Revert "Bionic loader is no longer hijacking libdl.so"

This reverts commit c12acef96bd80c419654e159e1dc24a69513a86d.

Breaks the Mips build.

Bug: 27106625
Change-Id: I27edb7114065c36e1b618e387530d58189cdb184

3 files changed, 29 insertions, 173 deletions

diff --git a/libdl/Android.bp b/libdl/Android.bp
index e9b79d79c..9db3a9426 100644
--- a/libdl/Android.bp
+++ b/libdl/Android.bp
@@ -57,55 +57,6 @@ cc_library {
     allow_undefined_symbols: true,
     system_shared_libs: [],
 
-    // This is placeholder library the actual implementation is (currently)
-    // provided by the linker.
-    shared_libs: [ "ld-android" ],
-
-    sanitize: {
-        never: true,
-    },
-}
-
-cc_library {
-    // NOTE: --exclude-libs=libgcc.a makes sure that any symbols libdl.so pulls from
-    // libgcc.a are made static to ld-android.so.  This in turn ensures that libraries that
-    // a) pull symbols from libgcc.a and b) depend on ld-android.so will not rely on ld-android.so
-    // to provide those symbols, but will instead pull them from libgcc.a.  Specifically,
-    // we use this property to make sure libc.so has its own copy of the code from
-    // libgcc.a it uses.
-    //
-    // DO NOT REMOVE --exclude-libs!
-
-    ldflags: ["-Wl,--exclude-libs=libgcc.a"],
-
-    // for x86, exclude libgcc_eh.a for the same reasons as above
-    arch: {
-        x86: {
-            ldflags: ["-Wl,--exclude-libs=libgcc_eh.a"],
-        },
-        x86_64: {
-            ldflags: ["-Wl,--exclude-libs=libgcc_eh.a"],
-        },
-    },
-    srcs: ["ld_android.c"],
-    cflags: [
-        "-Wall",
-        "-Wextra",
-        "-Wunused",
-        "-Werror",
-    ],
-    stl: "none",
-
-    name: "ld-android",
-
-    // NOTE: libdl needs __aeabi_unwind_cpp_pr0 from libgcc.a but libgcc.a needs a
-    // few symbols from libc. Using --no-undefined here results in having to link
-    // against libc creating a circular dependency which is removed and we end up
-    // with missing symbols. Since this library is just a bunch of stubs, we set
-    // LOCAL_ALLOW_UNDEFINED_SYMBOLS to remove --no-undefined from the linker flags.
-    allow_undefined_symbols: true,
-    system_shared_libs: [],
-
     sanitize: {
         never: true,
     },
diff --git a/libdl/ld_android.c b/libdl/ld_android.c
deleted file mode 100644
index 8b1378917..000000000
--- a/libdl/ld_android.c
+++ /dev/null
@@ -1 +0,0 @@
-
diff --git a/libdl/libdl.c b/libdl/libdl.c
index 832946841..4cc4deac8 100644
--- a/libdl/libdl.c
+++ b/libdl/libdl.c
@@ -20,148 +20,54 @@
 #include <stdbool.h>
 #include <android/dlext.h>
 
-// These functions are exported by the loader
-// TODO(dimitry): replace these with reference to libc.so
+// These are stubs for functions that are actually defined
+// in the dynamic linker and hijacked at runtime.
 
-__attribute__((__weak__, visibility("default")))
-void* __loader_dlopen(const char* filename, int flags, const void* caller_addr);
+void* dlopen(const char* filename __unused, int flag __unused) { return 0; }
 
-__attribute__((__weak__, visibility("default")))
-void* __loader_dlerror();
+char* dlerror(void) { return 0; }
 
-__attribute__((__weak__, visibility("default")))
-void* __loader_dlsym(void* handle, const char* symbol, const void* caller_addr);
+void* dlsym(void* handle __unused, const char* symbol __unused) { return 0; }
 
-__attribute__((__weak__, visibility("default")))
-void* __loader_dlvsym(void* handle,
-                      const char* symbol,
-                      const char* version,
-                      const void* caller_addr);
-
-__attribute__((__weak__, visibility("default")))
-int __loader_dladdr(const void* addr, Dl_info* info);
-
-__attribute__((__weak__, visibility("default")))
-int __loader_dlclose(void* handle);
-
-#if defined(__arm__)
-__attribute__((__weak__, visibility("default")))
-_Unwind_Ptr __loader_dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount);
-#endif
-
-__attribute__((__weak__, visibility("default")))
-int __loader_dl_iterate_phdr(int (*cb)(struct dl_phdr_info* info, size_t size, void* data),
-                             void* data);
-
-__attribute__((__weak__, visibility("default")))
-void __loader_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size);
-
-__attribute__((__weak__, visibility("default")))
-void __loader_android_update_LD_LIBRARY_PATH(const char* ld_library_path);
-
-__attribute__((__weak__, visibility("default")))
-void* __loader_android_dlopen_ext(const char* filename,
-                                  int flag,
-                                  const android_dlextinfo* extinfo,
-                                  const void* caller_addr);
-
-__attribute__((__weak__, visibility("default")))
-void __loader_android_set_application_target_sdk_version(uint32_t target);
-
-__attribute__((__weak__, visibility("default")))
-uint32_t __loader_android_get_application_target_sdk_version();
-
-__attribute__((__weak__, visibility("default")))
-bool __loader_android_init_namespaces(const char* public_ns_sonames,
-                                      const char* anon_ns_library_path);
-
-__attribute__((__weak__, visibility("default")))
-struct android_namespace_t* __loader_android_create_namespace(
-                                const char* name,
-                                const char* ld_library_path,
-                                const char* default_library_path,
-                                uint64_t type,
-                                const char* permitted_when_isolated_path,
-                                struct android_namespace_t* parent,
-                                const void* caller_addr);
-
-// Proxy calls to bionic loader
-void* dlopen(const char* filename, int flag) {
-  const void* caller_addr = __builtin_return_address(0);
-  return __loader_dlopen(filename, flag, caller_addr);
-}
-
-char* dlerror() {
-  return __loader_dlerror();
-}
-
-void* dlsym(void* handle, const char* symbol) {
-  const void* caller_addr = __builtin_return_address(0);
-  return __loader_dlsym(handle, symbol, caller_addr);
+void* dlvsym(void* handle __unused, const char* symbol __unused, const char* version __unused) {
+  return 0;
 }
 
-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);
-}
+int dladdr(const void* addr __unused, Dl_info* info __unused) { return 0; }
 
-int dladdr(const void* addr, Dl_info* info) {
-  return __loader_dladdr(addr, info);
-}
-
-int dlclose(void* handle) {
-  return __loader_dlclose(handle);
-}
+int dlclose(void* handle __unused) { return 0; }
 
 #if defined(__arm__)
-_Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) {
-  return __loader_dl_unwind_find_exidx(pc, pcount);
-}
+_Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc __unused, int* pcount __unused) { return 0; }
 #endif
 
-int dl_iterate_phdr(int (*cb)(struct dl_phdr_info* info, size_t size, void* data), void* data) {
-  return __loader_dl_iterate_phdr(cb, data);
+int dl_iterate_phdr(int (*cb)(struct dl_phdr_info* info, size_t size, void* data) __unused,
+                    void* data __unused) {
+  return 0;
 }
 
-void android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
-  __loader_android_get_LD_LIBRARY_PATH(buffer, buffer_size);
-}
-
-void android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
-  __loader_android_update_LD_LIBRARY_PATH(ld_library_path);
-}
+void android_get_LD_LIBRARY_PATH(char* buffer __unused, size_t buffer_size __unused) { }
+void android_update_LD_LIBRARY_PATH(const char* ld_library_path __unused) { }
 
-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);
+void* android_dlopen_ext(const char* filename __unused, int flag __unused,
+                         const android_dlextinfo* extinfo __unused) {
+  return 0;
 }
 
-void android_set_application_target_sdk_version(uint32_t target) {
-  __loader_android_set_application_target_sdk_version(target);
-}
-uint32_t android_get_application_target_sdk_version() {
-  return __loader_android_get_application_target_sdk_version();
-}
+void android_set_application_target_sdk_version(uint32_t target __unused) { }
+uint32_t android_get_application_target_sdk_version() { return 0; }
 
-bool android_init_namespaces(const char* public_ns_sonames,
-                             const char* anon_ns_library_path) {
-  return __loader_android_init_namespaces(public_ns_sonames, anon_ns_library_path);
+bool android_init_namespaces(const char* public_ns_sonames __unused,
+                             const char* anon_ns_library_path __unused) {
+  return false;
 }
 
-struct android_namespace_t* android_create_namespace(const char* name,
-                                                     const char* ld_library_path,
-                                                     const char* default_library_path,
-                                                     uint64_t type,
-                                                     const char* permitted_when_isolated_path,
-                                                     struct android_namespace_t* parent) {
-  const void* caller_addr = __builtin_return_address(0);
-  return __loader_android_create_namespace(name,
-                                           ld_library_path,
-                                           default_library_path,
-                                           type,
-                                           permitted_when_isolated_path,
-                                           parent,
-                                           caller_addr);
+struct android_namespace_t* android_create_namespace(const char* name __unused,
+                                                     const char* ld_library_path __unused,
+                                                     const char* default_library_path __unused,
+                                                     uint64_t type __unused,
+                                                     const char* permitted_when_isolated_path __unused) {
+  return 0;
 }
 
 void android_dlwarning(void* obj, void (*f)(void*, const char*)) { f(obj, 0); }