linux-hardening - Re: [PATCH 2/3] compiler.h: Introduce __must_be_char

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Message-ID: <20250206195658.79231973@pumpkin>
Date: Thu, 6 Feb 2025 19:56:58 +0000
From: David Laight <david.laight.linux@...il.com>
To: Kees Cook <kees@...nel.org>
Cc: Suren Baghdasaryan <surenb@...gle.com>, Kent Overstreet
 <kent.overstreet@...ux.dev>, Andy Shevchenko <andy@...nel.org>, Luc Van
 Oostenryck <luc.vanoostenryck@...il.com>, Nathan Chancellor
 <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, Bill
 Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>, Philipp
 Reisner <philipp.reisner@...bit.com>, Miguel Ojeda <ojeda@...nel.org>,
 linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
 llvm@...ts.linux.dev
Subject: Re: [PATCH 2/3] compiler.h: Introduce __must_be_char_array()

On Thu,  6 Feb 2025 10:11:29 -0800
Kees Cook <kees@...nel.org> wrote:

> In preparation for adding stricter type checking to the str/mem*()
> helpers, provide a way to check that a variable is a character array
> via __must_be_char_array().
> 
...
> +#define __is_char_array(a)	(__is_array(a) && sizeof((a)[0]) == 1)
> +#define __must_be_char_array(a)	__BUILD_BUG_ON_ZERO_MSG(!__is_char_array(a), \
> +							"must be byte array")

If you are only checking the size, perhaps __is_byte_array() would
be a better name.
(You've even used 'byte' in the error message.)

	David