linux-hardening - Re: [PATCH] docs: Explain the desired position of function attributes

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Date:   Fri, 24 Sep 2021 13:27:20 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Kees Cook <keescook@...omium.org>, Jonathan Corbet <corbet@....net>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Joe Perches <joe@...ches.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH] docs: Explain the desired position of function attributes

On 9/24/21 1:23 PM, Kees Cook wrote:
> While discussing how to format the addition of various function
> attributes, some "unwritten rules" of ordering surfaced[1]. Capture a
> synthesized version of Linus's, Joe's, and Rasmus's recommendations on
> this subject for future reference.
> 
> [1] https://lore.kernel.org/mm-commits/CAHk-=wiOCLRny5aifWNhr621kYrJwhfURsa0vFPeUEm8mF0ufg@mail.gmail.com
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>   Documentation/process/coding-style.rst | 27 ++++++++++++++++++++++++++
>   1 file changed, 27 insertions(+)
> 
> diff --git a/Documentation/process/coding-style.rst b/Documentation/process/coding-style.rst
> index 42969ab37b34..3559c34a9281 100644
> --- a/Documentation/process/coding-style.rst
> +++ b/Documentation/process/coding-style.rst
> @@ -487,6 +487,33 @@ because it is a simple way to add valuable information for the reader.
>   Do not use the ``extern`` keyword with function prototypes as this makes
>   lines longer and isn't strictly necessary.
>   
> +When writing a function prototype, please keep the `order of elements regular
> +<https://lore.kernel.org/mm-commits/CAHk-=wiOCLRny5aifWNhr621kYrJwhfURsa0vFPeUEm8mF0ufg@mail.gmail.com>`_. For example::
> +
> +	__must_check __printf(4, 5) __malloc __init
> +	static __always_inline void *action(enum magic value, size_t size,
> +					    u8 count, char *fmt, ...)
> +	{
> +		...
> +	}
> +
> +The preferred order of elements for a function prototype is:
> +
> +- attributes on the preceding lines
> +

I thought that idea was already nacked: (it's more of a BSD thing AFAIK)
(and I would NAK it if I could :)

"""
> Attributes should be on their own line, they can be quite lengthy.

No, no no. They really shouldn't.
""

from: https://lore.kernel.org/mm-commits/CAHk-=wjS-Jg7sGMwUPpDsjv392nDOOs0CtUtVkp=S6Q7JzFJRw@mail.gmail.com/

> +  - return type attributes (here, ``__must_check``)
> +  - function parameter attributes (here, ``__printf(4,5)``)
> +  - function behavior attributes (here, ``__malloc``)
> +  - storage class attributes (here, ``__init``)
> +
> +- main function prototype on the next lines
> +
> +  - storage class (here, ``static __always_inline`` -- even though
> +    ``__always_inline`` is technically an attribute, it is treated like
> +    ``inline``)
> +  - return type (here, ``void *``)
> +  - function name (here, ``action``)
> +  - function parameters (as described earlier: each with type and name)
>   
>   7) Centralized exiting of functions
>   -----------------------------------
> 


-- 
~Randy