[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. */
#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_init(void) __attribute__((constructor));
void side_exit(void) __attribute__((destructor));

void side_call(const struct side_event_description *desc, const struct side_arg_vec *side_arg_vec)
{
	const struct side_callback *side_cb;
	unsigned int rcu_period;
	uintptr_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.
	}
	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, side_arg_vec, 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 *side_arg_vec,
	const struct side_arg_dynamic_struct *var_struct)
{
	const struct side_callback *side_cb;
	unsigned int rcu_period;
	uintptr_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.
	}
	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, side_arg_vec, 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->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 *) 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);
	desc->nr_callbacks++;
	/* Increment concurrently with kernel setting the top bits. */
	if (!old_nr_cb)
		(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 *side_arg_vec,
			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 *side_arg_vec,
			const struct side_arg_dynamic_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->nr_callbacks;
	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);
	desc->nr_callbacks--;
	/* Decrement concurrently with kernel setting the top bits. */
	if (old_nr_cb == 1)
		(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 *side_arg_vec,
			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 *side_arg_vec,
			const struct side_arg_dynamic_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->nr_callbacks;
	struct side_callback *old_cb;

	if (!nr_cb)
		return;
	old_cb = (struct side_callback *) desc->callbacks;
	(void) __atomic_add_fetch(desc->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(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_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
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	13	/* Top 8 bits reserved for kernel tracer use. */
f61301bb MD	14	#if SIDE_BITS_PER_LONG == 64
	15	# define SIDE_EVENT_ENABLED_KERNEL_MASK 0xFF00000000000000ULL
	16	# define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK 0x8000000000000000ULL
	17
	18	/* Allow 2^56 tracer references on an event. */
	19	# define SIDE_EVENT_ENABLED_USER_MASK 0x00FFFFFFFFFFFFFFULL
	20	#else
	21	# define SIDE_EVENT_ENABLED_KERNEL_MASK 0xFF000000UL
	22	# define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK 0x80000000UL
29b3374e	23
45172226	24	/* Allow 2^24 tracer references on an event. */
f61301bb MD	25	# define SIDE_EVENT_ENABLED_USER_MASK 0x00FFFFFFUL
f61301bb MD	26	#endif
054b7b5c	27
6e46f5e6 MD	28	struct side_events_register_handle {
	29	struct side_list_node node;
	30	struct side_event_description **events;
	31	uint32_t nr_events;
	32	};
	33
a13c9d2e MD	34	struct side_tracer_handle {
	35	struct side_list_node node;
	36	void (*cb)(enum side_tracer_notification notif,
	37	struct side_event_description *events, uint32_t nr_events, void priv);
	38	void *priv;
	39	};
	40
a3f36db7	41	static struct side_rcu_gp_state rcu_gp;
075ceef7 MD	42
	43	/*
	44	* Lazy initialization for early use within library constructors.
	45	*/
	46	static bool initialized;
6e46f5e6 MD	47	/*
	48	* Do not register/unregister any more events after destructor.
	49	*/
	50	static bool finalized;
075ceef7	51
1e070341 MD	52	/*
	53	* Recursive mutex to allow tracer callbacks to use the side API.
	54	*/
	55	static pthread_mutex_t side_lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
a3f36db7	56
a13c9d2e MD	57	static DEFINE_SIDE_LIST_HEAD(side_events_list);
a13c9d2e MD	58	static DEFINE_SIDE_LIST_HEAD(side_tracer_list);
b59abc69	59
a3f36db7 MD	60	/*
	61	* The empty callback has a NULL function callback pointer, which stops
	62	* iteration on the array of callbacks immediately.
	63	*/
054b7b5c MD	64	const struct side_callback side_empty_callback;
054b7b5c MD	65
6e46f5e6 MD	66	void side_init(void) __attribute__((constructor));
	67	void side_exit(void) __attribute__((destructor));
	68
9a6ca773	69	void side_call(const struct side_event_description desc, const struct side_arg_vec side_arg_vec)
6841ae81	70	{
054b7b5c MD	71	const struct side_callback *side_cb;
054b7b5c MD	72	unsigned int rcu_period;
beea6e2e	73	uintptr_t enabled;
054b7b5c	74
6e46f5e6 MD	75	if (side_unlikely(finalized))
6e46f5e6 MD	76	return;
075ceef7 MD	77	if (side_unlikely(!initialized))
075ceef7 MD	78	side_init();
6841ae81 MD	79	if (side_unlikely(desc->flags & SIDE_EVENT_FLAG_VARIADIC)) {
	80	printf("ERROR: unexpected variadic event description\n");
	81	abort();
	82	}
3b4f86f6 MD	83	enabled = __atomic_load_n(desc->enabled, __ATOMIC_RELAXED);
3b4f86f6 MD	84	if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
dda82f46	85	// TODO: call kernel write.
6841ae81	86	}
054b7b5c MD	87	rcu_period = side_rcu_read_begin(&rcu_gp);
054b7b5c MD	88	for (side_cb = side_rcu_dereference(desc->callbacks); side_cb->u.call != NULL; side_cb++)
9a6ca773	89	side_cb->u.call(desc, side_arg_vec, side_cb->priv);
054b7b5c	90	side_rcu_read_end(&rcu_gp, rcu_period);
6841ae81 MD	91	}
	92
	93	void side_call_variadic(const struct side_event_description *desc,
9a6ca773	94	const struct side_arg_vec *side_arg_vec,
0c7abe2b	95	const struct side_arg_dynamic_struct *var_struct)
6841ae81	96	{
054b7b5c MD	97	const struct side_callback *side_cb;
054b7b5c MD	98	unsigned int rcu_period;
beea6e2e	99	uintptr_t enabled;
054b7b5c	100
6e46f5e6 MD	101	if (side_unlikely(finalized))
6e46f5e6 MD	102	return;
075ceef7 MD	103	if (side_unlikely(!initialized))
075ceef7 MD	104	side_init();
3b4f86f6 MD	105	if (side_unlikely(!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))) {
	106	printf("ERROR: unexpected non-variadic event description\n");
	107	abort();
	108	}
	109	enabled = __atomic_load_n(desc->enabled, __ATOMIC_RELAXED);
	110	if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
dda82f46	111	// TODO: call kernel write.
6841ae81	112	}
054b7b5c MD	113	rcu_period = side_rcu_read_begin(&rcu_gp);
054b7b5c MD	114	for (side_cb = side_rcu_dereference(desc->callbacks); side_cb->u.call_variadic != NULL; side_cb++)
9a6ca773	115	side_cb->u.call_variadic(desc, side_arg_vec, var_struct, side_cb->priv);
054b7b5c	116	side_rcu_read_end(&rcu_gp, rcu_period);
6841ae81	117	}
075ceef7	118
a3f36db7 MD	119	static
	120	const struct side_callback *side_tracer_callback_lookup(
	121	const struct side_event_description *desc,
	122	void (call)(), void priv)
	123	{
	124	const struct side_callback *cb;
	125
	126	for (cb = desc->callbacks; cb->u.call != NULL; cb++) {
	127	if (cb->u.call == call && cb->priv == priv)
	128	return cb;
	129	}
	130	return NULL;
	131	}
	132
	133	static
	134	int _side_tracer_callback_register(struct side_event_description *desc,
	135	void (call)(), void priv)
	136	{
	137	struct side_callback old_cb, new_cb;
	138	int ret = SIDE_ERROR_OK;
	139	uint32_t old_nr_cb;
	140
	141	if (!call)
	142	return SIDE_ERROR_INVAL;
6e46f5e6 MD	143	if (finalized)
6e46f5e6 MD	144	return SIDE_ERROR_EXITING;
a13c9d2e MD	145	if (!initialized)
a13c9d2e MD	146	side_init();
a3f36db7	147	pthread_mutex_lock(&side_lock);
45172226 MD	148	old_nr_cb = desc->nr_callbacks;
45172226 MD	149	if (old_nr_cb == UINT32_MAX) {
a3f36db7 MD	150	ret = SIDE_ERROR_INVAL;
	151	goto unlock;
	152	}
	153	/* Reject duplicate (call, priv) tuples. */
	154	if (side_tracer_callback_lookup(desc, call, priv)) {
	155	ret = SIDE_ERROR_EXIST;
	156	goto unlock;
	157	}
	158	old_cb = (struct side_callback *) desc->callbacks;
	159	/* old_nr_cb + 1 (new cb) + 1 (NULL) */
	160	new_cb = (struct side_callback *) calloc(old_nr_cb + 2, sizeof(struct side_callback));
	161	if (!new_cb) {
	162	ret = SIDE_ERROR_NOMEM;
	163	goto unlock;
	164	}
	165	memcpy(new_cb, old_cb, old_nr_cb);
	166	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	167	new_cb[old_nr_cb].u.call_variadic = call;
	168	else
	169	new_cb[old_nr_cb].u.call = call;
	170	new_cb[old_nr_cb].priv = priv;
	171	side_rcu_assign_pointer(desc->callbacks, new_cb);
	172	side_rcu_wait_grace_period(&rcu_gp);
	173	if (old_nr_cb)
	174	free(old_cb);
45172226	175	desc->nr_callbacks++;
a3f36db7	176	/* Increment concurrently with kernel setting the top bits. */
45172226 MD	177	if (!old_nr_cb)
45172226 MD	178	(void) __atomic_add_fetch(desc->enabled, 1, __ATOMIC_RELAXED);
a3f36db7 MD	179	unlock:
	180	pthread_mutex_unlock(&side_lock);
	181	return ret;
	182	}
	183
	184	int side_tracer_callback_register(struct side_event_description *desc,
	185	void (call)(const struct side_event_description desc,
9a6ca773	186	const struct side_arg_vec *side_arg_vec,
a3f36db7 MD	187	void *priv),
	188	void *priv)
	189	{
	190	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	191	return SIDE_ERROR_INVAL;
	192	return _side_tracer_callback_register(desc, call, priv);
	193	}
	194
	195	int side_tracer_callback_variadic_register(struct side_event_description *desc,
	196	void (call_variadic)(const struct side_event_description desc,
9a6ca773	197	const struct side_arg_vec *side_arg_vec,
0c7abe2b	198	const struct side_arg_dynamic_struct *var_struct,
a3f36db7 MD	199	void *priv),
	200	void *priv)
	201	{
	202	if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
	203	return SIDE_ERROR_INVAL;
	204	return _side_tracer_callback_register(desc, call_variadic, priv);
	205	}
	206
	207	int _side_tracer_callback_unregister(struct side_event_description *desc,
	208	void (call)(), void priv)
	209	{
	210	struct side_callback old_cb, new_cb;
	211	const struct side_callback *cb_pos;
	212	uint32_t pos_idx;
	213	int ret = SIDE_ERROR_OK;
	214	uint32_t old_nr_cb;
	215
	216	if (!call)
	217	return SIDE_ERROR_INVAL;
6e46f5e6 MD	218	if (finalized)
6e46f5e6 MD	219	return SIDE_ERROR_EXITING;
a13c9d2e MD	220	if (!initialized)
a13c9d2e MD	221	side_init();
a3f36db7	222	pthread_mutex_lock(&side_lock);
a3f36db7 MD	223	cb_pos = side_tracer_callback_lookup(desc, call, priv);
	224	if (!cb_pos) {
	225	ret = SIDE_ERROR_NOENT;
	226	goto unlock;
	227	}
45172226	228	old_nr_cb = desc->nr_callbacks;
9a83b759	229	old_cb = (struct side_callback *) desc->callbacks;
a3f36db7 MD	230	if (old_nr_cb == 1) {
	231	new_cb = (struct side_callback *) &side_empty_callback;
	232	} else {
	233	pos_idx = cb_pos - desc->callbacks;
	234	/* Remove entry at pos_idx. */
	235	/* old_nr_cb - 1 (removed cb) + 1 (NULL) */
	236	new_cb = (struct side_callback *) calloc(old_nr_cb, sizeof(struct side_callback));
	237	if (!new_cb) {
	238	ret = SIDE_ERROR_NOMEM;
	239	goto unlock;
	240	}
	241	memcpy(new_cb, old_cb, pos_idx);
	242	memcpy(&new_cb[pos_idx], &old_cb[pos_idx + 1], old_nr_cb - pos_idx - 1);
	243	}
	244	side_rcu_assign_pointer(desc->callbacks, new_cb);
	245	side_rcu_wait_grace_period(&rcu_gp);
	246	free(old_cb);
45172226	247	desc->nr_callbacks--;
a3f36db7	248	/* Decrement concurrently with kernel setting the top bits. */
45172226 MD	249	if (old_nr_cb == 1)
45172226 MD	250	(void) __atomic_add_fetch(desc->enabled, -1, __ATOMIC_RELAXED);
a3f36db7 MD	251	unlock:
	252	pthread_mutex_unlock(&side_lock);
	253	return ret;
	254	}
	255
	256	int side_tracer_callback_unregister(struct side_event_description *desc,
	257	void (call)(const struct side_event_description desc,
9a6ca773	258	const struct side_arg_vec *side_arg_vec,
a3f36db7 MD	259	void *priv),
	260	void *priv)
	261	{
	262	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	263	return SIDE_ERROR_INVAL;
	264	return _side_tracer_callback_unregister(desc, call, priv);
	265	}
	266
	267	int side_tracer_callback_variadic_unregister(struct side_event_description *desc,
	268	void (call_variadic)(const struct side_event_description desc,
9a6ca773	269	const struct side_arg_vec *side_arg_vec,
0c7abe2b	270	const struct side_arg_dynamic_struct *var_struct,
a3f36db7 MD	271	void *priv),
	272	void *priv)
	273	{
	274	if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
	275	return SIDE_ERROR_INVAL;
	276	return _side_tracer_callback_unregister(desc, call_variadic, priv);
	277	}
	278
6e46f5e6 MD	279	struct side_events_register_handle side_events_register(struct side_event_description *events, uint32_t nr_events)
6e46f5e6 MD	280	{
a13c9d2e MD	281	struct side_events_register_handle *events_handle = NULL;
a13c9d2e MD	282	struct side_tracer_handle *tracer_handle;
6e46f5e6 MD	283
	284	if (finalized)
	285	return NULL;
a13c9d2e MD	286	if (!initialized)
	287	side_init();
	288	events_handle = calloc(1, sizeof(struct side_events_register_handle));
	289	if (!events_handle)
6e46f5e6	290	return NULL;
a13c9d2e MD	291	events_handle->events = events;
	292	events_handle->nr_events = nr_events;
	293
6e46f5e6	294	pthread_mutex_lock(&side_lock);
a13c9d2e MD	295	side_list_insert_node_tail(&side_events_list, &events_handle->node);
	296	side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
	297	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
	298	events, nr_events, tracer_handle->priv);
	299	}
6e46f5e6 MD	300	pthread_mutex_unlock(&side_lock);
6e46f5e6 MD	301	//TODO: call event batch register ioctl
a13c9d2e	302	return events_handle;
6e46f5e6 MD	303	}
6e46f5e6 MD	304
a3f36db7	305	static
6e46f5e6 MD	306	void side_event_remove_callbacks(struct side_event_description *desc)
6e46f5e6 MD	307	{
ea0d2bea	308	uint32_t nr_cb = desc->nr_callbacks;
6e46f5e6 MD	309	struct side_callback *old_cb;
	310
	311	if (!nr_cb)
	312	return;
	313	old_cb = (struct side_callback *) desc->callbacks;
ea0d2bea	314	(void) __atomic_add_fetch(desc->enabled, -1, __ATOMIC_RELAXED);
6e46f5e6 MD	315	/*
	316	* Setting the state back to 0 cb and empty callbacks out of
	317	* caution. This should not matter because instrumentation is
	318	* unreachable.
	319	*/
45172226	320	desc->nr_callbacks = 0;
6e46f5e6 MD	321	side_rcu_assign_pointer(desc->callbacks, &side_empty_callback);
	322	/*
	323	* No need to wait for grace period because instrumentation is
	324	* unreachable.
	325	*/
	326	free(old_cb);
	327	}
	328
	329	/*
	330	* Unregister event handle. At this point, all side events in that
	331	* handle should be unreachable.
	332	*/
a13c9d2e	333	void side_events_unregister(struct side_events_register_handle *events_handle)
6e46f5e6	334	{
a13c9d2e	335	struct side_tracer_handle *tracer_handle;
6e46f5e6 MD	336	uint32_t i;
6e46f5e6 MD	337
314c22c3 MD	338	if (!events_handle)
314c22c3 MD	339	return;
6e46f5e6 MD	340	if (finalized)
6e46f5e6 MD	341	return;
a13c9d2e MD	342	if (!initialized)
a13c9d2e MD	343	side_init();
6e46f5e6	344	pthread_mutex_lock(&side_lock);
a13c9d2e MD	345	side_list_remove_node(&events_handle->node);
	346	side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
	347	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
	348	events_handle->events, events_handle->nr_events,
	349	tracer_handle->priv);
	350	}
	351	for (i = 0; i < events_handle->nr_events; i++) {
	352	struct side_event_description *event = events_handle->events[i];
6e46f5e6 MD	353
	354	/* Skip NULL pointers */
	355	if (!event)
	356	continue;
	357	side_event_remove_callbacks(event);
	358	}
	359	pthread_mutex_unlock(&side_lock);
	360	//TODO: call event batch unregister ioctl
a13c9d2e MD	361	free(events_handle);
	362	}
	363
	364	struct side_tracer_handle *side_tracer_event_notification_register(
	365	void (*cb)(enum side_tracer_notification notif,
	366	struct side_event_description *events, uint32_t nr_events, void priv),
	367	void *priv)
	368	{
	369	struct side_tracer_handle *tracer_handle;
	370	struct side_events_register_handle *events_handle;
	371
	372	if (finalized)
	373	return NULL;
	374	if (!initialized)
	375	side_init();
	376	tracer_handle = calloc(1, sizeof(struct side_tracer_handle));
	377	if (!tracer_handle)
	378	return NULL;
	379	pthread_mutex_lock(&side_lock);
	380	tracer_handle->cb = cb;
	381	tracer_handle->priv = priv;
	382	side_list_insert_node_tail(&side_tracer_list, &tracer_handle->node);
	383	side_list_for_each_entry(events_handle, &side_events_list, node) {
	384	cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
	385	events_handle->events, events_handle->nr_events, priv);
	386	}
	387	pthread_mutex_unlock(&side_lock);
	388	return tracer_handle;
	389	}
	390
	391	void side_tracer_event_notification_unregister(struct side_tracer_handle *tracer_handle)
	392	{
	393	struct side_events_register_handle *events_handle;
	394
	395	if (finalized)
	396	return;
	397	if (!initialized)
	398	side_init();
	399	pthread_mutex_lock(&side_lock);
	400	side_list_for_each_entry(events_handle, &side_events_list, node) {
	401	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
	402	events_handle->events, events_handle->nr_events,
	403	tracer_handle->priv);
	404	}
	405	side_list_remove_node(&tracer_handle->node);
	406	pthread_mutex_unlock(&side_lock);
6e46f5e6 MD	407	}
6e46f5e6 MD	408
075ceef7 MD	409	void side_init(void)
	410	{
	411	if (initialized)
	412	return;
054b7b5c	413	side_rcu_gp_init(&rcu_gp);
075ceef7 MD	414	initialized = true;
075ceef7 MD	415	}
6e46f5e6	416
aa584c16 MD	417	/*
	418	* side_exit() is executed from a library destructor. It can be called
	419	* explicitly at application exit as well. Concurrent side API use is
	420	* not expected at that point.
	421	*/
6e46f5e6 MD	422	void side_exit(void)
	423	{
	424	struct side_events_register_handle handle, tmp;
	425
	426	if (finalized)
	427	return;
a13c9d2e	428	side_list_for_each_entry_safe(handle, tmp, &side_events_list, node)
6e46f5e6	429	side_events_unregister(handle);
64d29894	430	side_rcu_gp_exit(&rcu_gp);
6e46f5e6 MD	431	finalized = true;
6e46f5e6 MD	432	}