linux-kernel - Re: [PATCH -v6 07/13] tracing: add dynamic function tracer support for MIPS

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Date:	Tue, 27 Oct 2009 01:35:40 +0800
From:	Wu Zhangjin <wuzhangjin@...il.com>
To:	rostedt@...dmis.org
Cc:	linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Richard Sandiford <rdsandiford@...glemail.com>,
	Nicholas Mc Guire <der.herr@...r.at>,
	David Daney <ddaney@...iumnetworks.com>,
	Adam Nemet <anemet@...iumnetworks.com>,
	Patrik Kluba <kpajko79@...il.com>
Subject: Re: [PATCH -v6 07/13] tracing: add dynamic function tracer support
 for MIPS

On Mon, 2009-10-26 at 12:45 -0400, Steven Rostedt wrote:
> On Tue, 2009-10-27 at 00:35 +0800, Wu Zhangjin wrote:
> 
> > If remove the long jump, we at least to change the $mcount_regex in
> > scripts/recordmcount.pl, the addr + 12 in arch/mips/include/asm/ftrace.h
> > and the _mcount & ftrace_caller in mcount.S and the ftrace_make_nop &
> > ftrace_make_call in arch/mips/kernel/ftrace.c back to the -v4 version.
> > 
> > I think this method of supporting module is not that BAD, no obvious
> > overhead added except the "lui...addiu..." and two more "nop"
> > instructions. and it's very understandable, so, just use this version?
> 
> You don't nop the lui and addiu do you? If you do you will crash the
> machine.

Not test it yet, Seems what you have mentioned in another thread:

b  1f
....
1:

is a good idea, it will only left one "lui" and one "b 1f" instruction
there.

(I'm sleepy now, the time is Tue Oct 27 01:34:51 CST 2009 in China, See
you~~)

Regards,
	Wu Zhangjin

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