[lldb] [Process/FreeBSDRemote] Fix handling user-generated SIGTRAP

Update the SIGTRAP handler to account for the possibility of SIGTRAP
being generated by the user, i.e. not having any specific debugging
event associated with it, as well as receiving unknown SIGTRAPs.  These
instances of SIGTRAP are passed to the regular signal handler.

Differential Revision: https://reviews.llvm.org/D91007

Author: mgorny

lldb/source/Plugins/Process/FreeBSDRemote/NativeProcessFreeBSD.cpp

@@ -192,7 +192,8 @@ void NativeProcessFreeBSD::MonitorSIGTRAP(lldb::pid_t pid) {
   }
   assert(info.pl_event == PL_EVENT_SIGNAL);
 
-  LLDB_LOG(log, "got SIGTRAP, pid = {0}, lwpid = {1}", pid, info.pl_lwpid);
+  LLDB_LOG(log, "got SIGTRAP, pid = {0}, lwpid = {1}, flags = {2:x}", pid,
+           info.pl_lwpid, info.pl_flags);
   NativeThreadFreeBSD *thread = nullptr;
 
   if (info.pl_flags & (PL_FLAG_BORN | PL_FLAG_EXITED)) {
@@ -240,6 +241,8 @@ void NativeProcessFreeBSD::MonitorSIGTRAP(lldb::pid_t pid) {
 
   if (info.pl_flags & PL_FLAG_SI) {
     assert(info.pl_siginfo.si_signo == SIGTRAP);
+    LLDB_LOG(log, "SIGTRAP siginfo: si_code = {0}, pid = {1}",
+             info.pl_siginfo.si_code, info.pl_siginfo.si_pid);
 
     switch (info.pl_siginfo.si_code) {
     case TRAP_BRKPT:
@@ -248,7 +251,7 @@ void NativeProcessFreeBSD::MonitorSIGTRAP(lldb::pid_t pid) {
         FixupBreakpointPCAsNeeded(*thread);
       }
       SetState(StateType::eStateStopped, true);
-      break;
+      return;
     case TRAP_TRACE:
       if (thread) {
         auto &regctx = static_cast<NativeRegisterContextFreeBSD &>(
@@ -272,9 +275,14 @@ void NativeProcessFreeBSD::MonitorSIGTRAP(lldb::pid_t pid) {
       }
 
       SetState(StateType::eStateStopped, true);
-      break;
+      return;
     }
   }
+
+  // Either user-generated SIGTRAP or an unknown event that would
+  // otherwise leave the debugger hanging.
+  LLDB_LOG(log, "unknown SIGTRAP, passing to generic handler");
+  MonitorSignal(pid, SIGTRAP);
 }
 
 void NativeProcessFreeBSD::MonitorSignal(lldb::pid_t pid, int signal) {

lldb/test/API/functionalities/signal/raise/TestRaise.py

@@ -30,7 +30,6 @@ def test_sigsigrtmin(self):
         self.signal_test('SIGRTMIN', True)
 
     @skipIfNetBSD  # Hangs on NetBSD
-    @skipIfFreeBSD  # hangs
     def test_sigtrap(self):
         self.build()
         self.signal_test('SIGTRAP', True)