[libside.git] / src / side.c

// SPDX-License-Identifier: MIT
/*
 * Copyright 2022 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 */

#include <side/trace.h>
#include <string.h>

#include "tracer.h"
#include "rcu.h"
#include "list.h"

/* Top 8 bits reserved for kernel tracer use. */
#define SIDE_EVENT_ENABLED_KERNEL_MASK			0xFF000000
#define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK	0x80000000

/* Allow 2^24 tracer callbacks to be registered on an event. */
#define SIDE_EVENT_ENABLED_USER_MASK			0x00FFFFFF

struct side_events_register_handle {
	struct side_list_node node;
	struct side_event_description **events;
	uint32_t nr_events;
};

struct side_tracer_handle {
	struct side_list_node node;
	void (*cb)(enum side_tracer_notification notif,
		struct side_event_description **events, uint32_t nr_events, void *priv);
	void *priv;
};

static struct side_rcu_gp_state rcu_gp;

/*
 * Lazy initialization for early use within library constructors.
 */
static bool initialized;
/*
 * Do not register/unregister any more events after destructor.
 */
static bool finalized;

static pthread_mutex_t side_lock = PTHREAD_MUTEX_INITIALIZER;

static DEFINE_SIDE_LIST_HEAD(side_events_list);
static DEFINE_SIDE_LIST_HEAD(side_tracer_list);

/*
 * The empty callback has a NULL function callback pointer, which stops
 * iteration on the array of callbacks immediately.
 */
const struct side_callback side_empty_callback;

void side_init(void) __attribute__((constructor));
void side_exit(void) __attribute__((destructor));

void side_call(const struct side_event_description *desc, const struct side_arg_vec_description *sav_desc)
{
	const struct side_callback *side_cb;
	unsigned int rcu_period;
	uint32_t enabled;

	if (side_unlikely(finalized))
		return;
	if (side_unlikely(!initialized))
		side_init();
	if (side_unlikely(desc->flags & SIDE_EVENT_FLAG_VARIADIC)) {
		printf("ERROR: unexpected variadic event description\n");
		abort();
	}
	enabled = __atomic_load_n(desc->enabled, __ATOMIC_RELAXED);
	if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
		// TODO: call kernel write.
	}
	if (side_unlikely(!(enabled & SIDE_EVENT_ENABLED_USER_MASK)))
		return;

	rcu_period = side_rcu_read_begin(&rcu_gp);
	for (side_cb = side_rcu_dereference(desc->callbacks); side_cb->u.call != NULL; side_cb++)
		side_cb->u.call(desc, sav_desc, side_cb->priv);
	side_rcu_read_end(&rcu_gp, rcu_period);
}

void side_call_variadic(const struct side_event_description *desc,
	const struct side_arg_vec_description *sav_desc,
	const struct side_arg_dynamic_event_struct *var_struct)
{
	const struct side_callback *side_cb;
	unsigned int rcu_period;
	uint32_t enabled;

	if (side_unlikely(finalized))
		return;
	if (side_unlikely(!initialized))
		side_init();
	if (side_unlikely(!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))) {
		printf("ERROR: unexpected non-variadic event description\n");
		abort();
	}
	enabled = __atomic_load_n(desc->enabled, __ATOMIC_RELAXED);
	if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
		// TODO: call kernel write.
	}
	if (side_unlikely(!(enabled & SIDE_EVENT_ENABLED_USER_MASK)))
		return;

	rcu_period = side_rcu_read_begin(&rcu_gp);
	for (side_cb = side_rcu_dereference(desc->callbacks); side_cb->u.call_variadic != NULL; side_cb++)
		side_cb->u.call_variadic(desc, sav_desc, var_struct, side_cb->priv);
	side_rcu_read_end(&rcu_gp, rcu_period);
}

static
const struct side_callback *side_tracer_callback_lookup(
		const struct side_event_description *desc,
		void (*call)(), void *priv)
{
	const struct side_callback *cb;

	for (cb = desc->callbacks; cb->u.call != NULL; cb++) {
		if (cb->u.call == call && cb->priv == priv)
			return cb;
	}
	return NULL;
}

static
int _side_tracer_callback_register(struct side_event_description *desc,
		void (*call)(), void *priv)
{
	struct side_callback *old_cb, *new_cb;
	int ret = SIDE_ERROR_OK;
	uint32_t old_nr_cb;

	if (!call)
		return SIDE_ERROR_INVAL;
	if (finalized)
		return SIDE_ERROR_EXITING;
	if (!initialized)
		side_init();
	pthread_mutex_lock(&side_lock);
	old_nr_cb = *desc->enabled & SIDE_EVENT_ENABLED_USER_MASK;
	if (old_nr_cb == SIDE_EVENT_ENABLED_USER_MASK) {
		ret = SIDE_ERROR_INVAL;
		goto unlock;
	}
	/* Reject duplicate (call, priv) tuples. */
	if (side_tracer_callback_lookup(desc, call, priv)) {
		ret = SIDE_ERROR_EXIST;
		goto unlock;
	}
	old_cb = (struct side_callback *) desc->callbacks;
	/* old_nr_cb + 1 (new cb) + 1 (NULL) */
	new_cb = (struct side_callback *) calloc(old_nr_cb + 2, sizeof(struct side_callback));
	if (!new_cb) {
		ret = SIDE_ERROR_NOMEM;
		goto unlock;
	}
	memcpy(new_cb, old_cb, old_nr_cb);
	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
		new_cb[old_nr_cb].u.call_variadic = call;
	else
		new_cb[old_nr_cb].u.call = call;
	new_cb[old_nr_cb].priv = priv;
	side_rcu_assign_pointer(desc->callbacks, new_cb);
	side_rcu_wait_grace_period(&rcu_gp);
	if (old_nr_cb)
		free(old_cb);
	/* Increment concurrently with kernel setting the top bits. */
	(void) __atomic_add_fetch(desc->enabled, 1, __ATOMIC_RELAXED);
unlock:
	pthread_mutex_unlock(&side_lock);
	return ret;
}

int side_tracer_callback_register(struct side_event_description *desc,
		void (*call)(const struct side_event_description *desc,
			const struct side_arg_vec_description *sav_desc,
			void *priv),
		void *priv)
{
	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
		return SIDE_ERROR_INVAL;
	return _side_tracer_callback_register(desc, call, priv);
}

int side_tracer_callback_variadic_register(struct side_event_description *desc,
		void (*call_variadic)(const struct side_event_description *desc,
			const struct side_arg_vec_description *sav_desc,
			const struct side_arg_dynamic_event_struct *var_struct,
			void *priv),
		void *priv)
{
	if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
		return SIDE_ERROR_INVAL;
	return _side_tracer_callback_register(desc, call_variadic, priv);
}

int _side_tracer_callback_unregister(struct side_event_description *desc,
		void (*call)(), void *priv)
{
	struct side_callback *old_cb, *new_cb;
	const struct side_callback *cb_pos;
	uint32_t pos_idx;
	int ret = SIDE_ERROR_OK;
	uint32_t old_nr_cb;

	if (!call)
		return SIDE_ERROR_INVAL;
	if (finalized)
		return SIDE_ERROR_EXITING;
	if (!initialized)
		side_init();
	pthread_mutex_lock(&side_lock);
	cb_pos = side_tracer_callback_lookup(desc, call, priv);
	if (!cb_pos) {
		ret = SIDE_ERROR_NOENT;
		goto unlock;
	}
	old_nr_cb = *desc->enabled & SIDE_EVENT_ENABLED_USER_MASK;
	old_cb = (struct side_callback *) desc->callbacks;
	if (old_nr_cb == 1) {
		new_cb = (struct side_callback *) &side_empty_callback;
	} else {
		pos_idx = cb_pos - desc->callbacks;
		/* Remove entry at pos_idx. */
		/* old_nr_cb - 1 (removed cb) + 1 (NULL) */
		new_cb = (struct side_callback *) calloc(old_nr_cb, sizeof(struct side_callback));
		if (!new_cb) {
			ret = SIDE_ERROR_NOMEM;
			goto unlock;
		}
		memcpy(new_cb, old_cb, pos_idx);
		memcpy(&new_cb[pos_idx], &old_cb[pos_idx + 1], old_nr_cb - pos_idx - 1);
	}
	side_rcu_assign_pointer(desc->callbacks, new_cb);
	side_rcu_wait_grace_period(&rcu_gp);
	free(old_cb);
	/* Decrement concurrently with kernel setting the top bits. */
	(void) __atomic_add_fetch(desc->enabled, -1, __ATOMIC_RELAXED);
unlock:
	pthread_mutex_unlock(&side_lock);
	return ret;
}

int side_tracer_callback_unregister(struct side_event_description *desc,
		void (*call)(const struct side_event_description *desc,
			const struct side_arg_vec_description *sav_desc,
			void *priv),
		void *priv)
{
	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
		return SIDE_ERROR_INVAL;
	return _side_tracer_callback_unregister(desc, call, priv);
}

int side_tracer_callback_variadic_unregister(struct side_event_description *desc,
		void (*call_variadic)(const struct side_event_description *desc,
			const struct side_arg_vec_description *sav_desc,
			const struct side_arg_dynamic_event_struct *var_struct,
			void *priv),
		void *priv)
{
	if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
		return SIDE_ERROR_INVAL;
	return _side_tracer_callback_unregister(desc, call_variadic, priv);
}

struct side_events_register_handle *side_events_register(struct side_event_description **events, uint32_t nr_events)
{
	struct side_events_register_handle *events_handle = NULL;
	struct side_tracer_handle *tracer_handle;

	if (finalized)
		return NULL;
	if (!initialized)
		side_init();
	events_handle = calloc(1, sizeof(struct side_events_register_handle));
	if (!events_handle)
		return NULL;
	events_handle->events = events;
	events_handle->nr_events = nr_events;

	pthread_mutex_lock(&side_lock);
	side_list_insert_node_tail(&side_events_list, &events_handle->node);
	side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
		tracer_handle->cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
			events, nr_events, tracer_handle->priv);
	}
	pthread_mutex_unlock(&side_lock);
	//TODO: call event batch register ioctl
	return events_handle;
}

static
void side_event_remove_callbacks(struct side_event_description *desc)
{
	uint32_t nr_cb = *desc->enabled & SIDE_EVENT_ENABLED_USER_MASK;
	struct side_callback *old_cb;

	if (!nr_cb)
		return;
	old_cb = (struct side_callback *) desc->callbacks;
	/*
	 * Setting the state back to 0 cb and empty callbacks out of
	 * caution. This should not matter because instrumentation is
	 * unreachable.
	 */
	(void) __atomic_add_fetch(desc->enabled, -nr_cb, __ATOMIC_RELAXED);
	side_rcu_assign_pointer(desc->callbacks, &side_empty_callback);
	/*
	 * No need to wait for grace period because instrumentation is
	 * unreachable.
	 */
	free(old_cb);
}

/*
 * Unregister event handle. At this point, all side events in that
 * handle should be unreachable.
 */
void side_events_unregister(struct side_events_register_handle *events_handle)
{
	struct side_tracer_handle *tracer_handle;
	uint32_t i;

	if (!events_handle)
		return;
	if (finalized)
		return;
	if (!initialized)
		side_init();
	pthread_mutex_lock(&side_lock);
	side_list_remove_node(&events_handle->node);
	side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
		tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
			events_handle->events, events_handle->nr_events,
			tracer_handle->priv);
	}
	for (i = 0; i < events_handle->nr_events; i++) {
		struct side_event_description *event = events_handle->events[i];

		/* Skip NULL pointers */
		if (!event)
			continue;
		side_event_remove_callbacks(event);
	}
	pthread_mutex_unlock(&side_lock);
	//TODO: call event batch unregister ioctl
	free(events_handle);
}

struct side_tracer_handle *side_tracer_event_notification_register(
		void (*cb)(enum side_tracer_notification notif,
			struct side_event_description **events, uint32_t nr_events, void *priv),
		void *priv)
{
	struct side_tracer_handle *tracer_handle;
	struct side_events_register_handle *events_handle;

	if (finalized)
		return NULL;
	if (!initialized)
		side_init();
	tracer_handle = calloc(1, sizeof(struct side_tracer_handle));
	if (!tracer_handle)
		return NULL;
	pthread_mutex_lock(&side_lock);
	tracer_handle->cb = cb;
	tracer_handle->priv = priv;
	side_list_insert_node_tail(&side_tracer_list, &tracer_handle->node);
	side_list_for_each_entry(events_handle, &side_events_list, node) {
		cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
			events_handle->events, events_handle->nr_events, priv);
	}
	pthread_mutex_unlock(&side_lock);
	return tracer_handle;
}

void side_tracer_event_notification_unregister(struct side_tracer_handle *tracer_handle)
{
	struct side_events_register_handle *events_handle;

	if (finalized)
		return;
	if (!initialized)
		side_init();
	pthread_mutex_lock(&side_lock);
	side_list_for_each_entry(events_handle, &side_events_list, node) {
		tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
			events_handle->events, events_handle->nr_events,
			tracer_handle->priv);
	}
	side_list_remove_node(&tracer_handle->node);
	pthread_mutex_unlock(&side_lock);
}

void side_init(void)
{
	if (initialized)
		return;
	side_rcu_gp_init(&rcu_gp);
	initialized = true;
}

/*
 * side_exit() is executed from a library destructor. It can be called
 * explicitly at application exit as well. Concurrent side API use is
 * not expected at that point.
 */
void side_exit(void)
{
	struct side_events_register_handle *handle, *tmp;

	if (finalized)
		return;
	side_rcu_gp_exit(&rcu_gp);
	side_list_for_each_entry_safe(handle, tmp, &side_events_list, node)
		side_events_unregister(handle);
	finalized = true;
}
Commit	Line	Data
6841ae81 MD	1	// SPDX-License-Identifier: MIT
	2	/*
	3	* Copyright 2022 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	4	*/
	5
	6	#include <side/trace.h>
a3f36db7 MD	7	#include <string.h>
a3f36db7 MD	8
6841ae81	9	#include "tracer.h"
85b765b8	10	#include "rcu.h"
b59abc69	11	#include "list.h"
6841ae81	12
054b7b5c MD	13	/* Top 8 bits reserved for kernel tracer use. */
054b7b5c MD	14	#define SIDE_EVENT_ENABLED_KERNEL_MASK 0xFF000000
29b3374e MD	15	#define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK 0x80000000
29b3374e MD	16
a3f36db7	17	/* Allow 2^24 tracer callbacks to be registered on an event. */
054b7b5c MD	18	#define SIDE_EVENT_ENABLED_USER_MASK 0x00FFFFFF
054b7b5c MD	19
6e46f5e6 MD	20	struct side_events_register_handle {
	21	struct side_list_node node;
	22	struct side_event_description **events;
	23	uint32_t nr_events;
	24	};
	25
a13c9d2e MD	26	struct side_tracer_handle {
	27	struct side_list_node node;
	28	void (*cb)(enum side_tracer_notification notif,
	29	struct side_event_description *events, uint32_t nr_events, void priv);
	30	void *priv;
	31	};
	32
a3f36db7	33	static struct side_rcu_gp_state rcu_gp;
075ceef7 MD	34
	35	/*
	36	* Lazy initialization for early use within library constructors.
	37	*/
	38	static bool initialized;
6e46f5e6 MD	39	/*
	40	* Do not register/unregister any more events after destructor.
	41	*/
	42	static bool finalized;
075ceef7	43
a3f36db7 MD	44	static pthread_mutex_t side_lock = PTHREAD_MUTEX_INITIALIZER;
a3f36db7 MD	45
a13c9d2e MD	46	static DEFINE_SIDE_LIST_HEAD(side_events_list);
a13c9d2e MD	47	static DEFINE_SIDE_LIST_HEAD(side_tracer_list);
b59abc69	48
a3f36db7 MD	49	/*
	50	* The empty callback has a NULL function callback pointer, which stops
	51	* iteration on the array of callbacks immediately.
	52	*/
054b7b5c MD	53	const struct side_callback side_empty_callback;
054b7b5c MD	54
6e46f5e6 MD	55	void side_init(void) __attribute__((constructor));
	56	void side_exit(void) __attribute__((destructor));
	57
6841ae81 MD	58	void side_call(const struct side_event_description desc, const struct side_arg_vec_description sav_desc)
6841ae81 MD	59	{
054b7b5c MD	60	const struct side_callback *side_cb;
054b7b5c MD	61	unsigned int rcu_period;
3b4f86f6	62	uint32_t enabled;
054b7b5c	63
6e46f5e6 MD	64	if (side_unlikely(finalized))
6e46f5e6 MD	65	return;
075ceef7 MD	66	if (side_unlikely(!initialized))
075ceef7 MD	67	side_init();
6841ae81 MD	68	if (side_unlikely(desc->flags & SIDE_EVENT_FLAG_VARIADIC)) {
	69	printf("ERROR: unexpected variadic event description\n");
	70	abort();
	71	}
3b4f86f6 MD	72	enabled = __atomic_load_n(desc->enabled, __ATOMIC_RELAXED);
3b4f86f6 MD	73	if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
dda82f46	74	// TODO: call kernel write.
6841ae81	75	}
3b4f86f6	76	if (side_unlikely(!(enabled & SIDE_EVENT_ENABLED_USER_MASK)))
054b7b5c MD	77	return;
054b7b5c MD	78
054b7b5c MD	79	rcu_period = side_rcu_read_begin(&rcu_gp);
	80	for (side_cb = side_rcu_dereference(desc->callbacks); side_cb->u.call != NULL; side_cb++)
	81	side_cb->u.call(desc, sav_desc, side_cb->priv);
	82	side_rcu_read_end(&rcu_gp, rcu_period);
6841ae81 MD	83	}
	84
	85	void side_call_variadic(const struct side_event_description *desc,
	86	const struct side_arg_vec_description *sav_desc,
	87	const struct side_arg_dynamic_event_struct *var_struct)
	88	{
054b7b5c MD	89	const struct side_callback *side_cb;
054b7b5c MD	90	unsigned int rcu_period;
3b4f86f6	91	uint32_t enabled;
054b7b5c	92
6e46f5e6 MD	93	if (side_unlikely(finalized))
6e46f5e6 MD	94	return;
075ceef7 MD	95	if (side_unlikely(!initialized))
075ceef7 MD	96	side_init();
3b4f86f6 MD	97	if (side_unlikely(!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))) {
	98	printf("ERROR: unexpected non-variadic event description\n");
	99	abort();
	100	}
	101	enabled = __atomic_load_n(desc->enabled, __ATOMIC_RELAXED);
	102	if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
dda82f46	103	// TODO: call kernel write.
6841ae81	104	}
3b4f86f6	105	if (side_unlikely(!(enabled & SIDE_EVENT_ENABLED_USER_MASK)))
054b7b5c MD	106	return;
054b7b5c MD	107
054b7b5c MD	108	rcu_period = side_rcu_read_begin(&rcu_gp);
	109	for (side_cb = side_rcu_dereference(desc->callbacks); side_cb->u.call_variadic != NULL; side_cb++)
	110	side_cb->u.call_variadic(desc, sav_desc, var_struct, side_cb->priv);
	111	side_rcu_read_end(&rcu_gp, rcu_period);
6841ae81	112	}
075ceef7	113
a3f36db7 MD	114	static
	115	const struct side_callback *side_tracer_callback_lookup(
	116	const struct side_event_description *desc,
	117	void (call)(), void priv)
	118	{
	119	const struct side_callback *cb;
	120
	121	for (cb = desc->callbacks; cb->u.call != NULL; cb++) {
	122	if (cb->u.call == call && cb->priv == priv)
	123	return cb;
	124	}
	125	return NULL;
	126	}
	127
	128	static
	129	int _side_tracer_callback_register(struct side_event_description *desc,
	130	void (call)(), void priv)
	131	{
	132	struct side_callback old_cb, new_cb;
	133	int ret = SIDE_ERROR_OK;
	134	uint32_t old_nr_cb;
	135
	136	if (!call)
	137	return SIDE_ERROR_INVAL;
6e46f5e6 MD	138	if (finalized)
6e46f5e6 MD	139	return SIDE_ERROR_EXITING;
a13c9d2e MD	140	if (!initialized)
a13c9d2e MD	141	side_init();
a3f36db7 MD	142	pthread_mutex_lock(&side_lock);
	143	old_nr_cb = *desc->enabled & SIDE_EVENT_ENABLED_USER_MASK;
	144	if (old_nr_cb == SIDE_EVENT_ENABLED_USER_MASK) {
	145	ret = SIDE_ERROR_INVAL;
	146	goto unlock;
	147	}
	148	/* Reject duplicate (call, priv) tuples. */
	149	if (side_tracer_callback_lookup(desc, call, priv)) {
	150	ret = SIDE_ERROR_EXIST;
	151	goto unlock;
	152	}
	153	old_cb = (struct side_callback *) desc->callbacks;
	154	/* old_nr_cb + 1 (new cb) + 1 (NULL) */
	155	new_cb = (struct side_callback *) calloc(old_nr_cb + 2, sizeof(struct side_callback));
	156	if (!new_cb) {
	157	ret = SIDE_ERROR_NOMEM;
	158	goto unlock;
	159	}
	160	memcpy(new_cb, old_cb, old_nr_cb);
	161	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	162	new_cb[old_nr_cb].u.call_variadic = call;
	163	else
	164	new_cb[old_nr_cb].u.call = call;
	165	new_cb[old_nr_cb].priv = priv;
	166	side_rcu_assign_pointer(desc->callbacks, new_cb);
	167	side_rcu_wait_grace_period(&rcu_gp);
	168	if (old_nr_cb)
	169	free(old_cb);
	170	/* Increment concurrently with kernel setting the top bits. */
	171	(void) __atomic_add_fetch(desc->enabled, 1, __ATOMIC_RELAXED);
	172	unlock:
	173	pthread_mutex_unlock(&side_lock);
	174	return ret;
	175	}
	176
	177	int side_tracer_callback_register(struct side_event_description *desc,
	178	void (call)(const struct side_event_description desc,
	179	const struct side_arg_vec_description *sav_desc,
	180	void *priv),
	181	void *priv)
	182	{
	183	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	184	return SIDE_ERROR_INVAL;
	185	return _side_tracer_callback_register(desc, call, priv);
	186	}
	187
	188	int side_tracer_callback_variadic_register(struct side_event_description *desc,
	189	void (call_variadic)(const struct side_event_description desc,
	190	const struct side_arg_vec_description *sav_desc,
	191	const struct side_arg_dynamic_event_struct *var_struct,
	192	void *priv),
	193	void *priv)
	194	{
	195	if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
	196	return SIDE_ERROR_INVAL;
	197	return _side_tracer_callback_register(desc, call_variadic, priv);
	198	}
	199
	200	int _side_tracer_callback_unregister(struct side_event_description *desc,
	201	void (call)(), void priv)
	202	{
	203	struct side_callback old_cb, new_cb;
	204	const struct side_callback *cb_pos;
	205	uint32_t pos_idx;
206	int ret = SIDE_ERROR_OK;
207	uint32_t old_nr_cb;
208
209	if (!call)
210	return SIDE_ERROR_INVAL;
6e46f5e6 MD	211	if (finalized)
6e46f5e6 MD	212	return SIDE_ERROR_EXITING;
a13c9d2e MD	213	if (!initialized)
a13c9d2e MD	214	side_init();
a3f36db7	215	pthread_mutex_lock(&side_lock);
a3f36db7 MD	216	cb_pos = side_tracer_callback_lookup(desc, call, priv);
	217	if (!cb_pos) {
	218	ret = SIDE_ERROR_NOENT;
	219	goto unlock;
	220	}
9a83b759 MD	221	old_nr_cb = *desc->enabled & SIDE_EVENT_ENABLED_USER_MASK;
9a83b759 MD	222	old_cb = (struct side_callback *) desc->callbacks;
a3f36db7 MD	223	if (old_nr_cb == 1) {
	224	new_cb = (struct side_callback *) &side_empty_callback;
	225	} else {
	226	pos_idx = cb_pos - desc->callbacks;
	227	/* Remove entry at pos_idx. */
	228	/* old_nr_cb - 1 (removed cb) + 1 (NULL) */
	229	new_cb = (struct side_callback *) calloc(old_nr_cb, sizeof(struct side_callback));
	230	if (!new_cb) {
	231	ret = SIDE_ERROR_NOMEM;
	232	goto unlock;
	233	}
	234	memcpy(new_cb, old_cb, pos_idx);
	235	memcpy(&new_cb[pos_idx], &old_cb[pos_idx + 1], old_nr_cb - pos_idx - 1);
	236	}
	237	side_rcu_assign_pointer(desc->callbacks, new_cb);
	238	side_rcu_wait_grace_period(&rcu_gp);
	239	free(old_cb);
	240	/* Decrement concurrently with kernel setting the top bits. */
	241	(void) __atomic_add_fetch(desc->enabled, -1, __ATOMIC_RELAXED);
	242	unlock:
	243	pthread_mutex_unlock(&side_lock);
	244	return ret;
	245	}
	246
	247	int side_tracer_callback_unregister(struct side_event_description *desc,
	248	void (call)(const struct side_event_description desc,
	249	const struct side_arg_vec_description *sav_desc,
	250	void *priv),
	251	void *priv)
	252	{
	253	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	254	return SIDE_ERROR_INVAL;
	255	return _side_tracer_callback_unregister(desc, call, priv);
	256	}
	257
	258	int side_tracer_callback_variadic_unregister(struct side_event_description *desc,
	259	void (call_variadic)(const struct side_event_description desc,
	260	const struct side_arg_vec_description *sav_desc,
	261	const struct side_arg_dynamic_event_struct *var_struct,
	262	void *priv),
	263	void *priv)
	264	{
	265	if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
	266	return SIDE_ERROR_INVAL;
	267	return _side_tracer_callback_unregister(desc, call_variadic, priv);
	268	}
	269
6e46f5e6 MD	270	struct side_events_register_handle side_events_register(struct side_event_description *events, uint32_t nr_events)
6e46f5e6 MD	271	{
a13c9d2e MD	272	struct side_events_register_handle *events_handle = NULL;
a13c9d2e MD	273	struct side_tracer_handle *tracer_handle;
6e46f5e6 MD	274
	275	if (finalized)
	276	return NULL;
a13c9d2e MD	277	if (!initialized)
	278	side_init();
	279	events_handle = calloc(1, sizeof(struct side_events_register_handle));
	280	if (!events_handle)
6e46f5e6	281	return NULL;
a13c9d2e MD	282	events_handle->events = events;
	283	events_handle->nr_events = nr_events;
	284
6e46f5e6	285	pthread_mutex_lock(&side_lock);
a13c9d2e MD	286	side_list_insert_node_tail(&side_events_list, &events_handle->node);
	287	side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
	288	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
	289	events, nr_events, tracer_handle->priv);
	290	}
6e46f5e6 MD	291	pthread_mutex_unlock(&side_lock);
6e46f5e6 MD	292	//TODO: call event batch register ioctl
a13c9d2e	293	return events_handle;
6e46f5e6 MD	294	}
6e46f5e6 MD	295
a3f36db7	296	static
6e46f5e6 MD	297	void side_event_remove_callbacks(struct side_event_description *desc)
	298	{
	299	uint32_t nr_cb = *desc->enabled & SIDE_EVENT_ENABLED_USER_MASK;
	300	struct side_callback *old_cb;
	301
	302	if (!nr_cb)
	303	return;
	304	old_cb = (struct side_callback *) desc->callbacks;
	305	/*
	306	* Setting the state back to 0 cb and empty callbacks out of
	307	* caution. This should not matter because instrumentation is
	308	* unreachable.
	309	*/
	310	(void) __atomic_add_fetch(desc->enabled, -nr_cb, __ATOMIC_RELAXED);
	311	side_rcu_assign_pointer(desc->callbacks, &side_empty_callback);
	312	/*
	313	* No need to wait for grace period because instrumentation is
	314	* unreachable.
	315	*/
	316	free(old_cb);
	317	}
	318
	319	/*
	320	* Unregister event handle. At this point, all side events in that
	321	* handle should be unreachable.
	322	*/
a13c9d2e	323	void side_events_unregister(struct side_events_register_handle *events_handle)
6e46f5e6	324	{
a13c9d2e	325	struct side_tracer_handle *tracer_handle;
6e46f5e6 MD	326	uint32_t i;
6e46f5e6 MD	327
314c22c3 MD	328	if (!events_handle)
314c22c3 MD	329	return;
6e46f5e6 MD	330	if (finalized)
6e46f5e6 MD	331	return;
a13c9d2e MD	332	if (!initialized)
a13c9d2e MD	333	side_init();
6e46f5e6	334	pthread_mutex_lock(&side_lock);
a13c9d2e MD	335	side_list_remove_node(&events_handle->node);
	336	side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
	337	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
	338	events_handle->events, events_handle->nr_events,
	339	tracer_handle->priv);
	340	}
	341	for (i = 0; i < events_handle->nr_events; i++) {
	342	struct side_event_description *event = events_handle->events[i];
6e46f5e6 MD	343
	344	/* Skip NULL pointers */
	345	if (!event)
	346	continue;
	347	side_event_remove_callbacks(event);
	348	}
	349	pthread_mutex_unlock(&side_lock);
	350	//TODO: call event batch unregister ioctl
a13c9d2e MD	351	free(events_handle);
	352	}
	353
	354	struct side_tracer_handle *side_tracer_event_notification_register(
	355	void (*cb)(enum side_tracer_notification notif,
	356	struct side_event_description *events, uint32_t nr_events, void priv),
	357	void *priv)
	358	{
	359	struct side_tracer_handle *tracer_handle;
	360	struct side_events_register_handle *events_handle;
	361
	362	if (finalized)
	363	return NULL;
	364	if (!initialized)
	365	side_init();
	366	tracer_handle = calloc(1, sizeof(struct side_tracer_handle));
	367	if (!tracer_handle)
	368	return NULL;
	369	pthread_mutex_lock(&side_lock);
	370	tracer_handle->cb = cb;
	371	tracer_handle->priv = priv;
	372	side_list_insert_node_tail(&side_tracer_list, &tracer_handle->node);
	373	side_list_for_each_entry(events_handle, &side_events_list, node) {
	374	cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
	375	events_handle->events, events_handle->nr_events, priv);
	376	}
	377	pthread_mutex_unlock(&side_lock);
	378	return tracer_handle;
	379	}
	380
	381	void side_tracer_event_notification_unregister(struct side_tracer_handle *tracer_handle)
	382	{
	383	struct side_events_register_handle *events_handle;
	384
	385	if (finalized)
	386	return;
	387	if (!initialized)
	388	side_init();
	389	pthread_mutex_lock(&side_lock);
	390	side_list_for_each_entry(events_handle, &side_events_list, node) {
	391	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
	392	events_handle->events, events_handle->nr_events,
	393	tracer_handle->priv);
	394	}
	395	side_list_remove_node(&tracer_handle->node);
	396	pthread_mutex_unlock(&side_lock);
6e46f5e6 MD	397	}
6e46f5e6 MD	398
075ceef7 MD	399	void side_init(void)
	400	{
	401	if (initialized)
	402	return;
054b7b5c	403	side_rcu_gp_init(&rcu_gp);
075ceef7 MD	404	initialized = true;
075ceef7 MD	405	}
6e46f5e6	406
aa584c16 MD	407	/*
	408	* side_exit() is executed from a library destructor. It can be called
	409	* explicitly at application exit as well. Concurrent side API use is
	410	* not expected at that point.
	411	*/
6e46f5e6 MD	412	void side_exit(void)
	413	{
	414	struct side_events_register_handle handle, tmp;
	415
	416	if (finalized)
	417	return;
	418	side_rcu_gp_exit(&rcu_gp);
a13c9d2e	419	side_list_for_each_entry_safe(handle, tmp, &side_events_list, node)
6e46f5e6 MD	420	side_events_unregister(handle);
	421	finalized = true;
	422	}