[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;

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;
	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.
	}
	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;
	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.
	}
	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->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_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->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_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->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_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	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
a3f36db7 MD	52	static pthread_mutex_t side_lock = PTHREAD_MUTEX_INITIALIZER;
a3f36db7 MD	53
a13c9d2e MD	54	static DEFINE_SIDE_LIST_HEAD(side_events_list);
a13c9d2e MD	55	static DEFINE_SIDE_LIST_HEAD(side_tracer_list);
b59abc69	56
a3f36db7 MD	57	/*
	58	* The empty callback has a NULL function callback pointer, which stops
	59	* iteration on the array of callbacks immediately.
	60	*/
054b7b5c MD	61	const struct side_callback side_empty_callback;
054b7b5c MD	62
6e46f5e6 MD	63	void side_init(void) __attribute__((constructor));
	64	void side_exit(void) __attribute__((destructor));
	65
6841ae81 MD	66	void side_call(const struct side_event_description desc, const struct side_arg_vec_description sav_desc)
6841ae81 MD	67	{
054b7b5c MD	68	const struct side_callback *side_cb;
054b7b5c MD	69	unsigned int rcu_period;
beea6e2e	70	uintptr_t enabled;
054b7b5c	71
6e46f5e6 MD	72	if (side_unlikely(finalized))
6e46f5e6 MD	73	return;
075ceef7 MD	74	if (side_unlikely(!initialized))
075ceef7 MD	75	side_init();
6841ae81 MD	76	if (side_unlikely(desc->flags & SIDE_EVENT_FLAG_VARIADIC)) {
	77	printf("ERROR: unexpected variadic event description\n");
	78	abort();
	79	}
3b4f86f6 MD	80	enabled = __atomic_load_n(desc->enabled, __ATOMIC_RELAXED);
3b4f86f6 MD	81	if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
dda82f46	82	// TODO: call kernel write.
6841ae81	83	}
3b4f86f6	84	if (side_unlikely(!(enabled & SIDE_EVENT_ENABLED_USER_MASK)))
054b7b5c MD	85	return;
054b7b5c MD	86
054b7b5c MD	87	rcu_period = side_rcu_read_begin(&rcu_gp);
	88	for (side_cb = side_rcu_dereference(desc->callbacks); side_cb->u.call != NULL; side_cb++)
	89	side_cb->u.call(desc, sav_desc, side_cb->priv);
	90	side_rcu_read_end(&rcu_gp, rcu_period);
6841ae81 MD	91	}
	92
	93	void side_call_variadic(const struct side_event_description *desc,
	94	const struct side_arg_vec_description *sav_desc,
	95	const struct side_arg_dynamic_event_struct *var_struct)
	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	}
3b4f86f6	113	if (side_unlikely(!(enabled & SIDE_EVENT_ENABLED_USER_MASK)))
054b7b5c MD	114	return;
054b7b5c MD	115
054b7b5c MD	116	rcu_period = side_rcu_read_begin(&rcu_gp);
	117	for (side_cb = side_rcu_dereference(desc->callbacks); side_cb->u.call_variadic != NULL; side_cb++)
	118	side_cb->u.call_variadic(desc, sav_desc, var_struct, side_cb->priv);
	119	side_rcu_read_end(&rcu_gp, rcu_period);
6841ae81	120	}
075ceef7	121
a3f36db7 MD	122	static
	123	const struct side_callback *side_tracer_callback_lookup(
	124	const struct side_event_description *desc,
	125	void (call)(), void priv)
	126	{
	127	const struct side_callback *cb;
	128
	129	for (cb = desc->callbacks; cb->u.call != NULL; cb++) {
	130	if (cb->u.call == call && cb->priv == priv)
	131	return cb;
	132	}
	133	return NULL;
	134	}
	135
	136	static
	137	int _side_tracer_callback_register(struct side_event_description *desc,
	138	void (call)(), void priv)
	139	{
	140	struct side_callback old_cb, new_cb;
	141	int ret = SIDE_ERROR_OK;
	142	uint32_t old_nr_cb;
	143
	144	if (!call)
	145	return SIDE_ERROR_INVAL;
6e46f5e6 MD	146	if (finalized)
6e46f5e6 MD	147	return SIDE_ERROR_EXITING;
a13c9d2e MD	148	if (!initialized)
a13c9d2e MD	149	side_init();
a3f36db7	150	pthread_mutex_lock(&side_lock);
45172226 MD	151	old_nr_cb = desc->nr_callbacks;
45172226 MD	152	if (old_nr_cb == UINT32_MAX) {
a3f36db7 MD	153	ret = SIDE_ERROR_INVAL;
	154	goto unlock;
	155	}
	156	/* Reject duplicate (call, priv) tuples. */
	157	if (side_tracer_callback_lookup(desc, call, priv)) {
	158	ret = SIDE_ERROR_EXIST;
	159	goto unlock;
	160	}
	161	old_cb = (struct side_callback *) desc->callbacks;
	162	/* old_nr_cb + 1 (new cb) + 1 (NULL) */
	163	new_cb = (struct side_callback *) calloc(old_nr_cb + 2, sizeof(struct side_callback));
	164	if (!new_cb) {
	165	ret = SIDE_ERROR_NOMEM;
	166	goto unlock;
	167	}
	168	memcpy(new_cb, old_cb, old_nr_cb);
	169	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	170	new_cb[old_nr_cb].u.call_variadic = call;
	171	else
	172	new_cb[old_nr_cb].u.call = call;
	173	new_cb[old_nr_cb].priv = priv;
	174	side_rcu_assign_pointer(desc->callbacks, new_cb);
	175	side_rcu_wait_grace_period(&rcu_gp);
	176	if (old_nr_cb)
	177	free(old_cb);
45172226	178	desc->nr_callbacks++;
a3f36db7	179	/* Increment concurrently with kernel setting the top bits. */
45172226 MD	180	if (!old_nr_cb)
45172226 MD	181	(void) __atomic_add_fetch(desc->enabled, 1, __ATOMIC_RELAXED);
a3f36db7 MD	182	unlock:
	183	pthread_mutex_unlock(&side_lock);
	184	return ret;
	185	}
	186
	187	int side_tracer_callback_register(struct side_event_description *desc,
	188	void (call)(const struct side_event_description desc,
	189	const struct side_arg_vec_description *sav_desc,
	190	void *priv),
	191	void *priv)
	192	{
	193	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	194	return SIDE_ERROR_INVAL;
	195	return _side_tracer_callback_register(desc, call, priv);
	196	}
	197
	198	int side_tracer_callback_variadic_register(struct side_event_description *desc,
	199	void (call_variadic)(const struct side_event_description desc,
	200	const struct side_arg_vec_description *sav_desc,
	201	const struct side_arg_dynamic_event_struct *var_struct,
	202	void *priv),
	203	void *priv)
	204	{
	205	if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
	206	return SIDE_ERROR_INVAL;
	207	return _side_tracer_callback_register(desc, call_variadic, priv);
	208	}
	209
	210	int _side_tracer_callback_unregister(struct side_event_description *desc,
	211	void (call)(), void priv)
	212	{
	213	struct side_callback old_cb, new_cb;
	214	const struct side_callback *cb_pos;
	215	uint32_t pos_idx;
	216	int ret = SIDE_ERROR_OK;
	217	uint32_t old_nr_cb;
	218
	219	if (!call)
	220	return SIDE_ERROR_INVAL;
6e46f5e6 MD	221	if (finalized)
6e46f5e6 MD	222	return SIDE_ERROR_EXITING;
a13c9d2e MD	223	if (!initialized)
a13c9d2e MD	224	side_init();
a3f36db7	225	pthread_mutex_lock(&side_lock);
a3f36db7 MD	226	cb_pos = side_tracer_callback_lookup(desc, call, priv);
	227	if (!cb_pos) {
	228	ret = SIDE_ERROR_NOENT;
	229	goto unlock;
	230	}
45172226	231	old_nr_cb = desc->nr_callbacks;
9a83b759	232	old_cb = (struct side_callback *) desc->callbacks;
a3f36db7 MD	233	if (old_nr_cb == 1) {
	234	new_cb = (struct side_callback *) &side_empty_callback;
	235	} else {
	236	pos_idx = cb_pos - desc->callbacks;
	237	/* Remove entry at pos_idx. */
	238	/* old_nr_cb - 1 (removed cb) + 1 (NULL) */
	239	new_cb = (struct side_callback *) calloc(old_nr_cb, sizeof(struct side_callback));
	240	if (!new_cb) {
	241	ret = SIDE_ERROR_NOMEM;
	242	goto unlock;
	243	}
	244	memcpy(new_cb, old_cb, pos_idx);
	245	memcpy(&new_cb[pos_idx], &old_cb[pos_idx + 1], old_nr_cb - pos_idx - 1);
	246	}
	247	side_rcu_assign_pointer(desc->callbacks, new_cb);
	248	side_rcu_wait_grace_period(&rcu_gp);
	249	free(old_cb);
45172226	250	desc->nr_callbacks--;
a3f36db7	251	/* Decrement concurrently with kernel setting the top bits. */
45172226 MD	252	if (old_nr_cb == 1)
45172226 MD	253	(void) __atomic_add_fetch(desc->enabled, -1, __ATOMIC_RELAXED);
a3f36db7 MD	254	unlock:
	255	pthread_mutex_unlock(&side_lock);
	256	return ret;
	257	}
	258
	259	int side_tracer_callback_unregister(struct side_event_description *desc,
	260	void (call)(const struct side_event_description desc,
	261	const struct side_arg_vec_description *sav_desc,
	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, priv);
	268	}
	269
	270	int side_tracer_callback_variadic_unregister(struct side_event_description *desc,
	271	void (call_variadic)(const struct side_event_description desc,
	272	const struct side_arg_vec_description *sav_desc,
	273	const struct side_arg_dynamic_event_struct *var_struct,
	274	void *priv),
	275	void *priv)
	276	{
	277	if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
	278	return SIDE_ERROR_INVAL;
	279	return _side_tracer_callback_unregister(desc, call_variadic, priv);
	280	}
	281
6e46f5e6 MD	282	struct side_events_register_handle side_events_register(struct side_event_description *events, uint32_t nr_events)
6e46f5e6 MD	283	{
a13c9d2e MD	284	struct side_events_register_handle *events_handle = NULL;
a13c9d2e MD	285	struct side_tracer_handle *tracer_handle;
6e46f5e6 MD	286
	287	if (finalized)
	288	return NULL;
a13c9d2e MD	289	if (!initialized)
	290	side_init();
	291	events_handle = calloc(1, sizeof(struct side_events_register_handle));
	292	if (!events_handle)
6e46f5e6	293	return NULL;
a13c9d2e MD	294	events_handle->events = events;
	295	events_handle->nr_events = nr_events;
	296
6e46f5e6	297	pthread_mutex_lock(&side_lock);
a13c9d2e MD	298	side_list_insert_node_tail(&side_events_list, &events_handle->node);
	299	side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
	300	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
	301	events, nr_events, tracer_handle->priv);
	302	}
6e46f5e6 MD	303	pthread_mutex_unlock(&side_lock);
6e46f5e6 MD	304	//TODO: call event batch register ioctl
a13c9d2e	305	return events_handle;
6e46f5e6 MD	306	}
6e46f5e6 MD	307
a3f36db7	308	static
6e46f5e6 MD	309	void side_event_remove_callbacks(struct side_event_description *desc)
6e46f5e6 MD	310	{
ea0d2bea	311	uint32_t nr_cb = desc->nr_callbacks;
6e46f5e6 MD	312	struct side_callback *old_cb;
	313
	314	if (!nr_cb)
	315	return;
	316	old_cb = (struct side_callback *) desc->callbacks;
ea0d2bea	317	(void) __atomic_add_fetch(desc->enabled, -1, __ATOMIC_RELAXED);
6e46f5e6 MD	318	/*
	319	* Setting the state back to 0 cb and empty callbacks out of
	320	* caution. This should not matter because instrumentation is
	321	* unreachable.
	322	*/
45172226	323	desc->nr_callbacks = 0;
6e46f5e6 MD	324	side_rcu_assign_pointer(desc->callbacks, &side_empty_callback);
	325	/*
	326	* No need to wait for grace period because instrumentation is
	327	* unreachable.
	328	*/
	329	free(old_cb);
	330	}
	331
	332	/*
	333	* Unregister event handle. At this point, all side events in that
	334	* handle should be unreachable.
	335	*/
a13c9d2e	336	void side_events_unregister(struct side_events_register_handle *events_handle)
6e46f5e6	337	{
a13c9d2e	338	struct side_tracer_handle *tracer_handle;
6e46f5e6 MD	339	uint32_t i;
6e46f5e6 MD	340
314c22c3 MD	341	if (!events_handle)
314c22c3 MD	342	return;
6e46f5e6 MD	343	if (finalized)
6e46f5e6 MD	344	return;
a13c9d2e MD	345	if (!initialized)
a13c9d2e MD	346	side_init();
6e46f5e6	347	pthread_mutex_lock(&side_lock);
a13c9d2e MD	348	side_list_remove_node(&events_handle->node);
	349	side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
	350	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
	351	events_handle->events, events_handle->nr_events,
	352	tracer_handle->priv);
	353	}
	354	for (i = 0; i < events_handle->nr_events; i++) {
	355	struct side_event_description *event = events_handle->events[i];
6e46f5e6 MD	356
	357	/* Skip NULL pointers */
	358	if (!event)
	359	continue;
	360	side_event_remove_callbacks(event);
	361	}
	362	pthread_mutex_unlock(&side_lock);
	363	//TODO: call event batch unregister ioctl
a13c9d2e MD	364	free(events_handle);
	365	}
	366
	367	struct side_tracer_handle *side_tracer_event_notification_register(
	368	void (*cb)(enum side_tracer_notification notif,
	369	struct side_event_description *events, uint32_t nr_events, void priv),
	370	void *priv)
	371	{
	372	struct side_tracer_handle *tracer_handle;
	373	struct side_events_register_handle *events_handle;
	374
	375	if (finalized)
	376	return NULL;
	377	if (!initialized)
	378	side_init();
	379	tracer_handle = calloc(1, sizeof(struct side_tracer_handle));
	380	if (!tracer_handle)
	381	return NULL;
	382	pthread_mutex_lock(&side_lock);
	383	tracer_handle->cb = cb;
	384	tracer_handle->priv = priv;
	385	side_list_insert_node_tail(&side_tracer_list, &tracer_handle->node);
	386	side_list_for_each_entry(events_handle, &side_events_list, node) {
	387	cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
	388	events_handle->events, events_handle->nr_events, priv);
	389	}
	390	pthread_mutex_unlock(&side_lock);
	391	return tracer_handle;
	392	}
	393
	394	void side_tracer_event_notification_unregister(struct side_tracer_handle *tracer_handle)
	395	{
	396	struct side_events_register_handle *events_handle;
	397
	398	if (finalized)
	399	return;
	400	if (!initialized)
	401	side_init();
	402	pthread_mutex_lock(&side_lock);
	403	side_list_for_each_entry(events_handle, &side_events_list, node) {
	404	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
	405	events_handle->events, events_handle->nr_events,
	406	tracer_handle->priv);
	407	}
	408	side_list_remove_node(&tracer_handle->node);
	409	pthread_mutex_unlock(&side_lock);
6e46f5e6 MD	410	}
6e46f5e6 MD	411
075ceef7 MD	412	void side_init(void)
	413	{
	414	if (initialized)
	415	return;
054b7b5c	416	side_rcu_gp_init(&rcu_gp);
075ceef7 MD	417	initialized = true;
075ceef7 MD	418	}
6e46f5e6	419
aa584c16 MD	420	/*
	421	* side_exit() is executed from a library destructor. It can be called
	422	* explicitly at application exit as well. Concurrent side API use is
	423	* not expected at that point.
	424	*/
6e46f5e6 MD	425	void side_exit(void)
	426	{
	427	struct side_events_register_handle handle, tmp;
	428
	429	if (finalized)
	430	return;
	431	side_rcu_gp_exit(&rcu_gp);
a13c9d2e	432	side_list_for_each_entry_safe(handle, tmp, &side_events_list, node)
6e46f5e6 MD	433	side_events_unregister(handle);
	434	finalized = true;
	435	}