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

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Date: Tue, 13 Feb 2024 14:38:16 -0800
From: Kees Cook <keescook@...omium.org>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: "Darrick J. Wong" <djwong@...nel.org>, akpm@...ux-foundation.org,
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Subject: Re: [PATCH v3 13/35] lib: add allocation tagging support for memory
 allocation profiling

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.

-- 
Kees Cook