llkd/tests/llkd_test.cpp - LeafOS-Project/android_system_core - Gitiles

 /*
  * Copyright (C) 2018 The Android Open Source Project
  *
  * 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 <fcntl.h>
 #include <signal.h>
 #include <stdint.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>

 #include <chrono>
 #include <iostream>
 #include <string>

 #include <android-base/properties.h>
 #include <gtest/gtest.h>
 #include <log/log_time.h>  // for MS_PER_SEC and US_PER_SEC

 #include "llkd.h"

 using namespace std::chrono;
 using namespace std::chrono_literals;

 namespace {

 milliseconds GetUintProperty(const std::string& key, milliseconds def) {
     return milliseconds(android::base::GetUintProperty(key, static_cast<uint64_t>(def.count()),
                                                        static_cast<uint64_t>(def.max().count())));
 }

 seconds GetUintProperty(const std::string& key, seconds def) {
     return seconds(android::base::GetUintProperty(key, static_cast<uint64_t>(def.count()),
                                                   static_cast<uint64_t>(def.max().count())));
 }

 // GTEST_LOG_(WARNING) output is fugly, this has much less noise
 // ToDo: look into fixing googletest to produce output that matches style of
 //       all the other status messages, and can switch off __line__ and
 //       __function__ noise
 #define GTEST_LOG_WARNING std::cerr << "[ WARNING  ] "
 #define GTEST_LOG_INFO std::cerr << "[   INFO   ] "

 // Properties is _not_ a high performance ABI!
 void rest() {
     usleep(200000);
 }

 void execute(const char* command) {
     if (getuid() || system(command)) {
         system((std::string("su root ") + command).c_str());
     }
 }

 seconds llkdSleepPeriod(char state) {
     auto default_eng = android::base::GetProperty(LLK_ENABLE_PROPERTY, "eng") == "eng";
     auto default_enable = LLK_ENABLE_DEFAULT;
     if (!LLK_ENABLE_DEFAULT && default_eng &&
         android::base::GetBoolProperty("ro.debuggable", false)) {
         default_enable = true;
     }
     default_enable = android::base::GetBoolProperty(LLK_ENABLE_PROPERTY, default_enable);
     if (default_eng) {
         GTEST_LOG_INFO << LLK_ENABLE_PROPERTY " defaults to \"eng\" thus "
                        << (default_enable ? "true" : "false") << "\n";
     }
     // Hail Mary hope is unconfigured.
     if ((GetUintProperty(LLK_TIMEOUT_MS_PROPERTY, LLK_TIMEOUT_MS_DEFAULT) !=
          duration_cast<milliseconds>(120s)) ||
         (GetUintProperty(LLK_CHECK_MS_PROPERTY,
                          LLK_TIMEOUT_MS_DEFAULT / LLK_CHECKS_PER_TIMEOUT_DEFAULT) !=
          duration_cast<milliseconds>(10s))) {
         execute("stop llkd-0");
         execute("stop llkd-1");
         rest();
         std::string setprop("setprop ");
         execute((setprop + LLK_CHECK_STACK_PROPERTY + " SyS_openat").c_str());
         rest();
         execute((setprop + LLK_ENABLE_WRITEABLE_PROPERTY + " false").c_str());
         rest();
         execute((setprop + LLK_TIMEOUT_MS_PROPERTY + " 120000").c_str());
         rest();
         execute((setprop + KHT_TIMEOUT_PROPERTY + " 130").c_str());
         rest();
         execute((setprop + LLK_CHECK_MS_PROPERTY + " 10000").c_str());
         rest();
         if (!default_enable) {
             execute((setprop + LLK_ENABLE_PROPERTY + " true").c_str());
             rest();
         }
         execute((setprop + LLK_ENABLE_WRITEABLE_PROPERTY + " true").c_str());
         rest();
     }
     default_enable = LLK_ENABLE_DEFAULT;
     if (!LLK_ENABLE_DEFAULT && (android::base::GetProperty(LLK_ENABLE_PROPERTY, "eng") == "eng") &&
         android::base::GetBoolProperty("ro.debuggable", false)) {
         default_enable = true;
     }
     default_enable = android::base::GetBoolProperty(LLK_ENABLE_PROPERTY, default_enable);
     if (default_enable) {
         execute("start llkd-1");
         rest();
         GTEST_LOG_INFO << "llkd enabled\n";
     } else {
         GTEST_LOG_WARNING << "llkd disabled\n";
     }

     /* KISS follows llk_init() */
     milliseconds llkTimeoutMs = LLK_TIMEOUT_MS_DEFAULT;
     seconds khtTimeout = duration_cast<seconds>(
         llkTimeoutMs * (1 + LLK_CHECKS_PER_TIMEOUT_DEFAULT) / LLK_CHECKS_PER_TIMEOUT_DEFAULT);
     khtTimeout = GetUintProperty(KHT_TIMEOUT_PROPERTY, khtTimeout);
     llkTimeoutMs =
         khtTimeout * LLK_CHECKS_PER_TIMEOUT_DEFAULT / (1 + LLK_CHECKS_PER_TIMEOUT_DEFAULT);
     llkTimeoutMs = GetUintProperty(LLK_TIMEOUT_MS_PROPERTY, llkTimeoutMs);
     if (llkTimeoutMs < LLK_TIMEOUT_MS_MINIMUM) {
         llkTimeoutMs = LLK_TIMEOUT_MS_MINIMUM;
     }
     milliseconds llkCheckMs = llkTimeoutMs / LLK_CHECKS_PER_TIMEOUT_DEFAULT;
     auto timeout = GetUintProperty((state == 'Z') ? LLK_Z_TIMEOUT_MS_PROPERTY
                                                   : (state == 'S') ? LLK_STACK_TIMEOUT_MS_PROPERTY
                                                                    : LLK_D_TIMEOUT_MS_PROPERTY,
                                    llkTimeoutMs);
     if (timeout < LLK_TIMEOUT_MS_MINIMUM) {
         timeout = LLK_TIMEOUT_MS_MINIMUM;
     }

     if (llkCheckMs > timeout) {
         llkCheckMs = timeout;
     }
     llkCheckMs = GetUintProperty(LLK_CHECK_MS_PROPERTY, llkCheckMs);
     timeout += llkCheckMs;
     auto sec = duration_cast<seconds>(timeout);
     if (sec == 0s) {
         ++sec;
     } else if (sec > 59s) {
         GTEST_LOG_WARNING << "llkd is configured for about " << duration_cast<minutes>(sec).count()
                           << " minutes to react\n";
     }

     // 33% margin for the test to naturally timeout waiting for llkd to respond
     return (sec * 4 + 2s) / 3;
 }

 inline void waitForPid(pid_t child_pid) {
     int wstatus;
     ASSERT_LE(0, waitpid(child_pid, &wstatus, 0));
     EXPECT_FALSE(WIFEXITED(wstatus)) << "[   INFO   ] exit=" << WEXITSTATUS(wstatus);
     ASSERT_TRUE(WIFSIGNALED(wstatus));
     ASSERT_EQ(WTERMSIG(wstatus), SIGKILL);
 }

 bool checkKill(const char* reason) {
     if (android::base::GetBoolProperty(LLK_KILLTEST_PROPERTY, LLK_KILLTEST_DEFAULT)) {
         return false;
     }
     auto bootreason = android::base::GetProperty("sys.boot.reason", "nothing");
     if (bootreason == reason) {
         GTEST_LOG_INFO << "Expected test result confirmed " << reason << "\n";
         return true;
     }
     GTEST_LOG_WARNING << "Expected test result is " << reason << "\n";

     // apct adjustment if needed (set LLK_KILLTEST_PROPERTY to "off" to allow test)
     //
     // if (android::base::GetProperty(LLK_KILLTEST_PROPERTY, "") == "false") {
     //     GTEST_LOG_WARNING << "Bypassing test\n";
     //     return true;
     // }

     return false;
 }

 }  // namespace

 // The tests that use this helper are to simulate processes stuck in 'D'
 // state that are experiencing forward scheduled progress. As such the
 // expectation is that llkd will _not_ perform any mitigations. The sleepfor
 // argument helps us set the amount of forward scheduler progress.
 static void llkd_driver_ABA(const microseconds sleepfor) {
     const auto period = llkdSleepPeriod('D');
     if (period <= sleepfor) {
         GTEST_LOG_WARNING << "llkd configuration too short for "
                           << duration_cast<milliseconds>(sleepfor).count() << "ms work cycle\n";
         return;
     }

     auto child_pid = fork();
     ASSERT_LE(0, child_pid);
     int wstatus;
     if (!child_pid) {
         auto ratio = period / sleepfor;
         ASSERT_LT(0, ratio);
         // vfork() parent is uninterruptable D state waiting for child to exec()
         while (--ratio > 0) {
             auto driver_pid = vfork();
             ASSERT_LE(0, driver_pid);
             if (driver_pid) {  // parent
                 waitpid(driver_pid, &wstatus, 0);
                 if (!WIFEXITED(wstatus)) {
                     exit(42);
                 }
                 if (WEXITSTATUS(wstatus) != 42) {
                     exit(42);
                 }
             } else {
                 usleep(sleepfor.count());
                 exit(42);
             }
         }
         exit(0);
     }
     ASSERT_LE(0, waitpid(child_pid, &wstatus, 0));
     EXPECT_TRUE(WIFEXITED(wstatus));
     if (WIFEXITED(wstatus)) {
         EXPECT_EQ(0, WEXITSTATUS(wstatus));
     }
     ASSERT_FALSE(WIFSIGNALED(wstatus)) << "[   INFO   ] signo=" << WTERMSIG(wstatus);
 }

 TEST(llkd, driver_ABA_fast) {
     llkd_driver_ABA(5ms);
 }

 TEST(llkd, driver_ABA_slow) {
     llkd_driver_ABA(1s);
 }

 TEST(llkd, driver_ABA_glacial) {
     llkd_driver_ABA(1min);
 }

 // Following tests must be last in this file to capture possible errant
 // kernel_panic mitigation failure.

 // The following tests simulate processes stick in 'Z' or 'D' state with
 // no forward scheduling progress, but interruptible. As such the expectation
 // is that llkd will perform kill mitigation and not progress to kernel_panic.

 TEST(llkd, zombie) {
     if (checkKill("kernel_panic,sysrq,livelock,zombie")) {
         return;
     }

     const auto period = llkdSleepPeriod('Z');

     /* Create a Persistent Zombie Process */
     pid_t child_pid = fork();
     ASSERT_LE(0, child_pid);
     if (!child_pid) {
         auto zombie_pid = fork();
         ASSERT_LE(0, zombie_pid);
         if (!zombie_pid) {
             sleep(1);
             exit(0);
         }
         sleep(period.count());
         exit(42);
     }

     waitForPid(child_pid);
 }

 TEST(llkd, driver) {
     if (checkKill("kernel_panic,sysrq,livelock,driver")) {
         return;
     }

     const auto period = llkdSleepPeriod('D');

     /* Create a Persistent Device Process */
     auto child_pid = fork();
     ASSERT_LE(0, child_pid);
     if (!child_pid) {
         // vfork() parent is uninterruptable D state waiting for child to exec()
         auto driver_pid = vfork();
         ASSERT_LE(0, driver_pid);
         sleep(period.count());
         exit(driver_pid ? 42 : 0);
     }

     waitForPid(child_pid);
 }

 TEST(llkd, sleep) {
     if (checkKill("kernel_panic,sysrq,livelock,sleeping")) {
         return;
     }
     if (!android::base::GetBoolProperty("ro.debuggable", false)) {
         GTEST_LOG_WARNING << "Features not available on user builds\n";
     }

     const auto period = llkdSleepPeriod('S');

     /* Create a Persistent SyS_openat for single-ended pipe */
     static constexpr char stack_pipe_file[] = "/dev/stack_pipe_file";
     unlink(stack_pipe_file);
     auto pipe_ret = mknod(stack_pipe_file, S_IFIFO | 0666, 0);
     ASSERT_LE(0, pipe_ret);

     auto child_pid = fork();
     ASSERT_LE(0, child_pid);
     if (!child_pid) {
         child_pid = fork();
         ASSERT_LE(0, child_pid);
         if (!child_pid) {
             sleep(period.count());
             auto fd = open(stack_pipe_file, O_RDONLY | O_CLOEXEC);
             close(fd);
             exit(0);
         } else {
             auto fd = open(stack_pipe_file, O_WRONLY | O_CLOEXEC);
             close(fd);
             exit(42);
         }
     }

     waitForPid(child_pid);

     unlink(stack_pipe_file);
 }
	/*
	* Copyright (C) 2018 The Android Open Source Project
	*
	* 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 <fcntl.h>
	#include <signal.h>
	#include <stdint.h>
	#include <sys/stat.h>
	#include <sys/types.h>
	#include <sys/wait.h>
	#include <unistd.h>

	#include <chrono>
	#include <iostream>
	#include <string>

	#include <android-base/properties.h>
	#include <gtest/gtest.h>
	#include <log/log_time.h> // for MS_PER_SEC and US_PER_SEC

	#include "llkd.h"

	using namespace std::chrono;
	using namespace std::chrono_literals;

	namespace {

	milliseconds GetUintProperty(const std::string& key, milliseconds def) {
	return milliseconds(android::base::GetUintProperty(key, static_cast<uint64_t>(def.count()),
	static_cast<uint64_t>(def.max().count())));
	}

	seconds GetUintProperty(const std::string& key, seconds def) {
	return seconds(android::base::GetUintProperty(key, static_cast<uint64_t>(def.count()),
	static_cast<uint64_t>(def.max().count())));
	}

	// GTEST_LOG_(WARNING) output is fugly, this has much less noise
	// ToDo: look into fixing googletest to produce output that matches style of
	// all the other status messages, and can switch off __line__ and
	// __function__ noise
	#define GTEST_LOG_WARNING std::cerr << "[ WARNING ] "
	#define GTEST_LOG_INFO std::cerr << "[ INFO ] "

	// Properties is _not_ a high performance ABI!
	void rest() {
	usleep(200000);
	}

	void execute(const char* command) {
	if (getuid() \|\| system(command)) {
	system((std::string("su root ") + command).c_str());
	}
	}

	seconds llkdSleepPeriod(char state) {
	auto default_eng = android::base::GetProperty(LLK_ENABLE_PROPERTY, "eng") == "eng";
	auto default_enable = LLK_ENABLE_DEFAULT;
	if (!LLK_ENABLE_DEFAULT && default_eng &&
	android::base::GetBoolProperty("ro.debuggable", false)) {
	default_enable = true;
	}
	default_enable = android::base::GetBoolProperty(LLK_ENABLE_PROPERTY, default_enable);
	if (default_eng) {
	GTEST_LOG_INFO << LLK_ENABLE_PROPERTY " defaults to \"eng\" thus "
	<< (default_enable ? "true" : "false") << "\n";
	}
	// Hail Mary hope is unconfigured.
	if ((GetUintProperty(LLK_TIMEOUT_MS_PROPERTY, LLK_TIMEOUT_MS_DEFAULT) !=
	duration_cast<milliseconds>(120s)) \|\|
	(GetUintProperty(LLK_CHECK_MS_PROPERTY,
	LLK_TIMEOUT_MS_DEFAULT / LLK_CHECKS_PER_TIMEOUT_DEFAULT) !=
	duration_cast<milliseconds>(10s))) {
	execute("stop llkd-0");
	execute("stop llkd-1");
	rest();
	std::string setprop("setprop ");
	execute((setprop + LLK_CHECK_STACK_PROPERTY + " SyS_openat").c_str());
	rest();
	execute((setprop + LLK_ENABLE_WRITEABLE_PROPERTY + " false").c_str());
	rest();
	execute((setprop + LLK_TIMEOUT_MS_PROPERTY + " 120000").c_str());
	rest();
	execute((setprop + KHT_TIMEOUT_PROPERTY + " 130").c_str());
	rest();
	execute((setprop + LLK_CHECK_MS_PROPERTY + " 10000").c_str());
	rest();
	if (!default_enable) {
	execute((setprop + LLK_ENABLE_PROPERTY + " true").c_str());
	rest();
	}
	execute((setprop + LLK_ENABLE_WRITEABLE_PROPERTY + " true").c_str());
	rest();
	}
	default_enable = LLK_ENABLE_DEFAULT;
	if (!LLK_ENABLE_DEFAULT && (android::base::GetProperty(LLK_ENABLE_PROPERTY, "eng") == "eng") &&
	android::base::GetBoolProperty("ro.debuggable", false)) {
	default_enable = true;
	}
	default_enable = android::base::GetBoolProperty(LLK_ENABLE_PROPERTY, default_enable);
	if (default_enable) {
	execute("start llkd-1");
	rest();
	GTEST_LOG_INFO << "llkd enabled\n";
	} else {
	GTEST_LOG_WARNING << "llkd disabled\n";
	}

	/* KISS follows llk_init() */
	milliseconds llkTimeoutMs = LLK_TIMEOUT_MS_DEFAULT;
	seconds khtTimeout = duration_cast<seconds>(
	llkTimeoutMs * (1 + LLK_CHECKS_PER_TIMEOUT_DEFAULT) / LLK_CHECKS_PER_TIMEOUT_DEFAULT);
	khtTimeout = GetUintProperty(KHT_TIMEOUT_PROPERTY, khtTimeout);
	llkTimeoutMs =
	khtTimeout * LLK_CHECKS_PER_TIMEOUT_DEFAULT / (1 + LLK_CHECKS_PER_TIMEOUT_DEFAULT);
	llkTimeoutMs = GetUintProperty(LLK_TIMEOUT_MS_PROPERTY, llkTimeoutMs);
	if (llkTimeoutMs < LLK_TIMEOUT_MS_MINIMUM) {
	llkTimeoutMs = LLK_TIMEOUT_MS_MINIMUM;
	}
	milliseconds llkCheckMs = llkTimeoutMs / LLK_CHECKS_PER_TIMEOUT_DEFAULT;
	auto timeout = GetUintProperty((state == 'Z') ? LLK_Z_TIMEOUT_MS_PROPERTY
	: (state == 'S') ? LLK_STACK_TIMEOUT_MS_PROPERTY
	: LLK_D_TIMEOUT_MS_PROPERTY,
	llkTimeoutMs);
	if (timeout < LLK_TIMEOUT_MS_MINIMUM) {
	timeout = LLK_TIMEOUT_MS_MINIMUM;
	}

	if (llkCheckMs > timeout) {
	llkCheckMs = timeout;
	}
	llkCheckMs = GetUintProperty(LLK_CHECK_MS_PROPERTY, llkCheckMs);
	timeout += llkCheckMs;
	auto sec = duration_cast<seconds>(timeout);
	if (sec == 0s) {
	++sec;
	} else if (sec > 59s) {
	GTEST_LOG_WARNING << "llkd is configured for about " << duration_cast<minutes>(sec).count()
	<< " minutes to react\n";
	}

	// 33% margin for the test to naturally timeout waiting for llkd to respond
	return (sec * 4 + 2s) / 3;
	}

	inline void waitForPid(pid_t child_pid) {
	int wstatus;
	ASSERT_LE(0, waitpid(child_pid, &wstatus, 0));
	EXPECT_FALSE(WIFEXITED(wstatus)) << "[ INFO ] exit=" << WEXITSTATUS(wstatus);
	ASSERT_TRUE(WIFSIGNALED(wstatus));
	ASSERT_EQ(WTERMSIG(wstatus), SIGKILL);
	}

	bool checkKill(const char* reason) {
	if (android::base::GetBoolProperty(LLK_KILLTEST_PROPERTY, LLK_KILLTEST_DEFAULT)) {
	return false;
	}
	auto bootreason = android::base::GetProperty("sys.boot.reason", "nothing");
	if (bootreason == reason) {
	GTEST_LOG_INFO << "Expected test result confirmed " << reason << "\n";
	return true;
	}
	GTEST_LOG_WARNING << "Expected test result is " << reason << "\n";

	// apct adjustment if needed (set LLK_KILLTEST_PROPERTY to "off" to allow test)
	//
	// if (android::base::GetProperty(LLK_KILLTEST_PROPERTY, "") == "false") {
	// GTEST_LOG_WARNING << "Bypassing test\n";
	// return true;
	// }

	return false;
	}

	} // namespace

	// The tests that use this helper are to simulate processes stuck in 'D'
	// state that are experiencing forward scheduled progress. As such the
	// expectation is that llkd will _not_ perform any mitigations. The sleepfor
	// argument helps us set the amount of forward scheduler progress.
	static void llkd_driver_ABA(const microseconds sleepfor) {
	const auto period = llkdSleepPeriod('D');
	if (period <= sleepfor) {
	GTEST_LOG_WARNING << "llkd configuration too short for "
	<< duration_cast<milliseconds>(sleepfor).count() << "ms work cycle\n";
	return;
	}

	auto child_pid = fork();
	ASSERT_LE(0, child_pid);
	int wstatus;
	if (!child_pid) {
	auto ratio = period / sleepfor;
	ASSERT_LT(0, ratio);
	// vfork() parent is uninterruptable D state waiting for child to exec()
	while (--ratio > 0) {
	auto driver_pid = vfork();
	ASSERT_LE(0, driver_pid);
	if (driver_pid) { // parent
	waitpid(driver_pid, &wstatus, 0);
	if (!WIFEXITED(wstatus)) {
	exit(42);
	}
	if (WEXITSTATUS(wstatus) != 42) {
	exit(42);
	}
	} else {
	usleep(sleepfor.count());
	exit(42);
	}
	}
	exit(0);
	}
	ASSERT_LE(0, waitpid(child_pid, &wstatus, 0));
	EXPECT_TRUE(WIFEXITED(wstatus));
	if (WIFEXITED(wstatus)) {
	EXPECT_EQ(0, WEXITSTATUS(wstatus));
	}
	ASSERT_FALSE(WIFSIGNALED(wstatus)) << "[ INFO ] signo=" << WTERMSIG(wstatus);
	}

	TEST(llkd, driver_ABA_fast) {
	llkd_driver_ABA(5ms);
	}

	TEST(llkd, driver_ABA_slow) {
	llkd_driver_ABA(1s);
	}

	TEST(llkd, driver_ABA_glacial) {
	llkd_driver_ABA(1min);
	}

	// Following tests must be last in this file to capture possible errant
	// kernel_panic mitigation failure.

	// The following tests simulate processes stick in 'Z' or 'D' state with
	// no forward scheduling progress, but interruptible. As such the expectation
	// is that llkd will perform kill mitigation and not progress to kernel_panic.

	TEST(llkd, zombie) {
	if (checkKill("kernel_panic,sysrq,livelock,zombie")) {
	return;
	}

	const auto period = llkdSleepPeriod('Z');

	/* Create a Persistent Zombie Process */
	pid_t child_pid = fork();
	ASSERT_LE(0, child_pid);
	if (!child_pid) {
	auto zombie_pid = fork();
	ASSERT_LE(0, zombie_pid);
	if (!zombie_pid) {
	sleep(1);
	exit(0);
	}
	sleep(period.count());
	exit(42);
	}

	waitForPid(child_pid);
	}

	TEST(llkd, driver) {
	if (checkKill("kernel_panic,sysrq,livelock,driver")) {
	return;
	}

	const auto period = llkdSleepPeriod('D');

	/* Create a Persistent Device Process */
	auto child_pid = fork();
	ASSERT_LE(0, child_pid);
	if (!child_pid) {
	// vfork() parent is uninterruptable D state waiting for child to exec()
	auto driver_pid = vfork();
	ASSERT_LE(0, driver_pid);
	sleep(period.count());
	exit(driver_pid ? 42 : 0);
	}

	waitForPid(child_pid);
	}

	TEST(llkd, sleep) {
	if (checkKill("kernel_panic,sysrq,livelock,sleeping")) {
	return;
	}
	if (!android::base::GetBoolProperty("ro.debuggable", false)) {
	GTEST_LOG_WARNING << "Features not available on user builds\n";
	}

	const auto period = llkdSleepPeriod('S');

	/* Create a Persistent SyS_openat for single-ended pipe */
	static constexpr char stack_pipe_file[] = "/dev/stack_pipe_file";
	unlink(stack_pipe_file);
	auto pipe_ret = mknod(stack_pipe_file, S_IFIFO \| 0666, 0);
	ASSERT_LE(0, pipe_ret);

	auto child_pid = fork();
	ASSERT_LE(0, child_pid);
	if (!child_pid) {
	child_pid = fork();
	ASSERT_LE(0, child_pid);
	if (!child_pid) {
	sleep(period.count());
	auto fd = open(stack_pipe_file, O_RDONLY \| O_CLOEXEC);
	close(fd);
	exit(0);
	} else {
	auto fd = open(stack_pipe_file, O_WRONLY \| O_CLOEXEC);
	close(fd);
	exit(42);
	}
	}

	waitForPid(child_pid);

	unlink(stack_pipe_file);
	}