powerpc/security: Add a helper to query stf_barrier type

stable inclusion
from stable-5.10.80
commit 7fcf86565bb67de1118b446397b5670fc69d3f51
bugzilla: 185821 https://gitee.com/openeuler/kernel/issues/I4L7CG

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7fcf86565bb67de1118b446397b5670fc69d3f51

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

upstream commit 03090592

Add a helper to return the stf_barrier type for the current processor.
Signed-off-by: NNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/3bd5d7f96ea1547991ac2ce3137dc2b220bae285.1633464148.git.naveen.n.rao@linux.vnet.ibm.comSigned-off-by: NNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Reviewed-by: NWeilong Chen <chenweilong@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/powerpc/include/asm/security_features.h

@@ -39,6 +39,11 @@ static inline bool security_ftr_enabled(u64 feature)
 	return !!(powerpc_security_features & feature);
 }
 
+#ifdef CONFIG_PPC_BOOK3S_64
+enum stf_barrier_type stf_barrier_type_get(void);
+#else
+static inline enum stf_barrier_type stf_barrier_type_get(void) { return STF_BARRIER_NONE; }
+#endif
 
 // Features indicating support for Spectre/Meltdown mitigations
 

arch/powerpc/kernel/security.c

@@ -261,6 +261,11 @@ static int __init handle_no_stf_barrier(char *p)
 
 early_param("no_stf_barrier", handle_no_stf_barrier);
 
+enum stf_barrier_type stf_barrier_type_get(void)
+{
+	return stf_enabled_flush_types;
+}
+
 /* This is the generic flag used by other architectures */
 static int __init handle_ssbd(char *p)
 {