lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [day] [month] [year] [list]
Date:	Mon, 31 May 2010 00:51:50 +0300
From:	Paul Fisher <>
Subject: kgdb debugger proxy question - using the same serial port for both 
	serial console and kgdb


I'm trying to get kgdb setup working. I have two PCs but unfortunately there is
only one serial port in each of those. So far everything worked great, but
several days ago one of the monitors was taken away from my desk, and the second
machine is now headless.

So now I need some kind of splitter to split the traffic between the gdb and
the minicom (serial console). Since Jason wrote in the kgdb documentation:

> 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 our primary console as well as using it to perform kernel debugging.

I assume that such splitter should exist. Moreover, Jason mentions that
'debugger proxy' several times throughout the docs. So I searched the archives
but found only Ingo's mail from 2008 where he asked for a link to such a proxy
but without any response.

After a deeper research I 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 system call level
(read, write, select syscalls) 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 line because
of the way this script is written. I assume that detach is not the only command
that does that...

So does a reliable splitter actually exist? If it doesn't, could you
please share
your experience - briefly describe your kgdb setup? I bet that someone already
had this problem...

Much appreciated,

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists