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 #include <linux/percpu.h>
  32 #include <linux/bug.h>
  33
  34 #include "kprobes.h"
  35 #include "probes-arm.h"
  36 #include "probes-thumb.h"
  37 #include "patch.h"
  38
  39 #define MIN_STACK_SIZE(addr)                            \
  40         min((unsigned long)MAX_STACK_SIZE,              \
  41             (unsigned long)current_thread_info() + THREAD_START_SP - (addr))
  42
  43 #define flush_insns(addr, size)                         \
  44         flush_icache_range((unsigned long)(addr),       \
  45                            (unsigned long)(addr) +      \
  46                            (size))
  47
  48 /* Used as a marker in ARM_pc to note when we're in a jprobe. */
  49 #define JPROBE_MAGIC_ADDR               0xffffffff
  50
  51 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  52 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  53
  54
  55 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  56 {
  57         kprobe_opcode_t insn;
  58         kprobe_opcode_t tmp_insn[MAX_INSN_SIZE];
  59         unsigned long addr = (unsigned long)p->addr;
  60         bool thumb;
  61         kprobe_decode_insn_t *decode_insn;
  62         const union decode_action *actions;
  63         int is;
  64
  65         if (in_exception_text(addr))
  66                 return -EINVAL;
  67
  68 #ifdef CONFIG_THUMB2_KERNEL
  69         thumb = true;
  70         addr &= ~1; /* Bit 0 would normally be set to indicate Thumb code */
  71         insn = __mem_to_opcode_thumb16(((u16 *)addr)[0]);
  72         if (is_wide_instruction(insn)) {
  73                 u16 inst2 = __mem_to_opcode_thumb16(((u16 *)addr)[1]);
  74                 insn = __opcode_thumb32_compose(insn, inst2);
  75                 decode_insn = thumb32_probes_decode_insn;
  76                 actions = kprobes_t32_actions;
  77         } else {
  78                 decode_insn = thumb16_probes_decode_insn;
  79                 actions = kprobes_t16_actions;
  80         }
  81 #else /* !CONFIG_THUMB2_KERNEL */
  82         thumb = false;
  83         if (addr & 0x3)
  84                 return -EINVAL;
  85         insn = __mem_to_opcode_arm(*p->addr);
  86         decode_insn = arm_probes_decode_insn;
  87         actions = kprobes_arm_actions;
  88 #endif
  89
  90         p->opcode = insn;
  91         p->ainsn.insn = tmp_insn;
  92
  93         switch ((*decode_insn)(insn, &p->ainsn, true, actions)) {
  94         case INSN_REJECTED:     /* not supported */
  95                 return -EINVAL;
  96
  97         case INSN_GOOD:         /* instruction uses slot */
  98                 p->ainsn.insn = get_insn_slot();
  99                 if (!p->ainsn.insn)
 100                         return -ENOMEM;
 101                 for (is = 0; is < MAX_INSN_SIZE; ++is)
 102                         p->ainsn.insn[is] = tmp_insn[is];
 103                 flush_insns(p->ainsn.insn,
 104                                 sizeof(p->ainsn.insn[0]) * MAX_INSN_SIZE);
 105                 p->ainsn.insn_fn = (probes_insn_fn_t *)
 106                                         ((uintptr_t)p->ainsn.insn | thumb);
 107                 break;
 108
 109         case INSN_GOOD_NO_SLOT: /* instruction doesn't need insn slot */
 110                 p->ainsn.insn = NULL;
 111                 break;
 112         }
 113
 114         return 0;
 115 }
 116
 117 void __kprobes arch_arm_kprobe(struct kprobe *p)
 118 {
 119         unsigned int brkp;
 120         void *addr;
 121
 122         if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
 123                 /* Remove any Thumb flag */
 124                 addr = (void *)((uintptr_t)p->addr & ~1);
 125
 126                 if (is_wide_instruction(p->opcode))
 127                         brkp = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION;
 128                 else
 129                         brkp = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION;
 130         } else {
 131                 kprobe_opcode_t insn = p->opcode;
 132
 133                 addr = p->addr;
 134                 brkp = KPROBE_ARM_BREAKPOINT_INSTRUCTION;
 135
 136                 if (insn >= 0xe0000000)
 137                         brkp |= 0xe0000000;  /* Unconditional instruction */
 138                 else
 139                         brkp |= insn & 0xf0000000;  /* Copy condition from insn */
 140         }
 141
 142         patch_text(addr, brkp);
 143 }
 144
 145 /*
 146  * The actual disarming is done here on each CPU and synchronized using
 147  * stop_machine. This synchronization is necessary on SMP to avoid removing
 148  * a probe between the moment the 'Undefined Instruction' exception is raised
 149  * and the moment the exception handler reads the faulting instruction from
 150  * memory. It is also needed to atomically set the two half-words of a 32-bit
 151  * Thumb breakpoint.
 152  */
 153 int __kprobes __arch_disarm_kprobe(void *p)
 154 {
 155         struct kprobe *kp = p;
 156         void *addr = (void *)((uintptr_t)kp->addr & ~1);
 157
 158         __patch_text(addr, kp->opcode);
 159
 160         return 0;
 161 }
 162
 163 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 164 {
 165         stop_machine(__arch_disarm_kprobe, p, cpu_online_mask);
 166 }
 167
 168 void __kprobes arch_remove_kprobe(struct kprobe *p)
 169 {
 170         if (p->ainsn.insn) {
 171                 free_insn_slot(p->ainsn.insn, 0);
 172                 p->ainsn.insn = NULL;
 173         }
 174 }
 175
 176 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 177 {
 178         kcb->prev_kprobe.kp = kprobe_running();
 179         kcb->prev_kprobe.status = kcb->kprobe_status;
 180 }
 181
 182 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 183 {
 184         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 185         kcb->kprobe_status = kcb->prev_kprobe.status;
 186 }
 187
 188 static void __kprobes set_current_kprobe(struct kprobe *p)
 189 {
 190         __this_cpu_write(current_kprobe, p);
 191 }
 192
 193 static void __kprobes
 194 singlestep_skip(struct kprobe *p, struct pt_regs *regs)
 195 {
 196 #ifdef CONFIG_THUMB2_KERNEL
 197         regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
 198         if (is_wide_instruction(p->opcode))
 199                 regs->ARM_pc += 4;
 200         else
 201                 regs->ARM_pc += 2;
 202 #else
 203         regs->ARM_pc += 4;
 204 #endif
 205 }
 206
 207 static inline void __kprobes
 208 singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 209 {
 210         p->ainsn.insn_singlestep(p->opcode, &p->ainsn, regs);
 211 }
 212
 213 /*
 214  * Called with IRQs disabled. IRQs must remain disabled from that point
 215  * all the way until processing this kprobe is complete.  The current
 216  * kprobes implementation cannot process more than one nested level of
 217  * kprobe, and that level is reserved for user kprobe handlers, so we can't
 218  * risk encountering a new kprobe in an interrupt handler.
 219  */
 220 void __kprobes kprobe_handler(struct pt_regs *regs)
 221 {
 222         struct kprobe *p, *cur;
 223         struct kprobe_ctlblk *kcb;
 224
 225         kcb = get_kprobe_ctlblk();
 226         cur = kprobe_running();
 227
 228 #ifdef CONFIG_THUMB2_KERNEL
 229         /*
 230          * First look for a probe which was registered using an address with
 231          * bit 0 set, this is the usual situation for pointers to Thumb code.
 232          * If not found, fallback to looking for one with bit 0 clear.
 233          */
 234         p = get_kprobe((kprobe_opcode_t *)(regs->ARM_pc | 1));
 235         if (!p)
 236                 p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
 237
 238 #else /* ! CONFIG_THUMB2_KERNEL */
 239         p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
 240 #endif
 241
 242         if (p) {
 243                 if (cur) {
 244                         /* Kprobe is pending, so we're recursing. */
 245                         switch (kcb->kprobe_status) {
 246                         case KPROBE_HIT_ACTIVE:
 247                         case KPROBE_HIT_SSDONE:
 248                                 /* A pre- or post-handler probe got us here. */
 249                                 kprobes_inc_nmissed_count(p);
 250                                 save_previous_kprobe(kcb);
 251                                 set_current_kprobe(p);
 252                                 kcb->kprobe_status = KPROBE_REENTER;
 253                                 singlestep(p, regs, kcb);
 254                                 restore_previous_kprobe(kcb);
 255                                 break;
 256                         default:
 257                                 /* impossible cases */
 258                                 BUG();
 259                         }
 260                 } else if (p->ainsn.insn_check_cc(regs->ARM_cpsr)) {
 261                         /* Probe hit and conditional execution check ok. */
 262                         set_current_kprobe(p);
 263                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 264
 265                         /*
 266                          * If we have no pre-handler or it returned 0, we
 267                          * continue with normal processing.  If we have a
 268                          * pre-handler and it returned non-zero, it prepped
 269                          * for calling the break_handler below on re-entry,
 270                          * so get out doing nothing more here.
 271                          */
 272                         if (!p->pre_handler || !p->pre_handler(p, regs)) {
 273                                 kcb->kprobe_status = KPROBE_HIT_SS;
 274                                 singlestep(p, regs, kcb);
 275                                 if (p->post_handler) {
 276                                         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 277                                         p->post_handler(p, regs, 0);
 278                                 }
 279                                 reset_current_kprobe();
 280                         }
 281                 } else {
 282                         /*
 283                          * Probe hit but conditional execution check failed,
 284                          * so just skip the instruction and continue as if
 285                          * nothing had happened.
 286                          */
 287                         singlestep_skip(p, regs);
 288                 }
 289         } else if (cur) {
 290                 /* We probably hit a jprobe.  Call its break handler. */
 291                 if (cur->break_handler && cur->break_handler(cur, regs)) {
 292                         kcb->kprobe_status = KPROBE_HIT_SS;
 293                         singlestep(cur, regs, kcb);
 294                         if (cur->post_handler) {
 295                                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 296                                 cur->post_handler(cur, regs, 0);
 297                         }
 298                 }
 299                 reset_current_kprobe();
 300         } else {
 301                 /*
 302                  * The probe was removed and a race is in progress.
 303                  * There is nothing we can do about it.  Let's restart
 304                  * the instruction.  By the time we can restart, the
 305                  * real instruction will be there.
 306                  */
 307         }
 308 }
 309
 310 static int __kprobes kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
 311 {
 312         unsigned long flags;
 313         local_irq_save(flags);
 314         kprobe_handler(regs);
 315         local_irq_restore(flags);
 316         return 0;
 317 }
 318
 319 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
 320 {
 321         struct kprobe *cur = kprobe_running();
 322         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 323
 324         switch (kcb->kprobe_status) {
 325         case KPROBE_HIT_SS:
 326         case KPROBE_REENTER:
 327                 /*
 328                  * We are here because the instruction being single
 329                  * stepped caused a page fault. We reset the current
 330                  * kprobe and the PC to point back to the probe address
 331                  * and allow the page fault handler to continue as a
 332                  * normal page fault.
 333                  */
 334                 regs->ARM_pc = (long)cur->addr;
 335                 if (kcb->kprobe_status == KPROBE_REENTER) {
 336                         restore_previous_kprobe(kcb);
 337                 } else {
 338                         reset_current_kprobe();
 339                 }
 340                 break;
 341
 342         case KPROBE_HIT_ACTIVE:
 343         case KPROBE_HIT_SSDONE:
 344                 /*
 345                  * We increment the nmissed count for accounting,
 346                  * we can also use npre/npostfault count for accounting
 347                  * these specific fault cases.
 348                  */
 349                 kprobes_inc_nmissed_count(cur);
 350
 351                 /*
 352                  * We come here because instructions in the pre/post
 353                  * handler caused the page_fault, this could happen
 354                  * if handler tries to access user space by
 355                  * copy_from_user(), get_user() etc. Let the
 356                  * user-specified handler try to fix it.
 357                  */
 358                 if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
 359                         return 1;
 360                 break;
 361
 362         default:
 363                 break;
 364         }
 365
 366         return 0;
 367 }
 368
 369 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 370                                        unsigned long val, void *data)
 371 {
 372         /*
 373          * notify_die() is currently never called on ARM,
 374          * so this callback is currently empty.
 375          */
 376         return NOTIFY_DONE;
 377 }
 378
 379 /*
 380  * When a retprobed function returns, trampoline_handler() is called,
 381  * calling the kretprobe's handler. We construct a struct pt_regs to
 382  * give a view of registers r0-r11 to the user return-handler.  This is
 383  * not a complete pt_regs structure, but that should be plenty sufficient
 384  * for kretprobe handlers which should normally be interested in r0 only
 385  * anyway.
 386  */
 387 void __naked __kprobes kretprobe_trampoline(void)
 388 {
 389         __asm__ __volatile__ (
 390                 "stmdb  sp!, {r0 - r11}         \n\t"
 391                 "mov    r0, sp                  \n\t"
 392                 "bl     trampoline_handler      \n\t"
 393                 "mov    lr, r0                  \n\t"
 394                 "ldmia  sp!, {r0 - r11}         \n\t"
 395 #ifdef CONFIG_THUMB2_KERNEL
 396                 "bx     lr                      \n\t"
 397 #else
 398                 "mov    pc, lr                  \n\t"
 399 #endif
 400                 : : : "memory");
 401 }
 402
 403 /* Called from kretprobe_trampoline */
 404 static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
 405 {
 406         struct kretprobe_instance *ri = NULL;
 407         struct hlist_head *head, empty_rp;
 408         struct hlist_node *tmp;
 409         unsigned long flags, orig_ret_address = 0;
 410         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 411
 412         INIT_HLIST_HEAD(&empty_rp);
 413         kretprobe_hash_lock(current, &head, &flags);
 414
 415         /*
 416          * It is possible to have multiple instances associated with a given
 417          * task either because multiple functions in the call path have
 418          * a return probe installed on them, and/or more than one return
 419          * probe was registered for a target function.
 420          *
 421          * We can handle this because:
 422          *     - instances are always inserted at the head of the list
 423          *     - when multiple return probes are registered for the same
 424          *       function, the first instance's ret_addr will point to the
 425          *       real return address, and all the rest will point to
 426          *       kretprobe_trampoline
 427          */
 428         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 429                 if (ri->task != current)
 430                         /* another task is sharing our hash bucket */
 431                         continue;
 432
 433                 if (ri->rp && ri->rp->handler) {
 434                         __this_cpu_write(current_kprobe, &ri->rp->kp);
 435                         get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
 436                         ri->rp->handler(ri, regs);
 437                         __this_cpu_write(current_kprobe, NULL);
 438                 }
 439
 440                 orig_ret_address = (unsigned long)ri->ret_addr;
 441                 recycle_rp_inst(ri, &empty_rp);
 442
 443                 if (orig_ret_address != trampoline_address)
 444                         /*
 445                          * This is the real return address. Any other
 446                          * instances associated with this task are for
 447                          * other calls deeper on the call stack
 448                          */
 449                         break;
 450         }
 451
 452         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 453         kretprobe_hash_unlock(current, &flags);
 454
 455         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 456                 hlist_del(&ri->hlist);
 457                 kfree(ri);
 458         }
 459
 460         return (void *)orig_ret_address;
 461 }
 462
 463 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 464                                       struct pt_regs *regs)
 465 {
 466         ri->ret_addr = (kprobe_opcode_t *)regs->ARM_lr;
 467
 468         /* Replace the return addr with trampoline addr. */
 469         regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
 470 }
 471
 472 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 473 {
 474         struct jprobe *jp = container_of(p, struct jprobe, kp);
 475         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 476         long sp_addr = regs->ARM_sp;
 477         long cpsr;
 478
 479         kcb->jprobe_saved_regs = *regs;
 480         memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
 481         regs->ARM_pc = (long)jp->entry;
 482
 483         cpsr = regs->ARM_cpsr | PSR_I_BIT;
 484 #ifdef CONFIG_THUMB2_KERNEL
 485         /* Set correct Thumb state in cpsr */
 486         if (regs->ARM_pc & 1)
 487                 cpsr |= PSR_T_BIT;
 488         else
 489                 cpsr &= ~PSR_T_BIT;
 490 #endif
 491         regs->ARM_cpsr = cpsr;
 492
 493         preempt_disable();
 494         return 1;
 495 }
 496
 497 void __kprobes jprobe_return(void)
 498 {
 499         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 500
 501         __asm__ __volatile__ (
 502                 /*
 503                  * Setup an empty pt_regs. Fill SP and PC fields as
 504                  * they're needed by longjmp_break_handler.
 505                  *
 506                  * We allocate some slack between the original SP and start of
 507                  * our fabricated regs. To be precise we want to have worst case
 508                  * covered which is STMFD with all 16 regs so we allocate 2 *
 509                  * sizeof(struct_pt_regs)).
 510                  *
 511                  * This is to prevent any simulated instruction from writing
 512                  * over the regs when they are accessing the stack.
 513                  */
 514 #ifdef CONFIG_THUMB2_KERNEL
 515                 "sub    r0, %0, %1              \n\t"
 516                 "mov    sp, r0                  \n\t"
 517 #else
 518                 "sub    sp, %0, %1              \n\t"
 519 #endif
 520                 "ldr    r0, ="__stringify(JPROBE_MAGIC_ADDR)"\n\t"
 521                 "str    %0, [sp, %2]            \n\t"
 522                 "str    r0, [sp, %3]            \n\t"
 523                 "mov    r0, sp                  \n\t"
 524                 "bl     kprobe_handler          \n\t"
 525
 526                 /*
 527                  * Return to the context saved by setjmp_pre_handler
 528                  * and restored by longjmp_break_handler.
 529                  */
 530 #ifdef CONFIG_THUMB2_KERNEL
 531                 "ldr    lr, [sp, %2]            \n\t" /* lr = saved sp */
 532                 "ldrd   r0, r1, [sp, %5]        \n\t" /* r0,r1 = saved lr,pc */
 533                 "ldr    r2, [sp, %4]            \n\t" /* r2 = saved psr */
 534                 "stmdb  lr!, {r0, r1, r2}       \n\t" /* push saved lr and */
 535                                                       /* rfe context */
 536                 "ldmia  sp, {r0 - r12}          \n\t"
 537                 "mov    sp, lr                  \n\t"
 538                 "ldr    lr, [sp], #4            \n\t"
 539                 "rfeia  sp!                     \n\t"
 540 #else
 541                 "ldr    r0, [sp, %4]            \n\t"
 542                 "msr    cpsr_cxsf, r0           \n\t"
 543                 "ldmia  sp, {r0 - pc}           \n\t"
 544 #endif
 545                 :
 546                 : "r" (kcb->jprobe_saved_regs.ARM_sp),
 547                   "I" (sizeof(struct pt_regs) * 2),
 548                   "J" (offsetof(struct pt_regs, ARM_sp)),
 549                   "J" (offsetof(struct pt_regs, ARM_pc)),
 550                   "J" (offsetof(struct pt_regs, ARM_cpsr)),
 551                   "J" (offsetof(struct pt_regs, ARM_lr))
 552                 : "memory", "cc");
 553 }
 554
 555 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 556 {
 557         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 558         long stack_addr = kcb->jprobe_saved_regs.ARM_sp;
 559         long orig_sp = regs->ARM_sp;
 560         struct jprobe *jp = container_of(p, struct jprobe, kp);
 561
 562         if (regs->ARM_pc == JPROBE_MAGIC_ADDR) {
 563                 if (orig_sp != stack_addr) {
 564                         struct pt_regs *saved_regs =
 565                                 (struct pt_regs *)kcb->jprobe_saved_regs.ARM_sp;
 566                         printk("current sp %lx does not match saved sp %lx\n",
 567                                orig_sp, stack_addr);
 568                         printk("Saved registers for jprobe %p\n", jp);
 569                         show_regs(saved_regs);
 570                         printk("Current registers\n");
 571                         show_regs(regs);
 572                         BUG();
 573                 }
 574                 *regs = kcb->jprobe_saved_regs;
 575                 memcpy((void *)stack_addr, kcb->jprobes_stack,
 576                        MIN_STACK_SIZE(stack_addr));
 577                 preempt_enable_no_resched();
 578                 return 1;
 579         }
 580         return 0;
 581 }
 582
 583 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 584 {
 585         return 0;
 586 }
 587
 588 #ifdef CONFIG_THUMB2_KERNEL
 589
 590 static struct undef_hook kprobes_thumb16_break_hook = {
 591         .instr_mask     = 0xffff,
 592         .instr_val      = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION,
 593         .cpsr_mask      = MODE_MASK,
 594         .cpsr_val       = SVC_MODE,
 595         .fn             = kprobe_trap_handler,
 596 };
 597
 598 static struct undef_hook kprobes_thumb32_break_hook = {
 599         .instr_mask     = 0xffffffff,
 600         .instr_val      = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION,
 601         .cpsr_mask      = MODE_MASK,
 602         .cpsr_val       = SVC_MODE,
 603         .fn             = kprobe_trap_handler,
 604 };
 605
 606 #else  /* !CONFIG_THUMB2_KERNEL */
 607
 608 static struct undef_hook kprobes_arm_break_hook = {
 609         .instr_mask     = 0x0fffffff,
 610         .instr_val      = KPROBE_ARM_BREAKPOINT_INSTRUCTION,
 611         .cpsr_mask      = MODE_MASK,
 612         .cpsr_val       = SVC_MODE,
 613         .fn             = kprobe_trap_handler,
 614 };
 615
 616 #endif /* !CONFIG_THUMB2_KERNEL */
 617
 618 int __init arch_init_kprobes()
 619 {
 620         arm_probes_decode_init();
 621 #ifdef CONFIG_THUMB2_KERNEL
 622         register_undef_hook(&kprobes_thumb16_break_hook);
 623         register_undef_hook(&kprobes_thumb32_break_hook);
 624 #else
 625         register_undef_hook(&kprobes_arm_break_hook);
 626 #endif
 627         return 0;
 628 }