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

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