On Mon, Nov 21, 2022 at 12:40:15PM -0500, Steven Rostedt wrote: > On Mon, 21 Nov 2022 17:26:15 +0000 > Mark Rutland <mark.rutland@xxxxxxx> 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. To be honest, we just didn't think to remove static ftrace; I'm happy to remove that for arm64. That said, I still think it makes sense to change the code to check CONFIG_DYNAMIC_FTRACE_WITH_ARGS rather than CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS, as mentioned below, unless you intend for that to have an effect on static ftrace on x86? Everywhere else with DYNAMIC_FTRACE_WITH_ARGS forces DYNAMIC_FTRACE, so it ends up equivalent; x86 and arm64 are the only exceptions today. Thanks, Mark. > > 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.
