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Date: Mon, 6 Nov 2023 22:06:17 -0500
From: Steven Rostedt <rostedt@goodmis.org>
To: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>, Alexei Starovoitov
 <alexei.starovoitov@gmail.com>, Florent Revest <revest@chromium.org>,
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 Guo Ren <guoren@kernel.org>
Subject: Re: [RFC PATCH 24/32] x86/ftrace: Enable HAVE_FUNCTION_GRAPH_FREGS
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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.

It's only needed if an architecture supports direct trampolines.

-- Steve