linux-kernel - [PATCH RFC 08/24] lockdep: Annotate lockdep assertions for capability analysis

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Message-ID: <20250206181711.1902989-9-elver@google.com>
Date: Thu,  6 Feb 2025 19:10:02 +0100
From: Marco Elver <elver@...gle.com>
To: elver@...gle.com
Cc: "Paul E. McKenney" <paulmck@...nel.org>, Alexander Potapenko <glider@...gle.com>, 
	Bart Van Assche <bvanassche@....org>, Bill Wendling <morbo@...gle.com>, Boqun Feng <boqun.feng@...il.com>, 
	Dmitry Vyukov <dvyukov@...gle.com>, Frederic Weisbecker <frederic@...nel.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Ingo Molnar <mingo@...nel.org>, 
	Jann Horn <jannh@...gle.com>, Joel Fernandes <joel@...lfernandes.org>, 
	Jonathan Corbet <corbet@....net>, Josh Triplett <josh@...htriplett.org>, 
	Justin Stitt <justinstitt@...gle.com>, Kees Cook <kees@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
	Miguel Ojeda <ojeda@...nel.org>, Nathan Chancellor <nathan@...nel.org>, 
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, 
	Peter Zijlstra <peterz@...radead.org>, Steven Rostedt <rostedt@...dmis.org>, 
	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
Subject: [PATCH RFC 08/24] lockdep: Annotate lockdep assertions for capability analysis

Clang's capability analysis can be made aware of functions that assert
that capabilities/locks are held.

Presence of these annotations causes the analysis to assume the
capability is held after calls to the annotated function, and avoid
false positives with complex control-flow; for example, where not all
control-flow paths in a function require a held lock, and therefore
marking the function with __must_hold(..) is inappropriate.

Signed-off-by: Marco Elver <elver@...gle.com>
---
 include/linux/lockdep.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 67964dc4db95..5cea929b2219 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -282,16 +282,16 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
 	do { WARN_ON_ONCE(debug_locks && !(cond)); } while (0)
 
 #define lockdep_assert_held(l)		\
-	lockdep_assert(lockdep_is_held(l) != LOCK_STATE_NOT_HELD)
+	do { lockdep_assert(lockdep_is_held(l) != LOCK_STATE_NOT_HELD); __assert_cap(l); } while (0)
 
 #define lockdep_assert_not_held(l)	\
 	lockdep_assert(lockdep_is_held(l) != LOCK_STATE_HELD)
 
 #define lockdep_assert_held_write(l)	\
-	lockdep_assert(lockdep_is_held_type(l, 0))
+	do { lockdep_assert(lockdep_is_held_type(l, 0)); __assert_cap(l); } while (0)
 
 #define lockdep_assert_held_read(l)	\
-	lockdep_assert(lockdep_is_held_type(l, 1))
+	do { lockdep_assert(lockdep_is_held_type(l, 1)); __assert_shared_cap(l); } while (0)
 
 #define lockdep_assert_held_once(l)		\
 	lockdep_assert_once(lockdep_is_held(l) != LOCK_STATE_NOT_HELD)
@@ -389,10 +389,10 @@ extern int lockdep_is_held(const void *);
 #define lockdep_assert(c)			do { } while (0)
 #define lockdep_assert_once(c)			do { } while (0)
 
-#define lockdep_assert_held(l)			do { (void)(l); } while (0)
+#define lockdep_assert_held(l)			__assert_cap(l)
 #define lockdep_assert_not_held(l)		do { (void)(l); } while (0)
-#define lockdep_assert_held_write(l)		do { (void)(l); } while (0)
-#define lockdep_assert_held_read(l)		do { (void)(l); } while (0)
+#define lockdep_assert_held_write(l)		__assert_cap(l)
+#define lockdep_assert_held_read(l)		__assert_shared_cap(l)
 #define lockdep_assert_held_once(l)		do { (void)(l); } while (0)
 #define lockdep_assert_none_held_once()	do { } while (0)
 
-- 
2.48.1.502.g6dc24dfdaf-goog