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

Thu May 26 05:28:24 UTC 2016

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