[Kgdb-bugreport] KGDB problem at first breakpoint

Fri May 20 00:23:41 EDT 2011

Enabling CONFIG_DEBUG_RODATA also didn't work.

-Prabhu

On Thu, May 19, 2011 at 6:45 AM, Dongdong Deng <libfetion at gmail.com> wrote:

> On Wed, May 18, 2011 at 7:23 PM, Prabhu nath <gprabhunath at gmail.com>
> wrote:
> > Dear All,
> >
> >       There is a problem with the KGDB at the very first break point
> after
> > executing the gdb command "target remote /dev/ttyS0" from the host.
> >       I have verbatim, followed the KGDB document
> > http://kernel.org/pub/linux/kernel/people/jwessel/kdb/
> >
> > Problem Logs:
> > ---------------------
> >
> > Details  of my hardware and system software:
> > -------------------------------------------------------------------
> >
> > *Host (Development machine): *
> >                      Intel Pentium IV Machine with Fedora Core 12
> >                      Linux Version : 2.6.31.5-127.fc12.i686.PAE
> >                      gdb version : GNU gdb (GDB) Fedora (7.0-3.fc12)
> >
> > *Target:*
> >                 Intel Pentium IV Machine with Fedora Core 12
> >                 Customized Linux Version :  2.6.38
> >
> > Host is connected to Target via a null modem cable
> >
> > *Snapshot of .config of linux version 2.6.38 on the target *
> > *
> > *
> > # CONFIG_DEBUG_RODATA is not set
>
>
> Hi Prabhu,
>
> The CONFIG_DEBUG_RODATA was suggested to set at KGDB,
> Could you enable it?
>
> CONFIG_DEBUG_RODATA = y
>
> Dongdong
>
>

>
> >
> > CONFIG_HAVE_ARCH_KGDB=y
> > CONFIG_FRAME_POINTER=y
> > CONFIG_DEBUG_INFO=y
> > CONFIG_KGDB=y
> > CONFIG_KGDB_SERIAL_CONSOLE=y
> > CONFIG_KGDB_LOW_LEVEL_TRAP=y
> >
> > *Grub config on the target machine*
> > *
> > *
> > title Fedora (2.6.38)
> >        root (hd0,0)
> >        kernel /boot/vmlinuz-2.6.38 ro
> > root=UUID=fb7800fb-cfe7-438d-bc7f-c153ba4353d1  LANG=en_US.UTF-8
> > SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc
> KEYTABLE=us*console=ttyS0,115200n8
> > kgdboc=ttyS0 kgdbwai*t
> >        initrd /boot/initrd-2.6.38.img
> >
> >
> > On power on of the target, linux kernel boots and the logs are seen on
> the
> > minicom console of the host and it will wait for the gdb on the host to
> > connect. Here is the last 4 lines of the logs seen on the minicom
> >
> > Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
> > serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
> > 00:06: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
> > kgdb: Registered I/O driver kgdboc.
> > kgdb: Waiting for connection from remote gdb..
> >
> > *--- Now I close the minicom console (Ctrl-A X) and start the gdb on the
> > host. Here is the steps I follow. *
> > *
> > *
> > *On the host machine:*
> > *
> > *
> >
> > [root at localhost kgdb]# gdb vmlinux
> >
> > GNU gdb (GDB) Fedora (7.0-3.fc12)
> > Copyright (C) 2009 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 "i686-redhat-linux-gnu".
> > For bug reporting instructions, please see:
> > <http://www.gnu.org/software/gdb/bugs/>...
> > Reading symbols from /root/kgdb/vmlinux...done.
> >
> > (gdb) set remotebaud 115200
> > (gdb) set debug remote 1
> > (gdb) target remote /dev/ttyS0
> > Remote debugging using /dev/ttyS0
> > Sending packet: $qSupported#37...Ack
> > Packet received:
> > Packet qSupported (supported-packets) is NOT supported
> > Sending packet: $Hg0#df...Ack
> > Packet received: OK
> > Sending packet: $?#3f...Ack
> > Packet received: S05
> > Sending packet: $Hc-1#09...Ack
> > Packet received: OK
> > Sending packet: $qC#b4...Ack
> > Packet received: QC01
> > Sending packet: $qAttached#8f...Ack
> > Packet received:
> > Packet qAttached (query-attached) is NOT supported
> > Sending packet: $qOffsets#4b...Ack
> > Packet received:
> > Sending packet: $g#67...Ack
> > Packet received:
> >
> 36000000ffffffff0abaffff20d98bc06c3f86de783f86de803ac8dd803f86de885747c00202000060000000680000007b00c8dd7b0086deffff0000ffff0000
> > Sending packet: $mc0475788,1#a4...Ack
> > Packet received: 0f
> > Sending packet: $mc0475788,8#ab...Ack
> > Packet received: 0faef889f6ff0d08
> > Sending packet: $mc0475788,7#aa...Ack
> > Packet received: 0faef889f6ff0d
> > 0xc0475788 in ?? ()
> > Sending packet: $qSymbol::#5b...Ack
> > Packet received:
> > Packet qSymbol (symbol-lookup) is NOT supported
> > (gdb) s
> > Cannot find bounds of current function
> > (gdb)
> >
> >
> > *Observation:*
> >                     *1.* Ideally the kernel being debugged should break
> at
> > legitimate address and the corresponding line number should
> >                         be displayed instead of " 0xc0475788 in ?? ()".
> >
> >                     2. On inspecting section header in vmlinux
> executable,
> > I found the .text section address range is from
> >                         0xC1000000 to 0xC1326e58  and no section's
> contents
> > associate with the address 0xC0475788.
> >
> >                     *3.* Hence on single stepping, gdb logs the error
> > as* "Cannot
> > find bounds of current function"*
> > *
> > *
> >  Humbly request you to help me in addressing this issue.
> >
> > Thanks and Regards,
> > Prabhu
> >
> ------------------------------------------------------------------------------
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