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    SubjectRe: [PATCH 1/3] retpolines: Only enable retpoline when compiler support it
    Hi,



    On Tue, Oct 30, 2018 at 3:57 PM Zhenzhong Duan
    <zhenzhong.duan@oracle.com> wrote:
    >
    > Since retpoline capable compilers are widely available, make
    > CONFIG_RETPOLINE hard depend on it.
    >
    > Change KBUILD to use CONFIG_RETPOLINE_SUPPORT to avoid conflict with
    > CONFIG_RETPOLINE which is used by kernel.
    >
    > With all that stuff, the check of RETPOLINE is changed to
    > CONFIG_RETPOLINE.
    >
    > This change is based on suggestion in https://lkml.org/lkml/2018/9/18/1016
    >
    > Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
    > Cc: Thomas Gleixner <tglx@linutronix.de>
    > Cc: Peter Zijlstra <peterz@infradead.org>
    > Cc: Borislav Petkov <bp@suse.de>
    > Cc: Daniel Borkmann <daniel@iogearbox.net>
    > Cc: David Woodhouse <dwmw@amazon.co.uk>
    > Cc: H. Peter Anvin <hpa@zytor.com>
    > Cc: Ingo Molnar <mingo@redhat.com>
    > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    > Cc: Andy Lutomirski <luto@kernel.org>
    > Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
    > Cc: Michal Marek <michal.lkml@markovi.net>
    > ---


    Instead of adding another CONFIG option,
    does it make sense to add compiler support checks
    to 'depends on' syntax ?


    config RETPOLINE
    bool "Avoid speculative indirect branches in kernel"
    depends on $(cc-option,-mindirect-branch=thunk-extern
    -mindirect-branch-register) || \
    $(cc-option,-mretpoline-external-thunk)
    default y
    select STACK_VALIDATION if HAVE_STACK_VALIDATION






    --
    Best Regards
    Masahiro Yamada

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