path: root/kernel/trace/trace_eprobe.c

// SPDX-License-Identifier: GPL-2.0
/*
 * event probes
 *
 * Part of this code was copied from kernel/trace/trace_kprobe.c written by
 * Masami Hiramatsu <mhiramat@kernel.org>
 *
 * Copyright (C) 2021, VMware Inc, Steven Rostedt <rostedt@goodmis.org>
 * Copyright (C) 2021, VMware Inc, Tzvetomir Stoyanov tz.stoyanov@gmail.com>
 *
 */
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/ftrace.h>

#include "trace_dynevent.h"
#include "trace_probe.h"
#include "trace_probe_tmpl.h"
#include "trace_probe_kernel.h"

#define EPROBE_EVENT_SYSTEM "eprobes"

struct trace_eprobe {
	/* tracepoint system */
	const char *event_system;

	/* tracepoint event */
	const char *event_name;

	/* filter string for the tracepoint */
	char *filter_str;

	struct trace_event_call *event;

	struct dyn_event	devent;
	struct trace_probe	tp;
};

struct eprobe_data {
	struct trace_event_file	*file;
	struct trace_eprobe	*ep;
};

static int __trace_eprobe_create(int argc, const char *argv[]);

static void trace_event_probe_cleanup(struct trace_eprobe *ep)
{
	if (!ep)
		return;
	trace_probe_cleanup(&ep->tp);
	kfree(ep->event_name);
	kfree(ep->event_system);
	if (ep->event)
		trace_event_put_ref(ep->event);
	kfree(ep->filter_str);
	kfree(ep);
}

static struct trace_eprobe *to_trace_eprobe(struct dyn_event *ev)
{
	return container_of(ev, struct trace_eprobe, devent);
}

static int eprobe_dyn_event_create(const char *raw_command)
{
	return trace_probe_create(raw_command, __trace_eprobe_create);
}

static int eprobe_dyn_event_show(struct seq_file *m, struct dyn_event *ev)
{
	struct trace_eprobe *ep = to_trace_eprobe(ev);
	int i;

	seq_printf(m, "e:%s/%s", trace_probe_group_name(&ep->tp),
				trace_probe_name(&ep->tp));
	seq_printf(m, " %s.%s", ep->event_system, ep->event_name);

	for (i = 0; i < ep->tp.nr_args; i++)
		seq_printf(m, " %s=%s", ep->tp.args[i].name, ep->tp.args[i].comm);
	seq_putc(m, '\n');

	return 0;
}

static int unregister_trace_eprobe(struct trace_eprobe *ep)
{
	/* If other probes are on the event, just unregister eprobe */
	if (trace_probe_has_sibling(&ep->tp))
		goto unreg;

	/* Enabled event can not be unregistered */
	if (trace_probe_is_enabled(&ep->tp))
		return -EBUSY;

	/* Will fail if probe is being used by ftrace or perf */
	if (trace_probe_unregister_event_call(&ep->tp))
		return -EBUSY;

unreg:
	dyn_event_remove(&ep->devent);
	trace_probe_unlink(&ep->tp);

	return 0;
}

static int eprobe_dyn_event_release(struct dyn_event *ev)
{
	struct trace_eprobe *ep = to_trace_eprobe(ev);
	int ret = unregister_trace_eprobe(ep);

	if (!ret)
		trace_event_probe_cleanup(ep);
	return ret;
}

static bool eprobe_dyn_event_is_busy(struct dyn_event *ev)
{
	struct trace_eprobe *ep = to_trace_eprobe(ev);

	return trace_probe_is_enabled(&ep->tp);
}

static bool eprobe_dyn_event_match(const char *system, const char *event,
			int argc, const char **argv, struct dyn_event *ev)
{
	struct trace_eprobe *ep = to_trace_eprobe(ev);
	const char *slash;

	/*
	 * We match the following:
	 *  event only			- match all eprobes with event name
	 *  system and event only	- match all system/event probes
	 *  system only			- match all system probes
	 *
	 * The below has the above satisfied with more arguments:
	 *
	 *  attached system/event	- If the arg has the system and event
	 *				  the probe is attached to, match
	 *				  probes with the attachment.
	 *
	 *  If any more args are given, then it requires a full match.
	 */

	/*
	 * If system exists, but this probe is not part of that system
	 * do not match.
	 */
	if (system && strcmp(trace_probe_group_name(&ep->tp), system) != 0)
		return false;

	/* Must match the event name */
	if (event[0] != '\0' && strcmp(trace_probe_name(&ep->tp), event) != 0)
		return false;

	/* No arguments match all */
	if (argc < 1)
		return true;

	/* First argument is the system/event the probe is attached to */

	slash = strchr(argv[0], '/');
	if (!slash)
		slash = strchr(argv[0], '.');
	if (!slash)
		return false;

	if (strncmp(ep->event_system, argv[0], slash - argv[0]))
		return false;
	if (strcmp(ep->event_name, slash + 1))
		return false;

	argc--;
	argv++;

	/* If there are no other args, then match */
	if (argc < 1)
		return true;

	return trace_probe_match_command_args(&ep->tp,