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References: <20240527094320.2653177-1-jani.nikula@intel.com>
In-Reply-To: <20240527094320.2653177-1-jani.nikula@intel.com>
From: Andy Shevchenko <andy.shevchenko@gmail.com>
Date: Mon, 27 May 2024 16:27:05 +0300
Message-ID: <CAHp75VcWXCeQo4n67cfq0VQaO-+YW-=iqKx+r4NtFfYnJBTBFA@mail.gmail.com>
Subject: Re: [PATCH 1/2] string: add mem_is_zero() helper to check if memory
 area is all zeros
To: Jani Nikula <jani.nikula@intel.com>
Cc: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, 
	intel-gfx@lists.freedesktop.org, Kees Cook <keescook@chromium.org>, 
	Andy Shevchenko <andy@kernel.org>
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On Mon, May 27, 2024 at 12:43=E2=80=AFPM Jani Nikula <jani.nikula@intel.com=
> wrote:
>
> Almost two thirds of the memchr_inv() usages check if the memory area is
> all zeros, with no interest in where in the buffer the first non-zero
> byte is located. Checking for !memchr_inv(s, 0, n) is also not very
> intuitive or discoverable. Add an explicit mem_is_zero() helper for this
> use case.

..

> +static inline bool mem_is_zero(const void *s, size_t n)
> +{
> +       return !memchr_inv(s, 0, n);
> +}

There are potential users for the 0xff check as well. Hence the
following question:
Are we going to have a new function per byte in question, or do we
come up with a common denominator, like mem_is_all_of(mem, byte)?


--=20
With Best Regards,
Andy Shevchenko