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