linux-kernel - Re: [PATCH v4 1/2] compiler_types: Introduce __flex

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Message-ID: <202503151133.3FCFCB70@keescook>
Date: Sat, 15 Mar 2025 11:34:28 -0700
From: Kees Cook <kees@...nel.org>
To: Randy Dunlap <rdunlap@...radead.org>
Cc: Vlastimil Babka <vbabka@...e.cz>, Miguel Ojeda <ojeda@...nel.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Marco Elver <elver@...gle.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	linux-hardening@...r.kernel.org, Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Hyeonggon Yoo <42.hyeyoo@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>, Jann Horn <jannh@...gle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sasha Levin <sashal@...nel.org>, Jonathan Corbet <corbet@....net>,
	Jakub Kicinski <kuba@...nel.org>,
	Yafang Shao <laoar.shao@...il.com>,
	Tony Ambardar <tony.ambardar@...il.com>,
	Alexander Lobakin <aleksander.lobakin@...el.com>,
	Jan Hendrik Farr <kernel@...rr.cc>,
	Alexander Potapenko <glider@...gle.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-doc@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH v4 1/2] compiler_types: Introduce __flex_counter() and
 family

On Fri, Mar 14, 2025 at 09:53:41PM -0700, Randy Dunlap wrote:
> Hi Kees,
> 
> 
> On 3/14/25 8:15 PM, Kees Cook wrote:
> 
> 
> > diff --git a/include/linux/overflow.h b/include/linux/overflow.h
> > index 0c7e3dcfe867..e2b81cb5576e 100644
> > --- a/include/linux/overflow.h
> > +++ b/include/linux/overflow.h
> > @@ -440,4 +440,40 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend)
> >  #define DEFINE_FLEX(TYPE, NAME, MEMBER, COUNTER, COUNT)	\
> >  	_DEFINE_FLEX(TYPE, NAME, MEMBER, COUNT, = { .obj.COUNTER = COUNT, })
> >  
> > +/**
> > + * typeof_flex_counter() - Return the type of the counter variable of a given
> > + *                         flexible array member annotated by __counted_by().
> > + * @FAM: Pointer to the flexible array member within a given struct.
> > + *
> > + * Returns "size_t" if no annotation exists.
> 
> Please use
>  * Returns: <text>
> instead so that kernel-doc can make a special doc section for it.

Ah! Thanks -- I hadn't realized that the ":" induced special sections. I
think I have a bunch of other kern-doc clean-ups to do as well.

> 
> Same for patch 2/2.
> 
> > + */
> > +#define typeof_flex_counter(FAM)				\
> > +	typeof(_Generic(__flex_counter(FAM),			\
> > +			void *: (size_t)0,			\
> > +			default: *__flex_counter(FAM)))
> > +
> > +/** can_set_flex_counter() - Check if the counter associated with the given
> 
> Needs a newline between /** and the function name, as in set_flex_counter() below.

Whoops, thanks!

-Kees

-- 
Kees Cook