Commit 2e549b2e authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Thomas Gleixner
Browse files

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 76b04384 ("x86/retpoline: Add initial retpoline support")
Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarMatt 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
parent f19f5c49

Makefile

+4 −0
Original line number Diff line number Diff line
@@ -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)

arch/x86/entry/vdso/Makefile

+4 −2
Original line number Diff line number Diff line
@@ -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 \

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