// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/kernel/panic.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

/*
 * 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/kgdb.h>
#include <linux/kmsg_dump.h>
#include <linux/kallsyms.h>
#include <linux/notifier.h>
#include <linux/vt_kern.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/panic_notifier.h>
#include <linux/sched.h>
#include <linux/string_helpers.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 <linux/sysfs.h>
#include <linux/context_tracking.h>
#include <linux/seq_buf.h>
#include <linux/sys_info.h>
#include <trace/events/error_report.h>
#include <asm/sections.h>

#define PANIC_TIMER_STEP 100
#define PANIC_BLINK_SPD 18
#define PANIC_MSG_BUFSZ 1024

#ifdef CONFIG_SMP
/*
 * Should we dump all CPUs backtraces in an oops event?
 * Defaults to 0, can be changed via sysctl.
 */
static unsigned int __read_mostly sysctl_oops_all_cpu_backtrace;
#else
#define sysctl_oops_all_cpu_backtrace 0
#endif /* CONFIG_SMP */

int panic_on_oops = IS_ENABLED(CONFIG_PANIC_ON_OOPS);
static unsigned long tainted_mask =
        IS_ENABLED(CONFIG_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;
unsigned long panic_on_taint;
bool panic_on_taint_nousertaint = false;
static unsigned int warn_limit __read_mostly;
static bool panic_console_replay;

bool panic_triggering_all_cpu_backtrace;
static bool panic_this_cpu_backtrace_printed;

int panic_timeout = CONFIG_PANIC_TIMEOUT;
EXPORT_SYMBOL_GPL(panic_timeout);

unsigned long panic_print;

static int panic_force_cpu = -1;

ATOMIC_NOTIFIER_HEAD(panic_notifier_list);

EXPORT_SYMBOL(panic_notifier_list);

static void panic_print_deprecated(void)
{
        pr_info_once("Kernel: The 'panic_print' parameter is now deprecated. Please use 'panic_sys_info' and 'panic_console_replay' instead.\n");
}

#ifdef CONFIG_SYSCTL

/*
 * Taint values can only be increased
 * This means we can safely use a temporary.
 */
static int proc_taint(const struct ctl_table *table, int write,
                               void *buffer, size_t *lenp, loff_t *ppos)
{
        struct ctl_table t;
        unsigned long tmptaint = get_taint();
        int err;

        if (write && !capable(CAP_SYS_ADMIN))
                return -EPERM;

        t = *table;
        t.data = &tmptaint;
        err = proc_doulongvec_minmax(&t, write, buffer, lenp, ppos);
        if (err < 0)
                return err;

        if (write) {
                int i;

                /*
                 * If we are relying on panic_on_taint not producing
                 * false positives due to userspace input, bail out
                 * before setting the requested taint flags.
                 */
                if (panic_on_taint_nousertaint && (tmptaint & panic_on_taint))
                        return -EINVAL;

                /*
                 * Poor man's atomic or. Not worth adding a primitive
                 * to everyone's atomic.h for this
                 */
                for (i = 0; i < TAINT_FLAGS_COUNT; i++)
                        if ((1UL << i) & tmptaint)
                                add_taint(i, LOCKDEP_STILL_OK);
        }

        return err;
}

static int sysctl_panic_print_handler(const struct ctl_table *table, int write,
                           void *buffer, size_t *lenp, loff_t *ppos)
{
        if (write)
                panic_print_deprecated();
        return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
}

static const struct ctl_table kern_panic_table[] = {
#ifdef CONFIG_SMP
        {
                .procname       = "oops_all_cpu_backtrace",
                .data           = &sysctl_oops_all_cpu_backtrace,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_minmax,
                .extra1         = SYSCTL_ZERO,
                .extra2         = SYSCTL_ONE,
        },
#endif
        {
                .procname       = "tainted",
                .maxlen         = sizeof(long),
                .mode           = 0644,
                .proc_handler   = proc_taint,
        },
        {
                .procname       = "panic",
                .data           = &panic_timeout,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec,
        },
        {
                .procname       = "panic_on_oops",
                .data           = &panic_on_oops,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec,
        },
        {
                .procname       = "panic_print",
                .data           = &panic_print,
                .maxlen         = sizeof(unsigned long),
                .mode           = 0644,
                .proc_handler   = sysctl_panic_print_handler,
        },
        {
                .procname       = "panic_on_warn",
                .data           = &panic_on_warn,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_minmax,
                .extra1         = SYSCTL_ZERO,
                .extra2         = SYSCTL_ONE,
        },
        {
                .procname       = "warn_limit",
                .data           = &warn_limit,
                .maxlen         = sizeof(warn_limit),
                .mode           = 0644,
                .proc_handler   = proc_douintvec,
        },
#if (defined(CONFIG_X86_32) || defined(CONFIG_PARISC)) && \
        defined(CONFIG_DEBUG_STACKOVERFLOW)
        {
                .procname       = "panic_on_stackoverflow",
                .data           = &sysctl_panic_on_stackoverflow,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec,
        },
#endif
        {
                .procname       = "panic_sys_info",
                .data           = &panic_print,
                .maxlen         = sizeof(panic_print),
                .mode           = 0644,
                .proc_handler   = sysctl_sys_info_handler,
        },
};

static __init int kernel_panic_sysctls_init(void)
{
        register_sysctl_init("kernel", kern_panic_table);
        return 0;
}
late_initcall(kernel_panic_sysctls_init);
#endif

/* The format is "panic_sys_info=tasks,mem,locks,ftrace,..." */
static int __init setup_panic_sys_info(char *buf)
{
        /* There is no risk of race in kernel boot phase */
        panic_print = sys_info_parse_param(buf);
        return 1;
}
__setup("panic_sys_info=", setup_panic_sys_info);

static atomic_t warn_count = ATOMIC_INIT(0);

#ifdef CONFIG_SYSFS
static ssize_t warn_count_show(struct kobject *kobj, struct kobj_attribute *attr,
                               char *page)
{
        return sysfs_emit(page, "%d\n", atomic_read(&warn_count));
}

static struct kobj_attribute warn_count_attr = __ATTR_RO(warn_count);

static __init int kernel_panic_sysfs_init(void)
{
        sysfs_add_file_to_group(kernel_kobj, &warn_count_attr.attr, NULL);
        return 0;
}
late_initcall(kernel_panic_sysfs_init);
#endif

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 __noreturn 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 __noreturn 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);
atomic_t panic_redirect_cpu = ATOMIC_INIT(PANIC_CPU_INVALID);

#if defined(CONFIG_SMP) && defined(CONFIG_CRASH_DUMP)
static char *panic_force_buf;

static int __init panic_force_cpu_setup(char *str)
{
        int cpu;

        if (!str)
                return -EINVAL;

        if (kstrtoint(str, 0, &cpu) || cpu < 0 || cpu >= nr_cpu_ids) {
                pr_warn("panic_force_cpu: invalid value '%s'\n", str);
                return -EINVAL;
        }

        panic_force_cpu = cpu;
        return 0;
}
early_param("panic_force_cpu", panic_force_cpu_setup);

static int __init panic_force_cpu_late_init(void)
{
        if (panic_force_cpu < 0)
                return 0;

        panic_force_buf = kmalloc(PANIC_MSG_BUFSZ, GFP_KERNEL);

        return 0;
}
late_initcall(panic_force_cpu_late_init);

static void do_panic_on_target_cpu(void *info)
{
        panic("%s", (char *)info);
}

/**
 * panic_smp_redirect_cpu - Redirect panic to target CPU
 * @target_cpu: CPU that should handle the panic
 * @msg: formatted panic message
 *
 * Default implementation uses IPI. Architectures with NMI support
 * can override this for more reliable delivery.
 *
 * Return: 0 on success, negative errno on failure
 */
int __weak panic_smp_redirect_cpu(int target_cpu, void *msg)
{
        static call_single_data_t panic_csd;

        panic_csd.func = do_panic_on_target_cpu;
        panic_csd.info = msg;

        return smp_call_function_single_async(target_cpu, &panic_csd);
}

/**
 * panic_try_force_cpu - Redirect panic to a specific CPU for crash kernel
 * @fmt: panic message format string
 * @args: arguments for format string
 *
 * Some platforms require panic handling to occur on a specific CPU
 * for the crash kernel to function correctly. This function redirects
 * panic handling to the CPU specified via the panic_force_cpu= boot parameter.
 *
 * Returns false if panic should proceed on current CPU.
 * Returns true if panic was redirected.
 */
__printf(1, 0)
static bool panic_try_force_cpu(const char *fmt, va_list args)
{
        int this_cpu = raw_smp_processor_id();
        int old_cpu = PANIC_CPU_INVALID;
        const char *msg;

        /* Feature not enabled via boot parameter */
        if (panic_force_cpu < 0)
                return false;

        /* Already on target CPU - proceed normally */
        if (this_cpu == panic_force_cpu)
                return false;

        /* Target CPU is offline, can't redirect */
        if (!cpu_online(panic_force_cpu)) {
                pr_warn("panic: target CPU %d is offline, continuing on CPU %d\n",
                        panic_force_cpu, this_cpu);
                return false;
        }

        /* Another panic already in progress */
        if (panic_in_progress())
                return false;

        /*
         * Only one CPU can do the redirect. Use atomic cmpxchg to ensure
         * we don't race with another CPU also trying to redirect.
         */
        if (!atomic_try_cmpxchg(&panic_redirect_cpu, &old_cpu, this_cpu))
                return false;

        /*
         * Use dynamically allocated buffer if available, otherwise
         * fall back to static message for early boot panics or allocation failure.
         */
        if (panic_force_buf) {
                vsnprintf(panic_force_buf, PANIC_MSG_BUFSZ, fmt, args);
                msg = panic_force_buf;
        } else {
                msg = "Redirected panic (buffer unavailable)";
        }

        console_verbose();
        bust_spinlocks(1);

        pr_emerg("panic: Redirecting from CPU %d to CPU %d for crash kernel.\n",
                 this_cpu, panic_force_cpu);

        /* Dump original CPU before redirecting */
        if (!test_taint(TAINT_DIE) &&
            oops_in_progress <= 1 &&
            IS_ENABLED(CONFIG_DEBUG_BUGVERBOSE)) {
                dump_stack();
        }

        if (panic_smp_redirect_cpu(panic_force_cpu, (void *)msg) != 0) {
                atomic_set(&panic_redirect_cpu, PANIC_CPU_INVALID);
                pr_warn("panic: failed to redirect to CPU %d, continuing on CPU %d\n",
                        panic_force_cpu, this_cpu);
                return false;
        }

        /* IPI/NMI sent, this CPU should stop */
        return true;
}
#else
__printf(1, 0)
static inline bool panic_try_force_cpu(const char *fmt, va_list args)
{
        return false;
}
#endif /* CONFIG_SMP && CONFIG_CRASH_DUMP */

bool panic_try_start(void)
{
        int old_cpu, this_cpu;

        /*
         * Only one CPU is allowed to execute the crash_kexec() code as with
         * panic().  Otherwise parallel calls of panic() and crash_kexec()
         * may stop each other.  To exclude them, we use panic_cpu here too.
         */
        old_cpu = PANIC_CPU_INVALID;
        this_cpu = raw_smp_processor_id();

        return atomic_try_cmpxchg(&panic_cpu, &old_cpu, this_cpu);
}
EXPORT_SYMBOL(panic_try_start);

void panic_reset(void)
{
        atomic_set(&panic_cpu, PANIC_CPU_INVALID);
}
EXPORT_SYMBOL(panic_reset);

bool panic_in_progress(void)
{
        return unlikely(atomic_read(&panic_cpu) != PANIC_CPU_INVALID);
}
EXPORT_SYMBOL(panic_in_progress);

/* Return true if a panic is in progress on the current CPU. */
bool panic_on_this_cpu(void)
{
        /*
         * We can use raw_smp_processor_id() here because it is impossible for
         * the task to be migrated to the panic_cpu, or away from it. If
         * panic_cpu has already been set, and we're not currently executing on
         * that CPU, then we never will be.
         */
        return unlikely(atomic_read(&panic_cpu) == raw_smp_processor_id());
}
EXPORT_SYMBOL(panic_on_this_cpu);

/*
 * Return true if a panic is in progress on a remote CPU.
 *
 * On true, the local CPU should immediately release any printing resources
 * that may be needed by the panic CPU.
 */
bool panic_on_other_cpu(void)
{
        return (panic_in_progress() && !panic_on_this_cpu());
}
EXPORT_SYMBOL(panic_on_other_cpu);

/*
 * 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)
{
        if (panic_try_start())
                panic("%s", msg);
        else if (panic_on_other_cpu())
                nmi_panic_self_stop(regs);
}
EXPORT_SYMBOL(nmi_panic);

void check_panic_on_warn(const char *origin)
{
        unsigned int limit;

        if (panic_on_warn)
                panic("%s: panic_on_warn set ...\n", origin);

        limit = READ_ONCE(warn_limit);
        if (atomic_inc_return(&warn_count) >= limit && limit)
                panic("%s: system warned too often (kernel.warn_limit is %d)",
                      origin, limit);
}

static void panic_trigger_all_cpu_backtrace(void)
{
        /* Temporary allow non-panic CPUs to write their backtraces. */
        panic_triggering_all_cpu_backtrace = true;

        if (panic_this_cpu_backtrace_printed)
                trigger_allbutcpu_cpu_backtrace(raw_smp_processor_id());
        else
                trigger_all_cpu_backtrace();

        panic_triggering_all_cpu_backtrace = false;
}

/*
 * Helper that triggers the NMI backtrace (if set in panic_print)
 * and then performs the secondary CPUs shutdown - we cannot have
 * the NMI backtrace after the CPUs are off!
 */
static void panic_other_cpus_shutdown(bool crash_kexec)
{
        if (panic_print & SYS_INFO_ALL_BT)
                panic_trigger_all_cpu_backtrace();

        /*
         * Note that smp_send_stop() is the usual SMP shutdown function,
         * which unfortunately may not be hardened to work in a panic
         * situation. If we want to do crash dump after notifier calls
         * and kmsg_dump, we will need architecture dependent extra
         * bits in addition to stopping other CPUs, hence we rely on
         * crash_smp_send_stop() for that.
         */
        if (!crash_kexec)
                smp_send_stop();
        else
                crash_smp_send_stop();
}

/**
 * vpanic - halt the system
 * @fmt: The text string to print
 * @args: Arguments for the format string
 *
 * Display a message, then perform cleanups. This function never returns.
 */
void vpanic(const char *fmt, va_list args)
{
        static char buf[PANIC_MSG_BUFSZ];
        long i, i_next = 0, len;
        int state = 0;
        bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers;

        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;
        }

        /*
         * 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();
        preempt_disable_notrace();

        /* Redirect panic to target CPU if configured via panic_force_cpu=. */
        if (panic_try_force_cpu(fmt, args)) {
                /*
                 * Mark ourselves offline so panic_other_cpus_shutdown() won't wait
                 * for us on architectures that check num_online_cpus().
                 */
                set_cpu_online(smp_processor_id(), false);
                panic_smp_self_stop();
        }
        /*
         * 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().
         *
         * cmpxchg success 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.
         */
        /* atomic_try_cmpxchg updates old_cpu on failure */
        if (panic_try_start()) {
                /* go ahead */
        } else if (panic_on_other_cpu())
                panic_smp_self_stop();

        console_verbose();
        bust_spinlocks(1);
        len = vscnprintf(buf, sizeof(buf), fmt, args);

        if (len && buf[len - 1] == '\n')
                buf[len - 1] = '\0';

        pr_emerg("Kernel panic - not syncing: %s\n", buf);
        /*
         * Avoid nested stack-dumping if a panic occurs during oops processing
         */
        if (atomic_read(&panic_redirect_cpu) != PANIC_CPU_INVALID &&
            panic_force_cpu == raw_smp_processor_id()) {
                pr_emerg("panic: Redirected from CPU %d, skipping stack dump.\n",
                         atomic_read(&panic_redirect_cpu));
        } else if (test_taint(TAINT_DIE) || oops_in_progress > 1) {
                panic_this_cpu_backtrace_printed = true;
        } else if (IS_ENABLED(CONFIG_DEBUG_BUGVERBOSE)) {
                dump_stack();
                panic_this_cpu_backtrace_printed = true;
        }

        /*
         * If kgdb is enabled, give it a chance to run before we stop all
         * the other CPUs or else we won't be able to debug processes left
         * running on them.
         */
        kgdb_panic(buf);

        /*
         * 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)
                __crash_kexec(NULL);

        panic_other_cpus_shutdown(_crash_kexec_post_notifiers);

        printk_legacy_allow_panic_sync();

        /*
         * 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);

        sys_info(panic_print);

        kmsg_dump_desc(KMSG_DUMP_PANIC, buf);

        /*
         * 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);

        console_unblank();

        /*
         * 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(CONSOLE_FLUSH_PENDING);

        if ((panic_print & SYS_INFO_PANIC_CONSOLE_REPLAY) ||
                panic_console_replay)
                console_flush_on_panic(CONSOLE_REPLAY_ALL);

        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.
                 */
                if (panic_reboot_mode != REBOOT_UNDEFINED)
                        reboot_mode = panic_reboot_mode;
                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)
        disabled_wait();
#endif
        pr_emerg("---[ end Kernel panic - not syncing: %s ]---\n", buf);

        /* Do not scroll important messages printed above */
        suppress_printk = 1;

        /*
         * The final messages may not have been printed if in a context that
         * defers printing (such as NMI) and irq_work is not available.
         * Explicitly flush the kernel log buffer one last time.
         */
        console_flush_on_panic(CONSOLE_FLUSH_PENDING);
        nbcon_atomic_flush_unsafe();

        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(vpanic);

/* Identical to vpanic(), except it takes variadic arguments instead of va_list */
void panic(const char *fmt, ...)
{
        va_list args;

        va_start(args, fmt);
        vpanic(fmt, args);
        va_end(args);
}
EXPORT_SYMBOL(panic);

#define TAINT_FLAG(taint, _c_true, _c_false)                            \
        [ TAINT_##taint ] = {                                           \
                .c_true = _c_true, .c_false = _c_false,                 \
                .desc = #taint,                                         \
        }

/*
 * NOTE: if you modify the taint_flags or TAINT_FLAGS_COUNT,
 * please also modify tools/debugging/kernel-chktaint and
 * Documentation/admin-guide/tainted-kernels.rst, including its
 * small shell script that prints the TAINT_FLAGS_COUNT bits of
 * /proc/sys/kernel/tainted.
 */
const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = {
        TAINT_FLAG(PROPRIETARY_MODULE,          'P', 'G'),
        TAINT_FLAG(FORCED_MODULE,               'F', ' '),
        TAINT_FLAG(CPU_OUT_OF_SPEC,             'S', ' '),
        TAINT_FLAG(FORCED_RMMOD,                'R', ' '),
        TAINT_FLAG(MACHINE_CHECK,               'M', ' '),
        TAINT_FLAG(BAD_PAGE,                    'B', ' '),
        TAINT_FLAG(USER,                        'U', ' '),
        TAINT_FLAG(DIE,                         'D', ' '),
        TAINT_FLAG(OVERRIDDEN_ACPI_TABLE,       'A', ' '),
        TAINT_FLAG(WARN,                        'W', ' '),
        TAINT_FLAG(CRAP,                        'C', ' '),
        TAINT_FLAG(FIRMWARE_WORKAROUND,         'I', ' '),
        TAINT_FLAG(OOT_MODULE,                  'O', ' '),
        TAINT_FLAG(UNSIGNED_MODULE,             'E', ' '),
        TAINT_FLAG(SOFTLOCKUP,                  'L', ' '),
        TAINT_FLAG(LIVEPATCH,                   'K', ' '),
        TAINT_FLAG(AUX,                         'X', ' '),
        TAINT_FLAG(RANDSTRUCT,                  'T', ' '),
        TAINT_FLAG(TEST,                        'N', ' '),
        TAINT_FLAG(FWCTL,                       'J', ' '),
};

#undef TAINT_FLAG

static void print_tainted_seq(struct seq_buf *s, bool verbose)
{
        const char *sep = "";
        int i;

        if (!tainted_mask) {
                seq_buf_puts(s, "Not tainted");
                return;
        }

        seq_buf_printf(s, "Tainted: ");
        for (i = 0; i < TAINT_FLAGS_COUNT; i++) {
                const struct taint_flag *t = &taint_flags[i];
                bool is_set = test_bit(i, &tainted_mask);
                char c = is_set ? t->c_true : t->c_false;

                if (verbose) {
                        if (is_set) {
                                seq_buf_printf(s, "%s[%c]=%s", sep, c, t->desc);
                                sep = ", ";
                        }
                } else {
                        seq_buf_putc(s, c);
                }
        }
}

static const char *_print_tainted(bool verbose)
{
        /* FIXME: what should the size be? */
        static char buf[sizeof(taint_flags)];
        struct seq_buf s;

        BUILD_BUG_ON(ARRAY_SIZE(taint_flags) != TAINT_FLAGS_COUNT);

        seq_buf_init(&s, buf, sizeof(buf));

        print_tainted_seq(&s, verbose);

        return seq_buf_str(&s);
}

/**
 * print_tainted - return a string to represent the kernel taint state.
 *
 * For individual taint flag meanings, see Documentation/admin-guide/sysctl/kernel.rst
 *
 * The string is overwritten by the next call to print_tainted(),
 * but is always NULL terminated.
 */
const char *print_tainted(void)
{
        return _print_tainted(false);
}

/**
 * print_tainted_verbose - A more verbose version of print_tainted()
 */
const char *print_tainted_verbose(void)
{
        return _print_tainted(true);
}

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);

        if (tainted_mask & panic_on_taint) {
                panic_on_taint = 0;
                panic("panic_on_taint set ...");
        }
}
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..
 */
bool 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)
{
        nbcon_cpu_emergency_enter();
        tracing_off();
        /* can't trust the integrity of the kernel anymore: */
        debug_locks_off();
        do_oops_enter_exit();

        if (sysctl_oops_all_cpu_backtrace)
                trigger_all_cpu_backtrace();
}

static void print_oops_end_marker(void)
{
        pr_warn("---[ end trace %016llx ]---\n", 0ULL);
}

/*
 * Called when the architecture exits its oops handler, after printing
 * everything.
 */
void oops_exit(void)
{
        do_oops_enter_exit();
        print_oops_end_marker();
        nbcon_cpu_emergency_exit();
        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)
{
        nbcon_cpu_emergency_enter();

        disable_trace_on_warning();

        if (file) {
                pr_warn("WARNING: %s:%d at %pS, CPU#%d: %s/%d\n",
                        file, line, caller,
                        raw_smp_processor_id(), current->comm, current->pid);
        } else {
                pr_warn("WARNING: at %pS, CPU#%d: %s/%d\n",
                        caller,
                        raw_smp_processor_id(), current->comm, current->pid);
        }

#pragma GCC diagnostic push
#ifndef __clang__
#pragma GCC diagnostic ignored "-Wsuggest-attribute=format"
#endif
        if (args)
                vprintk(args->fmt, args->args);
#pragma GCC diagnostic pop

        print_modules();

        if (regs)
                show_regs(regs);

        check_panic_on_warn("kernel");

        if (!regs)
                dump_stack();

        print_irqtrace_events(current);

        print_oops_end_marker();
        trace_error_report_end(ERROR_DETECTOR_WARN, (unsigned long)caller);

        /* Just a warning, don't kill lockdep. */
        add_taint(taint, LOCKDEP_STILL_OK);

        nbcon_cpu_emergency_exit();
}

#ifdef CONFIG_BUG
#ifndef __WARN_FLAGS
void warn_slowpath_fmt(const char *file, int line, unsigned taint,
                       const char *fmt, ...)
{
        bool rcu = warn_rcu_enter();
        struct warn_args args;

        pr_warn(CUT_HERE);

        if (!fmt) {
                __warn(file, line, __builtin_return_address(0), taint,
                       NULL, NULL);
                warn_rcu_exit(rcu);
                return;
        }

        args.fmt = fmt;
        va_start(args.args, fmt);
        __warn(file, line, __builtin_return_address(0), taint, NULL, &args);
        va_end(args.args);
        warn_rcu_exit(rcu);
}
EXPORT_SYMBOL(warn_slowpath_fmt);
#else
void __warn_printk(const char *fmt, ...)
{
        bool rcu = warn_rcu_enter();
        va_list args;

        pr_warn(CUT_HERE);

        va_start(args, fmt);
        vprintk(fmt, args);
        va_end(args);
        warn_rcu_exit(rcu);
}
EXPORT_SYMBOL(__warn_printk);
#endif

/* 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_DEBUGFS_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_unsafe("clear_warn_once", 0200, NULL, NULL,
                                   &clear_warn_once_fops);
        return 0;
}

device_initcall(register_warn_debugfs);
#endif

#ifdef CONFIG_STACKPROTECTOR

/*
 * Called when gcc's -fstack-protector feature is used, and
 * gcc detects corruption of the on-stack canary value
 */
__visible noinstr void __stack_chk_fail(void)
{
        unsigned long flags;

        instrumentation_begin();
        flags = user_access_save();

        panic("stack-protector: Kernel stack is corrupted in: %pB",
                __builtin_return_address(0));

        user_access_restore(flags);
        instrumentation_end();
}
EXPORT_SYMBOL(__stack_chk_fail);

#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);
core_param(panic_console_replay, panic_console_replay, bool, 0644);

static int panic_print_set(const char *val, const struct kernel_param *kp)
{
        panic_print_deprecated();
        return  param_set_ulong(val, kp);
}

static int panic_print_get(char *val, const struct kernel_param *kp)
{
        return  param_get_ulong(val, kp);
}

static const struct kernel_param_ops panic_print_ops = {
        .set    = panic_print_set,
        .get    = panic_print_get,
};
__core_param_cb(panic_print, &panic_print_ops, &panic_print, 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);

static int __init panic_on_taint_setup(char *s)
{
        char *taint_str;

        if (!s)
                return -EINVAL;

        taint_str = strsep(&s, ",");
        if (kstrtoul(taint_str, 16, &panic_on_taint))
                return -EINVAL;

        /* make sure panic_on_taint doesn't hold out-of-range TAINT flags */
        panic_on_taint &= TAINT_FLAGS_MAX;

        if (!panic_on_taint)
                return -EINVAL;

        if (s && !strcmp(s, "nousertaint"))
                panic_on_taint_nousertaint = true;

        pr_info("panic_on_taint: bitmask=0x%lx nousertaint_mode=%s\n",
                panic_on_taint, str_enabled_disabled(panic_on_taint_nousertaint));

        return 0;
}
early_param("panic_on_taint", panic_on_taint_setup);