820c2cd..2cfa57c5 100644
--- a/simpleperf/cmd_record_test.cpp
+++ b/simpleperf/cmd_record_test.cpp
@@ -136,6 +136,18 @@ TEST(record_cmd, fp_callchain_sampling) {
   ASSERT_TRUE(RunRecordCmd({"--call-graph", "fp"}));
 }
 
+TEST(record_cmd, fp_callchain_sampling_warning_on_arm) {
+  if (GetBuildArch() != ARCH_ARM) {
+    GTEST_LOG_(INFO) << "This test does nothing as it only tests on arm arch.";
+    return;
+  }
+  ASSERT_EXIT(
+      {
+        exit(RunRecordCmd({"--call-graph", "fp"}) ? 0 : 1);
+      },
+      testing::ExitedWithCode(0), "doesn't work well on arm");
+}
+
 TEST(record_cmd, system_wide_fp_callchain_sampling) {
   TEST_IN_ROOT(ASSERT_TRUE(RunRecordCmd({"-a", "--call-graph", "fp"})));
 }