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/kmsg_dump.h>
14#include <linux/kallsyms.h>
15#include <linux/notifier.h>
16#include <linux/module.h>
17#include <linux/random.h>
18#include <linux/reboot.h>
19#include <linux/delay.h>
20#include <linux/kexec.h>
21#include <linux/sched.h>
22#include <linux/sysrq.h>
23#include <linux/init.h>
24#include <linux/nmi.h>
25#include <linux/dmi.h>
26
27int panic_on_oops;
28static unsigned long tainted_mask;
29static int pause_on_oops;
30static int pause_on_oops_flag;
31static DEFINE_SPINLOCK(pause_on_oops_lock);
32
33int panic_timeout;
34
35ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
36
37EXPORT_SYMBOL(panic_notifier_list);
38
39/* Returns how long it waited in ms */
40long (*panic_blink)(long time);
41EXPORT_SYMBOL(panic_blink);
42
43static void panic_blink_one_second(void)
44{
45    static long i = 0, end;
46
47    if (panic_blink) {
48        end = i + MSEC_PER_SEC;
49
50        while (i < end) {
51            i += panic_blink(i);
52            mdelay(1);
53            i++;
54        }
55    } else {
56        /*
57         * When running under a hypervisor a small mdelay may get
58         * rounded up to the hypervisor timeslice. For example, with
59         * a 1ms in 10ms hypervisor timeslice we might inflate a
60         * mdelay(1) loop by 10x.
61         *
62         * If we have nothing to blink, spin on 1 second calls to
63         * mdelay to avoid this.
64         */
65        mdelay(MSEC_PER_SEC);
66    }
67}
68
69/**
70 * panic - halt the system
71 * @fmt: The text string to print
72 *
73 * Display a message, then perform cleanups.
74 *
75 * This function never returns.
76 */
77NORET_TYPE void panic(const char * fmt, ...)
78{
79    static char buf[1024];
80    va_list args;
81    long i;
82
83    /*
84     * It's possible to come here directly from a panic-assertion and
85     * not have preempt disabled. Some functions called from here want
86     * preempt to be disabled. No point enabling it later though...
87     */
88    preempt_disable();
89
90    bust_spinlocks(1);
91    va_start(args, fmt);
92    vsnprintf(buf, sizeof(buf), fmt, args);
93    va_end(args);
94    printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
95#ifdef CONFIG_DEBUG_BUGVERBOSE
96    dump_stack();
97#endif
98
99    /*
100     * If we have crashed and we have a crash kernel loaded let it handle
101     * everything else.
102     * Do we want to call this before we try to display a message?
103     */
104    crash_kexec(NULL);
105
106    kmsg_dump(KMSG_DUMP_PANIC);
107
108    /*
109     * Note smp_send_stop is the usual smp shutdown function, which
110     * unfortunately means it may not be hardened to work in a panic
111     * situation.
112     */
113    smp_send_stop();
114
115    atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
116
117    bust_spinlocks(0);
118
119    if (panic_timeout > 0) {
120        /*
121         * Delay timeout seconds before rebooting the machine.
122         * We can't use the "normal" timers since we just panicked.
123         */
124        printk(KERN_EMERG "Rebooting in %d seconds..", panic_timeout);
125
126        for (i = 0; i < panic_timeout; i++) {
127            touch_nmi_watchdog();
128            panic_blink_one_second();
129        }
130        /*
131         * This will not be a clean reboot, with everything
132         * shutting down. But if there is a chance of
133         * rebooting the system it will be rebooted.
134         */
135        emergency_restart();
136    }
137#ifdef __sparc__
138    {
139        extern int stop_a_enabled;
140        /* Make sure the user can actually press Stop-A (L1-A) */
141        stop_a_enabled = 1;
142        printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
143    }
144#endif
145#if defined(CONFIG_S390)
146    {
147        unsigned long caller;
148
149        caller = (unsigned long)__builtin_return_address(0);
150        disabled_wait(caller);
151    }
152#endif
153    local_irq_enable();
154    while (1) {
155        touch_softlockup_watchdog();
156        panic_blink_one_second();
157    }
158}
159
160EXPORT_SYMBOL(panic);
161
162
163struct tnt {
164    u8 bit;
165    char true;
166    char false;
167};
168
169static const struct tnt tnts[] = {
170    { TAINT_PROPRIETARY_MODULE, 'P', 'G' },
171    { TAINT_FORCED_MODULE, 'F', ' ' },
172    { TAINT_UNSAFE_SMP, 'S', ' ' },
173    { TAINT_FORCED_RMMOD, 'R', ' ' },
174    { TAINT_MACHINE_CHECK, 'M', ' ' },
175    { TAINT_BAD_PAGE, 'B', ' ' },
176    { TAINT_USER, 'U', ' ' },
177    { TAINT_DIE, 'D', ' ' },
178    { TAINT_OVERRIDDEN_ACPI_TABLE, 'A', ' ' },
179    { TAINT_WARN, 'W', ' ' },
180    { TAINT_CRAP, 'C', ' ' },
181};
182
183/**
184 * print_tainted - return a string to represent the kernel taint state.
185 *
186 * 'P' - Proprietary module has been loaded.
187 * 'F' - Module has been forcibly loaded.
188 * 'S' - SMP with CPUs not designed for SMP.
189 * 'R' - User forced a module unload.
190 * 'M' - System experienced a machine check exception.
191 * 'B' - System has hit bad_page.
192 * 'U' - Userspace-defined naughtiness.
193 * 'D' - Kernel has oopsed before
194 * 'A' - ACPI table overridden.
195 * 'W' - Taint on warning.
196 * 'C' - modules from drivers/staging are loaded.
197 *
198 * The string is overwritten by the next call to print_tainted().
199 */
200const char *print_tainted(void)
201{
202    static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ") + 1];
203
204    if (tainted_mask) {
205        char *s;
206        int i;
207
208        s = buf + sprintf(buf, "Tainted: ");
209        for (i = 0; i < ARRAY_SIZE(tnts); i++) {
210            const struct tnt *t = &tnts[i];
211            *s++ = test_bit(t->bit, &tainted_mask) ?
212                    t->true : t->false;
213        }
214        *s = 0;
215    } else
216        snprintf(buf, sizeof(buf), "Not tainted");
217
218    return buf;
219}
220
221int test_taint(unsigned flag)
222{
223    return test_bit(flag, &tainted_mask);
224}
225EXPORT_SYMBOL(test_taint);
226
227unsigned long get_taint(void)
228{
229    return tainted_mask;
230}
231
232void add_taint(unsigned flag)
233{
234    /*
235     * Can't trust the integrity of the kernel anymore.
236     * We don't call directly debug_locks_off() because the issue
237     * is not necessarily serious enough to set oops_in_progress to 1
238     * Also we want to keep up lockdep for staging development and
239     * post-warning case.
240     */
241    if (flag != TAINT_CRAP && flag != TAINT_WARN && __debug_locks_off())
242        printk(KERN_WARNING "Disabling lock debugging due to kernel taint\n");
243
244    set_bit(flag, &tainted_mask);
245}
246EXPORT_SYMBOL(add_taint);
247
248static void spin_msec(int msecs)
249{
250    int i;
251
252    for (i = 0; i < msecs; i++) {
253        touch_nmi_watchdog();
254        mdelay(1);
255    }
256}
257
258/*
259 * It just happens that oops_enter() and oops_exit() are identically
260 * implemented...
261 */
262static void do_oops_enter_exit(void)
263{
264    unsigned long flags;
265    static int spin_counter;
266
267    if (!pause_on_oops)
268        return;
269
270    spin_lock_irqsave(&pause_on_oops_lock, flags);
271    if (pause_on_oops_flag == 0) {
272        /* This CPU may now print the oops message */
273        pause_on_oops_flag = 1;
274    } else {
275        /* We need to stall this CPU */
276        if (!spin_counter) {
277            /* This CPU gets to do the counting */
278            spin_counter = pause_on_oops;
279            do {
280                spin_unlock(&pause_on_oops_lock);
281                spin_msec(MSEC_PER_SEC);
282                spin_lock(&pause_on_oops_lock);
283            } while (--spin_counter);
284            pause_on_oops_flag = 0;
285        } else {
286            /* This CPU waits for a different one */
287            while (spin_counter) {
288                spin_unlock(&pause_on_oops_lock);
289                spin_msec(1);
290                spin_lock(&pause_on_oops_lock);
291            }
292        }
293    }
294    spin_unlock_irqrestore(&pause_on_oops_lock, flags);
295}
296
297/*
298 * Return true if the calling CPU is allowed to print oops-related info.
299 * This is a bit racy..
300 */
301int oops_may_print(void)
302{
303    return pause_on_oops_flag == 0;
304}
305
306/*
307 * Called when the architecture enters its oops handler, before it prints
308 * anything. If this is the first CPU to oops, and it's oopsing the first
309 * time then let it proceed.
310 *
311 * This is all enabled by the pause_on_oops kernel boot option. We do all
312 * this to ensure that oopses don't scroll off the screen. It has the
313 * side-effect of preventing later-oopsing CPUs from mucking up the display,
314 * too.
315 *
316 * It turns out that the CPU which is allowed to print ends up pausing for
317 * the right duration, whereas all the other CPUs pause for twice as long:
318 * once in oops_enter(), once in oops_exit().
319 */
320void oops_enter(void)
321{
322    tracing_off();
323    /* can't trust the integrity of the kernel anymore: */
324    debug_locks_off();
325    do_oops_enter_exit();
326}
327
328/*
329 * 64-bit random ID for oopses:
330 */
331static u64 oops_id;
332
333static int init_oops_id(void)
334{
335    if (!oops_id)
336        get_random_bytes(&oops_id, sizeof(oops_id));
337    else
338        oops_id++;
339
340    return 0;
341}
342late_initcall(init_oops_id);
343
344static void print_oops_end_marker(void)
345{
346    init_oops_id();
347    printk(KERN_WARNING "---[ end trace %016llx ]---\n",
348        (unsigned long long)oops_id);
349}
350
351/*
352 * Called when the architecture exits its oops handler, after printing
353 * everything.
354 */
355void oops_exit(void)
356{
357    do_oops_enter_exit();
358    print_oops_end_marker();
359    kmsg_dump(KMSG_DUMP_OOPS);
360}
361
362#ifdef WANT_WARN_ON_SLOWPATH
363struct slowpath_args {
364    const char *fmt;
365    va_list args;
366};
367
368static void warn_slowpath_common(const char *file, int line, void *caller, struct slowpath_args *args)
369{
370    const char *board;
371
372    printk(KERN_WARNING "------------[ cut here ]------------\n");
373    printk(KERN_WARNING "WARNING: at %s:%d %pS()\n", file, line, caller);
374    board = dmi_get_system_info(DMI_PRODUCT_NAME);
375    if (board)
376        printk(KERN_WARNING "Hardware name: %s\n", board);
377
378    if (args)
379        vprintk(args->fmt, args->args);
380
381    print_modules();
382    dump_stack();
383    print_oops_end_marker();
384    add_taint(TAINT_WARN);
385}
386
387void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
388{
389    struct slowpath_args args;
390
391    args.fmt = fmt;
392    va_start(args.args, fmt);
393    warn_slowpath_common(file, line, __builtin_return_address(0), &args);
394    va_end(args.args);
395}
396EXPORT_SYMBOL(warn_slowpath_fmt);
397
398void warn_slowpath_null(const char *file, int line)
399{
400    warn_slowpath_common(file, line, __builtin_return_address(0), NULL);
401}
402EXPORT_SYMBOL(warn_slowpath_null);
403#endif
404
405#ifdef CONFIG_CC_STACKPROTECTOR
406
407/*
408 * Called when gcc's -fstack-protector feature is used, and
409 * gcc detects corruption of the on-stack canary value
410 */
411void __stack_chk_fail(void)
412{
413    panic("stack-protector: Kernel stack is corrupted in: %p\n",
414        __builtin_return_address(0));
415}
416EXPORT_SYMBOL(__stack_chk_fail);
417
418#endif
419
420core_param(panic, panic_timeout, int, 0644);
421core_param(pause_on_oops, pause_on_oops, int, 0644);
422

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