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