Re: [PATCH v2] tracing/kprobes: Add method to display private kprobes in tracefs

[Steven Rostedt <rostedt@goodmis.org>]

[ Adding Masami and Tom ]

On Mon, 25 Jul 2022 06:23:34 +0000
Jianlin Lv <iecedge@gmail.com> wrote:

> The private kprobes are not added to the global list dyn_event_list,
> so there is a missing interface to show probe hit and probe miss.
> This patch adds a profiling interface to check the number of hits or
> misses for private kprobes.

Masami, what do you think of this patch?

-- Steve

> 
> Signed-off-by: Jianlin Lv <iecedge@gmail.com>
> ---
> v2: update commit message
> ---
>  Documentation/trace/kprobetrace.rst |  6 +++-
>  kernel/trace/trace_dynevent.c       | 20 +++++++++++
>  kernel/trace/trace_dynevent.h       | 37 ++++++++++++++++++++
>  kernel/trace/trace_kprobe.c         | 54 +++++++++++++++++++++++++++++
>  4 files changed, 116 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/trace/kprobetrace.rst b/Documentation/trace/kprobetrace.rst
> index b175d88f31eb..8815d64dd8a6 100644
> --- a/Documentation/trace/kprobetrace.rst
> +++ b/Documentation/trace/kprobetrace.rst
> @@ -146,7 +146,11 @@ trigger:
>  Event Profiling
>  ---------------
>  You can check the total number of probe hits and probe miss-hits via
> -/sys/kernel/debug/tracing/kprobe_profile.
> +/sys/kernel/debug/tracing/kprobe_profile or
> +/sys/kernel/debug/tracing/kprobe_local_profile.
> +All kprobe events created by kprobe_events will be added to the global
> +list, you can get their profiling via kprobe_profile; kprobe_local_profile
> +shows profiling for private kprobe events created by perf_kprobe pmu.
>  The first column is event name, the second is the number of probe hits,
>  the third is the number of probe miss-hits.
>  
> diff --git a/kernel/trace/trace_dynevent.c b/kernel/trace/trace_dynevent.c
> index 076b447a1b88..70ec99cd9c53 100644
> --- a/kernel/trace/trace_dynevent.c
> +++ b/kernel/trace/trace_dynevent.c
> @@ -181,6 +181,26 @@ static const struct seq_operations dyn_event_seq_op = {
>  	.show	= dyn_event_seq_show
>  };
>  
> +#ifdef CONFIG_KPROBE_EVENTS
> +LIST_HEAD(local_event_list);
> +
> +void *local_event_seq_start(struct seq_file *m, loff_t *pos)
> +{
> +	mutex_lock(&event_mutex);
> +	return seq_list_start(&local_event_list, *pos);
> +}
> +
> +void *local_event_seq_next(struct seq_file *m, void *v, loff_t *pos)
> +{
> +	return seq_list_next(v, &local_event_list, pos);
> +}
> +
> +void local_event_seq_stop(struct seq_file *m, void *v)
> +{
> +	mutex_unlock(&event_mutex);
> +}
> +#endif /* CONFIG_KPROBE_EVENTS */
> +
>  /*
>   * dyn_events_release_all - Release all specific events
>   * @type:	the dyn_event_operations * which filters releasing events
> diff --git a/kernel/trace/trace_dynevent.h b/kernel/trace/trace_dynevent.h
> index 936477a111d3..e30193470295 100644
> --- a/kernel/trace/trace_dynevent.h
> +++ b/kernel/trace/trace_dynevent.h
> @@ -101,6 +101,43 @@ void dyn_event_seq_stop(struct seq_file *m, void *v);
>  int dyn_events_release_all(struct dyn_event_operations *type);
>  int dyn_event_release(const char *raw_command, struct dyn_event_operations *type);
>  
> +#ifdef CONFIG_KPROBE_EVENTS
> +extern struct list_head local_event_list;
> +
> +static inline
> +int local_event_init(struct dyn_event *ev, struct dyn_event_operations *ops)
> +{
> +	if (!ev || !ops)
> +		return -EINVAL;
> +
> +	INIT_LIST_HEAD(&ev->list);
> +	ev->ops = ops;
> +	return 0;
> +}
> +
> +static inline int local_event_add(struct dyn_event *ev)
> +{
> +	lockdep_assert_held(&event_mutex);
> +
> +	if (!ev || !ev->ops)
> +		return -EINVAL;
> +
> +	list_add_tail(&ev->list, &local_event_list);
> +	return 0;
> +}
> +
> +static inline void local_event_remove(struct dyn_event *ev)
> +{
> +	lockdep_assert_held(&event_mutex);
> +	list_del_init(&ev->list);
> +}
> +
> +void *local_event_seq_start(struct seq_file *m, loff_t *pos);
> +void *local_event_seq_next(struct seq_file *m, void *v, loff_t *pos);
> +void local_event_seq_stop(struct seq_file *m, void *v);
> +
> +#endif /* CONFIG_KPROBE_EVENTS */
> +
>  /*
>   * for_each_dyn_event	-	iterate over the dyn_event list
>   * @pos:	the struct dyn_event * to use as a loop cursor
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index a245ea673715..76f500b17b46 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -1213,6 +1213,52 @@ static const struct file_operations kprobe_profile_ops = {
>  	.release        = seq_release,
>  };
>  
> +#ifdef CONFIG_KPROBE_EVENTS
> +/* kprobe Local profile  */
> +static int local_probes_profile_seq_show(struct seq_file *m, void *v)
> +{
> +	struct dyn_event *ev = v;
> +	struct trace_kprobe *tk;
> +
> +	if (!is_trace_kprobe(ev))
> +		return 0;
> +
> +	tk = to_trace_kprobe(ev);
> +	seq_printf(m, "  %-44s %15lu %15lu\n",
> +		trace_probe_name(&tk->tp),
> +		trace_kprobe_nhit(tk),
> +		tk->rp.kp.nmissed);
> +
> +	return 0;
> +}
> +
> +static const struct seq_operations local_profile_seq_op = {
> +	.start  = local_event_seq_start,
> +	.next   = local_event_seq_next,
> +	.stop   = local_event_seq_stop,
> +	.show   = local_probes_profile_seq_show
> +};
> +
> +static int local_profile_open(struct inode *inode, struct file *file)
> +{
> +	int ret;
> +
> +	ret = security_locked_down(LOCKDOWN_TRACEFS);
> +	if (ret)
> +		return ret;
> +
> +	return seq_open(file, &local_profile_seq_op);
> +}
> +
> +static const struct file_operations kprobe_local_profile_ops = {
> +	.owner          = THIS_MODULE,
> +	.open           = local_profile_open,
> +	.read           = seq_read,
> +	.llseek         = seq_lseek,
> +	.release        = seq_release,
> +};
> +#endif /* CONFIG_KPROBE_EVENTS */
> +
>  /* Kprobe specific fetch functions */
>  
>  /* Return the length of string -- including null terminal byte */
> @@ -1830,6 +1876,7 @@ create_local_trace_kprobe(char *func, void *addr, unsigned long offs,
>  	if (ret < 0)
>  		goto error;
>  
> +	local_event_add(&tk->devent);
>  	return trace_probe_event_call(&tk->tp);
>  error:
>  	free_trace_kprobe(tk);
> @@ -1849,6 +1896,7 @@ void destroy_local_trace_kprobe(struct trace_event_call *event_call)
>  		return;
>  	}
>  
> +	local_event_remove(&tk->devent);
>  	__unregister_trace_kprobe(tk);
>  
>  	free_trace_kprobe(tk);
> @@ -1929,6 +1977,12 @@ static __init int init_kprobe_trace(void)
>  	trace_create_file("kprobe_profile", TRACE_MODE_READ,
>  			  NULL, NULL, &kprobe_profile_ops);
>  
> +#ifdef CONFIG_KPROBE_EVENTS
> +	/* kprobe Local profile */
> +	tracefs_create_file("kprobe_local_profile", TRACE_MODE_READ,
> +			  NULL, NULL, &kprobe_local_profile_ops);
> +#endif /* CONFIG_KPROBE_EVENTS */
> +
>  	setup_boot_kprobe_events();
>  
>  	return 0;