arch/arm/kernel/kprobes.c

   1 /*
   2  * arch/arm/kernel/kprobes.c
   3  *
   4  * Kprobes on ARM
   5  *
   6  * Abhishek Sagar <sagar.abhishek@gmail.com>
   7  * Copyright (C) 2006, 2007 Motorola Inc.
   8  *
   9  * Nicolas Pitre <nico@marvell.com>
  10  * Copyright (C) 2007 Marvell Ltd.
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License version 2 as
  14  * published by the Free Software Foundation.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  19  * General Public License for more details.
  20  */
  21
  22 #include <linux/kernel.h>
  23 #include <linux/kprobes.h>
  24 #include <linux/module.h>
  25 #include <linux/slab.h>
  26 #include <linux/stop_machine.h>
  27 #include <linux/stringify.h>
  28 #include <asm/traps.h>
  29 #include <asm/cacheflush.h>
  30 #include <linux/percpu.h>
  31 #include <linux/bug.h>
  32
  33 #include "kprobes.h"
  34 #include "patch.h"
  35
  36 #define MIN_STACK_SIZE(addr)                            \
  37         min((unsigned long)MAX_STACK_SIZE,              \
  38             (unsigned long)current_thread_info() + THREAD_START_SP - (addr))
  39
  40 #define flush_insns(addr, size)                         \
  41         flush_icache_range((unsigned long)(addr),       \
  42                            (unsigned long)(addr) +      \
  43                            (size))
  44
  45 /* Used as a marker in ARM_pc to note when we're in a jprobe. */
  46 #define JPROBE_MAGIC_ADDR               0xffffffff
  47
  48 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  49 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  50
  51
  52 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  53 {
  54         kprobe_opcode_t insn;
  55         kprobe_opcode_t tmp_insn[MAX_INSN_SIZE];
  56         unsigned long addr = (unsigned long)p->addr;
  57         bool thumb;
  58         kprobe_decode_insn_t *decode_insn;
  59         const union decode_action *actions;
  60         int is;
  61
  62         if (in_exception_text(addr))
  63                 return -EINVAL;
  64
  65 #ifdef CONFIG_THUMB2_KERNEL
  66         thumb = true;
  67         addr &= ~1; /* Bit 0 would normally be set to indicate Thumb code */
  68         insn = ((u16 *)addr)[0];
  69         if (is_wide_instruction(insn)) {
  70                 insn <<= 16;
  71                 insn |= ((u16 *)addr)[1];
  72                 decode_insn = thumb32_kprobe_decode_insn;
  73                 actions = kprobes_t32_actions;
  74         } else {
  75                 decode_insn = thumb16_kprobe_decode_insn;
  76                 actions = kprobes_t16_actions;
  77         }
  78 #else /* !CONFIG_THUMB2_KERNEL */
  79         thumb = false;
  80         if (addr & 0x3)
  81                 return -EINVAL;
  82         insn = *p->addr;
  83         decode_insn = arm_kprobe_decode_insn;
  84         actions = kprobes_arm_actions;
  85 #endif
  86
  87         p->opcode = insn;
  88         p->ainsn.insn = tmp_insn;
  89
  90         switch ((*decode_insn)(insn, &p->ainsn, actions)) {
  91         case INSN_REJECTED:     /* not supported */
  92                 return -EINVAL;
  93
  94         case INSN_GOOD:         /* instruction uses slot */
  95                 p->ainsn.insn = get_insn_slot();
  96                 if (!p->ainsn.insn)
  97                         return -ENOMEM;
  98                 for (is = 0; is < MAX_INSN_SIZE; ++is)
  99                         p->ainsn.insn[is] = tmp_insn[is];
 100                 flush_insns(p->ainsn.insn,
 101                                 sizeof(p->ainsn.insn[0]) * MAX_INSN_SIZE);
 102                 p->ainsn.insn_fn = (kprobe_insn_fn_t *)
 103                                         ((uintptr_t)p->ainsn.insn | thumb);
 104                 break;
 105
 106         case INSN_GOOD_NO_SLOT: /* instruction doesn't need insn slot */
 107                 p->ainsn.insn = NULL;
 108                 break;
 109         }
 110
 111         return 0;
 112 }
 113
 114 void __kprobes arch_arm_kprobe(struct kprobe *p)
 115 {
 116         unsigned int brkp;
 117         void *addr;
 118
 119         if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
 120                 /* Remove any Thumb flag */
 121                 addr = (void *)((uintptr_t)p->addr & ~1);
 122
 123                 if (is_wide_instruction(p->opcode))
 124                         brkp = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION;
 125                 else
 126                         brkp = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION;
 127         } else {
 128                 kprobe_opcode_t insn = p->opcode;
 129
 130                 addr = p->addr;
 131                 brkp = KPROBE_ARM_BREAKPOINT_INSTRUCTION;
 132
 133                 if (insn >= 0xe0000000)
 134                         brkp |= 0xe0000000;  /* Unconditional instruction */
 135                 else
 136                         brkp |= insn & 0xf0000000;  /* Copy condition from insn */
 137         }
 138
 139         patch_text(addr, brkp);
 140 }
 141
 142 /*
 143  * The actual disarming is done here on each CPU and synchronized using
 144  * stop_machine. This synchronization is necessary on SMP to avoid removing
 145  * a probe between the moment the 'Undefined Instruction' exception is raised
 146  * and the moment the exception handler reads the faulting instruction from
 147  * memory. It is also needed to atomically set the two half-words of a 32-bit
 148  * Thumb breakpoint.
 149  */
 150 int __kprobes __arch_disarm_kprobe(void *p)
 151 {
 152         struct kprobe *kp = p;
 153         void *addr = (void *)((uintptr_t)kp->addr & ~1);
 154
 155         __patch_text(addr, kp->opcode);
 156
 157         return 0;
 158 }
 159
 160 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 161 {
 162         stop_machine(__arch_disarm_kprobe, p, cpu_online_mask);
 163 }
 164
 165 void __kprobes arch_remove_kprobe(struct kprobe *p)
 166 {
 167         if (p->ainsn.insn) {
 168                 free_insn_slot(p->ainsn.insn, 0);
 169                 p->ainsn.insn = NULL;
 170         }
 171 }
 172
 173 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 174 {
 175         kcb->prev_kprobe.kp = kprobe_running();
 176         kcb->prev_kprobe.status = kcb->kprobe_status;
 177 }
 178
 179 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 180 {
 181         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 182         kcb->kprobe_status = kcb->prev_kprobe.status;
 183 }
 184
 185 static void __kprobes set_current_kprobe(struct kprobe *p)
 186 {
 187         __this_cpu_write(current_kprobe, p);
 188 }
 189
 190 static void __kprobes
 191 singlestep_skip(struct kprobe *p, struct pt_regs *regs)
 192 {
 193 #ifdef CONFIG_THUMB2_KERNEL
 194         regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
 195         if (is_wide_instruction(p->opcode))
 196                 regs->ARM_pc += 4;
 197         else
 198                 regs->ARM_pc += 2;
 199 #else
 200         regs->ARM_pc += 4;
 201 #endif
 202 }
 203
 204 static inline void __kprobes
 205 singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 206 {
 207         p->ainsn.insn_singlestep(p, regs);
 208 }
 209
 210 /*
 211  * Called with IRQs disabled. IRQs must remain disabled from that point
 212  * all the way until processing this kprobe is complete.  The current
 213  * kprobes implementation cannot process more than one nested level of
 214  * kprobe, and that level is reserved for user kprobe handlers, so we can't
 215  * risk encountering a new kprobe in an interrupt handler.
 216  */
 217 void __kprobes kprobe_handler(struct pt_regs *regs)
 218 {
 219         struct kprobe *p, *cur;
 220         struct kprobe_ctlblk *kcb;
 221
 222         kcb = get_kprobe_ctlblk();
 223         cur = kprobe_running();
 224
 225 #ifdef CONFIG_THUMB2_KERNEL
 226         /*
 227          * First look for a probe which was registered using an address with
 228          * bit 0 set, this is the usual situation for pointers to Thumb code.
 229          * If not found, fallback to looking for one with bit 0 clear.
 230          */
 231         p = get_kprobe((kprobe_opcode_t *)(regs->ARM_pc | 1));
 232         if (!p)
 233                 p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
 234
 235 #else /* ! CONFIG_THUMB2_KERNEL */
 236         p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
 237 #endif
 238
 239         if (p) {
 240                 if (cur) {
 241                         /* Kprobe is pending, so we're recursing. */
 242                         switch (kcb->kprobe_status) {
 243                         case KPROBE_HIT_ACTIVE:
 244                         case KPROBE_HIT_SSDONE:
 245                                 /* A pre- or post-handler probe got us here. */
 246                                 kprobes_inc_nmissed_count(p);
 247                                 save_previous_kprobe(kcb);
 248                                 set_current_kprobe(p);
 249                                 kcb->kprobe_status = KPROBE_REENTER;
 250                                 singlestep(p, regs, kcb);
 251                                 restore_previous_kprobe(kcb);
 252                                 break;
 253                         default:
 254                                 /* impossible cases */
 255                                 BUG();
 256                         }
 257                 } else if (p->ainsn.insn_check_cc(regs->ARM_cpsr)) {
 258                         /* Probe hit and conditional execution check ok. */
 259                         set_current_kprobe(p);
 260                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 261
 262                         /*
 263                          * If we have no pre-handler or it returned 0, we
 264                          * continue with normal processing.  If we have a
 265                          * pre-handler and it returned non-zero, it prepped
 266                          * for calling the break_handler below on re-entry,
 267                          * so get out doing nothing more here.
 268                          */
 269                         if (!p->pre_handler || !p->pre_handler(p, regs)) {
 270                                 kcb->kprobe_status = KPROBE_HIT_SS;
 271                                 singlestep(p, regs, kcb);
 272                                 if (p->post_handler) {
 273                                         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 274                                         p->post_handler(p, regs, 0);
 275                                 }
 276                                 reset_current_kprobe();
 277                         }
 278                 } else {
 279                         /*
 280                          * Probe hit but conditional execution check failed,
 281                          * so just skip the instruction and continue as if
 282                          * nothing had happened.
 283                          */
 284                         singlestep_skip(p, regs);
 285                 }
 286         } else if (cur) {
 287                 /* We probably hit a jprobe.  Call its break handler. */
 288                 if (cur->break_handler && cur->break_handler(cur, regs)) {
 289                         kcb->kprobe_status = KPROBE_HIT_SS;
 290                         singlestep(cur, regs, kcb);
 291                         if (cur->post_handler) {
 292                                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 293                                 cur->post_handler(cur, regs, 0);
 294                         }
 295                 }
 296                 reset_current_kprobe();
 297         } else {
 298                 /*
 299                  * The probe was removed and a race is in progress.
 300                  * There is nothing we can do about it.  Let's restart
 301                  * the instruction.  By the time we can restart, the
 302                  * real instruction will be there.
 303                  */
 304         }
 305 }
 306
 307 static int __kprobes kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
 308 {
 309         unsigned long flags;
 310         local_irq_save(flags);
 311         kprobe_handler(regs);
 312         local_irq_restore(flags);
 313         return 0;
 314 }
 315
 316 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
 317 {
 318         struct kprobe *cur = kprobe_running();
 319         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 320
 321         switch (kcb->kprobe_status) {
 322         case KPROBE_HIT_SS:
 323         case KPROBE_REENTER:
 324                 /*
 325                  * We are here because the instruction being single
 326                  * stepped caused a page fault. We reset the current
 327                  * kprobe and the PC to point back to the probe address
 328                  * and allow the page fault handler to continue as a
 329                  * normal page fault.
 330                  */
 331                 regs->ARM_pc = (long)cur->addr;
 332                 if (kcb->kprobe_status == KPROBE_REENTER) {
 333                         restore_previous_kprobe(kcb);
 334                 } else {
 335                         reset_current_kprobe();
 336                 }
 337                 break;
 338
 339         case KPROBE_HIT_ACTIVE:
 340         case KPROBE_HIT_SSDONE:
 341                 /*
 342                  * We increment the nmissed count for accounting,
 343                  * we can also use npre/npostfault count for accounting
 344                  * these specific fault cases.
 345                  */
 346                 kprobes_inc_nmissed_count(cur);
 347
 348                 /*
 349                  * We come here because instructions in the pre/post
 350                  * handler caused the page_fault, this could happen
 351                  * if handler tries to access user space by
 352                  * copy_from_user(), get_user() etc. Let the
 353                  * user-specified handler try to fix it.
 354                  */
 355                 if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
 356                         return 1;
 357                 break;
 358
 359         default:
 360                 break;
 361         }
 362
 363         return 0;
 364 }
 365
 366 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 367                                        unsigned long val, void *data)
 368 {
 369         /*
 370          * notify_die() is currently never called on ARM,
 371          * so this callback is currently empty.
 372          */
 373         return NOTIFY_DONE;
 374 }
 375
 376 /*
 377  * When a retprobed function returns, trampoline_handler() is called,
 378  * calling the kretprobe's handler. We construct a struct pt_regs to
 379  * give a view of registers r0-r11 to the user return-handler.  This is
 380  * not a complete pt_regs structure, but that should be plenty sufficient
 381  * for kretprobe handlers which should normally be interested in r0 only
 382  * anyway.
 383  */
 384 void __naked __kprobes kretprobe_trampoline(void)
 385 {
 386         __asm__ __volatile__ (
 387                 "stmdb  sp!, {r0 - r11}         \n\t"
 388                 "mov    r0, sp                  \n\t"
 389                 "bl     trampoline_handler      \n\t"
 390                 "mov    lr, r0                  \n\t"
 391                 "ldmia  sp!, {r0 - r11}         \n\t"
 392 #ifdef CONFIG_THUMB2_KERNEL
 393                 "bx     lr                      \n\t"
 394 #else
 395                 "mov    pc, lr                  \n\t"
 396 #endif
 397                 : : : "memory");
 398 }
 399
 400 /* Called from kretprobe_trampoline */
 401 static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
 402 {
 403         struct kretprobe_instance *ri = NULL;
 404         struct hlist_head *head, empty_rp;
 405         struct hlist_node *tmp;
 406         unsigned long flags, orig_ret_address = 0;
 407         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 408
 409         INIT_HLIST_HEAD(&empty_rp);
 410         kretprobe_hash_lock(current, &head, &flags);
 411
 412         /*
 413          * It is possible to have multiple instances associated with a given
 414          * task either because multiple functions in the call path have
 415          * a return probe installed on them, and/or more than one return
 416          * probe was registered for a target function.
 417          *
 418          * We can handle this because:
 419          *     - instances are always inserted at the head of the list
 420          *     - when multiple return probes are registered for the same
 421          *       function, the first instance's ret_addr will point to the
 422          *       real return address, and all the rest will point to
 423          *       kretprobe_trampoline
 424          */
 425         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 426                 if (ri->task != current)
 427                         /* another task is sharing our hash bucket */
 428                         continue;
 429
 430                 if (ri->rp && ri->rp->handler) {
 431                         __this_cpu_write(current_kprobe, &ri->rp->kp);
 432                         get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
 433                         ri->rp->handler(ri, regs);
 434                         __this_cpu_write(current_kprobe, NULL);
 435                 }
 436
 437                 orig_ret_address = (unsigned long)ri->ret_addr;
 438                 recycle_rp_inst(ri, &empty_rp);
 439
 440                 if (orig_ret_address != trampoline_address)
 441                         /*
 442                          * This is the real return address. Any other
 443                          * instances associated with this task are for
 444                          * other calls deeper on the call stack
 445                          */
 446                         break;
 447         }
 448
 449         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 450         kretprobe_hash_unlock(current, &flags);
 451
 452         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 453                 hlist_del(&ri->hlist);
 454                 kfree(ri);
 455         }
 456
 457         return (void *)orig_ret_address;
 458 }
 459
 460 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 461                                       struct pt_regs *regs)
 462 {
 463         ri->ret_addr = (kprobe_opcode_t *)regs->ARM_lr;
 464
 465         /* Replace the return addr with trampoline addr. */
 466         regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
 467 }
 468
 469 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 470 {
 471         struct jprobe *jp = container_of(p, struct jprobe, kp);
 472         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 473         long sp_addr = regs->ARM_sp;
 474         long cpsr;
 475
 476         kcb->jprobe_saved_regs = *regs;
 477         memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
 478         regs->ARM_pc = (long)jp->entry;
 479
 480         cpsr = regs->ARM_cpsr | PSR_I_BIT;
 481 #ifdef CONFIG_THUMB2_KERNEL
 482         /* Set correct Thumb state in cpsr */
 483         if (regs->ARM_pc & 1)
 484                 cpsr |= PSR_T_BIT;
 485         else
 486                 cpsr &= ~PSR_T_BIT;
 487 #endif
 488         regs->ARM_cpsr = cpsr;
 489
 490         preempt_disable();
 491         return 1;
 492 }
 493
 494 void __kprobes jprobe_return(void)
 495 {
 496         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 497
 498         __asm__ __volatile__ (
 499                 /*
 500                  * Setup an empty pt_regs. Fill SP and PC fields as
 501                  * they're needed by longjmp_break_handler.
 502                  *
 503                  * We allocate some slack between the original SP and start of
 504                  * our fabricated regs. To be precise we want to have worst case
 505                  * covered which is STMFD with all 16 regs so we allocate 2 *
 506                  * sizeof(struct_pt_regs)).
 507                  *
 508                  * This is to prevent any simulated instruction from writing
 509                  * over the regs when they are accessing the stack.
 510                  */
 511 #ifdef CONFIG_THUMB2_KERNEL
 512                 "sub    r0, %0, %1              \n\t"
 513                 "mov    sp, r0                  \n\t"
 514 #else
 515                 "sub    sp, %0, %1              \n\t"
 516 #endif
 517                 "ldr    r0, ="__stringify(JPROBE_MAGIC_ADDR)"\n\t"
 518                 "str    %0, [sp, %2]            \n\t"
 519                 "str    r0, [sp, %3]            \n\t"
 520                 "mov    r0, sp                  \n\t"
 521                 "bl     kprobe_handler          \n\t"
 522
 523                 /*
 524                  * Return to the context saved by setjmp_pre_handler
 525                  * and restored by longjmp_break_handler.
 526                  */
 527 #ifdef CONFIG_THUMB2_KERNEL
 528                 "ldr    lr, [sp, %2]            \n\t" /* lr = saved sp */
 529                 "ldrd   r0, r1, [sp, %5]        \n\t" /* r0,r1 = saved lr,pc */
 530                 "ldr    r2, [sp, %4]            \n\t" /* r2 = saved psr */
 531                 "stmdb  lr!, {r0, r1, r2}       \n\t" /* push saved lr and */
 532                                                       /* rfe context */
 533                 "ldmia  sp, {r0 - r12}          \n\t"
 534                 "mov    sp, lr                  \n\t"
 535                 "ldr    lr, [sp], #4            \n\t"
 536                 "rfeia  sp!                     \n\t"
 537 #else
 538                 "ldr    r0, [sp, %4]            \n\t"
 539                 "msr    cpsr_cxsf, r0           \n\t"
 540                 "ldmia  sp, {r0 - pc}           \n\t"
 541 #endif
 542                 :
 543                 : "r" (kcb->jprobe_saved_regs.ARM_sp),
 544                   "I" (sizeof(struct pt_regs) * 2),
 545                   "J" (offsetof(struct pt_regs, ARM_sp)),
 546                   "J" (offsetof(struct pt_regs, ARM_pc)),
 547                   "J" (offsetof(struct pt_regs, ARM_cpsr)),
 548                   "J" (offsetof(struct pt_regs, ARM_lr))
 549                 : "memory", "cc");
 550 }
 551
 552 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 553 {
 554         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 555         long stack_addr = kcb->jprobe_saved_regs.ARM_sp;
 556         long orig_sp = regs->ARM_sp;
 557         struct jprobe *jp = container_of(p, struct jprobe, kp);
 558
 559         if (regs->ARM_pc == JPROBE_MAGIC_ADDR) {
 560                 if (orig_sp != stack_addr) {
 561                         struct pt_regs *saved_regs =
 562                                 (struct pt_regs *)kcb->jprobe_saved_regs.ARM_sp;
 563                         printk("current sp %lx does not match saved sp %lx\n",
 564                                orig_sp, stack_addr);
 565                         printk("Saved registers for jprobe %p\n", jp);
 566                         show_regs(saved_regs);
 567                         printk("Current registers\n");
 568                         show_regs(regs);
 569                         BUG();
 570                 }
 571                 *regs = kcb->jprobe_saved_regs;
 572                 memcpy((void *)stack_addr, kcb->jprobes_stack,
 573                        MIN_STACK_SIZE(stack_addr));
 574                 preempt_enable_no_resched();
 575                 return 1;
 576         }
 577         return 0;
 578 }
 579
 580 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 581 {
 582         return 0;
 583 }
 584
 585 #ifdef CONFIG_THUMB2_KERNEL
 586
 587 static struct undef_hook kprobes_thumb16_break_hook = {
 588         .instr_mask     = 0xffff,
 589         .instr_val      = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION,
 590         .cpsr_mask      = MODE_MASK,
 591         .cpsr_val       = SVC_MODE,
 592         .fn             = kprobe_trap_handler,
 593 };
 594
 595 static struct undef_hook kprobes_thumb32_break_hook = {
 596         .instr_mask     = 0xffffffff,
 597         .instr_val      = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION,
 598         .cpsr_mask      = MODE_MASK,
 599         .cpsr_val       = SVC_MODE,
 600         .fn             = kprobe_trap_handler,
 601 };
 602
 603 #else  /* !CONFIG_THUMB2_KERNEL */
 604
 605 static struct undef_hook kprobes_arm_break_hook = {
 606         .instr_mask     = 0x0fffffff,
 607         .instr_val      = KPROBE_ARM_BREAKPOINT_INSTRUCTION,
 608         .cpsr_mask      = MODE_MASK,
 609         .cpsr_val       = SVC_MODE,
 610         .fn             = kprobe_trap_handler,
 611 };
 612
 613 #endif /* !CONFIG_THUMB2_KERNEL */
 614
 615 int __init arch_init_kprobes()
 616 {
 617         arm_kprobe_decode_init();
 618 #ifdef CONFIG_THUMB2_KERNEL
 619         register_undef_hook(&kprobes_thumb16_break_hook);
 620         register_undef_hook(&kprobes_thumb32_break_hook);
 621 #else
 622         register_undef_hook(&kprobes_arm_break_hook);
 623 #endif
 624         return 0;
 625 }