fs_mgr/fs_mgr_remount.cpp - third_party/android/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.
  */

 #include <errno.h>
 #include <getopt.h>
 #include <stdio.h>
 #include <sys/mount.h>
 #include <sys/types.h>
 #include <sys/vfs.h>
 #include <unistd.h>

 #include <iostream>
 #include <string>
 #include <thread>
 #include <utility>
 #include <vector>

 #include <android-base/file.h>
 #include <android-base/logging.h>
 #include <android-base/properties.h>
 #include <android-base/strings.h>
 #include <android/os/IVold.h>
 #include <binder/IServiceManager.h>
 #include <binder/ProcessState.h>
 #include <bootloader_message/bootloader_message.h>
 #include <cutils/android_reboot.h>
 #include <fs_mgr_overlayfs.h>
 #include <fs_mgr_priv.h>
 #include <fstab/fstab.h>
 #include <libavb_user/libavb_user.h>
 #include <libgsi/libgsid.h>

 #include "fs_mgr_priv_overlayfs.h"

 using namespace std::literals;
 using android::fs_mgr::Fstab;
 using android::fs_mgr::FstabEntry;

 namespace {

 void usage() {
     const std::string progname = getprogname();
     if (progname == "disable-verity" || progname == "enable-verity" ||
         progname == "set-verity-state") {
         std::cout << "Usage: disable-verity\n"
                   << "       enable-verity\n"
                   << "       set-verity-state [0|1]\n"
                   << R"(
 Options:
     -h --help       this help
     -R --reboot     automatic reboot if needed for new settings to take effect
     -v --verbose    be noisy)"
                   << std::endl;
     } else {
         std::cout << "Usage: " << progname << " [-h] [-R] [-T fstab_file] [partition]...\n"
                   << R"(
 Options:
     -h --help       this help
     -R --reboot     disable verity & reboot to facilitate remount
     -v --verbose    be noisy
     -T --fstab      custom fstab file location
     partition       specific partition(s) (empty does all)

 Remount specified partition(s) read-write, by name or mount point.
 -R notwithstanding, verity must be disabled on partition(s).
 -R within a DSU guest system reboots into the DSU instead of the host system,
 this command would enable DSU (one-shot) if not already enabled.)"
                   << std::endl;
     }
 }

 const std::string system_mount_point(const android::fs_mgr::FstabEntry& entry) {
     if (entry.mount_point == "/") return "/system";
     return entry.mount_point;
 }

 const FstabEntry* GetWrappedEntry(const Fstab& overlayfs_candidates, const FstabEntry& entry) {
     auto mount_point = system_mount_point(entry);
     auto it = std::find_if(overlayfs_candidates.begin(), overlayfs_candidates.end(),
                            [&mount_point](const auto& entry) {
                                return android::base::StartsWith(mount_point,
                                                                 system_mount_point(entry) + "/");
                            });
     if (it == overlayfs_candidates.end()) return nullptr;
     return &(*it);
 }

 class MyLogger {
   public:
     explicit MyLogger(bool verbose) : verbose_(verbose) {}

     void operator()(android::base::LogId id, android::base::LogSeverity severity, const char* tag,
                     const char* file, unsigned int line, const char* message) {
         // By default, print ERROR logs and logs of this program (does not start with '[')
         // Print [libfs_mgr] INFO logs only if -v is given.
         if (verbose_ || severity >= android::base::ERROR || message[0] != '[') {
             fprintf(stderr, "%s\n", message);
         }
         logd_(id, severity, tag, file, line, message);
     }

   private:
     android::base::LogdLogger logd_;
     bool verbose_;
 };

 [[noreturn]] void reboot(const std::string& name) {
     LOG(INFO) << "Rebooting device for new settings to take effect";
     ::sync();
     android::base::SetProperty(ANDROID_RB_PROPERTY, "reboot," + name);
     ::sleep(60);
     LOG(ERROR) << "Failed to reboot";
     ::exit(1);
 }

 static android::sp<android::os::IVold> GetVold() {
     while (true) {
         if (auto sm = android::defaultServiceManager()) {
             if (auto binder = sm->getService(android::String16("vold"))) {
                 if (auto vold = android::interface_cast<android::os::IVold>(binder)) {
                     return vold;
                 }
             }
         }
         std::this_thread::sleep_for(2s);
     }
 }

 static bool ReadFstab(const char* fstab_file, android::fs_mgr::Fstab* fstab) {
     if (fstab_file) {
         return android::fs_mgr::ReadFstabFromFile(fstab_file, fstab);
     }
     if (!android::fs_mgr::ReadDefaultFstab(fstab)) {
         return false;
     }

     // Manufacture a / entry from /proc/mounts if missing.
     if (!GetEntryForMountPoint(fstab, "/system") && !GetEntryForMountPoint(fstab, "/")) {
         android::fs_mgr::Fstab mounts;
         if (android::fs_mgr::ReadFstabFromFile("/proc/mounts", &mounts)) {
             if (auto entry = GetEntryForMountPoint(&mounts, "/")) {
                 if (entry->fs_type != "rootfs") fstab->emplace_back(*entry);
             }
         }
     }
     return true;
 }

 bool VerifyCheckpointing() {
     if (!android::base::GetBoolProperty("ro.virtual_ab.enabled", false) &&
         !android::base::GetBoolProperty("ro.virtual_ab.retrofit", false)) {
         return true;
     }

     // Virtual A/B devices can use /data as backing storage; make sure we're
     // not checkpointing.
     auto vold = GetVold();
     bool checkpointing = false;
     if (!vold->isCheckpointing(&checkpointing).isOk()) {
         LOG(ERROR) << "Could not determine checkpointing status.";
         return false;
     }
     if (checkpointing) {
         LOG(ERROR) << "Cannot use remount when a checkpoint is in progress.";
         LOG(ERROR) << "To force end checkpointing, call 'vdc checkpoint commitChanges'";
         LOG(ERROR) << "Warning: this can lead to data corruption if rolled back.";
         return false;
     }
     return true;
 }

 static bool IsRemountable(Fstab& candidates, const FstabEntry& entry) {
     if (entry.fs_mgr_flags.vold_managed || entry.fs_mgr_flags.recovery_only ||
         entry.fs_mgr_flags.slot_select_other) {
         return false;
     }
     if (!(entry.flags & MS_RDONLY)) {
         return false;
     }
     if (entry.fs_type == "vfat") {
         return false;
     }
     if (auto candidate_entry = GetEntryForMountPoint(&candidates, entry.mount_point)) {
         return candidate_entry->fs_type == entry.fs_type;
     }
     if (GetWrappedEntry(candidates, entry)) {
         return false;
     }
     return true;
 }

 static Fstab::const_iterator FindPartition(const Fstab& fstab, const std::string& partition) {
     Fstab mounts;
     if (!android::fs_mgr::ReadFstabFromFile("/proc/mounts", &mounts)) {
         LOG(ERROR) << "Failed to read /proc/mounts";
         return fstab.end();
     }

     for (auto iter = fstab.begin(); iter != fstab.end(); iter++) {
         const auto mount_point = system_mount_point(*iter);
         if (partition == mount_point || partition == android::base::Basename(mount_point)) {
             // In case fstab has multiple entries, pick the one that matches the
             // actual mounted filesystem type.
             auto proc_mount_point = (iter->mount_point == "/system") ? "/" : iter->mount_point;
             auto mounted = GetEntryForMountPoint(&mounts, proc_mount_point);
             if (mounted && mounted->fs_type == iter->fs_type) {
                 return iter;
             }
         }
     }
     return fstab.end();
 }

 static Fstab GetAllRemountablePartitions(Fstab& fstab) {
     auto candidates = fs_mgr_overlayfs_candidate_list(fstab);

     Fstab partitions;
     for (const auto& entry : fstab) {
         if (IsRemountable(candidates, entry)) {
             partitions.emplace_back(entry);
         }
     }
     return partitions;
 }

 bool GetRemountList(const Fstab& fstab, const std::vector<std::string>& argv, Fstab* partitions) {
     auto candidates = fs_mgr_overlayfs_candidate_list(fstab);

     for (const auto& arg : argv) {
         std::string partition = arg;
         if (partition == "/") {
             partition = "/system";
         }

         auto it = FindPartition(fstab, partition);
         if (it == fstab.end()) {
             LOG(ERROR) << "Unknown partition " << arg;
             return false;
         }

         const FstabEntry* entry = &*it;
         if (auto wrap = GetWrappedEntry(candidates, *entry); wrap != nullptr) {
             LOG(INFO) << "partition " << arg << " covered by overlayfs for " << wrap->mount_point
                       << ", switching";
             entry = wrap;
         }

         // If it's already remounted, include it so it gets gracefully skipped
         // later on.
         if (!fs_mgr_overlayfs_already_mounted(entry->mount_point) &&
             !IsRemountable(candidates, *entry)) {
             LOG(ERROR) << "Invalid partition " << arg;
             return false;
         }
         if (GetEntryForMountPoint(partitions, entry->mount_point) != nullptr) {
             continue;
         }
         partitions->emplace_back(*entry);
     }

     return true;
 }

 struct RemountCheckResult {
     bool reboot_later = false;
     bool setup_overlayfs = false;
     bool disabled_verity = false;
     bool verity_error = false;
     bool remounted_anything = false;
 };

 bool CheckOverlayfs(Fstab* partitions, RemountCheckResult* result) {
     bool ok = true;
     for (auto it = partitions->begin(); it != partitions->end();) {
         auto& entry = *it;
         const auto& mount_point = entry.mount_point;

         if (fs_mgr_wants_overlayfs(&entry)) {
             bool want_reboot = false;
             bool force = result->disabled_verity;
             if (!fs_mgr_overlayfs_setup(*partitions, mount_point.c_str(), &want_reboot, force)) {
                 LOG(ERROR) << "Overlayfs setup for " << mount_point << " failed, skipping";
                 ok = false;
                 it = partitions->erase(it);
                 continue;
             }
             if (want_reboot) {
                 LOG(INFO) << "Using overlayfs for " << mount_point;
                 result->reboot_later = true;
                 result->setup_overlayfs = true;
             }
         }
         it++;
     }
     return ok;
 }

 bool EnableDsuIfNeeded() {
     auto gsid = android::gsi::GetGsiService();
     if (!gsid) {
         return true;
     }

     auto dsu_running = false;
     if (auto status = gsid->isGsiRunning(&dsu_running); !status.isOk()) {
         LOG(ERROR) << "Failed to get DSU running state: " << status;
         return false;
     }
     auto dsu_enabled = false;
     if (auto status = gsid->isGsiEnabled(&dsu_enabled); !status.isOk()) {
         LOG(ERROR) << "Failed to get DSU enabled state: " << status;
         return false;
     }
     if (dsu_running && !dsu_enabled) {
         std::string dsu_slot;
         if (auto status = gsid->getActiveDsuSlot(&dsu_slot); !status.isOk()) {
             LOG(ERROR) << "Failed to get active DSU slot: " << status;
             return false;
         }
         LOG(INFO) << "DSU is running but disabled, enable DSU so that we stay within the "
                      "DSU guest system after reboot";
         int error = 0;
         if (auto status = gsid->enableGsi(/* oneShot = */ true, dsu_slot, &error); !status.isOk()) {
             LOG(ERROR) << "Failed to enable DSU: " << status;
             return false;
         }
         if (error != android::gsi::IGsiService::INSTALL_OK) {
             LOG(ERROR) << "Failed to enable DSU, error code: " << error;
             return false;
         }
         LOG(INFO) << "Successfully enabled DSU (one-shot mode)";
     }
     return true;
 }

 bool RemountPartition(Fstab& fstab, Fstab& mounts, FstabEntry& entry) {
     // unlock the r/o key for the mount point device
     if (entry.fs_mgr_flags.logical) {
         fs_mgr_update_logical_partition(&entry);
     }
     auto blk_device = entry.blk_device;
     auto mount_point = entry.mount_point;

     auto found = false;
     for (auto it = mounts.rbegin(); it != mounts.rend(); ++it) {
         auto& rentry = *it;
         if (mount_point == rentry.mount_point) {
             blk_device = rentry.blk_device;
             found = true;
             break;
         }
         // Find overlayfs mount point?
         if ((mount_point == "/" && rentry.mount_point == "/system") ||
             (mount_point == "/system" && rentry.mount_point == "/")) {
             blk_device = rentry.blk_device;
             mount_point = "/system";
             found = true;
             break;
         }
     }
     if (!found) {
         PLOG(INFO) << "skip unmounted partition dev:" << blk_device << " mnt:" << mount_point;
         return true;
     }
     if (blk_device == "/dev/root") {
         auto from_fstab = GetEntryForMountPoint(&fstab, mount_point);
         if (from_fstab) blk_device = from_fstab->blk_device;
     }
     fs_mgr_set_blk_ro(blk_device, false);

     // Find system-as-root mount point?
     if ((mount_point == "/system") && !GetEntryForMountPoint(&mounts, mount_point) &&
         GetEntryForMountPoint(&mounts, "/")) {
         mount_point = "/";
     }

     // Now remount!
     for (const auto& mnt_point : {mount_point, entry.mount_point}) {
         if (::mount(blk_device.c_str(), mnt_point.c_str(), entry.fs_type.c_str(), MS_REMOUNT,
                     nullptr) == 0) {
             LOG(INFO) << "Remounted " << mnt_point << " as RW";
             return true;
         }
         if (errno != EINVAL || mount_point == entry.mount_point) {
             break;
         }
     }

     PLOG(ERROR) << "failed to remount partition dev:" << blk_device << " mnt:" << mount_point;
     return false;
 }

 struct SetVerityStateResult {
     bool success = false;
     bool want_reboot = false;
 };

 SetVerityStateResult SetVerityState(bool enable_verity) {
     const auto ab_suffix = android::base::GetProperty("ro.boot.slot_suffix", "");
     std::unique_ptr<AvbOps, decltype(&avb_ops_user_free)> ops(avb_ops_user_new(),
                                                               &avb_ops_user_free);
     if (!ops) {
         LOG(ERROR) << "Error getting AVB ops";
         return {};
     }
     if (!avb_user_verity_set(ops.get(), ab_suffix.c_str(), enable_verity)) {
         LOG(ERROR) << "Error setting verity state";
         return {};
     }
     bool verification_enabled = false;
     if (!avb_user_verification_get(ops.get(), ab_suffix.c_str(), &verification_enabled)) {
         LOG(ERROR) << "Error getting verification state";
         return {};
     }
     if (!verification_enabled) {
         LOG(WARNING) << "AVB verification is disabled, "
                      << (enable_verity ? "enabling" : "disabling")
                      << " verity state may have no effect";
         return {.success = true, .want_reboot = false};
     }
     const auto verity_mode = android::base::GetProperty("ro.boot.veritymode", "");
     const bool was_enabled = (verity_mode != "disabled");
     if ((was_enabled && enable_verity) || (!was_enabled && !enable_verity)) {
         LOG(INFO) << "Verity is already " << (enable_verity ? "enabled" : "disabled");
         return {.success = true, .want_reboot = false};
     }
     LOG(INFO) << "Successfully " << (enable_verity ? "enabled" : "disabled") << " verity";
     return {.success = true, .want_reboot = true};
 }

 bool SetupOrTeardownOverlayfs(bool enable) {
     bool want_reboot = false;
     if (enable) {
         Fstab fstab;
         if (!ReadDefaultFstab(&fstab)) {
             LOG(ERROR) << "Could not read fstab.";
             return want_reboot;
         }
         if (!fs_mgr_overlayfs_setup(fstab, nullptr, &want_reboot)) {
             LOG(ERROR) << "Overlayfs setup failed.";
             return want_reboot;
         }
         if (want_reboot) {
             printf("enabling overlayfs\n");
         }
     } else {
         auto rv = fs_mgr_overlayfs_teardown(nullptr, &want_reboot);
         if (rv == OverlayfsTeardownResult::Error) {
             LOG(ERROR) << "Overlayfs teardown failed.";
             return want_reboot;
         }
         if (rv == OverlayfsTeardownResult::Busy) {
             LOG(ERROR) << "Overlayfs is still active until reboot.";
             return true;
         }
         if (want_reboot) {
             printf("disabling overlayfs\n");
         }
     }
     return want_reboot;
 }

 bool do_remount(Fstab& fstab, const std::vector<std::string>& partition_args,
                 RemountCheckResult* check_result) {
     Fstab partitions;
     if (partition_args.empty()) {
         partitions = GetAllRemountablePartitions(fstab);
     } else {
         if (!GetRemountList(fstab, partition_args, &partitions)) {
             return false;
         }
     }

     // Disable verity.
     auto verity_result = SetVerityState(false /* enable_verity */);

     // Treat error as fatal and suggest reboot only if verity is enabled.
     // TODO(b/260041315): We check the device mapper for any "<partition>-verity" device present
     // instead of checking ro.boot.veritymode because emulator has incorrect property value.
     bool must_disable_verity = false;
     for (const auto& partition : partitions) {
         if (fs_mgr_is_verity_enabled(partition)) {
             must_disable_verity = true;
             break;
         }
     }
     if (must_disable_verity) {
         if (!verity_result.success) {
             return false;
         }
         if (verity_result.want_reboot) {
             check_result->reboot_later = true;
             check_result->disabled_verity = true;
         }
     }

     // Optionally setup overlayfs backing.
     bool ok = CheckOverlayfs(&partitions, check_result);

     if (partitions.empty() || check_result->disabled_verity) {
         if (partitions.empty()) {
             LOG(WARNING) << "No remountable partitions were found.";
         }
         return ok;
     }

     // Mount overlayfs.
     if (!fs_mgr_overlayfs_mount_all(&partitions)) {
         LOG(WARNING) << "Cannot mount overlayfs for some partitions";
         // Continue regardless to handle raw remount case.
     }

     // Get actual mounts _after_ overlayfs has been added.
     android::fs_mgr::Fstab mounts;
     if (!android::fs_mgr::ReadFstabFromFile("/proc/mounts", &mounts) || mounts.empty()) {
         PLOG(ERROR) << "Failed to read /proc/mounts";
         return false;
     }

     // Remount selected partitions.
     for (auto& entry : partitions) {
         if (RemountPartition(fstab, mounts, entry)) {
             check_result->remounted_anything = true;
         } else {
             ok = false;
         }
     }
     return ok;
 }

 }  // namespace

 int main(int argc, char* argv[]) {
     // Do not use MyLogger() when running as clean_scratch_files, as stdout/stderr of daemon process
     // are discarded.
     if (argc > 0 && android::base::Basename(argv[0]) == "clean_scratch_files"s) {
         android::fs_mgr::CleanupOldScratchFiles();
         return EXIT_SUCCESS;
     }

     android::base::InitLogging(argv, MyLogger(false /* verbose */));

     const char* fstab_file = nullptr;
     bool auto_reboot = false;
     bool verbose = false;
     std::vector<std::string> partition_args;

     struct option longopts[] = {
             {"fstab", required_argument, nullptr, 'T'},
             {"help", no_argument, nullptr, 'h'},
             {"reboot", no_argument, nullptr, 'R'},
             {"verbose", no_argument, nullptr, 'v'},
             {0, 0, nullptr, 0},
     };
     for (int opt; (opt = ::getopt_long(argc, argv, "hRT:v", longopts, nullptr)) != -1;) {
         switch (opt) {
             case 'h':
                 usage();
                 return EXIT_SUCCESS;
             case 'R':
                 auto_reboot = true;
                 break;
             case 'T':
                 if (fstab_file) {
                     LOG(ERROR) << "Cannot supply two fstabs: -T " << fstab_file << " -T " << optarg;
                     usage();
                     return EXIT_FAILURE;
                 }
                 fstab_file = optarg;
                 break;
             case 'v':
                 verbose = true;
                 break;
             default:
                 LOG(ERROR) << "Bad argument -" << char(opt);
                 usage();
                 return EXIT_FAILURE;
         }
     }

     if (verbose) {
         android::base::SetLogger(MyLogger(verbose));
     }

     bool remount = false;
     bool enable_verity = false;
     const std::string progname = getprogname();
     if (progname == "enable-verity") {
         enable_verity = true;
     } else if (progname == "disable-verity") {
         enable_verity = false;
     } else if (progname == "set-verity-state") {
         if (optind < argc && (argv[optind] == "1"s || argv[optind] == "0"s)) {
             enable_verity = (argv[optind] == "1"s);
         } else {
             usage();
             return EXIT_FAILURE;
         }
     } else {
         remount = true;
         for (; optind < argc; ++optind) {
             partition_args.emplace_back(argv[optind]);
         }
     }

     // Make sure we are root.
     if (::getuid() != 0) {
         LOG(ERROR) << "Not running as root. Try \"adb root\" first.";
         return EXIT_FAILURE;
     }

     // If somehow this executable is delivered on a "user" build, it can
     // not function, so providing a clear message to the caller rather than
     // letting if fall through and provide a lot of confusing failure messages.
     if (!ALLOW_ADBD_DISABLE_VERITY || !android::base::GetBoolProperty("ro.debuggable", false)) {
         LOG(ERROR) << "Device must be userdebug build";
         return EXIT_FAILURE;
     }

     if (android::base::GetProperty("ro.boot.verifiedbootstate", "") != "orange") {
         LOG(ERROR) << "Device must be bootloader unlocked";
         return EXIT_FAILURE;
     }

     // Start a threadpool to service waitForService() callbacks as
     // fs_mgr_overlayfs_* might call waitForService() to get the image service.
     android::ProcessState::self()->startThreadPool();

     if (!remount) {
         auto ret = SetVerityState(enable_verity);

         // Disable any overlayfs unconditionally if we want verity enabled.
         // Enable overlayfs only if verity is successfully disabled or is already disabled.
         if (enable_verity || ret.success) {
             ret.want_reboot |= SetupOrTeardownOverlayfs(!enable_verity);
         }

         if (ret.want_reboot) {
             if (auto_reboot) {
                 reboot(progname);
             }
             std::cout << "Reboot the device for new settings to take effect" << std::endl;
         }
         return ret.success ? EXIT_SUCCESS : EXIT_FAILURE;
     }

     // Make sure checkpointing is disabled if necessary.
     if (!VerifyCheckpointing()) {
         return EXIT_FAILURE;
     }

     // Read the selected fstab.
     Fstab fstab;
     if (!ReadFstab(fstab_file, &fstab) || fstab.empty()) {
         PLOG(ERROR) << "Failed to read fstab";
         return EXIT_FAILURE;
     }

     RemountCheckResult check_result;
     bool remount_success = do_remount(fstab, partition_args, &check_result);

     if (check_result.disabled_verity && check_result.setup_overlayfs) {
         LOG(INFO) << "Verity disabled; overlayfs enabled.";
     } else if (check_result.disabled_verity) {
         LOG(INFO) << "Verity disabled.";
     } else if (check_result.setup_overlayfs) {
         LOG(INFO) << "Overlayfs enabled.";
     }
     if (remount_success && check_result.remounted_anything) {
         LOG(INFO) << "Remount succeeded";
     } else if (!remount_success) {
         LOG(ERROR) << "Remount failed";
     }
     if (check_result.reboot_later) {
         if (auto_reboot) {
             // If (1) remount requires a reboot to take effect, (2) system is currently
             // running a DSU guest and (3) DSU is disabled, then enable DSU so that the
             // next reboot would not take us back to the host system but stay within
             // the guest system.
             if (!EnableDsuIfNeeded()) {
                 LOG(ERROR) << "Unable to automatically enable DSU";
                 return EXIT_FAILURE;
             }
             reboot("remount");
         } else {
             LOG(INFO) << "Now reboot your device for settings to take effect";
         }
         return EXIT_SUCCESS;
     }
     return remount_success ? EXIT_SUCCESS : EXIT_FAILURE;
 }
	/*
	* 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.
	*/

	#include <errno.h>
	#include <getopt.h>
	#include <stdio.h>
	#include <sys/mount.h>
	#include <sys/types.h>
	#include <sys/vfs.h>
	#include <unistd.h>

	#include <iostream>
	#include <string>
	#include <thread>
	#include <utility>
	#include <vector>

	#include <android-base/file.h>
	#include <android-base/logging.h>
	#include <android-base/properties.h>
	#include <android-base/strings.h>
	#include <android/os/IVold.h>
	#include <binder/IServiceManager.h>
	#include <binder/ProcessState.h>
	#include <bootloader_message/bootloader_message.h>
	#include <cutils/android_reboot.h>
	#include <fs_mgr_overlayfs.h>
	#include <fs_mgr_priv.h>
	#include <fstab/fstab.h>
	#include <libavb_user/libavb_user.h>
	#include <libgsi/libgsid.h>

	#include "fs_mgr_priv_overlayfs.h"

	using namespace std::literals;
	using android::fs_mgr::Fstab;
	using android::fs_mgr::FstabEntry;

	namespace {

	void usage() {
	const std::string progname = getprogname();
	if (progname == "disable-verity" \|\| progname == "enable-verity" \|\|
	progname == "set-verity-state") {
	std::cout << "Usage: disable-verity\n"
	<< " enable-verity\n"
	<< " set-verity-state [0\|1]\n"
	<< R"(
	Options:
	-h --help this help
	-R --reboot automatic reboot if needed for new settings to take effect
	-v --verbose be noisy)"
	<< std::endl;
	} else {
	std::cout << "Usage: " << progname << " [-h] [-R] [-T fstab_file] [partition]...\n"
	<< R"(
	Options:
	-h --help this help
	-R --reboot disable verity & reboot to facilitate remount
	-v --verbose be noisy
	-T --fstab custom fstab file location
	partition specific partition(s) (empty does all)

	Remount specified partition(s) read-write, by name or mount point.
	-R notwithstanding, verity must be disabled on partition(s).
	-R within a DSU guest system reboots into the DSU instead of the host system,
	this command would enable DSU (one-shot) if not already enabled.)"
	<< std::endl;
	}
	}

	const std::string system_mount_point(const android::fs_mgr::FstabEntry& entry) {
	if (entry.mount_point == "/") return "/system";
	return entry.mount_point;
	}

	const FstabEntry* GetWrappedEntry(const Fstab& overlayfs_candidates, const FstabEntry& entry) {
	auto mount_point = system_mount_point(entry);
	auto it = std::find_if(overlayfs_candidates.begin(), overlayfs_candidates.end(),
	[&mount_point](const auto& entry) {
	return android::base::StartsWith(mount_point,
	system_mount_point(entry) + "/");
	});
	if (it == overlayfs_candidates.end()) return nullptr;
	return &(*it);
	}

	class MyLogger {
	public:
	explicit MyLogger(bool verbose) : verbose_(verbose) {}

	void operator()(android::base::LogId id, android::base::LogSeverity severity, const char* tag,
	const char* file, unsigned int line, const char* message) {
	// By default, print ERROR logs and logs of this program (does not start with '[')
	// Print [libfs_mgr] INFO logs only if -v is given.
	if (verbose_ \|\| severity >= android::base::ERROR \|\| message[0] != '[') {
	fprintf(stderr, "%s\n", message);
	}
	logd_(id, severity, tag, file, line, message);
	}

	private:
	android::base::LogdLogger logd_;
	bool verbose_;
	};

	[[noreturn]] void reboot(const std::string& name) {
	LOG(INFO) << "Rebooting device for new settings to take effect";
	::sync();
	android::base::SetProperty(ANDROID_RB_PROPERTY, "reboot," + name);
	::sleep(60);
	LOG(ERROR) << "Failed to reboot";
	::exit(1);
	}

	static android::sp<android::os::IVold> GetVold() {
	while (true) {
	if (auto sm = android::defaultServiceManager()) {
	if (auto binder = sm->getService(android::String16("vold"))) {
	if (auto vold = android::interface_cast<android::os::IVold>(binder)) {
	return vold;
	}
	}
	}
	std::this_thread::sleep_for(2s);
	}
	}

	static bool ReadFstab(const char* fstab_file, android::fs_mgr::Fstab* fstab) {
	if (fstab_file) {
	return android::fs_mgr::ReadFstabFromFile(fstab_file, fstab);
	}
	if (!android::fs_mgr::ReadDefaultFstab(fstab)) {
	return false;
	}

	// Manufacture a / entry from /proc/mounts if missing.
	if (!GetEntryForMountPoint(fstab, "/system") && !GetEntryForMountPoint(fstab, "/")) {
	android::fs_mgr::Fstab mounts;
	if (android::fs_mgr::ReadFstabFromFile("/proc/mounts", &mounts)) {
	if (auto entry = GetEntryForMountPoint(&mounts, "/")) {
	if (entry->fs_type != "rootfs") fstab->emplace_back(*entry);
	}
	}
	}
	return true;
	}

	bool VerifyCheckpointing() {
	if (!android::base::GetBoolProperty("ro.virtual_ab.enabled", false) &&
	!android::base::GetBoolProperty("ro.virtual_ab.retrofit", false)) {
	return true;
	}

	// Virtual A/B devices can use /data as backing storage; make sure we're
	// not checkpointing.
	auto vold = GetVold();
	bool checkpointing = false;
	if (!vold->isCheckpointing(&checkpointing).isOk()) {
	LOG(ERROR) << "Could not determine checkpointing status.";
	return false;
	}
	if (checkpointing) {
	LOG(ERROR) << "Cannot use remount when a checkpoint is in progress.";
	LOG(ERROR) << "To force end checkpointing, call 'vdc checkpoint commitChanges'";
	LOG(ERROR) << "Warning: this can lead to data corruption if rolled back.";
	return false;
	}
	return true;
	}

	static bool IsRemountable(Fstab& candidates, const FstabEntry& entry) {
	if (entry.fs_mgr_flags.vold_managed \|\| entry.fs_mgr_flags.recovery_only \|\|
	entry.fs_mgr_flags.slot_select_other) {
	return false;
	}
	if (!(entry.flags & MS_RDONLY)) {
	return false;
	}
	if (entry.fs_type == "vfat") {
	return false;
	}
	if (auto candidate_entry = GetEntryForMountPoint(&candidates, entry.mount_point)) {
	return candidate_entry->fs_type == entry.fs_type;
	}
	if (GetWrappedEntry(candidates, entry)) {
	return false;
	}
	return true;
	}

	static Fstab::const_iterator FindPartition(const Fstab& fstab, const std::string& partition) {
	Fstab mounts;
	if (!android::fs_mgr::ReadFstabFromFile("/proc/mounts", &mounts)) {
	LOG(ERROR) << "Failed to read /proc/mounts";
	return fstab.end();
	}

	for (auto iter = fstab.begin(); iter != fstab.end(); iter++) {
	const auto mount_point = system_mount_point(*iter);
	if (partition == mount_point \|\| partition == android::base::Basename(mount_point)) {
	// In case fstab has multiple entries, pick the one that matches the
	// actual mounted filesystem type.
	auto proc_mount_point = (iter->mount_point == "/system") ? "/" : iter->mount_point;
	auto mounted = GetEntryForMountPoint(&mounts, proc_mount_point);
	if (mounted && mounted->fs_type == iter->fs_type) {
	return iter;
	}
	}
	}
	return fstab.end();
	}

	static Fstab GetAllRemountablePartitions(Fstab& fstab) {
	auto candidates = fs_mgr_overlayfs_candidate_list(fstab);

	Fstab partitions;
	for (const auto& entry : fstab) {
	if (IsRemountable(candidates, entry)) {
	partitions.emplace_back(entry);
	}
	}
	return partitions;
	}

	bool GetRemountList(const Fstab& fstab, const std::vector<std::string>& argv, Fstab* partitions) {
	auto candidates = fs_mgr_overlayfs_candidate_list(fstab);

	for (const auto& arg : argv) {
	std::string partition = arg;
	if (partition == "/") {
	partition = "/system";
	}

	auto it = FindPartition(fstab, partition);
	if (it == fstab.end()) {
	LOG(ERROR) << "Unknown partition " << arg;
	return false;
	}

	const FstabEntry* entry = &*it;
	if (auto wrap = GetWrappedEntry(candidates, *entry); wrap != nullptr) {
	LOG(INFO) << "partition " << arg << " covered by overlayfs for " << wrap->mount_point
	<< ", switching";
	entry = wrap;
	}

	// If it's already remounted, include it so it gets gracefully skipped
	// later on.
	if (!fs_mgr_overlayfs_already_mounted(entry->mount_point) &&
	!IsRemountable(candidates, *entry)) {
	LOG(ERROR) << "Invalid partition " << arg;
	return false;
	}
	if (GetEntryForMountPoint(partitions, entry->mount_point) != nullptr) {
	continue;
	}
	partitions->emplace_back(*entry);
	}

	return true;
	}

	struct RemountCheckResult {
	bool reboot_later = false;
	bool setup_overlayfs = false;
	bool disabled_verity = false;
	bool verity_error = false;
	bool remounted_anything = false;
	};

	bool CheckOverlayfs(Fstab* partitions, RemountCheckResult* result) {
	bool ok = true;
	for (auto it = partitions->begin(); it != partitions->end();) {
	auto& entry = *it;
	const auto& mount_point = entry.mount_point;

	if (fs_mgr_wants_overlayfs(&entry)) {
	bool want_reboot = false;
	bool force = result->disabled_verity;
	if (!fs_mgr_overlayfs_setup(*partitions, mount_point.c_str(), &want_reboot, force)) {
	LOG(ERROR) << "Overlayfs setup for " << mount_point << " failed, skipping";
	ok = false;
	it = partitions->erase(it);
	continue;
	}
	if (want_reboot) {
	LOG(INFO) << "Using overlayfs for " << mount_point;
	result->reboot_later = true;
	result->setup_overlayfs = true;
	}
	}
	it++;
	}
	return ok;
	}

	bool EnableDsuIfNeeded() {
	auto gsid = android::gsi::GetGsiService();
	if (!gsid) {
	return true;
	}

	auto dsu_running = false;
	if (auto status = gsid->isGsiRunning(&dsu_running); !status.isOk()) {
	LOG(ERROR) << "Failed to get DSU running state: " << status;
	return false;
	}
	auto dsu_enabled = false;
	if (auto status = gsid->isGsiEnabled(&dsu_enabled); !status.isOk()) {
	LOG(ERROR) << "Failed to get DSU enabled state: " << status;
	return false;
	}
	if (dsu_running && !dsu_enabled) {
	std::string dsu_slot;
	if (auto status = gsid->getActiveDsuSlot(&dsu_slot); !status.isOk()) {
	LOG(ERROR) << "Failed to get active DSU slot: " << status;
	return false;
	}
	LOG(INFO) << "DSU is running but disabled, enable DSU so that we stay within the "
	"DSU guest system after reboot";
	int error = 0;
	if (auto status = gsid->enableGsi(/* oneShot = */ true, dsu_slot, &error); !status.isOk()) {
	LOG(ERROR) << "Failed to enable DSU: " << status;
	return false;
	}
	if (error != android::gsi::IGsiService::INSTALL_OK) {
	LOG(ERROR) << "Failed to enable DSU, error code: " << error;
	return false;
	}
	LOG(INFO) << "Successfully enabled DSU (one-shot mode)";
	}
	return true;
	}

	bool RemountPartition(Fstab& fstab, Fstab& mounts, FstabEntry& entry) {
	// unlock the r/o key for the mount point device
	if (entry.fs_mgr_flags.logical) {
	fs_mgr_update_logical_partition(&entry);
	}
	auto blk_device = entry.blk_device;
	auto mount_point = entry.mount_point;

	auto found = false;
	for (auto it = mounts.rbegin(); it != mounts.rend(); ++it) {
	auto& rentry = *it;
	if (mount_point == rentry.mount_point) {
	blk_device = rentry.blk_device;
	found = true;
	break;
	}
	// Find overlayfs mount point?
	if ((mount_point == "/" && rentry.mount_point == "/system") \|\|
	(mount_point == "/system" && rentry.mount_point == "/")) {
	blk_device = rentry.blk_device;
	mount_point = "/system";
	found = true;
	break;
	}
	}
	if (!found) {
	PLOG(INFO) << "skip unmounted partition dev:" << blk_device << " mnt:" << mount_point;
	return true;
	}
	if (blk_device == "/dev/root") {
	auto from_fstab = GetEntryForMountPoint(&fstab, mount_point);
	if (from_fstab) blk_device = from_fstab->blk_device;
	}
	fs_mgr_set_blk_ro(blk_device, false);

	// Find system-as-root mount point?
	if ((mount_point == "/system") && !GetEntryForMountPoint(&mounts, mount_point) &&
	GetEntryForMountPoint(&mounts, "/")) {
	mount_point = "/";
	}

	// Now remount!
	for (const auto& mnt_point : {mount_point, entry.mount_point}) {
	if (::mount(blk_device.c_str(), mnt_point.c_str(), entry.fs_type.c_str(), MS_REMOUNT,
	nullptr) == 0) {
	LOG(INFO) << "Remounted " << mnt_point << " as RW";
	return true;
	}
	if (errno != EINVAL \|\| mount_point == entry.mount_point) {
	break;
	}
	}

	PLOG(ERROR) << "failed to remount partition dev:" << blk_device << " mnt:" << mount_point;
	return false;
	}

	struct SetVerityStateResult {
	bool success = false;
	bool want_reboot = false;
	};

	SetVerityStateResult SetVerityState(bool enable_verity) {
	const auto ab_suffix = android::base::GetProperty("ro.boot.slot_suffix", "");
	std::unique_ptr<AvbOps, decltype(&avb_ops_user_free)> ops(avb_ops_user_new(),
	&avb_ops_user_free);
	if (!ops) {
	LOG(ERROR) << "Error getting AVB ops";
	return {};
	}
	if (!avb_user_verity_set(ops.get(), ab_suffix.c_str(), enable_verity)) {
	LOG(ERROR) << "Error setting verity state";
	return {};
	}
	bool verification_enabled = false;
	if (!avb_user_verification_get(ops.get(), ab_suffix.c_str(), &verification_enabled)) {
	LOG(ERROR) << "Error getting verification state";
	return {};
	}
	if (!verification_enabled) {
	LOG(WARNING) << "AVB verification is disabled, "
	<< (enable_verity ? "enabling" : "disabling")
	<< " verity state may have no effect";
	return {.success = true, .want_reboot = false};
	}
	const auto verity_mode = android::base::GetProperty("ro.boot.veritymode", "");
	const bool was_enabled = (verity_mode != "disabled");
	if ((was_enabled && enable_verity) \|\| (!was_enabled && !enable_verity)) {
	LOG(INFO) << "Verity is already " << (enable_verity ? "enabled" : "disabled");
	return {.success = true, .want_reboot = false};
	}
	LOG(INFO) << "Successfully " << (enable_verity ? "enabled" : "disabled") << " verity";
	return {.success = true, .want_reboot = true};
	}

	bool SetupOrTeardownOverlayfs(bool enable) {
	bool want_reboot = false;
	if (enable) {
	Fstab fstab;
	if (!ReadDefaultFstab(&fstab)) {
	LOG(ERROR) << "Could not read fstab.";
	return want_reboot;
	}
	if (!fs_mgr_overlayfs_setup(fstab, nullptr, &want_reboot)) {
	LOG(ERROR) << "Overlayfs setup failed.";
	return want_reboot;
	}
	if (want_reboot) {
	printf("enabling overlayfs\n");
	}
	} else {
	auto rv = fs_mgr_overlayfs_teardown(nullptr, &want_reboot);
	if (rv == OverlayfsTeardownResult::Error) {
	LOG(ERROR) << "Overlayfs teardown failed.";
	return want_reboot;
	}
	if (rv == OverlayfsTeardownResult::Busy) {
	LOG(ERROR) << "Overlayfs is still active until reboot.";
	return true;
	}
	if (want_reboot) {
	printf("disabling overlayfs\n");
	}
	}
	return want_reboot;
	}

	bool do_remount(Fstab& fstab, const std::vector<std::string>& partition_args,
	RemountCheckResult* check_result) {
	Fstab partitions;
	if (partition_args.empty()) {
	partitions = GetAllRemountablePartitions(fstab);
	} else {
	if (!GetRemountList(fstab, partition_args, &partitions)) {
	return false;
	}
	}

	// Disable verity.
	auto verity_result = SetVerityState(false /* enable_verity */);

	// Treat error as fatal and suggest reboot only if verity is enabled.
	// TODO(b/260041315): We check the device mapper for any "<partition>-verity" device present
	// instead of checking ro.boot.veritymode because emulator has incorrect property value.
	bool must_disable_verity = false;
	for (const auto& partition : partitions) {
	if (fs_mgr_is_verity_enabled(partition)) {
	must_disable_verity = true;
	break;
	}
	}
	if (must_disable_verity) {
	if (!verity_result.success) {
	return false;
	}
	if (verity_result.want_reboot) {
	check_result->reboot_later = true;
	check_result->disabled_verity = true;
	}
	}

	// Optionally setup overlayfs backing.
	bool ok = CheckOverlayfs(&partitions, check_result);

	if (partitions.empty() \|\| check_result->disabled_verity) {
	if (partitions.empty()) {
	LOG(WARNING) << "No remountable partitions were found.";
	}
	return ok;
	}

	// Mount overlayfs.
	if (!fs_mgr_overlayfs_mount_all(&partitions)) {
	LOG(WARNING) << "Cannot mount overlayfs for some partitions";
	// Continue regardless to handle raw remount case.
	}

	// Get actual mounts _after_ overlayfs has been added.
	android::fs_mgr::Fstab mounts;
	if (!android::fs_mgr::ReadFstabFromFile("/proc/mounts", &mounts) \|\| mounts.empty()) {
	PLOG(ERROR) << "Failed to read /proc/mounts";
	return false;
	}

	// Remount selected partitions.
	for (auto& entry : partitions) {
	if (RemountPartition(fstab, mounts, entry)) {
	check_result->remounted_anything = true;
	} else {
	ok = false;
	}
	}
	return ok;
	}

	} // namespace

	int main(int argc, char* argv[]) {
	// Do not use MyLogger() when running as clean_scratch_files, as stdout/stderr of daemon process
	// are discarded.
	if (argc > 0 && android::base::Basename(argv[0]) == "clean_scratch_files"s) {
	android::fs_mgr::CleanupOldScratchFiles();
	return EXIT_SUCCESS;
	}

	android::base::InitLogging(argv, MyLogger(false /* verbose */));

	const char* fstab_file = nullptr;
	bool auto_reboot = false;
	bool verbose = false;
	std::vector<std::string> partition_args;

	struct option longopts[] = {
	{"fstab", required_argument, nullptr, 'T'},
	{"help", no_argument, nullptr, 'h'},
	{"reboot", no_argument, nullptr, 'R'},
	{"verbose", no_argument, nullptr, 'v'},
	{0, 0, nullptr, 0},
	};
	for (int opt; (opt = ::getopt_long(argc, argv, "hRT:v", longopts, nullptr)) != -1;) {
	switch (opt) {
	case 'h':
	usage();
	return EXIT_SUCCESS;
	case 'R':
	auto_reboot = true;
	break;
	case 'T':
	if (fstab_file) {
	LOG(ERROR) << "Cannot supply two fstabs: -T " << fstab_file << " -T " << optarg;
	usage();
	return EXIT_FAILURE;
	}
	fstab_file = optarg;
	break;
	case 'v':
	verbose = true;
	break;
	default:
	LOG(ERROR) << "Bad argument -" << char(opt);
	usage();
	return EXIT_FAILURE;
	}
	}

	if (verbose) {
	android::base::SetLogger(MyLogger(verbose));
	}

	bool remount = false;
	bool enable_verity = false;
	const std::string progname = getprogname();
	if (progname == "enable-verity") {
	enable_verity = true;
	} else if (progname == "disable-verity") {
	enable_verity = false;
	} else if (progname == "set-verity-state") {
	if (optind < argc && (argv[optind] == "1"s \|\| argv[optind] == "0"s)) {
	enable_verity = (argv[optind] == "1"s);
	} else {
	usage();
	return EXIT_FAILURE;
	}
	} else {
	remount = true;
	for (; optind < argc; ++optind) {
	partition_args.emplace_back(argv[optind]);
	}
	}

	// Make sure we are root.
	if (::getuid() != 0) {
	LOG(ERROR) << "Not running as root. Try \"adb root\" first.";
	return EXIT_FAILURE;
	}

	// If somehow this executable is delivered on a "user" build, it can
	// not function, so providing a clear message to the caller rather than
	// letting if fall through and provide a lot of confusing failure messages.
	if (!ALLOW_ADBD_DISABLE_VERITY \|\| !android::base::GetBoolProperty("ro.debuggable", false)) {
	LOG(ERROR) << "Device must be userdebug build";
	return EXIT_FAILURE;
	}

	if (android::base::GetProperty("ro.boot.verifiedbootstate", "") != "orange") {
	LOG(ERROR) << "Device must be bootloader unlocked";
	return EXIT_FAILURE;
	}

	// Start a threadpool to service waitForService() callbacks as
	// fs_mgr_overlayfs_* might call waitForService() to get the image service.
	android::ProcessState::self()->startThreadPool();

	if (!remount) {
	auto ret = SetVerityState(enable_verity);

	// Disable any overlayfs unconditionally if we want verity enabled.
	// Enable overlayfs only if verity is successfully disabled or is already disabled.
	if (enable_verity \|\| ret.success) {
	ret.want_reboot \|= SetupOrTeardownOverlayfs(!enable_verity);
	}

	if (ret.want_reboot) {
	if (auto_reboot) {
	reboot(progname);
	}
	std::cout << "Reboot the device for new settings to take effect" << std::endl;
	}
	return ret.success ? EXIT_SUCCESS : EXIT_FAILURE;
	}

	// Make sure checkpointing is disabled if necessary.
	if (!VerifyCheckpointing()) {
	return EXIT_FAILURE;
	}

	// Read the selected fstab.
	Fstab fstab;
	if (!ReadFstab(fstab_file, &fstab) \|\| fstab.empty()) {
	PLOG(ERROR) << "Failed to read fstab";
	return EXIT_FAILURE;
	}

	RemountCheckResult check_result;
	bool remount_success = do_remount(fstab, partition_args, &check_result);

	if (check_result.disabled_verity && check_result.setup_overlayfs) {
	LOG(INFO) << "Verity disabled; overlayfs enabled.";
	} else if (check_result.disabled_verity) {
	LOG(INFO) << "Verity disabled.";
	} else if (check_result.setup_overlayfs) {
	LOG(INFO) << "Overlayfs enabled.";
	}
	if (remount_success && check_result.remounted_anything) {
	LOG(INFO) << "Remount succeeded";
	} else if (!remount_success) {
	LOG(ERROR) << "Remount failed";
	}
	if (check_result.reboot_later) {
	if (auto_reboot) {
	// If (1) remount requires a reboot to take effect, (2) system is currently
	// running a DSU guest and (3) DSU is disabled, then enable DSU so that the
	// next reboot would not take us back to the host system but stay within
	// the guest system.
	if (!EnableDsuIfNeeded()) {
	LOG(ERROR) << "Unable to automatically enable DSU";
	return EXIT_FAILURE;
	}
	reboot("remount");
	} else {
	LOG(INFO) << "Now reboot your device for settings to take effect";
	}
	return EXIT_SUCCESS;
	}
	return remount_success ? EXIT_SUCCESS : EXIT_FAILURE;
	}