[PATCH 05/18] arm64: kbuild: reserve reg x18 from general allocation by the compiler

Sami Tolvanen
2019-10-18T16:12:53Z

From: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Before we can start using register x18 for a special purpose (as permitted
by the AAPCS64 ABI), we need to tell the compiler that it is off limits
for general allocation. So tag it as 'fixed', and remove the mention from
the LL/SC compiler flag override.

Link: https://patchwork.kernel.org/patch/9836881/
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
arch/arm64/Makefile | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 2c0238ce0551..1c7b276bc7c5 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -55,7 +55,7 @@ endif

KBUILD_CFLAGS += -mgeneral-regs-only $(lseinstr) $(brokengasinst) \
$(compat_vdso) $(cc_has_k_constraint)
-KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
+KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -ffixed-x18
KBUILD_CFLAGS += $(call cc-disable-warning, psabi)
KBUILD_AFLAGS += $(lseinstr) $(brokengasinst) $(compat_vdso)

--
2.23.0.866.gb869b98d4c-goog