linux/kernel/panic.c at master · fabgithub/linux · GitHub

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* linux/kernel/panic.c

* This function is used through-out the kernel (including mm and fs)

* to indicate a major problem.

#include <linux/debug_locks.h>

#include <linux/interrupt.h>

#include <linux/kmsg_dump.h>

#include <linux/kallsyms.h>

#include <linux/notifier.h>

#include <linux/module.h>

#include <linux/random.h>

#include <linux/ftrace.h>

#include <linux/reboot.h>

#include <linux/delay.h>

#include <linux/kexec.h>

#include <linux/sched.h>

#include <linux/sysrq.h>

#include <linux/init.h>

#include <linux/nmi.h>

#define PANIC_TIMER_STEP 100

#define PANIC_BLINK_SPD 18

int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE;

static unsigned long tainted_mask;

static int pause_on_oops;

static int pause_on_oops_flag;

static DEFINE_SPINLOCK(pause_on_oops_lock);

int panic_timeout;

EXPORT_SYMBOL_GPL(panic_timeout);

ATOMIC_NOTIFIER_HEAD(panic_notifier_list);

EXPORT_SYMBOL(panic_notifier_list);

static long no_blink(int state)

{

return 0;

}

/* Returns how long it waited in ms */

long (*panic_blink)(int state);

EXPORT_SYMBOL(panic_blink);

* Stop ourself in panic -- architecture code may override this

void __weak panic_smp_self_stop(void)

{

while (1)

cpu_relax();

}

/**

* panic - halt the system

* @fmt: The text string to print

* Display a message, then perform cleanups.

* This function never returns.

void panic(const char *fmt, ...)

{

static DEFINE_SPINLOCK(panic_lock);

static char buf[1024];

va_list args;

long i, i_next = 0;

int state = 0;

* Disable local interrupts. This will prevent panic_smp_self_stop

* from deadlocking the first cpu that invokes the panic, since

* there is nothing to prevent an interrupt handler (that runs

* after the panic_lock is acquired) from invoking panic again.

local_irq_disable();

* It's possible to come here directly from a panic-assertion and

* not have preempt disabled. Some functions called from here want

* preempt to be disabled. No point enabling it later though...

* Only one CPU is allowed to execute the panic code from here. For

* multiple parallel invocations of panic, all other CPUs either

* stop themself or will wait until they are stopped by the 1st CPU

* with smp_send_stop().

if (!spin_trylock(&panic_lock))

panic_smp_self_stop();

console_verbose();

bust_spinlocks(1);

va_start(args, fmt);

vsnprintf(buf, sizeof(buf), fmt, args);

va_end(args);

printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);

#ifdef CONFIG_DEBUG_BUGVERBOSE

* Avoid nested stack-dumping if a panic occurs during oops processing

if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)

dump_stack();

#endif

* If we have crashed and we have a crash kernel loaded let it handle

* everything else.

* Do we want to call this before we try to display a message?

crash_kexec(NULL);

* Note smp_send_stop is the usual smp shutdown function, which

* unfortunately means it may not be hardened to work in a panic

* situation.

smp_send_stop();

kmsg_dump(KMSG_DUMP_PANIC);

atomic_notifier_call_chain(&panic_notifier_list, 0, buf);

bust_spinlocks(0);

if (!panic_blink)

panic_blink = no_blink;

if (panic_timeout > 0) {

* Delay timeout seconds before rebooting the machine.

* We can't use the "normal" timers since we just panicked.

printk(KERN_EMERG "Rebooting in %d seconds..", panic_timeout);

for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {

touch_nmi_watchdog();

if (i >= i_next) {

i += panic_blink(state ^= 1);

i_next = i + 3600 / PANIC_BLINK_SPD;

}

mdelay(PANIC_TIMER_STEP);

}

if (panic_timeout != 0) {

* This will not be a clean reboot, with everything

* shutting down. But if there is a chance of

* rebooting the system it will be rebooted.

emergency_restart();

}

#ifdef __sparc__

{

extern int stop_a_enabled;

/* Make sure the user can actually press Stop-A (L1-A) */

stop_a_enabled = 1;

printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");

}

#endif

#if defined(CONFIG_S390)

{

unsigned long caller;

caller = (unsigned long)__builtin_return_address(0);

disabled_wait(caller);

}

#endif

local_irq_enable();

for (i = 0; ; i += PANIC_TIMER_STEP) {

touch_softlockup_watchdog();

if (i >= i_next) {

i += panic_blink(state ^= 1);

i_next = i + 3600 / PANIC_BLINK_SPD;

}

mdelay(PANIC_TIMER_STEP);

}

EXPORT_SYMBOL(panic);

struct tnt {

u8 bit;

char true;

char false;

};

static const struct tnt tnts[] = {

{ TAINT_PROPRIETARY_MODULE, 'P', 'G' },

{ TAINT_FORCED_MODULE, 'F', ' ' },

{ TAINT_UNSAFE_SMP, 'S', ' ' },

{ TAINT_FORCED_RMMOD, 'R', ' ' },

{ TAINT_MACHINE_CHECK, 'M', ' ' },

{ TAINT_BAD_PAGE, 'B', ' ' },

{ TAINT_USER, 'U', ' ' },

{ TAINT_DIE, 'D', ' ' },

{ TAINT_OVERRIDDEN_ACPI_TABLE, 'A', ' ' },

{ TAINT_WARN, 'W', ' ' },

{ TAINT_CRAP, 'C', ' ' },

{ TAINT_FIRMWARE_WORKAROUND, 'I', ' ' },

{ TAINT_OOT_MODULE, 'O', ' ' },

};

/**

* print_tainted - return a string to represent the kernel taint state.

* 'P' - Proprietary module has been loaded.

* 'F' - Module has been forcibly loaded.

* 'S' - SMP with CPUs not designed for SMP.

* 'R' - User forced a module unload.

* 'M' - System experienced a machine check exception.

* 'B' - System has hit bad_page.

* 'U' - Userspace-defined naughtiness.

* 'D' - Kernel has oopsed before

* 'A' - ACPI table overridden.

* 'W' - Taint on warning.

* 'C' - modules from drivers/staging are loaded.

* 'I' - Working around severe firmware bug.

* 'O' - Out-of-tree module has been loaded.

* The string is overwritten by the next call to print_tainted().

const char *print_tainted(void)

{

static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ") + 1];

if (tainted_mask) {

char *s;

int i;

s = buf + sprintf(buf, "Tainted: ");

for (i = 0; i < ARRAY_SIZE(tnts); i++) {

const struct tnt *t = &tnts[i];

*s++ = test_bit(t->bit, &tainted_mask) ?

t->true : t->false;

}

*s = 0;

} else

snprintf(buf, sizeof(buf), "Not tainted");

return buf;

}

int test_taint(unsigned flag)

{

return test_bit(flag, &tainted_mask);

}

EXPORT_SYMBOL(test_taint);

unsigned long get_taint(void)

{

return tainted_mask;

}

/**

* add_taint: add a taint flag if not already set.

* @flag: one of the TAINT_* constants.

* @lockdep_ok: whether lock debugging is still OK.

* If something bad has gone wrong, you'll want @lockdebug_ok = false, but for

* some notewortht-but-not-corrupting cases, it can be set to true.

void add_taint(unsigned flag, enum lockdep_ok lockdep_ok)

{

if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off())

printk(KERN_WARNING

"Disabling lock debugging due to kernel taint\n");

set_bit(flag, &tainted_mask);

}

EXPORT_SYMBOL(add_taint);

static void spin_msec(int msecs)

{

int i;

for (i = 0; i < msecs; i++) {

touch_nmi_watchdog();

mdelay(1);

}

* It just happens that oops_enter() and oops_exit() are identically

* implemented...

static void do_oops_enter_exit(void)

{

unsigned long flags;

static int spin_counter;

if (!pause_on_oops)

return;

spin_lock_irqsave(&pause_on_oops_lock, flags);

if (pause_on_oops_flag == 0) {

/* This CPU may now print the oops message */

pause_on_oops_flag = 1;

} else {

/* We need to stall this CPU */

if (!spin_counter) {

/* This CPU gets to do the counting */

spin_counter = pause_on_oops;

do {

spin_unlock(&pause_on_oops_lock);

spin_msec(MSEC_PER_SEC);

spin_lock(&pause_on_oops_lock);

} while (--spin_counter);

pause_on_oops_flag = 0;

} else {

/* This CPU waits for a different one */

while (spin_counter) {

spin_unlock(&pause_on_oops_lock);

spin_msec(1);

spin_lock(&pause_on_oops_lock);

}

spin_unlock_irqrestore(&pause_on_oops_lock, flags);

}

* Return true if the calling CPU is allowed to print oops-related info.

* This is a bit racy..

int oops_may_print(void)

{

return pause_on_oops_flag == 0;

}

* Called when the architecture enters its oops handler, before it prints

* anything. If this is the first CPU to oops, and it's oopsing the first

* time then let it proceed.

* This is all enabled by the pause_on_oops kernel boot option. We do all

* this to ensure that oopses don't scroll off the screen. It has the

* side-effect of preventing later-oopsing CPUs from mucking up the display,

* too.

* It turns out that the CPU which is allowed to print ends up pausing for

* the right duration, whereas all the other CPUs pause for twice as long:

* once in oops_enter(), once in oops_exit().

void oops_enter(void)

{

tracing_off();

/* can't trust the integrity of the kernel anymore: */

debug_locks_off();

do_oops_enter_exit();

}

* 64-bit random ID for oopses:

static u64 oops_id;

static int init_oops_id(void)

{

if (!oops_id)

get_random_bytes(&oops_id, sizeof(oops_id));

else

oops_id++;

return 0;

}

late_initcall(init_oops_id);

void print_oops_end_marker(void)

{

init_oops_id();

printk(KERN_WARNING "---[ end trace %016llx ]---\n",

(unsigned long long)oops_id);

}

* Called when the architecture exits its oops handler, after printing

* everything.

void oops_exit(void)

{

do_oops_enter_exit();

print_oops_end_marker();

kmsg_dump(KMSG_DUMP_OOPS);

}

#ifdef WANT_WARN_ON_SLOWPATH

struct slowpath_args {

const char *fmt;

va_list args;

};

static void warn_slowpath_common(const char *file, int line, void *caller,

unsigned taint, struct slowpath_args *args)

{

disable_trace_on_warning();

pr_warn("------------[ cut here ]------------\n");

pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS()\n",

raw_smp_processor_id(), current->pid, file, line, caller);

if (args)

vprintk(args->fmt, args->args);

print_modules();

dump_stack();

print_oops_end_marker();

/* Just a warning, don't kill lockdep. */

add_taint(taint, LOCKDEP_STILL_OK);

}

void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)

{

struct slowpath_args args;

args.fmt = fmt;

va_start(args.args, fmt);

warn_slowpath_common(file, line, __builtin_return_address(0),

TAINT_WARN, &args);

va_end(args.args);

}

EXPORT_SYMBOL(warn_slowpath_fmt);

void warn_slowpath_fmt_taint(const char *file, int line,

unsigned taint, const char *fmt, ...)

{

struct slowpath_args args;

args.fmt = fmt;

va_start(args.args, fmt);

warn_slowpath_common(file, line, __builtin_return_address(0),

taint, &args);

va_end(args.args);

}

EXPORT_SYMBOL(warn_slowpath_fmt_taint);

void warn_slowpath_null(const char *file, int line)

{

warn_slowpath_common(file, line, __builtin_return_address(0),

TAINT_WARN, NULL);

}

EXPORT_SYMBOL(warn_slowpath_null);

#endif

#ifdef CONFIG_CC_STACKPROTECTOR

* Called when gcc's -fstack-protector feature is used, and

* gcc detects corruption of the on-stack canary value

void __stack_chk_fail(void)

{

panic("stack-protector: Kernel stack is corrupted in: %p\n",

__builtin_return_address(0));

}

EXPORT_SYMBOL(__stack_chk_fail);

#endif

core_param(panic, panic_timeout, int, 0644);

core_param(pause_on_oops, pause_on_oops, int, 0644);

static int __init oops_setup(char *s)

{

if (!s)

return -EINVAL;

if (!strcmp(s, "panic"))

panic_on_oops = 1;

return 0;

}

early_param("oops", oops_setup);

linux/kernel/panic.c at master · fabgithub/linux · GitHub

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