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    Subject[PATCH v5 06/15] ftrace: Use an opaque type for functions not callable from C
    From
    With CONFIG_CFI_CLANG, the compiler changes function references to
    point to the CFI jump table. As ftrace_call, ftrace_regs_call, and
    mcount_call are not called by C code, but are trampolines injected
    as calls replacing the nops at the start of functions added by the
    compiler, use DECLARE_NOT_CALLED_FROM_C to declare them.

    Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
    Tested-by: Nick Desaulniers <ndesaulniers@google.com>
    Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
    ---
    include/linux/ftrace.h | 7 ++++---
    1 file changed, 4 insertions(+), 3 deletions(-)

    diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
    index 832e65f06754..c53a00b96ba9 100644
    --- a/include/linux/ftrace.h
    +++ b/include/linux/ftrace.h
    @@ -578,9 +578,10 @@ extern void ftrace_replace_code(int enable);
    extern int ftrace_update_ftrace_func(ftrace_func_t func);
    extern void ftrace_caller(void);
    extern void ftrace_regs_caller(void);
    -extern void ftrace_call(void);
    -extern void ftrace_regs_call(void);
    -extern void mcount_call(void);
    +
    +DECLARE_NOT_CALLED_FROM_C(ftrace_call);
    +DECLARE_NOT_CALLED_FROM_C(ftrace_regs_call);
    +DECLARE_NOT_CALLED_FROM_C(mcount_call);

    void ftrace_modify_all_code(int command);

    --
    2.33.0.1079.g6e70778dc9-goog
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