linux-kernel - [PATCH 4.9 46/63] x86/boot: Disable the address-of-packed-member compiler warning

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Message-Id: <20190225195039.338175843@linuxfoundation.org>
Date:   Mon, 25 Feb 2019 22:11:46 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Matthias Kaehlcke <mka@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Nathan Chancellor <natechancellor@...il.com>
Subject: [PATCH 4.9 46/63] x86/boot: Disable the address-of-packed-member compiler warning

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matthias Kaehlcke <mka@...omium.org>

commit 20c6c189045539d29f4854d92b7ea9c329e1edfc upstream.

The clang warning 'address-of-packed-member' is disabled for the general
kernel code, also disable it for the x86 boot code.

This suppresses a bunch of warnings like this when building with clang:

./arch/x86/include/asm/processor.h:535:30: warning: taking address of
  packed member 'sp0' of class or structure 'x86_hw_tss' may result in an
  unaligned pointer value [-Waddress-of-packed-member]
    return this_cpu_read_stable(cpu_tss.x86_tss.sp0);
                                ^~~~~~~~~~~~~~~~~~~
./arch/x86/include/asm/percpu.h:391:59: note: expanded from macro
  'this_cpu_read_stable'
    #define this_cpu_read_stable(var)       percpu_stable_op("mov", var)
                                                                    ^~~
./arch/x86/include/asm/percpu.h:228:16: note: expanded from macro
  'percpu_stable_op'
    : "p" (&(var)));
             ^~~

Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
Cc: Doug Anderson <dianders@...omium.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/20170725215053.135586-1-mka@chromium.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/boot/compressed/Makefile |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -34,6 +34,7 @@ KBUILD_CFLAGS += $(cflags-y)
 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_AFLAGS  := $(KBUILD_CFLAGS) -D__ASSEMBLY__
 GCOV_PROFILE := n