KGDBOC testing on linux-2.6.30-rc4

srikanth krishnakar skrishnakar at gmail.com
Tue May 5 19:35:24 EST 2009


Hi all,

Target : PowerPC, Virtex-440 Generic
Serial port : Xilinx 16550 Uart ( depends on OF_PLATFORM)

Further investigation of KGDBOC on PowerPC shows that kgdboc hangs at :

In file : arch/powerpc/include/asm/kgdb.h

*static inline void* arch_kgdb_breakpoint(*void*)
{
        *asm*(*".long 0x7d821008"*); /* *twge r2, r2 **/     * << ----
KGDBOC Hangs here* * << ---*


-----------------------------------------
Debug Log:

root at 10.1.2.55:~# echo g >
/proc/sysrq-trigger
SysRq :
GDB

1------------------------>sysrq_handle_gdb

Entering KGDB
1-1----------------------->kgdb_breakpoint
1-2----------------------->kgdb_breakpoint
1-3----------------------->kgdb_breakpoint
1-1----------------------->arch_kgdb_breakpoint

---------------------------------------------


Any comments or suggestions ????

-Srikanth
----------

On Mon, May 4, 2009 at 8:12 PM, Bruce Ashfield <bruce.ashfield at gmail.com>wrote:

> On Mon, May 4, 2009 at 9:13 AM, srikanth krishnakar
> <skrishnakar at gmail.com> wrote:
> >
> >
> > Hi all,
> >
> > I need help in kgdboc  testing on PowerPC target.
>
> Have you tried contacting the maintainer ? (I noticed that Jason
> wasn't cc'd), just in case it isn't simply a use case problem and
> might be related to KGDB internals.
>
> KGDB
> P:      Jason Wessel
> M:      jason.wessel at windriver.com
>
> I've tested KGDBOC up to the 2.6.29 kernel and it worked fine
> on a series of 85xx boards. I haven't had a chance on 2.6.30-rcX
> yet, so something may have changed.
>
> >
> > Linux Kernel: 2.6.30-rc4
> > KGDB method : KGDBOC
> > Arch: PowerPC
> >
> > Note: Attached is the kernel config  used.
> >
> > Has anyone tested KGDBOC for Serial 8250, and the serial port has
> dependency
> > on OF_PLATFORM driver ?
> >
> > Here are the kernel config options:
> >
> > Device Drivers  --->
> >            Character devices  --->
> >                           Serial drivers  --->
> >                                                      <*> 8250/16550 and
> > compatible serial support
> >                                                      [*]   Console on
> > 8250/16550 and compatible serial port
> >                                                      (4) Number of
> > 8250/16550 serial ports to register at runtime
> >                                                      [ ] Extended
> 8250/16550
> > serial driver options
> >                                                      *** Non-8250 serial
> > port support ***
> >                                                      <*> Xilinx uartlite
> > serial port support
> >                                                      [*]   Support for
> > console on Xilinx uartlite serial port
> >                                                      < > Digi
> International
> > NEO PCI Support
> >                                                      <*> Serial port on
> Open
> > Firmware platform bus
> >                                                      < > NWP serial port
> > driver
> >
> > Kernel hacking  --->
> >            -*- Magic SysRq key
> >                             [*] Kernel debugging
> >                             [*] KGDB: kernel debugging with remote gdb
> --->
> >                             --- KGDB: kernel debugging with remote
> > gdb
> >                            <*> KGDB: use kgdb over the serial console
> >
> >
> > ----------------------------------------------
> > In the process :
> >
> >     On the target side :
> >
> >                              ...............
> >                              Serial: 8250/16550 driver, 4 ports, IRQ
> sharing
> > disabled
> >                              83e00000.serial: ttyS0 at MMIO 0x83e01003
> (irq
> > = 16) is a
> > 16550A
> >                              console [ttyS0]
> > enabled
> >                              kgdb: Registered I/O driver kgdboc.
> >                              .................
> >
> >                             root at 10.161.2.35:~# echo g >
> /proc/sysrq-trigger
> >                             SysRq : GDB
> >                             Entering KGDB
> >
> >
> >   On host side :
> >
> >                            [root at srikant linux-2.6]#
> powerpc-linux-gnu-gdb
> > vmlinux-puru
> >                            GNU gdb G++ 4.3-150) 6.8.50.20081022-cvs
> >                            Copyright (C) 2008 Free Software Foundation,
> Inc.
> >                            License GPLv3+: GNU GPL version 3 or later
> > <http://gnu.org/licenses/gpl.html>
> >                            This is free software: you are free to change
> and
> > redistribute it.
> >                            There is NO WARRANTY, to the extent permitted
> by
> > law.  Type "show copying"
> >                            and "show warranty" for details.
> >                            This GDB was configured as
> > "--host=i686-pc-linux-gnu --target=powerpc-linux-gnu".
> >                            For bug reporting instructions, please see:
> >                           (gdb) set remotebaud 9600
> >                           (gdb) target remote /dev/ttyS0
> >                            Remote debugging using /dev/ttyS0
> >                           Ignoring packet error, continuing...
> >                           warning: unrecognized item "timeout" in
> > "qSupported" response
> >                           Ignoring packet error, continuing...
> >                           Ignoring packet error, continuing...
> >                           Ignoring packet error, continuing...
> >                           Ignoring packet error, continuing...
> >                           Ignoring packet error, continuing...
> >                           Malformed response to offset query, timeout
>
> I'm wondering if there is a GDB protocol mismatch and your
> version of GDB is sending packets that KGDB can't handle.
> I'm no where near an expert on GDB's protocol and won't know
> if I'm seeing the same thing until I try 2.6.30-rc
>
> Bruce
>
> >
> > Can anybody comment on the steps followed in the process of testing or
> > something is missing with respect to of_serial.c for powerpc
> architecture.
> > Seems the target has never responded for gdb requests !!!
> >
> >
> > Regards
> > Srikanth
> >
> >
> >
> >
> > _______________________________________________
> > Linuxppc-dev mailing list
> > Linuxppc-dev at ozlabs.org
> > https://ozlabs.org/mailman/listinfo/linuxppc-dev
> >
>
>
>
> --
> "Thou shalt not follow the NULL pointer, for chaos and madness await
> thee at its end"
>



-- 
"The Good You Do, The Best You GET"

Regards
Srikanth Krishnakar
**********************
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