[tip: locking/urgent] static_call: Fix static_call_set_init()

["tip-bot2 for Peter Zijlstra" <tip-bot2@xxxxxxxxxxxxx>]

The following commit has been merged into the locking/urgent branch of tip:

Commit-ID:     68b1eddd421d2b16c6655eceb48918a1e896bbbc
Gitweb:        https://git.kernel.org/tip/68b1eddd421d2b16c6655eceb48918a1e896bbbc
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Thu, 18 Mar 2021 11:27:19 +01:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Fri, 19 Mar 2021 13:16:44 +01:00

static_call: Fix static_call_set_init()

It turns out that static_call_set_init() does not preserve the other
flags; IOW. it clears TAIL if it was set.

Fixes: 9183c3f9ed710 ("static_call: Add inline static call infrastructure")
Reported-by: Sumit Garg <sumit.garg@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
Tested-by: Sumit Garg <sumit.garg@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20210318113610.519406371@xxxxxxxxxxxxx
---
 kernel/static_call.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/kernel/static_call.c b/kernel/static_call.c
index ae82529..080c8a9 100644
--- a/kernel/static_call.c
+++ b/kernel/static_call.c
@@ -35,27 +35,30 @@ static inline void *static_call_addr(struct static_call_site *site)
 	return (void *)((long)site->addr + (long)&site->addr);
 }
 
+static inline unsigned long __static_call_key(const struct static_call_site *site)
+{
+	return (long)site->key + (long)&site->key;
+}
 
 static inline struct static_call_key *static_call_key(const struct static_call_site *site)
 {
-	return (struct static_call_key *)
-		(((long)site->key + (long)&site->key) & ~STATIC_CALL_SITE_FLAGS);
+	return (void *)(__static_call_key(site) & ~STATIC_CALL_SITE_FLAGS);
 }
 
 /* These assume the key is word-aligned. */
 static inline bool static_call_is_init(struct static_call_site *site)
 {
-	return ((long)site->key + (long)&site->key) & STATIC_CALL_SITE_INIT;
+	return __static_call_key(site) & STATIC_CALL_SITE_INIT;
 }
 
 static inline bool static_call_is_tail(struct static_call_site *site)
 {
-	return ((long)site->key + (long)&site->key) & STATIC_CALL_SITE_TAIL;
+	return __static_call_key(site) & STATIC_CALL_SITE_TAIL;
 }
 
 static inline void static_call_set_init(struct static_call_site *site)
 {
-	site->key = ((long)static_call_key(site) | STATIC_CALL_SITE_INIT) -
+	site->key = (__static_call_key(site) | STATIC_CALL_SITE_INIT) -
 		    (long)&site->key;
 }
 
@@ -190,7 +193,7 @@ void __static_call_update(struct static_call_key *key, void *tramp, void *func)
 			}
 
 			arch_static_call_transform(site_addr, NULL, func,
-				static_call_is_tail(site));
+						   static_call_is_tail(site));
 		}
 	}
 
@@ -349,7 +352,7 @@ static int static_call_add_module(struct module *mod)
 	struct static_call_site *site;
 
 	for (site = start; site != stop; site++) {
-		unsigned long s_key = (long)site->key + (long)&site->key;
+		unsigned long s_key = __static_call_key(site);
 		unsigned long addr = s_key & ~STATIC_CALL_SITE_FLAGS;
 		unsigned long key;