Using the gdb server to debug harvey processes

Introduction

You can debug processes running harvey using gdb, remotely. This is not working well yet, and we need help. Hint, hint.

gdbserver currently defaults to port 1666. If you are running our QEMU script they forward that port. If you are running qemu on your own, be sure to forward that port. See the scripts to see how that's done.

As an example, let's run the command dd and attach to it.

1. On the guest (harvey):

   1. Open 2 rio windows
   2. In one, run dd
   3. In the other run ps to get the process ID...
   4. Next, run gdbserver -p <processid> You can optionally add '-d' and gdbserver will print debugging messages.

2. On the host:

   1. Run gdb amd64/bin/dd
   2. Ensure the architecture is set to i386:x86-64. You can check with show architecture and set with set architecture i386:x86-64. (You probably don't need this step but at least show it to make sure).
   3. In gdb, enter target remote localhost:1666
   4. At this point you should have connected. To continue executing, enter c.

3. On the guest again:

   1. Hit return in the dd window. This allows the gdbserver to get control, since dd will run and do a system call.
   2. Now you can debug. Interact with the application, e.g. in the window running dd, hit return. Add breakpoints from the gdb command line, etc.

Gdbserver Development

gdbserver is still under development. It's missing lots of features, and has bugs. It's very useful to be able to see the packets going between the gdb client and gdbserver. You can see this in two ways.

• Either turn on debug info in gdb, which will show all packets, by entering set debug remote 1 before target remote....
• And/or enable gdbserver logging by creating the file sys/log/gdbserver.