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
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=usconsole=ttyS0,115200n8 kgdboc=ttyS0 kgdbwait
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@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:
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
Prabhu
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