linux-hardening - Re: [RFC v3 3/7] mm: Use seprintf() instead of less ergonomic APIs

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Message-ID: <CAEHU8x9+_9VdMCp2j20hQJFTmCfD9_R8yacGg67JeQYwo3KPww@mail.gmail.com>
Date: Mon, 14 Jul 2025 08:57:17 +0100
From: Christopher Bazley <chris.bazley.wg14@...il.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Alejandro Colomar <alx@...nel.org>, linux-mm@...ck.org, linux-hardening@...r.kernel.org, 
	Kees Cook <kees@...nel.org>, shadow <~hallyn/shadow@...ts.sr.ht>, 
	linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, 
	kasan-dev@...glegroups.com, Dmitry Vyukov <dvyukov@...gle.com>, 
	Alexander Potapenko <glider@...gle.com>, Marco Elver <elver@...gle.com>, Christoph Lameter <cl@...ux.com>, 
	David Rientjes <rientjes@...gle.com>, Vlastimil Babka <vbabka@...e.cz>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Harry Yoo <harry.yoo@...cle.com>, 
	Andrew Clayton <andrew@...ital-domain.net>, Sven Schnelle <svens@...ux.ibm.com>, 
	Heiko Carstens <hca@...ux.ibm.com>, Tvrtko Ursulin <tvrtko.ursulin@...lia.com>, 
	"Huang, Ying" <ying.huang@...el.com>, Lee Schermerhorn <lee.schermerhorn@...com>, 
	Christophe JAILLET <christophe.jaillet@...adoo.fr>, Hyeonggon Yoo <42.hyeyoo@...il.com>, 
	Chao Yu <chao.yu@...o.com>
Subject: Re: [RFC v3 3/7] mm: Use seprintf() instead of less ergonomic APIs

On Sat, Jul 12, 2025 at 9:58 PM Christopher Bazley
<chris.bazley.wg14@...il.com> wrote:
>
> Hi Linus,
>
> On Mon, Jul 7, 2025 at 8:17 PM Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> >
> > On Sun, 6 Jul 2025 at 22:06, Alejandro Colomar <alx@...nel.org> wrote:
> > >
> > > -       p += snprintf(p, ID_STR_LENGTH - (p - name), "%07u", s->size);
> > > +       p = seprintf(p, e, "%07u", s->size);
> >
> > I am *really* not a fan of introducing yet another random non-standard
> > string function.
> >
> > This 'seprintf' thing really seems to be a completely made-up thing.
> > Let's not go there. It just adds more confusion - it may be a simpler
> > interface, but it's another cogniitive load thing, and honestly, that
> > "beginning and end" interface is not great.
> >
> > I think we'd be better off with real "character buffer" interfaces,
> > and they should be *named* that way, not be yet another "random
> > character added to the printf family".
>
> I was really interested to see this comment because I presented a
> design for a standard character buffer interface, "strb_t", to WG14 in
> summer of 2014.

Ugh, that should have been 2024. I'm getting old!

Chris