Make libdl symbols weak.

Also make a static library which can be used to override these symbols
in other implementations of libdl.so

Test: make
Change-Id: Id433bb07ecbfc4955c3fb7591ace971c2cda7862

2 files changed, 41 insertions, 4 deletions

diff --git a/libdl/Android.bp b/libdl/Android.bp
index 9f67ee80d..b0bbe99c8 100644
--- a/libdl/Android.bp
+++ b/libdl/Android.bp
@@ -1,6 +1,28 @@
 //
 // libdl
 //
+cc_library_static {
+    name: "libdl_static",
+
+    srcs: ["libdl.c", "libdl_cfi.cpp"],
+
+    cflags: [
+        "-Wall",
+        "-Wextra",
+        "-Wunused",
+        "-Werror",
+    ],
+
+    // For private/CFIShadow.h.
+    include_dirs: ["bionic/libc"],
+
+    stl: "none",
+
+    sanitize: {
+        never: true,
+    },
+}
+
 cc_library {
     name: "libdl",
 
@@ -45,7 +67,7 @@ cc_library {
         },
     },
     shared: {
-        srcs: ["libdl.c", "libdl_cfi.cpp"],
+        whole_static_libs: ["libdl_static"],
     },
     static: {
         srcs: [ "libdl_static.c" ],
@@ -66,9 +88,6 @@ cc_library {
     allow_undefined_symbols: true,
     system_shared_libs: [],
 
-    // For private/CFIShadow.h.
-    include_dirs: ["bionic/libc"],
-
     // This is placeholder library the actual implementation is (currently)
     // provided by the linker.
     shared_libs: [ "ld-android" ],
diff --git a/libdl/libdl.c b/libdl/libdl.c
index 1a65b6776..b747c2289 100644
--- a/libdl/libdl.c
+++ b/libdl/libdl.c
@@ -98,34 +98,41 @@ __attribute__((__weak__, visibility("default")))
 struct android_namespace_t* __loader_android_get_exported_namespace(const char* name);
 
 // Proxy calls to bionic loader
+__attribute__((__weak__))
 void* dlopen(const char* filename, int flag) {
   const void* caller_addr = __builtin_return_address(0);
   return __loader_dlopen(filename, flag, caller_addr);
 }
 
+__attribute__((__weak__))
 char* dlerror() {
   return __loader_dlerror();
 }
 
+__attribute__((__weak__))
 void* dlsym(void* handle, const char* symbol) {
   const void* caller_addr = __builtin_return_address(0);
   return __loader_dlsym(handle, symbol, caller_addr);
 }
 
+__attribute__((__weak__))
 void* dlvsym(void* handle, const char* symbol, const char* version) {
   const void* caller_addr = __builtin_return_address(0);
   return __loader_dlvsym(handle, symbol, version, caller_addr);
 }
 
+__attribute__((__weak__))
 int dladdr(const void* addr, Dl_info* info) {
   return __loader_dladdr(addr, info);
 }
 
+__attribute__((__weak__))
 int dlclose(void* handle) {
   return __loader_dlclose(handle);
 }
 
 #if defined(__arm__)
+__attribute__((__weak__))
 _Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) {
   return __loader_dl_unwind_find_exidx(pc, pcount);
 }
@@ -140,31 +147,39 @@ int dl_iterate_phdr(int (*cb)(struct dl_phdr_info* info, size_t size, void* data
   return __loader_dl_iterate_phdr(cb, data);
 }
 
+__attribute__((__weak__))
 void android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
   __loader_android_get_LD_LIBRARY_PATH(buffer, buffer_size);
 }
 
+__attribute__((__weak__))
 void android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
   __loader_android_update_LD_LIBRARY_PATH(ld_library_path);
 }
 
+__attribute__((__weak__))
 void* android_dlopen_ext(const char* filename, int flag, const android_dlextinfo* extinfo) {
   const void* caller_addr = __builtin_return_address(0);
   return __loader_android_dlopen_ext(filename, flag, extinfo, caller_addr);
 }
 
+__attribute__((__weak__))
 void android_set_application_target_sdk_version(uint32_t target) {
   __loader_android_set_application_target_sdk_version(target);
 }
+
+__attribute__((__weak__))
 uint32_t android_get_application_target_sdk_version() {
   return __loader_android_get_application_target_sdk_version();
 }
 
+__attribute__((__weak__))
 bool android_init_anonymous_namespace(const char* shared_libs_sonames,
                                       const char* library_search_path) {
   return __loader_android_init_anonymous_namespace(shared_libs_sonames, library_search_path);
 }
 
+__attribute__((__weak__))
 struct android_namespace_t* android_create_namespace(const char* name,
                                                      const char* ld_library_path,
                                                      const char* default_library_path,
@@ -181,16 +196,19 @@ struct android_namespace_t* android_create_namespace(const char* name,
                                            caller_addr);
 }
 
+__attribute__((__weak__))
 bool android_link_namespaces(struct android_namespace_t* namespace_from,
                              struct android_namespace_t* namespace_to,
                              const char* shared_libs_sonames) {
   return __loader_android_link_namespaces(namespace_from, namespace_to, shared_libs_sonames);
 }
 
+__attribute__((__weak__))
 void android_dlwarning(void* obj, void (*f)(void*, const char*)) {
   __loader_android_dlwarning(obj, f);
 }
 
+__attribute__((__weak__))
 struct android_namespace_t* android_get_exported_namespace(const char* name) {
   return __loader_android_get_exported_namespace(name);
 }