Fix LLGS to enable read type watchpoints

[omjavaid]

Summary

LLGS was forcing lldb to use only write or read+write type watchpoints.

This patch fixes this behavior to enable read, write and read+write types of watchpoints.

Note: On x86_64 read watchpoints still dont work and they are disabled by NativeRegisterContextLinux_x86. We ll need to revisit this later because all three types of watchpoints should also work on x86.

[tberghammer]

LGTM

source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp

2230

(nit): Please initialize to 0

[clayborg]

Init "watch_flags" to zero and this is good to go.

source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp

2230

Yes, init to zero please.

source/Plugins/Process/Linux/NativeRegisterContextLinux_x86_64.cpp

 
 Error
 NativeRegisterContextLinux_x86_64::SetHardwareWatchpointWithIndex(
         lldb::addr_t addr, size_t size, uint32_t watch_flags, uint32_t wp_index) {
 
     if (wp_index >= NumSupportedHardwareWatchpoints())
         return Error ("Watchpoint index out of range");
 
+    if (watch_flags == 0x2)
+        return Error ("Read watchpoints currently unsupported on x86_64 architecture");
+
     if (watch_flags != 0x1 && watch_flags != 0x3)
         return Error ("Invalid read/write bits for watchpoint");
 
     if (size != 1 && size != 2 && size != 4 && size != 8)
         return Error ("Invalid size for watchpoint");
 
     bool is_vacant;
     Error error = IsWatchpointVacant (wp_index, is_vacant);

source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp

GDBRemoteCommunicationServerLLGS::Handle_Z (StringExtractorGDBRemote &packet)
 
     // Parse out software or hardware breakpoint or watchpoint requested.
     packet.SetFilePos (strlen("Z"));
     if (packet.GetBytesLeft() < 1)
         return SendIllFormedResponse(packet, "Too short Z packet, missing software/hardware specifier");
 
     bool want_breakpoint = true;
     bool want_hardware = false;
+    uint32_t watch_flags;
 
     const GDBStoppointType stoppoint_type =
         GDBStoppointType(packet.GetS32 (eStoppointInvalid));
     switch (stoppoint_type)
     {
         case eBreakpointSoftware:
             want_hardware = false; want_breakpoint = true;  break;
         case eBreakpointHardware:
             want_hardware = true;  want_breakpoint = true;  break;
         case eWatchpointWrite:
+            watch_flags = 1;
             want_hardware = true;  want_breakpoint = false; break;
         case eWatchpointRead:
+            watch_flags = 2;
             want_hardware = true;  want_breakpoint = false; break;
         case eWatchpointReadWrite:
+            watch_flags = 3;
             want_hardware = true;  want_breakpoint = false; break;
         case eStoppointInvalid:
             return SendIllFormedResponse(packet, "Z packet had invalid software/hardware specifier");
 
     }
 
     if ((packet.GetBytesLeft() < 1) || packet.GetChar () != ',')
         return SendIllFormedResponse(packet, "Malformed Z packet, expecting comma after stoppoint type");
if (want_breakpoint)
                     " failed to set breakpoint: %s",
                     __FUNCTION__,
                     m_debugged_process_sp->GetID (),
                     error.AsCString ());
         return SendErrorResponse (0x09);
     }
     else
     {
-        uint32_t watch_flags =
-            stoppoint_type == eWatchpointWrite
-            ? 0x1  // Write
-            : 0x3; // ReadWrite
-
         // Try to set the watchpoint.
         const Error error = m_debugged_process_sp->SetWatchpoint (
                 addr, size, watch_flags, want_hardware);
         if (error.Success ())
             return SendOKResponse ();
         Log *log (GetLogIfAnyCategoriesSet(LIBLLDB_LOG_WATCHPOINTS));
         if (log)
             log->Printf ("GDBRemoteCommunicationServerLLGS::%s pid %" PRIu64