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Subject[PATCH 4.14 14/45] x86/vdso: Only enable vDSO retpolines when enabled and supported
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andy Lutomirski <luto@kernel.org>

commit 4f166564014aba65ad6f15b612f6711fd0f117ee upstream.

When I fixed the vDSO build to use inline retpolines, I messed up
the Makefile logic and made it unconditional. It should have
depended on CONFIG_RETPOLINE and on the availability of compiler
support. This broke the build on some older compilers.

Reported-by: nikola.ciprich@linuxbox.cz
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Rickard <matt@softrans.com.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: jason.vas.dias@gmail.com
Cc: stable@vger.kernel.org
Fixes: 2e549b2ee0e3 ("x86/vdso: Fix vDSO build if a retpoline is emitted")
Link: http://lkml.kernel.org/r/08a1f29f2c238dd1f493945e702a521f8a5aa3ae.1538540801.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/entry/vdso/Makefile | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)

--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -74,7 +74,13 @@ $(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 $(RETPOLINE_VDSO_CFLAGS)
+ -DDISABLE_BRANCH_PROFILING -DBUILD_VDSO
+
+ifdef CONFIG_RETPOLINE
+ifneq ($(RETPOLINE_VDSO_CFLAGS),)
+ CFL += $(RETPOLINE_VDSO_CFLAGS)
+endif
+endif

$(vobjs): KBUILD_CFLAGS := $(filter-out $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)

@@ -153,7 +159,13 @@ KBUILD_CFLAGS_32 += $(call cc-option, -f
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 += $(RETPOLINE_VDSO_CFLAGS)
+
+ifdef CONFIG_RETPOLINE
+ifneq ($(RETPOLINE_VDSO_CFLAGS),)
+ KBUILD_CFLAGS_32 += $(RETPOLINE_VDSO_CFLAGS)
+endif
+endif
+
$(obj)/vdso32.so.dbg: KBUILD_CFLAGS = $(KBUILD_CFLAGS_32)

$(obj)/vdso32.so.dbg: FORCE \

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