[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 "rcu.h"
#include "list.h"

/* Top 8 bits reserved for kernel tracer use. */
#if SIDE_BITS_PER_LONG == 64
# define SIDE_EVENT_ENABLED_KERNEL_MASK			0xFF00000000000000ULL
# define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK 	0x8000000000000000ULL

/* Allow 2^56 tracer references on an event. */
# define SIDE_EVENT_ENABLED_USER_MASK			0x00FFFFFFFFFFFFFFULL
#else
# define SIDE_EVENT_ENABLED_KERNEL_MASK			0xFF000000UL
# define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK	0x80000000UL

/* Allow 2^24 tracer references on an event. */
# define SIDE_EVENT_ENABLED_USER_MASK			0x00FFFFFFUL
#endif

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;

/*
 * Recursive mutex to allow tracer callbacks to use the side API.
 */
static pthread_mutex_t side_lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;

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_call(const struct side_event_state *event_state, const struct side_arg_vec *side_arg_vec)
{
	struct side_rcu_read_state rcu_read_state;
	const struct side_callback *side_cb;
	uintptr_t enabled;

	if (side_unlikely(finalized))
		return;
	if (side_unlikely(!initialized))
		side_init();
	if (side_unlikely(event_state->desc->flags & SIDE_EVENT_FLAG_VARIADIC)) {
		printf("ERROR: unexpected variadic event description\n");
		abort();
	}
	enabled = __atomic_load_n(&event_state->enabled, __ATOMIC_RELAXED);
	if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
		// TODO: call kernel write.
	}
	side_rcu_read_begin(&rcu_gp, &rcu_read_state);
	for (side_cb = side_rcu_dereference(event_state->callbacks); side_cb->u.call != NULL; side_cb++)
		side_cb->u.call(event_state->desc, side_arg_vec, side_cb->priv);
	side_rcu_read_end(&rcu_gp, &rcu_read_state);
}

void side_call_variadic(const struct side_event_state *event_state,
	const struct side_arg_vec *side_arg_vec,
	const struct side_arg_dynamic_struct *var_struct)
{
	struct side_rcu_read_state rcu_read_state;
	const struct side_callback *side_cb;
	uintptr_t enabled;

	if (side_unlikely(finalized))
		return;
	if (side_unlikely(!initialized))
		side_init();
	if (side_unlikely(!(event_state->desc->flags & SIDE_EVENT_FLAG_VARIADIC))) {
		printf("ERROR: unexpected non-variadic event description\n");
		abort();
	}
	enabled = __atomic_load_n(&event_state->enabled, __ATOMIC_RELAXED);
	if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
		// TODO: call kernel write.
	}
	side_rcu_read_begin(&rcu_gp, &rcu_read_state);
	for (side_cb = side_rcu_dereference(event_state->callbacks); side_cb->u.call_variadic != NULL; side_cb++)
		side_cb->u.call_variadic(event_state->desc, side_arg_vec, var_struct, side_cb->priv);
	side_rcu_read_end(&rcu_gp, &rcu_read_state);
}

static
const struct side_callback *side_tracer_callback_lookup(
		const struct side_event_description *desc,
		void *call, void *priv)
{
	struct side_event_state *event_state = side_ptr_get(desc->state);
	const struct side_callback *cb;

	for (cb = event_state->callbacks; cb->u.call != NULL; cb++) {
		if ((void *) 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_event_state *event_state;
	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);
	event_state = side_ptr_get(desc->state);
	old_nr_cb = desc->nr_callbacks;
	if (old_nr_cb == UINT32_MAX) {
		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 *) event_state->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 =
			(side_tracer_callback_variadic_func) call;
	else
		new_cb[old_nr_cb].u.call =
			(side_tracer_callback_func) call;
	new_cb[old_nr_cb].priv = priv;
	side_rcu_assign_pointer(event_state->callbacks, new_cb);
	side_rcu_wait_grace_period(&rcu_gp);
	if (old_nr_cb)
		free(old_cb);
	desc->nr_callbacks++;
	/* Increment concurrently with kernel setting the top bits. */
	if (!old_nr_cb)
		(void) __atomic_add_fetch(&event_state->enabled, 1, __ATOMIC_RELAXED);
unlock:
	pthread_mutex_unlock(&side_lock);
	return ret;
}

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

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

static int _side_tracer_callback_unregister(struct side_event_description *desc,
		void *call, void *priv)
{
	struct side_event_state *event_state;
	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);
	event_state = side_ptr_get(desc->state);
	cb_pos = side_tracer_callback_lookup(desc, call, priv);
	if (!cb_pos) {
		ret = SIDE_ERROR_NOENT;
		goto unlock;
	}
	old_nr_cb = desc->nr_callbacks;
	old_cb = (struct side_callback *) event_state->callbacks;
	if (old_nr_cb == 1) {
		new_cb = (struct side_callback *) &side_empty_callback;
	} else {
		pos_idx = cb_pos - event_state->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(event_state->callbacks, new_cb);
	side_rcu_wait_grace_period(&rcu_gp);
	free(old_cb);
	desc->nr_callbacks--;
	/* Decrement concurrently with kernel setting the top bits. */
	if (old_nr_cb == 1)
		(void) __atomic_add_fetch(&event_state->enabled, -1, __ATOMIC_RELAXED);
unlock:
	pthread_mutex_unlock(&side_lock);
	return ret;
}

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

int side_tracer_callback_variadic_unregister(struct side_event_description *desc,
		side_tracer_callback_variadic_func call_variadic,
		void *priv)
{
	if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
		return SIDE_ERROR_INVAL;
	return _side_tracer_callback_unregister(desc, (void *) 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 = (struct side_events_register_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)
{
	struct side_event_state *event_state = side_ptr_get(desc->state);
	uint32_t nr_cb = desc->nr_callbacks;
	struct side_callback *old_cb;

	if (!nr_cb)
		return;
	old_cb = (struct side_callback *) event_state->callbacks;
	(void) __atomic_add_fetch(&event_state->enabled, -1, __ATOMIC_RELAXED);
	/*
	 * Setting the state back to 0 cb and empty callbacks out of
	 * caution. This should not matter because instrumentation is
	 * unreachable.
	 */
	desc->nr_callbacks = 0;
	side_rcu_assign_pointer(event_state->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 = (struct side_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);
	free(tracer_handle);
}

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_list_for_each_entry_safe(handle, tmp, &side_events_list, node)
		side_events_unregister(handle);
	side_rcu_gp_exit(&rcu_gp);
	finalized = true;
}
Commit	Line	Data
67337c4a MD	1	// SPDX-License-Identifier: MIT
	2	/*
	3	* Copyright 2022 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	4	*/
	5
	6	#include <side/trace.h>
	7	#include <string.h>
	8
	9	#include "rcu.h"
	10	#include "list.h"
	11
	12	/* Top 8 bits reserved for kernel tracer use. */
	13	#if SIDE_BITS_PER_LONG == 64
	14	# define SIDE_EVENT_ENABLED_KERNEL_MASK 0xFF00000000000000ULL
	15	# define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK 0x8000000000000000ULL
	16
	17	/* Allow 2^56 tracer references on an event. */
	18	# define SIDE_EVENT_ENABLED_USER_MASK 0x00FFFFFFFFFFFFFFULL
	19	#else
	20	# define SIDE_EVENT_ENABLED_KERNEL_MASK 0xFF000000UL
	21	# define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK 0x80000000UL
	22
	23	/* Allow 2^24 tracer references on an event. */
	24	# define SIDE_EVENT_ENABLED_USER_MASK 0x00FFFFFFUL
	25	#endif
	26
	27	struct side_events_register_handle {
	28	struct side_list_node node;
	29	struct side_event_description **events;
	30	uint32_t nr_events;
	31	};
	32
	33	struct side_tracer_handle {
	34	struct side_list_node node;
	35	void (*cb)(enum side_tracer_notification notif,
	36	struct side_event_description *events, uint32_t nr_events, void priv);
	37	void *priv;
	38	};
	39
	40	static struct side_rcu_gp_state rcu_gp;
	41
	42	/*
	43	* Lazy initialization for early use within library constructors.
	44	*/
	45	static bool initialized;
	46	/*
	47	* Do not register/unregister any more events after destructor.
	48	*/
	49	static bool finalized;
	50
	51	/*
	52	* Recursive mutex to allow tracer callbacks to use the side API.
	53	*/
	54	static pthread_mutex_t side_lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
	55
	56	static DEFINE_SIDE_LIST_HEAD(side_events_list);
	57	static DEFINE_SIDE_LIST_HEAD(side_tracer_list);
	58
	59	/*
	60	* The empty callback has a NULL function callback pointer, which stops
	61	* iteration on the array of callbacks immediately.
	62	*/
	63	const struct side_callback side_empty_callback = { };
	64
0d747f98	65	void side_call(const struct side_event_state event_state, const struct side_arg_vec side_arg_vec)
67337c4a MD	66	{
	67	struct side_rcu_read_state rcu_read_state;
	68	const struct side_callback *side_cb;
	69	uintptr_t enabled;
	70
	71	if (side_unlikely(finalized))
	72	return;
	73	if (side_unlikely(!initialized))
	74	side_init();
0d747f98	75	if (side_unlikely(event_state->desc->flags & SIDE_EVENT_FLAG_VARIADIC)) {
67337c4a MD	76	printf("ERROR: unexpected variadic event description\n");
	77	abort();
	78	}
0b9e59d6	79	enabled = __atomic_load_n(&event_state->enabled, __ATOMIC_RELAXED);
67337c4a MD	80	if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
	81	// TODO: call kernel write.
	82	}
	83	side_rcu_read_begin(&rcu_gp, &rcu_read_state);
0b9e59d6	84	for (side_cb = side_rcu_dereference(event_state->callbacks); side_cb->u.call != NULL; side_cb++)
0d747f98	85	side_cb->u.call(event_state->desc, side_arg_vec, side_cb->priv);
67337c4a MD	86	side_rcu_read_end(&rcu_gp, &rcu_read_state);
	87	}
	88
0d747f98	89	void side_call_variadic(const struct side_event_state *event_state,
67337c4a MD	90	const struct side_arg_vec *side_arg_vec,
	91	const struct side_arg_dynamic_struct *var_struct)
	92	{
	93	struct side_rcu_read_state rcu_read_state;
	94	const struct side_callback *side_cb;
	95	uintptr_t enabled;
	96
	97	if (side_unlikely(finalized))
	98	return;
	99	if (side_unlikely(!initialized))
	100	side_init();
0d747f98	101	if (side_unlikely(!(event_state->desc->flags & SIDE_EVENT_FLAG_VARIADIC))) {
67337c4a MD	102	printf("ERROR: unexpected non-variadic event description\n");
	103	abort();
	104	}
0b9e59d6	105	enabled = __atomic_load_n(&event_state->enabled, __ATOMIC_RELAXED);
67337c4a MD	106	if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
	107	// TODO: call kernel write.
	108	}
	109	side_rcu_read_begin(&rcu_gp, &rcu_read_state);
0b9e59d6	110	for (side_cb = side_rcu_dereference(event_state->callbacks); side_cb->u.call_variadic != NULL; side_cb++)
0d747f98	111	side_cb->u.call_variadic(event_state->desc, side_arg_vec, var_struct, side_cb->priv);
67337c4a MD	112	side_rcu_read_end(&rcu_gp, &rcu_read_state);
	113	}
	114
	115	static
	116	const struct side_callback *side_tracer_callback_lookup(
	117	const struct side_event_description *desc,
	118	void call, void priv)
	119	{
0b9e59d6	120	struct side_event_state *event_state = side_ptr_get(desc->state);
67337c4a MD	121	const struct side_callback *cb;
67337c4a MD	122
0b9e59d6	123	for (cb = event_state->callbacks; cb->u.call != NULL; cb++) {
67337c4a MD	124	if ((void *) cb->u.call == call && cb->priv == priv)
	125	return cb;
	126	}
	127	return NULL;
	128	}
	129
	130	static
	131	int _side_tracer_callback_register(struct side_event_description *desc,
	132	void call, void priv)
	133	{
0b9e59d6	134	struct side_event_state *event_state;
67337c4a MD	135	struct side_callback old_cb, new_cb;
	136	int ret = SIDE_ERROR_OK;
	137	uint32_t old_nr_cb;
	138
	139	if (!call)
	140	return SIDE_ERROR_INVAL;
	141	if (finalized)
	142	return SIDE_ERROR_EXITING;
	143	if (!initialized)
	144	side_init();
	145	pthread_mutex_lock(&side_lock);
0b9e59d6	146	event_state = side_ptr_get(desc->state);
f8188f94	147	old_nr_cb = desc->nr_callbacks;
67337c4a MD	148	if (old_nr_cb == UINT32_MAX) {
	149	ret = SIDE_ERROR_INVAL;
	150	goto unlock;
	151	}
	152	/* Reject duplicate (call, priv) tuples. */
	153	if (side_tracer_callback_lookup(desc, call, priv)) {
	154	ret = SIDE_ERROR_EXIST;
	155	goto unlock;
	156	}
0b9e59d6	157	old_cb = (struct side_callback *) event_state->callbacks;
67337c4a MD	158	/* old_nr_cb + 1 (new cb) + 1 (NULL) */
	159	new_cb = (struct side_callback *) calloc(old_nr_cb + 2, sizeof(struct side_callback));
	160	if (!new_cb) {
	161	ret = SIDE_ERROR_NOMEM;
	162	goto unlock;
	163	}
	164	memcpy(new_cb, old_cb, old_nr_cb);
	165	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	166	new_cb[old_nr_cb].u.call_variadic =
	167	(side_tracer_callback_variadic_func) call;
	168	else
	169	new_cb[old_nr_cb].u.call =
	170	(side_tracer_callback_func) call;
	171	new_cb[old_nr_cb].priv = priv;
0b9e59d6	172	side_rcu_assign_pointer(event_state->callbacks, new_cb);
67337c4a MD	173	side_rcu_wait_grace_period(&rcu_gp);
	174	if (old_nr_cb)
	175	free(old_cb);
f8188f94	176	desc->nr_callbacks++;
67337c4a MD	177	/* Increment concurrently with kernel setting the top bits. */
67337c4a MD	178	if (!old_nr_cb)
0b9e59d6	179	(void) __atomic_add_fetch(&event_state->enabled, 1, __ATOMIC_RELAXED);
67337c4a MD	180	unlock:
	181	pthread_mutex_unlock(&side_lock);
	182	return ret;
	183	}
	184
	185	int side_tracer_callback_register(struct side_event_description *desc,
	186	side_tracer_callback_func call,
	187	void *priv)
	188	{
	189	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	190	return SIDE_ERROR_INVAL;
	191	return _side_tracer_callback_register(desc, (void *) call, priv);
	192	}
	193
	194	int side_tracer_callback_variadic_register(struct side_event_description *desc,
	195	side_tracer_callback_variadic_func call_variadic,
	196	void *priv)
	197	{
	198	if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
	199	return SIDE_ERROR_INVAL;
	200	return _side_tracer_callback_register(desc, (void *) call_variadic, priv);
	201	}
	202
	203	static int _side_tracer_callback_unregister(struct side_event_description *desc,
	204	void call, void priv)
	205	{
0b9e59d6	206	struct side_event_state *event_state;
67337c4a MD	207	struct side_callback old_cb, new_cb;
	208	const struct side_callback *cb_pos;
	209	uint32_t pos_idx;
	210	int ret = SIDE_ERROR_OK;
	211	uint32_t old_nr_cb;
	212
	213	if (!call)
	214	return SIDE_ERROR_INVAL;
	215	if (finalized)
	216	return SIDE_ERROR_EXITING;
	217	if (!initialized)
	218	side_init();
	219	pthread_mutex_lock(&side_lock);
0b9e59d6	220	event_state = side_ptr_get(desc->state);
67337c4a MD	221	cb_pos = side_tracer_callback_lookup(desc, call, priv);
	222	if (!cb_pos) {
	223	ret = SIDE_ERROR_NOENT;
	224	goto unlock;
	225	}
f8188f94	226	old_nr_cb = desc->nr_callbacks;
0b9e59d6	227	old_cb = (struct side_callback *) event_state->callbacks;
67337c4a MD	228	if (old_nr_cb == 1) {
	229	new_cb = (struct side_callback *) &side_empty_callback;
	230	} else {
0b9e59d6	231	pos_idx = cb_pos - event_state->callbacks;
67337c4a MD	232	/* Remove entry at pos_idx. */
	233	/* old_nr_cb - 1 (removed cb) + 1 (NULL) */
	234	new_cb = (struct side_callback *) calloc(old_nr_cb, sizeof(struct side_callback));
	235	if (!new_cb) {
	236	ret = SIDE_ERROR_NOMEM;
	237	goto unlock;
	238	}
	239	memcpy(new_cb, old_cb, pos_idx);
	240	memcpy(&new_cb[pos_idx], &old_cb[pos_idx + 1], old_nr_cb - pos_idx - 1);
	241	}
0b9e59d6	242	side_rcu_assign_pointer(event_state->callbacks, new_cb);
67337c4a MD	243	side_rcu_wait_grace_period(&rcu_gp);
67337c4a MD	244	free(old_cb);
f8188f94	245	desc->nr_callbacks--;
67337c4a MD	246	/* Decrement concurrently with kernel setting the top bits. */
67337c4a MD	247	if (old_nr_cb == 1)
0b9e59d6	248	(void) __atomic_add_fetch(&event_state->enabled, -1, __ATOMIC_RELAXED);
67337c4a MD	249	unlock:
	250	pthread_mutex_unlock(&side_lock);
	251	return ret;
	252	}
	253
	254	int side_tracer_callback_unregister(struct side_event_description *desc,
	255	side_tracer_callback_func call,
	256	void *priv)
	257	{
	258	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	259	return SIDE_ERROR_INVAL;
	260	return _side_tracer_callback_unregister(desc, (void *) call, priv);
	261	}
	262
	263	int side_tracer_callback_variadic_unregister(struct side_event_description *desc,
	264	side_tracer_callback_variadic_func call_variadic,
	265	void *priv)
	266	{
	267	if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
	268	return SIDE_ERROR_INVAL;
	269	return _side_tracer_callback_unregister(desc, (void *) call_variadic, priv);
	270	}
	271
	272	struct side_events_register_handle side_events_register(struct side_event_description *events, uint32_t nr_events)
	273	{
	274	struct side_events_register_handle *events_handle = NULL;
	275	struct side_tracer_handle *tracer_handle;
	276
	277	if (finalized)
	278	return NULL;
	279	if (!initialized)
	280	side_init();
	281	events_handle = (struct side_events_register_handle *)
	282	calloc(1, sizeof(struct side_events_register_handle));
	283	if (!events_handle)
	284	return NULL;
	285	events_handle->events = events;
	286	events_handle->nr_events = nr_events;
	287
	288	pthread_mutex_lock(&side_lock);
	289	side_list_insert_node_tail(&side_events_list, &events_handle->node);
	290	side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
	291	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
	292	events, nr_events, tracer_handle->priv);
	293	}
	294	pthread_mutex_unlock(&side_lock);
	295	//TODO: call event batch register ioctl
	296	return events_handle;
	297	}
	298
	299	static
	300	void side_event_remove_callbacks(struct side_event_description *desc)
	301	{
0b9e59d6	302	struct side_event_state *event_state = side_ptr_get(desc->state);
f8188f94	303	uint32_t nr_cb = desc->nr_callbacks;
67337c4a MD	304	struct side_callback *old_cb;
	305
	306	if (!nr_cb)
	307	return;
0b9e59d6 MD	308	old_cb = (struct side_callback *) event_state->callbacks;
0b9e59d6 MD	309	(void) __atomic_add_fetch(&event_state->enabled, -1, __ATOMIC_RELAXED);
67337c4a MD	310	/*
	311	* Setting the state back to 0 cb and empty callbacks out of
	312	* caution. This should not matter because instrumentation is
	313	* unreachable.
	314	*/
f8188f94	315	desc->nr_callbacks = 0;
0b9e59d6	316	side_rcu_assign_pointer(event_state->callbacks, &side_empty_callback);
67337c4a MD	317	/*
	318	* No need to wait for grace period because instrumentation is
	319	* unreachable.
	320	*/
	321	free(old_cb);
	322	}
	323
	324	/*
	325	* Unregister event handle. At this point, all side events in that
	326	* handle should be unreachable.
	327	*/
	328	void side_events_unregister(struct side_events_register_handle *events_handle)
	329	{
	330	struct side_tracer_handle *tracer_handle;
	331	uint32_t i;
	332
	333	if (!events_handle)
	334	return;
	335	if (finalized)
	336	return;
	337	if (!initialized)
	338	side_init();
	339	pthread_mutex_lock(&side_lock);
	340	side_list_remove_node(&events_handle->node);
	341	side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
	342	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
	343	events_handle->events, events_handle->nr_events,
	344	tracer_handle->priv);
	345	}
	346	for (i = 0; i < events_handle->nr_events; i++) {
	347	struct side_event_description *event = events_handle->events[i];
	348
	349	/* Skip NULL pointers */
	350	if (!event)
	351	continue;
	352	side_event_remove_callbacks(event);
	353	}
	354	pthread_mutex_unlock(&side_lock);
	355	//TODO: call event batch unregister ioctl
	356	free(events_handle);
	357	}
	358
	359	struct side_tracer_handle *side_tracer_event_notification_register(
	360	void (*cb)(enum side_tracer_notification notif,
	361	struct side_event_description *events, uint32_t nr_events, void priv),
	362	void *priv)
	363	{
	364	struct side_tracer_handle *tracer_handle;
	365	struct side_events_register_handle *events_handle;
	366
	367	if (finalized)
	368	return NULL;
	369	if (!initialized)
	370	side_init();
	371	tracer_handle = (struct side_tracer_handle *)
	372	calloc(1, sizeof(struct side_tracer_handle));
	373	if (!tracer_handle)
	374	return NULL;
	375	pthread_mutex_lock(&side_lock);
	376	tracer_handle->cb = cb;
	377	tracer_handle->priv = priv;
	378	side_list_insert_node_tail(&side_tracer_list, &tracer_handle->node);
	379	side_list_for_each_entry(events_handle, &side_events_list, node) {
	380	cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
381	events_handle->events, events_handle->nr_events, priv);
382	}
383	pthread_mutex_unlock(&side_lock);
384	return tracer_handle;
385	}
386
387	void side_tracer_event_notification_unregister(struct side_tracer_handle *tracer_handle)
388	{
389	struct side_events_register_handle *events_handle;
390
391	if (finalized)
392	return;
393	if (!initialized)
394	side_init();
395	pthread_mutex_lock(&side_lock);
396	side_list_for_each_entry(events_handle, &side_events_list, node) {
397	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
398	events_handle->events, events_handle->nr_events,
399	tracer_handle->priv);
400	}
401	side_list_remove_node(&tracer_handle->node);
402	pthread_mutex_unlock(&side_lock);
be787080	403	free(tracer_handle);
67337c4a MD	404	}
	405
	406	void side_init(void)
	407	{
	408	if (initialized)
	409	return;
	410	side_rcu_gp_init(&rcu_gp);
	411	initialized = true;
	412	}
	413
	414	/*
	415	* side_exit() is executed from a library destructor. It can be called
	416	* explicitly at application exit as well. Concurrent side API use is
	417	* not expected at that point.
	418	*/
	419	void side_exit(void)
	420	{
	421	struct side_events_register_handle handle, tmp;
	422
	423	if (finalized)
	424	return;
	425	side_list_for_each_entry_safe(handle, tmp, &side_events_list, node)
	426	side_events_unregister(handle);
	427	side_rcu_gp_exit(&rcu_gp);
	428	finalized = true;
	429	}