1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * VMware VMCI Driver
4 *
5 * Copyright (C) 2012 VMware, Inc. All rights reserved.
6 */
7
8 #include <linux/vmw_vmci_defs.h>
9 #include <linux/vmw_vmci_api.h>
10 #include <linux/list.h>
11 #include <linux/module.h>
12 #include <linux/sched.h>
13 #include <linux/slab.h>
14 #include <linux/rculist.h>
15
16 #include "vmci_driver.h"
17 #include "vmci_event.h"
18
19 #define EVENT_MAGIC 0xEABE0000
20 #define VMCI_EVENT_MAX_ATTEMPTS 10
21
22 struct vmci_subscription {
23 u32 id;
24 u32 event;
25 vmci_event_cb callback;
26 void *callback_data;
27 struct list_head node; /* on one of subscriber lists */
28 };
29
30 static struct list_head subscriber_array[VMCI_EVENT_MAX];
31 static DEFINE_MUTEX(subscriber_mutex);
32
vmci_event_init(void)33 int __init vmci_event_init(void)
34 {
35 int i;
36
37 for (i = 0; i < VMCI_EVENT_MAX; i++)
38 INIT_LIST_HEAD(&subscriber_array[i]);
39
40 return VMCI_SUCCESS;
41 }
42
vmci_event_exit(void)43 void vmci_event_exit(void)
44 {
45 int e;
46
47 /* We free all memory at exit. */
48 for (e = 0; e < VMCI_EVENT_MAX; e++) {
49 struct vmci_subscription *cur, *p2;
50 list_for_each_entry_safe(cur, p2, &subscriber_array[e], node) {
51
52 /*
53 * We should never get here because all events
54 * should have been unregistered before we try
55 * to unload the driver module.
56 */
57 pr_warn("Unexpected free events occurring\n");
58 list_del(&cur->node);
59 kfree(cur);
60 }
61 }
62 }
63
64 /*
65 * Find entry. Assumes subscriber_mutex is held.
66 */
event_find(u32 sub_id)67 static struct vmci_subscription *event_find(u32 sub_id)
68 {
69 int e;
70
71 for (e = 0; e < VMCI_EVENT_MAX; e++) {
72 struct vmci_subscription *cur;
73 list_for_each_entry(cur, &subscriber_array[e], node) {
74 if (cur->id == sub_id)
75 return cur;
76 }
77 }
78 return NULL;
79 }
80
81 /*
82 * Actually delivers the events to the subscribers.
83 * The callback function for each subscriber is invoked.
84 */
event_deliver(struct vmci_event_msg * event_msg)85 static void event_deliver(struct vmci_event_msg *event_msg)
86 {
87 struct vmci_subscription *cur;
88 struct list_head *subscriber_list;
89
90 rcu_read_lock();
91 subscriber_list = &subscriber_array[event_msg->event_data.event];
92 list_for_each_entry_rcu(cur, subscriber_list, node) {
93 cur->callback(cur->id, &event_msg->event_data,
94 cur->callback_data);
95 }
96 rcu_read_unlock();
97 }
98
99 /*
100 * Dispatcher for the VMCI_EVENT_RECEIVE datagrams. Calls all
101 * subscribers for given event.
102 */
vmci_event_dispatch(struct vmci_datagram * msg)103 int vmci_event_dispatch(struct vmci_datagram *msg)
104 {
105 struct vmci_event_msg *event_msg = (struct vmci_event_msg *)msg;
106
107 if (msg->payload_size < sizeof(u32) ||
108 msg->payload_size > sizeof(struct vmci_event_data_max))
109 return VMCI_ERROR_INVALID_ARGS;
110
111 if (!VMCI_EVENT_VALID(event_msg->event_data.event))
112 return VMCI_ERROR_EVENT_UNKNOWN;
113
114 event_deliver(event_msg);
115 return VMCI_SUCCESS;
116 }
117
118 /*
119 * vmci_event_subscribe() - Subscribe to a given event.
120 * @event: The event to subscribe to.
121 * @callback: The callback to invoke upon the event.
122 * @callback_data: Data to pass to the callback.
123 * @subscription_id: ID used to track subscription. Used with
124 * vmci_event_unsubscribe()
125 *
126 * Subscribes to the provided event. The callback specified will be
127 * fired from RCU critical section and therefore must not sleep.
128 */
vmci_event_subscribe(u32 event,vmci_event_cb callback,void * callback_data,u32 * new_subscription_id)129 int vmci_event_subscribe(u32 event,
130 vmci_event_cb callback,
131 void *callback_data,
132 u32 *new_subscription_id)
133 {
134 struct vmci_subscription *sub;
135 int attempts;
136 int retval;
137 bool have_new_id = false;
138
139 if (!new_subscription_id) {
140 pr_devel("%s: Invalid subscription (NULL)\n", __func__);
141 return VMCI_ERROR_INVALID_ARGS;
142 }
143
144 if (!VMCI_EVENT_VALID(event) || !callback) {
145 pr_devel("%s: Failed to subscribe to event (type=%d) (callback=%p) (data=%p)\n",
146 __func__, event, callback, callback_data);
147 return VMCI_ERROR_INVALID_ARGS;
148 }
149
150 sub = kzalloc(sizeof(*sub), GFP_KERNEL);
151 if (!sub)
152 return VMCI_ERROR_NO_MEM;
153
154 sub->id = VMCI_EVENT_MAX;
155 sub->event = event;
156 sub->callback = callback;
157 sub->callback_data = callback_data;
158 INIT_LIST_HEAD(&sub->node);
159
160 mutex_lock(&subscriber_mutex);
161
162 /* Creation of a new event is always allowed. */
163 for (attempts = 0; attempts < VMCI_EVENT_MAX_ATTEMPTS; attempts++) {
164 static u32 subscription_id;
165 /*
166 * We try to get an id a couple of time before
167 * claiming we are out of resources.
168 */
169
170 /* Test for duplicate id. */
171 if (!event_find(++subscription_id)) {
172 sub->id = subscription_id;
173 have_new_id = true;
174 break;
175 }
176 }
177
178 if (have_new_id) {
179 list_add_rcu(&sub->node, &subscriber_array[event]);
180 retval = VMCI_SUCCESS;
181 } else {
182 retval = VMCI_ERROR_NO_RESOURCES;
183 }
184
185 mutex_unlock(&subscriber_mutex);
186
187 *new_subscription_id = sub->id;
188 return retval;
189 }
190 EXPORT_SYMBOL_GPL(vmci_event_subscribe);
191
192 /*
193 * vmci_event_unsubscribe() - unsubscribe from an event.
194 * @sub_id: A subscription ID as provided by vmci_event_subscribe()
195 *
196 * Unsubscribe from given event. Removes it from list and frees it.
197 * Will return callback_data if requested by caller.
198 */
vmci_event_unsubscribe(u32 sub_id)199 int vmci_event_unsubscribe(u32 sub_id)
200 {
201 struct vmci_subscription *s;
202
203 mutex_lock(&subscriber_mutex);
204 s = event_find(sub_id);
205 if (s)
206 list_del_rcu(&s->node);
207 mutex_unlock(&subscriber_mutex);
208
209 if (!s)
210 return VMCI_ERROR_NOT_FOUND;
211
212 synchronize_rcu();
213 kfree(s);
214
215 return VMCI_SUCCESS;
216 }
217 EXPORT_SYMBOL_GPL(vmci_event_unsubscribe);
218
