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