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    Subject[tip:x86/boot] x86/boot: Use common BUILD_BUG_ON
    Commit-ID:  d5a1baddf1585885868cbab55989401fb97118c6
    Gitweb: https://git.kernel.org/tip/d5a1baddf1585885868cbab55989401fb97118c6
    Author: Rikard Falkeborn <rikard.falkeborn@gmail.com>
    AuthorDate: Sun, 11 Aug 2019 20:49:36 +0200
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitDate: Fri, 16 Aug 2019 14:15:50 +0200

    x86/boot: Use common BUILD_BUG_ON

    Defining BUILD_BUG_ON causes redefinition warnings when adding includes of
    include/linux/build_bug.h in files unrelated to x86/boot. For example,
    adding an include of build_bug.h to include/linux/bits.h shows the
    following warnings:

    CC arch/x86/boot/cpucheck.o
    In file included from ./include/linux/bits.h:22,
    from ./arch/x86/include/asm/msr-index.h:5,
    from arch/x86/boot/cpucheck.c:28:
    ./include/linux/build_bug.h:49: warning: "BUILD_BUG_ON" redefined
    49 | #define BUILD_BUG_ON(condition) \
    |
    In file included from arch/x86/boot/cpucheck.c:22:
    arch/x86/boot/boot.h:31: note: this is the location of the previous definition
    31 | #define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
    |

    The macro was added to boot.h in commit 62bd0337d0c4 ("Top header file for
    new x86 setup code"). At that time, BUILD_BUG_ON was defined in
    kernel.h. Presumably BUILD_BUG_ON was redefined to avoid pulling in
    kernel.h. Since then, BUILD_BUG_ON and similar macros have been split to a
    separate header file.

    Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Reviewed-by: Kees Cook <keescook@chromium.org>
    Link: https://lkml.kernel.org/r/20190811184938.1796-2-rikard.falkeborn@gmail.com


    ---
    arch/x86/boot/boot.h | 2 --
    arch/x86/boot/main.c | 1 +
    2 files changed, 1 insertion(+), 2 deletions(-)

    diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h
    index 19eca14b49a0..ca866f1cca2e 100644
    --- a/arch/x86/boot/boot.h
    +++ b/arch/x86/boot/boot.h
    @@ -28,8 +28,6 @@
    #include "cpuflags.h"

    /* Useful macros */
    -#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
    -
    #define ARRAY_SIZE(x) (sizeof(x) / sizeof(*(x)))

    extern struct setup_header hdr;
    diff --git a/arch/x86/boot/main.c b/arch/x86/boot/main.c
    index 996df3d586f0..e3add857c2c9 100644
    --- a/arch/x86/boot/main.c
    +++ b/arch/x86/boot/main.c
    @@ -10,6 +10,7 @@
    /*
    * Main module for the real-mode kernel code
    */
    +#include <linux/build_bug.h>

    #include "boot.h"
    #include "string.h"
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