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    Subject[PATCH v25 6/9] x86/vdso: Insert endbr32/endbr64 to vDSO
    Date
    From: "H.J. Lu" <hjl.tools@gmail.com>

    When Indirect Branch Tracking (IBT) is enabled, vDSO functions may be
    called indirectly, and must have ENDBR32 or ENDBR64 as the first
    instruction. The compiler must support -fcf-protection=branch so that it
    can be used to compile vDSO.

    Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
    Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Kees Cook <keescook@chromium.org>
    ---
    v24:
    - Replace CONFIG_X86_CET with CONFIG_X86_IBT to reflect splitting of shadow
    stack and ibt.

    arch/x86/entry/vdso/Makefile | 4 ++++
    1 file changed, 4 insertions(+)

    diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
    index 05c4abc2fdfd..a773a5f03b63 100644
    --- a/arch/x86/entry/vdso/Makefile
    +++ b/arch/x86/entry/vdso/Makefile
    @@ -93,6 +93,10 @@ endif

    $(vobjs): KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO) $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)

    +ifdef CONFIG_X86_IBT
    +$(vobjs) $(vobjs32): KBUILD_CFLAGS += -fcf-protection=branch
    +endif
    +
    #
    # vDSO code runs in userspace and -pg doesn't help with profiling anyway.
    #
    --
    2.21.0
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