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/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
  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
  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  */
  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  */
  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  */
 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  */
 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  */
 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);