xref: /linux/kernel/panic.c (revision 6e8331ac6973435b1e7604c30f2ad394035b46e1)
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 
22 int panic_on_oops;
23 int tainted;
24 static int pause_on_oops;
25 static int pause_on_oops_flag;
26 static DEFINE_SPINLOCK(pause_on_oops_lock);
27 
28 int panic_timeout;
29 
30 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
31 
32 EXPORT_SYMBOL(panic_notifier_list);
33 
34 static int __init panic_setup(char *str)
35 {
36 	panic_timeout = simple_strtoul(str, NULL, 0);
37 	return 1;
38 }
39 __setup("panic=", panic_setup);
40 
41 static long no_blink(long time)
42 {
43 	return 0;
44 }
45 
46 /* Returns how long it waited in ms */
47 long (*panic_blink)(long time);
48 EXPORT_SYMBOL(panic_blink);
49 
50 /**
51  *	panic - halt the system
52  *	@fmt: The text string to print
53  *
54  *	Display a message, then perform cleanups.
55  *
56  *	This function never returns.
57  */
58 
59 NORET_TYPE void panic(const char * fmt, ...)
60 {
61 	long i;
62 	static char buf[1024];
63 	va_list args;
64 #if defined(CONFIG_S390)
65         unsigned long caller = (unsigned long) __builtin_return_address(0);
66 #endif
67 
68 	/*
69 	 * It's possible to come here directly from a panic-assertion and not
70 	 * have preempt disabled. Some functions called from here want
71 	 * preempt to be disabled. No point enabling it later though...
72 	 */
73 	preempt_disable();
74 
75 	bust_spinlocks(1);
76 	va_start(args, fmt);
77 	vsnprintf(buf, sizeof(buf), fmt, args);
78 	va_end(args);
79 	printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
80 	bust_spinlocks(0);
81 
82 	/*
83 	 * If we have crashed and we have a crash kernel loaded let it handle
84 	 * everything else.
85 	 * Do we want to call this before we try to display a message?
86 	 */
87 	crash_kexec(NULL);
88 
89 #ifdef CONFIG_SMP
90 	/*
91 	 * Note smp_send_stop is the usual smp shutdown function, which
92 	 * unfortunately means it may not be hardened to work in a panic
93 	 * situation.
94 	 */
95 	smp_send_stop();
96 #endif
97 
98 	atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
99 
100 	if (!panic_blink)
101 		panic_blink = no_blink;
102 
103 	if (panic_timeout > 0) {
104 		/*
105 	 	 * Delay timeout seconds before rebooting the machine.
106 		 * We can't use the "normal" timers since we just panicked..
107 	 	 */
108 		printk(KERN_EMERG "Rebooting in %d seconds..",panic_timeout);
109 		for (i = 0; i < panic_timeout*1000; ) {
110 			touch_nmi_watchdog();
111 			i += panic_blink(i);
112 			mdelay(1);
113 			i++;
114 		}
115 		/*	This will not be a clean reboot, with everything
116 		 *	shutting down.  But if there is a chance of
117 		 *	rebooting the system it will be rebooted.
118 		 */
119 		emergency_restart();
120 	}
121 #ifdef __sparc__
122 	{
123 		extern int stop_a_enabled;
124 		/* Make sure the user can actually press Stop-A (L1-A) */
125 		stop_a_enabled = 1;
126 		printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
127 	}
128 #endif
129 #if defined(CONFIG_S390)
130         disabled_wait(caller);
131 #endif
132 	local_irq_enable();
133 	for (i = 0;;) {
134 		touch_softlockup_watchdog();
135 		i += panic_blink(i);
136 		mdelay(1);
137 		i++;
138 	}
139 }
140 
141 EXPORT_SYMBOL(panic);
142 
143 /**
144  *	print_tainted - return a string to represent the kernel taint state.
145  *
146  *  'P' - Proprietary module has been loaded.
147  *  'F' - Module has been forcibly loaded.
148  *  'S' - SMP with CPUs not designed for SMP.
149  *  'R' - User forced a module unload.
150  *  'M' - Machine had a machine check experience.
151  *  'B' - System has hit bad_page.
152  *
153  *	The string is overwritten by the next call to print_taint().
154  */
155 
156 const char *print_tainted(void)
157 {
158 	static char buf[20];
159 	if (tainted) {
160 		snprintf(buf, sizeof(buf), "Tainted: %c%c%c%c%c%c",
161 			tainted & TAINT_PROPRIETARY_MODULE ? 'P' : 'G',
162 			tainted & TAINT_FORCED_MODULE ? 'F' : ' ',
163 			tainted & TAINT_UNSAFE_SMP ? 'S' : ' ',
164 			tainted & TAINT_FORCED_RMMOD ? 'R' : ' ',
165  			tainted & TAINT_MACHINE_CHECK ? 'M' : ' ',
166 			tainted & TAINT_BAD_PAGE ? 'B' : ' ');
167 	}
168 	else
169 		snprintf(buf, sizeof(buf), "Not tainted");
170 	return(buf);
171 }
172 
173 void add_taint(unsigned flag)
174 {
175 	debug_locks_off(); /* can't trust the integrity of the kernel anymore */
176 	tainted |= flag;
177 }
178 EXPORT_SYMBOL(add_taint);
179 
180 static int __init pause_on_oops_setup(char *str)
181 {
182 	pause_on_oops = simple_strtoul(str, NULL, 0);
183 	return 1;
184 }
185 __setup("pause_on_oops=", pause_on_oops_setup);
186 
187 static void spin_msec(int msecs)
188 {
189 	int i;
190 
191 	for (i = 0; i < msecs; i++) {
192 		touch_nmi_watchdog();
193 		mdelay(1);
194 	}
195 }
196 
197 /*
198  * It just happens that oops_enter() and oops_exit() are identically
199  * implemented...
200  */
201 static void do_oops_enter_exit(void)
202 {
203 	unsigned long flags;
204 	static int spin_counter;
205 
206 	if (!pause_on_oops)
207 		return;
208 
209 	spin_lock_irqsave(&pause_on_oops_lock, flags);
210 	if (pause_on_oops_flag == 0) {
211 		/* This CPU may now print the oops message */
212 		pause_on_oops_flag = 1;
213 	} else {
214 		/* We need to stall this CPU */
215 		if (!spin_counter) {
216 			/* This CPU gets to do the counting */
217 			spin_counter = pause_on_oops;
218 			do {
219 				spin_unlock(&pause_on_oops_lock);
220 				spin_msec(MSEC_PER_SEC);
221 				spin_lock(&pause_on_oops_lock);
222 			} while (--spin_counter);
223 			pause_on_oops_flag = 0;
224 		} else {
225 			/* This CPU waits for a different one */
226 			while (spin_counter) {
227 				spin_unlock(&pause_on_oops_lock);
228 				spin_msec(1);
229 				spin_lock(&pause_on_oops_lock);
230 			}
231 		}
232 	}
233 	spin_unlock_irqrestore(&pause_on_oops_lock, flags);
234 }
235 
236 /*
237  * Return true if the calling CPU is allowed to print oops-related info.  This
238  * is a bit racy..
239  */
240 int oops_may_print(void)
241 {
242 	return pause_on_oops_flag == 0;
243 }
244 
245 /*
246  * Called when the architecture enters its oops handler, before it prints
247  * anything.  If this is the first CPU to oops, and it's oopsing the first time
248  * then let it proceed.
249  *
250  * This is all enabled by the pause_on_oops kernel boot option.  We do all this
251  * to ensure that oopses don't scroll off the screen.  It has the side-effect
252  * of preventing later-oopsing CPUs from mucking up the display, too.
253  *
254  * It turns out that the CPU which is allowed to print ends up pausing for the
255  * right duration, whereas all the other CPUs pause for twice as long: once in
256  * oops_enter(), once in oops_exit().
257  */
258 void oops_enter(void)
259 {
260 	debug_locks_off(); /* can't trust the integrity of the kernel anymore */
261 	do_oops_enter_exit();
262 }
263 
264 /*
265  * Called when the architecture exits its oops handler, after printing
266  * everything.
267  */
268 void oops_exit(void)
269 {
270 	do_oops_enter_exit();
271 }
272