[SRU][F][PATCH 1/9] lockdep: Add preemption enabled/disabled assertion APIs

[Massimiliano Pellizzer]

From: "Ahmed S. Darwish" <a.darwish at linutronix.de>

Asserting that preemption is enabled or disabled is a critical sanity
check.  Developers are usually reluctant to add such a check in a
fastpath as reading the preemption count can be costly.

Extend the lockdep API with macros asserting that preemption is disabled
or enabled. If lockdep is disabled, or if the underlying architecture
does not support kernel preemption, this assert has no runtime overhead.

References: f54bb2ec02c8 ("locking/lockdep: Add IRQs disabled/enabled assertion APIs: ...")
Signed-off-by: Ahmed S. Darwish <a.darwish at linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org>
Link: https://lkml.kernel.org/r/20200720155530.1173732-8-a.darwish@linutronix.de
(cherry picked from commit 8fd8ad5c5dfcb09cf62abadd4043eaf1afbbd0ce)
CVE-2024-35887
Signed-off-by: Massimiliano Pellizzer <massimiliano.pellizzer at canonical.com>
---
 include/linux/lockdep.h | 19 +++++++++++++++++++
 lib/Kconfig.debug       |  1 +
 2 files changed, 20 insertions(+)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 410243038add..907820556316 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -655,12 +655,31 @@ do {									\
 			  "Not in hardirq as expected\n");		\
 	} while (0)
 
+#define lockdep_assert_preemption_enabled()				\
+do {									\
+	WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT)	&&		\
+		     debug_locks			&&		\
+		     (preempt_count() != 0		||		\
+		      !this_cpu_read(hardirqs_enabled)));		\
+} while (0)
+
+#define lockdep_assert_preemption_disabled()				\
+do {									\
+	WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT)	&&		\
+		     debug_locks			&&		\
+		     (preempt_count() == 0		&&		\
+		      this_cpu_read(hardirqs_enabled)));		\
+} while (0)
+
 #else
 # define might_lock(lock) do { } while (0)
 # define might_lock_read(lock) do { } while (0)
 # define lockdep_assert_irqs_enabled() do { } while (0)
 # define lockdep_assert_irqs_disabled() do { } while (0)
 # define lockdep_assert_in_irq() do { } while (0)
+
+# define lockdep_assert_preemption_enabled() do { } while (0)
+# define lockdep_assert_preemption_disabled() do { } while (0)
 #endif
 
 #ifdef CONFIG_LOCKDEP
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 6d79e7c3219c..1f06d0a7ec15 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1070,6 +1070,7 @@ config PROVE_LOCKING
 	select DEBUG_RWSEMS
 	select DEBUG_WW_MUTEX_SLOWPATH
 	select DEBUG_LOCK_ALLOC
+	select PREEMPT_COUNT if !ARCH_NO_PREEMPT
 	select TRACE_IRQFLAGS
 	default n
 	help
-- 
2.43.0