[Crash-utility] GCORE: add directly show backtrace function in crash

[HATAYAMA Daisuke]

From: Lei Wen <adrian.wenl at gmail.com>
Subject: Re: GCORE: add directly show backtrace function in crash
Date: Mon, 22 Oct 2012 15:36:47 +0800

> Hi Daisuke,
> 
> On Mon, Oct 22, 2012 at 3:29 PM, HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com
>> wrote:
> 
>> From: Lei Wen <adrian.wenl at gmail.com>
>> Subject: GCORE: add directly show backtrace function in crash
>> Date: Mon, 22 Oct 2012 12:21:49 +0800
>>
>> > Hi Daisuke,
>> >
>> > I create a new option "-tT" for gcore, so that it could display bt for
>> user
>> > space
>> > directly inside crash itself, without needing to dump a separated core
>> file
>> > image,
>> > and analyze it in a different gdb env.
>> >
>> > The attached patch is directly based on below patch, and verify over ARM
>> > platform.
>> > http://osdir.com/ml/general/2012-10/msg32677.html
>> >
>> > Before use the corresponding gcore command, we need set env in crash by:
>> >
>> > crash>> gdb set solib-search-path [system lib path]
>> >
>> > crash>> gdb file   [user space program symbol file]
>> >
>> > crash>> gcore -t [user space thread id]
>> >
>> > Thanks,
>> > Lei
>>
>> Hello Lei,
>>
>> That must be a useful feature, but I think it's very othogonal to
>> gcore command...
>>
>> Why not releasing your own extension module separately to gcore?
>>
> 
> I put this function in gcore, is for gcore already provide the function to
> get
> the general register for user space thread. If add another module, that
> part of function seems a little duplicated...
> 

I now understand why you want to add it in gcore.

> Also provide the gcore the capability to either dump into a core file
> or directly display, user may have more choice over this. :)
> 

But, users then need to do more work such as loading application's
symbol files. There seems not so big difference.

gdb has one symbol space only. If you load applications's symbols, it
can override kernel symbols. Then, gcore might behave abnormally. Can
users reset the loading of applications' symbols in any feature of
gdb?

32-bit compability mode support? On x86-64 task can be running in
32-bit comparitbility mode. If so, gdb backtrace need to do the work
in 32-bit mode, I think. Does the current version covers this?

Thanks.
HATAYAMA, Daisuke