linker: the global group is added to all built-in namespaces

With ld.config.txt, we now have multiple built-in namespaces other than
the default namespace. Libs (and their dependents) listed in LD_PRELOAD
must be visible to those additional namespaces as well.

This also adds a debugging only feature: path to the linker config file
can be customized via LD_CONFIG_FILE environment variable. This works
only for debuggable builds.

Bug: 38114603
Bug: 62815515
Test: 1. ./external/compiler-rt/lib/asan/scripts/asan_device_setup --lib
prebuilts/clang/host/linux-x86/clang-stable/lib64/clang/5.0/lib/linux
2. enable talkback shortcut
3. in the home screen, hold vol-up/down together
4. device does not reboots and talkback shortcut is toggled
Test: bionic-unit-tests and linker-unit-tests successful

Change-Id: I9a03591053f4a9caea82f0dcb23e7a3d324bb9bd
diff --git a/tests/dl_test.cpp b/tests/dl_test.cpp
index aa8bd57..857640a 100644
--- a/tests/dl_test.cpp
+++ b/tests/dl_test.cpp
@@ -23,6 +23,8 @@
 #include <stdint.h>
 
 #include <string>
+#include <iostream>
+#include <fstream>
 
 #include "gtest_globals.h"
 #include "utils.h"
@@ -109,4 +111,131 @@
 #endif
 }
 
-// TODO: Add tests for LD_PRELOADs
+
+TEST(dl, exec_without_ld_preload) {
+#if defined(__BIONIC__)
+  std::string helper = get_testlib_root() +
+      "/ld_preload_test_helper/ld_preload_test_helper";
+  chmod(helper.c_str(), 0755);
+  ExecTestHelper eth;
+  eth.SetArgs({ helper.c_str(), nullptr });
+  eth.Run([&]() { execve(helper.c_str(), eth.GetArgs(), eth.GetEnv()); }, 0, "12345");
+#endif
+}
+
+TEST(dl, exec_with_ld_preload) {
+#if defined(__BIONIC__)
+  std::string helper = get_testlib_root() +
+      "/ld_preload_test_helper/ld_preload_test_helper";
+  std::string env = std::string("LD_PRELOAD=") + get_testlib_root() + "/ld_preload_test_helper_lib2.so";
+  chmod(helper.c_str(), 0755);
+  ExecTestHelper eth;
+  eth.SetArgs({ helper.c_str(), nullptr });
+  eth.SetEnv({ env.c_str(), nullptr });
+  // ld_preload_test_helper calls get_value_from_lib() and returns the value.
+  // The symbol is defined by two libs: ld_preload_test_helper_lib.so and
+  // ld_preloaded_lib.so. The former is DT_NEEDED and the latter is LD_PRELOADED
+  // via this execution. The main executable is linked to the LD_PRELOADED lib
+  // and the value given from the lib is returned.
+  eth.Run([&]() { execve(helper.c_str(), eth.GetArgs(), eth.GetEnv()); }, 0, "54321");
+#endif
+}
+
+
+// ld_config_test_helper must fail because it is depending on a lib which is not
+// in the search path
+//
+// Call sequence is...
+// _helper -- (get_value_from_lib()) -->
+//     _lib1.so -- (get_value_from_another_lib()) -->
+//       _lib2.so (returns 12345)
+// The two libs are in ns2/ subdir.
+TEST(dl, exec_without_ld_config_file) {
+#if defined(__BIONIC__)
+  std::string error_message = "CANNOT LINK EXECUTABLE \"" + get_testlib_root() + "/ld_config_test_helper/ld_config_test_helper\": library \"ld_config_test_helper_lib1.so\" not found\n";
+  std::string helper = get_testlib_root() +
+      "/ld_config_test_helper/ld_config_test_helper";
+  chmod(helper.c_str(), 0755);
+  ExecTestHelper eth;
+  eth.SetArgs({ helper.c_str(), nullptr });
+  eth.Run([&]() { execve(helper.c_str(), eth.GetArgs(), eth.GetEnv()); }, -6, error_message.c_str());
+#endif
+}
+
+#if defined(__BIONIC__)
+static void create_ld_config_file(std::string& config_file) {
+  std::ofstream fout(config_file.c_str(), std::ios::out);
+  fout << "dir.test = " << get_testlib_root() << "/ld_config_test_helper/" << std::endl
+       << "[test]" << std::endl
+       << "additional.namespaces = ns2" << std::endl
+       << "namespace.default.search.paths = " << get_testlib_root() << std::endl
+       << "namespace.default.links = ns2" << std::endl
+       << "namespace.default.link.ns2.shared_libs = libc.so:libm.so:libdl.so:ld_config_test_helper_lib1.so" << std::endl
+       << "namespace.ns2.search.paths = /system/${LIB}:" << get_testlib_root() << "/ns2" << std::endl;
+  fout.close();
+}
+#endif
+
+#ifdef USE_LD_CONFIG_FILE
+
+// _lib1.so and _lib2.so are now searchable by having another namespace 'ns2'
+// whose search paths include the 'ns2/' subdir.
+TEST(dl, exec_with_ld_config_file) {
+#if defined(__BIONIC__)
+  std::string helper = get_testlib_root() +
+      "/ld_config_test_helper/ld_config_test_helper";
+  std::string config_file = get_testlib_root() + "/ld.config.txt";
+  create_ld_config_file(config_file);
+  std::string env = std::string("LD_CONFIG_FILE=") + config_file;
+  chmod(helper.c_str(), 0755);
+  ExecTestHelper eth;
+  eth.SetArgs({ helper.c_str(), nullptr });
+  eth.SetEnv({ env.c_str(), nullptr });
+  eth.Run([&]() { execve(helper.c_str(), eth.GetArgs(), eth.GetEnv()); }, 0, "12345");
+#endif
+}
+
+// _lib3.so has same symbol as lib2.so but returns 54321. _lib3.so is
+// LD_PRELOADed. This test is to ensure LD_PRELOADed libs are available to
+// additional namespaces other than the default namespace.
+TEST(dl, exec_with_ld_config_file_with_ld_preload) {
+#if defined(__BIONIC__)
+  std::string helper = get_testlib_root() +
+      "/ld_config_test_helper/ld_config_test_helper";
+  std::string config_file = get_testlib_root() + "/ld.config.txt";
+  create_ld_config_file(config_file);
+  std::string env = std::string("LD_CONFIG_FILE=") + config_file;
+  std::string env2 = std::string("LD_PRELOAD=") + get_testlib_root() + "/ld_config_test_helper_lib3.so";
+  chmod(helper.c_str(), 0755);
+  ExecTestHelper eth;
+  eth.SetArgs({ helper.c_str(), nullptr });
+  eth.SetEnv({ env.c_str(), env2.c_str(), nullptr });
+  eth.Run([&]() { execve(helper.c_str(), eth.GetArgs(), eth.GetEnv()); }, 0, "54321");
+#endif
+}
+
+#endif // USE_LD_CONFIG_FILE
+
+// ensures that LD_CONFIG_FILE env var does not work for production builds.
+// The test input is the same as exec_with_ld_config_file, but it must fail in
+// this case.
+TEST(dl, disable_ld_config_file) {
+#if defined(__BIONIC__)
+  if (getuid() == 0) {
+    // when executed from the shell (e.g. not as part of CTS), skip the test.
+    // This test is only for CTS.
+    return;
+  }
+  std::string error_message = "CANNOT LINK EXECUTABLE \"" + get_testlib_root() + "/ld_config_test_helper/ld_config_test_helper\": library \"ld_config_test_helper_lib1.so\" not found\n";
+  std::string helper = get_testlib_root() +
+      "/ld_config_test_helper/ld_config_test_helper";
+  std::string config_file = get_testlib_root() + "/ld.config.txt";
+  create_ld_config_file(config_file);
+  std::string env = std::string("LD_CONFIG_FILE=") + config_file;
+  chmod(helper.c_str(), 0755);
+  ExecTestHelper eth;
+  eth.SetArgs({ helper.c_str(), nullptr });
+  eth.SetEnv({ env.c_str(), nullptr });
+  eth.Run([&]() { execve(helper.c_str(), eth.GetArgs(), eth.GetEnv()); }, -6, error_message.c_str());
+#endif
+}