[lldb] [Process/FreeBSDRemote] Implement thread GetName()

[mgorny]

Summary

Implement NativeThreadFreeBSD::GetName(). This is based
on the equivalent code in the legacy FreeBSD plugin, except it is
modernized a bit to use llvm::Optional and std::vector for data storage.

[krytarowski]

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

151–187

It is probably fine, but I would use:

1. PT_GETNUMLWPS
2. PT_GETLWPLIST with optional caching
3. Read pl_tdname from ptrace_lwpinfo

164

Isn't this call always synchronous and all the threads are stopped?

[labath]

I am not sure that the caching is really needed, but this seems ok to me. I'm assuming that this fixes TestGdbRemoteThreadName.py...

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

164

I would certainly expect so

171

just m_state, it's cleaner

[mgorny]

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

151–187

PT_GETLWPLIST returns only LWP IDs. struct ptrace_lwpinfo is used by PT_LWPINFO which returns info about the thread causing the process to stop, not an arbitrary thread.

[mgorny]

Removed overallocation and put plain m_state into log message.

lldb/source/Plugins/Process/FreeBSDRemote/NativeThreadFreeBSD.h

private:
   // Member Variables
   lldb::StateType m_state;
   ThreadStopInfo m_stop_info;
   std::unique_ptr<NativeRegisterContextFreeBSD> m_reg_context_up;
   std::string m_stop_description;
   using WatchpointIndexMap = std::map<lldb::addr_t, uint32_t>;
   WatchpointIndexMap m_watchpoint_index_map;
   WatchpointIndexMap m_hw_break_index_map;
+  llvm::Optional<std::string> m_thread_name;
 };
 
 typedef std::shared_ptr<NativeThreadFreeBSD> NativeThreadFreeBSDSP;
 } // namespace process_freebsd
 } // namespace lldb_private
 
 #endif // #ifndef liblldb_NativeThreadFreeBSD_H_

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

 #include "lldb/Utility/RegisterValue.h"
 #include "lldb/Utility/State.h"
 #include "llvm/Support/Errno.h"
 
 // clang-format off
 #include <sys/types.h>
 #include <sys/ptrace.h>
 #include <sys/sysctl.h>
+#include <sys/user.h>
 // clang-format on
 
 #include <sstream>
+#include <vector>
 
 using namespace lldb;
 using namespace lldb_private;
 using namespace lldb_private::process_freebsd;
 
 NativeThreadFreeBSD::NativeThreadFreeBSD(NativeProcessFreeBSD &process,
                                          lldb::tid_t tid)
     : NativeThreadProtocol(process, tid), m_state(StateType::eStateInvalid),
void NativeThreadFreeBSD::SetRunning() {
   m_stop_info.reason = StopReason::eStopReasonNone;
 }
 
 void NativeThreadFreeBSD::SetStepping() {
   m_state = StateType::eStateStepping;
   m_stop_info.reason = StopReason::eStopReasonNone;
 }
 
-std::string NativeThreadFreeBSD::GetName() { return ""; }
+std::string NativeThreadFreeBSD::GetName() {
+  if (!m_thread_name) {
+    Log *log(ProcessPOSIXLog::GetLogIfAllCategoriesSet(POSIX_LOG_THREAD));
+
+    std::vector<struct kinfo_proc> kp;
+    int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PID | KERN_PROC_INC_THREAD,
+                  static_cast<int>(GetProcess().GetID())};
+
+    while (1) {
+      size_t len = kp.size() * sizeof(struct kinfo_proc);
+      void *ptr = len == 0 ? nullptr : kp.data();
+      int error = ::sysctl(mib, 4, ptr, &len, nullptr, 0);
+      if (ptr == nullptr || (error != 0 && errno == ENOMEM)) {
+        kp.resize(len / sizeof(struct kinfo_proc));
+        continue;
+      }
+      if (error != 0) {
+        len = 0;
+        LLDB_LOG(log, "tid = {0} in state {1} failed to get thread name: {2}", GetID(),
+                 m_state, strerror(errno));
+      }
+      kp.resize(len / sizeof(struct kinfo_proc));
+      break;
+    }
+
+    // empty == unknown
+    m_thread_name = std::string();
+    for (auto& procinfo : kp) {
+      if (procinfo.ki_tid == (lwpid_t)GetID()) {
+        m_thread_name = procinfo.ki_tdname;
+        break;
+      }
+    }
+  }
+
+  return m_thread_name.getValue();
+}
 
 lldb::StateType NativeThreadFreeBSD::GetState() { return m_state; }
 
 bool NativeThreadFreeBSD::GetStopReason(ThreadStopInfo &stop_info,
                                         std::string &description) {
   Log *log(ProcessPOSIXLog::GetLogIfAllCategoriesSet(POSIX_LOG_THREAD));
   description.clear();