[tip:x86/boot] x86/boot: Disable Clang warnings about GNU extensions

[tip-bot for Matthias Kaehlcke]

Commit-ID:  6c3b56b1973083e2bb4e87eb90ea5368455706dc
Gitweb:     https://git.kernel.org/tip/6c3b56b1973083e2bb4e87eb90ea5368455706dc
Author:     Matthias Kaehlcke <mka@xxxxxxxxxxxx>
AuthorDate: Mon, 30 Oct 2017 12:43:51 -0700
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 31 Oct 2017 10:54:30 +0100

x86/boot: Disable Clang warnings about GNU extensions

The kernel makes use of several GCC extensions, disable Clang warnings
about that in the boot code, as we already do for the rest of the kernel.

This suppresses the following warning when building with clang:

  ./include/linux/cgroup-defs.h:391:16: warning: field 'cgrp' with variable sized type 'struct cgroup' not at the end of a struct or class is a GNU extension [-Wgnu-variable-sized-type-not-at-end]
        struct cgroup cgrp;

Reported-by: Nick Desaulniers <nick.desaulniers@xxxxxxxxx>
Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
Acked-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Douglas Anderson <dianders@xxxxxxxxxxxx>
Cc: Guenter Roeck <groeck@xxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20171030194351.122090-1-mka@xxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/boot/compressed/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 8a95827..65a150a 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -35,6 +35,7 @@ KBUILD_CFLAGS += -mno-mmx -mno-sse
 KBUILD_CFLAGS += $(call cc-option,-ffreestanding)
 KBUILD_CFLAGS += $(call cc-option,-fno-stack-protector)
 KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
+KBUILD_CFLAGS += $(call cc-disable-warning, gnu)
 
 KBUILD_AFLAGS  := $(KBUILD_CFLAGS) -D__ASSEMBLY__
 GCOV_PROFILE := n