| 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: x86/vdso: Fix vDSO build if a retpoline is emitted |
| |
| From: Andy Lutomirski <luto@kernel.org> |
| |
| commit 2e549b2ee0e358bc758480e716b881f9cabedb6a upstream. |
| |
| 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 |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| Makefile | 4 ++++ |
| arch/x86/entry/vdso/Makefile | 6 ++++-- |
| 2 files changed, 8 insertions(+), 2 deletions(-) |
| |
| --- a/Makefile |
| +++ b/Makefile |
| @@ -490,9 +490,13 @@ KBUILD_AFLAGS += $(CLANG_TARGET) $(CLANG |
| 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 |
| |
| ifeq ($(config-targets),1) |
| # =========================================================================== |
| --- a/arch/x86/entry/vdso/Makefile |
| +++ b/arch/x86/entry/vdso/Makefile |
| @@ -74,9 +74,9 @@ $(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. |
| @@ -147,11 +147,13 @@ 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 \ |
