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Linux/arch/um/drivers/mconsole_kern.c

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  1 /*
  2  * Copyright (C) 2001 Lennert Buytenhek (buytenh@gnu.org)
  3  * Copyright (C) 2001 - 2008 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  4  * Licensed under the GPL
  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/proc_fs.h>
 17 #include <linux/slab.h>
 18 #include <linux/syscalls.h>
 19 #include <linux/utsname.h>
 20 #include <linux/socket.h>
 21 #include <linux/un.h>
 22 #include <linux/workqueue.h>
 23 #include <linux/mutex.h>
 24 #include <linux/fs.h>
 25 #include <linux/mount.h>
 26 #include <linux/file.h>
 27 #include <asm/uaccess.h>
 28 #include <asm/switch_to.h>
 29 
 30 #include <init.h>
 31 #include <irq_kern.h>
 32 #include <irq_user.h>
 33 #include <kern_util.h>
 34 #include "mconsole.h"
 35 #include "mconsole_kern.h"
 36 #include <os.h>
 37 
 38 static int do_unlink_socket(struct notifier_block *notifier,
 39                             unsigned long what, void *data)
 40 {
 41         return mconsole_unlink_socket();
 42 }
 43 
 44 
 45 static struct notifier_block reboot_notifier = {
 46         .notifier_call          = do_unlink_socket,
 47         .priority               = 0,
 48 };
 49 
 50 /* Safe without explicit locking for now.  Tasklets provide their own
 51  * locking, and the interrupt handler is safe because it can't interrupt
 52  * itself and it can only happen on CPU 0.
 53  */
 54 
 55 static LIST_HEAD(mc_requests);
 56 
 57 static void mc_work_proc(struct work_struct *unused)
 58 {
 59         struct mconsole_entry *req;
 60         unsigned long flags;
 61 
 62         while (!list_empty(&mc_requests)) {
 63                 local_irq_save(flags);
 64                 req = list_entry(mc_requests.next, struct mconsole_entry, list);
 65                 list_del(&req->list);
 66                 local_irq_restore(flags);
 67                 req->request.cmd->handler(&req->request);
 68                 kfree(req);
 69         }
 70 }
 71 
 72 static DECLARE_WORK(mconsole_work, mc_work_proc);
 73 
 74 static irqreturn_t mconsole_interrupt(int irq, void *dev_id)
 75 {
 76         /* long to avoid size mismatch warnings from gcc */
 77         long fd;
 78         struct mconsole_entry *new;
 79         static struct mc_request req;   /* that's OK */
 80 
 81         fd = (long) dev_id;
 82         while (mconsole_get_request(fd, &req)) {
 83                 if (req.cmd->context == MCONSOLE_INTR)
 84                         (*req.cmd->handler)(&req);
 85                 else {
 86                         new = kmalloc(sizeof(*new), GFP_NOWAIT);
 87                         if (new == NULL)
 88                                 mconsole_reply(&req, "Out of memory", 1, 0);
 89                         else {
 90                                 new->request = req;
 91                                 new->request.regs = get_irq_regs()->regs;
 92                                 list_add(&new->list, &mc_requests);
 93                         }
 94                 }
 95         }
 96         if (!list_empty(&mc_requests))
 97                 schedule_work(&mconsole_work);
 98         reactivate_fd(fd, MCONSOLE_IRQ);
 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 
133         ptr += strlen("proc");
134         ptr = skip_spaces(ptr);
135 
136         file = file_open_root(mnt->mnt_root, mnt, ptr, O_RDONLY);
137         if (IS_ERR(file)) {
138                 mconsole_reply(req, "Failed to open file", 1, 0);
139                 printk(KERN_ERR "open /proc/%s: %ld\n", ptr, PTR_ERR(file));
140                 goto out;
141         }
142 
143         buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
144         if (buf == NULL) {
145                 mconsole_reply(req, "Failed to allocate buffer", 1, 0);
146                 goto out_fput;
147         }
148 
149         do {
150                 loff_t pos = file->f_pos;
151                 mm_segment_t old_fs = get_fs();
152                 set_fs(KERNEL_DS);
153                 len = vfs_read(file, buf, PAGE_SIZE - 1, &pos);
154                 set_fs(old_fs);
155                 file->f_pos = pos;
156                 if (len < 0) {
157                         mconsole_reply(req, "Read of file failed", 1, 0);
158                         goto out_free;
159                 }
160                 /* Begin the file content on his own line. */
161                 if (first_chunk) {
162                         mconsole_reply(req, "\n", 0, 1);
163                         first_chunk = 0;
164                 }
165                 buf[len] = '\0';
166                 mconsole_reply(req, buf, 0, (len > 0));
167         } while (len > 0);
168  out_free:
169         kfree(buf);
170  out_fput:
171         fput(file);
172  out: ;
173 }
174 
175 #define UML_MCONSOLE_HELPTEXT \
176 "Commands: \n\
177     version - Get kernel version \n\
178     help - Print this message \n\
179     halt - Halt UML \n\
180     reboot - Reboot UML \n\
181     config <dev>=<config> - Add a new device to UML;  \n\
182         same syntax as command line \n\
183     config <dev> - Query the configuration of a device \n\
184     remove <dev> - Remove a device from UML \n\
185     sysrq <letter> - Performs the SysRq action controlled by the letter \n\
186     cad - invoke the Ctrl-Alt-Del handler \n\
187     stop - pause the UML; it will do nothing until it receives a 'go' \n\
188     go - continue the UML after a 'stop' \n\
189     log <string> - make UML enter <string> into the kernel log\n\
190     proc <file> - returns the contents of the UML's /proc/<file>\n\
191     stack <pid> - returns the stack of the specified pid\n\
192 "
193 
194 void mconsole_help(struct mc_request *req)
195 {
196         mconsole_reply(req, UML_MCONSOLE_HELPTEXT, 0, 0);
197 }
198 
199 void mconsole_halt(struct mc_request *req)
200 {
201         mconsole_reply(req, "", 0, 0);
202         machine_halt();
203 }
204 
205 void mconsole_reboot(struct mc_request *req)
206 {
207         mconsole_reply(req, "", 0, 0);
208         machine_restart(NULL);
209 }
210 
211 void mconsole_cad(struct mc_request *req)
212 {
213         mconsole_reply(req, "", 0, 0);
214         ctrl_alt_del();
215 }
216 
217 void mconsole_go(struct mc_request *req)
218 {
219         mconsole_reply(req, "Not stopped", 1, 0);
220 }
221 
222 void mconsole_stop(struct mc_request *req)
223 {
224         deactivate_fd(req->originating_fd, MCONSOLE_IRQ);
225         os_set_fd_block(req->originating_fd, 1);
226         mconsole_reply(req, "stopped", 0, 0);
227         for (;;) {
228                 if (!mconsole_get_request(req->originating_fd, req))
229                         continue;
230                 if (req->cmd->handler == mconsole_go)
231                         break;
232                 if (req->cmd->handler == mconsole_stop) {
233                         mconsole_reply(req, "Already stopped", 1, 0);
234                         continue;
235                 }
236                 if (req->cmd->handler == mconsole_sysrq) {
237                         struct pt_regs *old_regs;
238                         old_regs = set_irq_regs((struct pt_regs *)&req->regs);
239                         mconsole_sysrq(req);
240                         set_irq_regs(old_regs);
241                         continue;
242                 }
243                 (*req->cmd->handler)(req);
244         }
245         os_set_fd_block(req->originating_fd, 0);
246         reactivate_fd(req->originating_fd, MCONSOLE_IRQ);
247         mconsole_reply(req, "", 0, 0);
248 }
249 
250 static DEFINE_SPINLOCK(mc_devices_lock);
251 static LIST_HEAD(mconsole_devices);
252 
253 void mconsole_register_dev(struct mc_device *new)
254 {
255         spin_lock(&mc_devices_lock);
256         BUG_ON(!list_empty(&new->list));
257         list_add(&new->list, &mconsole_devices);
258         spin_unlock(&mc_devices_lock);
259 }
260 
261 static struct mc_device *mconsole_find_dev(char *name)
262 {
263         struct list_head *ele;
264         struct mc_device *dev;
265 
266         list_for_each(ele, &mconsole_devices) {
267                 dev = list_entry(ele, struct mc_device, list);
268                 if (!strncmp(name, dev->name, strlen(dev->name)))
269                         return dev;
270         }
271         return NULL;
272 }
273 
274 #define UNPLUGGED_PER_PAGE \
275         ((PAGE_SIZE - sizeof(struct list_head)) / sizeof(unsigned long))
276 
277 struct unplugged_pages {
278         struct list_head list;
279         void *pages[UNPLUGGED_PER_PAGE];
280 };
281 
282 static DEFINE_MUTEX(plug_mem_mutex);
283 static unsigned long long unplugged_pages_count = 0;
284 static LIST_HEAD(unplugged_pages);
285 static int unplug_index = UNPLUGGED_PER_PAGE;
286 
287 static int mem_config(char *str, char **error_out)
288 {
289         unsigned long long diff;
290         int err = -EINVAL, i, add;
291         char *ret;
292 
293         if (str[0] != '=') {
294                 *error_out = "Expected '=' after 'mem'";
295                 goto out;
296         }
297 
298         str++;
299         if (str[0] == '-')
300                 add = 0;
301         else if (str[0] == '+') {
302                 add = 1;
303         }
304         else {
305                 *error_out = "Expected increment to start with '-' or '+'";
306                 goto out;
307         }
308 
309         str++;
310         diff = memparse(str, &ret);
311         if (*ret != '\0') {
312                 *error_out = "Failed to parse memory increment";
313                 goto out;
314         }
315 
316         diff /= PAGE_SIZE;
317 
318         mutex_lock(&plug_mem_mutex);
319         for (i = 0; i < diff; i++) {
320                 struct unplugged_pages *unplugged;
321                 void *addr;
322 
323                 if (add) {
324                         if (list_empty(&unplugged_pages))
325                                 break;
326 
327                         unplugged = list_entry(unplugged_pages.next,
328                                                struct unplugged_pages, list);
329                         if (unplug_index > 0)
330                                 addr = unplugged->pages[--unplug_index];
331                         else {
332                                 list_del(&unplugged->list);
333                                 addr = unplugged;
334                                 unplug_index = UNPLUGGED_PER_PAGE;
335                         }
336 
337                         free_page((unsigned long) addr);
338                         unplugged_pages_count--;
339                 }
340                 else {
341                         struct page *page;
342 
343                         page = alloc_page(GFP_ATOMIC);
344                         if (page == NULL)
345                                 break;
346 
347                         unplugged = page_address(page);
348                         if (unplug_index == UNPLUGGED_PER_PAGE) {
349                                 list_add(&unplugged->list, &unplugged_pages);
350                                 unplug_index = 0;
351                         }
352                         else {
353                                 struct list_head *entry = unplugged_pages.next;
354                                 addr = unplugged;
355 
356                                 unplugged = list_entry(entry,
357                                                        struct unplugged_pages,
358                                                        list);
359                                 err = os_drop_memory(addr, PAGE_SIZE);
360                                 if (err) {
361                                         printk(KERN_ERR "Failed to release "
362                                                "memory - errno = %d\n", err);
363                                         *error_out = "Failed to release memory";
364                                         goto out_unlock;
365                                 }
366                                 unplugged->pages[unplug_index++] = addr;
367                         }
368 
369                         unplugged_pages_count++;
370                 }
371         }
372 
373         err = 0;
374 out_unlock:
375         mutex_unlock(&plug_mem_mutex);
376 out:
377         return err;
378 }
379 
380 static int mem_get_config(char *name, char *str, int size, char **error_out)
381 {
382         char buf[sizeof("18446744073709551615")];
383         int len = 0;
384 
385         sprintf(buf, "%ld", uml_physmem);
386         CONFIG_CHUNK(str, size, len, buf, 1);
387 
388         return len;
389 }
390 
391 static int mem_id(char **str, int *start_out, int *end_out)
392 {
393         *start_out = 0;
394         *end_out = 0;
395 
396         return 0;
397 }
398 
399 static int mem_remove(int n, char **error_out)
400 {
401         *error_out = "Memory doesn't support the remove operation";
402         return -EBUSY;
403 }
404 
405 static struct mc_device mem_mc = {
406         .list           = LIST_HEAD_INIT(mem_mc.list),
407         .name           = "mem",
408         .config         = mem_config,
409         .get_config     = mem_get_config,
410         .id             = mem_id,
411         .remove         = mem_remove,
412 };
413 
414 static int __init mem_mc_init(void)
415 {
416         if (can_drop_memory())
417                 mconsole_register_dev(&mem_mc);
418         else printk(KERN_ERR "Can't release memory to the host - memory "
419                     "hotplug won't be supported\n");
420         return 0;
421 }
422 
423 __initcall(mem_mc_init);
424 
425 #define CONFIG_BUF_SIZE 64
426 
427 static void mconsole_get_config(int (*get_config)(char *, char *, int,
428                                                   char **),
429                                 struct mc_request *req, char *name)
430 {
431         char default_buf[CONFIG_BUF_SIZE], *error, *buf;
432         int n, size;
433 
434         if (get_config == NULL) {
435                 mconsole_reply(req, "No get_config routine defined", 1, 0);
436                 return;
437         }
438 
439         error = NULL;
440         size = ARRAY_SIZE(default_buf);
441         buf = default_buf;
442 
443         while (1) {
444                 n = (*get_config)(name, buf, size, &error);
445                 if (error != NULL) {
446                         mconsole_reply(req, error, 1, 0);
447                         goto out;
448                 }
449 
450                 if (n <= size) {
451                         mconsole_reply(req, buf, 0, 0);
452                         goto out;
453                 }
454 
455                 if (buf != default_buf)
456                         kfree(buf);
457 
458                 size = n;
459                 buf = kmalloc(size, GFP_KERNEL);
460                 if (buf == NULL) {
461                         mconsole_reply(req, "Failed to allocate buffer", 1, 0);
462                         return;
463                 }
464         }
465  out:
466         if (buf != default_buf)
467                 kfree(buf);
468 }
469 
470 void mconsole_config(struct mc_request *req)
471 {
472         struct mc_device *dev;
473         char *ptr = req->request.data, *name, *error_string = "";
474         int err;
475 
476         ptr += strlen("config");
477         ptr = skip_spaces(ptr);
478         dev = mconsole_find_dev(ptr);
479         if (dev == NULL) {
480                 mconsole_reply(req, "Bad configuration option", 1, 0);
481                 return;
482         }
483 
484         name = &ptr[strlen(dev->name)];
485         ptr = name;
486         while ((*ptr != '=') && (*ptr != '\0'))
487                 ptr++;
488 
489         if (*ptr == '=') {
490                 err = (*dev->config)(name, &error_string);
491                 mconsole_reply(req, error_string, err, 0);
492         }
493         else mconsole_get_config(dev->get_config, req, name);
494 }
495 
496 void mconsole_remove(struct mc_request *req)
497 {
498         struct mc_device *dev;
499         char *ptr = req->request.data, *err_msg = "";
500         char error[256];
501         int err, start, end, n;
502 
503         ptr += strlen("remove");
504         ptr = skip_spaces(ptr);
505         dev = mconsole_find_dev(ptr);
506         if (dev == NULL) {
507                 mconsole_reply(req, "Bad remove option", 1, 0);
508                 return;
509         }
510 
511         ptr = &ptr[strlen(dev->name)];
512 
513         err = 1;
514         n = (*dev->id)(&ptr, &start, &end);
515         if (n < 0) {
516                 err_msg = "Couldn't parse device number";
517                 goto out;
518         }
519         else if ((n < start) || (n > end)) {
520                 sprintf(error, "Invalid device number - must be between "
521                         "%d and %d", start, end);
522                 err_msg = error;
523                 goto out;
524         }
525 
526         err_msg = NULL;
527         err = (*dev->remove)(n, &err_msg);
528         switch(err) {
529         case 0:
530                 err_msg = "";
531                 break;
532         case -ENODEV:
533                 if (err_msg == NULL)
534                         err_msg = "Device doesn't exist";
535                 break;
536         case -EBUSY:
537                 if (err_msg == NULL)
538                         err_msg = "Device is currently open";
539                 break;
540         default:
541                 break;
542         }
543 out:
544         mconsole_reply(req, err_msg, err, 0);
545 }
546 
547 struct mconsole_output {
548         struct list_head list;
549         struct mc_request *req;
550 };
551 
552 static DEFINE_SPINLOCK(client_lock);
553 static LIST_HEAD(clients);
554 static char console_buf[MCONSOLE_MAX_DATA];
555 
556 static void console_write(struct console *console, const char *string,
557                           unsigned int len)
558 {
559         struct list_head *ele;
560         int n;
561 
562         if (list_empty(&clients))
563                 return;
564 
565         while (len > 0) {
566                 n = min((size_t) len, ARRAY_SIZE(console_buf));
567                 strncpy(console_buf, string, n);
568                 string += n;
569                 len -= n;
570 
571                 list_for_each(ele, &clients) {
572                         struct mconsole_output *entry;
573 
574                         entry = list_entry(ele, struct mconsole_output, list);
575                         mconsole_reply_len(entry->req, console_buf, n, 0, 1);
576                 }
577         }
578 }
579 
580 static struct console mc_console = { .name      = "mc",
581                                      .write     = console_write,
582                                      .flags     = CON_ENABLED,
583                                      .index     = -1 };
584 
585 static int mc_add_console(void)
586 {
587         register_console(&mc_console);
588         return 0;
589 }
590 
591 late_initcall(mc_add_console);
592 
593 static void with_console(struct mc_request *req, void (*proc)(void *),
594                          void *arg)
595 {
596         struct mconsole_output entry;
597         unsigned long flags;
598 
599         entry.req = req;
600         spin_lock_irqsave(&client_lock, flags);
601         list_add(&entry.list, &clients);
602         spin_unlock_irqrestore(&client_lock, flags);
603 
604         (*proc)(arg);
605 
606         mconsole_reply_len(req, "", 0, 0, 0);
607 
608         spin_lock_irqsave(&client_lock, flags);
609         list_del(&entry.list);
610         spin_unlock_irqrestore(&client_lock, flags);
611 }
612 
613 #ifdef CONFIG_MAGIC_SYSRQ
614 
615 #include <linux/sysrq.h>
616 
617 static void sysrq_proc(void *arg)
618 {
619         char *op = arg;
620         handle_sysrq(*op);
621 }
622 
623 void mconsole_sysrq(struct mc_request *req)
624 {
625         char *ptr = req->request.data;
626 
627         ptr += strlen("sysrq");
628         ptr = skip_spaces(ptr);
629 
630         /*
631          * With 'b', the system will shut down without a chance to reply,
632          * so in this case, we reply first.
633          */
634         if (*ptr == 'b')
635                 mconsole_reply(req, "", 0, 0);
636 
637         with_console(req, sysrq_proc, ptr);
638 }
639 #else
640 void mconsole_sysrq(struct mc_request *req)
641 {
642         mconsole_reply(req, "Sysrq not compiled in", 1, 0);
643 }
644 #endif
645 
646 static void stack_proc(void *arg)
647 {
648         struct task_struct *task = arg;
649 
650         show_stack(task, NULL);
651 }
652 
653 /*
654  * Mconsole stack trace
655  *  Added by Allan Graves, Jeff Dike
656  *  Dumps a stacks registers to the linux console.
657  *  Usage stack <pid>.
658  */
659 void mconsole_stack(struct mc_request *req)
660 {
661         char *ptr = req->request.data;
662         int pid_requested= -1;
663         struct task_struct *to = NULL;
664 
665         /*
666          * Would be nice:
667          * 1) Send showregs output to mconsole.
668          * 2) Add a way to stack dump all pids.
669          */
670 
671         ptr += strlen("stack");
672         ptr = skip_spaces(ptr);
673 
674         /*
675          * Should really check for multiple pids or reject bad args here
676          */
677         /* What do the arguments in mconsole_reply mean? */
678         if (sscanf(ptr, "%d", &pid_requested) == 0) {
679                 mconsole_reply(req, "Please specify a pid", 1, 0);
680                 return;
681         }
682 
683         to = find_task_by_pid_ns(pid_requested, &init_pid_ns);
684         if ((to == NULL) || (pid_requested == 0)) {
685                 mconsole_reply(req, "Couldn't find that pid", 1, 0);
686                 return;
687         }
688         with_console(req, stack_proc, to);
689 }
690 
691 /*
692  * Changed by mconsole_setup, which is __setup, and called before SMP is
693  * active.
694  */
695 static char *notify_socket = NULL;
696 
697 static int __init mconsole_init(void)
698 {
699         /* long to avoid size mismatch warnings from gcc */
700         long sock;
701         int err;
702         char file[UNIX_PATH_MAX];
703 
704         if (umid_file_name("mconsole", file, sizeof(file)))
705                 return -1;
706         snprintf(mconsole_socket_name, sizeof(file), "%s", file);
707 
708         sock = os_create_unix_socket(file, sizeof(file), 1);
709         if (sock < 0) {
710                 printk(KERN_ERR "Failed to initialize management console\n");
711                 return 1;
712         }
713         if (os_set_fd_block(sock, 0))
714                 goto out;
715 
716         register_reboot_notifier(&reboot_notifier);
717 
718         err = um_request_irq(MCONSOLE_IRQ, sock, IRQ_READ, mconsole_interrupt,
719                              IRQF_SHARED, "mconsole", (void *)sock);
720         if (err) {
721                 printk(KERN_ERR "Failed to get IRQ for management console\n");
722                 goto out;
723         }
724 
725         if (notify_socket != NULL) {
726                 notify_socket = kstrdup(notify_socket, GFP_KERNEL);
727                 if (notify_socket != NULL)
728                         mconsole_notify(notify_socket, MCONSOLE_SOCKET,
729                                         mconsole_socket_name,
730                                         strlen(mconsole_socket_name) + 1);
731                 else printk(KERN_ERR "mconsole_setup failed to strdup "
732                             "string\n");
733         }
734 
735         printk(KERN_INFO "mconsole (version %d) initialized on %s\n",
736                MCONSOLE_VERSION, mconsole_socket_name);
737         return 0;
738 
739  out:
740         os_close_file(sock);
741         return 1;
742 }
743 
744 __initcall(mconsole_init);
745 
746 static ssize_t mconsole_proc_write(struct file *file,
747                 const char __user *buffer, size_t count, loff_t *pos)
748 {
749         char *buf;
750 
751         buf = kmalloc(count + 1, GFP_KERNEL);
752         if (buf == NULL)
753                 return -ENOMEM;
754 
755         if (copy_from_user(buf, buffer, count)) {
756                 count = -EFAULT;
757                 goto out;
758         }
759 
760         buf[count] = '\0';
761 
762         mconsole_notify(notify_socket, MCONSOLE_USER_NOTIFY, buf, count);
763  out:
764         kfree(buf);
765         return count;
766 }
767 
768 static const struct file_operations mconsole_proc_fops = {
769         .owner          = THIS_MODULE,
770         .write          = mconsole_proc_write,
771         .llseek         = noop_llseek,
772 };
773 
774 static int create_proc_mconsole(void)
775 {
776         struct proc_dir_entry *ent;
777 
778         if (notify_socket == NULL)
779                 return 0;
780 
781         ent = proc_create("mconsole", 0200, NULL, &mconsole_proc_fops);
782         if (ent == NULL) {
783                 printk(KERN_INFO "create_proc_mconsole : proc_create failed\n");
784                 return 0;
785         }
786         return 0;
787 }
788 
789 static DEFINE_SPINLOCK(notify_spinlock);
790 
791 void lock_notify(void)
792 {
793         spin_lock(&notify_spinlock);
794 }
795 
796 void unlock_notify(void)
797 {
798         spin_unlock(&notify_spinlock);
799 }
800 
801 __initcall(create_proc_mconsole);
802 
803 #define NOTIFY "notify:"
804 
805 static int mconsole_setup(char *str)
806 {
807         if (!strncmp(str, NOTIFY, strlen(NOTIFY))) {
808                 str += strlen(NOTIFY);
809                 notify_socket = str;
810         }
811         else printk(KERN_ERR "mconsole_setup : Unknown option - '%s'\n", str);
812         return 1;
813 }
814 
815 __setup("mconsole=", mconsole_setup);
816 
817 __uml_help(mconsole_setup,
818 "mconsole=notify:<socket>\n"
819 "    Requests that the mconsole driver send a message to the named Unix\n"
820 "    socket containing the name of the mconsole socket.  This also serves\n"
821 "    to notify outside processes when UML has booted far enough to respond\n"
822 "    to mconsole requests.\n\n"
823 );
824 
825 static int notify_panic(struct notifier_block *self, unsigned long unused1,
826                         void *ptr)
827 {
828         char *message = ptr;
829 
830         if (notify_socket == NULL)
831                 return 0;
832 
833         mconsole_notify(notify_socket, MCONSOLE_PANIC, message,
834                         strlen(message) + 1);
835         return 0;
836 }
837 
838 static struct notifier_block panic_exit_notifier = {
839         .notifier_call          = notify_panic,
840         .next                   = NULL,
841         .priority               = 1
842 };
843 
844 static int add_notifier(void)
845 {
846         atomic_notifier_chain_register(&panic_notifier_list,
847                         &panic_exit_notifier);
848         return 0;
849 }
850 
851 __initcall(add_notifier);
852 
853 char *mconsole_notify_socket(void)
854 {
855         return notify_socket;
856 }
857 
858 EXPORT_SYMBOL(mconsole_notify_socket);
859 

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