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Linux/arch/um/drivers/mconsole_kern.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * Copyright (C) 2001 Lennert Buytenhek (buytenh@gnu.org)
  4  * Copyright (C) 2001 - 2008 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  5  */
  6 
  7 #include <linux/console.h>
  8 #include <linux/ctype.h>
  9 #include <linux/string.h>
 10 #include <linux/interrupt.h>
 11 #include <linux/list.h>
 12 #include <linux/mm.h>
 13 #include <linux/module.h>
 14 #include <linux/notifier.h>
 15 #include <linux/reboot.h>
 16 #include <linux/sched/debug.h>
 17 #include <linux/proc_fs.h>
 18 #include <linux/slab.h>
 19 #include <linux/syscalls.h>
 20 #include <linux/utsname.h>
 21 #include <linux/socket.h>
 22 #include <linux/un.h>
 23 #include <linux/workqueue.h>
 24 #include <linux/mutex.h>
 25 #include <linux/fs.h>
 26 #include <linux/mount.h>
 27 #include <linux/file.h>
 28 #include <linux/uaccess.h>
 29 #include <asm/switch_to.h>
 30 
 31 #include <init.h>
 32 #include <irq_kern.h>
 33 #include <irq_user.h>
 34 #include <kern_util.h>
 35 #include "mconsole.h"
 36 #include "mconsole_kern.h"
 37 #include <os.h>
 38 
 39 static int do_unlink_socket(struct notifier_block *notifier,
 40                             unsigned long what, void *data)
 41 {
 42         return mconsole_unlink_socket();
 43 }
 44 
 45 
 46 static struct notifier_block reboot_notifier = {
 47         .notifier_call          = do_unlink_socket,
 48         .priority               = 0,
 49 };
 50 
 51 /* Safe without explicit locking for now.  Tasklets provide their own
 52  * locking, and the interrupt handler is safe because it can't interrupt
 53  * itself and it can only happen on CPU 0.
 54  */
 55 
 56 static LIST_HEAD(mc_requests);
 57 
 58 static void mc_work_proc(struct work_struct *unused)
 59 {
 60         struct mconsole_entry *req;
 61         unsigned long flags;
 62 
 63         while (!list_empty(&mc_requests)) {
 64                 local_irq_save(flags);
 65                 req = list_entry(mc_requests.next, struct mconsole_entry, list);
 66                 list_del(&req->list);
 67                 local_irq_restore(flags);
 68                 req->request.cmd->handler(&req->request);
 69                 kfree(req);
 70         }
 71 }
 72 
 73 static DECLARE_WORK(mconsole_work, mc_work_proc);
 74 
 75 static irqreturn_t mconsole_interrupt(int irq, void *dev_id)
 76 {
 77         /* long to avoid size mismatch warnings from gcc */
 78         long fd;
 79         struct mconsole_entry *new;
 80         static struct mc_request req;   /* that's OK */
 81 
 82         fd = (long) dev_id;
 83         while (mconsole_get_request(fd, &req)) {
 84                 if (req.cmd->context == MCONSOLE_INTR)
 85                         (*req.cmd->handler)(&req);
 86                 else {
 87                         new = kmalloc(sizeof(*new), GFP_NOWAIT);
 88                         if (new == NULL)
 89                                 mconsole_reply(&req, "Out of memory", 1, 0);
 90                         else {
 91                                 new->request = req;
 92                                 new->request.regs = get_irq_regs()->regs;
 93                                 list_add(&new->list, &mc_requests);
 94                         }
 95                 }
 96         }
 97         if (!list_empty(&mc_requests))
 98                 schedule_work(&mconsole_work);
 99         return IRQ_HANDLED;
100 }
101 
102 void mconsole_version(struct mc_request *req)
103 {
104         char version[256];
105 
106         sprintf(version, "%s %s %s %s %s", utsname()->sysname,
107                 utsname()->nodename, utsname()->release, utsname()->version,
108                 utsname()->machine);
109         mconsole_reply(req, version, 0, 0);
110 }
111 
112 void mconsole_log(struct mc_request *req)
113 {
114         int len;
115         char *ptr = req->request.data;
116 
117         ptr += strlen("log ");
118 
119         len = req->len - (ptr - req->request.data);
120         printk(KERN_WARNING "%.*s", len, ptr);
121         mconsole_reply(req, "", 0, 0);
122 }
123 
124 void mconsole_proc(struct mc_request *req)
125 {
126         struct vfsmount *mnt = task_active_pid_ns(current)->proc_mnt;
127         char *buf;
128         int len;
129         struct file *file;
130         int first_chunk = 1;
131         char *ptr = req->request.data;
132         loff_t pos = 0;
133 
134         ptr += strlen("proc");
135         ptr = skip_spaces(ptr);
136 
137         file = file_open_root(mnt->mnt_root, mnt, ptr, O_RDONLY, 0);
138         if (IS_ERR(file)) {
139                 mconsole_reply(req, "Failed to open file", 1, 0);
140                 printk(KERN_ERR "open /proc/%s: %ld\n", ptr, PTR_ERR(file));
141                 goto out;
142         }
143 
144         buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
145         if (buf == NULL) {
146                 mconsole_reply(req, "Failed to allocate buffer", 1, 0);
147                 goto out_fput;
148         }
149 
150         do {
151                 len = kernel_read(file, buf, PAGE_SIZE - 1, &pos);
152                 if (len < 0) {
153                         mconsole_reply(req, "Read of file failed", 1, 0);
154                         goto out_free;
155                 }
156                 /* Begin the file content on his own line. */
157                 if (first_chunk) {
158                         mconsole_reply(req, "\n", 0, 1);
159                         first_chunk = 0;
160                 }
161                 buf[len] = '\0';
162                 mconsole_reply(req, buf, 0, (len > 0));
163         } while (len > 0);
164  out_free:
165         kfree(buf);
166  out_fput:
167         fput(file);
168  out: ;
169 }
170 
171 #define UML_MCONSOLE_HELPTEXT \
172 "Commands: \n\
173     version - Get kernel version \n\
174     help - Print this message \n\
175     halt - Halt UML \n\
176     reboot - Reboot UML \n\
177     config <dev>=<config> - Add a new device to UML;  \n\
178         same syntax as command line \n\
179     config <dev> - Query the configuration of a device \n\
180     remove <dev> - Remove a device from UML \n\
181     sysrq <letter> - Performs the SysRq action controlled by the letter \n\
182     cad - invoke the Ctrl-Alt-Del handler \n\
183     stop - pause the UML; it will do nothing until it receives a 'go' \n\
184     go - continue the UML after a 'stop' \n\
185     log <string> - make UML enter <string> into the kernel log\n\
186     proc <file> - returns the contents of the UML's /proc/<file>\n\
187     stack <pid> - returns the stack of the specified pid\n\
188 "
189 
190 void mconsole_help(struct mc_request *req)
191 {
192         mconsole_reply(req, UML_MCONSOLE_HELPTEXT, 0, 0);
193 }
194 
195 void mconsole_halt(struct mc_request *req)
196 {
197         mconsole_reply(req, "", 0, 0);
198         machine_halt();
199 }
200 
201 void mconsole_reboot(struct mc_request *req)
202 {
203         mconsole_reply(req, "", 0, 0);
204         machine_restart(NULL);
205 }
206 
207 void mconsole_cad(struct mc_request *req)
208 {
209         mconsole_reply(req, "", 0, 0);
210         ctrl_alt_del();
211 }
212 
213 void mconsole_go(struct mc_request *req)
214 {
215         mconsole_reply(req, "Not stopped", 1, 0);
216 }
217 
218 void mconsole_stop(struct mc_request *req)
219 {
220         deactivate_fd(req->originating_fd, MCONSOLE_IRQ);
221         os_set_fd_block(req->originating_fd, 1);
222         mconsole_reply(req, "stopped", 0, 0);
223         for (;;) {
224                 if (!mconsole_get_request(req->originating_fd, req))
225                         continue;
226                 if (req->cmd->handler == mconsole_go)
227                         break;
228                 if (req->cmd->handler == mconsole_stop) {
229                         mconsole_reply(req, "Already stopped", 1, 0);
230                         continue;
231                 }
232                 if (req->cmd->handler == mconsole_sysrq) {
233                         struct pt_regs *old_regs;
234                         old_regs = set_irq_regs((struct pt_regs *)&req->regs);
235                         mconsole_sysrq(req);
236                         set_irq_regs(old_regs);
237                         continue;
238                 }
239                 (*req->cmd->handler)(req);
240         }
241         os_set_fd_block(req->originating_fd, 0);
242         mconsole_reply(req, "", 0, 0);
243 }
244 
245 static DEFINE_SPINLOCK(mc_devices_lock);
246 static LIST_HEAD(mconsole_devices);
247 
248 void mconsole_register_dev(struct mc_device *new)
249 {
250         spin_lock(&mc_devices_lock);
251         BUG_ON(!list_empty(&new->list));
252         list_add(&new->list, &mconsole_devices);
253         spin_unlock(&mc_devices_lock);
254 }
255 
256 static struct mc_device *mconsole_find_dev(char *name)
257 {
258         struct list_head *ele;
259         struct mc_device *dev;
260 
261         list_for_each(ele, &mconsole_devices) {
262                 dev = list_entry(ele, struct mc_device, list);
263                 if (!strncmp(name, dev->name, strlen(dev->name)))
264                         return dev;
265         }
266         return NULL;
267 }
268 
269 #define UNPLUGGED_PER_PAGE \
270         ((PAGE_SIZE - sizeof(struct list_head)) / sizeof(unsigned long))
271 
272 struct unplugged_pages {
273         struct list_head list;
274         void *pages[UNPLUGGED_PER_PAGE];
275 };
276 
277 static DEFINE_MUTEX(plug_mem_mutex);
278 static unsigned long long unplugged_pages_count = 0;
279 static LIST_HEAD(unplugged_pages);
280 static int unplug_index = UNPLUGGED_PER_PAGE;
281 
282 static int mem_config(char *str, char **error_out)
283 {
284         unsigned long long diff;
285         int err = -EINVAL, i, add;
286         char *ret;
287 
288         if (str[0] != '=') {
289                 *error_out = "Expected '=' after 'mem'";
290                 goto out;
291         }
292 
293         str++;
294         if (str[0] == '-')
295                 add = 0;
296         else if (str[0] == '+') {
297                 add = 1;
298         }
299         else {
300                 *error_out = "Expected increment to start with '-' or '+'";
301                 goto out;
302         }
303 
304         str++;
305         diff = memparse(str, &ret);
306         if (*ret != '\0') {
307                 *error_out = "Failed to parse memory increment";
308                 goto out;
309         }
310 
311         diff /= PAGE_SIZE;
312 
313         mutex_lock(&plug_mem_mutex);
314         for (i = 0; i < diff; i++) {
315                 struct unplugged_pages *unplugged;
316                 void *addr;
317 
318                 if (add) {
319                         if (list_empty(&unplugged_pages))
320                                 break;
321 
322                         unplugged = list_entry(unplugged_pages.next,
323                                                struct unplugged_pages, list);
324                         if (unplug_index > 0)
325                                 addr = unplugged->pages[--unplug_index];
326                         else {
327                                 list_del(&unplugged->list);
328                                 addr = unplugged;
329                                 unplug_index = UNPLUGGED_PER_PAGE;
330                         }
331 
332                         free_page((unsigned long) addr);
333                         unplugged_pages_count--;
334                 }
335                 else {
336                         struct page *page;
337 
338                         page = alloc_page(GFP_ATOMIC);
339                         if (page == NULL)
340                                 break;
341 
342                         unplugged = page_address(page);
343                         if (unplug_index == UNPLUGGED_PER_PAGE) {
344                                 list_add(&unplugged->list, &unplugged_pages);
345                                 unplug_index = 0;
346                         }
347                         else {
348                                 struct list_head *entry = unplugged_pages.next;
349                                 addr = unplugged;
350 
351                                 unplugged = list_entry(entry,
352                                                        struct unplugged_pages,
353                                                        list);
354                                 err = os_drop_memory(addr, PAGE_SIZE);
355                                 if (err) {
356                                         printk(KERN_ERR "Failed to release "
357                                                "memory - errno = %d\n", err);
358                                         *error_out = "Failed to release memory";
359                                         goto out_unlock;
360                                 }
361                                 unplugged->pages[unplug_index++] = addr;
362                         }
363 
364                         unplugged_pages_count++;
365                 }
366         }
367 
368         err = 0;
369 out_unlock:
370         mutex_unlock(&plug_mem_mutex);
371 out:
372         return err;
373 }
374 
375 static int mem_get_config(char *name, char *str, int size, char **error_out)
376 {
377         char buf[sizeof("18446744073709551615")];
378         int len = 0;
379 
380         sprintf(buf, "%ld", uml_physmem);
381         CONFIG_CHUNK(str, size, len, buf, 1);
382 
383         return len;
384 }
385 
386 static int mem_id(char **str, int *start_out, int *end_out)
387 {
388         *start_out = 0;
389         *end_out = 0;
390 
391         return 0;
392 }
393 
394 static int mem_remove(int n, char **error_out)
395 {
396         *error_out = "Memory doesn't support the remove operation";
397         return -EBUSY;
398 }
399 
400 static struct mc_device mem_mc = {
401         .list           = LIST_HEAD_INIT(mem_mc.list),
402         .name           = "mem",
403         .config         = mem_config,
404         .get_config     = mem_get_config,
405         .id             = mem_id,
406         .remove         = mem_remove,
407 };
408 
409 static int __init mem_mc_init(void)
410 {
411         if (can_drop_memory())
412                 mconsole_register_dev(&mem_mc);
413         else printk(KERN_ERR "Can't release memory to the host - memory "
414                     "hotplug won't be supported\n");
415         return 0;
416 }
417 
418 __initcall(mem_mc_init);
419 
420 #define CONFIG_BUF_SIZE 64
421 
422 static void mconsole_get_config(int (*get_config)(char *, char *, int,
423                                                   char **),
424                                 struct mc_request *req, char *name)
425 {
426         char default_buf[CONFIG_BUF_SIZE], *error, *buf;
427         int n, size;
428 
429         if (get_config == NULL) {
430                 mconsole_reply(req, "No get_config routine defined", 1, 0);
431                 return;
432         }
433 
434         error = NULL;
435         size = ARRAY_SIZE(default_buf);
436         buf = default_buf;
437 
438         while (1) {
439                 n = (*get_config)(name, buf, size, &error);
440                 if (error != NULL) {
441                         mconsole_reply(req, error, 1, 0);
442                         goto out;
443                 }
444 
445                 if (n <= size) {
446                         mconsole_reply(req, buf, 0, 0);
447                         goto out;
448                 }
449 
450                 if (buf != default_buf)
451                         kfree(buf);
452 
453                 size = n;
454                 buf = kmalloc(size, GFP_KERNEL);
455                 if (buf == NULL) {
456                         mconsole_reply(req, "Failed to allocate buffer", 1, 0);
457                         return;
458                 }
459         }
460  out:
461         if (buf != default_buf)
462                 kfree(buf);
463 }
464 
465 void mconsole_config(struct mc_request *req)
466 {
467         struct mc_device *dev;
468         char *ptr = req->request.data, *name, *error_string = "";
469         int err;
470 
471         ptr += strlen("config");
472         ptr = skip_spaces(ptr);
473         dev = mconsole_find_dev(ptr);
474         if (dev == NULL) {
475                 mconsole_reply(req, "Bad configuration option", 1, 0);
476                 return;
477         }
478 
479         name = &ptr[strlen(dev->name)];
480         ptr = name;
481         while ((*ptr != '=') && (*ptr != '\0'))
482                 ptr++;
483 
484         if (*ptr == '=') {
485                 err = (*dev->config)(name, &error_string);
486                 mconsole_reply(req, error_string, err, 0);
487         }
488         else mconsole_get_config(dev->get_config, req, name);
489 }
490 
491 void mconsole_remove(struct mc_request *req)
492 {
493         struct mc_device *dev;
494         char *ptr = req->request.data, *err_msg = "";
495         char error[256];
496         int err, start, end, n;
497 
498         ptr += strlen("remove");
499         ptr = skip_spaces(ptr);
500         dev = mconsole_find_dev(ptr);
501         if (dev == NULL) {
502                 mconsole_reply(req, "Bad remove option", 1, 0);
503                 return;
504         }
505 
506         ptr = &ptr[strlen(dev->name)];
507 
508         err = 1;
509         n = (*dev->id)(&ptr, &start, &end);
510         if (n < 0) {
511                 err_msg = "Couldn't parse device number";
512                 goto out;
513         }
514         else if ((n < start) || (n > end)) {
515                 sprintf(error, "Invalid device number - must be between "
516                         "%d and %d", start, end);
517                 err_msg = error;
518                 goto out;
519         }
520 
521         err_msg = NULL;
522         err = (*dev->remove)(n, &err_msg);
523         switch(err) {
524         case 0:
525                 err_msg = "";
526                 break;
527         case -ENODEV:
528                 if (err_msg == NULL)
529                         err_msg = "Device doesn't exist";
530                 break;
531         case -EBUSY:
532                 if (err_msg == NULL)
533                         err_msg = "Device is currently open";
534                 break;
535         default:
536                 break;
537         }
538 out:
539         mconsole_reply(req, err_msg, err, 0);
540 }
541 
542 struct mconsole_output {
543         struct list_head list;
544         struct mc_request *req;
545 };
546 
547 static DEFINE_SPINLOCK(client_lock);
548 static LIST_HEAD(clients);
549 static char console_buf[MCONSOLE_MAX_DATA];
550 
551 static void console_write(struct console *console, const char *string,
552                           unsigned int len)
553 {
554         struct list_head *ele;
555         int n;
556 
557         if (list_empty(&clients))
558                 return;
559 
560         while (len > 0) {
561                 n = min((size_t) len, ARRAY_SIZE(console_buf));
562                 strncpy(console_buf, string, n);
563                 string += n;
564                 len -= n;
565 
566                 list_for_each(ele, &clients) {
567                         struct mconsole_output *entry;
568 
569                         entry = list_entry(ele, struct mconsole_output, list);
570                         mconsole_reply_len(entry->req, console_buf, n, 0, 1);
571                 }
572         }
573 }
574 
575 static struct console mc_console = { .name      = "mc",
576                                      .write     = console_write,
577                                      .flags     = CON_ENABLED,
578                                      .index     = -1 };
579 
580 static int mc_add_console(void)
581 {
582         register_console(&mc_console);
583         return 0;
584 }
585 
586 late_initcall(mc_add_console);
587 
588 static void with_console(struct mc_request *req, void (*proc)(void *),
589                          void *arg)
590 {
591         struct mconsole_output entry;
592         unsigned long flags;
593 
594         entry.req = req;
595         spin_lock_irqsave(&client_lock, flags);
596         list_add(&entry.list, &clients);
597         spin_unlock_irqrestore(&client_lock, flags);
598 
599         (*proc)(arg);
600 
601         mconsole_reply_len(req, "", 0, 0, 0);
602 
603         spin_lock_irqsave(&client_lock, flags);
604         list_del(&entry.list);
605         spin_unlock_irqrestore(&client_lock, flags);
606 }
607 
608 #ifdef CONFIG_MAGIC_SYSRQ
609 
610 #include <linux/sysrq.h>
611 
612 static void sysrq_proc(void *arg)
613 {
614         char *op = arg;
615         handle_sysrq(*op);
616 }
617 
618 void mconsole_sysrq(struct mc_request *req)
619 {
620         char *ptr = req->request.data;
621 
622         ptr += strlen("sysrq");
623         ptr = skip_spaces(ptr);
624 
625         /*
626          * With 'b', the system will shut down without a chance to reply,
627          * so in this case, we reply first.
628          */
629         if (*ptr == 'b')
630                 mconsole_reply(req, "", 0, 0);
631 
632         with_console(req, sysrq_proc, ptr);
633 }
634 #else
635 void mconsole_sysrq(struct mc_request *req)
636 {
637         mconsole_reply(req, "Sysrq not compiled in", 1, 0);
638 }
639 #endif
640 
641 static void stack_proc(void *arg)
642 {
643         struct task_struct *task = arg;
644 
645         show_stack(task, NULL);
646 }
647 
648 /*
649  * Mconsole stack trace
650  *  Added by Allan Graves, Jeff Dike
651  *  Dumps a stacks registers to the linux console.
652  *  Usage stack <pid>.
653  */
654 void mconsole_stack(struct mc_request *req)
655 {
656         char *ptr = req->request.data;
657         int pid_requested= -1;
658         struct task_struct *to = NULL;
659 
660         /*
661          * Would be nice:
662          * 1) Send showregs output to mconsole.
663          * 2) Add a way to stack dump all pids.
664          */
665 
666         ptr += strlen("stack");
667         ptr = skip_spaces(ptr);
668 
669         /*
670          * Should really check for multiple pids or reject bad args here
671          */
672         /* What do the arguments in mconsole_reply mean? */
673         if (sscanf(ptr, "%d", &pid_requested) == 0) {
674                 mconsole_reply(req, "Please specify a pid", 1, 0);
675                 return;
676         }
677 
678         to = find_task_by_pid_ns(pid_requested, &init_pid_ns);
679         if ((to == NULL) || (pid_requested == 0)) {
680                 mconsole_reply(req, "Couldn't find that pid", 1, 0);
681                 return;
682         }
683         with_console(req, stack_proc, to);
684 }
685 
686 /*
687  * Changed by mconsole_setup, which is __setup, and called before SMP is
688  * active.
689  */
690 static char *notify_socket = NULL;
691 
692 static int __init mconsole_init(void)
693 {
694         /* long to avoid size mismatch warnings from gcc */
695         long sock;
696         int err;
697         char file[UNIX_PATH_MAX];
698 
699         if (umid_file_name("mconsole", file, sizeof(file)))
700                 return -1;
701         snprintf(mconsole_socket_name, sizeof(file), "%s", file);
702 
703         sock = os_create_unix_socket(file, sizeof(file), 1);
704         if (sock < 0) {
705                 printk(KERN_ERR "Failed to initialize management console\n");
706                 return 1;
707         }
708         if (os_set_fd_block(sock, 0))
709                 goto out;
710 
711         register_reboot_notifier(&reboot_notifier);
712 
713         err = um_request_irq(MCONSOLE_IRQ, sock, IRQ_READ, mconsole_interrupt,
714                              IRQF_SHARED, "mconsole", (void *)sock);
715         if (err) {
716                 printk(KERN_ERR "Failed to get IRQ for management console\n");
717                 goto out;
718         }
719 
720         if (notify_socket != NULL) {
721                 notify_socket = kstrdup(notify_socket, GFP_KERNEL);
722                 if (notify_socket != NULL)
723                         mconsole_notify(notify_socket, MCONSOLE_SOCKET,
724                                         mconsole_socket_name,
725                                         strlen(mconsole_socket_name) + 1);
726                 else printk(KERN_ERR "mconsole_setup failed to strdup "
727                             "string\n");
728         }
729 
730         printk(KERN_INFO "mconsole (version %d) initialized on %s\n",
731                MCONSOLE_VERSION, mconsole_socket_name);
732         return 0;
733 
734  out:
735         os_close_file(sock);
736         return 1;
737 }
738 
739 __initcall(mconsole_init);
740 
741 static ssize_t mconsole_proc_write(struct file *file,
742                 const char __user *buffer, size_t count, loff_t *pos)
743 {
744         char *buf;
745 
746         buf = memdup_user_nul(buffer, count);
747         if (IS_ERR(buf))
748                 return PTR_ERR(buf);
749 
750         mconsole_notify(notify_socket, MCONSOLE_USER_NOTIFY, buf, count);
751         kfree(buf);
752         return count;
753 }
754 
755 static const struct proc_ops mconsole_proc_ops = {
756         .proc_write     = mconsole_proc_write,
757         .proc_lseek     = noop_llseek,
758 };
759 
760 static int create_proc_mconsole(void)
761 {
762         struct proc_dir_entry *ent;
763 
764         if (notify_socket == NULL)
765                 return 0;
766 
767         ent = proc_create("mconsole", 0200, NULL, &mconsole_proc_ops);
768         if (ent == NULL) {
769                 printk(KERN_INFO "create_proc_mconsole : proc_create failed\n");
770                 return 0;
771         }
772         return 0;
773 }
774 
775 static DEFINE_SPINLOCK(notify_spinlock);
776 
777 void lock_notify(void)
778 {
779         spin_lock(&notify_spinlock);
780 }
781 
782 void unlock_notify(void)
783 {
784         spin_unlock(&notify_spinlock);
785 }
786 
787 __initcall(create_proc_mconsole);
788 
789 #define NOTIFY "notify:"
790 
791 static int mconsole_setup(char *str)
792 {
793         if (!strncmp(str, NOTIFY, strlen(NOTIFY))) {
794                 str += strlen(NOTIFY);
795                 notify_socket = str;
796         }
797         else printk(KERN_ERR "mconsole_setup : Unknown option - '%s'\n", str);
798         return 1;
799 }
800 
801 __setup("mconsole=", mconsole_setup);
802 
803 __uml_help(mconsole_setup,
804 "mconsole=notify:<socket>\n"
805 "    Requests that the mconsole driver send a message to the named Unix\n"
806 "    socket containing the name of the mconsole socket.  This also serves\n"
807 "    to notify outside processes when UML has booted far enough to respond\n"
808 "    to mconsole requests.\n\n"
809 );
810 
811 static int notify_panic(struct notifier_block *self, unsigned long unused1,
812                         void *ptr)
813 {
814         char *message = ptr;
815 
816         if (notify_socket == NULL)
817                 return 0;
818 
819         mconsole_notify(notify_socket, MCONSOLE_PANIC, message,
820                         strlen(message) + 1);
821         return 0;
822 }
823 
824 static struct notifier_block panic_exit_notifier = {
825         .notifier_call          = notify_panic,
826         .next                   = NULL,
827         .priority               = 1
828 };
829 
830 static int add_notifier(void)
831 {
832         atomic_notifier_chain_register(&panic_notifier_list,
833                         &panic_exit_notifier);
834         return 0;
835 }
836 
837 __initcall(add_notifier);
838 
839 char *mconsole_notify_socket(void)
840 {
841         return notify_socket;
842 }
843 
844 EXPORT_SYMBOL(mconsole_notify_socket);
845 

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