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 }; 230 231 /** 232 * print_tainted - return a string to represent the kernel taint state. 233 * 234 * 'P' - Proprietary module has been loaded. 235 * 'F' - Module has been forcibly loaded. 236 * 'S' - SMP with CPUs not designed for SMP. 237 * 'R' - User forced a module unload. 238 * 'M' - System experienced a machine check exception. 239 * 'B' - System has hit bad_page. 240 * 'U' - Userspace-defined naughtiness. 241 * 'D' - Kernel has oopsed before 242 * 'A' - ACPI table overridden. 243 * 'W' - Taint on warning. 244 * 'C' - modules from drivers/staging are loaded. 245 * 'I' - Working around severe firmware bug. 246 * 'O' - Out-of-tree module has been loaded. 247 * 'E' - Unsigned module has been loaded. 248 * 'L' - A soft lockup has previously occurred. 249 * 250 * The string is overwritten by the next call to print_tainted(). 251 */ 252 const char *print_tainted(void) 253 { 254 static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ")]; 255 256 if (tainted_mask) { 257 char *s; 258 int i; 259 260 s = buf + sprintf(buf, "Tainted: "); 261 for (i = 0; i < ARRAY_SIZE(tnts); i++) { 262 const struct tnt *t = &tnts[i]; 263 *s++ = test_bit(t->bit, &tainted_mask) ? 264 t->true : t->false; 265 } 266 *s = 0; 267 } else 268 snprintf(buf, sizeof(buf), "Not tainted"); 269 270 return buf; 271 } 272 273 int test_taint(unsigned flag) 274 { 275 return test_bit(flag, &tainted_mask); 276 } 277 EXPORT_SYMBOL(test_taint); 278 279 unsigned long get_taint(void) 280 { 281 return tainted_mask; 282 } 283 284 /** 285 * add_taint: add a taint flag if not already set. 286 * @flag: one of the TAINT_* constants. 287 * @lockdep_ok: whether lock debugging is still OK. 288 * 289 * If something bad has gone wrong, you'll want @lockdebug_ok = false, but for 290 * some notewortht-but-not-corrupting cases, it can be set to true. 291 */ 292 void add_taint(unsigned flag, enum lockdep_ok lockdep_ok) 293 { 294 if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off()) 295 pr_warn("Disabling lock debugging due to kernel taint\n"); 296 297 set_bit(flag, &tainted_mask); 298 } 299 EXPORT_SYMBOL(add_taint); 300 301 static void spin_msec(int msecs) 302 { 303 int i; 304 305 for (i = 0; i < msecs; i++) { 306 touch_nmi_watchdog(); 307 mdelay(1); 308 } 309 } 310 311 /* 312 * It just happens that oops_enter() and oops_exit() are identically 313 * implemented... 314 */ 315 static void do_oops_enter_exit(void) 316 { 317 unsigned long flags; 318 static int spin_counter; 319 320 if (!pause_on_oops) 321 return; 322 323 spin_lock_irqsave(&pause_on_oops_lock, flags); 324 if (pause_on_oops_flag == 0) { 325 /* This CPU may now print the oops message */ 326 pause_on_oops_flag = 1; 327 } else { 328 /* We need to stall this CPU */ 329 if (!spin_counter) { 330 /* This CPU gets to do the counting */ 331 spin_counter = pause_on_oops; 332 do { 333 spin_unlock(&pause_on_oops_lock); 334 spin_msec(MSEC_PER_SEC); 335 spin_lock(&pause_on_oops_lock); 336 } while (--spin_counter); 337 pause_on_oops_flag = 0; 338 } else { 339 /* This CPU waits for a different one */ 340 while (spin_counter) { 341 spin_unlock(&pause_on_oops_lock); 342 spin_msec(1); 343 spin_lock(&pause_on_oops_lock); 344 } 345 } 346 } 347 spin_unlock_irqrestore(&pause_on_oops_lock, flags); 348 } 349 350 /* 351 * Return true if the calling CPU is allowed to print oops-related info. 352 * This is a bit racy.. 353 */ 354 int oops_may_print(void) 355 { 356 return pause_on_oops_flag == 0; 357 } 358 359 /* 360 * Called when the architecture enters its oops handler, before it prints 361 * anything. If this is the first CPU to oops, and it's oopsing the first 362 * time then let it proceed. 363 * 364 * This is all enabled by the pause_on_oops kernel boot option. We do all 365 * this to ensure that oopses don't scroll off the screen. It has the 366 * side-effect of preventing later-oopsing CPUs from mucking up the display, 367 * too. 368 * 369 * It turns out that the CPU which is allowed to print ends up pausing for 370 * the right duration, whereas all the other CPUs pause for twice as long: 371 * once in oops_enter(), once in oops_exit(). 372 */ 373 void oops_enter(void) 374 { 375 tracing_off(); 376 /* can't trust the integrity of the kernel anymore: */ 377 debug_locks_off(); 378 do_oops_enter_exit(); 379 } 380 381 /* 382 * 64-bit random ID for oopses: 383 */ 384 static u64 oops_id; 385 386 static int init_oops_id(void) 387 { 388 if (!oops_id) 389 get_random_bytes(&oops_id, sizeof(oops_id)); 390 else 391 oops_id++; 392 393 return 0; 394 } 395 late_initcall(init_oops_id); 396 397 void print_oops_end_marker(void) 398 { 399 init_oops_id(); 400 pr_warn("---[ end trace %016llx ]---\n", (unsigned long long)oops_id); 401 } 402 403 /* 404 * Called when the architecture exits its oops handler, after printing 405 * everything. 406 */ 407 void oops_exit(void) 408 { 409 do_oops_enter_exit(); 410 print_oops_end_marker(); 411 kmsg_dump(KMSG_DUMP_OOPS); 412 } 413 414 #ifdef WANT_WARN_ON_SLOWPATH 415 struct slowpath_args { 416 const char *fmt; 417 va_list args; 418 }; 419 420 static void warn_slowpath_common(const char *file, int line, void *caller, 421 unsigned taint, struct slowpath_args *args) 422 { 423 disable_trace_on_warning(); 424 425 pr_warn("------------[ cut here ]------------\n"); 426 pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS()\n", 427 raw_smp_processor_id(), current->pid, file, line, caller); 428 429 if (args) 430 vprintk(args->fmt, args->args); 431 432 if (panic_on_warn) { 433 /* 434 * This thread may hit another WARN() in the panic path. 435 * Resetting this prevents additional WARN() from panicking the 436 * system on this thread. Other threads are blocked by the 437 * panic_mutex in panic(). 438 */ 439 panic_on_warn = 0; 440 panic("panic_on_warn set ...\n"); 441 } 442 443 print_modules(); 444 dump_stack(); 445 print_oops_end_marker(); 446 /* Just a warning, don't kill lockdep. */ 447 add_taint(taint, LOCKDEP_STILL_OK); 448 } 449 450 void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...) 451 { 452 struct slowpath_args args; 453 454 args.fmt = fmt; 455 va_start(args.args, fmt); 456 warn_slowpath_common(file, line, __builtin_return_address(0), 457 TAINT_WARN, &args); 458 va_end(args.args); 459 } 460 EXPORT_SYMBOL(warn_slowpath_fmt); 461 462 void warn_slowpath_fmt_taint(const char *file, int line, 463 unsigned taint, const char *fmt, ...) 464 { 465 struct slowpath_args args; 466 467 args.fmt = fmt; 468 va_start(args.args, fmt); 469 warn_slowpath_common(file, line, __builtin_return_address(0), 470 taint, &args); 471 va_end(args.args); 472 } 473 EXPORT_SYMBOL(warn_slowpath_fmt_taint); 474 475 void warn_slowpath_null(const char *file, int line) 476 { 477 warn_slowpath_common(file, line, __builtin_return_address(0), 478 TAINT_WARN, NULL); 479 } 480 EXPORT_SYMBOL(warn_slowpath_null); 481 #endif 482 483 #ifdef CONFIG_CC_STACKPROTECTOR 484 485 /* 486 * Called when gcc's -fstack-protector feature is used, and 487 * gcc detects corruption of the on-stack canary value 488 */ 489 __visible void __stack_chk_fail(void) 490 { 491 panic("stack-protector: Kernel stack is corrupted in: %p\n", 492 __builtin_return_address(0)); 493 } 494 EXPORT_SYMBOL(__stack_chk_fail); 495 496 #endif 497 498 core_param(panic, panic_timeout, int, 0644); 499 core_param(pause_on_oops, pause_on_oops, int, 0644); 500 core_param(panic_on_warn, panic_on_warn, int, 0644); 501 502 static int __init setup_crash_kexec_post_notifiers(char *s) 503 { 504 crash_kexec_post_notifiers = true; 505 return 0; 506 } 507 early_param("crash_kexec_post_notifiers", setup_crash_kexec_post_notifiers); 508 509 static int __init oops_setup(char *s) 510 { 511 if (!s) 512 return -EINVAL; 513 if (!strcmp(s, "panic")) 514 panic_on_oops = 1; 515 return 0; 516 } 517 early_param("oops", oops_setup); 518