[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 <assert.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();
	assert(!(side_ptr_get(event_state->desc)->flags & SIDE_EVENT_FLAG_VARIADIC));
	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(side_ptr_get(event_state->callbacks)); side_cb->u.call != NULL; side_cb++)
		side_cb->u.call(side_ptr_get(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();
	assert(side_ptr_get(event_state->desc)->flags & SIDE_EVENT_FLAG_VARIADIC);
	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(side_ptr_get(event_state->callbacks)); side_cb->u.call_variadic != NULL; side_cb++)
		side_cb->u.call_variadic(side_ptr_get(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 = side_ptr_get(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 *) side_ptr_get(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;
	/* High order bits are already zeroed. */
	side_rcu_assign_pointer(side_ptr_get(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 *) side_ptr_get(event_state->callbacks);
	if (old_nr_cb == 1) {
		new_cb = (struct side_callback *) &side_empty_callback;
	} else {
		pos_idx = cb_pos - side_ptr_get(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);
	}
	/* High order bits are already zeroed. */
	side_rcu_assign_pointer(side_ptr_get(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 *) side_ptr_get(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(side_ptr_get(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>
b1bf768c	8	#include <assert.h>
67337c4a MD	9
	10	#include "rcu.h"
	11	#include "list.h"
	12
	13	/* Top 8 bits reserved for kernel tracer use. */
	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
	23
	24	/* Allow 2^24 tracer references on an event. */
	25	# define SIDE_EVENT_ENABLED_USER_MASK 0x00FFFFFFUL
	26	#endif
	27
	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
	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
	41	static struct side_rcu_gp_state rcu_gp;
	42
	43	/*
	44	* Lazy initialization for early use within library constructors.
	45	*/
	46	static bool initialized;
	47	/*
	48	* Do not register/unregister any more events after destructor.
	49	*/
	50	static bool finalized;
	51
	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;
	56
	57	static DEFINE_SIDE_LIST_HEAD(side_events_list);
	58	static DEFINE_SIDE_LIST_HEAD(side_tracer_list);
	59
	60	/*
	61	* The empty callback has a NULL function callback pointer, which stops
	62	* iteration on the array of callbacks immediately.
	63	*/
	64	const struct side_callback side_empty_callback = { };
	65
0d747f98	66	void side_call(const struct side_event_state event_state, const struct side_arg_vec side_arg_vec)
67337c4a MD	67	{
	68	struct side_rcu_read_state rcu_read_state;
	69	const struct side_callback *side_cb;
	70	uintptr_t enabled;
	71
	72	if (side_unlikely(finalized))
	73	return;
	74	if (side_unlikely(!initialized))
	75	side_init();
f60d8121	76	assert(!(side_ptr_get(event_state->desc)->flags & SIDE_EVENT_FLAG_VARIADIC));
0b9e59d6	77	enabled = __atomic_load_n(&event_state->enabled, __ATOMIC_RELAXED);
67337c4a MD	78	if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
	79	// TODO: call kernel write.
	80	}
	81	side_rcu_read_begin(&rcu_gp, &rcu_read_state);
f60d8121 MD	82	for (side_cb = side_rcu_dereference(side_ptr_get(event_state->callbacks)); side_cb->u.call != NULL; side_cb++)
f60d8121 MD	83	side_cb->u.call(side_ptr_get(event_state->desc), side_arg_vec, side_cb->priv);
67337c4a MD	84	side_rcu_read_end(&rcu_gp, &rcu_read_state);
	85	}
	86
0d747f98	87	void side_call_variadic(const struct side_event_state *event_state,
67337c4a MD	88	const struct side_arg_vec *side_arg_vec,
	89	const struct side_arg_dynamic_struct *var_struct)
	90	{
	91	struct side_rcu_read_state rcu_read_state;
	92	const struct side_callback *side_cb;
	93	uintptr_t enabled;
	94
	95	if (side_unlikely(finalized))
	96	return;
	97	if (side_unlikely(!initialized))
	98	side_init();
f60d8121	99	assert(side_ptr_get(event_state->desc)->flags & SIDE_EVENT_FLAG_VARIADIC);
0b9e59d6	100	enabled = __atomic_load_n(&event_state->enabled, __ATOMIC_RELAXED);
67337c4a MD	101	if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
	102	// TODO: call kernel write.
	103	}
	104	side_rcu_read_begin(&rcu_gp, &rcu_read_state);
f60d8121 MD	105	for (side_cb = side_rcu_dereference(side_ptr_get(event_state->callbacks)); side_cb->u.call_variadic != NULL; side_cb++)
f60d8121 MD	106	side_cb->u.call_variadic(side_ptr_get(event_state->desc), side_arg_vec, var_struct, side_cb->priv);
67337c4a MD	107	side_rcu_read_end(&rcu_gp, &rcu_read_state);
	108	}
	109
	110	static
	111	const struct side_callback *side_tracer_callback_lookup(
	112	const struct side_event_description *desc,
	113	void call, void priv)
	114	{
0b9e59d6	115	struct side_event_state *event_state = side_ptr_get(desc->state);
67337c4a MD	116	const struct side_callback *cb;
67337c4a MD	117
f60d8121	118	for (cb = side_ptr_get(event_state->callbacks); cb->u.call != NULL; cb++) {
67337c4a MD	119	if ((void *) cb->u.call == call && cb->priv == priv)
	120	return cb;
	121	}
	122	return NULL;
	123	}
	124
	125	static
	126	int _side_tracer_callback_register(struct side_event_description *desc,
	127	void call, void priv)
	128	{
0b9e59d6	129	struct side_event_state *event_state;
67337c4a MD	130	struct side_callback old_cb, new_cb;
	131	int ret = SIDE_ERROR_OK;
	132	uint32_t old_nr_cb;
	133
	134	if (!call)
	135	return SIDE_ERROR_INVAL;
	136	if (finalized)
	137	return SIDE_ERROR_EXITING;
	138	if (!initialized)
	139	side_init();
	140	pthread_mutex_lock(&side_lock);
0b9e59d6	141	event_state = side_ptr_get(desc->state);
f8188f94	142	old_nr_cb = desc->nr_callbacks;
67337c4a MD	143	if (old_nr_cb == UINT32_MAX) {
	144	ret = SIDE_ERROR_INVAL;
	145	goto unlock;
	146	}
	147	/* Reject duplicate (call, priv) tuples. */
	148	if (side_tracer_callback_lookup(desc, call, priv)) {
	149	ret = SIDE_ERROR_EXIST;
	150	goto unlock;
	151	}
f60d8121	152	old_cb = (struct side_callback *) side_ptr_get(event_state->callbacks);
67337c4a MD	153	/* old_nr_cb + 1 (new cb) + 1 (NULL) */
	154	new_cb = (struct side_callback *) calloc(old_nr_cb + 2, sizeof(struct side_callback));
	155	if (!new_cb) {
	156	ret = SIDE_ERROR_NOMEM;
	157	goto unlock;
	158	}
	159	memcpy(new_cb, old_cb, old_nr_cb);
	160	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	161	new_cb[old_nr_cb].u.call_variadic =
	162	(side_tracer_callback_variadic_func) call;
	163	else
	164	new_cb[old_nr_cb].u.call =
	165	(side_tracer_callback_func) call;
	166	new_cb[old_nr_cb].priv = priv;
f60d8121 MD	167	/* High order bits are already zeroed. */
f60d8121 MD	168	side_rcu_assign_pointer(side_ptr_get(event_state->callbacks), new_cb);
67337c4a MD	169	side_rcu_wait_grace_period(&rcu_gp);
	170	if (old_nr_cb)
	171	free(old_cb);
f8188f94	172	desc->nr_callbacks++;
67337c4a MD	173	/* Increment concurrently with kernel setting the top bits. */
67337c4a MD	174	if (!old_nr_cb)
0b9e59d6	175	(void) __atomic_add_fetch(&event_state->enabled, 1, __ATOMIC_RELAXED);
67337c4a MD	176	unlock:
	177	pthread_mutex_unlock(&side_lock);
	178	return ret;
	179	}
	180
	181	int side_tracer_callback_register(struct side_event_description *desc,
	182	side_tracer_callback_func call,
	183	void *priv)
	184	{
	185	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	186	return SIDE_ERROR_INVAL;
	187	return _side_tracer_callback_register(desc, (void *) call, priv);
	188	}
	189
	190	int side_tracer_callback_variadic_register(struct side_event_description *desc,
	191	side_tracer_callback_variadic_func call_variadic,
	192	void *priv)
	193	{
	194	if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
	195	return SIDE_ERROR_INVAL;
	196	return _side_tracer_callback_register(desc, (void *) call_variadic, priv);
	197	}
	198
	199	static int _side_tracer_callback_unregister(struct side_event_description *desc,
	200	void call, void priv)
	201	{
0b9e59d6	202	struct side_event_state *event_state;
67337c4a MD	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;
	211	if (finalized)
	212	return SIDE_ERROR_EXITING;
	213	if (!initialized)
	214	side_init();
	215	pthread_mutex_lock(&side_lock);
0b9e59d6	216	event_state = side_ptr_get(desc->state);
67337c4a MD	217	cb_pos = side_tracer_callback_lookup(desc, call, priv);
	218	if (!cb_pos) {
	219	ret = SIDE_ERROR_NOENT;
	220	goto unlock;
	221	}
f8188f94	222	old_nr_cb = desc->nr_callbacks;
f60d8121	223	old_cb = (struct side_callback *) side_ptr_get(event_state->callbacks);
67337c4a MD	224	if (old_nr_cb == 1) {
	225	new_cb = (struct side_callback *) &side_empty_callback;
	226	} else {
f60d8121	227	pos_idx = cb_pos - side_ptr_get(event_state->callbacks);
67337c4a MD	228	/* Remove entry at pos_idx. */
	229	/* old_nr_cb - 1 (removed cb) + 1 (NULL) */
	230	new_cb = (struct side_callback *) calloc(old_nr_cb, sizeof(struct side_callback));
	231	if (!new_cb) {
	232	ret = SIDE_ERROR_NOMEM;
	233	goto unlock;
	234	}
	235	memcpy(new_cb, old_cb, pos_idx);
	236	memcpy(&new_cb[pos_idx], &old_cb[pos_idx + 1], old_nr_cb - pos_idx - 1);
	237	}
f60d8121 MD	238	/* High order bits are already zeroed. */
f60d8121 MD	239	side_rcu_assign_pointer(side_ptr_get(event_state->callbacks), new_cb);
67337c4a MD	240	side_rcu_wait_grace_period(&rcu_gp);
67337c4a MD	241	free(old_cb);
f8188f94	242	desc->nr_callbacks--;
67337c4a MD	243	/* Decrement concurrently with kernel setting the top bits. */
67337c4a MD	244	if (old_nr_cb == 1)
0b9e59d6	245	(void) __atomic_add_fetch(&event_state->enabled, -1, __ATOMIC_RELAXED);
67337c4a MD	246	unlock:
	247	pthread_mutex_unlock(&side_lock);
	248	return ret;
	249	}
	250
	251	int side_tracer_callback_unregister(struct side_event_description *desc,
	252	side_tracer_callback_func call,
	253	void *priv)
	254	{
	255	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	256	return SIDE_ERROR_INVAL;
	257	return _side_tracer_callback_unregister(desc, (void *) call, priv);
	258	}
	259
	260	int side_tracer_callback_variadic_unregister(struct side_event_description *desc,
	261	side_tracer_callback_variadic_func call_variadic,
	262	void *priv)
	263	{
	264	if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
	265	return SIDE_ERROR_INVAL;
	266	return _side_tracer_callback_unregister(desc, (void *) call_variadic, priv);
	267	}
	268
	269	struct side_events_register_handle side_events_register(struct side_event_description *events, uint32_t nr_events)
	270	{
	271	struct side_events_register_handle *events_handle = NULL;
	272	struct side_tracer_handle *tracer_handle;
	273
	274	if (finalized)
	275	return NULL;
	276	if (!initialized)
	277	side_init();
	278	events_handle = (struct side_events_register_handle *)
	279	calloc(1, sizeof(struct side_events_register_handle));
	280	if (!events_handle)
	281	return NULL;
	282	events_handle->events = events;
	283	events_handle->nr_events = nr_events;
	284
	285	pthread_mutex_lock(&side_lock);
	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	}
	291	pthread_mutex_unlock(&side_lock);
	292	//TODO: call event batch register ioctl
	293	return events_handle;
	294	}
	295
	296	static
	297	void side_event_remove_callbacks(struct side_event_description *desc)
	298	{
0b9e59d6	299	struct side_event_state *event_state = side_ptr_get(desc->state);
f8188f94	300	uint32_t nr_cb = desc->nr_callbacks;
67337c4a MD	301	struct side_callback *old_cb;
	302
	303	if (!nr_cb)
	304	return;
f60d8121	305	old_cb = (struct side_callback *) side_ptr_get(event_state->callbacks);
0b9e59d6	306	(void) __atomic_add_fetch(&event_state->enabled, -1, __ATOMIC_RELAXED);
67337c4a MD	307	/*
	308	* Setting the state back to 0 cb and empty callbacks out of
	309	* caution. This should not matter because instrumentation is
	310	* unreachable.
	311	*/
f8188f94	312	desc->nr_callbacks = 0;
f60d8121	313	side_rcu_assign_pointer(side_ptr_get(event_state->callbacks), &side_empty_callback);
67337c4a MD	314	/*
	315	* No need to wait for grace period because instrumentation is
	316	* unreachable.
	317	*/
	318	free(old_cb);
	319	}
	320
	321	/*
	322	* Unregister event handle. At this point, all side events in that
	323	* handle should be unreachable.
	324	*/
	325	void side_events_unregister(struct side_events_register_handle *events_handle)
	326	{
	327	struct side_tracer_handle *tracer_handle;
	328	uint32_t i;
	329
	330	if (!events_handle)
	331	return;
	332	if (finalized)
	333	return;
	334	if (!initialized)
	335	side_init();
	336	pthread_mutex_lock(&side_lock);
	337	side_list_remove_node(&events_handle->node);
	338	side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
	339	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
	340	events_handle->events, events_handle->nr_events,
	341	tracer_handle->priv);
	342	}
	343	for (i = 0; i < events_handle->nr_events; i++) {
	344	struct side_event_description *event = events_handle->events[i];
	345
	346	/* Skip NULL pointers */
	347	if (!event)
	348	continue;
	349	side_event_remove_callbacks(event);
	350	}
	351	pthread_mutex_unlock(&side_lock);
	352	//TODO: call event batch unregister ioctl
	353	free(events_handle);
	354	}
	355
	356	struct side_tracer_handle *side_tracer_event_notification_register(
	357	void (*cb)(enum side_tracer_notification notif,
	358	struct side_event_description *events, uint32_t nr_events, void priv),
	359	void *priv)
	360	{
	361	struct side_tracer_handle *tracer_handle;
	362	struct side_events_register_handle *events_handle;
	363
	364	if (finalized)
	365	return NULL;
	366	if (!initialized)
	367	side_init();
	368	tracer_handle = (struct side_tracer_handle *)
	369	calloc(1, sizeof(struct side_tracer_handle));
	370	if (!tracer_handle)
	371	return NULL;
	372	pthread_mutex_lock(&side_lock);
	373	tracer_handle->cb = cb;
	374	tracer_handle->priv = priv;
	375	side_list_insert_node_tail(&side_tracer_list, &tracer_handle->node);
	376	side_list_for_each_entry(events_handle, &side_events_list, node) {
	377	cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
378	events_handle->events, events_handle->nr_events, priv);
379	}
380	pthread_mutex_unlock(&side_lock);
381	return tracer_handle;
382	}
383
384	void side_tracer_event_notification_unregister(struct side_tracer_handle *tracer_handle)
385	{
386	struct side_events_register_handle *events_handle;
387
388	if (finalized)
389	return;
390	if (!initialized)
391	side_init();
392	pthread_mutex_lock(&side_lock);
393	side_list_for_each_entry(events_handle, &side_events_list, node) {
394	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
395	events_handle->events, events_handle->nr_events,
396	tracer_handle->priv);
397	}
398	side_list_remove_node(&tracer_handle->node);
399	pthread_mutex_unlock(&side_lock);
be787080	400	free(tracer_handle);
67337c4a MD	401	}
	402
	403	void side_init(void)
	404	{
	405	if (initialized)
	406	return;
	407	side_rcu_gp_init(&rcu_gp);
	408	initialized = true;
	409	}
	410
	411	/*
	412	* side_exit() is executed from a library destructor. It can be called
	413	* explicitly at application exit as well. Concurrent side API use is
	414	* not expected at that point.
	415	*/
	416	void side_exit(void)
	417	{
	418	struct side_events_register_handle handle, tmp;
	419
	420	if (finalized)
	421	return;
	422	side_list_for_each_entry_safe(handle, tmp, &side_events_list, node)
	423	side_events_unregister(handle);
	424	side_rcu_gp_exit(&rcu_gp);
	425	finalized = true;
	426	}