linux-kernel - Re: [PATCH] trace-cmd: Leave out absolute addresses to fix bogus symbol resolutions

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Message-ID: <20150915130044.5a88d661@gandalf.local.home>
Date:	Tue, 15 Sep 2015 13:00:44 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Jan Kiszka <jan.kiszka@...mens.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] trace-cmd: Leave out absolute addresses to fix bogus
 symbol resolutions

On Tue, 15 Sep 2015 18:30:22 +0200
Jan Kiszka <jan.kiszka@...mens.com> wrote:

> On 2015-07-31 16:04, Jan Kiszka wrote:
> > On x86, page_fault_* tracepoints report userspace address via kernel
> > symbols because all the per-cpu variable offsets are in kallsyms,
> > occupying the lower address space. Fix this by skipping over absolute
> > addresses while processing kallsyms.
> > 
> > Signed-off-by: Jan Kiszka <jan.kiszka@...mens.com>
> > ---
> >  trace-util.c | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> > 
> > diff --git a/trace-util.c b/trace-util.c
> > index 8a81dd0..da20e4c 100644
> > --- a/trace-util.c
> > +++ b/trace-util.c
> > @@ -434,8 +434,12 @@ void parse_proc_kallsyms(struct pevent *pevent,
> >  		if (mod)
> >  			mod[strlen(mod) - 1] = 0;
> >  
> > -		/* Hack for arm arch that adds a lot of bogus '$a' functions */
> > -		if (func[0] != '$')
> > +		/*
> > +		 * Hacks for
> > +		 *  - arm arch that adds a lot of bogus '$a' functions
> > +		 *  - x86-64 that reports per-cpu variable offsets as absolute
> > +		 */
> > +		if (func[0] != '$' && ch != 'A')
> >  			pevent_register_function(pevent, func, addr, mod);
> >  		free(func);
> >  		free(mod);
> > 
> 
> Ping.

Thanks for the reminder ping.

Hmm, I don't see anything marked 'A' in my kallsyms. Have a config I
can test to see what you are seeing?

-- Steve

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