[libside.git] / src / side.c

// SPDX-License-Identifier: MIT
/*
 * Copyright 2022 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 */

#include <side/trace.h>
#include <string.h>

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

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

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

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

struct side_events_register_handle {
	struct side_list_node node;
	struct side_event_description **events;
	uint32_t nr_events;
};

struct side_tracer_handle {
	struct side_list_node node;
	void (*cb)(enum side_tracer_notification notif,
		struct side_event_description **events, uint32_t nr_events, void *priv);
	void *priv;
};

static struct side_rcu_gp_state rcu_gp;

/*
 * Lazy initialization for early use within library constructors.
 */
static bool initialized;
/*
 * Do not register/unregister any more events after destructor.
 */
static bool finalized;

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

static DEFINE_SIDE_LIST_HEAD(side_events_list);
static DEFINE_SIDE_LIST_HEAD(side_tracer_list);

/*
 * The empty callback has a NULL function callback pointer, which stops
 * iteration on the array of callbacks immediately.
 */
const struct side_callback side_empty_callback = { };

void side_call(const struct side_event_description *desc, const struct side_arg_vec *side_arg_vec)
{
	struct side_rcu_read_state rcu_read_state;
	const struct side_callback *side_cb;
	uintptr_t enabled;

	if (side_unlikely(finalized))
		return;
	if (side_unlikely(!initialized))
		side_init();
	if (side_unlikely(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.
	}
	side_rcu_read_begin(&rcu_gp, &rcu_read_state);
	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_read_state);
}

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)
{
	struct side_rcu_read_state rcu_read_state;
	const struct side_callback *side_cb;
	uintptr_t enabled;

	if (side_unlikely(finalized))
		return;
	if (side_unlikely(!initialized))
		side_init();
	if (side_unlikely(!(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.
	}
	side_rcu_read_begin(&rcu_gp, &rcu_read_state);
	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_read_state);
}

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 ((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_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 =
			(side_tracer_callback_variadic_func) call;
	else
		new_cb[old_nr_cb].u.call =
			(side_tracer_callback_func) call;
	new_cb[old_nr_cb].priv = priv;
	side_rcu_assign_pointer(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,
		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_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,
		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)
{
	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 = (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);
}

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
85b765b8	9	#include "rcu.h"
b59abc69	10	#include "list.h"
6841ae81	11
054b7b5c	12	/* Top 8 bits reserved for kernel tracer use. */
f61301bb MD	13	#if SIDE_BITS_PER_LONG == 64
	14	# define SIDE_EVENT_ENABLED_KERNEL_MASK 0xFF00000000000000ULL
	15	# define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK 0x8000000000000000ULL
	16
	17	/* Allow 2^56 tracer references on an event. */
	18	# define SIDE_EVENT_ENABLED_USER_MASK 0x00FFFFFFFFFFFFFFULL
	19	#else
	20	# define SIDE_EVENT_ENABLED_KERNEL_MASK 0xFF000000UL
	21	# define SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK 0x80000000UL
29b3374e	22
45172226	23	/* Allow 2^24 tracer references on an event. */
f61301bb MD	24	# define SIDE_EVENT_ENABLED_USER_MASK 0x00FFFFFFUL
f61301bb MD	25	#endif
054b7b5c	26
6e46f5e6 MD	27	struct side_events_register_handle {
	28	struct side_list_node node;
	29	struct side_event_description **events;
	30	uint32_t nr_events;
	31	};
	32
a13c9d2e MD	33	struct side_tracer_handle {
	34	struct side_list_node node;
	35	void (*cb)(enum side_tracer_notification notif,
	36	struct side_event_description *events, uint32_t nr_events, void priv);
	37	void *priv;
	38	};
	39
a3f36db7	40	static struct side_rcu_gp_state rcu_gp;
075ceef7 MD	41
	42	/*
	43	* Lazy initialization for early use within library constructors.
	44	*/
	45	static bool initialized;
6e46f5e6 MD	46	/*
	47	* Do not register/unregister any more events after destructor.
	48	*/
	49	static bool finalized;
075ceef7	50
1e070341 MD	51	/*
	52	* Recursive mutex to allow tracer callbacks to use the side API.
	53	*/
	54	static pthread_mutex_t side_lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
a3f36db7	55
a13c9d2e MD	56	static DEFINE_SIDE_LIST_HEAD(side_events_list);
a13c9d2e MD	57	static DEFINE_SIDE_LIST_HEAD(side_tracer_list);
b59abc69	58
a3f36db7 MD	59	/*
	60	* The empty callback has a NULL function callback pointer, which stops
	61	* iteration on the array of callbacks immediately.
	62	*/
8bd36d3b	63	const struct side_callback side_empty_callback = { };
054b7b5c	64
9a6ca773	65	void side_call(const struct side_event_description desc, const struct side_arg_vec side_arg_vec)
6841ae81	66	{
cd50bc06	67	struct side_rcu_read_state rcu_read_state;
054b7b5c	68	const struct side_callback *side_cb;
beea6e2e	69	uintptr_t enabled;
054b7b5c	70
6e46f5e6 MD	71	if (side_unlikely(finalized))
6e46f5e6 MD	72	return;
075ceef7 MD	73	if (side_unlikely(!initialized))
075ceef7 MD	74	side_init();
6841ae81 MD	75	if (side_unlikely(desc->flags & SIDE_EVENT_FLAG_VARIADIC)) {
	76	printf("ERROR: unexpected variadic event description\n");
	77	abort();
	78	}
3b4f86f6 MD	79	enabled = __atomic_load_n(desc->enabled, __ATOMIC_RELAXED);
3b4f86f6 MD	80	if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
dda82f46	81	// TODO: call kernel write.
6841ae81	82	}
cd50bc06	83	side_rcu_read_begin(&rcu_gp, &rcu_read_state);
054b7b5c	84	for (side_cb = side_rcu_dereference(desc->callbacks); side_cb->u.call != NULL; side_cb++)
9a6ca773	85	side_cb->u.call(desc, side_arg_vec, side_cb->priv);
cd50bc06	86	side_rcu_read_end(&rcu_gp, &rcu_read_state);
6841ae81 MD	87	}
	88
	89	void side_call_variadic(const struct side_event_description *desc,
9a6ca773	90	const struct side_arg_vec *side_arg_vec,
0c7abe2b	91	const struct side_arg_dynamic_struct *var_struct)
6841ae81	92	{
cd50bc06	93	struct side_rcu_read_state rcu_read_state;
054b7b5c	94	const struct side_callback *side_cb;
beea6e2e	95	uintptr_t enabled;
054b7b5c	96
6e46f5e6 MD	97	if (side_unlikely(finalized))
6e46f5e6 MD	98	return;
075ceef7 MD	99	if (side_unlikely(!initialized))
075ceef7 MD	100	side_init();
3b4f86f6 MD	101	if (side_unlikely(!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))) {
	102	printf("ERROR: unexpected non-variadic event description\n");
	103	abort();
	104	}
	105	enabled = __atomic_load_n(desc->enabled, __ATOMIC_RELAXED);
	106	if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
dda82f46	107	// TODO: call kernel write.
6841ae81	108	}
cd50bc06	109	side_rcu_read_begin(&rcu_gp, &rcu_read_state);
054b7b5c	110	for (side_cb = side_rcu_dereference(desc->callbacks); side_cb->u.call_variadic != NULL; side_cb++)
9a6ca773	111	side_cb->u.call_variadic(desc, side_arg_vec, var_struct, side_cb->priv);
cd50bc06	112	side_rcu_read_end(&rcu_gp, &rcu_read_state);
6841ae81	113	}
075ceef7	114
a3f36db7 MD	115	static
	116	const struct side_callback *side_tracer_callback_lookup(
	117	const struct side_event_description *desc,
07e94ffc	118	void call, void priv)
a3f36db7 MD	119	{
	120	const struct side_callback *cb;
	121
	122	for (cb = desc->callbacks; cb->u.call != NULL; cb++) {
07e94ffc	123	if ((void *) cb->u.call == call && cb->priv == priv)
a3f36db7 MD	124	return cb;
	125	}
	126	return NULL;
	127	}
	128
	129	static
	130	int _side_tracer_callback_register(struct side_event_description *desc,
8bd36d3b	131	void call, void priv)
a3f36db7 MD	132	{
	133	struct side_callback old_cb, new_cb;
	134	int ret = SIDE_ERROR_OK;
	135	uint32_t old_nr_cb;
	136
	137	if (!call)
	138	return SIDE_ERROR_INVAL;
6e46f5e6 MD	139	if (finalized)
6e46f5e6 MD	140	return SIDE_ERROR_EXITING;
a13c9d2e MD	141	if (!initialized)
a13c9d2e MD	142	side_init();
a3f36db7	143	pthread_mutex_lock(&side_lock);
45172226 MD	144	old_nr_cb = desc->nr_callbacks;
45172226 MD	145	if (old_nr_cb == UINT32_MAX) {
a3f36db7 MD	146	ret = SIDE_ERROR_INVAL;
	147	goto unlock;
	148	}
	149	/* Reject duplicate (call, priv) tuples. */
	150	if (side_tracer_callback_lookup(desc, call, priv)) {
	151	ret = SIDE_ERROR_EXIST;
	152	goto unlock;
	153	}
	154	old_cb = (struct side_callback *) desc->callbacks;
	155	/* old_nr_cb + 1 (new cb) + 1 (NULL) */
	156	new_cb = (struct side_callback *) calloc(old_nr_cb + 2, sizeof(struct side_callback));
	157	if (!new_cb) {
	158	ret = SIDE_ERROR_NOMEM;
	159	goto unlock;
	160	}
	161	memcpy(new_cb, old_cb, old_nr_cb);
	162	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
07e94ffc MD	163	new_cb[old_nr_cb].u.call_variadic =
07e94ffc MD	164	(side_tracer_callback_variadic_func) call;
a3f36db7	165	else
07e94ffc MD	166	new_cb[old_nr_cb].u.call =
07e94ffc MD	167	(side_tracer_callback_func) call;
a3f36db7 MD	168	new_cb[old_nr_cb].priv = priv;
	169	side_rcu_assign_pointer(desc->callbacks, new_cb);
	170	side_rcu_wait_grace_period(&rcu_gp);
	171	if (old_nr_cb)
	172	free(old_cb);
45172226	173	desc->nr_callbacks++;
a3f36db7	174	/* Increment concurrently with kernel setting the top bits. */
45172226 MD	175	if (!old_nr_cb)
45172226 MD	176	(void) __atomic_add_fetch(desc->enabled, 1, __ATOMIC_RELAXED);
a3f36db7 MD	177	unlock:
	178	pthread_mutex_unlock(&side_lock);
	179	return ret;
	180	}
	181
	182	int side_tracer_callback_register(struct side_event_description *desc,
8bd36d3b	183	side_tracer_callback_func call,
a3f36db7 MD	184	void *priv)
	185	{
	186	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	187	return SIDE_ERROR_INVAL;
07e94ffc	188	return _side_tracer_callback_register(desc, (void *) call, priv);
a3f36db7 MD	189	}
	190
	191	int side_tracer_callback_variadic_register(struct side_event_description *desc,
8bd36d3b	192	side_tracer_callback_variadic_func call_variadic,
a3f36db7 MD	193	void *priv)
	194	{
	195	if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
	196	return SIDE_ERROR_INVAL;
07e94ffc	197	return _side_tracer_callback_register(desc, (void *) call_variadic, priv);
a3f36db7 MD	198	}
a3f36db7 MD	199
9365e936	200	static int _side_tracer_callback_unregister(struct side_event_description *desc,
8bd36d3b	201	void call, void priv)
a3f36db7 MD	202	{
	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;
6e46f5e6 MD	211	if (finalized)
6e46f5e6 MD	212	return SIDE_ERROR_EXITING;
a13c9d2e MD	213	if (!initialized)
a13c9d2e MD	214	side_init();
a3f36db7	215	pthread_mutex_lock(&side_lock);
a3f36db7 MD	216	cb_pos = side_tracer_callback_lookup(desc, call, priv);
	217	if (!cb_pos) {
	218	ret = SIDE_ERROR_NOENT;
	219	goto unlock;
	220	}
45172226	221	old_nr_cb = desc->nr_callbacks;
9a83b759	222	old_cb = (struct side_callback *) desc->callbacks;
a3f36db7 MD	223	if (old_nr_cb == 1) {
	224	new_cb = (struct side_callback *) &side_empty_callback;
	225	} else {
	226	pos_idx = cb_pos - desc->callbacks;
	227	/* Remove entry at pos_idx. */
	228	/* old_nr_cb - 1 (removed cb) + 1 (NULL) */
	229	new_cb = (struct side_callback *) calloc(old_nr_cb, sizeof(struct side_callback));
	230	if (!new_cb) {
	231	ret = SIDE_ERROR_NOMEM;
	232	goto unlock;
	233	}
	234	memcpy(new_cb, old_cb, pos_idx);
	235	memcpy(&new_cb[pos_idx], &old_cb[pos_idx + 1], old_nr_cb - pos_idx - 1);
	236	}
	237	side_rcu_assign_pointer(desc->callbacks, new_cb);
	238	side_rcu_wait_grace_period(&rcu_gp);
	239	free(old_cb);
45172226	240	desc->nr_callbacks--;
a3f36db7	241	/* Decrement concurrently with kernel setting the top bits. */
45172226 MD	242	if (old_nr_cb == 1)
45172226 MD	243	(void) __atomic_add_fetch(desc->enabled, -1, __ATOMIC_RELAXED);
a3f36db7 MD	244	unlock:
	245	pthread_mutex_unlock(&side_lock);
	246	return ret;
	247	}
	248
	249	int side_tracer_callback_unregister(struct side_event_description *desc,
8bd36d3b	250	side_tracer_callback_func call,
a3f36db7 MD	251	void *priv)
	252	{
	253	if (desc->flags & SIDE_EVENT_FLAG_VARIADIC)
	254	return SIDE_ERROR_INVAL;
07e94ffc	255	return _side_tracer_callback_unregister(desc, (void *) call, priv);
a3f36db7 MD	256	}
	257
	258	int side_tracer_callback_variadic_unregister(struct side_event_description *desc,
8bd36d3b	259	side_tracer_callback_variadic_func call_variadic,
a3f36db7 MD	260	void *priv)
	261	{
	262	if (!(desc->flags & SIDE_EVENT_FLAG_VARIADIC))
	263	return SIDE_ERROR_INVAL;
07e94ffc	264	return _side_tracer_callback_unregister(desc, (void *) call_variadic, priv);
a3f36db7 MD	265	}
a3f36db7 MD	266
6e46f5e6 MD	267	struct side_events_register_handle side_events_register(struct side_event_description *events, uint32_t nr_events)
6e46f5e6 MD	268	{
a13c9d2e MD	269	struct side_events_register_handle *events_handle = NULL;
a13c9d2e MD	270	struct side_tracer_handle *tracer_handle;
6e46f5e6 MD	271
	272	if (finalized)
	273	return NULL;
a13c9d2e MD	274	if (!initialized)
a13c9d2e MD	275	side_init();
07e94ffc MD	276	events_handle = (struct side_events_register_handle *)
07e94ffc MD	277	calloc(1, sizeof(struct side_events_register_handle));
a13c9d2e	278	if (!events_handle)
6e46f5e6	279	return NULL;
a13c9d2e MD	280	events_handle->events = events;
	281	events_handle->nr_events = nr_events;
	282
6e46f5e6	283	pthread_mutex_lock(&side_lock);
a13c9d2e MD	284	side_list_insert_node_tail(&side_events_list, &events_handle->node);
	285	side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
	286	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
	287	events, nr_events, tracer_handle->priv);
	288	}
6e46f5e6 MD	289	pthread_mutex_unlock(&side_lock);
6e46f5e6 MD	290	//TODO: call event batch register ioctl
a13c9d2e	291	return events_handle;
6e46f5e6 MD	292	}
6e46f5e6 MD	293
a3f36db7	294	static
6e46f5e6 MD	295	void side_event_remove_callbacks(struct side_event_description *desc)
6e46f5e6 MD	296	{
ea0d2bea	297	uint32_t nr_cb = desc->nr_callbacks;
6e46f5e6 MD	298	struct side_callback *old_cb;
	299
	300	if (!nr_cb)
	301	return;
	302	old_cb = (struct side_callback *) desc->callbacks;
ea0d2bea	303	(void) __atomic_add_fetch(desc->enabled, -1, __ATOMIC_RELAXED);
6e46f5e6 MD	304	/*
	305	* Setting the state back to 0 cb and empty callbacks out of
	306	* caution. This should not matter because instrumentation is
	307	* unreachable.
	308	*/
45172226	309	desc->nr_callbacks = 0;
6e46f5e6 MD	310	side_rcu_assign_pointer(desc->callbacks, &side_empty_callback);
	311	/*
	312	* No need to wait for grace period because instrumentation is
	313	* unreachable.
	314	*/
	315	free(old_cb);
	316	}
	317
	318	/*
	319	* Unregister event handle. At this point, all side events in that
	320	* handle should be unreachable.
	321	*/
a13c9d2e	322	void side_events_unregister(struct side_events_register_handle *events_handle)
6e46f5e6	323	{
a13c9d2e	324	struct side_tracer_handle *tracer_handle;
6e46f5e6 MD	325	uint32_t i;
6e46f5e6 MD	326
314c22c3 MD	327	if (!events_handle)
314c22c3 MD	328	return;
6e46f5e6 MD	329	if (finalized)
6e46f5e6 MD	330	return;
a13c9d2e MD	331	if (!initialized)
a13c9d2e MD	332	side_init();
6e46f5e6	333	pthread_mutex_lock(&side_lock);
a13c9d2e MD	334	side_list_remove_node(&events_handle->node);
	335	side_list_for_each_entry(tracer_handle, &side_tracer_list, node) {
	336	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
	337	events_handle->events, events_handle->nr_events,
	338	tracer_handle->priv);
	339	}
	340	for (i = 0; i < events_handle->nr_events; i++) {
	341	struct side_event_description *event = events_handle->events[i];
6e46f5e6 MD	342
	343	/* Skip NULL pointers */
	344	if (!event)
	345	continue;
	346	side_event_remove_callbacks(event);
	347	}
	348	pthread_mutex_unlock(&side_lock);
	349	//TODO: call event batch unregister ioctl
a13c9d2e MD	350	free(events_handle);
	351	}
	352
	353	struct side_tracer_handle *side_tracer_event_notification_register(
	354	void (*cb)(enum side_tracer_notification notif,
	355	struct side_event_description *events, uint32_t nr_events, void priv),
	356	void *priv)
	357	{
	358	struct side_tracer_handle *tracer_handle;
	359	struct side_events_register_handle *events_handle;
	360
	361	if (finalized)
	362	return NULL;
	363	if (!initialized)
	364	side_init();
07e94ffc MD	365	tracer_handle = (struct side_tracer_handle *)
07e94ffc MD	366	calloc(1, sizeof(struct side_tracer_handle));
a13c9d2e MD	367	if (!tracer_handle)
	368	return NULL;
	369	pthread_mutex_lock(&side_lock);
	370	tracer_handle->cb = cb;
	371	tracer_handle->priv = priv;
	372	side_list_insert_node_tail(&side_tracer_list, &tracer_handle->node);
	373	side_list_for_each_entry(events_handle, &side_events_list, node) {
	374	cb(SIDE_TRACER_NOTIFICATION_INSERT_EVENTS,
	375	events_handle->events, events_handle->nr_events, priv);
	376	}
	377	pthread_mutex_unlock(&side_lock);
	378	return tracer_handle;
	379	}
	380
	381	void side_tracer_event_notification_unregister(struct side_tracer_handle *tracer_handle)
	382	{
	383	struct side_events_register_handle *events_handle;
	384
	385	if (finalized)
	386	return;
	387	if (!initialized)
	388	side_init();
	389	pthread_mutex_lock(&side_lock);
	390	side_list_for_each_entry(events_handle, &side_events_list, node) {
	391	tracer_handle->cb(SIDE_TRACER_NOTIFICATION_REMOVE_EVENTS,
	392	events_handle->events, events_handle->nr_events,
	393	tracer_handle->priv);
	394	}
	395	side_list_remove_node(&tracer_handle->node);
	396	pthread_mutex_unlock(&side_lock);
6e46f5e6 MD	397	}
6e46f5e6 MD	398
075ceef7 MD	399	void side_init(void)
	400	{
	401	if (initialized)
	402	return;
054b7b5c	403	side_rcu_gp_init(&rcu_gp);
075ceef7 MD	404	initialized = true;
075ceef7 MD	405	}
6e46f5e6	406
aa584c16 MD	407	/*
	408	* side_exit() is executed from a library destructor. It can be called
	409	* explicitly at application exit as well. Concurrent side API use is
	410	* not expected at that point.
	411	*/
6e46f5e6 MD	412	void side_exit(void)
	413	{
	414	struct side_events_register_handle handle, tmp;
	415
	416	if (finalized)
	417	return;
a13c9d2e	418	side_list_for_each_entry_safe(handle, tmp, &side_events_list, node)
6e46f5e6	419	side_events_unregister(handle);
64d29894	420	side_rcu_gp_exit(&rcu_gp);
6e46f5e6 MD	421	finalized = true;
6e46f5e6 MD	422	}