drivers/char/sysrq.c

   1 /* -*- linux-c -*-
   2  *
   3  *      $Id: sysrq.c,v 1.15 1998/08/23 14:56:41 mj Exp $
   4  *
   5  *      Linux Magic System Request Key Hacks
   6  *
   7  *      (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
   8  *      based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz>
   9  *
  10  *      (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
  11  *      overhauled to use key registration
  12  *      based upon discusions in irc://irc.openprojects.net/#kernelnewbies
  13  */
  14
  15 #include <linux/sched.h>
  16 #include <linux/interrupt.h>
  17 #include <linux/mm.h>
  18 #include <linux/fs.h>
  19 #include <linux/tty.h>
  20 #include <linux/mount.h>
  21 #include <linux/kdev_t.h>
  22 #include <linux/major.h>
  23 #include <linux/reboot.h>
  24 #include <linux/sysrq.h>
  25 #include <linux/kbd_kern.h>
  26 #include <linux/proc_fs.h>
  27 #include <linux/quotaops.h>
  28 #include <linux/kernel.h>
  29 #include <linux/module.h>
  30 #include <linux/suspend.h>
  31 #include <linux/writeback.h>
  32 #include <linux/buffer_head.h>          /* for fsync_bdev() */
  33 #include <linux/swap.h>
  34 #include <linux/spinlock.h>
  35 #include <linux/vt_kern.h>
  36 #include <linux/workqueue.h>
  37 #include <linux/kexec.h>
  38 #include <linux/irq.h>
  39 #include <linux/hrtimer.h>
  40 #include <linux/oom.h>
  41
  42 #include <asm/ptrace.h>
  43 #include <asm/irq_regs.h>
  44
  45 /* Whether we react on sysrq keys or just ignore them */
  46 int __read_mostly __sysrq_enabled = 1;
  47
  48 static int __read_mostly sysrq_always_enabled;
  49
  50 int sysrq_on(void)
  51 {
  52         return __sysrq_enabled || sysrq_always_enabled;
  53 }
  54
  55 /*
  56  * A value of 1 means 'all', other nonzero values are an op mask:
  57  */
  58 static inline int sysrq_on_mask(int mask)
  59 {
  60         return sysrq_always_enabled || __sysrq_enabled == 1 ||
  61                                                 (__sysrq_enabled & mask);
  62 }
  63
  64 static int __init sysrq_always_enabled_setup(char *str)
  65 {
  66         sysrq_always_enabled = 1;
  67         printk(KERN_INFO "debug: sysrq always enabled.\n");
  68
  69         return 1;
  70 }
  71
  72 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
  73
  74
  75 static void sysrq_handle_loglevel(int key, struct tty_struct *tty)
  76 {
  77         int i;
  78         i = key - '0';
  79         console_loglevel = 7;
  80         printk("Loglevel set to %d\n", i);
  81         console_loglevel = i;
  82 }
  83 static struct sysrq_key_op sysrq_loglevel_op = {
  84         .handler        = sysrq_handle_loglevel,
  85         .help_msg       = "loglevel(0-9)",
  86         .action_msg     = "Changing Loglevel",
  87         .enable_mask    = SYSRQ_ENABLE_LOG,
  88 };
  89
  90 #ifdef CONFIG_VT
  91 static void sysrq_handle_SAK(int key, struct tty_struct *tty)
  92 {
  93         struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
  94         schedule_work(SAK_work);
  95 }
  96 static struct sysrq_key_op sysrq_SAK_op = {
  97         .handler        = sysrq_handle_SAK,
  98         .help_msg       = "saK",
  99         .action_msg     = "SAK",
 100         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 101 };
 102 #else
 103 #define sysrq_SAK_op (*(struct sysrq_key_op *)0)
 104 #endif
 105
 106 #ifdef CONFIG_VT
 107 static void sysrq_handle_unraw(int key, struct tty_struct *tty)
 108 {
 109         struct kbd_struct *kbd = &kbd_table[fg_console];
 110
 111         if (kbd)
 112                 kbd->kbdmode = default_utf8 ? VC_UNICODE : VC_XLATE;
 113 }
 114 static struct sysrq_key_op sysrq_unraw_op = {
 115         .handler        = sysrq_handle_unraw,
 116         .help_msg       = "unRaw",
 117         .action_msg     = "Keyboard mode set to system default",
 118         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 119 };
 120 #else
 121 #define sysrq_unraw_op (*(struct sysrq_key_op *)0)
 122 #endif /* CONFIG_VT */
 123
 124 #ifdef CONFIG_KEXEC
 125 static void sysrq_handle_crashdump(int key, struct tty_struct *tty)
 126 {
 127         crash_kexec(get_irq_regs());
 128 }
 129 static struct sysrq_key_op sysrq_crashdump_op = {
 130         .handler        = sysrq_handle_crashdump,
 131         .help_msg       = "Crashdump",
 132         .action_msg     = "Trigger a crashdump",
 133         .enable_mask    = SYSRQ_ENABLE_DUMP,
 134 };
 135 #else
 136 #define sysrq_crashdump_op (*(struct sysrq_key_op *)0)
 137 #endif
 138
 139 static void sysrq_handle_reboot(int key, struct tty_struct *tty)
 140 {
 141         lockdep_off();
 142         local_irq_enable();
 143         emergency_restart();
 144 }
 145 static struct sysrq_key_op sysrq_reboot_op = {
 146         .handler        = sysrq_handle_reboot,
 147         .help_msg       = "reBoot",
 148         .action_msg     = "Resetting",
 149         .enable_mask    = SYSRQ_ENABLE_BOOT,
 150 };
 151
 152 static void sysrq_handle_sync(int key, struct tty_struct *tty)
 153 {
 154         emergency_sync();
 155 }
 156 static struct sysrq_key_op sysrq_sync_op = {
 157         .handler        = sysrq_handle_sync,
 158         .help_msg       = "Sync",
 159         .action_msg     = "Emergency Sync",
 160         .enable_mask    = SYSRQ_ENABLE_SYNC,
 161 };
 162
 163 static void sysrq_handle_show_timers(int key, struct tty_struct *tty)
 164 {
 165         sysrq_timer_list_show();
 166 }
 167
 168 static struct sysrq_key_op sysrq_show_timers_op = {
 169         .handler        = sysrq_handle_show_timers,
 170         .help_msg       = "show-all-timers(Q)",
 171         .action_msg     = "Show clockevent devices & pending hrtimers (no others)",
 172 };
 173
 174 static void sysrq_handle_mountro(int key, struct tty_struct *tty)
 175 {
 176         emergency_remount();
 177 }
 178 static struct sysrq_key_op sysrq_mountro_op = {
 179         .handler        = sysrq_handle_mountro,
 180         .help_msg       = "Unmount",
 181         .action_msg     = "Emergency Remount R/O",
 182         .enable_mask    = SYSRQ_ENABLE_REMOUNT,
 183 };
 184
 185 #ifdef CONFIG_LOCKDEP
 186 static void sysrq_handle_showlocks(int key, struct tty_struct *tty)
 187 {
 188         debug_show_all_locks();
 189 }
 190
 191 static struct sysrq_key_op sysrq_showlocks_op = {
 192         .handler        = sysrq_handle_showlocks,
 193         .help_msg       = "show-all-locks(D)",
 194         .action_msg     = "Show Locks Held",
 195 };
 196 #else
 197 #define sysrq_showlocks_op (*(struct sysrq_key_op *)0)
 198 #endif
 199
 200 #ifdef CONFIG_SMP
 201 static DEFINE_SPINLOCK(show_lock);
 202
 203 static void showacpu(void *dummy)
 204 {
 205         unsigned long flags;
 206
 207         /* Idle CPUs have no interesting backtrace. */
 208         if (idle_cpu(smp_processor_id()))
 209                 return;
 210
 211         spin_lock_irqsave(&show_lock, flags);
 212         printk(KERN_INFO "CPU%d:\n", smp_processor_id());
 213         show_stack(NULL, NULL);
 214         spin_unlock_irqrestore(&show_lock, flags);
 215 }
 216
 217 static void sysrq_showregs_othercpus(struct work_struct *dummy)
 218 {
 219         smp_call_function(showacpu, NULL, 0);
 220 }
 221
 222 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
 223
 224 static void sysrq_handle_showallcpus(int key, struct tty_struct *tty)
 225 {
 226         struct pt_regs *regs = get_irq_regs();
 227         if (regs) {
 228                 printk(KERN_INFO "CPU%d:\n", smp_processor_id());
 229                 show_regs(regs);
 230         }
 231         schedule_work(&sysrq_showallcpus);
 232 }
 233
 234 static struct sysrq_key_op sysrq_showallcpus_op = {
 235         .handler        = sysrq_handle_showallcpus,
 236         .help_msg       = "show-backtrace-all-active-cpus(L)",
 237         .action_msg     = "Show backtrace of all active CPUs",
 238         .enable_mask    = SYSRQ_ENABLE_DUMP,
 239 };
 240 #endif
 241
 242 static void sysrq_handle_showregs(int key, struct tty_struct *tty)
 243 {
 244         struct pt_regs *regs = get_irq_regs();
 245         if (regs)
 246                 show_regs(regs);
 247 }
 248 static struct sysrq_key_op sysrq_showregs_op = {
 249         .handler        = sysrq_handle_showregs,
 250         .help_msg       = "show-registers(P)",
 251         .action_msg     = "Show Regs",
 252         .enable_mask    = SYSRQ_ENABLE_DUMP,
 253 };
 254
 255 static void sysrq_handle_showstate(int key, struct tty_struct *tty)
 256 {
 257         show_state();
 258 }
 259 static struct sysrq_key_op sysrq_showstate_op = {
 260         .handler        = sysrq_handle_showstate,
 261         .help_msg       = "show-task-states(T)",
 262         .action_msg     = "Show State",
 263         .enable_mask    = SYSRQ_ENABLE_DUMP,
 264 };
 265
 266 static void sysrq_handle_showstate_blocked(int key, struct tty_struct *tty)
 267 {
 268         show_state_filter(TASK_UNINTERRUPTIBLE);
 269 }
 270 static struct sysrq_key_op sysrq_showstate_blocked_op = {
 271         .handler        = sysrq_handle_showstate_blocked,
 272         .help_msg       = "show-blocked-tasks(W)",
 273         .action_msg     = "Show Blocked State",
 274         .enable_mask    = SYSRQ_ENABLE_DUMP,
 275 };
 276
 277 #ifdef CONFIG_TRACING
 278 #include <linux/ftrace.h>
 279
 280 static void sysrq_ftrace_dump(int key, struct tty_struct *tty)
 281 {
 282         ftrace_dump();
 283 }
 284 static struct sysrq_key_op sysrq_ftrace_dump_op = {
 285         .handler        = sysrq_ftrace_dump,
 286         .help_msg       = "dumpZ-ftrace-buffer",
 287         .action_msg     = "Dump ftrace buffer",
 288         .enable_mask    = SYSRQ_ENABLE_DUMP,
 289 };
 290 #else
 291 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)0)
 292 #endif
 293
 294 static void sysrq_handle_showmem(int key, struct tty_struct *tty)
 295 {
 296         show_mem();
 297 }
 298 static struct sysrq_key_op sysrq_showmem_op = {
 299         .handler        = sysrq_handle_showmem,
 300         .help_msg       = "show-memory-usage(M)",
 301         .action_msg     = "Show Memory",
 302         .enable_mask    = SYSRQ_ENABLE_DUMP,
 303 };
 304
 305 /*
 306  * Signal sysrq helper function.  Sends a signal to all user processes.
 307  */
 308 static void send_sig_all(int sig)
 309 {
 310         struct task_struct *p;
 311
 312         for_each_process(p) {
 313                 if (p->mm && !is_global_init(p))
 314                         /* Not swapper, init nor kernel thread */
 315                         force_sig(sig, p);
 316         }
 317 }
 318
 319 static void sysrq_handle_term(int key, struct tty_struct *tty)
 320 {
 321         send_sig_all(SIGTERM);
 322         console_loglevel = 8;
 323 }
 324 static struct sysrq_key_op sysrq_term_op = {
 325         .handler        = sysrq_handle_term,
 326         .help_msg       = "terminate-all-tasks(E)",
 327         .action_msg     = "Terminate All Tasks",
 328         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 329 };
 330
 331 static void moom_callback(struct work_struct *ignored)
 332 {
 333         out_of_memory(node_zonelist(0, GFP_KERNEL), GFP_KERNEL, 0);
 334 }
 335
 336 static DECLARE_WORK(moom_work, moom_callback);
 337
 338 static void sysrq_handle_moom(int key, struct tty_struct *tty)
 339 {
 340         schedule_work(&moom_work);
 341 }
 342 static struct sysrq_key_op sysrq_moom_op = {
 343         .handler        = sysrq_handle_moom,
 344         .help_msg       = "memory-full-oom-kill(F)",
 345         .action_msg     = "Manual OOM execution",
 346         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 347 };
 348
 349 static void sysrq_handle_kill(int key, struct tty_struct *tty)
 350 {
 351         send_sig_all(SIGKILL);
 352         console_loglevel = 8;
 353 }
 354 static struct sysrq_key_op sysrq_kill_op = {
 355         .handler        = sysrq_handle_kill,
 356         .help_msg       = "kill-all-tasks(I)",
 357         .action_msg     = "Kill All Tasks",
 358         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 359 };
 360
 361 static void sysrq_handle_unrt(int key, struct tty_struct *tty)
 362 {
 363         normalize_rt_tasks();
 364 }
 365 static struct sysrq_key_op sysrq_unrt_op = {
 366         .handler        = sysrq_handle_unrt,
 367         .help_msg       = "nice-all-RT-tasks(N)",
 368         .action_msg     = "Nice All RT Tasks",
 369         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 370 };
 371
 372 /* Key Operations table and lock */
 373 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 374
 375 static struct sysrq_key_op *sysrq_key_table[36] = {
 376         &sysrq_loglevel_op,             /* 0 */
 377         &sysrq_loglevel_op,             /* 1 */
 378         &sysrq_loglevel_op,             /* 2 */
 379         &sysrq_loglevel_op,             /* 3 */
 380         &sysrq_loglevel_op,             /* 4 */
 381         &sysrq_loglevel_op,             /* 5 */
 382         &sysrq_loglevel_op,             /* 6 */
 383         &sysrq_loglevel_op,             /* 7 */
 384         &sysrq_loglevel_op,             /* 8 */
 385         &sysrq_loglevel_op,             /* 9 */
 386
 387         /*
 388          * a: Don't use for system provided sysrqs, it is handled specially on
 389          * sparc and will never arrive.
 390          */
 391         NULL,                           /* a */
 392         &sysrq_reboot_op,               /* b */
 393         &sysrq_crashdump_op,            /* c & ibm_emac driver debug */
 394         &sysrq_showlocks_op,            /* d */
 395         &sysrq_term_op,                 /* e */
 396         &sysrq_moom_op,                 /* f */
 397         /* g: May be registered by ppc for kgdb */
 398         NULL,                           /* g */
 399         NULL,                           /* h */
 400         &sysrq_kill_op,                 /* i */
 401         NULL,                           /* j */
 402         &sysrq_SAK_op,                  /* k */
 403 #ifdef CONFIG_SMP
 404         &sysrq_showallcpus_op,          /* l */
 405 #else
 406         NULL,                           /* l */
 407 #endif
 408         &sysrq_showmem_op,              /* m */
 409         &sysrq_unrt_op,                 /* n */
 410         /* o: This will often be registered as 'Off' at init time */
 411         NULL,                           /* o */
 412         &sysrq_showregs_op,             /* p */
 413         &sysrq_show_timers_op,          /* q */
 414         &sysrq_unraw_op,                /* r */
 415         &sysrq_sync_op,                 /* s */
 416         &sysrq_showstate_op,            /* t */
 417         &sysrq_mountro_op,              /* u */
 418         /* v: May be registered at init time by SMP VOYAGER */
 419         NULL,                           /* v */
 420         &sysrq_showstate_blocked_op,    /* w */
 421         /* x: May be registered on ppc/powerpc for xmon */
 422         NULL,                           /* x */
 423         /* y: May be registered on sparc64 for global register dump */
 424         NULL,                           /* y */
 425         &sysrq_ftrace_dump_op,          /* z */
 426 };
 427
 428 /* key2index calculation, -1 on invalid index */
 429 static int sysrq_key_table_key2index(int key)
 430 {
 431         int retval;
 432
 433         if ((key >= '0') && (key <= '9'))
 434                 retval = key - '0';
 435         else if ((key >= 'a') && (key <= 'z'))
 436                 retval = key + 10 - 'a';
 437         else
 438                 retval = -1;
 439         return retval;
 440 }
 441
 442 /*
 443  * get and put functions for the table, exposed to modules.
 444  */
 445 struct sysrq_key_op *__sysrq_get_key_op(int key)
 446 {
 447         struct sysrq_key_op *op_p = NULL;
 448         int i;
 449
 450         i = sysrq_key_table_key2index(key);
 451         if (i != -1)
 452                 op_p = sysrq_key_table[i];
 453         return op_p;
 454 }
 455
 456 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
 457 {
 458         int i = sysrq_key_table_key2index(key);
 459
 460         if (i != -1)
 461                 sysrq_key_table[i] = op_p;
 462 }
 463
 464 /*
 465  * This is the non-locking version of handle_sysrq.  It must/can only be called
 466  * by sysrq key handlers, as they are inside of the lock
 467  */
 468 void __handle_sysrq(int key, struct tty_struct *tty, int check_mask)
 469 {
 470         struct sysrq_key_op *op_p;
 471         int orig_log_level;
 472         int i;
 473         unsigned long flags;
 474
 475         spin_lock_irqsave(&sysrq_key_table_lock, flags);
 476         /*
 477          * Raise the apparent loglevel to maximum so that the sysrq header
 478          * is shown to provide the user with positive feedback.  We do not
 479          * simply emit this at KERN_EMERG as that would change message
 480          * routing in the consumers of /proc/kmsg.
 481          */
 482         orig_log_level = console_loglevel;
 483         console_loglevel = 7;
 484         printk(KERN_INFO "SysRq : ");
 485
 486         op_p = __sysrq_get_key_op(key);
 487         if (op_p) {
 488                 /*
 489                  * Should we check for enabled operations (/proc/sysrq-trigger
 490                  * should not) and is the invoked operation enabled?
 491                  */
 492                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 493                         printk("%s\n", op_p->action_msg);
 494                         console_loglevel = orig_log_level;
 495                         op_p->handler(key, tty);
 496                 } else {
 497                         printk("This sysrq operation is disabled.\n");
 498                 }
 499         } else {
 500                 printk("HELP : ");
 501                 /* Only print the help msg once per handler */
 502                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 503                         if (sysrq_key_table[i]) {
 504                                 int j;
 505
 506                                 for (j = 0; sysrq_key_table[i] !=
 507                                                 sysrq_key_table[j]; j++)
 508                                         ;
 509                                 if (j != i)
 510                                         continue;
 511                                 printk("%s ", sysrq_key_table[i]->help_msg);
 512                         }
 513                 }
 514                 printk("\n");
 515                 console_loglevel = orig_log_level;
 516         }
 517         spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
 518 }
 519
 520 /*
 521  * This function is called by the keyboard handler when SysRq is pressed
 522  * and any other keycode arrives.
 523  */
 524 void handle_sysrq(int key, struct tty_struct *tty)
 525 {
 526         if (sysrq_on())
 527                 __handle_sysrq(key, tty, 1);
 528 }
 529 EXPORT_SYMBOL(handle_sysrq);
 530
 531 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
 532                                 struct sysrq_key_op *remove_op_p)
 533 {
 534
 535         int retval;
 536         unsigned long flags;
 537
 538         spin_lock_irqsave(&sysrq_key_table_lock, flags);
 539         if (__sysrq_get_key_op(key) == remove_op_p) {
 540                 __sysrq_put_key_op(key, insert_op_p);
 541                 retval = 0;
 542         } else {
 543                 retval = -1;
 544         }
 545         spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
 546         return retval;
 547 }
 548
 549 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
 550 {
 551         return __sysrq_swap_key_ops(key, op_p, NULL);
 552 }
 553 EXPORT_SYMBOL(register_sysrq_key);
 554
 555 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
 556 {
 557         return __sysrq_swap_key_ops(key, NULL, op_p);
 558 }
 559 EXPORT_SYMBOL(unregister_sysrq_key);
 560
 561 #ifdef CONFIG_PROC_FS
 562 /*
 563  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
 564  */
 565 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
 566                                    size_t count, loff_t *ppos)
 567 {
 568         if (count) {
 569                 char c;
 570
 571                 if (get_user(c, buf))
 572                         return -EFAULT;
 573                 __handle_sysrq(c, NULL, 0);
 574         }
 575         return count;
 576 }
 577
 578 static const struct file_operations proc_sysrq_trigger_operations = {
 579         .write          = write_sysrq_trigger,
 580 };
 581
 582 static int __init sysrq_init(void)
 583 {
 584         proc_create("sysrq-trigger", S_IWUSR, NULL, &proc_sysrq_trigger_operations);
 585         return 0;
 586 }
 587 module_init(sysrq_init);
 588 #endif