arch/x86_64/kernel/crash.c

   1 /*
   2  * Architecture specific (x86_64) 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/irq.h>
  15 #include <linux/reboot.h>
  16 #include <linux/kexec.h>
  17 #include <linux/delay.h>
  18 #include <linux/elf.h>
  19 #include <linux/elfcore.h>
  20
  21 #include <asm/processor.h>
  22 #include <asm/hardirq.h>
  23 #include <asm/nmi.h>
  24 #include <asm/hw_irq.h>
  25 #include <asm/mach_apic.h>
  26 #include <asm/kdebug.h>
  27
  28 /* This keeps a track of which one is crashing cpu. */
  29 static int crashing_cpu;
  30
  31 static u32 *append_elf_note(u32 *buf, char *name, unsigned type,
  32                                                 void *data, size_t data_len)
  33 {
  34         struct elf_note note;
  35
  36         note.n_namesz = strlen(name) + 1;
  37         note.n_descsz = data_len;
  38         note.n_type   = type;
  39         memcpy(buf, &note, sizeof(note));
  40         buf += (sizeof(note) +3)/4;
  41         memcpy(buf, name, note.n_namesz);
  42         buf += (note.n_namesz + 3)/4;
  43         memcpy(buf, data, note.n_descsz);
  44         buf += (note.n_descsz + 3)/4;
  45
  46         return buf;
  47 }
  48
  49 static void final_note(u32 *buf)
  50 {
  51         struct elf_note note;
  52
  53         note.n_namesz = 0;
  54         note.n_descsz = 0;
  55         note.n_type   = 0;
  56         memcpy(buf, &note, sizeof(note));
  57 }
  58
  59 static void crash_save_this_cpu(struct pt_regs *regs, int cpu)
  60 {
  61         struct elf_prstatus prstatus;
  62         u32 *buf;
  63
  64         if ((cpu < 0) || (cpu >= NR_CPUS))
  65                 return;
  66
  67         /* Using ELF notes here is opportunistic.
  68          * I need a well defined structure format
  69          * for the data I pass, and I need tags
  70          * on the data to indicate what information I have
  71          * squirrelled away.  ELF notes happen to provide
  72          * all of that, no need to invent something new.
  73          */
  74
  75         buf = (u32*)per_cpu_ptr(crash_notes, cpu);
  76
  77         if (!buf)
  78                 return;
  79
  80         memset(&prstatus, 0, sizeof(prstatus));
  81         prstatus.pr_pid = current->pid;
  82         elf_core_copy_regs(&prstatus.pr_reg, regs);
  83         buf = append_elf_note(buf, "CORE", NT_PRSTATUS, &prstatus,
  84                                         sizeof(prstatus));
  85         final_note(buf);
  86 }
  87
  88 static void crash_save_self(struct pt_regs *regs)
  89 {
  90         int cpu;
  91
  92         cpu = smp_processor_id();
  93         crash_save_this_cpu(regs, cpu);
  94 }
  95
  96 #ifdef CONFIG_SMP
  97 static atomic_t waiting_for_crash_ipi;
  98
  99 static int crash_nmi_callback(struct notifier_block *self,
 100                                 unsigned long val, void *data)
 101 {
 102         struct pt_regs *regs;
 103         int cpu;
 104
 105         if (val != DIE_NMI_IPI)
 106                 return NOTIFY_OK;
 107
 108         regs = ((struct die_args *)data)->regs;
 109         cpu = raw_smp_processor_id();
 110
 111         /*
 112          * Don't do anything if this handler is invoked on crashing cpu.
 113          * Otherwise, system will completely hang. Crashing cpu can get
 114          * an NMI if system was initially booted with nmi_watchdog parameter.
 115          */
 116         if (cpu == crashing_cpu)
 117                 return NOTIFY_STOP;
 118         local_irq_disable();
 119
 120         crash_save_this_cpu(regs, cpu);
 121         disable_local_APIC();
 122         atomic_dec(&waiting_for_crash_ipi);
 123         /* Assume hlt works */
 124         for(;;)
 125                 halt();
 126
 127         return 1;
 128 }
 129
 130 static void smp_send_nmi_allbutself(void)
 131 {
 132         send_IPI_allbutself(NMI_VECTOR);
 133 }
 134
 135 /*
 136  * This code is a best effort heuristic to get the
 137  * other cpus to stop executing. So races with
 138  * cpu hotplug shouldn't matter.
 139  */
 140
 141 static struct notifier_block crash_nmi_nb = {
 142         .notifier_call = crash_nmi_callback,
 143 };
 144
 145 static void nmi_shootdown_cpus(void)
 146 {
 147         unsigned long msecs;
 148
 149         atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
 150         if (register_die_notifier(&crash_nmi_nb))
 151                 return;         /* return what? */
 152
 153         /*
 154          * Ensure the new callback function is set before sending
 155          * out the NMI
 156          */
 157         wmb();
 158
 159         smp_send_nmi_allbutself();
 160
 161         msecs = 1000; /* Wait at most a second for the other cpus to stop */
 162         while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
 163                 mdelay(1);
 164                 msecs--;
 165         }
 166         /* Leave the nmi callback set */
 167         disable_local_APIC();
 168 }
 169 #else
 170 static void nmi_shootdown_cpus(void)
 171 {
 172         /* There are no cpus to shootdown */
 173 }
 174 #endif
 175
 176 void machine_crash_shutdown(struct pt_regs *regs)
 177 {
 178         /*
 179          * This function is only called after the system
 180          * has panicked or is otherwise in a critical state.
 181          * The minimum amount of code to allow a kexec'd kernel
 182          * to run successfully needs to happen here.
 183          *
 184          * In practice this means shooting down the other cpus in
 185          * an SMP system.
 186          */
 187         /* The kernel is broken so disable interrupts */
 188         local_irq_disable();
 189
 190         /* Make a note of crashing cpu. Will be used in NMI callback.*/
 191         crashing_cpu = smp_processor_id();
 192         nmi_shootdown_cpus();
 193
 194         if(cpu_has_apic)
 195                  disable_local_APIC();
 196
 197         disable_IO_APIC();
 198
 199         crash_save_self(regs);
 200 }