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    Subject[PATCH v2 09/12] x86/retpoline: Finally enable retpoline for C code
    Date
    From: Dave Hansen <dave.hansen@linux.intel.com>

    From: David Woodhouse <dwmw@amazon.co.uk>

    Add retpoline compile option in Makefile

    Update Makefile with retpoline compile options. This requires a gcc with the
    retpoline compiler patches enabled.

    Print a warning when the compiler doesn't support retpoline

    [Originally from David and Tim, but hacked by AK]

    v2: Use CONFIG option to enable
    Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
    Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
    ---
    arch/x86/Makefile | 11 +++++++++++
    1 file changed, 11 insertions(+)

    diff --git a/arch/x86/Makefile b/arch/x86/Makefile
    index 3e73bc255e4e..b02e35350244 100644
    --- a/arch/x86/Makefile
    +++ b/arch/x86/Makefile
    @@ -230,6 +230,17 @@ KBUILD_CFLAGS += -Wno-sign-compare
    #
    KBUILD_CFLAGS += -fno-asynchronous-unwind-tables

    +#
    +ifdef CONFIG_RETPOLINE
    + RETPOLINE_CFLAGS += $(call cc-option,-mindirect-branch=thunk-extern)
    + ifneq ($(RETPOLINE_CFLAGS),)
    + KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) -DRETPOLINE
    + KBUILD_AFLAGS += -DRETPOLINE
    + else
    + $(warning Retpoline not supported in compiler. System may be insecure.)
    + endif
    +endif
    +
    archscripts: scripts_basic
    $(Q)$(MAKE) $(build)=arch/x86/tools relocs

    --
    2.14.3
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