linux-kernel - Re: [PATCH 2/2] vsprintf: Add support for userspace strings

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Date:	Tue, 12 May 2015 09:31:09 +0200
From:	Richard Weinberger <richard@....at>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Joe Perches <joe@...ches.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] vsprintf: Add support for userspace strings

Am 12.05.2015 um 01:23 schrieb Andrew Morton:
> On Sun, 10 May 2015 13:16:22 -0700 Joe Perches <joe@...ches.com> wrote:
> 
>> On Sun, 2015-05-10 at 22:11 +0200, Richard Weinberger wrote:
>>> Am 10.05.2015 um 22:09 schrieb Joe Perches:
>>>> On Sun, 2015-05-10 at 21:42 +0200, Richard Weinberger wrote:
>>>>> Add %pL format string to print userspace strings.
>>>>> It works like %s but does copy_from_user() instead
>>>>> of a memcpy().
>>>>
>>>> I think this would be much simpler in a new
>>>> function rather than complicating string()
>>>
>>> -ENOPATCH.
>>
>> It's your patch, I'm just commenting on it.
>>
>> I'm not sure there's much value in it.
> 
> I can't say I'm terribly excited either.  Are there any existing
> callsites which might use this?  The %p namespace is already pretty
> crowded and if %pL is just for non-production developer debug use then
> it can reasonably live outside the main kernel tree...

My indention was to use it for two things:
a) Debugging (at least I use such code from time to time when debugging strange stuff)
b) Using this new format string in ftrace to print strings provided to syscalls instead of raw addresses.

Masami showed me that I can use "perf probe" for for both a) and b).
So let'S drop this patch.

Thanks,
//richard
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