The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2e549b2ee0e358bc758480e716b881f9cabedb6a Mon Sep 17 00:00:00 2001

From: Andy Lutomirski luto@kernel.org Date: Thu, 16 Aug 2018 12:41:15 -0700 Subject: [PATCH] x86/vdso: Fix vDSO build if a retpoline is emitted

Currently, if the vDSO ends up containing an indirect branch or call, GCC will emit the "external thunk" style of retpoline, and it will fail to link.

Fix it by building the vDSO with inline retpoline thunks.

I haven't seen any reports of this triggering on an unpatched kernel.

Fixes: commit 76b043848fd2 ("x86/retpoline: Add initial retpoline support") Signed-off-by: Andy Lutomirski luto@kernel.org Signed-off-by: Thomas Gleixner tglx@linutronix.de Acked-by: Matt Rickard matt@softrans.com.au Cc: Borislav Petkov bp@alien8.de Cc: Jason Vas Dias jason.vas.dias@gmail.com Cc: David Woodhouse dwmw2@infradead.org Cc: Peter Zijlstra peterz@infradead.org Cc: Andi Kleen ak@linux.intel.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/c76538cd3afbe19c6246c2d1715bc6a60bd63985.153444838...

diff --git a/Makefile b/Makefile index a0650bf79606..7bab2e90e4e1 100644 --- a/Makefile +++ b/Makefile @@ -507,9 +507,13 @@ KBUILD_AFLAGS += $(call cc-option, -no-integrated-as) endif

RETPOLINE_CFLAGS_GCC := -mindirect-branch=thunk-extern -mindirect-branch-register +RETPOLINE_VDSO_CFLAGS_GCC := -mindirect-branch=thunk-inline -mindirect-branch-register RETPOLINE_CFLAGS_CLANG := -mretpoline-external-thunk +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))) export RETPOLINE_CFLAGS +export RETPOLINE_VDSO_CFLAGS

KBUILD_CFLAGS += $(call cc-option,-fno-PIE) KBUILD_AFLAGS += $(call cc-option,-fno-PIE) diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile index 9f695f517747..fa3f439f0a92 100644 --- a/arch/x86/entry/vdso/Makefile +++ b/arch/x86/entry/vdso/Makefile @@ -68,9 +68,9 @@ $(obj)/vdso-image-%.c: $(obj)/vdso%.so.dbg $(obj)/vdso%.so $(obj)/vdso2c FORCE CFL := $(PROFILING) -mcmodel=small -fPIC -O2 -fasynchronous-unwind-tables -m64 \ $(filter -g%,$(KBUILD_CFLAGS)) $(call cc-option, -fno-stack-protector) \ -fno-omit-frame-pointer -foptimize-sibling-calls \ - -DDISABLE_BRANCH_PROFILING -DBUILD_VDSO + -DDISABLE_BRANCH_PROFILING -DBUILD_VDSO $(RETPOLINE_VDSO_CFLAGS)

-$(vobjs): KBUILD_CFLAGS := $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS)) $(CFL) +$(vobjs): KBUILD_CFLAGS := $(filter-out $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)

# # vDSO code runs in userspace and -pg doesn't help with profiling anyway. @@ -132,11 +132,13 @@ KBUILD_CFLAGS_32 := $(filter-out -mcmodel=kernel,$(KBUILD_CFLAGS_32)) KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32)) KBUILD_CFLAGS_32 := $(filter-out -mfentry,$(KBUILD_CFLAGS_32)) KBUILD_CFLAGS_32 := $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS_32)) +KBUILD_CFLAGS_32 := $(filter-out $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS_32)) KBUILD_CFLAGS_32 += -m32 -msoft-float -mregparm=0 -fpic KBUILD_CFLAGS_32 += $(call cc-option, -fno-stack-protector) KBUILD_CFLAGS_32 += $(call cc-option, -foptimize-sibling-calls) KBUILD_CFLAGS_32 += -fno-omit-frame-pointer KBUILD_CFLAGS_32 += -DDISABLE_BRANCH_PROFILING +KBUILD_CFLAGS_32 += $(RETPOLINE_VDSO_CFLAGS) $(obj)/vdso32.so.dbg: KBUILD_CFLAGS = $(KBUILD_CFLAGS_32)

$(obj)/vdso32.so.dbg: FORCE \