[lttng-modules.git] / probes / lttng-kretprobes.c

/*
* probes/lttng-kretprobes.c
 *
 * LTTng kretprobes integration module.
 *
 * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; only
 * version 2.1 of the License.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <linux/module.h>
#include <linux/kprobes.h>
#include <linux/slab.h>
#include <linux/kref.h>
#include <lttng-events.h>
#include <wrapper/ringbuffer/frontend_types.h>
#include <wrapper/vmalloc.h>
#include <wrapper/irqflags.h>
#include <lttng-tracer.h>

enum lttng_kretprobe_type {
	EVENT_ENTRY = 0,
	EVENT_RETURN = 1,
};

struct lttng_krp {
	struct kretprobe krp;
	struct lttng_event *event[2];	/* ENTRY and RETURN */
	struct kref kref_register;
	struct kref kref_alloc;
};

static
int _lttng_kretprobes_handler(struct kretprobe_instance *krpi,
			      struct pt_regs *regs,
			      enum lttng_kretprobe_type type)
{
	struct lttng_krp *lttng_krp =
		container_of(krpi->rp, struct lttng_krp, krp);
	struct lttng_event *event =
		lttng_krp->event[type];
	struct lttng_probe_ctx lttng_probe_ctx = {
		.event = event,
		.interruptible = !lttng_regs_irqs_disabled(regs),
	};
	struct lttng_channel *chan = event->chan;
	struct lib_ring_buffer_ctx ctx;
	int ret;
	struct {
		unsigned long ip;
		unsigned long parent_ip;
	} payload;

	if (unlikely(!READ_ONCE(chan->session->active)))
		return 0;
	if (unlikely(!READ_ONCE(chan->enabled)))
		return 0;
	if (unlikely(!READ_ONCE(event->enabled)))
		return 0;

	payload.ip = (unsigned long) krpi->rp->kp.addr;
	payload.parent_ip = (unsigned long) krpi->ret_addr;

	lib_ring_buffer_ctx_init(&ctx, chan->chan, &lttng_probe_ctx, sizeof(payload),
				 lttng_alignof(payload), -1);
	ret = chan->ops->event_reserve(&ctx, event->id);
	if (ret < 0)
		return 0;
	lib_ring_buffer_align_ctx(&ctx, lttng_alignof(payload));
	chan->ops->event_write(&ctx, &payload, sizeof(payload));
	chan->ops->event_commit(&ctx);
	return 0;
}

static
int lttng_kretprobes_handler_entry(struct kretprobe_instance *krpi,
				   struct pt_regs *regs)
{
	return _lttng_kretprobes_handler(krpi, regs, EVENT_ENTRY);
}

static
int lttng_kretprobes_handler_return(struct kretprobe_instance *krpi,
				    struct pt_regs *regs)
{
	return _lttng_kretprobes_handler(krpi, regs, EVENT_RETURN);
}

/*
 * Create event description
 */
static
int lttng_create_kprobe_event(const char *name, struct lttng_event *event,
			      enum lttng_kretprobe_type type)
{
	struct lttng_event_field *fields;
	struct lttng_event_desc *desc;
	int ret;
	char *alloc_name;
	size_t name_len;
	const char *suffix = NULL;

	desc = kzalloc(sizeof(*event->desc), GFP_KERNEL);
	if (!desc)
		return -ENOMEM;
	name_len = strlen(name);
	switch (type) {
	case EVENT_ENTRY:
		suffix = "_entry";
		break;
	case EVENT_RETURN:
		suffix = "_return";
		break;
	}
	name_len += strlen(suffix);
	alloc_name = kmalloc(name_len + 1, GFP_KERNEL);
	if (!alloc_name) {
		ret = -ENOMEM;
		goto error_str;
	}
	strcpy(alloc_name, name);
	strcat(alloc_name, suffix);
	desc->name = alloc_name;
	desc->nr_fields = 2;
	desc->fields = fields =
		kzalloc(2 * sizeof(struct lttng_event_field), GFP_KERNEL);
	if (!desc->fields) {
		ret = -ENOMEM;
		goto error_fields;
	}
	fields[0].name = "ip";
	fields[0].type.atype = atype_integer;
	fields[0].type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT;
	fields[0].type.u.basic.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
	fields[0].type.u.basic.integer.signedness = lttng_is_signed_type(unsigned long);
	fields[0].type.u.basic.integer.reverse_byte_order = 0;
	fields[0].type.u.basic.integer.base = 16;
	fields[0].type.u.basic.integer.encoding = lttng_encode_none;

	fields[1].name = "parent_ip";
	fields[1].type.atype = atype_integer;
	fields[1].type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT;
	fields[1].type.u.basic.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
	fields[1].type.u.basic.integer.signedness = lttng_is_signed_type(unsigned long);
	fields[1].type.u.basic.integer.reverse_byte_order = 0;
	fields[1].type.u.basic.integer.base = 16;
	fields[1].type.u.basic.integer.encoding = lttng_encode_none;

	desc->owner = THIS_MODULE;
	event->desc = desc;

	return 0;

error_fields:
	kfree(desc->name);
error_str:
	kfree(desc);
	return ret;
}

int lttng_kretprobes_register(const char *name,
			   const char *symbol_name,
			   uint64_t offset,
			   uint64_t addr,
			   struct lttng_event *event_entry,
			   struct lttng_event *event_return)
{
	int ret;
	struct lttng_krp *lttng_krp;

	/* Kprobes expects a NULL symbol name if unused */
	if (symbol_name[0] == '\0')
		symbol_name = NULL;

	ret = lttng_create_kprobe_event(name, event_entry, EVENT_ENTRY);
	if (ret)
		goto error;
	ret = lttng_create_kprobe_event(name, event_return, EVENT_RETURN);
	if (ret)
		goto event_return_error;
	lttng_krp = kzalloc(sizeof(*lttng_krp), GFP_KERNEL);
	if (!lttng_krp)
		goto krp_error;
	lttng_krp->krp.entry_handler = lttng_kretprobes_handler_entry;
	lttng_krp->krp.handler = lttng_kretprobes_handler_return;
	if (symbol_name) {
		char *alloc_symbol;

		alloc_symbol = kstrdup(symbol_name, GFP_KERNEL);
		if (!alloc_symbol) {
			ret = -ENOMEM;
			goto name_error;
		}
		lttng_krp->krp.kp.symbol_name =
			alloc_symbol;
		event_entry->u.kretprobe.symbol_name =
			alloc_symbol;
		event_return->u.kretprobe.symbol_name =
			alloc_symbol;
	}
	lttng_krp->krp.kp.offset = offset;
	lttng_krp->krp.kp.addr = (void *) (unsigned long) addr;

	/* Allow probe handler to find event structures */
	lttng_krp->event[EVENT_ENTRY] = event_entry;
	lttng_krp->event[EVENT_RETURN] = event_return;
	event_entry->u.kretprobe.lttng_krp = lttng_krp;
	event_return->u.kretprobe.lttng_krp = lttng_krp;

	/*
	 * Both events must be unregistered before the kretprobe is
	 * unregistered. Same for memory allocation.
	 */
	kref_init(&lttng_krp->kref_alloc);
	kref_get(&lttng_krp->kref_alloc);	/* inc refcount to 2, no overflow. */
	kref_init(&lttng_krp->kref_register);
	kref_get(&lttng_krp->kref_register);	/* inc refcount to 2, no overflow. */

	/*
	 * Ensure the memory we just allocated don't trigger page faults.
	 * Well.. kprobes itself puts the page fault handler on the blacklist,
	 * but we can never be too careful.
	 */
	wrapper_vmalloc_sync_all();

	ret = register_kretprobe(&lttng_krp->krp);
	if (ret)
		goto register_error;
	return 0;

register_error:
	kfree(lttng_krp->krp.kp.symbol_name);
name_error:
	kfree(lttng_krp);
krp_error:
	kfree(event_return->desc->fields);
	kfree(event_return->desc->name);
	kfree(event_return->desc);
event_return_error:
	kfree(event_entry->desc->fields);
	kfree(event_entry->desc->name);
	kfree(event_entry->desc);
error:
	return ret;
}
EXPORT_SYMBOL_GPL(lttng_kretprobes_register);

static
void _lttng_kretprobes_unregister_release(struct kref *kref)
{
	struct lttng_krp *lttng_krp =
		container_of(kref, struct lttng_krp, kref_register);
	unregister_kretprobe(&lttng_krp->krp);
}

void lttng_kretprobes_unregister(struct lttng_event *event)
{
	kref_put(&event->u.kretprobe.lttng_krp->kref_register,
		_lttng_kretprobes_unregister_release);
}
EXPORT_SYMBOL_GPL(lttng_kretprobes_unregister);

static
void _lttng_kretprobes_release(struct kref *kref)
{
	struct lttng_krp *lttng_krp =
		container_of(kref, struct lttng_krp, kref_alloc);
	kfree(lttng_krp->krp.kp.symbol_name);
}

void lttng_kretprobes_destroy_private(struct lttng_event *event)
{
	kfree(event->desc->fields);
	kfree(event->desc->name);
	kfree(event->desc);
	kref_put(&event->u.kretprobe.lttng_krp->kref_alloc,
		_lttng_kretprobes_release);
}
EXPORT_SYMBOL_GPL(lttng_kretprobes_destroy_private);

int lttng_kretprobes_event_enable_state(struct lttng_event *event,
		int enable)
{
	struct lttng_event *event_return;
	struct lttng_krp *lttng_krp;

	if (event->instrumentation != LTTNG_KERNEL_KRETPROBE) {
		return -EINVAL;
	}
	if (event->enabled == enable) {
		return -EBUSY;
	}
	lttng_krp = event->u.kretprobe.lttng_krp;
	event_return = lttng_krp->event[EVENT_RETURN];
	WRITE_ONCE(event->enabled, enable);
	WRITE_ONCE(event_return->enabled, enable);
	return 0;
}
EXPORT_SYMBOL_GPL(lttng_kretprobes_event_enable_state);

MODULE_LICENSE("GPL and additional rights");
MODULE_AUTHOR("Mathieu Desnoyers");
MODULE_DESCRIPTION("Linux Trace Toolkit Kretprobes Support");
MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
	__stringify(LTTNG_MODULES_MINOR_VERSION) "."
	__stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
	LTTNG_MODULES_EXTRAVERSION);
Commit	Line	Data
	1	/*
	2	* probes/lttng-kretprobes.c
	3	*
	4	* LTTng kretprobes integration module.
	5	*
	6	* Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	7	*
	8	* This library is free software; you can redistribute it and/or
	9	* modify it under the terms of the GNU Lesser General Public
	10	* License as published by the Free Software Foundation; only
	11	* version 2.1 of the License.
	12	*
	13	* This library is distributed in the hope that it will be useful,
	14	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	15	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	16	* Lesser General Public License for more details.
	17	*
	18	* You should have received a copy of the GNU Lesser General Public
	19	* License along with this library; if not, write to the Free Software
	20	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	21	*/
	22
	23	#include <linux/module.h>
	24	#include <linux/kprobes.h>
	25	#include <linux/slab.h>
	26	#include <linux/kref.h>
	27	#include <lttng-events.h>
	28	#include <wrapper/ringbuffer/frontend_types.h>
	29	#include <wrapper/vmalloc.h>
	30	#include <wrapper/irqflags.h>
	31	#include <lttng-tracer.h>
	32
	33	enum lttng_kretprobe_type {
	34	EVENT_ENTRY = 0,
	35	EVENT_RETURN = 1,
	36	};
	37
	38	struct lttng_krp {
	39	struct kretprobe krp;
	40	struct lttng_event event[2]; / ENTRY and RETURN */
	41	struct kref kref_register;
	42	struct kref kref_alloc;
	43	};
	44
	45	static
	46	int _lttng_kretprobes_handler(struct kretprobe_instance *krpi,
	47	struct pt_regs *regs,
	48	enum lttng_kretprobe_type type)
	49	{
	50	struct lttng_krp *lttng_krp =
	51	container_of(krpi->rp, struct lttng_krp, krp);
	52	struct lttng_event *event =
	53	lttng_krp->event[type];
	54	struct lttng_probe_ctx lttng_probe_ctx = {
	55	.event = event,
	56	.interruptible = !lttng_regs_irqs_disabled(regs),
	57	};
	58	struct lttng_channel *chan = event->chan;
	59	struct lib_ring_buffer_ctx ctx;
	60	int ret;
	61	struct {
	62	unsigned long ip;
	63	unsigned long parent_ip;
	64	} payload;
	65
	66	if (unlikely(!READ_ONCE(chan->session->active)))
	67	return 0;
	68	if (unlikely(!READ_ONCE(chan->enabled)))
	69	return 0;
	70	if (unlikely(!READ_ONCE(event->enabled)))
	71	return 0;
	72
	73	payload.ip = (unsigned long) krpi->rp->kp.addr;
	74	payload.parent_ip = (unsigned long) krpi->ret_addr;
	75
	76	lib_ring_buffer_ctx_init(&ctx, chan->chan, &lttng_probe_ctx, sizeof(payload),
	77	lttng_alignof(payload), -1);
	78	ret = chan->ops->event_reserve(&ctx, event->id);
	79	if (ret < 0)
	80	return 0;
	81	lib_ring_buffer_align_ctx(&ctx, lttng_alignof(payload));
	82	chan->ops->event_write(&ctx, &payload, sizeof(payload));
	83	chan->ops->event_commit(&ctx);
	84	return 0;
	85	}
	86
	87	static
	88	int lttng_kretprobes_handler_entry(struct kretprobe_instance *krpi,
	89	struct pt_regs *regs)
	90	{
	91	return _lttng_kretprobes_handler(krpi, regs, EVENT_ENTRY);
	92	}
	93
	94	static
	95	int lttng_kretprobes_handler_return(struct kretprobe_instance *krpi,
	96	struct pt_regs *regs)
	97	{
	98	return _lttng_kretprobes_handler(krpi, regs, EVENT_RETURN);
	99	}
	100
	101	/*
	102	* Create event description
	103	*/
	104	static
	105	int lttng_create_kprobe_event(const char name, struct lttng_event event,
	106	enum lttng_kretprobe_type type)
	107	{
	108	struct lttng_event_field *fields;
	109	struct lttng_event_desc *desc;
	110	int ret;
	111	char *alloc_name;
	112	size_t name_len;
	113	const char *suffix = NULL;
	114
	115	desc = kzalloc(sizeof(*event->desc), GFP_KERNEL);
	116	if (!desc)
	117	return -ENOMEM;
	118	name_len = strlen(name);
	119	switch (type) {
	120	case EVENT_ENTRY:
	121	suffix = "_entry";
	122	break;
	123	case EVENT_RETURN:
	124	suffix = "_return";
	125	break;
	126	}
	127	name_len += strlen(suffix);
	128	alloc_name = kmalloc(name_len + 1, GFP_KERNEL);
	129	if (!alloc_name) {
	130	ret = -ENOMEM;
	131	goto error_str;
	132	}
	133	strcpy(alloc_name, name);
	134	strcat(alloc_name, suffix);
	135	desc->name = alloc_name;
	136	desc->nr_fields = 2;
	137	desc->fields = fields =
	138	kzalloc(2 * sizeof(struct lttng_event_field), GFP_KERNEL);
	139	if (!desc->fields) {
	140	ret = -ENOMEM;
	141	goto error_fields;
	142	}
	143	fields[0].name = "ip";
	144	fields[0].type.atype = atype_integer;
	145	fields[0].type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT;
	146	fields[0].type.u.basic.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
	147	fields[0].type.u.basic.integer.signedness = lttng_is_signed_type(unsigned long);
	148	fields[0].type.u.basic.integer.reverse_byte_order = 0;
	149	fields[0].type.u.basic.integer.base = 16;
	150	fields[0].type.u.basic.integer.encoding = lttng_encode_none;
	151
	152	fields[1].name = "parent_ip";
	153	fields[1].type.atype = atype_integer;
	154	fields[1].type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT;
	155	fields[1].type.u.basic.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
	156	fields[1].type.u.basic.integer.signedness = lttng_is_signed_type(unsigned long);
	157	fields[1].type.u.basic.integer.reverse_byte_order = 0;
	158	fields[1].type.u.basic.integer.base = 16;
	159	fields[1].type.u.basic.integer.encoding = lttng_encode_none;
	160
	161	desc->owner = THIS_MODULE;
	162	event->desc = desc;
	163
	164	return 0;
	165
	166	error_fields:
	167	kfree(desc->name);
	168	error_str:
	169	kfree(desc);
	170	return ret;
	171	}
	172
	173	int lttng_kretprobes_register(const char *name,
	174	const char *symbol_name,
	175	uint64_t offset,
	176	uint64_t addr,
	177	struct lttng_event *event_entry,
	178	struct lttng_event *event_return)
	179	{
	180	int ret;
	181	struct lttng_krp *lttng_krp;
	182
	183	/* Kprobes expects a NULL symbol name if unused */
	184	if (symbol_name[0] == '\0')
	185	symbol_name = NULL;
	186
	187	ret = lttng_create_kprobe_event(name, event_entry, EVENT_ENTRY);
	188	if (ret)
	189	goto error;
	190	ret = lttng_create_kprobe_event(name, event_return, EVENT_RETURN);
	191	if (ret)
	192	goto event_return_error;
	193	lttng_krp = kzalloc(sizeof(*lttng_krp), GFP_KERNEL);
	194	if (!lttng_krp)
	195	goto krp_error;
	196	lttng_krp->krp.entry_handler = lttng_kretprobes_handler_entry;
	197	lttng_krp->krp.handler = lttng_kretprobes_handler_return;
	198	if (symbol_name) {
	199	char *alloc_symbol;
	200
	201	alloc_symbol = kstrdup(symbol_name, GFP_KERNEL);
	202	if (!alloc_symbol) {
	203	ret = -ENOMEM;
	204	goto name_error;
	205	}
	206	lttng_krp->krp.kp.symbol_name =
	207	alloc_symbol;
	208	event_entry->u.kretprobe.symbol_name =
	209	alloc_symbol;
	210	event_return->u.kretprobe.symbol_name =
	211	alloc_symbol;
	212	}
	213	lttng_krp->krp.kp.offset = offset;
	214	lttng_krp->krp.kp.addr = (void *) (unsigned long) addr;
	215
	216	/* Allow probe handler to find event structures */
	217	lttng_krp->event[EVENT_ENTRY] = event_entry;
	218	lttng_krp->event[EVENT_RETURN] = event_return;
	219	event_entry->u.kretprobe.lttng_krp = lttng_krp;
	220	event_return->u.kretprobe.lttng_krp = lttng_krp;
	221
	222	/*
	223	* Both events must be unregistered before the kretprobe is
	224	* unregistered. Same for memory allocation.
	225	*/
	226	kref_init(&lttng_krp->kref_alloc);
	227	kref_get(&lttng_krp->kref_alloc); /* inc refcount to 2, no overflow. */
	228	kref_init(&lttng_krp->kref_register);
	229	kref_get(&lttng_krp->kref_register); /* inc refcount to 2, no overflow. */
	230
	231	/*
	232	* Ensure the memory we just allocated don't trigger page faults.
	233	* Well.. kprobes itself puts the page fault handler on the blacklist,
	234	* but we can never be too careful.
	235	*/
	236	wrapper_vmalloc_sync_all();
	237
	238	ret = register_kretprobe(&lttng_krp->krp);
	239	if (ret)
	240	goto register_error;
	241	return 0;
	242
	243	register_error:
	244	kfree(lttng_krp->krp.kp.symbol_name);
	245	name_error:
	246	kfree(lttng_krp);
	247	krp_error:
	248	kfree(event_return->desc->fields);
	249	kfree(event_return->desc->name);
	250	kfree(event_return->desc);
	251	event_return_error:
	252	kfree(event_entry->desc->fields);
	253	kfree(event_entry->desc->name);
	254	kfree(event_entry->desc);
	255	error:
	256	return ret;
	257	}
	258	EXPORT_SYMBOL_GPL(lttng_kretprobes_register);
	259
	260	static
	261	void _lttng_kretprobes_unregister_release(struct kref *kref)
	262	{
	263	struct lttng_krp *lttng_krp =
	264	container_of(kref, struct lttng_krp, kref_register);
	265	unregister_kretprobe(&lttng_krp->krp);
	266	}
	267
	268	void lttng_kretprobes_unregister(struct lttng_event *event)
	269	{
	270	kref_put(&event->u.kretprobe.lttng_krp->kref_register,
	271	_lttng_kretprobes_unregister_release);
	272	}
	273	EXPORT_SYMBOL_GPL(lttng_kretprobes_unregister);
	274
	275	static
	276	void _lttng_kretprobes_release(struct kref *kref)
	277	{
	278	struct lttng_krp *lttng_krp =
	279	container_of(kref, struct lttng_krp, kref_alloc);
	280	kfree(lttng_krp->krp.kp.symbol_name);
	281	}
	282
	283	void lttng_kretprobes_destroy_private(struct lttng_event *event)
	284	{
	285	kfree(event->desc->fields);
	286	kfree(event->desc->name);
	287	kfree(event->desc);
	288	kref_put(&event->u.kretprobe.lttng_krp->kref_alloc,
	289	_lttng_kretprobes_release);
	290	}
	291	EXPORT_SYMBOL_GPL(lttng_kretprobes_destroy_private);
	292
	293	int lttng_kretprobes_event_enable_state(struct lttng_event *event,
	294	int enable)
	295	{
	296	struct lttng_event *event_return;
	297	struct lttng_krp *lttng_krp;
	298
	299	if (event->instrumentation != LTTNG_KERNEL_KRETPROBE) {
	300	return -EINVAL;
	301	}
	302	if (event->enabled == enable) {
	303	return -EBUSY;
	304	}
	305	lttng_krp = event->u.kretprobe.lttng_krp;
	306	event_return = lttng_krp->event[EVENT_RETURN];
	307	WRITE_ONCE(event->enabled, enable);
	308	WRITE_ONCE(event_return->enabled, enable);
	309	return 0;
	310	}
	311	EXPORT_SYMBOL_GPL(lttng_kretprobes_event_enable_state);
	312
	313	MODULE_LICENSE("GPL and additional rights");
	314	MODULE_AUTHOR("Mathieu Desnoyers");
	315	MODULE_DESCRIPTION("Linux Trace Toolkit Kretprobes Support");
	316	MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
	317	__stringify(LTTNG_MODULES_MINOR_VERSION) "."
	318	__stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
	319	LTTNG_MODULES_EXTRAVERSION);