From mboxrd@z Thu Jan 1 00:00:00 1970 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 CC81F311976 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=M7adCXYBRMPvGgo1RFed7VfAKTocTfh/Tr1Q0Vtj/REu3hYIGmMTEAw+OSPvCnWJBQ8Mx/A4PN1SBJmplAOCs5uRjKjGdHcvEg7IaQF2yjVWxJkWKr2C1H8xv8zbPfl/U/MCTKx3gd+e3UnBjqcrxba5h03aiAW2UiAgtPIl6Qc= 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=TzoJMG2n; 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="TzoJMG2n" Received: by mail-wr1-f73.google.com with SMTP id ffacd0b85a97d-3eb0a50a518so475567f8f.3 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=lists.linux.dev; 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=TzoJMG2nz5bd4r/NsFmT1ixbLsSq7Cmu9rkTyJpBLrBjBY1le6w4MUacAOBjrZfCT+ Ff1m6qgBp59jn4KmiexrsS0h6tDH1EhdOV6PZnHU64nj8+y8Ykg+gUYtmT/A9FM+I9FW KUBN7eVCARUWxKbPN6R50mrW90EOlJ7Eivbnwdo9fkOcjBQWZWOokSnNre7rPaP8Hsw4 Lxj3XRjBcop3b2CvztuuB2sEglJg5KueCGh1VnCDdiBn4kFcGnYg/9sOuKADUmfFsyFP D8CTfGlKynwKunYEt5aeB57b3JlN0nIe9fHyoXHWfKQxWgeEmjKfQZPrD9o8UCrIeP0v TGDw== 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=wQ5ArIWpCmab5v3N5XL6/wxSZEl+KrXpPtwbIecwjTqvp4tRBXcIq78hhsMJH250u4 O7e4kBoLMyy8SRb1AL31Pb2DGq/pHHaoJHMRfgKPr5LnmE5uRD6AyPk9wVlHpv2Cdf4s usur4u7HgRD5q/AOIqYq6EH+x9OCzrz7ggxWu+LIr4ssGLBKhST6Rt4PgHuEH5pKIbP2 M68dB/AOCc6aNXsvEwxXpQZ28+C5dOsVN9FENKoajcZbqjcTXqAnbFVWnN77SVolN6NQ 2hBNMEQ4mM+g3wp8ciseN3/fTXG+WX7wEmVPt6+YpjWijfsxbbDlcV2BjxD0POx9B3IJ xe8w== X-Forwarded-Encrypted: i=1; AJvYcCWYXgxqogwRuJN7zZMYmyjZo8hFNc4yZiDX/RFTb8Nn3/1ssIW0UGZZGHtkridn2nVqpDWG@lists.linux.dev X-Gm-Message-State: AOJu0YxFSLMwNuuPncCRLItjwf7GxWsWYnqyDozOMXL1FlB5K6Bhw8dr RJzF7LdvV4kiZdnmkCLdLaj2y7FdONqZ1zHg4m5dhlbVoycOghl0to3PcU4SVC0ZEe1vfU+HQzB z6w== 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: llvm@lists.linux.dev 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-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/Documentation/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 ~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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`. 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 @@ #include /* for cpu_relax() */ +/* + * For static capability 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 capability 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. + */ +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, unsigned long *addr) preempt_disable(); } #endif - __acquire(bitlock); + __acquire(__bitlock(bitnum, addr)); } /* * Return true if it was acquired */ static __always_inline int bit_spin_trylock(int bitnum, unsigned long *addr) + __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, unsigned long *addr) return 0; } #endif - __acquire(bitlock); + __acquire(__bitlock(bitnum, addr)); return 1; } @@ -57,6 +69,7 @@ static __always_inline int bit_spin_trylock(int bitnum, unsigned long *addr) * bit-based spin_unlock() */ static __always_inline void bit_spin_unlock(int bitnum, unsigned long *addr) + __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, unsigned long *addr) clear_bit_unlock(bitnum, addr); #endif preempt_enable(); - __release(bitlock); + __release(__bitlock(bitnum, addr)); } /* @@ -74,6 +87,7 @@ static __always_inline void bit_spin_unlock(int bitnum, unsigned long *addr) * protecting the rest of the flags in the word. */ static __always_inline void __bit_spin_unlock(int bitnum, unsigned long *addr) + __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)); } /* 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) } static inline void hlist_bl_lock(struct hlist_bl_head *b) + __acquires(__bitlock(0, b)) { bit_spin_lock(0, (unsigned long *)b); } 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. */ +#include #include #include #include @@ -251,3 +252,28 @@ static void __used test_seqlock_writer(struct test_seqlock_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); + } +} -- 2.51.0.384.g4c02a37b29-goog