1 /* 2 * Linux Magic System Request Key Hacks 3 * 4 * (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz> 5 * based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz> 6 * 7 * (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com> 8 * overhauled to use key registration 9 * based upon discusions in irc://irc.openprojects.net/#kernelnewbies 10 * 11 * Copyright (c) 2010 Dmitry Torokhov 12 * Input handler conversion 13 */ 14 15 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 16 17 #include <linux/sched/signal.h> 18 #include <linux/sched/rt.h> 19 #include <linux/sched/debug.h> 20 #include <linux/sched/task.h> 21 #include <linux/interrupt.h> 22 #include <linux/mm.h> 23 #include <linux/fs.h> 24 #include <linux/mount.h> 25 #include <linux/kdev_t.h> 26 #include <linux/major.h> 27 #include <linux/reboot.h> 28 #include <linux/sysrq.h> 29 #include <linux/kbd_kern.h> 30 #include <linux/proc_fs.h> 31 #include <linux/nmi.h> 32 #include <linux/quotaops.h> 33 #include <linux/perf_event.h> 34 #include <linux/kernel.h> 35 #include <linux/module.h> 36 #include <linux/suspend.h> 37 #include <linux/writeback.h> 38 #include <linux/swap.h> 39 #include <linux/spinlock.h> 40 #include <linux/vt_kern.h> 41 #include <linux/workqueue.h> 42 #include <linux/hrtimer.h> 43 #include <linux/oom.h> 44 #include <linux/slab.h> 45 #include <linux/input.h> 46 #include <linux/uaccess.h> 47 #include <linux/moduleparam.h> 48 #include <linux/jiffies.h> 49 #include <linux/syscalls.h> 50 #include <linux/of.h> 51 #include <linux/rcupdate.h> 52 53 #include <asm/ptrace.h> 54 #include <asm/irq_regs.h> 55 56 /* Whether we react on sysrq keys or just ignore them */ 57 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE; 58 static bool __read_mostly sysrq_always_enabled; 59 60 static bool sysrq_on(void) 61 { 62 return sysrq_enabled || sysrq_always_enabled; 63 } 64 65 /* 66 * A value of 1 means 'all', other nonzero values are an op mask: 67 */ 68 static bool sysrq_on_mask(int mask) 69 { 70 return sysrq_always_enabled || 71 sysrq_enabled == 1 || 72 (sysrq_enabled & mask); 73 } 74 75 static int __init sysrq_always_enabled_setup(char *str) 76 { 77 sysrq_always_enabled = true; 78 pr_info("sysrq always enabled.\n"); 79 80 return 1; 81 } 82 83 __setup("sysrq_always_enabled", sysrq_always_enabled_setup); 84 85 86 static void sysrq_handle_loglevel(int key) 87 { 88 int i; 89 90 i = key - '0'; 91 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 92 pr_info("Loglevel set to %d\n", i); 93 console_loglevel = i; 94 } 95 static struct sysrq_key_op sysrq_loglevel_op = { 96 .handler = sysrq_handle_loglevel, 97 .help_msg = "loglevel(0-9)", 98 .action_msg = "Changing Loglevel", 99 .enable_mask = SYSRQ_ENABLE_LOG, 100 }; 101 102 #ifdef CONFIG_VT 103 static void sysrq_handle_SAK(int key) 104 { 105 struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work; 106 schedule_work(SAK_work); 107 } 108 static struct sysrq_key_op sysrq_SAK_op = { 109 .handler = sysrq_handle_SAK, 110 .help_msg = "sak(k)", 111 .action_msg = "SAK", 112 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 113 }; 114 #else 115 #define sysrq_SAK_op (*(struct sysrq_key_op *)NULL) 116 #endif 117 118 #ifdef CONFIG_VT 119 static void sysrq_handle_unraw(int key) 120 { 121 vt_reset_unicode(fg_console); 122 } 123 124 static struct sysrq_key_op sysrq_unraw_op = { 125 .handler = sysrq_handle_unraw, 126 .help_msg = "unraw(r)", 127 .action_msg = "Keyboard mode set to system default", 128 .enable_mask = SYSRQ_ENABLE_KEYBOARD, 129 }; 130 #else 131 #define sysrq_unraw_op (*(struct sysrq_key_op *)NULL) 132 #endif /* CONFIG_VT */ 133 134 static void sysrq_handle_crash(int key) 135 { 136 char *killer = NULL; 137 138 /* we need to release the RCU read lock here, 139 * otherwise we get an annoying 140 * 'BUG: sleeping function called from invalid context' 141 * complaint from the kernel before the panic. 142 */ 143 rcu_read_unlock(); 144 panic_on_oops = 1; /* force panic */ 145 wmb(); 146 *killer = 1; 147 } 148 static struct sysrq_key_op sysrq_crash_op = { 149 .handler = sysrq_handle_crash, 150 .help_msg = "crash(c)", 151 .action_msg = "Trigger a crash", 152 .enable_mask = SYSRQ_ENABLE_DUMP, 153 }; 154 155 static void sysrq_handle_reboot(int key) 156 { 157 lockdep_off(); 158 local_irq_enable(); 159 emergency_restart(); 160 } 161 static struct sysrq_key_op sysrq_reboot_op = { 162 .handler = sysrq_handle_reboot, 163 .help_msg = "reboot(b)", 164 .action_msg = "Resetting", 165 .enable_mask = SYSRQ_ENABLE_BOOT, 166 }; 167 168 static void sysrq_handle_sync(int key) 169 { 170 emergency_sync(); 171 } 172 static struct sysrq_key_op sysrq_sync_op = { 173 .handler = sysrq_handle_sync, 174 .help_msg = "sync(s)", 175 .action_msg = "Emergency Sync", 176 .enable_mask = SYSRQ_ENABLE_SYNC, 177 }; 178 179 static void sysrq_handle_show_timers(int key) 180 { 181 sysrq_timer_list_show(); 182 } 183 184 static struct sysrq_key_op sysrq_show_timers_op = { 185 .handler = sysrq_handle_show_timers, 186 .help_msg = "show-all-timers(q)", 187 .action_msg = "Show clockevent devices & pending hrtimers (no others)", 188 }; 189 190 static void sysrq_handle_mountro(int key) 191 { 192 emergency_remount(); 193 } 194 static struct sysrq_key_op sysrq_mountro_op = { 195 .handler = sysrq_handle_mountro, 196 .help_msg = "unmount(u)", 197 .action_msg = "Emergency Remount R/O", 198 .enable_mask = SYSRQ_ENABLE_REMOUNT, 199 }; 200 201 #ifdef CONFIG_LOCKDEP 202 static void sysrq_handle_showlocks(int key) 203 { 204 debug_show_all_locks(); 205 } 206 207 static struct sysrq_key_op sysrq_showlocks_op = { 208 .handler = sysrq_handle_showlocks, 209 .help_msg = "show-all-locks(d)", 210 .action_msg = "Show Locks Held", 211 }; 212 #else 213 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL) 214 #endif 215 216 #ifdef CONFIG_SMP 217 static DEFINE_SPINLOCK(show_lock); 218 219 static void showacpu(void *dummy) 220 { 221 unsigned long flags; 222 223 /* Idle CPUs have no interesting backtrace. */ 224 if (idle_cpu(smp_processor_id())) 225 return; 226 227 spin_lock_irqsave(&show_lock, flags); 228 pr_info("CPU%d:\n", smp_processor_id()); 229 show_stack(NULL, NULL); 230 spin_unlock_irqrestore(&show_lock, flags); 231 } 232 233 static void sysrq_showregs_othercpus(struct work_struct *dummy) 234 { 235 smp_call_function(showacpu, NULL, 0); 236 } 237 238 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus); 239 240 static void sysrq_handle_showallcpus(int key) 241 { 242 /* 243 * Fall back to the workqueue based printing if the 244 * backtrace printing did not succeed or the 245 * architecture has no support for it: 246 */ 247 if (!trigger_all_cpu_backtrace()) { 248 struct pt_regs *regs = get_irq_regs(); 249 250 if (regs) { 251 pr_info("CPU%d:\n", smp_processor_id()); 252 show_regs(regs); 253 } 254 schedule_work(&sysrq_showallcpus); 255 } 256 } 257 258 static struct sysrq_key_op sysrq_showallcpus_op = { 259 .handler = sysrq_handle_showallcpus, 260 .help_msg = "show-backtrace-all-active-cpus(l)", 261 .action_msg = "Show backtrace of all active CPUs", 262 .enable_mask = SYSRQ_ENABLE_DUMP, 263 }; 264 #endif 265 266 static void sysrq_handle_showregs(int key) 267 { 268 struct pt_regs *regs = get_irq_regs(); 269 if (regs) 270 show_regs(regs); 271 perf_event_print_debug(); 272 } 273 static struct sysrq_key_op sysrq_showregs_op = { 274 .handler = sysrq_handle_showregs, 275 .help_msg = "show-registers(p)", 276 .action_msg = "Show Regs", 277 .enable_mask = SYSRQ_ENABLE_DUMP, 278 }; 279 280 static void sysrq_handle_showstate(int key) 281 { 282 show_state(); 283 show_workqueue_state(); 284 } 285 static struct sysrq_key_op sysrq_showstate_op = { 286 .handler = sysrq_handle_showstate, 287 .help_msg = "show-task-states(t)", 288 .action_msg = "Show State", 289 .enable_mask = SYSRQ_ENABLE_DUMP, 290 }; 291 292 static void sysrq_handle_showstate_blocked(int key) 293 { 294 show_state_filter(TASK_UNINTERRUPTIBLE); 295 } 296 static struct sysrq_key_op sysrq_showstate_blocked_op = { 297 .handler = sysrq_handle_showstate_blocked, 298 .help_msg = "show-blocked-tasks(w)", 299 .action_msg = "Show Blocked State", 300 .enable_mask = SYSRQ_ENABLE_DUMP, 301 }; 302 303 #ifdef CONFIG_TRACING 304 #include <linux/ftrace.h> 305 306 static void sysrq_ftrace_dump(int key) 307 { 308 ftrace_dump(DUMP_ALL); 309 } 310 static struct sysrq_key_op sysrq_ftrace_dump_op = { 311 .handler = sysrq_ftrace_dump, 312 .help_msg = "dump-ftrace-buffer(z)", 313 .action_msg = "Dump ftrace buffer", 314 .enable_mask = SYSRQ_ENABLE_DUMP, 315 }; 316 #else 317 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL) 318 #endif 319 320 static void sysrq_handle_showmem(int key) 321 { 322 show_mem(0, NULL); 323 } 324 static struct sysrq_key_op sysrq_showmem_op = { 325 .handler = sysrq_handle_showmem, 326 .help_msg = "show-memory-usage(m)", 327 .action_msg = "Show Memory", 328 .enable_mask = SYSRQ_ENABLE_DUMP, 329 }; 330 331 /* 332 * Signal sysrq helper function. Sends a signal to all user processes. 333 */ 334 static void send_sig_all(int sig) 335 { 336 struct task_struct *p; 337 338 read_lock(&tasklist_lock); 339 for_each_process(p) { 340 if (p->flags & PF_KTHREAD) 341 continue; 342 if (is_global_init(p)) 343 continue; 344 345 do_send_sig_info(sig, SEND_SIG_FORCED, p, true); 346 } 347 read_unlock(&tasklist_lock); 348 } 349 350 static void sysrq_handle_term(int key) 351 { 352 send_sig_all(SIGTERM); 353 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 354 } 355 static struct sysrq_key_op sysrq_term_op = { 356 .handler = sysrq_handle_term, 357 .help_msg = "terminate-all-tasks(e)", 358 .action_msg = "Terminate All Tasks", 359 .enable_mask = SYSRQ_ENABLE_SIGNAL, 360 }; 361 362 static void moom_callback(struct work_struct *ignored) 363 { 364 const gfp_t gfp_mask = GFP_KERNEL; 365 struct oom_control oc = { 366 .zonelist = node_zonelist(first_memory_node, gfp_mask), 367 .nodemask = NULL, 368 .memcg = NULL, 369 .gfp_mask = gfp_mask, 370 .order = -1, 371 }; 372 373 mutex_lock(&oom_lock); 374 if (!out_of_memory(&oc)) 375 pr_info("OOM request ignored because killer is disabled\n"); 376 mutex_unlock(&oom_lock); 377 } 378 379 static DECLARE_WORK(moom_work, moom_callback); 380 381 static void sysrq_handle_moom(int key) 382 { 383 schedule_work(&moom_work); 384 } 385 static struct sysrq_key_op sysrq_moom_op = { 386 .handler = sysrq_handle_moom, 387 .help_msg = "memory-full-oom-kill(f)", 388 .action_msg = "Manual OOM execution", 389 .enable_mask = SYSRQ_ENABLE_SIGNAL, 390 }; 391 392 #ifdef CONFIG_BLOCK 393 static void sysrq_handle_thaw(int key) 394 { 395 emergency_thaw_all(); 396 } 397 static struct sysrq_key_op sysrq_thaw_op = { 398 .handler = sysrq_handle_thaw, 399 .help_msg = "thaw-filesystems(j)", 400 .action_msg = "Emergency Thaw of all frozen filesystems", 401 .enable_mask = SYSRQ_ENABLE_SIGNAL, 402 }; 403 #endif 404 405 static void sysrq_handle_kill(int key) 406 { 407 send_sig_all(SIGKILL); 408 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 409 } 410 static struct sysrq_key_op sysrq_kill_op = { 411 .handler = sysrq_handle_kill, 412 .help_msg = "kill-all-tasks(i)", 413 .action_msg = "Kill All Tasks", 414 .enable_mask = SYSRQ_ENABLE_SIGNAL, 415 }; 416 417 static void sysrq_handle_unrt(int key) 418 { 419 normalize_rt_tasks(); 420 } 421 static struct sysrq_key_op sysrq_unrt_op = { 422 .handler = sysrq_handle_unrt, 423 .help_msg = "nice-all-RT-tasks(n)", 424 .action_msg = "Nice All RT Tasks", 425 .enable_mask = SYSRQ_ENABLE_RTNICE, 426 }; 427 428 /* Key Operations table and lock */ 429 static DEFINE_SPINLOCK(sysrq_key_table_lock); 430 431 static struct sysrq_key_op *sysrq_key_table[36] = { 432 &sysrq_loglevel_op, /* 0 */ 433 &sysrq_loglevel_op, /* 1 */ 434 &sysrq_loglevel_op, /* 2 */ 435 &sysrq_loglevel_op, /* 3 */ 436 &sysrq_loglevel_op, /* 4 */ 437 &sysrq_loglevel_op, /* 5 */ 438 &sysrq_loglevel_op, /* 6 */ 439 &sysrq_loglevel_op, /* 7 */ 440 &sysrq_loglevel_op, /* 8 */ 441 &sysrq_loglevel_op, /* 9 */ 442 443 /* 444 * a: Don't use for system provided sysrqs, it is handled specially on 445 * sparc and will never arrive. 446 */ 447 NULL, /* a */ 448 &sysrq_reboot_op, /* b */ 449 &sysrq_crash_op, /* c & ibm_emac driver debug */ 450 &sysrq_showlocks_op, /* d */ 451 &sysrq_term_op, /* e */ 452 &sysrq_moom_op, /* f */ 453 /* g: May be registered for the kernel debugger */ 454 NULL, /* g */ 455 NULL, /* h - reserved for help */ 456 &sysrq_kill_op, /* i */ 457 #ifdef CONFIG_BLOCK 458 &sysrq_thaw_op, /* j */ 459 #else 460 NULL, /* j */ 461 #endif 462 &sysrq_SAK_op, /* k */ 463 #ifdef CONFIG_SMP 464 &sysrq_showallcpus_op, /* l */ 465 #else 466 NULL, /* l */ 467 #endif 468 &sysrq_showmem_op, /* m */ 469 &sysrq_unrt_op, /* n */ 470 /* o: This will often be registered as 'Off' at init time */ 471 NULL, /* o */ 472 &sysrq_showregs_op, /* p */ 473 &sysrq_show_timers_op, /* q */ 474 &sysrq_unraw_op, /* r */ 475 &sysrq_sync_op, /* s */ 476 &sysrq_showstate_op, /* t */ 477 &sysrq_mountro_op, /* u */ 478 /* v: May be registered for frame buffer console restore */ 479 NULL, /* v */ 480 &sysrq_showstate_blocked_op, /* w */ 481 /* x: May be registered on mips for TLB dump */ 482 /* x: May be registered on ppc/powerpc for xmon */ 483 /* x: May be registered on sparc64 for global PMU dump */ 484 NULL, /* x */ 485 /* y: May be registered on sparc64 for global register dump */ 486 NULL, /* y */ 487 &sysrq_ftrace_dump_op, /* z */ 488 }; 489 490 /* key2index calculation, -1 on invalid index */ 491 static int sysrq_key_table_key2index(int key) 492 { 493 int retval; 494 495 if ((key >= '0') && (key <= '9')) 496 retval = key - '0'; 497 else if ((key >= 'a') && (key <= 'z')) 498 retval = key + 10 - 'a'; 499 else 500 retval = -1; 501 return retval; 502 } 503 504 /* 505 * get and put functions for the table, exposed to modules. 506 */ 507 struct sysrq_key_op *__sysrq_get_key_op(int key) 508 { 509 struct sysrq_key_op *op_p = NULL; 510 int i; 511 512 i = sysrq_key_table_key2index(key); 513 if (i != -1) 514 op_p = sysrq_key_table[i]; 515 516 return op_p; 517 } 518 519 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p) 520 { 521 int i = sysrq_key_table_key2index(key); 522 523 if (i != -1) 524 sysrq_key_table[i] = op_p; 525 } 526 527 void __handle_sysrq(int key, bool check_mask) 528 { 529 struct sysrq_key_op *op_p; 530 int orig_log_level; 531 int i; 532 533 rcu_sysrq_start(); 534 rcu_read_lock(); 535 /* 536 * Raise the apparent loglevel to maximum so that the sysrq header 537 * is shown to provide the user with positive feedback. We do not 538 * simply emit this at KERN_EMERG as that would change message 539 * routing in the consumers of /proc/kmsg. 540 */ 541 orig_log_level = console_loglevel; 542 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 543 pr_info("SysRq : "); 544 545 op_p = __sysrq_get_key_op(key); 546 if (op_p) { 547 /* 548 * Should we check for enabled operations (/proc/sysrq-trigger 549 * should not) and is the invoked operation enabled? 550 */ 551 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 552 pr_cont("%s\n", op_p->action_msg); 553 console_loglevel = orig_log_level; 554 op_p->handler(key); 555 } else { 556 pr_cont("This sysrq operation is disabled.\n"); 557 } 558 } else { 559 pr_cont("HELP : "); 560 /* Only print the help msg once per handler */ 561 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 562 if (sysrq_key_table[i]) { 563 int j; 564 565 for (j = 0; sysrq_key_table[i] != 566 sysrq_key_table[j]; j++) 567 ; 568 if (j != i) 569 continue; 570 pr_cont("%s ", sysrq_key_table[i]->help_msg); 571 } 572 } 573 pr_cont("\n"); 574 console_loglevel = orig_log_level; 575 } 576 rcu_read_unlock(); 577 rcu_sysrq_end(); 578 } 579 580 void handle_sysrq(int key) 581 { 582 if (sysrq_on()) 583 __handle_sysrq(key, true); 584 } 585 EXPORT_SYMBOL(handle_sysrq); 586 587 #ifdef CONFIG_INPUT 588 static int sysrq_reset_downtime_ms; 589 590 /* Simple translation table for the SysRq keys */ 591 static const unsigned char sysrq_xlate[KEY_CNT] = 592 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 593 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 594 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 595 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 596 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 597 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 598 "\r\000/"; /* 0x60 - 0x6f */ 599 600 struct sysrq_state { 601 struct input_handle handle; 602 struct work_struct reinject_work; 603 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 604 unsigned int alt; 605 unsigned int alt_use; 606 bool active; 607 bool need_reinject; 608 bool reinjecting; 609 610 /* reset sequence handling */ 611 bool reset_canceled; 612 bool reset_requested; 613 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 614 int reset_seq_len; 615 int reset_seq_cnt; 616 int reset_seq_version; 617 struct timer_list keyreset_timer; 618 }; 619 620 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 621 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 622 static unsigned int sysrq_reset_seq_len; 623 static unsigned int sysrq_reset_seq_version = 1; 624 625 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 626 { 627 int i; 628 unsigned short key; 629 630 state->reset_seq_cnt = 0; 631 632 for (i = 0; i < sysrq_reset_seq_len; i++) { 633 key = sysrq_reset_seq[i]; 634 635 if (key == KEY_RESERVED || key > KEY_MAX) 636 break; 637 638 __set_bit(key, state->reset_keybit); 639 state->reset_seq_len++; 640 641 if (test_bit(key, state->key_down)) 642 state->reset_seq_cnt++; 643 } 644 645 /* Disable reset until old keys are not released */ 646 state->reset_canceled = state->reset_seq_cnt != 0; 647 648 state->reset_seq_version = sysrq_reset_seq_version; 649 } 650 651 static void sysrq_do_reset(unsigned long _state) 652 { 653 struct sysrq_state *state = (struct sysrq_state *) _state; 654 655 state->reset_requested = true; 656 657 sys_sync(); 658 kernel_restart(NULL); 659 } 660 661 static void sysrq_handle_reset_request(struct sysrq_state *state) 662 { 663 if (state->reset_requested) 664 __handle_sysrq(sysrq_xlate[KEY_B], false); 665 666 if (sysrq_reset_downtime_ms) 667 mod_timer(&state->keyreset_timer, 668 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 669 else 670 sysrq_do_reset((unsigned long)state); 671 } 672 673 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 674 unsigned int code, int value) 675 { 676 if (!test_bit(code, state->reset_keybit)) { 677 /* 678 * Pressing any key _not_ in reset sequence cancels 679 * the reset sequence. Also cancelling the timer in 680 * case additional keys were pressed after a reset 681 * has been requested. 682 */ 683 if (value && state->reset_seq_cnt) { 684 state->reset_canceled = true; 685 del_timer(&state->keyreset_timer); 686 } 687 } else if (value == 0) { 688 /* 689 * Key release - all keys in the reset sequence need 690 * to be pressed and held for the reset timeout 691 * to hold. 692 */ 693 del_timer(&state->keyreset_timer); 694 695 if (--state->reset_seq_cnt == 0) 696 state->reset_canceled = false; 697 } else if (value == 1) { 698 /* key press, not autorepeat */ 699 if (++state->reset_seq_cnt == state->reset_seq_len && 700 !state->reset_canceled) { 701 sysrq_handle_reset_request(state); 702 } 703 } 704 } 705 706 #ifdef CONFIG_OF 707 static void sysrq_of_get_keyreset_config(void) 708 { 709 u32 key; 710 struct device_node *np; 711 struct property *prop; 712 const __be32 *p; 713 714 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 715 if (!np) { 716 pr_debug("No sysrq node found"); 717 return; 718 } 719 720 /* Reset in case a __weak definition was present */ 721 sysrq_reset_seq_len = 0; 722 723 of_property_for_each_u32(np, "keyset", prop, p, key) { 724 if (key == KEY_RESERVED || key > KEY_MAX || 725 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 726 break; 727 728 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 729 } 730 731 /* Get reset timeout if any. */ 732 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 733 } 734 #else 735 static void sysrq_of_get_keyreset_config(void) 736 { 737 } 738 #endif 739 740 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 741 { 742 struct sysrq_state *sysrq = 743 container_of(work, struct sysrq_state, reinject_work); 744 struct input_handle *handle = &sysrq->handle; 745 unsigned int alt_code = sysrq->alt_use; 746 747 if (sysrq->need_reinject) { 748 /* we do not want the assignment to be reordered */ 749 sysrq->reinjecting = true; 750 mb(); 751 752 /* Simulate press and release of Alt + SysRq */ 753 input_inject_event(handle, EV_KEY, alt_code, 1); 754 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 755 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 756 757 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 758 input_inject_event(handle, EV_KEY, alt_code, 0); 759 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 760 761 mb(); 762 sysrq->reinjecting = false; 763 } 764 } 765 766 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 767 unsigned int code, int value) 768 { 769 bool was_active = sysrq->active; 770 bool suppress; 771 772 switch (code) { 773 774 case KEY_LEFTALT: 775 case KEY_RIGHTALT: 776 if (!value) { 777 /* One of ALTs is being released */ 778 if (sysrq->active && code == sysrq->alt_use) 779 sysrq->active = false; 780 781 sysrq->alt = KEY_RESERVED; 782 783 } else if (value != 2) { 784 sysrq->alt = code; 785 sysrq->need_reinject = false; 786 } 787 break; 788 789 case KEY_SYSRQ: 790 if (value == 1 && sysrq->alt != KEY_RESERVED) { 791 sysrq->active = true; 792 sysrq->alt_use = sysrq->alt; 793 /* 794 * If nothing else will be pressed we'll need 795 * to re-inject Alt-SysRq keysroke. 796 */ 797 sysrq->need_reinject = true; 798 } 799 800 /* 801 * Pretend that sysrq was never pressed at all. This 802 * is needed to properly handle KGDB which will try 803 * to release all keys after exiting debugger. If we 804 * do not clear key bit it KGDB will end up sending 805 * release events for Alt and SysRq, potentially 806 * triggering print screen function. 807 */ 808 if (sysrq->active) 809 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 810 811 break; 812 813 default: 814 if (sysrq->active && value && value != 2) { 815 sysrq->need_reinject = false; 816 __handle_sysrq(sysrq_xlate[code], true); 817 } 818 break; 819 } 820 821 suppress = sysrq->active; 822 823 if (!sysrq->active) { 824 825 /* 826 * See if reset sequence has changed since the last time. 827 */ 828 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 829 sysrq_parse_reset_sequence(sysrq); 830 831 /* 832 * If we are not suppressing key presses keep track of 833 * keyboard state so we can release keys that have been 834 * pressed before entering SysRq mode. 835 */ 836 if (value) 837 set_bit(code, sysrq->key_down); 838 else 839 clear_bit(code, sysrq->key_down); 840 841 if (was_active) 842 schedule_work(&sysrq->reinject_work); 843 844 /* Check for reset sequence */ 845 sysrq_detect_reset_sequence(sysrq, code, value); 846 847 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 848 /* 849 * Pass on release events for keys that was pressed before 850 * entering SysRq mode. 851 */ 852 suppress = false; 853 } 854 855 return suppress; 856 } 857 858 static bool sysrq_filter(struct input_handle *handle, 859 unsigned int type, unsigned int code, int value) 860 { 861 struct sysrq_state *sysrq = handle->private; 862 bool suppress; 863 864 /* 865 * Do not filter anything if we are in the process of re-injecting 866 * Alt+SysRq combination. 867 */ 868 if (sysrq->reinjecting) 869 return false; 870 871 switch (type) { 872 873 case EV_SYN: 874 suppress = false; 875 break; 876 877 case EV_KEY: 878 suppress = sysrq_handle_keypress(sysrq, code, value); 879 break; 880 881 default: 882 suppress = sysrq->active; 883 break; 884 } 885 886 return suppress; 887 } 888 889 static int sysrq_connect(struct input_handler *handler, 890 struct input_dev *dev, 891 const struct input_device_id *id) 892 { 893 struct sysrq_state *sysrq; 894 int error; 895 896 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 897 if (!sysrq) 898 return -ENOMEM; 899 900 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 901 902 sysrq->handle.dev = dev; 903 sysrq->handle.handler = handler; 904 sysrq->handle.name = "sysrq"; 905 sysrq->handle.private = sysrq; 906 setup_timer(&sysrq->keyreset_timer, 907 sysrq_do_reset, (unsigned long)sysrq); 908 909 error = input_register_handle(&sysrq->handle); 910 if (error) { 911 pr_err("Failed to register input sysrq handler, error %d\n", 912 error); 913 goto err_free; 914 } 915 916 error = input_open_device(&sysrq->handle); 917 if (error) { 918 pr_err("Failed to open input device, error %d\n", error); 919 goto err_unregister; 920 } 921 922 return 0; 923 924 err_unregister: 925 input_unregister_handle(&sysrq->handle); 926 err_free: 927 kfree(sysrq); 928 return error; 929 } 930 931 static void sysrq_disconnect(struct input_handle *handle) 932 { 933 struct sysrq_state *sysrq = handle->private; 934 935 input_close_device(handle); 936 cancel_work_sync(&sysrq->reinject_work); 937 del_timer_sync(&sysrq->keyreset_timer); 938 input_unregister_handle(handle); 939 kfree(sysrq); 940 } 941 942 /* 943 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 944 * keyboards have SysRq key predefined and so user may add it to keymap 945 * later, but we expect all such keyboards to have left alt. 946 */ 947 static const struct input_device_id sysrq_ids[] = { 948 { 949 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 950 INPUT_DEVICE_ID_MATCH_KEYBIT, 951 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) }, 952 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) }, 953 }, 954 { }, 955 }; 956 957 static struct input_handler sysrq_handler = { 958 .filter = sysrq_filter, 959 .connect = sysrq_connect, 960 .disconnect = sysrq_disconnect, 961 .name = "sysrq", 962 .id_table = sysrq_ids, 963 }; 964 965 static bool sysrq_handler_registered; 966 967 static inline void sysrq_register_handler(void) 968 { 969 int error; 970 971 sysrq_of_get_keyreset_config(); 972 973 error = input_register_handler(&sysrq_handler); 974 if (error) 975 pr_err("Failed to register input handler, error %d", error); 976 else 977 sysrq_handler_registered = true; 978 } 979 980 static inline void sysrq_unregister_handler(void) 981 { 982 if (sysrq_handler_registered) { 983 input_unregister_handler(&sysrq_handler); 984 sysrq_handler_registered = false; 985 } 986 } 987 988 static int sysrq_reset_seq_param_set(const char *buffer, 989 const struct kernel_param *kp) 990 { 991 unsigned long val; 992 int error; 993 994 error = kstrtoul(buffer, 0, &val); 995 if (error < 0) 996 return error; 997 998 if (val > KEY_MAX) 999 return -EINVAL; 1000 1001 *((unsigned short *)kp->arg) = val; 1002 sysrq_reset_seq_version++; 1003 1004 return 0; 1005 } 1006 1007 static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 1008 .get = param_get_ushort, 1009 .set = sysrq_reset_seq_param_set, 1010 }; 1011 1012 #define param_check_sysrq_reset_seq(name, p) \ 1013 __param_check(name, p, unsigned short) 1014 1015 /* 1016 * not really modular, but the easiest way to keep compat with existing 1017 * bootargs behaviour is to continue using module_param here. 1018 */ 1019 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1020 &sysrq_reset_seq_len, 0644); 1021 1022 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1023 1024 #else 1025 1026 static inline void sysrq_register_handler(void) 1027 { 1028 } 1029 1030 static inline void sysrq_unregister_handler(void) 1031 { 1032 } 1033 1034 #endif /* CONFIG_INPUT */ 1035 1036 int sysrq_toggle_support(int enable_mask) 1037 { 1038 bool was_enabled = sysrq_on(); 1039 1040 sysrq_enabled = enable_mask; 1041 1042 if (was_enabled != sysrq_on()) { 1043 if (sysrq_on()) 1044 sysrq_register_handler(); 1045 else 1046 sysrq_unregister_handler(); 1047 } 1048 1049 return 0; 1050 } 1051 1052 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p, 1053 struct sysrq_key_op *remove_op_p) 1054 { 1055 int retval; 1056 1057 spin_lock(&sysrq_key_table_lock); 1058 if (__sysrq_get_key_op(key) == remove_op_p) { 1059 __sysrq_put_key_op(key, insert_op_p); 1060 retval = 0; 1061 } else { 1062 retval = -1; 1063 } 1064 spin_unlock(&sysrq_key_table_lock); 1065 1066 /* 1067 * A concurrent __handle_sysrq either got the old op or the new op. 1068 * Wait for it to go away before returning, so the code for an old 1069 * op is not freed (eg. on module unload) while it is in use. 1070 */ 1071 synchronize_rcu(); 1072 1073 return retval; 1074 } 1075 1076 int register_sysrq_key(int key, struct sysrq_key_op *op_p) 1077 { 1078 return __sysrq_swap_key_ops(key, op_p, NULL); 1079 } 1080 EXPORT_SYMBOL(register_sysrq_key); 1081 1082 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p) 1083 { 1084 return __sysrq_swap_key_ops(key, NULL, op_p); 1085 } 1086 EXPORT_SYMBOL(unregister_sysrq_key); 1087 1088 #ifdef CONFIG_PROC_FS 1089 /* 1090 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1091 */ 1092 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1093 size_t count, loff_t *ppos) 1094 { 1095 if (count) { 1096 char c; 1097 1098 if (get_user(c, buf)) 1099 return -EFAULT; 1100 __handle_sysrq(c, false); 1101 } 1102 1103 return count; 1104 } 1105 1106 static const struct file_operations proc_sysrq_trigger_operations = { 1107 .write = write_sysrq_trigger, 1108 .llseek = noop_llseek, 1109 }; 1110 1111 static void sysrq_init_procfs(void) 1112 { 1113 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1114 &proc_sysrq_trigger_operations)) 1115 pr_err("Failed to register proc interface\n"); 1116 } 1117 1118 #else 1119 1120 static inline void sysrq_init_procfs(void) 1121 { 1122 } 1123 1124 #endif /* CONFIG_PROC_FS */ 1125 1126 static int __init sysrq_init(void) 1127 { 1128 sysrq_init_procfs(); 1129 1130 if (sysrq_on()) 1131 sysrq_register_handler(); 1132 1133 return 0; 1134 } 1135 device_initcall(sysrq_init); 1136