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