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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 
line_interrupt(int irq,void * data)18 static 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, irq);
25 
26 	return IRQ_HANDLED;
27 }
28 
29 /*
30  * Returns the free space inside the ring buffer of this line.
31  *
32  * Should be called while holding line->lock (this does not modify data).
33  */
write_room(struct line * line)34 static int write_room(struct line *line)
35 {
36 	int n;
37 
38 	if (line->buffer == NULL)
39 		return LINE_BUFSIZE - 1;
40 
41 	/* This is for the case where the buffer is wrapped! */
42 	n = line->head - line->tail;
43 
44 	if (n <= 0)
45 		n += LINE_BUFSIZE; /* The other case */
46 	return n - 1;
47 }
48 
line_write_room(struct tty_struct * tty)49 int line_write_room(struct tty_struct *tty)
50 {
51 	struct line *line = tty->driver_data;
52 	unsigned long flags;
53 	int room;
54 
55 	spin_lock_irqsave(&line->lock, flags);
56 	room = write_room(line);
57 	spin_unlock_irqrestore(&line->lock, flags);
58 
59 	return room;
60 }
61 
line_chars_in_buffer(struct tty_struct * tty)62 int line_chars_in_buffer(struct tty_struct *tty)
63 {
64 	struct line *line = tty->driver_data;
65 	unsigned long flags;
66 	int ret;
67 
68 	spin_lock_irqsave(&line->lock, flags);
69 	/* write_room subtracts 1 for the needed NULL, so we readd it.*/
70 	ret = LINE_BUFSIZE - (write_room(line) + 1);
71 	spin_unlock_irqrestore(&line->lock, flags);
72 
73 	return ret;
74 }
75 
76 /*
77  * This copies the content of buf into the circular buffer associated with
78  * this line.
79  * The return value is the number of characters actually copied, i.e. the ones
80  * for which there was space: this function is not supposed to ever flush out
81  * the circular buffer.
82  *
83  * Must be called while holding line->lock!
84  */
buffer_data(struct line * line,const char * buf,int len)85 static int buffer_data(struct line *line, const char *buf, int len)
86 {
87 	int end, room;
88 
89 	if (line->buffer == NULL) {
90 		line->buffer = kmalloc(LINE_BUFSIZE, GFP_ATOMIC);
91 		if (line->buffer == NULL) {
92 			printk(KERN_ERR "buffer_data - atomic allocation "
93 			       "failed\n");
94 			return 0;
95 		}
96 		line->head = line->buffer;
97 		line->tail = line->buffer;
98 	}
99 
100 	room = write_room(line);
101 	len = (len > room) ? room : len;
102 
103 	end = line->buffer + LINE_BUFSIZE - line->tail;
104 
105 	if (len < end) {
106 		memcpy(line->tail, buf, len);
107 		line->tail += len;
108 	}
109 	else {
110 		/* The circular buffer is wrapping */
111 		memcpy(line->tail, buf, end);
112 		buf += end;
113 		memcpy(line->buffer, buf, len - end);
114 		line->tail = line->buffer + len - end;
115 	}
116 
117 	return len;
118 }
119 
120 /*
121  * Flushes the ring buffer to the output channels. That is, write_chan is
122  * called, passing it line->head as buffer, and an appropriate count.
123  *
124  * On exit, returns 1 when the buffer is empty,
125  * 0 when the buffer is not empty on exit,
126  * and -errno when an error occurred.
127  *
128  * Must be called while holding line->lock!*/
flush_buffer(struct line * line)129 static int flush_buffer(struct line *line)
130 {
131 	int n, count;
132 
133 	if ((line->buffer == NULL) || (line->head == line->tail))
134 		return 1;
135 
136 	if (line->tail < line->head) {
137 		/* line->buffer + LINE_BUFSIZE is the end of the buffer! */
138 		count = line->buffer + LINE_BUFSIZE - line->head;
139 
140 		n = write_chan(line->chan_out, line->head, count,
141 			       line->driver->write_irq);
142 		if (n < 0)
143 			return n;
144 		if (n == count) {
145 			/*
146 			 * We have flushed from ->head to buffer end, now we
147 			 * must flush only from the beginning to ->tail.
148 			 */
149 			line->head = line->buffer;
150 		} else {
151 			line->head += n;
152 			return 0;
153 		}
154 	}
155 
156 	count = line->tail - line->head;
157 	n = write_chan(line->chan_out, line->head, count,
158 		       line->driver->write_irq);
159 
160 	if (n < 0)
161 		return n;
162 
163 	line->head += n;
164 	return line->head == line->tail;
165 }
166 
line_flush_buffer(struct tty_struct * tty)167 void line_flush_buffer(struct tty_struct *tty)
168 {
169 	struct line *line = tty->driver_data;
170 	unsigned long flags;
171 
172 	spin_lock_irqsave(&line->lock, flags);
173 	flush_buffer(line);
174 	spin_unlock_irqrestore(&line->lock, flags);
175 }
176 
177 /*
178  * We map both ->flush_chars and ->put_char (which go in pair) onto
179  * ->flush_buffer and ->write. Hope it's not that bad.
180  */
line_flush_chars(struct tty_struct * tty)181 void line_flush_chars(struct tty_struct *tty)
182 {
183 	line_flush_buffer(tty);
184 }
185 
line_put_char(struct tty_struct * tty,unsigned char ch)186 int line_put_char(struct tty_struct *tty, unsigned char ch)
187 {
188 	return line_write(tty, &ch, sizeof(ch));
189 }
190 
line_write(struct tty_struct * tty,const unsigned char * buf,int len)191 int line_write(struct tty_struct *tty, const unsigned char *buf, int len)
192 {
193 	struct line *line = tty->driver_data;
194 	unsigned long flags;
195 	int n, ret = 0;
196 
197 	spin_lock_irqsave(&line->lock, flags);
198 	if (line->head != line->tail)
199 		ret = buffer_data(line, buf, len);
200 	else {
201 		n = write_chan(line->chan_out, buf, len,
202 			       line->driver->write_irq);
203 		if (n < 0) {
204 			ret = n;
205 			goto out_up;
206 		}
207 
208 		len -= n;
209 		ret += n;
210 		if (len > 0)
211 			ret += buffer_data(line, buf + n, len);
212 	}
213 out_up:
214 	spin_unlock_irqrestore(&line->lock, flags);
215 	return ret;
216 }
217 
line_set_termios(struct tty_struct * tty,struct ktermios * old)218 void line_set_termios(struct tty_struct *tty, struct ktermios * old)
219 {
220 	/* nothing */
221 }
222 
line_throttle(struct tty_struct * tty)223 void line_throttle(struct tty_struct *tty)
224 {
225 	struct line *line = tty->driver_data;
226 
227 	deactivate_chan(line->chan_in, line->driver->read_irq);
228 	line->throttled = 1;
229 }
230 
line_unthrottle(struct tty_struct * tty)231 void line_unthrottle(struct tty_struct *tty)
232 {
233 	struct line *line = tty->driver_data;
234 
235 	line->throttled = 0;
236 	chan_interrupt(line, line->driver->read_irq);
237 
238 	/*
239 	 * Maybe there is enough stuff pending that calling the interrupt
240 	 * throttles us again.  In this case, line->throttled will be 1
241 	 * again and we shouldn't turn the interrupt back on.
242 	 */
243 	if (!line->throttled)
244 		reactivate_chan(line->chan_in, line->driver->read_irq);
245 }
246 
line_write_interrupt(int irq,void * data)247 static irqreturn_t line_write_interrupt(int irq, void *data)
248 {
249 	struct chan *chan = data;
250 	struct line *line = chan->line;
251 	int err;
252 
253 	/*
254 	 * Interrupts are disabled here because genirq keep irqs disabled when
255 	 * calling the action handler.
256 	 */
257 
258 	spin_lock(&line->lock);
259 	err = flush_buffer(line);
260 	if (err == 0) {
261 		spin_unlock(&line->lock);
262 		return IRQ_NONE;
263 	} else if ((err < 0) && (err != -EAGAIN)) {
264 		line->head = line->buffer;
265 		line->tail = line->buffer;
266 	}
267 	spin_unlock(&line->lock);
268 
269 	tty_port_tty_wakeup(&line->port);
270 
271 	return IRQ_HANDLED;
272 }
273 
line_setup_irq(int fd,int input,int output,struct line * line,void * data)274 int line_setup_irq(int fd, int input, int output, struct line *line, void *data)
275 {
276 	const struct line_driver *driver = line->driver;
277 	int err = 0;
278 
279 	if (input)
280 		err = um_request_irq(driver->read_irq, fd, IRQ_READ,
281 				     line_interrupt, IRQF_SHARED,
282 				     driver->read_irq_name, data);
283 	if (err)
284 		return err;
285 	if (output)
286 		err = um_request_irq(driver->write_irq, fd, IRQ_WRITE,
287 				     line_write_interrupt, IRQF_SHARED,
288 				     driver->write_irq_name, data);
289 	return err;
290 }
291 
line_activate(struct tty_port * port,struct tty_struct * tty)292 static int line_activate(struct tty_port *port, struct tty_struct *tty)
293 {
294 	int ret;
295 	struct line *line = tty->driver_data;
296 
297 	ret = enable_chan(line);
298 	if (ret)
299 		return ret;
300 
301 	if (!line->sigio) {
302 		chan_enable_winch(line->chan_out, port);
303 		line->sigio = 1;
304 	}
305 
306 	chan_window_size(line, &tty->winsize.ws_row,
307 		&tty->winsize.ws_col);
308 
309 	return 0;
310 }
311 
312 static void unregister_winch(struct tty_struct *tty);
313 
line_destruct(struct tty_port * port)314 static void line_destruct(struct tty_port *port)
315 {
316 	struct tty_struct *tty = tty_port_tty_get(port);
317 	struct line *line = tty->driver_data;
318 
319 	if (line->sigio) {
320 		unregister_winch(tty);
321 		line->sigio = 0;
322 	}
323 }
324 
325 static const struct tty_port_operations line_port_ops = {
326 	.activate = line_activate,
327 	.destruct = line_destruct,
328 };
329 
line_open(struct tty_struct * tty,struct file * filp)330 int line_open(struct tty_struct *tty, struct file *filp)
331 {
332 	struct line *line = tty->driver_data;
333 
334 	return tty_port_open(&line->port, tty, filp);
335 }
336 
line_install(struct tty_driver * driver,struct tty_struct * tty,struct line * line)337 int line_install(struct tty_driver *driver, struct tty_struct *tty,
338 		 struct line *line)
339 {
340 	int ret;
341 
342 	ret = tty_standard_install(driver, tty);
343 	if (ret)
344 		return ret;
345 
346 	tty->driver_data = line;
347 
348 	return 0;
349 }
350 
line_close(struct tty_struct * tty,struct file * filp)351 void line_close(struct tty_struct *tty, struct file * filp)
352 {
353 	struct line *line = tty->driver_data;
354 
355 	tty_port_close(&line->port, tty, filp);
356 }
357 
line_hangup(struct tty_struct * tty)358 void line_hangup(struct tty_struct *tty)
359 {
360 	struct line *line = tty->driver_data;
361 
362 	tty_port_hangup(&line->port);
363 }
364 
close_lines(struct line * lines,int nlines)365 void close_lines(struct line *lines, int nlines)
366 {
367 	int i;
368 
369 	for(i = 0; i < nlines; i++)
370 		close_chan(&lines[i]);
371 }
372 
setup_one_line(struct line * lines,int n,char * init,const struct chan_opts * opts,char ** error_out)373 int setup_one_line(struct line *lines, int n, char *init,
374 		   const struct chan_opts *opts, char **error_out)
375 {
376 	struct line *line = &lines[n];
377 	struct tty_driver *driver = line->driver->driver;
378 	int err = -EINVAL;
379 
380 	if (line->port.count) {
381 		*error_out = "Device is already open";
382 		goto out;
383 	}
384 
385 	if (!strcmp(init, "none")) {
386 		if (line->valid) {
387 			line->valid = 0;
388 			kfree(line->init_str);
389 			tty_unregister_device(driver, n);
390 			parse_chan_pair(NULL, line, n, opts, error_out);
391 			err = 0;
392 		}
393 	} else {
394 		char *new = kstrdup(init, GFP_KERNEL);
395 		if (!new) {
396 			*error_out = "Failed to allocate memory";
397 			return -ENOMEM;
398 		}
399 		if (line->valid) {
400 			tty_unregister_device(driver, n);
401 			kfree(line->init_str);
402 		}
403 		line->init_str = new;
404 		line->valid = 1;
405 		err = parse_chan_pair(new, line, n, opts, error_out);
406 		if (!err) {
407 			struct device *d = tty_port_register_device(&line->port,
408 					driver, n, NULL);
409 			if (IS_ERR(d)) {
410 				*error_out = "Failed to register device";
411 				err = PTR_ERR(d);
412 				parse_chan_pair(NULL, line, n, opts, error_out);
413 			}
414 		}
415 		if (err) {
416 			line->init_str = NULL;
417 			line->valid = 0;
418 			kfree(new);
419 		}
420 	}
421 out:
422 	return err;
423 }
424 
425 /*
426  * Common setup code for both startup command line and mconsole initialization.
427  * @lines contains the array (of size @num) to modify;
428  * @init is the setup string;
429  * @error_out is an error string in the case of failure;
430  */
431 
line_setup(char ** conf,unsigned int num,char ** def,char * init,char * name)432 int line_setup(char **conf, unsigned int num, char **def,
433 	       char *init, char *name)
434 {
435 	char *error;
436 
437 	if (*init == '=') {
438 		/*
439 		 * We said con=/ssl= instead of con#=, so we are configuring all
440 		 * consoles at once.
441 		 */
442 		*def = init + 1;
443 	} else {
444 		char *end;
445 		unsigned n = simple_strtoul(init, &end, 0);
446 
447 		if (*end != '=') {
448 			error = "Couldn't parse device number";
449 			goto out;
450 		}
451 		if (n >= num) {
452 			error = "Device number out of range";
453 			goto out;
454 		}
455 		conf[n] = end + 1;
456 	}
457 	return 0;
458 
459 out:
460 	printk(KERN_ERR "Failed to set up %s with "
461 	       "configuration string \"%s\" : %s\n", name, init, error);
462 	return -EINVAL;
463 }
464 
line_config(struct line * lines,unsigned int num,char * str,const struct chan_opts * opts,char ** error_out)465 int line_config(struct line *lines, unsigned int num, char *str,
466 		const struct chan_opts *opts, char **error_out)
467 {
468 	char *end;
469 	int n;
470 
471 	if (*str == '=') {
472 		*error_out = "Can't configure all devices from mconsole";
473 		return -EINVAL;
474 	}
475 
476 	n = simple_strtoul(str, &end, 0);
477 	if (*end++ != '=') {
478 		*error_out = "Couldn't parse device number";
479 		return -EINVAL;
480 	}
481 	if (n >= num) {
482 		*error_out = "Device number out of range";
483 		return -EINVAL;
484 	}
485 
486 	return setup_one_line(lines, n, end, opts, error_out);
487 }
488 
line_get_config(char * name,struct line * lines,unsigned int num,char * str,int size,char ** error_out)489 int line_get_config(char *name, struct line *lines, unsigned int num, char *str,
490 		    int size, char **error_out)
491 {
492 	struct line *line;
493 	char *end;
494 	int dev, n = 0;
495 
496 	dev = simple_strtoul(name, &end, 0);
497 	if ((*end != '\0') || (end == name)) {
498 		*error_out = "line_get_config failed to parse device number";
499 		return 0;
500 	}
501 
502 	if ((dev < 0) || (dev >= num)) {
503 		*error_out = "device number out of range";
504 		return 0;
505 	}
506 
507 	line = &lines[dev];
508 
509 	if (!line->valid)
510 		CONFIG_CHUNK(str, size, n, "none", 1);
511 	else {
512 		struct tty_struct *tty = tty_port_tty_get(&line->port);
513 		if (tty == NULL) {
514 			CONFIG_CHUNK(str, size, n, line->init_str, 1);
515 		} else {
516 			n = chan_config_string(line, str, size, error_out);
517 			tty_kref_put(tty);
518 		}
519 	}
520 
521 	return n;
522 }
523 
line_id(char ** str,int * start_out,int * end_out)524 int line_id(char **str, int *start_out, int *end_out)
525 {
526 	char *end;
527 	int n;
528 
529 	n = simple_strtoul(*str, &end, 0);
530 	if ((*end != '\0') || (end == *str))
531 		return -1;
532 
533 	*str = end;
534 	*start_out = n;
535 	*end_out = n;
536 	return n;
537 }
538 
line_remove(struct line * lines,unsigned int num,int n,char ** error_out)539 int line_remove(struct line *lines, unsigned int num, int n, char **error_out)
540 {
541 	if (n >= num) {
542 		*error_out = "Device number out of range";
543 		return -EINVAL;
544 	}
545 	return setup_one_line(lines, n, "none", NULL, error_out);
546 }
547 
register_lines(struct line_driver * line_driver,const struct tty_operations * ops,struct line * lines,int nlines)548 int register_lines(struct line_driver *line_driver,
549 		   const struct tty_operations *ops,
550 		   struct line *lines, int nlines)
551 {
552 	struct tty_driver *driver = alloc_tty_driver(nlines);
553 	int err;
554 	int i;
555 
556 	if (!driver)
557 		return -ENOMEM;
558 
559 	driver->driver_name = line_driver->name;
560 	driver->name = line_driver->device_name;
561 	driver->major = line_driver->major;
562 	driver->minor_start = line_driver->minor_start;
563 	driver->type = line_driver->type;
564 	driver->subtype = line_driver->subtype;
565 	driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
566 	driver->init_termios = tty_std_termios;
567 
568 	for (i = 0; i < nlines; i++) {
569 		tty_port_init(&lines[i].port);
570 		lines[i].port.ops = &line_port_ops;
571 		spin_lock_init(&lines[i].lock);
572 		lines[i].driver = line_driver;
573 		INIT_LIST_HEAD(&lines[i].chan_list);
574 	}
575 	tty_set_operations(driver, ops);
576 
577 	err = tty_register_driver(driver);
578 	if (err) {
579 		printk(KERN_ERR "register_lines : can't register %s driver\n",
580 		       line_driver->name);
581 		put_tty_driver(driver);
582 		for (i = 0; i < nlines; i++)
583 			tty_port_destroy(&lines[i].port);
584 		return err;
585 	}
586 
587 	line_driver->driver = driver;
588 	mconsole_register_dev(&line_driver->mc);
589 	return 0;
590 }
591 
592 static DEFINE_SPINLOCK(winch_handler_lock);
593 static LIST_HEAD(winch_handlers);
594 
595 struct winch {
596 	struct list_head list;
597 	int fd;
598 	int tty_fd;
599 	int pid;
600 	struct tty_port *port;
601 	unsigned long stack;
602 	struct work_struct work;
603 };
604 
__free_winch(struct work_struct * work)605 static void __free_winch(struct work_struct *work)
606 {
607 	struct winch *winch = container_of(work, struct winch, work);
608 	um_free_irq(WINCH_IRQ, winch);
609 
610 	if (winch->pid != -1)
611 		os_kill_process(winch->pid, 1);
612 	if (winch->stack != 0)
613 		free_stack(winch->stack, 0);
614 	kfree(winch);
615 }
616 
free_winch(struct winch * winch)617 static void free_winch(struct winch *winch)
618 {
619 	int fd = winch->fd;
620 	winch->fd = -1;
621 	if (fd != -1)
622 		os_close_file(fd);
623 	list_del(&winch->list);
624 	__free_winch(&winch->work);
625 }
626 
winch_interrupt(int irq,void * data)627 static irqreturn_t winch_interrupt(int irq, void *data)
628 {
629 	struct winch *winch = data;
630 	struct tty_struct *tty;
631 	struct line *line;
632 	int fd = winch->fd;
633 	int err;
634 	char c;
635 	struct pid *pgrp;
636 
637 	if (fd != -1) {
638 		err = generic_read(fd, &c, NULL);
639 		if (err < 0) {
640 			if (err != -EAGAIN) {
641 				winch->fd = -1;
642 				list_del(&winch->list);
643 				os_close_file(fd);
644 				printk(KERN_ERR "winch_interrupt : "
645 				       "read failed, errno = %d\n", -err);
646 				printk(KERN_ERR "fd %d is losing SIGWINCH "
647 				       "support\n", winch->tty_fd);
648 				INIT_WORK(&winch->work, __free_winch);
649 				schedule_work(&winch->work);
650 				return IRQ_HANDLED;
651 			}
652 			goto out;
653 		}
654 	}
655 	tty = tty_port_tty_get(winch->port);
656 	if (tty != NULL) {
657 		line = tty->driver_data;
658 		if (line != NULL) {
659 			chan_window_size(line, &tty->winsize.ws_row,
660 					 &tty->winsize.ws_col);
661 			pgrp = tty_get_pgrp(tty);
662 			if (pgrp)
663 				kill_pgrp(pgrp, SIGWINCH, 1);
664 			put_pid(pgrp);
665 		}
666 		tty_kref_put(tty);
667 	}
668  out:
669 	if (winch->fd != -1)
670 		reactivate_fd(winch->fd, WINCH_IRQ);
671 	return IRQ_HANDLED;
672 }
673 
register_winch_irq(int fd,int tty_fd,int pid,struct tty_port * port,unsigned long stack)674 void register_winch_irq(int fd, int tty_fd, int pid, struct tty_port *port,
675 			unsigned long stack)
676 {
677 	struct winch *winch;
678 
679 	winch = kmalloc(sizeof(*winch), GFP_KERNEL);
680 	if (winch == NULL) {
681 		printk(KERN_ERR "register_winch_irq - kmalloc failed\n");
682 		goto cleanup;
683 	}
684 
685 	*winch = ((struct winch) { .list  	= LIST_HEAD_INIT(winch->list),
686 				   .fd  	= fd,
687 				   .tty_fd 	= tty_fd,
688 				   .pid  	= pid,
689 				   .port 	= port,
690 				   .stack	= stack });
691 
692 	if (um_request_irq(WINCH_IRQ, fd, IRQ_READ, winch_interrupt,
693 			   IRQF_SHARED, "winch", winch) < 0) {
694 		printk(KERN_ERR "register_winch_irq - failed to register "
695 		       "IRQ\n");
696 		goto out_free;
697 	}
698 
699 	spin_lock(&winch_handler_lock);
700 	list_add(&winch->list, &winch_handlers);
701 	spin_unlock(&winch_handler_lock);
702 
703 	return;
704 
705  out_free:
706 	kfree(winch);
707  cleanup:
708 	os_kill_process(pid, 1);
709 	os_close_file(fd);
710 	if (stack != 0)
711 		free_stack(stack, 0);
712 }
713 
unregister_winch(struct tty_struct * tty)714 static void unregister_winch(struct tty_struct *tty)
715 {
716 	struct list_head *ele, *next;
717 	struct winch *winch;
718 	struct tty_struct *wtty;
719 
720 	spin_lock(&winch_handler_lock);
721 
722 	list_for_each_safe(ele, next, &winch_handlers) {
723 		winch = list_entry(ele, struct winch, list);
724 		wtty = tty_port_tty_get(winch->port);
725 		if (wtty == tty) {
726 			free_winch(winch);
727 			break;
728 		}
729 		tty_kref_put(wtty);
730 	}
731 	spin_unlock(&winch_handler_lock);
732 }
733 
winch_cleanup(void)734 static void winch_cleanup(void)
735 {
736 	struct list_head *ele, *next;
737 	struct winch *winch;
738 
739 	spin_lock(&winch_handler_lock);
740 
741 	list_for_each_safe(ele, next, &winch_handlers) {
742 		winch = list_entry(ele, struct winch, list);
743 		free_winch(winch);
744 	}
745 
746 	spin_unlock(&winch_handler_lock);
747 }
748 __uml_exitcall(winch_cleanup);
749 
add_xterm_umid(char * base)750 char *add_xterm_umid(char *base)
751 {
752 	char *umid, *title;
753 	int len;
754 
755 	umid = get_umid();
756 	if (*umid == '\0')
757 		return base;
758 
759 	len = strlen(base) + strlen(" ()") + strlen(umid) + 1;
760 	title = kmalloc(len, GFP_KERNEL);
761 	if (title == NULL) {
762 		printk(KERN_ERR "Failed to allocate buffer for xterm title\n");
763 		return base;
764 	}
765 
766 	snprintf(title, len, "%s (%s)", base, umid);
767 	return title;
768 }
769