Re: [Xen-devel] Debugging the hypervisor

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

I'm rather confused about what you're trying to achieve. A good first step
would be to get Xen console output over the serial line. You achieve this by
specifying com1=115200 (for example) and console=com1,vga on Xen's command
line. If you can get that working then you can move onto the gdbstub. This
requires:
 1. that you add e.g. 'com1=115200 gdb=com1' to Xen's command line
 2. you connect to the gdbstub with gdb, not with minicom!
 3. Xen must crash for the gdbstub to be entered. The stub provides only
post-mortem debugging analysis support

 -- Keir

On 21/5/08 16:10, "Matthew Donovan" <matthew@xxxxxxxxxxxxxx> wrote:

> I am trying to debug the Xen hypervisor from a second computer over the
> serial port, but nothing seems to work.  Using mercurial, I got
> xen-3.2-testing.hg.  I followed the steps in crashdb.txt in the docs/misc/
> folder:
> set debug=y in Config.mk, crash_debug=y in xen/Rules.mk
> 
> I also added -fno-omit-frame-pointer to these file as well.
> 
> I compiled with no errors and booted with minicom connected to the
> workstation via com1 but when I do Ctrl-A three times to connect, nothing
> happens.  The debuggee boots find and gives me the login screen as normal.
> Is there a special time to hit the Ctrl-A in minicom?  Should the kernel
> wait for a connection from gdb?
> 
> I've tried various combinations of using nsplitd and a serial-split patch I
> found mentioned on mailing lists and setting the boot flags to com=1H and
> com=1.  Nothing seems to work.
> 
> Is the gdb stub working with this version of the code?
> 
> I have checked the serial connection by connecting minicom to the port and
> from the remote machine doing the command "echo test > /dev/ttyS0" and I
> receive the text.  I have minicom set for 9600 8n1 and I use the same boot
> flags set in the grub config file.
> 
> What am I missing?
> 
> Thanks
> -matthew
> 
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