Fix check for thread unwind.

If a process requires executing fallback unwinder and the thread
crashing is not the main thread, the wrong unwinder is used.
Fix this case, and add a new unit test that causes an abort in
the non main thread.

Bug: 233721755

Test: New unit test passes with fix and fails without.
Test: Ran debuggerd on swcodec process and it still dumps all threads.
Change-Id: I70fffc5d680256ce867e7a1d427593b584259160

debuggerd/debuggerd_test.cpp

@@ -1463,6 +1463,29 @@ TEST_F(CrasherTest, seccomp_tombstone) {
   ASSERT_BACKTRACE_FRAME(result, "bar");
 }
 
+TEST_F(CrasherTest, seccomp_tombstone_thread_abort) {
+  int intercept_result;
+  unique_fd output_fd;
+
+  static const auto dump_type = kDebuggerdTombstone;
+  StartProcess(
+      []() {
+        std::thread abort_thread([] { abort(); });
+        abort_thread.join();
+      },
+      &seccomp_fork);
+
+  StartIntercept(&output_fd, dump_type);
+  FinishCrasher();
+  AssertDeath(SIGABRT);
+  FinishIntercept(&intercept_result);
+  ASSERT_EQ(1, intercept_result) << "tombstoned reported failure";
+
+  std::string result;
+  ConsumeFd(std::move(output_fd), &result);
+  ASSERT_BACKTRACE_FRAME(result, "abort");
+}
+
 TEST_F(CrasherTest, seccomp_backtrace) {
   int intercept_result;
   unique_fd output_fd;

debuggerd/libdebuggerd/tombstone_proto.cpp

@@ -455,7 +455,7 @@ static void dump_thread(Tombstone* tombstone, unwindstack::Unwinder* unwinder,
   thread.set_tagged_addr_ctrl(thread_info.tagged_addr_ctrl);
   thread.set_pac_enabled_keys(thread_info.pac_enabled_keys);
 
-  if (thread_info.pid == getpid() && thread_info.pid != thread_info.tid) {
+  if (thread_info.registers == nullptr) {
     // Fallback path for non-main thread, doing unwind from running process.
     unwindstack::ThreadUnwinder thread_unwinder(kMaxFrames, unwinder->GetMaps());
     if (!thread_unwinder.Init()) {