linux-kernel - Re: [PATCH v2 02/34] compiler-capability-analysis: Add infrastructure for Clang's capability analysis

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Message-ID: <CANpmjNOR=EaPPhnkj+WwV8mDYNuM7fY2r_xdjORv2MGGxxH_0g@mail.gmail.com>
Date: Tue, 4 Mar 2025 17:05:34 +0100
From: Marco Elver <elver@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: "David S. Miller" <davem@...emloft.net>, Luc Van Oostenryck <luc.vanoostenryck@...il.com>, 
	"Paul E. McKenney" <paulmck@...nel.org>, Alexander Potapenko <glider@...gle.com>, Arnd Bergmann <arnd@...db.de>, 
	Bart Van Assche <bvanassche@....org>, Bill Wendling <morbo@...gle.com>, Boqun Feng <boqun.feng@...il.com>, 
	Dmitry Vyukov <dvyukov@...gle.com>, Eric Dumazet <edumazet@...gle.com>, 
	Frederic Weisbecker <frederic@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Herbert Xu <herbert@...dor.apana.org.au>, Ingo Molnar <mingo@...nel.org>, 
	Jann Horn <jannh@...gle.com>, Jiri Slaby <jirislaby@...nel.org>, 
	Joel Fernandes <joel@...lfernandes.org>, Jonathan Corbet <corbet@....net>, 
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	Kees Cook <kees@...nel.org>, Kentaro Takeda <takedakn@...data.co.jp>, 
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	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>, Steven Rostedt <rostedt@...dmis.org>, 
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>, Thomas Gleixner <tglx@...utronix.de>, 
	Uladzislau Rezki <urezki@...il.com>, Waiman Long <longman@...hat.com>, Will Deacon <will@...nel.org>, 
	kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org, 
	llvm@...ts.linux.dev, rcu@...r.kernel.org, linux-crypto@...r.kernel.org, 
	linux-serial@...r.kernel.org
Subject: Re: [PATCH v2 02/34] compiler-capability-analysis: Add infrastructure
 for Clang's capability analysis

On Tue, 4 Mar 2025 at 16:29, Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Tue, Mar 04, 2025 at 10:21:01AM +0100, Marco Elver wrote:
>
> > +# define __asserts_cap(var)                  __attribute__((assert_capability(var)))
> > +# define __asserts_shared_cap(var)           __attribute__((assert_shared_capability(var)))
>
> > +     static __always_inline void __assert_cap(const struct name *var)                                \
> > +             __attribute__((overloadable)) __asserts_cap(var) { }                                    \
> > +     static __always_inline void __assert_shared_cap(const struct name *var)                         \
> > +             __attribute__((overloadable)) __asserts_shared_cap(var) { }                             \
>
> Since this does not in fact check -- that's __must_hold(), I would
> suggest renaming these like s/assert/assume/.

Yeah, that's better.

FTR - the "asserts_capability" attribute was originally meant to be
used on runtime functions that check that a lock is held at runtime;
what Clang does underneath is simply adding the given capability/lock
to the held lockset, so no real checking is enforced. In this series
it's used for a lot more than just our lockdep_assert*() helpers, so
the "assert" naming is indeed confusing.

Thanks!