diff --git a/.clang-format b/.clang-format
index 5322788..0e0f4d1 100644
--- a/.clang-format
+++ b/.clang-format
@@ -10,6 +10,5 @@
 PointerAlignment: Left
 TabWidth: 2
 UseTab: Never
-PenaltyExcessCharacter: 32
 
 Cpp11BracedListStyle: false
diff --git a/applypatch/imgdiff.cpp b/applypatch/imgdiff.cpp
index 2eb618f..c887a85 100644
--- a/applypatch/imgdiff.cpp
+++ b/applypatch/imgdiff.cpp
@@ -15,53 +15,44 @@
  */
 
 /*
- * This program constructs binary patches for images -- such as boot.img
- * and recovery.img -- that consist primarily of large chunks of gzipped
- * data interspersed with uncompressed data.  Doing a naive bsdiff of
- * these files is not useful because small changes in the data lead to
- * large changes in the compressed bitstream; bsdiff patches of gzipped
- * data are typically as large as the data itself.
+ * This program constructs binary patches for images -- such as boot.img and recovery.img -- that
+ * consist primarily of large chunks of gzipped data interspersed with uncompressed data.  Doing a
+ * naive bsdiff of these files is not useful because small changes in the data lead to large
+ * changes in the compressed bitstream; bsdiff patches of gzipped data are typically as large as
+ * the data itself.
  *
- * To patch these usefully, we break the source and target images up into
- * chunks of two types: "normal" and "gzip".  Normal chunks are simply
- * patched using a plain bsdiff.  Gzip chunks are first expanded, then a
- * bsdiff is applied to the uncompressed data, then the patched data is
- * gzipped using the same encoder parameters.  Patched chunks are
- * concatenated together to create the output file; the output image
- * should be *exactly* the same series of bytes as the target image used
- * originally to generate the patch.
+ * To patch these usefully, we break the source and target images up into chunks of two types:
+ * "normal" and "gzip".  Normal chunks are simply patched using a plain bsdiff.  Gzip chunks are
+ * first expanded, then a bsdiff is applied to the uncompressed data, then the patched data is
+ * gzipped using the same encoder parameters.  Patched chunks are concatenated together to create
+ * the output file; the output image should be *exactly* the same series of bytes as the target
+ * image used originally to generate the patch.
  *
- * To work well with this tool, the gzipped sections of the target
- * image must have been generated using the same deflate encoder that
- * is available in applypatch, namely, the one in the zlib library.
- * In practice this means that images should be compressed using the
- * "minigzip" tool included in the zlib distribution, not the GNU gzip
- * program.
+ * To work well with this tool, the gzipped sections of the target image must have been generated
+ * using the same deflate encoder that is available in applypatch, namely, the one in the zlib
+ * library.  In practice this means that images should be compressed using the "minigzip" tool
+ * included in the zlib distribution, not the GNU gzip program.
  *
- * An "imgdiff" patch consists of a header describing the chunk structure
- * of the file and any encoding parameters needed for the gzipped
- * chunks, followed by N bsdiff patches, one per chunk.
+ * An "imgdiff" patch consists of a header describing the chunk structure of the file and any
+ * encoding parameters needed for the gzipped chunks, followed by N bsdiff patches, one per chunk.
  *
- * For a diff to be generated, the source and target images must have the
- * same "chunk" structure: that is, the same number of gzipped and normal
- * chunks in the same order.  Android boot and recovery images currently
- * consist of five chunks:  a small normal header, a gzipped kernel, a
- * small normal section, a gzipped ramdisk, and finally a small normal
- * footer.
+ * For a diff to be generated, the source and target must be in well-formed zip archive format;
+ * or they are image files with the same "chunk" structure: that is, the same number of gzipped and
+ * normal chunks in the same order.  Android boot and recovery images currently consist of five
+ * chunks: a small normal header, a gzipped kernel, a small normal section, a gzipped ramdisk, and
+ * finally a small normal footer.
  *
- * Caveats:  we locate gzipped sections within the source and target
- * images by searching for the byte sequence 1f8b0800:  1f8b is the gzip
- * magic number; 08 specifies the "deflate" encoding [the only encoding
- * supported by the gzip standard]; and 00 is the flags byte.  We do not
- * currently support any extra header fields (which would be indicated by
- * a nonzero flags byte).  We also don't handle the case when that byte
- * sequence appears spuriously in the file.  (Note that it would have to
- * occur spuriously within a normal chunk to be a problem.)
+ * Caveats:  we locate gzipped sections within the source and target images by searching for the
+ * byte sequence 1f8b0800:  1f8b is the gzip magic number; 08 specifies the "deflate" encoding
+ * [the only encoding supported by the gzip standard]; and 00 is the flags byte.  We do not
+ * currently support any extra header fields (which would be indicated by a nonzero flags byte).
+ * We also don't handle the case when that byte sequence appears spuriously in the file.  (Note
+ * that it would have to occur spuriously within a normal chunk to be a problem.)
  *
  *
  * The imgdiff patch header looks like this:
  *
- *    "IMGDIFF1"                  (8)   [magic number and version]
+ *    "IMGDIFF2"                  (8)   [magic number and version]
  *    chunk count                 (4)
  *    for each chunk:
  *        chunk type              (4)   [CHUNK_{NORMAL, GZIP, DEFLATE, RAW}]
@@ -98,27 +89,55 @@
  *           target len           (4)
  *           data                 (target len)
  *
- * All integers are little-endian.  "source start" and "source len"
- * specify the section of the input image that comprises this chunk,
- * including the gzip header and footer for gzip chunks.  "source
- * expanded len" is the size of the uncompressed source data.  "target
- * expected len" is the size of the uncompressed data after applying
- * the bsdiff patch.  The next five parameters specify the zlib
- * parameters to be used when compressing the patched data, and the
- * next three specify the header and footer to be wrapped around the
- * compressed data to create the output chunk (so that header contents
- * like the timestamp are recreated exactly).
+ * All integers are little-endian.  "source start" and "source len" specify the section of the
+ * input image that comprises this chunk, including the gzip header and footer for gzip chunks.
+ * "source expanded len" is the size of the uncompressed source data.  "target expected len" is the
+ * size of the uncompressed data after applying the bsdiff patch.  The next five parameters
+ * specify the zlib parameters to be used when compressing the patched data, and the next three
+ * specify the header and footer to be wrapped around the compressed data to create the output
+ * chunk (so that header contents like the timestamp are recreated exactly).
  *
- * After the header there are 'chunk count' bsdiff patches; the offset
- * of each from the beginning of the file is specified in the header.
+ * After the header there are 'chunk count' bsdiff patches; the offset of each from the beginning
+ * of the file is specified in the header.
  *
- * This tool can take an optional file of "bonus data".  This is an
- * extra file of data that is appended to chunk #1 after it is
- * compressed (it must be a CHUNK_DEFLATE chunk).  The same file must
- * be available (and passed to applypatch with -b) when applying the
- * patch.  This is used to reduce the size of recovery-from-boot
- * patches by combining the boot image with recovery ramdisk
+ * This tool can take an optional file of "bonus data".  This is an extra file of data that is
+ * appended to chunk #1 after it is compressed (it must be a CHUNK_DEFLATE chunk).  The same file
+ * must be available (and passed to applypatch with -b) when applying the patch.  This is used to
+ * reduce the size of recovery-from-boot patches by combining the boot image with recovery ramdisk
  * information that is stored on the system partition.
+ *
+ * When generating the patch between two zip files, this tool has an option "--block-limit" to
+ * split the large source/target files into several pair of pieces, with each piece has at most
+ * *limit* blocks.  When this option is used, we also need to output the split info into the file
+ * path specified by "--split-info".
+ *
+ * Format of split info file:
+ *   2                                      [version of imgdiff]
+ *   n                                      [count of split pieces]
+ *   <patch_size>, <tgt_size>, <src_range>  [size and ranges for split piece#1]
+ *   ...
+ *   <patch_size>, <tgt_size>, <src_range>  [size and ranges for split piece#n]
+ *
+ * To split a pair of large zip files, we walk through the chunks in target zip and search by its
+ * entry_name in the source zip.  If the entry_name is non-empty and a matching entry in source
+ * is found, we'll add the source entry to the current split source image; otherwise we'll skip
+ * this chunk and later do bsdiff between all the skipped trunks and the whole split source image.
+ * We move on to the next pair of pieces if the size of the split source image reaches the block
+ * limit.
+ *
+ * After the split, the target pieces are continuous and block aligned, while the source pieces
+ * are mutually exclusive.  Some of the source blocks may not be used if there's no matching
+ * entry_name in the target; as a result, they won't be included in any of these split source
+ * images.  Then we will generate patches accordingly between each split image pairs; in particular,
+ * the unmatched trunks in the split target will diff against the entire split source image.
+ *
+ * For example:
+ * Input: [src_image, tgt_image]
+ * Split: [src-0, tgt-0; src-1, tgt-1, src-2, tgt-2]
+ * Diff:  [  patch-0;      patch-1;      patch-2]
+ *
+ * Patch: [(src-0, patch-0) = tgt-0; (src-1, patch-1) = tgt-1; (src-2, patch-2) = tgt-2]
+ * Concatenate: [tgt-0 + tgt-1 + tgt-2 = tgt_image]
  */
 
 #include "applypatch/imgdiff.h"
@@ -151,6 +170,11 @@
 
 using android::base::get_unaligned;
 
+static constexpr size_t VERSION = 2;
+
+// We assume the header "IMGDIFF#" is 8 bytes.
+static_assert(VERSION <= 9, "VERSION occupies more than one byte.");
+
 static constexpr size_t BLOCK_SIZE = 4096;
 static constexpr size_t BUFFER_SIZE = 0x8000;
 
@@ -224,6 +248,7 @@
   { "bonus-file", required_argument, nullptr, 'b' },
   { "block-limit", required_argument, nullptr, 0 },
   { "debug-dir", required_argument, nullptr, 0 },
+  { "split-info", required_argument, nullptr, 0 },
   { nullptr, 0, nullptr, 0 },
 };
 
@@ -497,6 +522,13 @@
   }
 }
 
+size_t PatchChunk::PatchSize() const {
+  if (type_ == CHUNK_RAW) {
+    return GetHeaderSize();
+  }
+  return GetHeaderSize() + data_.size();
+}
+
 // Write the contents of |patch_chunks| to |patch_fd|.
 bool PatchChunk::WritePatchDataToFd(const std::vector<PatchChunk>& patch_chunks, int patch_fd) {
   // Figure out how big the imgdiff file header is going to be, so that we can correctly compute
@@ -509,8 +541,8 @@
   size_t offset = total_header_size;
 
   // Write out the headers.
-  if (!android::base::WriteStringToFd("IMGDIFF2", patch_fd)) {
-    printf("failed to write \"IMGDIFF2\": %s\n", strerror(errno));
+  if (!android::base::WriteStringToFd("IMGDIFF" + std::to_string(VERSION), patch_fd)) {
+    printf("failed to write \"IMGDIFF%zu\": %s\n", VERSION, strerror(errno));
     return false;
   }
 
@@ -1107,7 +1139,9 @@
 bool ZipModeImage::GeneratePatches(const std::vector<ZipModeImage>& split_tgt_images,
                                    const std::vector<ZipModeImage>& split_src_images,
                                    const std::vector<SortedRangeSet>& split_src_ranges,
-                                   const std::string& patch_name, const std::string& debug_dir) {
+                                   const std::string& patch_name,
+                                   const std::string& split_info_file,
+                                   const std::string& debug_dir) {
   printf("Construct patches for %zu split images...\n", split_tgt_images.size());
 
   android::base::unique_fd patch_fd(
@@ -1117,6 +1151,7 @@
     return false;
   }
 
+  std::vector<std::string> split_info_list;
   for (size_t i = 0; i < split_tgt_images.size(); i++) {
     std::vector<PatchChunk> patch_chunks;
     if (!ZipModeImage::GeneratePatchesInternal(split_tgt_images[i], split_src_images[i],
@@ -1125,14 +1160,23 @@
       return false;
     }
 
+    size_t total_patch_size = 12;
     for (auto& p : patch_chunks) {
       p.UpdateSourceOffset(split_src_ranges[i]);
+      total_patch_size += p.PatchSize();
     }
 
     if (!PatchChunk::WritePatchDataToFd(patch_chunks, patch_fd)) {
       return false;
     }
 
+    size_t split_tgt_size = split_tgt_images[i].chunks_.back().GetStartOffset() +
+                            split_tgt_images[i].chunks_.back().GetRawDataLength() -
+                            split_tgt_images[i].chunks_.front().GetStartOffset();
+    std::string split_info = android::base::StringPrintf(
+        "%zu %zu %s", total_patch_size, split_tgt_size, split_src_ranges[i].ToString().c_str());
+    split_info_list.push_back(split_info);
+
     // Write the split source & patch into the debug directory.
     if (!debug_dir.empty()) {
       std::string src_name = android::base::StringPrintf("%s/src-%zu", debug_dir.c_str(), i);
@@ -1161,6 +1205,21 @@
       }
     }
   }
+
+  // Store the split in the following format:
+  // Line 0:   imgdiff version#
+  // Line 1:   number of pieces
+  // Line 2:   patch_size_1 tgt_size_1 src_range_1
+  // ...
+  // Line n+1: patch_size_n tgt_size_n src_range_n
+  std::string split_info_string = android::base::StringPrintf(
+      "%zu\n%zu\n", VERSION, split_info_list.size()) + android::base::Join(split_info_list, '\n');
+  if (!android::base::WriteStringToFile(split_info_string, split_info_file)) {
+    printf("failed to write split info to \"%s\": %s\n", split_info_file.c_str(),
+           strerror(errno));
+    return false;
+  }
+
   return true;
 }
 
@@ -1396,6 +1455,7 @@
   bool zip_mode = false;
   std::vector<uint8_t> bonus_data;
   size_t blocks_limit = 0;
+  std::string split_info_file;
   std::string debug_dir;
 
   int opt;
@@ -1432,6 +1492,8 @@
         if (name == "block-limit" && !android::base::ParseUint(optarg, &blocks_limit)) {
           printf("failed to parse size blocks_limit: %s\n", optarg);
           return 1;
+        } else if (name == "split-info") {
+          split_info_file = optarg;
         } else if (name == "debug-dir") {
           debug_dir = optarg;
         }
@@ -1451,6 +1513,8 @@
         "  --block-limit,    For large zips, split the src and tgt based on the block limit;\n"
         "                    and generate patches between each pair of pieces. Concatenate these\n"
         "                    patches together and output them into <patch-file>.\n"
+        "  --split-info,     Output the split information (patch_size, tgt_size, src_ranges);\n"
+        "                    zip mode with block-limit only.\n"
         "  --debug_dir,      Debug directory to put the split srcs and patches, zip mode only.\n");
     return 2;
   }
@@ -1476,6 +1540,11 @@
     // Compute bsdiff patches for each chunk's data (the uncompressed data, in the case of
     // deflate chunks).
     if (blocks_limit > 0) {
+      if (split_info_file.empty()) {
+        printf("split-info path cannot be empty when generating patches with a block-limit.\n");
+        return 1;
+      }
+
       std::vector<ZipModeImage> split_tgt_images;
       std::vector<ZipModeImage> split_src_images;
       std::vector<SortedRangeSet> split_src_ranges;
@@ -1483,7 +1552,7 @@
                                                &split_src_images, &split_src_ranges);
 
       if (!ZipModeImage::GeneratePatches(split_tgt_images, split_src_images, split_src_ranges,
-                                         argv[optind + 2], debug_dir)) {
+                                         argv[optind + 2], split_info_file, debug_dir)) {
         return 1;
       }
 
diff --git a/applypatch/include/applypatch/imgdiff_image.h b/applypatch/include/applypatch/imgdiff_image.h
index 9fb844b..491043d 100644
--- a/applypatch/include/applypatch/imgdiff_image.h
+++ b/applypatch/include/applypatch/imgdiff_image.h
@@ -132,6 +132,9 @@
   // Update the source start with the new offset within the source range.
   void UpdateSourceOffset(const SortedRangeSet& src_range);
 
+  // Return the total size (header + data) of the patch.
+  size_t PatchSize() const;
+
   static bool WritePatchDataToFd(const std::vector<PatchChunk>& patch_chunks, int patch_fd);
 
  private:
@@ -241,7 +244,8 @@
   static bool GeneratePatches(const std::vector<ZipModeImage>& split_tgt_images,
                               const std::vector<ZipModeImage>& split_src_images,
                               const std::vector<SortedRangeSet>& split_src_ranges,
-                              const std::string& patch_name, const std::string& debug_dir);
+                              const std::string& patch_name, const std::string& split_info_file,
+                              const std::string& debug_dir);
 
   // Split the tgt chunks and src chunks based on the size limit.
   static bool SplitZipModeImageWithLimit(const ZipModeImage& tgt_image,
diff --git a/common.h b/common.h
index 62fb132..8b336f8 100644
--- a/common.h
+++ b/common.h
@@ -22,8 +22,9 @@
 
 #include <string>
 
-#define STRINGIFY(x) #x
-#define EXPAND(x) STRINGIFY(x)
+// Not using the command-line defined macro here because this header could be included by
+// device-specific recovery libraries. We static assert the value consistency in recovery.cpp.
+static constexpr int kRecoveryApiVersion = 3;
 
 class RecoveryUI;
 
diff --git a/device.cpp b/device.cpp
index 6150186..f881daf 100644
--- a/device.cpp
+++ b/device.cpp
@@ -17,34 +17,36 @@
 #include "device.h"
 
 static const char* MENU_ITEMS[] = {
-    "Reboot system now",
-    "Reboot to bootloader",
-    "Apply update from ADB",
-    "Apply update from SD card",
-    "Wipe data/factory reset",
+  "Reboot system now",
+  "Reboot to bootloader",
+  "Apply update from ADB",
+  "Apply update from SD card",
+  "Wipe data/factory reset",
 #ifndef AB_OTA_UPDATER
-    "Wipe cache partition",
+  "Wipe cache partition",
 #endif  // !AB_OTA_UPDATER
-    "Mount /system",
-    "View recovery logs",
-    "Run graphics test",
-    "Power off",
-    NULL,
+  "Mount /system",
+  "View recovery logs",
+  "Run graphics test",
+  "Run locale test",
+  "Power off",
+  nullptr,
 };
 
 static const Device::BuiltinAction MENU_ACTIONS[] = {
-    Device::REBOOT,
-    Device::REBOOT_BOOTLOADER,
-    Device::APPLY_ADB_SIDELOAD,
-    Device::APPLY_SDCARD,
-    Device::WIPE_DATA,
+  Device::REBOOT,
+  Device::REBOOT_BOOTLOADER,
+  Device::APPLY_ADB_SIDELOAD,
+  Device::APPLY_SDCARD,
+  Device::WIPE_DATA,
 #ifndef AB_OTA_UPDATER
-    Device::WIPE_CACHE,
+  Device::WIPE_CACHE,
 #endif  // !AB_OTA_UPDATER
-    Device::MOUNT_SYSTEM,
-    Device::VIEW_RECOVERY_LOGS,
-    Device::RUN_GRAPHICS_TEST,
-    Device::SHUTDOWN,
+  Device::MOUNT_SYSTEM,
+  Device::VIEW_RECOVERY_LOGS,
+  Device::RUN_GRAPHICS_TEST,
+  Device::RUN_LOCALE_TEST,
+  Device::SHUTDOWN,
 };
 
 static_assert(sizeof(MENU_ITEMS) / sizeof(MENU_ITEMS[0]) ==
diff --git a/device.h b/device.h
index 639e2bf..74745b3 100644
--- a/device.h
+++ b/device.h
@@ -66,6 +66,7 @@
     VIEW_RECOVERY_LOGS = 9,
     MOUNT_SYSTEM = 10,
     RUN_GRAPHICS_TEST = 11,
+    RUN_LOCALE_TEST = 12,
   };
 
   // Return the list of menu items (an array of strings, NULL-terminated). The menu_position passed
diff --git a/install.cpp b/install.cpp
index 586dbbe..507161c 100644
--- a/install.cpp
+++ b/install.cpp
@@ -290,7 +290,7 @@
 
   *cmd = {
     binary_path,
-    EXPAND(RECOVERY_API_VERSION),  // defined in Android.mk
+    std::to_string(kRecoveryApiVersion),
     std::to_string(status_fd),
     package,
   };
diff --git a/minui/include/minui/minui.h b/minui/include/minui/minui.h
index 017ddde..27e6031 100644
--- a/minui/include/minui/minui.h
+++ b/minui/include/minui/minui.h
@@ -21,6 +21,7 @@
 
 #include <functional>
 #include <string>
+#include <vector>
 
 //
 // Graphics.
@@ -129,6 +130,9 @@
 int res_create_localized_alpha_surface(const char* name, const char* locale,
                                        GRSurface** pSurface);
 
+// Return a list of locale strings embedded in |png_name|. Return a empty list in case of failure.
+std::vector<std::string> get_locales_in_png(const std::string& png_name);
+
 // Free a surface allocated by any of the res_create_*_surface()
 // functions.
 void res_free_surface(GRSurface* surface);
diff --git a/minui/resources.cpp b/minui/resources.cpp
index 8f8d36d..756f29d 100644
--- a/minui/resources.cpp
+++ b/minui/resources.cpp
@@ -396,6 +396,41 @@
   return std::regex_match(locale, loc_regex);
 }
 
+std::vector<std::string> get_locales_in_png(const std::string& png_name) {
+  png_structp png_ptr = nullptr;
+  png_infop info_ptr = nullptr;
+  png_uint_32 width, height;
+  png_byte channels;
+
+  int status = open_png(png_name.c_str(), &png_ptr, &info_ptr, &width, &height, &channels);
+  if (status < 0) {
+    printf("Failed to open %s\n", png_name.c_str());
+    return {};
+  }
+  if (channels != 1) {
+    printf("Expect input png to have 1 data channel, this file has %d\n", channels);
+    png_destroy_read_struct(&png_ptr, &info_ptr, nullptr);
+    return {};
+  }
+
+  std::vector<std::string> result;
+  std::vector<unsigned char> row(width);
+  for (png_uint_32 y = 0; y < height; ++y) {
+    png_read_row(png_ptr, row.data(), nullptr);
+    int h = (row[3] << 8) | row[2];
+    std::string loc(reinterpret_cast<char*>(&row[5]));
+    if (!loc.empty()) {
+      result.push_back(loc);
+    }
+    for (int i = 0; i < h; ++i, ++y) {
+      png_read_row(png_ptr, row.data(), NULL);
+    }
+  }
+
+  png_destroy_read_struct(&png_ptr, &info_ptr, nullptr);
+  return result;
+}
+
 int res_create_localized_alpha_surface(const char* name,
                                        const char* locale,
                                        GRSurface** pSurface) {
diff --git a/recovery-persist.rc b/recovery-persist.rc
index 6761627..135a3c3 100644
--- a/recovery-persist.rc
+++ b/recovery-persist.rc
@@ -1,3 +1,3 @@
 on post-fs-data
     mkdir /data/misc/recovery 0770 system log
-    exec - system log -- /system/bin/recovery-persist
+    exec_background - system log -- /system/bin/recovery-persist
diff --git a/recovery-refresh.rc b/recovery-refresh.rc
index 14b05cc..9fefc81 100644
--- a/recovery-refresh.rc
+++ b/recovery-refresh.rc
@@ -1,2 +1,2 @@
 on post-fs
-    exec - system log -- /system/bin/recovery-refresh
+    exec_background - system log -- /system/bin/recovery-refresh
diff --git a/recovery.cpp b/recovery.cpp
index 6f62ff1..076b449 100644
--- a/recovery.cpp
+++ b/recovery.cpp
@@ -125,6 +125,10 @@
 static constexpr const char* RECOVERY_WIPE = "/etc/recovery.wipe";
 static constexpr const char* DEFAULT_LOCALE = "en-US";
 
+// We define RECOVERY_API_VERSION in Android.mk, which will be picked up by build system and packed
+// into target_files.zip. Assert the version defined in code and in Android.mk are consistent.
+static_assert(kRecoveryApiVersion == RECOVERY_API_VERSION, "Mismatching recovery API versions.");
+
 static std::string locale;
 static bool has_cache = false;
 
@@ -1187,6 +1191,11 @@
         run_graphics_test();
         break;
 
+      case Device::RUN_LOCALE_TEST: {
+        ScreenRecoveryUI* screen_ui = static_cast<ScreenRecoveryUI*>(ui);
+        screen_ui->CheckBackgroundTextImages(locale);
+        break;
+      }
       case Device::MOUNT_SYSTEM:
         // For a system image built with the root directory (i.e. system_root_image == "true"), we
         // mount it to /system_root, and symlink /system to /system_root/system to make adb shell
@@ -1498,7 +1507,7 @@
     property_list(print_property, NULL);
     printf("\n");
 
-    ui->Print("Supported API: %d\n", RECOVERY_API_VERSION);
+    ui->Print("Supported API: %d\n", kRecoveryApiVersion);
 
     int status = INSTALL_SUCCESS;
 
diff --git a/res-hdpi/images/erasing_text.png b/res-hdpi/images/erasing_text.png
index 0982544..34c56a9 100644
--- a/res-hdpi/images/erasing_text.png
+++ b/res-hdpi/images/erasing_text.png
Binary files differ
diff --git a/res-hdpi/images/error_text.png b/res-hdpi/images/error_text.png
index 3a06f6e..2a96053 100644
--- a/res-hdpi/images/error_text.png
+++ b/res-hdpi/images/error_text.png
Binary files differ
diff --git a/res-hdpi/images/installing_security_text.png b/res-hdpi/images/installing_security_text.png
index b1acd23..97e1f11 100644
--- a/res-hdpi/images/installing_security_text.png
+++ b/res-hdpi/images/installing_security_text.png
Binary files differ
diff --git a/res-hdpi/images/installing_text.png b/res-hdpi/images/installing_text.png
index f0f5d8b..1d591eb 100644
--- a/res-hdpi/images/installing_text.png
+++ b/res-hdpi/images/installing_text.png
Binary files differ
diff --git a/res-hdpi/images/no_command_text.png b/res-hdpi/images/no_command_text.png
index def5036..977fcfa 100644
--- a/res-hdpi/images/no_command_text.png
+++ b/res-hdpi/images/no_command_text.png
Binary files differ
diff --git a/res-mdpi/images/erasing_text.png b/res-mdpi/images/erasing_text.png
index 82b4461..dcd0ea6 100644
--- a/res-mdpi/images/erasing_text.png
+++ b/res-mdpi/images/erasing_text.png
Binary files differ
diff --git a/res-mdpi/images/error_text.png b/res-mdpi/images/error_text.png
index adb4513..2152dad 100644
--- a/res-mdpi/images/error_text.png
+++ b/res-mdpi/images/error_text.png
Binary files differ
diff --git a/res-mdpi/images/installing_security_text.png b/res-mdpi/images/installing_security_text.png
index 54e5564..d1ac4ca 100644
--- a/res-mdpi/images/installing_security_text.png
+++ b/res-mdpi/images/installing_security_text.png
Binary files differ
diff --git a/res-mdpi/images/installing_text.png b/res-mdpi/images/installing_text.png
index d423318..c9b6d71 100644
--- a/res-mdpi/images/installing_text.png
+++ b/res-mdpi/images/installing_text.png
Binary files differ
diff --git a/res-mdpi/images/no_command_text.png b/res-mdpi/images/no_command_text.png
index cd77ff4..f77ad13 100644
--- a/res-mdpi/images/no_command_text.png
+++ b/res-mdpi/images/no_command_text.png
Binary files differ
diff --git a/res-xhdpi/images/erasing_text.png b/res-xhdpi/images/erasing_text.png
index 333edbe..e22b274 100644
--- a/res-xhdpi/images/erasing_text.png
+++ b/res-xhdpi/images/erasing_text.png
Binary files differ
diff --git a/res-xhdpi/images/error_text.png b/res-xhdpi/images/error_text.png
index e262584..e4c27e1 100644
--- a/res-xhdpi/images/error_text.png
+++ b/res-xhdpi/images/error_text.png
Binary files differ
diff --git a/res-xhdpi/images/installing_security_text.png b/res-xhdpi/images/installing_security_text.png
index e0f0f3e..7ba12b6 100644
--- a/res-xhdpi/images/installing_security_text.png
+++ b/res-xhdpi/images/installing_security_text.png
Binary files differ
diff --git a/res-xhdpi/images/installing_text.png b/res-xhdpi/images/installing_text.png
index a7e67f5..567988e 100644
--- a/res-xhdpi/images/installing_text.png
+++ b/res-xhdpi/images/installing_text.png
Binary files differ
diff --git a/res-xhdpi/images/no_command_text.png b/res-xhdpi/images/no_command_text.png
index 13aef7b..a682abb 100644
--- a/res-xhdpi/images/no_command_text.png
+++ b/res-xhdpi/images/no_command_text.png
Binary files differ
diff --git a/res-xxhdpi/images/erasing_text.png b/res-xxhdpi/images/erasing_text.png
index 80e7c47..6cc953b 100644
--- a/res-xxhdpi/images/erasing_text.png
+++ b/res-xxhdpi/images/erasing_text.png
Binary files differ
diff --git a/res-xxhdpi/images/error_text.png b/res-xxhdpi/images/error_text.png
index 32a1965..0d5cea8 100644
--- a/res-xxhdpi/images/error_text.png
+++ b/res-xxhdpi/images/error_text.png
Binary files differ
diff --git a/res-xxhdpi/images/installing_security_text.png b/res-xxhdpi/images/installing_security_text.png
index c53c9ac..5d10598 100644
--- a/res-xxhdpi/images/installing_security_text.png
+++ b/res-xxhdpi/images/installing_security_text.png
Binary files differ
diff --git a/res-xxhdpi/images/installing_text.png b/res-xxhdpi/images/installing_text.png
index 38b18d2..6e94fa2 100644
--- a/res-xxhdpi/images/installing_text.png
+++ b/res-xxhdpi/images/installing_text.png
Binary files differ
diff --git a/res-xxhdpi/images/no_command_text.png b/res-xxhdpi/images/no_command_text.png
index a0666d8..40ab484 100644
--- a/res-xxhdpi/images/no_command_text.png
+++ b/res-xxhdpi/images/no_command_text.png
Binary files differ
diff --git a/res-xxxhdpi/images/erasing_text.png b/res-xxxhdpi/images/erasing_text.png
index 4f7b37b..cc73099 100644
--- a/res-xxxhdpi/images/erasing_text.png
+++ b/res-xxxhdpi/images/erasing_text.png
Binary files differ
diff --git a/res-xxxhdpi/images/error_text.png b/res-xxxhdpi/images/error_text.png
index 052bf21..fea3cfc 100644
--- a/res-xxxhdpi/images/error_text.png
+++ b/res-xxxhdpi/images/error_text.png
Binary files differ
diff --git a/res-xxxhdpi/images/installing_security_text.png b/res-xxxhdpi/images/installing_security_text.png
index a9e739b..ed77d08 100644
--- a/res-xxxhdpi/images/installing_security_text.png
+++ b/res-xxxhdpi/images/installing_security_text.png
Binary files differ
diff --git a/res-xxxhdpi/images/installing_text.png b/res-xxxhdpi/images/installing_text.png
index 2d19486..9659106 100644
--- a/res-xxxhdpi/images/installing_text.png
+++ b/res-xxxhdpi/images/installing_text.png
Binary files differ
diff --git a/res-xxxhdpi/images/no_command_text.png b/res-xxxhdpi/images/no_command_text.png
index ee0c238..4e6f363 100644
--- a/res-xxxhdpi/images/no_command_text.png
+++ b/res-xxxhdpi/images/no_command_text.png
Binary files differ
diff --git a/roots.cpp b/roots.cpp
index 26602a7..7d7d1bd 100644
--- a/roots.cpp
+++ b/roots.cpp
@@ -69,8 +69,27 @@
   printf("\n");
 }
 
+// Finds the volume specified by the given path. fs_mgr_get_entry_for_mount_point() does exact match
+// only, so it attempts the prefixes recursively (e.g. "/cache/recovery/last_log",
+// "/cache/recovery", "/cache", "/" for a given path of "/cache/recovery/last_log") and returns the
+// first match or nullptr.
 Volume* volume_for_path(const char* path) {
-  return fs_mgr_get_entry_for_mount_point(fstab, path);
+  if (path == nullptr || path[0] == '\0') return nullptr;
+  std::string str(path);
+  while (true) {
+    Volume* result = fs_mgr_get_entry_for_mount_point(fstab, str.c_str());
+    if (result != nullptr || str == "/") {
+      return result;
+    }
+    size_t slash = str.find_last_of('/');
+    if (slash == std::string::npos) return nullptr;
+    if (slash == 0) {
+      str = "/";
+    } else {
+      str = str.substr(0, slash);
+    }
+  }
+  return nullptr;
 }
 
 // Mount the volume specified by path at the given mount_point.
diff --git a/screen_ui.cpp b/screen_ui.cpp
index d65d656..bc5c5c3 100644
--- a/screen_ui.cpp
+++ b/screen_ui.cpp
@@ -31,7 +31,9 @@
 #include <time.h>
 #include <unistd.h>
 
+#include <memory>
 #include <string>
+#include <unordered_map>
 #include <vector>
 
 #include <android-base/logging.h>
@@ -258,6 +260,81 @@
   }
 }
 
+void ScreenRecoveryUI::SelectAndShowBackgroundText(const std::vector<std::string>& locales_entries,
+                                                   size_t sel) {
+  SetLocale(locales_entries[sel]);
+  std::vector<std::string> text_name = { "erasing_text", "error_text", "installing_text",
+                                         "installing_security_text", "no_command_text" };
+  std::unordered_map<std::string, std::unique_ptr<GRSurface, decltype(&free)>> surfaces;
+  for (const auto& name : text_name) {
+    GRSurface* text_image = nullptr;
+    LoadLocalizedBitmap(name.c_str(), &text_image);
+    if (!text_image) {
+      Print("Failed to load %s\n", name.c_str());
+      return;
+    }
+    surfaces.emplace(name, std::unique_ptr<GRSurface, decltype(&free)>(text_image, &free));
+  }
+
+  pthread_mutex_lock(&updateMutex);
+  gr_color(0, 0, 0, 255);
+  gr_clear();
+
+  int text_y = kMarginHeight;
+  int text_x = kMarginWidth;
+  int line_spacing = gr_sys_font()->char_height;  // Put some extra space between images.
+  // Write the header and descriptive texts.
+  SetColor(INFO);
+  std::string header = "Show background text image";
+  text_y += DrawTextLine(text_x, text_y, header.c_str(), true);
+  std::string locale_selection = android::base::StringPrintf(
+      "Current locale: %s, %zu/%zu", locales_entries[sel].c_str(), sel, locales_entries.size());
+  const char* instruction[] = { locale_selection.c_str(),
+                                "Use volume up/down to switch locales and power to exit.",
+                                nullptr };
+  text_y += DrawWrappedTextLines(text_x, text_y, instruction);
+
+  // Iterate through the text images and display them in order for the current locale.
+  for (const auto& p : surfaces) {
+    text_y += line_spacing;
+    SetColor(LOG);
+    text_y += DrawTextLine(text_x, text_y, p.first.c_str(), false);
+    gr_color(255, 255, 255, 255);
+    gr_texticon(text_x, text_y, p.second.get());
+    text_y += gr_get_height(p.second.get());
+  }
+  // Update the whole screen.
+  gr_flip();
+  pthread_mutex_unlock(&updateMutex);
+}
+
+void ScreenRecoveryUI::CheckBackgroundTextImages(const std::string& saved_locale) {
+  // Load a list of locales embedded in one of the resource files.
+  std::vector<std::string> locales_entries = get_locales_in_png("installing_text");
+  if (locales_entries.empty()) {
+    Print("Failed to load locales from the resource files\n");
+    return;
+  }
+  size_t selected = 0;
+  SelectAndShowBackgroundText(locales_entries, selected);
+
+  FlushKeys();
+  while (true) {
+    int key = WaitKey();
+    if (key == KEY_POWER || key == KEY_ENTER) {
+      break;
+    } else if (key == KEY_UP || key == KEY_VOLUMEUP) {
+      selected = (selected == 0) ? locales_entries.size() - 1 : selected - 1;
+      SelectAndShowBackgroundText(locales_entries, selected);
+    } else if (key == KEY_DOWN || key == KEY_VOLUMEDOWN) {
+      selected = (selected == locales_entries.size() - 1) ? 0 : selected + 1;
+      SelectAndShowBackgroundText(locales_entries, selected);
+    }
+  }
+
+  SetLocale(saved_locale);
+}
+
 int ScreenRecoveryUI::DrawHorizontalRule(int y) const {
   gr_fill(0, y + 4, gr_fb_width(), y + 6);
   return 8;
diff --git a/screen_ui.h b/screen_ui.h
index eaac2a6..3a28a09 100644
--- a/screen_ui.h
+++ b/screen_ui.h
@@ -80,6 +80,10 @@
 
   void SetColor(UIElement e) const;
 
+  // Check the background text image. Use volume up/down button to cycle through the locales
+  // embedded in the png file, and power button to go back to recovery main menu.
+  void CheckBackgroundTextImages(const std::string& saved_locale);
+
  protected:
   // The margin that we don't want to use for showing texts (e.g. round screen, or screen with
   // rounded corners).
@@ -199,6 +203,10 @@
 
  private:
   void SetLocale(const std::string&);
+
+  // Display the background texts for "erasing", "error", "no_command" and "installing" for the
+  // selected locale.
+  void SelectAndShowBackgroundText(const std::vector<std::string>& locales_entries, size_t sel);
 };
 
 #endif  // RECOVERY_UI_H
diff --git a/tests/component/imgdiff_test.cpp b/tests/component/imgdiff_test.cpp
index 3163a57..161d58d 100644
--- a/tests/component/imgdiff_test.cpp
+++ b/tests/component/imgdiff_test.cpp
@@ -778,10 +778,13 @@
 
   // Compute patch.
   TemporaryFile patch_file;
+  TemporaryFile split_info_file;
   TemporaryDir debug_dir;
+  std::string split_info_arg = android::base::StringPrintf("--split-info=%s", split_info_file.path);
+  std::string debug_dir_arg = android::base::StringPrintf("--debug-dir=%s", debug_dir.path);
   std::vector<const char*> args = {
-    "imgdiff", "-z", "--block-limit=10", android::base::StringPrintf(
-          "--debug-dir=%s", debug_dir.path).c_str(), src_file.path, tgt_file.path, patch_file.path,
+    "imgdiff", "-z", "--block-limit=10", split_info_arg.c_str(), debug_dir_arg.c_str(),
+    src_file.path, tgt_file.path, patch_file.path,
   };
   ASSERT_EQ(0, imgdiff(args.size(), args.data()));
 
@@ -863,14 +866,40 @@
 
   // Compute patch.
   TemporaryFile patch_file;
+  TemporaryFile split_info_file;
   TemporaryDir debug_dir;
   ASSERT_TRUE(ZipModeImage::GeneratePatches(split_tgt_images, split_src_images, split_src_ranges,
-                                            patch_file.path, debug_dir.path));
+                                            patch_file.path, split_info_file.path, debug_dir.path));
+
+  // Verify the content of split info.
+  // Expect 5 pieces of patch. ["a","b"; "c"; "d-0"; "d-1"; "e"]
+  std::string split_info_string;
+  android::base::ReadFileToString(split_info_file.path, &split_info_string);
+  std::vector<std::string> info_list =
+      android::base::Split(android::base::Trim(split_info_string), "\n");
+
+  ASSERT_EQ(static_cast<size_t>(7), info_list.size());
+  ASSERT_EQ("2", android::base::Trim(info_list[0]));
+  ASSERT_EQ("5", android::base::Trim(info_list[1]));
+
+  std::vector<size_t> patch_size;
+  for (size_t i = 0; i < 5; i++) {
+    struct stat st = {};
+    std::string path = android::base::StringPrintf("%s/patch-%zu", debug_dir.path, i);
+    ASSERT_EQ(0, stat(path.c_str(), &st));
+    patch_size.push_back(st.st_size);
+  }
+
+  ASSERT_EQ(std::to_string(patch_size[0]) + " 36864 2,22,31", android::base::Trim(info_list[2]));
+  ASSERT_EQ(std::to_string(patch_size[1]) + " 32768 2,31,40", android::base::Trim(info_list[3]));
+  ASSERT_EQ(std::to_string(patch_size[2]) + " 40960 2,0,11", android::base::Trim(info_list[4]));
+  ASSERT_EQ(std::to_string(patch_size[3]) + " 40960 2,11,21", android::base::Trim(info_list[5]));
+  ASSERT_EQ(std::to_string(patch_size[4]) + " 8833 4,21,22,40,41",
+            android::base::Trim(info_list[6]));
 
   std::string tgt;
   ASSERT_TRUE(android::base::ReadFileToString(tgt_file.path, &tgt));
 
-  // Expect 5 pieces of patch. ["a","b"; "c"; "d-0"; "d-1"; "e"]
   GenerateAndCheckSplitTarget(debug_dir.path, 5, tgt);
 }
 
@@ -900,10 +929,13 @@
 
   // Compute patch.
   TemporaryFile patch_file;
+  TemporaryFile split_info_file;
   TemporaryDir debug_dir;
+  std::string split_info_arg = android::base::StringPrintf("--split-info=%s", split_info_file.path);
+  std::string debug_dir_arg = android::base::StringPrintf("--debug-dir=%s", debug_dir.path);
   std::vector<const char*> args = {
-    "imgdiff", "-z", "--block-limit=10", android::base::StringPrintf(
-          "--debug-dir=%s", debug_dir.path).c_str(), src_file.path, tgt_file.path, patch_file.path,
+    "imgdiff", "-z", "--block-limit=10", debug_dir_arg.c_str(), split_info_arg.c_str(),
+    src_file.path, tgt_file.path, patch_file.path,
   };
   ASSERT_EQ(0, imgdiff(args.size(), args.data()));
 
@@ -939,10 +971,13 @@
 
   // Compute patch with a limit of 20 blocks.
   TemporaryFile patch_file;
+  TemporaryFile split_info_file;
   TemporaryDir debug_dir;
+  std::string split_info_arg = android::base::StringPrintf("--split-info=%s", split_info_file.path);
+  std::string debug_dir_arg = android::base::StringPrintf("--debug-dir=%s", debug_dir.path);
   std::vector<const char*> args = {
-    "imgdiff", "-z", "--block-limit=20", android::base::StringPrintf(
-          "--debug-dir=%s", debug_dir.path).c_str(), src_file.path, tgt_file.path, patch_file.path,
+    "imgdiff", "-z", "--block-limit=20", split_info_arg.c_str(), debug_dir_arg.c_str(),
+    src_file.path, tgt_file.path, patch_file.path,
   };
   ASSERT_EQ(0, imgdiff(args.size(), args.data()));
 
diff --git a/tests/component/updater_test.cpp b/tests/component/updater_test.cpp
index 6c341c1..2a0575a 100644
--- a/tests/component/updater_test.cpp
+++ b/tests/component/updater_test.cpp
@@ -383,7 +383,7 @@
 
   TemporaryFile tf;
   UpdaterInfo updater_info;
-  updater_info.cmd_pipe = fdopen(tf.fd, "w");
+  updater_info.cmd_pipe = fdopen(tf.release(), "w");
   expect(".52", "set_progress(\".52\")", kNoCause, &updater_info);
   fflush(updater_info.cmd_pipe);
 
@@ -392,6 +392,7 @@
   ASSERT_EQ(android::base::StringPrintf("set_progress %f\n", .52), cmd);
   // recovery-updater protocol expects 2 tokens ("set_progress <frac>").
   ASSERT_EQ(2U, android::base::Split(cmd, " ").size());
+  ASSERT_EQ(0, fclose(updater_info.cmd_pipe));
 }
 
 TEST_F(UpdaterTest, show_progress) {
@@ -407,7 +408,7 @@
 
   TemporaryFile tf;
   UpdaterInfo updater_info;
-  updater_info.cmd_pipe = fdopen(tf.fd, "w");
+  updater_info.cmd_pipe = fdopen(tf.release(), "w");
   expect(".52", "show_progress(\".52\", \"10\")", kNoCause, &updater_info);
   fflush(updater_info.cmd_pipe);
 
@@ -416,12 +417,13 @@
   ASSERT_EQ(android::base::StringPrintf("progress %f %d\n", .52, 10), cmd);
   // recovery-updater protocol expects 3 tokens ("progress <frac> <secs>").
   ASSERT_EQ(3U, android::base::Split(cmd, " ").size());
+  ASSERT_EQ(0, fclose(updater_info.cmd_pipe));
 }
 
 TEST_F(UpdaterTest, block_image_update) {
   // Create a zip file with new_data and patch_data.
   TemporaryFile zip_file;
-  FILE* zip_file_ptr = fdopen(zip_file.fd, "wb");
+  FILE* zip_file_ptr = fdopen(zip_file.release(), "wb");
   ZipWriter zip_writer(zip_file_ptr);
 
   // Add a dummy new data.
@@ -485,7 +487,7 @@
   UpdaterInfo updater_info;
   updater_info.package_zip = handle;
   TemporaryFile temp_pipe;
-  updater_info.cmd_pipe = fopen(temp_pipe.path, "wbe");
+  updater_info.cmd_pipe = fdopen(temp_pipe.release(), "wbe");
   updater_info.package_zip_addr = map.addr;
   updater_info.package_zip_len = map.length;
 
@@ -518,7 +520,7 @@
 TEST_F(UpdaterTest, new_data_short_write) {
   // Create a zip file with new_data.
   TemporaryFile zip_file;
-  FILE* zip_file_ptr = fdopen(zip_file.fd, "wb");
+  FILE* zip_file_ptr = fdopen(zip_file.release(), "wb");
   ZipWriter zip_writer(zip_file_ptr);
 
   // Add the empty new data.
@@ -561,7 +563,7 @@
   UpdaterInfo updater_info;
   updater_info.package_zip = handle;
   TemporaryFile temp_pipe;
-  updater_info.cmd_pipe = fopen(temp_pipe.path, "wbe");
+  updater_info.cmd_pipe = fdopen(temp_pipe.release(), "wbe");
   updater_info.package_zip_addr = map.addr;
   updater_info.package_zip_len = map.length;
 
@@ -579,13 +581,15 @@
   std::string script_exact_data = "block_image_update(\"" + std::string(update_file.path) +
       R"(", package_extract_file("transfer_list"), "exact_new_data", "patch_data"))";
   expect("t", script_exact_data.c_str(), kNoCause, &updater_info);
+
+  ASSERT_EQ(0, fclose(updater_info.cmd_pipe));
   CloseArchive(handle);
 }
 
 TEST_F(UpdaterTest, brotli_new_data) {
   // Create a zip file with new_data.
   TemporaryFile zip_file;
-  FILE* zip_file_ptr = fdopen(zip_file.fd, "wb");
+  FILE* zip_file_ptr = fdopen(zip_file.release(), "wb");
   ZipWriter zip_writer(zip_file_ptr);
 
   // Add a brotli compressed new data entry.
@@ -639,7 +643,7 @@
   UpdaterInfo updater_info;
   updater_info.package_zip = handle;
   TemporaryFile temp_pipe;
-  updater_info.cmd_pipe = fopen(temp_pipe.path, "wb");
+  updater_info.cmd_pipe = fdopen(temp_pipe.release(), "wb");
   updater_info.package_zip_addr = map.addr;
   updater_info.package_zip_len = map.length;
 
@@ -653,5 +657,7 @@
   std::string updated_content;
   ASSERT_TRUE(android::base::ReadFileToString(update_file.path, &updated_content));
   ASSERT_EQ(brotli_new_data, updated_content);
+
+  ASSERT_EQ(0, fclose(updater_info.cmd_pipe));
   CloseArchive(handle);
 }