Add verity stat benchmark test

PiperOrigin-RevId: 390284683

test/perf/BUILD

@@ -174,3 +174,10 @@ syscall_test(
     test = "//test/perf/linux:verity_open_read_close_benchmark",
     vfs1 = False,
 )
+
+syscall_test(
+    size = "large",
+    debug = False,
+    test = "//test/perf/linux:verity_stat_benchmark",
+    vfs1 = False,
+)

test/perf/linux/BUILD

@@ -462,3 +462,23 @@ cc_binary(
         "//test/util:verity_util",
     ],
 )
+
+cc_binary(
+    name = "verity_stat_benchmark",
+    testonly = 1,
+    srcs = [
+        "verity_stat_benchmark.cc",
+    ],
+    deps = [
+        gbenchmark,
+        gtest,
+        "//test/util:capability_util",
+        "//test/util:fs_util",
+        "//test/util:logging",
+        "//test/util:temp_path",
+        "//test/util:test_main",
+        "//test/util:test_util",
+        "//test/util:verity_util",
+        "@com_google_absl//absl/strings",
+    ],
+)

test/perf/linux/verity_stat_benchmark.cc

@@ -0,0 +1,84 @@
+// Copyright 2021 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <algorithm>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "absl/strings/str_cat.h"
+#include "benchmark/benchmark.h"
+#include "test/util/fs_util.h"
+#include "test/util/temp_path.h"
+#include "test/util/test_util.h"
+#include "test/util/verity_util.h"
+
+namespace gvisor {
+namespace testing {
+
+namespace {
+
+// Creates a file in a nested directory hierarchy at least `depth` directories
+// deep, and stats that file multiple times.
+void BM_VerityStat(benchmark::State& state) {
+  // Create nested directories with given depth.
+  int depth = state.range(0);
+
+  // Mount a tmpfs file system to be wrapped by a verity fs.
+  TempPath top_dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+  TEST_CHECK(mount("", top_dir.path().c_str(), "tmpfs", 0, "") == 0);
+  std::string dir_path = top_dir.path();
+  std::string child_path = "";
+  std::vector<EnableTarget> targets;
+
+  while (depth-- > 0) {
+    // Don't use TempPath because it will make paths too long to use.
+    //
+    // The top_dir destructor will clean up this whole tree.
+    dir_path = JoinPath(dir_path, absl::StrCat(depth));
+    ASSERT_NO_ERRNO(Mkdir(dir_path, 0755));
+    child_path = JoinPath(child_path, Basename(dir_path));
+    targets.emplace_back(EnableTarget(child_path, O_RDONLY));
+  }
+
+  // Create the file that will be stat'd.
+  const TempPath file =
+      ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFileIn(dir_path));
+
+  targets.emplace_back(
+      EnableTarget(JoinPath(child_path, Basename(file.path())), O_RDONLY));
+
+  // Reverse the targets because verity should be enabled from the lowest level.
+  std::reverse(targets.begin(), targets.end());
+
+  std::string verity_dir =
+      TEST_CHECK_NO_ERRNO_AND_VALUE(MountVerity(top_dir.path(), targets));
+
+  struct stat st;
+  for (auto _ : state) {
+    ASSERT_THAT(stat(JoinPath(verity_dir, targets[0].path).c_str(), &st),
+                SyscallSucceeds());
+  }
+}
+
+BENCHMARK(BM_VerityStat)->Range(1, 100)->UseRealTime();
+
+}  // namespace
+
+}  // namespace testing
+}  // namespace gvisor