1/*
  2 * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  3 * Licensed under the GPL
  4 */
  5
  6#include "linux/irqreturn.h"
  7#include "linux/kd.h"
  8#include "linux/sched.h"
  9#include "linux/slab.h"
 10#include "chan.h"
 11#include "irq_kern.h"
 12#include "irq_user.h"
 13#include "kern_util.h"
 14#include "os.h"
 15
 16#define LINE_BUFSIZE 4096
 17
 18static irqreturn_t line_interrupt(int irq, void *data)
 19{
 20	struct chan *chan = data;
 21	struct line *line = chan->line;
 22
 23	if (line)
 24		chan_interrupt(line, line->tty, irq);
 
 25	return IRQ_HANDLED;
 26}
 27
 28/*
 29 * Returns the free space inside the ring buffer of this line.
 30 *
 31 * Should be called while holding line->lock (this does not modify data).
 32 */
 33static int write_room(struct line *line)
 34{
 35	int n;
 36
 37	if (line->buffer == NULL)
 38		return LINE_BUFSIZE - 1;
 39
 40	/* This is for the case where the buffer is wrapped! */
 41	n = line->head - line->tail;
 42
 43	if (n <= 0)
 44		n += LINE_BUFSIZE; /* The other case */
 45	return n - 1;
 46}
 47
 48int line_write_room(struct tty_struct *tty)
 49{
 50	struct line *line = tty->driver_data;
 51	unsigned long flags;
 52	int room;
 53
 54	spin_lock_irqsave(&line->lock, flags);
 55	room = write_room(line);
 56	spin_unlock_irqrestore(&line->lock, flags);
 57
 58	return room;
 59}
 60
 61int line_chars_in_buffer(struct tty_struct *tty)
 62{
 63	struct line *line = tty->driver_data;
 64	unsigned long flags;
 65	int ret;
 66
 67	spin_lock_irqsave(&line->lock, flags);
 68	/* write_room subtracts 1 for the needed NULL, so we readd it.*/
 69	ret = LINE_BUFSIZE - (write_room(line) + 1);
 70	spin_unlock_irqrestore(&line->lock, flags);
 71
 72	return ret;
 73}
 74
 75/*
 76 * This copies the content of buf into the circular buffer associated with
 77 * this line.
 78 * The return value is the number of characters actually copied, i.e. the ones
 79 * for which there was space: this function is not supposed to ever flush out
 80 * the circular buffer.
 81 *
 82 * Must be called while holding line->lock!
 83 */
 84static int buffer_data(struct line *line, const char *buf, int len)
 85{
 86	int end, room;
 87
 88	if (line->buffer == NULL) {
 89		line->buffer = kmalloc(LINE_BUFSIZE, GFP_ATOMIC);
 90		if (line->buffer == NULL) {
 91			printk(KERN_ERR "buffer_data - atomic allocation "
 92			       "failed\n");
 93			return 0;
 94		}
 95		line->head = line->buffer;
 96		line->tail = line->buffer;
 97	}
 98
 99	room = write_room(line);
100	len = (len > room) ? room : len;
101
102	end = line->buffer + LINE_BUFSIZE - line->tail;
103
104	if (len < end) {
105		memcpy(line->tail, buf, len);
106		line->tail += len;
107	}
108	else {
109		/* The circular buffer is wrapping */
110		memcpy(line->tail, buf, end);
111		buf += end;
112		memcpy(line->buffer, buf, len - end);
113		line->tail = line->buffer + len - end;
114	}
115
116	return len;
117}
118
119/*
120 * Flushes the ring buffer to the output channels. That is, write_chan is
121 * called, passing it line->head as buffer, and an appropriate count.
122 *
123 * On exit, returns 1 when the buffer is empty,
124 * 0 when the buffer is not empty on exit,
125 * and -errno when an error occurred.
126 *
127 * Must be called while holding line->lock!*/
128static int flush_buffer(struct line *line)
129{
130	int n, count;
131
132	if ((line->buffer == NULL) || (line->head == line->tail))
133		return 1;
134
135	if (line->tail < line->head) {
136		/* line->buffer + LINE_BUFSIZE is the end of the buffer! */
137		count = line->buffer + LINE_BUFSIZE - line->head;
138
139		n = write_chan(line->chan_out, line->head, count,
140			       line->driver->write_irq);
141		if (n < 0)
142			return n;
143		if (n == count) {
144			/*
145			 * We have flushed from ->head to buffer end, now we
146			 * must flush only from the beginning to ->tail.
147			 */
148			line->head = line->buffer;
149		} else {
150			line->head += n;
151			return 0;
152		}
153	}
154
155	count = line->tail - line->head;
156	n = write_chan(line->chan_out, line->head, count,
157		       line->driver->write_irq);
158
159	if (n < 0)
160		return n;
161
162	line->head += n;
163	return line->head == line->tail;
164}
165
166void line_flush_buffer(struct tty_struct *tty)
167{
168	struct line *line = tty->driver_data;
169	unsigned long flags;
170
171	spin_lock_irqsave(&line->lock, flags);
172	flush_buffer(line);
173	spin_unlock_irqrestore(&line->lock, flags);
174}
175
176/*
177 * We map both ->flush_chars and ->put_char (which go in pair) onto
178 * ->flush_buffer and ->write. Hope it's not that bad.
179 */
180void line_flush_chars(struct tty_struct *tty)
181{
182	line_flush_buffer(tty);
183}
184
185int line_put_char(struct tty_struct *tty, unsigned char ch)
186{
187	return line_write(tty, &ch, sizeof(ch));
188}
189
190int line_write(struct tty_struct *tty, const unsigned char *buf, int len)
191{
192	struct line *line = tty->driver_data;
193	unsigned long flags;
194	int n, ret = 0;
195
196	spin_lock_irqsave(&line->lock, flags);
197	if (line->head != line->tail)
198		ret = buffer_data(line, buf, len);
199	else {
200		n = write_chan(line->chan_out, buf, len,
201			       line->driver->write_irq);
202		if (n < 0) {
203			ret = n;
204			goto out_up;
205		}
206
207		len -= n;
208		ret += n;
209		if (len > 0)
210			ret += buffer_data(line, buf + n, len);
211	}
212out_up:
213	spin_unlock_irqrestore(&line->lock, flags);
214	return ret;
215}
216
217void line_set_termios(struct tty_struct *tty, struct ktermios * old)
218{
219	/* nothing */
220}
221
222static const struct {
223	int  cmd;
224	char *level;
225	char *name;
226} tty_ioctls[] = {
227	/* don't print these, they flood the log ... */
228	{ TCGETS,      NULL,       "TCGETS"      },
229	{ TCSETS,      NULL,       "TCSETS"      },
230	{ TCSETSW,     NULL,       "TCSETSW"     },
231	{ TCFLSH,      NULL,       "TCFLSH"      },
232	{ TCSBRK,      NULL,       "TCSBRK"      },
233
234	/* general tty stuff */
235	{ TCSETSF,     KERN_DEBUG, "TCSETSF"     },
236	{ TCGETA,      KERN_DEBUG, "TCGETA"      },
237	{ TIOCMGET,    KERN_DEBUG, "TIOCMGET"    },
238	{ TCSBRKP,     KERN_DEBUG, "TCSBRKP"     },
239	{ TIOCMSET,    KERN_DEBUG, "TIOCMSET"    },
240
241	/* linux-specific ones */
242	{ TIOCLINUX,   KERN_INFO,  "TIOCLINUX"   },
243	{ KDGKBMODE,   KERN_INFO,  "KDGKBMODE"   },
244	{ KDGKBTYPE,   KERN_INFO,  "KDGKBTYPE"   },
245	{ KDSIGACCEPT, KERN_INFO,  "KDSIGACCEPT" },
246};
247
248int line_ioctl(struct tty_struct *tty, unsigned int cmd,
249				unsigned long arg)
250{
251	int ret;
252	int i;
253
254	ret = 0;
255	switch(cmd) {
256#ifdef TIOCGETP
257	case TIOCGETP:
258	case TIOCSETP:
259	case TIOCSETN:
260#endif
261#ifdef TIOCGETC
262	case TIOCGETC:
263	case TIOCSETC:
264#endif
265#ifdef TIOCGLTC
266	case TIOCGLTC:
267	case TIOCSLTC:
268#endif
269	/* Note: these are out of date as we now have TCGETS2 etc but this
270	   whole lot should probably go away */
271	case TCGETS:
272	case TCSETSF:
273	case TCSETSW:
274	case TCSETS:
275	case TCGETA:
276	case TCSETAF:
277	case TCSETAW:
278	case TCSETA:
279	case TCXONC:
280	case TCFLSH:
281	case TIOCOUTQ:
282	case TIOCINQ:
283	case TIOCGLCKTRMIOS:
284	case TIOCSLCKTRMIOS:
285	case TIOCPKT:
286	case TIOCGSOFTCAR:
287	case TIOCSSOFTCAR:
288		return -ENOIOCTLCMD;
289#if 0
290	case TCwhatever:
291		/* do something */
292		break;
293#endif
294	default:
295		for (i = 0; i < ARRAY_SIZE(tty_ioctls); i++)
296			if (cmd == tty_ioctls[i].cmd)
297				break;
298		if (i == ARRAY_SIZE(tty_ioctls)) {
299			printk(KERN_ERR "%s: %s: unknown ioctl: 0x%x\n",
300			       __func__, tty->name, cmd);
301		}
302		ret = -ENOIOCTLCMD;
303		break;
304	}
305	return ret;
306}
307
308void line_throttle(struct tty_struct *tty)
309{
310	struct line *line = tty->driver_data;
311
312	deactivate_chan(line->chan_in, line->driver->read_irq);
313	line->throttled = 1;
314}
315
316void line_unthrottle(struct tty_struct *tty)
317{
318	struct line *line = tty->driver_data;
319
320	line->throttled = 0;
321	chan_interrupt(line, tty, line->driver->read_irq);
322
323	/*
324	 * Maybe there is enough stuff pending that calling the interrupt
325	 * throttles us again.  In this case, line->throttled will be 1
326	 * again and we shouldn't turn the interrupt back on.
327	 */
328	if (!line->throttled)
329		reactivate_chan(line->chan_in, line->driver->read_irq);
330}
331
332static irqreturn_t line_write_interrupt(int irq, void *data)
333{
334	struct chan *chan = data;
335	struct line *line = chan->line;
336	struct tty_struct *tty = line->tty;
337	int err;
338
339	/*
340	 * Interrupts are disabled here because genirq keep irqs disabled when
341	 * calling the action handler.
342	 */
343
344	spin_lock(&line->lock);
345	err = flush_buffer(line);
346	if (err == 0) {
347		spin_unlock(&line->lock);
348		return IRQ_NONE;
349	} else if (err < 0) {
350		line->head = line->buffer;
351		line->tail = line->buffer;
352	}
353	spin_unlock(&line->lock);
354
355	if (tty == NULL)
356		return IRQ_NONE;
357
358	tty_wakeup(tty);
359	return IRQ_HANDLED;
360}
361
362int line_setup_irq(int fd, int input, int output, struct line *line, void *data)
363{
364	const struct line_driver *driver = line->driver;
365	int err = 0, flags = IRQF_SHARED | IRQF_SAMPLE_RANDOM;
366
367	if (input)
368		err = um_request_irq(driver->read_irq, fd, IRQ_READ,
369				       line_interrupt, flags,
370				       driver->read_irq_name, data);
371	if (err)
372		return err;
373	if (output)
374		err = um_request_irq(driver->write_irq, fd, IRQ_WRITE,
375					line_write_interrupt, flags,
376					driver->write_irq_name, data);
377	return err;
378}
379
380/*
381 * Normally, a driver like this can rely mostly on the tty layer
382 * locking, particularly when it comes to the driver structure.
383 * However, in this case, mconsole requests can come in "from the
384 * side", and race with opens and closes.
385 *
386 * mconsole config requests will want to be sure the device isn't in
387 * use, and get_config, open, and close will want a stable
388 * configuration.  The checking and modification of the configuration
389 * is done under a spinlock.  Checking whether the device is in use is
390 * line->tty->count > 1, also under the spinlock.
391 *
392 * line->count serves to decide whether the device should be enabled or
393 * disabled on the host.  If it's equal to 0, then we are doing the
394 * first open or last close.  Otherwise, open and close just return.
395 */
396
397int line_open(struct line *lines, struct tty_struct *tty)
398{
399	struct line *line = &lines[tty->index];
400	int err = -ENODEV;
401
402	mutex_lock(&line->count_lock);
403	if (!line->valid)
404		goto out_unlock;
405
406	err = 0;
407	if (line->count++)
408		goto out_unlock;
409
410	BUG_ON(tty->driver_data);
411	tty->driver_data = line;
412	line->tty = tty;
413
414	err = enable_chan(line);
415	if (err) /* line_close() will be called by our caller */
416		goto out_unlock;
417
418	if (!line->sigio) {
419		chan_enable_winch(line->chan_out, tty);
420		line->sigio = 1;
421	}
422
423	chan_window_size(line, &tty->winsize.ws_row,
424			 &tty->winsize.ws_col);
425out_unlock:
426	mutex_unlock(&line->count_lock);
427	return err;
428}
429
430static void unregister_winch(struct tty_struct *tty);
431
432void line_close(struct tty_struct *tty, struct file * filp)
433{
 
434	struct line *line = tty->driver_data;
435
436	/*
437	 * If line_open fails (and tty->driver_data is never set),
438	 * tty_open will call line_close.  So just return in this case.
439	 */
440	if (line == NULL)
441		return;
442
443	/* We ignore the error anyway! */
444	flush_buffer(line);
 
 
445
446	mutex_lock(&line->count_lock);
447	BUG_ON(!line->valid);
 
448
449	if (--line->count)
450		goto out_unlock;
451
452	line->tty = NULL;
453	tty->driver_data = NULL;
 
 
454
455	if (line->sigio) {
456		unregister_winch(tty);
457		line->sigio = 0;
458	}
459
460out_unlock:
461	mutex_unlock(&line->count_lock);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
462}
463
464void close_lines(struct line *lines, int nlines)
465{
466	int i;
467
468	for(i = 0; i < nlines; i++)
469		close_chan(&lines[i]);
470}
471
472int setup_one_line(struct line *lines, int n, char *init,
473		   const struct chan_opts *opts, char **error_out)
474{
475	struct line *line = &lines[n];
476	struct tty_driver *driver = line->driver->driver;
477	int err = -EINVAL;
478
479	mutex_lock(&line->count_lock);
480
481	if (line->count) {
482		*error_out = "Device is already open";
483		goto out;
484	}
485
486	if (!strcmp(init, "none")) {
487		if (line->valid) {
488			line->valid = 0;
489			kfree(line->init_str);
490			tty_unregister_device(driver, n);
491			parse_chan_pair(NULL, line, n, opts, error_out);
492			err = 0;
493		}
494	} else {
495		char *new = kstrdup(init, GFP_KERNEL);
496		if (!new) {
497			*error_out = "Failed to allocate memory";
498			return -ENOMEM;
499		}
500		if (line->valid) {
501			tty_unregister_device(driver, n);
502			kfree(line->init_str);
503		}
504		line->init_str = new;
505		line->valid = 1;
506		err = parse_chan_pair(new, line, n, opts, error_out);
507		if (!err) {
508			struct device *d = tty_register_device(driver, n, NULL);
 
509			if (IS_ERR(d)) {
510				*error_out = "Failed to register device";
511				err = PTR_ERR(d);
512				parse_chan_pair(NULL, line, n, opts, error_out);
513			}
514		}
515		if (err) {
516			line->init_str = NULL;
517			line->valid = 0;
518			kfree(new);
519		}
520	}
521out:
522	mutex_unlock(&line->count_lock);
523	return err;
524}
525
526/*
527 * Common setup code for both startup command line and mconsole initialization.
528 * @lines contains the array (of size @num) to modify;
529 * @init is the setup string;
530 * @error_out is an error string in the case of failure;
531 */
532
533int line_setup(char **conf, unsigned int num, char **def,
534	       char *init, char *name)
535{
536	char *error;
537
538	if (*init == '=') {
539		/*
540		 * We said con=/ssl= instead of con#=, so we are configuring all
541		 * consoles at once.
542		 */
543		*def = init + 1;
544	} else {
545		char *end;
546		unsigned n = simple_strtoul(init, &end, 0);
547
548		if (*end != '=') {
549			error = "Couldn't parse device number";
550			goto out;
551		}
552		if (n >= num) {
553			error = "Device number out of range";
554			goto out;
555		}
556		conf[n] = end + 1;
557	}
558	return 0;
559
560out:
561	printk(KERN_ERR "Failed to set up %s with "
562	       "configuration string \"%s\" : %s\n", name, init, error);
563	return -EINVAL;
564}
565
566int line_config(struct line *lines, unsigned int num, char *str,
567		const struct chan_opts *opts, char **error_out)
568{
569	char *end;
570	int n;
571
572	if (*str == '=') {
573		*error_out = "Can't configure all devices from mconsole";
574		return -EINVAL;
575	}
576
577	n = simple_strtoul(str, &end, 0);
578	if (*end++ != '=') {
579		*error_out = "Couldn't parse device number";
580		return -EINVAL;
581	}
582	if (n >= num) {
583		*error_out = "Device number out of range";
584		return -EINVAL;
585	}
586
587	return setup_one_line(lines, n, end, opts, error_out);
588}
589
590int line_get_config(char *name, struct line *lines, unsigned int num, char *str,
591		    int size, char **error_out)
592{
593	struct line *line;
594	char *end;
595	int dev, n = 0;
596
597	dev = simple_strtoul(name, &end, 0);
598	if ((*end != '\0') || (end == name)) {
599		*error_out = "line_get_config failed to parse device number";
600		return 0;
601	}
602
603	if ((dev < 0) || (dev >= num)) {
604		*error_out = "device number out of range";
605		return 0;
606	}
607
608	line = &lines[dev];
609
610	mutex_lock(&line->count_lock);
611	if (!line->valid)
612		CONFIG_CHUNK(str, size, n, "none", 1);
613	else if (line->tty == NULL)
614		CONFIG_CHUNK(str, size, n, line->init_str, 1);
615	else n = chan_config_string(line, str, size, error_out);
616	mutex_unlock(&line->count_lock);
 
 
 
 
 
617
618	return n;
619}
620
621int line_id(char **str, int *start_out, int *end_out)
622{
623	char *end;
624	int n;
625
626	n = simple_strtoul(*str, &end, 0);
627	if ((*end != '\0') || (end == *str))
628		return -1;
629
630	*str = end;
631	*start_out = n;
632	*end_out = n;
633	return n;
634}
635
636int line_remove(struct line *lines, unsigned int num, int n, char **error_out)
637{
638	if (n >= num) {
639		*error_out = "Device number out of range";
640		return -EINVAL;
641	}
642	return setup_one_line(lines, n, "none", NULL, error_out);
643}
644
645int register_lines(struct line_driver *line_driver,
646		   const struct tty_operations *ops,
647		   struct line *lines, int nlines)
648{
649	struct tty_driver *driver = alloc_tty_driver(nlines);
650	int err;
651	int i;
652
653	if (!driver)
654		return -ENOMEM;
655
656	driver->driver_name = line_driver->name;
657	driver->name = line_driver->device_name;
658	driver->major = line_driver->major;
659	driver->minor_start = line_driver->minor_start;
660	driver->type = line_driver->type;
661	driver->subtype = line_driver->subtype;
662	driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
663	driver->init_termios = tty_std_termios;
664	
665	for (i = 0; i < nlines; i++) {
 
 
666		spin_lock_init(&lines[i].lock);
667		mutex_init(&lines[i].count_lock);
668		lines[i].driver = line_driver;
669		INIT_LIST_HEAD(&lines[i].chan_list);
670	}
671	tty_set_operations(driver, ops);
672
673	err = tty_register_driver(driver);
674	if (err) {
675		printk(KERN_ERR "register_lines : can't register %s driver\n",
676		       line_driver->name);
677		put_tty_driver(driver);
 
 
678		return err;
679	}
680
681	line_driver->driver = driver;
682	mconsole_register_dev(&line_driver->mc);
683	return 0;
684}
685
686static DEFINE_SPINLOCK(winch_handler_lock);
687static LIST_HEAD(winch_handlers);
688
689struct winch {
690	struct list_head list;
691	int fd;
692	int tty_fd;
693	int pid;
694	struct tty_struct *tty;
695	unsigned long stack;
696	struct work_struct work;
697};
698
699static void __free_winch(struct work_struct *work)
700{
701	struct winch *winch = container_of(work, struct winch, work);
702	um_free_irq(WINCH_IRQ, winch);
703
704	if (winch->pid != -1)
705		os_kill_process(winch->pid, 1);
706	if (winch->stack != 0)
707		free_stack(winch->stack, 0);
708	kfree(winch);
709}
710
711static void free_winch(struct winch *winch)
712{
713	int fd = winch->fd;
714	winch->fd = -1;
715	if (fd != -1)
716		os_close_file(fd);
717	list_del(&winch->list);
718	__free_winch(&winch->work);
719}
720
721static irqreturn_t winch_interrupt(int irq, void *data)
722{
723	struct winch *winch = data;
724	struct tty_struct *tty;
725	struct line *line;
726	int fd = winch->fd;
727	int err;
728	char c;
 
729
730	if (fd != -1) {
731		err = generic_read(fd, &c, NULL);
732		if (err < 0) {
733			if (err != -EAGAIN) {
734				winch->fd = -1;
735				list_del(&winch->list);
736				os_close_file(fd);
737				printk(KERN_ERR "winch_interrupt : "
738				       "read failed, errno = %d\n", -err);
739				printk(KERN_ERR "fd %d is losing SIGWINCH "
740				       "support\n", winch->tty_fd);
741				INIT_WORK(&winch->work, __free_winch);
742				schedule_work(&winch->work);
743				return IRQ_HANDLED;
744			}
745			goto out;
746		}
747	}
748	tty = winch->tty;
749	if (tty != NULL) {
750		line = tty->driver_data;
751		if (line != NULL) {
752			chan_window_size(line, &tty->winsize.ws_row,
753					 &tty->winsize.ws_col);
754			kill_pgrp(tty->pgrp, SIGWINCH, 1);
 
 
 
755		}
 
756	}
757 out:
758	if (winch->fd != -1)
759		reactivate_fd(winch->fd, WINCH_IRQ);
760	return IRQ_HANDLED;
761}
762
763void register_winch_irq(int fd, int tty_fd, int pid, struct tty_struct *tty,
764			unsigned long stack)
765{
766	struct winch *winch;
767
768	winch = kmalloc(sizeof(*winch), GFP_KERNEL);
769	if (winch == NULL) {
770		printk(KERN_ERR "register_winch_irq - kmalloc failed\n");
771		goto cleanup;
772	}
773
774	*winch = ((struct winch) { .list  	= LIST_HEAD_INIT(winch->list),
775				   .fd  	= fd,
776				   .tty_fd 	= tty_fd,
777				   .pid  	= pid,
778				   .tty 	= tty,
779				   .stack	= stack });
780
781	if (um_request_irq(WINCH_IRQ, fd, IRQ_READ, winch_interrupt,
782			   IRQF_SHARED | IRQF_SAMPLE_RANDOM,
783			   "winch", winch) < 0) {
784		printk(KERN_ERR "register_winch_irq - failed to register "
785		       "IRQ\n");
786		goto out_free;
787	}
788
789	spin_lock(&winch_handler_lock);
790	list_add(&winch->list, &winch_handlers);
791	spin_unlock(&winch_handler_lock);
792
793	return;
794
795 out_free:
796	kfree(winch);
797 cleanup:
798	os_kill_process(pid, 1);
799	os_close_file(fd);
800	if (stack != 0)
801		free_stack(stack, 0);
802}
803
804static void unregister_winch(struct tty_struct *tty)
805{
806	struct list_head *ele, *next;
807	struct winch *winch;
 
808
809	spin_lock(&winch_handler_lock);
810
811	list_for_each_safe(ele, next, &winch_handlers) {
812		winch = list_entry(ele, struct winch, list);
813		if (winch->tty == tty) {
 
814			free_winch(winch);
815			break;
816		}
 
817	}
818	spin_unlock(&winch_handler_lock);
819}
820
821static void winch_cleanup(void)
822{
823	struct list_head *ele, *next;
824	struct winch *winch;
825
826	spin_lock(&winch_handler_lock);
827
828	list_for_each_safe(ele, next, &winch_handlers) {
829		winch = list_entry(ele, struct winch, list);
830		free_winch(winch);
831	}
832
833	spin_unlock(&winch_handler_lock);
834}
835__uml_exitcall(winch_cleanup);
836
837char *add_xterm_umid(char *base)
838{
839	char *umid, *title;
840	int len;
841
842	umid = get_umid();
843	if (*umid == '\0')
844		return base;
845
846	len = strlen(base) + strlen(" ()") + strlen(umid) + 1;
847	title = kmalloc(len, GFP_KERNEL);
848	if (title == NULL) {
849		printk(KERN_ERR "Failed to allocate buffer for xterm title\n");
850		return base;
851	}
852
853	snprintf(title, len, "%s (%s)", base, umid);
854	return title;
855}