Messages in this thread | | | Date | Tue, 7 Nov 2023 14:43:28 +0900 | From | Masami Hiramatsu (Google) <> | Subject | Re: [RFC PATCH 24/32] x86/ftrace: Enable HAVE_FUNCTION_GRAPH_FREGS |
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On Mon, 6 Nov 2023 22:06:17 -0500 Steven Rostedt <rostedt@goodmis.org> wrote:
> On Tue, 7 Nov 2023 09:42:58 +0900 > Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote: > > > Got it. So does ftrace_regs need a placeholder for direct trampoline? > > (Or, can we use a register to pass it?) > > I think we don't need to clear it for return_to_handler() but if > > `ftrace_regs` spec requires it, it is better to do so. > > It's per arch defined. I think I wrote somewhere that it just needs to pass > back something that can tell if the handler is to return to a direct > trampoline or not. It could be a unused register, or something else.
Oh, I meant the flag (address) for "return" trampoline. If we have direct "return" trampoline we may use it, but currently not.
> > It's only needed if an architecture supports direct trampolines.
I see, and x86_64 needs it. OK, maybe better to keep it clear on x86-64 even on the return handler.
Thank you,
> > -- Steve
-- Masami Hiramatsu (Google) <mhiramat@kernel.org>
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