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
27#define PANIC_TIMER_STEP 100
28#define PANIC_BLINK_SPD 18
29
30int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE;
31static unsigned long tainted_mask;
32static int pause_on_oops;
33static int pause_on_oops_flag;
34static DEFINE_SPINLOCK(pause_on_oops_lock);
35
36int panic_timeout;
37EXPORT_SYMBOL_GPL(panic_timeout);
38
39ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
40
41EXPORT_SYMBOL(panic_notifier_list);
42
43static long no_blink(int state)
44{
45    return 0;
46}
47
48/* Returns how long it waited in ms */
49long (*panic_blink)(int state);
50EXPORT_SYMBOL(panic_blink);
51
52/*
53 * Stop ourself in panic -- architecture code may override this
54 */
55void __weak panic_smp_self_stop(void)
56{
57    while (1)
58        cpu_relax();
59}
60
61/**
62 * panic - halt the system
63 * @fmt: The text string to print
64 *
65 * Display a message, then perform cleanups.
66 *
67 * This function never returns.
68 */
69void panic(const char *fmt, ...)
70{
71    static DEFINE_SPINLOCK(panic_lock);
72    static char buf[1024];
73    va_list args;
74    long i, i_next = 0;
75    int state = 0;
76
77    /*
78     * It's possible to come here directly from a panic-assertion and
79     * not have preempt disabled. Some functions called from here want
80     * preempt to be disabled. No point enabling it later though...
81     *
82     * Only one CPU is allowed to execute the panic code from here. For
83     * multiple parallel invocations of panic, all other CPUs either
84     * stop themself or will wait until they are stopped by the 1st CPU
85     * with smp_send_stop().
86     */
87    if (!spin_trylock(&panic_lock))
88        panic_smp_self_stop();
89
90    console_verbose();
91    bust_spinlocks(1);
92    va_start(args, fmt);
93    vsnprintf(buf, sizeof(buf), fmt, args);
94    va_end(args);
95    printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
96#ifdef CONFIG_DEBUG_BUGVERBOSE
97    /*
98     * Avoid nested stack-dumping if a panic occurs during oops processing
99     */
100    if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)
101        dump_stack();
102#endif
103
104    /*
105     * If we have crashed and we have a crash kernel loaded let it handle
106     * everything else.
107     * Do we want to call this before we try to display a message?
108     */
109    crash_kexec(NULL);
110
111    /*
112     * Note smp_send_stop is the usual smp shutdown function, which
113     * unfortunately means it may not be hardened to work in a panic
114     * situation.
115     */
116    smp_send_stop();
117
118    kmsg_dump(KMSG_DUMP_PANIC);
119
120    atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
121
122    bust_spinlocks(0);
123
124    if (!panic_blink)
125        panic_blink = no_blink;
126
127    if (panic_timeout > 0) {
128        /*
129         * Delay timeout seconds before rebooting the machine.
130         * We can't use the "normal" timers since we just panicked.
131         */
132        printk(KERN_EMERG "Rebooting in %d seconds..", panic_timeout);
133
134        for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
135            touch_nmi_watchdog();
136            if (i >= i_next) {
137                i += panic_blink(state ^= 1);
138                i_next = i + 3600 / PANIC_BLINK_SPD;
139            }
140            mdelay(PANIC_TIMER_STEP);
141        }
142    }
143    if (panic_timeout != 0) {
144        /*
145         * This will not be a clean reboot, with everything
146         * shutting down. But if there is a chance of
147         * rebooting the system it will be rebooted.
148         */
149        emergency_restart();
150    }
151#ifdef __sparc__
152    {
153        extern int stop_a_enabled;
154        /* Make sure the user can actually press Stop-A (L1-A) */
155        stop_a_enabled = 1;
156        printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
157    }
158#endif
159#if defined(CONFIG_S390)
160    {
161        unsigned long caller;
162
163        caller = (unsigned long)__builtin_return_address(0);
164        disabled_wait(caller);
165    }
166#endif
167    local_irq_enable();
168    for (i = 0; ; i += PANIC_TIMER_STEP) {
169        touch_softlockup_watchdog();
170        if (i >= i_next) {
171            i += panic_blink(state ^= 1);
172            i_next = i + 3600 / PANIC_BLINK_SPD;
173        }
174        mdelay(PANIC_TIMER_STEP);
175    }
176}
177
178EXPORT_SYMBOL(panic);
179
180
181struct tnt {
182    u8 bit;
183    char true;
184    char false;
185};
186
187static const struct tnt tnts[] = {
188    { TAINT_PROPRIETARY_MODULE, 'P', 'G' },
189    { TAINT_FORCED_MODULE, 'F', ' ' },
190    { TAINT_UNSAFE_SMP, 'S', ' ' },
191    { TAINT_FORCED_RMMOD, 'R', ' ' },
192    { TAINT_MACHINE_CHECK, 'M', ' ' },
193    { TAINT_BAD_PAGE, 'B', ' ' },
194    { TAINT_USER, 'U', ' ' },
195    { TAINT_DIE, 'D', ' ' },
196    { TAINT_OVERRIDDEN_ACPI_TABLE, 'A', ' ' },
197    { TAINT_WARN, 'W', ' ' },
198    { TAINT_CRAP, 'C', ' ' },
199    { TAINT_FIRMWARE_WORKAROUND, 'I', ' ' },
200    { TAINT_OOT_MODULE, 'O', ' ' },
201};
202
203/**
204 * print_tainted - return a string to represent the kernel taint state.
205 *
206 * 'P' - Proprietary module has been loaded.
207 * 'F' - Module has been forcibly loaded.
208 * 'S' - SMP with CPUs not designed for SMP.
209 * 'R' - User forced a module unload.
210 * 'M' - System experienced a machine check exception.
211 * 'B' - System has hit bad_page.
212 * 'U' - Userspace-defined naughtiness.
213 * 'D' - Kernel has oopsed before
214 * 'A' - ACPI table overridden.
215 * 'W' - Taint on warning.
216 * 'C' - modules from drivers/staging are loaded.
217 * 'I' - Working around severe firmware bug.
218 * 'O' - Out-of-tree module has been loaded.
219 *
220 * The string is overwritten by the next call to print_tainted().
221 */
222const char *print_tainted(void)
223{
224    static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ") + 1];
225
226    if (tainted_mask) {
227        char *s;
228        int i;
229
230        s = buf + sprintf(buf, "Tainted: ");
231        for (i = 0; i < ARRAY_SIZE(tnts); i++) {
232            const struct tnt *t = &tnts[i];
233            *s++ = test_bit(t->bit, &tainted_mask) ?
234                    t->true : t->false;
235        }
236        *s = 0;
237    } else
238        snprintf(buf, sizeof(buf), "Not tainted");
239
240    return buf;
241}
242
243int test_taint(unsigned flag)
244{
245    return test_bit(flag, &tainted_mask);
246}
247EXPORT_SYMBOL(test_taint);
248
249unsigned long get_taint(void)
250{
251    return tainted_mask;
252}
253
254void add_taint(unsigned flag)
255{
256    /*
257     * Can't trust the integrity of the kernel anymore.
258     * We don't call directly debug_locks_off() because the issue
259     * is not necessarily serious enough to set oops_in_progress to 1
260     * Also we want to keep up lockdep for staging/out-of-tree
261     * development and post-warning case.
262     */
263    switch (flag) {
264    case TAINT_CRAP:
265    case TAINT_OOT_MODULE:
266    case TAINT_WARN:
267    case TAINT_FIRMWARE_WORKAROUND:
268        break;
269
270    default:
271        if (__debug_locks_off())
272            printk(KERN_WARNING "Disabling lock debugging due to kernel taint\n");
273    }
274
275    set_bit(flag, &tainted_mask);
276}
277EXPORT_SYMBOL(add_taint);
278
279static void spin_msec(int msecs)
280{
281    int i;
282
283    for (i = 0; i < msecs; i++) {
284        touch_nmi_watchdog();
285        mdelay(1);
286    }
287}
288
289/*
290 * It just happens that oops_enter() and oops_exit() are identically
291 * implemented...
292 */
293static void do_oops_enter_exit(void)
294{
295    unsigned long flags;
296    static int spin_counter;
297
298    if (!pause_on_oops)
299        return;
300
301    spin_lock_irqsave(&pause_on_oops_lock, flags);
302    if (pause_on_oops_flag == 0) {
303        /* This CPU may now print the oops message */
304        pause_on_oops_flag = 1;
305    } else {
306        /* We need to stall this CPU */
307        if (!spin_counter) {
308            /* This CPU gets to do the counting */
309            spin_counter = pause_on_oops;
310            do {
311                spin_unlock(&pause_on_oops_lock);
312                spin_msec(MSEC_PER_SEC);
313                spin_lock(&pause_on_oops_lock);
314            } while (--spin_counter);
315            pause_on_oops_flag = 0;
316        } else {
317            /* This CPU waits for a different one */
318            while (spin_counter) {
319                spin_unlock(&pause_on_oops_lock);
320                spin_msec(1);
321                spin_lock(&pause_on_oops_lock);
322            }
323        }
324    }
325    spin_unlock_irqrestore(&pause_on_oops_lock, flags);
326}
327
328/*
329 * Return true if the calling CPU is allowed to print oops-related info.
330 * This is a bit racy..
331 */
332int oops_may_print(void)
333{
334    return pause_on_oops_flag == 0;
335}
336
337/*
338 * Called when the architecture enters its oops handler, before it prints
339 * anything. If this is the first CPU to oops, and it's oopsing the first
340 * time then let it proceed.
341 *
342 * This is all enabled by the pause_on_oops kernel boot option. We do all
343 * this to ensure that oopses don't scroll off the screen. It has the
344 * side-effect of preventing later-oopsing CPUs from mucking up the display,
345 * too.
346 *
347 * It turns out that the CPU which is allowed to print ends up pausing for
348 * the right duration, whereas all the other CPUs pause for twice as long:
349 * once in oops_enter(), once in oops_exit().
350 */
351void oops_enter(void)
352{
353    tracing_off();
354    /* can't trust the integrity of the kernel anymore: */
355    debug_locks_off();
356    do_oops_enter_exit();
357}
358
359/*
360 * 64-bit random ID for oopses:
361 */
362static u64 oops_id;
363
364static int init_oops_id(void)
365{
366    if (!oops_id)
367        get_random_bytes(&oops_id, sizeof(oops_id));
368    else
369        oops_id++;
370
371    return 0;
372}
373late_initcall(init_oops_id);
374
375void print_oops_end_marker(void)
376{
377    init_oops_id();
378    printk(KERN_WARNING "---[ end trace %016llx ]---\n",
379        (unsigned long long)oops_id);
380}
381
382/*
383 * Called when the architecture exits its oops handler, after printing
384 * everything.
385 */
386void oops_exit(void)
387{
388    do_oops_enter_exit();
389    print_oops_end_marker();
390    kmsg_dump(KMSG_DUMP_OOPS);
391}
392
393#ifdef WANT_WARN_ON_SLOWPATH
394struct slowpath_args {
395    const char *fmt;
396    va_list args;
397};
398
399static void warn_slowpath_common(const char *file, int line, void *caller,
400                 unsigned taint, struct slowpath_args *args)
401{
402    const char *board;
403
404    printk(KERN_WARNING "------------[ cut here ]------------\n");
405    printk(KERN_WARNING "WARNING: at %s:%d %pS()\n", file, line, caller);
406    board = dmi_get_system_info(DMI_PRODUCT_NAME);
407    if (board)
408        printk(KERN_WARNING "Hardware name: %s\n", board);
409
410    if (args)
411        vprintk(args->fmt, args->args);
412
413    print_modules();
414    dump_stack();
415    print_oops_end_marker();
416    add_taint(taint);
417}
418
419void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
420{
421    struct slowpath_args args;
422
423    args.fmt = fmt;
424    va_start(args.args, fmt);
425    warn_slowpath_common(file, line, __builtin_return_address(0),
426                 TAINT_WARN, &args);
427    va_end(args.args);
428}
429EXPORT_SYMBOL(warn_slowpath_fmt);
430
431void warn_slowpath_fmt_taint(const char *file, int line,
432                 unsigned taint, const char *fmt, ...)
433{
434    struct slowpath_args args;
435
436    args.fmt = fmt;
437    va_start(args.args, fmt);
438    warn_slowpath_common(file, line, __builtin_return_address(0),
439                 taint, &args);
440    va_end(args.args);
441}
442EXPORT_SYMBOL(warn_slowpath_fmt_taint);
443
444void warn_slowpath_null(const char *file, int line)
445{
446    warn_slowpath_common(file, line, __builtin_return_address(0),
447                 TAINT_WARN, NULL);
448}
449EXPORT_SYMBOL(warn_slowpath_null);
450#endif
451
452#ifdef CONFIG_CC_STACKPROTECTOR
453
454/*
455 * Called when gcc's -fstack-protector feature is used, and
456 * gcc detects corruption of the on-stack canary value
457 */
458void __stack_chk_fail(void)
459{
460    panic("stack-protector: Kernel stack is corrupted in: %p\n",
461        __builtin_return_address(0));
462}
463EXPORT_SYMBOL(__stack_chk_fail);
464
465#endif
466
467core_param(panic, panic_timeout, int, 0644);
468core_param(pause_on_oops, pause_on_oops, int, 0644);
469
470static int __init oops_setup(char *s)
471{
472    if (!s)
473        return -EINVAL;
474    if (!strcmp(s, "panic"))
475        panic_on_oops = 1;
476    return 0;
477}
478early_param("oops", oops_setup);
479

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