From nobody Thu Oct 2 10:55:49 2025 Received: from mail-wr1-f73.google.com (mail-wr1-f73.google.com [209.85.221.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CC740311972 for ; Thu, 18 Sep 2025 14:06:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.73 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758204366; cv=none; b=huHIYBophFuiLznVO3QxF2NxiXsMYJMRD65V170bff92J8klJfEFCMzlMLrgjEK1G9w+bxl8MEaTynGZhvM0r8HFN3OxKaY9W352h/uh3LJBvSDtMwPE4JtndKYwEo+9g/JtgJPwQjMrOcKMvHNWIkeXEliWPOKklTzz6m4cUTs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758204366; c=relaxed/simple; bh=Pwlqj5LHc8WIOsnrjNBXe/u+KWnz/Ub68SgGp8Ie42E=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=DPrqqRlNKoShdtEzQiuyxXCGJl1u9gaOPQNGeLxIqMFR1Q9wDuP1RA//HDmaKH6NbiDa3monYKPGl+FCLtuzRxSxwb84k1b0+0dI32Q3twLrGpkvxD5RU2Qfm4fnDVY8EbvFNWArFvLqBz5DXTdhIOsrbdbxKbu6ilpX/hNhyvM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--elver.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=QFimnFCW; arc=none smtp.client-ip=209.85.221.73 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--elver.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="QFimnFCW" Received: by mail-wr1-f73.google.com with SMTP id ffacd0b85a97d-3ee13baf21dso516616f8f.0 for ; Thu, 18 Sep 2025 07:06:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1758204362; x=1758809162; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=DCWUNblN4U9kpWEcSaN4JvbXJbXAoJAUqhw7MiIdu4A=; b=QFimnFCWQySSdksaO+lBc+3+KErAiDF6KNoqZt9IyjUMYmxbsn5KeYm89w+DqifqyT lE4S3BELD6w+hgqY2+zgmTQLrUnmBE0jufrwkozSsf4ZvKu87WnsgoZTPRHwb7ylOYly 9SyQPjEoEavP1VP/XICnMGVSbI2Rp4CFb2z2Q9ap1uBC4exBoy65a+nlp10idKcX5TlC IoF7f/Bn8lkM3wE2d0RcJ8lwQcX2eYvafU0n+ZPSqef0u8zzCmbDxPD6VGwEGl+pqsno bvWiIc6E6yPL0811ChzWK7QKFgp0i3mcTULgAlDrjoQld+8N+enwP7zxPP/0DwVU5+KW tEQQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1758204362; x=1758809162; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=DCWUNblN4U9kpWEcSaN4JvbXJbXAoJAUqhw7MiIdu4A=; b=e3fq4mkDqOV1hKjVB5AXG6Kuyg7t9+oDl40vJ62GrmxpUo3YbsaK1lo2DCwUn5obxi JvqLYSY7mbGmUx69cL1lhVe5JEzrFsmhpe+HIlfBhXXW5DoHAo/fa+Ju8yS+jd9OfNeB VJe5KFYUzfGC55mjveoZcPLN1qxfEwDjOBVoaIJYJjjQYnfXjx7fBIKhnehaoQ6OdvFK 6TVo/thg0KHAl7PV1zX5bJ2XxGxnAJxCr08BULzyuUshMCylRYiZE7M9pbsLOuCzbmBh qCB26pK+tOwyjR/th3whvUzrQHHda0eVFsyfjG3Txn0PjDMBpKMqGzsRli1YlsXzgg+U 8e1A== X-Forwarded-Encrypted: i=1; AJvYcCWPUNO4q54oiV3HEwJ66IbJ622iVh3TpV8r64rfX5LnUcMa7q/W8J2+8KAMSCXrdXoHeCMn7NrX2TzTitk=@vger.kernel.org X-Gm-Message-State: AOJu0Yz3PKFMmc1j8l/jSF1q7G0iZlDDT/vFEudpafBsrYfzVAjmFJ5y tTpGm17p6AgVWh5CiltU/ZCjDpKOFG8inUVXyCW32yadFeL7CdXVj0ly1S6mnwS4SxvTAfcrllr eUw== X-Google-Smtp-Source: AGHT+IGAFK8f67wVc7JjdjAkvlmoLrHOsH5U3beSFy9Ow5NcTVtufHzqymZVp3Tv4ibjMmj/rOVtkfQ1Iw== X-Received: from wrbbs1.prod.google.com ([2002:a05:6000:701:b0:3ec:d97e:c0bb]) (user=elver job=prod-delivery.src-stubby-dispatcher) by 2002:adf:fac7:0:b0:3ec:e285:546b with SMTP id ffacd0b85a97d-3ece285566fmr3233104f8f.50.1758204362163; Thu, 18 Sep 2025 07:06:02 -0700 (PDT) Date: Thu, 18 Sep 2025 15:59:24 +0200 In-Reply-To: <20250918140451.1289454-1-elver@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250918140451.1289454-1-elver@google.com> X-Mailer: git-send-email 2.51.0.384.g4c02a37b29-goog Message-ID: <20250918140451.1289454-14-elver@google.com> Subject: [PATCH v3 13/35] bit_spinlock: Support Clang's capability analysis From: Marco Elver To: elver@google.com, Peter Zijlstra , Boqun Feng , Ingo Molnar , Will Deacon Cc: "David S. Miller" , Luc Van Oostenryck , "Paul E. McKenney" , Alexander Potapenko , Arnd Bergmann , Bart Van Assche , Bill Wendling , Christoph Hellwig , Dmitry Vyukov , Eric Dumazet , Frederic Weisbecker , Greg Kroah-Hartman , Herbert Xu , Ian Rogers , Jann Horn , Joel Fernandes , 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, llvm@lists.linux.dev, rcu@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The annotations for bit_spinlock.h have simply been using "bitlock" as the token. For Sparse, that was likely sufficient in most cases. But Clang's capability analysis is more precise, and we need to ensure we can distinguish different bitlocks. To do so, add a token capability, and a macro __bitlock(bitnum, addr) that is used to construct unique per-bitlock tokens. Add the appropriate test. is implicitly included through other includes, and requires 2 annotations to indicate that acquisition (without release) and release (without prior acquisition) of its bitlock is intended. Signed-off-by: Marco Elver --- .../dev-tools/capability-analysis.rst | 3 ++- include/linux/bit_spinlock.h | 22 +++++++++++++--- include/linux/list_bl.h | 2 ++ lib/test_capability-analysis.c | 26 +++++++++++++++++++ 4 files changed, 48 insertions(+), 5 deletions(-) diff --git a/Documentation/dev-tools/capability-analysis.rst b/Documentatio= n/dev-tools/capability-analysis.rst index 4789de7b019a..56c6ba7205aa 100644 --- a/Documentation/dev-tools/capability-analysis.rst +++ b/Documentation/dev-tools/capability-analysis.rst @@ -81,7 +81,8 @@ Supported Kernel Primitives ~~~~~~~~~~~~~~~~~~~~~~~~~~~ =20 Currently the following synchronization primitives are supported: -`raw_spinlock_t`, `spinlock_t`, `rwlock_t`, `mutex`, `seqlock_t`. +`raw_spinlock_t`, `spinlock_t`, `rwlock_t`, `mutex`, `seqlock_t`, +`bit_spinlock`. =20 For capabilities with an initialization function (e.g., `spin_lock_init()`= ), calling this function on the capability instance before initializing any diff --git a/include/linux/bit_spinlock.h b/include/linux/bit_spinlock.h index 59e345f74b0e..ba3a67f39f0c 100644 --- a/include/linux/bit_spinlock.h +++ b/include/linux/bit_spinlock.h @@ -9,6 +9,16 @@ =20 #include /* for cpu_relax() */ =20 +/* + * For static capability analysis, we need a unique token for each possibl= e bit + * that can be used as a bit_spinlock. The easiest way to do that is to cr= eate a + * fake capability that we can cast to with the __bitlock(bitnum, addr) ma= cro + * below, which will give us unique instances for each (bit, addr) pair th= at the + * static analysis can use. + */ +struct_with_capability(__capability_bitlock) { }; +#define __bitlock(bitnum, addr) (struct __capability_bitlock *)(bitnum + (= addr)) + /* * bit-based spin_lock() * @@ -16,6 +26,7 @@ * are significantly faster. */ static __always_inline void bit_spin_lock(int bitnum, unsigned long *addr) + __acquires(__bitlock(bitnum, addr)) { /* * Assuming the lock is uncontended, this never enters @@ -34,13 +45,14 @@ static __always_inline void bit_spin_lock(int bitnum, u= nsigned long *addr) preempt_disable(); } #endif - __acquire(bitlock); + __acquire(__bitlock(bitnum, addr)); } =20 /* * Return true if it was acquired */ static __always_inline int bit_spin_trylock(int bitnum, unsigned long *add= r) + __cond_acquires(true, __bitlock(bitnum, addr)) { preempt_disable(); #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) @@ -49,7 +61,7 @@ static __always_inline int bit_spin_trylock(int bitnum, u= nsigned long *addr) return 0; } #endif - __acquire(bitlock); + __acquire(__bitlock(bitnum, addr)); return 1; } =20 @@ -57,6 +69,7 @@ static __always_inline int bit_spin_trylock(int bitnum, u= nsigned long *addr) * bit-based spin_unlock() */ static __always_inline void bit_spin_unlock(int bitnum, unsigned long *add= r) + __releases(__bitlock(bitnum, addr)) { #ifdef CONFIG_DEBUG_SPINLOCK BUG_ON(!test_bit(bitnum, addr)); @@ -65,7 +78,7 @@ static __always_inline void bit_spin_unlock(int bitnum, u= nsigned long *addr) clear_bit_unlock(bitnum, addr); #endif preempt_enable(); - __release(bitlock); + __release(__bitlock(bitnum, addr)); } =20 /* @@ -74,6 +87,7 @@ static __always_inline void bit_spin_unlock(int bitnum, u= nsigned long *addr) * protecting the rest of the flags in the word. */ static __always_inline void __bit_spin_unlock(int bitnum, unsigned long *a= ddr) + __releases(__bitlock(bitnum, addr)) { #ifdef CONFIG_DEBUG_SPINLOCK BUG_ON(!test_bit(bitnum, addr)); @@ -82,7 +96,7 @@ static __always_inline void __bit_spin_unlock(int bitnum,= unsigned long *addr) __clear_bit_unlock(bitnum, addr); #endif preempt_enable(); - __release(bitlock); + __release(__bitlock(bitnum, addr)); } =20 /* diff --git a/include/linux/list_bl.h b/include/linux/list_bl.h index ae1b541446c9..df9eebe6afca 100644 --- a/include/linux/list_bl.h +++ b/include/linux/list_bl.h @@ -144,11 +144,13 @@ static inline void hlist_bl_del_init(struct hlist_bl_= node *n) } =20 static inline void hlist_bl_lock(struct hlist_bl_head *b) + __acquires(__bitlock(0, b)) { bit_spin_lock(0, (unsigned long *)b); } =20 static inline void hlist_bl_unlock(struct hlist_bl_head *b) + __releases(__bitlock(0, b)) { __bit_spin_unlock(0, (unsigned long *)b); } diff --git a/lib/test_capability-analysis.c b/lib/test_capability-analysis.c index 74d287740bb8..ad362d5a7916 100644 --- a/lib/test_capability-analysis.c +++ b/lib/test_capability-analysis.c @@ -4,6 +4,7 @@ * positive errors when compiled with Clang's capability analysis. */ =20 +#include #include #include #include @@ -251,3 +252,28 @@ static void __used test_seqlock_writer(struct test_seq= lock_data *d) d->counter++; write_sequnlock_irqrestore(&d->sl, flags); } + +struct test_bit_spinlock_data { + unsigned long bits; + int counter __guarded_by(__bitlock(3, &bits)); +}; + +static void __used test_bit_spin_lock(struct test_bit_spinlock_data *d) +{ + /* + * Note, the analysis seems to have false negatives, because it won't + * precisely recognize the bit of the fake __bitlock() token. + */ + bit_spin_lock(3, &d->bits); + d->counter++; + bit_spin_unlock(3, &d->bits); + + bit_spin_lock(3, &d->bits); + d->counter++; + __bit_spin_unlock(3, &d->bits); + + if (bit_spin_trylock(3, &d->bits)) { + d->counter++; + bit_spin_unlock(3, &d->bits); + } +} --=20 2.51.0.384.g4c02a37b29-goog