diff --git a/mkbootimg/bootimg.h b/mkbootimg/bootimg.h
index 60834fe..1be8c22 100644
--- a/mkbootimg/bootimg.h
+++ b/mkbootimg/bootimg.h
@@ -20,16 +20,18 @@
 #ifndef _BOOT_IMAGE_H_
 #define _BOOT_IMAGE_H_
 
-typedef struct boot_img_hdr boot_img_hdr;
-
 #define BOOT_MAGIC "ANDROID!"
 #define BOOT_MAGIC_SIZE 8
 #define BOOT_NAME_SIZE 16
 #define BOOT_ARGS_SIZE 512
 #define BOOT_EXTRA_ARGS_SIZE 1024
 
-struct boot_img_hdr
-{
+#define BOOT_HEADER_VERSION_ZERO 0
+/*
+ *  Bootloader expects the structure of boot_img_hdr with header version
+ *  BOOT_HEADER_VERSION_ZERO to be as follows:
+ */
+struct boot_img_hdr_v0 {
     uint8_t magic[BOOT_MAGIC_SIZE];
 
     uint32_t kernel_size;  /* size in bytes */
@@ -43,7 +45,10 @@
 
     uint32_t tags_addr;    /* physical addr for kernel tags */
     uint32_t page_size;    /* flash page size we assume */
-    uint32_t unused;       /* reserved for future expansion: MUST be 0 */
+    /*
+     * version for the boot image header.
+     */
+    uint32_t header_version;
 
     /* operating system version and security patch level; for
      * version "A.B.C" and patch level "Y-M-D":
@@ -64,31 +69,79 @@
 } __attribute__((packed));
 
 /*
-** +-----------------+ 
-** | boot header     | 1 page
-** +-----------------+
-** | kernel          | n pages  
-** +-----------------+
-** | ramdisk         | m pages  
-** +-----------------+
-** | second stage    | o pages
-** +-----------------+
-**
-** n = (kernel_size + page_size - 1) / page_size
-** m = (ramdisk_size + page_size - 1) / page_size
-** o = (second_size + page_size - 1) / page_size
-**
-** 0. all entities are page_size aligned in flash
-** 1. kernel and ramdisk are required (size != 0)
-** 2. second is optional (second_size == 0 -> no second)
-** 3. load each element (kernel, ramdisk, second) at
-**    the specified physical address (kernel_addr, etc)
-** 4. prepare tags at tag_addr.  kernel_args[] is
-**    appended to the kernel commandline in the tags.
-** 5. r0 = 0, r1 = MACHINE_TYPE, r2 = tags_addr
-** 6. if second_size != 0: jump to second_addr
-**    else: jump to kernel_addr
-*/
+ * It is expected that callers would explicitly specify which version of the
+ * boot image header they need to use.
+ */
+typedef struct boot_img_hdr_v0 boot_img_hdr;
+
+/* When a boot header is of version BOOT_HEADER_VERSION_ZERO, the structure of boot image is as
+ * follows:
+ *
+ * +-----------------+
+ * | boot header     | 1 page
+ * +-----------------+
+ * | kernel          | n pages
+ * +-----------------+
+ * | ramdisk         | m pages
+ * +-----------------+
+ * | second stage    | o pages
+ * +-----------------+
+ *
+ * n = (kernel_size + page_size - 1) / page_size
+ * m = (ramdisk_size + page_size - 1) / page_size
+ * o = (second_size + page_size - 1) / page_size
+ *
+ * 0. all entities are page_size aligned in flash
+ * 1. kernel and ramdisk are required (size != 0)
+ * 2. second is optional (second_size == 0 -> no second)
+ * 3. load each element (kernel, ramdisk, second) at
+ *    the specified physical address (kernel_addr, etc)
+ * 4. prepare tags at tag_addr.  kernel_args[] is
+ *    appended to the kernel commandline in the tags.
+ * 5. r0 = 0, r1 = MACHINE_TYPE, r2 = tags_addr
+ * 6. if second_size != 0: jump to second_addr
+ *    else: jump to kernel_addr
+ */
+
+#define BOOT_HEADER_VERSION_ONE 1
+
+struct boot_img_hdr_v1 : public boot_img_hdr_v0 {
+    uint32_t recovery_dtbo_size;   /* size in bytes for recovery DTBO image */
+    uint64_t recovery_dtbo_offset; /* physical load addr */
+    uint32_t header_size;
+} __attribute__((packed));
+
+/* When the boot image header has a version of BOOT_HEADER_VERSION_ONE, the structure of the boot
+ * image is as follows:
+ *
+ * +-----------------+
+ * | boot header     | 1 page
+ * +-----------------+
+ * | kernel          | n pages
+ * +-----------------+
+ * | ramdisk         | m pages
+ * +-----------------+
+ * | second stage    | o pages
+ * +-----------------+
+ * | recovery dtbo   | p pages
+ * +-----------------+
+ * n = (kernel_size + page_size - 1) / page_size
+ * m = (ramdisk_size + page_size - 1) / page_size
+ * o = (second_size + page_size - 1) / page_size
+ * p = (recovery_dtbo_size + page_size - 1) / page_size
+ *
+ * 0. all entities are page_size aligned in flash
+ * 1. kernel and ramdisk are required (size != 0)
+ * 2. recovery_dtbo is required for recovery.img in non-A/B devices(recovery_dtbo_size != 0)
+ * 3. second is optional (second_size == 0 -> no second)
+ * 4. load each element (kernel, ramdisk, second, recovery_dtbo) at
+ *    the specified physical address (kernel_addr, etc)
+ * 5. prepare tags at tag_addr.  kernel_args[] is
+ *    appended to the kernel commandline in the tags.
+ * 6. r0 = 0, r1 = MACHINE_TYPE, r2 = tags_addr
+ * 7. if second_size != 0: jump to second_addr
+ *    else: jump to kernel_addr
+ */
 
 #if 0
 typedef struct ptentry ptentry;
diff --git a/mkbootimg/mkbootimg b/mkbootimg/mkbootimg
index 5a13da2..ac20d05 100755
--- a/mkbootimg/mkbootimg
+++ b/mkbootimg/mkbootimg
@@ -57,7 +57,7 @@
         args.base + args.second_offset,                 # physical load addr
         args.base + args.tags_offset,                   # physical addr for kernel tags
         args.pagesize,                                  # flash page size we assume
-        0,                                              # future expansion: MUST be 0
+        args.header_version,                            # version of bootimage header
         (args.os_version << 11) | args.os_patch_level)) # os version and patch level
     args.output.write(pack('16s', args.board.encode())) # asciiz product name
     args.output.write(pack('512s', args.cmdline[:512].encode()))
@@ -66,10 +66,20 @@
     update_sha(sha, args.kernel)
     update_sha(sha, args.ramdisk)
     update_sha(sha, args.second)
+
+    if args.header_version > 0:
+        update_sha(sha, args.recovery_dtbo)
+
     img_id = pack('32s', sha.digest())
 
     args.output.write(img_id)
     args.output.write(pack('1024s', args.cmdline[512:].encode()))
+
+    if args.header_version > 0:
+        args.output.write(pack('I', filesize(args.recovery_dtbo)))           # size in bytes
+        args.output.write(pack('Q', args.base + args.recovery_dtbo_offset))  # physical load addr
+        args.output.write(pack('I', args.output.tell() + 4))                 # size of boot header
+
     pad_file(args.output, args.pagesize)
     return img_id
 
@@ -132,6 +142,7 @@
                         required=True)
     parser.add_argument('--ramdisk', help='path to the ramdisk', type=FileType('rb'))
     parser.add_argument('--second', help='path to the 2nd bootloader', type=FileType('rb'))
+    parser.add_argument('--recovery_dtbo', help='path to the recovery DTBO', type=FileType('rb'))
     parser.add_argument('--cmdline', help='extra arguments to be passed on the '
                         'kernel command line', default='', action=ValidateStrLenAction, maxlen=1536)
     parser.add_argument('--base', help='base address', type=parse_int, default=0x10000000)
@@ -139,6 +150,8 @@
     parser.add_argument('--ramdisk_offset', help='ramdisk offset', type=parse_int, default=0x01000000)
     parser.add_argument('--second_offset', help='2nd bootloader offset', type=parse_int,
                         default=0x00f00000)
+    parser.add_argument('--recovery_dtbo_offset', help='recovery dtbo offset', type=parse_int,
+                        default=0x0f000000)
     parser.add_argument('--os_version', help='operating system version', type=parse_os_version,
                         default=0)
     parser.add_argument('--os_patch_level', help='operating system patch level',
@@ -150,6 +163,7 @@
                         choices=[2**i for i in range(11,15)], default=2048)
     parser.add_argument('--id', help='print the image ID on standard output',
                         action='store_true')
+    parser.add_argument('--header_version', help='boot image header version', type=parse_int, default=0)
     parser.add_argument('-o', '--output', help='output file name', type=FileType('wb'),
                         required=True)
     return parser.parse_args()
@@ -160,6 +174,8 @@
     write_padded_file(args.output, args.ramdisk, args.pagesize)
     write_padded_file(args.output, args.second, args.pagesize)
 
+    if args.header_version > 0:
+        write_padded_file(args.output, args.recovery_dtbo, args.pagesize)
 
 def main():
     args = parse_cmdline()