Ensure same order of global group members in all NS's

During "step 1" of find_libraries, the linker finds the transitive
closure of dependencies, in BFS order. As it finds each library, it
adds the library to its primary namespace (so that, if some other
library also depends on it, find_loaded_library_by_soname can find the
library in the process of being loaded).

LD_PRELOAD libraries are automatically marked DF_1_GLOBAL, and any
DF_1_GLOBAL library is added to every linker namespace. Previously,
this secondary namespace registration happened after step 1. The result
is that across different namespaces, the order of libraries could vary.
In general, a namespace's primary members will all appear before
secondary members. This is undesirable for libsigchain.so, which we
want to have appear before any other non-preloaded library.

Instead, when an soinfo is added to its primary namespace, immediately
add it to all the other namespaces, too. This ensures that the order of
soinfo objects is the same across namespaces.

Expand the dl.exec_with_ld_config_file_with_ld_preload and
dl.exec_with_ld_config_file tests to cover the new behavior. Mark
lib1.so DF_1_GLOBAL and use a "foo" symbol to mimic the behavior of a
signal API interposed by (e.g.) libsigchain.so and a ASAN preload.

Test: bionic unit tests
Bug: http://b/143219447
Change-Id: I9fd90f6f0d14caf1aca6d414b3e9aab77deca3ff

1 files changed, 39 insertions, 6 deletions

diff --git a/tests/dl_test.cpp b/tests/dl_test.cpp
index 6adba1906..6c9bf3fb5 100644
--- a/tests/dl_test.cpp
+++ b/tests/dl_test.cpp
@@ -268,8 +268,16 @@ static bool is_debuggable_build() {
 }
 #endif
 
-// _lib1.so and _lib2.so are now searchable by having another namespace 'ns2'
+// lib1.so and lib2.so are now searchable by having another namespace 'ns2'
 // whose search paths include the 'ns2/' subdir.
+//
+// lib1.so is linked with DF_1_GLOBAL, so both it and the executable are added
+// to every namespace.
+//
+// namespace configuration ('*' indicates primary ns)
+//  - default: exe[*], lib1.so
+//  - ns2: exe, lib1.so[*], lib2.so[*]
+//
 TEST(dl, exec_with_ld_config_file) {
 #if defined(__BIONIC__)
   SKIP_WITH_HWASAN << "libclang_rt.hwasan is not found with custom ld config";
@@ -285,13 +293,28 @@ TEST(dl, exec_with_ld_config_file) {
   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");
+  eth.Run([&]() { execve(helper.c_str(), eth.GetArgs(), eth.GetEnv()); }, 0,
+          "foo lib1\n"
+          "lib1_call_funcs\n"
+          "foo lib1\n"
+          "bar lib2\n");
 #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.
+// lib3.so has same foo and bar symbols as lib2.so. lib3.so is LD_PRELOADed.
+// This test ensures that LD_PRELOADed libs are available to all namespaces.
+//
+// namespace configuration ('*' indicates primary ns)
+//  - default: exe[*], lib3.so[*], lib1.so
+//  - ns2: exe, lib3.so, lib1.so[*], lib2.so[*]
+//
+// Ensure that, in both namespaces, a call to foo calls the lib3.so symbol,
+// which then calls the lib1.so symbol using RTLD_NEXT. Ensure that RTLD_NEXT
+// finds nothing when called from lib1.so.
+//
+// For the bar symbol, lib3.so's primary namespace is the default namespace, but
+// lib2.so is not in the default namespace, so using RTLD_NEXT from lib3.so
+// doesn't find the symbol in lib2.so.
 TEST(dl, exec_with_ld_config_file_with_ld_preload) {
 #if defined(__BIONIC__)
   SKIP_WITH_HWASAN << "libclang_rt.hwasan is not found with custom ld config";
@@ -308,7 +331,17 @@ TEST(dl, exec_with_ld_config_file_with_ld_preload) {
   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");
+  eth.Run([&]() { execve(helper.c_str(), eth.GetArgs(), eth.GetEnv()); }, 0,
+          "foo lib3\n"
+          "foo lib1\n"
+          "lib1_call_funcs\n"
+          "foo lib3\n"
+          "foo lib1\n"
+          "bar lib3\n"
+          "lib3_call_funcs\n"
+          "foo lib3\n"
+          "foo lib1\n"
+          "bar lib3\n");
 #endif
 }