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 <[email protected]>
Cc: Jason Vas Dias <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Andi Kleen <[email protected]>
Fixes: commit 76b043848fd2 ("x86/retpoline: Add initial retpoline support")
Signed-off-by: Andy Lutomirski <[email protected]>
---
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 \
--
2.17.1
On Thu, 2018-08-16 at 12:41 -0700, 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 <[email protected]>
> Cc: Jason Vas Dias <[email protected]>
> Cc: David Woodhouse <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Cc: Andi Kleen <[email protected]>
> Fixes: commit 76b043848fd2 ("x86/retpoline: Add initial retpoline support")
> Signed-off-by: Andy Lutomirski <[email protected]>
Acked-by: David Woodhouse <[email protected]>
Thanks.
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 <[email protected]>
> Cc: Jason Vas Dias <[email protected]>
> Cc: David Woodhouse <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Cc: Andi Kleen <[email protected]>
> Fixes: commit 76b043848fd2 ("x86/retpoline: Add initial retpoline support")
> Signed-off-by: Andy Lutomirski <[email protected]>
> ---
>
> 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 <[email protected]>
Commit-ID: 2e549b2ee0e358bc758480e716b881f9cabedb6a
Gitweb: https://git.kernel.org/tip/2e549b2ee0e358bc758480e716b881f9cabedb6a
Author: Andy Lutomirski <[email protected]>
AuthorDate: Thu, 16 Aug 2018 12:41:15 -0700
Committer: Thomas Gleixner <[email protected]>
CommitDate: Mon, 20 Aug 2018 18:04:41 +0200
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 <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Matt Rickard <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Jason Vas Dias <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/c76538cd3afbe19c6246c2d1715bc6a60bd63985.1534448381.git.luto@kernel.org
---
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 \