linux-kernel - Re: [PATCH v3 13/35] lib: add allocation tagging support for memory allocation profiling

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Message-ID: <af9eab14-367b-4832-8b78-66ca7e6ab328@suse.cz>
Date: Fri, 16 Feb 2024 09:50:43 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Kees Cook <keescook@...omium.org>, Suren Baghdasaryan <surenb@...gle.com>
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Subject: Re: [PATCH v3 13/35] lib: add allocation tagging support for memory
 allocation profiling

On 2/13/24 23:38, Kees Cook wrote:
> On Tue, Feb 13, 2024 at 02:35:29PM -0800, Suren Baghdasaryan wrote:
>> On Tue, Feb 13, 2024 at 2:29 PM Darrick J. Wong <djwong@...nel.org> wrote:
>> >
>> > On Mon, Feb 12, 2024 at 05:01:19PM -0800, Suren Baghdasaryan wrote:
>> > > On Mon, Feb 12, 2024 at 2:40 PM Kees Cook <keescook@...omium.org> wrote:
>> > > >
>> > > > On Mon, Feb 12, 2024 at 01:38:59PM -0800, Suren Baghdasaryan wrote:
>> > > > > Introduce CONFIG_MEM_ALLOC_PROFILING which provides definitions to easily
>> > > > > instrument memory allocators. It registers an "alloc_tags" codetag type
>> > > > > with /proc/allocinfo interface to output allocation tag information when
>> > > >
>> > > > Please don't add anything new to the top-level /proc directory. This
>> > > > should likely live in /sys.
>> > >
>> > > Ack. I'll find a more appropriate place for it then.
>> > > It just seemed like such generic information which would belong next
>> > > to meminfo/zoneinfo and such...
>> >
>> > Save yourself a cycle of "rework the whole fs interface only to have
>> > someone else tell you no" and put it in debugfs, not sysfs.  Wrangling
>> > with debugfs is easier than all the macro-happy sysfs stuff; you don't
>> > have to integrate with the "device" model; and there is no 'one value
>> > per file' rule.
>> 
>> Thanks for the input. This file used to be in debugfs but reviewers
>> felt it belonged in /proc if it's to be used in production
>> environments. Some distros (like Android) disable debugfs in
>> production.
> 
> FWIW, I agree debugfs is not right. If others feel it's right in /proc,
> I certainly won't NAK -- it's just been that we've traditionally been
> trying to avoid continuing to pollute the top-level /proc and instead
> associate new things with something in /sys.

Sysfs is really a "one value per file" thing though. /proc might be ok for a
single overview file.