On library load failure, retry without shared RELRO.

https://codereview.chromium.org/443393003 introduced code for service
processes that turns off RELRO sharing and retries a library load in
the event of an address clash or other failure to load a library with
shared RELRO.

This change adds the same back off and retry strategy to the libraries
loaded in the main browser process, for cases where low memory devices
aggressively share RELRO as widely as possible.

BUG=411928
TBR=rmcilroy@chromium.org

Review URL: https://codereview.chromium.org/551373004

Cr-Commit-Position: refs/heads/master@{#294393}

base/android/java/src/org/chromium/base/library_loader/LibraryLoader.java

@@ -148,19 +148,47 @@ public class LibraryLoader {
                 long startTime = SystemClock.uptimeMillis();
                 boolean useChromiumLinker = Linker.isUsed();
 
-                if (useChromiumLinker) Linker.prepareLibraryLoad();
+                if (useChromiumLinker) {
+                    // Load libraries using the Chromium linker.
+                    Linker.prepareLibraryLoad();
 
-                for (String library : NativeLibraries.LIBRARIES) {
-                    if (useChromiumLinker) {
+                    for (String library : NativeLibraries.LIBRARIES) {
+                        String zipfile = null;
                         if (Linker.isInZipFile()) {
-                            String zipfile = context.getApplicationInfo().sourceDir;
+                            zipfile = context.getApplicationInfo().sourceDir;
                             Log.i(TAG, "Loading " + library + " from within " + zipfile);
-                            Linker.loadLibraryInZipFile(zipfile, library);
                         } else {
                             Log.i(TAG, "Loading: " + library);
-                            Linker.loadLibrary(library);
                         }
-                    } else {
+
+                        boolean isLoaded = false;
+                        if (Linker.isUsingBrowserSharedRelros()) {
+                            try {
+                                if (zipfile != null) {
+                                    Linker.loadLibraryInZipFile(zipfile, library);
+                                } else {
+                                    Linker.loadLibrary(library);
+                                }
+                                isLoaded = true;
+                            } catch (UnsatisfiedLinkError e) {
+                                Log.w(TAG, "Failed to load native library with shared RELRO, " +
+                                      "retrying without");
+                                Linker.disableSharedRelros();
+                            }
+                        }
+                        if (!isLoaded) {
+                            if (zipfile != null) {
+                                Linker.loadLibraryInZipFile(zipfile, library);
+                            } else {
+                                Linker.loadLibrary(library);
+                            }
+                        }
+                    }
+
+                    Linker.finishLibraryLoad();
+                } else {
+                    // Load libraries using the system linker.
+                    for (String library : NativeLibraries.LIBRARIES) {
                         try {
                             System.loadLibrary(library);
                         } catch (UnsatisfiedLinkError e) {
@@ -174,7 +202,6 @@ public class LibraryLoader {
                         }
                     }
                 }
-                if (useChromiumLinker) Linker.finishLibraryLoad();
 
                 if (context != null
                     && shouldDeleteOldWorkaroundLibraries

base/android/java/src/org/chromium/base/library_loader/Linker.java

@@ -373,6 +373,17 @@ public class Linker {
         }
     }
 
+    /**
+     * Call this method to determine if the linker will try to use shared RELROs
+     * for the browser process.
+     */
+    public static boolean isUsingBrowserSharedRelros() {
+        synchronized (Linker.class) {
+            ensureInitializedLocked();
+            return sBrowserUsesSharedRelro;
+        }
+    }
+
     /**
      * Call this method to determine if the chromium project must load
      * the library directly from the zip file.