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/nmi.h>
  28 #include <linux/quotaops.h>
  29 #include <linux/perf_event.h>
  30 #include <linux/kernel.h>
  31 #include <linux/module.h>
  32 #include <linux/suspend.h>
  33 #include <linux/writeback.h>
  34 #include <linux/buffer_head.h>          /* for fsync_bdev() */
  35 #include <linux/swap.h>
  36 #include <linux/spinlock.h>
  37 #include <linux/vt_kern.h>
  38 #include <linux/workqueue.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 static void sysrq_handle_crash(int key, struct tty_struct *tty)
 125 {
 126         char *killer = NULL;
 127
 128         panic_on_oops = 1;      /* force panic */
 129         wmb();
 130         *killer = 1;
 131 }
 132 static struct sysrq_key_op sysrq_crash_op = {
 133         .handler        = sysrq_handle_crash,
 134         .help_msg       = "Crash",
 135         .action_msg     = "Trigger a crash",
 136         .enable_mask    = SYSRQ_ENABLE_DUMP,
 137 };
 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         /*
 227          * Fall back to the workqueue based printing if the
 228          * backtrace printing did not succeed or the
 229          * architecture has no support for it:
 230          */
 231         if (!trigger_all_cpu_backtrace()) {
 232                 struct pt_regs *regs = get_irq_regs();
 233
 234                 if (regs) {
 235                         printk(KERN_INFO "CPU%d:\n", smp_processor_id());
 236                         show_regs(regs);
 237                 }
 238                 schedule_work(&sysrq_showallcpus);
 239         }
 240 }
 241
 242 static struct sysrq_key_op sysrq_showallcpus_op = {
 243         .handler        = sysrq_handle_showallcpus,
 244         .help_msg       = "show-backtrace-all-active-cpus(L)",
 245         .action_msg     = "Show backtrace of all active CPUs",
 246         .enable_mask    = SYSRQ_ENABLE_DUMP,
 247 };
 248 #endif
 249
 250 static void sysrq_handle_showregs(int key, struct tty_struct *tty)
 251 {
 252         struct pt_regs *regs = get_irq_regs();
 253         if (regs)
 254                 show_regs(regs);
 255         perf_event_print_debug();
 256 }
 257 static struct sysrq_key_op sysrq_showregs_op = {
 258         .handler        = sysrq_handle_showregs,
 259         .help_msg       = "show-registers(P)",
 260         .action_msg     = "Show Regs",
 261         .enable_mask    = SYSRQ_ENABLE_DUMP,
 262 };
 263
 264 static void sysrq_handle_showstate(int key, struct tty_struct *tty)
 265 {
 266         show_state();
 267 }
 268 static struct sysrq_key_op sysrq_showstate_op = {
 269         .handler        = sysrq_handle_showstate,
 270         .help_msg       = "show-task-states(T)",
 271         .action_msg     = "Show State",
 272         .enable_mask    = SYSRQ_ENABLE_DUMP,
 273 };
 274
 275 static void sysrq_handle_showstate_blocked(int key, struct tty_struct *tty)
 276 {
 277         show_state_filter(TASK_UNINTERRUPTIBLE);
 278 }
 279 static struct sysrq_key_op sysrq_showstate_blocked_op = {
 280         .handler        = sysrq_handle_showstate_blocked,
 281         .help_msg       = "show-blocked-tasks(W)",
 282         .action_msg     = "Show Blocked State",
 283         .enable_mask    = SYSRQ_ENABLE_DUMP,
 284 };
 285
 286 #ifdef CONFIG_TRACING
 287 #include <linux/ftrace.h>
 288
 289 static void sysrq_ftrace_dump(int key, struct tty_struct *tty)
 290 {
 291         ftrace_dump();
 292 }
 293 static struct sysrq_key_op sysrq_ftrace_dump_op = {
 294         .handler        = sysrq_ftrace_dump,
 295         .help_msg       = "dump-ftrace-buffer(Z)",
 296         .action_msg     = "Dump ftrace buffer",
 297         .enable_mask    = SYSRQ_ENABLE_DUMP,
 298 };
 299 #else
 300 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)0)
 301 #endif
 302
 303 static void sysrq_handle_showmem(int key, struct tty_struct *tty)
 304 {
 305         show_mem();
 306 }
 307 static struct sysrq_key_op sysrq_showmem_op = {
 308         .handler        = sysrq_handle_showmem,
 309         .help_msg       = "show-memory-usage(M)",
 310         .action_msg     = "Show Memory",
 311         .enable_mask    = SYSRQ_ENABLE_DUMP,
 312 };
 313
 314 /*
 315  * Signal sysrq helper function.  Sends a signal to all user processes.
 316  */
 317 static void send_sig_all(int sig)
 318 {
 319         struct task_struct *p;
 320
 321         for_each_process(p) {
 322                 if (p->mm && !is_global_init(p))
 323                         /* Not swapper, init nor kernel thread */
 324                         force_sig(sig, p);
 325         }
 326 }
 327
 328 static void sysrq_handle_term(int key, struct tty_struct *tty)
 329 {
 330         send_sig_all(SIGTERM);
 331         console_loglevel = 8;
 332 }
 333 static struct sysrq_key_op sysrq_term_op = {
 334         .handler        = sysrq_handle_term,
 335         .help_msg       = "terminate-all-tasks(E)",
 336         .action_msg     = "Terminate All Tasks",
 337         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 338 };
 339
 340 static void moom_callback(struct work_struct *ignored)
 341 {
 342         out_of_memory(node_zonelist(0, GFP_KERNEL), GFP_KERNEL, 0);
 343 }
 344
 345 static DECLARE_WORK(moom_work, moom_callback);
 346
 347 static void sysrq_handle_moom(int key, struct tty_struct *tty)
 348 {
 349         schedule_work(&moom_work);
 350 }
 351 static struct sysrq_key_op sysrq_moom_op = {
 352         .handler        = sysrq_handle_moom,
 353         .help_msg       = "memory-full-oom-kill(F)",
 354         .action_msg     = "Manual OOM execution",
 355         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 356 };
 357
 358 #ifdef CONFIG_BLOCK
 359 static void sysrq_handle_thaw(int key, struct tty_struct *tty)
 360 {
 361         emergency_thaw_all();
 362 }
 363 static struct sysrq_key_op sysrq_thaw_op = {
 364         .handler        = sysrq_handle_thaw,
 365         .help_msg       = "thaw-filesystems(J)",
 366         .action_msg     = "Emergency Thaw of all frozen filesystems",
 367         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 368 };
 369 #endif
 370
 371 static void sysrq_handle_kill(int key, struct tty_struct *tty)
 372 {
 373         send_sig_all(SIGKILL);
 374         console_loglevel = 8;
 375 }
 376 static struct sysrq_key_op sysrq_kill_op = {
 377         .handler        = sysrq_handle_kill,
 378         .help_msg       = "kill-all-tasks(I)",
 379         .action_msg     = "Kill All Tasks",
 380         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 381 };
 382
 383 static void sysrq_handle_unrt(int key, struct tty_struct *tty)
 384 {
 385         normalize_rt_tasks();
 386 }
 387 static struct sysrq_key_op sysrq_unrt_op = {
 388         .handler        = sysrq_handle_unrt,
 389         .help_msg       = "nice-all-RT-tasks(N)",
 390         .action_msg     = "Nice All RT Tasks",
 391         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 392 };
 393
 394 /* Key Operations table and lock */
 395 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 396
 397 static struct sysrq_key_op *sysrq_key_table[36] = {
 398         &sysrq_loglevel_op,             /* 0 */
 399         &sysrq_loglevel_op,             /* 1 */
 400         &sysrq_loglevel_op,             /* 2 */
 401         &sysrq_loglevel_op,             /* 3 */
 402         &sysrq_loglevel_op,             /* 4 */
 403         &sysrq_loglevel_op,             /* 5 */
 404         &sysrq_loglevel_op,             /* 6 */
 405         &sysrq_loglevel_op,             /* 7 */
 406         &sysrq_loglevel_op,             /* 8 */
 407         &sysrq_loglevel_op,             /* 9 */
 408
 409         /*
 410          * a: Don't use for system provided sysrqs, it is handled specially on
 411          * sparc and will never arrive.
 412          */
 413         NULL,                           /* a */
 414         &sysrq_reboot_op,               /* b */
 415         &sysrq_crash_op,                /* c & ibm_emac driver debug */
 416         &sysrq_showlocks_op,            /* d */
 417         &sysrq_term_op,                 /* e */
 418         &sysrq_moom_op,                 /* f */
 419         /* g: May be registered for the kernel debugger */
 420         NULL,                           /* g */
 421         NULL,                           /* h - reserved for help */
 422         &sysrq_kill_op,                 /* i */
 423 #ifdef CONFIG_BLOCK
 424         &sysrq_thaw_op,                 /* j */
 425 #else
 426         NULL,                           /* j */
 427 #endif
 428         &sysrq_SAK_op,                  /* k */
 429 #ifdef CONFIG_SMP
 430         &sysrq_showallcpus_op,          /* l */
 431 #else
 432         NULL,                           /* l */
 433 #endif
 434         &sysrq_showmem_op,              /* m */
 435         &sysrq_unrt_op,                 /* n */
 436         /* o: This will often be registered as 'Off' at init time */
 437         NULL,                           /* o */
 438         &sysrq_showregs_op,             /* p */
 439         &sysrq_show_timers_op,          /* q */
 440         &sysrq_unraw_op,                /* r */
 441         &sysrq_sync_op,                 /* s */
 442         &sysrq_showstate_op,            /* t */
 443         &sysrq_mountro_op,              /* u */
 444         /* v: May be registered for frame buffer console restore */
 445         NULL,                           /* v */
 446         &sysrq_showstate_blocked_op,    /* w */
 447         /* x: May be registered on ppc/powerpc for xmon */
 448         NULL,                           /* x */
 449         /* y: May be registered on sparc64 for global register dump */
 450         NULL,                           /* y */
 451         &sysrq_ftrace_dump_op,          /* z */
 452 };
 453
 454 /* key2index calculation, -1 on invalid index */
 455 static int sysrq_key_table_key2index(int key)
 456 {
 457         int retval;
 458
 459         if ((key >= '0') && (key <= '9'))
 460                 retval = key - '0';
 461         else if ((key >= 'a') && (key <= 'z'))
 462                 retval = key + 10 - 'a';
 463         else
 464                 retval = -1;
 465         return retval;
 466 }
 467
 468 /*
 469  * get and put functions for the table, exposed to modules.
 470  */
 471 struct sysrq_key_op *__sysrq_get_key_op(int key)
 472 {
 473         struct sysrq_key_op *op_p = NULL;
 474         int i;
 475
 476         i = sysrq_key_table_key2index(key);
 477         if (i != -1)
 478                 op_p = sysrq_key_table[i];
 479         return op_p;
 480 }
 481
 482 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
 483 {
 484         int i = sysrq_key_table_key2index(key);
 485
 486         if (i != -1)
 487                 sysrq_key_table[i] = op_p;
 488 }
 489
 490 /*
 491  * This is the non-locking version of handle_sysrq.  It must/can only be called
 492  * by sysrq key handlers, as they are inside of the lock
 493  */
 494 void __handle_sysrq(int key, struct tty_struct *tty, int check_mask)
 495 {
 496         struct sysrq_key_op *op_p;
 497         int orig_log_level;
 498         int i;
 499         unsigned long flags;
 500
 501         spin_lock_irqsave(&sysrq_key_table_lock, flags);
 502         /*
 503          * Raise the apparent loglevel to maximum so that the sysrq header
 504          * is shown to provide the user with positive feedback.  We do not
 505          * simply emit this at KERN_EMERG as that would change message
 506          * routing in the consumers of /proc/kmsg.
 507          */
 508         orig_log_level = console_loglevel;
 509         console_loglevel = 7;
 510         printk(KERN_INFO "SysRq : ");
 511
 512         op_p = __sysrq_get_key_op(key);
 513         if (op_p) {
 514                 /*
 515                  * Should we check for enabled operations (/proc/sysrq-trigger
 516                  * should not) and is the invoked operation enabled?
 517                  */
 518                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 519                         printk("%s\n", op_p->action_msg);
 520                         console_loglevel = orig_log_level;
 521                         op_p->handler(key, tty);
 522                 } else {
 523                         printk("This sysrq operation is disabled.\n");
 524                 }
 525         } else {
 526                 printk("HELP : ");
 527                 /* Only print the help msg once per handler */
 528                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 529                         if (sysrq_key_table[i]) {
 530                                 int j;
 531
 532                                 for (j = 0; sysrq_key_table[i] !=
 533                                                 sysrq_key_table[j]; j++)
 534                                         ;
 535                                 if (j != i)
 536                                         continue;
 537                                 printk("%s ", sysrq_key_table[i]->help_msg);
 538                         }
 539                 }
 540                 printk("\n");
 541                 console_loglevel = orig_log_level;
 542         }
 543         spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
 544 }
 545
 546 /*
 547  * This function is called by the keyboard handler when SysRq is pressed
 548  * and any other keycode arrives.
 549  */
 550 void handle_sysrq(int key, struct tty_struct *tty)
 551 {
 552         if (sysrq_on())
 553                 __handle_sysrq(key, tty, 1);
 554 }
 555 EXPORT_SYMBOL(handle_sysrq);
 556
 557 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
 558                                 struct sysrq_key_op *remove_op_p)
 559 {
 560
 561         int retval;
 562         unsigned long flags;
 563
 564         spin_lock_irqsave(&sysrq_key_table_lock, flags);
 565         if (__sysrq_get_key_op(key) == remove_op_p) {
 566                 __sysrq_put_key_op(key, insert_op_p);
 567                 retval = 0;
 568         } else {
 569                 retval = -1;
 570         }
 571         spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
 572         return retval;
 573 }
 574
 575 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
 576 {
 577         return __sysrq_swap_key_ops(key, op_p, NULL);
 578 }
 579 EXPORT_SYMBOL(register_sysrq_key);
 580
 581 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
 582 {
 583         return __sysrq_swap_key_ops(key, NULL, op_p);
 584 }
 585 EXPORT_SYMBOL(unregister_sysrq_key);
 586
 587 #ifdef CONFIG_PROC_FS
 588 /*
 589  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
 590  */
 591 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
 592                                    size_t count, loff_t *ppos)
 593 {
 594         if (count) {
 595                 char c;
 596
 597                 if (get_user(c, buf))
 598                         return -EFAULT;
 599                 __handle_sysrq(c, NULL, 0);
 600         }
 601         return count;
 602 }
 603
 604 static const struct file_operations proc_sysrq_trigger_operations = {
 605         .write          = write_sysrq_trigger,
 606 };
 607
 608 static int __init sysrq_init(void)
 609 {
 610         proc_create("sysrq-trigger", S_IWUSR, NULL, &proc_sysrq_trigger_operations);
 611         return 0;
 612 }
 613 module_init(sysrq_init);
 614 #endif