[PATCH v3] retpoline: Add retpoline tag to VERMAGIC

[Andi Kleen <andi@firstfloor.org>]

From: Andi Kleen <ak@linux.intel.com>

Add a marker for retpoline to the module VERMAGIC. This catches
the case when a non RETPOLINE compiled module gets loaded into
a retpoline kernel, making it insecure.

It doesn't handle the case when retpoline has been runtime disabled.
Even in this case the match of the retcompile status will be enforced.
This implies that even with retpoline run time disabled all modules
loaded need to be recompiled.

This supersedes an earlier patch that did the same checking using
a new module tag (so it's really a v3)

Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 include/linux/vermagic.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/linux/vermagic.h b/include/linux/vermagic.h
index bae807eb2933..853291714ae0 100644
--- a/include/linux/vermagic.h
+++ b/include/linux/vermagic.h
@@ -31,11 +31,17 @@
 #else
 #define MODULE_RANDSTRUCT_PLUGIN
 #endif
+#ifdef RETPOLINE
+#define MODULE_VERMAGIC_RETPOLINE "retpoline "
+#else
+#define MODULE_VERMAGIC_RETPOLINE ""
+#endif
 
 #define VERMAGIC_STRING 						\
 	UTS_RELEASE " "							\
 	MODULE_VERMAGIC_SMP MODULE_VERMAGIC_PREEMPT 			\
 	MODULE_VERMAGIC_MODULE_UNLOAD MODULE_VERMAGIC_MODVERSIONS	\
 	MODULE_ARCH_VERMAGIC						\
-	MODULE_RANDSTRUCT_PLUGIN
+	MODULE_RANDSTRUCT_PLUGIN					\
+	MODULE_VERMAGIC_RETPOLINE
 
-- 
2.14.3