1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Linux Magic System Request Key Hacks 4 * 5 * (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz> 6 * based on ideas by Pavel Machek <pavel@atrey.karlin.mff.cuni.cz> 7 * 8 * (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com> 9 * overhauled to use key registration 10 * based upon discusions in irc://irc.openprojects.net/#kernelnewbies 11 * 12 * Copyright (c) 2010 Dmitry Torokhov 13 * Input handler conversion 14 */ 15 16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 17 18 #include <linux/sched/signal.h> 19 #include <linux/sched/rt.h> 20 #include <linux/sched/debug.h> 21 #include <linux/sched/task.h> 22 #include <linux/interrupt.h> 23 #include <linux/mm.h> 24 #include <linux/fs.h> 25 #include <linux/mount.h> 26 #include <linux/kdev_t.h> 27 #include <linux/major.h> 28 #include <linux/reboot.h> 29 #include <linux/sysrq.h> 30 #include <linux/kbd_kern.h> 31 #include <linux/proc_fs.h> 32 #include <linux/nmi.h> 33 #include <linux/quotaops.h> 34 #include <linux/perf_event.h> 35 #include <linux/kernel.h> 36 #include <linux/module.h> 37 #include <linux/suspend.h> 38 #include <linux/writeback.h> 39 #include <linux/swap.h> 40 #include <linux/spinlock.h> 41 #include <linux/vt_kern.h> 42 #include <linux/workqueue.h> 43 #include <linux/hrtimer.h> 44 #include <linux/oom.h> 45 #include <linux/slab.h> 46 #include <linux/input.h> 47 #include <linux/uaccess.h> 48 #include <linux/moduleparam.h> 49 #include <linux/jiffies.h> 50 #include <linux/syscalls.h> 51 #include <linux/of.h> 52 #include <linux/rcupdate.h> 53 54 #include <asm/ptrace.h> 55 #include <asm/irq_regs.h> 56 57 /* Whether we react on sysrq keys or just ignore them */ 58 static int __read_mostly sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE; 59 static bool __read_mostly sysrq_always_enabled; 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 /* release the RCU read lock before crashing */ 138 rcu_read_unlock(); 139 140 panic("sysrq triggered crash\n"); 141 } 142 static struct sysrq_key_op sysrq_crash_op = { 143 .handler = sysrq_handle_crash, 144 .help_msg = "crash(c)", 145 .action_msg = "Trigger a crash", 146 .enable_mask = SYSRQ_ENABLE_DUMP, 147 }; 148 149 static void sysrq_handle_reboot(int key) 150 { 151 lockdep_off(); 152 local_irq_enable(); 153 emergency_restart(); 154 } 155 static struct sysrq_key_op sysrq_reboot_op = { 156 .handler = sysrq_handle_reboot, 157 .help_msg = "reboot(b)", 158 .action_msg = "Resetting", 159 .enable_mask = SYSRQ_ENABLE_BOOT, 160 }; 161 162 static void sysrq_handle_sync(int key) 163 { 164 emergency_sync(); 165 } 166 static struct sysrq_key_op sysrq_sync_op = { 167 .handler = sysrq_handle_sync, 168 .help_msg = "sync(s)", 169 .action_msg = "Emergency Sync", 170 .enable_mask = SYSRQ_ENABLE_SYNC, 171 }; 172 173 static void sysrq_handle_show_timers(int key) 174 { 175 sysrq_timer_list_show(); 176 } 177 178 static struct sysrq_key_op sysrq_show_timers_op = { 179 .handler = sysrq_handle_show_timers, 180 .help_msg = "show-all-timers(q)", 181 .action_msg = "Show clockevent devices & pending hrtimers (no others)", 182 }; 183 184 static void sysrq_handle_mountro(int key) 185 { 186 emergency_remount(); 187 } 188 static struct sysrq_key_op sysrq_mountro_op = { 189 .handler = sysrq_handle_mountro, 190 .help_msg = "unmount(u)", 191 .action_msg = "Emergency Remount R/O", 192 .enable_mask = SYSRQ_ENABLE_REMOUNT, 193 }; 194 195 #ifdef CONFIG_LOCKDEP 196 static void sysrq_handle_showlocks(int key) 197 { 198 debug_show_all_locks(); 199 } 200 201 static struct sysrq_key_op sysrq_showlocks_op = { 202 .handler = sysrq_handle_showlocks, 203 .help_msg = "show-all-locks(d)", 204 .action_msg = "Show Locks Held", 205 }; 206 #else 207 #define sysrq_showlocks_op (*(struct sysrq_key_op *)NULL) 208 #endif 209 210 #ifdef CONFIG_SMP 211 static DEFINE_RAW_SPINLOCK(show_lock); 212 213 static void showacpu(void *dummy) 214 { 215 unsigned long flags; 216 217 /* Idle CPUs have no interesting backtrace. */ 218 if (idle_cpu(smp_processor_id())) 219 return; 220 221 raw_spin_lock_irqsave(&show_lock, flags); 222 pr_info("CPU%d:\n", smp_processor_id()); 223 show_stack(NULL, NULL); 224 raw_spin_unlock_irqrestore(&show_lock, flags); 225 } 226 227 static void sysrq_showregs_othercpus(struct work_struct *dummy) 228 { 229 smp_call_function(showacpu, NULL, 0); 230 } 231 232 static DECLARE_WORK(sysrq_showallcpus, sysrq_showregs_othercpus); 233 234 static void sysrq_handle_showallcpus(int key) 235 { 236 /* 237 * Fall back to the workqueue based printing if the 238 * backtrace printing did not succeed or the 239 * architecture has no support for it: 240 */ 241 if (!trigger_all_cpu_backtrace()) { 242 struct pt_regs *regs = NULL; 243 244 if (in_irq()) 245 regs = get_irq_regs(); 246 if (regs) { 247 pr_info("CPU%d:\n", smp_processor_id()); 248 show_regs(regs); 249 } 250 schedule_work(&sysrq_showallcpus); 251 } 252 } 253 254 static struct sysrq_key_op sysrq_showallcpus_op = { 255 .handler = sysrq_handle_showallcpus, 256 .help_msg = "show-backtrace-all-active-cpus(l)", 257 .action_msg = "Show backtrace of all active CPUs", 258 .enable_mask = SYSRQ_ENABLE_DUMP, 259 }; 260 #endif 261 262 static void sysrq_handle_showregs(int key) 263 { 264 struct pt_regs *regs = NULL; 265 266 if (in_irq()) 267 regs = get_irq_regs(); 268 if (regs) 269 show_regs(regs); 270 perf_event_print_debug(); 271 } 272 static struct sysrq_key_op sysrq_showregs_op = { 273 .handler = sysrq_handle_showregs, 274 .help_msg = "show-registers(p)", 275 .action_msg = "Show Regs", 276 .enable_mask = SYSRQ_ENABLE_DUMP, 277 }; 278 279 static void sysrq_handle_showstate(int key) 280 { 281 show_state(); 282 show_workqueue_state(); 283 } 284 static struct sysrq_key_op sysrq_showstate_op = { 285 .handler = sysrq_handle_showstate, 286 .help_msg = "show-task-states(t)", 287 .action_msg = "Show State", 288 .enable_mask = SYSRQ_ENABLE_DUMP, 289 }; 290 291 static void sysrq_handle_showstate_blocked(int key) 292 { 293 show_state_filter(TASK_UNINTERRUPTIBLE); 294 } 295 static struct sysrq_key_op sysrq_showstate_blocked_op = { 296 .handler = sysrq_handle_showstate_blocked, 297 .help_msg = "show-blocked-tasks(w)", 298 .action_msg = "Show Blocked State", 299 .enable_mask = SYSRQ_ENABLE_DUMP, 300 }; 301 302 #ifdef CONFIG_TRACING 303 #include <linux/ftrace.h> 304 305 static void sysrq_ftrace_dump(int key) 306 { 307 ftrace_dump(DUMP_ALL); 308 } 309 static struct sysrq_key_op sysrq_ftrace_dump_op = { 310 .handler = sysrq_ftrace_dump, 311 .help_msg = "dump-ftrace-buffer(z)", 312 .action_msg = "Dump ftrace buffer", 313 .enable_mask = SYSRQ_ENABLE_DUMP, 314 }; 315 #else 316 #define sysrq_ftrace_dump_op (*(struct sysrq_key_op *)NULL) 317 #endif 318 319 static void sysrq_handle_showmem(int key) 320 { 321 show_mem(0, NULL); 322 } 323 static struct sysrq_key_op sysrq_showmem_op = { 324 .handler = sysrq_handle_showmem, 325 .help_msg = "show-memory-usage(m)", 326 .action_msg = "Show Memory", 327 .enable_mask = SYSRQ_ENABLE_DUMP, 328 }; 329 330 /* 331 * Signal sysrq helper function. Sends a signal to all user processes. 332 */ 333 static void send_sig_all(int sig) 334 { 335 struct task_struct *p; 336 337 read_lock(&tasklist_lock); 338 for_each_process(p) { 339 if (p->flags & PF_KTHREAD) 340 continue; 341 if (is_global_init(p)) 342 continue; 343 344 do_send_sig_info(sig, SEND_SIG_PRIV, p, PIDTYPE_MAX); 345 } 346 read_unlock(&tasklist_lock); 347 } 348 349 static void sysrq_handle_term(int key) 350 { 351 send_sig_all(SIGTERM); 352 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 353 } 354 static struct sysrq_key_op sysrq_term_op = { 355 .handler = sysrq_handle_term, 356 .help_msg = "terminate-all-tasks(e)", 357 .action_msg = "Terminate All Tasks", 358 .enable_mask = SYSRQ_ENABLE_SIGNAL, 359 }; 360 361 static void moom_callback(struct work_struct *ignored) 362 { 363 const gfp_t gfp_mask = GFP_KERNEL; 364 struct oom_control oc = { 365 .zonelist = node_zonelist(first_memory_node, gfp_mask), 366 .nodemask = NULL, 367 .memcg = NULL, 368 .gfp_mask = gfp_mask, 369 .order = -1, 370 }; 371 372 mutex_lock(&oom_lock); 373 if (!out_of_memory(&oc)) 374 pr_info("OOM request ignored. No task eligible\n"); 375 mutex_unlock(&oom_lock); 376 } 377 378 static DECLARE_WORK(moom_work, moom_callback); 379 380 static void sysrq_handle_moom(int key) 381 { 382 schedule_work(&moom_work); 383 } 384 static struct sysrq_key_op sysrq_moom_op = { 385 .handler = sysrq_handle_moom, 386 .help_msg = "memory-full-oom-kill(f)", 387 .action_msg = "Manual OOM execution", 388 .enable_mask = SYSRQ_ENABLE_SIGNAL, 389 }; 390 391 #ifdef CONFIG_BLOCK 392 static void sysrq_handle_thaw(int key) 393 { 394 emergency_thaw_all(); 395 } 396 static struct sysrq_key_op sysrq_thaw_op = { 397 .handler = sysrq_handle_thaw, 398 .help_msg = "thaw-filesystems(j)", 399 .action_msg = "Emergency Thaw of all frozen filesystems", 400 .enable_mask = SYSRQ_ENABLE_SIGNAL, 401 }; 402 #endif 403 404 static void sysrq_handle_kill(int key) 405 { 406 send_sig_all(SIGKILL); 407 console_loglevel = CONSOLE_LOGLEVEL_DEBUG; 408 } 409 static struct sysrq_key_op sysrq_kill_op = { 410 .handler = sysrq_handle_kill, 411 .help_msg = "kill-all-tasks(i)", 412 .action_msg = "Kill All Tasks", 413 .enable_mask = SYSRQ_ENABLE_SIGNAL, 414 }; 415 416 static void sysrq_handle_unrt(int key) 417 { 418 normalize_rt_tasks(); 419 } 420 static struct sysrq_key_op sysrq_unrt_op = { 421 .handler = sysrq_handle_unrt, 422 .help_msg = "nice-all-RT-tasks(n)", 423 .action_msg = "Nice All RT Tasks", 424 .enable_mask = SYSRQ_ENABLE_RTNICE, 425 }; 426 427 /* Key Operations table and lock */ 428 static DEFINE_SPINLOCK(sysrq_key_table_lock); 429 430 static struct sysrq_key_op *sysrq_key_table[36] = { 431 &sysrq_loglevel_op, /* 0 */ 432 &sysrq_loglevel_op, /* 1 */ 433 &sysrq_loglevel_op, /* 2 */ 434 &sysrq_loglevel_op, /* 3 */ 435 &sysrq_loglevel_op, /* 4 */ 436 &sysrq_loglevel_op, /* 5 */ 437 &sysrq_loglevel_op, /* 6 */ 438 &sysrq_loglevel_op, /* 7 */ 439 &sysrq_loglevel_op, /* 8 */ 440 &sysrq_loglevel_op, /* 9 */ 441 442 /* 443 * a: Don't use for system provided sysrqs, it is handled specially on 444 * sparc and will never arrive. 445 */ 446 NULL, /* a */ 447 &sysrq_reboot_op, /* b */ 448 &sysrq_crash_op, /* c */ 449 &sysrq_showlocks_op, /* d */ 450 &sysrq_term_op, /* e */ 451 &sysrq_moom_op, /* f */ 452 /* g: May be registered for the kernel debugger */ 453 NULL, /* g */ 454 NULL, /* h - reserved for help */ 455 &sysrq_kill_op, /* i */ 456 #ifdef CONFIG_BLOCK 457 &sysrq_thaw_op, /* j */ 458 #else 459 NULL, /* j */ 460 #endif 461 &sysrq_SAK_op, /* k */ 462 #ifdef CONFIG_SMP 463 &sysrq_showallcpus_op, /* l */ 464 #else 465 NULL, /* l */ 466 #endif 467 &sysrq_showmem_op, /* m */ 468 &sysrq_unrt_op, /* n */ 469 /* o: This will often be registered as 'Off' at init time */ 470 NULL, /* o */ 471 &sysrq_showregs_op, /* p */ 472 &sysrq_show_timers_op, /* q */ 473 &sysrq_unraw_op, /* r */ 474 &sysrq_sync_op, /* s */ 475 &sysrq_showstate_op, /* t */ 476 &sysrq_mountro_op, /* u */ 477 /* v: May be registered for frame buffer console restore */ 478 NULL, /* v */ 479 &sysrq_showstate_blocked_op, /* w */ 480 /* x: May be registered on mips for TLB dump */ 481 /* x: May be registered on ppc/powerpc for xmon */ 482 /* x: May be registered on sparc64 for global PMU dump */ 483 NULL, /* x */ 484 /* y: May be registered on sparc64 for global register dump */ 485 NULL, /* y */ 486 &sysrq_ftrace_dump_op, /* z */ 487 }; 488 489 /* key2index calculation, -1 on invalid index */ 490 static int sysrq_key_table_key2index(int key) 491 { 492 int retval; 493 494 if ((key >= '0') && (key <= '9')) 495 retval = key - '0'; 496 else if ((key >= 'a') && (key <= 'z')) 497 retval = key + 10 - 'a'; 498 else 499 retval = -1; 500 return retval; 501 } 502 503 /* 504 * get and put functions for the table, exposed to modules. 505 */ 506 struct sysrq_key_op *__sysrq_get_key_op(int key) 507 { 508 struct sysrq_key_op *op_p = NULL; 509 int i; 510 511 i = sysrq_key_table_key2index(key); 512 if (i != -1) 513 op_p = sysrq_key_table[i]; 514 515 return op_p; 516 } 517 518 static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p) 519 { 520 int i = sysrq_key_table_key2index(key); 521 522 if (i != -1) 523 sysrq_key_table[i] = op_p; 524 } 525 526 void __handle_sysrq(int key, bool check_mask) 527 { 528 struct sysrq_key_op *op_p; 529 int orig_log_level; 530 int orig_suppress_printk; 531 int i; 532 533 orig_suppress_printk = suppress_printk; 534 suppress_printk = 0; 535 536 rcu_sysrq_start(); 537 rcu_read_lock(); 538 /* 539 * Raise the apparent loglevel to maximum so that the sysrq header 540 * is shown to provide the user with positive feedback. We do not 541 * simply emit this at KERN_EMERG as that would change message 542 * routing in the consumers of /proc/kmsg. 543 */ 544 orig_log_level = console_loglevel; 545 console_loglevel = CONSOLE_LOGLEVEL_DEFAULT; 546 547 op_p = __sysrq_get_key_op(key); 548 if (op_p) { 549 /* 550 * Should we check for enabled operations (/proc/sysrq-trigger 551 * should not) and is the invoked operation enabled? 552 */ 553 if (!check_mask || sysrq_on_mask(op_p->enable_mask)) { 554 pr_info("%s\n", op_p->action_msg); 555 console_loglevel = orig_log_level; 556 op_p->handler(key); 557 } else { 558 pr_info("This sysrq operation is disabled.\n"); 559 console_loglevel = orig_log_level; 560 } 561 } else { 562 pr_info("HELP : "); 563 /* Only print the help msg once per handler */ 564 for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) { 565 if (sysrq_key_table[i]) { 566 int j; 567 568 for (j = 0; sysrq_key_table[i] != 569 sysrq_key_table[j]; j++) 570 ; 571 if (j != i) 572 continue; 573 pr_cont("%s ", sysrq_key_table[i]->help_msg); 574 } 575 } 576 pr_cont("\n"); 577 console_loglevel = orig_log_level; 578 } 579 rcu_read_unlock(); 580 rcu_sysrq_end(); 581 582 suppress_printk = orig_suppress_printk; 583 } 584 585 void handle_sysrq(int key) 586 { 587 if (sysrq_on()) 588 __handle_sysrq(key, true); 589 } 590 EXPORT_SYMBOL(handle_sysrq); 591 592 #ifdef CONFIG_INPUT 593 static int sysrq_reset_downtime_ms; 594 595 /* Simple translation table for the SysRq keys */ 596 static const unsigned char sysrq_xlate[KEY_CNT] = 597 "\000\0331234567890-=\177\t" /* 0x00 - 0x0f */ 598 "qwertyuiop[]\r\000as" /* 0x10 - 0x1f */ 599 "dfghjkl;'`\000\\zxcv" /* 0x20 - 0x2f */ 600 "bnm,./\000*\000 \000\201\202\203\204\205" /* 0x30 - 0x3f */ 601 "\206\207\210\211\212\000\000789-456+1" /* 0x40 - 0x4f */ 602 "230\177\000\000\213\214\000\000\000\000\000\000\000\000\000\000" /* 0x50 - 0x5f */ 603 "\r\000/"; /* 0x60 - 0x6f */ 604 605 struct sysrq_state { 606 struct input_handle handle; 607 struct work_struct reinject_work; 608 unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; 609 unsigned int alt; 610 unsigned int alt_use; 611 bool active; 612 bool need_reinject; 613 bool reinjecting; 614 615 /* reset sequence handling */ 616 bool reset_canceled; 617 bool reset_requested; 618 unsigned long reset_keybit[BITS_TO_LONGS(KEY_CNT)]; 619 int reset_seq_len; 620 int reset_seq_cnt; 621 int reset_seq_version; 622 struct timer_list keyreset_timer; 623 }; 624 625 #define SYSRQ_KEY_RESET_MAX 20 /* Should be plenty */ 626 static unsigned short sysrq_reset_seq[SYSRQ_KEY_RESET_MAX]; 627 static unsigned int sysrq_reset_seq_len; 628 static unsigned int sysrq_reset_seq_version = 1; 629 630 static void sysrq_parse_reset_sequence(struct sysrq_state *state) 631 { 632 int i; 633 unsigned short key; 634 635 state->reset_seq_cnt = 0; 636 637 for (i = 0; i < sysrq_reset_seq_len; i++) { 638 key = sysrq_reset_seq[i]; 639 640 if (key == KEY_RESERVED || key > KEY_MAX) 641 break; 642 643 __set_bit(key, state->reset_keybit); 644 state->reset_seq_len++; 645 646 if (test_bit(key, state->key_down)) 647 state->reset_seq_cnt++; 648 } 649 650 /* Disable reset until old keys are not released */ 651 state->reset_canceled = state->reset_seq_cnt != 0; 652 653 state->reset_seq_version = sysrq_reset_seq_version; 654 } 655 656 static void sysrq_do_reset(struct timer_list *t) 657 { 658 struct sysrq_state *state = from_timer(state, t, keyreset_timer); 659 660 state->reset_requested = true; 661 662 orderly_reboot(); 663 } 664 665 static void sysrq_handle_reset_request(struct sysrq_state *state) 666 { 667 if (state->reset_requested) 668 __handle_sysrq(sysrq_xlate[KEY_B], false); 669 670 if (sysrq_reset_downtime_ms) 671 mod_timer(&state->keyreset_timer, 672 jiffies + msecs_to_jiffies(sysrq_reset_downtime_ms)); 673 else 674 sysrq_do_reset(&state->keyreset_timer); 675 } 676 677 static void sysrq_detect_reset_sequence(struct sysrq_state *state, 678 unsigned int code, int value) 679 { 680 if (!test_bit(code, state->reset_keybit)) { 681 /* 682 * Pressing any key _not_ in reset sequence cancels 683 * the reset sequence. Also cancelling the timer in 684 * case additional keys were pressed after a reset 685 * has been requested. 686 */ 687 if (value && state->reset_seq_cnt) { 688 state->reset_canceled = true; 689 del_timer(&state->keyreset_timer); 690 } 691 } else if (value == 0) { 692 /* 693 * Key release - all keys in the reset sequence need 694 * to be pressed and held for the reset timeout 695 * to hold. 696 */ 697 del_timer(&state->keyreset_timer); 698 699 if (--state->reset_seq_cnt == 0) 700 state->reset_canceled = false; 701 } else if (value == 1) { 702 /* key press, not autorepeat */ 703 if (++state->reset_seq_cnt == state->reset_seq_len && 704 !state->reset_canceled) { 705 sysrq_handle_reset_request(state); 706 } 707 } 708 } 709 710 #ifdef CONFIG_OF 711 static void sysrq_of_get_keyreset_config(void) 712 { 713 u32 key; 714 struct device_node *np; 715 struct property *prop; 716 const __be32 *p; 717 718 np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); 719 if (!np) { 720 pr_debug("No sysrq node found"); 721 return; 722 } 723 724 /* Reset in case a __weak definition was present */ 725 sysrq_reset_seq_len = 0; 726 727 of_property_for_each_u32(np, "keyset", prop, p, key) { 728 if (key == KEY_RESERVED || key > KEY_MAX || 729 sysrq_reset_seq_len == SYSRQ_KEY_RESET_MAX) 730 break; 731 732 sysrq_reset_seq[sysrq_reset_seq_len++] = (unsigned short)key; 733 } 734 735 /* Get reset timeout if any. */ 736 of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); 737 738 of_node_put(np); 739 } 740 #else 741 static void sysrq_of_get_keyreset_config(void) 742 { 743 } 744 #endif 745 746 static void sysrq_reinject_alt_sysrq(struct work_struct *work) 747 { 748 struct sysrq_state *sysrq = 749 container_of(work, struct sysrq_state, reinject_work); 750 struct input_handle *handle = &sysrq->handle; 751 unsigned int alt_code = sysrq->alt_use; 752 753 if (sysrq->need_reinject) { 754 /* we do not want the assignment to be reordered */ 755 sysrq->reinjecting = true; 756 mb(); 757 758 /* Simulate press and release of Alt + SysRq */ 759 input_inject_event(handle, EV_KEY, alt_code, 1); 760 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 1); 761 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 762 763 input_inject_event(handle, EV_KEY, KEY_SYSRQ, 0); 764 input_inject_event(handle, EV_KEY, alt_code, 0); 765 input_inject_event(handle, EV_SYN, SYN_REPORT, 1); 766 767 mb(); 768 sysrq->reinjecting = false; 769 } 770 } 771 772 static bool sysrq_handle_keypress(struct sysrq_state *sysrq, 773 unsigned int code, int value) 774 { 775 bool was_active = sysrq->active; 776 bool suppress; 777 778 switch (code) { 779 780 case KEY_LEFTALT: 781 case KEY_RIGHTALT: 782 if (!value) { 783 /* One of ALTs is being released */ 784 if (sysrq->active && code == sysrq->alt_use) 785 sysrq->active = false; 786 787 sysrq->alt = KEY_RESERVED; 788 789 } else if (value != 2) { 790 sysrq->alt = code; 791 sysrq->need_reinject = false; 792 } 793 break; 794 795 case KEY_SYSRQ: 796 if (value == 1 && sysrq->alt != KEY_RESERVED) { 797 sysrq->active = true; 798 sysrq->alt_use = sysrq->alt; 799 /* 800 * If nothing else will be pressed we'll need 801 * to re-inject Alt-SysRq keysroke. 802 */ 803 sysrq->need_reinject = true; 804 } 805 806 /* 807 * Pretend that sysrq was never pressed at all. This 808 * is needed to properly handle KGDB which will try 809 * to release all keys after exiting debugger. If we 810 * do not clear key bit it KGDB will end up sending 811 * release events for Alt and SysRq, potentially 812 * triggering print screen function. 813 */ 814 if (sysrq->active) 815 clear_bit(KEY_SYSRQ, sysrq->handle.dev->key); 816 817 break; 818 819 default: 820 if (sysrq->active && value && value != 2) { 821 sysrq->need_reinject = false; 822 __handle_sysrq(sysrq_xlate[code], true); 823 } 824 break; 825 } 826 827 suppress = sysrq->active; 828 829 if (!sysrq->active) { 830 831 /* 832 * See if reset sequence has changed since the last time. 833 */ 834 if (sysrq->reset_seq_version != sysrq_reset_seq_version) 835 sysrq_parse_reset_sequence(sysrq); 836 837 /* 838 * If we are not suppressing key presses keep track of 839 * keyboard state so we can release keys that have been 840 * pressed before entering SysRq mode. 841 */ 842 if (value) 843 set_bit(code, sysrq->key_down); 844 else 845 clear_bit(code, sysrq->key_down); 846 847 if (was_active) 848 schedule_work(&sysrq->reinject_work); 849 850 /* Check for reset sequence */ 851 sysrq_detect_reset_sequence(sysrq, code, value); 852 853 } else if (value == 0 && test_and_clear_bit(code, sysrq->key_down)) { 854 /* 855 * Pass on release events for keys that was pressed before 856 * entering SysRq mode. 857 */ 858 suppress = false; 859 } 860 861 return suppress; 862 } 863 864 static bool sysrq_filter(struct input_handle *handle, 865 unsigned int type, unsigned int code, int value) 866 { 867 struct sysrq_state *sysrq = handle->private; 868 bool suppress; 869 870 /* 871 * Do not filter anything if we are in the process of re-injecting 872 * Alt+SysRq combination. 873 */ 874 if (sysrq->reinjecting) 875 return false; 876 877 switch (type) { 878 879 case EV_SYN: 880 suppress = false; 881 break; 882 883 case EV_KEY: 884 suppress = sysrq_handle_keypress(sysrq, code, value); 885 break; 886 887 default: 888 suppress = sysrq->active; 889 break; 890 } 891 892 return suppress; 893 } 894 895 static int sysrq_connect(struct input_handler *handler, 896 struct input_dev *dev, 897 const struct input_device_id *id) 898 { 899 struct sysrq_state *sysrq; 900 int error; 901 902 sysrq = kzalloc(sizeof(struct sysrq_state), GFP_KERNEL); 903 if (!sysrq) 904 return -ENOMEM; 905 906 INIT_WORK(&sysrq->reinject_work, sysrq_reinject_alt_sysrq); 907 908 sysrq->handle.dev = dev; 909 sysrq->handle.handler = handler; 910 sysrq->handle.name = "sysrq"; 911 sysrq->handle.private = sysrq; 912 timer_setup(&sysrq->keyreset_timer, sysrq_do_reset, 0); 913 914 error = input_register_handle(&sysrq->handle); 915 if (error) { 916 pr_err("Failed to register input sysrq handler, error %d\n", 917 error); 918 goto err_free; 919 } 920 921 error = input_open_device(&sysrq->handle); 922 if (error) { 923 pr_err("Failed to open input device, error %d\n", error); 924 goto err_unregister; 925 } 926 927 return 0; 928 929 err_unregister: 930 input_unregister_handle(&sysrq->handle); 931 err_free: 932 kfree(sysrq); 933 return error; 934 } 935 936 static void sysrq_disconnect(struct input_handle *handle) 937 { 938 struct sysrq_state *sysrq = handle->private; 939 940 input_close_device(handle); 941 cancel_work_sync(&sysrq->reinject_work); 942 del_timer_sync(&sysrq->keyreset_timer); 943 input_unregister_handle(handle); 944 kfree(sysrq); 945 } 946 947 /* 948 * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all 949 * keyboards have SysRq key predefined and so user may add it to keymap 950 * later, but we expect all such keyboards to have left alt. 951 */ 952 static const struct input_device_id sysrq_ids[] = { 953 { 954 .flags = INPUT_DEVICE_ID_MATCH_EVBIT | 955 INPUT_DEVICE_ID_MATCH_KEYBIT, 956 .evbit = { [BIT_WORD(EV_KEY)] = BIT_MASK(EV_KEY) }, 957 .keybit = { [BIT_WORD(KEY_LEFTALT)] = BIT_MASK(KEY_LEFTALT) }, 958 }, 959 { }, 960 }; 961 962 static struct input_handler sysrq_handler = { 963 .filter = sysrq_filter, 964 .connect = sysrq_connect, 965 .disconnect = sysrq_disconnect, 966 .name = "sysrq", 967 .id_table = sysrq_ids, 968 }; 969 970 static bool sysrq_handler_registered; 971 972 static inline void sysrq_register_handler(void) 973 { 974 int error; 975 976 sysrq_of_get_keyreset_config(); 977 978 error = input_register_handler(&sysrq_handler); 979 if (error) 980 pr_err("Failed to register input handler, error %d", error); 981 else 982 sysrq_handler_registered = true; 983 } 984 985 static inline void sysrq_unregister_handler(void) 986 { 987 if (sysrq_handler_registered) { 988 input_unregister_handler(&sysrq_handler); 989 sysrq_handler_registered = false; 990 } 991 } 992 993 static int sysrq_reset_seq_param_set(const char *buffer, 994 const struct kernel_param *kp) 995 { 996 unsigned long val; 997 int error; 998 999 error = kstrtoul(buffer, 0, &val); 1000 if (error < 0) 1001 return error; 1002 1003 if (val > KEY_MAX) 1004 return -EINVAL; 1005 1006 *((unsigned short *)kp->arg) = val; 1007 sysrq_reset_seq_version++; 1008 1009 return 0; 1010 } 1011 1012 static const struct kernel_param_ops param_ops_sysrq_reset_seq = { 1013 .get = param_get_ushort, 1014 .set = sysrq_reset_seq_param_set, 1015 }; 1016 1017 #define param_check_sysrq_reset_seq(name, p) \ 1018 __param_check(name, p, unsigned short) 1019 1020 /* 1021 * not really modular, but the easiest way to keep compat with existing 1022 * bootargs behaviour is to continue using module_param here. 1023 */ 1024 module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, 1025 &sysrq_reset_seq_len, 0644); 1026 1027 module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); 1028 1029 #else 1030 1031 static inline void sysrq_register_handler(void) 1032 { 1033 } 1034 1035 static inline void sysrq_unregister_handler(void) 1036 { 1037 } 1038 1039 #endif /* CONFIG_INPUT */ 1040 1041 int sysrq_toggle_support(int enable_mask) 1042 { 1043 bool was_enabled = sysrq_on(); 1044 1045 sysrq_enabled = enable_mask; 1046 1047 if (was_enabled != sysrq_on()) { 1048 if (sysrq_on()) 1049 sysrq_register_handler(); 1050 else 1051 sysrq_unregister_handler(); 1052 } 1053 1054 return 0; 1055 } 1056 1057 static int __sysrq_swap_key_ops(int key, struct sysrq_key_op *insert_op_p, 1058 struct sysrq_key_op *remove_op_p) 1059 { 1060 int retval; 1061 1062 spin_lock(&sysrq_key_table_lock); 1063 if (__sysrq_get_key_op(key) == remove_op_p) { 1064 __sysrq_put_key_op(key, insert_op_p); 1065 retval = 0; 1066 } else { 1067 retval = -1; 1068 } 1069 spin_unlock(&sysrq_key_table_lock); 1070 1071 /* 1072 * A concurrent __handle_sysrq either got the old op or the new op. 1073 * Wait for it to go away before returning, so the code for an old 1074 * op is not freed (eg. on module unload) while it is in use. 1075 */ 1076 synchronize_rcu(); 1077 1078 return retval; 1079 } 1080 1081 int register_sysrq_key(int key, struct sysrq_key_op *op_p) 1082 { 1083 return __sysrq_swap_key_ops(key, op_p, NULL); 1084 } 1085 EXPORT_SYMBOL(register_sysrq_key); 1086 1087 int unregister_sysrq_key(int key, struct sysrq_key_op *op_p) 1088 { 1089 return __sysrq_swap_key_ops(key, NULL, op_p); 1090 } 1091 EXPORT_SYMBOL(unregister_sysrq_key); 1092 1093 #ifdef CONFIG_PROC_FS 1094 /* 1095 * writing 'C' to /proc/sysrq-trigger is like sysrq-C 1096 */ 1097 static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf, 1098 size_t count, loff_t *ppos) 1099 { 1100 if (count) { 1101 char c; 1102 1103 if (get_user(c, buf)) 1104 return -EFAULT; 1105 __handle_sysrq(c, false); 1106 } 1107 1108 return count; 1109 } 1110 1111 static const struct file_operations proc_sysrq_trigger_operations = { 1112 .write = write_sysrq_trigger, 1113 .llseek = noop_llseek, 1114 }; 1115 1116 static void sysrq_init_procfs(void) 1117 { 1118 if (!proc_create("sysrq-trigger", S_IWUSR, NULL, 1119 &proc_sysrq_trigger_operations)) 1120 pr_err("Failed to register proc interface\n"); 1121 } 1122 1123 #else 1124 1125 static inline void sysrq_init_procfs(void) 1126 { 1127 } 1128 1129 #endif /* CONFIG_PROC_FS */ 1130 1131 static int __init sysrq_init(void) 1132 { 1133 sysrq_init_procfs(); 1134 1135 if (sysrq_on()) 1136 sysrq_register_handler(); 1137 1138 return 0; 1139 } 1140 device_initcall(sysrq_init); 1141