[Crash-utility] [PATCH v2] arm64: fix kernel memory map handling for kaslr-enabled kernel

Thu May 26 07:04:08 UTC 2016

Pratyush,

Just for debug purpose.
Please add the following line to *your* arch_crash_save_vmcoreinfo():
> vmcoreinfo_append_str("NUMBER(kimage_voffset)=%llx\n", kimage_voffset);

I will add this to my next kdump patch.

Thanks,
-Takahiro AKASHI

On Thu, May 26, 2016 at 10:58:24AM +0530, Pratyush Anand wrote:
> On 24/05/2016:01:59:06 PM, Dave Anderson wrote:
> > 
> > 
> > ----- Original Message -----
> > > Yet some issues, but ...
> > >
> > 
> > Hi Takahiro,
> > 
> > Here are my general comments on my testing of the v2 patch, followed 
> > by a few comments in the patch itself. 
> > 
> > First, the combination of the new memory map layout and KASLR is somewhat
> > confusing.  I am testing your patch on a 4.6.0-0.rc7.git2.1.fc25 kernel
> > that has this configuration:
> > 
> >   config-arm64:# CONFIG_RANDOMIZE_BASE is not set
> > 
> > So KASLR doesn't really enter into the picture.  But when bringing
> > up the crash session, it shows the "kaslr kernel" WARNING:
> > 
> >   # ./crash
> >   
> >   crash 7.1.5++
> >   Copyright (C) 2002-2016  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.
> >    
> >   WARNING: kimage_voffset not identified for kaslr kernel
> >   GNU gdb (GDB) 7.6
> >   Copyright (C) 2013 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 "aarch64-unknown-linux-gnu"...
> >   
> >         KERNEL: /usr/lib/debug/lib/modules/4.6.0-0.rc7.git2.1.fc25.aarch64/vmlinux
> >       DUMPFILE: /dev/crash
> >           CPUS: 8
> >           DATE: Tue May 24 10:08:08 2016
> >         UPTIME: 11 days, 18:32:41
> >   LOAD AVERAGE: 0.17, 0.09, 0.12
> >          TASKS: 197
> >       NODENAME: apm-mustang-ev3-36.khw.lab.eng.bos.redhat.com
> >        RELEASE: 4.6.0-0.rc7.git2.1.fc25.aarch64
> >        VERSION: #1 SMP Thu May 12 13:28:43 UTC 2016
> >        MACHINE: aarch64  (unknown Mhz)
> >         MEMORY: 16 GB
> >            PID: 7556
> >        COMMAND: "crash"
> >           TASK: fffffe00beb45400  [THREAD_INFO: fffffe00beb98000]
> >            CPU: 7
> >          STATE: TASK_RUNNING (ACTIVE)
> >   
> >   crash>
> 
> Do not know whats missing, I am yet not able to reach "crash>" prompt. I have
> crash utility having this patch on top of "commit
> 8ceb1ac628bf6a0a7f0bbfff030ec93081bca4cd" [1]. I have kernel code v4.6+kexec-v15 [2].
> 
> In my .config:
> # CONFIG_KASAN is not set
> # CONFIG_RANDOMIZE_BASE is not set
> 
> This is what I get:
> 
> [root at dhcppc15 crash]# ./crash /lib/modules/4.6.0+/build/vmlinux /var/crash/127.0.0.1-2016-05-26-09\:40\:05/vmcore
> 
> crash 7.1.5++
> Copyright (C) 2002-2016  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) 7.6
> Copyright (C) 2013 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 "aarch64-unknown-linux-gnu"...
> 
> crash: read error: kernel virtual address: fffffc0008b80fd8  type: "possible"
> WARNING: cannot read cpu_possible_map
> crash: read error: kernel virtual address: fffffc0008b80dd8  type: "present"
> WARNING: cannot read cpu_present_map
> crash: read error: kernel virtual address: fffffc0008b80bd8  type: "online"
> WARNING: cannot read cpu_online_map
> crash: read error: kernel virtual address: fffffc0008b811d8  type: "active"
> WARNING: cannot read cpu_active_map
> crash: read error: kernel virtual address: fffffc00091f6c78  type: "shadow_timekeeper xtime_sec"
> crash: read error: kernel virtual address: fffffc0008b9223c  type: "init_uts_ns"
> crash: /lib/modules/4.6.0+/build/vmlinux and /var/crash/127.0.0.1-2016-05-26-09:40:05/vmcore do not match!
> 
> Usage:
> 
>   crash [OPTION]... NAMELIST MEMORY-IMAGE[@ADDRESS]     (dumpfile form)
>   crash [OPTION]... [NAMELIST]                          (live system form)
> 
> Enter "crash -h" for details.
> 
> 
> ~Pratyush
> 
> [1] https://github.com/pratyushanand/crash/commits/master
> [2] https://github.com/pratyushanand/linux/commits/upstream_arm64_devel_test
> 

-- 
Thanks,
-Takahiro AKASHI