1 /* 2 * linux/kernel/panic.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 */ 6 7 /* 8 * This function is used through-out the kernel (including mm and fs) 9 * to indicate a major problem. 10 */ 11 #include <linux/debug_locks.h> 12 #include <linux/sched/debug.h> 13 #include <linux/interrupt.h> 14 #include <linux/kmsg_dump.h> 15 #include <linux/kallsyms.h> 16 #include <linux/notifier.h> 17 #include <linux/module.h> 18 #include <linux/random.h> 19 #include <linux/ftrace.h> 20 #include <linux/reboot.h> 21 #include <linux/delay.h> 22 #include <linux/kexec.h> 23 #include <linux/sched.h> 24 #include <linux/sysrq.h> 25 #include <linux/init.h> 26 #include <linux/nmi.h> 27 #include <linux/console.h> 28 #include <linux/bug.h> 29 #include <linux/ratelimit.h> 30 31 #define PANIC_TIMER_STEP 100 32 #define PANIC_BLINK_SPD 18 33 34 int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE; 35 static unsigned long tainted_mask; 36 static int pause_on_oops; 37 static int pause_on_oops_flag; 38 static DEFINE_SPINLOCK(pause_on_oops_lock); 39 bool crash_kexec_post_notifiers; 40 int panic_on_warn __read_mostly; 41 42 int panic_timeout = CONFIG_PANIC_TIMEOUT; 43 EXPORT_SYMBOL_GPL(panic_timeout); 44 45 ATOMIC_NOTIFIER_HEAD(panic_notifier_list); 46 47 EXPORT_SYMBOL(panic_notifier_list); 48 49 static long no_blink(int state) 50 { 51 return 0; 52 } 53 54 /* Returns how long it waited in ms */ 55 long (*panic_blink)(int state); 56 EXPORT_SYMBOL(panic_blink); 57 58 /* 59 * Stop ourself in panic -- architecture code may override this 60 */ 61 void __weak panic_smp_self_stop(void) 62 { 63 while (1) 64 cpu_relax(); 65 } 66 67 /* 68 * Stop ourselves in NMI context if another CPU has already panicked. Arch code 69 * may override this to prepare for crash dumping, e.g. save regs info. 70 */ 71 void __weak nmi_panic_self_stop(struct pt_regs *regs) 72 { 73 panic_smp_self_stop(); 74 } 75 76 /* 77 * Stop other CPUs in panic. Architecture dependent code may override this 78 * with more suitable version. For example, if the architecture supports 79 * crash dump, it should save registers of each stopped CPU and disable 80 * per-CPU features such as virtualization extensions. 81 */ 82 void __weak crash_smp_send_stop(void) 83 { 84 static int cpus_stopped; 85 86 /* 87 * This function can be called twice in panic path, but obviously 88 * we execute this only once. 89 */ 90 if (cpus_stopped) 91 return; 92 93 /* 94 * Note smp_send_stop is the usual smp shutdown function, which 95 * unfortunately means it may not be hardened to work in a panic 96 * situation. 97 */ 98 smp_send_stop(); 99 cpus_stopped = 1; 100 } 101 102 atomic_t panic_cpu = ATOMIC_INIT(PANIC_CPU_INVALID); 103 104 /* 105 * A variant of panic() called from NMI context. We return if we've already 106 * panicked on this CPU. If another CPU already panicked, loop in 107 * nmi_panic_self_stop() which can provide architecture dependent code such 108 * as saving register state for crash dump. 109 */ 110 void nmi_panic(struct pt_regs *regs, const char *msg) 111 { 112 int old_cpu, cpu; 113 114 cpu = raw_smp_processor_id(); 115 old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, cpu); 116 117 if (old_cpu == PANIC_CPU_INVALID) 118 panic("%s", msg); 119 else if (old_cpu != cpu) 120 nmi_panic_self_stop(regs); 121 } 122 EXPORT_SYMBOL(nmi_panic); 123 124 /** 125 * panic - halt the system 126 * @fmt: The text string to print 127 * 128 * Display a message, then perform cleanups. 129 * 130 * This function never returns. 131 */ 132 void panic(const char *fmt, ...) 133 { 134 static char buf[1024]; 135 va_list args; 136 long i, i_next = 0; 137 int state = 0; 138 int old_cpu, this_cpu; 139 bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers; 140 141 /* 142 * Disable local interrupts. This will prevent panic_smp_self_stop 143 * from deadlocking the first cpu that invokes the panic, since 144 * there is nothing to prevent an interrupt handler (that runs 145 * after setting panic_cpu) from invoking panic() again. 146 */ 147 local_irq_disable(); 148 149 /* 150 * It's possible to come here directly from a panic-assertion and 151 * not have preempt disabled. Some functions called from here want 152 * preempt to be disabled. No point enabling it later though... 153 * 154 * Only one CPU is allowed to execute the panic code from here. For 155 * multiple parallel invocations of panic, all other CPUs either 156 * stop themself or will wait until they are stopped by the 1st CPU 157 * with smp_send_stop(). 158 * 159 * `old_cpu == PANIC_CPU_INVALID' means this is the 1st CPU which 160 * comes here, so go ahead. 161 * `old_cpu == this_cpu' means we came from nmi_panic() which sets 162 * panic_cpu to this CPU. In this case, this is also the 1st CPU. 163 */ 164 this_cpu = raw_smp_processor_id(); 165 old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, this_cpu); 166 167 if (old_cpu != PANIC_CPU_INVALID && old_cpu != this_cpu) 168 panic_smp_self_stop(); 169 170 console_verbose(); 171 bust_spinlocks(1); 172 va_start(args, fmt); 173 vsnprintf(buf, sizeof(buf), fmt, args); 174 va_end(args); 175 pr_emerg("Kernel panic - not syncing: %s\n", buf); 176 #ifdef CONFIG_DEBUG_BUGVERBOSE 177 /* 178 * Avoid nested stack-dumping if a panic occurs during oops processing 179 */ 180 if (!test_taint(TAINT_DIE) && oops_in_progress <= 1) 181 dump_stack(); 182 #endif 183 184 /* 185 * If we have crashed and we have a crash kernel loaded let it handle 186 * everything else. 187 * If we want to run this after calling panic_notifiers, pass 188 * the "crash_kexec_post_notifiers" option to the kernel. 189 * 190 * Bypass the panic_cpu check and call __crash_kexec directly. 191 */ 192 if (!_crash_kexec_post_notifiers) { 193 printk_safe_flush_on_panic(); 194 __crash_kexec(NULL); 195 196 /* 197 * Note smp_send_stop is the usual smp shutdown function, which 198 * unfortunately means it may not be hardened to work in a 199 * panic situation. 200 */ 201 smp_send_stop(); 202 } else { 203 /* 204 * If we want to do crash dump after notifier calls and 205 * kmsg_dump, we will need architecture dependent extra 206 * works in addition to stopping other CPUs. 207 */ 208 crash_smp_send_stop(); 209 } 210 211 /* 212 * Run any panic handlers, including those that might need to 213 * add information to the kmsg dump output. 214 */ 215 atomic_notifier_call_chain(&panic_notifier_list, 0, buf); 216 217 /* Call flush even twice. It tries harder with a single online CPU */ 218 printk_safe_flush_on_panic(); 219 kmsg_dump(KMSG_DUMP_PANIC); 220 221 /* 222 * If you doubt kdump always works fine in any situation, 223 * "crash_kexec_post_notifiers" offers you a chance to run 224 * panic_notifiers and dumping kmsg before kdump. 225 * Note: since some panic_notifiers can make crashed kernel 226 * more unstable, it can increase risks of the kdump failure too. 227 * 228 * Bypass the panic_cpu check and call __crash_kexec directly. 229 */ 230 if (_crash_kexec_post_notifiers) 231 __crash_kexec(NULL); 232 233 bust_spinlocks(0); 234 235 /* 236 * We may have ended up stopping the CPU holding the lock (in 237 * smp_send_stop()) while still having some valuable data in the console 238 * buffer. Try to acquire the lock then release it regardless of the 239 * result. The release will also print the buffers out. Locks debug 240 * should be disabled to avoid reporting bad unlock balance when 241 * panic() is not being callled from OOPS. 242 */ 243 debug_locks_off(); 244 console_flush_on_panic(); 245 246 if (!panic_blink) 247 panic_blink = no_blink; 248 249 if (panic_timeout > 0) { 250 /* 251 * Delay timeout seconds before rebooting the machine. 252 * We can't use the "normal" timers since we just panicked. 253 */ 254 pr_emerg("Rebooting in %d seconds..\n", panic_timeout); 255 256 for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) { 257 touch_nmi_watchdog(); 258 if (i >= i_next) { 259 i += panic_blink(state ^= 1); 260 i_next = i + 3600 / PANIC_BLINK_SPD; 261 } 262 mdelay(PANIC_TIMER_STEP); 263 } 264 } 265 if (panic_timeout != 0) { 266 /* 267 * This will not be a clean reboot, with everything 268 * shutting down. But if there is a chance of 269 * rebooting the system it will be rebooted. 270 */ 271 emergency_restart(); 272 } 273 #ifdef __sparc__ 274 { 275 extern int stop_a_enabled; 276 /* Make sure the user can actually press Stop-A (L1-A) */ 277 stop_a_enabled = 1; 278 pr_emerg("Press Stop-A (L1-A) from sun keyboard or send break\n" 279 "twice on console to return to the boot prom\n"); 280 } 281 #endif 282 #if defined(CONFIG_S390) 283 { 284 unsigned long caller; 285 286 caller = (unsigned long)__builtin_return_address(0); 287 disabled_wait(caller); 288 } 289 #endif 290 pr_emerg("---[ end Kernel panic - not syncing: %s\n", buf); 291 local_irq_enable(); 292 for (i = 0; ; i += PANIC_TIMER_STEP) { 293 touch_softlockup_watchdog(); 294 if (i >= i_next) { 295 i += panic_blink(state ^= 1); 296 i_next = i + 3600 / PANIC_BLINK_SPD; 297 } 298 mdelay(PANIC_TIMER_STEP); 299 } 300 } 301 302 EXPORT_SYMBOL(panic); 303 304 /* 305 * TAINT_FORCED_RMMOD could be a per-module flag but the module 306 * is being removed anyway. 307 */ 308 const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = { 309 { 'P', 'G', true }, /* TAINT_PROPRIETARY_MODULE */ 310 { 'F', ' ', true }, /* TAINT_FORCED_MODULE */ 311 { 'S', ' ', false }, /* TAINT_CPU_OUT_OF_SPEC */ 312 { 'R', ' ', false }, /* TAINT_FORCED_RMMOD */ 313 { 'M', ' ', false }, /* TAINT_MACHINE_CHECK */ 314 { 'B', ' ', false }, /* TAINT_BAD_PAGE */ 315 { 'U', ' ', false }, /* TAINT_USER */ 316 { 'D', ' ', false }, /* TAINT_DIE */ 317 { 'A', ' ', false }, /* TAINT_OVERRIDDEN_ACPI_TABLE */ 318 { 'W', ' ', false }, /* TAINT_WARN */ 319 { 'C', ' ', true }, /* TAINT_CRAP */ 320 { 'I', ' ', false }, /* TAINT_FIRMWARE_WORKAROUND */ 321 { 'O', ' ', true }, /* TAINT_OOT_MODULE */ 322 { 'E', ' ', true }, /* TAINT_UNSIGNED_MODULE */ 323 { 'L', ' ', false }, /* TAINT_SOFTLOCKUP */ 324 { 'K', ' ', true }, /* TAINT_LIVEPATCH */ 325 }; 326 327 /** 328 * print_tainted - return a string to represent the kernel taint state. 329 * 330 * 'P' - Proprietary module has been loaded. 331 * 'F' - Module has been forcibly loaded. 332 * 'S' - SMP with CPUs not designed for SMP. 333 * 'R' - User forced a module unload. 334 * 'M' - System experienced a machine check exception. 335 * 'B' - System has hit bad_page. 336 * 'U' - Userspace-defined naughtiness. 337 * 'D' - Kernel has oopsed before 338 * 'A' - ACPI table overridden. 339 * 'W' - Taint on warning. 340 * 'C' - modules from drivers/staging are loaded. 341 * 'I' - Working around severe firmware bug. 342 * 'O' - Out-of-tree module has been loaded. 343 * 'E' - Unsigned module has been loaded. 344 * 'L' - A soft lockup has previously occurred. 345 * 'K' - Kernel has been live patched. 346 * 347 * The string is overwritten by the next call to print_tainted(). 348 */ 349 const char *print_tainted(void) 350 { 351 static char buf[TAINT_FLAGS_COUNT + sizeof("Tainted: ")]; 352 353 if (tainted_mask) { 354 char *s; 355 int i; 356 357 s = buf + sprintf(buf, "Tainted: "); 358 for (i = 0; i < TAINT_FLAGS_COUNT; i++) { 359 const struct taint_flag *t = &taint_flags[i]; 360 *s++ = test_bit(i, &tainted_mask) ? 361 t->c_true : t->c_false; 362 } 363 *s = 0; 364 } else 365 snprintf(buf, sizeof(buf), "Not tainted"); 366 367 return buf; 368 } 369 370 int test_taint(unsigned flag) 371 { 372 return test_bit(flag, &tainted_mask); 373 } 374 EXPORT_SYMBOL(test_taint); 375 376 unsigned long get_taint(void) 377 { 378 return tainted_mask; 379 } 380 381 /** 382 * add_taint: add a taint flag if not already set. 383 * @flag: one of the TAINT_* constants. 384 * @lockdep_ok: whether lock debugging is still OK. 385 * 386 * If something bad has gone wrong, you'll want @lockdebug_ok = false, but for 387 * some notewortht-but-not-corrupting cases, it can be set to true. 388 */ 389 void add_taint(unsigned flag, enum lockdep_ok lockdep_ok) 390 { 391 if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off()) 392 pr_warn("Disabling lock debugging due to kernel taint\n"); 393 394 set_bit(flag, &tainted_mask); 395 } 396 EXPORT_SYMBOL(add_taint); 397 398 static void spin_msec(int msecs) 399 { 400 int i; 401 402 for (i = 0; i < msecs; i++) { 403 touch_nmi_watchdog(); 404 mdelay(1); 405 } 406 } 407 408 /* 409 * It just happens that oops_enter() and oops_exit() are identically 410 * implemented... 411 */ 412 static void do_oops_enter_exit(void) 413 { 414 unsigned long flags; 415 static int spin_counter; 416 417 if (!pause_on_oops) 418 return; 419 420 spin_lock_irqsave(&pause_on_oops_lock, flags); 421 if (pause_on_oops_flag == 0) { 422 /* This CPU may now print the oops message */ 423 pause_on_oops_flag = 1; 424 } else { 425 /* We need to stall this CPU */ 426 if (!spin_counter) { 427 /* This CPU gets to do the counting */ 428 spin_counter = pause_on_oops; 429 do { 430 spin_unlock(&pause_on_oops_lock); 431 spin_msec(MSEC_PER_SEC); 432 spin_lock(&pause_on_oops_lock); 433 } while (--spin_counter); 434 pause_on_oops_flag = 0; 435 } else { 436 /* This CPU waits for a different one */ 437 while (spin_counter) { 438 spin_unlock(&pause_on_oops_lock); 439 spin_msec(1); 440 spin_lock(&pause_on_oops_lock); 441 } 442 } 443 } 444 spin_unlock_irqrestore(&pause_on_oops_lock, flags); 445 } 446 447 /* 448 * Return true if the calling CPU is allowed to print oops-related info. 449 * This is a bit racy.. 450 */ 451 int oops_may_print(void) 452 { 453 return pause_on_oops_flag == 0; 454 } 455 456 /* 457 * Called when the architecture enters its oops handler, before it prints 458 * anything. If this is the first CPU to oops, and it's oopsing the first 459 * time then let it proceed. 460 * 461 * This is all enabled by the pause_on_oops kernel boot option. We do all 462 * this to ensure that oopses don't scroll off the screen. It has the 463 * side-effect of preventing later-oopsing CPUs from mucking up the display, 464 * too. 465 * 466 * It turns out that the CPU which is allowed to print ends up pausing for 467 * the right duration, whereas all the other CPUs pause for twice as long: 468 * once in oops_enter(), once in oops_exit(). 469 */ 470 void oops_enter(void) 471 { 472 tracing_off(); 473 /* can't trust the integrity of the kernel anymore: */ 474 debug_locks_off(); 475 do_oops_enter_exit(); 476 } 477 478 /* 479 * 64-bit random ID for oopses: 480 */ 481 static u64 oops_id; 482 483 static int init_oops_id(void) 484 { 485 if (!oops_id) 486 get_random_bytes(&oops_id, sizeof(oops_id)); 487 else 488 oops_id++; 489 490 return 0; 491 } 492 late_initcall(init_oops_id); 493 494 void print_oops_end_marker(void) 495 { 496 init_oops_id(); 497 pr_warn("---[ end trace %016llx ]---\n", (unsigned long long)oops_id); 498 } 499 500 /* 501 * Called when the architecture exits its oops handler, after printing 502 * everything. 503 */ 504 void oops_exit(void) 505 { 506 do_oops_enter_exit(); 507 print_oops_end_marker(); 508 kmsg_dump(KMSG_DUMP_OOPS); 509 } 510 511 struct warn_args { 512 const char *fmt; 513 va_list args; 514 }; 515 516 void __warn(const char *file, int line, void *caller, unsigned taint, 517 struct pt_regs *regs, struct warn_args *args) 518 { 519 disable_trace_on_warning(); 520 521 pr_warn("------------[ cut here ]------------\n"); 522 523 if (file) 524 pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS\n", 525 raw_smp_processor_id(), current->pid, file, line, 526 caller); 527 else 528 pr_warn("WARNING: CPU: %d PID: %d at %pS\n", 529 raw_smp_processor_id(), current->pid, caller); 530 531 if (args) 532 vprintk(args->fmt, args->args); 533 534 if (panic_on_warn) { 535 /* 536 * This thread may hit another WARN() in the panic path. 537 * Resetting this prevents additional WARN() from panicking the 538 * system on this thread. Other threads are blocked by the 539 * panic_mutex in panic(). 540 */ 541 panic_on_warn = 0; 542 panic("panic_on_warn set ...\n"); 543 } 544 545 print_modules(); 546 547 if (regs) 548 show_regs(regs); 549 else 550 dump_stack(); 551 552 print_oops_end_marker(); 553 554 /* Just a warning, don't kill lockdep. */ 555 add_taint(taint, LOCKDEP_STILL_OK); 556 } 557 558 #ifdef WANT_WARN_ON_SLOWPATH 559 void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...) 560 { 561 struct warn_args args; 562 563 args.fmt = fmt; 564 va_start(args.args, fmt); 565 __warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL, 566 &args); 567 va_end(args.args); 568 } 569 EXPORT_SYMBOL(warn_slowpath_fmt); 570 571 void warn_slowpath_fmt_taint(const char *file, int line, 572 unsigned taint, const char *fmt, ...) 573 { 574 struct warn_args args; 575 576 args.fmt = fmt; 577 va_start(args.args, fmt); 578 __warn(file, line, __builtin_return_address(0), taint, NULL, &args); 579 va_end(args.args); 580 } 581 EXPORT_SYMBOL(warn_slowpath_fmt_taint); 582 583 void warn_slowpath_null(const char *file, int line) 584 { 585 __warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL, NULL); 586 } 587 EXPORT_SYMBOL(warn_slowpath_null); 588 #endif 589 590 #ifdef CONFIG_CC_STACKPROTECTOR 591 592 /* 593 * Called when gcc's -fstack-protector feature is used, and 594 * gcc detects corruption of the on-stack canary value 595 */ 596 __visible void __stack_chk_fail(void) 597 { 598 panic("stack-protector: Kernel stack is corrupted in: %p\n", 599 __builtin_return_address(0)); 600 } 601 EXPORT_SYMBOL(__stack_chk_fail); 602 603 #endif 604 605 #ifdef CONFIG_ARCH_HAS_REFCOUNT 606 void refcount_error_report(struct pt_regs *regs, const char *err) 607 { 608 WARN_RATELIMIT(1, "refcount_t %s at %pB in %s[%d], uid/euid: %u/%u\n", 609 err, (void *)instruction_pointer(regs), 610 current->comm, task_pid_nr(current), 611 from_kuid_munged(&init_user_ns, current_uid()), 612 from_kuid_munged(&init_user_ns, current_euid())); 613 } 614 #endif 615 616 core_param(panic, panic_timeout, int, 0644); 617 core_param(pause_on_oops, pause_on_oops, int, 0644); 618 core_param(panic_on_warn, panic_on_warn, int, 0644); 619 core_param(crash_kexec_post_notifiers, crash_kexec_post_notifiers, bool, 0644); 620 621 static int __init oops_setup(char *s) 622 { 623 if (!s) 624 return -EINVAL; 625 if (!strcmp(s, "panic")) 626 panic_on_oops = 1; 627 return 0; 628 } 629 early_param("oops", oops_setup); 630