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/hrtimer.h>
  39 #include <linux/oom.h>
  40
  41 #include <asm/ptrace.h>
  42 #include <asm/irq_regs.h>
  43
  44 /* Whether we react on sysrq keys or just ignore them */
  45 int __read_mostly __sysrq_enabled = 1;
  46
  47 static int __read_mostly sysrq_always_enabled;
  48
  49 int sysrq_on(void)
  50 {
  51         return __sysrq_enabled || sysrq_always_enabled;
  52 }
  53
  54 /*
  55  * A value of 1 means 'all', other nonzero values are an op mask:
  56  */
  57 static inline int sysrq_on_mask(int mask)
  58 {
  59         return sysrq_always_enabled || __sysrq_enabled == 1 ||
  60                                                 (__sysrq_enabled & mask);
  61 }
  62
  63 static int __init sysrq_always_enabled_setup(char *str)
  64 {
  65         sysrq_always_enabled = 1;
  66         printk(KERN_INFO "debug: sysrq always enabled.\n");
  67
  68         return 1;
  69 }
  70
  71 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
  72
  73
  74 static void sysrq_handle_loglevel(int key, struct tty_struct *tty)
  75 {
  76         int i;
  77         i = key - '0';
  78         console_loglevel = 7;
  79         printk("Loglevel set to %d\n", i);
  80         console_loglevel = i;
  81 }
  82 static struct sysrq_key_op sysrq_loglevel_op = {
  83         .handler        = sysrq_handle_loglevel,
  84         .help_msg       = "loglevel(0-9)",
  85         .action_msg     = "Changing Loglevel",
  86         .enable_mask    = SYSRQ_ENABLE_LOG,
  87 };
  88
  89 #ifdef CONFIG_VT
  90 static void sysrq_handle_SAK(int key, struct tty_struct *tty)
  91 {
  92         struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
  93         schedule_work(SAK_work);
  94 }
  95 static struct sysrq_key_op sysrq_SAK_op = {
  96         .handler        = sysrq_handle_SAK,
  97         .help_msg       = "saK",
  98         .action_msg     = "SAK",
  99         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 100 };
 101 #else
 102 #define sysrq_SAK_op (*(struct sysrq_key_op *)0)
 103 #endif
 104
 105 #ifdef CONFIG_VT
 106 static void sysrq_handle_unraw(int key, struct tty_struct *tty)
 107 {
 108         struct kbd_struct *kbd = &kbd_table[fg_console];
 109
 110         if (kbd)
 111                 kbd->kbdmode = default_utf8 ? VC_UNICODE : VC_XLATE;
 112 }
 113 static struct sysrq_key_op sysrq_unraw_op = {
 114         .handler        = sysrq_handle_unraw,
 115         .help_msg       = "unRaw",
 116         .action_msg     = "Keyboard mode set to system default",
 117         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 118 };
 119 #else
 120 #define sysrq_unraw_op (*(struct sysrq_key_op *)0)
 121 #endif /* CONFIG_VT */
 122
 123 #ifdef CONFIG_KEXEC
 124 static void sysrq_handle_crashdump(int key, struct tty_struct *tty)
 125 {
 126         crash_kexec(get_irq_regs());
 127 }
 128 static struct sysrq_key_op sysrq_crashdump_op = {
 129         .handler        = sysrq_handle_crashdump,
 130         .help_msg       = "Crashdump",
 131         .action_msg     = "Trigger a crashdump",
 132         .enable_mask    = SYSRQ_ENABLE_DUMP,
 133 };
 134 #else
 135 #define sysrq_crashdump_op (*(struct sysrq_key_op *)0)
 136 #endif
 137
 138 static void sysrq_handle_reboot(int key, struct tty_struct *tty)
 139 {
 140         lockdep_off();
 141         local_irq_enable();
 142         emergency_restart();
 143 }
 144 static struct sysrq_key_op sysrq_reboot_op = {
 145         .handler        = sysrq_handle_reboot,
 146         .help_msg       = "reBoot",
 147         .action_msg     = "Resetting",
 148         .enable_mask    = SYSRQ_ENABLE_BOOT,
 149 };
 150
 151 static void sysrq_handle_sync(int key, struct tty_struct *tty)
 152 {
 153         emergency_sync();
 154 }
 155 static struct sysrq_key_op sysrq_sync_op = {
 156         .handler        = sysrq_handle_sync,
 157         .help_msg       = "Sync",
 158         .action_msg     = "Emergency Sync",
 159         .enable_mask    = SYSRQ_ENABLE_SYNC,
 160 };
 161
 162 static void sysrq_handle_show_timers(int key, struct tty_struct *tty)
 163 {
 164         sysrq_timer_list_show();
 165 }
 166
 167 static struct sysrq_key_op sysrq_show_timers_op = {
 168         .handler        = sysrq_handle_show_timers,
 169         .help_msg       = "show-all-timers(Q)",
 170         .action_msg     = "Show clockevent devices & pending hrtimers (no others)",
 171 };
 172
 173 static void sysrq_handle_mountro(int key, struct tty_struct *tty)
 174 {
 175         emergency_remount();
 176 }
 177 static struct sysrq_key_op sysrq_mountro_op = {
 178         .handler        = sysrq_handle_mountro,
 179         .help_msg       = "Unmount",
 180         .action_msg     = "Emergency Remount R/O",
 181         .enable_mask    = SYSRQ_ENABLE_REMOUNT,
 182 };
 183
 184 #ifdef CONFIG_LOCKDEP
 185 static void sysrq_handle_showlocks(int key, struct tty_struct *tty)
 186 {
 187         debug_show_all_locks();
 188 }
 189
 190 static struct sysrq_key_op sysrq_showlocks_op = {
 191         .handler        = sysrq_handle_showlocks,
 192         .help_msg       = "show-all-locks(D)",
 193         .action_msg     = "Show Locks Held",
 194 };
 195 #else
 196 #define sysrq_showlocks_op (*(struct sysrq_key_op *)0)
 197 #endif
 198
 199 #ifdef CONFIG_SMP
 200 static DEFINE_SPINLOCK(show_lock);
 201
 202 static void showacpu(void *dummy)
 203 {
 204         unsigned long flags;
 205
 206         /* Idle CPUs have no interesting backtrace. */
 207         if (idle_cpu(smp_processor_id()))
 208                 return;
 209
 210         spin_lock_irqsave(&show_lock, flags);
 211         printk(KERN_INFO "CPU%d:\n", smp_processor_id());
 212         show_stack(NULL, NULL);
 213         spin_unlock_irqrestore(&show_lock, flags);
 214 }
 215
 216 static void sysrq_showregs_othercpus(struct work_struct *dummy)
 217 {
 218         smp_call_function(showacpu, NULL, 0);
 219 }
 220
 221 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
 222
 223 static void sysrq_handle_showallcpus(int key, struct tty_struct *tty)
 224 {
 225         struct pt_regs *regs = get_irq_regs();
 226         if (regs) {
 227                 printk(KERN_INFO "CPU%d:\n", smp_processor_id());
 228                 show_regs(regs);
 229         }
 230         schedule_work(&sysrq_showallcpus);
 231 }
 232
 233 static struct sysrq_key_op sysrq_showallcpus_op = {
 234         .handler        = sysrq_handle_showallcpus,
 235         .help_msg       = "show-backtrace-all-active-cpus(L)",
 236         .action_msg     = "Show backtrace of all active CPUs",
 237         .enable_mask    = SYSRQ_ENABLE_DUMP,
 238 };
 239 #endif
 240
 241 static void sysrq_handle_showregs(int key, struct tty_struct *tty)
 242 {
 243         struct pt_regs *regs = get_irq_regs();
 244         if (regs)
 245                 show_regs(regs);
 246 }
 247 static struct sysrq_key_op sysrq_showregs_op = {
 248         .handler        = sysrq_handle_showregs,
 249         .help_msg       = "show-registers(P)",
 250         .action_msg     = "Show Regs",
 251         .enable_mask    = SYSRQ_ENABLE_DUMP,
 252 };
 253
 254 static void sysrq_handle_showstate(int key, struct tty_struct *tty)
 255 {
 256         show_state();
 257 }
 258 static struct sysrq_key_op sysrq_showstate_op = {
 259         .handler        = sysrq_handle_showstate,
 260         .help_msg       = "show-task-states(T)",
 261         .action_msg     = "Show State",
 262         .enable_mask    = SYSRQ_ENABLE_DUMP,
 263 };
 264
 265 static void sysrq_handle_showstate_blocked(int key, struct tty_struct *tty)
 266 {
 267         show_state_filter(TASK_UNINTERRUPTIBLE);
 268 }
 269 static struct sysrq_key_op sysrq_showstate_blocked_op = {
 270         .handler        = sysrq_handle_showstate_blocked,
 271         .help_msg       = "show-blocked-tasks(W)",
 272         .action_msg     = "Show Blocked State",
 273         .enable_mask    = SYSRQ_ENABLE_DUMP,
 274 };
 275
 276 #ifdef CONFIG_TRACING
 277 #include <linux/ftrace.h>
 278
 279 static void sysrq_ftrace_dump(int key, struct tty_struct *tty)
 280 {
 281         ftrace_dump();
 282 }
 283 static struct sysrq_key_op sysrq_ftrace_dump_op = {
 284         .handler        = sysrq_ftrace_dump,
 285         .help_msg       = "dump-ftrace-buffer(Z)",
 286         .action_msg     = "Dump ftrace buffer",
 287         .enable_mask    = SYSRQ_ENABLE_DUMP,
 288 };
 289 #else
 290 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)0)
 291 #endif
 292
 293 static void sysrq_handle_showmem(int key, struct tty_struct *tty)
 294 {
 295         show_mem();
 296 }
 297 static struct sysrq_key_op sysrq_showmem_op = {
 298         .handler        = sysrq_handle_showmem,
 299         .help_msg       = "show-memory-usage(M)",
 300         .action_msg     = "Show Memory",
 301         .enable_mask    = SYSRQ_ENABLE_DUMP,
 302 };
 303
 304 /*
 305  * Signal sysrq helper function.  Sends a signal to all user processes.
 306  */
 307 static void send_sig_all(int sig)
 308 {
 309         struct task_struct *p;
 310
 311         for_each_process(p) {
 312                 if (p->mm && !is_global_init(p))
 313                         /* Not swapper, init nor kernel thread */
 314                         force_sig(sig, p);
 315         }
 316 }
 317
 318 static void sysrq_handle_term(int key, struct tty_struct *tty)
 319 {
 320         send_sig_all(SIGTERM);
 321         console_loglevel = 8;
 322 }
 323 static struct sysrq_key_op sysrq_term_op = {
 324         .handler        = sysrq_handle_term,
 325         .help_msg       = "terminate-all-tasks(E)",
 326         .action_msg     = "Terminate All Tasks",
 327         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 328 };
 329
 330 static void moom_callback(struct work_struct *ignored)
 331 {
 332         out_of_memory(node_zonelist(0, GFP_KERNEL), GFP_KERNEL, 0);
 333 }
 334
 335 static DECLARE_WORK(moom_work, moom_callback);
 336
 337 static void sysrq_handle_moom(int key, struct tty_struct *tty)
 338 {
 339         schedule_work(&moom_work);
 340 }
 341 static struct sysrq_key_op sysrq_moom_op = {
 342         .handler        = sysrq_handle_moom,
 343         .help_msg       = "memory-full-oom-kill(F)",
 344         .action_msg     = "Manual OOM execution",
 345         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 346 };
 347
 348 #ifdef CONFIG_BLOCK
 349 static void sysrq_handle_thaw(int key, struct tty_struct *tty)
 350 {
 351         emergency_thaw_all();
 352 }
 353 static struct sysrq_key_op sysrq_thaw_op = {
 354         .handler        = sysrq_handle_thaw,
 355         .help_msg       = "thaw-filesystems(J)",
 356         .action_msg     = "Emergency Thaw of all frozen filesystems",
 357         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 358 };
 359 #endif
 360
 361 static void sysrq_handle_kill(int key, struct tty_struct *tty)
 362 {
 363         send_sig_all(SIGKILL);
 364         console_loglevel = 8;
 365 }
 366 static struct sysrq_key_op sysrq_kill_op = {
 367         .handler        = sysrq_handle_kill,
 368         .help_msg       = "kill-all-tasks(I)",
 369         .action_msg     = "Kill All Tasks",
 370         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 371 };
 372
 373 static void sysrq_handle_unrt(int key, struct tty_struct *tty)
 374 {
 375         normalize_rt_tasks();
 376 }
 377 static struct sysrq_key_op sysrq_unrt_op = {
 378         .handler        = sysrq_handle_unrt,
 379         .help_msg       = "nice-all-RT-tasks(N)",
 380         .action_msg     = "Nice All RT Tasks",
 381         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 382 };
 383
 384 /* Key Operations table and lock */
 385 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 386
 387 static struct sysrq_key_op *sysrq_key_table[36] = {
 388         &sysrq_loglevel_op,             /* 0 */
 389         &sysrq_loglevel_op,             /* 1 */
 390         &sysrq_loglevel_op,             /* 2 */
 391         &sysrq_loglevel_op,             /* 3 */
 392         &sysrq_loglevel_op,             /* 4 */
 393         &sysrq_loglevel_op,             /* 5 */
 394         &sysrq_loglevel_op,             /* 6 */
 395         &sysrq_loglevel_op,             /* 7 */
 396         &sysrq_loglevel_op,             /* 8 */
 397         &sysrq_loglevel_op,             /* 9 */
 398
 399         /*
 400          * a: Don't use for system provided sysrqs, it is handled specially on
 401          * sparc and will never arrive.
 402          */
 403         NULL,                           /* a */
 404         &sysrq_reboot_op,               /* b */
 405         &sysrq_crashdump_op,            /* c & ibm_emac driver debug */
 406         &sysrq_showlocks_op,            /* d */
 407         &sysrq_term_op,                 /* e */
 408         &sysrq_moom_op,                 /* f */
 409         /* g: May be registered by ppc for kgdb */
 410         NULL,                           /* g */
 411         NULL,                           /* h - reserved for help */
 412         &sysrq_kill_op,                 /* i */
 413 #ifdef CONFIG_BLOCK
 414         &sysrq_thaw_op,                 /* j */
 415 #else
 416         NULL,                           /* j */
 417 #endif
 418         &sysrq_SAK_op,                  /* k */
 419 #ifdef CONFIG_SMP
 420         &sysrq_showallcpus_op,          /* l */
 421 #else
 422         NULL,                           /* l */
 423 #endif
 424         &sysrq_showmem_op,              /* m */
 425         &sysrq_unrt_op,                 /* n */
 426         /* o: This will often be registered as 'Off' at init time */
 427         NULL,                           /* o */
 428         &sysrq_showregs_op,             /* p */
 429         &sysrq_show_timers_op,          /* q */
 430         &sysrq_unraw_op,                /* r */
 431         &sysrq_sync_op,                 /* s */
 432         &sysrq_showstate_op,            /* t */
 433         &sysrq_mountro_op,              /* u */
 434         /* v: May be registered at init time by SMP VOYAGER */
 435         NULL,                           /* v */
 436         &sysrq_showstate_blocked_op,    /* w */
 437         /* x: May be registered on ppc/powerpc for xmon */
 438         NULL,                           /* x */
 439         /* y: May be registered on sparc64 for global register dump */
 440         NULL,                           /* y */
 441         &sysrq_ftrace_dump_op,          /* z */
 442 };
 443
 444 /* key2index calculation, -1 on invalid index */
 445 static int sysrq_key_table_key2index(int key)
 446 {
 447         int retval;
 448
 449         if ((key >= '0') && (key <= '9'))
 450                 retval = key - '0';
 451         else if ((key >= 'a') && (key <= 'z'))
 452                 retval = key + 10 - 'a';
 453         else
 454                 retval = -1;
 455         return retval;
 456 }
 457
 458 /*
 459  * get and put functions for the table, exposed to modules.
 460  */
 461 struct sysrq_key_op *__sysrq_get_key_op(int key)
 462 {
 463         struct sysrq_key_op *op_p = NULL;
 464         int i;
 465
 466         i = sysrq_key_table_key2index(key);
 467         if (i != -1)
 468                 op_p = sysrq_key_table[i];
 469         return op_p;
 470 }
 471
 472 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
 473 {
 474         int i = sysrq_key_table_key2index(key);
 475
 476         if (i != -1)
 477                 sysrq_key_table[i] = op_p;
 478 }
 479
 480 /*
 481  * This is the non-locking version of handle_sysrq.  It must/can only be called
 482  * by sysrq key handlers, as they are inside of the lock
 483  */
 484 void __handle_sysrq(int key, struct tty_struct *tty, int check_mask)
 485 {
 486         struct sysrq_key_op *op_p;
 487         int orig_log_level;
 488         int i;
 489         unsigned long flags;
 490
 491         spin_lock_irqsave(&sysrq_key_table_lock, flags);
 492         /*
 493          * Raise the apparent loglevel to maximum so that the sysrq header
 494          * is shown to provide the user with positive feedback.  We do not
 495          * simply emit this at KERN_EMERG as that would change message
 496          * routing in the consumers of /proc/kmsg.
 497          */
 498         orig_log_level = console_loglevel;
 499         console_loglevel = 7;
 500         printk(KERN_INFO "SysRq : ");
 501
 502         op_p = __sysrq_get_key_op(key);
 503         if (op_p) {
 504                 /*
 505                  * Should we check for enabled operations (/proc/sysrq-trigger
 506                  * should not) and is the invoked operation enabled?
 507                  */
 508                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 509                         printk("%s\n", op_p->action_msg);
 510                         console_loglevel = orig_log_level;
 511                         op_p->handler(key, tty);
 512                 } else {
 513                         printk("This sysrq operation is disabled.\n");
 514                 }
 515         } else {
 516                 printk("HELP : ");
 517                 /* Only print the help msg once per handler */
 518                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 519                         if (sysrq_key_table[i]) {
 520                                 int j;
 521
 522                                 for (j = 0; sysrq_key_table[i] !=
 523                                                 sysrq_key_table[j]; j++)
 524                                         ;
 525                                 if (j != i)
 526                                         continue;
 527                                 printk("%s ", sysrq_key_table[i]->help_msg);
 528                         }
 529                 }
 530                 printk("\n");
 531                 console_loglevel = orig_log_level;
 532         }
 533         spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
 534 }
 535
 536 /*
 537  * This function is called by the keyboard handler when SysRq is pressed
 538  * and any other keycode arrives.
 539  */
 540 void handle_sysrq(int key, struct tty_struct *tty)
 541 {
 542         if (sysrq_on())
 543                 __handle_sysrq(key, tty, 1);
 544 }
 545 EXPORT_SYMBOL(handle_sysrq);
 546
 547 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
 548                                 struct sysrq_key_op *remove_op_p)
 549 {
 550
 551         int retval;
 552         unsigned long flags;
 553
 554         spin_lock_irqsave(&sysrq_key_table_lock, flags);
 555         if (__sysrq_get_key_op(key) == remove_op_p) {
 556                 __sysrq_put_key_op(key, insert_op_p);
 557                 retval = 0;
 558         } else {
 559                 retval = -1;
 560         }
 561         spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
 562         return retval;
 563 }
 564
 565 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
 566 {
 567         return __sysrq_swap_key_ops(key, op_p, NULL);
 568 }
 569 EXPORT_SYMBOL(register_sysrq_key);
 570
 571 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
 572 {
 573         return __sysrq_swap_key_ops(key, NULL, op_p);
 574 }
 575 EXPORT_SYMBOL(unregister_sysrq_key);
 576
 577 #ifdef CONFIG_PROC_FS
 578 /*
 579  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
 580  */
 581 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
 582                                    size_t count, loff_t *ppos)
 583 {
 584         if (count) {
 585                 char c;
 586
 587                 if (get_user(c, buf))
 588                         return -EFAULT;
 589                 __handle_sysrq(c, NULL, 0);
 590         }
 591         return count;
 592 }
 593
 594 static const struct file_operations proc_sysrq_trigger_operations = {
 595         .write          = write_sysrq_trigger,
 596 };
 597
 598 static int __init sysrq_init(void)
 599 {
 600         proc_create("sysrq-trigger", S_IWUSR, NULL, &proc_sysrq_trigger_operations);
 601         return 0;
 602 }
 603 module_init(sysrq_init);
 604 #endif