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/irq.h>
  21 #include <linux/types.h>
  22
  23 #include <asm/processor.h>
  24 #include <asm/machdep.h>
  25 #include <asm/kexec.h>
  26 #include <asm/kdump.h>
  27 #include <asm/prom.h>
  28 #include <asm/smp.h>
  29 #include <asm/setjmp.h>
  30 #include <asm/debug.h>
  31
  32 /*
  33  * The primary CPU waits a while for all secondary CPUs to enter. This is to
  34  * avoid sending an IPI if the secondary CPUs are entering
  35  * crash_kexec_secondary on their own (eg via a system reset).
  36  *
  37  * The secondary timeout has to be longer than the primary. Both timeouts are
  38  * in milliseconds.
  39  */
  40 #define PRIMARY_TIMEOUT         500
  41 #define SECONDARY_TIMEOUT       1000
  42
  43 #define IPI_TIMEOUT             10000
  44 #define REAL_MODE_TIMEOUT       10000
  45
  46 /* This keeps a track of which one is the crashing cpu. */
  47 int crashing_cpu = -1;
  48 static int time_to_dump;
  49
  50 #define CRASH_HANDLER_MAX 3
  51 /* List of shutdown handles */
  52 static crash_shutdown_t crash_shutdown_handles[CRASH_HANDLER_MAX];
  53 static DEFINE_SPINLOCK(crash_handlers_lock);
  54
  55 static unsigned long crash_shutdown_buf[JMP_BUF_LEN];
  56 static int crash_shutdown_cpu = -1;
  57
  58 static int handle_fault(struct pt_regs *regs)
  59 {
  60         if (crash_shutdown_cpu == smp_processor_id())
  61                 longjmp(crash_shutdown_buf, 1);
  62         return 0;
  63 }
  64
  65 #ifdef CONFIG_SMP
  66
  67 static atomic_t cpus_in_crash;
  68 static void crash_ipi_callback(struct pt_regs *regs)
  69 {
  70         static cpumask_t cpus_state_saved = CPU_MASK_NONE;
  71
  72         int cpu = smp_processor_id();
  73
  74         if (!cpu_online(cpu))
  75                 return;
  76
  77         hard_irq_disable();
  78         if (!cpumask_test_cpu(cpu, &cpus_state_saved)) {
  79                 crash_save_cpu(regs, cpu);
  80                 cpumask_set_cpu(cpu, &cpus_state_saved);
  81         }
  82
  83         atomic_inc(&cpus_in_crash);
  84         smp_mb__after_atomic();
  85
  86         /*
  87          * Starting the kdump boot.
  88          * This barrier is needed to make sure that all CPUs are stopped.
  89          */
  90         while (!time_to_dump)
  91                 cpu_relax();
  92
  93         if (ppc_md.kexec_cpu_down)
  94                 ppc_md.kexec_cpu_down(1, 1);
  95
  96 #ifdef CONFIG_PPC64
  97         kexec_smp_wait();
  98 #else
  99         for (;;);       /* FIXME */
 100 #endif
 101
 102         /* NOTREACHED */
 103 }
 104
 105 static void crash_kexec_prepare_cpus(int cpu)
 106 {
 107         unsigned int msecs;
 108         unsigned int ncpus = num_online_cpus() - 1;/* Excluding the panic cpu */
 109         int tries = 0;
 110         int (*old_handler)(struct pt_regs *regs);
 111
 112         printk(KERN_EMERG "Sending IPI to other CPUs\n");
 113
 114         crash_send_ipi(crash_ipi_callback);
 115         smp_wmb();
 116
 117 again:
 118         /*
 119          * FIXME: Until we will have the way to stop other CPUs reliably,
 120          * the crash CPU will send an IPI and wait for other CPUs to
 121          * respond.
 122          */
 123         msecs = IPI_TIMEOUT;
 124         while ((atomic_read(&cpus_in_crash) < ncpus) && (--msecs > 0))
 125                 mdelay(1);
 126
 127         /* Would it be better to replace the trap vector here? */
 128
 129         if (atomic_read(&cpus_in_crash) >= ncpus) {
 130                 printk(KERN_EMERG "IPI complete\n");
 131                 return;
 132         }
 133
 134         printk(KERN_EMERG "ERROR: %d cpu(s) not responding\n",
 135                 ncpus - atomic_read(&cpus_in_crash));
 136
 137         /*
 138          * If we have a panic timeout set then we can't wait indefinitely
 139          * for someone to activate system reset. We also give up on the
 140          * second time through if system reset fail to work.
 141          */
 142         if ((panic_timeout > 0) || (tries > 0))
 143                 return;
 144
 145         /*
 146          * A system reset will cause all CPUs to take an 0x100 exception.
 147          * The primary CPU returns here via setjmp, and the secondary
 148          * CPUs reexecute the crash_kexec_secondary path.
 149          */
 150         old_handler = __debugger;
 151         __debugger = handle_fault;
 152         crash_shutdown_cpu = smp_processor_id();
 153
 154         if (setjmp(crash_shutdown_buf) == 0) {
 155                 printk(KERN_EMERG "Activate system reset (dumprestart) "
 156                                   "to stop other cpu(s)\n");
 157
 158                 /*
 159                  * A system reset will force all CPUs to execute the
 160                  * crash code again. We need to reset cpus_in_crash so we
 161                  * wait for everyone to do this.
 162                  */
 163                 atomic_set(&cpus_in_crash, 0);
 164                 smp_mb();
 165
 166                 while (atomic_read(&cpus_in_crash) < ncpus)
 167                         cpu_relax();
 168         }
 169
 170         crash_shutdown_cpu = -1;
 171         __debugger = old_handler;
 172
 173         tries++;
 174         goto again;
 175 }
 176
 177 /*
 178  * This function will be called by secondary cpus.
 179  */
 180 void crash_kexec_secondary(struct pt_regs *regs)
 181 {
 182         unsigned long flags;
 183         int msecs = SECONDARY_TIMEOUT;
 184
 185         local_irq_save(flags);
 186
 187         /* Wait for the primary crash CPU to signal its progress */
 188         while (crashing_cpu < 0) {
 189                 if (--msecs < 0) {
 190                         /* No response, kdump image may not have been loaded */
 191                         local_irq_restore(flags);
 192                         return;
 193                 }
 194
 195                 mdelay(1);
 196         }
 197
 198         crash_ipi_callback(regs);
 199 }
 200
 201 #else   /* ! CONFIG_SMP */
 202
 203 static void crash_kexec_prepare_cpus(int cpu)
 204 {
 205         /*
 206          * move the secondaries to us so that we can copy
 207          * the new kernel 0-0x100 safely
 208          *
 209          * do this if kexec in setup.c ?
 210          */
 211 #ifdef CONFIG_PPC64
 212         smp_release_cpus();
 213 #else
 214         /* FIXME */
 215 #endif
 216 }
 217
 218 void crash_kexec_secondary(struct pt_regs *regs)
 219 {
 220 }
 221 #endif  /* CONFIG_SMP */
 222
 223 /* wait for all the CPUs to hit real mode but timeout if they don't come in */
 224 #if defined(CONFIG_SMP) && defined(CONFIG_PPC64)
 225 static void __maybe_unused crash_kexec_wait_realmode(int cpu)
 226 {
 227         unsigned int msecs;
 228         int i;
 229
 230         msecs = REAL_MODE_TIMEOUT;
 231         for (i=0; i < nr_cpu_ids && msecs > 0; i++) {
 232                 if (i == cpu)
 233                         continue;
 234
 235                 while (paca[i].kexec_state < KEXEC_STATE_REAL_MODE) {
 236                         barrier();
 237                         if (!cpu_possible(i) || !cpu_online(i) || (msecs <= 0))
 238                                 break;
 239                         msecs--;
 240                         mdelay(1);
 241                 }
 242         }
 243         mb();
 244 }
 245 #else
 246 static inline void crash_kexec_wait_realmode(int cpu) {}
 247 #endif  /* CONFIG_SMP && CONFIG_PPC64 */
 248
 249 /*
 250  * Register a function to be called on shutdown.  Only use this if you
 251  * can't reset your device in the second kernel.
 252  */
 253 int crash_shutdown_register(crash_shutdown_t handler)
 254 {
 255         unsigned int i, rc;
 256
 257         spin_lock(&crash_handlers_lock);
 258         for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
 259                 if (!crash_shutdown_handles[i]) {
 260                         /* Insert handle at first empty entry */
 261                         crash_shutdown_handles[i] = handler;
 262                         rc = 0;
 263                         break;
 264                 }
 265
 266         if (i == CRASH_HANDLER_MAX) {
 267                 printk(KERN_ERR "Crash shutdown handles full, "
 268                        "not registered.\n");
 269                 rc = 1;
 270         }
 271
 272         spin_unlock(&crash_handlers_lock);
 273         return rc;
 274 }
 275 EXPORT_SYMBOL(crash_shutdown_register);
 276
 277 int crash_shutdown_unregister(crash_shutdown_t handler)
 278 {
 279         unsigned int i, rc;
 280
 281         spin_lock(&crash_handlers_lock);
 282         for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
 283                 if (crash_shutdown_handles[i] == handler)
 284                         break;
 285
 286         if (i == CRASH_HANDLER_MAX) {
 287                 printk(KERN_ERR "Crash shutdown handle not found\n");
 288                 rc = 1;
 289         } else {
 290                 /* Shift handles down */
 291                 for (; i < (CRASH_HANDLER_MAX - 1); i++)
 292                         crash_shutdown_handles[i] =
 293                                 crash_shutdown_handles[i+1];
 294                 /*
 295                  * Reset last entry to NULL now that it has been shifted down,
 296                  * this will allow new handles to be added here.
 297                  */
 298                 crash_shutdown_handles[i] = NULL;
 299                 rc = 0;
 300         }
 301
 302         spin_unlock(&crash_handlers_lock);
 303         return rc;
 304 }
 305 EXPORT_SYMBOL(crash_shutdown_unregister);
 306
 307 void default_machine_crash_shutdown(struct pt_regs *regs)
 308 {
 309         unsigned int i;
 310         int (*old_handler)(struct pt_regs *regs);
 311
 312         /*
 313          * This function is only called after the system
 314          * has panicked or is otherwise in a critical state.
 315          * The minimum amount of code to allow a kexec'd kernel
 316          * to run successfully needs to happen here.
 317          *
 318          * In practice this means stopping other cpus in
 319          * an SMP system.
 320          * The kernel is broken so disable interrupts.
 321          */
 322         hard_irq_disable();
 323
 324         /*
 325          * Make a note of crashing cpu. Will be used in machine_kexec
 326          * such that another IPI will not be sent.
 327          */
 328         crashing_cpu = smp_processor_id();
 329
 330         /*
 331          * If we came in via system reset, wait a while for the secondary
 332          * CPUs to enter.
 333          */
 334         if (TRAP(regs) == 0x100)
 335                 mdelay(PRIMARY_TIMEOUT);
 336
 337         crash_kexec_prepare_cpus(crashing_cpu);
 338
 339         crash_save_cpu(regs, crashing_cpu);
 340
 341         time_to_dump = 1;
 342
 343         crash_kexec_wait_realmode(crashing_cpu);
 344
 345         machine_kexec_mask_interrupts();
 346
 347         /*
 348          * Call registered shutdown routines safely.  Swap out
 349          * __debugger_fault_handler, and replace on exit.
 350          */
 351         old_handler = __debugger_fault_handler;
 352         __debugger_fault_handler = handle_fault;
 353         crash_shutdown_cpu = smp_processor_id();
 354         for (i = 0; i < CRASH_HANDLER_MAX && crash_shutdown_handles[i]; i++) {
 355                 if (setjmp(crash_shutdown_buf) == 0) {
 356                         /*
 357                          * Insert syncs and delay to ensure
 358                          * instructions in the dangerous region don't
 359                          * leak away from this protected region.
 360                          */
 361                         asm volatile("sync; isync");
 362                         /* dangerous region */
 363                         crash_shutdown_handles[i]();
 364                         asm volatile("sync; isync");
 365                 }
 366         }
 367         crash_shutdown_cpu = -1;
 368         __debugger_fault_handler = old_handler;
 369
 370         if (ppc_md.kexec_cpu_down)
 371                 ppc_md.kexec_cpu_down(1, 0);
 372 }