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