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#1178134

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. ]
---
 Makefile |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/Makefile
+++ b/Makefile
@@ -700,13 +700,15 @@ endif
 
 RETPOLINE_CFLAGS_GCC := -mindirect-branch=thunk-extern -mindirect-branch-register
 RETPOLINE_CFLAGS_GCC += $(call cc-option,-mindirect-branch-cs-prefix)
-RETPOLINE_CFLAGS_GCC += $(call cc-option,-mfunction-return=thunk-extern)
 RETPOLINE_VDSO_CFLAGS_GCC := -mindirect-branch=thunk-inline -mindirect-branch-register
 RETPOLINE_CFLAGS_CLANG := -mretpoline-external-thunk
-RETPOLINE_CFLAGS_CLANG += $(call cc-option,-mfunction-return=thunk-extern)
 RETPOLINE_VDSO_CFLAGS_CLANG := -mretpoline
 RETPOLINE_CFLAGS := $(call cc-option,$(RETPOLINE_CFLAGS_GCC),$(call cc-option,$(RETPOLINE_CFLAGS_CLANG)))
 RETPOLINE_VDSO_CFLAGS := $(call cc-option,$(RETPOLINE_VDSO_CFLAGS_GCC),$(call cc-option,$(RETPOLINE_VDSO_CFLAGS_CLANG)))
+
+RETHUNK_CFLAGS		:= -mfunction-return=thunk-extern
+RETPOLINE_CFLAGS	+= $(RETHUNK_CFLAGS)
+
 export RETPOLINE_CFLAGS
 export RETPOLINE_VDSO_CFLAGS