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Subject: Re: [PATCH -v6 07/13] tracing: add dynamic function tracer support
 for MIPS
From: Wu Zhangjin <wuzhangjin@gmail.com>
Reply-To: wuzhangjin@gmail.com
To: rostedt@goodmis.org
Cc: linux-mips@linux-mips.org, linux-kernel@vger.kernel.org,
       Frederic Weisbecker <fweisbec@gmail.com>,
       Thomas Gleixner <tglx@linutronix.de>,
       Ralf Baechle <ralf@linux-mips.org>,
       Richard Sandiford <rdsandiford@googlemail.com>,
       Nicholas Mc Guire <der.herr@hofr.at>,
       David Daney <ddaney@caviumnetworks.com>,
       Adam Nemet <anemet@caviumnetworks.com>,
       Patrik Kluba <kpajko79@gmail.com>
In-Reply-To: <1256575500.26028.323.camel@gandalf.stny.rr.com>
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Content-Type: text/plain
Organization: DSLab, Lanzhou University, China
Date: Tue, 27 Oct 2009 01:35:40 +0800
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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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