kernel debugging nodes missing from /sys/kernel

[amit mehta]

I've two 64 bit machines,both have Linux kernel running, but on one of
the machines
I'm not seeing any node under /sys/kernel/debug.
I checked some config(CONFIG_*) in the kernel configuration file on
both machines
but they seem to be the same. More information below:

1: SuseX86_64:~ # uname -a
Linux SuseX86_64 2.6.32.12-0.7-default #1 SMP 2010-05-20 11:14:20
+0200 x86_64 x86_64 x86_64 GNU/Linux

SuseX86_64:~ # ls /sys/kernel/debug/
bdi  dri  dynamic_debug  gpio  ipoib  kprobes  mce  sched_features
slow_work  usb  x86

SuseX86_64:~ # grep ^CONFIG_DEBUG /boot/config-2.6.32.12-0.7-default
CONFIG_DEBUG_FS=y
CONFIG_DEBUG_KERNEL=y
CONFIG_DEBUG_BUGVERBOSE=y
CONFIG_DEBUG_INFO=y
CONFIG_DEBUG_MEMORY_INIT=y
CONFIG_DEBUG_BLOCK_EXT_DEVT=y
CONFIG_DEBUG_FORCE_WEAK_PER_CPU=y
CONFIG_DEBUG_RODATA=y

SuseX86_64:~ # cat /etc/SuSE-release
SUSE Linux Enterprise Server 11 (x86_64)
VERSION = 11
PATCHLEVEL = 1


2: Now on a different machine, here I don't see the kernel/debug nodes
under /sys FS
[root at redhatx86_64]# uname -a
Linux lredhatx86_64 2.6.32-71.el6.x86_64 #1 SMP Wed Sep 1 01:33:01 EDT
2010 x86_64 x86_64 x86_64 GNU/Linux

[root at redhatx86_64 ~]# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 6.0 (Santiago)

[root at redhatx86_64 ~]# ls -l /sys/kernel/debug/
total 0 < -- ------------ -----------

[root at redhatx86_64 ]# grep ^CONFIG_DEBUG /boot/config-2.6.32-71.el6.x86_64
CONFIG_DEBUG_FS=y
CONFIG_DEBUG_KERNEL=y
CONFIG_DEBUG_SHIRQ=y
CONFIG_DEBUG_NMI_TIMEOUT=30
CONFIG_DEBUG_BUGVERBOSE=y
CONFIG_DEBUG_INFO=y
CONFIG_DEBUG_MEMORY_INIT=y
CONFIG_DEBUG_LIST=y
CONFIG_DEBUG_FORCE_WEAK_PER_CPU=y
CONFIG_DEBUG_STACKOVERFLOW=y
CONFIG_DEBUG_RODATA=y
CONFIG_DEBUG_RODATA_TEST=y
CONFIG_DEBUG_NX_TEST=m
CONFIG_DEBUG_BOOT_PARAMS=y

I'm specifically interested in /sys/kernel/debug/kprobes/enabled
According to kprobes.txt(http://lxr.linux.no/linux+v2.6.39/Documentation/kprobes.txt#L692)
I can enable/disable kprobes infrastructure through this node.

Though on both these two servers, I was successfully insert and test
some modules
using kprobes.

Please let me know what I'm missing on server2( redhatx86_64 )

Regards,
Amit


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