Add loader library to handle relro sharing.

Create a small native library that just contains the JNI code for
WebViewFactory, to enable loading of the full WebView native library
using android_dlopen_ext.

Bug: 13005501
Change-Id: I9608431a66868124f1c1ac618b2c24e2f2608631

1 files changed, 250 insertions, 0 deletions

diff --git a/chromium/loader/loader.cpp b/chromium/loader/loader.cpp
new file mode 100644
index 0000000..a5e4e7f
--- /dev/null
+++ b/chromium/loader/loader.cpp
@@ -0,0 +1,250 @@
+/*
+ * Copyright (C) 2014 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.
+ */
+
+// Uncomment for verbose logging.
+// #define LOG_NDEBUG 0
+#define LOG_TAG "webviewchromiumloader"
+
+#include <dlfcn.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include <jni.h>
+#include <android/dlext.h>
+#include <utils/Log.h>
+
+#define NELEM(x) ((int) (sizeof(x) / sizeof((x)[0])))
+
+namespace android {
+namespace {
+
+void* gReservedAddress = NULL;
+size_t gReservedSize = 0;
+
+jboolean DoReserveAddressSpace(const char* lib) {
+  size_t vsize = 0;
+
+  // First check for a file which explicitly specifies the virtual size needed.
+  // The file has a .so suffix so that the package manager will extract it
+  // alongside the real library.
+  static const char vsize_suffix[] = ".vsize.so";
+  char vsize_name[strlen(lib) + sizeof(vsize_suffix)];
+  strlcpy(vsize_name, lib, sizeof(vsize_name));
+  strlcat(vsize_name, vsize_suffix, sizeof(vsize_name));
+  FILE* vsize_file = fopen(vsize_name, "r");
+  if (vsize_file != NULL) {
+    fscanf(vsize_file, "%zd", &vsize);
+    fclose(vsize_file);
+  }
+
+  // If the file didn't exist or was unparseable, just stat() the library to see
+  // how big it is.
+  if (vsize == 0) {
+    struct stat libstat;
+    if (stat(lib, &libstat) != 0) {
+      ALOGE("Failed to stat %s: %s", lib, strerror(errno));
+      return JNI_FALSE;
+    }
+    // The required memory can be larger than the file on disk due to the .bss
+    // section, and an upgraded version of the library installed later may also
+    // be larger, so we need to allocate more than the size of the file.
+    vsize = libstat.st_size * 2;
+  }
+
+  void* addr = mmap(NULL, vsize, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+  if (addr == MAP_FAILED) {
+    ALOGE("Failed to reserve %zd bytes of address space for future load of %s: %s",
+          vsize, lib, strerror(errno));
+    return JNI_FALSE;
+  }
+  gReservedAddress = addr;
+  gReservedSize = vsize;
+  ALOGV("Reserved %zd bytes at %p", vsize, addr);
+  return JNI_TRUE;
+}
+
+jboolean DoCreateRelroFile(const char* lib, const char* relro) {
+  // Try to unlink the old file, since if this is being called, the old one is
+  // obsolete.
+  if (unlink(relro) != 0 && errno != ENOENT) {
+    // If something went wrong other than the file not existing, log a warning
+    // but continue anyway in the hope that we can successfully overwrite the
+    // existing file with rename() later.
+    ALOGW("Failed to unlink old file %s: %s", relro, strerror(errno));
+  }
+  static const char tmpsuffix[] = ".XXXXXX";
+  char relro_tmp[strlen(relro) + sizeof(tmpsuffix)];
+  strlcpy(relro_tmp, relro, sizeof(relro_tmp));
+  strlcat(relro_tmp, tmpsuffix, sizeof(relro_tmp));
+  int tmp_fd = TEMP_FAILURE_RETRY(mkstemp(relro_tmp));
+  if (tmp_fd == -1) {
+    ALOGE("Failed to create temporary file %s: %s", relro_tmp, strerror(errno));
+    return JNI_FALSE;
+  }
+  android_dlextinfo extinfo;
+  extinfo.flags = ANDROID_DLEXT_RESERVED_ADDRESS | ANDROID_DLEXT_WRITE_RELRO;
+  extinfo.reserved_addr = gReservedAddress;
+  extinfo.reserved_size = gReservedSize;
+  extinfo.relro_fd = tmp_fd;
+  void* handle = android_dlopen_ext(lib, RTLD_NOW, &extinfo);
+  int close_result = close(tmp_fd);
+  if (handle == NULL) {
+    ALOGE("Failed to load library %s: %s", lib, dlerror());
+    unlink(relro_tmp);
+    return JNI_FALSE;
+  }
+  if (close_result != 0 ||
+      chmod(relro_tmp, S_IRUSR | S_IRGRP | S_IROTH) != 0 ||
+      rename(relro_tmp, relro) != 0) {
+    ALOGE("Failed to update relro file %s: %s", relro, strerror(errno));
+    unlink(relro_tmp);
+    return JNI_FALSE;
+  }
+  ALOGV("Created relro file %s for library %s", relro, lib);
+  return JNI_TRUE;
+}
+
+jboolean DoLoadWithRelroFile(const char* lib, const char* relro) {
+  int relro_fd = TEMP_FAILURE_RETRY(open(relro, O_RDONLY));
+  if (relro_fd == -1) {
+    ALOGE("Failed to open relro file %s: %s", relro, strerror(errno));
+    return JNI_FALSE;
+  }
+  android_dlextinfo extinfo;
+  extinfo.flags = ANDROID_DLEXT_RESERVED_ADDRESS | ANDROID_DLEXT_USE_RELRO;
+  extinfo.reserved_addr = gReservedAddress;
+  extinfo.reserved_size = gReservedSize;
+  extinfo.relro_fd = relro_fd;
+  void* handle = android_dlopen_ext(lib, RTLD_NOW, &extinfo);
+  close(relro_fd);
+  if (handle == NULL) {
+    ALOGE("Failed to load library %s: %s", lib, dlerror());
+    return JNI_FALSE;
+  }
+  ALOGV("Loaded library %s with relro file %s", lib, relro);
+  return JNI_TRUE;
+}
+
+/******************************************************************************/
+/* JNI wrappers - handle string lifetimes and 32/64 ABI choice                */
+/******************************************************************************/
+
+jboolean ReserveAddressSpace(JNIEnv* env, jclass, jstring lib32, jstring lib64) {
+#ifdef __LP64__
+  jstring lib = lib64;
+  (void)lib32;
+#else
+  jstring lib = lib32;
+  (void)lib64;
+#endif
+  jboolean ret = JNI_FALSE;
+  const char* lib_utf8 = env->GetStringUTFChars(lib, NULL);
+  if (lib_utf8 != NULL) {
+    ret = DoReserveAddressSpace(lib_utf8);
+    env->ReleaseStringUTFChars(lib, lib_utf8);
+  }
+  return ret;
+}
+
+jboolean CreateRelroFile(JNIEnv* env, jclass, jstring lib32, jstring lib64,
+                         jstring relro32, jstring relro64) {
+#ifdef __LP64__
+  jstring lib = lib64;
+  jstring relro = relro64;
+  (void)lib32; (void)relro32;
+#else
+  jstring lib = lib32;
+  jstring relro = relro32;
+  (void)lib64; (void)relro64;
+#endif
+  jboolean ret = JNI_FALSE;
+  const char* lib_utf8 = env->GetStringUTFChars(lib, NULL);
+  if (lib_utf8 != NULL) {
+    const char* relro_utf8 = env->GetStringUTFChars(relro, NULL);
+    if (relro_utf8 != NULL) {
+      ret = DoCreateRelroFile(lib_utf8, relro_utf8);
+      env->ReleaseStringUTFChars(relro, relro_utf8);
+    }
+    env->ReleaseStringUTFChars(lib, lib_utf8);
+  }
+  return ret;
+}
+
+jboolean LoadWithRelroFile(JNIEnv* env, jclass, jstring lib32, jstring lib64,
+                           jstring relro32, jstring relro64) {
+#ifdef __LP64__
+  jstring lib = lib64;
+  jstring relro = relro64;
+  (void)lib32; (void)relro32;
+#else
+  jstring lib = lib32;
+  jstring relro = relro32;
+  (void)lib64; (void)relro64;
+#endif
+  jboolean ret = JNI_FALSE;
+  const char* lib_utf8 = env->GetStringUTFChars(lib, NULL);
+  if (lib_utf8 != NULL) {
+    const char* relro_utf8 = env->GetStringUTFChars(relro, NULL);
+    if (relro_utf8 != NULL) {
+      ret = DoLoadWithRelroFile(lib_utf8, relro_utf8);
+      env->ReleaseStringUTFChars(relro, relro_utf8);
+    }
+    env->ReleaseStringUTFChars(lib, lib_utf8);
+  }
+  return ret;
+}
+
+const char kClassName[] = "android/webkit/WebViewFactory";
+const JNINativeMethod kJniMethods[] = {
+  { "nativeReserveAddressSpace", "(Ljava/lang/String;Ljava/lang/String;)Z",
+      reinterpret_cast<void*>(ReserveAddressSpace) },
+  { "nativeCreateRelroFile",
+      "(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;)Z",
+      reinterpret_cast<void*>(CreateRelroFile) },
+  { "nativeLoadWithRelroFile",
+      "(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;)Z",
+      reinterpret_cast<void*>(LoadWithRelroFile) },
+};
+
+}  // namespace
+
+void RegisterWebViewFactory(JNIEnv* env) {
+  // If either of these fail, it will set an exception that will be thrown on
+  // return, so no need to handle errors here.
+  jclass clazz = env->FindClass(kClassName);
+  if (clazz) {
+    env->RegisterNatives(clazz, kJniMethods, NELEM(kJniMethods));
+  }
+}
+
+}  // namespace android
+
+JNIEXPORT jint JNI_OnLoad(JavaVM* vm, void*) {
+  JNIEnv* env = NULL;
+  if (vm->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_6) != JNI_OK) {
+    ALOGE("GetEnv failed");
+    return JNI_ERR;
+  }
+  android::RegisterWebViewFactory(env);
+  return JNI_VERSION_1_6;
+}