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Fri, 19 Dec 2025 13:09:59 -0800 (PST) MIME-Version: 1.0 References: <20251219154418.3592607-1-elver@google.com> <20251219154418.3592607-14-elver@google.com> <3b070057-5fda-410e-a047-d9061d56a82f@acm.org> In-Reply-To: <3b070057-5fda-410e-a047-d9061d56a82f@acm.org> From: Marco Elver Date: Fri, 19 Dec 2025 22:09:23 +0100 X-Gm-Features: AQt7F2racRCVQBtX1XHCEqHFLvRozCqLgqx9fCp_0Wp28A2qceHYZ0Bj23R_eEk Message-ID: Subject: Re: [PATCH v5 13/36] bit_spinlock: Support Clang's context analysis To: Bart Van Assche Cc: Peter Zijlstra , Boqun Feng , Ingo Molnar , Will Deacon , "David S. Miller" , Luc Van Oostenryck , Chris Li , "Paul E. McKenney" , Alexander Potapenko , Arnd Bergmann , Christoph Hellwig , Dmitry Vyukov , Eric Dumazet , Frederic Weisbecker , Greg Kroah-Hartman , Herbert Xu , Ian Rogers , Jann Horn , Joel Fernandes , Johannes Berg , Jonathan Corbet , Josh Triplett , Justin Stitt , Kees Cook , Kentaro Takeda , Lukas Bulwahn , Mark Rutland , Mathieu Desnoyers , Miguel Ojeda , Nathan Chancellor , Neeraj Upadhyay , Nick Desaulniers , Steven Rostedt , Tetsuo Handa , Thomas Gleixner , Thomas Graf , Uladzislau Rezki , Waiman Long , kasan-dev@googlegroups.com, linux-crypto@vger.kernel.org, linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, linux-sparse@vger.kernel.org, linux-wireless@vger.kernel.org, llvm@lists.linux.dev, rcu@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Queue-Id: E2C9780011 X-Rspamd-Server: rspam10 X-Stat-Signature: swbsxyi5k63gaw4z6gzqkodsrrwag3mg X-HE-Tag: 1766178600-791057 X-HE-Meta: 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 AtHGS67V 709j9UnFvc4Bhw5AuRcgSlAlUESQXjM5nDmfxeM4eBeMpMeAu1FEbgn4+Vf6VWfhXHv3aENOUkTToivdeOq4684JYUD7iE5pg6Uq0ccJ+XSxjEvAeA81en9160AdBU9Do3JOccf+3eUMSWSHYOxU4dbk3/CQ+PzX8kJP5N6kbE/wqsp1F9gDpdp7BqUkcc28J6hrjwiRdtESJ4+NCD/nRNX6KjsD4JEAX11fP7vb+B/JBqp47LLZgNev0wwursyKKXlw9nXhezKMki3cSWaNN2EBzZzV4C9Dw29Z8SRA6gDP3iuMPt/W/yRSn+BxEzzjk8TackreYuPZfMnaq+vxGxPf2V1MTYABNUWK6tmf/2FKfTdBem6ByVz3/Kg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 19 Dec 2025 at 21:48, 'Bart Van Assche' via kasan-dev wrote: > > On 12/19/25 7:40 AM, Marco Elver wrote: > > +/* > > + * For static context analysis, we need a unique token for each possible bit > > + * that can be used as a bit_spinlock. The easiest way to do that is to create a > > + * fake context that we can cast to with the __bitlock(bitnum, addr) macro > > + * below, which will give us unique instances for each (bit, addr) pair that the > > + * static analysis can use. > > + */ > > +context_lock_struct(__context_bitlock) { }; > > +#define __bitlock(bitnum, addr) (struct __context_bitlock *)(bitnum + (addr)) > > Will this cause static analyzers to complain about out-of-bounds > accesses for (bitnum + (addr)), which is equivalent to &(addr)[bitnum]? Only if they decide to interpret never-executed code (i think the kernel has various dead code that's optimized out that might trigger static analyzers if they analyzed it). But this could probably be improved by using a different idiom, and using an empty inline function that takes bitnum, addr as args, and Clang simply takes the call to that function as the context lock identity.