perfprofd: add env to disable change of perf_event_paranoid.

This is to avoid a cts test failure (which checks the value of
perf_event_paranoid) while perfprofd is running.

Bug: 111855759
Test: run perfprofd_test and perf_event_paranoid isn't changed.
Change-Id: Ifa610a21b560d0eb536cb76914b116bd1e769634

2 files changed, 13 insertions, 5 deletions

diff --git a/perfprofd/perfprofd_perf.cc b/perfprofd/perfprofd_perf.cc
index 6ca1ef30..15dde6fb 100644
--- a/perfprofd/perfprofd_perf.cc
+++ b/perfprofd/perfprofd_perf.cc
@@ -63,6 +63,8 @@ PerfResult InvokePerf(Config& config,
 {
   std::vector<std::string> argv_backing;
   std::vector<const char*> argv_vector;
+  char paranoid_env[] = "PERFPROFD_DISABLE_PERF_EVENT_PARANOID_CHANGE=1";
+  char* envp[2] = {paranoid_env, nullptr};
 
   {
     auto add = [&argv_backing](auto arg) {
@@ -184,7 +186,7 @@ PerfResult InvokePerf(Config& config,
     fprintf(stderr, "\n");
 
     // exec
-    execvp(argv_vector[0], const_cast<char* const*>(argv_vector.data()));
+    execvpe(argv_vector[0], const_cast<char* const*>(argv_vector.data()), envp);
     fprintf(stderr, "exec failed: %s\n", strerror(errno));
     exit(1);
 
@@ -235,6 +237,8 @@ PerfResult InvokePerf(Config& config,
 
 bool FindSupportedPerfCounters(const std::string& perf_path) {
   const char* argv[] = { perf_path.c_str(), "list", nullptr };
+  char paranoid_env[] = "PERFPROFD_DISABLE_PERF_EVENT_PARANOID_CHANGE=1";
+  char* envp[2] = {paranoid_env, nullptr};
 
   base::unique_fd link[2];
   {
@@ -266,7 +270,7 @@ bool FindSupportedPerfCounters(const std::string& perf_path) {
     link[1].reset();
 
     // exec
-    execvp(argv[0], const_cast<char* const*>(argv));
+    execvpe(argv[0], const_cast<char* const*>(argv), envp);
     PLOG(WARNING) << "exec failed";
     exit(1);
     __builtin_unreachable();
diff --git a/simpleperf/environment.cpp b/simpleperf/environment.cpp
index f223bfcd..eed4ee42 100644
--- a/simpleperf/environment.cpp
+++ b/simpleperf/environment.cpp
@@ -321,7 +321,7 @@ static bool ReadPerfEventParanoid(int* value) {
 
 bool CanRecordRawData() {
   int value;
-  return IsRoot() || (ReadPerfEventParanoid(&value) && value == -1);
+  return ReadPerfEventParanoid(&value) && value == -1;
 }
 
 static const char* GetLimitLevelDescription(int limit_level) {
@@ -340,8 +340,12 @@ bool CheckPerfEventLimit() {
   // may create child processes not running as root. To make sure the child processes have
   // enough permission to create inherited tracepoint events, write -1 to perf_event_paranoid.
   // See http://b/62230699.
-  if (IsRoot() && android::base::WriteStringToFile("-1", "/proc/sys/kernel/perf_event_paranoid")) {
-    return true;
+  if (IsRoot()) {
+    char* env = getenv("PERFPROFD_DISABLE_PERF_EVENT_PARANOID_CHANGE");
+    if (env != nullptr && strcmp(env, "1") == 0) {
+      return true;
+    }
+    return android::base::WriteStringToFile("-1", "/proc/sys/kernel/perf_event_paranoid");
   }
   int limit_level;
   bool can_read_paranoid = ReadPerfEventParanoid(&limit_level);