linux-kernel - Re: Re: [PATCH v3 3/3] perf probe: Show better error message when failed to find variable

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Date:	Mon, 11 May 2015 10:44:20 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	He Kuang <hekuang@...wei.com>, Ingo Molnar <mingo@...nel.org>,
	a.p.zijlstra@...llo.nl, jolsa@...nel.org, mingo@...hat.com,
	wangnan0@...wei.com, linux-kernel@...r.kernel.org
Subject: Re: Re: [PATCH v3 3/3] perf probe: Show better error message when
 failed to find variable

Em Mon, May 11, 2015 at 10:35:27AM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Mon, May 11, 2015 at 09:02:47PM +0900, Masami Hiramatsu escreveu:
> > On 2015/05/11 19:15, He Kuang wrote:
> > > On 2015/5/11 17:50, Ingo Molnar wrote:
> > >> * He Kuang <hekuang@...wei.com> wrote:
> > >>> On 2015/5/11 17:30, Ingo Molnar wrote:
> > >>>>> After this patch:
> > >>>>>    $ perf probe --add 'generic_perform_write+118 bytes'
> > >>>>>    Failed to find the location of bytes at this address.
> > >>>> What does this sentence mean? I thought 'address' means 'location of
> > >>>> bytes'. So the address identifies the location and obviously we know
> > >>>> that. So this message wants to say something else.
> > >>> 'generic_perform_write' is a function name, while 'bytes' is a local
> > >>> variable in this function. Maybe the variable I chose make you confused.
> 
> > >>> This maybe clear:
> > >>>    Failed to find the location of 'bytes' at this address.
> > >> Yeah, absolutely! This highlights the importance of putting
> > >> user-supplied symbols into quotes and such.
> 
> > >> Maybe even write:
> 
> > >>      Failed to find the location of the 'bytes' variable at this address.
>  
> > OK, He, could you also include this fix?
> 
> I agree with the change, makes things clearer, will do the change
> myself. If He has any objection to that, I can fix things up before
> pushing it to Ingo,

So, this is the end result:

-       if (ret == -ENOENT || ret == -EINVAL)
-               pr_err("Failed to find the location of %s at this address.\n"
-                      " Perhaps, it has been optimized out.\n", pf->pvar->var);
-       else if (ret == -ENOTSUP)
+       if (ret == -ENOENT || ret == -EINVAL) {
+               pr_err("Failed to find the location of the '%s' variable at this address.\n"
+                      " Perhaps it has been optimized out.\n"
+                      " Use -V with the --range option to show '%s' location range.\n",
+                      pf->pvar->var, pf->pvar->var);
+       } else if (ret == -ENOTSUP)


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