[PATCH] 3/5: LSM hooks rework

[Kurt Garloff]

From: Kurt Garloff <garloff@xxxxxxx>
Subject: Replace indirect calls by a branch
References: 40217, 39439

In the LSM stub collection, rather do a branch than an indirect
call. Many of the functions called do only return 0 or do nothing
for the default (capability) case.
This is a fast-path optimization; a branch is faster than an
indirect call, even more so if correctly predicted.
This shows a >3% perf. increase in netperf -t TCP_RR benchmark on IA64.
(More exactly: The benchmark was taken with the next two patches
 applied as well, but I attribute the main effect to this patch.)

This is patch 3/5 of the LSM overhaul.

 include/linux/security.h |    6 +++++-
 security/security.c      |    2 --
 2 files changed, 5 insertions(+), 3 deletions(-)

Signed-off-by: Kurt Garloff <garloff@xxxxxxx>

Index: linux-2.6.10/include/linux/security.h
===================================================================
--- linux-2.6.10.orig/include/linux/security.h
+++ linux-2.6.10/include/linux/security.h
@@ -1241,17 +1241,21 @@ struct security_operations {
 };
 
 /* global variables */
 extern struct security_operations *security_ops;
+/* default security ops */
+extern struct security_operations capability_security_ops;
 
 /* prototypes */
 extern int security_init	(void);
 extern int register_security	(struct security_operations *ops);
 extern int unregister_security	(struct security_operations *ops);
 extern int mod_reg_security	(const char *name, struct security_operations *ops);
 extern int mod_unreg_security	(const char *name, struct security_operations *ops);
 
-#define COND_SECURITY(seop, def) security_ops->seop
+/* Condition for invocation of non-default security_op */
+#define COND_SECURITY(seop, def) 	\
+	(security_ops == &capability_security_ops)? def: security_ops->seop
 
 #else /* CONFIG_SECURITY */
 static inline int security_init(void)
 {
Index: linux-2.6.10/security/security.c
===================================================================
--- linux-2.6.10.orig/security/security.c
+++ linux-2.6.10/security/security.c
@@ -21,10 +21,8 @@
 #define SECURITY_FRAMEWORK_VERSION	"1.0.0"
 
 /* things that live in dummy.c */
 extern void security_fixup_ops (struct security_operations *ops);
-/* default security ops */
-extern struct security_operations capability_security_ops;
 
 struct security_operations *security_ops;	/* Initialized to NULL */
 
 static inline int verify(struct security_operations *ops)
-- 
Kurt Garloff, Director SUSE Labs, Novell Inc.

Attachment: pgp00000.pgp
Description: PGP signature