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- Subject: Re: [Crash-utility] crash warnings
- From: Dave Anderson <anderson@xxxxxxxxxx>
- Date: Thu, 27 Apr 2006 14:04:32 -0400
Badari Pulavarty wrote: > On Thu, 2006-04-27 at 13:21 -0400, Dave Anderson wrote: > > Badari Pulavarty wrote: > > > > > On Thu, 2006-04-27 at 12:21 -0400, Dave Anderson wrote: > > > > Badari, > > > > > > > > What happens when you disassemble sys_read() on a live > > > > system running that particular kernel? Use "dis sys_read" as the > > > > crash command. > > > > > > > > Thanks, > > > > Dave > > > > > > Dave, > > > > > > crash shows wrong dis-assembly for even live machine... > > > > > > Thanks, > > > Badari > > > > > > elm3a242:~/crash-4.0-2.23 # ./crash /usr/src/linux/vmlinux > > > > > > crash 4.0-2.23 > > > Copyright (C) 2002, 2003, 2004, 2005, 2006 Red Hat, Inc. > > > Copyright (C) 2004, 2005, 2006 IBM Corporation > > > Copyright (C) 1999-2006 Hewlett-Packard Co > > > Copyright (C) 2005 Fujitsu Limited > > > Copyright (C) 2005 NEC Corporation > > > Copyright (C) 1999, 2002 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 6.1 > > > Copyright 2004 Free Software Foundation, Inc. > > > GDB 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. > > > Type "show copying" to see the conditions. > > > There is absolutely no warranty for GDB. Type "show warranty" for > > > details. > > > This GDB was configured as "x86_64-unknown-linux-gnu"... > > > > > > SYSTEM MAP: /usr/src/linux/System.map > > > DEBUG KERNEL: /usr/src/linux/vmlinux (2.6.16-20-smp) > > > > Strange -- why is it even using /usr/src/linux/System.map? > > You didn't enter it on the boot command line, and so I believe > > the only way that it would possibly be set would be by the > > find_booted_system_map() function -- which only would be > > called by match_proc_version() when the vmlinux file doesn't > > match the live system. > > > > What happens when you do this: > > > > $ strings /usr/src/linux/vmlinux | grep "Linux ver" > > > > $ cat /proc/version > > > > Are the outputs identical? > > Long sad story :( > > I am testing one of the distro build (SLES10 Beta) kernels. > Since there is no (easy) way to get debug-info kernel for each and > every beta kernel, I have been asked to build my own kernel from > exact sources and config. I used source.rpm and default config > files (only change is -g). But I am running distro shipped kernel > instead of currently built vmlinux. > > elm3a242:~/crash-4.0-2.23 # strings /usr/src/linux/vmlinux | grep "Linux > ver" > Linux version 2.6.16-20-smp (geeko@buildhost) (gcc version 4.1.0 (SUSE > Linux)) #1 SMP Mon Apr 24 08:19:31 PDT 2006 > elm3a242:~/crash-4.0-2.23 # > elm3a242:~/crash-4.0-2.23 # cat /proc/version > Linux version 2.6.16-20-smp (geeko@buildhost) (gcc version 4.1.0 (SUSE > Linux)) #1 SMP Mon Apr 10 04:51:13 UTC 2006 > > Thanks, > Badari OK, so as I understand it, neither the System.map nor the vmlinux symbol sets, most notably the text addresses found within them, would necessarily match the text in the vmcore -- which comes from the distro's vmlinux that was built without -g. Using -g has been shown to "shift" text. I used to pull this kind of bait-and-switch with Red Hat's AS2.1, whose distro was built without -g. So I would rebuild the same kernel's src.rpm, and use the newly-built vmlinux (call it vmlinux.dbg) like this: $ crash vmlinux.dbg /boot/System.map [vmcore] In this case, the vmlinux.dbg file won't match the live system or vmcore, but by explicitly using the "/boot/System.map" associated with the original non-g built vmlinux, things would work. In your case, it's defaulting to the /usr/src/linux/System.map, which is associated with the vmlinux that you built with -g. Presuming you have the /boot/System.map associated with the original distro's vmlinux file (the kernel that's running), what happens if you do this: $ crash vmlinux /boot/System.map [vmcore] Dave
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