Re: kgdb on EM64T

[George Anzinger <george@mvista.com>]

George Anzinger wrote:
> Wilkerson, Bryan P wrote:
> 
>> Thanks you Tom and George for the tips on using kgdb with
>> 2.6.13-rc4-mm1. 
>> I almost have it working but kgdb seems to have a few issues.  I can get
>> it running from the dev machine using the kgdb and console=kgdb boot
>> options on the test kernel.  The kernel waits as it should and when I
>> attach with "target remote /dev/ttyS0" and I can continue the boot but
>> eventually it gets to a point in the boot where it frees unused kernel
>> memory successfully and then a warning, "unable to open an initial
>> console",  followed by, "Kernel panic - not syncing: Attempted to kill
>> init!"
>>
>> Removing the console=kgdb boot option and the machine boots all the way
>> to run level 5.   I tried to break into kgdb at this point using the 
>>     $echo -e "\003" > /dev/ttyS0
>> from the dev machine but the test kernel panics at gdb_interrupt+75 when
>> it receives anything on the serial port.  Hmmm...
>>
>> I'm wondering if I'm maybe just the first to try this on EM64T (kernel
>> builds in the arch/x86_64 tree).   
> 
> 
> Possibly:).  Since the serial port seems to work (i.e. the first test 
> above), the fault seems to be in handling the int3.  Is int3 the right 
> instruction for this machine?  If not you would make the change in 
> kgdb.h.  I think that is the only place it is defined.

Well, I checked, it is "int $3".  Why then the panic?  If you try the 
boot with kgdb (i.e. wait) and the do:
(gdb) disass gdb_interrupt
What do you find at +75?
> 
>>

-- 
George Anzinger   george@mvista.com
HRT (High-res-timers):  http://sourceforge.net/projects/high-res-timers/