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crash.c

/*
 * Architecture specific (i386/x86_64) functions for kexec based crash dumps.
 *
 * Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
 *
 * Copyright (C) IBM Corporation, 2004. All rights reserved.
 *
 */

#include <linux/init.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/smp.h>
#include <linux/reboot.h>
#include <linux/kexec.h>
#include <linux/delay.h>
#include <linux/elf.h>
#include <linux/elfcore.h>

#include <asm/processor.h>
#include <asm/hardirq.h>
#include <asm/nmi.h>
#include <asm/hw_irq.h>
#include <asm/apic.h>
#include <asm/hpet.h>
#include <linux/kdebug.h>
#include <asm/smp.h>

#ifdef CONFIG_X86_32
#include <mach_ipi.h>
#else
#include <asm/mach_apic.h>
#endif

/* This keeps a track of which one is crashing cpu. */
static int crashing_cpu;

#if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC)
static atomic_t waiting_for_crash_ipi;

static int crash_nmi_callback(struct notifier_block *self,
                  unsigned long val, void *data)
{
      struct pt_regs *regs;
#ifdef CONFIG_X86_32
      struct pt_regs fixed_regs;
#endif
      int cpu;

      if (val != DIE_NMI_IPI)
            return NOTIFY_OK;

      regs = ((struct die_args *)data)->regs;
      cpu = raw_smp_processor_id();

      /* Don't do anything if this handler is invoked on crashing cpu.
       * Otherwise, system will completely hang. Crashing cpu can get
       * an NMI if system was initially booted with nmi_watchdog parameter.
       */
      if (cpu == crashing_cpu)
            return NOTIFY_STOP;
      local_irq_disable();

#ifdef CONFIG_X86_32
      if (!user_mode_vm(regs)) {
            crash_fixup_ss_esp(&fixed_regs, regs);
            regs = &fixed_regs;
      }
#endif
      crash_save_cpu(regs, cpu);
      disable_local_APIC();
      atomic_dec(&waiting_for_crash_ipi);
      /* Assume hlt works */
      halt();
      for (;;)
            cpu_relax();

      return 1;
}

static void smp_send_nmi_allbutself(void)
{
      cpumask_t mask = cpu_online_map;
      cpu_clear(safe_smp_processor_id(), mask);
      if (!cpus_empty(mask))
            send_IPI_mask(mask, NMI_VECTOR);
}

static struct notifier_block crash_nmi_nb = {
      .notifier_call = crash_nmi_callback,
};

static void nmi_shootdown_cpus(void)
{
      unsigned long msecs;

      atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
      /* Would it be better to replace the trap vector here? */
      if (register_die_notifier(&crash_nmi_nb))
            return;           /* return what? */
      /* Ensure the new callback function is set before sending
       * out the NMI
       */
      wmb();

      smp_send_nmi_allbutself();

      msecs = 1000; /* Wait at most a second for the other cpus to stop */
      while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
            mdelay(1);
            msecs--;
      }

      /* Leave the nmi callback set */
      disable_local_APIC();
}
#else
static void nmi_shootdown_cpus(void)
{
      /* There are no cpus to shootdown */
}
#endif

void machine_crash_shutdown(struct pt_regs *regs)
{
      /* This function is only called after the system
       * has panicked or is otherwise in a critical state.
       * The minimum amount of code to allow a kexec'd kernel
       * to run successfully needs to happen here.
       *
       * In practice this means shooting down the other cpus in
       * an SMP system.
       */
      /* The kernel is broken so disable interrupts */
      local_irq_disable();

      /* Make a note of crashing cpu. Will be used in NMI callback.*/
      crashing_cpu = safe_smp_processor_id();
      nmi_shootdown_cpus();
      lapic_shutdown();
#if defined(CONFIG_X86_IO_APIC)
      disable_IO_APIC();
#endif
#ifdef CONFIG_HPET_TIMER
      hpet_disable();
#endif
      crash_save_cpu(regs, safe_smp_processor_id());
}

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