[PATCH] powerpc/security: Provide stubs for when PPC_BARRIER_NOSPEC isn't enabled

[Naveen N. Rao]

kernel test robot reported the below build error with a randconfig:
  powerpc64-linux-ld: arch/powerpc/net/bpf_jit_comp64.o:(.toc+0x0):
  undefined reference to `powerpc_security_features'

This can happen if CONFIG_PPC_BARRIER_NOSPEC is not enabled. Address
this by providing stub functions for security_ftr_enabled() and related
helpers when the config option is not enabled.

Reported-by: kernel test robot <lkp at intel.com>
Signed-off-by: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/security_features.h | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/security_features.h b/arch/powerpc/include/asm/security_features.h
index 27574f218b371f..f2b990052641a0 100644
--- a/arch/powerpc/include/asm/security_features.h
+++ b/arch/powerpc/include/asm/security_features.h
@@ -8,10 +8,6 @@
 #ifndef _ASM_POWERPC_SECURITY_FEATURES_H
 #define _ASM_POWERPC_SECURITY_FEATURES_H
 
-
-extern u64 powerpc_security_features;
-extern bool rfi_flush;
-
 /* These are bit flags */
 enum stf_barrier_type {
 	STF_BARRIER_NONE	= 0x1,
@@ -20,6 +16,10 @@ enum stf_barrier_type {
 	STF_BARRIER_SYNC_ORI	= 0x8,
 };
 
+#ifdef CONFIG_PPC_BARRIER_NOSPEC
+extern u64 powerpc_security_features;
+extern bool rfi_flush;
+
 void setup_stf_barrier(void);
 void do_stf_barrier_fixups(enum stf_barrier_type types);
 void setup_count_cache_flush(void);
@@ -45,6 +45,13 @@ enum stf_barrier_type stf_barrier_type_get(void);
 static inline enum stf_barrier_type stf_barrier_type_get(void) { return STF_BARRIER_NONE; }
 #endif
 
+#else /* CONFIG_PPC_BARRIER_NOSPEC */
+static inline void security_ftr_set(u64 feature) { }
+static inline void security_ftr_clear(u64 feature) { }
+static inline bool security_ftr_enabled(u64 feature) { return false; }
+static inline enum stf_barrier_type stf_barrier_type_get(void) { return STF_BARRIER_NONE; }
+#endif /* CONFIG_PPC_BARRIER_NOSPEC */
+
 // Features indicating support for Spectre/Meltdown mitigations
 
 // The L1-D cache can be flushed with ori r30,r30,0

base-commit: bdcf18e133f656b2c97390a594fc95e37849e682
-- 
2.34.1