arch/powerpc/kernel/crash.c

   1 /*
   2  * Architecture specific (PPC64) functions for kexec based crash dumps.
   3  *
   4  * Copyright (C) 2005, IBM Corp.
   5  *
   6  * Created by: Haren Myneni
   7  *
   8  * This source code is licensed under the GNU General Public License,
   9  * Version 2.  See the file COPYING for more details.
  10  *
  11  */
  12
  13 #undef DEBUG
  14
  15 #include <linux/kernel.h>
  16 #include <linux/smp.h>
  17 #include <linux/reboot.h>
  18 #include <linux/kexec.h>
  19 #include <linux/bootmem.h>
  20 #include <linux/crash_dump.h>
  21 #include <linux/delay.h>
  22 #include <linux/elf.h>
  23 #include <linux/elfcore.h>
  24 #include <linux/init.h>
  25 #include <linux/types.h>
  26
  27 #include <asm/processor.h>
  28 #include <asm/machdep.h>
  29 #include <asm/kdump.h>
  30 #include <asm/lmb.h>
  31 #include <asm/firmware.h>
  32 #include <asm/smp.h>
  33
  34 #ifdef DEBUG
  35 #include <asm/udbg.h>
  36 #define DBG(fmt...) udbg_printf(fmt)
  37 #else
  38 #define DBG(fmt...)
  39 #endif
  40
  41 /* This keeps a track of which one is crashing cpu. */
  42 int crashing_cpu = -1;
  43
  44 static u32 *append_elf_note(u32 *buf, char *name, unsigned type, void *data,
  45                                                                size_t data_len)
  46 {
  47         struct elf_note note;
  48
  49         note.n_namesz = strlen(name) + 1;
  50         note.n_descsz = data_len;
  51         note.n_type   = type;
  52         memcpy(buf, &note, sizeof(note));
  53         buf += (sizeof(note) +3)/4;
  54         memcpy(buf, name, note.n_namesz);
  55         buf += (note.n_namesz + 3)/4;
  56         memcpy(buf, data, note.n_descsz);
  57         buf += (note.n_descsz + 3)/4;
  58
  59         return buf;
  60 }
  61
  62 static void final_note(u32 *buf)
  63 {
  64         struct elf_note note;
  65
  66         note.n_namesz = 0;
  67         note.n_descsz = 0;
  68         note.n_type   = 0;
  69         memcpy(buf, &note, sizeof(note));
  70 }
  71
  72 static void crash_save_this_cpu(struct pt_regs *regs, int cpu)
  73 {
  74         struct elf_prstatus prstatus;
  75         u32 *buf;
  76
  77         if ((cpu < 0) || (cpu >= NR_CPUS))
  78                 return;
  79
  80         /* Using ELF notes here is opportunistic.
  81          * I need a well defined structure format
  82          * for the data I pass, and I need tags
  83          * on the data to indicate what information I have
  84          * squirrelled away.  ELF notes happen to provide
  85          * all of that that no need to invent something new.
  86          */
  87         buf = (u32*)per_cpu_ptr(crash_notes, cpu);
  88         if (!buf)
  89                 return;
  90
  91         memset(&prstatus, 0, sizeof(prstatus));
  92         prstatus.pr_pid = current->pid;
  93         elf_core_copy_regs(&prstatus.pr_reg, regs);
  94         buf = append_elf_note(buf, "CORE", NT_PRSTATUS, &prstatus,
  95                         sizeof(prstatus));
  96         final_note(buf);
  97 }
  98
  99 #ifdef CONFIG_SMP
 100 static atomic_t waiting_for_crash_ipi;
 101
 102 void crash_ipi_callback(struct pt_regs *regs)
 103 {
 104         int cpu = smp_processor_id();
 105
 106         if (cpu == crashing_cpu)
 107                 return;
 108
 109         if (!cpu_online(cpu))
 110                 return;
 111
 112         if (ppc_md.kexec_cpu_down)
 113                 ppc_md.kexec_cpu_down(1, 1);
 114
 115         local_irq_disable();
 116
 117         crash_save_this_cpu(regs, cpu);
 118         atomic_dec(&waiting_for_crash_ipi);
 119         kexec_smp_wait();
 120         /* NOTREACHED */
 121 }
 122
 123 static void crash_kexec_prepare_cpus(void)
 124 {
 125         unsigned int msecs;
 126
 127         atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
 128
 129         crash_send_ipi(crash_ipi_callback);
 130         smp_wmb();
 131
 132         /*
 133          * FIXME: Until we will have the way to stop other CPUSs reliabally,
 134          * the crash CPU will send an IPI and wait for other CPUs to
 135          * respond. If not, proceed the kexec boot even though we failed to
 136          * capture other CPU states.
 137          * Delay of at least 10 seconds.
 138          */
 139         printk(KERN_ALERT "Sending IPI to other cpus...\n");
 140         msecs = 10000;
 141         while ((atomic_read(&waiting_for_crash_ipi) > 0) && (--msecs > 0)) {
 142                 barrier();
 143                 mdelay(1);
 144         }
 145
 146         /* Would it be better to replace the trap vector here? */
 147
 148         /*
 149          * FIXME: In case if we do not get all CPUs, one possibility: ask the
 150          * user to do soft reset such that we get all.
 151          * IPI handler is already set by the panic cpu initially. Therefore,
 152          * all cpus could invoke this handler from die() and the panic CPU
 153          * will call machine_kexec() directly from this handler to do
 154          * kexec boot.
 155          */
 156         if (atomic_read(&waiting_for_crash_ipi))
 157                 printk(KERN_ALERT "done waiting: %d cpus not responding\n",
 158                         atomic_read(&waiting_for_crash_ipi));
 159         /* Leave the IPI callback set */
 160 }
 161 #else
 162 static void crash_kexec_prepare_cpus(void)
 163 {
 164         /*
 165          * move the secondarys to us so that we can copy
 166          * the new kernel 0-0x100 safely
 167          *
 168          * do this if kexec in setup.c ?
 169          */
 170         smp_release_cpus();
 171 }
 172
 173 #endif
 174
 175 void default_machine_crash_shutdown(struct pt_regs *regs)
 176 {
 177         /*
 178          * This function is only called after the system
 179          * has paniced or is otherwise in a critical state.
 180          * The minimum amount of code to allow a kexec'd kernel
 181          * to run successfully needs to happen here.
 182          *
 183          * In practice this means stopping other cpus in
 184          * an SMP system.
 185          * The kernel is broken so disable interrupts.
 186          */
 187         local_irq_disable();
 188
 189         if (ppc_md.kexec_cpu_down)
 190                 ppc_md.kexec_cpu_down(1, 0);
 191
 192         /*
 193          * Make a note of crashing cpu. Will be used in machine_kexec
 194          * such that another IPI will not be sent.
 195          */
 196         crashing_cpu = smp_processor_id();
 197         crash_kexec_prepare_cpus();
 198         crash_save_this_cpu(regs, crashing_cpu);
 199 }