Hi Paul, On Sat, 2010-05-29 at 00:52 +0300, Paul Fisher wrote: > Hello list, > > I'm trying to get kgdb setup working. I have two PCs but unfortunately only one > serial port in each of those. So far everything worked great, but several days > ago the monitor of the second machine was taken away from my desk, and now one > of the machines is headless. > > As I already said, I got only one serial port, and now I use it to provide a > serial console. Obviously, kgdb now doesn't work.. I've read somewhere that it > is practically impossible to use one serial link for both a serial console and > kgdb, but I think that's wrong, because kgdb documentation ( > http://kernel.org/pub/linux/kernel/people/jwessel/kdb/ch03.html#kgdboc) says: > > For kgdb/gdb, kgdboc is designed to work with a single serial port. It is > intended to cover the circumstance where you want to use a serial console as > your primary console as well as using it to perform kernel debugging. It is also > possible to use kgdb on a serial port which is not designated as a system > console. > > So that should be possible. I googled a bit and found a kdmx (kgdb demux) > script, and in fact it works, but in a very limited and weird way. For one, you > can't send a BRK (break) from minicom (Ctrl-A f) because it operates on the > library level (read, write, select system calls) and the BRK is sent by means of > ioctl(). Sending a break is essential, because that's the way to stop kernel > execution and break into the debugger. Also detach gdb command freezes the whole > serial communication because of the way this script is written. > > So, is there any reliable way to do this? Any help, hint, etc is appreciated. > > Thank you, > > --paul > > -- > To unsubscribe from this list: send an email with > "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx > Please read the FAQ at http://kernelnewbies.org/FAQ > I ploughed and struggled with similar issues some time ago, albeit on an embedded target. I certainly never got multiplexing going, I don't know what black art is required there..... but I do plan to revisit all this again in near future, as it's essential when I want to start (remote) kernel module debugging again. Perhaps this tip might help though (?) - If you have problems breaking into the debugger, you can type ASCII : "echo g > /proc/sysrq-trigger" HTH B rgds Kris -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
