linux-kernel - Re: [PATCH 4/5] scripts/gdb: Add mount point list command

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Date:	Wed, 20 Jan 2016 13:08:08 +0100
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Kieran Bingham <kieran.bingham@...aro.org>
Cc:	linux-kernel@...r.kernel.org, maxime.coquelin@...com,
	peter.griffin@...aro.org, lee.jones@...aro.org
Subject: Re: [PATCH 4/5] scripts/gdb: Add mount point list command

On 2016-01-20 12:51, Kieran Bingham wrote:
> Hi Jan,
> 
> On 20/01/16 11:42, Jan Kiszka wrote:
>> Hi Kieran,
>>
>> just a couple of quick comments:
>>
>> On 2016-01-20 12:15, Kieran Bingham wrote:
>>> lx-mounts will identify current mount points based on the 'init_task'
>>> namespace by default, as we do not yet have a kernel thread list
>>> implementation to select the current running thread.
>>
>> current_task? See LxCurrentFunc, could be factored out if usable. Or
>> what are you looking for?
> 
> LxCurrentFunc relies on gdb.parse_and_eval("&current_task") which is not
> available on ARM.

Good point, not only affecting ARM. Needs to be fixed - lx-current() is
an important service.

> 
> Although that is not what I was referring to in the comment. My meaning
> was that once we have gdb-thread objects created, (my next phase of
> work) then this command would operate on the thread currently selected
> in gdb, based on the inferior_ptid.

I see. However, to have thread selection run with reasonable defaults,
we will need current() support as well.

> 
> 
>>>
>>> Optionally, a user can specify a PID to list from that process'
>>> namespace
>>>
>>> This is somewhat limited vs the /proc/mounts file, as that calls into
>>> vfs hooks through the s_op functions to obtain extra information.
>>>
>>> Signed-off-by: Kieran Bingham <kieran.bingham@...aro.org>
>>> ---
>>>
>>>
>>> In this patch, I'm interested in your opinions on coding styles.
>>> Would you prefer to see the function helpers, (dentry_name, info_opts) where
>>> they are, or inside the command as class members? Or perhaps defined in utils?
>>
>> Need to look into this.
>>
>>>
>>> This also shows where I need to take constant information from the kernel.
>>> In this case, they are simple numerical bitflags, and unlikely to change but
>>> I didn't want to duplicate their values.
>>
>> Maybe we can generate python files with the required constants from the
>> C headers during build? Similar to asm-offsets.c stuff.
>>
> 
> 
> Yes, this is what I've implemented in [PATCH 1/5] ? Perhaps the mails
> have reached you out-of-order.
> 

No, they were only processed in random order. Perfect!

Jan

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