GDB remote debugging: make GDB wait for gdbserver to be started

Question

The normal way I know to remote debug is to start gdbserver on a target and then remotely connect from gdb (using target remote).

But, is it possible that GDB be made to wait on a port until gdbserver comes up on that port?

Thanks in advance.

Answer 1

You can do this with a bit of python code. gdb.execute("command ...") will raise a python exception if the command gets an error. So we can have python run the target remote host:port command repeatedly, for as long as it gets a timeout error (which should resemble host:port: Connection timed out.).

Put the following into a file and use gdb's source command to read it in. It will define a new subcommand target waitremote host:port .

define target waitremote
python connectwithwait("$arg0")
end

document target waitremote
Use a remote gdbserver, waiting until it's connected.
end

python
def connectwithwait(hostandport):
  while 1:
    try:
      gdb.execute("target remote " + hostandport)
      return True
    except gdb.error, e:
      if "Connection timed out" in str(e):
        print "timed out, retrying"
        continue
      else:
        print "Cannot connect: " + str(e)
        return e
end

Answer 2

There's nothing built in, but there are a couple ways I think you can make it work.

One is to run gdbserver on demand on the target, say from inetd or equivalent.

Another is to run a proxy on the target, and have the proxy accept a connection but otherwise do nothing until gdbserver is ready. I'm not sure offhand if this would run into timeout problems on the gdb side, though.