[Crash-utility] user-space enhancements

[S.Iguchi]

Hi, 

> We ported it to crash as a loadable extension, but only did the i386
> stuff.
> 
> If there's enough interest we could see about liberating our internal
> code.

Cool.

I also have such crash extention module works only on x86-64...
and tested only with 2.6.10 and 2.6.20 .

# crash -s vmlinux-2.6.20-1.2320.fc5 /mnt/fc5/var/crash/2008-01-28-18
\:17/vmcore
  :
crash> extend elfcoredump.so
elfcoredump.so: shared object loaded
crash> elfdump 1
elfdump: write elfcore.1 done...
crash>
# gdb /sbin/init elfcore.1
   :

To enable dump shmem, add -s option .

But unfortunately , the module is coredump_filter unaware.
and has a lots TBD code .

BTW, Oda-san mentioned page swapout case on another thread , 
in that case , I decided simply seek to next page (same as ZERO page case).
sigh... i know its incorrect.

I think this module contains incomplete functionality , but 
should be maintained in crash community .

Castor, how about merge mine and your i386 module ?

Thanks.

Seigo Iguchi.


From: "Castor Fu" <Castor.Fu at 3PAR.com>
Subject: RE: [Crash-utility] user-space enhancements
Date: Thu, 4 Dec 2008 14:06:29 -0800

> 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.
> 
> We ported it to crash as a loadable extension, but only did the i386
> stuff.
> 
> If there's enough interest we could see about liberating our internal
> code.
> 
> 	-castor
> 
> 
> 
> -----Original Message-----
> From: crash-utility-bounces at redhat.com
> [mailto:crash-utility-bounces at redhat.com] On Behalf Of Bradshaw, James
> Sent: Thursday, December 04, 2008 12:58 PM
> To: Discussion list for crash utility usage, maintenance and development
> Subject: RE: [Crash-utility] user-space enhancements
> 
> 
> Right. To be able to examine user space, you'd have to build an elf core
> 
> file by processing the desired task structure in the kdump file, find
> all 
> the user pages, etc.--essentially what elf_core_dump() does in a running
> 
> kernel. Then you could use gdb offline or the embedded gdb.
> 
> I understand your desire not to burden crash with user space stuff, 
> although the extensions facility seems to provide a mechanism for
> cleanly 
> excluding such functionality from the standard configuration. Just a 
> thought.
> 
> -----Original Message-----
> From: crash-utility-bounces at redhat.com 
> [mailto:crash-utility-bounces at redhat.com] On Behalf Of Dave Anderson
> Sent: Thursday, December 04, 2008 3:25 PM
> To: Discussion list for crash utility usage, maintenance and development
> Subject: Re: [Crash-utility] user-space enhancements
> 
> 
> ----- "James Bradshaw" <jbradsha at enterasys.com> wrote:
> 
> > One of the items in the bug list is the following:
> >
> > DESCRIPTION:
> > User space enhancements:
> > - show user space stack backtrace, if present in the dump file,
> > - ability to link user space namelist (debug object files),
> >
> > RESOLUTION STATUS: TBD
> >
> > Is anyone currently working on this?
> 
> The items in the TODO list, with the exception of the first
> one about the "search" command, are all essentially "wish-list"
> items.  They were originally requested to be put there by IBM
> several years ago when the http://people.redhat.com/anderson
> site was instantiated as the "upstream" source of the crash
> utility.
> 
> The only item that I'm aware of that somebody is actually looking
> into is the one regarding "local variables", where I believe the
> guy looking into it is part of the IBM LTC in India.  I don't
> expect much to come out of it, though, because for one thing
> it presumes that the crash utility's backtrace frame information
> is etched in stone -- and with the exception of ia64 which has
> unwind information actually built into the kernel -- the backtrace
> is essentially a "best-guess" operation.  So trying to pull local
> arguments (or function arguments for that matter) from a
> dubious source doesn't make a whole lot of sense.
> 
> As far as a user-space backtrace, I still think the way to go
> is to work on creating a core dump file of the requested task,
> and then use gdb externally on that core file, completely outside
> of the crash utility.  Trying to overload the crash utility with
> a bunch of user-space stuff is something I don't have a lot of
> interest in.
> 
> Dave
> 
> 
> 
> 
> 
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