From: Andy Lutomirski <luto@kernel.org>
Date: Thu, 16 Aug 2018 12:41:15 -0700
Subject: x86/vdso: Fix vDSO build if a retpoline is emitted
Git-commit: 2e549b2ee0e358bc758480e716b881f9cabedb6a
Patch-mainline: v4.19-rc1
References: bsc#1114648
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/c76538cd3afbe19c6246c2d1715bc6a60bd63985.1534448381.git.luto@kernel.org
Acked-by: Borislav Petkov <bp@suse.de>
---
Makefile | 5 +++++
arch/x86/entry/vdso/Makefile | 6 ++++--
2 files changed, 9 insertions(+), 2 deletions(-)
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -73,9 +73,9 @@ $(obj)/vdso-image-%.c: $(obj)/vdso%.so.d
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.
@@ -146,11 +146,13 @@ KBUILD_CFLAGS_32 := $(filter-out -mcmode
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 \
--- a/Makefile
+++ b/Makefile
KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
endif
+RETPOLINE_VDSO_CFLAGS_GCC := -mindirect-branch=thunk-inline -mindirect-branch-register
+RETPOLINE_VDSO_CFLAGS := $(call cc-option,$(RETPOLINE_VDSO_CFLAGS_GCC))
+export RETPOLINE_VDSO_CFLAGS
+
# Support for using generic headers in asm-generic
PHONY += asm-generic
asm-generic: