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References: <20240207152317.do.560-kees@kernel.org> <20240207152422.3855315-3-keescook@chromium.org>
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From: Andy Shevchenko <andy.shevchenko@gmail.com>
Date: Wed, 7 Feb 2024 17:31:54 +0200
Message-ID: <CAHp75Vf3emnw-=it-Smb_NG+xYjWhB+U0+i1hcNPWA=BByN6nw@mail.gmail.com>
Subject: Re: [PATCH v5 3/3] overflow: Introduce wrapping_inc() and wrapping_dec()
To: Kees Cook <keescook@chromium.org>
Cc: Andy Shevchenko <andy@kernel.org>, Rasmus Villemoes <rasmus.villemoes@prevas.dk>, 
	Marco Elver <elver@google.com>, Eric Biggers <ebiggers@kernel.org>, 
	Mark Rutland <mark.rutland@arm.com>, "Gustavo A. R. Silva" <gustavoars@kernel.org>, 
	linux-hardening@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>, 
	linux-kernel@vger.kernel.org
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On Wed, Feb 7, 2024 at 5:24=E2=80=AFPM Kees Cook <keescook@chromium.org> wr=
ote:
>
> This allows replacements of the idioms "var +=3D offset" and "var -=3D of=
fset"
> with the wrapping_inc() and wrapping_dec() helpers respectively. They
> will avoid wrap-around sanitizer instrumentation.
>
> Add to the selftests to validate behavior and lack of side-effects.

I would expect inc/dec to add/subtract 1. So, to me the terminology is
confusing. The list of the C/C++ operators on Wikipedia describes
above as

+=3D Assignment by sum
-=3D Assignment by difference


Hence the proposal is to have

wrapping_sum()
wrapping_diff()

--=20
With Best Regards,
Andy Shevchenko