From: Alistair Strachan astrachan@google.com

(commit 41f1c48420709470c51ee0e54b6fb28b956bb4e0 upstream)

When building with CONFIG_EFI and CONFIG_EFI_STUB on ARM, the libstub Makefile would use -mno-single-pic-base without checking it was supported by the compiler. As the ARM (32-bit) clang backend does not support this flag, the build would fail.

This changes the Makefile to check the compiler's support for -mno-single-pic-base before using it, similar to c1c386681bd7 ("ARM: 8767/1: add support for building ARM kernel with clang").

Signed-off-by: Alistair Strachan astrachan@google.com Reviewed-by: Stefan Agner stefan@agner.ch Signed-off-by: Ard Biesheuvel ard.biesheuvel@linaro.org Signed-off-by: Nick Desaulniers ndesaulniers@google.com --- Please land in 4.19, 4.18. I'm preparing backports for 4.9 and 4.4 I will send today or tomorrow. This is for building the Linux kernel for arm32 with Clang.

drivers/firmware/efi/libstub/Makefile | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile index 14c40a7750d1..c51627660dbb 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -16,7 +16,8 @@ cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ -O2 \ cflags-$(CONFIG_ARM64) := $(subst -pg,,$(KBUILD_CFLAGS)) -fpie \ $(DISABLE_STACKLEAK_PLUGIN) cflags-$(CONFIG_ARM) := $(subst -pg,,$(KBUILD_CFLAGS)) \ - -fno-builtin -fpic -mno-single-pic-base + -fno-builtin -fpic \ + $(call cc-option,-mno-single-pic-base)

cflags-$(CONFIG_EFI_ARMSTUB) += -I$(srctree)/scripts/dtc/libfdt