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

[Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>]

(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@kernel.org>

Thanks,

> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.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) {
> 
> --
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> 
> 


-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com