1 /*
2 * Copyright (C) 2021 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 #include <cstdlib>
20 #include <iostream>
21 #include <string>
22
23 #include <android/dlext.h>
24
25 extern "C" {
26 enum {
27 ANDROID_NAMESPACE_TYPE_REGULAR = 0,
28 ANDROID_NAMESPACE_TYPE_ISOLATED = 1,
29 ANDROID_NAMESPACE_TYPE_SHARED = 2,
30 };
31
32 extern struct android_namespace_t* android_create_namespace(
33 const char* name, const char* ld_library_path, const char* default_library_path,
34 uint64_t type, const char* permitted_when_isolated_path,
35 struct android_namespace_t* parent);
36 } // extern "C"
37
38 static void* load(const std::string& libname);
39
main(int argc,char * argv[])40 int main(int argc, char* argv[]) {
41 if (argc < 2) {
42 std::cout << "Usage:\n";
43 std::cout << " " << argv[0] << " LIBNAME [ARGS...]\n";
44 return EXIT_FAILURE;
45 }
46
47 const char* libname = argv[1];
48 void* handle = load(libname);
49 if (handle == nullptr) {
50 std::cerr << "Failed to load " << libname << ": " << dlerror() << "\n";
51 return EXIT_FAILURE;
52 }
53
54 int (*entry)(int argc, char* argv[]) = nullptr;
55 entry = reinterpret_cast<decltype(entry)>(dlsym(handle, "android_native_main"));
56 if (entry == nullptr) {
57 std::cerr << "Failed to find entrypoint `android_native_main`: " << dlerror() << "\n";
58 return EXIT_FAILURE;
59 }
60
61 return entry(argc - 1, argv + 1);
62 }
63
64 // Create a new linker namespace whose search path is set to the directory of the library. Then
65 // load it from there. Returns the handle to the loaded library if successful. Returns nullptr
66 // if failed.
load(const std::string & libname)67 void* load(const std::string& libname) {
68 // Parent as nullptr means the default namespace
69 android_namespace_t* parent = nullptr;
70 // The search paths of the new namespace are inherited from the parent namespace.
71 const uint64_t type = ANDROID_NAMESPACE_TYPE_SHARED;
72 // The directory of the library is appended to the search paths
73 const std::string libdir = libname.substr(0, libname.find_last_of("/"));
74 const char* ld_library_path = libdir.c_str();
75 const char* default_library_path = libdir.c_str();
76
77 android_namespace_t* new_ns = nullptr;
78 new_ns = android_create_namespace("microdroid_app", ld_library_path, default_library_path, type,
79 /* permitted_when_isolated_path */ nullptr, parent);
80 if (new_ns == nullptr) {
81 std::cerr << "Failed to create linker namespace: " << dlerror() << "\n";
82 return nullptr;
83 }
84
85 const android_dlextinfo info = {
86 .flags = ANDROID_DLEXT_USE_NAMESPACE,
87 .library_namespace = new_ns,
88 };
89 return android_dlopen_ext(libname.c_str(), RTLD_NOW, &info);
90 }
91