Merge changes from topic "libdm"

am: b066bbebd1

Change-Id: I2e7c1c71c9c7e25797a79702ceeafe756f457d26

fs_mgr/Android.bp

@@ -56,12 +56,15 @@ cc_library_static {
         "libselinux",
         "libavb",
         "libfstab",
+        "libdm",
     ],
     export_static_lib_headers: [
         "libfstab",
+        "libdm",
     ],
     whole_static_libs: [
         "liblogwrap",
+        "libdm",
         "libfstab",
     ],
     cppflags: [

fs_mgr/libdm/Android.bp

@@ -0,0 +1,37 @@
+//
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+cc_library_static {
+    name: "libdm",
+    recovery_available: true,
+
+    export_include_dirs: ["include"],
+    cflags: [
+        // TODO(b/110035986): Allows us to create a skeleton of required classes
+        "-Wno-unused-private-field",
+    ],
+
+    srcs: [
+        "dm_table.cpp",
+        "dm_target.cpp",
+        "dm.cpp"
+    ],
+
+    header_libs: [
+        "libbase_headers",
+        "liblog_headers",
+    ],
+}

fs_mgr/libdm/dm.cpp

@@ -0,0 +1,270 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/dm-ioctl.h>
+#include <stdint.h>
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include <android-base/logging.h>
+#include <android-base/macros.h>
+#include <android-base/unique_fd.h>
+
+#include "dm.h"
+
+namespace android {
+namespace dm {
+
+DeviceMapper& DeviceMapper::Instance() {
+    static DeviceMapper instance;
+    return instance;
+}
+// Creates a new device mapper device
+bool DeviceMapper::CreateDevice(const std::string& name) {
+    if (name.empty()) {
+        LOG(ERROR) << "Unnamed device mapper device creation is not supported";
+        return false;
+    }
+
+    if (name.size() >= DM_NAME_LEN) {
+        LOG(ERROR) << "[" << name << "] is too long to be device mapper name";
+        return false;
+    }
+
+    std::unique_ptr<struct dm_ioctl, decltype(&free)> io(
+            static_cast<struct dm_ioctl*>(malloc(sizeof(struct dm_ioctl))), free);
+    if (io == nullptr) {
+        LOG(ERROR) << "Failed to allocate dm_ioctl";
+        return false;
+    }
+    InitIo(io.get(), name);
+
+    if (ioctl(fd_, DM_DEV_CREATE, io.get())) {
+        PLOG(ERROR) << "DM_DEV_CREATE failed to create [" << name << "]";
+        return false;
+    }
+
+    // Check to make sure the newly created device doesn't already have targets
+    // added or opened by someone
+    CHECK(io->target_count == 0) << "Unexpected targets for newly created [" << name << "] device";
+    CHECK(io->open_count == 0) << "Unexpected opens for newly created [" << name << "] device";
+
+    // Creates a new device mapper device with the name passed in
+    return true;
+}
+
+bool DeviceMapper::DeleteDevice(const std::string& name) {
+    if (name.empty()) {
+        LOG(ERROR) << "Unnamed device mapper device creation is not supported";
+        return false;
+    }
+
+    if (name.size() >= DM_NAME_LEN) {
+        LOG(ERROR) << "[" << name << "] is too long to be device mapper name";
+        return false;
+    }
+
+    std::unique_ptr<struct dm_ioctl, decltype(&free)> io(
+            static_cast<struct dm_ioctl*>(malloc(sizeof(struct dm_ioctl))), free);
+    if (io == nullptr) {
+        LOG(ERROR) << "Failed to allocate dm_ioctl";
+        return false;
+    }
+    InitIo(io.get(), name);
+
+    if (ioctl(fd_, DM_DEV_REMOVE, io.get())) {
+        PLOG(ERROR) << "DM_DEV_REMOVE failed to create [" << name << "]";
+        return false;
+    }
+
+    // Check to make sure appropriate uevent is generated so ueventd will
+    // do the right thing and remove the corresponding device node and symlinks.
+    CHECK(io->flags & DM_UEVENT_GENERATED_FLAG)
+            << "Didn't generate uevent for [" << name << "] removal";
+
+    return true;
+}
+
+const std::unique_ptr<DmTable> DeviceMapper::table(const std::string& /* name */) const {
+    // TODO(b/110035986): Return the table, as read from the kernel instead
+    return nullptr;
+}
+
+DmDeviceState DeviceMapper::state(const std::string& /* name */) const {
+    // TODO(b/110035986): Return the state, as read from the kernel instead
+    return DmDeviceState::INVALID;
+}
+
+bool DeviceMapper::LoadTableAndActivate(const std::string& /* name */, const DmTable& /* table */) {
+    return false;
+}
+
+// Reads all the available device mapper targets and their corresponding
+// versions from the kernel and returns in a vector
+bool DeviceMapper::GetAvailableTargets(std::vector<DmTarget>* targets) {
+    targets->clear();
+
+    // calculate the space needed to read a maximum of kMaxPossibleDmTargets
+    uint32_t payload_size = sizeof(struct dm_target_versions);
+    payload_size += DM_MAX_TYPE_NAME;
+    // device mapper wants every target spec to be aligned at 8-byte boundary
+    payload_size = DM_ALIGN(payload_size);
+    payload_size *= kMaxPossibleDmTargets;
+
+    uint32_t data_size = sizeof(struct dm_ioctl) + payload_size;
+    auto buffer = std::unique_ptr<void, void (*)(void*)>(calloc(1, data_size), free);
+    if (buffer == nullptr) {
+        LOG(ERROR) << "failed to allocate memory";
+        return false;
+    }
+
+    // Sets appropriate data size and data_start to make sure we tell kernel
+    // about the total size of the buffer we are passing and where to start
+    // writing the list of targets.
+    struct dm_ioctl* io = reinterpret_cast<struct dm_ioctl*>(buffer.get());
+    InitIo(io);
+    io->data_size = data_size;
+    io->data_start = sizeof(*io);
+
+    if (ioctl(fd_, DM_LIST_VERSIONS, io)) {
+        PLOG(ERROR) << "Failed to get DM_LIST_VERSIONS from kernel";
+        return false;
+    }
+
+    // If the provided buffer wasn't enough to list all targets, note that
+    // any data beyond sizeof(*io) must not be read in this case
+    if (io->flags & DM_BUFFER_FULL_FLAG) {
+        LOG(INFO) << data_size << " is not enough memory to list all dm targets";
+        return false;
+    }
+
+    // if there are no targets registered, return success with empty vector
+    if (io->data_size == sizeof(*io)) {
+        return true;
+    }
+
+    // Parse each target and list the name and version
+    // TODO(b/110035986): Templatize this
+    uint32_t next = sizeof(*io);
+    data_size = io->data_size - next;
+    struct dm_target_versions* vers =
+            reinterpret_cast<struct dm_target_versions*>(static_cast<char*>(buffer.get()) + next);
+    while (next && data_size) {
+        targets->emplace_back((vers));
+        if (vers->next == 0) {
+            break;
+        }
+        next += vers->next;
+        data_size -= vers->next;
+        vers = reinterpret_cast<struct dm_target_versions*>(static_cast<char*>(buffer.get()) + next);
+    }
+
+    return true;
+}
+
+bool DeviceMapper::GetAvailableDevices(std::vector<DmBlockDevice>* devices) {
+    devices->clear();
+
+    // calculate the space needed to read a maximum of 256 targets, each with
+    // name with maximum length of 16 bytes
+    uint32_t payload_size = sizeof(struct dm_name_list);
+    // 128-bytes for the name
+    payload_size += DM_NAME_LEN;
+    // dm wants every device spec to be aligned at 8-byte boundary
+    payload_size = DM_ALIGN(payload_size);
+    payload_size *= kMaxPossibleDmDevices;
+    uint32_t data_size = sizeof(struct dm_ioctl) + payload_size;
+    auto buffer = std::unique_ptr<void, void (*)(void*)>(calloc(1, data_size), free);
+    if (buffer == nullptr) {
+        LOG(ERROR) << "failed to allocate memory";
+        return false;
+    }
+
+    // Sets appropriate data size and data_start to make sure we tell kernel
+    // about the total size of the buffer we are passing and where to start
+    // writing the list of targets.
+    struct dm_ioctl* io = reinterpret_cast<struct dm_ioctl*>(buffer.get());
+    InitIo(io);
+    io->data_size = data_size;
+    io->data_start = sizeof(*io);
+
+    if (ioctl(fd_, DM_LIST_DEVICES, io)) {
+        PLOG(ERROR) << "Failed to get DM_LIST_DEVICES from kernel";
+        return false;
+    }
+
+    // If the provided buffer wasn't enough to list all devices any data
+    // beyond sizeof(*io) must not be read.
+    if (io->flags & DM_BUFFER_FULL_FLAG) {
+        LOG(INFO) << data_size << " is not enough memory to list all dm devices";
+        return false;
+    }
+
+    // if there are no devices created yet, return success with empty vector
+    if (io->data_size == sizeof(*io)) {
+        return true;
+    }
+
+    // Parse each device and add a new DmBlockDevice to the vector
+    // created from the kernel data.
+    uint32_t next = sizeof(*io);
+    data_size = io->data_size - next;
+    struct dm_name_list* dm_dev =
+            reinterpret_cast<struct dm_name_list*>(static_cast<char*>(buffer.get()) + next);
+
+    while (next && data_size) {
+        devices->emplace_back((dm_dev));
+        if (dm_dev->next == 0) {
+            break;
+        }
+        next += dm_dev->next;
+        data_size -= dm_dev->next;
+        dm_dev = reinterpret_cast<struct dm_name_list*>(static_cast<char*>(buffer.get()) + next);
+    }
+
+    return true;
+}
+
+// Accepts a device mapper device name (like system_a, vendor_b etc) and
+// returns the path to it's device node (or symlink to the device node)
+std::string DeviceMapper::GetDmDevicePathByName(const std::string& /* name */) {
+    return "";
+}
+
+// private methods of DeviceMapper
+void DeviceMapper::InitIo(struct dm_ioctl* io, const std::string& name) const {
+    CHECK(io != nullptr) << "nullptr passed to dm_ioctl initialization";
+    memset(io, 0, sizeof(*io));
+
+    io->version[0] = DM_VERSION0;
+    io->version[1] = DM_VERSION1;
+    io->version[2] = DM_VERSION2;
+    io->data_size = sizeof(*io);
+    io->data_start = 0;
+    if (!name.empty()) {
+        strlcpy(io->name, name.c_str(), sizeof(io->name));
+    }
+}
+
+}  // namespace dm
+}  // namespace android

fs_mgr/libdm/dm_table.cpp

@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <android-base/logging.h>
+#include <android-base/macros.h>
+
+#include <string>
+#include <vector>
+
+#include "dm_table.h"
+
+namespace android {
+namespace dm {
+
+bool DmTable::AddTarget(std::unique_ptr<DmTarget>&& /* target */) {
+    return true;
+}
+
+bool DmTable::RemoveTarget(std::unique_ptr<DmTarget>&& /* target */) {
+    return true;
+}
+
+bool DmTable::valid() const {
+    return true;
+}
+
+uint64_t DmTable::size() const {
+    return valid() ? size_ : 0;
+}
+
+// Returns a string represnetation of the table that is ready to be passed
+// down to the kernel for loading
+//
+// Implementation must verify there are no gaps in the table, table starts
+// with sector == 0, and iterate over each target to get its table
+// serialized.
+std::string DmTable::Serialize() const {
+    return "";
+}
+
+}  // namespace dm
+}  // namespace android

fs_mgr/libdm/dm_target.cpp

@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <android-base/logging.h>
+#include <android-base/macros.h>
+
+#include <stdint.h>
+
+#include <string>
+#include <vector>
+
+#include "dm_target.h"
+
+namespace android {
+namespace dm {}  // namespace dm
+}  // namespace android

fs_mgr/libdm/include/dm.h

@@ -0,0 +1,152 @@
+/*
+ *  Copyright 2018 Google, Inc
+ *
+ *  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.
+ */
+
+#ifndef _LIBDM_DM_H_
+#define _LIBDM_DM_H_
+
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/dm-ioctl.h>
+#include <linux/kdev_t.h>
+#include <sys/sysmacros.h>
+#include <unistd.h>
+
+#include <memory>
+
+#include <android-base/logging.h>
+
+#include <dm_table.h>
+
+// The minimum expected device mapper major.minor version
+#define DM_VERSION0 (4)
+#define DM_VERSION1 (0)
+#define DM_VERSION2 (0)
+
+#define DM_ALIGN_MASK (7)
+#define DM_ALIGN(x) ((x + DM_ALIGN_MASK) & ~DM_ALIGN_MASK)
+
+namespace android {
+namespace dm {
+
+enum class DmDeviceState { INVALID, SUSPENDED, ACTIVE };
+
+class DeviceMapper final {
+  public:
+    class DmBlockDevice final {
+      public:
+        // only allow creating this with dm_name_list
+        DmBlockDevice() = delete;
+
+        explicit DmBlockDevice(struct dm_name_list* d) : name_(d->name), dev_(d->dev){};
+
+        // Returs device mapper name associated with the block device
+        const std::string& name() const { return name_; }
+
+        // Return major number for the block device
+        uint32_t Major() const { return major(dev_); }
+
+        // Return minor number for the block device
+        uint32_t Minor() const { return minor(dev_); }
+        ~DmBlockDevice() = default;
+
+      private:
+        std::string name_;
+        uint64_t dev_;
+    };
+
+    // Creates a device mapper device with given name.
+    // Return 'true' on success and 'false' on failure to
+    // create OR if a device mapper device with the same name already
+    // exists.
+    // TODO(b/110035986): Make this method private and to be only
+    // called through LoadTableAndActivate() below.
+    bool CreateDevice(const std::string& name);
+
+    // Removes a device mapper device with the given name.
+    // Returns 'true' on success, false otherwise.
+    bool DeleteDevice(const std::string& name);
+
+    // Reads the device mapper table from the device with given anme and
+    // returns it in a DmTable object.
+    const std::unique_ptr<DmTable> table(const std::string& name) const;
+
+    // Returns the current state of the underlying device mapper device
+    // with given name.
+    // One of INVALID, SUSPENDED or ACTIVE.
+    DmDeviceState state(const std::string& name) const;
+
+    // Loads the device mapper table from parameter into the underlying
+    // device mapper device with given name and activate / resumes the device in the process.
+    // If a device mapper device with the 'name', doesn't exist, it will be created.
+    // Returns 'true' on success, false otherwise.
+    bool LoadTableAndActivate(const std::string& name, const DmTable& table);
+
+    // Returns true if a list of available device mapper targets registered in the kernel was
+    // successfully read and stored in 'targets'. Returns 'false' otherwise.
+    bool GetAvailableTargets(std::vector<DmTarget>* targets);
+
+    // Return 'true' if it can successfully read the list of device mapper block devices
+    // currently created. 'devices' will be empty if the kernel interactions
+    // were successful and there are no block devices at the moment. Returns
+    // 'false' in case of any failure along the way.
+    bool GetAvailableDevices(std::vector<DmBlockDevice>* devices);
+
+    // Returns the path to the device mapper device node in '/dev' corresponding to
+    // 'name'.
+    std::string GetDmDevicePathByName(const std::string& name);
+
+    // The only way to create a DeviceMapper object.
+    static DeviceMapper& Instance();
+
+    ~DeviceMapper() {
+        if (fd_ != -1) {
+            ::close(fd_);
+        }
+    }
+
+  private:
+    // Maximum possible device mapper targets registered in the kernel.
+    // This is only used to read the list of targets from kernel so we allocate
+    // a finite amount of memory. This limit is in no way enforced by the kernel.
+    static constexpr uint32_t kMaxPossibleDmTargets = 256;
+
+    // Maximum possible device mapper created block devices. Note that this is restricted by
+    // the minor numbers (that used to be 8 bits) that can be range from 0 to 2^20-1 in newer
+    // kernels. In Android systems however, we never expect these to grow beyond the artificial
+    // limit we are imposing here of 256.
+    static constexpr uint32_t kMaxPossibleDmDevices = 256;
+
+    void InitIo(struct dm_ioctl* io, const std::string& name = std::string()) const;
+
+    DeviceMapper() : fd_(-1) {
+        fd_ = TEMP_FAILURE_RETRY(open("/dev/device-mapper", O_RDWR | O_CLOEXEC));
+        if (fd_ < 0) {
+            PLOG(ERROR) << "Failed to open device-mapper";
+        }
+    }
+
+    int fd_;
+    // Non-copyable & Non-movable
+    DeviceMapper(const DeviceMapper&) = delete;
+    DeviceMapper& operator=(const DeviceMapper&) = delete;
+    DeviceMapper& operator=(DeviceMapper&&) = delete;
+    DeviceMapper(DeviceMapper&&) = delete;
+};
+
+}  // namespace dm
+}  // namespace android
+
+#endif /* _LIBDM_DM_H_ */

fs_mgr/libdm/include/dm_table.h

@@ -0,0 +1,75 @@
+/*
+ *  Copyright 2018 Google, Inc
+ *
+ *  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.
+ */
+
+#ifndef _LIBDM_DMTABLE_H_
+#define _LIBDM_DMTABLE_H_
+
+#include <stdint.h>
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "dm_target.h"
+
+namespace android {
+namespace dm {
+
+class DmTable {
+  public:
+    DmTable() : size_(0){};
+
+    // Adds a target to the device mapper table for a range specified in the target object.
+    // The function will return 'true' if the target was successfully added and doesn't overlap with
+    // any of the existing targets in the table. Gaps are allowed. The final check, including
+    // overlaps and gaps are done before loading the table. Returns 'false' on failure.
+    bool AddTarget(std::unique_ptr<DmTarget>&& target);
+
+    // Removes a target from the table for the range specified in the target object. Returns 'false'
+    // if the target name doesn't match with the one in the table. Returns 'true' if target is
+    // successfully removed.
+    bool RemoveTarget(std::unique_ptr<DmTarget>&& target);
+
+    // Checks the table to make sure it is valid. i.e. Checks for range overlaps, range gaps
+    // and returns 'true' if the table is ready to be loaded into kernel. Returns 'false' if the
+    // table is malformed.
+    bool valid() const;
+
+    // Returns the total size represented by the table in terms of number of 512-byte sectors.
+    // NOTE: This function will overlook if there are any gaps in the targets added in the table.
+    uint64_t size() const;
+
+    // Returns the string represntation of the table that is ready to be passed into the kernel
+    // as part of the DM_TABLE_LOAD ioctl.
+    std::string Serialize() const;
+
+    ~DmTable() = default;
+
+  private:
+    // list of targets defined in this table sorted by
+    // their start and end sectors.
+    // Note: Overlapping targets MUST never be added in this list.
+    std::vector<std::unique_ptr<DmTarget>> targets_;
+
+    // Total size in terms of # of sectors, as calculated by looking at the last and the first
+    // target in 'target_'.
+    uint64_t size_;
+};
+
+}  // namespace dm
+}  // namespace android
+
+#endif /* _LIBDM_DMTABLE_H_ */

fs_mgr/libdm/include/dm_target.h

@@ -0,0 +1,77 @@
+/*
+ *  Copyright 2018 Google, Inc
+ *
+ *  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.
+ */
+
+#ifndef _LIBDM_DMTARGET_H_
+#define _LIBDM_DMTARGET_H_
+
+#include <linux/dm-ioctl.h>
+#include <stdint.h>
+
+#include <android-base/logging.h>
+
+#include <string>
+
+namespace android {
+namespace dm {
+
+class DmTarget {
+  public:
+    DmTarget(const std::string& name, uint64_t start = 0, uint64_t length = 0)
+        : name_(name), v0_(0), v1_(0), v2_(0), start_(start), length_(length){};
+
+    // Creates a DmTarget object from dm_target_version as read from kernel
+    // with DM_LIST_VERSION ioctl.
+    DmTarget(const struct dm_target_versions* vers) : start_(0), length_(0) {
+        CHECK(vers != nullptr) << "Can't create DmTarget with dm_target_versions set to nullptr";
+        v0_ = vers->version[0];
+        v1_ = vers->version[1];
+        v2_ = vers->version[2];
+        name_ = vers->name;
+    }
+
+    virtual ~DmTarget() = default;
+
+    // Returns name of the target.
+    const std::string& name() const { return name_; }
+
+    // Returns size in number of sectors when this target is part of
+    // a DmTable, return 0 otherwise.
+    uint64_t size() const { return length_; }
+
+    // Return string representation of the device mapper target version.
+    std::string version() const {
+        return std::to_string(v0_) + "." + std::to_string(v1_) + "." + std::to_string(v2_);
+    }
+
+    // Function that converts this object to a string of arguments that can
+    // be passed to the kernel for adding this target in a table. Each target (e.g. verity, linear)
+    // must implement this, for it to be used on a device.
+    virtual std::string Serialize() const { return ""; }
+
+  private:
+    // Name of the target.
+    std::string name_;
+    // Target version.
+    uint32_t v0_, v1_, v2_;
+    // logical sector number start and total length (in terms of 512-byte sectors) represented
+    // by this target within a DmTable.
+    uint64_t start_, length_;
+};
+
+}  // namespace dm
+}  // namespace android
+
+#endif /* _LIBDM_DMTARGET_H_ */

fs_mgr/tools/Android.bp

@@ -0,0 +1,31 @@
+//
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+cc_binary {
+    name: "dmctl",
+    srcs: ["dmctl.cpp"],
+
+    static_libs: [
+        "libfs_mgr",
+    ],
+
+    shared_libs: [
+        "libbase",
+        "liblog",
+    ],
+
+    cflags: ["-Werror"],
+}

fs_mgr/tools/dmctl.cpp

@@ -0,0 +1,174 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <getopt.h>
+#include <linux/dm-ioctl.h>
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <android-base/unique_fd.h>
+#include <dm.h>
+
+#include <functional>
+#include <iomanip>
+#include <ios>
+#include <iostream>
+#include <map>
+#include <string>
+#include <vector>
+
+using DeviceMapper = ::android::dm::DeviceMapper;
+using DmTarget = ::android::dm::DmTarget;
+using DmBlockDevice = ::android::dm::DeviceMapper::DmBlockDevice;
+
+static int Usage(void) {
+    std::cerr << "usage: dmctl <command> [command options]";
+    std::cerr << "commands:";
+    std::cerr << "  create <dm-name> [dm-target> [-lo <filename>] <dm-target-args>]";
+    std::cerr, "  delete <dm-name>";
+    std::cerr, "  list <devices | targets>";
+    std::cerr, "  help";
+    return -EINVAL;
+}
+
+static int DmCreateCmdHandler(int argc, char** argv) {
+    if (argc < 1) {
+        std::cerr << "DmCreateCmdHandler: atleast 'name' MUST be provided for target device";
+        return -EINVAL;
+    }
+
+    std::string name = argv[0];
+    DeviceMapper& dm = DeviceMapper::Instance();
+    if (!dm.CreateDevice(name)) {
+        std::cerr << "DmCreateCmdHandler: Failed to create " << name << " device";
+        return -EIO;
+    }
+
+    // if we also have target specified
+    if (argc > 1) {
+        // fall through for now. This will eventually create a DmTarget() based on the target name
+        // passing it the table that is specified at the command line
+    }
+
+    return 0;
+}
+
+static int DmDeleteCmdHandler(int argc, char** argv) {
+    if (argc < 1) {
+        std::cerr << "DmCreateCmdHandler: atleast 'name' MUST be provided for target device";
+        return -EINVAL;
+    }
+
+    std::string name = argv[0];
+    DeviceMapper& dm = DeviceMapper::Instance();
+    if (!dm.DeleteDevice(name)) {
+        std::cerr << "DmCreateCmdHandler: Failed to create " << name << " device";
+        return -EIO;
+    }
+
+    return 0;
+}
+
+static int DmListTargets(DeviceMapper& dm) {
+    std::vector<DmTarget> targets;
+    if (!dm.GetAvailableTargets(&targets)) {
+        std::cerr << "Failed to read available device mapper targets" << std::endl;
+        return -errno;
+    }
+
+    std::cout << "Available Device Mapper Targets:" << std::endl;
+    if (targets.empty()) {
+        std::cout << "  <empty>" << std::endl;
+        return 0;
+    }
+
+    for (const auto& target : targets) {
+        std::cout << std::left << std::setw(20) << target.name() << " : " << target.version()
+                  << std::endl;
+    }
+
+    return 0;
+}
+
+static int DmListDevices(DeviceMapper& dm) {
+    std::vector<DmBlockDevice> devices;
+    if (!dm.GetAvailableDevices(&devices)) {
+        std::cerr << "Failed to read available device mapper devices" << std::endl;
+        return -errno;
+    }
+    std::cout << "Available Device Mapper Devices:" << std::endl;
+    if (devices.empty()) {
+        std::cout << "  <empty>" << std::endl;
+        return 0;
+    }
+
+    for (const auto& dev : devices) {
+        std::cout << std::left << std::setw(20) << dev.name() << " : " << dev.Major() << ":"
+                  << dev.Minor() << std::endl;
+    }
+
+    return 0;
+}
+
+static const std::map<std::string, std::function<int(DeviceMapper&)>> listmap = {
+        {"targets", DmListTargets},
+        {"devices", DmListDevices},
+};
+
+static int DmListCmdHandler(int argc, char** argv) {
+    if (argc < 1) {
+        std::cerr << "Invalid arguments, see \'dmctl help\'" << std::endl;
+        return -EINVAL;
+    }
+
+    DeviceMapper& dm = DeviceMapper::Instance();
+    for (const auto& l : listmap) {
+        if (l.first == argv[0]) return l.second(dm);
+    }
+
+    std::cerr << "Invalid argument to \'dmctl list\': " << argv[0] << std::endl;
+    return -EINVAL;
+}
+
+static int HelpCmdHandler(int /* argc */, char** /* argv */) {
+    Usage();
+    return 0;
+}
+
+static std::map<std::string, std::function<int(int, char**)>> cmdmap = {
+        {"create", DmCreateCmdHandler},
+        {"delete", DmDeleteCmdHandler},
+        {"list", DmListCmdHandler},
+        {"help", HelpCmdHandler},
+};
+
+int main(int argc, char** argv) {
+    android::base::InitLogging(argv, &android::base::StderrLogger);
+    if (argc < 2) {
+        return Usage();
+    }
+
+    for (const auto& cmd : cmdmap) {
+        if (cmd.first == argv[1]) {
+            return cmd.second(argc - 2, argv + 2);
+        }
+    }
+
+    return Usage();
+}