libprocessgroup/setup/cgroup_map_write.cpp - third_party/android.googlesource.com/platform/system/core - Git at Google

 /*
  * Copyright (C) 2019 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.
  */

 //#define LOG_NDEBUG 0
 #define LOG_TAG "libprocessgroup"

 #include <dirent.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <grp.h>
 #include <pwd.h>
 #include <sys/mman.h>
 #include <sys/mount.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <time.h>
 #include <unistd.h>

 #include <regex>

 #include <android-base/file.h>
 #include <android-base/logging.h>
 #include <android-base/properties.h>
 #include <android-base/stringprintf.h>
 #include <android-base/unique_fd.h>
 #include <android/cgrouprc.h>
 #include <json/reader.h>
 #include <json/value.h>
 #include <processgroup/format/cgroup_file.h>
 #include <processgroup/processgroup.h>
 #include <processgroup/setup.h>

 #include "cgroup_descriptor.h"

 using android::base::GetUintProperty;
 using android::base::StringPrintf;
 using android::base::unique_fd;

 namespace android {
 namespace cgrouprc {

 static constexpr const char* CGROUPS_DESC_FILE = "/etc/cgroups.json";
 static constexpr const char* CGROUPS_DESC_VENDOR_FILE = "/vendor/etc/cgroups.json";

 static constexpr const char* TEMPLATE_CGROUPS_DESC_API_FILE = "/etc/task_profiles/cgroups_%u.json";

 static bool ChangeDirModeAndOwner(const std::string& path, mode_t mode, const std::string& uid,
                                   const std::string& gid, bool permissive_mode = false) {
     uid_t pw_uid = -1;
     gid_t gr_gid = -1;

     if (!uid.empty()) {
         passwd* uid_pwd = getpwnam(uid.c_str());
         if (!uid_pwd) {
             PLOG(ERROR) << "Unable to decode UID for '" << uid << "'";
             return false;
         }

         pw_uid = uid_pwd->pw_uid;
         gr_gid = -1;

         if (!gid.empty()) {
             group* gid_pwd = getgrnam(gid.c_str());
             if (!gid_pwd) {
                 PLOG(ERROR) << "Unable to decode GID for '" << gid << "'";
                 return false;
             }
             gr_gid = gid_pwd->gr_gid;
         }
     }

     auto dir = std::unique_ptr<DIR, decltype(&closedir)>(opendir(path.c_str()), closedir);

     if (dir == NULL) {
         PLOG(ERROR) << "opendir failed for " << path;
         return false;
     }

     struct dirent* dir_entry;
     while ((dir_entry = readdir(dir.get()))) {
         if (!strcmp("..", dir_entry->d_name)) {
             continue;
         }

         std::string file_path = path + "/" + dir_entry->d_name;

         if (pw_uid != -1 && lchown(file_path.c_str(), pw_uid, gr_gid) < 0) {
             PLOG(ERROR) << "lchown() failed for " << file_path;
             return false;
         }

         if (fchmodat(AT_FDCWD, file_path.c_str(), mode, AT_SYMLINK_NOFOLLOW) != 0 &&
             (errno != EROFS || !permissive_mode)) {
             PLOG(ERROR) << "fchmodat() failed for " << path;
             return false;
         }
     }

     return true;
 }

 static bool Mkdir(const std::string& path, mode_t mode, const std::string& uid,
                   const std::string& gid) {
     bool permissive_mode = false;

     if (mode == 0) {
         /* Allow chmod to fail */
         permissive_mode = true;
         mode = 0755;
     }

     if (mkdir(path.c_str(), mode) != 0) {
         // /acct is a special case when the directory already exists
         if (errno != EEXIST) {
             PLOG(ERROR) << "mkdir() failed for " << path;
             return false;
         } else {
             permissive_mode = true;
         }
     }

     if (uid.empty() && permissive_mode) {
         return true;
     }

     if (!ChangeDirModeAndOwner(path, mode, uid, gid, permissive_mode)) {
         PLOG(ERROR) << "change of ownership or mode failed for " << path;
         return false;
     }

     return true;
 }

 static void MergeCgroupToDescriptors(std::map<std::string, CgroupDescriptor>* descriptors,
                                      const Json::Value& cgroup, const std::string& name,
                                      const std::string& root_path, int cgroups_version) {
     std::string path;

     if (!root_path.empty()) {
         path = root_path + "/" + cgroup["Path"].asString();
     } else {
         path = cgroup["Path"].asString();
     }

     uint32_t controller_flags = 0;

     if (cgroup["NeedsActivation"].isBool() && cgroup["NeedsActivation"].asBool()) {
         controller_flags |= CGROUPRC_CONTROLLER_FLAG_NEEDS_ACTIVATION;
     }

     CgroupDescriptor descriptor(
             cgroups_version, name, path, std::strtoul(cgroup["Mode"].asString().c_str(), 0, 8),
             cgroup["UID"].asString(), cgroup["GID"].asString(), controller_flags);

     auto iter = descriptors->find(name);
     if (iter == descriptors->end()) {
         descriptors->emplace(name, descriptor);
     } else {
         iter->second = descriptor;
     }
 }

 static bool ReadDescriptorsFromFile(const std::string& file_name,
                                     std::map<std::string, CgroupDescriptor>* descriptors) {
     std::vector<CgroupDescriptor> result;
     std::string json_doc;

     if (!android::base::ReadFileToString(file_name, &json_doc)) {
         PLOG(ERROR) << "Failed to read task profiles from " << file_name;
         return false;
     }

     Json::Reader reader;
     Json::Value root;
     if (!reader.parse(json_doc, root)) {
         LOG(ERROR) << "Failed to parse cgroups description: " << reader.getFormattedErrorMessages();
         return false;
     }

     if (root.isMember("Cgroups")) {
         const Json::Value& cgroups = root["Cgroups"];
         for (Json::Value::ArrayIndex i = 0; i < cgroups.size(); ++i) {
             std::string name = cgroups[i]["Controller"].asString();
             MergeCgroupToDescriptors(descriptors, cgroups[i], name, "", 1);
         }
     }

     if (root.isMember("Cgroups2")) {
         const Json::Value& cgroups2 = root["Cgroups2"];
         std::string root_path = cgroups2["Path"].asString();
         MergeCgroupToDescriptors(descriptors, cgroups2, CGROUPV2_CONTROLLER_NAME, "", 2);

         const Json::Value& childGroups = cgroups2["Controllers"];
         for (Json::Value::ArrayIndex i = 0; i < childGroups.size(); ++i) {
             std::string name = childGroups[i]["Controller"].asString();
             MergeCgroupToDescriptors(descriptors, childGroups[i], name, root_path, 2);
         }
     }

     return true;
 }

 static bool ReadDescriptors(std::map<std::string, CgroupDescriptor>* descriptors) {
     // load system cgroup descriptors
     if (!ReadDescriptorsFromFile(CGROUPS_DESC_FILE, descriptors)) {
         return false;
     }

     // load API-level specific system cgroups descriptors if available
     unsigned int api_level = GetUintProperty<unsigned int>("ro.product.first_api_level", 0);
     if (api_level > 0) {
         std::string api_cgroups_path =
                 android::base::StringPrintf(TEMPLATE_CGROUPS_DESC_API_FILE, api_level);
         if (!access(api_cgroups_path.c_str(), F_OK) || errno != ENOENT) {
             if (!ReadDescriptorsFromFile(api_cgroups_path, descriptors)) {
                 return false;
             }
         }
     }

     // load vendor cgroup descriptors if the file exists
     if (!access(CGROUPS_DESC_VENDOR_FILE, F_OK) &&
         !ReadDescriptorsFromFile(CGROUPS_DESC_VENDOR_FILE, descriptors)) {
         return false;
     }

     return true;
 }

 // To avoid issues in sdk_mac build
 #if defined(__ANDROID__)

 static bool SetupCgroup(const CgroupDescriptor& descriptor) {
     const format::CgroupController* controller = descriptor.controller();

     int result;
     if (controller->version() == 2) {
         result = 0;
         if (!strcmp(controller->name(), CGROUPV2_CONTROLLER_NAME)) {
             // /sys/fs/cgroup is created by cgroup2 with specific selinux permissions,
             // try to create again in case the mount point is changed
             if (!Mkdir(controller->path(), 0, "", "")) {
                 LOG(ERROR) << "Failed to create directory for " << controller->name() << " cgroup";
                 return false;
             }

             result = mount("none", controller->path(), "cgroup2", MS_NODEV | MS_NOEXEC | MS_NOSUID,
                            nullptr);

             // selinux permissions change after mounting, so it's ok to change mode and owner now
             if (!ChangeDirModeAndOwner(controller->path(), descriptor.mode(), descriptor.uid(),
                                        descriptor.gid())) {
                 LOG(ERROR) << "Failed to create directory for " << controller->name() << " cgroup";
                 result = -1;
             } else {
                 LOG(ERROR) << "restored ownership for " << controller->name() << " cgroup";
             }
         } else {
             if (!Mkdir(controller->path(), descriptor.mode(), descriptor.uid(), descriptor.gid())) {
                 LOG(ERROR) << "Failed to create directory for " << controller->name() << " cgroup";
                 return false;
             }

             if (controller->flags() & CGROUPRC_CONTROLLER_FLAG_NEEDS_ACTIVATION) {
                 std::string str = std::string("+") + controller->name();
                 std::string path = std::string(controller->path()) + "/cgroup.subtree_control";

                 if (!base::WriteStringToFile(str, path)) {
                     LOG(ERROR) << "Failed to activate controller " << controller->name();
                     return false;
                 }
             }
         }
     } else {
         // mkdir <path> [mode] [owner] [group]
         if (!Mkdir(controller->path(), descriptor.mode(), descriptor.uid(), descriptor.gid())) {
             LOG(ERROR) << "Failed to create directory for " << controller->name() << " cgroup";
             return false;
         }

         // Unfortunately historically cpuset controller was mounted using a mount command
         // different from all other controllers. This results in controller attributes not
         // to be prepended with controller name. For example this way instead of
         // /dev/cpuset/cpuset.cpus the attribute becomes /dev/cpuset/cpus which is what
         // the system currently expects.
         if (!strcmp(controller->name(), "cpuset")) {
             // mount cpuset none /dev/cpuset nodev noexec nosuid
             result = mount("none", controller->path(), controller->name(),
                            MS_NODEV | MS_NOEXEC | MS_NOSUID, nullptr);
         } else {
             // mount cgroup none <path> nodev noexec nosuid <controller>
             result = mount("none", controller->path(), "cgroup", MS_NODEV | MS_NOEXEC | MS_NOSUID,
                            controller->name());
         }
     }

     if (result < 0) {
         PLOG(ERROR) << "Failed to mount " << controller->name() << " cgroup";
         return false;
     }

     return true;
 }

 #else

 // Stubs for non-Android targets.
 static bool SetupCgroup(const CgroupDescriptor&) {
     return false;
 }

 #endif

 static bool WriteRcFile(const std::map<std::string, CgroupDescriptor>& descriptors) {
     unique_fd fd(TEMP_FAILURE_RETRY(open(CGROUPS_RC_PATH, O_CREAT | O_WRONLY | O_TRUNC | O_CLOEXEC,
                                          S_IRUSR | S_IRGRP | S_IROTH)));
     if (fd < 0) {
         PLOG(ERROR) << "open() failed for " << CGROUPS_RC_PATH;
         return false;
     }

     format::CgroupFile fl;
     fl.version_ = format::CgroupFile::FILE_CURR_VERSION;
     fl.controller_count_ = descriptors.size();
     int ret = TEMP_FAILURE_RETRY(write(fd, &fl, sizeof(fl)));
     if (ret < 0) {
         PLOG(ERROR) << "write() failed for " << CGROUPS_RC_PATH;
         return false;
     }

     for (const auto& [name, descriptor] : descriptors) {
         ret = TEMP_FAILURE_RETRY(
                 write(fd, descriptor.controller(), sizeof(format::CgroupController)));
         if (ret < 0) {
             PLOG(ERROR) << "write() failed for " << CGROUPS_RC_PATH;
             return false;
         }
     }

     return true;
 }

 CgroupDescriptor::CgroupDescriptor(uint32_t version, const std::string& name,
                                    const std::string& path, mode_t mode, const std::string& uid,
                                    const std::string& gid, uint32_t flags = 0)
     : controller_(version, flags, name, path), mode_(mode), uid_(uid), gid_(gid) {}

 void CgroupDescriptor::set_mounted(bool mounted) {
     uint32_t flags = controller_.flags();
     if (mounted) {
         flags |= CGROUPRC_CONTROLLER_FLAG_MOUNTED;
     } else {
         flags &= ~CGROUPRC_CONTROLLER_FLAG_MOUNTED;
     }
     controller_.set_flags(flags);
 }

 }  // namespace cgrouprc
 }  // namespace android

 bool CgroupSetup() {
     using namespace android::cgrouprc;

     std::map<std::string, CgroupDescriptor> descriptors;

     if (getpid() != 1) {
         LOG(ERROR) << "Cgroup setup can be done only by init process";
         return false;
     }

     // Make sure we do this only one time. No need for std::call_once because
     // init is a single-threaded process
     if (access(CGROUPS_RC_PATH, F_OK) == 0) {
         LOG(WARNING) << "Attempt to call SetupCgroups more than once";
         return true;
     }

     // load cgroups.json file
     if (!ReadDescriptors(&descriptors)) {
         LOG(ERROR) << "Failed to load cgroup description file";
         return false;
     }

     // setup cgroups
     for (auto& [name, descriptor] : descriptors) {
         if (SetupCgroup(descriptor)) {
             descriptor.set_mounted(true);
         } else {
             // issue a warning and proceed with the next cgroup
             LOG(WARNING) << "Failed to setup " << name << " cgroup";
         }
     }

     // mkdir <CGROUPS_RC_DIR> 0711 system system
     if (!Mkdir(android::base::Dirname(CGROUPS_RC_PATH), 0711, "system", "system")) {
         LOG(ERROR) << "Failed to create directory for " << CGROUPS_RC_PATH << " file";
         return false;
     }

     // Generate <CGROUPS_RC_FILE> file which can be directly mmapped into
     // process memory. This optimizes performance, memory usage
     // and limits infrormation shared with unprivileged processes
     // to the minimum subset of information from cgroups.json
     if (!WriteRcFile(descriptors)) {
         LOG(ERROR) << "Failed to write " << CGROUPS_RC_PATH << " file";
         return false;
     }

     // chmod 0644 <CGROUPS_RC_PATH>
     if (fchmodat(AT_FDCWD, CGROUPS_RC_PATH, 0644, AT_SYMLINK_NOFOLLOW) < 0) {
         PLOG(ERROR) << "fchmodat() failed";
         return false;
     }

     return true;
 }
	/*
	* Copyright (C) 2019 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.
	*/

	//#define LOG_NDEBUG 0
	#define LOG_TAG "libprocessgroup"

	#include <dirent.h>
	#include <errno.h>
	#include <fcntl.h>
	#include <grp.h>
	#include <pwd.h>
	#include <sys/mman.h>
	#include <sys/mount.h>
	#include <sys/stat.h>
	#include <sys/types.h>
	#include <time.h>
	#include <unistd.h>

	#include <regex>

	#include <android-base/file.h>
	#include <android-base/logging.h>
	#include <android-base/properties.h>
	#include <android-base/stringprintf.h>
	#include <android-base/unique_fd.h>
	#include <android/cgrouprc.h>
	#include <json/reader.h>
	#include <json/value.h>
	#include <processgroup/format/cgroup_file.h>
	#include <processgroup/processgroup.h>
	#include <processgroup/setup.h>

	#include "cgroup_descriptor.h"

	using android::base::GetUintProperty;
	using android::base::StringPrintf;
	using android::base::unique_fd;

	namespace android {
	namespace cgrouprc {

	static constexpr const char* CGROUPS_DESC_FILE = "/etc/cgroups.json";
	static constexpr const char* CGROUPS_DESC_VENDOR_FILE = "/vendor/etc/cgroups.json";

	static constexpr const char* TEMPLATE_CGROUPS_DESC_API_FILE = "/etc/task_profiles/cgroups_%u.json";

	static bool ChangeDirModeAndOwner(const std::string& path, mode_t mode, const std::string& uid,
	const std::string& gid, bool permissive_mode = false) {
	uid_t pw_uid = -1;
	gid_t gr_gid = -1;

	if (!uid.empty()) {
	passwd* uid_pwd = getpwnam(uid.c_str());
	if (!uid_pwd) {
	PLOG(ERROR) << "Unable to decode UID for '" << uid << "'";
	return false;
	}

	pw_uid = uid_pwd->pw_uid;
	gr_gid = -1;

	if (!gid.empty()) {
	group* gid_pwd = getgrnam(gid.c_str());
	if (!gid_pwd) {
	PLOG(ERROR) << "Unable to decode GID for '" << gid << "'";
	return false;
	}
	gr_gid = gid_pwd->gr_gid;
	}
	}

	auto dir = std::unique_ptr<DIR, decltype(&closedir)>(opendir(path.c_str()), closedir);

	if (dir == NULL) {
	PLOG(ERROR) << "opendir failed for " << path;
	return false;
	}

	struct dirent* dir_entry;
	while ((dir_entry = readdir(dir.get()))) {
	if (!strcmp("..", dir_entry->d_name)) {
	continue;
	}

	std::string file_path = path + "/" + dir_entry->d_name;

	if (pw_uid != -1 && lchown(file_path.c_str(), pw_uid, gr_gid) < 0) {
	PLOG(ERROR) << "lchown() failed for " << file_path;
	return false;
	}

	if (fchmodat(AT_FDCWD, file_path.c_str(), mode, AT_SYMLINK_NOFOLLOW) != 0 &&
	(errno != EROFS \|\| !permissive_mode)) {
	PLOG(ERROR) << "fchmodat() failed for " << path;
	return false;
	}
	}

	return true;
	}

	static bool Mkdir(const std::string& path, mode_t mode, const std::string& uid,
	const std::string& gid) {
	bool permissive_mode = false;

	if (mode == 0) {
	/* Allow chmod to fail */
	permissive_mode = true;
	mode = 0755;
	}

	if (mkdir(path.c_str(), mode) != 0) {
	// /acct is a special case when the directory already exists
	if (errno != EEXIST) {
	PLOG(ERROR) << "mkdir() failed for " << path;
	return false;
	} else {
	permissive_mode = true;
	}
	}

	if (uid.empty() && permissive_mode) {
	return true;
	}

	if (!ChangeDirModeAndOwner(path, mode, uid, gid, permissive_mode)) {
	PLOG(ERROR) << "change of ownership or mode failed for " << path;
	return false;
	}

	return true;
	}

	static void MergeCgroupToDescriptors(std::map<std::string, CgroupDescriptor>* descriptors,
	const Json::Value& cgroup, const std::string& name,
	const std::string& root_path, int cgroups_version) {
	std::string path;

	if (!root_path.empty()) {
	path = root_path + "/" + cgroup["Path"].asString();
	} else {
	path = cgroup["Path"].asString();
	}

	uint32_t controller_flags = 0;

	if (cgroup["NeedsActivation"].isBool() && cgroup["NeedsActivation"].asBool()) {
	controller_flags \|= CGROUPRC_CONTROLLER_FLAG_NEEDS_ACTIVATION;
	}

	CgroupDescriptor descriptor(
	cgroups_version, name, path, std::strtoul(cgroup["Mode"].asString().c_str(), 0, 8),
	cgroup["UID"].asString(), cgroup["GID"].asString(), controller_flags);

	auto iter = descriptors->find(name);
	if (iter == descriptors->end()) {
	descriptors->emplace(name, descriptor);
	} else {
	iter->second = descriptor;
	}
	}

	static bool ReadDescriptorsFromFile(const std::string& file_name,
	std::map<std::string, CgroupDescriptor>* descriptors) {
	std::vector<CgroupDescriptor> result;
	std::string json_doc;

	if (!android::base::ReadFileToString(file_name, &json_doc)) {
	PLOG(ERROR) << "Failed to read task profiles from " << file_name;
	return false;
	}

	Json::Reader reader;
	Json::Value root;
	if (!reader.parse(json_doc, root)) {
	LOG(ERROR) << "Failed to parse cgroups description: " << reader.getFormattedErrorMessages();
	return false;
	}

	if (root.isMember("Cgroups")) {
	const Json::Value& cgroups = root["Cgroups"];
	for (Json::Value::ArrayIndex i = 0; i < cgroups.size(); ++i) {
	std::string name = cgroups[i]["Controller"].asString();
	MergeCgroupToDescriptors(descriptors, cgroups[i], name, "", 1);
	}
	}

	if (root.isMember("Cgroups2")) {
	const Json::Value& cgroups2 = root["Cgroups2"];
	std::string root_path = cgroups2["Path"].asString();
	MergeCgroupToDescriptors(descriptors, cgroups2, CGROUPV2_CONTROLLER_NAME, "", 2);

	const Json::Value& childGroups = cgroups2["Controllers"];
	for (Json::Value::ArrayIndex i = 0; i < childGroups.size(); ++i) {
	std::string name = childGroups[i]["Controller"].asString();
	MergeCgroupToDescriptors(descriptors, childGroups[i], name, root_path, 2);
	}
	}

	return true;
	}

	static bool ReadDescriptors(std::map<std::string, CgroupDescriptor>* descriptors) {
	// load system cgroup descriptors
	if (!ReadDescriptorsFromFile(CGROUPS_DESC_FILE, descriptors)) {
	return false;
	}

	// load API-level specific system cgroups descriptors if available
	unsigned int api_level = GetUintProperty<unsigned int>("ro.product.first_api_level", 0);
	if (api_level > 0) {
	std::string api_cgroups_path =
	android::base::StringPrintf(TEMPLATE_CGROUPS_DESC_API_FILE, api_level);
	if (!access(api_cgroups_path.c_str(), F_OK) \|\| errno != ENOENT) {
	if (!ReadDescriptorsFromFile(api_cgroups_path, descriptors)) {
	return false;
	}
	}
	}

	// load vendor cgroup descriptors if the file exists
	if (!access(CGROUPS_DESC_VENDOR_FILE, F_OK) &&
	!ReadDescriptorsFromFile(CGROUPS_DESC_VENDOR_FILE, descriptors)) {
	return false;
	}

	return true;
	}

	// To avoid issues in sdk_mac build
	#if defined(__ANDROID__)

	static bool SetupCgroup(const CgroupDescriptor& descriptor) {
	const format::CgroupController* controller = descriptor.controller();

	int result;
	if (controller->version() == 2) {
	result = 0;
	if (!strcmp(controller->name(), CGROUPV2_CONTROLLER_NAME)) {
	// /sys/fs/cgroup is created by cgroup2 with specific selinux permissions,
	// try to create again in case the mount point is changed
	if (!Mkdir(controller->path(), 0, "", "")) {
	LOG(ERROR) << "Failed to create directory for " << controller->name() << " cgroup";
	return false;
	}

	result = mount("none", controller->path(), "cgroup2", MS_NODEV \| MS_NOEXEC \| MS_NOSUID,
	nullptr);

	// selinux permissions change after mounting, so it's ok to change mode and owner now
	if (!ChangeDirModeAndOwner(controller->path(), descriptor.mode(), descriptor.uid(),
	descriptor.gid())) {
	LOG(ERROR) << "Failed to create directory for " << controller->name() << " cgroup";
	result = -1;
	} else {
	LOG(ERROR) << "restored ownership for " << controller->name() << " cgroup";
	}
	} else {
	if (!Mkdir(controller->path(), descriptor.mode(), descriptor.uid(), descriptor.gid())) {
	LOG(ERROR) << "Failed to create directory for " << controller->name() << " cgroup";
	return false;
	}

	if (controller->flags() & CGROUPRC_CONTROLLER_FLAG_NEEDS_ACTIVATION) {
	std::string str = std::string("+") + controller->name();
	std::string path = std::string(controller->path()) + "/cgroup.subtree_control";

	if (!base::WriteStringToFile(str, path)) {
	LOG(ERROR) << "Failed to activate controller " << controller->name();
	return false;
	}
	}
	}
	} else {
	// mkdir <path> [mode] [owner] [group]
	if (!Mkdir(controller->path(), descriptor.mode(), descriptor.uid(), descriptor.gid())) {
	LOG(ERROR) << "Failed to create directory for " << controller->name() << " cgroup";
	return false;
	}

	// Unfortunately historically cpuset controller was mounted using a mount command
	// different from all other controllers. This results in controller attributes not
	// to be prepended with controller name. For example this way instead of
	// /dev/cpuset/cpuset.cpus the attribute becomes /dev/cpuset/cpus which is what
	// the system currently expects.
	if (!strcmp(controller->name(), "cpuset")) {
	// mount cpuset none /dev/cpuset nodev noexec nosuid
	result = mount("none", controller->path(), controller->name(),
	MS_NODEV \| MS_NOEXEC \| MS_NOSUID, nullptr);
	} else {
	// mount cgroup none <path> nodev noexec nosuid <controller>
	result = mount("none", controller->path(), "cgroup", MS_NODEV \| MS_NOEXEC \| MS_NOSUID,
	controller->name());
	}
	}

	if (result < 0) {
	PLOG(ERROR) << "Failed to mount " << controller->name() << " cgroup";
	return false;
	}

	return true;
	}

	#else

	// Stubs for non-Android targets.
	static bool SetupCgroup(const CgroupDescriptor&) {
	return false;
	}

	#endif

	static bool WriteRcFile(const std::map<std::string, CgroupDescriptor>& descriptors) {
	unique_fd fd(TEMP_FAILURE_RETRY(open(CGROUPS_RC_PATH, O_CREAT \| O_WRONLY \| O_TRUNC \| O_CLOEXEC,
	S_IRUSR \| S_IRGRP \| S_IROTH)));
	if (fd < 0) {
	PLOG(ERROR) << "open() failed for " << CGROUPS_RC_PATH;
	return false;
	}

	format::CgroupFile fl;
	fl.version_ = format::CgroupFile::FILE_CURR_VERSION;
	fl.controller_count_ = descriptors.size();
	int ret = TEMP_FAILURE_RETRY(write(fd, &fl, sizeof(fl)));
	if (ret < 0) {
	PLOG(ERROR) << "write() failed for " << CGROUPS_RC_PATH;
	return false;
	}

	for (const auto& [name, descriptor] : descriptors) {
	ret = TEMP_FAILURE_RETRY(
	write(fd, descriptor.controller(), sizeof(format::CgroupController)));
	if (ret < 0) {
	PLOG(ERROR) << "write() failed for " << CGROUPS_RC_PATH;
	return false;
	}
	}

	return true;
	}

	CgroupDescriptor::CgroupDescriptor(uint32_t version, const std::string& name,
	const std::string& path, mode_t mode, const std::string& uid,
	const std::string& gid, uint32_t flags = 0)
	: controller_(version, flags, name, path), mode_(mode), uid_(uid), gid_(gid) {}

	void CgroupDescriptor::set_mounted(bool mounted) {
	uint32_t flags = controller_.flags();
	if (mounted) {
	flags \|= CGROUPRC_CONTROLLER_FLAG_MOUNTED;
	} else {
	flags &= ~CGROUPRC_CONTROLLER_FLAG_MOUNTED;
	}
	controller_.set_flags(flags);
	}

	} // namespace cgrouprc
	} // namespace android

	bool CgroupSetup() {
	using namespace android::cgrouprc;

	std::map<std::string, CgroupDescriptor> descriptors;

	if (getpid() != 1) {
	LOG(ERROR) << "Cgroup setup can be done only by init process";
	return false;
	}

	// Make sure we do this only one time. No need for std::call_once because
	// init is a single-threaded process
	if (access(CGROUPS_RC_PATH, F_OK) == 0) {
	LOG(WARNING) << "Attempt to call SetupCgroups more than once";
	return true;
	}

	// load cgroups.json file
	if (!ReadDescriptors(&descriptors)) {
	LOG(ERROR) << "Failed to load cgroup description file";
	return false;
	}

	// setup cgroups
	for (auto& [name, descriptor] : descriptors) {
	if (SetupCgroup(descriptor)) {
	descriptor.set_mounted(true);
	} else {
	// issue a warning and proceed with the next cgroup
	LOG(WARNING) << "Failed to setup " << name << " cgroup";
	}
	}

	// mkdir <CGROUPS_RC_DIR> 0711 system system
	if (!Mkdir(android::base::Dirname(CGROUPS_RC_PATH), 0711, "system", "system")) {
	LOG(ERROR) << "Failed to create directory for " << CGROUPS_RC_PATH << " file";
	return false;
	}

	// Generate <CGROUPS_RC_FILE> file which can be directly mmapped into
	// process memory. This optimizes performance, memory usage
	// and limits infrormation shared with unprivileged processes
	// to the minimum subset of information from cgroups.json
	if (!WriteRcFile(descriptors)) {
	LOG(ERROR) << "Failed to write " << CGROUPS_RC_PATH << " file";
	return false;
	}

	// chmod 0644 <CGROUPS_RC_PATH>
	if (fchmodat(AT_FDCWD, CGROUPS_RC_PATH, 0644, AT_SYMLINK_NOFOLLOW) < 0) {
	PLOG(ERROR) << "fchmodat() failed";
	return false;
	}

	return true;
	}