arch/i386/kernel/crash.c

   1 /*
   2  * Architecture specific (i386) functions for kexec based crash dumps.
   3  *
   4  * Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
   5  *
   6  * Copyright (C) IBM Corporation, 2004. All rights reserved.
   7  *
   8  */
   9
  10 #include <linux/init.h>
  11 #include <linux/types.h>
  12 #include <linux/kernel.h>
  13 #include <linux/smp.h>
  14 #include <linux/reboot.h>
  15 #include <linux/kexec.h>
  16 #include <linux/delay.h>
  17 #include <linux/elf.h>
  18 #include <linux/elfcore.h>
  19
  20 #include <asm/processor.h>
  21 #include <asm/hardirq.h>
  22 #include <asm/nmi.h>
  23 #include <asm/hw_irq.h>
  24 #include <asm/apic.h>
  25 #include <asm/kdebug.h>
  26 #include <asm/smp.h>
  27
  28 #include <mach_ipi.h>
  29
  30
  31 /* This keeps a track of which one is crashing cpu. */
  32 static int crashing_cpu;
  33
  34 #if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC)
  35 static atomic_t waiting_for_crash_ipi;
  36
  37 static int crash_nmi_callback(struct notifier_block *self,
  38                         unsigned long val, void *data)
  39 {
  40         struct pt_regs *regs;
  41         struct pt_regs fixed_regs;
  42         int cpu;
  43
  44         if (val != DIE_NMI_IPI)
  45                 return NOTIFY_OK;
  46
  47         regs = ((struct die_args *)data)->regs;
  48         cpu = raw_smp_processor_id();
  49
  50         /* Don't do anything if this handler is invoked on crashing cpu.
  51          * Otherwise, system will completely hang. Crashing cpu can get
  52          * an NMI if system was initially booted with nmi_watchdog parameter.
  53          */
  54         if (cpu == crashing_cpu)
  55                 return NOTIFY_STOP;
  56         local_irq_disable();
  57
  58         if (!user_mode_vm(regs)) {
  59                 crash_fixup_ss_esp(&fixed_regs, regs);
  60                 regs = &fixed_regs;
  61         }
  62         crash_save_cpu(regs, cpu);
  63         disable_local_APIC();
  64         atomic_dec(&waiting_for_crash_ipi);
  65         /* Assume hlt works */
  66         halt();
  67         for (;;)
  68                 cpu_relax();
  69
  70         return 1;
  71 }
  72
  73 static void smp_send_nmi_allbutself(void)
  74 {
  75         cpumask_t mask = cpu_online_map;
  76         cpu_clear(safe_smp_processor_id(), mask);
  77         if (!cpus_empty(mask))
  78                 send_IPI_mask(mask, NMI_VECTOR);
  79 }
  80
  81 static struct notifier_block crash_nmi_nb = {
  82         .notifier_call = crash_nmi_callback,
  83 };
  84
  85 static void nmi_shootdown_cpus(void)
  86 {
  87         unsigned long msecs;
  88
  89         atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
  90         /* Would it be better to replace the trap vector here? */
  91         if (register_die_notifier(&crash_nmi_nb))
  92                 return;         /* return what? */
  93         /* Ensure the new callback function is set before sending
  94          * out the NMI
  95          */
  96         wmb();
  97
  98         smp_send_nmi_allbutself();
  99
 100         msecs = 1000; /* Wait at most a second for the other cpus to stop */
 101         while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
 102                 mdelay(1);
 103                 msecs--;
 104         }
 105
 106         /* Leave the nmi callback set */
 107         disable_local_APIC();
 108 }
 109 #else
 110 static void nmi_shootdown_cpus(void)
 111 {
 112         /* There are no cpus to shootdown */
 113 }
 114 #endif
 115
 116 void machine_crash_shutdown(struct pt_regs *regs)
 117 {
 118         /* This function is only called after the system
 119          * has panicked or is otherwise in a critical state.
 120          * The minimum amount of code to allow a kexec'd kernel
 121          * to run successfully needs to happen here.
 122          *
 123          * In practice this means shooting down the other cpus in
 124          * an SMP system.
 125          */
 126         /* The kernel is broken so disable interrupts */
 127         local_irq_disable();
 128
 129         /* Make a note of crashing cpu. Will be used in NMI callback.*/
 130         crashing_cpu = safe_smp_processor_id();
 131         nmi_shootdown_cpus();
 132         lapic_shutdown();
 133 #if defined(CONFIG_X86_IO_APIC)
 134         disable_IO_APIC();
 135 #endif
 136         crash_save_cpu(regs, safe_smp_processor_id());
 137 }