1 /*
2  * Copyright (C) 2015 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #include <dlfcn.h>
18 
19 static const char* g_local_string = "This string is local to root library";
20 extern "C" const char* g_private_extern_string;
21 extern "C" const char* g_public_extern_string;
22 
23 // This is resolved only if public library is in the same namespace as
24 // the root one. It should remain unresolved if looking up for public library
25 // crosses namespace boundary.
26 //
27 // Defined in libnstest_public_internal.so on which libnstest_public.so
28 // depends on
29 extern "C" const char* __attribute__((weak)) internal_extern_string();
30 
31 bool g_dlopened = false;
32 
ns_get_local_string()33 extern "C" const char* ns_get_local_string() {
34   return g_local_string;
35 }
36 
ns_get_private_extern_string()37 extern "C" const char* ns_get_private_extern_string() {
38   return g_private_extern_string;
39 }
40 
ns_get_public_extern_string()41 extern "C" const char* ns_get_public_extern_string() {
42   return g_public_extern_string;
43 }
44 
ns_get_internal_extern_string()45 extern "C" const char* ns_get_internal_extern_string() {
46   if (internal_extern_string != nullptr) {
47     return internal_extern_string();
48   } else {
49     return nullptr;
50   }
51 }
52 
ns_get_dlopened_string()53 extern "C" const char* ns_get_dlopened_string() {
54   void* handle = dlopen("libnstest_dlopened.so", RTLD_NOW | RTLD_GLOBAL);
55   if (handle == nullptr) {
56     return nullptr;
57   }
58 
59   const char** result = static_cast<const char**>(dlsym(handle, "g_private_dlopened_string"));
60   if (result == nullptr) {
61     return nullptr;
62   } else {
63     g_dlopened = true;
64   }
65 
66   return *result;
67 }
68