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