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Subject[tip:timers/vdso] arm64: vdso: Build vDSO with -ffixed-x18
Commit-ID:  98cd3c3f83fbba27a6bacd75ad12e8388a61a32a
Author: Peter Collingbourne <>
AuthorDate: Fri, 21 Jun 2019 10:52:32 +0100
Committer: Thomas Gleixner <>
CommitDate: Sat, 22 Jun 2019 21:21:06 +0200

arm64: vdso: Build vDSO with -ffixed-x18

The vDSO needs to be built with x18 reserved in order to accommodate
userspace platform ABIs built on top of Linux that use the register
to carry inter-procedural state, as provided for by the AAPCS.
An example of such a platform ABI is the one that will be used by an
upcoming version of Android.

Although this change is currently a no-op due to the fact that the vDSO
is currently implemented in pure assembly on arm64, it is necessary
in order to prepare for using the generic C implementation of the vDSO.

[ tglx: Massaged changelog ]

Signed-off-by: Peter Collingbourne <>
Signed-off-by: Vincenzo Frascino <>
Signed-off-by: Thomas Gleixner <>
Tested-by: Shijith Thotton <>
Tested-by: Andre Przywara <>
Cc: Catalin Marinas <>
Cc: Will Deacon <>
Cc: Arnd Bergmann <>
Cc: Russell King <>
Cc: Ralf Baechle <>
Cc: Paul Burton <>
Cc: Daniel Lezcano <>
Cc: Mark Salyzyn <>
Cc: Shuah Khan <>
Cc: Dmitry Safonov <>
Cc: Rasmus Villemoes <>
Cc: Huw Davies <>
Cc: Mark Salyzyn <>

arch/arm64/kernel/vdso/Makefile | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
index 3acfc813e966..ec81d28aeb5d 100644
--- a/arch/arm64/kernel/vdso/Makefile
+++ b/arch/arm64/kernel/vdso/Makefile
@@ -20,7 +20,7 @@ obj-vdso := $(addprefix $(obj)/, $(obj-vdso))
ldflags-y := -shared -nostdlib --hash-style=sysv \
--build-id -n -T

-ccflags-y := -fno-common -fno-builtin -fno-stack-protector
+ccflags-y := -fno-common -fno-builtin -fno-stack-protector -ffixed-x18

VDSO_LDFLAGS := -Bsymbolic
 \ /
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