1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Character device driver for reading z/VM *MONITOR service records.
4  *
5  * Copyright IBM Corp. 2004, 2009
6  *
7  * Author: Gerald Schaefer <gerald.schaefer@de.ibm.com>
8  */
9 
10 #define KMSG_COMPONENT "monreader"
11 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
12 
13 #include <linux/module.h>
14 #include <linux/moduleparam.h>
15 #include <linux/init.h>
16 #include <linux/errno.h>
17 #include <linux/types.h>
18 #include <linux/kernel.h>
19 #include <linux/miscdevice.h>
20 #include <linux/ctype.h>
21 #include <linux/spinlock.h>
22 #include <linux/interrupt.h>
23 #include <linux/poll.h>
24 #include <linux/slab.h>
25 #include <net/iucv/iucv.h>
26 #include <linux/uaccess.h>
27 #include <asm/machine.h>
28 #include <asm/ebcdic.h>
29 #include <asm/extmem.h>
30 
31 
32 #define MON_COLLECT_SAMPLE 0x80
33 #define MON_COLLECT_EVENT  0x40
34 #define MON_SERVICE	   "*MONITOR"
35 #define MON_IN_USE	   0x01
36 #define MON_MSGLIM	   255
37 
38 static char mon_dcss_name[9] = "MONDCSS\0";
39 
40 struct mon_msg {
41 	u32 pos;
42 	u32 mca_offset;
43 	struct iucv_message msg;
44 	char msglim_reached;
45 	char replied_msglim;
46 };
47 
48 struct mon_private {
49 	struct iucv_path *path;
50 	struct mon_msg *msg_array[MON_MSGLIM];
51 	unsigned int   write_index;
52 	unsigned int   read_index;
53 	atomic_t msglim_count;
54 	atomic_t read_ready;
55 	atomic_t iucv_connected;
56 	atomic_t iucv_severed;
57 };
58 
59 static unsigned long mon_in_use = 0;
60 
61 static unsigned long mon_dcss_start;
62 static unsigned long mon_dcss_end;
63 
64 static DECLARE_WAIT_QUEUE_HEAD(mon_read_wait_queue);
65 static DECLARE_WAIT_QUEUE_HEAD(mon_conn_wait_queue);
66 
67 static u8 user_data_connect[16] = {
68 	/* Version code, must be 0x01 for shared mode */
69 	0x01,
70 	/* what to collect */
71 	MON_COLLECT_SAMPLE | MON_COLLECT_EVENT,
72 	/* DCSS name in EBCDIC, 8 bytes padded with blanks */
73 	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
74 	0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
75 };
76 
77 static u8 user_data_sever[16] = {
78 	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
79 	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
80 };
81 
82 /******************************************************************************
83  *                             helper functions                               *
84  *****************************************************************************/
85 /*
86  * Create the 8 bytes EBCDIC DCSS segment name from
87  * an ASCII name, incl. padding
88  */
89 static void dcss_mkname(char *ascii_name, char *ebcdic_name)
90 {
91 	int i;
92 
93 	for (i = 0; i < 8; i++) {
94 		if (ascii_name[i] == '\0')
95 			break;
96 		ebcdic_name[i] = toupper(ascii_name[i]);
97 	}
98 	for (; i < 8; i++)
99 		ebcdic_name[i] = ' ';
100 	ASCEBC(ebcdic_name, 8);
101 }
102 
103 static inline unsigned long mon_mca_start(struct mon_msg *monmsg)
104 {
105 	return *(u32 *) &monmsg->msg.rmmsg;
106 }
107 
108 static inline unsigned long mon_mca_end(struct mon_msg *monmsg)
109 {
110 	return *(u32 *) &monmsg->msg.rmmsg[4];
111 }
112 
113 static inline u8 mon_mca_type(struct mon_msg *monmsg, u8 index)
114 {
115 	return *((u8 *)__va(mon_mca_start(monmsg)) + monmsg->mca_offset + index);
116 }
117 
118 static inline u32 mon_mca_size(struct mon_msg *monmsg)
119 {
120 	return mon_mca_end(monmsg) - mon_mca_start(monmsg) + 1;
121 }
122 
123 static inline u32 mon_rec_start(struct mon_msg *monmsg)
124 {
125 	return *((u32 *)(__va(mon_mca_start(monmsg)) + monmsg->mca_offset + 4));
126 }
127 
128 static inline u32 mon_rec_end(struct mon_msg *monmsg)
129 {
130 	return *((u32 *)(__va(mon_mca_start(monmsg)) + monmsg->mca_offset + 8));
131 }
132 
133 static int mon_check_mca(struct mon_msg *monmsg)
134 {
135 	if ((mon_rec_end(monmsg) <= mon_rec_start(monmsg)) ||
136 	    (mon_rec_start(monmsg) < mon_dcss_start) ||
137 	    (mon_rec_end(monmsg) > mon_dcss_end) ||
138 	    (mon_mca_type(monmsg, 0) == 0) ||
139 	    (mon_mca_size(monmsg) % 12 != 0) ||
140 	    (mon_mca_end(monmsg) <= mon_mca_start(monmsg)) ||
141 	    (mon_mca_end(monmsg) > mon_dcss_end) ||
142 	    (mon_mca_start(monmsg) < mon_dcss_start) ||
143 	    ((mon_mca_type(monmsg, 1) == 0) && (mon_mca_type(monmsg, 2) == 0)))
144 		return -EINVAL;
145 	return 0;
146 }
147 
148 static int mon_send_reply(struct mon_msg *monmsg,
149 			  struct mon_private *monpriv)
150 {
151 	int rc;
152 
153 	rc = iucv_message_reply(monpriv->path, &monmsg->msg,
154 				IUCV_IPRMDATA, NULL, 0);
155 	atomic_dec(&monpriv->msglim_count);
156 	if (likely(!monmsg->msglim_reached)) {
157 		monmsg->pos = 0;
158 		monmsg->mca_offset = 0;
159 		monpriv->read_index = (monpriv->read_index + 1) %
160 				      MON_MSGLIM;
161 		atomic_dec(&monpriv->read_ready);
162 	} else
163 		monmsg->replied_msglim = 1;
164 	if (rc) {
165 		pr_err("Reading monitor data failed with rc=%i\n", rc);
166 		return -EIO;
167 	}
168 	return 0;
169 }
170 
171 static void mon_free_mem(struct mon_private *monpriv)
172 {
173 	int i;
174 
175 	for (i = 0; i < MON_MSGLIM; i++)
176 		kfree(monpriv->msg_array[i]);
177 	kfree(monpriv);
178 }
179 
180 static struct mon_private *mon_alloc_mem(void)
181 {
182 	int i;
183 	struct mon_private *monpriv;
184 
185 	monpriv = kzalloc(sizeof(struct mon_private), GFP_KERNEL);
186 	if (!monpriv)
187 		return NULL;
188 	for (i = 0; i < MON_MSGLIM; i++) {
189 		monpriv->msg_array[i] = kzalloc(sizeof(struct mon_msg),
190 						    GFP_KERNEL);
191 		if (!monpriv->msg_array[i]) {
192 			mon_free_mem(monpriv);
193 			return NULL;
194 		}
195 	}
196 	return monpriv;
197 }
198 
199 static inline void mon_next_mca(struct mon_msg *monmsg)
200 {
201 	if (likely((mon_mca_size(monmsg) - monmsg->mca_offset) == 12))
202 		return;
203 	monmsg->mca_offset += 12;
204 	monmsg->pos = 0;
205 }
206 
207 static struct mon_msg *mon_next_message(struct mon_private *monpriv)
208 {
209 	struct mon_msg *monmsg;
210 
211 	if (!atomic_read(&monpriv->read_ready))
212 		return NULL;
213 	monmsg = monpriv->msg_array[monpriv->read_index];
214 	if (unlikely(monmsg->replied_msglim)) {
215 		monmsg->replied_msglim = 0;
216 		monmsg->msglim_reached = 0;
217 		monmsg->pos = 0;
218 		monmsg->mca_offset = 0;
219 		monpriv->read_index = (monpriv->read_index + 1) %
220 				      MON_MSGLIM;
221 		atomic_dec(&monpriv->read_ready);
222 		return ERR_PTR(-EOVERFLOW);
223 	}
224 	return monmsg;
225 }
226 
227 
228 /******************************************************************************
229  *                               IUCV handler                                 *
230  *****************************************************************************/
231 static void mon_iucv_path_complete(struct iucv_path *path, u8 *ipuser)
232 {
233 	struct mon_private *monpriv = path->private;
234 
235 	atomic_set(&monpriv->iucv_connected, 1);
236 	wake_up(&mon_conn_wait_queue);
237 }
238 
239 static void mon_iucv_path_severed(struct iucv_path *path, u8 *ipuser)
240 {
241 	struct mon_private *monpriv = path->private;
242 
243 	pr_err("z/VM *MONITOR system service disconnected with rc=%i\n",
244 	       ipuser[0]);
245 	iucv_path_sever(path, NULL);
246 	atomic_set(&monpriv->iucv_severed, 1);
247 	wake_up(&mon_conn_wait_queue);
248 	wake_up_interruptible(&mon_read_wait_queue);
249 }
250 
251 static void mon_iucv_message_pending(struct iucv_path *path,
252 				     struct iucv_message *msg)
253 {
254 	struct mon_private *monpriv = path->private;
255 
256 	memcpy(&monpriv->msg_array[monpriv->write_index]->msg,
257 	       msg, sizeof(*msg));
258 	if (atomic_inc_return(&monpriv->msglim_count) == MON_MSGLIM) {
259 		pr_warn("The read queue for monitor data is full\n");
260 		monpriv->msg_array[monpriv->write_index]->msglim_reached = 1;
261 	}
262 	monpriv->write_index = (monpriv->write_index + 1) % MON_MSGLIM;
263 	atomic_inc(&monpriv->read_ready);
264 	wake_up_interruptible(&mon_read_wait_queue);
265 }
266 
267 static struct iucv_handler monreader_iucv_handler = {
268 	.path_complete	 = mon_iucv_path_complete,
269 	.path_severed	 = mon_iucv_path_severed,
270 	.message_pending = mon_iucv_message_pending,
271 };
272 
273 /******************************************************************************
274  *                               file operations                              *
275  *****************************************************************************/
276 static int mon_open(struct inode *inode, struct file *filp)
277 {
278 	struct mon_private *monpriv;
279 	int rc;
280 
281 	/*
282 	 * only one user allowed
283 	 */
284 	rc = -EBUSY;
285 	if (test_and_set_bit(MON_IN_USE, &mon_in_use))
286 		goto out;
287 
288 	rc = -ENOMEM;
289 	monpriv = mon_alloc_mem();
290 	if (!monpriv)
291 		goto out_use;
292 
293 	/*
294 	 * Connect to *MONITOR service
295 	 */
296 	monpriv->path = iucv_path_alloc(MON_MSGLIM, IUCV_IPRMDATA, GFP_KERNEL);
297 	if (!monpriv->path)
298 		goto out_priv;
299 	rc = iucv_path_connect(monpriv->path, &monreader_iucv_handler,
300 			       MON_SERVICE, NULL, user_data_connect, monpriv);
301 	if (rc) {
302 		pr_err("Connecting to the z/VM *MONITOR system service "
303 		       "failed with rc=%i\n", rc);
304 		rc = -EIO;
305 		goto out_path;
306 	}
307 	/*
308 	 * Wait for connection confirmation
309 	 */
310 	wait_event(mon_conn_wait_queue,
311 		   atomic_read(&monpriv->iucv_connected) ||
312 		   atomic_read(&monpriv->iucv_severed));
313 	if (atomic_read(&monpriv->iucv_severed)) {
314 		atomic_set(&monpriv->iucv_severed, 0);
315 		atomic_set(&monpriv->iucv_connected, 0);
316 		rc = -EIO;
317 		goto out_path;
318 	}
319 	filp->private_data = monpriv;
320 	return nonseekable_open(inode, filp);
321 
322 out_path:
323 	iucv_path_free(monpriv->path);
324 out_priv:
325 	mon_free_mem(monpriv);
326 out_use:
327 	clear_bit(MON_IN_USE, &mon_in_use);
328 out:
329 	return rc;
330 }
331 
332 static int mon_close(struct inode *inode, struct file *filp)
333 {
334 	int rc, i;
335 	struct mon_private *monpriv = filp->private_data;
336 
337 	/*
338 	 * Close IUCV connection and unregister
339 	 */
340 	if (monpriv->path) {
341 		rc = iucv_path_sever(monpriv->path, user_data_sever);
342 		if (rc)
343 			pr_warn("Disconnecting the z/VM *MONITOR system service failed with rc=%i\n",
344 				rc);
345 		iucv_path_free(monpriv->path);
346 	}
347 
348 	atomic_set(&monpriv->iucv_severed, 0);
349 	atomic_set(&monpriv->iucv_connected, 0);
350 	atomic_set(&monpriv->read_ready, 0);
351 	atomic_set(&monpriv->msglim_count, 0);
352 	monpriv->write_index  = 0;
353 	monpriv->read_index   = 0;
354 
355 	for (i = 0; i < MON_MSGLIM; i++)
356 		kfree(monpriv->msg_array[i]);
357 	kfree(monpriv);
358 	clear_bit(MON_IN_USE, &mon_in_use);
359 	return 0;
360 }
361 
362 static ssize_t mon_read(struct file *filp, char __user *data,
363 			size_t count, loff_t *ppos)
364 {
365 	struct mon_private *monpriv = filp->private_data;
366 	struct mon_msg *monmsg;
367 	int ret;
368 	u32 mce_start;
369 
370 	monmsg = mon_next_message(monpriv);
371 	if (IS_ERR(monmsg))
372 		return PTR_ERR(monmsg);
373 
374 	if (!monmsg) {
375 		if (filp->f_flags & O_NONBLOCK)
376 			return -EAGAIN;
377 		ret = wait_event_interruptible(mon_read_wait_queue,
378 					atomic_read(&monpriv->read_ready) ||
379 					atomic_read(&monpriv->iucv_severed));
380 		if (ret)
381 			return ret;
382 		if (unlikely(atomic_read(&monpriv->iucv_severed)))
383 			return -EIO;
384 		monmsg = monpriv->msg_array[monpriv->read_index];
385 	}
386 
387 	if (!monmsg->pos)
388 		monmsg->pos = mon_mca_start(monmsg) + monmsg->mca_offset;
389 	if (mon_check_mca(monmsg))
390 		goto reply;
391 
392 	/* read monitor control element (12 bytes) first */
393 	mce_start = mon_mca_start(monmsg) + monmsg->mca_offset;
394 	if ((monmsg->pos >= mce_start) && (monmsg->pos < mce_start + 12)) {
395 		count = min(count, (size_t) mce_start + 12 - monmsg->pos);
396 		ret = copy_to_user(data, __va(monmsg->pos), count);
397 		if (ret)
398 			return -EFAULT;
399 		monmsg->pos += count;
400 		if (monmsg->pos == mce_start + 12)
401 			monmsg->pos = mon_rec_start(monmsg);
402 		goto out_copy;
403 	}
404 
405 	/* read records */
406 	if (monmsg->pos <= mon_rec_end(monmsg)) {
407 		count = min(count, (size_t) mon_rec_end(monmsg) - monmsg->pos
408 					    + 1);
409 		ret = copy_to_user(data, __va(monmsg->pos), count);
410 		if (ret)
411 			return -EFAULT;
412 		monmsg->pos += count;
413 		if (monmsg->pos > mon_rec_end(monmsg))
414 			mon_next_mca(monmsg);
415 		goto out_copy;
416 	}
417 reply:
418 	ret = mon_send_reply(monmsg, monpriv);
419 	return ret;
420 
421 out_copy:
422 	*ppos += count;
423 	return count;
424 }
425 
426 static __poll_t mon_poll(struct file *filp, struct poll_table_struct *p)
427 {
428 	struct mon_private *monpriv = filp->private_data;
429 
430 	poll_wait(filp, &mon_read_wait_queue, p);
431 	if (unlikely(atomic_read(&monpriv->iucv_severed)))
432 		return EPOLLERR;
433 	if (atomic_read(&monpriv->read_ready))
434 		return EPOLLIN | EPOLLRDNORM;
435 	return 0;
436 }
437 
438 static const struct file_operations mon_fops = {
439 	.owner   = THIS_MODULE,
440 	.open    = &mon_open,
441 	.release = &mon_close,
442 	.read    = &mon_read,
443 	.poll    = &mon_poll,
444 	.llseek  = noop_llseek,
445 };
446 
447 static struct miscdevice mon_dev = {
448 	.name       = "monreader",
449 	.fops       = &mon_fops,
450 	.minor      = MISC_DYNAMIC_MINOR,
451 };
452 
453 /******************************************************************************
454  *                              module init/exit                              *
455  *****************************************************************************/
456 static int __init mon_init(void)
457 {
458 	int rc;
459 
460 	if (!machine_is_vm()) {
461 		pr_err("The z/VM *MONITOR record device driver cannot be "
462 		       "loaded without z/VM\n");
463 		return -ENODEV;
464 	}
465 
466 	/*
467 	 * Register with IUCV and connect to *MONITOR service
468 	 */
469 	rc = iucv_register(&monreader_iucv_handler, 1);
470 	if (rc) {
471 		pr_err("The z/VM *MONITOR record device driver failed to "
472 		       "register with IUCV\n");
473 		return rc;
474 	}
475 
476 	rc = segment_type(mon_dcss_name);
477 	if (rc < 0) {
478 		segment_warning(rc, mon_dcss_name);
479 		goto out_iucv;
480 	}
481 	if (rc != SEG_TYPE_SC) {
482 		pr_err("The specified *MONITOR DCSS %s does not have the "
483 		       "required type SC\n", mon_dcss_name);
484 		rc = -EINVAL;
485 		goto out_iucv;
486 	}
487 
488 	rc = segment_load(mon_dcss_name, SEGMENT_SHARED,
489 			  &mon_dcss_start, &mon_dcss_end);
490 	if (rc < 0) {
491 		segment_warning(rc, mon_dcss_name);
492 		rc = -EINVAL;
493 		goto out_iucv;
494 	}
495 	dcss_mkname(mon_dcss_name, &user_data_connect[8]);
496 
497 	/*
498 	 * misc_register() has to be the last action in module_init(), because
499 	 * file operations will be available right after this.
500 	 */
501 	rc = misc_register(&mon_dev);
502 	if (rc < 0 )
503 		goto out;
504 	return 0;
505 
506 out:
507 	segment_unload(mon_dcss_name);
508 out_iucv:
509 	iucv_unregister(&monreader_iucv_handler, 1);
510 	return rc;
511 }
512 
513 static void __exit mon_exit(void)
514 {
515 	segment_unload(mon_dcss_name);
516 	misc_deregister(&mon_dev);
517 	iucv_unregister(&monreader_iucv_handler, 1);
518 	return;
519 }
520 
521 
522 module_init(mon_init);
523 module_exit(mon_exit);
524 
525 module_param_string(mondcss, mon_dcss_name, 9, 0444);
526 MODULE_PARM_DESC(mondcss, "Name of DCSS segment to be used for *MONITOR "
527 		 "service, max. 8 chars. Default is MONDCSS");
528 
529 MODULE_AUTHOR("Gerald Schaefer <geraldsc@de.ibm.com>");
530 MODULE_DESCRIPTION("Character device driver for reading z/VM "
531 		   "monitor service records.");
532 MODULE_LICENSE("GPL");
533