[Crash-utility] [PATCH] add arm support for libgcore

[Lei Wen]

Hi HATAYAMA,

On Tue, Feb 14, 2012 at 9:37 AM, HATAYAMA Daisuke
<d.hatayama at jp.fujitsu.com> wrote:
> From: Lei Wen <adrian.wenl at gmail.com>
> Subject: Re: [Crash-utility] [PATCH] add arm support for libgcore
> Date: Mon, 13 Feb 2012 17:03:02 +0800
>
>> Hi Hatayama,
>>
>> On Mon, Feb 13, 2012 at 4:33 PM, HATAYAMA Daisuke
>> <d.hatayama at jp.fujitsu.com> wrote:
>>> Hello Lei,
>>>
>>> Thanks for making patch. I'll check your patch this week, but I have
>>> two things to ask you.
>>>
>>> 1. I don't know arm architecture at all and I don't have arm
>>> machine. What I can do is only testing common part and regression test
>>> on x86 architecture. Please maintain arm part yourself.
>>
>> Sure, it is my pleasure. :)
>>
>>>
>>> 2. Could you tell me specific kernel versions you have tested this
>>> patch in? I myself have yet to do this, but now I think it necessary
>>> to make such a list. I imagine just like makedumpfile's SUPPORTED
>>> KERNELS described in its README. I'll put them in gcore's README and
>>> then ask Dave to add them into description in distribution page.
>>
>> I am current testing with kernel 2.6.35.7 and 3.0.8, and they are both ok.
>
> I see.
>
>> But I see below warnings during extracting, while the extracted core
>> dump image is
>> OK for gdb, I don't know whether it there is still some missing in
>> original implementation,
>> or those pages just don't existed in memory?
>>
>> gcore: PT_LOAD[165]: af900000 - af90e000
>> gcore: WARNING: page fault at af909000
>> gcore: WARNING: page fault at af90d000
>
> These are verbose messages, which you can specify which to display via
> -v option. Please see help message in detail. However, important is
> "page fault" message below.
>
>> gcore: WARNING: page fault at af909000
>> gcore: WARNING: page fault at af90d000
>
> Most of crash dump mechanism doesn't collect swap space, such as
> kdump, diskdump, so in essence, crash gcore doesn't try to collect
> such paged-out user-space memory.
>
> crash gcore instead fills the paged-out memory with zero; this
> is easier implementation than reconstracting program headers.
>
> The reason why I've included the ``page fault'' in the default warning
> message is to avoid the situation where users get confused they have
> successfully got complete user-space coredump.
>
> GDB tends to work well because part of user stack necessary for
> backtrace is not paged out most of time; of course, the backtrace
> would fail if paged-out.
>
> Thanks.
> HATAYAMA, Daisuke
>

I see, thanks for detailed explanation.
My another curious is whether we could refill those missing swapped page, if
we provide whole swap partition data?

Thanks,
Lei