summaryrefslogtreecommitdiffstats
path: root/arch/um/drivers/mconsole_kern.c
blob: 5026e7b9adfe54960544600244e5b6b59cc15c7e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2001 Lennert Buytenhek (buytenh@gnu.org)
 * Copyright (C) 2001 - 2008 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 */

#include <linux/console.h>
#include <linux/ctype.h>
#include <linux/string.h>
#include <linux/interrupt.h>
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/panic_notifier.h>
#include <linux/reboot.h>
#include <linux/sched/debug.h>
#include <linux/proc_fs.h>
#include <linux/slab.h>
#include <linux/syscalls.h>
#include <linux/utsname.h>
#include <linux/socket.h>
#include <linux/un.h>
#include <linux/workqueue.h>
#include <linux/mutex.h>
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/file.h>
#include <linux/uaccess.h>
#include <asm/switch_to.h>

#include <init.h>
#include <irq_kern.h>
#include <irq_user.h>
#include <kern_util.h>
#include "mconsole.h"
#include "mconsole_kern.h"
#include <os.h>

static struct vfsmount *proc_mnt = NULL;

static int do_unlink_socket(struct notifier_block *notifier,
			    unsigned long what, void *data)
{
	return mconsole_unlink_socket();
}


static struct notifier_block reboot_notifier = {
	.notifier_call		= do_unlink_socket,
	.priority		= 0,
};

/* Safe without explicit locking for now.  Tasklets provide their own
 * locking, and the interrupt handler is safe because it can't interrupt
 * itself and it can only happen on CPU 0.
 */

static LIST_HEAD(mc_requests);

static void mc_work_proc(struct work_struct *unused)
{
	struct mconsole_entry *req;
	unsigned long flags;

	while (!list_empty(&mc_requests)) {
		local_irq_save(flags);
		req = list_entry(mc_requests.next, struct mconsole_entry, list);
		list_del(&req->list);
		local_irq_restore(flags);
		req->request.cmd->handler(&req->request);
		kfree(req);
	}
}

static DECLARE_WORK(mconsole_work, mc_work_proc);

static irqreturn_t mconsole_interrupt(int irq, void *dev_id)
{
	/* long to avoid size mismatch warnings from gcc */
	long fd;
	struct mconsole_entry *new;
	static struct mc_request req;	/* that's OK */

	fd = (long) dev_id;
	while (mconsole_get_request(fd, &req)) {
		if (req.cmd->context == MCONSOLE_INTR)
			(*req.cmd->handler)(&req);
		else {
			new = kmalloc(sizeof(*new), GFP_NOWAIT);
			if (new == NULL)
				mconsole_reply(&req, "Out of memory", 1, 0);
			else {
				new->request = req;
				new->request.regs = get_irq_regs()->regs;
				list_add(&new->list, &mc_requests);
			}
		}
	}
	if (!list_empty(&mc_requests))
		schedule_work(&mconsole_work);
	return IRQ_HANDLED;
}

void mconsole_version(struct mc_request *req)
{
	char version[256];

	sprintf(version, "%s %s %s %s %s", utsname()->sysname,
		utsname()->nodename, utsname()->release, utsname()->version,
		utsname()->machine);
	mconsole_reply(req, version, 0, 0);
}

void mconsole_log(struct mc_request *req)
{
	int len;
	char *ptr = req->request.data;

	ptr += strlen("log ");

	len = req->len - (ptr - req->request.data);
	printk(KERN_WARNING "%.*s", len, ptr);
	mconsole_reply(req, "", 0, 0);
}

void mconsole_proc(struct mc_request *req)
{
	struct vfsmount *mnt = proc_mnt;
	char *buf;
	int len;
	struct file *file;
	int first_chunk = 1;
	char *ptr = req->request.data;
	loff_t pos = 0;

	ptr += strlen("proc");
	ptr = skip_spaces(ptr);

	if (!mnt) {
		mconsole_reply(req, "Proc not available", 1, 0);
		goto out;
	}
	file = file_open_root_mnt(mnt, ptr, O_RDONLY, 0);
	if (IS_ERR(file)) {
		mconsole_reply(req, "Failed to open file", 1, 0);
		printk(KERN_ERR "open /proc/%s: %ld\n", ptr, PTR_ERR(file));
		goto out;
	}

	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
	if (buf == NULL) {
		mconsole_reply(req, "Failed to allocate buffer", 1, 0);
		goto out_fput;
	}

	do {
		len = kernel_read(file, buf, PAGE_SIZE - 1, &pos);
		if (len < 0) {
			mconsole_reply(req, "Read of file failed", 1, 0);
			goto out_free;
		}
		/* Begin the file content on his own line. */
		if (first_chunk) {
			mconsole_reply(req, "\n", 0, 1);
			first_chunk = 0;
		}
		buf[len] = '\0';
		mconsole_reply(req, buf, 0, (len > 0));
	} while (len > 0);
 out_free:
	kfree(buf);
 out_fput:
	fput(file);
 out: ;
}

#define UML_MCONSOLE_HELPTEXT \
"Commands: \n\
    version - Get kernel version \n\
    help - Print this message \n\
    halt - Halt UML \n\
    reboot - Reboot UML \n\
    config <dev>=<config> - Add a new device to UML;  \n\
	same syntax as command line \n\
    config <dev> - Query the configuration of a device \n\
    remove <dev> - Remove a device from UML \n\
    sysrq <letter> - Performs the SysRq action controlled by the letter \n\
    cad - invoke the Ctrl-Alt-Del handler \n\
    stop - pause the UML; it will do nothing until it receives a 'go' \n\
    go - continue the UML after a 'stop' \n\
    log <string> - make UML enter <string> into the kernel log\n\
    proc <file> - returns the contents of the UML's /proc/<file>\n\
    stack <pid> - returns the stack of the specified pid\n\
"

void mconsole_help(struct mc_request *req)
{
	mconsole_reply(req, UML_MCONSOLE_HELPTEXT, 0, 0);
}

void mconsole_halt(struct mc_request *req)
{
	mconsole_reply(req, "", 0, 0);
	machine_halt();
}

void mconsole_reboot(struct mc_request *req)
{
	mconsole_reply(req, "", 0, 0);
	machine_restart(NULL);
}

void mconsole_cad(struct mc_request *req)
{
	mconsole_reply(req, "", 0, 0);
	ctrl_alt_del();
}

void mconsole_go(struct mc_request *req)
{
	mconsole_reply(req, "Not stopped", 1, 0);
}

void mconsole_stop(struct mc_request *req)
{
	block_signals();
	os_set_fd_block(req->originating_fd, 1);
	mconsole_reply(req, "stopped", 0, 0);
	for (;;) {
		if (!mconsole_get_request(req->originating_fd, req))
			continue;
		if (req->cmd->handler == mconsole_go)
			break;
		if (req->cmd->handler == mconsole_stop) {
			mconsole_reply(req, "Already stopped", 1, 0);
			continue;
		}
		if (req->cmd->handler == mconsole_sysrq) {
			struct pt_regs *old_regs;
			old_regs = set_irq_regs((struct pt_regs *)&req->regs);
			mconsole_sysrq(req);
			set_irq_regs(old_regs);
			continue;
		}
		(*req->cmd->handler)(req);
	}
	os_set_fd_block(req->originating_fd, 0);
	mconsole_reply(req, "", 0, 0);
	unblock_signals();
}

static DEFINE_SPINLOCK(mc_devices_lock);
static LIST_HEAD(mconsole_devices);

void mconsole_register_dev(struct mc_device *new)
{
	spin_lock(&mc_devices_lock);
	BUG_ON(!list_empty(&new->list));
	list_add(&new->list, &mconsole_devices);
	spin_unlock(&mc_devices_lock);
}

static struct mc_device *mconsole_find_dev(char *name)
{
	struct list_head *ele;
	struct mc_device *dev;

	list_for_each(ele, &mconsole_devices) {
		dev = list_entry(ele, struct mc_device, list);
		if (!strncmp(name, dev->name, strlen(dev->name)))
			return dev;
	}
	return NULL;
}

#define UNPLUGGED_PER_PAGE \
	((PAGE_SIZE - sizeof(struct list_head)) / sizeof(unsigned long))

struct unplugged_pages {
	struct list_head list;
	void *pages[UNPLUGGED_PER_PAGE];
};

static DEFINE_MUTEX(plug_mem_mutex);
static unsigned long long unplugged_pages_count;
static LIST_HEAD(unplugged_pages);
static int unplug_index = UNPLUGGED_PER_PAGE;

static int mem_config(char *str, char **error_out)
{
	unsigned long long diff;
	int err = -EINVAL, i, add;
	char *ret;

	if (str[0] != '=') {
		*error_out = "Expected '=' after 'mem'";
		goto out;
	}

	str++;
	if (str[0] == '-')
		add = 0;
	else if (str[0] == '+') {
		add = 1;
	}
	else {
		*error_out = "Expected increment to start with '-' or '+'";
		goto out;
	}

	str++;
	diff = memparse(str, &ret);
	if (*ret != '\0') {
		*error_out = "Failed to parse memory increment";
		goto out;
	}

	diff /= PAGE_SIZE;

	mutex_lock(&plug_mem_mutex);
	for (i = 0; i < diff; i++) {
		struct unplugged_pages *unplugged;
		void *addr;

		if (add) {
			if (list_empty(&unplugged_pages))
				break;

			unplugged = list_entry(unplugged_pages.next,
					       struct unplugged_pages, list);
			if (unplug_index > 0)
				addr = unplugged->pages[--unplug_index];
			else {
				list_del(&unplugged->list);
				addr = unplugged;
				unplug_index = UNPLUGGED_PER_PAGE;
			}

			free_page((unsigned long) addr);
			unplugged_pages_count--;
		}
		else {
			struct page *page;

			page = alloc_page(GFP_ATOMIC);
			if (page == NULL)
				break;

			unplugged = page_address(page);
			if (unplug_index == UNPLUGGED_PER_PAGE) {
				list_add(&unplugged->list, &unplugged_pages);
				unplug_index = 0;
			}
			else {
				struct list_head *entry = unplugged_pages.next;
				addr = unplugged;

				unplugged = list_entry(entry,
						       struct unplugged_pages,
						       list);
				err = os_drop_memory(addr, PAGE_SIZE);
				if (err) {
					printk(KERN_ERR "Failed to release "
					       "memory - errno = %d\n", err);
					*error_out = "Failed to release memory";
					goto out_unlock;
				}
				unplugged->pages[unplug_index++] = addr;
			}

			unplugged_pages_count++;
		}
	}

	err = 0;
out_unlock:
	mutex_unlock(&plug_mem_mutex);
out:
	return err;
}

static int mem_get_config(char *name, char *str, int size, char **error_out)
{
	char buf[sizeof("18446744073709551615")];
	int len = 0;

	sprintf(buf, "%ld", uml_physmem);
	CONFIG_CHUNK(str, size, len, buf, 1);

	return len;
}

static int mem_id(char **str, int *start_out, int *end_out)
{
	*start_out = 0;
	*end_out = 0;

	return 0;
}

static int mem_remove(int n, char **error_out)
{
	*error_out = "Memory doesn't support the remove operation";
	return -EBUSY;
}

static struct mc_device mem_mc = {
	.list		= LIST_HEAD_INIT(mem_mc.list),
	.name		= "mem",
	.config		= mem_config,
	.get_config	= mem_get_config,
	.id		= mem_id,
	.remove		= mem_remove,
};

static int __init mem_mc_init(void)
{
	if (can_drop_memory())
		mconsole_register_dev(&mem_mc);
	else printk(KERN_ERR "Can't release memory to the host - memory "
		    "hotplug won't be supported\n");
	return 0;
}

__initcall(mem_mc_init);

#define CONFIG_BUF_SIZE 64

static void mconsole_get_config(int (*get_config)(char *, char *, int,
						  char **),
				struct mc_request *req, char *name)
{
	char default_buf[CONFIG_BUF_SIZE], *error, *buf;
	int n, size;

	if (get_config == NULL) {
		mconsole_reply(req, "No get_config routine defined", 1, 0);
		return;
	}

	error = NULL;
	size = ARRAY_SIZE(default_buf);
	buf = default_buf;

	while (1) {
		n = (*get_config)(name, buf, size, &error);
		if (error != NULL) {
			mconsole_reply(req, error, 1, 0);
			goto out;
		}

		if (n <= size) {
			mconsole_reply(req, buf, 0, 0);
			goto out;
		}

		if (buf != default_buf)
			kfree(buf);

		size = n;
		buf = kmalloc(size, GFP_KERNEL);
		if (buf == NULL) {
			mconsole_reply(req, "Failed to allocate buffer", 1, 0);
			return;
		}
	}
 out:
	if (buf != default_buf)
		kfree(buf);
}

void mconsole_config(struct mc_request *req)
{
	struct mc_device *dev;
	char *ptr = req->request.data, *name, *error_string = "";
	int err;

	ptr += strlen("config");
	ptr = skip_spaces(ptr);
	dev = mconsole_find_dev(ptr);
	if (dev == NULL) {
		mconsole_reply(req, "Bad configuration option", 1, 0);
		return;
	}

	name = &ptr[strlen(dev->name)];
	ptr = name;
	while ((*ptr != '=') && (*ptr != '\0'))
		ptr++;

	if (*ptr == '=') {
		err = (*dev->config)(name, &error_string);
		mconsole_reply(req, error_string, err, 0);
	}
	else mconsole_get_config(dev->get_config, req, name);
}

void mconsole_remove(struct mc_request *req)
{
	struct mc_device *dev;
	char *ptr = req->request.data, *err_msg = "";
	char error[256];
	int err, start, end, n;

	ptr += strlen("remove");
	ptr = skip_spaces(ptr);
	dev = mconsole_find_dev(ptr);
	if (dev == NULL) {
		mconsole_reply(req, "Bad remove option", 1, 0);
		return;
	}

	ptr = &ptr[strlen(dev->name)];

	err = 1;
	n = (*dev->id)(&ptr, &start, &end);
	if (n < 0) {
		err_msg = "Couldn't parse device number";
		goto out;
	}
	else if ((n < start) || (n > end)) {
		sprintf(error, "Invalid device number - must be between "
			"%d and %d", start, end);
		err_msg = error;
		goto out;
	}

	err_msg = NULL;
	err = (*dev->remove)(n, &err_msg);
	switch(err) {
	case 0:
		err_msg = "";
		break;
	case -ENODEV:
		if (err_msg == NULL)
			err_msg = "Device doesn't exist";
		break;
	case -EBUSY:
		if (err_msg == NULL)
			err_msg = "Device is currently open";
		break;
	default:
		break;
	}
out:
	mconsole_reply(req, err_msg, err, 0);
}

struct mconsole_output {
	struct list_head list;
	struct mc_request *req;
};

static DEFINE_SPINLOCK(client_lock);
static LIST_HEAD(clients);
static char console_buf[MCONSOLE_MAX_DATA];

static void console_write(struct console *console, const char *string,
			  unsigned int len)
{
	struct list_head *ele;
	int n;

	if (list_empty(&clients))
		return;

	while (len > 0) {
		n = min((size_t) len, ARRAY_SIZE(console_buf));
		strncpy(console_buf, string, n);
		string += n;
		len -= n;

		list_for_each(ele, &clients) {
			struct mconsole_output *entry;

			entry = list_entry(ele, struct mconsole_output, list);
			mconsole_reply_len(entry->req, console_buf, n, 0, 1);
		}
	}
}

static struct console mc_console = { .name	= "mc",
				     .write	= console_write,
				     .flags	= CON_ENABLED,
				     .index	= -1 };

static int mc_add_console(void)
{
	register_console(&mc_console);
	return 0;
}

late_initcall(mc_add_console);

static void with_console(struct mc_request *req, void (*proc)(void *),
			 void *arg)
{
	struct mconsole_output entry;
	unsigned long flags;

	entry.req = req;
	spin_lock_irqsave(&client_lock, flags);
	list_add(&entry.list, &clients);
	spin_unlock_irqrestore(&client_lock, flags);

	(*proc)(arg);

	mconsole_reply_len(req, "", 0, 0, 0);

	spin_lock_irqsave(&client_lock, flags);
	list_del(&entry.list);
	spin_unlock_irqrestore(&client_lock, flags);
}

#ifdef CONFIG_MAGIC_SYSRQ

#include <linux/sysrq.h>

static void sysrq_proc(void *arg)
{
	char *op = arg;
	handle_sysrq(*op);
}

void mconsole_sysrq(struct mc_request *req)
{
	char *ptr = req->request.data;

	ptr += strlen("sysrq");
	ptr = skip_spaces(ptr);

	/*
	 * With 'b', the system will shut down without a chance to reply,
	 * so in this case, we reply first.
	 */
	if (*ptr == 'b')
		mconsole_reply(req, "", 0, 0);

	with_console(req, sysrq_proc, ptr);
}
#else
void mconsole_sysrq(struct mc_request *req)
{
	mconsole_reply(req, "Sysrq not compiled in", 1, 0);
}
#endif

static void stack_proc(void *arg)
{
	struct task_struct *task = arg;

	show_stack(task, NULL, KERN_INFO);
}

/*
 * Mconsole stack trace
 *  Added by Allan Graves, Jeff Dike
 *  Dumps a stacks registers to the linux console.
 *  Usage stack <pid>.
 */
void mconsole_stack(struct mc_request *req)
{
	char *ptr = req->request.data;
	int pid_requested= -1;
	struct task_struct *to = NULL;

	/*
	 * Would be nice:
	 * 1) Send showregs output to mconsole.
	 * 2) Add a way to stack dump all pids.
	 */

	ptr += strlen("stack");
	ptr = skip_spaces(ptr);

	/*
	 * Should really check for multiple pids or reject bad args here
	 */
	/* What do the arguments in mconsole_reply mean? */
	if (sscanf(ptr, "%d", &pid_requested) == 0) {
		mconsole_reply(req, "Please specify a pid", 1, 0);
		return;
	}

	to = find_task_by_pid_ns(pid_requested, &init_pid_ns);
	if ((to == NULL) || (pid_requested == 0)) {
		mconsole_reply(req, "Couldn't find that pid", 1, 0);
		return;
	}
	with_console(req, stack_proc, to);
}

static int __init mount_proc(void)
{
	struct file_system_type *proc_fs_type;
	struct vfsmount *mnt;

	proc_fs_type = get_fs_type("proc");
	if (!proc_fs_type)
		return -ENODEV;

	mnt = kern_mount(proc_fs_type);
	put_filesystem(proc_fs_type);
	if (IS_ERR(mnt))
		return PTR_ERR(mnt);

	proc_mnt = mnt;
	return 0;
}

/*
 * Changed by mconsole_setup, which is __setup, and called before SMP is
 * active.
 */
static char *notify_socket = NULL;

static int __init mconsole_init(void)
{
	/* long to avoid size mismatch warnings from gcc */
	long sock;
	int err;
	char file[UNIX_PATH_MAX];

	mount_proc();

	if (umid_file_name("mconsole", file, sizeof(file)))
		return -1;
	snprintf(mconsole_socket_name, sizeof(file), "%s", file);

	sock = os_create_unix_socket(file, sizeof(file), 1);
	if (sock < 0) {
		printk(KERN_ERR "Failed to initialize management console\n");
		return 1;
	}
	if (os_set_fd_block(sock, 0))
		goto out;

	register_reboot_notifier(&reboot_notifier);

	err = um_request_irq(MCONSOLE_IRQ, sock, IRQ_READ, mconsole_interrupt,
			     IRQF_SHARED, "mconsole", (void *)sock);
	if (err < 0) {
		printk(KERN_ERR "Failed to get IRQ for management console\n");
		goto out;
	}

	if (notify_socket != NULL) {
		notify_socket = kstrdup(notify_socket, GFP_KERNEL);
		if (notify_socket != NULL)
			mconsole_notify(notify_socket, MCONSOLE_SOCKET,
					mconsole_socket_name,
					strlen(mconsole_socket_name) + 1);
		else printk(KERN_ERR "mconsole_setup failed to strdup "
			    "string\n");
	}

	printk(KERN_INFO "mconsole (version %d) initialized on %s\n",
	       MCONSOLE_VERSION, mconsole_socket_name);
	return 0;

 out:
	os_close_file(sock);
	return 1;
}

__initcall(mconsole_init);

static ssize_t mconsole_proc_write(struct file *file,
		const char __user *buffer, size_t count, loff_t *pos)
{
	char *buf;

	buf = memdup_user_nul(buffer, count);
	if (IS_ERR(buf))
		return PTR_ERR(buf);

	mconsole_notify(notify_socket, MCONSOLE_USER_NOTIFY, buf, count);
	kfree(buf);
	return count;
}

static const struct proc_ops mconsole_proc_ops = {
	.proc_write	= mconsole_proc_write,
	.proc_lseek	= noop_llseek,
};

static int create_proc_mconsole(void)
{
	struct proc_dir_entry *ent;

	if (notify_socket == NULL)
		return 0;

	ent = proc_create("mconsole", 0200, NULL, &mconsole_proc_ops);
	if (ent == NULL) {
		printk(KERN_INFO "create_proc_mconsole : proc_create failed\n");
		return 0;
	}
	return 0;
}

static DEFINE_SPINLOCK(notify_spinlock);

void lock_notify(void)
{
	spin_lock(&notify_spinlock);
}

void unlock_notify(void)
{
	spin_unlock(&notify_spinlock);
}

__initcall(create_proc_mconsole);

#define NOTIFY "notify:"

static int mconsole_setup(char *str)
{
	if (!strncmp(str, NOTIFY, strlen(NOTIFY))) {
		str += strlen(NOTIFY);
		notify_socket = str;
	}
	else printk(KERN_ERR "mconsole_setup : Unknown option - '%s'\n", str);
	return 1;
}

__setup("mconsole=", mconsole_setup);

__uml_help(mconsole_setup,
"mconsole=notify:<socket>\n"
"    Requests that the mconsole driver send a message to the named Unix\n"
"    socket containing the name of the mconsole socket.  This also serves\n"
"    to notify outside processes when UML has booted far enough to respond\n"
"    to mconsole requests.\n\n"
);

static int notify_panic(struct notifier_block *self, unsigned long unused1,
			void *ptr)
{
	char *message = ptr;

	if (notify_socket == NULL)
		return 0;

	mconsole_notify(notify_socket, MCONSOLE_PANIC, message,
			strlen(message) + 1);
	return NOTIFY_DONE;
}

static struct notifier_block panic_exit_notifier = {
	.notifier_call	= notify_panic,
	.priority	= INT_MAX, /* run as soon as possible */
};

static int add_notifier(void)
{
	atomic_notifier_chain_register(&panic_notifier_list,
			&panic_exit_notifier);
	return 0;
}

__initcall(add_notifier);

char *mconsole_notify_socket(void)
{
	return notify_socket;
}

EXPORT_SYMBOL(mconsole_notify_socket);