linux-kernel - [PATCH 04/11] efi/libstub: arm: support building with clang

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Message-Id: <20180927085039.8391-5-ard.biesheuvel@linaro.org>
Date:   Thu, 27 Sep 2018 10:50:31 +0200
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-efi@...r.kernel.org, Aaron Ma <aaron.ma@...onical.com>,
        Alistair Strachan <astrachan@...gle.com>,
        Ben Hutchings <ben@...adent.org.uk>,
        Bhupesh Sharma <bhsharma@...hat.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Ivan Hu <ivan.hu@...onical.com>,
        Jeremy Linton <jeremy.linton@....com>,
        Marc Zyngier <marc.zyngier@....com>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Peter Robinson <pbrobinson@...hat.com>,
        Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Stefan Agner <stefan@...er.ch>
Subject: [PATCH 04/11] efi/libstub: arm: support building with clang

From: Alistair Strachan <astrachan@...gle.com>

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@...gle.com>
Reviewed-by: Stefan Agner <stefan@...er.ch>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
---
 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
 
-- 
2.18.0