arch/arm64/kernel/traps.c

   1 /*
   2  * Based on arch/arm/kernel/traps.c
   3  *
   4  * Copyright (C) 1995-2009 Russell King
   5  * Copyright (C) 2012 ARM Ltd.
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <linux/bug.h>
  21 #include <linux/signal.h>
  22 #include <linux/personality.h>
  23 #include <linux/kallsyms.h>
  24 #include <linux/spinlock.h>
  25 #include <linux/uaccess.h>
  26 #include <linux/hardirq.h>
  27 #include <linux/kdebug.h>
  28 #include <linux/module.h>
  29 #include <linux/kexec.h>
  30 #include <linux/delay.h>
  31 #include <linux/init.h>
  32 #include <linux/sched.h>
  33 #include <linux/syscalls.h>
  34
  35 #include <asm/atomic.h>
  36 #include <asm/barrier.h>
  37 #include <asm/bug.h>
  38 #include <asm/debug-monitors.h>
  39 #include <asm/esr.h>
  40 #include <asm/insn.h>
  41 #include <asm/traps.h>
  42 #include <asm/stack_pointer.h>
  43 #include <asm/stacktrace.h>
  44 #include <asm/exception.h>
  45 #include <asm/system_misc.h>
  46 #include <asm/esr.h>
  47 #include <asm/edac.h>
  48
  49 #include <trace/events/exception.h>
  50
  51 static const char *handler[]= {
  52         "Synchronous Abort",
  53         "IRQ",
  54         "FIQ",
  55         "Error"
  56 };
  57
  58 int show_unhandled_signals = 0;
  59
  60 /*
  61  * Dump out the contents of some memory nicely...
  62  */
  63 static void dump_mem(const char *lvl, const char *str, unsigned long bottom,
  64                      unsigned long top, bool compat)
  65 {
  66         unsigned long first;
  67         mm_segment_t fs;
  68         int i;
  69         unsigned int width = compat ? 4 : 8;
  70
  71         /*
  72          * We need to switch to kernel mode so that we can use __get_user
  73          * to safely read from kernel space.
  74          */
  75         fs = get_fs();
  76         set_fs(KERNEL_DS);
  77
  78         printk("%s%s(0x%016lx to 0x%016lx)\n", lvl, str, bottom, top);
  79
  80         for (first = bottom & ~31; first < top; first += 32) {
  81                 unsigned long p;
  82                 char str[sizeof(" 12345678") * 8 + 1];
  83
  84                 memset(str, ' ', sizeof(str));
  85                 str[sizeof(str) - 1] = '\0';
  86
  87                 for (p = first, i = 0; i < (32 / width)
  88                                         && p < top; i++, p += width) {
  89                         if (p >= bottom && p < top) {
  90                                 unsigned long val;
  91
  92                                 if (width == 8) {
  93                                         if (__get_user(val, (unsigned long *)p) == 0)
  94                                                 sprintf(str + i * 17, " %016lx", val);
  95                                         else
  96                                                 sprintf(str + i * 17, " ????????????????");
  97                                 } else {
  98                                         if (__get_user(val, (unsigned int *)p) == 0)
  99                                                 sprintf(str + i * 9, " %08lx", val);
 100                                         else
 101                                                 sprintf(str + i * 9, " ????????");
 102                                 }
 103                         }
 104                 }
 105                 printk("%s%04lx:%s\n", lvl, first & 0xffff, str);
 106         }
 107
 108         set_fs(fs);
 109 }
 110
 111 static void dump_backtrace_entry(unsigned long where)
 112 {
 113         /*
 114          * Note that 'where' can have a physical address, but it's not handled.
 115          */
 116         print_ip_sym(where);
 117 }
 118
 119 static void __dump_instr(const char *lvl, struct pt_regs *regs)
 120 {
 121         unsigned long addr = instruction_pointer(regs);
 122         char str[sizeof("00000000 ") * 5 + 2 + 1], *p = str;
 123         int i;
 124
 125         for (i = -4; i < 1; i++) {
 126                 unsigned int val, bad;
 127
 128                 bad = get_user(val, &((u32 *)addr)[i]);
 129
 130                 if (!bad)
 131                         p += sprintf(p, i == 0 ? "(%08x) " : "%08x ", val);
 132                 else {
 133                         p += sprintf(p, "bad PC value");
 134                         break;
 135                 }
 136         }
 137         printk("%sCode: %s\n", lvl, str);
 138 }
 139
 140 static void dump_instr(const char *lvl, struct pt_regs *regs)
 141 {
 142         if (!user_mode(regs)) {
 143                 mm_segment_t fs = get_fs();
 144                 set_fs(KERNEL_DS);
 145                 __dump_instr(lvl, regs);
 146                 set_fs(fs);
 147         } else {
 148                 __dump_instr(lvl, regs);
 149         }
 150 }
 151
 152 static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 153 {
 154         struct stackframe frame;
 155         unsigned long irq_stack_ptr;
 156         int skip;
 157
 158         pr_debug("%s(regs = %pK tsk = %pK)\n", __func__, regs, tsk);
 159
 160         if (!tsk)
 161                 tsk = current;
 162
 163         if (!try_get_task_stack(tsk))
 164                 return;
 165
 166         /*
 167          * Switching between stacks is valid when tracing current and in
 168          * non-preemptible context.
 169          */
 170         if (tsk == current && !preemptible())
 171                 irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
 172         else
 173                 irq_stack_ptr = 0;
 174
 175         pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
 176
 177         if (!tsk)
 178                 tsk = current;
 179
 180         if (tsk == current) {
 181                 frame.fp = (unsigned long)__builtin_frame_address(0);
 182                 frame.sp = current_stack_pointer;
 183                 frame.pc = (unsigned long)dump_backtrace;
 184         } else {
 185                 /*
 186                  * task blocked in __switch_to
 187                  */
 188                 frame.fp = thread_saved_fp(tsk);
 189                 frame.sp = thread_saved_sp(tsk);
 190                 frame.pc = thread_saved_pc(tsk);
 191         }
 192 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 193         frame.graph = tsk->curr_ret_stack;
 194 #endif
 195
 196         skip = !!regs;
 197         printk("Call trace:\n");
 198         while (1) {
 199                 unsigned long where = frame.pc;
 200                 unsigned long stack;
 201                 int ret;
 202
 203                 /* skip until specified stack frame */
 204                 if (!skip) {
 205                         dump_backtrace_entry(where);
 206                 } else if (frame.fp == regs->regs[29]) {
 207                         skip = 0;
 208                         /*
 209                          * Mostly, this is the case where this function is
 210                          * called in panic/abort. As exception handler's
 211                          * stack frame does not contain the corresponding pc
 212                          * at which an exception has taken place, use regs->pc
 213                          * instead.
 214                          */
 215                         dump_backtrace_entry(regs->pc);
 216                 }
 217                 ret = unwind_frame(tsk, &frame);
 218                 if (ret < 0)
 219                         break;
 220                 stack = frame.sp;
 221                 if (in_exception_text(where)) {
 222                         /*
 223                          * If we switched to the irq_stack before calling this
 224                          * exception handler, then the pt_regs will be on the
 225                          * task stack. The easiest way to tell is if the large
 226                          * pt_regs would overlap with the end of the irq_stack.
 227                          */
 228                         if (stack < irq_stack_ptr &&
 229                             (stack + sizeof(struct pt_regs)) > irq_stack_ptr)
 230                                 stack = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);
 231
 232                         dump_mem("", "Exception stack", stack,
 233                                  stack + sizeof(struct pt_regs), false);
 234                 }
 235         }
 236
 237         put_task_stack(tsk);
 238 }
 239
 240 void show_stack(struct task_struct *tsk, unsigned long *sp)
 241 {
 242         dump_backtrace(NULL, tsk);
 243         barrier();
 244 }
 245
 246 #ifdef CONFIG_PREEMPT
 247 #define S_PREEMPT " PREEMPT"
 248 #else
 249 #define S_PREEMPT ""
 250 #endif
 251 #define S_SMP " SMP"
 252
 253 static int __die(const char *str, int err, struct pt_regs *regs)
 254 {
 255         struct task_struct *tsk = current;
 256         static int die_counter;
 257         int ret;
 258
 259         pr_emerg("Internal error: %s: %x [#%d]" S_PREEMPT S_SMP "\n",
 260                  str, err, ++die_counter);
 261
 262         /* trap and error numbers are mostly meaningless on ARM */
 263         ret = notify_die(DIE_OOPS, str, regs, err, 0, SIGSEGV);
 264         if (ret == NOTIFY_STOP)
 265                 return ret;
 266
 267         print_modules();
 268         __show_regs(regs);
 269         pr_emerg("Process %.*s (pid: %d, stack limit = 0x%p)\n",
 270                  TASK_COMM_LEN, tsk->comm, task_pid_nr(tsk),
 271                  end_of_stack(tsk));
 272
 273         if (!user_mode(regs) || in_interrupt()) {
 274                 dump_backtrace(regs, tsk);
 275                 dump_instr(KERN_EMERG, regs);
 276         }
 277
 278         return ret;
 279 }
 280
 281 static arch_spinlock_t die_lock = __ARCH_SPIN_LOCK_UNLOCKED;
 282 static int die_owner = -1;
 283 static unsigned int die_nest_count;
 284
 285 static unsigned long oops_begin(void)
 286 {
 287         int cpu;
 288         unsigned long flags;
 289
 290         oops_enter();
 291
 292         /* racy, but better than risking deadlock. */
 293         raw_local_irq_save(flags);
 294         cpu = smp_processor_id();
 295         if (!arch_spin_trylock(&die_lock)) {
 296                 if (cpu == die_owner)
 297                         /* nested oops. should stop eventually */;
 298                 else
 299                         arch_spin_lock(&die_lock);
 300         }
 301         die_nest_count++;
 302         die_owner = cpu;
 303         console_verbose();
 304         bust_spinlocks(1);
 305         return flags;
 306 }
 307
 308 static void oops_end(unsigned long flags, struct pt_regs *regs, int notify)
 309 {
 310         if (regs && kexec_should_crash(current))
 311                 crash_kexec(regs);
 312
 313         bust_spinlocks(0);
 314         die_owner = -1;
 315         add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
 316         die_nest_count--;
 317         if (!die_nest_count)
 318                 /* Nest count reaches zero, release the lock. */
 319                 arch_spin_unlock(&die_lock);
 320         raw_local_irq_restore(flags);
 321         oops_exit();
 322
 323         if (in_interrupt())
 324                 panic("Fatal exception in interrupt");
 325         if (panic_on_oops)
 326                 panic("Fatal exception");
 327         if (notify != NOTIFY_STOP)
 328                 do_exit(SIGSEGV);
 329 }
 330
 331 /*
 332  * This function is protected against re-entrancy.
 333  */
 334 void die(const char *str, struct pt_regs *regs, int err)
 335 {
 336         enum bug_trap_type bug_type = BUG_TRAP_TYPE_NONE;
 337         unsigned long flags = oops_begin();
 338         int ret;
 339
 340         if (!user_mode(regs))
 341                 bug_type = report_bug(regs->pc, regs);
 342         if (bug_type != BUG_TRAP_TYPE_NONE)
 343                 str = "Oops - BUG";
 344
 345         ret = __die(str, err, regs);
 346
 347         oops_end(flags, regs, ret);
 348 }
 349
 350 void arm64_notify_die(const char *str, struct pt_regs *regs,
 351                       struct siginfo *info, int err)
 352 {
 353         if (user_mode(regs)) {
 354                 current->thread.fault_address = 0;
 355                 current->thread.fault_code = err;
 356                 force_sig_info(info->si_signo, info, current);
 357         } else {
 358                 die(str, regs, err);
 359         }
 360 }
 361
 362 static LIST_HEAD(undef_hook);
 363 static DEFINE_RAW_SPINLOCK(undef_lock);
 364
 365 void register_undef_hook(struct undef_hook *hook)
 366 {
 367         unsigned long flags;
 368
 369         raw_spin_lock_irqsave(&undef_lock, flags);
 370         list_add(&hook->node, &undef_hook);
 371         raw_spin_unlock_irqrestore(&undef_lock, flags);
 372 }
 373
 374 void unregister_undef_hook(struct undef_hook *hook)
 375 {
 376         unsigned long flags;
 377
 378         raw_spin_lock_irqsave(&undef_lock, flags);
 379         list_del(&hook->node);
 380         raw_spin_unlock_irqrestore(&undef_lock, flags);
 381 }
 382
 383 static int call_undef_hook(struct pt_regs *regs)
 384 {
 385         struct undef_hook *hook;
 386         unsigned long flags;
 387         u32 instr;
 388         int (*fn)(struct pt_regs *regs, u32 instr) = NULL;
 389         void __user *pc = (void __user *)instruction_pointer(regs);
 390
 391         if (!user_mode(regs))
 392                 return 1;
 393
 394         if (compat_thumb_mode(regs)) {
 395                 /* 16-bit Thumb instruction */
 396                 if (get_user(instr, (u16 __user *)pc))
 397                         goto exit;
 398                 instr = le16_to_cpu(instr);
 399                 if (aarch32_insn_is_wide(instr)) {
 400                         u32 instr2;
 401
 402                         if (get_user(instr2, (u16 __user *)(pc + 2)))
 403                                 goto exit;
 404                         instr2 = le16_to_cpu(instr2);
 405                         instr = (instr << 16) | instr2;
 406                 }
 407         } else {
 408                 /* 32-bit ARM instruction */
 409                 if (get_user(instr, (u32 __user *)pc))
 410                         goto exit;
 411                 instr = le32_to_cpu(instr);
 412         }
 413
 414         raw_spin_lock_irqsave(&undef_lock, flags);
 415         list_for_each_entry(hook, &undef_hook, node)
 416                 if ((instr & hook->instr_mask) == hook->instr_val &&
 417                         (regs->pstate & hook->pstate_mask) == hook->pstate_val)
 418                         fn = hook->fn;
 419
 420         raw_spin_unlock_irqrestore(&undef_lock, flags);
 421 exit:
 422         return fn ? fn(regs, instr) : 1;
 423 }
 424
 425 asmlinkage void __exception do_undefinstr(struct pt_regs *regs)
 426 {
 427         siginfo_t info;
 428         void __user *pc = (void __user *)instruction_pointer(regs);
 429
 430         /* check for AArch32 breakpoint instructions */
 431         if (!aarch32_break_handler(regs))
 432                 return;
 433
 434         if (call_undef_hook(regs) == 0)
 435                 return;
 436
 437         trace_undef_instr(regs, (void *)pc);
 438
 439         if (unhandled_signal(current, SIGILL) && show_unhandled_signals_ratelimited()) {
 440                 pr_info("%s[%d]: undefined instruction: pc=%p\n",
 441                         current->comm, task_pid_nr(current), pc);
 442                 dump_instr(KERN_INFO, regs);
 443         }
 444
 445         info.si_signo = SIGILL;
 446         info.si_errno = 0;
 447         info.si_code  = ILL_ILLOPC;
 448         info.si_addr  = pc;
 449
 450         arm64_notify_die("Oops - undefined instruction", regs, &info, 0);
 451 }
 452
 453 static void cntvct_read_handler(unsigned int esr, struct pt_regs *regs)
 454 {
 455         int rt = (esr & ESR_ELx_SYS64_ISS_RT_MASK) >> ESR_ELx_SYS64_ISS_RT_SHIFT;
 456
 457         isb();
 458         if (rt != 31)
 459                 regs->regs[rt] = arch_counter_get_cntvct();
 460         regs->pc += 4;
 461 }
 462
 463 static void cntfrq_read_handler(unsigned int esr, struct pt_regs *regs)
 464 {
 465         int rt = (esr & ESR_ELx_SYS64_ISS_RT_MASK) >> ESR_ELx_SYS64_ISS_RT_SHIFT;
 466
 467         if (rt != 31)
 468                 regs->regs[rt] = read_sysreg(cntfrq_el0);
 469         regs->pc += 4;
 470 }
 471
 472 asmlinkage void __exception do_sysinstr(unsigned int esr, struct pt_regs *regs)
 473 {
 474         if ((esr & ESR_ELx_SYS64_ISS_SYS_OP_MASK) == ESR_ELx_SYS64_ISS_SYS_CNTVCT) {
 475                 cntvct_read_handler(esr, regs);
 476                 return;
 477         } else if ((esr & ESR_ELx_SYS64_ISS_SYS_OP_MASK) == ESR_ELx_SYS64_ISS_SYS_CNTFRQ) {
 478                 cntfrq_read_handler(esr, regs);
 479                 return;
 480         }
 481
 482         do_undefinstr(regs);
 483 }
 484
 485 long compat_arm_syscall(struct pt_regs *regs);
 486
 487 asmlinkage long do_ni_syscall(struct pt_regs *regs)
 488 {
 489 #ifdef CONFIG_COMPAT
 490         long ret;
 491         if (is_compat_task()) {
 492                 ret = compat_arm_syscall(regs);
 493                 if (ret != -ENOSYS)
 494                         return ret;
 495         }
 496 #endif
 497
 498         if (show_unhandled_signals_ratelimited()) {
 499                 pr_info("%s[%d]: syscall %d\n", current->comm,
 500                         task_pid_nr(current), (int)regs->syscallno);
 501                 dump_instr("", regs);
 502                 if (user_mode(regs))
 503                         __show_regs(regs);
 504         }
 505
 506         return sys_ni_syscall();
 507 }
 508
 509 static const char *esr_class_str[] = {
 510         [0 ... ESR_ELx_EC_MAX]          = "UNRECOGNIZED EC",
 511         [ESR_ELx_EC_UNKNOWN]            = "Unknown/Uncategorized",
 512         [ESR_ELx_EC_WFx]                = "WFI/WFE",
 513         [ESR_ELx_EC_CP15_32]            = "CP15 MCR/MRC",
 514         [ESR_ELx_EC_CP15_64]            = "CP15 MCRR/MRRC",
 515         [ESR_ELx_EC_CP14_MR]            = "CP14 MCR/MRC",
 516         [ESR_ELx_EC_CP14_LS]            = "CP14 LDC/STC",
 517         [ESR_ELx_EC_FP_ASIMD]           = "ASIMD",
 518         [ESR_ELx_EC_CP10_ID]            = "CP10 MRC/VMRS",
 519         [ESR_ELx_EC_CP14_64]            = "CP14 MCRR/MRRC",
 520         [ESR_ELx_EC_ILL]                = "PSTATE.IL",
 521         [ESR_ELx_EC_SVC32]              = "SVC (AArch32)",
 522         [ESR_ELx_EC_HVC32]              = "HVC (AArch32)",
 523         [ESR_ELx_EC_SMC32]              = "SMC (AArch32)",
 524         [ESR_ELx_EC_SVC64]              = "SVC (AArch64)",
 525         [ESR_ELx_EC_HVC64]              = "HVC (AArch64)",
 526         [ESR_ELx_EC_SMC64]              = "SMC (AArch64)",
 527         [ESR_ELx_EC_SYS64]              = "MSR/MRS (AArch64)",
 528         [ESR_ELx_EC_IMP_DEF]            = "EL3 IMP DEF",
 529         [ESR_ELx_EC_IABT_LOW]           = "IABT (lower EL)",
 530         [ESR_ELx_EC_IABT_CUR]           = "IABT (current EL)",
 531         [ESR_ELx_EC_PC_ALIGN]           = "PC Alignment",
 532         [ESR_ELx_EC_DABT_LOW]           = "DABT (lower EL)",
 533         [ESR_ELx_EC_DABT_CUR]           = "DABT (current EL)",
 534         [ESR_ELx_EC_SP_ALIGN]           = "SP Alignment",
 535         [ESR_ELx_EC_FP_EXC32]           = "FP (AArch32)",
 536         [ESR_ELx_EC_FP_EXC64]           = "FP (AArch64)",
 537         [ESR_ELx_EC_SERROR]             = "SError",
 538         [ESR_ELx_EC_BREAKPT_LOW]        = "Breakpoint (lower EL)",
 539         [ESR_ELx_EC_BREAKPT_CUR]        = "Breakpoint (current EL)",
 540         [ESR_ELx_EC_SOFTSTP_LOW]        = "Software Step (lower EL)",
 541         [ESR_ELx_EC_SOFTSTP_CUR]        = "Software Step (current EL)",
 542         [ESR_ELx_EC_WATCHPT_LOW]        = "Watchpoint (lower EL)",
 543         [ESR_ELx_EC_WATCHPT_CUR]        = "Watchpoint (current EL)",
 544         [ESR_ELx_EC_BKPT32]             = "BKPT (AArch32)",
 545         [ESR_ELx_EC_VECTOR32]           = "Vector catch (AArch32)",
 546         [ESR_ELx_EC_BRK64]              = "BRK (AArch64)",
 547 };
 548
 549 const char *esr_get_class_string(u32 esr)
 550 {
 551         return esr_class_str[ESR_ELx_EC(esr)];
 552 }
 553
 554 /*
 555  * bad_mode handles the impossible case in the exception vector. This is always
 556  * fatal.
 557  */
 558 asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr)
 559 {
 560         console_verbose();
 561
 562         pr_crit("Bad mode in %s handler detected, code 0x%08x -- %s\n",
 563                 handler[reason], esr, esr_get_class_string(esr));
 564
 565         if (esr >> ESR_ELx_EC_SHIFT == ESR_ELx_EC_SERROR) {
 566                 pr_crit("System error detected. ESR.ISS = %08x\n",
 567                         esr & 0xffffff);
 568                 arm64_check_cache_ecc(NULL);
 569         }
 570
 571         local_irq_disable();
 572         panic("bad mode");
 573 }
 574
 575 /*
 576  * bad_el0_sync handles unexpected, but potentially recoverable synchronous
 577  * exceptions taken from EL0. Unlike bad_mode, this returns.
 578  */
 579 asmlinkage void bad_el0_sync(struct pt_regs *regs, int reason, unsigned int esr)
 580 {
 581         siginfo_t info;
 582         void __user *pc = (void __user *)instruction_pointer(regs);
 583         console_verbose();
 584
 585         pr_crit("Bad EL0 synchronous exception detected on CPU%d, code 0x%08x -- %s\n",
 586                 smp_processor_id(), esr, esr_get_class_string(esr));
 587         __show_regs(regs);
 588
 589         info.si_signo = SIGILL;
 590         info.si_errno = 0;
 591         info.si_code  = ILL_ILLOPC;
 592         info.si_addr  = pc;
 593
 594         current->thread.fault_address = 0;
 595         current->thread.fault_code = 0;
 596
 597         force_sig_info(info.si_signo, &info, current);
 598 }
 599
 600 void __pte_error(const char *file, int line, unsigned long val)
 601 {
 602         pr_err("%s:%d: bad pte %016lx.\n", file, line, val);
 603 }
 604
 605 void __pmd_error(const char *file, int line, unsigned long val)
 606 {
 607         pr_err("%s:%d: bad pmd %016lx.\n", file, line, val);
 608 }
 609
 610 void __pud_error(const char *file, int line, unsigned long val)
 611 {
 612         pr_err("%s:%d: bad pud %016lx.\n", file, line, val);
 613 }
 614
 615 void __pgd_error(const char *file, int line, unsigned long val)
 616 {
 617         pr_err("%s:%d: bad pgd %016lx.\n", file, line, val);
 618 }
 619
 620 /* GENERIC_BUG traps */
 621
 622 int is_valid_bugaddr(unsigned long addr)
 623 {
 624         /*
 625          * bug_handler() only called for BRK #BUG_BRK_IMM.
 626          * So the answer is trivial -- any spurious instances with no
 627          * bug table entry will be rejected by report_bug() and passed
 628          * back to the debug-monitors code and handled as a fatal
 629          * unexpected debug exception.
 630          */
 631         return 1;
 632 }
 633
 634 static int bug_handler(struct pt_regs *regs, unsigned int esr)
 635 {
 636         if (user_mode(regs))
 637                 return DBG_HOOK_ERROR;
 638
 639         switch (report_bug(regs->pc, regs)) {
 640         case BUG_TRAP_TYPE_BUG:
 641                 die("Oops - BUG", regs, 0);
 642                 break;
 643
 644         case BUG_TRAP_TYPE_WARN:
 645                 /* Ideally, report_bug() should backtrace for us... but no. */
 646                 dump_backtrace(regs, NULL);
 647                 break;
 648
 649         default:
 650                 /* unknown/unrecognised bug trap type */
 651                 return DBG_HOOK_ERROR;
 652         }
 653
 654         /* If thread survives, skip over the BUG instruction and continue: */
 655         regs->pc += AARCH64_INSN_SIZE;  /* skip BRK and resume */
 656         return DBG_HOOK_HANDLED;
 657 }
 658
 659 static struct break_hook bug_break_hook = {
 660         .esr_val = 0xf2000000 | BUG_BRK_IMM,
 661         .esr_mask = 0xffffffff,
 662         .fn = bug_handler,
 663 };
 664
 665 /*
 666  * Initial handler for AArch64 BRK exceptions
 667  * This handler only used until debug_traps_init().
 668  */
 669 int __init early_brk64(unsigned long addr, unsigned int esr,
 670                 struct pt_regs *regs)
 671 {
 672         return bug_handler(regs, esr) != DBG_HOOK_HANDLED;
 673 }
 674
 675 /* This registration must happen early, before debug_traps_init(). */
 676 void __init trap_init(void)
 677 {
 678         register_break_hook(&bug_break_hook);
 679 }