From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner+w=401wt.eu-S1752401AbZJZQfT@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1752401AbZJZQfT (ORCPT <rfc822;w@1wt.eu>);
	Mon, 26 Oct 2009 12:35:19 -0400
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752038AbZJZQfS
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Mon, 26 Oct 2009 12:35:18 -0400
Received: from qw-out-2122.google.com ([74.125.92.27]:26668 "EHLO
	qw-out-2122.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752037AbZJZQfR (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Mon, 26 Oct 2009 12:35:17 -0400
DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=gamma;
        h=subject:from:reply-to:to:cc:in-reply-to:references:content-type
         :organization:date:message-id:mime-version:x-mailer
         :content-transfer-encoding;
        b=XaAwX015DJkpoPUm1vNYannQQuKLRWTgbUNRybNIJ5GBYzDeyw3NtIDihGZpuvqO5W
         W7kRiqX8OpIzSLkZWLUw3RG2JjFnQojPvY4eF/ALmWspJ55iLRd1JsI0c8mFFivvdgNl
         XLesV7rKVJx2gvwt8Zc8g2YYYK0O9X2kKVdu4=
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: <1256573175.26028.310.camel@gandalf.stny.rr.com>
References: <cover.1256569489.git.wuzhangjin@gmail.com>
	 <747deea2f18d5ccffe842df95a9dd1c86251a958.1256569489.git.wuzhangjin@gmail.com>
	 <3f47087b70a965fd679b17a59521671296457df1.1256569489.git.wuzhangjin@gmail.com>
	 <f290e125634d164ec65b09b24b269815f78455ab.1256569489.git.wuzhangjin@gmail.com>
	 <07dc907ec62353b1aca99b2850d3b2e4b734189a.1256569489.git.wuzhangjin@gmail.com>
	 <374da7039d2e1b97083edd8bcd7811356884d427.1256569489.git.wuzhangjin@gmail.com>
	 <3c82af564d70be05b92687949ed134ce034bf8db.1256569489.git.wuzhangjin@gmail.com>
	 <a11775df0ec9665fab5861f4fa63a3e192b9ffec.1256569489.git.wuzhangjin@gmail.com>
	 <1256573175.26028.310.camel@gandalf.stny.rr.com>
Content-Type: text/plain
Organization: DSLab, Lanzhou University, China
Date: Tue, 27 Oct 2009 00:35:10 +0800
Message-Id: <1256574910.5642.228.camel@falcon>
Mime-Version: 1.0
X-Mailer: Evolution 2.26.1 
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi,

[...]
> > +
> > +NESTED(ftrace_caller, PT_SIZE, ra)
> > +	.globl _mcount
> > +_mcount:
> > +	j	ftrace_stub
> > +	nop
> > +	lw	t0, function_trace_stop
> > +	bnez	t0, ftrace_stub
> > +	nop
> > +
> > +	MCOUNT_SAVE_REGS
> > +
> > +	MCOUNT_SET_ARGS
> > +	.globl ftrace_call
> > +ftrace_call:
> > +	nop	/* a placeholder for the call to a real tracing function */
> > +	nop	/* Do not touch me, I'm in the dealy slot of "jal func" */
> 
> Indent the second nop ;-)
> 

Yup, later in -v7.

> > +    $mcount_regex = "^\\s*([0-9a-fA-F]+): R_MIPS_HI16\\s+_mcount\$";
> > +    $objdump .= " -Melf-trad".$endian."mips ";
> > +
> > +    if ($endian eq "big") {
> > +	    $endian = " -EB ";
> > +	    $ld .= " -melf".$bits."btsmip";
> > +    } else {
> > +	    $endian = " -EL ";
> > +	    $ld .= " -melf".$bits."ltsmip";
> > +    }
> > +
> > +    $cc .= " -mno-abicalls -fno-pic -mabi=" . $bits . $endian;
> > +    $ld .= $endian;
> > +
> > +    if ($bits == 64) {
> > +	    $function_regex =
> > +		"^([0-9a-fA-F]+)\\s+<(.|[^\$]L.*?|\$[^L].*?|[^\$][^L].*?)>:";
> > +	    $type = ".dword";
> > +    }
> > +
> >  } else {
> >      die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
> >  }
> 
> So if I convert mips to do what ppc does, we can remove the long jump
> thing, right?
> 

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?

Regards,
	Wu Zhangjin