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    Subject[PATCH 4.19 44/44] x86/build: Fix compiler support check for CONFIG_RETPOLINE
    Date
    4.19-stable review patch.  If anyone has any objections, please let me know.

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

    From: Masahiro Yamada <yamada.masahiro@socionext.com>

    commit 25896d073d8a0403b07e6dec56f58e6c33678207 upstream.

    It is troublesome to add a diagnostic like this to the Makefile
    parse stage because the top-level Makefile could be parsed with
    a stale include/config/auto.conf.

    Once you are hit by the error about non-retpoline compiler, the
    compilation still breaks even after disabling CONFIG_RETPOLINE.

    The easiest fix is to move this check to the "archprepare" like
    this commit did:

    829fe4aa9ac1 ("x86: Allow generating user-space headers without a compiler")

    Reported-by: Meelis Roos <mroos@linux.ee>
    Tested-by: Meelis Roos <mroos@linux.ee>
    Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
    Acked-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Zhenzhong Duan <zhenzhong.duan@oracle.com>
    Fixes: 4cd24de3a098 ("x86/retpoline: Make CONFIG_RETPOLINE depend on compiler support")
    Link: http://lkml.kernel.org/r/1543991239-18476-1-git-send-email-yamada.masahiro@socionext.com
    Link: https://lkml.org/lkml/2018/12/4/206
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    Cc: Gi-Oh Kim <gi-oh.kim@cloud.ionos.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/Makefile | 10 +++++++---
    1 file changed, 7 insertions(+), 3 deletions(-)

    --- a/arch/x86/Makefile
    +++ b/arch/x86/Makefile
    @@ -223,9 +223,6 @@ KBUILD_CFLAGS += -fno-asynchronous-unwin

    # Avoid indirect branches in kernel to deal with Spectre
    ifdef CONFIG_RETPOLINE
    -ifeq ($(RETPOLINE_CFLAGS),)
    - $(error You are building kernel with non-retpoline compiler, please update your compiler.)
    -endif
    KBUILD_CFLAGS += $(RETPOLINE_CFLAGS)
    endif

    @@ -303,6 +300,13 @@ ifndef CC_HAVE_ASM_GOTO
    @echo Compiler lacks asm-goto support.
    @exit 1
    endif
    +ifdef CONFIG_RETPOLINE
    +ifeq ($(RETPOLINE_CFLAGS),)
    + @echo "You are building kernel with non-retpoline compiler." >&2
    + @echo "Please update your compiler." >&2
    + @false
    +endif
    +endif

    archclean:
    $(Q)rm -rf $(objtree)/arch/i386

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