From 53727072385d3e9327e2f7c466b49078b09286ae Mon Sep 17 00:00:00 2001
From: Sedat Dilek <sedat.dilek@credativ.de>
Date: Thu, 3 Jan 2019 15:03:12 +0100
Subject: [PATCH] x86: Workaround clang does not support asm-goto

Only warn once that Clang does not support asm-goto (see LLVM bug #9295).

Avoid and thus reduce warnings by adding '-D__BPF_TRACING__' argument to KBUILD_CFLAGS where needed (inspired by [1]).

Testing: The patch "jump_label: move 'asm goto' support test to Kconfig" from [2].

[1] https://github.com/ClangBuiltLinux/continuous-integration/blob/master/patches/linux/x86_64/0001-DO-NOT-UPSTREAM-x86-Avoid-warnings-errors-due-to-lac.patch
[2] https://lore.kernel.org/patchwork/patch/1028282/
[3] https://github.com/ClangBuiltLinux/linux/issues/6

---
 arch/x86/Makefile                     | 5 +++--
 arch/x86/boot/compressed/Makefile     | 4 ++++
 arch/x86/include/asm/cpufeature.h     | 8 --------
 drivers/firmware/efi/libstub/Makefile | 4 ++++
 4 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 9c5a67d1b9c1..ba8ee0de0397 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -290,8 +290,9 @@ vdso_install:
 archprepare: checkbin
 checkbin:
 ifndef CONFIG_CC_HAS_ASM_GOTO
-	@echo Compiler lacks asm-goto support.
-	@exit 1
+	@echo Warning: Compiler lacks asm-goto support.
+	@exit 0
+KBUILD_CFLAGS += -D__BPF_TRACING__
 endif
 ifdef CONFIG_RETPOLINE
 ifeq ($(RETPOLINE_CFLAGS),)
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 466f66c8a7f8..bc8991fede60 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -39,6 +39,10 @@ KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
 KBUILD_CFLAGS += $(call cc-disable-warning, gnu)
 KBUILD_CFLAGS += -Wno-pointer-sign
 
+ifndef CONFIG_CC_HAS_ASM_GOTO
+KBUILD_CFLAGS += -D__BPF_TRACING__
+endif
+
 KBUILD_AFLAGS  := $(KBUILD_CFLAGS) -D__ASSEMBLY__
 GCOV_PROFILE := n
 UBSAN_SANITIZE :=n
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index ce95b8cbd229..4774fafee82b 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -142,14 +142,6 @@ extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit);
 
 #if defined(__clang__) && !defined(CONFIG_CC_HAS_ASM_GOTO)
 
-/*
- * Workaround for the sake of BPF compilation which utilizes kernel
- * headers, but clang does not support ASM GOTO and fails the build.
- */
-#ifndef __BPF_TRACING__
-#warning "Compiler lacks ASM_GOTO support. Add -D __BPF_TRACING__ to your compiler arguments"
-#endif
-
 #define static_cpu_has(bit)            boot_cpu_has(bit)
 
 #else
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index d9845099635e..68ff33dc075d 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -24,6 +24,10 @@ cflags-$(CONFIG_ARM)		:= $(subst -pg,,$(KBUILD_CFLAGS)) \
 
 cflags-$(CONFIG_EFI_ARMSTUB)	+= -I$(srctree)/scripts/dtc/libfdt
 
+ifndef CONFIG_CC_HAS_ASM_GOTO
+cflags-$(CONFIG_X86)		+= -D__BPF_TRACING__
+endif
+
 KBUILD_CFLAGS			:= $(cflags-y) -DDISABLE_BRANCH_PROFILING \
 				   -D__NO_FORTIFY \
 				   $(call cc-option,-ffreestanding) \
-- 
2.20.1