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// 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();
}
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