xref: /openbmc/linux/kernel/panic.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
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 
23 int panic_on_oops;
24 int tainted;
25 static int pause_on_oops;
26 static int pause_on_oops_flag;
27 static DEFINE_SPINLOCK(pause_on_oops_lock);
28 
29 int panic_timeout;
30 
31 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
32 
33 EXPORT_SYMBOL(panic_notifier_list);
34 
35 static int __init panic_setup(char *str)
36 {
37 	panic_timeout = simple_strtoul(str, NULL, 0);
38 	return 1;
39 }
40 __setup("panic=", panic_setup);
41 
42 static long no_blink(long time)
43 {
44 	return 0;
45 }
46 
47 /* Returns how long it waited in ms */
48 long (*panic_blink)(long time);
49 EXPORT_SYMBOL(panic_blink);
50 
51 /**
52  *	panic - halt the system
53  *	@fmt: The text string to print
54  *
55  *	Display a message, then perform cleanups.
56  *
57  *	This function never returns.
58  */
59 
60 NORET_TYPE void panic(const char * fmt, ...)
61 {
62 	long i;
63 	static char buf[1024];
64 	va_list args;
65 #if defined(CONFIG_S390)
66         unsigned long caller = (unsigned long) __builtin_return_address(0);
67 #endif
68 
69 	/*
70 	 * It's possible to come here directly from a panic-assertion and not
71 	 * have preempt disabled. Some functions called from here want
72 	 * preempt to be disabled. No point enabling it later though...
73 	 */
74 	preempt_disable();
75 
76 	bust_spinlocks(1);
77 	va_start(args, fmt);
78 	vsnprintf(buf, sizeof(buf), fmt, args);
79 	va_end(args);
80 	printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
81 	bust_spinlocks(0);
82 
83 	/*
84 	 * If we have crashed and we have a crash kernel loaded let it handle
85 	 * everything else.
86 	 * Do we want to call this before we try to display a message?
87 	 */
88 	crash_kexec(NULL);
89 
90 #ifdef CONFIG_SMP
91 	/*
92 	 * Note smp_send_stop is the usual smp shutdown function, which
93 	 * unfortunately means it may not be hardened to work in a panic
94 	 * situation.
95 	 */
96 	smp_send_stop();
97 #endif
98 
99 	atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
100 
101 	if (!panic_blink)
102 		panic_blink = no_blink;
103 
104 	if (panic_timeout > 0) {
105 		/*
106 	 	 * Delay timeout seconds before rebooting the machine.
107 		 * We can't use the "normal" timers since we just panicked..
108 	 	 */
109 		printk(KERN_EMERG "Rebooting in %d seconds..",panic_timeout);
110 		for (i = 0; i < panic_timeout*1000; ) {
111 			touch_nmi_watchdog();
112 			i += panic_blink(i);
113 			mdelay(1);
114 			i++;
115 		}
116 		/*	This will not be a clean reboot, with everything
117 		 *	shutting down.  But if there is a chance of
118 		 *	rebooting the system it will be rebooted.
119 		 */
120 		emergency_restart();
121 	}
122 #ifdef __sparc__
123 	{
124 		extern int stop_a_enabled;
125 		/* Make sure the user can actually press Stop-A (L1-A) */
126 		stop_a_enabled = 1;
127 		printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
128 	}
129 #endif
130 #if defined(CONFIG_S390)
131         disabled_wait(caller);
132 #endif
133 	local_irq_enable();
134 	for (i = 0;;) {
135 		touch_softlockup_watchdog();
136 		i += panic_blink(i);
137 		mdelay(1);
138 		i++;
139 	}
140 }
141 
142 EXPORT_SYMBOL(panic);
143 
144 /**
145  *	print_tainted - return a string to represent the kernel taint state.
146  *
147  *  'P' - Proprietary module has been loaded.
148  *  'F' - Module has been forcibly loaded.
149  *  'S' - SMP with CPUs not designed for SMP.
150  *  'R' - User forced a module unload.
151  *  'M' - Machine had a machine check experience.
152  *  'B' - System has hit bad_page.
153  *  'U' - Userspace-defined naughtiness.
154  *
155  *	The string is overwritten by the next call to print_taint().
156  */
157 
158 const char *print_tainted(void)
159 {
160 	static char buf[20];
161 	if (tainted) {
162 		snprintf(buf, sizeof(buf), "Tainted: %c%c%c%c%c%c%c",
163 			tainted & TAINT_PROPRIETARY_MODULE ? 'P' : 'G',
164 			tainted & TAINT_FORCED_MODULE ? 'F' : ' ',
165 			tainted & TAINT_UNSAFE_SMP ? 'S' : ' ',
166 			tainted & TAINT_FORCED_RMMOD ? 'R' : ' ',
167  			tainted & TAINT_MACHINE_CHECK ? 'M' : ' ',
168 			tainted & TAINT_BAD_PAGE ? 'B' : ' ',
169 			tainted & TAINT_USER ? 'U' : ' ');
170 	}
171 	else
172 		snprintf(buf, sizeof(buf), "Not tainted");
173 	return(buf);
174 }
175 
176 void add_taint(unsigned flag)
177 {
178 	debug_locks = 0; /* can't trust the integrity of the kernel anymore */
179 	tainted |= flag;
180 }
181 EXPORT_SYMBOL(add_taint);
182 
183 static int __init pause_on_oops_setup(char *str)
184 {
185 	pause_on_oops = simple_strtoul(str, NULL, 0);
186 	return 1;
187 }
188 __setup("pause_on_oops=", pause_on_oops_setup);
189 
190 static void spin_msec(int msecs)
191 {
192 	int i;
193 
194 	for (i = 0; i < msecs; i++) {
195 		touch_nmi_watchdog();
196 		mdelay(1);
197 	}
198 }
199 
200 /*
201  * It just happens that oops_enter() and oops_exit() are identically
202  * implemented...
203  */
204 static void do_oops_enter_exit(void)
205 {
206 	unsigned long flags;
207 	static int spin_counter;
208 
209 	if (!pause_on_oops)
210 		return;
211 
212 	spin_lock_irqsave(&pause_on_oops_lock, flags);
213 	if (pause_on_oops_flag == 0) {
214 		/* This CPU may now print the oops message */
215 		pause_on_oops_flag = 1;
216 	} else {
217 		/* We need to stall this CPU */
218 		if (!spin_counter) {
219 			/* This CPU gets to do the counting */
220 			spin_counter = pause_on_oops;
221 			do {
222 				spin_unlock(&pause_on_oops_lock);
223 				spin_msec(MSEC_PER_SEC);
224 				spin_lock(&pause_on_oops_lock);
225 			} while (--spin_counter);
226 			pause_on_oops_flag = 0;
227 		} else {
228 			/* This CPU waits for a different one */
229 			while (spin_counter) {
230 				spin_unlock(&pause_on_oops_lock);
231 				spin_msec(1);
232 				spin_lock(&pause_on_oops_lock);
233 			}
234 		}
235 	}
236 	spin_unlock_irqrestore(&pause_on_oops_lock, flags);
237 }
238 
239 /*
240  * Return true if the calling CPU is allowed to print oops-related info.  This
241  * is a bit racy..
242  */
243 int oops_may_print(void)
244 {
245 	return pause_on_oops_flag == 0;
246 }
247 
248 /*
249  * Called when the architecture enters its oops handler, before it prints
250  * anything.  If this is the first CPU to oops, and it's oopsing the first time
251  * then let it proceed.
252  *
253  * This is all enabled by the pause_on_oops kernel boot option.  We do all this
254  * to ensure that oopses don't scroll off the screen.  It has the side-effect
255  * of preventing later-oopsing CPUs from mucking up the display, too.
256  *
257  * It turns out that the CPU which is allowed to print ends up pausing for the
258  * right duration, whereas all the other CPUs pause for twice as long: once in
259  * oops_enter(), once in oops_exit().
260  */
261 void oops_enter(void)
262 {
263 	debug_locks_off(); /* can't trust the integrity of the kernel anymore */
264 	do_oops_enter_exit();
265 }
266 
267 /*
268  * Called when the architecture exits its oops handler, after printing
269  * everything.
270  */
271 void oops_exit(void)
272 {
273 	do_oops_enter_exit();
274 }
275 
276 #ifdef CONFIG_CC_STACKPROTECTOR
277 /*
278  * Called when gcc's -fstack-protector feature is used, and
279  * gcc detects corruption of the on-stack canary value
280  */
281 void __stack_chk_fail(void)
282 {
283 	panic("stack-protector: Kernel stack is corrupted");
284 }
285 EXPORT_SYMBOL(__stack_chk_fail);
286 #endif
287