[PATCH v26 0/7] arm64: add kdump support
AKASHI Takahiro
takahiro.akashi at linaro.org
Mon Oct 3 04:04:25 PDT 2016
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
>
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