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/interrupt.h> 13 #include <linux/kmsg_dump.h> 14 #include <linux/kallsyms.h> 15 #include <linux/notifier.h> 16 #include <linux/module.h> 17 #include <linux/random.h> 18 #include <linux/ftrace.h> 19 #include <linux/reboot.h> 20 #include <linux/delay.h> 21 #include <linux/kexec.h> 22 #include <linux/sched.h> 23 #include <linux/sysrq.h> 24 #include <linux/init.h> 25 #include <linux/nmi.h> 26 27 #define PANIC_TIMER_STEP 100 28 #define PANIC_BLINK_SPD 18 29 30 int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE; 31 static unsigned long tainted_mask; 32 static int pause_on_oops; 33 static int pause_on_oops_flag; 34 static DEFINE_SPINLOCK(pause_on_oops_lock); 35 static bool crash_kexec_post_notifiers; 36 int panic_on_warn __read_mostly; 37 38 int panic_timeout = CONFIG_PANIC_TIMEOUT; 39 EXPORT_SYMBOL_GPL(panic_timeout); 40 41 ATOMIC_NOTIFIER_HEAD(panic_notifier_list); 42 43 EXPORT_SYMBOL(panic_notifier_list); 44 45 static long no_blink(int state) 46 { 47 return 0; 48 } 49 50 /* Returns how long it waited in ms */ 51 long (*panic_blink)(int state); 52 EXPORT_SYMBOL(panic_blink); 53 54 /* 55 * Stop ourself in panic -- architecture code may override this 56 */ 57 void __weak panic_smp_self_stop(void) 58 { 59 while (1) 60 cpu_relax(); 61 } 62 63 /** 64 * panic - halt the system 65 * @fmt: The text string to print 66 * 67 * Display a message, then perform cleanups. 68 * 69 * This function never returns. 70 */ 71 void panic(const char *fmt, ...) 72 { 73 static DEFINE_SPINLOCK(panic_lock); 74 static char buf[1024]; 75 va_list args; 76 long i, i_next = 0; 77 int state = 0; 78 79 /* 80 * Disable local interrupts. This will prevent panic_smp_self_stop 81 * from deadlocking the first cpu that invokes the panic, since 82 * there is nothing to prevent an interrupt handler (that runs 83 * after the panic_lock is acquired) from invoking panic again. 84 */ 85 local_irq_disable(); 86 87 /* 88 * It's possible to come here directly from a panic-assertion and 89 * not have preempt disabled. Some functions called from here want 90 * preempt to be disabled. No point enabling it later though... 91 * 92 * Only one CPU is allowed to execute the panic code from here. For 93 * multiple parallel invocations of panic, all other CPUs either 94 * stop themself or will wait until they are stopped by the 1st CPU 95 * with smp_send_stop(). 96 */ 97 if (!spin_trylock(&panic_lock)) 98 panic_smp_self_stop(); 99 100 console_verbose(); 101 bust_spinlocks(1); 102 va_start(args, fmt); 103 vsnprintf(buf, sizeof(buf), fmt, args); 104 va_end(args); 105 pr_emerg("Kernel panic - not syncing: %s\n", buf); 106 #ifdef CONFIG_DEBUG_BUGVERBOSE 107 /* 108 * Avoid nested stack-dumping if a panic occurs during oops processing 109 */ 110 if (!test_taint(TAINT_DIE) && oops_in_progress <= 1) 111 dump_stack(); 112 #endif 113 114 /* 115 * If we have crashed and we have a crash kernel loaded let it handle 116 * everything else. 117 * If we want to run this after calling panic_notifiers, pass 118 * the "crash_kexec_post_notifiers" option to the kernel. 119 */ 120 if (!crash_kexec_post_notifiers) 121 crash_kexec(NULL); 122 123 /* 124 * Note smp_send_stop is the usual smp shutdown function, which 125 * unfortunately means it may not be hardened to work in a panic 126 * situation. 127 */ 128 smp_send_stop(); 129 130 /* 131 * Run any panic handlers, including those that might need to 132 * add information to the kmsg dump output. 133 */ 134 atomic_notifier_call_chain(&panic_notifier_list, 0, buf); 135 136 kmsg_dump(KMSG_DUMP_PANIC); 137 138 /* 139 * If you doubt kdump always works fine in any situation, 140 * "crash_kexec_post_notifiers" offers you a chance to run 141 * panic_notifiers and dumping kmsg before kdump. 142 * Note: since some panic_notifiers can make crashed kernel 143 * more unstable, it can increase risks of the kdump failure too. 144 */ 145 crash_kexec(NULL); 146 147 bust_spinlocks(0); 148 149 if (!panic_blink) 150 panic_blink = no_blink; 151 152 if (panic_timeout > 0) { 153 /* 154 * Delay timeout seconds before rebooting the machine. 155 * We can't use the "normal" timers since we just panicked. 156 */ 157 pr_emerg("Rebooting in %d seconds..", panic_timeout); 158 159 for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) { 160 touch_nmi_watchdog(); 161 if (i >= i_next) { 162 i += panic_blink(state ^= 1); 163 i_next = i + 3600 / PANIC_BLINK_SPD; 164 } 165 mdelay(PANIC_TIMER_STEP); 166 } 167 } 168 if (panic_timeout != 0) { 169 /* 170 * This will not be a clean reboot, with everything 171 * shutting down. But if there is a chance of 172 * rebooting the system it will be rebooted. 173 */ 174 emergency_restart(); 175 } 176 #ifdef __sparc__ 177 { 178 extern int stop_a_enabled; 179 /* Make sure the user can actually press Stop-A (L1-A) */ 180 stop_a_enabled = 1; 181 pr_emerg("Press Stop-A (L1-A) to return to the boot prom\n"); 182 } 183 #endif 184 #if defined(CONFIG_S390) 185 { 186 unsigned long caller; 187 188 caller = (unsigned long)__builtin_return_address(0); 189 disabled_wait(caller); 190 } 191 #endif 192 pr_emerg("---[ end Kernel panic - not syncing: %s\n", buf); 193 local_irq_enable(); 194 for (i = 0; ; i += PANIC_TIMER_STEP) { 195 touch_softlockup_watchdog(); 196 if (i >= i_next) { 197 i += panic_blink(state ^= 1); 198 i_next = i + 3600 / PANIC_BLINK_SPD; 199 } 200 mdelay(PANIC_TIMER_STEP); 201 } 202 } 203 204 EXPORT_SYMBOL(panic); 205 206 207 struct tnt { 208 u8 bit; 209 char true; 210 char false; 211 }; 212 213 static const struct tnt tnts[] = { 214 { TAINT_PROPRIETARY_MODULE, 'P', 'G' }, 215 { TAINT_FORCED_MODULE, 'F', ' ' }, 216 { TAINT_CPU_OUT_OF_SPEC, 'S', ' ' }, 217 { TAINT_FORCED_RMMOD, 'R', ' ' }, 218 { TAINT_MACHINE_CHECK, 'M', ' ' }, 219 { TAINT_BAD_PAGE, 'B', ' ' }, 220 { TAINT_USER, 'U', ' ' }, 221 { TAINT_DIE, 'D', ' ' }, 222 { TAINT_OVERRIDDEN_ACPI_TABLE, 'A', ' ' }, 223 { TAINT_WARN, 'W', ' ' }, 224 { TAINT_CRAP, 'C', ' ' }, 225 { TAINT_FIRMWARE_WORKAROUND, 'I', ' ' }, 226 { TAINT_OOT_MODULE, 'O', ' ' }, 227 { TAINT_UNSIGNED_MODULE, 'E', ' ' }, 228 { TAINT_SOFTLOCKUP, 'L', ' ' }, 229 { TAINT_LIVEPATCH, 'K', ' ' }, 230 }; 231 232 /** 233 * print_tainted - return a string to represent the kernel taint state. 234 * 235 * 'P' - Proprietary module has been loaded. 236 * 'F' - Module has been forcibly loaded. 237 * 'S' - SMP with CPUs not designed for SMP. 238 * 'R' - User forced a module unload. 239 * 'M' - System experienced a machine check exception. 240 * 'B' - System has hit bad_page. 241 * 'U' - Userspace-defined naughtiness. 242 * 'D' - Kernel has oopsed before 243 * 'A' - ACPI table overridden. 244 * 'W' - Taint on warning. 245 * 'C' - modules from drivers/staging are loaded. 246 * 'I' - Working around severe firmware bug. 247 * 'O' - Out-of-tree module has been loaded. 248 * 'E' - Unsigned module has been loaded. 249 * 'L' - A soft lockup has previously occurred. 250 * 'K' - Kernel has been live patched. 251 * 252 * The string is overwritten by the next call to print_tainted(). 253 */ 254 const char *print_tainted(void) 255 { 256 static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ")]; 257 258 if (tainted_mask) { 259 char *s; 260 int i; 261 262 s = buf + sprintf(buf, "Tainted: "); 263 for (i = 0; i < ARRAY_SIZE(tnts); i++) { 264 const struct tnt *t = &tnts[i]; 265 *s++ = test_bit(t->bit, &tainted_mask) ? 266 t->true : t->false; 267 } 268 *s = 0; 269 } else 270 snprintf(buf, sizeof(buf), "Not tainted"); 271 272 return buf; 273 } 274 275 int test_taint(unsigned flag) 276 { 277 return test_bit(flag, &tainted_mask); 278 } 279 EXPORT_SYMBOL(test_taint); 280 281 unsigned long get_taint(void) 282 { 283 return tainted_mask; 284 } 285 286 /** 287 * add_taint: add a taint flag if not already set. 288 * @flag: one of the TAINT_* constants. 289 * @lockdep_ok: whether lock debugging is still OK. 290 * 291 * If something bad has gone wrong, you'll want @lockdebug_ok = false, but for 292 * some notewortht-but-not-corrupting cases, it can be set to true. 293 */ 294 void add_taint(unsigned flag, enum lockdep_ok lockdep_ok) 295 { 296 if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off()) 297 pr_warn("Disabling lock debugging due to kernel taint\n"); 298 299 set_bit(flag, &tainted_mask); 300 } 301 EXPORT_SYMBOL(add_taint); 302 303 static void spin_msec(int msecs) 304 { 305 int i; 306 307 for (i = 0; i < msecs; i++) { 308 touch_nmi_watchdog(); 309 mdelay(1); 310 } 311 } 312 313 /* 314 * It just happens that oops_enter() and oops_exit() are identically 315 * implemented... 316 */ 317 static void do_oops_enter_exit(void) 318 { 319 unsigned long flags; 320 static int spin_counter; 321 322 if (!pause_on_oops) 323 return; 324 325 spin_lock_irqsave(&pause_on_oops_lock, flags); 326 if (pause_on_oops_flag == 0) { 327 /* This CPU may now print the oops message */ 328 pause_on_oops_flag = 1; 329 } else { 330 /* We need to stall this CPU */ 331 if (!spin_counter) { 332 /* This CPU gets to do the counting */ 333 spin_counter = pause_on_oops; 334 do { 335 spin_unlock(&pause_on_oops_lock); 336 spin_msec(MSEC_PER_SEC); 337 spin_lock(&pause_on_oops_lock); 338 } while (--spin_counter); 339 pause_on_oops_flag = 0; 340 } else { 341 /* This CPU waits for a different one */ 342 while (spin_counter) { 343 spin_unlock(&pause_on_oops_lock); 344 spin_msec(1); 345 spin_lock(&pause_on_oops_lock); 346 } 347 } 348 } 349 spin_unlock_irqrestore(&pause_on_oops_lock, flags); 350 } 351 352 /* 353 * Return true if the calling CPU is allowed to print oops-related info. 354 * This is a bit racy.. 355 */ 356 int oops_may_print(void) 357 { 358 return pause_on_oops_flag == 0; 359 } 360 361 /* 362 * Called when the architecture enters its oops handler, before it prints 363 * anything. If this is the first CPU to oops, and it's oopsing the first 364 * time then let it proceed. 365 * 366 * This is all enabled by the pause_on_oops kernel boot option. We do all 367 * this to ensure that oopses don't scroll off the screen. It has the 368 * side-effect of preventing later-oopsing CPUs from mucking up the display, 369 * too. 370 * 371 * It turns out that the CPU which is allowed to print ends up pausing for 372 * the right duration, whereas all the other CPUs pause for twice as long: 373 * once in oops_enter(), once in oops_exit(). 374 */ 375 void oops_enter(void) 376 { 377 tracing_off(); 378 /* can't trust the integrity of the kernel anymore: */ 379 debug_locks_off(); 380 do_oops_enter_exit(); 381 } 382 383 /* 384 * 64-bit random ID for oopses: 385 */ 386 static u64 oops_id; 387 388 static int init_oops_id(void) 389 { 390 if (!oops_id) 391 get_random_bytes(&oops_id, sizeof(oops_id)); 392 else 393 oops_id++; 394 395 return 0; 396 } 397 late_initcall(init_oops_id); 398 399 void print_oops_end_marker(void) 400 { 401 init_oops_id(); 402 pr_warn("---[ end trace %016llx ]---\n", (unsigned long long)oops_id); 403 } 404 405 /* 406 * Called when the architecture exits its oops handler, after printing 407 * everything. 408 */ 409 void oops_exit(void) 410 { 411 do_oops_enter_exit(); 412 print_oops_end_marker(); 413 kmsg_dump(KMSG_DUMP_OOPS); 414 } 415 416 #ifdef WANT_WARN_ON_SLOWPATH 417 struct slowpath_args { 418 const char *fmt; 419 va_list args; 420 }; 421 422 static void warn_slowpath_common(const char *file, int line, void *caller, 423 unsigned taint, struct slowpath_args *args) 424 { 425 disable_trace_on_warning(); 426 427 pr_warn("------------[ cut here ]------------\n"); 428 pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS()\n", 429 raw_smp_processor_id(), current->pid, file, line, caller); 430 431 if (args) 432 vprintk(args->fmt, args->args); 433 434 if (panic_on_warn) { 435 /* 436 * This thread may hit another WARN() in the panic path. 437 * Resetting this prevents additional WARN() from panicking the 438 * system on this thread. Other threads are blocked by the 439 * panic_mutex in panic(). 440 */ 441 panic_on_warn = 0; 442 panic("panic_on_warn set ...\n"); 443 } 444 445 print_modules(); 446 dump_stack(); 447 print_oops_end_marker(); 448 /* Just a warning, don't kill lockdep. */ 449 add_taint(taint, LOCKDEP_STILL_OK); 450 } 451 452 void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...) 453 { 454 struct slowpath_args args; 455 456 args.fmt = fmt; 457 va_start(args.args, fmt); 458 warn_slowpath_common(file, line, __builtin_return_address(0), 459 TAINT_WARN, &args); 460 va_end(args.args); 461 } 462 EXPORT_SYMBOL(warn_slowpath_fmt); 463 464 void warn_slowpath_fmt_taint(const char *file, int line, 465 unsigned taint, const char *fmt, ...) 466 { 467 struct slowpath_args args; 468 469 args.fmt = fmt; 470 va_start(args.args, fmt); 471 warn_slowpath_common(file, line, __builtin_return_address(0), 472 taint, &args); 473 va_end(args.args); 474 } 475 EXPORT_SYMBOL(warn_slowpath_fmt_taint); 476 477 void warn_slowpath_null(const char *file, int line) 478 { 479 warn_slowpath_common(file, line, __builtin_return_address(0), 480 TAINT_WARN, NULL); 481 } 482 EXPORT_SYMBOL(warn_slowpath_null); 483 #endif 484 485 #ifdef CONFIG_CC_STACKPROTECTOR 486 487 /* 488 * Called when gcc's -fstack-protector feature is used, and 489 * gcc detects corruption of the on-stack canary value 490 */ 491 __visible void __stack_chk_fail(void) 492 { 493 panic("stack-protector: Kernel stack is corrupted in: %p\n", 494 __builtin_return_address(0)); 495 } 496 EXPORT_SYMBOL(__stack_chk_fail); 497 498 #endif 499 500 core_param(panic, panic_timeout, int, 0644); 501 core_param(pause_on_oops, pause_on_oops, int, 0644); 502 core_param(panic_on_warn, panic_on_warn, int, 0644); 503 504 static int __init setup_crash_kexec_post_notifiers(char *s) 505 { 506 crash_kexec_post_notifiers = true; 507 return 0; 508 } 509 early_param("crash_kexec_post_notifiers", setup_crash_kexec_post_notifiers); 510 511 static int __init oops_setup(char *s) 512 { 513 if (!s) 514 return -EINVAL; 515 if (!strcmp(s, "panic")) 516 panic_on_oops = 1; 517 return 0; 518 } 519 early_param("oops", oops_setup); 520