On Thu, 2015-10-29 at 18:11 +0900, Namhyung Kim wrote:
> On Thu, Oct 22, 2015 at 01:14:13PM -0500, Tom Zanussi wrote:
> > 'hist' triggers allow users to continually aggregate trace events,
> > which can then be viewed afterwards by simply reading a 'hist' file
> > containing the aggregation in a human-readable format.
> >
> > The basic idea is very simple and boils down to a mechanism whereby
> > trace events, rather than being exhaustively dumped in raw form and
> > viewed directly, are automatically 'compressed' into meaningful tables
> > completely defined by the user.
> >
> > This is done strictly via single-line command-line commands and
> > without the aid of any kind of programming language or interpreter.
> >
> > A surprising number of typical use cases can be accomplished by users
> > via this simple mechanism. In fact, a large number of the tasks that
> > users typically do using the more complicated script-based tracing
> > tools, at least during the initial stages of an investigation, can be
> > accomplished by simply specifying a set of keys and values to be used
> > in the creation of a hash table.
> >
> > The Linux kernel trace event subsystem happens to provide an extensive
> > list of keys and values ready-made for such a purpose in the form of
> > the event format files associated with each trace event. By simply
> > consulting the format file for field names of interest and by plugging
> > them into the hist trigger command, users can create an endless number
> > of useful aggregations to help with investigating various properties
> > of the system. See Documentation/trace/events.txt for examples.
> >
> > hist triggers are implemented on top of the existing event trigger
> > infrastructure, and as such are consistent with the existing triggers
> > from a user's perspective as well.
> >
> > The basic syntax follows the existing trigger syntax. Users start an
> > aggregation by writing a 'hist' trigger to the event of interest's
> > trigger file:
> >
> > # echo hist:keys=xxx [ if filter] > event/trigger
> >
> > Once a hist trigger has been set up, by default it continually
> > aggregates every matching event into a hash table using the event key
> > and a value field named 'hitcount'.
> >
> > To view the aggregation at any point in time, simply read the 'hist'
> > file in the same directory as the 'trigger' file:
> >
> > # cat event/hist
> >
> > The detailed syntax provides additional options for user control, and
> > is described exhaustively in Documentation/trace/events.txt and in the
> > virtual tracing/README file in the tracing subsystem.
> >
> > Signed-off-by: Tom Zanussi <tom.zanu...@linux.intel.com>
> > Tested-by: Masami Hiramatsu <masami.hiramatsu...@hitachi.com>
> > ---
>
> [SNIP]
> > +static int event_hist_trigger_func(struct event_command *cmd_ops,
> > + struct trace_event_file *file,
> > + char *glob, char *cmd, char *param)
> > +{
> > + unsigned int hist_trigger_bits = TRACING_MAP_BITS_DEFAULT;
> > + struct event_trigger_data *trigger_data;
> > + struct hist_trigger_attrs *attrs;
> > + struct event_trigger_ops *trigger_ops;
> > + struct hist_trigger_data *hist_data;
> > + char *trigger;
> > + int ret = 0;
> > +
> > + if (!param)
> > + return -EINVAL;
> > +
> > + /* separate the trigger from the filter (k:v [if filter]) */
> > + trigger = strsep(¶m, " \t");
> > + if (!trigger)
> > + return -EINVAL;
> > +
> > + attrs = parse_hist_trigger_attrs(trigger);
> > + if (IS_ERR(attrs))
> > + return PTR_ERR(attrs);
> > +
> > + if (!attrs->keys_str)
> > + return -EINVAL;
>
> Wouldn't it leak the attrs?
>
>
> > +
> > + if (attrs->map_bits)
> > + hist_trigger_bits = attrs->map_bits;
> > +
> > + hist_data = create_hist_data(hist_trigger_bits, attrs, file);
> > + if (IS_ERR(hist_data))
> > + return PTR_ERR(hist_data);
>
> It also can leak the attrs IMHO.
>
>
> > +
> > + trigger_ops = cmd_ops->get_trigger_ops(cmd, trigger);
> > +
> > + ret = -ENOMEM;
> > + trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL);
> > + if (!trigger_data)
> > + goto out;
>
> Here, the hist_data and the attr can be leaked.
>
You're correct, thanks for catching all of the above, will fix in the
next version..
Thanks,
Tom
> Thanks,
> Namhyung
>
>
> > +
> > + trigger_data->count = -1;
> > + trigger_data->ops = trigger_ops;
> > + trigger_data->cmd_ops = cmd_ops;
> > +
> > + INIT_LIST_HEAD(&trigger_data->list);
> > + RCU_INIT_POINTER(trigger_data->filter, NULL);
> > +
> > + trigger_data->private_data = hist_data;
> > +
> > + if (glob[0] == '!') {
> > + cmd_ops->unreg(glob+1, trigger_ops, trigger_data, file);
> > + ret = 0;
> > + goto out_free;
> > + }
> > +
> > + if (!param) /* if param is non-empty, it's supposed to be a filter */
> > + goto out_reg;
> > +
> > + if (!cmd_ops->set_filter)
> > + goto out_reg;
> > +
> > + ret = cmd_ops->set_filter(param, trigger_data, file);
> > + if (ret < 0)
> > + goto out_free;
> > + out_reg:
> > + ret = cmd_ops->reg(glob, trigger_ops, trigger_data, file);
> > + /*
> > + * The above returns on success the # of triggers registered,
> > + * but if it didn't register any it returns zero. Consider no
> > + * triggers registered a failure too.
> > + */
> > + if (!ret) {
> > + ret = -ENOENT;
> > + goto out_free;
> > + } else if (ret < 0)
> > + goto out_free;
> > + /* Just return zero, not the number of registered triggers */
> > + ret = 0;
> > + out:
> > + return ret;
> > + out_free:
> > + if (cmd_ops->set_filter)
> > + cmd_ops->set_filter(NULL, trigger_data, NULL);
> > +
> > + kfree(trigger_data);
> > +
> > + destroy_hist_data(hist_data);
> > + goto out;
> > +}
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
