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
  31 #include "kprobes.h"
  32
  33 #define MIN_STACK_SIZE(addr)                            \
  34         min((unsigned long)MAX_STACK_SIZE,              \
  35             (unsigned long)current_thread_info() + THREAD_START_SP - (addr))
  36
  37 #define flush_insns(addr, size)                         \
  38         flush_icache_range((unsigned long)(addr),       \
  39                            (unsigned long)(addr) +      \
  40                            (size))
  41
  42 /* Used as a marker in ARM_pc to note when we're in a jprobe. */
  43 #define JPROBE_MAGIC_ADDR               0xffffffff
  44
  45 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  46 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  47
  48
  49 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  50 {
  51         kprobe_opcode_t insn;
  52         kprobe_opcode_t tmp_insn[MAX_INSN_SIZE];
  53         unsigned long addr = (unsigned long)p->addr;
  54         kprobe_decode_insn_t *decode_insn;
  55         int is;
  56
  57         if (in_exception_text(addr))
  58                 return -EINVAL;
  59
  60 #ifdef CONFIG_THUMB2_KERNEL
  61         addr &= ~1; /* Bit 0 would normally be set to indicate Thumb code */
  62         insn = ((u16 *)addr)[0];
  63         if (is_wide_instruction(insn)) {
  64                 insn <<= 16;
  65                 insn |= ((u16 *)addr)[1];
  66                 decode_insn = thumb32_kprobe_decode_insn;
  67         } else
  68                 decode_insn = thumb16_kprobe_decode_insn;
  69 #else /* !CONFIG_THUMB2_KERNEL */
  70         if (addr & 0x3)
  71                 return -EINVAL;
  72         insn = *p->addr;
  73         decode_insn = arm_kprobe_decode_insn;
  74 #endif
  75
  76         p->opcode = insn;
  77         p->ainsn.insn = tmp_insn;
  78
  79         switch ((*decode_insn)(insn, &p->ainsn)) {
  80         case INSN_REJECTED:     /* not supported */
  81                 return -EINVAL;
  82
  83         case INSN_GOOD:         /* instruction uses slot */
  84                 p->ainsn.insn = get_insn_slot();
  85                 if (!p->ainsn.insn)
  86                         return -ENOMEM;
  87                 for (is = 0; is < MAX_INSN_SIZE; ++is)
  88                         p->ainsn.insn[is] = tmp_insn[is];
  89                 flush_insns(p->ainsn.insn,
  90                                 sizeof(p->ainsn.insn[0]) * MAX_INSN_SIZE);
  91                 break;
  92
  93         case INSN_GOOD_NO_SLOT: /* instruction doesn't need insn slot */
  94                 p->ainsn.insn = NULL;
  95                 break;
  96         }
  97
  98         return 0;
  99 }
 100
 101 #ifdef CONFIG_THUMB2_KERNEL
 102
 103 /*
 104  * For a 32-bit Thumb breakpoint spanning two memory words we need to take
 105  * special precautions to insert the breakpoint atomically, especially on SMP
 106  * systems. This is achieved by calling this arming function using stop_machine.
 107  */
 108 static int __kprobes set_t32_breakpoint(void *addr)
 109 {
 110         ((u16 *)addr)[0] = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION >> 16;
 111         ((u16 *)addr)[1] = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION & 0xffff;
 112         flush_insns(addr, 2*sizeof(u16));
 113         return 0;
 114 }
 115
 116 void __kprobes arch_arm_kprobe(struct kprobe *p)
 117 {
 118         uintptr_t addr = (uintptr_t)p->addr & ~1; /* Remove any Thumb flag */
 119
 120         if (!is_wide_instruction(p->opcode)) {
 121                 *(u16 *)addr = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION;
 122                 flush_insns(addr, sizeof(u16));
 123         } else if (addr & 2) {
 124                 /* A 32-bit instruction spanning two words needs special care */
 125                 stop_machine(set_t32_breakpoint, (void *)addr, &cpu_online_map);
 126         } else {
 127                 /* Word aligned 32-bit instruction can be written atomically */
 128                 u32 bkp = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION;
 129 #ifndef __ARMEB__ /* Swap halfwords for little-endian */
 130                 bkp = (bkp >> 16) | (bkp << 16);
 131 #endif
 132                 *(u32 *)addr = bkp;
 133                 flush_insns(addr, sizeof(u32));
 134         }
 135 }
 136
 137 #else /* !CONFIG_THUMB2_KERNEL */
 138
 139 void __kprobes arch_arm_kprobe(struct kprobe *p)
 140 {
 141         kprobe_opcode_t insn = p->opcode;
 142         kprobe_opcode_t brkp = KPROBE_ARM_BREAKPOINT_INSTRUCTION;
 143         if (insn >= 0xe0000000)
 144                 brkp |= 0xe0000000;  /* Unconditional instruction */
 145         else
 146                 brkp |= insn & 0xf0000000;  /* Copy condition from insn */
 147         *p->addr = brkp;
 148         flush_insns(p->addr, sizeof(p->addr[0]));
 149 }
 150
 151 #endif /* !CONFIG_THUMB2_KERNEL */
 152
 153 /*
 154  * The actual disarming is done here on each CPU and synchronized using
 155  * stop_machine. This synchronization is necessary on SMP to avoid removing
 156  * a probe between the moment the 'Undefined Instruction' exception is raised
 157  * and the moment the exception handler reads the faulting instruction from
 158  * memory. It is also needed to atomically set the two half-words of a 32-bit
 159  * Thumb breakpoint.
 160  */
 161 int __kprobes __arch_disarm_kprobe(void *p)
 162 {
 163         struct kprobe *kp = p;
 164 #ifdef CONFIG_THUMB2_KERNEL
 165         u16 *addr = (u16 *)((uintptr_t)kp->addr & ~1);
 166         kprobe_opcode_t insn = kp->opcode;
 167         unsigned int len;
 168
 169         if (is_wide_instruction(insn)) {
 170                 ((u16 *)addr)[0] = insn>>16;
 171                 ((u16 *)addr)[1] = insn;
 172                 len = 2*sizeof(u16);
 173         } else {
 174                 ((u16 *)addr)[0] = insn;
 175                 len = sizeof(u16);
 176         }
 177         flush_insns(addr, len);
 178
 179 #else /* !CONFIG_THUMB2_KERNEL */
 180         *kp->addr = kp->opcode;
 181         flush_insns(kp->addr, sizeof(kp->addr[0]));
 182 #endif
 183         return 0;
 184 }
 185
 186 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 187 {
 188         stop_machine(__arch_disarm_kprobe, p, &cpu_online_map);
 189 }
 190
 191 void __kprobes arch_remove_kprobe(struct kprobe *p)
 192 {
 193         if (p->ainsn.insn) {
 194                 free_insn_slot(p->ainsn.insn, 0);
 195                 p->ainsn.insn = NULL;
 196         }
 197 }
 198
 199 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 200 {
 201         kcb->prev_kprobe.kp = kprobe_running();
 202         kcb->prev_kprobe.status = kcb->kprobe_status;
 203 }
 204
 205 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 206 {
 207         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
 208         kcb->kprobe_status = kcb->prev_kprobe.status;
 209 }
 210
 211 static void __kprobes set_current_kprobe(struct kprobe *p)
 212 {
 213         __get_cpu_var(current_kprobe) = p;
 214 }
 215
 216 static void __kprobes
 217 singlestep_skip(struct kprobe *p, struct pt_regs *regs)
 218 {
 219 #ifdef CONFIG_THUMB2_KERNEL
 220         regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
 221         if (is_wide_instruction(p->opcode))
 222                 regs->ARM_pc += 4;
 223         else
 224                 regs->ARM_pc += 2;
 225 #else
 226         regs->ARM_pc += 4;
 227 #endif
 228 }
 229
 230 static inline void __kprobes
 231 singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 232 {
 233         p->ainsn.insn_singlestep(p, regs);
 234 }
 235
 236 /*
 237  * Called with IRQs disabled. IRQs must remain disabled from that point
 238  * all the way until processing this kprobe is complete.  The current
 239  * kprobes implementation cannot process more than one nested level of
 240  * kprobe, and that level is reserved for user kprobe handlers, so we can't
 241  * risk encountering a new kprobe in an interrupt handler.
 242  */
 243 void __kprobes kprobe_handler(struct pt_regs *regs)
 244 {
 245         struct kprobe *p, *cur;
 246         struct kprobe_ctlblk *kcb;
 247
 248         kcb = get_kprobe_ctlblk();
 249         cur = kprobe_running();
 250
 251 #ifdef CONFIG_THUMB2_KERNEL
 252         /*
 253          * First look for a probe which was registered using an address with
 254          * bit 0 set, this is the usual situation for pointers to Thumb code.
 255          * If not found, fallback to looking for one with bit 0 clear.
 256          */
 257         p = get_kprobe((kprobe_opcode_t *)(regs->ARM_pc | 1));
 258         if (!p)
 259                 p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
 260
 261 #else /* ! CONFIG_THUMB2_KERNEL */
 262         p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
 263 #endif
 264
 265         if (p) {
 266                 if (cur) {
 267                         /* Kprobe is pending, so we're recursing. */
 268                         switch (kcb->kprobe_status) {
 269                         case KPROBE_HIT_ACTIVE:
 270                         case KPROBE_HIT_SSDONE:
 271                                 /* A pre- or post-handler probe got us here. */
 272                                 kprobes_inc_nmissed_count(p);
 273                                 save_previous_kprobe(kcb);
 274                                 set_current_kprobe(p);
 275                                 kcb->kprobe_status = KPROBE_REENTER;
 276                                 singlestep(p, regs, kcb);
 277                                 restore_previous_kprobe(kcb);
 278                                 break;
 279                         default:
 280                                 /* impossible cases */
 281                                 BUG();
 282                         }
 283                 } else if (p->ainsn.insn_check_cc(regs->ARM_cpsr)) {
 284                         /* Probe hit and conditional execution check ok. */
 285                         set_current_kprobe(p);
 286                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 287
 288                         /*
 289                          * If we have no pre-handler or it returned 0, we
 290                          * continue with normal processing.  If we have a
 291                          * pre-handler and it returned non-zero, it prepped
 292                          * for calling the break_handler below on re-entry,
 293                          * so get out doing nothing more here.
 294                          */
 295                         if (!p->pre_handler || !p->pre_handler(p, regs)) {
 296                                 kcb->kprobe_status = KPROBE_HIT_SS;
 297                                 singlestep(p, regs, kcb);
 298                                 if (p->post_handler) {
 299                                         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 300                                         p->post_handler(p, regs, 0);
 301                                 }
 302                                 reset_current_kprobe();
 303                         }
 304                 } else {
 305                         /*
 306                          * Probe hit but conditional execution check failed,
 307                          * so just skip the instruction and continue as if
 308                          * nothing had happened.
 309                          */
 310                         singlestep_skip(p, regs);
 311                 }
 312         } else if (cur) {
 313                 /* We probably hit a jprobe.  Call its break handler. */
 314                 if (cur->break_handler && cur->break_handler(cur, regs)) {
 315                         kcb->kprobe_status = KPROBE_HIT_SS;
 316                         singlestep(cur, regs, kcb);
 317                         if (cur->post_handler) {
 318                                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 319                                 cur->post_handler(cur, regs, 0);
 320                         }
 321                 }
 322                 reset_current_kprobe();
 323         } else {
 324                 /*
 325                  * The probe was removed and a race is in progress.
 326                  * There is nothing we can do about it.  Let's restart
 327                  * the instruction.  By the time we can restart, the
 328                  * real instruction will be there.
 329                  */
 330         }
 331 }
 332
 333 static int __kprobes kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
 334 {
 335         unsigned long flags;
 336         local_irq_save(flags);
 337         kprobe_handler(regs);
 338         local_irq_restore(flags);
 339         return 0;
 340 }
 341
 342 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
 343 {
 344         struct kprobe *cur = kprobe_running();
 345         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 346
 347         switch (kcb->kprobe_status) {
 348         case KPROBE_HIT_SS:
 349         case KPROBE_REENTER:
 350                 /*
 351                  * We are here because the instruction being single
 352                  * stepped caused a page fault. We reset the current
 353                  * kprobe and the PC to point back to the probe address
 354                  * and allow the page fault handler to continue as a
 355                  * normal page fault.
 356                  */
 357                 regs->ARM_pc = (long)cur->addr;
 358                 if (kcb->kprobe_status == KPROBE_REENTER) {
 359                         restore_previous_kprobe(kcb);
 360                 } else {
 361                         reset_current_kprobe();
 362                 }
 363                 break;
 364
 365         case KPROBE_HIT_ACTIVE:
 366         case KPROBE_HIT_SSDONE:
 367                 /*
 368                  * We increment the nmissed count for accounting,
 369                  * we can also use npre/npostfault count for accounting
 370                  * these specific fault cases.
 371                  */
 372                 kprobes_inc_nmissed_count(cur);
 373
 374                 /*
 375                  * We come here because instructions in the pre/post
 376                  * handler caused the page_fault, this could happen
 377                  * if handler tries to access user space by
 378                  * copy_from_user(), get_user() etc. Let the
 379                  * user-specified handler try to fix it.
 380                  */
 381                 if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
 382                         return 1;
 383                 break;
 384
 385         default:
 386                 break;
 387         }
 388
 389         return 0;
 390 }
 391
 392 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 393                                        unsigned long val, void *data)
 394 {
 395         /*
 396          * notify_die() is currently never called on ARM,
 397          * so this callback is currently empty.
 398          */
 399         return NOTIFY_DONE;
 400 }
 401
 402 /*
 403  * When a retprobed function returns, trampoline_handler() is called,
 404  * calling the kretprobe's handler. We construct a struct pt_regs to
 405  * give a view of registers r0-r11 to the user return-handler.  This is
 406  * not a complete pt_regs structure, but that should be plenty sufficient
 407  * for kretprobe handlers which should normally be interested in r0 only
 408  * anyway.
 409  */
 410 void __naked __kprobes kretprobe_trampoline(void)
 411 {
 412         __asm__ __volatile__ (
 413                 "stmdb  sp!, {r0 - r11}         \n\t"
 414                 "mov    r0, sp                  \n\t"
 415                 "bl     trampoline_handler      \n\t"
 416                 "mov    lr, r0                  \n\t"
 417                 "ldmia  sp!, {r0 - r11}         \n\t"
 418 #ifdef CONFIG_THUMB2_KERNEL
 419                 "bx     lr                      \n\t"
 420 #else
 421                 "mov    pc, lr                  \n\t"
 422 #endif
 423                 : : : "memory");
 424 }
 425
 426 /* Called from kretprobe_trampoline */
 427 static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
 428 {
 429         struct kretprobe_instance *ri = NULL;
 430         struct hlist_head *head, empty_rp;
 431         struct hlist_node *node, *tmp;
 432         unsigned long flags, orig_ret_address = 0;
 433         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 434
 435         INIT_HLIST_HEAD(&empty_rp);
 436         kretprobe_hash_lock(current, &head, &flags);
 437
 438         /*
 439          * It is possible to have multiple instances associated with a given
 440          * task either because multiple functions in the call path have
 441          * a return probe installed on them, and/or more than one return
 442          * probe was registered for a target function.
 443          *
 444          * We can handle this because:
 445          *     - instances are always inserted at the head of the list
 446          *     - when multiple return probes are registered for the same
 447          *       function, the first instance's ret_addr will point to the
 448          *       real return address, and all the rest will point to
 449          *       kretprobe_trampoline
 450          */
 451         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
 452                 if (ri->task != current)
 453                         /* another task is sharing our hash bucket */
 454                         continue;
 455
 456                 if (ri->rp && ri->rp->handler) {
 457                         __get_cpu_var(current_kprobe) = &ri->rp->kp;
 458                         get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
 459                         ri->rp->handler(ri, regs);
 460                         __get_cpu_var(current_kprobe) = NULL;
 461                 }
 462
 463                 orig_ret_address = (unsigned long)ri->ret_addr;
 464                 recycle_rp_inst(ri, &empty_rp);
 465
 466                 if (orig_ret_address != trampoline_address)
 467                         /*
 468                          * This is the real return address. Any other
 469                          * instances associated with this task are for
 470                          * other calls deeper on the call stack
 471                          */
 472                         break;
 473         }
 474
 475         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 476         kretprobe_hash_unlock(current, &flags);
 477
 478         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
 479                 hlist_del(&ri->hlist);
 480                 kfree(ri);
 481         }
 482
 483         return (void *)orig_ret_address;
 484 }
 485
 486 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 487                                       struct pt_regs *regs)
 488 {
 489         ri->ret_addr = (kprobe_opcode_t *)regs->ARM_lr;
 490
 491         /* Replace the return addr with trampoline addr. */
 492         regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
 493 }
 494
 495 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 496 {
 497         struct jprobe *jp = container_of(p, struct jprobe, kp);
 498         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 499         long sp_addr = regs->ARM_sp;
 500         long cpsr;
 501
 502         kcb->jprobe_saved_regs = *regs;
 503         memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
 504         regs->ARM_pc = (long)jp->entry;
 505
 506         cpsr = regs->ARM_cpsr | PSR_I_BIT;
 507 #ifdef CONFIG_THUMB2_KERNEL
 508         /* Set correct Thumb state in cpsr */
 509         if (regs->ARM_pc & 1)
 510                 cpsr |= PSR_T_BIT;
 511         else
 512                 cpsr &= ~PSR_T_BIT;
 513 #endif
 514         regs->ARM_cpsr = cpsr;
 515
 516         preempt_disable();
 517         return 1;
 518 }
 519
 520 void __kprobes jprobe_return(void)
 521 {
 522         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 523
 524         __asm__ __volatile__ (
 525                 /*
 526                  * Setup an empty pt_regs. Fill SP and PC fields as
 527                  * they're needed by longjmp_break_handler.
 528                  *
 529                  * We allocate some slack between the original SP and start of
 530                  * our fabricated regs. To be precise we want to have worst case
 531                  * covered which is STMFD with all 16 regs so we allocate 2 *
 532                  * sizeof(struct_pt_regs)).
 533                  *
 534                  * This is to prevent any simulated instruction from writing
 535                  * over the regs when they are accessing the stack.
 536                  */
 537 #ifdef CONFIG_THUMB2_KERNEL
 538                 "sub    r0, %0, %1              \n\t"
 539                 "mov    sp, r0                  \n\t"
 540 #else
 541                 "sub    sp, %0, %1              \n\t"
 542 #endif
 543                 "ldr    r0, ="__stringify(JPROBE_MAGIC_ADDR)"\n\t"
 544                 "str    %0, [sp, %2]            \n\t"
 545                 "str    r0, [sp, %3]            \n\t"
 546                 "mov    r0, sp                  \n\t"
 547                 "bl     kprobe_handler          \n\t"
 548
 549                 /*
 550                  * Return to the context saved by setjmp_pre_handler
 551                  * and restored by longjmp_break_handler.
 552                  */
 553 #ifdef CONFIG_THUMB2_KERNEL
 554                 "ldr    lr, [sp, %2]            \n\t" /* lr = saved sp */
 555                 "ldrd   r0, r1, [sp, %5]        \n\t" /* r0,r1 = saved lr,pc */
 556                 "ldr    r2, [sp, %4]            \n\t" /* r2 = saved psr */
 557                 "stmdb  lr!, {r0, r1, r2}       \n\t" /* push saved lr and */
 558                                                       /* rfe context */
 559                 "ldmia  sp, {r0 - r12}          \n\t"
 560                 "mov    sp, lr                  \n\t"
 561                 "ldr    lr, [sp], #4            \n\t"
 562                 "rfeia  sp!                     \n\t"
 563 #else
 564                 "ldr    r0, [sp, %4]            \n\t"
 565                 "msr    cpsr_cxsf, r0           \n\t"
 566                 "ldmia  sp, {r0 - pc}           \n\t"
 567 #endif
 568                 :
 569                 : "r" (kcb->jprobe_saved_regs.ARM_sp),
 570                   "I" (sizeof(struct pt_regs) * 2),
 571                   "J" (offsetof(struct pt_regs, ARM_sp)),
 572                   "J" (offsetof(struct pt_regs, ARM_pc)),
 573                   "J" (offsetof(struct pt_regs, ARM_cpsr)),
 574                   "J" (offsetof(struct pt_regs, ARM_lr))
 575                 : "memory", "cc");
 576 }
 577
 578 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 579 {
 580         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 581         long stack_addr = kcb->jprobe_saved_regs.ARM_sp;
 582         long orig_sp = regs->ARM_sp;
 583         struct jprobe *jp = container_of(p, struct jprobe, kp);
 584
 585         if (regs->ARM_pc == JPROBE_MAGIC_ADDR) {
 586                 if (orig_sp != stack_addr) {
 587                         struct pt_regs *saved_regs =
 588                                 (struct pt_regs *)kcb->jprobe_saved_regs.ARM_sp;
 589                         printk("current sp %lx does not match saved sp %lx\n",
 590                                orig_sp, stack_addr);
 591                         printk("Saved registers for jprobe %p\n", jp);
 592                         show_regs(saved_regs);
 593                         printk("Current registers\n");
 594                         show_regs(regs);
 595                         BUG();
 596                 }
 597                 *regs = kcb->jprobe_saved_regs;
 598                 memcpy((void *)stack_addr, kcb->jprobes_stack,
 599                        MIN_STACK_SIZE(stack_addr));
 600                 preempt_enable_no_resched();
 601                 return 1;
 602         }
 603         return 0;
 604 }
 605
 606 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 607 {
 608         return 0;
 609 }
 610
 611 #ifdef CONFIG_THUMB2_KERNEL
 612
 613 static struct undef_hook kprobes_thumb16_break_hook = {
 614         .instr_mask     = 0xffff,
 615         .instr_val      = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION,
 616         .cpsr_mask      = MODE_MASK,
 617         .cpsr_val       = SVC_MODE,
 618         .fn             = kprobe_trap_handler,
 619 };
 620
 621 static struct undef_hook kprobes_thumb32_break_hook = {
 622         .instr_mask     = 0xffffffff,
 623         .instr_val      = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION,
 624         .cpsr_mask      = MODE_MASK,
 625         .cpsr_val       = SVC_MODE,
 626         .fn             = kprobe_trap_handler,
 627 };
 628
 629 #else  /* !CONFIG_THUMB2_KERNEL */
 630
 631 static struct undef_hook kprobes_arm_break_hook = {
 632         .instr_mask     = 0x0fffffff,
 633         .instr_val      = KPROBE_ARM_BREAKPOINT_INSTRUCTION,
 634         .cpsr_mask      = MODE_MASK,
 635         .cpsr_val       = SVC_MODE,
 636         .fn             = kprobe_trap_handler,
 637 };
 638
 639 #endif /* !CONFIG_THUMB2_KERNEL */
 640
 641 int __init arch_init_kprobes()
 642 {
 643         arm_kprobe_decode_init();
 644 #ifdef CONFIG_THUMB2_KERNEL
 645         register_undef_hook(&kprobes_thumb16_break_hook);
 646         register_undef_hook(&kprobes_thumb32_break_hook);
 647 #else
 648         register_undef_hook(&kprobes_arm_break_hook);
 649 #endif
 650         return 0;
 651 }