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

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