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 #include <linux/slab.h>
  42
  43 #include <asm/ptrace.h>
  44 #include <asm/irq_regs.h>
  45
  46 /* Whether we react on sysrq keys or just ignore them */
  47 int __read_mostly __sysrq_enabled = 1;
  48
  49 static int __read_mostly sysrq_always_enabled;
  50
  51 int sysrq_on(void)
  52 {
  53         return __sysrq_enabled || sysrq_always_enabled;
  54 }
  55
  56 /*
  57  * A value of 1 means 'all', other nonzero values are an op mask:
  58  */
  59 static inline int sysrq_on_mask(int mask)
  60 {
  61         return sysrq_always_enabled || __sysrq_enabled == 1 ||
  62                                                 (__sysrq_enabled & mask);
  63 }
  64
  65 static int __init sysrq_always_enabled_setup(char *str)
  66 {
  67         sysrq_always_enabled = 1;
  68         printk(KERN_INFO "debug: sysrq always enabled.\n");
  69
  70         return 1;
  71 }
  72
  73 __setup("sysrq_always_enabled", sysrq_always_enabled_setup);
  74
  75
  76 static void sysrq_handle_loglevel(int key, struct tty_struct *tty)
  77 {
  78         int i;
  79         i = key - '0';
  80         console_loglevel = 7;
  81         printk("Loglevel set to %d\n", i);
  82         console_loglevel = i;
  83 }
  84 static struct sysrq_key_op sysrq_loglevel_op = {
  85         .handler        = sysrq_handle_loglevel,
  86         .help_msg       = "loglevel(0-9)",
  87         .action_msg     = "Changing Loglevel",
  88         .enable_mask    = SYSRQ_ENABLE_LOG,
  89 };
  90
  91 #ifdef CONFIG_VT
  92 static void sysrq_handle_SAK(int key, struct tty_struct *tty)
  93 {
  94         struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
  95         schedule_work(SAK_work);
  96 }
  97 static struct sysrq_key_op sysrq_SAK_op = {
  98         .handler        = sysrq_handle_SAK,
  99         .help_msg       = "saK",
 100         .action_msg     = "SAK",
 101         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 102 };
 103 #else
 104 #define sysrq_SAK_op (*(struct sysrq_key_op *)0)
 105 #endif
 106
 107 #ifdef CONFIG_VT
 108 static void sysrq_handle_unraw(int key, struct tty_struct *tty)
 109 {
 110         struct kbd_struct *kbd = &kbd_table[fg_console];
 111
 112         if (kbd)
 113                 kbd->kbdmode = default_utf8 ? VC_UNICODE : VC_XLATE;
 114 }
 115 static struct sysrq_key_op sysrq_unraw_op = {
 116         .handler        = sysrq_handle_unraw,
 117         .help_msg       = "unRaw",
 118         .action_msg     = "Keyboard mode set to system default",
 119         .enable_mask    = SYSRQ_ENABLE_KEYBOARD,
 120 };
 121 #else
 122 #define sysrq_unraw_op (*(struct sysrq_key_op *)0)
 123 #endif /* CONFIG_VT */
 124
 125 static void sysrq_handle_crash(int key, struct tty_struct *tty)
 126 {
 127         char *killer = NULL;
 128
 129         panic_on_oops = 1;      /* force panic */
 130         wmb();
 131         *killer = 1;
 132 }
 133 static struct sysrq_key_op sysrq_crash_op = {
 134         .handler        = sysrq_handle_crash,
 135         .help_msg       = "Crash",
 136         .action_msg     = "Trigger a crash",
 137         .enable_mask    = SYSRQ_ENABLE_DUMP,
 138 };
 139
 140 static void sysrq_handle_reboot(int key, struct tty_struct *tty)
 141 {
 142         lockdep_off();
 143         local_irq_enable();
 144         emergency_restart();
 145 }
 146 static struct sysrq_key_op sysrq_reboot_op = {
 147         .handler        = sysrq_handle_reboot,
 148         .help_msg       = "reBoot",
 149         .action_msg     = "Resetting",
 150         .enable_mask    = SYSRQ_ENABLE_BOOT,
 151 };
 152
 153 static void sysrq_handle_sync(int key, struct tty_struct *tty)
 154 {
 155         emergency_sync();
 156 }
 157 static struct sysrq_key_op sysrq_sync_op = {
 158         .handler        = sysrq_handle_sync,
 159         .help_msg       = "Sync",
 160         .action_msg     = "Emergency Sync",
 161         .enable_mask    = SYSRQ_ENABLE_SYNC,
 162 };
 163
 164 static void sysrq_handle_show_timers(int key, struct tty_struct *tty)
 165 {
 166         sysrq_timer_list_show();
 167 }
 168
 169 static struct sysrq_key_op sysrq_show_timers_op = {
 170         .handler        = sysrq_handle_show_timers,
 171         .help_msg       = "show-all-timers(Q)",
 172         .action_msg     = "Show clockevent devices & pending hrtimers (no others)",
 173 };
 174
 175 static void sysrq_handle_mountro(int key, struct tty_struct *tty)
 176 {
 177         emergency_remount();
 178 }
 179 static struct sysrq_key_op sysrq_mountro_op = {
 180         .handler        = sysrq_handle_mountro,
 181         .help_msg       = "Unmount",
 182         .action_msg     = "Emergency Remount R/O",
 183         .enable_mask    = SYSRQ_ENABLE_REMOUNT,
 184 };
 185
 186 #ifdef CONFIG_LOCKDEP
 187 static void sysrq_handle_showlocks(int key, struct tty_struct *tty)
 188 {
 189         debug_show_all_locks();
 190 }
 191
 192 static struct sysrq_key_op sysrq_showlocks_op = {
 193         .handler        = sysrq_handle_showlocks,
 194         .help_msg       = "show-all-locks(D)",
 195         .action_msg     = "Show Locks Held",
 196 };
 197 #else
 198 #define sysrq_showlocks_op (*(struct sysrq_key_op *)0)
 199 #endif
 200
 201 #ifdef CONFIG_SMP
 202 static DEFINE_SPINLOCK(show_lock);
 203
 204 static void showacpu(void *dummy)
 205 {
 206         unsigned long flags;
 207
 208         /* Idle CPUs have no interesting backtrace. */
 209         if (idle_cpu(smp_processor_id()))
 210                 return;
 211
 212         spin_lock_irqsave(&show_lock, flags);
 213         printk(KERN_INFO "CPU%d:\n", smp_processor_id());
 214         show_stack(NULL, NULL);
 215         spin_unlock_irqrestore(&show_lock, flags);
 216 }
 217
 218 static void sysrq_showregs_othercpus(struct work_struct *dummy)
 219 {
 220         smp_call_function(showacpu, NULL, 0);
 221 }
 222
 223 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus);
 224
 225 static void sysrq_handle_showallcpus(int key, struct tty_struct *tty)
 226 {
 227         /*
 228          * Fall back to the workqueue based printing if the
 229          * backtrace printing did not succeed or the
 230          * architecture has no support for it:
 231          */
 232         if (!trigger_all_cpu_backtrace()) {
 233                 struct pt_regs *regs = get_irq_regs();
 234
 235                 if (regs) {
 236                         printk(KERN_INFO "CPU%d:\n", smp_processor_id());
 237                         show_regs(regs);
 238                 }
 239                 schedule_work(&sysrq_showallcpus);
 240         }
 241 }
 242
 243 static struct sysrq_key_op sysrq_showallcpus_op = {
 244         .handler        = sysrq_handle_showallcpus,
 245         .help_msg       = "show-backtrace-all-active-cpus(L)",
 246         .action_msg     = "Show backtrace of all active CPUs",
 247         .enable_mask    = SYSRQ_ENABLE_DUMP,
 248 };
 249 #endif
 250
 251 static void sysrq_handle_showregs(int key, struct tty_struct *tty)
 252 {
 253         struct pt_regs *regs = get_irq_regs();
 254         if (regs)
 255                 show_regs(regs);
 256         perf_event_print_debug();
 257 }
 258 static struct sysrq_key_op sysrq_showregs_op = {
 259         .handler        = sysrq_handle_showregs,
 260         .help_msg       = "show-registers(P)",
 261         .action_msg     = "Show Regs",
 262         .enable_mask    = SYSRQ_ENABLE_DUMP,
 263 };
 264
 265 static void sysrq_handle_showstate(int key, struct tty_struct *tty)
 266 {
 267         show_state();
 268 }
 269 static struct sysrq_key_op sysrq_showstate_op = {
 270         .handler        = sysrq_handle_showstate,
 271         .help_msg       = "show-task-states(T)",
 272         .action_msg     = "Show State",
 273         .enable_mask    = SYSRQ_ENABLE_DUMP,
 274 };
 275
 276 static void sysrq_handle_showstate_blocked(int key, struct tty_struct *tty)
 277 {
 278         show_state_filter(TASK_UNINTERRUPTIBLE);
 279 }
 280 static struct sysrq_key_op sysrq_showstate_blocked_op = {
 281         .handler        = sysrq_handle_showstate_blocked,
 282         .help_msg       = "show-blocked-tasks(W)",
 283         .action_msg     = "Show Blocked State",
 284         .enable_mask    = SYSRQ_ENABLE_DUMP,
 285 };
 286
 287 #ifdef CONFIG_TRACING
 288 #include <linux/ftrace.h>
 289
 290 static void sysrq_ftrace_dump(int key, struct tty_struct *tty)
 291 {
 292         ftrace_dump();
 293 }
 294 static struct sysrq_key_op sysrq_ftrace_dump_op = {
 295         .handler        = sysrq_ftrace_dump,
 296         .help_msg       = "dump-ftrace-buffer(Z)",
 297         .action_msg     = "Dump ftrace buffer",
 298         .enable_mask    = SYSRQ_ENABLE_DUMP,
 299 };
 300 #else
 301 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)0)
 302 #endif
 303
 304 static void sysrq_handle_showmem(int key, struct tty_struct *tty)
 305 {
 306         show_mem();
 307 }
 308 static struct sysrq_key_op sysrq_showmem_op = {
 309         .handler        = sysrq_handle_showmem,
 310         .help_msg       = "show-memory-usage(M)",
 311         .action_msg     = "Show Memory",
 312         .enable_mask    = SYSRQ_ENABLE_DUMP,
 313 };
 314
 315 /*
 316  * Signal sysrq helper function.  Sends a signal to all user processes.
 317  */
 318 static void send_sig_all(int sig)
 319 {
 320         struct task_struct *p;
 321
 322         for_each_process(p) {
 323                 if (p->mm && !is_global_init(p))
 324                         /* Not swapper, init nor kernel thread */
 325                         force_sig(sig, p);
 326         }
 327 }
 328
 329 static void sysrq_handle_term(int key, struct tty_struct *tty)
 330 {
 331         send_sig_all(SIGTERM);
 332         console_loglevel = 8;
 333 }
 334 static struct sysrq_key_op sysrq_term_op = {
 335         .handler        = sysrq_handle_term,
 336         .help_msg       = "terminate-all-tasks(E)",
 337         .action_msg     = "Terminate All Tasks",
 338         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 339 };
 340
 341 static void moom_callback(struct work_struct *ignored)
 342 {
 343         out_of_memory(node_zonelist(0, GFP_KERNEL), GFP_KERNEL, 0, NULL);
 344 }
 345
 346 static DECLARE_WORK(moom_work, moom_callback);
 347
 348 static void sysrq_handle_moom(int key, struct tty_struct *tty)
 349 {
 350         schedule_work(&moom_work);
 351 }
 352 static struct sysrq_key_op sysrq_moom_op = {
 353         .handler        = sysrq_handle_moom,
 354         .help_msg       = "memory-full-oom-kill(F)",
 355         .action_msg     = "Manual OOM execution",
 356         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 357 };
 358
 359 #ifdef CONFIG_BLOCK
 360 static void sysrq_handle_thaw(int key, struct tty_struct *tty)
 361 {
 362         emergency_thaw_all();
 363 }
 364 static struct sysrq_key_op sysrq_thaw_op = {
 365         .handler        = sysrq_handle_thaw,
 366         .help_msg       = "thaw-filesystems(J)",
 367         .action_msg     = "Emergency Thaw of all frozen filesystems",
 368         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 369 };
 370 #endif
 371
 372 static void sysrq_handle_kill(int key, struct tty_struct *tty)
 373 {
 374         send_sig_all(SIGKILL);
 375         console_loglevel = 8;
 376 }
 377 static struct sysrq_key_op sysrq_kill_op = {
 378         .handler        = sysrq_handle_kill,
 379         .help_msg       = "kill-all-tasks(I)",
 380         .action_msg     = "Kill All Tasks",
 381         .enable_mask    = SYSRQ_ENABLE_SIGNAL,
 382 };
 383
 384 static void sysrq_handle_unrt(int key, struct tty_struct *tty)
 385 {
 386         normalize_rt_tasks();
 387 }
 388 static struct sysrq_key_op sysrq_unrt_op = {
 389         .handler        = sysrq_handle_unrt,
 390         .help_msg       = "nice-all-RT-tasks(N)",
 391         .action_msg     = "Nice All RT Tasks",
 392         .enable_mask    = SYSRQ_ENABLE_RTNICE,
 393 };
 394
 395 /* Key Operations table and lock */
 396 static DEFINE_SPINLOCK(sysrq_key_table_lock);
 397
 398 static struct sysrq_key_op *sysrq_key_table[36] = {
 399         &sysrq_loglevel_op,             /* 0 */
 400         &sysrq_loglevel_op,             /* 1 */
 401         &sysrq_loglevel_op,             /* 2 */
 402         &sysrq_loglevel_op,             /* 3 */
 403         &sysrq_loglevel_op,             /* 4 */
 404         &sysrq_loglevel_op,             /* 5 */
 405         &sysrq_loglevel_op,             /* 6 */
 406         &sysrq_loglevel_op,             /* 7 */
 407         &sysrq_loglevel_op,             /* 8 */
 408         &sysrq_loglevel_op,             /* 9 */
 409
 410         /*
 411          * a: Don't use for system provided sysrqs, it is handled specially on
 412          * sparc and will never arrive.
 413          */
 414         NULL,                           /* a */
 415         &sysrq_reboot_op,               /* b */
 416         &sysrq_crash_op,                /* c & ibm_emac driver debug */
 417         &sysrq_showlocks_op,            /* d */
 418         &sysrq_term_op,                 /* e */
 419         &sysrq_moom_op,                 /* f */
 420         /* g: May be registered for the kernel debugger */
 421         NULL,                           /* g */
 422         NULL,                           /* h - reserved for help */
 423         &sysrq_kill_op,                 /* i */
 424 #ifdef CONFIG_BLOCK
 425         &sysrq_thaw_op,                 /* j */
 426 #else
 427         NULL,                           /* j */
 428 #endif
 429         &sysrq_SAK_op,                  /* k */
 430 #ifdef CONFIG_SMP
 431         &sysrq_showallcpus_op,          /* l */
 432 #else
 433         NULL,                           /* l */
 434 #endif
 435         &sysrq_showmem_op,              /* m */
 436         &sysrq_unrt_op,                 /* n */
 437         /* o: This will often be registered as 'Off' at init time */
 438         NULL,                           /* o */
 439         &sysrq_showregs_op,             /* p */
 440         &sysrq_show_timers_op,          /* q */
 441         &sysrq_unraw_op,                /* r */
 442         &sysrq_sync_op,                 /* s */
 443         &sysrq_showstate_op,            /* t */
 444         &sysrq_mountro_op,              /* u */
 445         /* v: May be registered for frame buffer console restore */
 446         NULL,                           /* v */
 447         &sysrq_showstate_blocked_op,    /* w */
 448         /* x: May be registered on ppc/powerpc for xmon */
 449         NULL,                           /* x */
 450         /* y: May be registered on sparc64 for global register dump */
 451         NULL,                           /* y */
 452         &sysrq_ftrace_dump_op,          /* z */
 453 };
 454
 455 /* key2index calculation, -1 on invalid index */
 456 static int sysrq_key_table_key2index(int key)
 457 {
 458         int retval;
 459
 460         if ((key >= '0') && (key <= '9'))
 461                 retval = key - '0';
 462         else if ((key >= 'a') && (key <= 'z'))
 463                 retval = key + 10 - 'a';
 464         else
 465                 retval = -1;
 466         return retval;
 467 }
 468
 469 /*
 470  * get and put functions for the table, exposed to modules.
 471  */
 472 struct sysrq_key_op *__sysrq_get_key_op(int key)
 473 {
 474         struct sysrq_key_op *op_p = NULL;
 475         int i;
 476
 477         i = sysrq_key_table_key2index(key);
 478         if (i != -1)
 479                 op_p = sysrq_key_table[i];
 480         return op_p;
 481 }
 482
 483 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
 484 {
 485         int i = sysrq_key_table_key2index(key);
 486
 487         if (i != -1)
 488                 sysrq_key_table[i] = op_p;
 489 }
 490
 491 /*
 492  * This is the non-locking version of handle_sysrq.  It must/can only be called
 493  * by sysrq key handlers, as they are inside of the lock
 494  */
 495 void __handle_sysrq(int key, struct tty_struct *tty, int check_mask)
 496 {
 497         struct sysrq_key_op *op_p;
 498         int orig_log_level;
 499         int i;
 500         unsigned long flags;
 501
 502         spin_lock_irqsave(&sysrq_key_table_lock, flags);
 503         /*
 504          * Raise the apparent loglevel to maximum so that the sysrq header
 505          * is shown to provide the user with positive feedback.  We do not
 506          * simply emit this at KERN_EMERG as that would change message
 507          * routing in the consumers of /proc/kmsg.
 508          */
 509         orig_log_level = console_loglevel;
 510         console_loglevel = 7;
 511         printk(KERN_INFO "SysRq : ");
 512
 513         op_p = __sysrq_get_key_op(key);
 514         if (op_p) {
 515                 /*
 516                  * Should we check for enabled operations (/proc/sysrq-trigger
 517                  * should not) and is the invoked operation enabled?
 518                  */
 519                 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
 520                         printk("%s\n", op_p->action_msg);
 521                         console_loglevel = orig_log_level;
 522                         op_p->handler(key, tty);
 523                 } else {
 524                         printk("This sysrq operation is disabled.\n");
 525                 }
 526         } else {
 527                 printk("HELP : ");
 528                 /* Only print the help msg once per handler */
 529                 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
 530                         if (sysrq_key_table[i]) {
 531                                 int j;
 532
 533                                 for (j = 0; sysrq_key_table[i] !=
 534                                                 sysrq_key_table[j]; j++)
 535                                         ;
 536                                 if (j != i)
 537                                         continue;
 538                                 printk("%s ", sysrq_key_table[i]->help_msg);
 539                         }
 540                 }
 541                 printk("\n");
 542                 console_loglevel = orig_log_level;
 543         }
 544         spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
 545 }
 546
 547 /*
 548  * This function is called by the keyboard handler when SysRq is pressed
 549  * and any other keycode arrives.
 550  */
 551 void handle_sysrq(int key, struct tty_struct *tty)
 552 {
 553         if (sysrq_on())
 554                 __handle_sysrq(key, tty, 1);
 555 }
 556 EXPORT_SYMBOL(handle_sysrq);
 557
 558 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p,
 559                                 struct sysrq_key_op *remove_op_p)
 560 {
 561
 562         int retval;
 563         unsigned long flags;
 564
 565         spin_lock_irqsave(&sysrq_key_table_lock, flags);
 566         if (__sysrq_get_key_op(key) == remove_op_p) {
 567                 __sysrq_put_key_op(key, insert_op_p);
 568                 retval = 0;
 569         } else {
 570                 retval = -1;
 571         }
 572         spin_unlock_irqrestore(&sysrq_key_table_lock, flags);
 573         return retval;
 574 }
 575
 576 int register_sysrq_key(int key, struct sysrq_key_op *op_p)
 577 {
 578         return __sysrq_swap_key_ops(key, op_p, NULL);
 579 }
 580 EXPORT_SYMBOL(register_sysrq_key);
 581
 582 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p)
 583 {
 584         return __sysrq_swap_key_ops(key, NULL, op_p);
 585 }
 586 EXPORT_SYMBOL(unregister_sysrq_key);
 587
 588 #ifdef CONFIG_PROC_FS
 589 /*
 590  * writing 'C' to /proc/sysrq-trigger is like sysrq-C
 591  */
 592 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
 593                                    size_t count, loff_t *ppos)
 594 {
 595         if (count) {
 596                 char c;
 597
 598                 if (get_user(c, buf))
 599                         return -EFAULT;
 600                 __handle_sysrq(c, NULL, 0);
 601         }
 602         return count;
 603 }
 604
 605 static const struct file_operations proc_sysrq_trigger_operations = {
 606         .write          = write_sysrq_trigger,
 607 };
 608
 609 static int __init sysrq_init(void)
 610 {
 611         proc_create("sysrq-trigger", S_IWUSR, NULL, &proc_sysrq_trigger_operations);
 612         return 0;
 613 }
 614 module_init(sysrq_init);
 615 #endif