linux-kernel - [PATCH] efi/libstub: Indicate clang the relocation mode for arm64

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Date:   Tue,  9 May 2017 12:36:12 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Matt Fleming <matt@...eblueprint.co.uk>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Grant Grundler <grundler@...omium.org>,
        Greg Hackmann <ghackmann@...gle.com>,
        Michael Davidson <md@...gle.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        Bernhard Rosenkränzer 
        <Bernhard.Rosenkranzer@...aro.org>
Subject: [PATCH] efi/libstub: Indicate clang the relocation mode for arm64

From: Greg Hackmann <ghackmann@...gle.com>

Without any extra guidance, clang will generate libstub with either
absolute or relative ELF relocations. Use the right combination of
-fpic and -fno-pic on different files to avoid this.

Signed-off-by: Greg Hackmann <ghackmann@...gle.com>
Signed-off-by: Bernhard Rosenkränzer <Bernhard.Rosenkranzer@...aro.org>
Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
---
 drivers/firmware/efi/libstub/Makefile | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index f7425960f6a5..ccbaaf4d8650 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -11,6 +11,9 @@ cflags-$(CONFIG_X86)		+= -m$(BITS) -D__KERNEL__ -O2 \
 				   -mno-mmx -mno-sse
 
 cflags-$(CONFIG_ARM64)		:= $(subst -pg,,$(KBUILD_CFLAGS))
+ifeq ($(cc-name),clang)
+cflags-$(CONFIG_ARM64)		+= -fpic
+endif
 cflags-$(CONFIG_ARM)		:= $(subst -pg,,$(KBUILD_CFLAGS)) \
 				   -fno-builtin -fpic -mno-single-pic-base
 
@@ -38,6 +41,9 @@ $(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
 
 lib-$(CONFIG_EFI_ARMSTUB)	+= arm-stub.o fdt.o string.o random.o \
 				   $(patsubst %.c,lib-%.o,$(arm-deps))
+ifeq ($(cc-name),clang)
+CFLAGS_arm64-stub.o            += -fno-pic
+endif
 
 lib-$(CONFIG_ARM)		+= arm32-stub.o
 lib-$(CONFIG_ARM64)		+= arm64-stub.o
-- 
2.13.0.rc2.291.g57267f2277-goog