// Copyright 2018 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 <errno.h> #include <sys/types.h> #include <sys/wait.h> #include <unistd.h> #include <string> #include <utility> #include "gmock/gmock.h" #include "gtest/gtest.h" #include "absl/flags/flag.h" #include "absl/time/time.h" #include "test/util/logging.h" #include "test/util/multiprocess_util.h" #include "test/util/test_util.h" #include "test/util/time_util.h" ABSL_FLAG(bool, vfork_test_child, false, "If true, run the VforkTest child workload."); namespace gvisor { namespace testing { namespace { // We don't test with raw CLONE_VFORK to avoid interacting with glibc's use of // TLS. // // Even with vfork(2), we must be careful to do little more in the child than // call execve(2). We use the simplest sleep function possible, though this is // still precarious, as we're officially only allowed to call execve(2) and // _exit(2). constexpr absl::Duration kChildDelay = absl::Seconds(10); // Exit code for successful child subprocesses. We don't want to use 0 since // it's too common, and an execve(2) failure causes the child to exit with the // errno, so kChildExitCode is chosen to be an unlikely errno: constexpr int kChildExitCode = 118; // ENOTNAM: Not a XENIX named type file int64_t MonotonicNow() { struct timespec now; TEST_PCHECK(clock_gettime(CLOCK_MONOTONIC, &now) == 0); return now.tv_sec * 1000000000ll + now.tv_nsec; } TEST(VforkTest, ParentStopsUntilChildExits) { const auto test = [] { // N.B. Run the test in a single-threaded subprocess because // vfork is not safe in a multi-threaded process. const int64_t start = MonotonicNow(); pid_t pid = vfork(); if (pid == 0) { SleepSafe(kChildDelay); _exit(kChildExitCode); } TEST_PCHECK_MSG(pid > 0, "vfork failed"); MaybeSave(); const int64_t end = MonotonicNow(); absl::Duration dur = absl::Nanoseconds(end - start); TEST_CHECK(dur >= kChildDelay); int status = 0; TEST_PCHECK(RetryEINTR(waitpid)(pid, &status, 0)); TEST_CHECK(WIFEXITED(status)); TEST_CHECK(WEXITSTATUS(status) == kChildExitCode); }; EXPECT_THAT(InForkedProcess(test), IsPosixErrorOkAndHolds(0)); } TEST(VforkTest, ParentStopsUntilChildExecves_NoRandomSave) { ExecveArray const owned_child_argv = {"/proc/self/exe", "--vfork_test_child"}; char* const* const child_argv = owned_child_argv.get(); const auto test = [&] { const int64_t start = MonotonicNow(); pid_t pid = vfork(); if (pid == 0) { SleepSafe(kChildDelay); execve(child_argv[0], child_argv, /* envp = */ nullptr); _exit(errno); } // Don't attempt save/restore until after recording end_time, // since the test expects an upper bound on the time spent // stopped. int saved_errno = errno; const int64_t end = MonotonicNow(); errno = saved_errno; TEST_PCHECK_MSG(pid > 0, "vfork failed"); MaybeSave(); absl::Duration dur = absl::Nanoseconds(end - start); // The parent should resume execution after execve, but before // the post-execve test child exits. TEST_CHECK(dur >= kChildDelay); TEST_CHECK(dur <= 2 * kChildDelay); int status = 0; TEST_PCHECK(RetryEINTR(waitpid)(pid, &status, 0)); TEST_CHECK(WIFEXITED(status)); TEST_CHECK(WEXITSTATUS(status) == kChildExitCode); }; EXPECT_THAT(InForkedProcess(test), IsPosixErrorOkAndHolds(0)); } // A vfork child does not unstop the parent a second time when it exits after // exec. TEST(VforkTest, ExecedChildExitDoesntUnstopParent_NoRandomSave) { ExecveArray const owned_child_argv = {"/proc/self/exe", "--vfork_test_child"}; char* const* const child_argv = owned_child_argv.get(); const auto test = [&] { pid_t pid1 = vfork(); if (pid1 == 0) { execve(child_argv[0], child_argv, /* envp = */ nullptr); _exit(errno); } TEST_PCHECK_MSG(pid1 > 0, "vfork failed"); MaybeSave(); // pid1 exec'd and is now sleeping. SleepSafe(kChildDelay / 2); const int64_t start = MonotonicNow(); pid_t pid2 = vfork(); if (pid2 == 0) { SleepSafe(kChildDelay); _exit(kChildExitCode); } TEST_PCHECK_MSG(pid2 > 0, "vfork failed"); MaybeSave(); const int64_t end = MonotonicNow(); absl::Duration dur = absl::Nanoseconds(end - start); // The parent should resume execution only after pid2 exits, not // when pid1 exits. TEST_CHECK(dur >= kChildDelay); int status = 0; TEST_PCHECK(RetryEINTR(waitpid)(pid1, &status, 0)); TEST_CHECK(WIFEXITED(status)); TEST_CHECK(WEXITSTATUS(status) == kChildExitCode); TEST_PCHECK(RetryEINTR(waitpid)(pid2, &status, 0)); TEST_CHECK(WIFEXITED(status)); TEST_CHECK(WEXITSTATUS(status) == kChildExitCode); }; EXPECT_THAT(InForkedProcess(test), IsPosixErrorOkAndHolds(0)); } int RunChild() { SleepSafe(kChildDelay); return kChildExitCode; } } // namespace } // namespace testing } // namespace gvisor int main(int argc, char** argv) { gvisor::testing::TestInit(&argc, &argv); if (absl::GetFlag(FLAGS_vfork_test_child)) { return gvisor::testing::RunChild(); } return RUN_ALL_TESTS(); }