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

[mjaggi@caviumnetworks.com (Manish Jaggi)]

On 10/03/2016 04:34 PM, AKASHI Takahiro wrote:
> 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 I am saying it that If the first kernel is booted using mem= option and crashkernel= option
the memory for second kernel has to be withing the crashkernel size.
As per /proc/iomem System RAM the information is correct, but the /proc/meminfo is showing total memory
much more than the first kernel had in first place.
> What about if you don't specify "crashkernel=...?"
> 
In that case the second kernel will not boot as kexec tools will complain that memory not reserved.
>> 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.
If I run with debug logs phys address accessed is > 64G. (10413ffcc0)
Could be that somehow 64 + 1G + (addr) = 10413ffcc0 and actually addr was required.
addr = 413ffcc0 which seems in line with 424b0c50


Logs:
<read_dev_mem: addr: ffff0000090b3008 paddr: 424b3008 cnt: 8>
node_online_map: [1] -> nodes online: 1
<readmem: ffff0000090b0c50, KVADDR, ""node_data"", 8, (ROE), ffffc330eb00>
<read_dev_mem: addr: ffff0000090b0c50 paddr: 424b0c50 cnt: 8>
<readmem: ffff800ffffffcc0, KVADDR, ""pglist node_id"", 4, (FOE), ffffc330f1e4>
<read_dev_mem: addr: ffff800ffffffcc0 paddr: 10413ffcc0 cnt: 4>
/dev/mem: Bad address
crash: read(/dev/mem, 10413ffcc0, 4): 4294967295 (ffffffff)
crash: read error: kernel virtual address: ffff800ffffffcc0  type: ""pglist node_id""
"
> 
>> 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?"
> 
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.
The same patch as below ?
Can you please share your 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
>>