path: root/kernel/trace/trace_uprobe.c

/*
 * uprobes-based tracing events
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Copyright (C) IBM Corporation, 2010-2012
 * Author:	Srikar Dronamraju <srikar@linux.vnet.ibm.com>
 */

#include <linux/module.h>
#include <linux/uaccess.h>
#include <linux/uprobes.h>
#include <linux/namei.h>
#include <linux/string.h>

#include "trace_probe.h"

#define UPROBE_EVENT_SYSTEM	"uprobes"

struct uprobe_trace_entry_head {
	struct trace_entry	ent;
	unsigned long		vaddr[];
};

#define SIZEOF_TRACE_ENTRY(is_return)			\
	(sizeof(struct uprobe_trace_entry_head) +	\
	 sizeof(unsigned long) * (is_return ? 2 : 1))

#define DATAOF_TRACE_ENTRY(entry, is_return)		\
	((void*)(entry) + SIZEOF_TRACE_ENTRY(is_return))

struct trace_uprobe_filter {
	rwlock_t		rwlock;
	int			nr_systemwide;
	struct list_head	perf_events;
};

/*
 * uprobe event core functions
 */
struct trace_uprobe {
	struct list_head		list;
	struct ftrace_event_class	class;
	struct ftrace_event_call	call;
	struct trace_uprobe_filter	filter;
	struct uprobe_consumer		consumer;
	struct inode			*inode;
	char				*filename;
	unsigned long			offset;
	unsigned long			nhit;
	unsigned int			flags;	/* For TP_FLAG_* */
	ssize_t				size;	/* trace entry size */
	unsigned int			nr_args;
	struct probe_arg		args[];
};

#define SIZEOF_TRACE_UPROBE(n)			\
	(offsetof(struct trace_uprobe, args) +	\
	(sizeof(struct probe_arg) * (n)))

static int register_uprobe_event(struct trace_uprobe *tu);
static void unregister_uprobe_event(struct trace_uprobe *tu);

static DEFINE_MUTEX(uprobe_lock);
static LIST_HEAD(uprobe_list);

static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs);
static int uretprobe_dispatcher(struct uprobe_consumer *con,
				unsigned long func, struct pt_regs *regs);

static inline void init_trace_uprobe_filter(struct trace_uprobe_filter *filter)
{
	rwlock_init(&filter->rwlock);
	filter->nr_systemwide = 0;
	INIT_LIST_HEAD(&filter->perf_events);
}

static inline bool uprobe_filter_is_empty(struct trace_uprobe_filter *filter)
{
	return !filter->nr_systemwide && list_empty(&filter->perf_events);
}

static inline bool is_ret_probe(struct trace_uprobe *tu)
{
	return tu->consumer.ret_handler != NULL;
}

/*
 * Allocate new trace_uprobe and initialize it (including uprobes).
 */
static struct trace_uprobe *
alloc_trace_uprobe(const char *group, const char *event, int nargs, bool is_ret)
{
	struct trace_uprobe *tu;

	if (!event || !is_good_name(event))
		return ERR_PTR(-EINVAL);

	if (!group || !is_good_name(group))
		return ERR_PTR(-EINVAL);

	tu = kzalloc(SIZEOF_TRACE_UPROBE(nargs), GFP_KERNEL);
	if (!tu)
		return ERR_PTR(-ENOMEM);

	tu->call.class = &tu->class;
	tu->call.name = kstrdup(event, GFP_KERNEL);
	if (!tu->call.name)
		goto error;

	tu->class.system = kstrdup(group, GFP_KERNEL);
	if (!tu->class.system)
		goto error;

	INIT_LIST_HEAD(&tu->list);
	tu->consumer.handler = uprobe_dispatcher;
	if (is_ret)
		tu->consumer.ret_handler = uretprobe_dispatcher;
	init_trace_uprobe_filter(&tu->filter);
	return tu;

error:
	kfree(tu->call.name);
	kfree(tu);

	return ERR_PTR(-ENOMEM);
}

static void free_trace_uprobe(struct trace_uprobe *tu)
{
	int i;

	for (i = 0; i < tu->nr_args; i++)
		traceprobe_free_probe_arg(&tu->args[i]);

	iput(tu->inode);
	kfree(tu->call.class->system);
	kfree(tu->call.name);
	kfree(tu->filename);
	kfree(tu);
}

static struct trace_uprobe *find_probe_event(const char *event, const char *group)
{
	struct trace_uprobe *tu;

	list_for_each_entry(tu, &uprobe_list, list)
		if (strcmp(tu->call.name, event) == 0 &&
		    strcmp(tu->