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 #include <linux/kernel.h>
  14 #include <linux/smp.h>
  15 #include <linux/reboot.h>
  16 #include <linux/kexec.h>
  17 #include <linux/export.h>
  18 #include <linux/crash_dump.h>
  19 #include <linux/delay.h>
  20 #include <linux/init.h>
  21 #include <linux/irq.h>
  22 #include <linux/types.h>
  23
  24 #include <asm/processor.h>
  25 #include <asm/machdep.h>
  26 #include <asm/kexec.h>
  27 #include <asm/kdump.h>
  28 #include <asm/prom.h>
  29 #include <asm/smp.h>
  30 #include <asm/system.h>
  31 #include <asm/setjmp.h>
  32
  33 /*
  34  * The primary CPU waits a while for all secondary CPUs to enter. This is to
  35  * avoid sending an IPI if the secondary CPUs are entering
  36  * crash_kexec_secondary on their own (eg via a system reset).
  37  *
  38  * The secondary timeout has to be longer than the primary. Both timeouts are
  39  * in milliseconds.
  40  */
  41 #define PRIMARY_TIMEOUT         500
  42 #define SECONDARY_TIMEOUT       1000
  43
  44 #define IPI_TIMEOUT             10000
  45 #define REAL_MODE_TIMEOUT       10000
  46
  47 /* This keeps a track of which one is the crashing cpu. */
  48 int crashing_cpu = -1;
  49 static int time_to_dump;
  50
  51 #define CRASH_HANDLER_MAX 3
  52 /* NULL terminated list of shutdown handles */
  53 static crash_shutdown_t crash_shutdown_handles[CRASH_HANDLER_MAX+1];
  54 static DEFINE_SPINLOCK(crash_handlers_lock);
  55
  56 static unsigned long crash_shutdown_buf[JMP_BUF_LEN];
  57 static int crash_shutdown_cpu = -1;
  58
  59 static int handle_fault(struct pt_regs *regs)
  60 {
  61         if (crash_shutdown_cpu == smp_processor_id())
  62                 longjmp(crash_shutdown_buf, 1);
  63         return 0;
  64 }
  65
  66 #ifdef CONFIG_SMP
  67
  68 static atomic_t cpus_in_crash;
  69 void crash_ipi_callback(struct pt_regs *regs)
  70 {
  71         static cpumask_t cpus_state_saved = CPU_MASK_NONE;
  72
  73         int cpu = smp_processor_id();
  74
  75         if (!cpu_online(cpu))
  76                 return;
  77
  78         hard_irq_disable();
  79         if (!cpumask_test_cpu(cpu, &cpus_state_saved)) {
  80                 crash_save_cpu(regs, cpu);
  81                 cpumask_set_cpu(cpu, &cpus_state_saved);
  82         }
  83
  84         atomic_inc(&cpus_in_crash);
  85         smp_mb__after_atomic_inc();
  86
  87         /*
  88          * Starting the kdump boot.
  89          * This barrier is needed to make sure that all CPUs are stopped.
  90          */
  91         while (!time_to_dump)
  92                 cpu_relax();
  93
  94         if (ppc_md.kexec_cpu_down)
  95                 ppc_md.kexec_cpu_down(1, 1);
  96
  97 #ifdef CONFIG_PPC64
  98         kexec_smp_wait();
  99 #else
 100         for (;;);       /* FIXME */
 101 #endif
 102
 103         /* NOTREACHED */
 104 }
 105
 106 static void crash_kexec_prepare_cpus(int cpu)
 107 {
 108         unsigned int msecs;
 109         unsigned int ncpus = num_online_cpus() - 1;/* Excluding the panic cpu */
 110         int tries = 0;
 111         int (*old_handler)(struct pt_regs *regs);
 112
 113         printk(KERN_EMERG "Sending IPI to other CPUs\n");
 114
 115         crash_send_ipi(crash_ipi_callback);
 116         smp_wmb();
 117
 118 again:
 119         /*
 120          * FIXME: Until we will have the way to stop other CPUs reliably,
 121          * the crash CPU will send an IPI and wait for other CPUs to
 122          * respond.
 123          */
 124         msecs = IPI_TIMEOUT;
 125         while ((atomic_read(&cpus_in_crash) < ncpus) && (--msecs > 0))
 126                 mdelay(1);
 127
 128         /* Would it be better to replace the trap vector here? */
 129
 130         if (atomic_read(&cpus_in_crash) >= ncpus) {
 131                 printk(KERN_EMERG "IPI complete\n");
 132                 return;
 133         }
 134
 135         printk(KERN_EMERG "ERROR: %d cpu(s) not responding\n",
 136                 ncpus - atomic_read(&cpus_in_crash));
 137
 138         /*
 139          * If we have a panic timeout set then we can't wait indefinitely
 140          * for someone to activate system reset. We also give up on the
 141          * second time through if system reset fail to work.
 142          */
 143         if ((panic_timeout > 0) || (tries > 0))
 144                 return;
 145
 146         /*
 147          * A system reset will cause all CPUs to take an 0x100 exception.
 148          * The primary CPU returns here via setjmp, and the secondary
 149          * CPUs reexecute the crash_kexec_secondary path.
 150          */
 151         old_handler = __debugger;
 152         __debugger = handle_fault;
 153         crash_shutdown_cpu = smp_processor_id();
 154
 155         if (setjmp(crash_shutdown_buf) == 0) {
 156                 printk(KERN_EMERG "Activate system reset (dumprestart) "
 157                                   "to stop other cpu(s)\n");
 158
 159                 /*
 160                  * A system reset will force all CPUs to execute the
 161                  * crash code again. We need to reset cpus_in_crash so we
 162                  * wait for everyone to do this.
 163                  */
 164                 atomic_set(&cpus_in_crash, 0);
 165                 smp_mb();
 166
 167                 while (atomic_read(&cpus_in_crash) < ncpus)
 168                         cpu_relax();
 169         }
 170
 171         crash_shutdown_cpu = -1;
 172         __debugger = old_handler;
 173
 174         tries++;
 175         goto again;
 176 }
 177
 178 /*
 179  * This function will be called by secondary cpus.
 180  */
 181 void crash_kexec_secondary(struct pt_regs *regs)
 182 {
 183         unsigned long flags;
 184         int msecs = SECONDARY_TIMEOUT;
 185
 186         local_irq_save(flags);
 187
 188         /* Wait for the primary crash CPU to signal its progress */
 189         while (crashing_cpu < 0) {
 190                 if (--msecs < 0) {
 191                         /* No response, kdump image may not have been loaded */
 192                         local_irq_restore(flags);
 193                         return;
 194                 }
 195
 196                 mdelay(1);
 197         }
 198
 199         crash_ipi_callback(regs);
 200 }
 201
 202 #else   /* ! CONFIG_SMP */
 203
 204 static void crash_kexec_prepare_cpus(int cpu)
 205 {
 206         /*
 207          * move the secondaries to us so that we can copy
 208          * the new kernel 0-0x100 safely
 209          *
 210          * do this if kexec in setup.c ?
 211          */
 212 #ifdef CONFIG_PPC64
 213         smp_release_cpus();
 214 #else
 215         /* FIXME */
 216 #endif
 217 }
 218
 219 void crash_kexec_secondary(struct pt_regs *regs)
 220 {
 221 }
 222 #endif  /* CONFIG_SMP */
 223
 224 /* wait for all the CPUs to hit real mode but timeout if they don't come in */
 225 #if defined(CONFIG_SMP) && defined(CONFIG_PPC_STD_MMU_64)
 226 static void crash_kexec_wait_realmode(int cpu)
 227 {
 228         unsigned int msecs;
 229         int i;
 230
 231         msecs = REAL_MODE_TIMEOUT;
 232         for (i=0; i < nr_cpu_ids && msecs > 0; i++) {
 233                 if (i == cpu)
 234                         continue;
 235
 236                 while (paca[i].kexec_state < KEXEC_STATE_REAL_MODE) {
 237                         barrier();
 238                         if (!cpu_possible(i) || !cpu_online(i) || (msecs <= 0))
 239                                 break;
 240                         msecs--;
 241                         mdelay(1);
 242                 }
 243         }
 244         mb();
 245 }
 246 #else
 247 static inline void crash_kexec_wait_realmode(int cpu) {}
 248 #endif  /* CONFIG_SMP && CONFIG_PPC_STD_MMU_64 */
 249
 250 /*
 251  * Register a function to be called on shutdown.  Only use this if you
 252  * can't reset your device in the second kernel.
 253  */
 254 int crash_shutdown_register(crash_shutdown_t handler)
 255 {
 256         unsigned int i, rc;
 257
 258         spin_lock(&crash_handlers_lock);
 259         for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
 260                 if (!crash_shutdown_handles[i]) {
 261                         /* Insert handle at first empty entry */
 262                         crash_shutdown_handles[i] = handler;
 263                         rc = 0;
 264                         break;
 265                 }
 266
 267         if (i == CRASH_HANDLER_MAX) {
 268                 printk(KERN_ERR "Crash shutdown handles full, "
 269                        "not registered.\n");
 270                 rc = 1;
 271         }
 272
 273         spin_unlock(&crash_handlers_lock);
 274         return rc;
 275 }
 276 EXPORT_SYMBOL(crash_shutdown_register);
 277
 278 int crash_shutdown_unregister(crash_shutdown_t handler)
 279 {
 280         unsigned int i, rc;
 281
 282         spin_lock(&crash_handlers_lock);
 283         for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
 284                 if (crash_shutdown_handles[i] == handler)
 285                         break;
 286
 287         if (i == CRASH_HANDLER_MAX) {
 288                 printk(KERN_ERR "Crash shutdown handle not found\n");
 289                 rc = 1;
 290         } else {
 291                 /* Shift handles down */
 292                 for (; crash_shutdown_handles[i]; i++)
 293                         crash_shutdown_handles[i] =
 294                                 crash_shutdown_handles[i+1];
 295                 rc = 0;
 296         }
 297
 298         spin_unlock(&crash_handlers_lock);
 299         return rc;
 300 }
 301 EXPORT_SYMBOL(crash_shutdown_unregister);
 302
 303 void default_machine_crash_shutdown(struct pt_regs *regs)
 304 {
 305         unsigned int i;
 306         int (*old_handler)(struct pt_regs *regs);
 307
 308         /*
 309          * This function is only called after the system
 310          * has panicked or is otherwise in a critical state.
 311          * The minimum amount of code to allow a kexec'd kernel
 312          * to run successfully needs to happen here.
 313          *
 314          * In practice this means stopping other cpus in
 315          * an SMP system.
 316          * The kernel is broken so disable interrupts.
 317          */
 318         hard_irq_disable();
 319
 320         /*
 321          * Make a note of crashing cpu. Will be used in machine_kexec
 322          * such that another IPI will not be sent.
 323          */
 324         crashing_cpu = smp_processor_id();
 325
 326         /*
 327          * If we came in via system reset, wait a while for the secondary
 328          * CPUs to enter.
 329          */
 330         if (TRAP(regs) == 0x100)
 331                 mdelay(PRIMARY_TIMEOUT);
 332
 333         crash_kexec_prepare_cpus(crashing_cpu);
 334
 335         crash_save_cpu(regs, crashing_cpu);
 336
 337         time_to_dump = 1;
 338
 339         crash_kexec_wait_realmode(crashing_cpu);
 340
 341         machine_kexec_mask_interrupts();
 342
 343         /*
 344          * Call registered shutdown routines safely.  Swap out
 345          * __debugger_fault_handler, and replace on exit.
 346          */
 347         old_handler = __debugger_fault_handler;
 348         __debugger_fault_handler = handle_fault;
 349         crash_shutdown_cpu = smp_processor_id();
 350         for (i = 0; crash_shutdown_handles[i]; i++) {
 351                 if (setjmp(crash_shutdown_buf) == 0) {
 352                         /*
 353                          * Insert syncs and delay to ensure
 354                          * instructions in the dangerous region don't
 355                          * leak away from this protected region.
 356                          */
 357                         asm volatile("sync; isync");
 358                         /* dangerous region */
 359                         crash_shutdown_handles[i]();
 360                         asm volatile("sync; isync");
 361                 }
 362         }
 363         crash_shutdown_cpu = -1;
 364         __debugger_fault_handler = old_handler;
 365
 366         if (ppc_md.kexec_cpu_down)
 367                 ppc_md.kexec_cpu_down(1, 0);
 368 }