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 "probes-arm.h"
  35 #include "probes-thumb.h"
  36 #include "patch.h"
  37
  38 #define MIN_STACK_SIZE(addr)                            \
  39         min((unsigned long)MAX_STACK_SIZE,              \
  40             (unsigned long)current_thread_info() + THREAD_START_SP - (addr))
  41
  42 #define flush_insns(addr, size)                         \
  43         flush_icache_range((unsigned long)(addr),       \
  44                            (unsigned long)(addr) +      \
  45                            (size))
  46
  47 /* Used as a marker in ARM_pc to note when we're in a jprobe. */
  48 #define JPROBE_MAGIC_ADDR               0xffffffff
  49
  50 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  51 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  52
  53
  54 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  55 {
  56         kprobe_opcode_t insn;
  57         kprobe_opcode_t tmp_insn[MAX_INSN_SIZE];
  58         unsigned long addr = (unsigned long)p->addr;
  59         bool thumb;
  60         kprobe_decode_insn_t *decode_insn;
  61         const union decode_action *actions;
  62         int is;
  63
  64         if (in_exception_text(addr))
  65                 return -EINVAL;
  66
  67 #ifdef CONFIG_THUMB2_KERNEL
  68         thumb = true;
  69         addr &= ~1; /* Bit 0 would normally be set to indicate Thumb code */
  70         insn = ((u16 *)addr)[0];
  71         if (is_wide_instruction(insn)) {
  72                 insn <<= 16;
  73                 insn |= ((u16 *)addr)[1];
  74                 decode_insn = thumb32_probes_decode_insn;
  75                 actions = kprobes_t32_actions;
  76         } else {
  77                 decode_insn = thumb16_probes_decode_insn;
  78                 actions = kprobes_t16_actions;
  79         }
  80 #else /* !CONFIG_THUMB2_KERNEL */
  81         thumb = false;
  82         if (addr & 0x3)
  83                 return -EINVAL;
  84         insn = *p->addr;
  85         decode_insn = arm_probes_decode_insn;
  86         actions = kprobes_arm_actions;
  87 #endif
  88
  89         p->opcode = insn;
  90         p->ainsn.insn = tmp_insn;
  91
  92         switch ((*decode_insn)(insn, &p->ainsn, true, actions)) {
  93         case INSN_REJECTED:     /* not supported */
  94                 return -EINVAL;
  95
  96         case INSN_GOOD:         /* instruction uses slot */
  97                 p->ainsn.insn = get_insn_slot();
  98                 if (!p->ainsn.insn)
  99                         return -ENOMEM;
 100                 for (is = 0; is < MAX_INSN_SIZE; ++is)
 101                         p->ainsn.insn[is] = tmp_insn[is];
 102                 flush_insns(p->ainsn.insn,
 103                                 sizeof(p->ainsn.insn[0]) * MAX_INSN_SIZE);
 104                 p->ainsn.insn_fn = (probes_insn_fn_t *)
 105                                         ((uintptr_t)p->ainsn.insn | thumb);
 106                 break;
 107
 108         case INSN_GOOD_NO_SLOT: /* instruction doesn't need insn slot */
 109                 p->ainsn.insn = NULL;
 110                 break;
 111         }
 112
 113         return 0;
 114 }
 115
 116 void __kprobes arch_arm_kprobe(struct kprobe *p)
 117 {
 118         unsigned int brkp;
 119         void *addr;
 120
 121         if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
 122                 /* Remove any Thumb flag */
 123                 addr = (void *)((uintptr_t)p->addr & ~1);
 124
 125                 if (is_wide_instruction(p->opcode))
 126                         brkp = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION;
 127                 else
 128                         brkp = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION;
 129         } else {
 130                 kprobe_opcode_t insn = p->opcode;
 131
 132                 addr = p->addr;
 133                 brkp = KPROBE_ARM_BREAKPOINT_INSTRUCTION;
 134
 135                 if (insn >= 0xe0000000)
 136                         brkp |= 0xe0000000;  /* Unconditional instruction */
 137                 else
 138                         brkp |= insn & 0xf0000000;  /* Copy condition from insn */
 139         }
 140
 141         patch_text(addr, brkp);
 142 }
 143
 144 /*
 145  * The actual disarming is done here on each CPU and synchronized using
 146  * stop_machine. This synchronization is necessary on SMP to avoid removing
 147  * a probe between the moment the 'Undefined Instruction' exception is raised
 148  * and the moment the exception handler reads the faulting instruction from
 149  * memory. It is also needed to atomically set the two half-words of a 32-bit
 150  * Thumb breakpoint.
 151  */
 152 int __kprobes __arch_disarm_kprobe(void *p)
 153 {
 154         struct kprobe *kp = p;
 155         void *addr = (void *)((uintptr_t)kp->addr & ~1);
 156
 157         __patch_text(addr, kp->opcode);
 158
 159         return 0;
 160 }
 161
 162 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 163 {
 164         stop_machine(__arch_disarm_kprobe, p, cpu_online_mask);
 165 }
 166
 167 void __kprobes arch_remove_kprobe(struct kprobe *p)
 168 {
 169         if (p->ainsn.insn) {
 170                 free_insn_slot(p->ainsn.insn, 0);
 171                 p->ainsn.insn = NULL;
 172         }
 173 }
 174
 175 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 176 {
 177         kcb->prev_kprobe.kp = kprobe_running();
 178         kcb->prev_kprobe.status = kcb->kprobe_status;
 179 }
 180
 181 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 182 {
 183         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 184         kcb->kprobe_status = kcb->prev_kprobe.status;
 185 }
 186
 187 static void __kprobes set_current_kprobe(struct kprobe *p)
 188 {
 189         __this_cpu_write(current_kprobe, p);
 190 }
 191
 192 static void __kprobes
 193 singlestep_skip(struct kprobe *p, struct pt_regs *regs)
 194 {
 195 #ifdef CONFIG_THUMB2_KERNEL
 196         regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
 197         if (is_wide_instruction(p->opcode))
 198                 regs->ARM_pc += 4;
 199         else
 200                 regs->ARM_pc += 2;
 201 #else
 202         regs->ARM_pc += 4;
 203 #endif
 204 }
 205
 206 static inline void __kprobes
 207 singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 208 {
 209         p->ainsn.insn_singlestep(p->opcode, &p->ainsn, regs);
 210 }
 211
 212 /*
 213  * Called with IRQs disabled. IRQs must remain disabled from that point
 214  * all the way until processing this kprobe is complete.  The current
 215  * kprobes implementation cannot process more than one nested level of
 216  * kprobe, and that level is reserved for user kprobe handlers, so we can't
 217  * risk encountering a new kprobe in an interrupt handler.
 218  */
 219 void __kprobes kprobe_handler(struct pt_regs *regs)
 220 {
 221         struct kprobe *p, *cur;
 222         struct kprobe_ctlblk *kcb;
 223
 224         kcb = get_kprobe_ctlblk();
 225         cur = kprobe_running();
 226
 227 #ifdef CONFIG_THUMB2_KERNEL
 228         /*
 229          * First look for a probe which was registered using an address with
 230          * bit 0 set, this is the usual situation for pointers to Thumb code.
 231          * If not found, fallback to looking for one with bit 0 clear.
 232          */
 233         p = get_kprobe((kprobe_opcode_t *)(regs->ARM_pc | 1));
 234         if (!p)
 235                 p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
 236
 237 #else /* ! CONFIG_THUMB2_KERNEL */
 238         p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
 239 #endif
 240
 241         if (p) {
 242                 if (cur) {
 243                         /* Kprobe is pending, so we're recursing. */
 244                         switch (kcb->kprobe_status) {
 245                         case KPROBE_HIT_ACTIVE:
 246                         case KPROBE_HIT_SSDONE:
 247                                 /* A pre- or post-handler probe got us here. */
 248                                 kprobes_inc_nmissed_count(p);
 249                                 save_previous_kprobe(kcb);
 250                                 set_current_kprobe(p);
 251                                 kcb->kprobe_status = KPROBE_REENTER;
 252                                 singlestep(p, regs, kcb);
 253                                 restore_previous_kprobe(kcb);
 254                                 break;
 255                         default:
 256                                 /* impossible cases */
 257                                 BUG();
 258                         }
 259                 } else if (p->ainsn.insn_check_cc(regs->ARM_cpsr)) {
 260                         /* Probe hit and conditional execution check ok. */
 261                         set_current_kprobe(p);
 262                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 263
 264                         /*
 265                          * If we have no pre-handler or it returned 0, we
 266                          * continue with normal processing.  If we have a
 267                          * pre-handler and it returned non-zero, it prepped
 268                          * for calling the break_handler below on re-entry,
 269                          * so get out doing nothing more here.
 270                          */
 271                         if (!p->pre_handler || !p->pre_handler(p, regs)) {
 272                                 kcb->kprobe_status = KPROBE_HIT_SS;
 273                                 singlestep(p, regs, kcb);
 274                                 if (p->post_handler) {
 275                                         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 276                                         p->post_handler(p, regs, 0);
 277                                 }
 278                                 reset_current_kprobe();
 279                         }
 280                 } else {
 281                         /*
 282                          * Probe hit but conditional execution check failed,
 283                          * so just skip the instruction and continue as if
 284                          * nothing had happened.
 285                          */
 286                         singlestep_skip(p, regs);
 287                 }
 288         } else if (cur) {
 289                 /* We probably hit a jprobe.  Call its break handler. */
 290                 if (cur->break_handler && cur->break_handler(cur, regs)) {
 291                         kcb->kprobe_status = KPROBE_HIT_SS;
 292                         singlestep(cur, regs, kcb);
 293                         if (cur->post_handler) {
 294                                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 295                                 cur->post_handler(cur, regs, 0);
 296                         }
 297                 }
 298                 reset_current_kprobe();
 299         } else {
 300                 /*
 301                  * The probe was removed and a race is in progress.
 302                  * There is nothing we can do about it.  Let's restart
 303                  * the instruction.  By the time we can restart, the
 304                  * real instruction will be there.
 305                  */
 306         }
 307 }
 308
 309 static int __kprobes kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
 310 {
 311         unsigned long flags;
 312         local_irq_save(flags);
 313         kprobe_handler(regs);
 314         local_irq_restore(flags);
 315         return 0;
 316 }
 317
 318 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
 319 {
 320         struct kprobe *cur = kprobe_running();
 321         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 322
 323         switch (kcb->kprobe_status) {
 324         case KPROBE_HIT_SS:
 325         case KPROBE_REENTER:
 326                 /*
 327                  * We are here because the instruction being single
 328                  * stepped caused a page fault. We reset the current
 329                  * kprobe and the PC to point back to the probe address
 330                  * and allow the page fault handler to continue as a
 331                  * normal page fault.
 332                  */
 333                 regs->ARM_pc = (long)cur->addr;
 334                 if (kcb->kprobe_status == KPROBE_REENTER) {
 335                         restore_previous_kprobe(kcb);
 336                 } else {
 337                         reset_current_kprobe();
 338                 }
 339                 break;
 340
 341         case KPROBE_HIT_ACTIVE:
 342         case KPROBE_HIT_SSDONE:
 343                 /*
 344                  * We increment the nmissed count for accounting,
 345                  * we can also use npre/npostfault count for accounting
 346                  * these specific fault cases.
 347                  */
 348                 kprobes_inc_nmissed_count(cur);
 349
 350                 /*
 351                  * We come here because instructions in the pre/post
 352                  * handler caused the page_fault, this could happen
 353                  * if handler tries to access user space by
 354                  * copy_from_user(), get_user() etc. Let the
 355                  * user-specified handler try to fix it.
 356                  */
 357                 if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
 358                         return 1;
 359                 break;
 360
 361         default:
 362                 break;
 363         }
 364
 365         return 0;
 366 }
 367
 368 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 369                                        unsigned long val, void *data)
 370 {
 371         /*
 372          * notify_die() is currently never called on ARM,
 373          * so this callback is currently empty.
 374          */
 375         return NOTIFY_DONE;
 376 }
 377
 378 /*
 379  * When a retprobed function returns, trampoline_handler() is called,
 380  * calling the kretprobe's handler. We construct a struct pt_regs to
 381  * give a view of registers r0-r11 to the user return-handler.  This is
 382  * not a complete pt_regs structure, but that should be plenty sufficient
 383  * for kretprobe handlers which should normally be interested in r0 only
 384  * anyway.
 385  */
 386 void __naked __kprobes kretprobe_trampoline(void)
 387 {
 388         __asm__ __volatile__ (
 389                 "stmdb  sp!, {r0 - r11}         \n\t"
 390                 "mov    r0, sp                  \n\t"
 391                 "bl     trampoline_handler      \n\t"
 392                 "mov    lr, r0                  \n\t"
 393                 "ldmia  sp!, {r0 - r11}         \n\t"
 394 #ifdef CONFIG_THUMB2_KERNEL
 395                 "bx     lr                      \n\t"
 396 #else
 397                 "mov    pc, lr                  \n\t"
 398 #endif
 399                 : : : "memory");
 400 }
 401
 402 /* Called from kretprobe_trampoline */
 403 static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
 404 {
 405         struct kretprobe_instance *ri = NULL;
 406         struct hlist_head *head, empty_rp;
 407         struct hlist_node *tmp;
 408         unsigned long flags, orig_ret_address = 0;
 409         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 410
 411         INIT_HLIST_HEAD(&empty_rp);
 412         kretprobe_hash_lock(current, &head, &flags);
 413
 414         /*
 415          * It is possible to have multiple instances associated with a given
 416          * task either because multiple functions in the call path have
 417          * a return probe installed on them, and/or more than one return
 418          * probe was registered for a target function.
 419          *
 420          * We can handle this because:
 421          *     - instances are always inserted at the head of the list
 422          *     - when multiple return probes are registered for the same
 423          *       function, the first instance's ret_addr will point to the
 424          *       real return address, and all the rest will point to
 425          *       kretprobe_trampoline
 426          */
 427         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 428                 if (ri->task != current)
 429                         /* another task is sharing our hash bucket */
 430                         continue;
 431
 432                 if (ri->rp && ri->rp->handler) {
 433                         __this_cpu_write(current_kprobe, &ri->rp->kp);
 434                         get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
 435                         ri->rp->handler(ri, regs);
 436                         __this_cpu_write(current_kprobe, NULL);
 437                 }
 438
 439                 orig_ret_address = (unsigned long)ri->ret_addr;
 440                 recycle_rp_inst(ri, &empty_rp);
 441
 442                 if (orig_ret_address != trampoline_address)
 443                         /*
 444                          * This is the real return address. Any other
 445                          * instances associated with this task are for
 446                          * other calls deeper on the call stack
 447                          */
 448                         break;
 449         }
 450
 451         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 452         kretprobe_hash_unlock(current, &flags);
 453
 454         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 455                 hlist_del(&ri->hlist);
 456                 kfree(ri);
 457         }
 458
 459         return (void *)orig_ret_address;
 460 }
 461
 462 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 463                                       struct pt_regs *regs)
 464 {
 465         ri->ret_addr = (kprobe_opcode_t *)regs->ARM_lr;
 466
 467         /* Replace the return addr with trampoline addr. */
 468         regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
 469 }
 470
 471 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 472 {
 473         struct jprobe *jp = container_of(p, struct jprobe, kp);
 474         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 475         long sp_addr = regs->ARM_sp;
 476         long cpsr;
 477
 478         kcb->jprobe_saved_regs = *regs;
 479         memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
 480         regs->ARM_pc = (long)jp->entry;
 481
 482         cpsr = regs->ARM_cpsr | PSR_I_BIT;
 483 #ifdef CONFIG_THUMB2_KERNEL
 484         /* Set correct Thumb state in cpsr */
 485         if (regs->ARM_pc & 1)
 486                 cpsr |= PSR_T_BIT;
 487         else
 488                 cpsr &= ~PSR_T_BIT;
 489 #endif
 490         regs->ARM_cpsr = cpsr;
 491
 492         preempt_disable();
 493         return 1;
 494 }
 495
 496 void __kprobes jprobe_return(void)
 497 {
 498         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 499
 500         __asm__ __volatile__ (
 501                 /*
 502                  * Setup an empty pt_regs. Fill SP and PC fields as
 503                  * they're needed by longjmp_break_handler.
 504                  *
 505                  * We allocate some slack between the original SP and start of
 506                  * our fabricated regs. To be precise we want to have worst case
 507                  * covered which is STMFD with all 16 regs so we allocate 2 *
 508                  * sizeof(struct_pt_regs)).
 509                  *
 510                  * This is to prevent any simulated instruction from writing
 511                  * over the regs when they are accessing the stack.
 512                  */
 513 #ifdef CONFIG_THUMB2_KERNEL
 514                 "sub    r0, %0, %1              \n\t"
 515                 "mov    sp, r0                  \n\t"
 516 #else
 517                 "sub    sp, %0, %1              \n\t"
 518 #endif
 519                 "ldr    r0, ="__stringify(JPROBE_MAGIC_ADDR)"\n\t"
 520                 "str    %0, [sp, %2]            \n\t"
 521                 "str    r0, [sp, %3]            \n\t"
 522                 "mov    r0, sp                  \n\t"
 523                 "bl     kprobe_handler          \n\t"
 524
 525                 /*
 526                  * Return to the context saved by setjmp_pre_handler
 527                  * and restored by longjmp_break_handler.
 528                  */
 529 #ifdef CONFIG_THUMB2_KERNEL
 530                 "ldr    lr, [sp, %2]            \n\t" /* lr = saved sp */
 531                 "ldrd   r0, r1, [sp, %5]        \n\t" /* r0,r1 = saved lr,pc */
 532                 "ldr    r2, [sp, %4]            \n\t" /* r2 = saved psr */
 533                 "stmdb  lr!, {r0, r1, r2}       \n\t" /* push saved lr and */
 534                                                       /* rfe context */
 535                 "ldmia  sp, {r0 - r12}          \n\t"
 536                 "mov    sp, lr                  \n\t"
 537                 "ldr    lr, [sp], #4            \n\t"
 538                 "rfeia  sp!                     \n\t"
 539 #else
 540                 "ldr    r0, [sp, %4]            \n\t"
 541                 "msr    cpsr_cxsf, r0           \n\t"
 542                 "ldmia  sp, {r0 - pc}           \n\t"
 543 #endif
 544                 :
 545                 : "r" (kcb->jprobe_saved_regs.ARM_sp),
 546                   "I" (sizeof(struct pt_regs) * 2),
 547                   "J" (offsetof(struct pt_regs, ARM_sp)),
 548                   "J" (offsetof(struct pt_regs, ARM_pc)),
 549                   "J" (offsetof(struct pt_regs, ARM_cpsr)),
 550                   "J" (offsetof(struct pt_regs, ARM_lr))
 551                 : "memory", "cc");
 552 }
 553
 554 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 555 {
 556         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 557         long stack_addr = kcb->jprobe_saved_regs.ARM_sp;
 558         long orig_sp = regs->ARM_sp;
 559         struct jprobe *jp = container_of(p, struct jprobe, kp);
 560
 561         if (regs->ARM_pc == JPROBE_MAGIC_ADDR) {
 562                 if (orig_sp != stack_addr) {
 563                         struct pt_regs *saved_regs =
 564                                 (struct pt_regs *)kcb->jprobe_saved_regs.ARM_sp;
 565                         printk("current sp %lx does not match saved sp %lx\n",
 566                                orig_sp, stack_addr);
 567                         printk("Saved registers for jprobe %p\n", jp);
 568                         show_regs(saved_regs);
 569                         printk("Current registers\n");
 570                         show_regs(regs);
 571                         BUG();
 572                 }
 573                 *regs = kcb->jprobe_saved_regs;
 574                 memcpy((void *)stack_addr, kcb->jprobes_stack,
 575                        MIN_STACK_SIZE(stack_addr));
 576                 preempt_enable_no_resched();
 577                 return 1;
 578         }
 579         return 0;
 580 }
 581
 582 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 583 {
 584         return 0;
 585 }
 586
 587 #ifdef CONFIG_THUMB2_KERNEL
 588
 589 static struct undef_hook kprobes_thumb16_break_hook = {
 590         .instr_mask     = 0xffff,
 591         .instr_val      = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION,
 592         .cpsr_mask      = MODE_MASK,
 593         .cpsr_val       = SVC_MODE,
 594         .fn             = kprobe_trap_handler,
 595 };
 596
 597 static struct undef_hook kprobes_thumb32_break_hook = {
 598         .instr_mask     = 0xffffffff,
 599         .instr_val      = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION,
 600         .cpsr_mask      = MODE_MASK,
 601         .cpsr_val       = SVC_MODE,
 602         .fn             = kprobe_trap_handler,
 603 };
 604
 605 #else  /* !CONFIG_THUMB2_KERNEL */
 606
 607 static struct undef_hook kprobes_arm_break_hook = {
 608         .instr_mask     = 0x0fffffff,
 609         .instr_val      = KPROBE_ARM_BREAKPOINT_INSTRUCTION,
 610         .cpsr_mask      = MODE_MASK,
 611         .cpsr_val       = SVC_MODE,
 612         .fn             = kprobe_trap_handler,
 613 };
 614
 615 #endif /* !CONFIG_THUMB2_KERNEL */
 616
 617 int __init arch_init_kprobes()
 618 {
 619         arm_probes_decode_init();
 620 #ifdef CONFIG_THUMB2_KERNEL
 621         register_undef_hook(&kprobes_thumb16_break_hook);
 622         register_undef_hook(&kprobes_thumb32_break_hook);
 623 #else
 624         register_undef_hook(&kprobes_arm_break_hook);
 625 #endif
 626         return 0;
 627 }