Merge "Add more shell command for font" into sc-dev

12 files changed, 949 insertions, 128 deletions

diff --git a/core/java/android/graphics/fonts/FontManager.java b/core/java/android/graphics/fonts/FontManager.java
index ea6cf2f44be9..eca56b375dd4 100644
--- a/core/java/android/graphics/fonts/FontManager.java
+++ b/core/java/android/graphics/fonts/FontManager.java
@@ -16,6 +16,7 @@
 
 package android.graphics.fonts;
 
+import android.annotation.IntDef;
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.SystemApi;
@@ -28,6 +29,8 @@ import android.util.Log;
 
 import com.android.internal.graphics.fonts.IFontManager;
 
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
 import java.util.Objects;
 
 /**
@@ -41,6 +44,116 @@ public class FontManager {
     private static final String TAG = "FontManager";
     private final @NonNull IFontManager mIFontManager;
 
+    /** @hide */
+    @IntDef(prefix = "ERROR_CODE_",
+            value = { ERROR_CODE_OK, ERROR_CODE_FAILED_TO_WRITE_FONT_FILE,
+                    ERROR_CODE_VERIFICATION_FAILURE, ERROR_CODE_FONT_NAME_MISMATCH,
+                    ERROR_CODE_INVALID_FONT_FILE, ERROR_CODE_MISSING_POST_SCRIPT_NAME,
+                    ERROR_CODE_DOWNGRADING, ERROR_CODE_FAILED_TO_CREATE_CONFIG_FILE,
+                    ERROR_CODE_FONT_UPDATER_DISABLED })
+    @Retention(RetentionPolicy.SOURCE)
+    public @interface ErrorCode {}
+
+    /**
+     * Indicates an operation has processed successfully.
+     * @hide
+     */
+    public static final int ERROR_CODE_OK = 0;
+
+    /**
+     * Indicates a failure of writing font files.
+     * @hide
+     */
+    public static final int ERROR_CODE_FAILED_TO_WRITE_FONT_FILE = -1;
+
+    /**
+     * Indicates a failure of fs-verity setup.
+     * @hide
+     */
+    public static final int ERROR_CODE_VERIFICATION_FAILURE = -2;
+
+    /**
+     * Indicates a failure of verifying the font name with PostScript name.
+     * @hide
+     */
+    public static final int ERROR_CODE_FONT_NAME_MISMATCH = -3;
+
+    /**
+     * Indicates a failure of placing fonts due to unexpected font contents.
+     * @hide
+     */
+    public static final int ERROR_CODE_INVALID_FONT_FILE = -4;
+
+    /**
+     * Indicates a failure due to missing PostScript name in name table.
+     * @hide
+     */
+    public static final int ERROR_CODE_MISSING_POST_SCRIPT_NAME = -5;
+
+    /**
+     * Indicates a failure of placing fonts due to downgrading.
+     * @hide
+     */
+    public static final int ERROR_CODE_DOWNGRADING = -6;
+
+    /**
+     * Indicates a failure of writing system font configuration XML file.
+     * @hide
+     */
+    public static final int ERROR_CODE_FAILED_TO_CREATE_CONFIG_FILE = -7;
+
+    /**
+     * Indicates a failure due to disabled font updater.
+     * @hide
+     */
+    public static final int ERROR_CODE_FONT_UPDATER_DISABLED = -8;
+
+    /**
+     * Indicates a failure of opening font file.
+     *
+     * This error code is only used with the shell command interaction.
+     *
+     * @hide
+     */
+    public static final int ERROR_CODE_FAILED_TO_OPEN_FONT_FILE = -10001;
+
+    /**
+     * Indicates a failure of opening signature file.
+     *
+     * This error code is only used with the shell command interaction.
+     *
+     * @hide
+     */
+    public static final int ERROR_CODE_FAILED_TO_OPEN_SIGNATURE_FILE = -10002;
+
+    /**
+     * Indicates a failure of invalid shell command arguments.
+     *
+     * This error code is only used with the shell command interaction.
+     *
+     * @hide
+     */
+    public static final int ERROR_CODE_INVALID_SHELL_ARGUMENT = -10003;
+
+    /**
+     * Indicates a failure of reading signature file.
+     *
+     * This error code is only used with the shell command interaction.
+     *
+     * @hide
+     */
+    public static final int ERROR_CODE_INVALID_SIGNATURE_FILE = -10004;
+
+    /**
+     * Indicates a failure due to exceeding allowed signature file size (8kb).
+     *
+     * This error code is only used with the shell command interaction.
+     *
+     * @hide
+     */
+    public static final int ERROR_CODE_SIGNATURE_TOO_LARGE = -10005;
+
+
     private FontManager(@NonNull IFontManager iFontManager) {
         mIFontManager = iFontManager;
     }
diff --git a/core/java/android/text/FontConfig.java b/core/java/android/text/FontConfig.java
index 82d7399c86e0..53fe1ba9c4b4 100644
--- a/core/java/android/text/FontConfig.java
+++ b/core/java/android/text/FontConfig.java
@@ -53,6 +53,8 @@ import java.util.List;
 public final class FontConfig implements Parcelable {
     private final @NonNull List<FontFamily> mFamilies;
     private final @NonNull List<Alias> mAliases;
+    private final long mLastModifiedDate;
+    private final int mConfigVersion;
 
     /**
      * Construct a FontConfig instance.
@@ -62,9 +64,12 @@ public final class FontConfig implements Parcelable {
      *
      * @hide Only system server can create this instance and passed via IPC.
      */
-    public FontConfig(@NonNull List<FontFamily> families, @NonNull List<Alias> aliases) {
+    public FontConfig(@NonNull List<FontFamily> families, @NonNull List<Alias> aliases,
+            long lastModifiedDate, @IntRange(from = 0) int configVersion) {
         mFamilies = families;
         mAliases = aliases;
+        mLastModifiedDate = lastModifiedDate;
+        mConfigVersion = configVersion;
     }
 
     /**
@@ -88,6 +93,26 @@ public final class FontConfig implements Parcelable {
     }
 
     /**
+     * Returns the last modified date as Java epoch seconds.
+     *
+     * If there is no update, this return 0.
+     * @hide
+     */
+    public long getLastModifiedDate() {
+        return mLastModifiedDate;
+    }
+
+    /**
+     * Returns the monotonically increasing config version value.
+     *
+     * The config version is reset to 0 when the system is restarted.
+     * @hide
+     */
+    public @IntRange(from = 0) int getConfigVersion() {
+        return mConfigVersion;
+    }
+
+    /**
      * Returns the ordered list of families included in the system fonts.
      * @deprecated Use getFontFamilies instead.
      * @hide
@@ -107,6 +132,8 @@ public final class FontConfig implements Parcelable {
     public void writeToParcel(@NonNull Parcel dest, int flags) {
         dest.writeParcelableList(mFamilies, flags);
         dest.writeParcelableList(mAliases, flags);
+        dest.writeLong(mLastModifiedDate);
+        dest.writeInt(mConfigVersion);
     }
 
     public static final @NonNull Creator<FontConfig> CREATOR = new Creator<FontConfig>() {
@@ -116,7 +143,9 @@ public final class FontConfig implements Parcelable {
                     FontFamily.class.getClassLoader());
             List<Alias> aliases = source.readParcelableList(new ArrayList<>(),
                     Alias.class.getClassLoader());
-            return new FontConfig(families, aliases);
+            long lastModifiedDate = source.readLong();
+            int configVersion = source.readInt();
+            return new FontConfig(families, aliases, lastModifiedDate, configVersion);
         }
 
         @Override
diff --git a/core/tests/coretests/src/android/graphics/TypefaceSystemFallbackTest.java b/core/tests/coretests/src/android/graphics/TypefaceSystemFallbackTest.java
index 65ea2a8373aa..3df2e90241ff 100644
--- a/core/tests/coretests/src/android/graphics/TypefaceSystemFallbackTest.java
+++ b/core/tests/coretests/src/android/graphics/TypefaceSystemFallbackTest.java
@@ -171,7 +171,8 @@ public class TypefaceSystemFallbackTest {
         FontConfig fontConfig;
         try {
             fontConfig = FontListParser.parse(
-                    TEST_FONTS_XML, TEST_FONT_DIR, oemXmlPath, TEST_OEM_DIR, updatableFontMap);
+                    TEST_FONTS_XML, TEST_FONT_DIR, oemXmlPath, TEST_OEM_DIR, updatableFontMap, 0,
+                    0);
         } catch (IOException | XmlPullParserException e) {
             throw new RuntimeException(e);
         }
@@ -199,7 +200,7 @@ public class TypefaceSystemFallbackTest {
         FontConfig fontConfig;
         try {
             fontConfig = FontListParser.parse(
-                    SYSTEM_FONTS_XML, SYSTEM_FONT_DIR, null, TEST_OEM_DIR, null);
+                    SYSTEM_FONTS_XML, SYSTEM_FONT_DIR, null, TEST_OEM_DIR, null, 0, 0);
         } catch (IOException | XmlPullParserException e) {
             throw new RuntimeException(e);
         }
diff --git a/core/tests/coretests/src/android/text/FontFallbackSetup.java b/core/tests/coretests/src/android/text/FontFallbackSetup.java
index e301037d01f1..90a6ca3cd1d1 100644
--- a/core/tests/coretests/src/android/text/FontFallbackSetup.java
+++ b/core/tests/coretests/src/android/text/FontFallbackSetup.java
@@ -79,7 +79,7 @@ public class FontFallbackSetup implements AutoCloseable {
 
         FontConfig fontConfig;
         try {
-            fontConfig = FontListParser.parse(testFontsXml, mTestFontsDir, null, null, null);
+            fontConfig = FontListParser.parse(testFontsXml, mTestFontsDir, null, null, null, 0, 0);
         } catch (IOException | XmlPullParserException e) {
             throw new RuntimeException(e);
         }
diff --git a/graphics/java/android/graphics/FontListParser.java b/graphics/java/android/graphics/FontListParser.java
index c8ff95d15626..bb795cd99e6e 100644
--- a/graphics/java/android/graphics/FontListParser.java
+++ b/graphics/java/android/graphics/FontListParser.java
@@ -51,7 +51,8 @@ public class FontListParser {
         XmlPullParser parser = Xml.newPullParser();
         parser.setInput(in, null);
         parser.nextTag();
-        return readFamilies(parser, "/system/fonts/", new FontCustomizationParser.Result(), null);
+        return readFamilies(parser, "/system/fonts/", new FontCustomizationParser.Result(), null,
+                0, 0);
     }
 
     /**
@@ -71,7 +72,9 @@ public class FontListParser {
             @NonNull String systemFontDir,
             @Nullable String oemCustomizationXmlPath,
             @Nullable String productFontDir,
-            @Nullable Map<String, File> updatableFontMap
+            @Nullable Map<String, File> updatableFontMap,
+            long lastModifiedDate,
+            int configVersion
     ) throws IOException, XmlPullParserException {
         FontCustomizationParser.Result oemCustomization;
         if (oemCustomizationXmlPath != null) {
@@ -90,7 +93,8 @@ public class FontListParser {
             XmlPullParser parser = Xml.newPullParser();
             parser.setInput(is, null);
             parser.nextTag();
-            return readFamilies(parser, systemFontDir, oemCustomization, updatableFontMap);
+            return readFamilies(parser, systemFontDir, oemCustomization, updatableFontMap,
+                    lastModifiedDate, configVersion);
         }
     }
 
@@ -98,7 +102,9 @@ public class FontListParser {
             @NonNull XmlPullParser parser,
             @NonNull String fontDir,
             @NonNull FontCustomizationParser.Result customization,
-            @Nullable Map<String, File> updatableFontMap)
+            @Nullable Map<String, File> updatableFontMap,
+            long lastModifiedDate,
+            int configVersion)
             throws XmlPullParserException, IOException {
         List<FontConfig.FontFamily> families = new ArrayList<>();
         List<FontConfig.Alias> aliases = new ArrayList<>(customization.getAdditionalAliases());
@@ -126,7 +132,7 @@ public class FontListParser {
         }
 
         families.addAll(oemNamedFamilies.values());
-        return new FontConfig(families, aliases);
+        return new FontConfig(families, aliases, lastModifiedDate, configVersion);
     }
 
     /**
diff --git a/graphics/java/android/graphics/fonts/SystemFonts.java b/graphics/java/android/graphics/fonts/SystemFonts.java
index a41215f9cae1..c166e12fc6bf 100644
--- a/graphics/java/android/graphics/fonts/SystemFonts.java
+++ b/graphics/java/android/graphics/fonts/SystemFonts.java
@@ -240,10 +240,12 @@ public final class SystemFonts {
      * @hide
      */
     public static @NonNull FontConfig getSystemFontConfig(
-            @Nullable Map<String, File> updatableFontMap
+            @Nullable Map<String, File> updatableFontMap,
+            long lastModifiedDate,
+            int configVersion
     ) {
         return getSystemFontConfigInternal(FONTS_XML, SYSTEM_FONT_DIR, OEM_XML, OEM_FONT_DIR,
-                updatableFontMap);
+                updatableFontMap, lastModifiedDate, configVersion);
     }
 
     /**
@@ -251,7 +253,8 @@ public final class SystemFonts {
      * @hide
      */
     public static @NonNull FontConfig getSystemPreinstalledFontConfig() {
-        return getSystemFontConfigInternal(FONTS_XML, SYSTEM_FONT_DIR, OEM_XML, OEM_FONT_DIR, null);
+        return getSystemFontConfigInternal(FONTS_XML, SYSTEM_FONT_DIR, OEM_XML, OEM_FONT_DIR, null,
+                0, 0);
     }
 
     /* package */ static @NonNull FontConfig getSystemFontConfigInternal(
@@ -259,17 +262,19 @@ public final class SystemFonts {
             @NonNull String systemFontDir,
             @Nullable String oemXml,
             @Nullable String productFontDir,
-            @Nullable Map<String, File> updatableFontMap
+            @Nullable Map<String, File> updatableFontMap,
+            long lastModifiedDate,
+            int configVersion
     ) {
         try {
             return FontListParser.parse(fontsXml, systemFontDir, oemXml, productFontDir,
-                                                updatableFontMap);
+                                                updatableFontMap, lastModifiedDate, configVersion);
         } catch (IOException e) {
             Log.e(TAG, "Failed to open/read system font configurations.", e);
-            return new FontConfig(Collections.emptyList(), Collections.emptyList());
+            return new FontConfig(Collections.emptyList(), Collections.emptyList(), 0, 0);
         } catch (XmlPullParserException e) {
             Log.e(TAG, "Failed to parse the system font configuration.", e);
-            return new FontConfig(Collections.emptyList(), Collections.emptyList());
+            return new FontConfig(Collections.emptyList(), Collections.emptyList(), 0, 0);
         }
     }
 
diff --git a/services/core/java/com/android/server/graphics/fonts/FontManagerService.java b/services/core/java/com/android/server/graphics/fonts/FontManagerService.java
index bda4240a5858..5b3db011b427 100644
--- a/services/core/java/com/android/server/graphics/fonts/FontManagerService.java
+++ b/services/core/java/com/android/server/graphics/fonts/FontManagerService.java
@@ -22,12 +22,15 @@ import android.content.Context;
 import android.graphics.Typeface;
 import android.graphics.fonts.FontFamily;
 import android.graphics.fonts.FontFileUtil;
+import android.graphics.fonts.FontManager;
 import android.graphics.fonts.SystemFonts;
-import android.os.ParcelFileDescriptor;
 import android.os.RemoteException;
+import android.os.ResultReceiver;
 import android.os.SharedMemory;
+import android.os.ShellCallback;
 import android.system.ErrnoException;
 import android.text.FontConfig;
+import android.util.AndroidException;
 import android.util.IndentingPrintWriter;
 import android.util.Slog;
 
@@ -48,6 +51,7 @@ import java.nio.ByteBuffer;
 import java.nio.NioUtils;
 import java.nio.channels.FileChannel;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Map;
 
 /** A service for managing system fonts. */
@@ -55,8 +59,6 @@ import java.util.Map;
 public final class FontManagerService extends IFontManager.Stub {
     private static final String TAG = "FontManagerService";
 
-    // TODO: make this a DeviceConfig flag.
-    private static final boolean ENABLE_FONT_UPDATES = false;
     private static final String FONT_FILES_DIR = "/data/fonts/files";
 
     @Override
@@ -64,6 +66,24 @@ public final class FontManagerService extends IFontManager.Stub {
         return getCurrentFontSettings().getSystemFontConfig();
     }
 
+    /* package */ static class SystemFontException extends AndroidException {
+        private final int mErrorCode;
+
+        SystemFontException(@FontManager.ErrorCode int errorCode, String msg, Throwable cause) {
+            super(msg, cause);
+            mErrorCode = errorCode;
+        }
+
+        SystemFontException(int errorCode, String msg) {
+            super(msg);
+            mErrorCode = errorCode;
+        }
+
+        @FontManager.ErrorCode int getErrorCode() {
+            return mErrorCode;
+        }
+    }
+
     /** Class to manage FontManagerService's lifecycle. */
     public static final class Lifecycle extends SystemService {
         private final FontManagerService mService;
@@ -151,7 +171,6 @@ public final class FontManagerService extends IFontManager.Stub {
 
     @Nullable
     private static UpdatableFontDir createUpdatableFontDir() {
-        if (!ENABLE_FONT_UPDATES) return null;
         // If apk verity is supported, fs-verity should be available.
         if (!FileIntegrityService.isApkVeritySupported()) return null;
         return new UpdatableFontDir(new File(FONT_FILES_DIR),
@@ -178,19 +197,34 @@ public final class FontManagerService extends IFontManager.Stub {
         }
     }
 
-    // TODO(b/173619554): Expose as API.
-    private boolean installFontFile(FileDescriptor fd, byte[] pkcs7Signature) {
-        if (mUpdatableFontDir == null) return false;
+    /* package */ void installFontFile(FileDescriptor fd, byte[] pkcs7Signature)
+            throws SystemFontException {
+        if (mUpdatableFontDir == null) {
+            throw new SystemFontException(
+                    FontManager.ERROR_CODE_FONT_UPDATER_DISABLED,
+                    "The font updater is disabled.");
+        }
         synchronized (FontManagerService.this) {
-            try {
-                mUpdatableFontDir.installFontFile(fd, pkcs7Signature);
-            } catch (IOException e) {
-                Slog.w(TAG, "Failed to install font file");
-                return false;
-            }
+            mUpdatableFontDir.installFontFile(fd, pkcs7Signature);
             // Create updated font map in the next getSerializedSystemFontMap() call.
             mCurrentFontSettings = null;
-            return true;
+        }
+    }
+
+    /* package */ void clearUpdates() throws SystemFontException {
+        if (mUpdatableFontDir == null) {
+            throw new SystemFontException(
+                    FontManager.ERROR_CODE_FONT_UPDATER_DISABLED,
+                    "The font updater is disabled.");
+        }
+        mUpdatableFontDir.clearUpdates();
+    }
+
+    /* package */ Map<String, File> getFontFileMap() {
+        if (mUpdatableFontDir == null) {
+            return Collections.emptyMap();
+        } else {
+            return mUpdatableFontDir.getFontFileMap();
         }
     }
 
@@ -202,11 +236,13 @@ public final class FontManagerService extends IFontManager.Stub {
     }
 
     @Override
-    public int handleShellCommand(@NonNull ParcelFileDescriptor in,
-            @NonNull ParcelFileDescriptor out, @NonNull ParcelFileDescriptor err,
-            @NonNull String[] args) {
-        return new FontManagerShellCommand(this).exec(this,
-                in.getFileDescriptor(), out.getFileDescriptor(), err.getFileDescriptor(), args);
+    public void onShellCommand(@Nullable FileDescriptor in,
+            @Nullable FileDescriptor out,
+            @Nullable FileDescriptor err,
+            @NonNull String[] args,
+            @Nullable ShellCallback callback,
+            @NonNull ResultReceiver result) throws RemoteException {
+        new FontManagerShellCommand(this).exec(this, in, out, err, args, callback, result);
     }
 
     /* package */ static class SystemFontSettings {
@@ -245,8 +281,7 @@ public final class FontManagerService extends IFontManager.Stub {
         public static @Nullable SystemFontSettings create(
                 @Nullable UpdatableFontDir updatableFontDir) {
             if (updatableFontDir != null) {
-                final FontConfig fontConfig = SystemFonts.getSystemFontConfig(
-                        updatableFontDir.getFontFileMap());
+                final FontConfig fontConfig = updatableFontDir.getSystemFontConfig();
                 final Map<String, FontFamily[]> fallback =
                         SystemFonts.buildSystemFallback(fontConfig);
                 final Map<String, Typeface> typefaceMap =
@@ -274,4 +309,5 @@ public final class FontManagerService extends IFontManager.Stub {
             return null;
         }
     }
+
 }
diff --git a/services/core/java/com/android/server/graphics/fonts/FontManagerShellCommand.java b/services/core/java/com/android/server/graphics/fonts/FontManagerShellCommand.java
index acb582637e55..fd5c020b1a15 100644
--- a/services/core/java/com/android/server/graphics/fonts/FontManagerShellCommand.java
+++ b/services/core/java/com/android/server/graphics/fonts/FontManagerShellCommand.java
@@ -16,19 +16,33 @@
 
 package com.android.server.graphics.fonts;
 
+import static com.android.server.graphics.fonts.FontManagerService.SystemFontException;
+
 import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.content.Context;
 import android.graphics.fonts.Font;
 import android.graphics.fonts.FontFamily;
+import android.graphics.fonts.FontManager;
 import android.graphics.fonts.FontVariationAxis;
+import android.os.Binder;
+import android.os.ParcelFileDescriptor;
+import android.os.Process;
 import android.os.ShellCommand;
 import android.text.FontConfig;
 import android.util.IndentingPrintWriter;
+import android.util.Slog;
 
 import com.android.internal.util.DumpUtils;
 
 import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
 import java.io.PrintWriter;
+import java.time.LocalDateTime;
+import java.time.ZoneOffset;
+import java.time.format.DateTimeFormatter;
+import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
 
@@ -38,6 +52,13 @@ import java.util.Map;
 public class FontManagerShellCommand extends ShellCommand {
     private static final String TAG = "FontManagerShellCommand";
 
+    /**
+     * The maximum size of signature file.  This is just to avoid potential abuse.
+     *
+     * This is copied from VerityUtils.java.
+     */
+    private static final int MAX_SIGNATURE_FILE_SIZE_BYTES = 8192;
+
     @NonNull private final FontManagerService mService;
 
     FontManagerShellCommand(@NonNull FontManagerService service) {
@@ -46,12 +67,31 @@ public class FontManagerShellCommand extends ShellCommand {
 
     @Override
     public int onCommand(String cmd) {
+        final int callingUid = Binder.getCallingUid();
+        if (callingUid != Process.ROOT_UID && callingUid != Process.SHELL_UID) {
+            // Do not change this string since this string is expected in the CTS.
+            getErrPrintWriter().println("Only shell or root user can execute font command.");
+            return 1;
+        }
         return execCommand(this, cmd);
     }
 
     @Override
     public void onHelp() {
-        dumpHelp(getOutPrintWriter());
+        PrintWriter w = getOutPrintWriter();
+        w.println("Font service (font) commands");
+        w.println("help");
+        w.println("    Print this help text.");
+        w.println();
+        w.println("dump [family name]");
+        w.println("    Dump all font files in the specified family name.");
+        w.println("    Dump current system font configuration if no family name was specified.");
+        w.println();
+        w.println("update [font file path] [signature file path]");
+        w.println("    Update installed font files with new font file.");
+        w.println();
+        w.println("clear");
+        w.println("    Remove all installed font files and reset to the initial state.");
     }
 
     /* package */ void dumpAll(@NonNull IndentingPrintWriter w) {
@@ -165,16 +205,6 @@ public class FontManagerShellCommand extends ShellCommand {
         w.decreaseIndent();
     }
 
-    private static void dumpHelp(@NonNull PrintWriter w) {
-        w.println("Font service (font) commands");
-        w.println("help");
-        w.println("    Print this help text.");
-        w.println();
-        w.println("dump [family name]");
-        w.println("    Dump all font files in the specified family name.");
-        w.println("    Dump current system font configuration if no family name was specified.");
-    }
-
     private void dumpFallback(@NonNull IndentingPrintWriter writer,
             @NonNull FontFamily[] families) {
         for (FontFamily family : families) {
@@ -233,37 +263,143 @@ public class FontManagerShellCommand extends ShellCommand {
         writer.println(sb.toString());
     }
 
-    private int execCommand(@NonNull ShellCommand shell, @NonNull String cmd) {
+    private void writeCommandResult(ShellCommand shell, SystemFontException e) {
+        // Print short summary to the stderr.
+        PrintWriter pw = shell.getErrPrintWriter();
+        pw.println(e.getErrorCode());
+        pw.println(e.getMessage());
+
+        // Dump full stack trace to logcat.
+
+        Slog.e(TAG, "Command failed: " + Arrays.toString(shell.getAllArgs()), e);
+    }
+
+    private int dump(ShellCommand shell) {
         final Context ctx = mService.getContext();
-        if (cmd == null) {
-            return shell.handleDefaultCommands(null);
+        final FontManagerService.SystemFontSettings settings =
+                mService.getCurrentFontSettings();
+        if (!DumpUtils.checkDumpPermission(ctx, TAG, shell.getErrPrintWriter())) {
+            return 1;
+        }
+        final IndentingPrintWriter writer =
+                new IndentingPrintWriter(shell.getOutPrintWriter(), "  ");
+        String nextArg = shell.getNextArg();
+        if (nextArg == null) {
+            dumpFontConfig(writer, settings.getSystemFontConfig());
+        } else {
+            final Map<String, FontFamily[]> fallbackMap =
+                    settings.getSystemFallbackMap();
+            FontFamily[] families = fallbackMap.get(nextArg);
+            if (families == null) {
+                writer.println("Font Family \"" + nextArg + "\" not found");
+            } else {
+                dumpFallback(writer, families);
+            }
         }
+        return 0;
+    }
 
-        final FontManagerService.SystemFontSettings settings = mService.getCurrentFontSettings();
+    private int update(ShellCommand shell) throws SystemFontException {
+        String fontPath = shell.getNextArg();
+        if (fontPath == null) {
+            throw new SystemFontException(
+                    FontManager.ERROR_CODE_INVALID_SHELL_ARGUMENT,
+                    "Font file path argument is required.");
+        }
+        String signaturePath = shell.getNextArg();
+        if (signaturePath == null) {
+            throw new SystemFontException(
+                    FontManager.ERROR_CODE_INVALID_SHELL_ARGUMENT,
+                    "Signature file argument is required.");
+        }
+
+        ParcelFileDescriptor fontFd = shell.openFileForSystem(fontPath, "r");
+        if (fontFd == null) {
+            throw new SystemFontException(
+                    FontManager.ERROR_CODE_FAILED_TO_OPEN_FONT_FILE,
+                    "Failed to open font file");
+        }
 
-        switch (cmd) {
-            case "dump":
-                if (!DumpUtils.checkDumpPermission(ctx, TAG, shell.getErrPrintWriter())) {
-                    return 1;
+        ParcelFileDescriptor sigFd = shell.openFileForSystem(signaturePath, "r");
+        if (sigFd == null) {
+            throw new SystemFontException(
+                    FontManager.ERROR_CODE_FAILED_TO_OPEN_SIGNATURE_FILE,
+                    "Failed to open signature file");
+        }
+
+        try (FileInputStream sigFis = new FileInputStream(sigFd.getFileDescriptor())) {
+            try (FileInputStream fontFis = new FileInputStream(fontFd.getFileDescriptor())) {
+                int len = sigFis.available();
+                if (len > MAX_SIGNATURE_FILE_SIZE_BYTES) {
+                    throw new SystemFontException(
+                            FontManager.ERROR_CODE_SIGNATURE_TOO_LARGE,
+                            "Signature file is too large");
                 }
-                final IndentingPrintWriter writer =
-                        new IndentingPrintWriter(shell.getOutPrintWriter(), "  ");
-                String nextArg = shell.getNextArg();
-                if (nextArg == null) {
-                    dumpFontConfig(writer, settings.getSystemFontConfig());
-                } else {
-                    final Map<String, FontFamily[]> fallbackMap = settings.getSystemFallbackMap();
-                    FontFamily[] families = fallbackMap.get(nextArg);
-                    if (families == null) {
-                        writer.println("Font Family \"" + nextArg + "\" not found");
-                    } else {
-                        dumpFallback(writer, families);
-                    }
+                byte[] signature = new byte[len];
+                if (sigFis.read(signature, 0, len) != len) {
+                    throw new SystemFontException(
+                            FontManager.ERROR_CODE_INVALID_SIGNATURE_FILE,
+                            "Invalid read length");
                 }
-                return 0;
-            default:
-                shell.handleDefaultCommands(cmd);
+                mService.installFontFile(fontFis.getFD(), signature);
+            } catch (IOException e) {
+                throw new SystemFontException(
+                        FontManager.ERROR_CODE_INVALID_SIGNATURE_FILE,
+                        "Failed to read signature file.", e);
+            }
+        } catch (IOException e) {
+            throw new SystemFontException(
+                    FontManager.ERROR_CODE_INVALID_FONT_FILE,
+                    "Failed to read font files.", e);
         }
+
+        shell.getOutPrintWriter().println("Success");  // TODO: Output more details.
         return 0;
     }
+
+    private int clear(ShellCommand shell) throws SystemFontException {
+        mService.clearUpdates();
+        shell.getOutPrintWriter().println("Success");
+        return 0;
+    }
+
+    private int status(ShellCommand shell) throws SystemFontException {
+        final FontManagerService.SystemFontSettings settings = mService.getCurrentFontSettings();
+        final IndentingPrintWriter writer =
+                new IndentingPrintWriter(shell.getOutPrintWriter(), "  ");
+        FontConfig config = settings.getSystemFontConfig();
+
+        writer.println("Current Version: " + config.getConfigVersion());
+        LocalDateTime dt = LocalDateTime.ofEpochSecond(config.getLastModifiedDate(), 0,
+                ZoneOffset.UTC);
+        writer.println("Last Modified Date: " + dt.format(DateTimeFormatter.ISO_DATE_TIME));
+
+        Map<String, File> fontFileMap = mService.getFontFileMap();
+        writer.println("Number of updated font files: " + fontFileMap.size());
+        return 0;
+    }
+
+    private int execCommand(@NonNull ShellCommand shell, @Nullable String cmd) {
+        if (cmd == null) {
+            return shell.handleDefaultCommands(null);
+        }
+
+        try {
+            switch (cmd) {
+                case "dump":
+                    return dump(shell);
+                case "update":
+                    return update(shell);
+                case "clear":
+                    return clear(shell);
+                case "status":
+                    return status(shell);
+                default:
+                    return shell.handleDefaultCommands(cmd);
+            }
+        } catch (SystemFontException e) {
+            writeCommandResult(shell, e);
+            return 1;
+        }
+    }
 }
diff --git a/services/core/java/com/android/server/graphics/fonts/PersistentSystemFontConfig.java b/services/core/java/com/android/server/graphics/fonts/PersistentSystemFontConfig.java
new file mode 100644
index 000000000000..f0d14ba80383
--- /dev/null
+++ b/services/core/java/com/android/server/graphics/fonts/PersistentSystemFontConfig.java
@@ -0,0 +1,114 @@
+/*
+ * Copyright (C) 2021 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.
+ */
+
+package com.android.server.graphics.fonts;
+
+import android.annotation.NonNull;
+import android.text.TextUtils;
+import android.util.Slog;
+import android.util.TypedXmlPullParser;
+import android.util.TypedXmlSerializer;
+import android.util.Xml;
+
+import org.xmlpull.v1.XmlPullParser;
+import org.xmlpull.v1.XmlPullParserException;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+
+/* package */ class PersistentSystemFontConfig {
+    private static final String TAG = "PersistentSystemFontConfig";
+
+    private static final String TAG_ROOT = "fontConfig";
+    private static final String TAG_LAST_MODIFIED_DATE = "lastModifiedDate";
+    private static final String TAG_VALUE = "value";
+
+    /* package */ static class Config {
+        public long lastModifiedDate;
+
+        public void reset() {
+            lastModifiedDate = 0;
+        }
+
+        public void copyTo(@NonNull Config out) {
+            out.lastModifiedDate = lastModifiedDate;
+        }
+    }
+
+    /**
+     * Read config XML and write to out argument.
+     */
+    public static void loadFromXml(@NonNull InputStream is, @NonNull Config out)
+            throws XmlPullParserException, IOException {
+        out.reset();
+        TypedXmlPullParser parser = Xml.resolvePullParser(is);
+
+        int type;
+        while ((type = parser.next()) != XmlPullParser.END_DOCUMENT) {
+            if (type != XmlPullParser.START_TAG) {
+                continue;
+            }
+            final int depth = parser.getDepth();
+            final String tag = parser.getName();
+            if (depth == 1) {
+                if (!TAG_ROOT.equals(tag)) {
+                    Slog.e(TAG, "Invalid root tag: " + tag);
+                    return;
+                }
+            } else if (depth == 2) {
+                switch (tag) {
+                    case TAG_LAST_MODIFIED_DATE:
+                        out.lastModifiedDate = parseLongAttribute(parser, TAG_VALUE, 0);
+                        break;
+                    default:
+                        Slog.w(TAG, "Skipping unknown tag: " + tag);
+                }
+            }
+        }
+
+    }
+
+    /**
+     * Write config to OutputStream as XML file.
+     */
+    public static void writeToXml(@NonNull OutputStream os, @NonNull Config config)
+            throws IOException {
+        TypedXmlSerializer out = Xml.resolveSerializer(os);
+        out.startDocument(null /* encoding */, true /* standalone */);
+
+        out.startTag(null, TAG_ROOT);
+        out.startTag(null, TAG_LAST_MODIFIED_DATE);
+        out.attribute(null, TAG_VALUE, Long.toString(config.lastModifiedDate));
+        out.endTag(null, TAG_LAST_MODIFIED_DATE);
+        out.endTag(null, TAG_ROOT);
+
+        out.endDocument();
+    }
+
+    private static long parseLongAttribute(TypedXmlPullParser parser, String attr, long defValue) {
+        final String value = parser.getAttributeValue(null /* namespace */, attr);
+        if (TextUtils.isEmpty(value)) {
+            return defValue;
+        }
+        try {
+            return Long.parseLong(value);
+        } catch (NumberFormatException e) {
+            return defValue;
+        }
+    }
+
+}
diff --git a/services/core/java/com/android/server/graphics/fonts/UpdatableFontDir.java b/services/core/java/com/android/server/graphics/fonts/UpdatableFontDir.java
index 8da579fd4fa3..8ec72770d782 100644
--- a/services/core/java/com/android/server/graphics/fonts/UpdatableFontDir.java
+++ b/services/core/java/com/android/server/graphics/fonts/UpdatableFontDir.java
@@ -16,18 +16,28 @@
 
 package com.android.server.graphics.fonts;
 
+import static com.android.server.graphics.fonts.FontManagerService.SystemFontException;
+
+import android.annotation.NonNull;
 import android.annotation.Nullable;
+import android.graphics.fonts.FontManager;
+import android.graphics.fonts.SystemFonts;
 import android.os.FileUtils;
+import android.text.FontConfig;
 import android.util.Base64;
 import android.util.Slog;
 
 import com.android.internal.annotations.GuardedBy;
 
+import org.xmlpull.v1.XmlPullParserException;
+
 import java.io.File;
 import java.io.FileDescriptor;
+import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.security.SecureRandom;
+import java.time.Instant;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -39,6 +49,8 @@ final class UpdatableFontDir {
     // TODO: Support .otf
     private static final String ALLOWED_EXTENSION = ".ttf";
 
+    private static final String CONFIG_XML_FILE = "/data/fonts/config/config.xml";
+
     /** Interface to mock font file access in tests. */
     interface FontFileParser {
         String getPostScriptName(File file) throws IOException;
@@ -55,6 +67,15 @@ final class UpdatableFontDir {
         boolean rename(File src, File dest);
     }
 
+    /** Interface to mock persistent configuration */
+    interface PersistentConfig {
+        void loadFromXml(PersistentSystemFontConfig.Config out)
+                throws XmlPullParserException, IOException;
+        void writeToXml(PersistentSystemFontConfig.Config config)
+                throws IOException;
+        boolean rename(File src, File dest);
+    }
+
     /** Data class to hold font file path and revision. */
     private static final class FontFileInfo {
         private final File mFile;
@@ -87,6 +108,16 @@ final class UpdatableFontDir {
     private final List<File> mPreinstalledFontDirs;
     private final FontFileParser mParser;
     private final FsverityUtil mFsverityUtil;
+    private final File mConfigFile;
+    private final File mTmpConfigFile;
+
+    @GuardedBy("UpdatableFontDir.this")
+    private final PersistentSystemFontConfig.Config mConfig =
+            new PersistentSystemFontConfig.Config();
+
+    @GuardedBy("UpdatableFontDir.this")
+    private int mConfigVersion = 1;
+
     /**
      * A mutable map containing mapping from font file name (e.g. "NotoColorEmoji.ttf") to {@link
      * FontFileInfo}. All files in this map are validated, and have higher revision numbers than
@@ -101,6 +132,20 @@ final class UpdatableFontDir {
         mPreinstalledFontDirs = preinstalledFontDirs;
         mParser = parser;
         mFsverityUtil = fsverityUtil;
+        mConfigFile = new File(CONFIG_XML_FILE);
+        mTmpConfigFile = new File(CONFIG_XML_FILE + ".tmp");
+        loadFontFileMap();
+    }
+
+    // For unit testing
+    UpdatableFontDir(File filesDir, List<File> preinstalledFontDirs, FontFileParser parser,
+            FsverityUtil fsverityUtil, File configFile) {
+        mFilesDir = filesDir;
+        mPreinstalledFontDirs = preinstalledFontDirs;
+        mParser = parser;
+        mFsverityUtil = fsverityUtil;
+        mConfigFile = configFile;
+        mTmpConfigFile = new File(configFile.getAbsoluteFile() + ".tmp");
         loadFontFileMap();
     }
 
@@ -108,6 +153,13 @@ final class UpdatableFontDir {
         // TODO: SIGBUS crash protection
         synchronized (UpdatableFontDir.this) {
             boolean success = false;
+
+            try (FileInputStream fis = new FileInputStream(mConfigFile)) {
+                PersistentSystemFontConfig.loadFromXml(fis, mConfig);
+            } catch (IOException | XmlPullParserException e) {
+                mConfig.reset();
+            }
+
             mFontFileInfoMap.clear();
             try {
                 File[] dirs = mFilesDir.listFiles();
@@ -117,13 +169,13 @@ final class UpdatableFontDir {
                     File[] files = dir.listFiles();
                     if (files == null || files.length != 1) return;
                     FontFileInfo fontFileInfo = validateFontFile(files[0]);
-                    if (fontFileInfo == null) {
-                        Slog.w(TAG, "Broken file is found. Clearing files.");
-                        return;
-                    }
-                    addFileToMapLocked(fontFileInfo, true /* deleteOldFile */);
+                    addFileToMapIfNewerLocked(fontFileInfo, true /* deleteOldFile */);
                 }
                 success = true;
+            } catch (Throwable t) {
+                // If something happened during loading system fonts, clear all contents in finally
+                // block. Here, just dumping errors.
+                Slog.e(TAG, "Failed to load font mappings.", t);
             } finally {
                 // Delete all files just in case if we find a problematic file.
                 if (!success) {
@@ -134,6 +186,24 @@ final class UpdatableFontDir {
         }
     }
 
+    /* package */ void clearUpdates() throws SystemFontException {
+        synchronized (UpdatableFontDir.this) {
+            mFontFileInfoMap.clear();
+            FileUtils.deleteContents(mFilesDir);
+
+            mConfig.reset();
+            mConfig.lastModifiedDate = Instant.now().getEpochSecond();
+            try (FileOutputStream fos = new FileOutputStream(mConfigFile)) {
+                PersistentSystemFontConfig.writeToXml(fos, mConfig);
+            } catch (Exception e) {
+                throw new SystemFontException(
+                        FontManager.ERROR_CODE_FAILED_TO_CREATE_CONFIG_FILE,
+                        "Failed to write config XML.", e);
+            }
+            mConfigVersion++;
+        }
+    }
+
     /**
      * Installs a new font file, or updates an existing font file.
      *
@@ -143,38 +213,92 @@ final class UpdatableFontDir {
      *
      * @param fd             A file descriptor to the font file.
      * @param pkcs7Signature A PKCS#7 detached signature to enable fs-verity for the font file.
+     * @throws SystemFontException if error occurs.
      */
-    void installFontFile(FileDescriptor fd, byte[] pkcs7Signature) throws IOException {
+    void installFontFile(FileDescriptor fd, byte[] pkcs7Signature) throws SystemFontException {
         synchronized (UpdatableFontDir.this) {
             File newDir = getRandomDir(mFilesDir);
             if (!newDir.mkdir()) {
-                // TODO: Define and return an error code for API
-                throw new IOException("Failed to create a new dir");
+                throw new SystemFontException(
+                        FontManager.ERROR_CODE_FAILED_TO_WRITE_FONT_FILE,
+                        "Failed to create font directory.");
             }
             boolean success = false;
             try {
                 File tempNewFontFile = new File(newDir, "font.ttf");
                 try (FileOutputStream out = new FileOutputStream(tempNewFontFile)) {
                     FileUtils.copy(fd, out.getFD());
+                } catch (IOException e) {
+                    throw new SystemFontException(
+                            FontManager.ERROR_CODE_FAILED_TO_WRITE_FONT_FILE,
+                            "Failed to write font file to storage.", e);
+                }
+                try {
+                    // Do not parse font file before setting up fs-verity.
+                    // setUpFsverity throws IOException if failed.
+                    mFsverityUtil.setUpFsverity(tempNewFontFile.getAbsolutePath(),
+                            pkcs7Signature);
+                } catch (IOException e) {
+                    throw new SystemFontException(
+                            FontManager.ERROR_CODE_VERIFICATION_FAILURE,
+                            "Failed to setup fs-verity.", e);
+                }
+                String postScriptName;
+                try {
+                    postScriptName = mParser.getPostScriptName(tempNewFontFile);
+                } catch (IOException e) {
+                    throw new SystemFontException(
+                            FontManager.ERROR_CODE_INVALID_FONT_FILE,
+                            "Failed to read PostScript name from font file", e);
+                }
+                if (postScriptName == null) {
+                    throw new SystemFontException(
+                            FontManager.ERROR_CODE_MISSING_POST_SCRIPT_NAME,
+                            "Failed to read PostScript name from font file");
                 }
-                // Do not parse font file before setting up fs-verity.
-                // setUpFsverity throws IOException if failed.
-                mFsverityUtil.setUpFsverity(tempNewFontFile.getAbsolutePath(), pkcs7Signature);
-                String postScriptName = mParser.getPostScriptName(tempNewFontFile);
                 File newFontFile = new File(newDir, postScriptName + ALLOWED_EXTENSION);
                 if (!mFsverityUtil.rename(tempNewFontFile, newFontFile)) {
-                    // TODO: Define and return an error code for API
-                    throw new IOException("Failed to rename");
+                    throw new SystemFontException(
+                            FontManager.ERROR_CODE_FAILED_TO_WRITE_FONT_FILE,
+                            "Failed to move verified font file.");
                 }
                 FontFileInfo fontFileInfo = validateFontFile(newFontFile);
-                if (fontFileInfo == null) {
-                    // TODO: Define and return an error code for API
-                    throw new IllegalArgumentException("Invalid file");
+
+                // Write config file.
+                PersistentSystemFontConfig.Config copied = new PersistentSystemFontConfig.Config();
+                mConfig.copyTo(copied);
+
+                copied.lastModifiedDate = Instant.now().getEpochSecond();
+                try (FileOutputStream fos = new FileOutputStream(mTmpConfigFile)) {
+                    PersistentSystemFontConfig.writeToXml(fos, copied);
+                } catch (Exception e) {
+                    throw new SystemFontException(
+                            FontManager.ERROR_CODE_FAILED_TO_CREATE_CONFIG_FILE,
+                            "Failed to write config XML.", e);
                 }
-                if (!addFileToMapLocked(fontFileInfo, false)) {
-                    // TODO: Define and return an error code for API
-                    throw new IllegalArgumentException("Version downgrade");
+
+                // Backup the mapping for rollback.
+                HashMap<String, FontFileInfo> backup = new HashMap<>(mFontFileInfoMap);
+                if (!addFileToMapIfNewerLocked(fontFileInfo, false)) {
+                    throw new SystemFontException(
+                            FontManager.ERROR_CODE_DOWNGRADING,
+                            "Downgrading font file is forbidden.");
+                }
+
+                if (!mFsverityUtil.rename(mTmpConfigFile, mConfigFile)) {
+                    // If we fail to stage the config file, need to rollback the config.
+                    mFontFileInfoMap.clear();
+                    mFontFileInfoMap.putAll(backup);
+                    throw new SystemFontException(
+                            FontManager.ERROR_CODE_FAILED_TO_CREATE_CONFIG_FILE,
+                            "Failed to stage the config file.");
                 }
+
+
+                // Now font update is succeeded. Update config version.
+                copied.copyTo(mConfig);
+                mConfigVersion++;
+
                 success = true;
             } finally {
                 if (!success) {
@@ -207,7 +331,7 @@ final class UpdatableFontDir {
      * higher than the currently used font file (either in {@link #mFontFileInfoMap} or {@link
      * #mPreinstalledFontDirs}).
      */
-    private boolean addFileToMapLocked(FontFileInfo fontFileInfo, boolean deleteOldFile) {
+    private boolean addFileToMapIfNewerLocked(FontFileInfo fontFileInfo, boolean deleteOldFile) {
         String name = fontFileInfo.getFile().getName();
         FontFileInfo existingInfo = mFontFileInfoMap.get(name);
         final boolean shouldAddToMap;
@@ -224,13 +348,12 @@ final class UpdatableFontDir {
                 FileUtils.deleteContentsAndDir(existingInfo.getRandomizedFontDir());
             }
             mFontFileInfoMap.put(name, fontFileInfo);
-            return true;
         } else {
             if (deleteOldFile) {
                 FileUtils.deleteContentsAndDir(fontFileInfo.getRandomizedFontDir());
             }
-            return false;
         }
+        return shouldAddToMap;
     }
 
     private long getPreinstalledFontRevision(String name) {
@@ -255,20 +378,23 @@ final class UpdatableFontDir {
      * returns a {@link FontFileInfo} on success. This method does not check if the font revision
      * is higher than the currently used font.
      */
-    @Nullable
-    private FontFileInfo validateFontFile(File file) {
+    @NonNull
+    private FontFileInfo validateFontFile(File file) throws SystemFontException {
         if (!mFsverityUtil.hasFsverity(file.getAbsolutePath())) {
-            Slog.w(TAG, "Font validation failed. Fs-verity is not enabled: " + file);
-            return null;
+            throw new SystemFontException(
+                    FontManager.ERROR_CODE_VERIFICATION_FAILURE,
+                    "Font validation failed. Fs-verity is not enabled: " + file);
         }
         if (!validateFontFileName(file)) {
-            Slog.w(TAG, "Font validation failed. Could not validate font file name: " + file);
-            return null;
+            throw new SystemFontException(
+                    FontManager.ERROR_CODE_FONT_NAME_MISMATCH,
+                    "Font validation failed. Could not validate font file name: " + file);
         }
         long revision = getFontRevision(file);
         if (revision == -1) {
-            Slog.w(TAG, "Font validation failed. Could not read font revision: " + file);
-            return null;
+            throw new SystemFontException(
+                    FontManager.ERROR_CODE_INVALID_FONT_FILE,
+                    "Font validation failed. Could not read font revision: " + file);
         }
         return new FontFileInfo(file, revision);
     }
@@ -318,4 +444,14 @@ final class UpdatableFontDir {
         }
         return map;
     }
+
+    /* package */ FontConfig getSystemFontConfig() {
+        synchronized (UpdatableFontDir.this) {
+            return SystemFonts.getSystemFontConfig(
+                    getFontFileMap(),
+                    mConfig.lastModifiedDate,
+                    mConfigVersion
+            );
+        }
+    }
 }
diff --git a/services/tests/servicestests/src/com/android/server/graphics/fonts/PersistentSystemFontConfigTest.java b/services/tests/servicestests/src/com/android/server/graphics/fonts/PersistentSystemFontConfigTest.java
new file mode 100644
index 000000000000..c10cee9b4c3d
--- /dev/null
+++ b/services/tests/servicestests/src/com/android/server/graphics/fonts/PersistentSystemFontConfigTest.java
@@ -0,0 +1,75 @@
+/*
+ * Copyright (C) 2021 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.
+ */
+
+package com.android.server.graphics.fonts;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import android.platform.test.annotations.Presubmit;
+
+import androidx.test.filters.SmallTest;
+import androidx.test.runner.AndroidJUnit4;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.xmlpull.v1.XmlPullParserException;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+
+@Presubmit
+@SmallTest
+@RunWith(AndroidJUnit4.class)
+public final class PersistentSystemFontConfigTest {
+
+    @Test
+    public void testWriteRead() throws IOException, XmlPullParserException {
+        long expectedModifiedDate = 1234567890;
+        PersistentSystemFontConfig.Config config = new PersistentSystemFontConfig.Config();
+        config.lastModifiedDate = expectedModifiedDate;
+
+        try (ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
+            PersistentSystemFontConfig.writeToXml(baos, config);
+
+            byte[] written = baos.toByteArray();
+            assertThat(written).isNotEmpty();
+
+            try (ByteArrayInputStream bais = new ByteArrayInputStream(written)) {
+                PersistentSystemFontConfig.Config another = new PersistentSystemFontConfig.Config();
+                PersistentSystemFontConfig.loadFromXml(bais, another);
+
+                assertThat(another.lastModifiedDate).isEqualTo(expectedModifiedDate);
+            }
+        }
+    }
+
+    @Test
+    public void testWrongType() throws IOException, XmlPullParserException {
+        String xml = "<fontConfig>"
+                + "  <lastModifiedDate value=\"string\" />"
+                + "</fontConfig>";
+
+        try (ByteArrayInputStream bais =
+                     new ByteArrayInputStream(xml.getBytes(StandardCharsets.UTF_8))) {
+            PersistentSystemFontConfig.Config config = new PersistentSystemFontConfig.Config();
+            PersistentSystemFontConfig.loadFromXml(bais, config);
+            assertThat(config.lastModifiedDate).isEqualTo(0);
+        }
+    }
+
+}
diff --git a/services/tests/servicestests/src/com/android/server/graphics/fonts/UpdatableFontDirTest.java b/services/tests/servicestests/src/com/android/server/graphics/fonts/UpdatableFontDirTest.java
index 75bf1e6bd485..0e872d96bd85 100644
--- a/services/tests/servicestests/src/com/android/server/graphics/fonts/UpdatableFontDirTest.java
+++ b/services/tests/servicestests/src/com/android/server/graphics/fonts/UpdatableFontDirTest.java
@@ -22,6 +22,7 @@ import static com.google.common.truth.Truth.assertWithMessage;
 import static org.junit.Assert.fail;
 
 import android.content.Context;
+import android.graphics.fonts.FontManager;
 import android.os.FileUtils;
 import android.platform.test.annotations.Presubmit;
 
@@ -36,6 +37,7 @@ import org.junit.runner.RunWith;
 
 import java.io.File;
 import java.io.FileInputStream;
+import java.io.FileOutputStream;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
@@ -107,6 +109,7 @@ public final class UpdatableFontDirTest {
 
     private File mCacheDir;
     private File mUpdatableFontFilesDir;
+    private File mConfigFile;
     private List<File> mPreinstalledFontDirs;
 
     @SuppressWarnings("ResultOfMethodCallIgnored")
@@ -124,6 +127,7 @@ public final class UpdatableFontDirTest {
         for (File dir : mPreinstalledFontDirs) {
             dir.mkdir();
         }
+        mConfigFile = new File(mCacheDir, "config.xml");
     }
 
     @After
@@ -133,19 +137,30 @@ public final class UpdatableFontDirTest {
 
     @Test
     public void construct() throws Exception {
+        long expectedModifiedDate = 1234567890;
         FakeFontFileParser parser = new FakeFontFileParser();
         FakeFsverityUtil fakeFsverityUtil = new FakeFsverityUtil();
+        PersistentSystemFontConfig.Config config = new PersistentSystemFontConfig.Config();
+        config.lastModifiedDate = expectedModifiedDate;
+        writeConfig(config, mConfigFile);
         UpdatableFontDir dirForPreparation = new UpdatableFontDir(
-                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil);
+                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil,
+                mConfigFile);
+        assertThat(dirForPreparation.getSystemFontConfig().getLastModifiedDate())
+                .isEqualTo(expectedModifiedDate);
         installFontFile(dirForPreparation, "foo,1", GOOD_SIGNATURE);
         installFontFile(dirForPreparation, "bar,2", GOOD_SIGNATURE);
         installFontFile(dirForPreparation, "foo,3", GOOD_SIGNATURE);
         installFontFile(dirForPreparation, "bar,4", GOOD_SIGNATURE);
         // Four font dirs are created.
         assertThat(mUpdatableFontFilesDir.list()).hasLength(4);
+        //
+        assertThat(dirForPreparation.getSystemFontConfig().getLastModifiedDate())
+                .isNotEqualTo(expectedModifiedDate);
 
         UpdatableFontDir dir = new UpdatableFontDir(
-                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil);
+                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil,
+                mConfigFile);
         assertThat(dir.getFontFileMap()).containsKey("foo.ttf");
         assertThat(parser.getRevision(dir.getFontFileMap().get("foo.ttf"))).isEqualTo(3);
         assertThat(dir.getFontFileMap()).containsKey("bar.ttf");
@@ -159,7 +174,8 @@ public final class UpdatableFontDirTest {
         FakeFontFileParser parser = new FakeFontFileParser();
         FakeFsverityUtil fakeFsverityUtil = new FakeFsverityUtil();
         UpdatableFontDir dir = new UpdatableFontDir(
-                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil);
+                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil,
+                mConfigFile);
         assertThat(dir.getFontFileMap()).isEmpty();
     }
 
@@ -168,7 +184,8 @@ public final class UpdatableFontDirTest {
         FakeFontFileParser parser = new FakeFontFileParser();
         FakeFsverityUtil fakeFsverityUtil = new FakeFsverityUtil();
         UpdatableFontDir dirForPreparation = new UpdatableFontDir(
-                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil);
+                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil,
+                mConfigFile);
         installFontFile(dirForPreparation, "foo,1", GOOD_SIGNATURE);
         installFontFile(dirForPreparation, "bar,2", GOOD_SIGNATURE);
         installFontFile(dirForPreparation, "foo,3", GOOD_SIGNATURE);
@@ -179,7 +196,8 @@ public final class UpdatableFontDirTest {
         fakeFsverityUtil.remove(
                 dirForPreparation.getFontFileMap().get("foo.ttf").getAbsolutePath());
         UpdatableFontDir dir = new UpdatableFontDir(
-                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil);
+                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil,
+                mConfigFile);
         assertThat(dir.getFontFileMap()).isEmpty();
         // All font dirs (including dir for "bar.ttf") should be deleted.
         assertThat(mUpdatableFontFilesDir.list()).hasLength(0);
@@ -190,7 +208,8 @@ public final class UpdatableFontDirTest {
         FakeFontFileParser parser = new FakeFontFileParser();
         FakeFsverityUtil fakeFsverityUtil = new FakeFsverityUtil();
         UpdatableFontDir dirForPreparation = new UpdatableFontDir(
-                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil);
+                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil,
+                mConfigFile);
         installFontFile(dirForPreparation, "foo,1", GOOD_SIGNATURE);
         installFontFile(dirForPreparation, "bar,2", GOOD_SIGNATURE);
         installFontFile(dirForPreparation, "foo,3", GOOD_SIGNATURE);
@@ -202,7 +221,8 @@ public final class UpdatableFontDirTest {
         FileUtils.stringToFile(dirForPreparation.getFontFileMap().get("foo.ttf"), "bar,4");
 
         UpdatableFontDir dir = new UpdatableFontDir(
-                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil);
+                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil,
+                mConfigFile);
         assertThat(dir.getFontFileMap()).isEmpty();
         // All font dirs (including dir for "bar.ttf") should be deleted.
         assertThat(mUpdatableFontFilesDir.list()).hasLength(0);
@@ -213,7 +233,8 @@ public final class UpdatableFontDirTest {
         FakeFontFileParser parser = new FakeFontFileParser();
         FakeFsverityUtil fakeFsverityUtil = new FakeFsverityUtil();
         UpdatableFontDir dirForPreparation = new UpdatableFontDir(
-                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil);
+                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil,
+                mConfigFile);
         installFontFile(dirForPreparation, "foo,1", GOOD_SIGNATURE);
         installFontFile(dirForPreparation, "bar,2", GOOD_SIGNATURE);
         installFontFile(dirForPreparation, "foo,3", GOOD_SIGNATURE);
@@ -226,7 +247,8 @@ public final class UpdatableFontDirTest {
         FileUtils.stringToFile(new File(mPreinstalledFontDirs.get(0), "bar.ttf"), "bar,1");
         FileUtils.stringToFile(new File(mPreinstalledFontDirs.get(1), "bar.ttf"), "bar,2");
         UpdatableFontDir dir = new UpdatableFontDir(
-                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil);
+                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil,
+                mConfigFile);
         // For foo.ttf, preinstalled font (revision 5) should be used.
         assertThat(dir.getFontFileMap()).doesNotContainKey("foo.ttf");
         // For bar.ttf, updated font (revision 4) should be used.
@@ -239,11 +261,22 @@ public final class UpdatableFontDirTest {
     }
 
     @Test
+    public void construct_failedToLoadConfig() throws Exception {
+        FakeFontFileParser parser = new FakeFontFileParser();
+        FakeFsverityUtil fakeFsverityUtil = new FakeFsverityUtil();
+        UpdatableFontDir dir = new UpdatableFontDir(
+                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil,
+                new File("/dev/null"));
+        assertThat(dir.getFontFileMap()).isEmpty();
+    }
+
+    @Test
     public void installFontFile() throws Exception {
         FakeFontFileParser parser = new FakeFontFileParser();
         FakeFsverityUtil fakeFsverityUtil = new FakeFsverityUtil();
         UpdatableFontDir dir = new UpdatableFontDir(
-                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil);
+                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil,
+                mConfigFile);
 
         installFontFile(dir, "test,1", GOOD_SIGNATURE);
         assertThat(dir.getFontFileMap()).containsKey("test.ttf");
@@ -255,7 +288,8 @@ public final class UpdatableFontDirTest {
         FakeFontFileParser parser = new FakeFontFileParser();
         FakeFsverityUtil fakeFsverityUtil = new FakeFsverityUtil();
         UpdatableFontDir dir = new UpdatableFontDir(
-                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil);
+                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil,
+                mConfigFile);
 
         installFontFile(dir, "test,1", GOOD_SIGNATURE);
         Map<String, File> mapBeforeUpgrade = dir.getFontFileMap();
@@ -272,14 +306,15 @@ public final class UpdatableFontDirTest {
         FakeFontFileParser parser = new FakeFontFileParser();
         FakeFsverityUtil fakeFsverityUtil = new FakeFsverityUtil();
         UpdatableFontDir dir = new UpdatableFontDir(
-                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil);
+                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil,
+                mConfigFile);
 
         installFontFile(dir, "test,2", GOOD_SIGNATURE);
         try {
             installFontFile(dir, "test,1", GOOD_SIGNATURE);
             fail("Expect IllegalArgumentException");
-        } catch (IllegalArgumentException e) {
-            // Expect
+        } catch (FontManagerService.SystemFontException e) {
+            assertThat(e.getErrorCode()).isEqualTo(FontManager.ERROR_CODE_DOWNGRADING);
         }
         assertThat(dir.getFontFileMap()).containsKey("test.ttf");
         assertWithMessage("Font should not be downgraded to an older revision")
@@ -291,7 +326,8 @@ public final class UpdatableFontDirTest {
         FakeFontFileParser parser = new FakeFontFileParser();
         FakeFsverityUtil fakeFsverityUtil = new FakeFsverityUtil();
         UpdatableFontDir dir = new UpdatableFontDir(
-                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil);
+                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil,
+                mConfigFile);
 
         installFontFile(dir, "foo,1", GOOD_SIGNATURE);
         installFontFile(dir, "bar,2", GOOD_SIGNATURE);
@@ -302,17 +338,19 @@ public final class UpdatableFontDirTest {
     }
 
     @Test
-    public void installFontFile_invalidSignature() {
+    public void installFontFile_invalidSignature() throws Exception {
         FakeFontFileParser parser = new FakeFontFileParser();
         FakeFsverityUtil fakeFsverityUtil = new FakeFsverityUtil();
         UpdatableFontDir dir = new UpdatableFontDir(
-                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil);
+                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil,
+                mConfigFile);
 
         try {
             installFontFile(dir, "test,1", "Invalid signature");
-            fail("Expect IOException");
-        } catch (IOException e) {
-            // Expect
+            fail("Expect SystemFontException");
+        } catch (FontManagerService.SystemFontException e) {
+            assertThat(e.getErrorCode())
+                    .isEqualTo(FontManager.ERROR_CODE_VERIFICATION_FAILURE);
         }
         assertThat(dir.getFontFileMap()).isEmpty();
     }
@@ -323,23 +361,155 @@ public final class UpdatableFontDirTest {
         FakeFsverityUtil fakeFsverityUtil = new FakeFsverityUtil();
         FileUtils.stringToFile(new File(mPreinstalledFontDirs.get(0), "test.ttf"), "test,1");
         UpdatableFontDir dir = new UpdatableFontDir(
-                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil);
+                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil,
+                mConfigFile);
 
         try {
             installFontFile(dir, "test,1", GOOD_SIGNATURE);
             fail("Expect IllegalArgumentException");
-        } catch (IllegalArgumentException e) {
-            // Expect
+        } catch (FontManagerService.SystemFontException e) {
+            assertThat(e.getErrorCode()).isEqualTo(FontManager.ERROR_CODE_DOWNGRADING);
+        }
+        assertThat(dir.getFontFileMap()).isEmpty();
+    }
+
+    @Test
+    public void installFontFile_failedToWriteConfigXml() throws Exception {
+        long expectedModifiedDate = 1234567890;
+        FakeFontFileParser parser = new FakeFontFileParser();
+        FakeFsverityUtil fakeFsverityUtil = new FakeFsverityUtil();
+        FileUtils.stringToFile(new File(mPreinstalledFontDirs.get(0), "test.ttf"), "test,1");
+
+        File readonlyDir = new File(mCacheDir, "readonly");
+        assertThat(readonlyDir.mkdir()).isTrue();
+        File readonlyFile = new File(readonlyDir, "readonly_config.xml");
+
+        PersistentSystemFontConfig.Config config = new PersistentSystemFontConfig.Config();
+        config.lastModifiedDate = expectedModifiedDate;
+        writeConfig(config, readonlyFile);
+
+        assertThat(readonlyDir.setWritable(false, false)).isTrue();
+        try {
+            UpdatableFontDir dir = new UpdatableFontDir(
+                    mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil,
+                    readonlyFile);
+
+            try {
+                installFontFile(dir, "test,2", GOOD_SIGNATURE);
+            } catch (FontManagerService.SystemFontException e) {
+                assertThat(e.getErrorCode())
+                        .isEqualTo(FontManager.ERROR_CODE_FAILED_TO_CREATE_CONFIG_FILE);
+            }
+            assertThat(dir.getSystemFontConfig().getLastModifiedDate())
+                    .isEqualTo(expectedModifiedDate);
+            assertThat(dir.getFontFileMap()).isEmpty();
+        } finally {
+            assertThat(readonlyDir.setWritable(true, true)).isTrue();
+        }
+    }
+
+    @Test
+    public void installFontFile_failedToParsePostScript() throws Exception {
+        FakeFsverityUtil fakeFsverityUtil = new FakeFsverityUtil();
+        UpdatableFontDir dir = new UpdatableFontDir(
+                mUpdatableFontFilesDir, mPreinstalledFontDirs,
+                new UpdatableFontDir.FontFileParser() {
+                    @Override
+                    public String getPostScriptName(File file) throws IOException {
+                        return null;
+                    }
+
+                    @Override
+                    public long getRevision(File file) throws IOException {
+                        return 0;
+                    }
+                }, fakeFsverityUtil, mConfigFile);
+
+        try {
+            installFontFile(dir, "foo,1", GOOD_SIGNATURE);
+            fail("Expect SystemFontException");
+        } catch (FontManagerService.SystemFontException e) {
+            assertThat(e.getErrorCode())
+                    .isEqualTo(FontManager.ERROR_CODE_MISSING_POST_SCRIPT_NAME);
+        }
+        assertThat(dir.getFontFileMap()).isEmpty();
+    }
+
+    @Test
+    public void installFontFile_failedToParsePostScriptName_invalidFont() throws Exception {
+        FakeFsverityUtil fakeFsverityUtil = new FakeFsverityUtil();
+        UpdatableFontDir dir = new UpdatableFontDir(
+                mUpdatableFontFilesDir, mPreinstalledFontDirs,
+                new UpdatableFontDir.FontFileParser() {
+                    @Override
+                    public String getPostScriptName(File file) throws IOException {
+                        throw new IOException();
+                    }
+
+                    @Override
+                    public long getRevision(File file) throws IOException {
+                        return 0;
+                    }
+                }, fakeFsverityUtil, mConfigFile);
+
+        try {
+            installFontFile(dir, "foo,1", GOOD_SIGNATURE);
+            fail("Expect SystemFontException");
+        } catch (FontManagerService.SystemFontException e) {
+            assertThat(e.getErrorCode())
+                    .isEqualTo(FontManager.ERROR_CODE_INVALID_FONT_FILE);
+        }
+        assertThat(dir.getFontFileMap()).isEmpty();
+    }
+
+    @Test
+    public void installFontFile_renameToPsNameFailure() throws Exception {
+        UpdatableFontDir.FsverityUtil fakeFsverityUtil = new UpdatableFontDir.FsverityUtil() {
+            private final FakeFsverityUtil mFake = new FakeFsverityUtil();
+
+            @Override
+            public boolean hasFsverity(String path) {
+                return mFake.hasFsverity(path);
+            }
+
+            @Override
+            public void setUpFsverity(String path, byte[] pkcs7Signature) throws IOException {
+                mFake.setUpFsverity(path, pkcs7Signature);
+            }
+
+            @Override
+            public boolean rename(File src, File dest) {
+                return false;
+            }
+        };
+        FakeFontFileParser parser = new FakeFontFileParser();
+        UpdatableFontDir dir = new UpdatableFontDir(
+                mUpdatableFontFilesDir, mPreinstalledFontDirs, parser, fakeFsverityUtil,
+                mConfigFile);
+
+        try {
+            installFontFile(dir, "foo,1", GOOD_SIGNATURE);
+            fail("Expect SystemFontException");
+        } catch (FontManagerService.SystemFontException e) {
+            assertThat(e.getErrorCode())
+                    .isEqualTo(FontManager.ERROR_CODE_FAILED_TO_WRITE_FONT_FILE);
         }
         assertThat(dir.getFontFileMap()).isEmpty();
     }
 
     private void installFontFile(UpdatableFontDir dir, String content, String signature)
-            throws IOException {
+            throws Exception {
         File file = File.createTempFile("font", "ttf", mCacheDir);
         FileUtils.stringToFile(file, content);
         try (FileInputStream in = new FileInputStream(file)) {
             dir.installFontFile(in.getFD(), signature.getBytes());
         }
     }
+
+    private void writeConfig(PersistentSystemFontConfig.Config config,
+            File file) throws IOException {
+        try (FileOutputStream fos = new FileOutputStream(file)) {
+            PersistentSystemFontConfig.writeToXml(fos, config);
+        }
+    }
 }