Move libboot_control to boot_control 1.1

It should belong to the default /misc implementation of boot control
1.1. Right now, the library as well as the bootloader_message_ab
are only used by cuttlefish. So move it over to reduce the confusion
in libbootloader_message.

Bug: 131775112
Test: build
Change-Id: I599678bf90d19718de811b9e34d82cf8fe1571a4

boot/1.1/default/boot_control/Android.bp

@@ -0,0 +1,61 @@
+//
+// 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_defaults {
+    name: "libboot_control_defaults",
+    vendor: true,
+    recovery_available: true,
+    relative_install_path: "hw",
+
+    cflags: [
+        "-D_FILE_OFFSET_BITS=64",
+        "-Werror",
+        "-Wall",
+        "-Wextra",
+    ],
+
+    shared_libs: [
+        "android.hardware.boot@1.1",
+        "libbase",
+        "liblog",
+    ],
+    static_libs: [
+        "libbootloader_message_vendor",
+        "libfstab",
+    ],
+}
+
+cc_library_static {
+    name: "libboot_control",
+    defaults: ["libboot_control_defaults"],
+    export_include_dirs: ["include"],
+
+    srcs: ["libboot_control.cpp"],
+}
+
+cc_library_shared {
+    name: "bootctrl.default",
+    defaults: ["libboot_control_defaults"],
+
+    srcs: ["legacy_boot_control.cpp"],
+
+    static_libs: [
+        "libboot_control",
+    ],
+    shared_libs: [
+        "libhardware",
+    ],
+}

boot/1.1/default/boot_control/include/libboot_control/libboot_control.h

@@ -0,0 +1,89 @@
+//
+// 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.
+//
+
+#pragma once
+
+#include <string>
+
+#include <android/hardware/boot/1.1/IBootControl.h>
+
+namespace android {
+namespace bootable {
+
+// Helper library to implement the IBootControl HAL using the misc partition.
+class BootControl {
+  using MergeStatus = ::android::hardware::boot::V1_1::MergeStatus;
+
+ public:
+  bool Init();
+  unsigned int GetNumberSlots();
+  unsigned int GetCurrentSlot();
+  bool MarkBootSuccessful();
+  bool SetActiveBootSlot(unsigned int slot);
+  bool SetSlotAsUnbootable(unsigned int slot);
+  bool SetSlotBootable(unsigned int slot);
+  bool IsSlotBootable(unsigned int slot);
+  const char* GetSuffix(unsigned int slot);
+  bool IsSlotMarkedSuccessful(unsigned int slot);
+  bool SetSnapshotMergeStatus(MergeStatus status);
+  MergeStatus GetSnapshotMergeStatus();
+
+  bool IsValidSlot(unsigned int slot);
+
+  const std::string& misc_device() const {
+    return misc_device_;
+  }
+
+ private:
+  // Whether this object was initialized with data from the bootloader message
+  // that doesn't change until next reboot.
+  bool initialized_ = false;
+
+  // The path to the misc_device as reported in the fstab.
+  std::string misc_device_;
+
+  // The number of slots present on the device.
+  unsigned int num_slots_ = 0;
+
+  // The slot where we are running from.
+  unsigned int current_slot_ = 0;
+};
+
+// Helper functions to write the Virtual A/B merge status message. These are
+// separate because BootControl uses bootloader_control_ab in vendor space,
+// whereas the Virtual A/B merge status is in system space. A HAL might not
+// use bootloader_control_ab, but may want to use the AOSP method of maintaining
+// the merge status.
+
+// If the Virtual A/B message has not yet been initialized, then initialize it.
+// This should be called when the BootControl HAL first loads.
+//
+// If the Virtual A/B message in misc was already initialized, true is returned.
+// If initialization was attempted, but failed, false is returned, and the HAL
+// should fail to load.
+bool InitMiscVirtualAbMessageIfNeeded();
+
+// Save the current merge status as well as the current slot.
+bool SetMiscVirtualAbMergeStatus(unsigned int current_slot,
+                                 android::hardware::boot::V1_1::MergeStatus status);
+
+// Return the current merge status. If the saved status is SNAPSHOTTED but the
+// slot hasn't changed, the status returned will be NONE.
+bool GetMiscVirtualAbMergeStatus(unsigned int current_slot,
+                                 android::hardware::boot::V1_1::MergeStatus* status);
+
+}  // namespace bootable
+}  // namespace android

boot/1.1/default/boot_control/include/private/boot_control_definition.h

@@ -0,0 +1,111 @@
+/*
+ * 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.
+ */
+
+
+/**
+ * The A/B-specific bootloader message structure (4-KiB).
+ *
+ * We separate A/B boot control metadata from the regular bootloader
+ * message struct and keep it here. Everything that's A/B-specific
+ * stays after struct bootloader_message, which belongs to the vendor
+ * space of /misc partition. Also, the A/B-specific contents should be
+ * managed by the A/B-bootloader or boot control HAL.
+ *
+ * The slot_suffix field is used for A/B implementations where the
+ * bootloader does not set the androidboot.ro.boot.slot_suffix kernel
+ * commandline parameter. This is used by fs_mgr to mount /system and
+ * other partitions with the slotselect flag set in fstab. A/B
+ * implementations are free to use all 32 bytes and may store private
+ * data past the first NUL-byte in this field. It is encouraged, but
+ * not mandatory, to use 'struct bootloader_control' described below.
+ *
+ * The update_channel field is used to store the Omaha update channel
+ * if update_engine is compiled with Omaha support.
+ */
+struct bootloader_message_ab {
+    struct bootloader_message message;
+    char slot_suffix[32];
+    char update_channel[128];
+
+    // Round up the entire struct to 4096-byte.
+    char reserved[1888];
+};
+
+/**
+ * Be cautious about the struct size change, in case we put anything post
+ * bootloader_message_ab struct (b/29159185).
+ */
+#if (__STDC_VERSION__ >= 201112L) || defined(__cplusplus)
+static_assert(sizeof(struct bootloader_message_ab) == 4096,
+              "struct bootloader_message_ab size changes");
+#endif
+
+#define BOOT_CTRL_MAGIC   0x42414342 /* Bootloader Control AB */
+#define BOOT_CTRL_VERSION 1
+
+struct slot_metadata {
+    // Slot priority with 15 meaning highest priority, 1 lowest
+    // priority and 0 the slot is unbootable.
+    uint8_t priority : 4;
+    // Number of times left attempting to boot this slot.
+    uint8_t tries_remaining : 3;
+    // 1 if this slot has booted successfully, 0 otherwise.
+    uint8_t successful_boot : 1;
+    // 1 if this slot is corrupted from a dm-verity corruption, 0
+    // otherwise.
+    uint8_t verity_corrupted : 1;
+    // Reserved for further use.
+    uint8_t reserved : 7;
+} __attribute__((packed));
+
+/* Bootloader Control AB
+ *
+ * This struct can be used to manage A/B metadata. It is designed to
+ * be put in the 'slot_suffix' field of the 'bootloader_message'
+ * structure described above. It is encouraged to use the
+ * 'bootloader_control' structure to store the A/B metadata, but not
+ * mandatory.
+ */
+struct bootloader_control {
+    // NUL terminated active slot suffix.
+    char slot_suffix[4];
+    // Bootloader Control AB magic number (see BOOT_CTRL_MAGIC).
+    uint32_t magic;
+    // Version of struct being used (see BOOT_CTRL_VERSION).
+    uint8_t version;
+    // Number of slots being managed.
+    uint8_t nb_slot : 3;
+    // Number of times left attempting to boot recovery.
+    uint8_t recovery_tries_remaining : 3;
+    // Status of any pending snapshot merge of dynamic partitions.
+    uint8_t merge_status : 3;
+    // Ensure 4-bytes alignment for slot_info field.
+    uint8_t reserved0[1];
+    // Per-slot information.  Up to 4 slots.
+    struct slot_metadata slot_info[4];
+    // Reserved for further use.
+    uint8_t reserved1[8];
+    // CRC32 of all 28 bytes preceding this field (little endian
+    // format).
+    uint32_t crc32_le;
+} __attribute__((packed));
+
+#if (__STDC_VERSION__ >= 201112L) || defined(__cplusplus)
+static_assert(sizeof(struct bootloader_control) ==
+              sizeof(((struct bootloader_message_ab *)0)->slot_suffix),
+              "struct bootloader_control has wrong size");
+#endif
+

boot/1.1/default/boot_control/legacy_boot_control.cpp

@@ -0,0 +1,115 @@
+/*
+ * Copyright (C) 2015 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 <string>
+
+#include <hardware/boot_control.h>
+#include <hardware/hardware.h>
+
+#include <libboot_control/libboot_control.h>
+
+using android::bootable::BootControl;
+
+struct boot_control_private_t {
+  // The base struct needs to be first in the list.
+  boot_control_module_t base;
+
+  BootControl impl;
+};
+
+namespace {
+
+void BootControl_init(boot_control_module_t* module) {
+  auto& impl = reinterpret_cast<boot_control_private_t*>(module)->impl;
+  impl.Init();
+}
+
+unsigned int BootControl_getNumberSlots(boot_control_module_t* module) {
+  auto& impl = reinterpret_cast<boot_control_private_t*>(module)->impl;
+  return impl.GetNumberSlots();
+}
+
+unsigned int BootControl_getCurrentSlot(boot_control_module_t* module) {
+  auto& impl = reinterpret_cast<boot_control_private_t*>(module)->impl;
+  return impl.GetCurrentSlot();
+}
+
+int BootControl_markBootSuccessful(boot_control_module_t* module) {
+  auto& impl = reinterpret_cast<boot_control_private_t*>(module)->impl;
+  return impl.MarkBootSuccessful() ? 0 : -1;
+}
+
+int BootControl_setActiveBootSlot(boot_control_module_t* module, unsigned int slot) {
+  auto& impl = reinterpret_cast<boot_control_private_t*>(module)->impl;
+  return impl.SetActiveBootSlot(slot) ? 0 : -1;
+}
+
+int BootControl_setSlotAsUnbootable(struct boot_control_module* module, unsigned int slot) {
+  auto& impl = reinterpret_cast<boot_control_private_t*>(module)->impl;
+  return impl.SetSlotAsUnbootable(slot) ? 0 : -1;
+}
+
+int BootControl_isSlotBootable(struct boot_control_module* module, unsigned int slot) {
+  auto& impl = reinterpret_cast<boot_control_private_t*>(module)->impl;
+  return impl.IsSlotBootable(slot) ? 0 : -1;
+}
+
+int BootControl_isSlotMarkedSuccessful(struct boot_control_module* module, unsigned int slot) {
+  auto& impl = reinterpret_cast<boot_control_private_t*>(module)->impl;
+  return impl.IsSlotMarkedSuccessful(slot) ? 0 : -1;
+}
+
+const char* BootControl_getSuffix(boot_control_module_t* module, unsigned int slot) {
+  auto& impl = reinterpret_cast<boot_control_private_t*>(module)->impl;
+  return impl.GetSuffix(slot);
+}
+
+static int BootControl_open(const hw_module_t* module __unused, const char* id __unused,
+                            hw_device_t** device __unused) {
+  /* Nothing to do currently. */
+  return 0;
+}
+
+struct hw_module_methods_t BootControl_methods = {
+  .open = BootControl_open,
+};
+
+}  // namespace
+
+boot_control_private_t HAL_MODULE_INFO_SYM = {
+  .base =
+      {
+          .common =
+              {
+                  .tag = HARDWARE_MODULE_TAG,
+                  .module_api_version = BOOT_CONTROL_MODULE_API_VERSION_0_1,
+                  .hal_api_version = HARDWARE_HAL_API_VERSION,
+                  .id = BOOT_CONTROL_HARDWARE_MODULE_ID,
+                  .name = "AOSP reference bootctrl HAL",
+                  .author = "The Android Open Source Project",
+                  .methods = &BootControl_methods,
+              },
+          .init = BootControl_init,
+          .getNumberSlots = BootControl_getNumberSlots,
+          .getCurrentSlot = BootControl_getCurrentSlot,
+          .markBootSuccessful = BootControl_markBootSuccessful,
+          .setActiveBootSlot = BootControl_setActiveBootSlot,
+          .setSlotAsUnbootable = BootControl_setSlotAsUnbootable,
+          .isSlotBootable = BootControl_isSlotBootable,
+          .getSuffix = BootControl_getSuffix,
+          .isSlotMarkedSuccessful = BootControl_isSlotMarkedSuccessful,
+      },
+};

boot/1.1/default/boot_control/libboot_control.cpp

@@ -0,0 +1,425 @@
+/*
+ * Copyright (C) 2015 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 <libboot_control/libboot_control.h>
+
+#include <endian.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+
+#include <string>
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/properties.h>
+#include <android-base/stringprintf.h>
+#include <android-base/unique_fd.h>
+#include <bootloader_message/bootloader_message.h>
+
+#include "private/boot_control_definition.h"
+
+namespace android {
+namespace bootable {
+
+using ::android::hardware::boot::V1_1::MergeStatus;
+
+// The number of boot attempts that should be made from a new slot before
+// rolling back to the previous slot.
+constexpr unsigned int kDefaultBootAttempts = 7;
+static_assert(kDefaultBootAttempts < 8, "tries_remaining field only has 3 bits");
+
+constexpr unsigned int kMaxNumSlots =
+    sizeof(bootloader_control::slot_info) / sizeof(bootloader_control::slot_info[0]);
+constexpr const char* kSlotSuffixes[kMaxNumSlots] = { "_a", "_b", "_c", "_d" };
+constexpr off_t kBootloaderControlOffset = offsetof(bootloader_message_ab, slot_suffix);
+
+static uint32_t CRC32(const uint8_t* buf, size_t size) {
+  static uint32_t crc_table[256];
+
+  // Compute the CRC-32 table only once.
+  if (!crc_table[1]) {
+    for (uint32_t i = 0; i < 256; ++i) {
+      uint32_t crc = i;
+      for (uint32_t j = 0; j < 8; ++j) {
+        uint32_t mask = -(crc & 1);
+        crc = (crc >> 1) ^ (0xEDB88320 & mask);
+      }
+      crc_table[i] = crc;
+    }
+  }
+
+  uint32_t ret = -1;
+  for (size_t i = 0; i < size; ++i) {
+    ret = (ret >> 8) ^ crc_table[(ret ^ buf[i]) & 0xFF];
+  }
+
+  return ~ret;
+}
+
+// Return the little-endian representation of the CRC-32 of the first fields
+// in |boot_ctrl| up to the crc32_le field.
+uint32_t BootloaderControlLECRC(const bootloader_control* boot_ctrl) {
+  return htole32(
+      CRC32(reinterpret_cast<const uint8_t*>(boot_ctrl), offsetof(bootloader_control, crc32_le)));
+}
+
+bool LoadBootloaderControl(const std::string& misc_device, bootloader_control* buffer) {
+  android::base::unique_fd fd(open(misc_device.c_str(), O_RDONLY));
+  if (fd.get() == -1) {
+    PLOG(ERROR) << "failed to open " << misc_device;
+    return false;
+  }
+  if (lseek(fd, kBootloaderControlOffset, SEEK_SET) != kBootloaderControlOffset) {
+    PLOG(ERROR) << "failed to lseek " << misc_device;
+    return false;
+  }
+  if (!android::base::ReadFully(fd.get(), buffer, sizeof(bootloader_control))) {
+    PLOG(ERROR) << "failed to read " << misc_device;
+    return false;
+  }
+  return true;
+}
+
+bool UpdateAndSaveBootloaderControl(const std::string& misc_device, bootloader_control* buffer) {
+  buffer->crc32_le = BootloaderControlLECRC(buffer);
+  android::base::unique_fd fd(open(misc_device.c_str(), O_WRONLY | O_SYNC));
+  if (fd.get() == -1) {
+    PLOG(ERROR) << "failed to open " << misc_device;
+    return false;
+  }
+  if (lseek(fd.get(), kBootloaderControlOffset, SEEK_SET) != kBootloaderControlOffset) {
+    PLOG(ERROR) << "failed to lseek " << misc_device;
+    return false;
+  }
+  if (!android::base::WriteFully(fd.get(), buffer, sizeof(bootloader_control))) {
+    PLOG(ERROR) << "failed to write " << misc_device;
+    return false;
+  }
+  return true;
+}
+
+void InitDefaultBootloaderControl(BootControl* control, bootloader_control* boot_ctrl) {
+  memset(boot_ctrl, 0, sizeof(*boot_ctrl));
+
+  unsigned int current_slot = control->GetCurrentSlot();
+  if (current_slot < kMaxNumSlots) {
+    strlcpy(boot_ctrl->slot_suffix, kSlotSuffixes[current_slot], sizeof(boot_ctrl->slot_suffix));
+  }
+  boot_ctrl->magic = BOOT_CTRL_MAGIC;
+  boot_ctrl->version = BOOT_CTRL_VERSION;
+
+  // Figure out the number of slots by checking if the partitions exist,
+  // otherwise assume the maximum supported by the header.
+  boot_ctrl->nb_slot = kMaxNumSlots;
+  std::string base_path = control->misc_device();
+  size_t last_path_sep = base_path.rfind('/');
+  if (last_path_sep != std::string::npos) {
+    // We test the existence of the "boot" partition on each possible slot,
+    // which is a partition required by Android Bootloader Requirements.
+    base_path = base_path.substr(0, last_path_sep + 1) + "boot";
+    int last_existing_slot = -1;
+    int first_missing_slot = -1;
+    for (unsigned int slot = 0; slot < kMaxNumSlots; ++slot) {
+      std::string partition_path = base_path + kSlotSuffixes[slot];
+      struct stat part_stat;
+      int err = stat(partition_path.c_str(), &part_stat);
+      if (!err) {
+        last_existing_slot = slot;
+        LOG(INFO) << "Found slot: " << kSlotSuffixes[slot];
+      } else if (err < 0 && errno == ENOENT && first_missing_slot == -1) {
+        first_missing_slot = slot;
+      }
+    }
+    // We only declare that we found the actual number of slots if we found all
+    // the boot partitions up to the number of slots, and no boot partition
+    // after that. Not finding any of the boot partitions implies a problem so
+    // we just leave the number of slots in the maximum value.
+    if ((last_existing_slot != -1 && last_existing_slot + 1 == first_missing_slot) ||
+        (first_missing_slot == -1 && last_existing_slot + 1 == kMaxNumSlots)) {
+      boot_ctrl->nb_slot = last_existing_slot + 1;
+      LOG(INFO) << "Found a system with " << last_existing_slot + 1 << " slots.";
+    }
+  }
+
+  for (unsigned int slot = 0; slot < kMaxNumSlots; ++slot) {
+    slot_metadata entry = {};
+
+    if (slot < boot_ctrl->nb_slot) {
+      entry.priority = 7;
+      entry.tries_remaining = kDefaultBootAttempts;
+      entry.successful_boot = 0;
+    } else {
+      entry.priority = 0;  // Unbootable
+    }
+
+    // When the boot_control stored on disk is invalid, we assume that the
+    // current slot is successful. The bootloader should repair this situation
+    // before booting and write a valid boot_control slot, so if we reach this
+    // stage it means that the misc partition was corrupted since boot.
+    if (current_slot == slot) {
+      entry.successful_boot = 1;
+    }
+
+    boot_ctrl->slot_info[slot] = entry;
+  }
+  boot_ctrl->recovery_tries_remaining = 0;
+
+  boot_ctrl->crc32_le = BootloaderControlLECRC(boot_ctrl);
+}
+
+// Return the index of the slot suffix passed or -1 if not a valid slot suffix.
+int SlotSuffixToIndex(const char* suffix) {
+  for (unsigned int slot = 0; slot < kMaxNumSlots; ++slot) {
+    if (!strcmp(kSlotSuffixes[slot], suffix)) return slot;
+  }
+  return -1;
+}
+
+// Initialize the boot_control_private struct with the information from
+// the bootloader_message buffer stored in |boot_ctrl|. Returns whether the
+// initialization succeeded.
+bool BootControl::Init() {
+  if (initialized_) return true;
+
+  // Initialize the current_slot from the read-only property. If the property
+  // was not set (from either the command line or the device tree), we can later
+  // initialize it from the bootloader_control struct.
+  std::string suffix_prop = android::base::GetProperty("ro.boot.slot_suffix", "");
+  if (suffix_prop.empty()) {
+    LOG(ERROR) << "Slot suffix property is not set";
+    return false;
+  }
+  current_slot_ = SlotSuffixToIndex(suffix_prop.c_str());
+
+  std::string err;
+  std::string device = get_bootloader_message_blk_device(&err);
+  if (device.empty()) {
+    LOG(ERROR) << "Could not find bootloader message block device: " << err;
+    return false;
+  }
+
+  bootloader_control boot_ctrl;
+  if (!LoadBootloaderControl(device.c_str(), &boot_ctrl)) {
+    LOG(ERROR) << "Failed to load bootloader control block";
+    return false;
+  }
+
+  // Note that since there isn't a module unload function this memory is leaked.
+  // We use `device` below sometimes, so it's not moved out of here.
+  misc_device_ = device;
+  initialized_ = true;
+
+  // Validate the loaded data, otherwise we will destroy it and re-initialize it
+  // with the current information.
+  uint32_t computed_crc32 = BootloaderControlLECRC(&boot_ctrl);
+  if (boot_ctrl.crc32_le != computed_crc32) {
+    LOG(WARNING) << "Invalid boot control found, expected CRC-32 0x" << std::hex << computed_crc32
+                 << " but found 0x" << std::hex << boot_ctrl.crc32_le << ". Re-initializing.";
+    InitDefaultBootloaderControl(this, &boot_ctrl);
+    UpdateAndSaveBootloaderControl(device.c_str(), &boot_ctrl);
+  }
+
+  if (!InitMiscVirtualAbMessageIfNeeded()) {
+    return false;
+  }
+
+  num_slots_ = boot_ctrl.nb_slot;
+  return true;
+}
+
+unsigned int BootControl::GetNumberSlots() {
+  return num_slots_;
+}
+
+unsigned int BootControl::GetCurrentSlot() {
+  return current_slot_;
+}
+
+bool BootControl::MarkBootSuccessful() {
+  bootloader_control bootctrl;
+  if (!LoadBootloaderControl(misc_device_, &bootctrl)) return false;
+
+  bootctrl.slot_info[current_slot_].successful_boot = 1;
+  // tries_remaining == 0 means that the slot is not bootable anymore, make
+  // sure we mark the current slot as bootable if it succeeds in the last
+  // attempt.
+  bootctrl.slot_info[current_slot_].tries_remaining = 1;
+  return UpdateAndSaveBootloaderControl(misc_device_, &bootctrl);
+}
+
+bool BootControl::SetActiveBootSlot(unsigned int slot) {
+  if (slot >= kMaxNumSlots || slot >= num_slots_) {
+    // Invalid slot number.
+    return false;
+  }
+
+  bootloader_control bootctrl;
+  if (!LoadBootloaderControl(misc_device_, &bootctrl)) return false;
+
+  // Set every other slot with a lower priority than the new "active" slot.
+  const unsigned int kActivePriority = 15;
+  const unsigned int kActiveTries = 6;
+  for (unsigned int i = 0; i < num_slots_; ++i) {
+    if (i != slot) {
+      if (bootctrl.slot_info[i].priority >= kActivePriority)
+        bootctrl.slot_info[i].priority = kActivePriority - 1;
+    }
+  }
+
+  // Note that setting a slot as active doesn't change the successful bit.
+  // The successful bit will only be changed by setSlotAsUnbootable().
+  bootctrl.slot_info[slot].priority = kActivePriority;
+  bootctrl.slot_info[slot].tries_remaining = kActiveTries;
+
+  // Setting the current slot as active is a way to revert the operation that
+  // set *another* slot as active at the end of an updater. This is commonly
+  // used to cancel the pending update. We should only reset the verity_corrpted
+  // bit when attempting a new slot, otherwise the verity bit on the current
+  // slot would be flip.
+  if (slot != current_slot_) bootctrl.slot_info[slot].verity_corrupted = 0;
+
+  return UpdateAndSaveBootloaderControl(misc_device_, &bootctrl);
+}
+
+bool BootControl::SetSlotAsUnbootable(unsigned int slot) {
+  if (slot >= kMaxNumSlots || slot >= num_slots_) {
+    // Invalid slot number.
+    return false;
+  }
+
+  bootloader_control bootctrl;
+  if (!LoadBootloaderControl(misc_device_, &bootctrl)) return false;
+
+  // The only way to mark a slot as unbootable, regardless of the priority is to
+  // set the tries_remaining to 0.
+  bootctrl.slot_info[slot].successful_boot = 0;
+  bootctrl.slot_info[slot].tries_remaining = 0;
+  return UpdateAndSaveBootloaderControl(misc_device_, &bootctrl);
+}
+
+bool BootControl::IsSlotBootable(unsigned int slot) {
+  if (slot >= kMaxNumSlots || slot >= num_slots_) {
+    // Invalid slot number.
+    return false;
+  }
+
+  bootloader_control bootctrl;
+  if (!LoadBootloaderControl(misc_device_, &bootctrl)) return false;
+
+  return bootctrl.slot_info[slot].tries_remaining != 0;
+}
+
+bool BootControl::IsSlotMarkedSuccessful(unsigned int slot) {
+  if (slot >= kMaxNumSlots || slot >= num_slots_) {
+    // Invalid slot number.
+    return false;
+  }
+
+  bootloader_control bootctrl;
+  if (!LoadBootloaderControl(misc_device_, &bootctrl)) return false;
+
+  return bootctrl.slot_info[slot].successful_boot && bootctrl.slot_info[slot].tries_remaining;
+}
+
+bool BootControl::IsValidSlot(unsigned int slot) {
+  return slot < kMaxNumSlots && slot < num_slots_;
+}
+
+bool BootControl::SetSnapshotMergeStatus(MergeStatus status) {
+  return SetMiscVirtualAbMergeStatus(current_slot_, status);
+}
+
+MergeStatus BootControl::GetSnapshotMergeStatus() {
+  MergeStatus status;
+  if (!GetMiscVirtualAbMergeStatus(current_slot_, &status)) {
+    return MergeStatus::UNKNOWN;
+  }
+  return status;
+}
+
+const char* BootControl::GetSuffix(unsigned int slot) {
+  if (slot >= kMaxNumSlots || slot >= num_slots_) {
+    return nullptr;
+  }
+  return kSlotSuffixes[slot];
+}
+
+bool InitMiscVirtualAbMessageIfNeeded() {
+  std::string err;
+  misc_virtual_ab_message message;
+  if (!ReadMiscVirtualAbMessage(&message, &err)) {
+    LOG(ERROR) << "Could not read merge status: " << err;
+    return false;
+  }
+
+  if (message.version == MISC_VIRTUAL_AB_MESSAGE_VERSION &&
+      message.magic == MISC_VIRTUAL_AB_MAGIC_HEADER) {
+    // Already initialized.
+    return true;
+  }
+
+  message = {};
+  message.version = MISC_VIRTUAL_AB_MESSAGE_VERSION;
+  message.magic = MISC_VIRTUAL_AB_MAGIC_HEADER;
+  if (!WriteMiscVirtualAbMessage(message, &err)) {
+    LOG(ERROR) << "Could not write merge status: " << err;
+    return false;
+  }
+  return true;
+}
+
+bool SetMiscVirtualAbMergeStatus(unsigned int current_slot,
+                                 android::hardware::boot::V1_1::MergeStatus status) {
+  std::string err;
+  misc_virtual_ab_message message;
+
+  if (!ReadMiscVirtualAbMessage(&message, &err)) {
+    LOG(ERROR) << "Could not read merge status: " << err;
+    return false;
+  }
+
+  message.merge_status = static_cast<uint8_t>(status);
+  message.source_slot = current_slot;
+  if (!WriteMiscVirtualAbMessage(message, &err)) {
+    LOG(ERROR) << "Could not write merge status: " << err;
+    return false;
+  }
+  return true;
+}
+
+bool GetMiscVirtualAbMergeStatus(unsigned int current_slot,
+                                 android::hardware::boot::V1_1::MergeStatus* status) {
+  std::string err;
+  misc_virtual_ab_message message;
+
+  if (!ReadMiscVirtualAbMessage(&message, &err)) {
+    LOG(ERROR) << "Could not read merge status: " << err;
+    return false;
+  }
+
+  // If the slot reverted after having created a snapshot, then the snapshot will
+  // be thrown away at boot. Thus we don't count this as being in a snapshotted
+  // state.
+  *status = static_cast<MergeStatus>(message.merge_status);
+  if (*status == MergeStatus::SNAPSHOTTED && current_slot == message.source_slot) {
+    *status = MergeStatus::NONE;
+  }
+  return true;
+}
+
+}  // namespace bootable
+}  // namespace android