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 static u32 *append_elf_note(u32 *buf, char *name, unsigned type, void *data,
  35                                                                size_t data_len)
  36 {
  37         struct elf_note note;
  38
  39         note.n_namesz = strlen(name) + 1;
  40         note.n_descsz = data_len;
  41         note.n_type   = type;
  42         memcpy(buf, &note, sizeof(note));
  43         buf += (sizeof(note) +3)/4;
  44         memcpy(buf, name, note.n_namesz);
  45         buf += (note.n_namesz + 3)/4;
  46         memcpy(buf, data, note.n_descsz);
  47         buf += (note.n_descsz + 3)/4;
  48
  49         return buf;
  50 }
  51
  52 static void final_note(u32 *buf)
  53 {
  54         struct elf_note note;
  55
  56         note.n_namesz = 0;
  57         note.n_descsz = 0;
  58         note.n_type   = 0;
  59         memcpy(buf, &note, sizeof(note));
  60 }
  61
  62 static void crash_save_this_cpu(struct pt_regs *regs, int cpu)
  63 {
  64         struct elf_prstatus prstatus;
  65         u32 *buf;
  66
  67         if ((cpu < 0) || (cpu >= NR_CPUS))
  68                 return;
  69
  70         /* Using ELF notes here is opportunistic.
  71          * I need a well defined structure format
  72          * for the data I pass, and I need tags
  73          * on the data to indicate what information I have
  74          * squirrelled away.  ELF notes happen to provide
  75          * all of that, so there is no need to invent something new.
  76          */
  77         buf = (u32*)per_cpu_ptr(crash_notes, cpu);
  78         if (!buf)
  79                 return;
  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 = safe_smp_processor_id();
  93         crash_save_this_cpu(regs, cpu);
  94 }
  95
  96 #if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC)
  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         struct pt_regs fixed_regs;
 104         int cpu;
 105
 106         if (val != DIE_NMI_IPI)
 107                 return NOTIFY_OK;
 108
 109         regs = ((struct die_args *)data)->regs;
 110         cpu = raw_smp_processor_id();
 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         if (!user_mode_vm(regs)) {
 121                 crash_fixup_ss_esp(&fixed_regs, regs);
 122                 regs = &fixed_regs;
 123         }
 124         crash_save_this_cpu(regs, cpu);
 125         disable_local_APIC();
 126         atomic_dec(&waiting_for_crash_ipi);
 127         /* Assume hlt works */
 128         halt();
 129         for (;;)
 130                 cpu_relax();
 131
 132         return 1;
 133 }
 134
 135 static void smp_send_nmi_allbutself(void)
 136 {
 137         cpumask_t mask = cpu_online_map;
 138         cpu_clear(safe_smp_processor_id(), mask);
 139         if (!cpus_empty(mask))
 140                 send_IPI_mask(mask, NMI_VECTOR);
 141 }
 142
 143 static struct notifier_block crash_nmi_nb = {
 144         .notifier_call = crash_nmi_callback,
 145 };
 146
 147 static void nmi_shootdown_cpus(void)
 148 {
 149         unsigned long msecs;
 150
 151         atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
 152         /* Would it be better to replace the trap vector here? */
 153         if (register_die_notifier(&crash_nmi_nb))
 154                 return;         /* return what? */
 155         /* Ensure the new callback function is set before sending
 156          * out the NMI
 157          */
 158         wmb();
 159
 160         smp_send_nmi_allbutself();
 161
 162         msecs = 1000; /* Wait at most a second for the other cpus to stop */
 163         while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
 164                 mdelay(1);
 165                 msecs--;
 166         }
 167
 168         /* Leave the nmi callback set */
 169         disable_local_APIC();
 170 }
 171 #else
 172 static void nmi_shootdown_cpus(void)
 173 {
 174         /* There are no cpus to shootdown */
 175 }
 176 #endif
 177
 178 void machine_crash_shutdown(struct pt_regs *regs)
 179 {
 180         /* This function is only called after the system
 181          * has panicked or is otherwise in a critical state.
 182          * The minimum amount of code to allow a kexec'd kernel
 183          * to run successfully needs to happen here.
 184          *
 185          * In practice this means shooting down the other cpus in
 186          * an SMP system.
 187          */
 188         /* The kernel is broken so disable interrupts */
 189         local_irq_disable();
 190
 191         /* Make a note of crashing cpu. Will be used in NMI callback.*/
 192         crashing_cpu = safe_smp_processor_id();
 193         nmi_shootdown_cpus();
 194         lapic_shutdown();
 195 #if defined(CONFIG_X86_IO_APIC)
 196         disable_IO_APIC();
 197 #endif
 198         crash_save_self(regs);
 199 }