cmds/installd/otapreopt_chroot.cpp - android_frameworks_native - Gitiles

 /*
  ** Copyright 2016, 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 <linux/unistd.h>
 #include <sys/mount.h>
 #include <sys/stat.h>
 #include <sys/wait.h>

 #include <array>
 #include <fstream>
 #include <sstream>

 #include <android-base/file.h>
 #include <android-base/logging.h>
 #include <android-base/macros.h>
 #include <android-base/scopeguard.h>
 #include <android-base/stringprintf.h>
 #include <android-base/unique_fd.h>
 #include <libdm/dm.h>
 #include <selinux/android.h>

 #include "installd_constants.h"
 #include "otapreopt_utils.h"

 #ifndef LOG_TAG
 #define LOG_TAG "otapreopt"
 #endif

 using android::base::StringPrintf;

 namespace android {
 namespace installd {

 static void CloseDescriptor(int fd) {
     if (fd >= 0) {
         int result = close(fd);
         UNUSED(result);  // Ignore result. Printing to logcat will open a new descriptor
                          // that we do *not* want.
     }
 }

 static void CloseDescriptor(const char* descriptor_string) {
     int fd = -1;
     std::istringstream stream(descriptor_string);
     stream >> fd;
     if (!stream.fail()) {
         CloseDescriptor(fd);
     }
 }

 static void ActivateApexPackages() {
     std::vector<std::string> apexd_cmd{"/system/bin/apexd", "--otachroot-bootstrap"};
     std::string apexd_error_msg;

     bool exec_result = Exec(apexd_cmd, &apexd_error_msg);
     if (!exec_result) {
         PLOG(ERROR) << "Running otapreopt failed: " << apexd_error_msg;
         exit(220);
     }
 }

 static void DeactivateApexPackages() {
     std::vector<std::string> apexd_cmd{"/system/bin/apexd", "--unmount-all"};
     std::string apexd_error_msg;
     bool exec_result = Exec(apexd_cmd, &apexd_error_msg);
     if (!exec_result) {
         PLOG(ERROR) << "Running /system/bin/apexd --unmount-all failed: " << apexd_error_msg;
     }
 }

 static void TryExtraMount(const char* name, const char* slot, const char* target) {
     std::string partition_name = StringPrintf("%s%s", name, slot);

     // See whether update_engine mounted a logical partition.
     {
         auto& dm = dm::DeviceMapper::Instance();
         if (dm.GetState(partition_name) != dm::DmDeviceState::INVALID) {
             std::string path;
             if (dm.GetDmDevicePathByName(partition_name, &path)) {
                 int mount_result = mount(path.c_str(),
                                          target,
                                          "ext4",
                                          MS_RDONLY,
                                          /* data */ nullptr);
                 if (mount_result == 0) {
                     return;
                 }
             }
         }
     }

     // Fall back and attempt a direct mount.
     std::string block_device = StringPrintf("/dev/block/by-name/%s", partition_name.c_str());
     int mount_result = mount(block_device.c_str(),
                              target,
                              "ext4",
                              MS_RDONLY,
                              /* data */ nullptr);
     UNUSED(mount_result);
 }

 // Entry for otapreopt_chroot. Expected parameters are:
 //   [cmd] [status-fd] [target-slot] "dexopt" [dexopt-params]
 // The file descriptor denoted by status-fd will be closed. The rest of the parameters will
 // be passed on to otapreopt in the chroot.
 static int otapreopt_chroot(const int argc, char **arg) {
     // Validate arguments
     // We need the command, status channel and target slot, at a minimum.
     if(argc < 3) {
         PLOG(ERROR) << "Not enough arguments.";
         exit(208);
     }
     // Close all file descriptors. They are coming from the caller, we do not want to pass them
     // on across our fork/exec into a different domain.
     // 1) Default descriptors.
     CloseDescriptor(STDIN_FILENO);
     CloseDescriptor(STDOUT_FILENO);
     CloseDescriptor(STDERR_FILENO);
     // 2) The status channel.
     CloseDescriptor(arg[1]);

     // We need to run the otapreopt tool from the postinstall partition. As such, set up a
     // mount namespace and change root.

     // Create our own mount namespace.
     if (unshare(CLONE_NEWNS) != 0) {
         PLOG(ERROR) << "Failed to unshare() for otapreopt.";
         exit(200);
     }

     // Make postinstall private, so that our changes don't propagate.
     if (mount("", "/postinstall", nullptr, MS_PRIVATE, nullptr) != 0) {
         PLOG(ERROR) << "Failed to mount private.";
         exit(201);
     }

     // Bind mount necessary directories.
     constexpr const char* kBindMounts[] = {
             "/data", "/dev", "/proc", "/sys"
     };
     for (size_t i = 0; i < arraysize(kBindMounts); ++i) {
         std::string trg = StringPrintf("/postinstall%s", kBindMounts[i]);
         if (mount(kBindMounts[i], trg.c_str(), nullptr, MS_BIND, nullptr) != 0) {
             PLOG(ERROR) << "Failed to bind-mount " << kBindMounts[i];
             exit(202);
         }
     }

     // Try to mount the vendor partition. update_engine doesn't do this for us, but we
     // want it for vendor APKs.
     // Notes:
     //  1) We pretty much guess a name here and hope to find the partition by name.
     //     It is just as complicated and brittle to scan /proc/mounts. But this requires
     //     validating the target-slot so as not to try to mount some totally random path.
     //  2) We're in a mount namespace here, so when we die, this will be cleaned up.
     //  3) Ignore errors. Printing anything at this stage will open a file descriptor
     //     for logging.
     if (!ValidateTargetSlotSuffix(arg[2])) {
         LOG(ERROR) << "Target slot suffix not legal: " << arg[2];
         exit(207);
     }
     TryExtraMount("vendor", arg[2], "/postinstall/vendor");

     // Try to mount the product partition. update_engine doesn't do this for us, but we
     // want it for product APKs. Same notes as vendor above.
     TryExtraMount("product", arg[2], "/postinstall/product");

     constexpr const char* kPostInstallLinkerconfig = "/postinstall/linkerconfig";
     // Try to mount /postinstall/linkerconfig. we will set it up after performing the chroot
     if (mount("tmpfs", kPostInstallLinkerconfig, "tmpfs", 0, nullptr) != 0) {
         PLOG(ERROR) << "Failed to mount a tmpfs for " << kPostInstallLinkerconfig;
         exit(215);
     }

     // Setup APEX mount point and its security context.
     static constexpr const char* kPostinstallApexDir = "/postinstall/apex";
     // The following logic is similar to the one in system/core/rootdir/init.rc:
     //
     //   mount tmpfs tmpfs /apex nodev noexec nosuid
     //   chmod 0755 /apex
     //   chown root root /apex
     //   restorecon /apex
     //
     // except we perform the `restorecon` step just after mounting the tmpfs
     // filesystem in /postinstall/apex, so that this directory is correctly
     // labeled (with type `postinstall_apex_mnt_dir`) and may be manipulated in
     // following operations (`chmod`, `chown`, etc.) following policies
     // restricted to `postinstall_apex_mnt_dir`:
     //
     //   mount tmpfs tmpfs /postinstall/apex nodev noexec nosuid
     //   restorecon /postinstall/apex
     //   chmod 0755 /postinstall/apex
     //   chown root root /postinstall/apex
     //
     if (mount("tmpfs", kPostinstallApexDir, "tmpfs", MS_NODEV | MS_NOEXEC | MS_NOSUID, nullptr)
         != 0) {
         PLOG(ERROR) << "Failed to mount tmpfs in " << kPostinstallApexDir;
         exit(209);
     }
     if (selinux_android_restorecon(kPostinstallApexDir, 0) < 0) {
         PLOG(ERROR) << "Failed to restorecon " << kPostinstallApexDir;
         exit(214);
     }
     if (chmod(kPostinstallApexDir, 0755) != 0) {
         PLOG(ERROR) << "Failed to chmod " << kPostinstallApexDir << " to 0755";
         exit(210);
     }
     if (chown(kPostinstallApexDir, 0, 0) != 0) {
         PLOG(ERROR) << "Failed to chown " << kPostinstallApexDir << " to root:root";
         exit(211);
     }

     // Chdir into /postinstall.
     if (chdir("/postinstall") != 0) {
         PLOG(ERROR) << "Unable to chdir into /postinstall.";
         exit(203);
     }

     // Make /postinstall the root in our mount namespace.
     if (chroot(".")  != 0) {
         PLOG(ERROR) << "Failed to chroot";
         exit(204);
     }

     if (chdir("/") != 0) {
         PLOG(ERROR) << "Unable to chdir into /.";
         exit(205);
     }

     // Call apexd --unmount-all to free up loop and dm block devices, so that we can re-use
     // them during the next invocation. Since otapreopt_chroot calls exit in case something goes
     // wrong we need to register our own atexit handler.
     // We want to register this handler before actually activating apex packages. This is mostly
     // due to the fact that if fail to unmount apexes, then on the next run of otapreopt_chroot
     // we will ask for new loop devices instead of re-using existing ones, and we really don't want
     // to do that. :)
     if (atexit(DeactivateApexPackages) != 0) {
         LOG(ERROR) << "Failed to register atexit hander";
         exit(206);
     }

     // Try to mount APEX packages in "/apex" in the chroot dir. We need at least
     // the ART APEX, as it is required by otapreopt to run dex2oat.
     ActivateApexPackages();

     auto cleanup = android::base::make_scope_guard([](){
         std::vector<std::string> apexd_cmd{"/system/bin/apexd", "--unmount-all"};
         std::string apexd_error_msg;
         bool exec_result = Exec(apexd_cmd, &apexd_error_msg);
         if (!exec_result) {
             PLOG(ERROR) << "Running /system/bin/apexd --unmount-all failed: " << apexd_error_msg;
         }
     });
     // Check that an ART APEX has been activated; clean up and exit
     // early otherwise.
     static constexpr const std::string_view kRequiredApexs[] = {
       "com.android.art",
       "com.android.runtime",
     };
     std::array<bool, arraysize(kRequiredApexs)> found_apexs{ false, false };
     DIR* apex_dir = opendir("/apex");
     if (apex_dir == nullptr) {
         PLOG(ERROR) << "unable to open /apex";
         exit(220);
     }
     for (dirent* entry = readdir(apex_dir); entry != nullptr; entry = readdir(apex_dir)) {
         for (int i = 0; i < found_apexs.size(); i++) {
             if (kRequiredApexs[i] == std::string_view(entry->d_name)) {
                 found_apexs[i] = true;
                 break;
             }
         }
     }
     closedir(apex_dir);
     auto it = std::find(found_apexs.cbegin(), found_apexs.cend(), false);
     if (it != found_apexs.cend()) {
         LOG(ERROR) << "No activated " << kRequiredApexs[std::distance(found_apexs.cbegin(), it)]
                    << " package!";
         exit(221);
     }

     // Setup /linkerconfig. Doing it after the chroot means it doesn't need its own category
     if (selinux_android_restorecon("/linkerconfig", 0) < 0) {
         PLOG(ERROR) << "Failed to restorecon /linkerconfig";
         exit(219);
     }
     std::vector<std::string> linkerconfig_cmd{"/apex/com.android.runtime/bin/linkerconfig",
                                               "--target", "/linkerconfig"};
     std::string linkerconfig_error_msg;
     bool linkerconfig_exec_result = Exec(linkerconfig_cmd, &linkerconfig_error_msg);
     if (!linkerconfig_exec_result) {
         LOG(ERROR) << "Running linkerconfig failed: " << linkerconfig_error_msg;
         exit(218);
     }

     // Now go on and run otapreopt.

     // Incoming:  cmd + status-fd + target-slot + cmd...      | Incoming | = argc
     // Outgoing:  cmd             + target-slot + cmd...      | Outgoing | = argc - 1
     std::vector<std::string> cmd;
     cmd.reserve(argc);
     cmd.push_back("/system/bin/otapreopt");

     // The first parameter is the status file descriptor, skip.
     for (size_t i = 2; i < static_cast<size_t>(argc); ++i) {
         cmd.push_back(arg[i]);
     }

     // Fork and execute otapreopt in its own process.
     std::string error_msg;
     bool exec_result = Exec(cmd, &error_msg);
     if (!exec_result) {
         LOG(ERROR) << "Running otapreopt failed: " << error_msg;
     }

     if (!exec_result) {
         exit(213);
     }

     return 0;
 }

 }  // namespace installd
 }  // namespace android

 int main(const int argc, char *argv[]) {
     return android::installd::otapreopt_chroot(argc, argv);
 }
	/*
	** Copyright 2016, 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 <linux/unistd.h>
	#include <sys/mount.h>
	#include <sys/stat.h>
	#include <sys/wait.h>

	#include <array>
	#include <fstream>
	#include <sstream>

	#include <android-base/file.h>
	#include <android-base/logging.h>
	#include <android-base/macros.h>
	#include <android-base/scopeguard.h>
	#include <android-base/stringprintf.h>
	#include <android-base/unique_fd.h>
	#include <libdm/dm.h>
	#include <selinux/android.h>

	#include "installd_constants.h"
	#include "otapreopt_utils.h"

	#ifndef LOG_TAG
	#define LOG_TAG "otapreopt"
	#endif

	using android::base::StringPrintf;

	namespace android {
	namespace installd {

	static void CloseDescriptor(int fd) {
	if (fd >= 0) {
	int result = close(fd);
	UNUSED(result); // Ignore result. Printing to logcat will open a new descriptor
	// that we do not want.
	}
	}

	static void CloseDescriptor(const char* descriptor_string) {
	int fd = -1;
	std::istringstream stream(descriptor_string);
	stream >> fd;
	if (!stream.fail()) {
	CloseDescriptor(fd);
	}
	}

	static void ActivateApexPackages() {
	std::vector<std::string> apexd_cmd{"/system/bin/apexd", "--otachroot-bootstrap"};
	std::string apexd_error_msg;

	bool exec_result = Exec(apexd_cmd, &apexd_error_msg);
	if (!exec_result) {
	PLOG(ERROR) << "Running otapreopt failed: " << apexd_error_msg;
	exit(220);
	}
	}

	static void DeactivateApexPackages() {
	std::vector<std::string> apexd_cmd{"/system/bin/apexd", "--unmount-all"};
	std::string apexd_error_msg;
	bool exec_result = Exec(apexd_cmd, &apexd_error_msg);
	if (!exec_result) {
	PLOG(ERROR) << "Running /system/bin/apexd --unmount-all failed: " << apexd_error_msg;
	}
	}

	static void TryExtraMount(const char* name, const char* slot, const char* target) {
	std::string partition_name = StringPrintf("%s%s", name, slot);

	// See whether update_engine mounted a logical partition.
	{
	auto& dm = dm::DeviceMapper::Instance();
	if (dm.GetState(partition_name) != dm::DmDeviceState::INVALID) {
	std::string path;
	if (dm.GetDmDevicePathByName(partition_name, &path)) {
	int mount_result = mount(path.c_str(),
	target,
	"ext4",
	MS_RDONLY,
	/* data */ nullptr);
	if (mount_result == 0) {
	return;
	}
	}
	}
	}

	// Fall back and attempt a direct mount.
	std::string block_device = StringPrintf("/dev/block/by-name/%s", partition_name.c_str());
	int mount_result = mount(block_device.c_str(),
	target,
	"ext4",
	MS_RDONLY,
	/* data */ nullptr);
	UNUSED(mount_result);
	}

	// Entry for otapreopt_chroot. Expected parameters are:
	// [cmd] [status-fd] [target-slot] "dexopt" [dexopt-params]
	// The file descriptor denoted by status-fd will be closed. The rest of the parameters will
	// be passed on to otapreopt in the chroot.
	static int otapreopt_chroot(const int argc, char **arg) {
	// Validate arguments
	// We need the command, status channel and target slot, at a minimum.
	if(argc < 3) {
	PLOG(ERROR) << "Not enough arguments.";
	exit(208);
	}
	// Close all file descriptors. They are coming from the caller, we do not want to pass them
	// on across our fork/exec into a different domain.
	// 1) Default descriptors.
	CloseDescriptor(STDIN_FILENO);
	CloseDescriptor(STDOUT_FILENO);
	CloseDescriptor(STDERR_FILENO);
	// 2) The status channel.
	CloseDescriptor(arg[1]);

	// We need to run the otapreopt tool from the postinstall partition. As such, set up a
	// mount namespace and change root.

	// Create our own mount namespace.
	if (unshare(CLONE_NEWNS) != 0) {
	PLOG(ERROR) << "Failed to unshare() for otapreopt.";
	exit(200);
	}

	// Make postinstall private, so that our changes don't propagate.
	if (mount("", "/postinstall", nullptr, MS_PRIVATE, nullptr) != 0) {
	PLOG(ERROR) << "Failed to mount private.";
	exit(201);
	}

	// Bind mount necessary directories.
	constexpr const char* kBindMounts[] = {
	"/data", "/dev", "/proc", "/sys"
	};
	for (size_t i = 0; i < arraysize(kBindMounts); ++i) {
	std::string trg = StringPrintf("/postinstall%s", kBindMounts[i]);
	if (mount(kBindMounts[i], trg.c_str(), nullptr, MS_BIND, nullptr) != 0) {
	PLOG(ERROR) << "Failed to bind-mount " << kBindMounts[i];
	exit(202);
	}
	}

	// Try to mount the vendor partition. update_engine doesn't do this for us, but we
	// want it for vendor APKs.
	// Notes:
	// 1) We pretty much guess a name here and hope to find the partition by name.
	// It is just as complicated and brittle to scan /proc/mounts. But this requires
	// validating the target-slot so as not to try to mount some totally random path.
	// 2) We're in a mount namespace here, so when we die, this will be cleaned up.
	// 3) Ignore errors. Printing anything at this stage will open a file descriptor
	// for logging.
	if (!ValidateTargetSlotSuffix(arg[2])) {
	LOG(ERROR) << "Target slot suffix not legal: " << arg[2];
	exit(207);
	}
	TryExtraMount("vendor", arg[2], "/postinstall/vendor");

	// Try to mount the product partition. update_engine doesn't do this for us, but we
	// want it for product APKs. Same notes as vendor above.
	TryExtraMount("product", arg[2], "/postinstall/product");

	constexpr const char* kPostInstallLinkerconfig = "/postinstall/linkerconfig";
	// Try to mount /postinstall/linkerconfig. we will set it up after performing the chroot
	if (mount("tmpfs", kPostInstallLinkerconfig, "tmpfs", 0, nullptr) != 0) {
	PLOG(ERROR) << "Failed to mount a tmpfs for " << kPostInstallLinkerconfig;
	exit(215);
	}

	// Setup APEX mount point and its security context.
	static constexpr const char* kPostinstallApexDir = "/postinstall/apex";
	// The following logic is similar to the one in system/core/rootdir/init.rc:
	//
	// mount tmpfs tmpfs /apex nodev noexec nosuid
	// chmod 0755 /apex
	// chown root root /apex
	// restorecon /apex
	//
	// except we perform the `restorecon` step just after mounting the tmpfs
	// filesystem in /postinstall/apex, so that this directory is correctly
	// labeled (with type `postinstall_apex_mnt_dir`) and may be manipulated in
	// following operations (`chmod`, `chown`, etc.) following policies
	// restricted to `postinstall_apex_mnt_dir`:
	//
	// mount tmpfs tmpfs /postinstall/apex nodev noexec nosuid
	// restorecon /postinstall/apex
	// chmod 0755 /postinstall/apex
	// chown root root /postinstall/apex
	//
	if (mount("tmpfs", kPostinstallApexDir, "tmpfs", MS_NODEV \| MS_NOEXEC \| MS_NOSUID, nullptr)
	!= 0) {
	PLOG(ERROR) << "Failed to mount tmpfs in " << kPostinstallApexDir;
	exit(209);
	}
	if (selinux_android_restorecon(kPostinstallApexDir, 0) < 0) {
	PLOG(ERROR) << "Failed to restorecon " << kPostinstallApexDir;
	exit(214);
	}
	if (chmod(kPostinstallApexDir, 0755) != 0) {
	PLOG(ERROR) << "Failed to chmod " << kPostinstallApexDir << " to 0755";
	exit(210);
	}
	if (chown(kPostinstallApexDir, 0, 0) != 0) {
	PLOG(ERROR) << "Failed to chown " << kPostinstallApexDir << " to root:root";
	exit(211);
	}

	// Chdir into /postinstall.
	if (chdir("/postinstall") != 0) {
	PLOG(ERROR) << "Unable to chdir into /postinstall.";
	exit(203);
	}

	// Make /postinstall the root in our mount namespace.
	if (chroot(".") != 0) {
	PLOG(ERROR) << "Failed to chroot";
	exit(204);
	}

	if (chdir("/") != 0) {
	PLOG(ERROR) << "Unable to chdir into /.";
	exit(205);
	}

	// Call apexd --unmount-all to free up loop and dm block devices, so that we can re-use
	// them during the next invocation. Since otapreopt_chroot calls exit in case something goes
	// wrong we need to register our own atexit handler.
	// We want to register this handler before actually activating apex packages. This is mostly
	// due to the fact that if fail to unmount apexes, then on the next run of otapreopt_chroot
	// we will ask for new loop devices instead of re-using existing ones, and we really don't want
	// to do that. :)
	if (atexit(DeactivateApexPackages) != 0) {
	LOG(ERROR) << "Failed to register atexit hander";
	exit(206);
	}

	// Try to mount APEX packages in "/apex" in the chroot dir. We need at least
	// the ART APEX, as it is required by otapreopt to run dex2oat.
	ActivateApexPackages();

	auto cleanup = android::base::make_scope_guard([](){
	std::vector<std::string> apexd_cmd{"/system/bin/apexd", "--unmount-all"};
	std::string apexd_error_msg;
	bool exec_result = Exec(apexd_cmd, &apexd_error_msg);
	if (!exec_result) {
	PLOG(ERROR) << "Running /system/bin/apexd --unmount-all failed: " << apexd_error_msg;
	}
	});
	// Check that an ART APEX has been activated; clean up and exit
	// early otherwise.
	static constexpr const std::string_view kRequiredApexs[] = {
	"com.android.art",
	"com.android.runtime",
	};
	std::array<bool, arraysize(kRequiredApexs)> found_apexs{ false, false };
	DIR* apex_dir = opendir("/apex");
	if (apex_dir == nullptr) {
	PLOG(ERROR) << "unable to open /apex";
	exit(220);
	}
	for (dirent* entry = readdir(apex_dir); entry != nullptr; entry = readdir(apex_dir)) {
	for (int i = 0; i < found_apexs.size(); i++) {
	if (kRequiredApexs[i] == std::string_view(entry->d_name)) {
	found_apexs[i] = true;
	break;
	}
	}
	}
	closedir(apex_dir);
	auto it = std::find(found_apexs.cbegin(), found_apexs.cend(), false);
	if (it != found_apexs.cend()) {
	LOG(ERROR) << "No activated " << kRequiredApexs[std::distance(found_apexs.cbegin(), it)]
	<< " package!";
	exit(221);
	}

	// Setup /linkerconfig. Doing it after the chroot means it doesn't need its own category
	if (selinux_android_restorecon("/linkerconfig", 0) < 0) {
	PLOG(ERROR) << "Failed to restorecon /linkerconfig";
	exit(219);
	}
	std::vector<std::string> linkerconfig_cmd{"/apex/com.android.runtime/bin/linkerconfig",
	"--target", "/linkerconfig"};
	std::string linkerconfig_error_msg;
	bool linkerconfig_exec_result = Exec(linkerconfig_cmd, &linkerconfig_error_msg);
	if (!linkerconfig_exec_result) {
	LOG(ERROR) << "Running linkerconfig failed: " << linkerconfig_error_msg;
	exit(218);
	}

	// Now go on and run otapreopt.

	// Incoming: cmd + status-fd + target-slot + cmd... \| Incoming \| = argc
	// Outgoing: cmd + target-slot + cmd... \| Outgoing \| = argc - 1
	std::vector<std::string> cmd;
	cmd.reserve(argc);
	cmd.push_back("/system/bin/otapreopt");

	// The first parameter is the status file descriptor, skip.
	for (size_t i = 2; i < static_cast<size_t>(argc); ++i) {
	cmd.push_back(arg[i]);
	}

	// Fork and execute otapreopt in its own process.
	std::string error_msg;
	bool exec_result = Exec(cmd, &error_msg);
	if (!exec_result) {
	LOG(ERROR) << "Running otapreopt failed: " << error_msg;
	}

	if (!exec_result) {
	exit(213);
	}

	return 0;
	}

	} // namespace installd
	} // namespace android

	int main(const int argc, char *argv[]) {
	return android::installd::otapreopt_chroot(argc, argv);
	}