linux-kernel - Re: [RFC PATCH] ftrace/x86: Move the mcount/fentry code out of entry

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Message-ID: <alpine.DEB.2.02.1405090019510.6261@ionos.tec.linutronix.de>
Date:	Fri, 9 May 2014 00:21:37 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Steven Rostedt <rostedt@...dmis.org>
cc:	LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Jiri Kosina <jkosina@...e.cz>
Subject: Re: [RFC PATCH] ftrace/x86: Move the mcount/fentry code out of
 entry_64.S

On Thu, 8 May 2014, Steven Rostedt wrote:

> 
> As the mcount code gets more complex, it really does not belong
> in the entry.S file. By moving it into its own file "mcount.S"
> keeps things a bit cleaner.
> 
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> ---
> 
> Note:
> With changes to the ftrace infrastructure to help with the current
> influx of live patching facilities that we are seeing, I'm going to
> have to make new changes to mcount trampolines. Currently they live in
> entry*.S. They were only placed there for convenience, but not because
> that was the proper place to place it. As other architectures have a
> separate mcount.S file, I think it would be prudent to have x86 do the
> same. Especially as the trampoline code may start to expand for the
> live patching work. Currently, only x86_64 is converted, but there's no
> reason that i386 can't have it as well.
> 
> Thoughts?

I'm fine with the code move per se. That's a good thing.

The live patcher argumentation for it is more than questionable.

Thanks,

	tglx
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