linux/kernel/panic.c at master · flexbed/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/sched/debug.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>

#include <linux/console.h>

#include <linux/bug.h>

#include <linux/ratelimit.h>

#include <linux/debugfs.h>

#include <asm/sections.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 =

IS_ENABLED(CONFIG_GCC_PLUGIN_RANDSTRUCT) ? (1 << TAINT_RANDSTRUCT) : 0;

static int pause_on_oops;

static int pause_on_oops_flag;

static DEFINE_SPINLOCK(pause_on_oops_lock);

bool crash_kexec_post_notifiers;

int panic_on_warn __read_mostly;

int panic_timeout = CONFIG_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();

}

* Stop ourselves in NMI context if another CPU has already panicked. Arch code

* may override this to prepare for crash dumping, e.g. save regs info.

void __weak nmi_panic_self_stop(struct pt_regs *regs)

{

panic_smp_self_stop();

}

* Stop other CPUs in panic. Architecture dependent code may override this

* with more suitable version. For example, if the architecture supports

* crash dump, it should save registers of each stopped CPU and disable

* per-CPU features such as virtualization extensions.

void __weak crash_smp_send_stop(void)

{

static int cpus_stopped;

* This function can be called twice in panic path, but obviously

* we execute this only once.

if (cpus_stopped)

return;

* 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();

cpus_stopped = 1;

}

atomic_t panic_cpu = ATOMIC_INIT(PANIC_CPU_INVALID);

* A variant of panic() called from NMI context. We return if we've already

* panicked on this CPU. If another CPU already panicked, loop in

* nmi_panic_self_stop() which can provide architecture dependent code such

* as saving register state for crash dump.

void nmi_panic(struct pt_regs *regs, const char *msg)

{

int old_cpu, cpu;

cpu = raw_smp_processor_id();

old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, cpu);

if (old_cpu == PANIC_CPU_INVALID)

panic("%s", msg);

else if (old_cpu != cpu)

nmi_panic_self_stop(regs);

}

EXPORT_SYMBOL(nmi_panic);

/**

* 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 char buf[1024];

va_list args;

long i, i_next = 0;

int state = 0;

int old_cpu, this_cpu;

bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers;

* 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 setting panic_cpu) 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().

* `old_cpu == PANIC_CPU_INVALID' means this is the 1st CPU which

* comes here, so go ahead.

* `old_cpu == this_cpu' means we came from nmi_panic() which sets

* panic_cpu to this CPU. In this case, this is also the 1st CPU.

this_cpu = raw_smp_processor_id();

old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, this_cpu);

if (old_cpu != PANIC_CPU_INVALID && old_cpu != this_cpu)

panic_smp_self_stop();

console_verbose();

bust_spinlocks(1);

va_start(args, fmt);

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

va_end(args);

pr_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.

* If we want to run this after calling panic_notifiers, pass

* the "crash_kexec_post_notifiers" option to the kernel.

* Bypass the panic_cpu check and call __crash_kexec directly.

if (!_crash_kexec_post_notifiers) {

printk_safe_flush_on_panic();

__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();

} else {

* If we want to do crash dump after notifier calls and

* kmsg_dump, we will need architecture dependent extra

* works in addition to stopping other CPUs.

crash_smp_send_stop();

}

* Run any panic handlers, including those that might need to

* add information to the kmsg dump output.

atomic_notifier_call_chain(&panic_notifier_list, 0, buf);

/* Call flush even twice. It tries harder with a single online CPU */

printk_safe_flush_on_panic();

kmsg_dump(KMSG_DUMP_PANIC);

* If you doubt kdump always works fine in any situation,

* "crash_kexec_post_notifiers" offers you a chance to run

* panic_notifiers and dumping kmsg before kdump.

* Note: since some panic_notifiers can make crashed kernel

* more unstable, it can increase risks of the kdump failure too.

* Bypass the panic_cpu check and call __crash_kexec directly.

if (_crash_kexec_post_notifiers)

__crash_kexec(NULL);

bust_spinlocks(0);

* We may have ended up stopping the CPU holding the lock (in

* smp_send_stop()) while still having some valuable data in the console

* buffer. Try to acquire the lock then release it regardless of the

* result. The release will also print the buffers out. Locks debug

* should be disabled to avoid reporting bad unlock balance when

* panic() is not being callled from OOPS.

debug_locks_off();

console_flush_on_panic();

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.

pr_emerg("Rebooting in %d seconds..\n", 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;

pr_emerg("Press Stop-A (L1-A) from sun keyboard or send break\n"

"twice on console 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

pr_emerg("---[ end Kernel panic - not syncing: %s ]---\n", buf);

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);

* TAINT_FORCED_RMMOD could be a per-module flag but the module

* is being removed anyway.

const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = {

[ TAINT_PROPRIETARY_MODULE ] = { 'P', 'G', true },

[ TAINT_FORCED_MODULE ] = { 'F', ' ', true },

[ TAINT_CPU_OUT_OF_SPEC ] = { 'S', ' ', false },

[ TAINT_FORCED_RMMOD ] = { 'R', ' ', false },

[ TAINT_MACHINE_CHECK ] = { 'M', ' ', false },

[ TAINT_BAD_PAGE ] = { 'B', ' ', false },

[ TAINT_USER ] = { 'U', ' ', false },

[ TAINT_DIE ] = { 'D', ' ', false },

[ TAINT_OVERRIDDEN_ACPI_TABLE ] = { 'A', ' ', false },

[ TAINT_WARN ] = { 'W', ' ', false },

[ TAINT_CRAP ] = { 'C', ' ', true },

[ TAINT_FIRMWARE_WORKAROUND ] = { 'I', ' ', false },

[ TAINT_OOT_MODULE ] = { 'O', ' ', true },

[ TAINT_UNSIGNED_MODULE ] = { 'E', ' ', true },

[ TAINT_SOFTLOCKUP ] = { 'L', ' ', false },

[ TAINT_LIVEPATCH ] = { 'K', ' ', true },

[ TAINT_AUX ] = { 'X', ' ', true },

[ TAINT_RANDSTRUCT ] = { 'T', ' ', true },

};

/**

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

* For individual taint flag meanings, see Documentation/sysctl/kernel.txt

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

* but is always NULL terminated.

const char *print_tainted(void)

{

static char buf[TAINT_FLAGS_COUNT + sizeof("Tainted: ")];

BUILD_BUG_ON(ARRAY_SIZE(taint_flags) != TAINT_FLAGS_COUNT);

if (tainted_mask) {

char *s;

int i;

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

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

const struct taint_flag *t = &taint_flags[i];

*s++ = test_bit(i, &tainted_mask) ?

t->c_true : t->c_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())

pr_warn("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();

pr_warn("---[ 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);

}

struct warn_args {

const char *fmt;

va_list args;

};

void __warn(const char *file, int line, void *caller, unsigned taint,

struct pt_regs *regs, struct warn_args *args)

{

disable_trace_on_warning();

if (args)

pr_warn(CUT_HERE);

if (file)

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

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

caller);

else

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

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

if (args)

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

if (panic_on_warn) {

* This thread may hit another WARN() in the panic path.

* Resetting this prevents additional WARN() from panicking the

* system on this thread. Other threads are blocked by the

* panic_mutex in panic().

panic_on_warn = 0;

panic("panic_on_warn set ...\n");

}

print_modules();

if (regs)

show_regs(regs);

else

dump_stack();

print_irqtrace_events(current);

print_oops_end_marker();

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

add_taint(taint, LOCKDEP_STILL_OK);

}

#ifdef WANT_WARN_ON_SLOWPATH

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

{

struct warn_args args;

args.fmt = fmt;

va_start(args.args, fmt);

__warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL,

&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 warn_args args;

args.fmt = fmt;

va_start(args.args, fmt);

__warn(file, line, __builtin_return_address(0), taint, NULL, &args);

va_end(args.args);

}

EXPORT_SYMBOL(warn_slowpath_fmt_taint);

void warn_slowpath_null(const char *file, int line)

{

pr_warn(CUT_HERE);

__warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL, NULL);

}

EXPORT_SYMBOL(warn_slowpath_null);

#else

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

{

va_list args;

pr_warn(CUT_HERE);

va_start(args, fmt);

vprintk(fmt, args);

va_end(args);

}

EXPORT_SYMBOL(__warn_printk);

#endif

#ifdef CONFIG_BUG

/* Support resetting WARN*_ONCE state */

static int clear_warn_once_set(void *data, u64 val)

{

generic_bug_clear_once();

memset(__start_once, 0, __end_once - __start_once);

return 0;

}

DEFINE_SIMPLE_ATTRIBUTE(clear_warn_once_fops,

NULL,

clear_warn_once_set,

"%lld\n");

static __init int register_warn_debugfs(void)

{

/* Don't care about failure */

debugfs_create_file("clear_warn_once", 0200, NULL,

NULL, &clear_warn_once_fops);

return 0;

}

device_initcall(register_warn_debugfs);

#endif

#ifdef CONFIG_CC_STACKPROTECTOR

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

* gcc detects corruption of the on-stack canary value

__visible void __stack_chk_fail(void)

{

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

__builtin_return_address(0));

}

EXPORT_SYMBOL(__stack_chk_fail);

#endif

#ifdef CONFIG_ARCH_HAS_REFCOUNT

void refcount_error_report(struct pt_regs *regs, const char *err)

{

WARN_RATELIMIT(1, "refcount_t %s at %pB in %s[%d], uid/euid: %u/%u\n",

err, (void *)instruction_pointer(regs),

current->comm, task_pid_nr(current),

from_kuid_munged(&init_user_ns, current_uid()),

from_kuid_munged(&init_user_ns, current_euid()));

}

#endif

core_param(panic, panic_timeout, int, 0644);

core_param(pause_on_oops, pause_on_oops, int, 0644);

core_param(panic_on_warn, panic_on_warn, int, 0644);

core_param(crash_kexec_post_notifiers, crash_kexec_post_notifiers, bool, 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 · flexbed/linux · GitHub

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