Subject: [PATCH v26 0/7] arm64: add kdump support

From: [email-masked] (AKASHI Takahiro)
Date: Mon, 3 Oct 2016 20:04:25 +0900

Manish,

On Mon, Oct 03, 2016 at 01:24:34PM +0530, Manish Jaggi wrote:
> Hi Akashi,
> 
> On 09/07/2016 09:59 AM, AKASHI Takahiro wrote:
> >     v26-specific note: After a comment from Rob[0], an idea of adding
> >     "linux,usable-memory-range" was dropped. Instead, an existing
> >     "reserved-memory" node will be used to limit usable memory ranges
> >     on crash dump kernel.
> >     This works not only on UEFI/ACPI systems but also on DT-only systems,
> >     but if he really insists on using DT-specific "usable-memory" property,
> >     I will post additional patches for kexec-tools. Those would be
> >     redundant, though.
> >     Even in that case, the kernel will not have to be changed.
> > 
> > This patch series adds kdump support on arm64.
> > There are some prerequisite patches [1],[2].
> > 
> > To load a crash-dump kernel to the systems, a series of patches to
> > kexec-tools, which have not yet been merged upstream, are needed.
> > Please always use my latest kdump patches, v3 [3].
> > 
> > To examine vmcore (/proc/vmcore) on a crash-dump kernel, you can use
> >   - crash utility (coming v7.1.6 or later) [4]
> >     (Necessary patches have already been queued in the master.)
> > 
> > 
> > [0] http://lists.infradead.org/pipermail/linux-arm-kernel/2016-August/452582.html
> > [1] "arm64: mark reserved memblock regions explicitly in iomem"
> >     http://lists.infradead.org/pipermail/linux-arm-kernel/2016-August/450433.html
> > [2] "efi: arm64: treat regions with WT/WC set but WB cleared as memory"
> >     http://lists.infradead.org/pipermail/linux-arm-kernel/2016-August/451491.html
> > [3] T.B.D.
> > [4] https://github.com/crash-utility/crash.git
> > 
> 
> With the v26 kdump and v3 kexec-tools and top of tree crash.git, below are the tests done
> Attached is a patch in crash.git (symbols.c) to make crash utility work on my setup.
> Can you please have a look and provide your comments.
> 
> To generate a panic, i have a kernel module which on init calls panic.
> 
> Observations:
> 1.1. Dump capture kernel shows different memory map.
> ---------------------------------------------------
> In dump capture kernel /proc/meminfo and /proc/iomem differ
> 
> root at arm64:/home/ubuntu/CODE/crash#
> MemTotal:       65882432 kB
> MemFree:        65507136 kB
> MemAvailable:   60373632 kB
> Buffers:           29248 kB
> Cached:            46720 kB
> SwapCached:            0 kB
> Active:            63872 kB
> Inactive:          19776 kB
> Active(anon):       8256 kB
> Inactive(anon):     7616 kB
> 
> First kernel is booted with mem=2G crashkernel=1G command line option.
> While the system has 64G memory.
> 
> root at arm64:/home/ubuntu/CODE/crash# cat /proc/iomem
> 41400000-fffeffff : System RAM
>   41480000-420cffff : Kernel code
>   42490000-4278ffff : Kernel data
> ffff0000-ffffffff : reserved
> 100000000-ffaa7ffff : System RAM
> ffaa80000-ffaabffff : reserved
> ffaac0000-fffa6ffff : System RAM
> fffa70000-fffacffff : reserved
> fffad0000-fffffffff : System RAM

Are you saying that "mem=..." doesn't have any effect?
What about if you don't specify "crashkernel=...?"

> 1.2 Live crash dump fails with error
> --------------------------------------
> $crash vmlinux
> 
> 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: ffff800ffffffcc0  type: "pglist node_id"

I have no ideas here.

> Observation 2
> ------------
> If saved vmcore file is used
> 
> $crash vmlinux vmcore_saved
> Got the below error.
> 
> please wait... (gathering module symbol data)crash: malloc.c:2846: mremap_chunk: Assertion `((size + offset) & (_rtld_global_ro._dl_pagesize - 1)) == 0' failed.
> Aborted

I have no ideas here.

> Experiment 3
> ------------
> If crash.git is modified with a hack patch in symbols.c. Crash utility works fine log, bt commands work.

In which case, "crash vmlinux" or "crash vmlinux vmcore_saved?"

I was able to reproduce this issue in the latter case
(but with a different error message).
It seems to be a crash util's bug.
Please report it to crash-util mailing list.
I will post a patch.

Thanks,
-Takahiro AKASHI

> -------------------
> Patch: symbols.c
> git diff symbols.c
> diff --git a/symbols.c b/symbols.c
> index 13282f4..f7c6cac 100644
> --- a/symbols.c
> +++ b/symbols.c
> @@ -2160,6 +2160,7 @@ store_module_kallsyms_v2(struct load_module *lm, int start
>                  FREEBUF(module_buf);
>                  return 0;
>          }
> +       lm->mod_init_size = 0;
> 
>         if (lm->mod_init_size > 0) {
>                 module_buf_init = GETBUF(lm->mod_init_size);
> ------------------
> 
> $ crash vmlinux vmcore_saved
>     KERNEL: /home/ubuntu/CODE/linux/vmlinux
>     DUMPFILE: vm
>         CPUS: 48 [OFFLINE: 46]
>         DATE: Mon Oct  3 00:11:47 2016
>       UPTIME: 00:02:41
> LOAD AVERAGE: 0.36, 0.14, 0.05
>        TASKS: 171
>     NODENAME: arm64
>      RELEASE: 4.8.0-rc3-00044-g070a615-dirty
>      VERSION: #63 SMP Sat Oct 1 01:39:45 PDT 2016
>      MACHINE: aarch64  (unknown Mhz)
>       MEMORY: 2 GB
>        PANIC: "Kernel panic - not syncing: crash module starting"
>          PID: 958
>      COMMAND: "insmod"
>         TASK: ffff800007859300  [THREAD_INFO: ffff80000c940000]
>          CPU: 0
>        STATE: TASK_RUNNING (PANIC)
> 
> crash> bt
> PID: 958    TASK: ffff800007859300  CPU: 0   COMMAND: "insmod"
>  #0 [ffff80000c943980] __crash_kexec at ffff000008144fe8
>  #1 [ffff80000c943ae0] panic at ffff0000081ae704
>  #2 [ffff80000c943ba0] init_module at ffff000000900014 [crash]
>  #3 [ffff80000c943bb0] do_one_initcall at ffff000008083bb4
>  #4 [ffff80000c943c40] do_init_module at ffff0000081af6f0
>  #5 [ffff80000c943c70] load_module at ffff000008140b7c
>  #6 [ffff80000c943e10] sys_finit_module at ffff000008141634
>  #7 [ffff80000c943ed0] el0_svc_naked at ffff0000080833ec
>      PC: 00000003  LR: ffffaca050a0  SP: ffffaca865a0  PSTATE: 00000111
>     X12: ffffac941a5c X11: 00000080 X10: 00000004  X9: 00000030
>      X8: ffffffff  X7: fefefefefefeff40  X6: 00000111  X5: 00000001
>      X4: 00000001  X3: 0002ed61  X2: 00000000  X1: 00000003
>      X0: 00000000
> crash>
> 
> 
> ---
> Thanks,
> manish
>