Messages in this thread | | | Subject | Re: [PATCH] x86/vdso: Fix vDSO build if a retpoline is emitted | From | Matthew Rickard <> | Date | Fri, 17 Aug 2018 12:45:51 +1000 |
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On 17/08/2018 5:41 AM, Andy Lutomirski wrote: > 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. > > Cc: Matt Rickard <matt@softrans.com.au> > 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> > Fixes: commit 76b043848fd2 ("x86/retpoline: Add initial retpoline support") > Signed-off-by: Andy Lutomirski <luto@kernel.org> > --- > > This is a bit of a marginal candidate for the merge window. There are > a couple of reports of people hitting this while hacking on the vDSO, > but I haven't seen any report of anyone hitting this on a stock kernel. > > Feel free to tell me to buzz of and send it later :) > > Makefile | 4 ++++ > arch/x86/entry/vdso/Makefile | 6 ++++-- > 2 files changed, 8 insertions(+), 2 deletions(-) > > 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 \ >
That solves my issue, thanks. Acked-by: Matt Rickard <matt@softrans.com.au>
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