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