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Old 06-20-2012, 02:42 PM
Dave Anderson
 
Default Pages excluded in dump RHEL 6.2 - set to ffffffffffffffff

----- Original Message -----
> Hi Dave,
>
> OK, makes sense. I still spend 95% of my time in the RHEL 5 kernels
> so it's just lack of enough time in the RHEL 6 kernels.
> I did not have the debuginfo so I built a vmkernel with debug from
> source and used that. I was able to get what I wanted out of the
> dump, specifically needed to look at the net_dev structures.
>
> Is there a write up somewhere on changes with crash for the 2.6.32.x
> kernels that you can share.

No, not specifically for the 2.6.32 or any other kernel version.

The crash utility is constantly updated to handle the shifting sands
of the underlying Linux kernel. But it's also kept backwards-compatible,
so the crash sources are full of checks for kernel differences such as
the cpu maps to mask changes.

But I'm still not clear why you are reading the ffffffffffffffff's at
those symbolic locations if the System.map's symbol values (which
over-write the ones in the vmlinux file) match what's in the dumped
kernel? I believe that the vmlinux file that you built -- even with
the correct System.map -- is different enough from the crashed kernel
so that there are inequities that cannot be overcome with just a System.map.

Dave


> Thanks
> Laurence
>
>
> -----Original Message-----
> From: crash-utility-bounces@redhat.com
> [mailto:crash-utility-bounces@redhat.com] On Behalf Of Dave Anderson
> Sent: Wednesday, June 20, 2012 9:22 AM
> To: Discussion list for crash utility usage, maintenance and
> development
> Subject: Re: [Crash-utility] Pages excluded in dump RHEL 6.2 - set to
> ffffffffffffffff
>
>
>
> ----- Original Message -----
> > I have a dump from RHEL 6.2 with all these masks set to all f's, so
> > obviously crash excludes them.
> >
> > crash: page excluded: kernel virtual address: ffffffffffffffff
> > type: "possible"
> > WARNING: cannot read cpu_possible_map
> > crash: page excluded: kernel virtual address: ffffffffffffffff
> > type: "present"
> > WARNING: cannot read cpu_present_map
> > crash: page excluded: kernel virtual address: ffffffffffffffff
> > type: "online"
> > WARNING: cannot read cpu_online_map
> >
> > typedef struct cpumask { DECLARE_BITMAP(bits, NR_CPUS); }
> > cpumask_t;
> >
> > #ifndef CONFIG_DISABLE_OBSOLETE_CPUMASK_FUNCTIONS
> > /* These strip const, as traditionally they weren't const. */
> > #define cpu_possible_map (*(cpumask_t *)cpu_possible_mask)
> > #define cpu_online_map (*(cpumask_t *)cpu_online_mask)
> > #define cpu_present_map (*(cpumask_t *)cpu_present_mask)
> > #define cpu_active_map (*(cpumask_t *)cpu_active_mask)
> >
> > Are these deprecated now and is that why they are fixed at all f's.
>
> No, that's just a common error message for accessing the maps or
> masks.
>
> When reading them, crash checks first whether there is the older
> kernel symbol named "cpu_xxx_map", and if it doesn't exists, then it
> checks for the symbol named "cpu_xxx_mask". It then tried to read
> the memory that those symbols point to, which all contained values
> of ffffffffffffffff. So clearly there's some kind of mis-match
> between the symbol values -- modified by using a System.map file --
> and what's in the vmcore file.
>
> (FWIW, the dumpfile couldn't find the page for bogus address, and
> presumed that it was "excluded" since it's a filtered dump, so
> that's a non-issue...)
>
> First question: it appears that you are analyzing a RHEL6 kernel, so
> why are you using a "System.map" argument? Did you rebuild the
> kernel but when you did that, you didn't save the rebuilt vmlinux
> file?
>
> Dave
>
> >
> > [root@centos62 crash]# crash System.map vmlinux
> > va102.2012-06-14.vmcore
> >
> > crash 6.0.7
> > Copyright (C) 2002-2012 Red Hat, Inc.
> > Copyright (C) 2004, 2005, 2006, 2010 IBM Corporation Copyright (C)
> > 1999-2006 Hewlett-Packard Co Copyright (C) 2005, 2006, 2011, 2012
> > Fujitsu Limited Copyright (C) 2006, 2007 VA Linux Systems Japan
> > K.K.
> > Copyright (C) 2005, 2011 NEC Corporation Copyright (C) 1999, 2002,
> > 2007 Silicon Graphics, Inc.
> > Copyright (C) 1999, 2000, 2001, 2002 Mission Critical Linux, Inc.
> > This program is free software, covered by the GNU General Public
> > License, and you are welcome to change it and/or distribute copies
> > of
> > it under certain conditions. Enter "help copying" to see the
> > conditions.
> > This program has absolutely no warranty. Enter "help warranty" for
> > details.
> >
> > GNU gdb (GDB) 7.3.1
> > Copyright (C) 2011 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 "x86_64-unknown-linux-gnu"...
> >
> > crash: page excluded: kernel virtual address: ffffffffffffffff
> > type: "possible"
> > WARNING: cannot read cpu_possible_map
> > crash: page excluded: kernel virtual address: ffffffffffffffff
> > type: "present"
> > WARNING: cannot read cpu_present_map
> > crash: page excluded: kernel virtual address: ffffffffffffffff
> > type: "online"
> > WARNING: cannot read cpu_online_map
> > crash: page excluded: kernel virtual address: ffffffffffffffff
> > type: "cpu_present_map"
> > crash: page excluded: kernel virtual address: ffffffffffffffff
> > type: "cpu_present_map"
> > crash: page excluded: kernel virtual address: ffffffffffffffff
> > type: "cpu_online_map"
> > SYSTEM MAP: System.map
> > DEBUG KERNEL: vmlinux (2.6.32-220.7.1.el6)
> > DUMPFILE: va102.2012-06-14.vmcore [PARTIAL DUMP]
> > CPUS: 32
> > DATE: Thu Jun 14 05:24:17 2012
> > UPTIME: 11:13:23
> > LOAD AVERAGE: 215.00, 196.78, 135.81
> > TASKS: 1778
> > NODENAME: va1splunkindex02.va1.swtor.int
> > RELEASE: 2.6.32-220.7.1.el6.x86_64
> > VERSION: #1 SMP Tue Mar 6 13:54:51 EST 2012
> > MACHINE: x86_64 (2799 Mhz)
> > MEMORY: 48 GB
> > PANIC: "Oops: 0002 [#1] SMP " (check log for details)
> > PID: 2428
> > COMMAND: "bash"
> > TASK: ffff88063874ab40 [THREAD_INFO: ffff8806dcd1a000]
> > CPU: 0
> > STATE: TASK_RUNNING (PANIC)
> >
> > Thanks
> > Laurence
> >
> > --
> > Crash-utility mailing list
> > Crash-utility@redhat.com
> > https://www.redhat.com/mailman/listinfo/crash-utility
> >
>
> --
> Crash-utility mailing list
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> https://www.redhat.com/mailman/listinfo/crash-utility
>
> --
> Crash-utility mailing list
> Crash-utility@redhat.com
> https://www.redhat.com/mailman/listinfo/crash-utility
>

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