Don't create anonymous namespace

Anonymous namespace is not created separately. When a regular namespace
is created with ANDROID_NAMESPACE_TYPE_ALSO_USED_AS_ANONYMOUS, that
namespace is used as the anonymous namespace.

Bug: 130388701
Test: CtsBionicTestCases
Change-Id: Ie449a59f303487a7a9ff6fff98e6148e9f968fd2

linker/linker.cpp

@@ -76,6 +76,7 @@
 
 static std::unordered_map<void*, size_t> g_dso_handle_counters;
 
+static bool g_anonymous_namespace_set = false;
 static android_namespace_t* g_anonymous_namespace = &g_default_namespace;
 static std::unordered_map<std::string, android_namespace_t*> g_exported_namespaces;
 
@@ -270,8 +271,6 @@ static bool translateSystemPathToApexPath(const char* name, std::string* out_nam
 
 static std::vector<std::string> g_ld_preload_names;
 
-static bool g_anonymous_namespace_initialized;
-
 #if STATS
 struct linker_stats_t {
   int count[kRelocMax];
@@ -2471,14 +2470,29 @@ int do_dlclose(void* handle) {
   return 0;
 }
 
-bool init_anonymous_namespace(const char* shared_lib_sonames, const char* library_search_path) {
-  if (g_anonymous_namespace_initialized) {
-    DL_ERR("anonymous namespace has already been initialized.");
-    return false;
+// Make ns as the anonymous namespace that is a namespace used when
+// we fail to determine the caller address (e.g., call from mono-jited code)
+// Since there can be multiple anonymous namespace in a process, subsequent
+// call to this function causes an error.
+static bool set_anonymous_namespace(android_namespace_t* ns) {
+  if (!g_anonymous_namespace_set && ns != nullptr) {
+    CHECK(ns->is_also_used_as_anonymous());
+    g_anonymous_namespace = ns;
+    g_anonymous_namespace_set = true;
+    return true;
   }
+  return false;
+}
 
+// TODO(b/130388701) remove this. Currently, this is used only for testing
+// where we don't have classloader namespace.
+bool init_anonymous_namespace(const char* shared_lib_sonames, const char* library_search_path) {
   ProtectedDataGuard guard;
 
+  // Test-only feature: we need to change the anonymous namespace multiple times
+  // while the test is running.
+  g_anonymous_namespace_set = false;
+
   // create anonymous namespace
   // When the caller is nullptr - create_namespace will take global group
   // from the anonymous namespace, which is fine because anonymous namespace
@@ -2488,21 +2502,18 @@ bool init_anonymous_namespace(const char* shared_lib_sonames, const char* librar
                        "(anonymous)",
                        nullptr,
                        library_search_path,
-                       ANDROID_NAMESPACE_TYPE_ISOLATED,
+                       ANDROID_NAMESPACE_TYPE_ISOLATED |
+                       ANDROID_NAMESPACE_TYPE_ALSO_USED_AS_ANONYMOUS,
                        nullptr,
                        &g_default_namespace);
 
-  if (anon_ns == nullptr) {
-    return false;
-  }
+  CHECK(anon_ns != nullptr);
 
   if (!link_namespaces(anon_ns, &g_default_namespace, shared_lib_sonames)) {
+    // TODO: delete anon_ns
     return false;
   }
 
-  g_anonymous_namespace = anon_ns;
-  g_anonymous_namespace_initialized = true;
-
   return true;
 }
 
@@ -2542,6 +2553,7 @@ android_namespace_t* create_namespace(const void* caller_addr,
   ns->set_name(name);
   ns->set_isolated((type & ANDROID_NAMESPACE_TYPE_ISOLATED) != 0);
   ns->set_greylist_enabled((type & ANDROID_NAMESPACE_TYPE_GREYLIST_ENABLED) != 0);
+  ns->set_also_used_as_anonymous((type & ANDROID_NAMESPACE_TYPE_ALSO_USED_AS_ANONYMOUS) != 0);
 
   if ((type & ANDROID_NAMESPACE_TYPE_SHARED) != 0) {
     // append parent namespace paths.
@@ -2573,6 +2585,16 @@ android_namespace_t* create_namespace(const void* caller_addr,
   ns->set_default_library_paths(std::move(default_library_paths));
   ns->set_permitted_paths(std::move(permitted_paths));
 
+  if (ns->is_also_used_as_anonymous() && !set_anonymous_namespace(ns)) {
+    DL_ERR("failed to set namespace: [name=\"%s\", ld_library_path=\"%s\", default_library_paths=\"%s\""
+           " permitted_paths=\"%s\"] as the anonymous namespace",
+           ns->get_name(),
+           android::base::Join(ns->get_ld_library_paths(), ':').c_str(),
+           android::base::Join(ns->get_default_library_paths(), ':').c_str(),
+           android::base::Join(ns->get_permitted_paths(), ':').c_str());
+    return nullptr;
+  }
+
   return ns;
 }
 

linker/linker.h

@@ -165,6 +165,13 @@ enum {
    */
   ANDROID_NAMESPACE_TYPE_GREYLIST_ENABLED = 0x08000000,
 
+  /* This flag instructs linker to use this namespace as the anonymous
+   * namespace. There can be only one anonymous namespace in a process. If there
+   * already an anonymous namespace in the process, using this flag when
+   * creating a new namespace causes an error
+   */
+  ANDROID_NAMESPACE_TYPE_ALSO_USED_AS_ANONYMOUS = 0x10000000,
+
   ANDROID_NAMESPACE_TYPE_SHARED_ISOLATED = ANDROID_NAMESPACE_TYPE_SHARED |
                                            ANDROID_NAMESPACE_TYPE_ISOLATED,
 };

linker/linker_namespaces.h

@@ -72,7 +72,10 @@ struct android_namespace_link_t {
 
 struct android_namespace_t {
  public:
-  android_namespace_t() : is_isolated_(false), is_greylist_enabled_(false) {}
+  android_namespace_t() :
+    is_isolated_(false),
+    is_greylist_enabled_(false),
+    is_also_used_as_anonymous_(false) {}
 
   const char* get_name() const { return name_.c_str(); }
   void set_name(const char* name) { name_ = name; }
@@ -83,6 +86,9 @@ struct android_namespace_t {
   bool is_greylist_enabled() const { return is_greylist_enabled_; }
   void set_greylist_enabled(bool enabled) { is_greylist_enabled_ = enabled; }
 
+  bool is_also_used_as_anonymous() const { return is_also_used_as_anonymous_; }
+  void set_also_used_as_anonymous(bool yes) { is_also_used_as_anonymous_ = yes; }
+
   const std::vector<std::string>& get_ld_library_paths() const {
     return ld_library_paths_;
   }
@@ -164,6 +170,7 @@ struct android_namespace_t {
   std::string name_;
   bool is_isolated_;
   bool is_greylist_enabled_;
+  bool is_also_used_as_anonymous_;
   std::vector<std::string> ld_library_paths_;
   std::vector<std::string> default_library_paths_;
   std::vector<std::string> permitted_paths_;