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/opcodes.h>
  30 #include <asm/cacheflush.h>
  31
  32 #include "kprobes.h"
  33 #include "patch.h"
  34
  35 #define MIN_STACK_SIZE(addr)                            \
  36         min((unsigned long)MAX_STACK_SIZE,              \
  37             (unsigned long)current_thread_info() + THREAD_START_SP - (addr))
  38
  39 #define flush_insns(addr, size)                         \
  40         flush_icache_range((unsigned long)(addr),       \
  41                            (unsigned long)(addr) +      \
  42                            (size))
  43
  44 /* Used as a marker in ARM_pc to note when we're in a jprobe. */
  45 #define JPROBE_MAGIC_ADDR               0xffffffff
  46
  47 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  48 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  49
  50
  51 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  52 {
  53         kprobe_opcode_t insn;
  54         kprobe_opcode_t tmp_insn[MAX_INSN_SIZE];
  55         unsigned long addr = (unsigned long)p->addr;
  56         bool thumb;
  57         kprobe_decode_insn_t *decode_insn;
  58         int is;
  59
  60         if (in_exception_text(addr))
  61                 return -EINVAL;
  62
  63 #ifdef CONFIG_THUMB2_KERNEL
  64         thumb = true;
  65         addr &= ~1; /* Bit 0 would normally be set to indicate Thumb code */
  66         insn = __mem_to_opcode_thumb16(((u16 *)addr)[0]);
  67         if (is_wide_instruction(insn)) {
  68                 u16 inst2 = __mem_to_opcode_thumb16(((u16 *)addr)[1]);
  69                 insn = __opcode_thumb32_compose(insn, inst2);
  70                 decode_insn = thumb32_kprobe_decode_insn;
  71         } else
  72                 decode_insn = thumb16_kprobe_decode_insn;
  73 #else /* !CONFIG_THUMB2_KERNEL */
  74         thumb = false;
  75         if (addr & 0x3)
  76                 return -EINVAL;
  77         insn = __mem_to_opcode_arm(*p->addr);
  78         decode_insn = arm_kprobe_decode_insn;
  79 #endif
  80
  81         p->opcode = insn;
  82         p->ainsn.insn = tmp_insn;
  83
  84         switch ((*decode_insn)(insn, &p->ainsn)) {
  85         case INSN_REJECTED:     /* not supported */
  86                 return -EINVAL;
  87
  88         case INSN_GOOD:         /* instruction uses slot */
  89                 p->ainsn.insn = get_insn_slot();
  90                 if (!p->ainsn.insn)
  91                         return -ENOMEM;
  92                 for (is = 0; is < MAX_INSN_SIZE; ++is)
  93                         p->ainsn.insn[is] = tmp_insn[is];
  94                 flush_insns(p->ainsn.insn,
  95                                 sizeof(p->ainsn.insn[0]) * MAX_INSN_SIZE);
  96                 p->ainsn.insn_fn = (kprobe_insn_fn_t *)
  97                                         ((uintptr_t)p->ainsn.insn | thumb);
  98                 break;
  99
 100         case INSN_GOOD_NO_SLOT: /* instruction doesn't need insn slot */
 101                 p->ainsn.insn = NULL;
 102                 break;
 103         }
 104
 105         return 0;
 106 }
 107
 108 void __kprobes arch_arm_kprobe(struct kprobe *p)
 109 {
 110         unsigned int brkp;
 111         void *addr;
 112
 113         if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
 114                 /* Remove any Thumb flag */
 115                 addr = (void *)((uintptr_t)p->addr & ~1);
 116
 117                 if (is_wide_instruction(p->opcode))
 118                         brkp = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION;
 119                 else
 120                         brkp = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION;
 121         } else {
 122                 kprobe_opcode_t insn = p->opcode;
 123
 124                 addr = p->addr;
 125                 brkp = KPROBE_ARM_BREAKPOINT_INSTRUCTION;
 126
 127                 if (insn >= 0xe0000000)
 128                         brkp |= 0xe0000000;  /* Unconditional instruction */
 129                 else
 130                         brkp |= insn & 0xf0000000;  /* Copy condition from insn */
 131         }
 132
 133         patch_text(addr, brkp);
 134 }
 135
 136 /*
 137  * The actual disarming is done here on each CPU and synchronized using
 138  * stop_machine. This synchronization is necessary on SMP to avoid removing
 139  * a probe between the moment the 'Undefined Instruction' exception is raised
 140  * and the moment the exception handler reads the faulting instruction from
 141  * memory. It is also needed to atomically set the two half-words of a 32-bit
 142  * Thumb breakpoint.
 143  */
 144 int __kprobes __arch_disarm_kprobe(void *p)
 145 {
 146         struct kprobe *kp = p;
 147         void *addr = (void *)((uintptr_t)kp->addr & ~1);
 148
 149         __patch_text(addr, kp->opcode);
 150
 151         return 0;
 152 }
 153
 154 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 155 {
 156         stop_machine(__arch_disarm_kprobe, p, cpu_online_mask);
 157 }
 158
 159 void __kprobes arch_remove_kprobe(struct kprobe *p)
 160 {
 161         if (p->ainsn.insn) {
 162                 free_insn_slot(p->ainsn.insn, 0);
 163                 p->ainsn.insn = NULL;
 164         }
 165 }
 166
 167 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 168 {
 169         kcb->prev_kprobe.kp = kprobe_running();
 170         kcb->prev_kprobe.status = kcb->kprobe_status;
 171 }
 172
 173 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 174 {
 175         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
 176         kcb->kprobe_status = kcb->prev_kprobe.status;
 177 }
 178
 179 static void __kprobes set_current_kprobe(struct kprobe *p)
 180 {
 181         __get_cpu_var(current_kprobe) = p;
 182 }
 183
 184 static void __kprobes
 185 singlestep_skip(struct kprobe *p, struct pt_regs *regs)
 186 {
 187 #ifdef CONFIG_THUMB2_KERNEL
 188         regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
 189         if (is_wide_instruction(p->opcode))
 190                 regs->ARM_pc += 4;
 191         else
 192                 regs->ARM_pc += 2;
 193 #else
 194         regs->ARM_pc += 4;
 195 #endif
 196 }
 197
 198 static inline void __kprobes
 199 singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 200 {
 201         p->ainsn.insn_singlestep(p, regs);
 202 }
 203
 204 /*
 205  * Called with IRQs disabled. IRQs must remain disabled from that point
 206  * all the way until processing this kprobe is complete.  The current
 207  * kprobes implementation cannot process more than one nested level of
 208  * kprobe, and that level is reserved for user kprobe handlers, so we can't
 209  * risk encountering a new kprobe in an interrupt handler.
 210  */
 211 void __kprobes kprobe_handler(struct pt_regs *regs)
 212 {
 213         struct kprobe *p, *cur;
 214         struct kprobe_ctlblk *kcb;
 215
 216         kcb = get_kprobe_ctlblk();
 217         cur = kprobe_running();
 218
 219 #ifdef CONFIG_THUMB2_KERNEL
 220         /*
 221          * First look for a probe which was registered using an address with
 222          * bit 0 set, this is the usual situation for pointers to Thumb code.
 223          * If not found, fallback to looking for one with bit 0 clear.
 224          */
 225         p = get_kprobe((kprobe_opcode_t *)(regs->ARM_pc | 1));
 226         if (!p)
 227                 p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
 228
 229 #else /* ! CONFIG_THUMB2_KERNEL */
 230         p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
 231 #endif
 232
 233         if (p) {
 234                 if (cur) {
 235                         /* Kprobe is pending, so we're recursing. */
 236                         switch (kcb->kprobe_status) {
 237                         case KPROBE_HIT_ACTIVE:
 238                         case KPROBE_HIT_SSDONE:
 239                                 /* A pre- or post-handler probe got us here. */
 240                                 kprobes_inc_nmissed_count(p);
 241                                 save_previous_kprobe(kcb);
 242                                 set_current_kprobe(p);
 243                                 kcb->kprobe_status = KPROBE_REENTER;
 244                                 singlestep(p, regs, kcb);
 245                                 restore_previous_kprobe(kcb);
 246                                 break;
 247                         default:
 248                                 /* impossible cases */
 249                                 BUG();
 250                         }
 251                 } else if (p->ainsn.insn_check_cc(regs->ARM_cpsr)) {
 252                         /* Probe hit and conditional execution check ok. */
 253                         set_current_kprobe(p);
 254                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 255
 256                         /*
 257                          * If we have no pre-handler or it returned 0, we
 258                          * continue with normal processing.  If we have a
 259                          * pre-handler and it returned non-zero, it prepped
 260                          * for calling the break_handler below on re-entry,
 261                          * so get out doing nothing more here.
 262                          */
 263                         if (!p->pre_handler || !p->pre_handler(p, regs)) {
 264                                 kcb->kprobe_status = KPROBE_HIT_SS;
 265                                 singlestep(p, regs, kcb);
 266                                 if (p->post_handler) {
 267                                         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 268                                         p->post_handler(p, regs, 0);
 269                                 }
 270                                 reset_current_kprobe();
 271                         }
 272                 } else {
 273                         /*
 274                          * Probe hit but conditional execution check failed,
 275                          * so just skip the instruction and continue as if
 276                          * nothing had happened.
 277                          */
 278                         singlestep_skip(p, regs);
 279                 }
 280         } else if (cur) {
 281                 /* We probably hit a jprobe.  Call its break handler. */
 282                 if (cur->break_handler && cur->break_handler(cur, regs)) {
 283                         kcb->kprobe_status = KPROBE_HIT_SS;
 284                         singlestep(cur, regs, kcb);
 285                         if (cur->post_handler) {
 286                                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 287                                 cur->post_handler(cur, regs, 0);
 288                         }
 289                 }
 290                 reset_current_kprobe();
 291         } else {
 292                 /*
 293                  * The probe was removed and a race is in progress.
 294                  * There is nothing we can do about it.  Let's restart
 295                  * the instruction.  By the time we can restart, the
 296                  * real instruction will be there.
 297                  */
 298         }
 299 }
 300
 301 static int __kprobes kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
 302 {
 303         unsigned long flags;
 304         local_irq_save(flags);
 305         kprobe_handler(regs);
 306         local_irq_restore(flags);
 307         return 0;
 308 }
 309
 310 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
 311 {
 312         struct kprobe *cur = kprobe_running();
 313         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 314
 315         switch (kcb->kprobe_status) {
 316         case KPROBE_HIT_SS:
 317         case KPROBE_REENTER:
 318                 /*
 319                  * We are here because the instruction being single
 320                  * stepped caused a page fault. We reset the current
 321                  * kprobe and the PC to point back to the probe address
 322                  * and allow the page fault handler to continue as a
 323                  * normal page fault.
 324                  */
 325                 regs->ARM_pc = (long)cur->addr;
 326                 if (kcb->kprobe_status == KPROBE_REENTER) {
 327                         restore_previous_kprobe(kcb);
 328                 } else {
 329                         reset_current_kprobe();
 330                 }
 331                 break;
 332
 333         case KPROBE_HIT_ACTIVE:
 334         case KPROBE_HIT_SSDONE:
 335                 /*
 336                  * We increment the nmissed count for accounting,
 337                  * we can also use npre/npostfault count for accounting
 338                  * these specific fault cases.
 339                  */
 340                 kprobes_inc_nmissed_count(cur);
 341
 342                 /*
 343                  * We come here because instructions in the pre/post
 344                  * handler caused the page_fault, this could happen
 345                  * if handler tries to access user space by
 346                  * copy_from_user(), get_user() etc. Let the
 347                  * user-specified handler try to fix it.
 348                  */
 349                 if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
 350                         return 1;
 351                 break;
 352
 353         default:
 354                 break;
 355         }
 356
 357         return 0;
 358 }
 359
 360 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 361                                        unsigned long val, void *data)
 362 {
 363         /*
 364          * notify_die() is currently never called on ARM,
 365          * so this callback is currently empty.
 366          */
 367         return NOTIFY_DONE;
 368 }
 369
 370 /*
 371  * When a retprobed function returns, trampoline_handler() is called,
 372  * calling the kretprobe's handler. We construct a struct pt_regs to
 373  * give a view of registers r0-r11 to the user return-handler.  This is
 374  * not a complete pt_regs structure, but that should be plenty sufficient
 375  * for kretprobe handlers which should normally be interested in r0 only
 376  * anyway.
 377  */
 378 void __naked __kprobes kretprobe_trampoline(void)
 379 {
 380         __asm__ __volatile__ (
 381                 "stmdb  sp!, {r0 - r11}         \n\t"
 382                 "mov    r0, sp                  \n\t"
 383                 "bl     trampoline_handler      \n\t"
 384                 "mov    lr, r0                  \n\t"
 385                 "ldmia  sp!, {r0 - r11}         \n\t"
 386 #ifdef CONFIG_THUMB2_KERNEL
 387                 "bx     lr                      \n\t"
 388 #else
 389                 "mov    pc, lr                  \n\t"
 390 #endif
 391                 : : : "memory");
 392 }
 393
 394 /* Called from kretprobe_trampoline */
 395 static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
 396 {
 397         struct kretprobe_instance *ri = NULL;
 398         struct hlist_head *head, empty_rp;
 399         struct hlist_node *tmp;
 400         unsigned long flags, orig_ret_address = 0;
 401         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 402
 403         INIT_HLIST_HEAD(&empty_rp);
 404         kretprobe_hash_lock(current, &head, &flags);
 405
 406         /*
 407          * It is possible to have multiple instances associated with a given
 408          * task either because multiple functions in the call path have
 409          * a return probe installed on them, and/or more than one return
 410          * probe was registered for a target function.
 411          *
 412          * We can handle this because:
 413          *     - instances are always inserted at the head of the list
 414          *     - when multiple return probes are registered for the same
 415          *       function, the first instance's ret_addr will point to the
 416          *       real return address, and all the rest will point to
 417          *       kretprobe_trampoline
 418          */
 419         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 420                 if (ri->task != current)
 421                         /* another task is sharing our hash bucket */
 422                         continue;
 423
 424                 if (ri->rp && ri->rp->handler) {
 425                         __get_cpu_var(current_kprobe) = &ri->rp->kp;
 426                         get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
 427                         ri->rp->handler(ri, regs);
 428                         __get_cpu_var(current_kprobe) = NULL;
 429                 }
 430
 431                 orig_ret_address = (unsigned long)ri->ret_addr;
 432                 recycle_rp_inst(ri, &empty_rp);
 433
 434                 if (orig_ret_address != trampoline_address)
 435                         /*
 436                          * This is the real return address. Any other
 437                          * instances associated with this task are for
 438                          * other calls deeper on the call stack
 439                          */
 440                         break;
 441         }
 442
 443         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 444         kretprobe_hash_unlock(current, &flags);
 445
 446         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 447                 hlist_del(&ri->hlist);
 448                 kfree(ri);
 449         }
 450
 451         return (void *)orig_ret_address;
 452 }
 453
 454 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 455                                       struct pt_regs *regs)
 456 {
 457         ri->ret_addr = (kprobe_opcode_t *)regs->ARM_lr;
 458
 459         /* Replace the return addr with trampoline addr. */
 460         regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
 461 }
 462
 463 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 464 {
 465         struct jprobe *jp = container_of(p, struct jprobe, kp);
 466         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 467         long sp_addr = regs->ARM_sp;
 468         long cpsr;
 469
 470         kcb->jprobe_saved_regs = *regs;
 471         memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
 472         regs->ARM_pc = (long)jp->entry;
 473
 474         cpsr = regs->ARM_cpsr | PSR_I_BIT;
 475 #ifdef CONFIG_THUMB2_KERNEL
 476         /* Set correct Thumb state in cpsr */
 477         if (regs->ARM_pc & 1)
 478                 cpsr |= PSR_T_BIT;
 479         else
 480                 cpsr &= ~PSR_T_BIT;
 481 #endif
 482         regs->ARM_cpsr = cpsr;
 483
 484         preempt_disable();
 485         return 1;
 486 }
 487
 488 void __kprobes jprobe_return(void)
 489 {
 490         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 491
 492         __asm__ __volatile__ (
 493                 /*
 494                  * Setup an empty pt_regs. Fill SP and PC fields as
 495                  * they're needed by longjmp_break_handler.
 496                  *
 497                  * We allocate some slack between the original SP and start of
 498                  * our fabricated regs. To be precise we want to have worst case
 499                  * covered which is STMFD with all 16 regs so we allocate 2 *
 500                  * sizeof(struct_pt_regs)).
 501                  *
 502                  * This is to prevent any simulated instruction from writing
 503                  * over the regs when they are accessing the stack.
 504                  */
 505 #ifdef CONFIG_THUMB2_KERNEL
 506                 "sub    r0, %0, %1              \n\t"
 507                 "mov    sp, r0                  \n\t"
 508 #else
 509                 "sub    sp, %0, %1              \n\t"
 510 #endif
 511                 "ldr    r0, ="__stringify(JPROBE_MAGIC_ADDR)"\n\t"
 512                 "str    %0, [sp, %2]            \n\t"
 513                 "str    r0, [sp, %3]            \n\t"
 514                 "mov    r0, sp                  \n\t"
 515                 "bl     kprobe_handler          \n\t"
 516
 517                 /*
 518                  * Return to the context saved by setjmp_pre_handler
 519                  * and restored by longjmp_break_handler.
 520                  */
 521 #ifdef CONFIG_THUMB2_KERNEL
 522                 "ldr    lr, [sp, %2]            \n\t" /* lr = saved sp */
 523                 "ldrd   r0, r1, [sp, %5]        \n\t" /* r0,r1 = saved lr,pc */
 524                 "ldr    r2, [sp, %4]            \n\t" /* r2 = saved psr */
 525                 "stmdb  lr!, {r0, r1, r2}       \n\t" /* push saved lr and */
 526                                                       /* rfe context */
 527                 "ldmia  sp, {r0 - r12}          \n\t"
 528                 "mov    sp, lr                  \n\t"
 529                 "ldr    lr, [sp], #4            \n\t"
 530                 "rfeia  sp!                     \n\t"
 531 #else
 532                 "ldr    r0, [sp, %4]            \n\t"
 533                 "msr    cpsr_cxsf, r0           \n\t"
 534                 "ldmia  sp, {r0 - pc}           \n\t"
 535 #endif
 536                 :
 537                 : "r" (kcb->jprobe_saved_regs.ARM_sp),
 538                   "I" (sizeof(struct pt_regs) * 2),
 539                   "J" (offsetof(struct pt_regs, ARM_sp)),
 540                   "J" (offsetof(struct pt_regs, ARM_pc)),
 541                   "J" (offsetof(struct pt_regs, ARM_cpsr)),
 542                   "J" (offsetof(struct pt_regs, ARM_lr))
 543                 : "memory", "cc");
 544 }
 545
 546 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 547 {
 548         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 549         long stack_addr = kcb->jprobe_saved_regs.ARM_sp;
 550         long orig_sp = regs->ARM_sp;
 551         struct jprobe *jp = container_of(p, struct jprobe, kp);
 552
 553         if (regs->ARM_pc == JPROBE_MAGIC_ADDR) {
 554                 if (orig_sp != stack_addr) {
 555                         struct pt_regs *saved_regs =
 556                                 (struct pt_regs *)kcb->jprobe_saved_regs.ARM_sp;
 557                         printk("current sp %lx does not match saved sp %lx\n",
 558                                orig_sp, stack_addr);
 559                         printk("Saved registers for jprobe %p\n", jp);
 560                         show_regs(saved_regs);
 561                         printk("Current registers\n");
 562                         show_regs(regs);
 563                         BUG();
 564                 }
 565                 *regs = kcb->jprobe_saved_regs;
 566                 memcpy((void *)stack_addr, kcb->jprobes_stack,
 567                        MIN_STACK_SIZE(stack_addr));
 568                 preempt_enable_no_resched();
 569                 return 1;
 570         }
 571         return 0;
 572 }
 573
 574 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 575 {
 576         return 0;
 577 }
 578
 579 #ifdef CONFIG_THUMB2_KERNEL
 580
 581 static struct undef_hook kprobes_thumb16_break_hook = {
 582         .instr_mask     = 0xffff,
 583         .instr_val      = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION,
 584         .cpsr_mask      = MODE_MASK,
 585         .cpsr_val       = SVC_MODE,
 586         .fn             = kprobe_trap_handler,
 587 };
 588
 589 static struct undef_hook kprobes_thumb32_break_hook = {
 590         .instr_mask     = 0xffffffff,
 591         .instr_val      = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION,
 592         .cpsr_mask      = MODE_MASK,
 593         .cpsr_val       = SVC_MODE,
 594         .fn             = kprobe_trap_handler,
 595 };
 596
 597 #else  /* !CONFIG_THUMB2_KERNEL */
 598
 599 static struct undef_hook kprobes_arm_break_hook = {
 600         .instr_mask     = 0x0fffffff,
 601         .instr_val      = KPROBE_ARM_BREAKPOINT_INSTRUCTION,
 602         .cpsr_mask      = MODE_MASK,
 603         .cpsr_val       = SVC_MODE,
 604         .fn             = kprobe_trap_handler,
 605 };
 606
 607 #endif /* !CONFIG_THUMB2_KERNEL */
 608
 609 int __init arch_init_kprobes()
 610 {
 611         arm_kprobe_decode_init();
 612 #ifdef CONFIG_THUMB2_KERNEL
 613         register_undef_hook(&kprobes_thumb16_break_hook);
 614         register_undef_hook(&kprobes_thumb32_break_hook);
 615 #else
 616         register_undef_hook(&kprobes_arm_break_hook);
 617 #endif
 618         return 0;
 619 }