From: Peter Zijlstra <peterz@infradead.org>
Date: Mon, 27 Jun 2022 22:21:17 +0000
Subject: x86/retbleed: Add fine grained Kconfig knobs
Git-commit: f43b9876e857c739d407bc56df288b0ebe1a9164
Patch-mainline: v5.19-rc7
References: bsc#1114648

Do fine-grained Kconfig for all the various retbleed parts.

NOTE: if your compiler doesn't support return thunks this will
silently 'upgrade' your mitigation to IBPB, you might not like this.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>

  [ bp: just the RETPOLINE_CFLAGS changes in order to simplify a later backport. ]
---
---
 arch/x86/Makefile |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -230,10 +230,12 @@ KBUILD_AFLAGS += $(mflags-y)
 # Avoid indirect branches in kernel to deal with Spectre
 ifdef CONFIG_RETPOLINE
     RETPOLINE_CFLAGS += $(call cc-option,-mindirect-branch=thunk-extern -mindirect-branch-register)
-    RETPOLINE_CFLAGS += $(call cc-option,-mfunction-return=thunk-extern)
     KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) -DRETPOLINE
 endif
 
+RETHUNK_CFLAGS		:= -mfunction-return=thunk-extern
+RETPOLINE_CFLAGS	+= $(RETHUNK_CFLAGS)
+
 # for vdso Makefile to exclude
 export RETPOLINE_CFLAGS