[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;
};

struct side_callback {
	union {
		void (*call)(const struct side_event_description *desc,
			const struct side_arg_vec *side_arg_vec,
			void *priv);
		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);
	} u;
	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 char side_empty_callback[sizeof(struct side_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_event_state_0 *es0;
	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->version != 0))
		abort();
	es0 = side_container_of(event_state, const struct side_event_state_0, parent);
	assert(!(es0->desc->flags & SIDE_EVENT_FLAG_VARIADIC));
	enabled = __atomic_load_n(&es0->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(es0->callbacks); side_cb->u.call != NULL; side_cb++)
		side_cb->u.call(es0->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_event_state_0 *es0;
	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->version != 0))
		abort();
	es0 = side_container_of(event_state, const struct side_event_state_0, parent);
	assert(es0->desc->flags & SIDE_EVENT_FLAG_VARIADIC);
	enabled = __atomic_load_n(&es0->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(es0->callbacks); side_cb->u.call_variadic != NULL; side_cb++)
		side_cb->u.call_variadic(es0->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_event_state_0 *es0;
	const struct side_callback *cb;

	if (side_unlikely(event_state->version != 0))
		abort();
	es0 = side_container_of(event_state, const struct side_event_state_0, parent);
	for (cb = es0->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;
	struct side_event_state_0 *es0;
	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);
	if (side_unlikely(event_state->version != 0))
		abort();
	es0 = side_container_of(event_state, struct side_event_state_0, parent);
	old_nr_cb = es0->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 *) es0->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(es0->callbacks, new_cb);
	side_rcu_wait_grace_period(&rcu_gp);
	if (old_nr_cb)
		free(old_cb);
	es0->nr_callbacks++;
	/* Increment concurrently with kernel setting the top bits. */
	if (!old_nr_cb)
		(void) __atomic_add_fetch(&es0->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;
	struct side_event_state_0 *es0;
	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);
	if (side_unlikely(event_state->version != 0))
		abort();
	es0 = side_container_of(event_state, struct side_event_state_0, parent);
	cb_pos = side_tracer_callback_lookup(desc, call, priv);
	if (!cb_pos) {
		ret = SIDE_ERROR_NOENT;
		goto unlock;
	}
	old_nr_cb = es0->nr_callbacks;
	old_cb = (struct side_callback *) es0->callbacks;
	if (old_nr_cb == 1) {
		new_cb = (struct side_callback *) &side_empty_callback;
	} else {
		pos_idx = cb_pos - es0->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(es0->callbacks, new_cb);
	side_rcu_wait_grace_period(&rcu_gp);
	free(old_cb);
	es0->nr_callbacks--;
	/* Decrement concurrently with kernel setting the top bits. */
	if (old_nr_cb == 1)
		(void) __atomic_add_fetch(&es0->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);
	struct side_event_state_0 *es0;
	struct side_callback *old_cb;
	uint32_t nr_cb;

	if (side_unlikely(event_state->version != 0))
		abort();
	es0 = side_container_of(event_state, struct side_event_state_0, parent);
	nr_cb = es0->nr_callbacks;
	if (!nr_cb)
		return;
	old_cb = (struct side_callback *) es0->callbacks;
	(void) __atomic_add_fetch(&es0->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.
	 */
	es0->nr_callbacks = 0;
	side_rcu_assign_pointer(es0->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
867b4725 MD	41	struct side_callback {
	42	union {
	43	void (call)(const struct side_event_description desc,
	44	const struct side_arg_vec *side_arg_vec,
	45	void *priv);
	46	void (call_variadic)(const struct side_event_description desc,
	47	const struct side_arg_vec *side_arg_vec,
	48	const struct side_arg_dynamic_struct *var_struct,
	49	void *priv);
	50	} u;
	51	void *priv;
	52	};
	53
67337c4a MD	54	static struct side_rcu_gp_state rcu_gp;
	55
	56	/*
	57	* Lazy initialization for early use within library constructors.
	58	*/
	59	static bool initialized;
	60	/*
	61	* Do not register/unregister any more events after destructor.
	62	*/
	63	static bool finalized;
	64
	65	/*
	66	* Recursive mutex to allow tracer callbacks to use the side API.
	67	*/
	68	static pthread_mutex_t side_lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
	69
	70	static DEFINE_SIDE_LIST_HEAD(side_events_list);
	71	static DEFINE_SIDE_LIST_HEAD(side_tracer_list);
	72
	73	/*
	74	* The empty callback has a NULL function callback pointer, which stops
	75	* iteration on the array of callbacks immediately.
	76	*/
867b4725	77	const char side_empty_callback[sizeof(struct side_callback)];
67337c4a	78
0d747f98	79	void side_call(const struct side_event_state event_state, const struct side_arg_vec side_arg_vec)
67337c4a MD	80	{
67337c4a MD	81	struct side_rcu_read_state rcu_read_state;
b2a84b9f	82	const struct side_event_state_0 *es0;
67337c4a MD	83	const struct side_callback *side_cb;
	84	uintptr_t enabled;
	85
	86	if (side_unlikely(finalized))
	87	return;
	88	if (side_unlikely(!initialized))
	89	side_init();
b2a84b9f MD	90	if (side_unlikely(event_state->version != 0))
b2a84b9f MD	91	abort();
49aea3ef	92	es0 = side_container_of(event_state, const struct side_event_state_0, parent);
7269a8a3	93	assert(!(es0->desc->flags & SIDE_EVENT_FLAG_VARIADIC));
b2a84b9f	94	enabled = __atomic_load_n(&es0->enabled, __ATOMIC_RELAXED);
67337c4a MD	95	if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
	96	// TODO: call kernel write.
	97	}
	98	side_rcu_read_begin(&rcu_gp, &rcu_read_state);
7269a8a3 MD	99	for (side_cb = side_rcu_dereference(es0->callbacks); side_cb->u.call != NULL; side_cb++)
7269a8a3 MD	100	side_cb->u.call(es0->desc, side_arg_vec, side_cb->priv);
67337c4a MD	101	side_rcu_read_end(&rcu_gp, &rcu_read_state);
	102	}
	103
0d747f98	104	void side_call_variadic(const struct side_event_state *event_state,
67337c4a MD	105	const struct side_arg_vec *side_arg_vec,
	106	const struct side_arg_dynamic_struct *var_struct)
	107	{
	108	struct side_rcu_read_state rcu_read_state;
b2a84b9f	109	const struct side_event_state_0 *es0;
67337c4a MD	110	const struct side_callback *side_cb;
	111	uintptr_t enabled;
	112
	113	if (side_unlikely(finalized))
	114	return;
	115	if (side_unlikely(!initialized))
	116	side_init();
b2a84b9f MD	117	if (side_unlikely(event_state->version != 0))
b2a84b9f MD	118	abort();
49aea3ef	119	es0 = side_container_of(event_state, const struct side_event_state_0, parent);
7269a8a3	120	assert(es0->desc->flags & SIDE_EVENT_FLAG_VARIADIC);
b2a84b9f	121	enabled = __atomic_load_n(&es0->enabled, __ATOMIC_RELAXED);
67337c4a MD	122	if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
	123	// TODO: call kernel write.
	124	}
	125	side_rcu_read_begin(&rcu_gp, &rcu_read_state);
7269a8a3 MD	126	for (side_cb = side_rcu_dereference(es0->callbacks); side_cb->u.call_variadic != NULL; side_cb++)
7269a8a3 MD	127	side_cb->u.call_variadic(es0->desc, side_arg_vec, var_struct, side_cb->priv);
67337c4a MD	128	side_rcu_read_end(&rcu_gp, &rcu_read_state);
	129	}
	130
	131	static
	132	const struct side_callback *side_tracer_callback_lookup(
	133	const struct side_event_description *desc,
	134	void call, void priv)
	135	{
0b9e59d6	136	struct side_event_state *event_state = side_ptr_get(desc->state);
b2a84b9f	137	const struct side_event_state_0 *es0;
67337c4a MD	138	const struct side_callback *cb;
67337c4a MD	139
b2a84b9f MD	140	if (side_unlikely(event_state->version != 0))
b2a84b9f MD	141	abort();
49aea3ef	142	es0 = side_container_of(event_state, const struct side_event_state_0, parent);
7269a8a3	143	for (cb = es0->callbacks; cb->u.call != NULL; cb++) {
67337c4a MD	144	if ((void *) cb->u.call == call && cb->priv == priv)
	145	return cb;
	146	}
	147	return NULL;
	148	}
	149
	150	static
	151	int _side_tracer_callback_register(struct side_event_description *desc,
	152	void call, void priv)
	153	{
0b9e59d6	154	struct side_event_state *event_state;
67337c4a	155	struct side_callback old_cb, new_cb;
b2a84b9f	156	struct side_event_state_0 *es0;
67337c4a MD	157	int ret = SIDE_ERROR_OK;
	158	uint32_t old_nr_cb;
	159
	160	if (!call)
	161	return SIDE_ERROR_INVAL;
	162	if (finalized)
	163	return SIDE_ERROR_EXITING;
	164	if (!initialized)
	165	side_init();
	166	pthread_mutex_lock(&side_lock);
0b9e59d6	167	event_state = side_ptr_get(desc->state);
b2a84b9f MD	168	if (side_unlikely(event_state->version != 0))
b2a84b9f MD	169	abort();
49aea3ef	170	es0 = side_container_of(event_state, struct side_event_state_0, parent);
3cac1780	171	old_nr_cb = es0->nr_callbacks;
67337c4a MD	172	if (old_nr_cb == UINT32_MAX) {
	173	ret = SIDE_ERROR_INVAL;
	174	goto unlock;
	175	}
	176	/* Reject duplicate (call, priv) tuples. */
	177	if (side_tracer_callback_lookup(desc, call, priv)) {
	178	ret = SIDE_ERROR_EXIST;
	179	goto unlock;
	180	}
7269a8a3	181	old_cb = (struct side_callback *) es0->callbacks;
67337c4a MD	182	/* old_nr_cb + 1 (new cb) + 1 (NULL) */
	183	new_cb = (struct side_callback *) calloc(old_nr_cb + 2, sizeof(struct side_callback));
	184	if (!new_cb) {
	185	ret = SIDE_ERROR_NOMEM;
	186	goto unlock;
	187	}
	188	memcpy(new_cb, old_cb, old_nr_cb);
	189	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	190	new_cb[old_nr_cb].u.call_variadic =
	191	(side_tracer_callback_variadic_func) call;
	192	else
	193	new_cb[old_nr_cb].u.call =
	194	(side_tracer_callback_func) call;
	195	new_cb[old_nr_cb].priv = priv;
f60d8121	196	/* High order bits are already zeroed. */
7269a8a3	197	side_rcu_assign_pointer(es0->callbacks, new_cb);
67337c4a MD	198	side_rcu_wait_grace_period(&rcu_gp);
	199	if (old_nr_cb)
	200	free(old_cb);
3cac1780	201	es0->nr_callbacks++;
67337c4a MD	202	/* Increment concurrently with kernel setting the top bits. */
67337c4a MD	203	if (!old_nr_cb)
b2a84b9f	204	(void) __atomic_add_fetch(&es0->enabled, 1, __ATOMIC_RELAXED);
67337c4a MD	205	unlock:
	206	pthread_mutex_unlock(&side_lock);
	207	return ret;
	208	}
	209
	210	int side_tracer_callback_register(struct side_event_description *desc,
	211	side_tracer_callback_func call,
	212	void *priv)
	213	{
	214	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	215	return SIDE_ERROR_INVAL;
	216	return _side_tracer_callback_register(desc, (void *) call, priv);
	217	}
	218
	219	int side_tracer_callback_variadic_register(struct side_event_description *desc,
	220	side_tracer_callback_variadic_func call_variadic,
	221	void *priv)
	222	{
	223	if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
	224	return SIDE_ERROR_INVAL;
	225	return _side_tracer_callback_register(desc, (void *) call_variadic, priv);
	226	}
	227
	228	static int _side_tracer_callback_unregister(struct side_event_description *desc,
	229	void call, void priv)
	230	{
0b9e59d6	231	struct side_event_state *event_state;
67337c4a MD	232	struct side_callback old_cb, new_cb;
67337c4a MD	233	const struct side_callback *cb_pos;
b2a84b9f	234	struct side_event_state_0 *es0;
67337c4a MD	235	uint32_t pos_idx;
	236	int ret = SIDE_ERROR_OK;
	237	uint32_t old_nr_cb;
	238
	239	if (!call)
	240	return SIDE_ERROR_INVAL;
	241	if (finalized)
	242	return SIDE_ERROR_EXITING;
	243	if (!initialized)
	244	side_init();
	245	pthread_mutex_lock(&side_lock);
0b9e59d6	246	event_state = side_ptr_get(desc->state);
b2a84b9f MD	247	if (side_unlikely(event_state->version != 0))
b2a84b9f MD	248	abort();
49aea3ef	249	es0 = side_container_of(event_state, struct side_event_state_0, parent);
67337c4a MD	250	cb_pos = side_tracer_callback_lookup(desc, call, priv);
	251	if (!cb_pos) {
	252	ret = SIDE_ERROR_NOENT;
	253	goto unlock;
	254	}
3cac1780	255	old_nr_cb = es0->nr_callbacks;
7269a8a3	256	old_cb = (struct side_callback *) es0->callbacks;
67337c4a MD	257	if (old_nr_cb == 1) {
	258	new_cb = (struct side_callback *) &side_empty_callback;
	259	} else {
7269a8a3	260	pos_idx = cb_pos - es0->callbacks;
67337c4a MD	261	/* Remove entry at pos_idx. */
	262	/* old_nr_cb - 1 (removed cb) + 1 (NULL) */
	263	new_cb = (struct side_callback *) calloc(old_nr_cb, sizeof(struct side_callback));
	264	if (!new_cb) {
	265	ret = SIDE_ERROR_NOMEM;
	266	goto unlock;
	267	}
	268	memcpy(new_cb, old_cb, pos_idx);
	269	memcpy(&new_cb[pos_idx], &old_cb[pos_idx + 1], old_nr_cb - pos_idx - 1);
	270	}
f60d8121	271	/* High order bits are already zeroed. */
7269a8a3	272	side_rcu_assign_pointer(es0->callbacks, new_cb);
67337c4a MD	273	side_rcu_wait_grace_period(&rcu_gp);
67337c4a MD	274	free(old_cb);
3cac1780	275	es0->nr_callbacks--;
67337c4a MD	276	/* Decrement concurrently with kernel setting the top bits. */
67337c4a MD	277	if (old_nr_cb == 1)
b2a84b9f	278	(void) __atomic_add_fetch(&es0->enabled, -1, __ATOMIC_RELAXED);
67337c4a MD	279	unlock:
	280	pthread_mutex_unlock(&side_lock);
	281	return ret;
	282	}
	283
	284	int side_tracer_callback_unregister(struct side_event_description *desc,
	285	side_tracer_callback_func call,
	286	void *priv)
	287	{
	288	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	289	return SIDE_ERROR_INVAL;
	290	return _side_tracer_callback_unregister(desc, (void *) call, priv);
	291	}
	292
	293	int side_tracer_callback_variadic_unregister(struct side_event_description *desc,
	294	side_tracer_callback_variadic_func call_variadic,
	295	void *priv)
	296	{
	297	if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
	298	return SIDE_ERROR_INVAL;
	299	return _side_tracer_callback_unregister(desc, (void *) call_variadic, priv);
	300	}
	301
	302	struct side_events_register_handle side_events_register(struct side_event_description *events, uint32_t nr_events)
	303	{
	304	struct side_events_register_handle *events_handle = NULL;
	305	struct side_tracer_handle *tracer_handle;
	306
	307	if (finalized)
	308	return NULL;
	309	if (!initialized)
	310	side_init();
	311	events_handle = (struct side_events_register_handle *)
	312	calloc(1, sizeof(struct side_events_register_handle));
	313	if (!events_handle)
	314	return NULL;
	315	events_handle->events = events;
	316	events_handle->nr_events = nr_events;
	317
	318	pthread_mutex_lock(&side_lock);
	319	side_list_insert_node_tail(&side_events_list, &events_handle->node);
	320	side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
	321	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
	322	events, nr_events, tracer_handle->priv);
	323	}
	324	pthread_mutex_unlock(&side_lock);
	325	//TODO: call event batch register ioctl
	326	return events_handle;
	327	}
	328
	329	static
	330	void side_event_remove_callbacks(struct side_event_description *desc)
	331	{
0b9e59d6	332	struct side_event_state *event_state = side_ptr_get(desc->state);
b2a84b9f	333	struct side_event_state_0 *es0;
67337c4a	334	struct side_callback *old_cb;
3cac1780	335	uint32_t nr_cb;
67337c4a	336
b2a84b9f MD	337	if (side_unlikely(event_state->version != 0))
b2a84b9f MD	338	abort();
49aea3ef	339	es0 = side_container_of(event_state, struct side_event_state_0, parent);
3cac1780 MD	340	nr_cb = es0->nr_callbacks;
	341	if (!nr_cb)
	342	return;
7269a8a3	343	old_cb = (struct side_callback *) es0->callbacks;
b2a84b9f	344	(void) __atomic_add_fetch(&es0->enabled, -1, __ATOMIC_RELAXED);
67337c4a MD	345	/*
	346	* Setting the state back to 0 cb and empty callbacks out of
	347	* caution. This should not matter because instrumentation is
	348	* unreachable.
	349	*/
3cac1780	350	es0->nr_callbacks = 0;
7269a8a3	351	side_rcu_assign_pointer(es0->callbacks, &side_empty_callback);
67337c4a MD	352	/*
	353	* No need to wait for grace period because instrumentation is
	354	* unreachable.
	355	*/
	356	free(old_cb);
	357	}
	358
	359	/*
	360	* Unregister event handle. At this point, all side events in that
	361	* handle should be unreachable.
	362	*/
	363	void side_events_unregister(struct side_events_register_handle *events_handle)
	364	{
	365	struct side_tracer_handle *tracer_handle;
	366	uint32_t i;
	367
	368	if (!events_handle)
	369	return;
	370	if (finalized)
	371	return;
	372	if (!initialized)
	373	side_init();
	374	pthread_mutex_lock(&side_lock);
	375	side_list_remove_node(&events_handle->node);
	376	side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
	377	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
	378	events_handle->events, events_handle->nr_events,
	379	tracer_handle->priv);
	380	}
	381	for (i = 0; i < events_handle->nr_events; i++) {
	382	struct side_event_description *event = events_handle->events[i];
	383
	384	/* Skip NULL pointers */
	385	if (!event)
	386	continue;
	387	side_event_remove_callbacks(event);
	388	}
	389	pthread_mutex_unlock(&side_lock);
	390	//TODO: call event batch unregister ioctl
	391	free(events_handle);
	392	}
	393
	394	struct side_tracer_handle *side_tracer_event_notification_register(
	395	void (*cb)(enum side_tracer_notification notif,
	396	struct side_event_description *events, uint32_t nr_events, void priv),
	397	void *priv)
	398	{
	399	struct side_tracer_handle *tracer_handle;
	400	struct side_events_register_handle *events_handle;
	401
	402	if (finalized)
	403	return NULL;
	404	if (!initialized)
	405	side_init();
	406	tracer_handle = (struct side_tracer_handle *)
	407	calloc(1, sizeof(struct side_tracer_handle));
	408	if (!tracer_handle)
	409	return NULL;
	410	pthread_mutex_lock(&side_lock);
	411	tracer_handle->cb = cb;
	412	tracer_handle->priv = priv;
	413	side_list_insert_node_tail(&side_tracer_list, &tracer_handle->node);
	414	side_list_for_each_entry(events_handle, &side_events_list, node) {
	415	cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
416	events_handle->events, events_handle->nr_events, priv);
417	}
418	pthread_mutex_unlock(&side_lock);
419	return tracer_handle;
420	}
421
422	void side_tracer_event_notification_unregister(struct side_tracer_handle *tracer_handle)
423	{
424	struct side_events_register_handle *events_handle;
425
426	if (finalized)
427	return;
428	if (!initialized)
429	side_init();
430	pthread_mutex_lock(&side_lock);
431	side_list_for_each_entry(events_handle, &side_events_list, node) {
432	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
433	events_handle->events, events_handle->nr_events,
434	tracer_handle->priv);
435	}
436	side_list_remove_node(&tracer_handle->node);
437	pthread_mutex_unlock(&side_lock);
be787080	438	free(tracer_handle);
67337c4a MD	439	}
	440
	441	void side_init(void)
	442	{
	443	if (initialized)
	444	return;
	445	side_rcu_gp_init(&rcu_gp);
	446	initialized = true;
	447	}
	448
	449	/*
	450	* side_exit() is executed from a library destructor. It can be called
	451	* explicitly at application exit as well. Concurrent side API use is
	452	* not expected at that point.
	453	*/
	454	void side_exit(void)
	455	{
	456	struct side_events_register_handle handle, tmp;
	457
	458	if (finalized)
	459	return;
	460	side_list_for_each_entry_safe(handle, tmp, &side_events_list, node)
	461	side_events_unregister(handle);
	462	side_rcu_gp_exit(&rcu_gp);
	463	finalized = true;
	464	}