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// SPDX-License-Identifier: GPL-2.0-only
/*
* VMware VMCI Driver
*
* Copyright (C) 2012 VMware, Inc. All rights reserved.
*/
#include <linux/vmw_vmci_defs.h>
#include <linux/vmw_vmci_api.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/nospec.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/rculist.h>
#include "vmci_driver.h"
#include "vmci_event.h"
#define EVENT_MAGIC 0xEABE0000
#define VMCI_EVENT_MAX_ATTEMPTS 10
struct vmci_subscription {
u32 id;
u32 event;
vmci_event_cb callback;
void *callback_data;
struct list_head node; /* on one of subscriber lists */
};
static struct list_head subscriber_array[VMCI_EVENT_MAX];
static DEFINE_MUTEX(subscriber_mutex);
int __init vmci_event_init(void)
{
int i;
for (i = 0; i < VMCI_EVENT_MAX; i++)
INIT_LIST_HEAD(&subscriber_array[i]);
return VMCI_SUCCESS;
}
void vmci_event_exit(void)
{
int e;
/* We free all memory at exit. */
for (e = 0; e < VMCI_EVENT_MAX; e++) {
struct vmci_subscription *cur, *p2;
list_for_each_entry_safe(cur, p2, &subscriber_array[e], node) {
/*
* We should never get here because all events
* should have been unregistered before we try
* to unload the driver module.
*/
pr_warn("Unexpected free events occurring\n");
list_del(&cur->node);
kfree(cur);
}
}
}
/*
* Find entry. Assumes subscriber_mutex is held.
*/
static struct vmci_subscription *event_find(u32 sub_id)
{
int e;
for (e = 0; e < VMCI_EVENT_MAX; e++) {
struct vmci_subscription *cur;
list_for_each_entry(cur, &subscriber_array[e], node) {
if (cur->id == sub_id)
return cur;
}
}
return NULL;
}
/*
* Actually delivers the events to the subscribers.
* The callback function for each subscriber is invoked.
*/
static void event_deliver(struct vmci_event_msg *event_msg)
{
struct vmci_subscription *cur;
struct list_head *subscriber_list;
u32 sanitized_event, max_vmci_event;
rcu_read_lock();
max_vmci_event = ARRAY_SIZE(subscriber_array);
sanitized_event = array_index_nospec(event_msg->event_data.event, max_vmci_event);
subscriber_list = &subscriber_array[sanitized_event];
list_for_each_entry_rcu(cur, subscriber_list, node) {
cur->callback(cur->id, &event_msg->event_data,
cur->callback_data);
}
rcu_read_unlock();
}
/*
* Dispatcher for the VMCI_EVENT_RECEIVE datagrams. Calls all
* subscribers for given event.
*/
int vmci_event_dispatch(struct vmci_datagram *msg)
{
struct vmci_event_msg *event_msg = (struct vmci_event_msg *)msg;
if (msg->payload_size < sizeof(u32) ||
msg->payload_size > sizeof(struct vmci_event_data_max))
return VMCI_ERROR_INVALID_ARGS;
if (!VMCI_EVENT_VALID(event_msg->event_data.event))
return VMCI_ERROR_EVENT_UNKNOWN;
event_deliver(event_msg);
return VMCI_SUCCESS;
}
/*
* vmci_event_subscribe() - Subscribe to a given event.
* @event: The event to subscribe to.
* @callback: The callback to invoke upon the event.
* @callback_data: Data to pass to the callback.
* @subscription_id: ID used to track subscription. Used with
* vmci_event_unsubscribe()
*
* Subscribes to the provided event. The callback specified will be
* fired from RCU critical section and therefore must not sleep.
*/
int vmci_event_subscribe(u32 event,
vmci_event_cb callback,
void *callback_data,
u32 *new_subscription_id)
{
struct vmci_subscription *sub;
int attempts;
int retval;
bool have_new_id = false;
if (!new_subscription_id) {
pr_devel("%s: Invalid subscription (NULL)\n", __func__);
return VMCI_ERROR_INVALID_ARGS;
}
if (!VMCI_EVENT_VALID(event) || !callback) {
pr_devel("%s: Failed to subscribe to event (type=%d) (callback=%p) (data=%p)\n",
__func__, event, callback, callback_data);
return VMCI_ERROR_INVALID_ARGS;
}
sub = kzalloc(sizeof(*sub), GFP_KERNEL);
if (!sub)
return VMCI_ERROR_NO_MEM;
sub->id = VMCI_EVENT_MAX;
sub->event = event;
sub->callback = callback;
sub->callback_data = callback_data;
INIT_LIST_HEAD(&sub->node);
mutex_lock(&subscriber_mutex);
/* Creation of a new event is always allowed. */
for (attempts = 0; attempts < VMCI_EVENT_MAX_ATTEMPTS; attempts++) {
static u32 subscription_id;
/*
* We try to get an id a couple of time before
* claiming we are out of resources.
*/
/* Test for duplicate id. */
if (!event_find(++subscription_id)) {
sub->id = subscription_id;
have_new_id = true;
break;
}
}
if (have_new_id) {
list_add_rcu(&sub->node, &subscriber_array[event]);
retval = VMCI_SUCCESS;
} else {
retval = VMCI_ERROR_NO_RESOURCES;
}
mutex_unlock(&subscriber_mutex);
*new_subscription_id = sub->id;
return retval;
}
EXPORT_SYMBOL_GPL(vmci_event_subscribe);
/*
* vmci_event_unsubscribe() - unsubscribe from an event.
* @sub_id: A subscription ID as provided by vmci_event_subscribe()
*
* Unsubscribe from given event. Removes it from list and frees it.
* Will return callback_data if requested by caller.
*/
int vmci_event_unsubscribe(u32 sub_id)
{
struct vmci_subscription *s;
mutex_lock(&subscriber_mutex);
s = event_find(sub_id);
if (s)
list_del_rcu(&s->node);
mutex_unlock(&subscriber_mutex);
if (!s)
return VMCI_ERROR_NOT_FOUND;
kvfree_rcu_mightsleep(s);
return VMCI_SUCCESS;
}
EXPORT_SYMBOL_GPL(vmci_event_unsubscribe);
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