linux-kernel - Re: Does perf support different length of user-space hw

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Message-ID: <20140513150613.GC13828@localhost.localdomain>
Date:	Tue, 13 May 2014 17:06:15 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Jiri Olsa <jolsa@...hat.com>,
	Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Cc:	xiakaixu <xiakaixu@...wei.com>, linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org, paulus@...ba.org,
	Ingo Molnar <mingo@...nel.org>, a.p.zijlstra@...llo.nl,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Namhyung Kim <namhyung@...nel.org>,
	Huxinwei <huxinwei@...wei.com>, peifeiyue@...wei.com
Subject: Re: Does perf support different length of user-space hw_breakpoint?

On Tue, May 13, 2014 at 02:00:46PM +0200, Jiri Olsa wrote:
> On Mon, May 12, 2014 at 03:52:54PM +0800, xiakaixu wrote:
> > Hi guys,
> > 
> > Does perf support different length of user-space hw_breakpoint,
> > such as  HW_BREAKPOINT_LEN_1/HW_BREAKPOINT_LEN_2/HW_BREAKPOINT_LEN_4/
> > HW_BREAKPOINT_LEN_8?
> > 
> > Seems perf only support HW_BREAKPOINT_LEN_4/sizeof(long)
> > by default from the source code and simple test.
> 
> right..
> 
>         /*
>          * We should find a nice way to override the access length
>          * Provide some defaults for now
>          */
>         if (attr.bp_type == HW_BREAKPOINT_X)
>                 attr.bp_len = sizeof(long);
>         else
>                 attr.bp_len = HW_BREAKPOINT_LEN_4;
> 
> > 
> > May I have your opinions if I want to trace different bytes of
> > hw_breakpoint addr?
> 
> I guess that depends on what you want to do ;-)

Ah, I have a patchset from Jacob Shin and Suravee Suthikulpanit that does
that. Also it has been hanging around for too long by my fault. I'm posting
it now.
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