arch/powerpc/kexec/crash.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Architecture specific (PPC64) functions for kexec based crash dumps.
   4  *
   5  * Copyright (C) 2005, IBM Corp.
   6  *
   7  * Created by: Haren Myneni
   8  */
   9
  10 #include <linux/kernel.h>
  11 #include <linux/smp.h>
  12 #include <linux/reboot.h>
  13 #include <linux/kexec.h>
  14 #include <linux/export.h>
  15 #include <linux/crash_dump.h>
  16 #include <linux/delay.h>
  17 #include <linux/irq.h>
  18 #include <linux/types.h>
  19
  20 #include <asm/processor.h>
  21 #include <asm/machdep.h>
  22 #include <asm/kexec.h>
  23 #include <asm/prom.h>
  24 #include <asm/smp.h>
  25 #include <asm/setjmp.h>
  26 #include <asm/debug.h>
  27
  28 /*
  29  * The primary CPU waits a while for all secondary CPUs to enter. This is to
  30  * avoid sending an IPI if the secondary CPUs are entering
  31  * crash_kexec_secondary on their own (eg via a system reset).
  32  *
  33  * The secondary timeout has to be longer than the primary. Both timeouts are
  34  * in milliseconds.
  35  */
  36 #define PRIMARY_TIMEOUT         500
  37 #define SECONDARY_TIMEOUT       1000
  38
  39 #define IPI_TIMEOUT             10000
  40 #define REAL_MODE_TIMEOUT       10000
  41
  42 static int time_to_dump;
  43 /*
  44  * crash_wake_offline should be set to 1 by platforms that intend to wake
  45  * up offline cpus prior to jumping to a kdump kernel. Currently powernv
  46  * sets it to 1, since we want to avoid things from happening when an
  47  * offline CPU wakes up due to something like an HMI (malfunction error),
  48  * which propagates to all threads.
  49  */
  50 int crash_wake_offline;
  51
  52 #define CRASH_HANDLER_MAX 3
  53 /* List of shutdown handles */
  54 static crash_shutdown_t crash_shutdown_handles[CRASH_HANDLER_MAX];
  55 static DEFINE_SPINLOCK(crash_handlers_lock);
  56
  57 static unsigned long crash_shutdown_buf[JMP_BUF_LEN];
  58 static int crash_shutdown_cpu = -1;
  59
  60 static int handle_fault(struct pt_regs *regs)
  61 {
  62         if (crash_shutdown_cpu == smp_processor_id())
  63                 longjmp(crash_shutdown_buf, 1);
  64         return 0;
  65 }
  66
  67 #ifdef CONFIG_SMP
  68
  69 static atomic_t cpus_in_crash;
  70 void crash_ipi_callback(struct pt_regs *regs)
  71 {
  72         static cpumask_t cpus_state_saved = CPU_MASK_NONE;
  73
  74         int cpu = smp_processor_id();
  75
  76         hard_irq_disable();
  77         if (!cpumask_test_cpu(cpu, &cpus_state_saved)) {
  78                 crash_save_cpu(regs, cpu);
  79                 cpumask_set_cpu(cpu, &cpus_state_saved);
  80         }
  81
  82         atomic_inc(&cpus_in_crash);
  83         smp_mb__after_atomic();
  84
  85         /*
  86          * Starting the kdump boot.
  87          * This barrier is needed to make sure that all CPUs are stopped.
  88          */
  89         while (!time_to_dump)
  90                 cpu_relax();
  91
  92         if (ppc_md.kexec_cpu_down)
  93                 ppc_md.kexec_cpu_down(1, 1);
  94
  95 #ifdef CONFIG_PPC64
  96         kexec_smp_wait();
  97 #else
  98         for (;;);       /* FIXME */
  99 #endif
 100
 101         /* NOTREACHED */
 102 }
 103
 104 static void crash_kexec_prepare_cpus(int cpu)
 105 {
 106         unsigned int msecs;
 107         unsigned int ncpus = num_online_cpus() - 1;/* Excluding the panic cpu */
 108         int tries = 0;
 109         int (*old_handler)(struct pt_regs *regs);
 110
 111         printk(KERN_EMERG "Sending IPI to other CPUs\n");
 112
 113         if (crash_wake_offline)
 114                 ncpus = num_present_cpus() - 1;
 115
 116         crash_send_ipi(crash_ipi_callback);
 117         smp_wmb();
 118
 119 again:
 120         /*
 121          * FIXME: Until we will have the way to stop other CPUs reliably,
 122          * the crash CPU will send an IPI and wait for other CPUs to
 123          * respond.
 124          */
 125         msecs = IPI_TIMEOUT;
 126         while ((atomic_read(&cpus_in_crash) < ncpus) && (--msecs > 0))
 127                 mdelay(1);
 128
 129         /* Would it be better to replace the trap vector here? */
 130
 131         if (atomic_read(&cpus_in_crash) >= ncpus) {
 132                 printk(KERN_EMERG "IPI complete\n");
 133                 return;
 134         }
 135
 136         printk(KERN_EMERG "ERROR: %d cpu(s) not responding\n",
 137                 ncpus - atomic_read(&cpus_in_crash));
 138
 139         /*
 140          * If we have a panic timeout set then we can't wait indefinitely
 141          * for someone to activate system reset. We also give up on the
 142          * second time through if system reset fail to work.
 143          */
 144         if ((panic_timeout > 0) || (tries > 0))
 145                 return;
 146
 147         /*
 148          * A system reset will cause all CPUs to take an 0x100 exception.
 149          * The primary CPU returns here via setjmp, and the secondary
 150          * CPUs reexecute the crash_kexec_secondary path.
 151          */
 152         old_handler = __debugger;
 153         __debugger = handle_fault;
 154         crash_shutdown_cpu = smp_processor_id();
 155
 156         if (setjmp(crash_shutdown_buf) == 0) {
 157                 printk(KERN_EMERG "Activate system reset (dumprestart) "
 158                                   "to stop other cpu(s)\n");
 159
 160                 /*
 161                  * A system reset will force all CPUs to execute the
 162                  * crash code again. We need to reset cpus_in_crash so we
 163                  * wait for everyone to do this.
 164                  */
 165                 atomic_set(&cpus_in_crash, 0);
 166                 smp_mb();
 167
 168                 while (atomic_read(&cpus_in_crash) < ncpus)
 169                         cpu_relax();
 170         }
 171
 172         crash_shutdown_cpu = -1;
 173         __debugger = old_handler;
 174
 175         tries++;
 176         goto again;
 177 }
 178
 179 /*
 180  * This function will be called by secondary cpus.
 181  */
 182 void crash_kexec_secondary(struct pt_regs *regs)
 183 {
 184         unsigned long flags;
 185         int msecs = SECONDARY_TIMEOUT;
 186
 187         local_irq_save(flags);
 188
 189         /* Wait for the primary crash CPU to signal its progress */
 190         while (crashing_cpu < 0) {
 191                 if (--msecs < 0) {
 192                         /* No response, kdump image may not have been loaded */
 193                         local_irq_restore(flags);
 194                         return;
 195                 }
 196
 197                 mdelay(1);
 198         }
 199
 200         crash_ipi_callback(regs);
 201 }
 202
 203 #else   /* ! CONFIG_SMP */
 204
 205 static void crash_kexec_prepare_cpus(int cpu)
 206 {
 207         /*
 208          * move the secondaries to us so that we can copy
 209          * the new kernel 0-0x100 safely
 210          *
 211          * do this if kexec in setup.c ?
 212          */
 213 #ifdef CONFIG_PPC64
 214         smp_release_cpus();
 215 #else
 216         /* FIXME */
 217 #endif
 218 }
 219
 220 void crash_kexec_secondary(struct pt_regs *regs)
 221 {
 222 }
 223 #endif  /* CONFIG_SMP */
 224
 225 /* wait for all the CPUs to hit real mode but timeout if they don't come in */
 226 #if defined(CONFIG_SMP) && defined(CONFIG_PPC64)
 227 static void __maybe_unused crash_kexec_wait_realmode(int cpu)
 228 {
 229         unsigned int msecs;
 230         int i;
 231
 232         msecs = REAL_MODE_TIMEOUT;
 233         for (i=0; i < nr_cpu_ids && msecs > 0; i++) {
 234                 if (i == cpu)
 235                         continue;
 236
 237                 while (paca_ptrs[i]->kexec_state < KEXEC_STATE_REAL_MODE) {
 238                         barrier();
 239                         if (!cpu_possible(i) || !cpu_online(i) || (msecs <= 0))
 240                                 break;
 241                         msecs--;
 242                         mdelay(1);
 243                 }
 244         }
 245         mb();
 246 }
 247 #else
 248 static inline void crash_kexec_wait_realmode(int cpu) {}
 249 #endif  /* CONFIG_SMP && CONFIG_PPC64 */
 250
 251 /*
 252  * Register a function to be called on shutdown.  Only use this if you
 253  * can't reset your device in the second kernel.
 254  */
 255 int crash_shutdown_register(crash_shutdown_t handler)
 256 {
 257         unsigned int i, rc;
 258
 259         spin_lock(&crash_handlers_lock);
 260         for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
 261                 if (!crash_shutdown_handles[i]) {
 262                         /* Insert handle at first empty entry */
 263                         crash_shutdown_handles[i] = handler;
 264                         rc = 0;
 265                         break;
 266                 }
 267
 268         if (i == CRASH_HANDLER_MAX) {
 269                 printk(KERN_ERR "Crash shutdown handles full, "
 270                        "not registered.\n");
 271                 rc = 1;
 272         }
 273
 274         spin_unlock(&crash_handlers_lock);
 275         return rc;
 276 }
 277 EXPORT_SYMBOL(crash_shutdown_register);
 278
 279 int crash_shutdown_unregister(crash_shutdown_t handler)
 280 {
 281         unsigned int i, rc;
 282
 283         spin_lock(&crash_handlers_lock);
 284         for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
 285                 if (crash_shutdown_handles[i] == handler)
 286                         break;
 287
 288         if (i == CRASH_HANDLER_MAX) {
 289                 printk(KERN_ERR "Crash shutdown handle not found\n");
 290                 rc = 1;
 291         } else {
 292                 /* Shift handles down */
 293                 for (; i < (CRASH_HANDLER_MAX - 1); i++)
 294                         crash_shutdown_handles[i] =
 295                                 crash_shutdown_handles[i+1];
 296                 /*
 297                  * Reset last entry to NULL now that it has been shifted down,
 298                  * this will allow new handles to be added here.
 299                  */
 300                 crash_shutdown_handles[i] = NULL;
 301                 rc = 0;
 302         }
 303
 304         spin_unlock(&crash_handlers_lock);
 305         return rc;
 306 }
 307 EXPORT_SYMBOL(crash_shutdown_unregister);
 308
 309 void default_machine_crash_shutdown(struct pt_regs *regs)
 310 {
 311         unsigned int i;
 312         int (*old_handler)(struct pt_regs *regs);
 313
 314         /* Avoid hardlocking with irresponsive CPU holding logbuf_lock */
 315         printk_nmi_enter();
 316
 317         /*
 318          * This function is only called after the system
 319          * has panicked or is otherwise in a critical state.
 320          * The minimum amount of code to allow a kexec'd kernel
 321          * to run successfully needs to happen here.
 322          *
 323          * In practice this means stopping other cpus in
 324          * an SMP system.
 325          * The kernel is broken so disable interrupts.
 326          */
 327         hard_irq_disable();
 328
 329         /*
 330          * Make a note of crashing cpu. Will be used in machine_kexec
 331          * such that another IPI will not be sent.
 332          */
 333         crashing_cpu = smp_processor_id();
 334
 335         /*
 336          * If we came in via system reset, wait a while for the secondary
 337          * CPUs to enter.
 338          */
 339         if (TRAP(regs) == 0x100)
 340                 mdelay(PRIMARY_TIMEOUT);
 341
 342         crash_kexec_prepare_cpus(crashing_cpu);
 343
 344         crash_save_cpu(regs, crashing_cpu);
 345
 346         time_to_dump = 1;
 347
 348         crash_kexec_wait_realmode(crashing_cpu);
 349
 350         machine_kexec_mask_interrupts();
 351
 352         /*
 353          * Call registered shutdown routines safely.  Swap out
 354          * __debugger_fault_handler, and replace on exit.
 355          */
 356         old_handler = __debugger_fault_handler;
 357         __debugger_fault_handler = handle_fault;
 358         crash_shutdown_cpu = smp_processor_id();
 359         for (i = 0; i < CRASH_HANDLER_MAX && crash_shutdown_handles[i]; i++) {
 360                 if (setjmp(crash_shutdown_buf) == 0) {
 361                         /*
 362                          * Insert syncs and delay to ensure
 363                          * instructions in the dangerous region don't
 364                          * leak away from this protected region.
 365                          */
 366                         asm volatile("sync; isync");
 367                         /* dangerous region */
 368                         crash_shutdown_handles[i]();
 369                         asm volatile("sync; isync");
 370                 }
 371         }
 372         crash_shutdown_cpu = -1;
 373         __debugger_fault_handler = old_handler;
 374
 375         if (ppc_md.kexec_cpu_down)
 376                 ppc_md.kexec_cpu_down(1, 0);
 377 }