[Crash-utility] user-space enhancements

[Dave Anderson]

----- "James Bradshaw" <jbradsha at enterasys.com> wrote:

> Thanks. I gather that lkcd/lcrash was an earlier effort unrelated to
> crash. Is that correct?

The LKCD project consisting of both the LKCD kernel patch and its
associated "lcrash" user-space command, was first posted by SGI in 1999,
literally within days of a parallel effort done by Mission Critical Linux
when we posted our "mcore" kernel patch and our original "crash"
utility.  After the demise of Mission Critical Linux in 2002, I was hired
by Red Hat, and brought the crash utility with me.

While still at Mission Critical, however, I did add support for the
LKCD dumpfile format in the crash utility, and the LKCD developers and
I have passed stuff back-and-forth over the years.  

Anyway, neither mcore or the LKCD kernel patches were ever adopted upstream.
After what seems to have been an eternity, finally the kdump facility
was accepted.  It seems highly unlikely that the kdump facility
would ever be modified to also capture swap contents, although I
suppose anything's possible.   

That all being said, given the core-dump masking support in the
current kernels, you can now set /proc/<pid>/coredump_filter to
pretty much strip almost everything out of the user core file, while
still being able to debug the basics.  Even when filtering out 
anonymous private and shared memory pages (which strips out user 
stack pages), the core dump is still usable by gdb, and will at
least pinpoint the last known location.

Dave



> 
> -----Original Message-----
> From: crash-utility-bounces at redhat.com
> [mailto:crash-utility-bounces at redhat.com] On Behalf Of Michael
> Holzheu
> Sent: Friday, December 05, 2008 4:35 AM
> To: Discussion list for crash utility usage, maintenance and
> development
> Cc: Dan Stein
> Subject: RE: [Crash-utility] user-space enhancements
> 
> Am Donnerstag, den 04.12.2008, 14:06 -0800 schrieb Castor Fu:
> > There was a group at IBM (Stefan Schlosser <sschloss at de.ibm.com>)
> > a few years ago which set up stuff to generate
> > a elf corefile for a user space process for lcrash.
> 
> Stefan did that as diploma thesis in our department at IBM. The ugly
> part was the swap file handling. The swap files had to be saved after
> a
> dump in order to access all user space memory. We added the save
> function in lcrash:
> 
> lcrash -S <swapdump>
> 
> to generate a dump-file containing all used swapped out pages of all
> swap areas.
> 
> And we added an extra parameter <swapdump> when starting lcrash to
> analyze the dump:
> 
> lcrash map.x dump.x kerntypes.x <swapdump>
> 
> Here the posting on the lkcd mailing list:
> 
> http://sourceforge.net/mailarchive/message.php?msg_id=OF7160ABF7.B54F4970-ONC1256BCE.004FD0A0-C1256BCE.0054E5BA%40de.ibm.com
> 
> But the code was never integrated officially in lcrash.
> 
> Michael
> 
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