Problem while debugging with gdbserver in IDA Pro

Question

I'm new to debugging with IDA Pro and I ran into the problem that my breakpoint is not hit while attempting to debug with gdbserver. The program is written by myself and it is simple to debug with gdb. Can someone please help me regarding debugging with IDA? Here are the steps I perform for debugging:

1. Start gdbserver version 7.7 configured as "x86_64-linux-gnu" in a terminal on my localhost like so:

   $ gdbserver --multi localhost:1234
   Listening on port 1234
   

2. Open a new database in IDA Pro version 6.6, set a breakpoint in the code, chose the "Remote GDB Debugger" and start a new process. The IDA output window shows the following message:

   FFFFFFFFFFFFFFFF: process /home/benny/3-challenge has started (pid=0)
   FFFFD8F8: got SIGTRAP signal (Trace/breakpoint trap) (exc.code 5, tid 27171)
   

3. A Warning pops up in IDA giving me the following message:

   FFFFD8F8: got SIGTRAP signal (Trace/breakpoint trap) (exc.code 5, tid 27171)
   

4. The terminal where the gdbserver is running shows the following message:

   Remote debugging from host 127.0.0.1
   Process /home/benny/3-challenge created; pid = 27171
   

I guess the SIGTRAP may already be a problem, however, I don't understand why I get it. What am I doing wrong?

Anyway going further by ignoring the warning:

5. The IDA Debug View shows the RIP at memory position FFFFD8F8 which is in an unexplored region of the binary: MEMORY:FFFFD8F8 db ?;

6. Press F9 in IDA pops-up an "Exception Handling" dialog, which looks like this

7. Click "Yes (pass to app)", which terminates the execution of the debugging session and the IDA output window prints

   Debugger: process has exited (exit code 5)
   

While the output on the terminal running gdbserver prints

Child terminated with signal = 0x5 (SIGTRAP)
readchar: Got EOF
Remote side has terminated connection.  GDBserver will reopen the connection.
Listening on port 1234

Please let me know if you need more info.

UPDATE: I got fed up with GDB server and am now using Intel PIN for debugging, which works like a charm with IDA Pro.

Answer 1

The SIGTRAP is generally raised by a debug break exception (int 3).

When IDA receives it, it's asking you whether to pass it to the program (unhandled). If you do, and you do not have a signal handler installed for SIGTRAP, the program will die with a SIGTRAP error, as you see.

You want IDA to discard the exception, and continue execution (if you want to continue) or suspend to investigate state in IDA.