Re: [PATCH 0/7] objtool: retpoline validation

[Peter Zijlstra]

On Thu, Feb 01, 2018 at 04:32:35PM +0100, Peter Zijlstra wrote:
> On Thu, Feb 01, 2018 at 09:28:56AM -0600, Josh Poimboeuf wrote:
> > On Thu, Feb 01, 2018 at 03:34:21PM +0100, Peter Zijlstra wrote:
> > > There are the retpoline validation patches; they work with the __noretpoline
> > > thing from David.
> > 
> > Have you run this through 0-day bot yet? 
> 
> Yes, it complains a _lot_ because no retpoline supported compiler.

I think I finally got something that works there... Damn I hate
makefiles..


--- a/Makefile
+++ b/Makefile
@@ -486,6 +486,11 @@ KBUILD_CFLAGS += $(CLANG_TARGET) $(CLANG
 KBUILD_AFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC)
 endif
 
+ifneq ($(call cc-option,-mindirect-branch=thunk-extern -mindirect-branch-register),)
+  CC_HAS_RETPOLINE := 1
+endif
+export CC_HAS_RETPOLINE
+
 ifeq ($(config-targets),1)
 # ===========================================================================
 # *config targets only - make sure prerequisites are updated, and descend
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -267,8 +267,10 @@ else
 objtool_args += $(call cc-ifversion, -lt, 0405, --no-unreachable)
 endif
 ifdef CONFIG_RETPOLINE
+ifdef CC_HAS_RETPOLINE
   objtool_args += --retpoline
 endif
+endif
 
 
 ifdef CONFIG_MODVERSIONS