Re: [PATCH v5 06/15] ftrace: Use an opaque type for functions not callable from C

Steven Rostedt
2021-10-13T19:20:59Z

On Wed, 13 Oct 2021 11:16:49 -0700
Sami Tolvanen <samitolvanen@google.com> wrote:

> 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);
>

Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

-- Steve