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

/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
 *
 * lttng-probes.c
 *
 * Holds LTTng probes registry.
 *
 * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 */

#include <linux/module.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/seq_file.h>

#include <lttng/events.h>
#include <lttng/events-internal.h>

/*
 * probe list is protected by sessions lock.
 */
static LIST_HEAD(_probe_list);

/*
 * List of probes registered by not yet processed.
 */
static LIST_HEAD(lazy_probe_init);

/*
 * lazy_nesting counter ensures we don't notify lazy probe registration
 * fixup while we are performing the fixup. It is protected by the
 * sessions lock.
 */
static int lazy_nesting;

DEFINE_PER_CPU(struct lttng_dynamic_len_stack, lttng_dynamic_len_stack);

EXPORT_PER_CPU_SYMBOL_GPL(lttng_dynamic_len_stack);

/*
 * Called under sessions lock.
 */
static
int check_event_provider(struct lttng_kernel_probe_desc *desc)
{
	int i, mismatch = 0;
	size_t provider_name_len;

	provider_name_len = strnlen(desc->provider_name,
				LTTNG_KERNEL_ABI_SYM_NAME_LEN - 1);
	for (i = 0; i < desc->nr_events; i++) {
		/*
		 * The event name needs to start with provider name + _ +
		 * one or more letter.
		 */
		if (strncmp(desc->event_desc[i]->event_name, desc->provider_name, provider_name_len))
			mismatch = 1;
		else if (strlen(desc->event_desc[i]->event_name) <= provider_name_len + 1)
			mismatch = 1;
		else if (desc->event_desc[i]->event_name[provider_name_len] != '_')
			mismatch = 1;

		if (mismatch) {
			printk(KERN_WARNING "LTTng: event provider mismatch: "
				"The event name needs to start with provider "
				"name + _ + one or more letter, "
				"provider: %s, event name: %s\n",
				desc->provider_name, desc->event_desc[i]->event_name);
			return 0;
		}
	}
	return 1;
}

/*
 * Called under sessions lock.
 */
static
void lttng_lazy_probe_register(struct lttng_kernel_probe_desc *desc)
{
	struct lttng_kernel_probe_desc *iter;
	struct list_head *probe_list;

	/*
	 * Each provider enforce that every event name begins with the
	 * provider name. Check this in an assertion for extra
	 * carefulness. This ensures we cannot have duplicate event
	 * names across providers.
	 */
	WARN_ON_ONCE(!check_event_provider(desc));

	/*
	 * The provider ensures there are no duplicate event names.
	 * Duplicated TRACEPOINT_EVENT event names would generate a
	 * compile-time error due to duplicated symbol names.
	 */

	/*
	 * We sort the providers by struct lttng_kernel_probe_desc pointer
	 * address.
	 */
	probe_list = &_probe_list;
	list_for_each_entry_reverse(iter, probe_list, head) {
		BUG_ON(iter == desc); /* Should never be in the list twice */
		if (iter < desc) {
			/* We belong to the location right after iter. */
			list_add(&desc->head, &iter->head);
			goto desc_added;
		}
	}
	/* We should be added at the head of the list */
	list_add(&desc->head, probe_list);
desc_added:
	pr_debug("LTTng: just registered probe %s containing %u events\n",
		desc->provider_name, desc->nr_events);
}

/*
 * Called under sessions lock.
 */
static
void fixup_lazy_probes(void)
{
	struct lttng_kernel_probe_desc *iter, *tmp;
	int ret;

	lazy_nesting++;
	list_for_each_entry_safe(iter, tmp,
			&lazy_probe_init, lazy_init_head) {
		lttng_lazy_probe_register(iter);
		iter->lazy = 0;
		list_del(&iter->lazy_init_head);
	}
	ret = lttng_fix_pending_events();
	WARN_ON_ONCE(ret);
	ret = lttng_fix_pending_event_notifiers();
	WARN_ON_ONCE(ret);
	lazy_nesting--;
}

/*
 * Called under sessions lock.
 */
struct list_head *lttng_get_probe_list_head(void)
{
	if (!lazy_nesting && !list_empty(&lazy_probe_init))
		fixup_lazy_probes();
	return &_probe_list;
}

static
const struct lttng_kernel_probe_desc *find_provider(const char *provider)
{
	struct lttng_kernel_probe_desc *iter;
	struct list_head *probe_list;

	probe_list = lttng_get_probe_list_head();
	list_for_each_entry(iter, probe_list, head) {
		if (!strcmp(iter->provider_name, provider))
			return iter;
	}
	return NULL;
}

int lttng_kernel_probe_register(struct lttng_kernel_probe_desc *desc)
{
	int ret = 0;

	lttng_lock_sessions();

	/*
	 * Check if the provider has already been registered.
	 */
	if (find_provider(desc->provider_name)) {
		ret = -EEXIST;
		goto end;
	}
	list_add(&desc->lazy_init_head, &lazy_probe_init);
	desc->lazy = 1;
	pr_debug("LTTng: adding probe %s containing %u events to lazy registration list\n",
		desc->provider_name, desc->nr_events);
	/*
	 * If there is at least one active session, we need to register
	 * the probe immediately, since we cannot delay event
	 * registration because they are needed ASAP.
	 */
	if (lttng_session_active() || lttng_event_notifier_active())
		fixup_lazy_probes();
end:
	lttng_unlock_sessions();
	return ret;
}
EXPORT_SYMBOL_GPL(lttng_kernel_probe_register);

void lttng_kernel_probe_unregister(struct lttng_kernel_probe_desc *desc)
{
	lttng_lock_sessions();
	if (!desc->lazy)
		list_del(&desc->head);
	else
		list_del(&desc->lazy_init_head);
	pr_debug("LTTng: just unregistered probe %s\n", desc->provider_name);
	lttng_unlock_sessions();
}
EXPORT_SYMBOL_GPL(lttng_kernel_probe_unregister);

/*
 * TODO: this is O(nr_probes * nb_events), could be faster.
 * Called with sessions lock held.
 */
static
const struct lttng_kernel_event_desc *find_event_desc(const char *name)
{
	struct lttng_kernel_probe_desc *probe_desc;
	int i;

	list_for_each_entry(probe_desc, &_probe_list, head) {
		for (i = 0; i < probe_desc->nr_events; i++) {
			if (!strcmp(probe_desc->event_desc[i]->event_name, name))
				return probe_desc->event_desc[i];
			}
	}
	return NULL;
}

/*
 * Called with sessions lock held.
 */
const struct lttng_kernel_event_desc *lttng_event_desc_get(const char *name)
{
	const struct lttng_kernel_event_desc *event_desc;
	int ret;

	event_desc = find_event_desc(name);
	if (!event_desc)
		return NULL;
	ret = try_module_get(event_desc->owner);
	WARN_ON_ONCE(!ret);
	return event_desc;
}
EXPORT_SYMBOL_GPL(lttng_event_desc_get);

/*
 * Called with sessions lock held.
 */
void lttng_event_desc_put(const struct lttng_kernel_event_desc *event_desc)
{
	module_put(event_desc->owner);
}
EXPORT_SYMBOL_GPL(lttng_event_desc_put);

static
void *tp_list_start(struct seq_file *m, loff_t *pos)
{
	struct lttng_kernel_probe_desc *probe_desc;
	struct list_head *probe_list;
	int iter = 0, i;

	lttng_lock_sessions();
	probe_list = lttng_get_probe_list_head();
	list_for_each_entry(probe_desc, probe_list, head) {
		for (i = 0; i < probe_desc->nr_events; i++) {
			if (iter++ >= *pos)
				return (void *) probe_desc->event_desc[i];
		}
	}
	/* End of list */
	return NULL;
}

static
void *tp_list_next(struct seq_file *m, void *p, loff_t *ppos)
{
	struct lttng_kernel_probe_desc *probe_desc;
	struct list_head *probe_list;
	int iter = 0, i;

	(*ppos)++;
	probe_list = lttng_get_probe_list_head();
	list_for_each_entry(probe_desc, probe_list, head) {
		for (i = 0; i < probe_desc->nr_events; i++) {
			if (iter++ >= *ppos)
				return (void *) probe_desc->event_desc[i];
		}
	}
	/* End of list */
	return NULL;
}

static
void tp_list_stop(struct seq_file *m, void *p)
{
	lttng_unlock_sessions();
}

static
int tp_list_show(struct seq_file *m, void *p)
{
	const struct lttng_kernel_event_desc *probe_desc = p;

	seq_printf(m,	"event { name = %s; };\n",
		   probe_desc->event_name);
	return 0;
}

static
const struct seq_operations lttng_tracepoint_list_seq_ops = {
	.start = tp_list_start,
	.next = tp_list_next,
	.stop = tp_list_stop,
	.show = tp_list_show,
};

static
int lttng_tracepoint_list_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &lttng_tracepoint_list_seq_ops);
}

const struct file_operations lttng_tracepoint_list_fops = {
	.owner = THIS_MODULE,
	.open = lttng_tracepoint_list_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = seq_release,
};

int lttng_probes_init(void)
{
	int cpu;

	for_each_possible_cpu(cpu)
		per_cpu_ptr(&lttng_dynamic_len_stack, cpu)->offset = 0;
	return 0;
}
Commit	Line	Data
b7cdc182	1	/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
9f36eaed	2	*
a90917c3	3	* lttng-probes.c
02119ee5	4	*
02119ee5	5	* Holds LTTng probes registry.
17baffe2	6	*
886d51a3	7	* Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
02119ee5 MD	8	*/
	9
	10	#include <linux/module.h>
	11	#include <linux/list.h>
	12	#include <linux/mutex.h>
271b6681	13	#include <linux/seq_file.h>
02119ee5	14
2df37e95	15	#include <lttng/events.h>
e8c0bbd3	16	#include <lttng/events-internal.h>
02119ee5	17
3c997079 MD	18	/*
	19	* probe list is protected by sessions lock.
	20	*/
	21	static LIST_HEAD(_probe_list);
	22
	23	/*
	24	* List of probes registered by not yet processed.
	25	*/
	26	static LIST_HEAD(lazy_probe_init);
02119ee5	27
3c997079	28	/*
196bfc6a	29	* lazy_nesting counter ensures we don't notify lazy probe registration
3c997079 MD	30	* fixup while we are performing the fixup. It is protected by the
	31	* sessions lock.
	32	*/
	33	static int lazy_nesting;
	34
114667d5 MD	35	DEFINE_PER_CPU(struct lttng_dynamic_len_stack, lttng_dynamic_len_stack);
	36
	37	EXPORT_PER_CPU_SYMBOL_GPL(lttng_dynamic_len_stack);
	38
3c997079 MD	39	/*
	40	* Called under sessions lock.
	41	*/
85a9ca7f	42	static
437d5aa5	43	int check_event_provider(struct lttng_kernel_probe_desc *desc)
02119ee5	44	{
0c87bcc6	45	int i, mismatch = 0;
3c997079	46	size_t provider_name_len;
02119ee5	47
437d5aa5	48	provider_name_len = strnlen(desc->provider_name,
606828e4	49	LTTNG_KERNEL_ABI_SYM_NAME_LEN - 1);
3c997079	50	for (i = 0; i < desc->nr_events; i++) {
021153c0	51	/*
0c87bcc6	52	* The event name needs to start with provider name + _ +
021153c0 MD	53	* one or more letter.
021153c0 MD	54	*/
0c87bcc6 HZ	55	if (strncmp(desc->event_desc[i]->event_name, desc->provider_name, provider_name_len))
	56	mismatch = 1;
	57	else if (strlen(desc->event_desc[i]->event_name) <= provider_name_len + 1)
	58	mismatch = 1;
	59	else if (desc->event_desc[i]->event_name[provider_name_len] != '_')
	60	mismatch = 1;
	61
	62	if (mismatch) {
	63	printk(KERN_WARNING "LTTng: event provider mismatch: "
	64	"The event name needs to start with provider "
	65	"name + _ + one or more letter, "
	66	"provider: %s, event name: %s\n",
	67	desc->provider_name, desc->event_desc[i]->event_name);
	68	return 0;
	69	}
3c997079 MD	70	}
	71	return 1;
	72	}
	73
	74	/*
	75	* Called under sessions lock.
	76	*/
	77	static
437d5aa5	78	void lttng_lazy_probe_register(struct lttng_kernel_probe_desc *desc)
3c997079	79	{
437d5aa5	80	struct lttng_kernel_probe_desc *iter;
3c997079 MD	81	struct list_head *probe_list;
	82
	83	/*
	84	* Each provider enforce that every event name begins with the
	85	* provider name. Check this in an assertion for extra
	86	* carefulness. This ensures we cannot have duplicate event
	87	* names across providers.
	88	*/
	89	WARN_ON_ONCE(!check_event_provider(desc));
	90
	91	/*
	92	* The provider ensures there are no duplicate event names.
	93	* Duplicated TRACEPOINT_EVENT event names would generate a
	94	* compile-time error due to duplicated symbol names.
	95	*/
	96
	97	/*
437d5aa5	98	* We sort the providers by struct lttng_kernel_probe_desc pointer
3c997079 MD	99	* address.
	100	*/
	101	probe_list = &_probe_list;
	102	list_for_each_entry_reverse(iter, probe_list, head) {
	103	BUG_ON(iter == desc); /* Should never be in the list twice */
	104	if (iter < desc) {
	105	/* We belong to the location right after iter. */
	106	list_add(&desc->head, &iter->head);
	107	goto desc_added;
85a9ca7f	108	}
02119ee5	109	}
3c997079 MD	110	/* We should be added at the head of the list */
	111	list_add(&desc->head, probe_list);
	112	desc_added:
33a39a3c	113	pr_debug("LTTng: just registered probe %s containing %u events\n",
437d5aa5	114	desc->provider_name, desc->nr_events);
3c997079 MD	115	}
	116
	117	/*
	118	* Called under sessions lock.
	119	*/
	120	static
	121	void fixup_lazy_probes(void)
	122	{
437d5aa5	123	struct lttng_kernel_probe_desc iter, tmp;
3c997079 MD	124	int ret;
	125
	126	lazy_nesting++;
	127	list_for_each_entry_safe(iter, tmp,
	128	&lazy_probe_init, lazy_init_head) {
	129	lttng_lazy_probe_register(iter);
	130	iter->lazy = 0;
	131	list_del(&iter->lazy_init_head);
	132	}
	133	ret = lttng_fix_pending_events();
	134	WARN_ON_ONCE(ret);
b01155ba FD	135	ret = lttng_fix_pending_event_notifiers();
b01155ba FD	136	WARN_ON_ONCE(ret);
3c997079 MD	137	lazy_nesting--;
	138	}
	139
	140	/*
	141	* Called under sessions lock.
	142	*/
	143	struct list_head *lttng_get_probe_list_head(void)
	144	{
	145	if (!lazy_nesting && !list_empty(&lazy_probe_init))
	146	fixup_lazy_probes();
	147	return &_probe_list;
	148	}
	149
	150	static
437d5aa5	151	const struct lttng_kernel_probe_desc find_provider(const char provider)
3c997079	152	{
437d5aa5	153	struct lttng_kernel_probe_desc *iter;
3c997079 MD	154	struct list_head *probe_list;
	155
	156	probe_list = lttng_get_probe_list_head();
	157	list_for_each_entry(iter, probe_list, head) {
437d5aa5	158	if (!strcmp(iter->provider_name, provider))
3c997079 MD	159	return iter;
3c997079 MD	160	}
02119ee5 MD	161	return NULL;
	162	}
	163
d1769981	164	int lttng_kernel_probe_register(struct lttng_kernel_probe_desc *desc)
02119ee5	165	{
02119ee5	166	int ret = 0;
02119ee5	167
3c997079 MD	168	lttng_lock_sessions();
3c997079 MD	169
85a9ca7f	170	/*
3c997079	171	* Check if the provider has already been registered.
85a9ca7f	172	*/
437d5aa5	173	if (find_provider(desc->provider_name)) {
3c997079 MD	174	ret = -EEXIST;
3c997079 MD	175	goto end;
02119ee5	176	}
3c997079 MD	177	list_add(&desc->lazy_init_head, &lazy_probe_init);
3c997079 MD	178	desc->lazy = 1;
33a39a3c	179	pr_debug("LTTng: adding probe %s containing %u events to lazy registration list\n",
437d5aa5	180	desc->provider_name, desc->nr_events);
3c997079 MD	181	/*
	182	* If there is at least one active session, we need to register
	183	* the probe immediately, since we cannot delay event
	184	* registration because they are needed ASAP.
	185	*/
b01155ba	186	if (lttng_session_active() \|\| lttng_event_notifier_active())
3c997079	187	fixup_lazy_probes();
02119ee5	188	end:
3c997079	189	lttng_unlock_sessions();
02119ee5 MD	190	return ret;
02119ee5 MD	191	}
d1769981	192	EXPORT_SYMBOL_GPL(lttng_kernel_probe_register);
02119ee5	193
d1769981	194	void lttng_kernel_probe_unregister(struct lttng_kernel_probe_desc *desc)
02119ee5	195	{
3c997079 MD	196	lttng_lock_sessions();
	197	if (!desc->lazy)
	198	list_del(&desc->head);
	199	else
	200	list_del(&desc->lazy_init_head);
437d5aa5	201	pr_debug("LTTng: just unregistered probe %s\n", desc->provider_name);
3c997079	202	lttng_unlock_sessions();
02119ee5	203	}
d1769981	204	EXPORT_SYMBOL_GPL(lttng_kernel_probe_unregister);
02119ee5	205
3c997079 MD	206	/*
	207	* TODO: this is O(nr_probes * nb_events), could be faster.
	208	* Called with sessions lock held.
	209	*/
	210	static
437d5aa5	211	const struct lttng_kernel_event_desc find_event_desc(const char name)
3c997079	212	{
437d5aa5	213	struct lttng_kernel_probe_desc *probe_desc;
3c997079 MD	214	int i;
	215
	216	list_for_each_entry(probe_desc, &_probe_list, head) {
	217	for (i = 0; i < probe_desc->nr_events; i++) {
437d5aa5	218	if (!strcmp(probe_desc->event_desc[i]->event_name, name))
3c997079 MD	219	return probe_desc->event_desc[i];
	220	}
	221	}
	222	return NULL;
	223	}
	224
	225	/*
	226	* Called with sessions lock held.
	227	*/
437d5aa5	228	const struct lttng_kernel_event_desc lttng_event_desc_get(const char name)
02119ee5	229	{
437d5aa5	230	const struct lttng_kernel_event_desc *event_desc;
02119ee5 MD	231	int ret;
02119ee5 MD	232
0bcedee9 FD	233	event_desc = find_event_desc(name);
0bcedee9 FD	234	if (!event_desc)
c099397a	235	return NULL;
0bcedee9	236	ret = try_module_get(event_desc->owner);
02119ee5	237	WARN_ON_ONCE(!ret);
0bcedee9	238	return event_desc;
02119ee5	239	}
0bcedee9	240	EXPORT_SYMBOL_GPL(lttng_event_desc_get);
02119ee5	241
3c997079 MD	242	/*
	243	* Called with sessions lock held.
	244	*/
437d5aa5	245	void lttng_event_desc_put(const struct lttng_kernel_event_desc *event_desc)
02119ee5	246	{
0bcedee9	247	module_put(event_desc->owner);
02119ee5	248	}
0bcedee9	249	EXPORT_SYMBOL_GPL(lttng_event_desc_put);
271b6681 MD	250
	251	static
	252	void tp_list_start(struct seq_file m, loff_t *pos)
	253	{
437d5aa5	254	struct lttng_kernel_probe_desc *probe_desc;
a1031097	255	struct list_head *probe_list;
271b6681 MD	256	int iter = 0, i;
271b6681 MD	257
3c997079	258	lttng_lock_sessions();
a1031097 MD	259	probe_list = lttng_get_probe_list_head();
a1031097 MD	260	list_for_each_entry(probe_desc, probe_list, head) {
271b6681 MD	261	for (i = 0; i < probe_desc->nr_events; i++) {
271b6681 MD	262	if (iter++ >= *pos)
f7bdf4db	263	return (void *) probe_desc->event_desc[i];
271b6681 MD	264	}
	265	}
	266	/* End of list */
	267	return NULL;
	268	}
	269
	270	static
	271	void tp_list_next(struct seq_file m, void p, loff_t ppos)
	272	{
437d5aa5	273	struct lttng_kernel_probe_desc *probe_desc;
a1031097	274	struct list_head *probe_list;
271b6681 MD	275	int iter = 0, i;
	276
	277	(*ppos)++;
a1031097 MD	278	probe_list = lttng_get_probe_list_head();
a1031097 MD	279	list_for_each_entry(probe_desc, probe_list, head) {
271b6681 MD	280	for (i = 0; i < probe_desc->nr_events; i++) {
271b6681 MD	281	if (iter++ >= *ppos)
f7bdf4db	282	return (void *) probe_desc->event_desc[i];
271b6681 MD	283	}
	284	}
	285	/* End of list */
	286	return NULL;
	287	}
	288
	289	static
	290	void tp_list_stop(struct seq_file m, void p)
	291	{
3c997079	292	lttng_unlock_sessions();
271b6681 MD	293	}
	294
	295	static
	296	int tp_list_show(struct seq_file m, void p)
	297	{
437d5aa5	298	const struct lttng_kernel_event_desc *probe_desc = p;
271b6681 MD	299
271b6681 MD	300	seq_printf(m, "event { name = %s; };\n",
437d5aa5	301	probe_desc->event_name);
271b6681 MD	302	return 0;
	303	}
	304
	305	static
	306	const struct seq_operations lttng_tracepoint_list_seq_ops = {
	307	.start = tp_list_start,
	308	.next = tp_list_next,
	309	.stop = tp_list_stop,
	310	.show = tp_list_show,
	311	};
	312
	313	static
	314	int lttng_tracepoint_list_open(struct inode inode, struct file file)
	315	{
	316	return seq_open(file, &lttng_tracepoint_list_seq_ops);
	317	}
	318
	319	const struct file_operations lttng_tracepoint_list_fops = {
2e54c205	320	.owner = THIS_MODULE,
271b6681 MD	321	.open = lttng_tracepoint_list_open,
	322	.read = seq_read,
	323	.llseek = seq_lseek,
a51729c7	324	.release = seq_release,
271b6681	325	};
114667d5 MD	326
	327	int lttng_probes_init(void)
	328	{
	329	int cpu;
	330
	331	for_each_possible_cpu(cpu)
	332	per_cpu_ptr(&lttng_dynamic_len_stack, cpu)->offset = 0;
	333	return 0;
	334	}