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/module.h> 12 #include <linux/sched.h> 13 #include <linux/delay.h> 14 #include <linux/reboot.h> 15 #include <linux/notifier.h> 16 #include <linux/init.h> 17 #include <linux/sysrq.h> 18 #include <linux/interrupt.h> 19 #include <linux/nmi.h> 20 #include <linux/kexec.h> 21 #include <linux/debug_locks.h> 22 #include <linux/random.h> 23 24 int panic_on_oops; 25 int tainted; 26 static int pause_on_oops; 27 static int pause_on_oops_flag; 28 static DEFINE_SPINLOCK(pause_on_oops_lock); 29 30 int panic_timeout; 31 32 ATOMIC_NOTIFIER_HEAD(panic_notifier_list); 33 34 EXPORT_SYMBOL(panic_notifier_list); 35 36 static int __init panic_setup(char *str) 37 { 38 panic_timeout = simple_strtoul(str, NULL, 0); 39 return 1; 40 } 41 __setup("panic=", panic_setup); 42 43 static long no_blink(long time) 44 { 45 return 0; 46 } 47 48 /* Returns how long it waited in ms */ 49 long (*panic_blink)(long time); 50 EXPORT_SYMBOL(panic_blink); 51 52 /** 53 * panic - halt the system 54 * @fmt: The text string to print 55 * 56 * Display a message, then perform cleanups. 57 * 58 * This function never returns. 59 */ 60 61 NORET_TYPE void panic(const char * fmt, ...) 62 { 63 long i; 64 static char buf[1024]; 65 va_list args; 66 #if defined(CONFIG_S390) 67 unsigned long caller = (unsigned long) __builtin_return_address(0); 68 #endif 69 70 /* 71 * It's possible to come here directly from a panic-assertion and not 72 * have preempt disabled. Some functions called from here want 73 * preempt to be disabled. No point enabling it later though... 74 */ 75 preempt_disable(); 76 77 bust_spinlocks(1); 78 va_start(args, fmt); 79 vsnprintf(buf, sizeof(buf), fmt, args); 80 va_end(args); 81 printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf); 82 bust_spinlocks(0); 83 84 /* 85 * If we have crashed and we have a crash kernel loaded let it handle 86 * everything else. 87 * Do we want to call this before we try to display a message? 88 */ 89 crash_kexec(NULL); 90 91 #ifdef CONFIG_SMP 92 /* 93 * Note smp_send_stop is the usual smp shutdown function, which 94 * unfortunately means it may not be hardened to work in a panic 95 * situation. 96 */ 97 smp_send_stop(); 98 #endif 99 100 atomic_notifier_call_chain(&panic_notifier_list, 0, buf); 101 102 if (!panic_blink) 103 panic_blink = no_blink; 104 105 if (panic_timeout > 0) { 106 /* 107 * Delay timeout seconds before rebooting the machine. 108 * We can't use the "normal" timers since we just panicked.. 109 */ 110 printk(KERN_EMERG "Rebooting in %d seconds..",panic_timeout); 111 for (i = 0; i < panic_timeout*1000; ) { 112 touch_nmi_watchdog(); 113 i += panic_blink(i); 114 mdelay(1); 115 i++; 116 } 117 /* This will not be a clean reboot, with everything 118 * shutting down. But if there is a chance of 119 * rebooting the system it will be rebooted. 120 */ 121 emergency_restart(); 122 } 123 #ifdef __sparc__ 124 { 125 extern int stop_a_enabled; 126 /* Make sure the user can actually press Stop-A (L1-A) */ 127 stop_a_enabled = 1; 128 printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n"); 129 } 130 #endif 131 #if defined(CONFIG_S390) 132 disabled_wait(caller); 133 #endif 134 local_irq_enable(); 135 for (i = 0;;) { 136 touch_softlockup_watchdog(); 137 i += panic_blink(i); 138 mdelay(1); 139 i++; 140 } 141 } 142 143 EXPORT_SYMBOL(panic); 144 145 /** 146 * print_tainted - return a string to represent the kernel taint state. 147 * 148 * 'P' - Proprietary module has been loaded. 149 * 'F' - Module has been forcibly loaded. 150 * 'S' - SMP with CPUs not designed for SMP. 151 * 'R' - User forced a module unload. 152 * 'M' - System experienced a machine check exception. 153 * 'B' - System has hit bad_page. 154 * 'U' - Userspace-defined naughtiness. 155 * 156 * The string is overwritten by the next call to print_taint(). 157 */ 158 159 const char *print_tainted(void) 160 { 161 static char buf[20]; 162 if (tainted) { 163 snprintf(buf, sizeof(buf), "Tainted: %c%c%c%c%c%c%c%c", 164 tainted & TAINT_PROPRIETARY_MODULE ? 'P' : 'G', 165 tainted & TAINT_FORCED_MODULE ? 'F' : ' ', 166 tainted & TAINT_UNSAFE_SMP ? 'S' : ' ', 167 tainted & TAINT_FORCED_RMMOD ? 'R' : ' ', 168 tainted & TAINT_MACHINE_CHECK ? 'M' : ' ', 169 tainted & TAINT_BAD_PAGE ? 'B' : ' ', 170 tainted & TAINT_USER ? 'U' : ' ', 171 tainted & TAINT_DIE ? 'D' : ' '); 172 } 173 else 174 snprintf(buf, sizeof(buf), "Not tainted"); 175 return(buf); 176 } 177 178 void add_taint(unsigned flag) 179 { 180 debug_locks = 0; /* can't trust the integrity of the kernel anymore */ 181 tainted |= flag; 182 } 183 EXPORT_SYMBOL(add_taint); 184 185 static int __init pause_on_oops_setup(char *str) 186 { 187 pause_on_oops = simple_strtoul(str, NULL, 0); 188 return 1; 189 } 190 __setup("pause_on_oops=", pause_on_oops_setup); 191 192 static void spin_msec(int msecs) 193 { 194 int i; 195 196 for (i = 0; i < msecs; i++) { 197 touch_nmi_watchdog(); 198 mdelay(1); 199 } 200 } 201 202 /* 203 * It just happens that oops_enter() and oops_exit() are identically 204 * implemented... 205 */ 206 static void do_oops_enter_exit(void) 207 { 208 unsigned long flags; 209 static int spin_counter; 210 211 if (!pause_on_oops) 212 return; 213 214 spin_lock_irqsave(&pause_on_oops_lock, flags); 215 if (pause_on_oops_flag == 0) { 216 /* This CPU may now print the oops message */ 217 pause_on_oops_flag = 1; 218 } else { 219 /* We need to stall this CPU */ 220 if (!spin_counter) { 221 /* This CPU gets to do the counting */ 222 spin_counter = pause_on_oops; 223 do { 224 spin_unlock(&pause_on_oops_lock); 225 spin_msec(MSEC_PER_SEC); 226 spin_lock(&pause_on_oops_lock); 227 } while (--spin_counter); 228 pause_on_oops_flag = 0; 229 } else { 230 /* This CPU waits for a different one */ 231 while (spin_counter) { 232 spin_unlock(&pause_on_oops_lock); 233 spin_msec(1); 234 spin_lock(&pause_on_oops_lock); 235 } 236 } 237 } 238 spin_unlock_irqrestore(&pause_on_oops_lock, flags); 239 } 240 241 /* 242 * Return true if the calling CPU is allowed to print oops-related info. This 243 * is a bit racy.. 244 */ 245 int oops_may_print(void) 246 { 247 return pause_on_oops_flag == 0; 248 } 249 250 /* 251 * Called when the architecture enters its oops handler, before it prints 252 * anything. If this is the first CPU to oops, and it's oopsing the first time 253 * then let it proceed. 254 * 255 * This is all enabled by the pause_on_oops kernel boot option. We do all this 256 * to ensure that oopses don't scroll off the screen. It has the side-effect 257 * of preventing later-oopsing CPUs from mucking up the display, too. 258 * 259 * It turns out that the CPU which is allowed to print ends up pausing for the 260 * right duration, whereas all the other CPUs pause for twice as long: once in 261 * oops_enter(), once in oops_exit(). 262 */ 263 void oops_enter(void) 264 { 265 debug_locks_off(); /* can't trust the integrity of the kernel anymore */ 266 do_oops_enter_exit(); 267 } 268 269 /* 270 * 64-bit random ID for oopses: 271 */ 272 static u64 oops_id; 273 274 static int init_oops_id(void) 275 { 276 if (!oops_id) 277 get_random_bytes(&oops_id, sizeof(oops_id)); 278 279 return 0; 280 } 281 late_initcall(init_oops_id); 282 283 /* 284 * Called when the architecture exits its oops handler, after printing 285 * everything. 286 */ 287 void oops_exit(void) 288 { 289 do_oops_enter_exit(); 290 init_oops_id(); 291 printk(KERN_WARNING "---[ end trace %016llx ]---\n", 292 (unsigned long long)oops_id); 293 } 294 295 #ifdef CONFIG_CC_STACKPROTECTOR 296 /* 297 * Called when gcc's -fstack-protector feature is used, and 298 * gcc detects corruption of the on-stack canary value 299 */ 300 void __stack_chk_fail(void) 301 { 302 panic("stack-protector: Kernel stack is corrupted"); 303 } 304 EXPORT_SYMBOL(__stack_chk_fail); 305 #endif 306