[Crash-utility] Crash, won't read my vmcore "crash: page excluded: kernel virtual address:"

[Dave Anderson]

----- Original Message -----
> [root at kvm7 127.0.0.1-2014-02-07-19:17:09]# crash /boot/System.map-2.6.32-220.el6.x86_64.debug /usr/lib/debug/lib/modules/2.6.32-220.el6.x86_64.debug/vmlinux vmcore
> 
> crash 5.1.8-1.el6
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> Copyright (C) 2005 NEC Corporation
> Copyright (C) 1999, 2002, 2007 Silicon Graphics, Inc.
> Copyright (C) 1999, 2000, 2001, 2002 Mission Critical Linux, Inc.
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> This program has absolutely no warranty. Enter "help warranty" for details.
> GNU gdb (GDB) 7.0
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> 
> crash: page excluded: kernel virtual address: ffffffff81542000 type: "cpu_possible_mask"
> 
> I can go into minimal,
> 
> 
> nm -Bn /usr/lib/debug/lib/modules/2.6.32-220.el6.x86_64.debug/vmlinux | grep _stext
> ffffffff81000198 T _stext
> 
> cat /proc/kallsyms | grep _stext
> ffffffff81000198 T _stext
> 
> If I use the System Map parm I get this warning
> 
> WARNING: kernels compiled by different gcc versions:
> /usr/lib/debug/lib/modules/2.6.32-220.el6.x86_64.debug/vmlinux: 4.4.5
> vmcore kernel: 4.4.6
> 
> 
> Would really like to understand why this system crashed. I know I'm a bit
> behind on my kernel versions however, but I should be able to look at this
> kernel??
> 
> Thanks
> Tory

It looks like the vmcore and vmlinux file don't match, like maybe the crashing
system was running the standard 2.6.32-220.el6.x86_64 kernel, and you're trying
to debug it using the 2.6.32-220.el6.x86_64.debug kernel variant?

First thing -- *never* use a System.map file unless for some reason you don't
have the original kernel's vmlinux available *and* you feel that the vmlinux
file you have is very close to the crashing kernel's vmlinux.  Bit with any 
RHEL standard (unmodified) vmlinux/vmcore setup, the System.map is completely
useless.

So the first question is: what kernel generated the vmcore?

Do this:

 $ strings vmcore | grep '2.6.32'
 
Dave