Re: [RFC] ftrace: Add support to keep some functions out of ftrace

[Steven Rostedt]

On Sat, 13 Aug 2022 15:02:52 -0400
Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:

> Index: linux-trace.git/scripts/Makefile.lib
> ===================================================================
> --- linux-trace.git.orig/scripts/Makefile.lib
> +++ linux-trace.git/scripts/Makefile.lib
> @@ -233,7 +233,8 @@ objtool_args =								\
>  	$(if $(CONFIG_HAVE_JUMP_LABEL_HACK), --hacks=jump_label)	\
>  	$(if $(CONFIG_HAVE_NOINSTR_HACK), --hacks=noinstr)		\
>  	$(if $(CONFIG_X86_KERNEL_IBT), --ibt)				\
> -	$(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount)		\
> +	$(if $(filter $(shell basename $@),$(NO_MCOUNT_FILES)),,	\
> +		$(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount))	\

I believe there's some security and other validations that objtool does
that requires it to know about the mcount locations.

If BPF is doing something unique, and modifying code as well (outside
the jump label and ftrace work), does objtool need to know about that too?

-- Steve


>  	$(if $(CONFIG_UNWINDER_ORC), --orc)				\
>  	$(if $(CONFIG_RETPOLINE), --retpoline)				\
>  	$(if $(CONFIG_SLS), --sls)					\