Re: [PATCH 3/4] tracing: add per-event filtering

From: Steven Rostedt
Date: Mon Mar 23 2009 - 14:08:51 EST



On Sun, 22 Mar 2009, Tom Zanussi wrote:
>
> +static ssize_t
> +event_filter_read(struct file *filp, char __user *ubuf, size_t cnt,
> + loff_t *ppos)
> +{
> + struct ftrace_event_call *call = filp->private_data;
> + struct trace_seq *s;
> + int r;
> +
> + if (*ppos)
> + return 0;
> +
> + s = kmalloc(sizeof(*s), GFP_KERNEL);
> + if (!s)
> + return -ENOMEM;
> +
> + trace_seq_init(s);
> +
> + r = filter_print_preds(call->preds, s->buffer);

You're not using any of the features of the trace_seq structure.
Might as well just allocate your own buffer.

> + r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, r);
> +
> + kfree(s);
> +
> + return r;
> +}
> +
> +static ssize_t
> +event_filter_write(struct file *filp, const char __user *ubuf, size_t cnt,
> + loff_t *ppos)
> +{
> + struct ftrace_event_call *call = filp->private_data;
> + char buf[64], *pbuf = buf;
> + struct filter_pred *pred;
> + int err;
> +
> + if (cnt >= sizeof(buf))
> + return -EINVAL;
> +
> + if (copy_from_user(&buf, ubuf, cnt))
> + return -EFAULT;
> +
> + pred = kzalloc(sizeof(*pred), GFP_KERNEL);
> + if (!pred)
> + return -ENOMEM;
> +
> + err = filter_parse(&pbuf, pred);
> + if (err < 0) {
> + filter_free_pred(pred);
> + return err;
> + }
> +
> + if (pred->clear) {
> + filter_free_preds(call);

The above is very confusing. Why are we passing in "call"?

> + return cnt;
> + }
> +
> + if (filter_add_pred(call, pred)) {
> + filter_free_pred(pred);
> + return -EINVAL;
> + }
> +
> + *ppos += cnt;
> +
> + return cnt;
> +}
> +
> static const struct seq_operations show_event_seq_ops = {
> .start = t_start,
> .next = t_next,
> @@ -504,6 +569,12 @@ static const struct file_operations ftrace_event_id_fops = {
> .read = event_id_read,
> };
>
> +static const struct file_operations ftrace_event_filter_fops = {
> + .open = tracing_open_generic,
> + .read = event_filter_read,
> + .write = event_filter_write,
> +};
> +
> static struct dentry *event_trace_events_dir(void)
> {
> static struct dentry *d_tracer;
> @@ -619,6 +690,12 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events)
> }
> }
>
> + entry = debugfs_create_file("filter", 0444, call->dir, call,
> + &ftrace_event_filter_fops);
> + if (!entry)
> + pr_warning("Could not create debugfs "
> + "'%s/filter' entry\n", call->name);
> +
> /* A trace may not want to export its format */
> if (!call->show_format)
> return 0;

[...]

> +
> diff --git a/kernel/trace/trace_events_stage_3.h b/kernel/trace/trace_events_stage_3.h
> index 468938f..ebf215e 100644
> --- a/kernel/trace/trace_events_stage_3.h
> +++ b/kernel/trace/trace_events_stage_3.h
> @@ -204,6 +204,7 @@ static struct ftrace_event_call event_##call; \
> \
> static void ftrace_raw_event_##call(proto) \
> { \
> + struct ftrace_event_call *call = &event_##call; \
> struct ring_buffer_event *event; \
> struct ftrace_raw_##call *entry; \
> unsigned long irq_flags; \
> @@ -222,6 +223,9 @@ static void ftrace_raw_event_##call(proto) \
> assign; \
> \
> trace_current_buffer_unlock_commit(event, irq_flags, pc); \
> + \
> + if (call->preds && !filter_match_preds(call, entry)) \
> + ring_buffer_event_discard(event); \
> } \

Again, this would need to be within the commit.

-- Steve

> \
> static int ftrace_raw_reg_event_##call(void) \
> --
> 1.5.6.3
>
>
>
>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/