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