Add PreloadPublicNativeLibraries function

Shift responsibility of preloading native libraries to the user
of the library. This lets applications that do not use jni but
depend on libnative_loader.so to avoid unnecessary preloads of
public libraries which could be expensive.

Bug: http://b/27245894
Change-Id: I12a8100de5da639c068769bca21ecebff2b2d538
(cherry picked from commit 426799d77014888315233253e96277bef13158eb)

2 files changed, 11 insertions, 4 deletions

diff --git a/libnativeloader/include/nativeloader/native_loader.h b/libnativeloader/include/nativeloader/native_loader.h
index 2dec71f1e..5644aa637 100644
--- a/libnativeloader/include/nativeloader/native_loader.h
+++ b/libnativeloader/include/nativeloader/native_loader.h
@@ -26,6 +26,9 @@
 namespace android {
 
 __attribute__((visibility("default")))
+void PreloadPublicNativeLibraries();
+
+__attribute__((visibility("default")))
 void* OpenNativeLibrary(JNIEnv* env, int32_t target_sdk_version, const char* path,
                         jobject class_loader, bool is_shared, jstring library_path,
                         jstring permitted_path);
diff --git a/libnativeloader/native_loader.cpp b/libnativeloader/native_loader.cpp
index a64b9720c..f8bb5fdd1 100644
--- a/libnativeloader/native_loader.cpp
+++ b/libnativeloader/native_loader.cpp
@@ -57,9 +57,7 @@ static const char* kPublicNativeLibraries = "libandroid.so:"
 
 class LibraryNamespaces {
  public:
-  LibraryNamespaces() : initialized_(false) {
-    PreloadPublicLibraries();
-  }
+  LibraryNamespaces() : initialized_(false) { }
 
   android_namespace_t* GetOrCreate(JNIEnv* env, jobject class_loader,
                                    bool is_shared,
@@ -111,7 +109,6 @@ class LibraryNamespaces {
     return it != namespaces_.end() ? it->second : nullptr;
   }
 
- private:
   void PreloadPublicLibraries() {
     // android_init_namespaces() expects all the public libraries
     // to be loaded so that they can be found by soname alone.
@@ -121,6 +118,7 @@ class LibraryNamespaces {
     }
   }
 
+ private:
   bool InitPublicNamespace(const char* library_path) {
     // Some apps call dlopen from generated code unknown to linker in which
     // case linker uses anonymous namespace. See b/25844435 for details.
@@ -139,6 +137,12 @@ class LibraryNamespaces {
 static LibraryNamespaces* g_namespaces = new LibraryNamespaces;
 #endif
 
+void PreloadPublicNativeLibraries() {
+#if defined(__ANDROID__)
+  g_namespaces->PreloadPublicLibraries();
+#endif
+}
+
 
 void* OpenNativeLibrary(JNIEnv* env, int32_t target_sdk_version, const char* path,
                         jobject class_loader, bool is_shared, jstring java_library_path,