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smsgiucv_app.c
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1 /*
2  * Deliver z/VM CP special messages (SMSG) as uevents.
3  *
4  * The driver registers for z/VM CP special messages with the
5  * "APP" prefix. Incoming messages are delivered to user space
6  * as uevents.
7  *
8  * Copyright IBM Corp. 2010
9  * Author(s): Hendrik Brueckner <[email protected]>
10  *
11  */
12 #define KMSG_COMPONENT "smsgiucv_app"
13 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
14 
15 #include <linux/ctype.h>
16 #include <linux/err.h>
17 #include <linux/device.h>
18 #include <linux/list.h>
19 #include <linux/kobject.h>
20 #include <linux/module.h>
21 #include <linux/slab.h>
22 #include <linux/spinlock.h>
23 #include <linux/workqueue.h>
24 #include <net/iucv/iucv.h>
25 #include "smsgiucv.h"
26 
27 /* prefix used for SMSG registration */
28 #define SMSG_PREFIX "APP"
29 
30 /* SMSG related uevent environment variables */
31 #define ENV_SENDER_STR "SMSG_SENDER="
32 #define ENV_SENDER_LEN (strlen(ENV_SENDER_STR) + 8 + 1)
33 #define ENV_PREFIX_STR "SMSG_ID="
34 #define ENV_PREFIX_LEN (strlen(ENV_PREFIX_STR) + \
35  strlen(SMSG_PREFIX) + 1)
36 #define ENV_TEXT_STR "SMSG_TEXT="
37 #define ENV_TEXT_LEN(msg) (strlen(ENV_TEXT_STR) + strlen((msg)) + 1)
38 
39 /* z/VM user ID which is permitted to send SMSGs
40  * If the value is undefined or empty (""), special messages are
41  * accepted from any z/VM user ID. */
42 static char *sender;
43 module_param(sender, charp, 0400);
44 MODULE_PARM_DESC(sender, "z/VM user ID from which CP SMSGs are accepted");
45 
46 /* SMSG device representation */
47 static struct device *smsg_app_dev;
48 
49 /* list element for queuing received messages for delivery */
51  struct list_head list;
52  char *buf;
53  char *envp[4];
54 };
55 
56 /* queue for outgoing uevents */
57 static LIST_HEAD(smsg_event_queue);
58 static DEFINE_SPINLOCK(smsg_event_queue_lock);
59 
60 static void smsg_app_event_free(struct smsg_app_event *ev)
61 {
62  kfree(ev->buf);
63  kfree(ev);
64 }
65 
66 static struct smsg_app_event *smsg_app_event_alloc(const char *from,
67  const char *msg)
68 {
69  struct smsg_app_event *ev;
70 
71  ev = kzalloc(sizeof(*ev), GFP_ATOMIC);
72  if (!ev)
73  return NULL;
74 
75  ev->buf = kzalloc(ENV_SENDER_LEN + ENV_PREFIX_LEN +
76  ENV_TEXT_LEN(msg), GFP_ATOMIC);
77  if (!ev->buf) {
78  kfree(ev);
79  return NULL;
80  }
81 
82  /* setting up environment pointers into buf */
83  ev->envp[0] = ev->buf;
84  ev->envp[1] = ev->envp[0] + ENV_SENDER_LEN;
85  ev->envp[2] = ev->envp[1] + ENV_PREFIX_LEN;
86  ev->envp[3] = NULL;
87 
88  /* setting up environment: sender, prefix name, and message text */
89  snprintf(ev->envp[0], ENV_SENDER_LEN, ENV_SENDER_STR "%s", from);
91  snprintf(ev->envp[2], ENV_TEXT_LEN(msg), ENV_TEXT_STR "%s", msg);
92 
93  return ev;
94 }
95 
96 static void smsg_event_work_fn(struct work_struct *work)
97 {
99  struct smsg_app_event *p, *n;
100  struct device *dev;
101 
102  dev = get_device(smsg_app_dev);
103  if (!dev)
104  return;
105 
106  spin_lock_bh(&smsg_event_queue_lock);
107  list_splice_init(&smsg_event_queue, &event_queue);
108  spin_unlock_bh(&smsg_event_queue_lock);
109 
111  list_del(&p->list);
113  smsg_app_event_free(p);
114  }
115 
116  put_device(dev);
117 }
118 static DECLARE_WORK(smsg_event_work, smsg_event_work_fn);
119 
120 static void smsg_app_callback(const char *from, char *msg)
121 {
122  struct smsg_app_event *se;
123 
124  /* check if the originating z/VM user ID matches
125  * the configured sender. */
126  if (sender && strlen(sender) > 0 && strcmp(from, sender) != 0)
127  return;
128 
129  /* get start of message text (skip prefix and leading blanks) */
130  msg += strlen(SMSG_PREFIX);
131  while (*msg && isspace(*msg))
132  msg++;
133  if (*msg == '\0')
134  return;
135 
136  /* allocate event list element and its environment */
137  se = smsg_app_event_alloc(from, msg);
138  if (!se)
139  return;
140 
141  /* queue event and schedule work function */
142  spin_lock(&smsg_event_queue_lock);
143  list_add_tail(&se->list, &smsg_event_queue);
144  spin_unlock(&smsg_event_queue_lock);
145 
146  schedule_work(&smsg_event_work);
147  return;
148 }
149 
150 static int __init smsgiucv_app_init(void)
151 {
152  struct device_driver *smsgiucv_drv;
153  int rc;
154 
155  if (!MACHINE_IS_VM)
156  return -ENODEV;
157 
158  smsg_app_dev = kzalloc(sizeof(*smsg_app_dev), GFP_KERNEL);
159  if (!smsg_app_dev)
160  return -ENOMEM;
161 
162  smsgiucv_drv = driver_find(SMSGIUCV_DRV_NAME, &iucv_bus);
163  if (!smsgiucv_drv) {
164  kfree(smsg_app_dev);
165  return -ENODEV;
166  }
167 
168  rc = dev_set_name(smsg_app_dev, KMSG_COMPONENT);
169  if (rc) {
170  kfree(smsg_app_dev);
171  goto fail;
172  }
173  smsg_app_dev->bus = &iucv_bus;
174  smsg_app_dev->parent = iucv_root;
175  smsg_app_dev->release = (void (*)(struct device *)) kfree;
176  smsg_app_dev->driver = smsgiucv_drv;
177  rc = device_register(smsg_app_dev);
178  if (rc) {
179  put_device(smsg_app_dev);
180  goto fail;
181  }
182 
183  /* convert sender to uppercase characters */
184  if (sender) {
185  int len = strlen(sender);
186  while (len--)
187  sender[len] = toupper(sender[len]);
188  }
189 
190  /* register with the smsgiucv device driver */
191  rc = smsg_register_callback(SMSG_PREFIX, smsg_app_callback);
192  if (rc) {
193  device_unregister(smsg_app_dev);
194  goto fail;
195  }
196 
197  rc = 0;
198 fail:
199  return rc;
200 }
201 module_init(smsgiucv_app_init);
202 
203 static void __exit smsgiucv_app_exit(void)
204 {
205  /* unregister callback */
206  smsg_unregister_callback(SMSG_PREFIX, smsg_app_callback);
207 
208  /* cancel pending work and flush any queued event work */
209  cancel_work_sync(&smsg_event_work);
210  smsg_event_work_fn(&smsg_event_work);
211 
212  device_unregister(smsg_app_dev);
213 }
214 module_exit(smsgiucv_app_exit);
215 
216 MODULE_LICENSE("GPL v2");
217 MODULE_DESCRIPTION("Deliver z/VM CP SMSG as uevents");
218 MODULE_AUTHOR("Hendrik Brueckner <[email protected]>");