// 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 <trace/events/error_report.h>
#include <asm/sections.h>

#define PANIC_TIMER_STEP 100
#define PANIC_BLINK_SPD 18

#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 = CONFIG_PANIC_ON_OOPS_VALUE;
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;

bool panic_triggering_all_cpu_backtrace;

int panic_timeout = CONFIG_PANIC_TIMEOUT;
EXPORT_SYMBOL_GPL(panic_timeout);

#define PANIC_PRINT_TASK_INFO		0x00000001
#define PANIC_PRINT_MEM_INFO		0x00000002
#define PANIC_PRINT_TIMER_INFO		0x00000004
#define PANIC_PRINT_LOCK_INFO		0x00000008
#define PANIC_PRINT_FTRACE_INFO		0x00000010
#define PANIC_PRINT_ALL_PRINTK_MSG	0x00000020
#define PANIC_PRINT_ALL_CPU_BT		0x00000040
#define PANIC_PRINT_BLOCKED_TASKS	0x00000080
unsigned long panic_print;

ATOMIC_NOTIFIER_HEAD(panic_notifier_list);

EXPORT_SYMBOL(panic_notifier_list);

#ifdef CONFIG_SYSCTL
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       = "warn_limit",
		.data           = &warn_limit,
		.maxlen         = sizeof(warn_limit),
		.mode           = 0644,
		.proc_handler   = proc_douintvec,
	},
};

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

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);

/*
 * 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, this_cpu;

	old_cpu = PANIC_CPU_INVALID;
	this_cpu = raw_smp_processor_id();

	/* atomic_try_cmpxchg updates old_cpu on failure */
	if (atomic_try_cmpxchg(&panic_cpu, &old_cpu, this_cpu))
		panic("%s", msg);
	else if (old_cpu != this_cpu)
		nmi_panic_self_stop(regs);
}
EXPORT_SYMBOL(nmi_panic);

static void panic_print_sys_info(bool console_flush)
{
	if (console_flush) {
		if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG)
			console_flush_on_panic(CONSOLE_REPLAY_ALL);
		return;
	}

	if (panic_print & PANIC_PRINT_TASK_INFO)
		show_state();

	if (panic_print & PANIC_PRINT_MEM_INFO)
		show_mem();

	if (panic_print & PANIC_PRINT_TIMER_INFO)
		sysrq_timer_list_show();

	if (panic_print & PANIC_PRINT_LOCK_INFO)
		debug_show_all_locks();

	if (panic_print & PANIC_PRINT_FTRACE_INFO)
		ftrace_dump(DUMP_ALL);

	if (panic_print & PANIC_PRINT_BLOCKED_TASKS)
		show_state_filter(TASK_UNINTERRUPTIBLE);
}

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);
}

/*
 * 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 & PANIC_PRINT_ALL_CPU_BT) {
		/* Temporary allow non-panic CPUs to write their backtraces. */
		panic_triggering_all_cpu_backtrace = true;
		trigger_all_cpu_backtrace();
		panic_triggering_all_cpu_backtrace = false;
	}

	/*
	 * 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();
}

/**
 *	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, len;
	int state = 0;
	int old_cpu, this_cpu;
	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_sto