Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756693AbZJVTNh (ORCPT ); Thu, 22 Oct 2009 15:13:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756323AbZJVTNg (ORCPT ); Thu, 22 Oct 2009 15:13:36 -0400 Received: from mail-bw0-f227.google.com ([209.85.218.227]:61874 "EHLO mail-bw0-f227.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756202AbZJVTNf (ORCPT ); Thu, 22 Oct 2009 15:13:35 -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=E+i5ewnceXTFOtdqDHOKR83fgYq0C6/Zhp9N6WMgUNbe6VsMqpbxdpd3d/vKthCTvZ BlyShgFOmQi0KIbWVncrvmDUF/QVwbCnRST3AClbr9ZUF2agBAzfKZ+b1A1rUkAXxdI2 /5krL4ryyiW2NreXTwPXVMekfe6h49z8Gw+jQ= Subject: Re: [PATCH -v4 4/9] tracing: add static function tracer support for MIPS From: Wu Zhangjin Reply-To: wuzhangjin@gmail.com To: David Daney Cc: Richard Sandiford , Adam Nemet , rostedt@goodmis.org, linux-kernel@vger.kernel.org, linux-mips@linux-mips.org, Thomas Gleixner , Ralf Baechle , Nicholas Mc Guire In-Reply-To: <4AE0A5BE.8000601@caviumnetworks.com> References: <028867b99ec532b84963a35e7d552becc783cafc.1256135456.git.wuzhangjin@gmail.com> <2f73eae542c47ac5bbb9f7280e6c0271d193e90d.1256135456.git.wuzhangjin@gmail.com> <3f0d3515f74a58f4cfd11e61b62a129fdc21e3a7.1256135456.git.wuzhangjin@gmail.com> <1256138686.18347.3039.camel@gandalf.stny.rr.com> <1256233679.23653.7.camel@falcon> <4AE0A5BE.8000601@caviumnetworks.com> Content-Type: text/plain Organization: DSLab, Lanzhou University, China Date: Fri, 23 Oct 2009 03:13:21 +0800 Message-Id: <1256238801.4848.6.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: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1822 Lines: 56 Hi, On Thu, 2009-10-22 at 11:34 -0700, David Daney wrote: > Wu Zhangjin wrote: > > On Wed, 2009-10-21 at 11:24 -0400, Steven Rostedt wrote: > [...] > >>> + > >>> +NESTED(_mcount, PT_SIZE, ra) > >>> + RESTORE_SP_FOR_32BIT > >>> + PTR_LA t0, ftrace_stub > >>> + PTR_L t1, ftrace_trace_function /* please don't use t1 later, safe? */ > >> Is t0 and t1 safe for mcount to use? Remember, mcount does not follow > >> the dynamics of C function ABI. > > > > So, perhaps we can use the saved registers(a0,a1...) instead. > > > > a0..a7 may not always be saved. I mean I have saved/restored them as the _mcount of /lib/libc.so.6 for MIPS did, so I can use them safely. > > You can use at, v0, v1 and all the temporary registers. Note that for > the 64-bit ABIs sometimes the names t0-t4 shadow a4-a7. So for a 64-bit > kernel, you can use: $1, $2, $3, $12, $13, $14, $15, $24, $25, noting > that at == $1 and contains the callers ra. For a 32-bit kernel you can > add $8, $9, $10, and $11 > In a generic function, they should be okay, but _mcount is a little specific. so, Not sure these rules are suitable to it or not. > This whole thing seems a little fragile. > > I think it might be a good idea to get input from Richard Sandiford, > and/or Adam Nemet about this approach (so I add them to the CC). > > This e-mail thread starts here: > > http://www.linux-mips.org/archives/linux-mips/2009-10/msg00286.html > > and here: > > http://www.linux-mips.org/archives/linux-mips/2009-10/msg00290.html looking forward to their reply, thanks! Regards! Wu Zhangjin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/