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    Subject[tip: x86/core] x86/ibt: Add ANNOTATE_NOENDBR
    The following commit has been merged into the x86/core branch of tip:

    Commit-ID: 34963d5e9be5911d93d4a543aa1d07e719599371
    Gitweb: https://git.kernel.org/tip/34963d5e9be5911d93d4a543aa1d07e719599371
    Author: Peter Zijlstra <peterz@infradead.org>
    AuthorDate: Tue, 08 Mar 2022 16:30:18 +01:00
    Committer: Peter Zijlstra <peterz@infradead.org>
    CommitterDate: Tue, 08 Mar 2022 23:53:28 +01:00

    x86/ibt: Add ANNOTATE_NOENDBR

    In order to have objtool warn about code references to !ENDBR
    instruction, we need an annotation to allow this for non-control-flow
    instances -- consider text range checks, text patching, or return
    trampolines etc.

    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Reviewed-by: Kees Cook <keescook@chromium.org>
    Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
    Link: https://lore.kernel.org/r/20220308154317.578968224@infradead.org
    ---
    include/linux/objtool.h | 16 ++++++++++++++++
    tools/include/linux/objtool.h | 16 ++++++++++++++++
    2 files changed, 32 insertions(+)

    diff --git a/include/linux/objtool.h b/include/linux/objtool.h
    index aca52db..f797368 100644
    --- a/include/linux/objtool.h
    +++ b/include/linux/objtool.h
    @@ -77,6 +77,12 @@ struct unwind_hint {
    #define STACK_FRAME_NON_STANDARD_FP(func)
    #endif

    +#define ANNOTATE_NOENDBR \
    + "986: \n\t" \
    + ".pushsection .discard.noendbr\n\t" \
    + _ASM_PTR " 986b\n\t" \
    + ".popsection\n\t"
    +
    #else /* __ASSEMBLY__ */

    /*
    @@ -129,6 +135,13 @@ struct unwind_hint {
    .popsection
    .endm

    +.macro ANNOTATE_NOENDBR
    +.Lhere_\@:
    + .pushsection .discard.noendbr
    + .quad .Lhere_\@
    + .popsection
    +.endm
    +
    #endif /* __ASSEMBLY__ */

    #else /* !CONFIG_STACK_VALIDATION */
    @@ -139,12 +152,15 @@ struct unwind_hint {
    "\n\t"
    #define STACK_FRAME_NON_STANDARD(func)
    #define STACK_FRAME_NON_STANDARD_FP(func)
    +#define ANNOTATE_NOENDBR
    #else
    #define ANNOTATE_INTRA_FUNCTION_CALL
    .macro UNWIND_HINT sp_reg:req sp_offset=0 type:req end=0
    .endm
    .macro STACK_FRAME_NON_STANDARD func:req
    .endm
    +.macro ANNOTATE_NOENDBR
    +.endm
    #endif

    #endif /* CONFIG_STACK_VALIDATION */
    diff --git a/tools/include/linux/objtool.h b/tools/include/linux/objtool.h
    index aca52db..f797368 100644
    --- a/tools/include/linux/objtool.h
    +++ b/tools/include/linux/objtool.h
    @@ -77,6 +77,12 @@ struct unwind_hint {
    #define STACK_FRAME_NON_STANDARD_FP(func)
    #endif

    +#define ANNOTATE_NOENDBR \
    + "986: \n\t" \
    + ".pushsection .discard.noendbr\n\t" \
    + _ASM_PTR " 986b\n\t" \
    + ".popsection\n\t"
    +
    #else /* __ASSEMBLY__ */

    /*
    @@ -129,6 +135,13 @@ struct unwind_hint {
    .popsection
    .endm

    +.macro ANNOTATE_NOENDBR
    +.Lhere_\@:
    + .pushsection .discard.noendbr
    + .quad .Lhere_\@
    + .popsection
    +.endm
    +
    #endif /* __ASSEMBLY__ */

    #else /* !CONFIG_STACK_VALIDATION */
    @@ -139,12 +152,15 @@ struct unwind_hint {
    "\n\t"
    #define STACK_FRAME_NON_STANDARD(func)
    #define STACK_FRAME_NON_STANDARD_FP(func)
    +#define ANNOTATE_NOENDBR
    #else
    #define ANNOTATE_INTRA_FUNCTION_CALL
    .macro UNWIND_HINT sp_reg:req sp_offset=0 type:req end=0
    .endm
    .macro STACK_FRAME_NON_STANDARD func:req
    .endm
    +.macro ANNOTATE_NOENDBR
    +.endm
    #endif

    #endif /* CONFIG_STACK_VALIDATION */
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