linux-kernel - Re: [PATCH perf/core ] perf-probe: Warn if given uprobe event accesses memory on older kernel

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Message-ID: <20150228204554.GF28401@kernel.org>
Date:	Sat, 28 Feb 2015 17:45:54 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Jiri Olsa <jolsa@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>
Subject: Re: [PATCH perf/core ] perf-probe: Warn if given uprobe event
 accesses memory on older kernel

Em Sat, Feb 28, 2015 at 12:21:05PM +0900, Masami Hiramatsu escreveu:
> (2015/02/28 11:53), Masami Hiramatsu wrote:
> > Warn if given uprobe event accesses memory on older kernel.
> > Until 3.14, uprobe event only supports accessing registers
> > so this warns to upgrade kernel if uprobe-event returns
> > -EINVAL and an argument of the event accesses memory ($stack,
> > @+offset, and +|-offs() symtax).
> > 
> > With this patch (on 3.10.0-123.13.2.el7.x86_64);
> >   -----
> >   # ./perf probe -x ./perf warn_uprobe_event_compat stack=-0\(%sp\)
> >   Added new event:
> >   Failed to write event: Invalid argument
> >   Please upgrade your kernel to at least 3.14 to have access to feature -0(%sp)
> >     Error: Failed to add events.
> >   -----
> > 
> 
> Oops,
> 
> Suggested-by: Arnaldo Carvalho de Melo <acme@...nel.org>

:-)

Thanks for considering my suggestion and coming up with a patch so
quickly!

I'll test it and merge,

- Arnaldo
 
> Thanks,
> 
> > Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> > ---
> >  tools/perf/util/probe-event.c |   23 +++++++++++++++++++++++
> >  1 file changed, 23 insertions(+)
> > 
> > diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> > index 7c0e765..1c570c2fa7 100644
> > --- a/tools/perf/util/probe-event.c
> > +++ b/tools/perf/util/probe-event.c
> > @@ -2199,6 +2199,27 @@ static int get_new_event_name(char *buf, size_t len, const char *base,
> >  	return ret;
> >  }
> >  
> > +/* Warn if the current kernel's uprobe implementation is old */
> > +static void warn_uprobe_event_compat(struct probe_trace_event *tev)
> > +{
> > +	int i;
> > +	char *buf = synthesize_probe_trace_command(tev);
> > +
> > +	/* Old uprobe event doesn't support memory dereference */
> > +	if (!tev->uprobes || tev->nargs == 0 || !buf)
> > +		goto out;
> > +
> > +	for (i = 0; i < tev->nargs; i++)
> > +		if (strglobmatch(tev->args[i].value, "[$@+-]*")) {
> > +			pr_warning("Please upgrade your kernel to at least "
> > +				   "3.14 to have access to feature %s\n",
> > +				   tev->args[i].value);
> > +			break;
> > +		}
> > +out:
> > +	free(buf);
> > +}
> > +
> >  static int __add_probe_trace_events(struct perf_probe_event *pev,
> >  				     struct probe_trace_event *tevs,
> >  				     int ntevs, bool allow_suffix)
> > @@ -2295,6 +2316,8 @@ static int __add_probe_trace_events(struct perf_probe_event *pev,
> >  		 */
> >  		allow_suffix = true;
> >  	}
> > +	if (ret == -EINVAL && pev->uprobes)
> > +		warn_uprobe_event_compat(tev);
> >  
> >  	/* Note that it is possible to skip all events because of blacklist */
> >  	if (ret >= 0 && tev->event) {
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to majordomo@...r.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at  http://www.tux.org/lkml/
> > 
> > 
> > 
> 
> 
> -- 
> Masami HIRAMATSU
> Software Platform Research Dept. Linux Technology Research Center
> Hitachi, Ltd., Yokohama Research Laboratory
> E-mail: masami.hiramatsu.pt@...achi.com
> 
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