Re: [linux-next:master 8539/9537] include/linux/ftrace.h:126:16: error: implicit declaration of function 'arch_ftrace_get_regs'; did you mean 'ftrace_get_regs'?

[Steven Rostedt <rostedt@goodmis.org>]

On Mon, 21 Nov 2022 17:26:15 +0000
Mark Rutland <mark.rutland@arm.com> wrote:

> ... and since arm64 can be built with DYNAMIC_FTRACE=n we end up with:
> 
>   CONFIG_DYNAMIC_FTRACE=n

Is there any reason to have CONFIG_DYNAMIC_FTRACE=n and
CONFIG_FUNCTION_TRACE=y?

The only reason I keep the option to turn off DYNAMIC_FTRACE is for
debugging purposes.

That is, if you have HAVE_DYNAMIC_FTRACE, then DYNAMIC_FTRACE should be
enabled whenever it is needed by something else.

The reason for static ftrace is simply to help new architectures work their
way to having DYNAMIC_FTRACE enabled. Perhaps the solution is to get rid of
the DYNAMIC_FRACE prompt, and have it set whenever FUNCTION_TRACER is set
and HAVE_DYNAMIC_FTRACE is set.

For debugging purposes, I may add

HAVE_DEBUG_DYNAMIC_FTRACE

which brings back the prompt (for x86 only).

-- Steve


>   CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS=y
>   CONFIG_DYNAMIC_FTRACE_WITH_ARGS=n
> 
> Looking at this some more, ftrace_regs_has_args() should check for
> CONFIG_DYNAMIC_FTRACE_WITH_ARGS rather than
> CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS, or it'll bogusly report we have args when
> CONFIG_DYNAMIC_FTRACE=n.
> 
> I'd prefer to change the core ftrace code to check for
> CONFIG_DYNAMIC_FTRACE_WITH_ARGS for consistency with that, but I'll need to
> check how that affects other architectures.