From: Peter Collingbourne <[email protected]> The vDSO needs to be build 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 another change [1] that will add C code to the vDSO. [1] https://patchwork.kernel.org/patch/10044501/ Signed-off-by: Peter Collingbourne <[email protected]> Signed-off-by: Vincenzo Frascino <[email protected]> Cc: Mark Salyzyn <[email protected]> Cc: Will Deacon <[email protected]> Cc: [email protected] --- 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 00bcfd2672cf..d98230f70caf 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 -soname=linux-vdso.so.1 --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 ccflags-y += -DDISABLE_BRANCH_PROFILING VDSO_LDFLAGS := -Bsymbolic -- 2.21.0
