android_system_core/init/block_dev_initializer.cpp

// Copyright (C) 2020 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 <chrono>
#include <string_view>
#include <vector>

#include <android-base/chrono_utils.h>
#include <android-base/logging.h>
#include <android-base/strings.h>
#include <fs_mgr.h>

#include "block_dev_initializer.h"

namespace android {
namespace init {

using android::base::Timer;
using namespace std::chrono_literals;

BlockDevInitializer::BlockDevInitializer() : uevent_listener_(16 * 1024 * 1024) {
    auto boot_devices = android::fs_mgr::GetBootDevices();
    device_handler_ = std::make_unique<DeviceHandler>(
            std::vector<Permissions>{}, std::vector<SysfsPermissions>{}, std::vector<Subsystem>{},
            std::vector<Subsystem>{}, std::move(boot_devices), android::fs_mgr::GetBootPartUuid(),
            false);
}

// If boot_part_uuid is specified, use it to set boot_devices
//
// When `androidboot.boot_part_uuid` is specified then that's the partition UUID
// of the kernel. Look for that partition and then set `boot_devices` to be
// exactly one item: the block device containing that partition.
//
// NOTE that `boot_part_uuid` is only specified on newer devices. Older devices
// specified `boot_devices` directly.
bool BlockDevInitializer::InitBootDevicesFromPartUuid() {
    bool uuid_check_done = false;

    auto boot_part_callback = [&, this](const Uevent& uevent) -> ListenerAction {
        uuid_check_done = device_handler_->CheckUeventForBootPartUuid(uevent);
        return uuid_check_done ? ListenerAction::kStop : ListenerAction::kContinue;
    };

    // Re-run already arrived uevents looking for the boot partition UUID.
    //
    // NOTE: If we're not using the boot partition UUID to find the boot
    // device then the first uevent we analyze will cause us to stop looking
    // and set `uuid_check_done`. This will shortcut all of the UUID logic.
    // Replaying one uevent is not expected to be slow.
    uevent_listener_.RegenerateUevents(boot_part_callback);

    // If we're not done looking, poll for uevents for longer
    if (!uuid_check_done) {
        Timer t;
        uevent_listener_.Poll(boot_part_callback, 10s);
        LOG(INFO) << "Wait for boot partition returned after " << t;
    }

    // Give a nicer error message if we were expecting to find the kernel boot
    // partition but didn't. Later code would fail too but the message there
    // is a bit further from the root cause of the problem.
    if (!uuid_check_done) {
        LOG(ERROR) << __PRETTY_FUNCTION__ << ": boot partition not found after polling timeout.";
        return false;
    }

    return true;
}

bool BlockDevInitializer::InitDeviceMapper() {
    return InitMiscDevice("device-mapper");
}

bool BlockDevInitializer::InitDmUser(const std::string& name) {
    return InitMiscDevice("dm-user!" + name);
}

bool BlockDevInitializer::InitMiscDevice(const std::string& name) {
    const std::string dm_path = "/devices/virtual/misc/" + name;
    bool found = false;
    auto dm_callback = [this, &dm_path, &found](const Uevent& uevent) {
        if (uevent.path == dm_path) {
            device_handler_->HandleUevent(uevent);
            found = true;
            return ListenerAction::kStop;
        }
        return ListenerAction::kContinue;
    };
    uevent_listener_.RegenerateUeventsForPath("/sys" + dm_path, dm_callback);
    if (!found) {
        LOG(INFO) << name << " device not found in /sys, waiting for its uevent";
        Timer t;
        uevent_listener_.Poll(dm_callback, 10s);
        LOG(INFO) << "Wait for " << name << " returned after " << t;
    }
    if (!found) {
        LOG(ERROR) << name << " device not found after polling timeout";
        return false;
    }
    return true;
}

ListenerAction BlockDevInitializer::HandleUevent(const Uevent& uevent,
                                                 std::set<std::string>* devices) {
    // Ignore everything that is not a block device.
    if (uevent.subsystem != "block") {
        return ListenerAction::kContinue;
    }

    auto name = uevent.partition_name;
    if (name.empty()) {
        size_t base_idx = uevent.path.rfind('/');
        if (base_idx == std::string::npos) {
            return ListenerAction::kContinue;
        }
        name = uevent.path.substr(base_idx + 1);
    }

    auto iter = devices->find(name);
    if (iter == devices->end()) {
        auto partition_name = DeviceHandler::GetPartitionNameForDevice(uevent.device_name);
        if (!partition_name.empty()) {
            iter = devices->find(partition_name);
        }
        if (iter == devices->end()) {
            return ListenerAction::kContinue;
        }
    }

    LOG(VERBOSE) << __PRETTY_FUNCTION__ << ": found partition: " << name;

    // Remove the partition from the list of partitions we're waiting for.
    //
    // Partitions that we're waiting for here are expected to be on the boot
    // device, so only remove from the list if they're on the boot device.
    // This prevents us from being confused if there are multiple disks (some
    // perhaps connected via USB) that have matching partition names.
    //
    // ...but...
    //
    // Some products (especialy emulators) don't seem to set up boot_devices
    // or possibly not all the partitions that we need to wait for are on the
    // specified boot device. Thus, only require partitions to be on the boot
    // device in "strict" mode, which should be used on newer systems.
    if (device_handler_->IsBootDevice(uevent) || !device_handler_->IsBootDeviceStrict()) {
        devices->erase(iter);
    }

    device_handler_->HandleUevent(uevent);
    return devices->empty() ? ListenerAction::kStop : ListenerAction::kContinue;
}

// Wait for partitions that are expected to be on the "boot device" to initialize.
//
// Wait (for up to 10 seconds) for partitions passed in `devices` to show up.
// All block devices found while waiting will be initialized, which includes
// creating symlinks for them in /dev/block. Once all `devices` are found we'll
// return success (true). If any devices aren't found we'll return failure
// (false). As devices are found they will be removed from `devices`.
//
// The contents of `devices` is the names of the partitions. This can be:
// - The `partition_name` reported by a uevent, or the final component in the
//   `path` reported by a uevent if the `partition_name` is blank.
// - The result of DeviceHandler::GetPartitionNameForDevice() on the
//   `device_name` reported by a uevent.
//
// NOTE: on newer systems partitions _must_ be on the "boot device". See
// comments inside HandleUevent().
bool BlockDevInitializer::InitDevices(std::set<std::string> devices) {
    auto uevent_callback = [&, this](const Uevent& uevent) -> ListenerAction {
        return HandleUevent(uevent, &devices);
    };
    uevent_listener_.RegenerateUevents(uevent_callback);

    // UeventCallback() will remove found partitions from |devices|. So if it
    // isn't empty here, it means some partitions are not found.
    if (!devices.empty()) {
        LOG(INFO) << __PRETTY_FUNCTION__
                  << ": partition(s) not found in /sys, waiting for their uevent(s): "
                  << android::base::Join(devices, ", ");
        Timer t;
        uevent_listener_.Poll(uevent_callback, 10s);
        LOG(INFO) << "Wait for partitions returned after " << t;
    }

    if (!devices.empty()) {
        LOG(ERROR) << __PRETTY_FUNCTION__ << ": partition(s) not found after polling timeout: "
                   << android::base::Join(devices, ", ");
        return false;
    }
    return true;
}

// Creates "/dev/block/dm-XX" for dm nodes by running coldboot on /sys/block/dm-XX.
bool BlockDevInitializer::InitDmDevice(const std::string& device) {
    const std::string device_name(basename(device.c_str()));
    const std::string syspath = "/sys/block/" + device_name;
    return InitDevice(syspath, device_name);
}

bool BlockDevInitializer::InitPlatformDevice(const std::string& dev_name) {
    return InitDevice("/sys/devices/platform", dev_name);
}

bool BlockDevInitializer::InitHvcDevice(const std::string& dev_name) {
    return InitDevice("/sys/devices/virtual/tty", dev_name);
}

bool BlockDevInitializer::InitDevice(const std::string& syspath, const std::string& device_name) {
    bool found = false;

    auto uevent_callback = [&device_name, this, &found](const Uevent& uevent) {
        if (uevent.device_name == device_name) {
            LOG(VERBOSE) << "Creating device : " << device_name;
            device_handler_->HandleUevent(uevent);
            found = true;
            return ListenerAction::kStop;
        }
        return ListenerAction::kContinue;
    };

    uevent_listener_.RegenerateUeventsForPath(syspath, uevent_callback);
    if (!found) {
        LOG(INFO) << "device '" << device_name << "' not found in /sys, waiting for its uevent";
        Timer t;
        uevent_listener_.Poll(uevent_callback, 10s);
        LOG(INFO) << "wait for device '" << device_name << "' returned after " << t;
    }
    if (!found) {
        LOG(ERROR) << "device '" << device_name << "' not found after polling timeout";
        return false;
    }
    return true;
}

}  // namespace init
}  // namespace android