1 files changed, 104 insertions, 0 deletions
diff --git a/test/syscalls/linux/vdso_clock_gettime.cc b/test/syscalls/linux/vdso_clock_gettime.cc
new file mode 100644
index 000000000..59dd78833
--- /dev/null
+++ b/test/syscalls/linux/vdso_clock_gettime.cc
@@ -0,0 +1,104 @@
+// Copyright 2018 Google LLC
+//
+// 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 <stdint.h>
+#include <sys/time.h>
+#include <syscall.h>
+#include <time.h>
+#include <unistd.h>
+#include <map>
+#include <string>
+#include <utility>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/strings/numbers.h"
+#include "absl/time/clock.h"
+#include "absl/time/time.h"
+#include "test/util/test_util.h"
+
+namespace gvisor {
+namespace testing {
+
+namespace {
+
+std::string PrintClockId(::testing::TestParamInfo<clockid_t> info) {
+  switch (info.param) {
+    case CLOCK_MONOTONIC:
+      return "CLOCK_MONOTONIC";
+    case CLOCK_REALTIME:
+      return "CLOCK_REALTIME";
+    default:
+      return absl::StrCat(info.param);
+  }
+}
+
+class CorrectVDSOClockTest : public ::testing::TestWithParam<clockid_t> {};
+
+TEST_P(CorrectVDSOClockTest, IsCorrect) {
+  struct timespec tvdso, tsys;
+  absl::Time vdso_time, sys_time;
+  uint64_t total_calls = 0;
+
+  // It is expected that 82.5% of clock_gettime calls will be less than 100us
+  // skewed from the system time.
+  // Unfortunately this is not only influenced by the VDSO clock skew, but also
+  // by arbitrary scheduling delays and the like. The test is therefore
+  // regularly disabled.
+  std::map<absl::Duration, std::tuple<double, uint64_t, uint64_t>> confidence =
+      {
+          {absl::Microseconds(100), std::make_tuple(0.825, 0, 0)},
+          {absl::Microseconds(250), std::make_tuple(0.94, 0, 0)},
+          {absl::Milliseconds(1), std::make_tuple(0.999, 0, 0)},
+      };
+
+  absl::Time start = absl::Now();
+  while (absl::Now() < start + absl::Seconds(30)) {
+    EXPECT_THAT(clock_gettime(GetParam(), &tvdso), SyscallSucceeds());
+    EXPECT_THAT(syscall(__NR_clock_gettime, GetParam(), &tsys),
+                SyscallSucceeds());
+
+    vdso_time = absl::TimeFromTimespec(tvdso);
+
+    for (auto const& conf : confidence) {
+      std::get<1>(confidence[conf.first]) +=
+          (sys_time - vdso_time) < conf.first;
+    }
+
+    sys_time = absl::TimeFromTimespec(tsys);
+
+    for (auto const& conf : confidence) {
+      std::get<2>(confidence[conf.first]) +=
+          (vdso_time - sys_time) < conf.first;
+    }
+
+    ++total_calls;
+  }
+
+  for (auto const& conf : confidence) {
+    EXPECT_GE(std::get<1>(conf.second) / static_cast<double>(total_calls),
+              std::get<0>(conf.second));
+    EXPECT_GE(std::get<2>(conf.second) / static_cast<double>(total_calls),
+              std::get<0>(conf.second));
+  }
+}
+
+INSTANTIATE_TEST_CASE_P(ClockGettime, CorrectVDSOClockTest,
+                        ::testing::Values(CLOCK_MONOTONIC, CLOCK_REALTIME),
+                        PrintClockId);
+
+}  // namespace
+
+}  // namespace testing
+}  // namespace gvisor