Add benchmarks that run simple programs

Specifically, test the wall-clock time for running:
 * a C program that does nothing (i.e. no STL)
 * a C++ program that does nothing
 * a statically-linked C++ program
 * toybox true (in /system/bin and /vendor/bin)
 * mksh -c true (in /system/bin and /vendor/bin)

Test: bionic-spawn-benchmarks
Change-Id: I961850ec90004cac83088feab5783f4f27768be1
diff --git a/benchmarks/spawn/spawn_benchmarks.cpp b/benchmarks/spawn/spawn_benchmarks.cpp
new file mode 100644
index 0000000..e8f7c17
--- /dev/null
+++ b/benchmarks/spawn/spawn_benchmarks.cpp
@@ -0,0 +1,101 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <errno.h>
+#include <spawn.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include <android-base/file.h>
+#include <android-base/stringprintf.h>
+#include <benchmark/benchmark.h>
+
+static std::string test_program(const char* name) {
+#if defined(__LP64__)
+  return android::base::GetExecutableDirectory() + "/" + name + "64";
+#else
+  return android::base::GetExecutableDirectory() + "/" + name + "32";
+#endif
+}
+
+extern char** environ;
+
+static void BM_spawn_test(benchmark::State& state, const char* const* argv) {
+  for (auto _ : state) {
+    pid_t child = 0;
+    if (int spawn_err = posix_spawn(&child, argv[0], nullptr, nullptr, const_cast<char**>(argv),
+                                    environ)) {
+      state.SkipWithError(android::base::StringPrintf(
+          "posix_spawn of %s failed: %s", argv[0], strerror(spawn_err)).c_str());
+      break;
+    }
+
+    int wstatus = 0;
+    const pid_t wait_result = TEMP_FAILURE_RETRY(waitpid(child, &wstatus, 0));
+    if (wait_result != child) {
+      state.SkipWithError(android::base::StringPrintf(
+          "waitpid on pid %d for %s failed: %s",
+          static_cast<int>(child), argv[0], strerror(errno)).c_str());
+      break;
+    }
+    if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) == 127) {
+      state.SkipWithError(android::base::StringPrintf("could not exec %s", argv[0]).c_str());
+      break;
+    }
+  }
+}
+
+#define SPAWN_BENCHMARK(name, ...)                                                    \
+    BENCHMARK_CAPTURE(BM_spawn_test, name, (const char*[]) { __VA_ARGS__, nullptr })  \
+        ->UseRealTime()                                                               \
+        ->Unit(benchmark::kMicrosecond)                                               \
+
+SPAWN_BENCHMARK(noop, test_program("bench_noop").c_str());
+SPAWN_BENCHMARK(noop_nostl, test_program("bench_noop_nostl").c_str());
+SPAWN_BENCHMARK(noop_static, test_program("bench_noop_static").c_str());
+
+// Android has a /bin -> /system/bin symlink, but use /system/bin explicitly so we can more easily
+// compare Bionic-vs-glibc on a Linux desktop machine.
+#if defined(__GLIBC__)
+
+SPAWN_BENCHMARK(bin_true, "/bin/true");
+SPAWN_BENCHMARK(sh_true, "/bin/sh", "-c", "true");
+
+#elif defined(__ANDROID__)
+
+SPAWN_BENCHMARK(system_bin_true, "/system/bin/true");
+SPAWN_BENCHMARK(vendor_bin_true, "/vendor/bin/true");
+SPAWN_BENCHMARK(system_sh_true, "/system/bin/sh", "-c", "true");
+SPAWN_BENCHMARK(vendor_sh_true, "/vendor/bin/sh", "-c", "true");
+
+#endif
+
+BENCHMARK_MAIN();