drivers/misc/vmw_vmci/vmci_event.c

   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/nospec.h>
  13 #include <linux/sched.h>
  14 #include <linux/slab.h>
  15 #include <linux/rculist.h>
  16
  17 #include "vmci_driver.h"
  18 #include "vmci_event.h"
  19
  20 #define EVENT_MAGIC 0xEABE0000
  21 #define VMCI_EVENT_MAX_ATTEMPTS 10
  22
  23 struct vmci_subscription {
  24         u32 id;
  25         u32 event;
  26         vmci_event_cb callback;
  27         void *callback_data;
  28         struct list_head node;  /* on one of subscriber lists */
  29 };
  30
  31 static struct list_head subscriber_array[VMCI_EVENT_MAX];
  32 static DEFINE_MUTEX(subscriber_mutex);
  33
  34 int __init vmci_event_init(void)
  35 {
  36         int i;
  37
  38         for (i = 0; i < VMCI_EVENT_MAX; i++)
  39                 INIT_LIST_HEAD(&subscriber_array[i]);
  40
  41         return VMCI_SUCCESS;
  42 }
  43
  44 void vmci_event_exit(void)
  45 {
  46         int e;
  47
  48         /* We free all memory at exit. */
  49         for (e = 0; e < VMCI_EVENT_MAX; e++) {
  50                 struct vmci_subscription *cur, *p2;
  51                 list_for_each_entry_safe(cur, p2, &subscriber_array[e], node) {
  52
  53                         /*
  54                          * We should never get here because all events
  55                          * should have been unregistered before we try
  56                          * to unload the driver module.
  57                          */
  58                         pr_warn("Unexpected free events occurring\n");
  59                         list_del(&cur->node);
  60                         kfree(cur);
  61                 }
  62         }
  63 }
  64
  65 /*
  66  * Find entry. Assumes subscriber_mutex is held.
  67  */
  68 static struct vmci_subscription *event_find(u32 sub_id)
  69 {
  70         int e;
  71
  72         for (e = 0; e < VMCI_EVENT_MAX; e++) {
  73                 struct vmci_subscription *cur;
  74                 list_for_each_entry(cur, &subscriber_array[e], node) {
  75                         if (cur->id == sub_id)
  76                                 return cur;
  77                 }
  78         }
  79         return NULL;
  80 }
  81
  82 /*
  83  * Actually delivers the events to the subscribers.
  84  * The callback function for each subscriber is invoked.
  85  */
  86 static void event_deliver(struct vmci_event_msg *event_msg)
  87 {
  88         struct vmci_subscription *cur;
  89         struct list_head *subscriber_list;
  90         u32 sanitized_event, max_vmci_event;
  91
  92         rcu_read_lock();
  93         max_vmci_event = ARRAY_SIZE(subscriber_array);
  94         sanitized_event = array_index_nospec(event_msg->event_data.event, max_vmci_event);
  95         subscriber_list = &subscriber_array[sanitized_event];
  96         list_for_each_entry_rcu(cur, subscriber_list, node) {
  97                 cur->callback(cur->id, &event_msg->event_data,
  98                               cur->callback_data);
  99         }
 100         rcu_read_unlock();
 101 }
 102
 103 /*
 104  * Dispatcher for the VMCI_EVENT_RECEIVE datagrams. Calls all
 105  * subscribers for given event.
 106  */
 107 int vmci_event_dispatch(struct vmci_datagram *msg)
 108 {
 109         struct vmci_event_msg *event_msg = (struct vmci_event_msg *)msg;
 110
 111         if (msg->payload_size < sizeof(u32) ||
 112             msg->payload_size > sizeof(struct vmci_event_data_max))
 113                 return VMCI_ERROR_INVALID_ARGS;
 114
 115         if (!VMCI_EVENT_VALID(event_msg->event_data.event))
 116                 return VMCI_ERROR_EVENT_UNKNOWN;
 117
 118         event_deliver(event_msg);
 119         return VMCI_SUCCESS;
 120 }
 121
 122 /*
 123  * vmci_event_subscribe() - Subscribe to a given event.
 124  * @event:      The event to subscribe to.
 125  * @callback:   The callback to invoke upon the event.
 126  * @callback_data:      Data to pass to the callback.
 127  * @subscription_id:    ID used to track subscription.  Used with
 128  *              vmci_event_unsubscribe()
 129  *
 130  * Subscribes to the provided event. The callback specified will be
 131  * fired from RCU critical section and therefore must not sleep.
 132  */
 133 int vmci_event_subscribe(u32 event,
 134                          vmci_event_cb callback,
 135                          void *callback_data,
 136                          u32 *new_subscription_id)
 137 {
 138         struct vmci_subscription *sub;
 139         int attempts;
 140         int retval;
 141         bool have_new_id = false;
 142
 143         if (!new_subscription_id) {
 144                 pr_devel("%s: Invalid subscription (NULL)\n", __func__);
 145                 return VMCI_ERROR_INVALID_ARGS;
 146         }
 147
 148         if (!VMCI_EVENT_VALID(event) || !callback) {
 149                 pr_devel("%s: Failed to subscribe to event (type=%d) (callback=%p) (data=%p)\n",
 150                          __func__, event, callback, callback_data);
 151                 return VMCI_ERROR_INVALID_ARGS;
 152         }
 153
 154         sub = kzalloc(sizeof(*sub), GFP_KERNEL);
 155         if (!sub)
 156                 return VMCI_ERROR_NO_MEM;
 157
 158         sub->id = VMCI_EVENT_MAX;
 159         sub->event = event;
 160         sub->callback = callback;
 161         sub->callback_data = callback_data;
 162         INIT_LIST_HEAD(&sub->node);
 163
 164         mutex_lock(&subscriber_mutex);
 165
 166         /* Creation of a new event is always allowed. */
 167         for (attempts = 0; attempts < VMCI_EVENT_MAX_ATTEMPTS; attempts++) {
 168                 static u32 subscription_id;
 169                 /*
 170                  * We try to get an id a couple of time before
 171                  * claiming we are out of resources.
 172                  */
 173
 174                 /* Test for duplicate id. */
 175                 if (!event_find(++subscription_id)) {
 176                         sub->id = subscription_id;
 177                         have_new_id = true;
 178                         break;
 179                 }
 180         }
 181
 182         if (have_new_id) {
 183                 list_add_rcu(&sub->node, &subscriber_array[event]);
 184                 retval = VMCI_SUCCESS;
 185         } else {
 186                 retval = VMCI_ERROR_NO_RESOURCES;
 187         }
 188
 189         mutex_unlock(&subscriber_mutex);
 190
 191         *new_subscription_id = sub->id;
 192         return retval;
 193 }
 194 EXPORT_SYMBOL_GPL(vmci_event_subscribe);
 195
 196 /*
 197  * vmci_event_unsubscribe() - unsubscribe from an event.
 198  * @sub_id:     A subscription ID as provided by vmci_event_subscribe()
 199  *
 200  * Unsubscribe from given event. Removes it from list and frees it.
 201  * Will return callback_data if requested by caller.
 202  */
 203 int vmci_event_unsubscribe(u32 sub_id)
 204 {
 205         struct vmci_subscription *s;
 206
 207         mutex_lock(&subscriber_mutex);
 208         s = event_find(sub_id);
 209         if (s)
 210                 list_del_rcu(&s->node);
 211         mutex_unlock(&subscriber_mutex);
 212
 213         if (!s)
 214                 return VMCI_ERROR_NOT_FOUND;
 215
 216         kvfree_rcu_mightsleep(s);
 217
 218         return VMCI_SUCCESS;
 219 }
 220 EXPORT_SYMBOL_GPL(vmci_event_unsubscribe);