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    Subject[PATCH 4.14 137/140] objtool, retpolines: Integrate objtool with retpoline support more closely
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

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

    From: Peter Zijlstra <peterz@infradead.org>

    commit d5028ba8ee5a18c9d0bb926d883c28b370f89009 upstream.

    Disable retpoline validation in objtool if your compiler sucks, and otherwise
    select the validation stuff for CONFIG_RETPOLINE=y (most builds would already
    have it set due to ORC).

    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Acked-by: Thomas Gleixner <tglx@linutronix.de>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Arjan van de Ven <arjan@linux.intel.com>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Dan Williams <dan.j.williams@intel.com>
    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: David Woodhouse <dwmw2@infradead.org>
    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Cc: Josh Poimboeuf <jpoimboe@redhat.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    Makefile | 5 +++++
    arch/x86/Kconfig | 1 +
    arch/x86/Makefile | 10 +++-------
    scripts/Makefile.build | 2 ++
    4 files changed, 11 insertions(+), 7 deletions(-)

    --- a/Makefile
    +++ b/Makefile
    @@ -494,6 +494,11 @@ KBUILD_CFLAGS += $(CLANG_TARGET) $(CLANG
    KBUILD_AFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC)
    endif

    +RETPOLINE_CFLAGS_GCC := -mindirect-branch=thunk-extern -mindirect-branch-register
    +RETPOLINE_CFLAGS_CLANG := -mretpoline-external-thunk
    +RETPOLINE_CFLAGS := $(call cc-option,$(RETPOLINE_CFLAGS_GCC),$(call cc-option,$(RETPOLINE_CFLAGS_CLANG)))
    +export RETPOLINE_CFLAGS
    +
    ifeq ($(config-targets),1)
    # ===========================================================================
    # *config targets only - make sure prerequisites are updated, and descend
    --- a/arch/x86/Kconfig
    +++ b/arch/x86/Kconfig
    @@ -431,6 +431,7 @@ config GOLDFISH
    config RETPOLINE
    bool "Avoid speculative indirect branches in kernel"
    default y
    + select STACK_VALIDATION if HAVE_STACK_VALIDATION
    help
    Compile kernel with the retpoline compiler options to guard against
    kernel-to-user data leaks by avoiding speculative indirect
    --- a/arch/x86/Makefile
    +++ b/arch/x86/Makefile
    @@ -232,13 +232,9 @@ KBUILD_CFLAGS += -fno-asynchronous-unwin

    # Avoid indirect branches in kernel to deal with Spectre
    ifdef CONFIG_RETPOLINE
    - RETPOLINE_CFLAGS_GCC := -mindirect-branch=thunk-extern -mindirect-branch-register
    - RETPOLINE_CFLAGS_CLANG := -mretpoline-external-thunk
    -
    - RETPOLINE_CFLAGS += $(call cc-option,$(RETPOLINE_CFLAGS_GCC),$(call cc-option,$(RETPOLINE_CFLAGS_CLANG)))
    - ifneq ($(RETPOLINE_CFLAGS),)
    - KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) -DRETPOLINE
    - endif
    +ifneq ($(RETPOLINE_CFLAGS),)
    + KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) -DRETPOLINE
    +endif
    endif

    archscripts: scripts_basic
    --- a/scripts/Makefile.build
    +++ b/scripts/Makefile.build
    @@ -272,8 +272,10 @@ else
    objtool_args += $(call cc-ifversion, -lt, 0405, --no-unreachable)
    endif
    ifdef CONFIG_RETPOLINE
    +ifneq ($(RETPOLINE_CFLAGS),)
    objtool_args += --retpoline
    endif
    +endif


    ifdef CONFIG_MODVERSIONS

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