Report actual tids from FreeBSD core files

[emaste]

Summary

As noted in the thread "Question (bug?) about thread tids when lldb loads a core dump." on lldb-dev, lldb is not showing tids for core files.

For FreeBSD the tid is (somewhat unintuitively) found in the pr_pid field of the NT_PRSTATUS note. Collect it when parsing the note and store it in the thread data. I'm not sure how to obtain it on Linux. I'll update the patch if/when I find out -- this patch isn't committable as-is until then.

[emaste]

Keep existing behaviour for Linux until updated to fetch the tid from the core file: assign 0, 1, 2, ... for tids

[amccarth]

Looks good.

source/Plugins/Process/elf-core/ProcessElfCore.cpp

 {
     const uint32_t num_threads = GetNumThreadContexts ();
     if (!m_thread_data_valid)
         return false;
 
     for (lldb::tid_t tid = 0; tid < num_threads; ++tid)
     {
         const ThreadData &td = m_thread_data[tid];
-        lldb::ThreadSP thread_sp(new ThreadElfCore (*this, tid, td));
+        lldb::ThreadSP thread_sp(new ThreadElfCore (*this, td));
         new_thread_list.AddThread (thread_sp);
     }
     return new_thread_list.GetSize(false) > 0;
 }
 
 void
 ProcessElfCore::RefreshStateAfterStop ()
 {
ParseFreeBSDPrStatus(ThreadData &thread_data, DataExtractor &data,
 
     // Skip padding, pr_statussz, pr_gregsetsz, pr_fpregsetsz, pr_osreldate
     if (lp64)
         offset += 32;
     else
         offset += 16;
 
     thread_data.signo = data.GetU32(&offset); // pr_cursig
-    offset += 4;        // pr_pid
+    thread_data.tid = data.GetU32(&offset); // pr_pid
     if (lp64)
         offset += 4;
 
     size_t len = data.GetByteSize() - offset;
     thread_data.gpregset = DataExtractor(data, offset, len);
 }
 
 static void
while (offset < segment_header->p_filesz)
             {
                 case NT_PRSTATUS:
                     have_prstatus = true;
                     prstatus.Parse(note_data, arch);
                     thread_data->signo = prstatus.pr_cursig;
                     header_size = ELFLinuxPrStatus::GetSize(arch);
                     len = note_data.GetByteSize() - header_size;
                     thread_data->gpregset = DataExtractor(note_data, header_size, len);
+                    // FIXME: Obtain actual tid on Linux
+                    thread_data->tid = m_thread_data.size();
                     break;
                 case NT_FPREGSET:
                     thread_data->fpregset = note_data;
                     break;
                 case NT_PRPSINFO:
                     have_prpsinfo = true;
                     prpsinfo.Parse(note_data, arch);
                     thread_data->name = prpsinfo.pr_fname;

source/Plugins/Process/elf-core/ThreadElfCore.h

 
 };
 
 struct ThreadData
 {
     lldb_private::DataExtractor gpregset;
     lldb_private::DataExtractor fpregset;
     lldb_private::DataExtractor vregset;
+    lldb::tid_t tid;
     int signo;
     std::string name;
 };
 
 class ThreadElfCore : public lldb_private::Thread
 {
 public:
-    ThreadElfCore (lldb_private::Process &process, lldb::tid_t tid,
-                   const ThreadData &td);
+    ThreadElfCore (lldb_private::Process &process, const ThreadData &td);
 
     virtual
     ~ThreadElfCore ();
 
     virtual void
     RefreshStateAfterStop();
 
     virtual lldb::RegisterContextSP

source/Plugins/Process/elf-core/ThreadElfCore.cpp

 #include "RegisterContextPOSIXCore_x86_64.h"
 
 using namespace lldb;
 using namespace lldb_private;
 
 //----------------------------------------------------------------------
 // Construct a Thread object with given data
 //----------------------------------------------------------------------
-ThreadElfCore::ThreadElfCore (Process &process, tid_t tid,
-                              const ThreadData &td) :
-    Thread(process, tid),
+ThreadElfCore::ThreadElfCore (Process &process, const ThreadData &td) :
+    Thread(process, td.tid),
     m_thread_name(td.name),
     m_thread_reg_ctx_sp (),
     m_signo(td.signo),
     m_gpregset_data(td.gpregset),
     m_fpregset_data(td.fpregset),
     m_vregset_data(td.vregset)
 {
 }