10 files changed, 328 insertions, 397 deletions

diff --git a/Android.mk b/Android.mk
index 2034d604f..43236fe3c 100644
--- a/Android.mk
+++ b/Android.mk
@@ -41,7 +41,6 @@ include $(CLEAR_VARS)
 LOCAL_SRC_FILES := \
     adb_install.cpp \
     asn1_decoder.cpp \
-    bootloader.cpp \
     device.cpp \
     fuse_sdcard_provider.cpp \
     install.cpp \
@@ -76,6 +75,7 @@ LOCAL_C_INCLUDES += \
 
 LOCAL_STATIC_LIBRARIES := \
     libbatterymonitor \
+    libbootloader_message \
     libext4_utils_static \
     libsparse_static \
     libminzip \
@@ -152,14 +152,16 @@ LOCAL_SRC_FILES := \
 LOCAL_STATIC_LIBRARIES := libcrypto_utils_static libcrypto_static
 include $(BUILD_STATIC_LIBRARY)
 
-include $(LOCAL_PATH)/minui/Android.mk \
-    $(LOCAL_PATH)/minzip/Android.mk \
+include \
+    $(LOCAL_PATH)/applypatch/Android.mk \
+    $(LOCAL_PATH)/bootloader_message/Android.mk \
+    $(LOCAL_PATH)/edify/Android.mk \
     $(LOCAL_PATH)/minadbd/Android.mk \
+    $(LOCAL_PATH)/minui/Android.mk \
+    $(LOCAL_PATH)/minzip/Android.mk \
+    $(LOCAL_PATH)/otafault/Android.mk \
     $(LOCAL_PATH)/tests/Android.mk \
     $(LOCAL_PATH)/tools/Android.mk \
-    $(LOCAL_PATH)/edify/Android.mk \
     $(LOCAL_PATH)/uncrypt/Android.mk \
-    $(LOCAL_PATH)/otafault/Android.mk \
     $(LOCAL_PATH)/updater/Android.mk \
     $(LOCAL_PATH)/update_verifier/Android.mk \
-    $(LOCAL_PATH)/applypatch/Android.mk
diff --git a/bootloader.cpp b/bootloader.cpp
deleted file mode 100644
index 6b86c17a7..000000000
--- a/bootloader.cpp
+++ /dev/null
@@ -1,150 +0,0 @@
-/*
- * Copyright (C) 2008 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 <inttypes.h>
-#include <stdio.h>
-#include <string.h>
-#include <sys/stat.h>
-#include <sys/types.h>
-#include <unistd.h>
-
-#include <fs_mgr.h>
-
-#include <android-base/file.h>
-#include <android-base/unique_fd.h>
-
-#include "bootloader.h"
-#include "common.h"
-#include "roots.h"
-
-static bool read_misc_partition(const Volume* v, size_t offset, size_t size, std::string* out);
-static bool write_misc_partition(const Volume* v, size_t offset, const std::string& in);
-
-int get_bootloader_message(bootloader_message* out) {
-    Volume* v = volume_for_path("/misc");
-    if (v == nullptr) {
-        LOGE("Cannot load volume /misc!\n");
-        return -1;
-    }
-    if (strcmp(v->fs_type, "emmc") == 0) {
-        std::string s;
-        if (!read_misc_partition(v, BOOTLOADER_MESSAGE_OFFSET_IN_MISC, sizeof(bootloader_message),
-                                 &s)) {
-            return -1;
-        }
-        memcpy(out, s.data(), s.size());
-        return 0;
-    }
-    LOGE("Unknown misc partition fs_type \"%s\"\n", v->fs_type);
-    return -1;
-}
-
-bool read_wipe_package(size_t size, std::string* out) {
-    Volume* v = volume_for_path("/misc");
-    if (v == nullptr) {
-        LOGE("Cannot load volume /misc!\n");
-        return false;
-    }
-    if (strcmp(v->fs_type, "mtd") == 0) {
-        LOGE("Read wipe package on mtd is not supported.\n");
-        return false;
-    } else if (strcmp(v->fs_type, "emmc") == 0) {
-        return read_misc_partition(v, WIPE_PACKAGE_OFFSET_IN_MISC, size, out);
-    }
-    LOGE("Unknown misc partition fs_type \"%s\"\n", v->fs_type);
-    return false;
-}
-
-int set_bootloader_message(const bootloader_message* in) {
-    Volume* v = volume_for_path("/misc");
-    if (v == nullptr) {
-        LOGE("Cannot load volume /misc!\n");
-        return -1;
-    }
-    if (strcmp(v->fs_type, "emmc") == 0) {
-        std::string s(reinterpret_cast<const char*>(in), sizeof(*in));
-        bool success = write_misc_partition(v, BOOTLOADER_MESSAGE_OFFSET_IN_MISC, s);
-        return success ? 0 : -1;
-    }
-    LOGE("Unknown misc partition fs_type \"%s\"\n", v->fs_type);
-    return -1;
-}
-
-// ------------------------------------
-// for misc partitions on block devices
-// ------------------------------------
-
-static void wait_for_device(const char* fn) {
-    int tries = 0;
-    int ret;
-    do {
-        ++tries;
-        struct stat buf;
-        ret = stat(fn, &buf);
-        if (ret == -1) {
-            printf("failed to stat \"%s\" try %d: %s\n", fn, tries, strerror(errno));
-            sleep(1);
-        }
-    } while (ret && tries < 10);
-
-    if (ret) {
-        printf("failed to stat \"%s\"\n", fn);
-    }
-}
-
-static bool read_misc_partition(const Volume* v, size_t offset, size_t size, std::string* out) {
-    wait_for_device(v->blk_device);
-    android::base::unique_fd fd(open(v->blk_device, O_RDONLY));
-    if (fd == -1) {
-        LOGE("Failed to open \"%s\": %s\n", v->blk_device, strerror(errno));
-        return false;
-    }
-    if (lseek(fd, static_cast<off_t>(offset), SEEK_SET) != static_cast<off_t>(offset)) {
-        LOGE("Failed to lseek \"%s\": %s\n", v->blk_device, strerror(errno));
-        return false;
-    }
-    out->resize(size);
-    if (!android::base::ReadFully(fd, &(*out)[0], size)) {
-        LOGE("Failed to read \"%s\": %s\n", v->blk_device, strerror(errno));
-        return false;
-    }
-    return true;
-}
-
-static bool write_misc_partition(const Volume* v, size_t offset, const std::string& in) {
-    wait_for_device(v->blk_device);
-    android::base::unique_fd fd(open(v->blk_device, O_WRONLY | O_SYNC));
-    if (fd == -1) {
-        LOGE("Failed to open \"%s\": %s\n", v->blk_device, strerror(errno));
-        return false;
-    }
-    if (lseek(fd, static_cast<off_t>(offset), SEEK_SET) != static_cast<off_t>(offset)) {
-        LOGE("Failed to lseek \"%s\": %s\n", v->blk_device, strerror(errno));
-        return false;
-    }
-    if (!android::base::WriteFully(fd, in.data(), in.size())) {
-        LOGE("Failed to write \"%s\": %s\n", v->blk_device, strerror(errno));
-        return false;
-    }
-
-    if (fsync(fd) == -1) {
-        LOGE("Failed to fsync \"%s\": %s\n", v->blk_device, strerror(errno));
-        return false;
-    }
-    return true;
-}
diff --git a/bootloader.h b/bootloader.h
index 341bcadbd..9c84a1cf9 100644
--- a/bootloader.h
+++ b/bootloader.h
@@ -14,176 +14,5 @@
  * limitations under the License.
  */
 
-#ifndef _RECOVERY_BOOTLOADER_H
-#define _RECOVERY_BOOTLOADER_H
-
-#include <assert.h>
-#include <stddef.h>
-
-// Spaces used by misc partition are as below:
-// 0   - 2K     For bootloader_message
-// 2K  - 16K    Used by Vendor's bootloader (the 2K - 4K range may be optionally used
-//              as bootloader_message_ab struct)
-// 16K - 64K    Used by uncrypt and recovery to store wipe_package for A/B devices
-// Note that these offsets are admitted by bootloader,recovery and uncrypt, so they
-// are not configurable without changing all of them.
-static const size_t BOOTLOADER_MESSAGE_OFFSET_IN_MISC = 0;
-static const size_t WIPE_PACKAGE_OFFSET_IN_MISC = 16 * 1024;
-
-/* Bootloader Message (2-KiB)
- *
- * This structure describes the content of a block in flash
- * that is used for recovery and the bootloader to talk to
- * each other.
- *
- * The command field is updated by linux when it wants to
- * reboot into recovery or to update radio or bootloader firmware.
- * It is also updated by the bootloader when firmware update
- * is complete (to boot into recovery for any final cleanup)
- *
- * The status field is written by the bootloader after the
- * completion of an "update-radio" or "update-hboot" command.
- *
- * The recovery field is only written by linux and used
- * for the system to send a message to recovery or the
- * other way around.
- *
- * The stage field is written by packages which restart themselves
- * multiple times, so that the UI can reflect which invocation of the
- * package it is.  If the value is of the format "#/#" (eg, "1/3"),
- * the UI will add a simple indicator of that status.
- *
- * We used to have slot_suffix field for A/B boot control metadata in
- * this struct, which gets unintentionally cleared by recovery or
- * uncrypt. Move it into struct bootloader_message_ab to avoid the
- * issue.
- */
-struct bootloader_message {
-    char command[32];
-    char status[32];
-    char recovery[768];
-
-    // The 'recovery' field used to be 1024 bytes.  It has only ever
-    // been used to store the recovery command line, so 768 bytes
-    // should be plenty.  We carve off the last 256 bytes to store the
-    // stage string (for multistage packages) and possible future
-    // expansion.
-    char stage[32];
-
-    // The 'reserved' field used to be 224 bytes when it was initially
-    // carved off from the 1024-byte recovery field. Bump it up to
-    // 1184-byte so that the entire bootloader_message struct rounds up
-    // to 2048-byte.
-    char reserved[1184];
-};
-
-/**
- * We must be cautious when changing the bootloader_message struct size,
- * because A/B-specific fields may end up with different offsets.
- */
-#if (__STDC_VERSION__ >= 201112L) || defined(__cplusplus)
-static_assert(sizeof(struct bootloader_message) == 2048,
-              "struct bootloader_message size changes, which may break A/B devices");
-#endif
-
-/**
- * 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 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.
- */
-struct bootloader_message_ab {
-    struct bootloader_message message;
-    char slot_suffix[32];
-
-    // Round up the entire struct to 4096-byte.
-    char reserved[2016];
-};
-
-/**
- * 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;
-    // Ensure 4-bytes alignment for slot_info field.
-    uint8_t reserved0[2];
-    // 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
-
-/* Read and write the bootloader command from the "misc" partition.
- * These return zero on success.
- */
-int get_bootloader_message(struct bootloader_message *out);
-int set_bootloader_message(const struct bootloader_message *in);
-
-#ifdef __cplusplus
-
-#include <string>
-
-bool read_wipe_package(size_t size, std::string* out);
-#endif
-
-#endif
+// TODO: Remove this file once we remove all places that include this file.
+#include "bootloader_message/include/bootloader_message/bootloader_message.h"
diff --git a/bootloader_message/Android.mk b/bootloader_message/Android.mk
new file mode 100644
index 000000000..815ac67d7
--- /dev/null
+++ b/bootloader_message/Android.mk
@@ -0,0 +1,24 @@
+# Copyright (C) 2016 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+LOCAL_PATH := $(call my-dir)
+
+include $(CLEAR_VARS)
+LOCAL_CLANG := true
+LOCAL_SRC_FILES := bootloader_message.cpp
+LOCAL_MODULE := libbootloader_message
+LOCAL_STATIC_LIBRARIES := libbase libfs_mgr
+LOCAL_C_INCLUDES := $(LOCAL_PATH)/include
+LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)/include
+include $(BUILD_STATIC_LIBRARY)
diff --git a/uncrypt/bootloader_message_writer.cpp b/bootloader_message/bootloader_message.cpp
index 42df31efa..e7195ae9d 100644
--- a/uncrypt/bootloader_message_writer.cpp
+++ b/bootloader_message/bootloader_message.cpp
@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+#include <bootloader_message/bootloader_message.h>
+
 #include <errno.h>
 #include <fcntl.h>
 #include <string.h>
@@ -27,8 +29,6 @@
 #include <android-base/unique_fd.h>
 #include <fs_mgr.h>
 
-#include "bootloader.h"
-
 static struct fstab* read_fstab(std::string* err) {
   // The fstab path is always "/fstab.${ro.hardware}".
   std::string fstab_path = "/fstab.";
@@ -58,19 +58,68 @@ static std::string get_misc_blk_device(std::string* err) {
   return record->blk_device;
 }
 
-static bool write_misc_partition(const void* p, size_t size, size_t misc_offset, std::string* err) {
+// In recovery mode, recovery can get started and try to access the misc
+// device before the kernel has actually created it.
+static bool wait_for_device(const std::string& blk_device, std::string* err) {
+  int tries = 0;
+  int ret;
+  err->clear();
+  do {
+    ++tries;
+    struct stat buf;
+    ret = stat(blk_device.c_str(), &buf);
+    if (ret == -1) {
+      *err += android::base::StringPrintf("failed to stat %s try %d: %s\n",
+                                          blk_device.c_str(), tries, strerror(errno));
+      sleep(1);
+    }
+  } while (ret && tries < 10);
+
+  if (ret) {
+    *err += android::base::StringPrintf("failed to stat %s\n", blk_device.c_str());
+  }
+  return ret == 0;
+}
+
+static bool read_misc_partition(void* p, size_t size, size_t offset, std::string* err) {
   std::string misc_blk_device = get_misc_blk_device(err);
   if (misc_blk_device.empty()) {
     return false;
   }
+  if (!wait_for_device(misc_blk_device, err)) {
+    return false;
+  }
   android::base::unique_fd fd(open(misc_blk_device.c_str(), O_WRONLY | O_SYNC));
   if (fd.get() == -1) {
     *err = android::base::StringPrintf("failed to open %s: %s", misc_blk_device.c_str(),
                                        strerror(errno));
     return false;
   }
-  if (lseek(fd.get(), static_cast<off_t>(misc_offset), SEEK_SET) !=
-      static_cast<off_t>(misc_offset)) {
+  if (lseek(fd.get(), static_cast<off_t>(offset), SEEK_SET) != static_cast<off_t>(offset)) {
+    *err = android::base::StringPrintf("failed to lseek %s: %s", misc_blk_device.c_str(),
+                                       strerror(errno));
+    return false;
+  }
+  if (!android::base::ReadFully(fd.get(), p, size)) {
+    *err = android::base::StringPrintf("failed to read %s: %s", misc_blk_device.c_str(),
+                                       strerror(errno));
+    return false;
+  }
+  return true;
+}
+
+static bool write_misc_partition(const void* p, size_t size, size_t offset, std::string* err) {
+  std::string misc_blk_device = get_misc_blk_device(err);
+  if (misc_blk_device.empty()) {
+    return false;
+  }
+  android::base::unique_fd fd(open(misc_blk_device.c_str(), O_WRONLY | O_SYNC));
+  if (fd.get() == -1) {
+    *err = android::base::StringPrintf("failed to open %s: %s", misc_blk_device.c_str(),
+                                       strerror(errno));
+    return false;
+  }
+  if (lseek(fd.get(), static_cast<off_t>(offset), SEEK_SET) != static_cast<off_t>(offset)) {
     *err = android::base::StringPrintf("failed to lseek %s: %s", misc_blk_device.c_str(),
                                        strerror(errno));
     return false;
@@ -90,7 +139,11 @@ static bool write_misc_partition(const void* p, size_t size, size_t misc_offset,
   return true;
 }
 
-static bool write_bootloader_message(const bootloader_message& boot, std::string* err) {
+bool read_bootloader_message(bootloader_message* boot, std::string* err) {
+  return read_misc_partition(boot, sizeof(*boot), BOOTLOADER_MESSAGE_OFFSET_IN_MISC, err);
+}
+
+bool write_bootloader_message(const bootloader_message& boot, std::string* err) {
   return write_misc_partition(&boot, sizeof(boot), BOOTLOADER_MESSAGE_OFFSET_IN_MISC, err);
 }
 
@@ -112,6 +165,11 @@ bool write_bootloader_message(const std::vector<std::string>& options, std::stri
   return write_bootloader_message(boot, err);
 }
 
+bool read_wipe_package(std::string* package_data, size_t size, std::string* err) {
+  package_data->resize(size);
+  return read_misc_partition(&(*package_data)[0], size, WIPE_PACKAGE_OFFSET_IN_MISC, err);
+}
+
 bool write_wipe_package(const std::string& package_data, std::string* err) {
   return write_misc_partition(package_data.data(), package_data.size(),
                               WIPE_PACKAGE_OFFSET_IN_MISC, err);
diff --git a/bootloader_message/include/bootloader_message/bootloader_message.h b/bootloader_message/include/bootloader_message/bootloader_message.h
new file mode 100644
index 000000000..f343c64ac
--- /dev/null
+++ b/bootloader_message/include/bootloader_message/bootloader_message.h
@@ -0,0 +1,199 @@
+/*
+ * Copyright (C) 2008 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.
+ */
+
+#ifndef _BOOTLOADER_MESSAGE_H
+#define _BOOTLOADER_MESSAGE_H
+
+#include <assert.h>
+#include <stddef.h>
+#include <stdint.h>
+
+// Spaces used by misc partition are as below:
+// 0   - 2K     For bootloader_message
+// 2K  - 16K    Used by Vendor's bootloader (the 2K - 4K range may be optionally used
+//              as bootloader_message_ab struct)
+// 16K - 64K    Used by uncrypt and recovery to store wipe_package for A/B devices
+// Note that these offsets are admitted by bootloader,recovery and uncrypt, so they
+// are not configurable without changing all of them.
+static const size_t BOOTLOADER_MESSAGE_OFFSET_IN_MISC = 0;
+static const size_t WIPE_PACKAGE_OFFSET_IN_MISC = 16 * 1024;
+
+/* Bootloader Message (2-KiB)
+ *
+ * This structure describes the content of a block in flash
+ * that is used for recovery and the bootloader to talk to
+ * each other.
+ *
+ * The command field is updated by linux when it wants to
+ * reboot into recovery or to update radio or bootloader firmware.
+ * It is also updated by the bootloader when firmware update
+ * is complete (to boot into recovery for any final cleanup)
+ *
+ * The status field is written by the bootloader after the
+ * completion of an "update-radio" or "update-hboot" command.
+ *
+ * The recovery field is only written by linux and used
+ * for the system to send a message to recovery or the
+ * other way around.
+ *
+ * The stage field is written by packages which restart themselves
+ * multiple times, so that the UI can reflect which invocation of the
+ * package it is.  If the value is of the format "#/#" (eg, "1/3"),
+ * the UI will add a simple indicator of that status.
+ *
+ * We used to have slot_suffix field for A/B boot control metadata in
+ * this struct, which gets unintentionally cleared by recovery or
+ * uncrypt. Move it into struct bootloader_message_ab to avoid the
+ * issue.
+ */
+struct bootloader_message {
+    char command[32];
+    char status[32];
+    char recovery[768];
+
+    // The 'recovery' field used to be 1024 bytes.  It has only ever
+    // been used to store the recovery command line, so 768 bytes
+    // should be plenty.  We carve off the last 256 bytes to store the
+    // stage string (for multistage packages) and possible future
+    // expansion.
+    char stage[32];
+
+    // The 'reserved' field used to be 224 bytes when it was initially
+    // carved off from the 1024-byte recovery field. Bump it up to
+    // 1184-byte so that the entire bootloader_message struct rounds up
+    // to 2048-byte.
+    char reserved[1184];
+};
+
+/**
+ * We must be cautious when changing the bootloader_message struct size,
+ * because A/B-specific fields may end up with different offsets.
+ */
+#if (__STDC_VERSION__ >= 201112L) || defined(__cplusplus)
+static_assert(sizeof(struct bootloader_message) == 2048,
+              "struct bootloader_message size changes, which may break A/B devices");
+#endif
+
+/**
+ * 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 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.
+ */
+struct bootloader_message_ab {
+    struct bootloader_message message;
+    char slot_suffix[32];
+
+    // Round up the entire struct to 4096-byte.
+    char reserved[2016];
+};
+
+/**
+ * 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;
+    // Ensure 4-bytes alignment for slot_info field.
+    uint8_t reserved0[2];
+    // 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
+
+#ifdef __cplusplus
+
+#include <string>
+#include <vector>
+
+bool read_bootloader_message(bootloader_message* boot, std::string* err);
+bool write_bootloader_message(const bootloader_message& boot, std::string* err);
+bool write_bootloader_message(const std::vector<std::string>& options, std::string* err);
+bool clear_bootloader_message(std::string* err);
+
+bool read_wipe_package(std::string* package_data, size_t size, std::string* err);
+bool write_wipe_package(const std::string& package_data, std::string* err);
+
+#else
+
+#include <stdbool.h>
+
+// C Interface.
+bool write_bootloader_message(const char* options);
+
+#endif  // ifdef __cplusplus
+
+#endif  // _BOOTLOADER_MESSAGE_H
diff --git a/recovery.cpp b/recovery.cpp
index e9ded7178..c0f5a386a 100644
--- a/recovery.cpp
+++ b/recovery.cpp
@@ -45,6 +45,7 @@
 #include <android-base/stringprintf.h>
 #include <android-base/strings.h>
 #include <android-base/unique_fd.h>
+#include <bootloader_message/bootloader_message.h>
 #include <cutils/android_reboot.h>
 #include <cutils/properties.h>
 #include <healthd/BatteryMonitor.h>
@@ -54,7 +55,6 @@
 #include <selinux/selinux.h>
 
 #include "adb_install.h"
-#include "bootloader.h"
 #include "common.h"
 #include "device.h"
 #include "error_code.h"
@@ -300,9 +300,13 @@ static void redirect_stdio(const char* filename) {
 //   - the contents of COMMAND_FILE (one per line)
 static void
 get_args(int *argc, char ***argv) {
-    struct bootloader_message boot;
-    memset(&boot, 0, sizeof(boot));
-    get_bootloader_message(&boot);  // this may fail, leaving a zeroed structure
+    bootloader_message boot = {};
+    std::string err;
+    if (!read_bootloader_message(&boot, &err)) {
+        LOGE("%s\n", err.c_str());
+        // If fails, leave a zeroed bootloader_message.
+        memset(&boot, 0, sizeof(boot));
+    }
     stage = strndup(boot.stage, sizeof(boot.stage));
 
     if (boot.command[0] != 0 && boot.command[0] != 255) {
@@ -364,16 +368,20 @@ get_args(int *argc, char ***argv) {
         strlcat(boot.recovery, (*argv)[i], sizeof(boot.recovery));
         strlcat(boot.recovery, "\n", sizeof(boot.recovery));
     }
-    set_bootloader_message(&boot);
+    if (!write_bootloader_message(boot, &err)) {
+        LOGE("%s\n", err.c_str());
+    }
 }
 
 static void
 set_sdcard_update_bootloader_message() {
-    struct bootloader_message boot;
-    memset(&boot, 0, sizeof(boot));
+    bootloader_message boot = {};
     strlcpy(boot.command, "boot-recovery", sizeof(boot.command));
     strlcpy(boot.recovery, "recovery\n", sizeof(boot.recovery));
-    set_bootloader_message(&boot);
+    std::string err;
+    if (!write_bootloader_message(boot, &err)) {
+        LOGE("%s\n", err.c_str());
+    }
 }
 
 // Read from kernel log into buffer and write out to file.
@@ -522,9 +530,11 @@ finish_recovery() {
     copy_logs();
 
     // Reset to normal system boot so recovery won't cycle indefinitely.
-    struct bootloader_message boot;
-    memset(&boot, 0, sizeof(boot));
-    set_bootloader_message(&boot);
+    bootloader_message boot = {};
+    std::string err;
+    if (!write_bootloader_message(boot, &err)) {
+        LOGE("%s\n", err.c_str());
+    }
 
     // Remove the command file, so recovery won't repeat indefinitely.
     if (has_cache) {
@@ -901,8 +911,9 @@ static bool check_wipe_package(size_t wipe_package_size) {
         return false;
     }
     std::string wipe_package;
-    if (!read_wipe_package(wipe_package_size, &wipe_package)) {
-        LOGE("Failed to read wipe package.\n");
+    std::string err_str;
+    if (!read_wipe_package(&wipe_package, wipe_package_size, &err_str)) {
+        LOGE("Failed to read wipe package: %s\n", err_str.c_str());
         return false;
     }
     if (!verify_package(reinterpret_cast<const unsigned char*>(wipe_package.data()),
@@ -1354,7 +1365,7 @@ static bool is_battery_ok() {
 }
 
 static void set_retry_bootloader_message(int retry_count, int argc, char** argv) {
-    struct bootloader_message boot {};
+    bootloader_message boot = {};
     strlcpy(boot.command, "boot-recovery", sizeof(boot.command));
     strlcpy(boot.recovery, "recovery\n", sizeof(boot.recovery));
 
@@ -1373,7 +1384,10 @@ static void set_retry_bootloader_message(int retry_count, int argc, char** argv)
         snprintf(buffer, sizeof(buffer), "--retry_count=%d\n", retry_count+1);
         strlcat(boot.recovery, buffer, sizeof(boot.recovery));
     }
-    set_bootloader_message(&boot);
+    std::string err;
+    if (!write_bootloader_message(boot, &err)) {
+        LOGE("%s\n", err.c_str());
+    }
 }
 
 static ssize_t logbasename(
diff --git a/uncrypt/Android.mk b/uncrypt/Android.mk
index 09cfdfca5..bb276edd5 100644
--- a/uncrypt/Android.mk
+++ b/uncrypt/Android.mk
@@ -15,15 +15,6 @@
 LOCAL_PATH := $(call my-dir)
 
 include $(CLEAR_VARS)
-LOCAL_CLANG := true
-LOCAL_SRC_FILES := bootloader_message_writer.cpp
-LOCAL_MODULE := libbootloader_message_writer
-LOCAL_STATIC_LIBRARIES := libbase libfs_mgr
-LOCAL_C_INCLUDES := $(LOCAL_PATH)/..
-LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)/include
-include $(BUILD_STATIC_LIBRARY)
-
-include $(CLEAR_VARS)
 
 LOCAL_CLANG := true
 
@@ -33,7 +24,7 @@ LOCAL_C_INCLUDES := $(LOCAL_PATH)/..
 
 LOCAL_MODULE := uncrypt
 
-LOCAL_STATIC_LIBRARIES := libbootloader_message_writer libbase \
+LOCAL_STATIC_LIBRARIES := libbootloader_message libbase \
                           liblog libfs_mgr libcutils \
 
 LOCAL_INIT_RC := uncrypt.rc
diff --git a/uncrypt/include/bootloader_message_writer.h b/uncrypt/include/bootloader_message_writer.h
deleted file mode 100644
index 1344bc835..000000000
--- a/uncrypt/include/bootloader_message_writer.h
+++ /dev/null
@@ -1,36 +0,0 @@
-/*
- * Copyright (C) 2016 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#ifndef BOOTLOADER_MESSAGE_WRITER_H
-#define BOOTLOADER_MESSAGE_WRITER_H
-
-#ifdef __cplusplus
-#include <string>
-#include <vector>
-
-bool clear_bootloader_message(std::string* err);
-
-bool write_bootloader_message(const std::vector<std::string>& options, std::string* err);
-bool write_wipe_package(const std::string& package_data, std::string* err);
-
-#else
-#include <stdbool.h>
-
-// C Interface.
-bool write_bootloader_message(const char* options);
-#endif
-
-#endif  // BOOTLOADER_MESSAGE_WRITER_H
diff --git a/uncrypt/uncrypt.cpp b/uncrypt/uncrypt.cpp
index 0f2487d3f..c19943fa7 100644
--- a/uncrypt/uncrypt.cpp
+++ b/uncrypt/uncrypt.cpp
@@ -110,7 +110,7 @@
 #include <android-base/stringprintf.h>
 #include <android-base/strings.h>
 #include <android-base/unique_fd.h>
-#include <bootloader_message_writer.h>
+#include <bootloader_message/bootloader_message.h>
 #include <cutils/android_reboot.h>
 #include <cutils/properties.h>
 #include <cutils/sockets.h>