How to Check Kgdb is enabled or not?

Question

I have a kernel image and would like to debug with kgdb. The .config also not available, otherwise I could check the flags in it.

In /proc/sys/ folder also there is no entry about kgdb.

Is there any way to check whether that image is kgdb enabled or not?

Have you tried just connecting it. What are you running on, is it an official distribution of a kernel? [Typically, there is .config copied to `/boot/config-.origin.arch` e.g on my FC16 system I have `/boot/config-3.6.6-1.fc16.x86_64`... — Mats Petersson, Dec 26 '12 at 11:51
Its unofficial one. while trying to connect, it doesn't wait for kgdb.. — Jeyaram, Dec 26 '12 at 11:58
So sounds like it doesn't have kgdb then... Check with whoever built the kernel - yes, I know, it may be a tad difficult today! — Mats Petersson, Dec 26 '12 at 11:58
@MatsPetersson, anyway I will check. Meanwhile if u get any alternate method to ensure plz share :) — Jeyaram, Dec 26 '12 at 12:02
Do you have kernel symbols? If so, you could search for `kgdb_arch_init` - I'm 99% sure it's not there in a kernel that has KGBD disabled. — Mats Petersson, Dec 26 '12 at 12:15

score 2 · Accepted Answer · answered Dec 26 '12 at 16:52

If your kernel image was compiled with the options

CONFIG_IKCONFIG=y
CONFIG_IKCONFIG_PROC=y

then you can get the kernel image's configuration from /proc/config.gz or by using

/pathtokernelsource/scripts/extract-ikconfig pathtokernelimage > /tmp/config

From there you can search for CONFIG_KGDB using grep or zgrep depending on whether you are viewing the compressed or uncompressed configuration file.

/pathtokernelsource/scripts/extract-vmlinux pathtokernelimage > /tmp/vmlinux will also extract the vmlinux executable from the image.

If this has symbols them you can search for kgdb_arch_init or kgdb_arch_* in either the output of nm on this file or in the System.map for your kernel image as Mats Petersson mentioned in the comments.

/proc/config.gz helps me to get the config file. Thanks. – Jeyaram Jan 02 '13 at 03:29 — Jeyaram, Jan 02 '13 at 03:29

How to Check Kgdb is enabled or not?

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