text: // SPDX-License-Identifier: GPL-2.0-only
  /* Pseudo NMI support on sparc64 systems.
   *
   * Copyright (C) 2009 David S. Miller <davem@davemloft.net>
   *
   * The NMI watchdog support and infrastructure is based almost
   * entirely upon the x86 NMI support code.
   */
  #include <linux/kernel.h>
  #include <linux/param.h>
  #include <linux/init.h>
  #include <linux/percpu.h>
  #include <linux/nmi.h>
  #include <linux/export.h>
  #include <linux/kprobes.h>
  #include <linux/kernel_stat.h>
  #include <linux/reboot.h>
  #include <linux/slab.h>
  #include <linux/kdebug.h>
  #include <linux/delay.h>
  #include <linux/smp.h>
  
  #include <asm/perf_event.h>
  #include <asm/ptrace.h>
  #include <asm/pcr.h>
  
  #include "kstack.h"
  
  /* We don't have a real NMI on sparc64, but we can fake one
   * up using profiling counter overflow interrupts and interrupt
   * levels.
   *
   * The profile overflow interrupts at level 15, so we use
   * level 14 as our IRQ off level.
   */
  
  static int panic_on_timeout;
  
  /* nmi_active:
   * >0: the NMI watchdog is active, but can be disabled
   * <0: the NMI watchdog has not been set up, and cannot be enabled
   *  0: the NMI watchdog is disabled, but can be enabled
   */
  atomic_t nmi_active = ATOMIC_INIT(0);		/* oprofile uses this */
  EXPORT_SYMBOL(nmi_active);
  static int nmi_init_done;
  static unsigned int nmi_hz = HZ;
  static DEFINE_PER_CPU(short, wd_enabled);
  static int endflag __initdata;
  
  static DEFINE_PER_CPU(unsigned int, last_irq_sum);
  static DEFINE_PER_CPU(long, alert_counter);
  static DEFINE_PER_CPU(int, nmi_touch);
  
  void arch_touch_nmi_watchdog(void)
  {
  	if (atomic_read(&nmi_active)) {
  		int cpu;
  
  		for_each_present_cpu(cpu) {
  			if (per_cpu(nmi_touch, cpu) != 1)
  				per_cpu(nmi_touch, cpu) = 1;
  		}
  	}
  }
  EXPORT_SYMBOL(arch_touch_nmi_watchdog);
  
  static void die_nmi(const char *str, struct pt_regs *regs, int do_panic)
  {
  	int this_cpu = smp_processor_id();
  
  	if (notify_die(DIE_NMIWATCHDOG, str, regs, 0,
  		       pt_regs_trap_type(regs), SIGINT) == NOTIFY_STOP)
  		return;
  
  	if (do_panic || panic_on_oops)
  		panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
  	else
  		WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
  }
  
  notrace __kprobes void perfctr_irq(int irq, struct pt_regs *regs)
  {
  	unsigned int sum, touched = 0;
  	void *orig_sp;
  
  	clear_softint(1 << irq);
  
  	local_cpu_data().__nmi_count++;
  
  	nmi_enter();
  
  	orig_sp = set_hardirq_stack();
  
  	if (notify_die(DIE_NMI, "nmi", regs, 0,
  		       pt_regs_trap_type(regs), SIGINT) == NOTIFY_STOP)
  		touched = 1;
  	else
  		pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
  
  	sum = local_cpu_data().irq0_irqs;
  	if (__this_cpu_read(nmi_touch)) {
  		__this_cpu_write(nmi_touch, 0);
  		touched = 1;
  	}
  	if (!touched && __this_cpu_read(last_irq_sum) == sum) {
  		__this_cpu_inc(alert_counter);
  		if (__this_cpu_read(alert_counter) == 30 * nmi_hz)
  			die_nmi("BUG: NMI Watchdog detected LOCKUP",
  				regs, panic_on_timeout);
  	} else {
  		__this_cpu_write(last_irq_sum, sum);
  		__this_cpu_write(alert_counter, 0);
  	}
  	if (__this_cpu_read(wd_enabled)) {
  		pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
  		pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
  	}
  
  	restore_hardirq_stack(orig_sp);
  
  	nmi_exit();
  }
  
  static inline unsigned int get_nmi_count(int cpu)
  {
  	return cpu_data(cpu).__nmi_count;
  }
  
  static __init void nmi_cpu_busy(void *data)
  {
  	while (endflag == 0)
  		mb();
  }
  
  static void report_broken_nmi(int cpu, int *prev_nmi_count)
  {
  	printk(KERN_CONT "\n");
  
  	printk(KERN_WARNING
  		"WARNING: CPU#%d: NMI appears to be stuck (%d->%d)!\n",
  			cpu, prev_nmi_count[cpu], get_nmi_count(cpu));
  
  	printk(KERN_WARNING
  		"Please report this to bugzilla.kernel.org,\n");
  	printk(KERN_WARNING
  		"and attach the output of the 'dmesg' command.\n");
  
  	per_cpu(wd_enabled, cpu) = 0;
  	atomic_dec(&nmi_active);
  }
  
  void stop_nmi_watchdog(void *unused)
  {
  	if (!__this_cpu_read(wd_enabled))
  		return;
  	pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
  	__this_cpu_write(wd_enabled, 0);
  	atomic_dec(&nmi_active);
  }
  
  static int __init check_nmi_watchdog(void)
  {
  	unsigned int *prev_nmi_count;
  	int cpu, err;
  
  	if (!atomic_read(&nmi_active))
  		return 0;
  
  	prev_nmi_count = kmalloc_array(nr_cpu_ids, sizeof(unsigned int),
  				       GFP_KERNEL);
  	if (!prev_nmi_count) {
  		err = -ENOMEM;
  		goto error;
  	}
  
  	printk(KERN_INFO "Testing NMI watchdog ... ");
  
  	smp_call_function(nmi_cpu_busy, (void *)&endflag, 0);
  
  	for_each_possible_cpu(cpu)
  		prev_nmi_count[cpu] = get_nmi_count(cpu);
  	local_irq_enable();
  	mdelay((20 * 1000) / nmi_hz); /* wait 20 ticks */
  
  	for_each_online_cpu(cpu) {
  		if (!per_cpu(wd_enabled, cpu))
  			continue;
  		if (get_nmi_count(cpu) - prev_nmi_count[cpu] <= 5)
  			report_broken_nmi(cpu, prev_nmi_count);
  	}
  	endflag = 1;
  	if (!atomic_read(&nmi_active)) {
  		kfree(prev_nmi_count);
  		atomic_set(&nmi_active, -1);
  		err = -ENODEV;
  		goto error;
  	}
  	printk("OK.\n");
  
  	nmi_hz = 1;
  
  	kfree(prev_nmi_count);
  	return 0;
  error:
  	on_each_cpu(stop_nmi_watchdog, NULL, 1);
  	return err;
  }
  
  void start_nmi_watchdog(void *unused)
  {
  	if (__this_cpu_read(wd_enabled))
  		return;
  
  	__this_cpu_write(wd_enabled, 1);
  	atomic_inc(&nmi_active);
  
  	pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
  	pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
  
  	pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
  }
  
  static void nmi_adjust_hz_one(void *unused)
  {
  	if (!__this_cpu_read(wd_enabled))
  		return;
  
  	pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
  	pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
  
  	pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
  }
  
  void nmi_adjust_hz(unsigned int new_hz)
  {
  	nmi_hz = new_hz;
  	on_each_cpu(nmi_adjust_hz_one, NULL, 1);
  }
  EXPORT_SYMBOL_GPL(nmi_adjust_hz);
  
  static int nmi_shutdown(struct notifier_block *nb, unsigned long cmd, void *p)
  {
  	on_each_cpu(stop_nmi_watchdog, NULL, 1);
  	return 0;
  }
  
  static struct notifier_block nmi_reboot_notifier = {
  	.notifier_call = nmi_shutdown,
  };
  
  int __init nmi_init(void)
  {
  	int err;
  
  	on_each_cpu(start_nmi_watchdog, NULL, 1);
  
  	err = check_nmi_watchdog();
  	if (!err) {
  		err = register_reboot_notifier(&nmi_reboot_notifier);
  		if (err) {
  			on_each_cpu(stop_nmi_watchdog, NULL, 1);
  			atomic_set(&nmi_active, -1);
  		}
  	}
  
  	nmi_init_done = 1;
  
  	return err;
  }
  
  static int __init setup_nmi_watchdog(char *str)
  {
  	if (!strncmp(str, "panic", 5))
  		panic_on_timeout = 1;
  
  	return 0;
  }
  __setup("nmi_watchdog=", setup_nmi_watchdog);
  
  /*
   * sparc specific NMI watchdog enable function.
   * Enables watchdog if it is not enabled already.
   */
  int watchdog_nmi_enable(unsigned int cpu)
  {
  	if (atomic_read(&nmi_active) == -1) {
  		pr_warn("NMI watchdog cannot be enabled or disabled\n");
  		return -1;
  	}
  
  	/*
  	 * watchdog thread could start even before nmi_init is called.
  	 * Just Return in that case. Let nmi_init finish the init
  	 * process first.
  	 */
  	if (!nmi_init_done)
  		return 0;
  
  	smp_call_function_single(cpu, start_nmi_watchdog, NULL, 1);
  
  	return 0;
  }
  /*
   * sparc specific NMI watchdog disable function.
   * Disables watchdog if it is not disabled already.
   */
  void watchdog_nmi_disable(unsigned int cpu)
  {
  	if (atomic_read(&nmi_active) == -1)
  		pr_warn_once("NMI watchdog cannot be enabled or disabled\n");
  	else
  		smp_call_function_single(cpu, stop_nmi_watchdog, NULL, 1);
  }
  