[PATCH tip/core/rcu 0/3] kfree_rcu() updates for v5.12

[PATCH tip/core/rcu 0/3] kfree_rcu() updates for v5.12

[Paul E. McKenney]

Hello!

This series provides kfree_rcu() updates:

1.	Record kvfree_call_rcu() call stack for KASAN, courtesy of Zqiang.

2.	Introduce kfree_rcu() single-argument macro, courtesy of
	Uladzislau Rezki.

3.	Eliminate the __kvfree_rcu() macro, courtesy of Uladzislau Rezki.

						Thanx, Paul

------------------------------------------------------------------------

 include/linux/rcupdate.h |   40 ++++++++++++++++++----------------------
 kernel/rcu/tree.c        |    1 +
 2 files changed, 19 insertions(+), 22 deletions(-)

[PATCH tip/core/rcu 1/3] rcu: Record kvfree_call_rcu() call stack for KASAN

[paulmck]

From: Zqiang <qiang.zhang@windriver.com>

This commit adds a call to kasan_record_aux_stack() in kvfree_call_rcu()
in order to record the call stack of the code that caused the object
to be freed.  Please note that this function does not update the
allocated/freed state, which is important because RCU readers might
still be referencing this object.

Acked-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Zqiang <qiang.zhang@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/tree.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 40e5e3d..2db736c 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3498,6 +3498,7 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
 		goto unlock_return;
 	}
 
+	kasan_record_aux_stack(ptr);
 	success = kvfree_call_rcu_add_ptr_to_bulk(krcp, ptr);
 	if (!success) {
 		run_page_cache_worker(krcp);
-- 
2.9.5

[PATCH tip/core/rcu 2/3] rcu: Introduce kfree_rcu() single-argument macro

[paulmck]

From: "Uladzislau Rezki (Sony)" <urezki@gmail.com>

There is a kvfree_rcu() single argument macro that handles pointers
returned by kvmalloc(). Even though it also handles pointer returned by
kmalloc(), readability suffers.

This commit therefore updates the kfree_rcu() macro to explicitly pair
with kmalloc(), thus improving readability.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 include/linux/rcupdate.h | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index de08264..b95373e 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -851,8 +851,9 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
 
 /**
  * kfree_rcu() - kfree an object after a grace period.
- * @ptr:	pointer to kfree
- * @rhf:	the name of the struct rcu_head within the type of @ptr.
+ * @ptr: pointer to kfree for both single- and double-argument invocations.
+ * @rhf: the name of the struct rcu_head within the type of @ptr,
+ *       but only for double-argument invocations.
  *
  * Many rcu callbacks functions just call kfree() on the base structure.
  * These functions are trivial, but their size adds up, and furthermore
@@ -875,13 +876,7 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
  * The BUILD_BUG_ON check must not involve any function calls, hence the
  * checks are done in macros here.
  */
-#define kfree_rcu(ptr, rhf)						\
-do {									\
-	typeof (ptr) ___p = (ptr);					\
-									\
-	if (___p)							\
-		__kvfree_rcu(&((___p)->rhf), offsetof(typeof(*(ptr)), rhf)); \
-} while (0)
+#define kfree_rcu kvfree_rcu
 
 /**
  * kvfree_rcu() - kvfree an object after a grace period.
@@ -913,7 +908,14 @@ do {									\
 	kvfree_rcu_arg_2, kvfree_rcu_arg_1)(__VA_ARGS__)
 
 #define KVFREE_GET_MACRO(_1, _2, NAME, ...) NAME
-#define kvfree_rcu_arg_2(ptr, rhf) kfree_rcu(ptr, rhf)
+#define kvfree_rcu_arg_2(ptr, rhf)					\
+do {									\
+	typeof (ptr) ___p = (ptr);					\
+									\
+	if (___p)							\
+		__kvfree_rcu(&((___p)->rhf), offsetof(typeof(*(ptr)), rhf)); \
+} while (0)
+
 #define kvfree_rcu_arg_1(ptr)					\
 do {								\
 	typeof(ptr) ___p = (ptr);				\
-- 
2.9.5

[PATCH tip/core/rcu 3/3] rcu: Eliminate the __kvfree_rcu() macro

[paulmck]

From: "Uladzislau Rezki (Sony)" <urezki@gmail.com>

This commit open-codes the __kvfree_rcu() macro, thus saving a
few lines of code and improving readability.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 include/linux/rcupdate.h | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index b95373e..f1576cd 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -840,15 +840,6 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
  */
 #define __is_kvfree_rcu_offset(offset) ((offset) < 4096)
 
-/*
- * Helper macro for kfree_rcu() to prevent argument-expansion eyestrain.
- */
-#define __kvfree_rcu(head, offset) \
-	do { \
-		BUILD_BUG_ON(!__is_kvfree_rcu_offset(offset)); \
-		kvfree_call_rcu(head, (rcu_callback_t)(unsigned long)(offset)); \
-	} while (0)
-
 /**
  * kfree_rcu() - kfree an object after a grace period.
  * @ptr: pointer to kfree for both single- and double-argument invocations.
@@ -866,7 +857,7 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
  * Because the functions are not allowed in the low-order 4096 bytes of
  * kernel virtual memory, offsets up to 4095 bytes can be accommodated.
  * If the offset is larger than 4095 bytes, a compile-time error will
- * be generated in __kvfree_rcu(). If this error is triggered, you can
+ * be generated in kvfree_rcu_arg_2(). If this error is triggered, you can
  * either fall back to use of call_rcu() or rearrange the structure to
  * position the rcu_head structure into the first 4096 bytes.
  *
@@ -912,8 +903,11 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
 do {									\
 	typeof (ptr) ___p = (ptr);					\
 									\
-	if (___p)							\
-		__kvfree_rcu(&((___p)->rhf), offsetof(typeof(*(ptr)), rhf)); \
+	if (___p) {									\
+		BUILD_BUG_ON(!__is_kvfree_rcu_offset(offsetof(typeof(*(ptr)), rhf)));	\
+		kvfree_call_rcu(&((___p)->rhf), (rcu_callback_t)(unsigned long)		\
+			(offsetof(typeof(*(ptr)), rhf)));				\
+	}										\
 } while (0)
 
 #define kvfree_rcu_arg_1(ptr)					\
-- 
2.9.5