Root/kernel/panic.c

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/kallsyms.h>
14#include <linux/notifier.h>
15#include <linux/module.h>
16#include <linux/random.h>
17#include <linux/reboot.h>
18#include <linux/delay.h>
19#include <linux/kexec.h>
20#include <linux/sched.h>
21#include <linux/sysrq.h>
22#include <linux/init.h>
23#include <linux/nmi.h>
24#include <linux/dmi.h>
25
26int panic_on_oops;
27static unsigned long tainted_mask;
28static int pause_on_oops;
29static int pause_on_oops_flag;
30static DEFINE_SPINLOCK(pause_on_oops_lock);
31
32int panic_timeout;
33
34ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
35
36EXPORT_SYMBOL(panic_notifier_list);
37
38static long no_blink(long time)
39{
40    return 0;
41}
42
43/* Returns how long it waited in ms */
44long (*panic_blink)(long time);
45EXPORT_SYMBOL(panic_blink);
46
47/**
48 * panic - halt the system
49 * @fmt: The text string to print
50 *
51 * Display a message, then perform cleanups.
52 *
53 * This function never returns.
54 */
55NORET_TYPE void panic(const char * fmt, ...)
56{
57    static char buf[1024];
58    va_list args;
59    long i;
60
61    /*
62     * It's possible to come here directly from a panic-assertion and
63     * not have preempt disabled. Some functions called from here want
64     * preempt to be disabled. No point enabling it later though...
65     */
66    preempt_disable();
67
68    bust_spinlocks(1);
69    va_start(args, fmt);
70    vsnprintf(buf, sizeof(buf), fmt, args);
71    va_end(args);
72    printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
73#ifdef CONFIG_DEBUG_BUGVERBOSE
74    dump_stack();
75#endif
76
77    /*
78     * If we have crashed and we have a crash kernel loaded let it handle
79     * everything else.
80     * Do we want to call this before we try to display a message?
81     */
82    crash_kexec(NULL);
83
84    /*
85     * Note smp_send_stop is the usual smp shutdown function, which
86     * unfortunately means it may not be hardened to work in a panic
87     * situation.
88     */
89    smp_send_stop();
90
91    atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
92
93    bust_spinlocks(0);
94
95    if (!panic_blink)
96        panic_blink = no_blink;
97
98    if (panic_timeout > 0) {
99        /*
100         * Delay timeout seconds before rebooting the machine.
101         * We can't use the "normal" timers since we just panicked.
102         */
103        printk(KERN_EMERG "Rebooting in %d seconds..", panic_timeout);
104
105        for (i = 0; i < panic_timeout*1000; ) {
106            touch_nmi_watchdog();
107            i += panic_blink(i);
108            mdelay(1);
109            i++;
110        }
111        /*
112         * This will not be a clean reboot, with everything
113         * shutting down. But if there is a chance of
114         * rebooting the system it will be rebooted.
115         */
116        emergency_restart();
117    }
118#ifdef __sparc__
119    {
120        extern int stop_a_enabled;
121        /* Make sure the user can actually press Stop-A (L1-A) */
122        stop_a_enabled = 1;
123        printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
124    }
125#endif
126#if defined(CONFIG_S390)
127    {
128        unsigned long caller;
129
130        caller = (unsigned long)__builtin_return_address(0);
131        disabled_wait(caller);
132    }
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
143EXPORT_SYMBOL(panic);
144
145
146struct tnt {
147    u8 bit;
148    char true;
149    char false;
150};
151
152static const struct tnt tnts[] = {
153    { TAINT_PROPRIETARY_MODULE, 'P', 'G' },
154    { TAINT_FORCED_MODULE, 'F', ' ' },
155    { TAINT_UNSAFE_SMP, 'S', ' ' },
156    { TAINT_FORCED_RMMOD, 'R', ' ' },
157    { TAINT_MACHINE_CHECK, 'M', ' ' },
158    { TAINT_BAD_PAGE, 'B', ' ' },
159    { TAINT_USER, 'U', ' ' },
160    { TAINT_DIE, 'D', ' ' },
161    { TAINT_OVERRIDDEN_ACPI_TABLE, 'A', ' ' },
162    { TAINT_WARN, 'W', ' ' },
163    { TAINT_CRAP, 'C', ' ' },
164};
165
166/**
167 * print_tainted - return a string to represent the kernel taint state.
168 *
169 * 'P' - Proprietary module has been loaded.
170 * 'F' - Module has been forcibly loaded.
171 * 'S' - SMP with CPUs not designed for SMP.
172 * 'R' - User forced a module unload.
173 * 'M' - System experienced a machine check exception.
174 * 'B' - System has hit bad_page.
175 * 'U' - Userspace-defined naughtiness.
176 * 'D' - Kernel has oopsed before
177 * 'A' - ACPI table overridden.
178 * 'W' - Taint on warning.
179 * 'C' - modules from drivers/staging are loaded.
180 *
181 * The string is overwritten by the next call to print_tainted().
182 */
183const char *print_tainted(void)
184{
185    static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ") + 1];
186
187    if (tainted_mask) {
188        char *s;
189        int i;
190
191        s = buf + sprintf(buf, "Tainted: ");
192        for (i = 0; i < ARRAY_SIZE(tnts); i++) {
193            const struct tnt *t = &tnts[i];
194            *s++ = test_bit(t->bit, &tainted_mask) ?
195                    t->true : t->false;
196        }
197        *s = 0;
198    } else
199        snprintf(buf, sizeof(buf), "Not tainted");
200
201    return buf;
202}
203
204int test_taint(unsigned flag)
205{
206    return test_bit(flag, &tainted_mask);
207}
208EXPORT_SYMBOL(test_taint);
209
210unsigned long get_taint(void)
211{
212    return tainted_mask;
213}
214
215void add_taint(unsigned flag)
216{
217    /*
218     * Can't trust the integrity of the kernel anymore.
219     * We don't call directly debug_locks_off() because the issue
220     * is not necessarily serious enough to set oops_in_progress to 1
221     * Also we want to keep up lockdep for staging development and
222     * post-warning case.
223     */
224    if (flag != TAINT_CRAP && flag != TAINT_WARN && __debug_locks_off())
225        printk(KERN_WARNING "Disabling lock debugging due to kernel taint\n");
226
227    set_bit(flag, &tainted_mask);
228}
229EXPORT_SYMBOL(add_taint);
230
231static void spin_msec(int msecs)
232{
233    int i;
234
235    for (i = 0; i < msecs; i++) {
236        touch_nmi_watchdog();
237        mdelay(1);
238    }
239}
240
241/*
242 * It just happens that oops_enter() and oops_exit() are identically
243 * implemented...
244 */
245static void do_oops_enter_exit(void)
246{
247    unsigned long flags;
248    static int spin_counter;
249
250    if (!pause_on_oops)
251        return;
252
253    spin_lock_irqsave(&pause_on_oops_lock, flags);
254    if (pause_on_oops_flag == 0) {
255        /* This CPU may now print the oops message */
256        pause_on_oops_flag = 1;
257    } else {
258        /* We need to stall this CPU */
259        if (!spin_counter) {
260            /* This CPU gets to do the counting */
261            spin_counter = pause_on_oops;
262            do {
263                spin_unlock(&pause_on_oops_lock);
264                spin_msec(MSEC_PER_SEC);
265                spin_lock(&pause_on_oops_lock);
266            } while (--spin_counter);
267            pause_on_oops_flag = 0;
268        } else {
269            /* This CPU waits for a different one */
270            while (spin_counter) {
271                spin_unlock(&pause_on_oops_lock);
272                spin_msec(1);
273                spin_lock(&pause_on_oops_lock);
274            }
275        }
276    }
277    spin_unlock_irqrestore(&pause_on_oops_lock, flags);
278}
279
280/*
281 * Return true if the calling CPU is allowed to print oops-related info.
282 * This is a bit racy..
283 */
284int oops_may_print(void)
285{
286    return pause_on_oops_flag == 0;
287}
288
289/*
290 * Called when the architecture enters its oops handler, before it prints
291 * anything. If this is the first CPU to oops, and it's oopsing the first
292 * time then let it proceed.
293 *
294 * This is all enabled by the pause_on_oops kernel boot option. We do all
295 * this to ensure that oopses don't scroll off the screen. It has the
296 * side-effect of preventing later-oopsing CPUs from mucking up the display,
297 * too.
298 *
299 * It turns out that the CPU which is allowed to print ends up pausing for
300 * the right duration, whereas all the other CPUs pause for twice as long:
301 * once in oops_enter(), once in oops_exit().
302 */
303void oops_enter(void)
304{
305    tracing_off();
306    /* can't trust the integrity of the kernel anymore: */
307    debug_locks_off();
308    do_oops_enter_exit();
309}
310
311/*
312 * 64-bit random ID for oopses:
313 */
314static u64 oops_id;
315
316static int init_oops_id(void)
317{
318    if (!oops_id)
319        get_random_bytes(&oops_id, sizeof(oops_id));
320    else
321        oops_id++;
322
323    return 0;
324}
325late_initcall(init_oops_id);
326
327static void print_oops_end_marker(void)
328{
329    init_oops_id();
330    printk(KERN_WARNING "---[ end trace %016llx ]---\n",
331        (unsigned long long)oops_id);
332}
333
334/*
335 * Called when the architecture exits its oops handler, after printing
336 * everything.
337 */
338void oops_exit(void)
339{
340    do_oops_enter_exit();
341    print_oops_end_marker();
342}
343
344#ifdef WANT_WARN_ON_SLOWPATH
345struct slowpath_args {
346    const char *fmt;
347    va_list args;
348};
349
350static void warn_slowpath_common(const char *file, int line, void *caller, struct slowpath_args *args)
351{
352    const char *board;
353
354    printk(KERN_WARNING "------------[ cut here ]------------\n");
355    printk(KERN_WARNING "WARNING: at %s:%d %pS()\n", file, line, caller);
356    board = dmi_get_system_info(DMI_PRODUCT_NAME);
357    if (board)
358        printk(KERN_WARNING "Hardware name: %s\n", board);
359
360    if (args)
361        vprintk(args->fmt, args->args);
362
363    print_modules();
364    dump_stack();
365    print_oops_end_marker();
366    add_taint(TAINT_WARN);
367}
368
369void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
370{
371    struct slowpath_args args;
372
373    args.fmt = fmt;
374    va_start(args.args, fmt);
375    warn_slowpath_common(file, line, __builtin_return_address(0), &args);
376    va_end(args.args);
377}
378EXPORT_SYMBOL(warn_slowpath_fmt);
379
380void warn_slowpath_null(const char *file, int line)
381{
382    warn_slowpath_common(file, line, __builtin_return_address(0), NULL);
383}
384EXPORT_SYMBOL(warn_slowpath_null);
385#endif
386
387#ifdef CONFIG_CC_STACKPROTECTOR
388
389/*
390 * Called when gcc's -fstack-protector feature is used, and
391 * gcc detects corruption of the on-stack canary value
392 */
393void __stack_chk_fail(void)
394{
395    panic("stack-protector: Kernel stack is corrupted in: %p\n",
396        __builtin_return_address(0));
397}
398EXPORT_SYMBOL(__stack_chk_fail);
399
400#endif
401
402core_param(panic, panic_timeout, int, 0644);
403core_param(pause_on_oops, pause_on_oops, int, 0644);
404

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