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         bool thumb;
  55         kprobe_decode_insn_t *decode_insn;
  56         int is;
  57
  58         if (in_exception_text(addr))
  59                 return -EINVAL;
  60
  61 #ifdef CONFIG_THUMB2_KERNEL
  62         thumb = true;
  63         addr &= ~1; /* Bit 0 would normally be set to indicate Thumb code */
  64         insn = ((u16 *)addr)[0];
  65         if (is_wide_instruction(insn)) {
  66                 insn <<= 16;
  67                 insn |= ((u16 *)addr)[1];
  68                 decode_insn = thumb32_kprobe_decode_insn;
  69         } else
  70                 decode_insn = thumb16_kprobe_decode_insn;
  71 #else /* !CONFIG_THUMB2_KERNEL */
  72         thumb = false;
  73         if (addr & 0x3)
  74                 return -EINVAL;
  75         insn = *p->addr;
  76         decode_insn = arm_kprobe_decode_insn;
  77 #endif
  78
  79         p->opcode = insn;
  80         p->ainsn.insn = tmp_insn;
  81
  82         switch ((*decode_insn)(insn, &p->ainsn)) {
  83         case INSN_REJECTED:     /* not supported */
  84                 return -EINVAL;
  85
  86         case INSN_GOOD:         /* instruction uses slot */
  87                 p->ainsn.insn = get_insn_slot();
  88                 if (!p->ainsn.insn)
  89                         return -ENOMEM;
  90                 for (is = 0; is < MAX_INSN_SIZE; ++is)
  91                         p->ainsn.insn[is] = tmp_insn[is];
  92                 flush_insns(p->ainsn.insn,
  93                                 sizeof(p->ainsn.insn[0]) * MAX_INSN_SIZE);
  94                 p->ainsn.insn_fn = (kprobe_insn_fn_t *)
  95                                         ((uintptr_t)p->ainsn.insn | thumb);
  96                 break;
  97
  98         case INSN_GOOD_NO_SLOT: /* instruction doesn't need insn slot */
  99                 p->ainsn.insn = NULL;
 100                 break;
 101         }
 102
 103         return 0;
 104 }
 105
 106 #ifdef CONFIG_THUMB2_KERNEL
 107
 108 /*
 109  * For a 32-bit Thumb breakpoint spanning two memory words we need to take
 110  * special precautions to insert the breakpoint atomically, especially on SMP
 111  * systems. This is achieved by calling this arming function using stop_machine.
 112  */
 113 static int __kprobes set_t32_breakpoint(void *addr)
 114 {
 115         ((u16 *)addr)[0] = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION >> 16;
 116         ((u16 *)addr)[1] = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION & 0xffff;
 117         flush_insns(addr, 2*sizeof(u16));
 118         return 0;
 119 }
 120
 121 void __kprobes arch_arm_kprobe(struct kprobe *p)
 122 {
 123         uintptr_t addr = (uintptr_t)p->addr & ~1; /* Remove any Thumb flag */
 124
 125         if (!is_wide_instruction(p->opcode)) {
 126                 *(u16 *)addr = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION;
 127                 flush_insns(addr, sizeof(u16));
 128         } else if (addr & 2) {
 129                 /* A 32-bit instruction spanning two words needs special care */
 130                 stop_machine(set_t32_breakpoint, (void *)addr, &cpu_online_map);
 131         } else {
 132                 /* Word aligned 32-bit instruction can be written atomically */
 133                 u32 bkp = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION;
 134 #ifndef __ARMEB__ /* Swap halfwords for little-endian */
 135                 bkp = (bkp >> 16) | (bkp << 16);
 136 #endif
 137                 *(u32 *)addr = bkp;
 138                 flush_insns(addr, sizeof(u32));
 139         }
 140 }
 141
 142 #else /* !CONFIG_THUMB2_KERNEL */
 143
 144 void __kprobes arch_arm_kprobe(struct kprobe *p)
 145 {
 146         kprobe_opcode_t insn = p->opcode;
 147         kprobe_opcode_t brkp = KPROBE_ARM_BREAKPOINT_INSTRUCTION;
 148         if (insn >= 0xe0000000)
 149                 brkp |= 0xe0000000;  /* Unconditional instruction */
 150         else
 151                 brkp |= insn & 0xf0000000;  /* Copy condition from insn */
 152         *p->addr = brkp;
 153         flush_insns(p->addr, sizeof(p->addr[0]));
 154 }
 155
 156 #endif /* !CONFIG_THUMB2_KERNEL */
 157
 158 /*
 159  * The actual disarming is done here on each CPU and synchronized using
 160  * stop_machine. This synchronization is necessary on SMP to avoid removing
 161  * a probe between the moment the 'Undefined Instruction' exception is raised
 162  * and the moment the exception handler reads the faulting instruction from
 163  * memory. It is also needed to atomically set the two half-words of a 32-bit
 164  * Thumb breakpoint.
 165  */
 166 int __kprobes __arch_disarm_kprobe(void *p)
 167 {
 168         struct kprobe *kp = p;
 169 #ifdef CONFIG_THUMB2_KERNEL
 170         u16 *addr = (u16 *)((uintptr_t)kp->addr & ~1);
 171         kprobe_opcode_t insn = kp->opcode;
 172         unsigned int len;
 173
 174         if (is_wide_instruction(insn)) {
 175                 ((u16 *)addr)[0] = insn>>16;
 176                 ((u16 *)addr)[1] = insn;
 177                 len = 2*sizeof(u16);
 178         } else {
 179                 ((u16 *)addr)[0] = insn;
 180                 len = sizeof(u16);
 181         }
 182         flush_insns(addr, len);
 183
 184 #else /* !CONFIG_THUMB2_KERNEL */
 185         *kp->addr = kp->opcode;
 186         flush_insns(kp->addr, sizeof(kp->addr[0]));
 187 #endif
 188         return 0;
 189 }
 190
 191 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 192 {
 193         stop_machine(__arch_disarm_kprobe, p, &cpu_online_map);
 194 }
 195
 196 void __kprobes arch_remove_kprobe(struct kprobe *p)
 197 {
 198         if (p->ainsn.insn) {
 199                 free_insn_slot(p->ainsn.insn, 0);
 200                 p->ainsn.insn = NULL;
 201         }
 202 }
 203
 204 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 205 {
 206         kcb->prev_kprobe.kp = kprobe_running();
 207         kcb->prev_kprobe.status = kcb->kprobe_status;
 208 }
 209
 210 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 211 {
 212         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
 213         kcb->kprobe_status = kcb->prev_kprobe.status;
 214 }
 215
 216 static void __kprobes set_current_kprobe(struct kprobe *p)
 217 {
 218         __get_cpu_var(current_kprobe) = p;
 219 }
 220
 221 static void __kprobes
 222 singlestep_skip(struct kprobe *p, struct pt_regs *regs)
 223 {
 224 #ifdef CONFIG_THUMB2_KERNEL
 225         regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
 226         if (is_wide_instruction(p->opcode))
 227                 regs->ARM_pc += 4;
 228         else
 229                 regs->ARM_pc += 2;
 230 #else
 231         regs->ARM_pc += 4;
 232 #endif
 233 }
 234
 235 static inline void __kprobes
 236 singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 237 {
 238         p->ainsn.insn_singlestep(p, regs);
 239 }
 240
 241 /*
 242  * Called with IRQs disabled. IRQs must remain disabled from that point
 243  * all the way until processing this kprobe is complete.  The current
 244  * kprobes implementation cannot process more than one nested level of
 245  * kprobe, and that level is reserved for user kprobe handlers, so we can't
 246  * risk encountering a new kprobe in an interrupt handler.
 247  */
 248 void __kprobes kprobe_handler(struct pt_regs *regs)
 249 {
 250         struct kprobe *p, *cur;
 251         struct kprobe_ctlblk *kcb;
 252
 253         kcb = get_kprobe_ctlblk();
 254         cur = kprobe_running();
 255
 256 #ifdef CONFIG_THUMB2_KERNEL
 257         /*
 258          * First look for a probe which was registered using an address with
 259          * bit 0 set, this is the usual situation for pointers to Thumb code.
 260          * If not found, fallback to looking for one with bit 0 clear.
 261          */
 262         p = get_kprobe((kprobe_opcode_t *)(regs->ARM_pc | 1));
 263         if (!p)
 264                 p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
 265
 266 #else /* ! CONFIG_THUMB2_KERNEL */
 267         p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
 268 #endif
 269
 270         if (p) {
 271                 if (cur) {
 272                         /* Kprobe is pending, so we're recursing. */
 273                         switch (kcb->kprobe_status) {
 274                         case KPROBE_HIT_ACTIVE:
 275                         case KPROBE_HIT_SSDONE:
 276                                 /* A pre- or post-handler probe got us here. */
 277                                 kprobes_inc_nmissed_count(p);
 278                                 save_previous_kprobe(kcb);
 279                                 set_current_kprobe(p);
 280                                 kcb->kprobe_status = KPROBE_REENTER;
 281                                 singlestep(p, regs, kcb);
 282                                 restore_previous_kprobe(kcb);
 283                                 break;
 284                         default:
 285                                 /* impossible cases */
 286                                 BUG();
 287                         }
 288                 } else if (p->ainsn.insn_check_cc(regs->ARM_cpsr)) {
 289                         /* Probe hit and conditional execution check ok. */
 290                         set_current_kprobe(p);
 291                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 292
 293                         /*
 294                          * If we have no pre-handler or it returned 0, we
 295                          * continue with normal processing.  If we have a
 296                          * pre-handler and it returned non-zero, it prepped
 297                          * for calling the break_handler below on re-entry,
 298                          * so get out doing nothing more here.
 299                          */
 300                         if (!p->pre_handler || !p->pre_handler(p, regs)) {
 301                                 kcb->kprobe_status = KPROBE_HIT_SS;
 302                                 singlestep(p, regs, kcb);
 303                                 if (p->post_handler) {
 304                                         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 305                                         p->post_handler(p, regs, 0);
 306                                 }
 307                                 reset_current_kprobe();
 308                         }
 309                 } else {
 310                         /*
 311                          * Probe hit but conditional execution check failed,
 312                          * so just skip the instruction and continue as if
 313                          * nothing had happened.
 314                          */
 315                         singlestep_skip(p, regs);
 316                 }
 317         } else if (cur) {
 318                 /* We probably hit a jprobe.  Call its break handler. */
 319                 if (cur->break_handler && cur->break_handler(cur, regs)) {
 320                         kcb->kprobe_status = KPROBE_HIT_SS;
 321                         singlestep(cur, regs, kcb);
 322                         if (cur->post_handler) {
 323                                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 324                                 cur->post_handler(cur, regs, 0);
 325                         }
 326                 }
 327                 reset_current_kprobe();
 328         } else {
 329                 /*
 330                  * The probe was removed and a race is in progress.
 331                  * There is nothing we can do about it.  Let's restart
 332                  * the instruction.  By the time we can restart, the
 333                  * real instruction will be there.
 334                  */
 335         }
 336 }
 337
 338 static int __kprobes kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
 339 {
 340         unsigned long flags;
 341         local_irq_save(flags);
 342         kprobe_handler(regs);
 343         local_irq_restore(flags);
 344         return 0;
 345 }
 346
 347 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
 348 {
 349         struct kprobe *cur = kprobe_running();
 350         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 351
 352         switch (kcb->kprobe_status) {
 353         case KPROBE_HIT_SS:
 354         case KPROBE_REENTER:
 355                 /*
 356                  * We are here because the instruction being single
 357                  * stepped caused a page fault. We reset the current
 358                  * kprobe and the PC to point back to the probe address
 359                  * and allow the page fault handler to continue as a
 360                  * normal page fault.
 361                  */
 362                 regs->ARM_pc = (long)cur->addr;
 363                 if (kcb->kprobe_status == KPROBE_REENTER) {
 364                         restore_previous_kprobe(kcb);
 365                 } else {
 366                         reset_current_kprobe();
 367                 }
 368                 break;
 369
 370         case KPROBE_HIT_ACTIVE:
 371         case KPROBE_HIT_SSDONE:
 372                 /*
 373                  * We increment the nmissed count for accounting,
 374                  * we can also use npre/npostfault count for accounting
 375                  * these specific fault cases.
 376                  */
 377                 kprobes_inc_nmissed_count(cur);
 378
 379                 /*
 380                  * We come here because instructions in the pre/post
 381                  * handler caused the page_fault, this could happen
 382                  * if handler tries to access user space by
 383                  * copy_from_user(), get_user() etc. Let the
 384                  * user-specified handler try to fix it.
 385                  */
 386                 if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
 387                         return 1;
 388                 break;
 389
 390         default:
 391                 break;
 392         }
 393
 394         return 0;
 395 }
 396
 397 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 398                                        unsigned long val, void *data)
 399 {
 400         /*
 401          * notify_die() is currently never called on ARM,
 402          * so this callback is currently empty.
 403          */
 404         return NOTIFY_DONE;
 405 }
 406
 407 /*
 408  * When a retprobed function returns, trampoline_handler() is called,
 409  * calling the kretprobe's handler. We construct a struct pt_regs to
 410  * give a view of registers r0-r11 to the user return-handler.  This is
 411  * not a complete pt_regs structure, but that should be plenty sufficient
 412  * for kretprobe handlers which should normally be interested in r0 only
 413  * anyway.
 414  */
 415 void __naked __kprobes kretprobe_trampoline(void)
 416 {
 417         __asm__ __volatile__ (
 418                 "stmdb  sp!, {r0 - r11}         \n\t"
 419                 "mov    r0, sp                  \n\t"
 420                 "bl     trampoline_handler      \n\t"
 421                 "mov    lr, r0                  \n\t"
 422                 "ldmia  sp!, {r0 - r11}         \n\t"
 423 #ifdef CONFIG_THUMB2_KERNEL
 424                 "bx     lr                      \n\t"
 425 #else
 426                 "mov    pc, lr                  \n\t"
 427 #endif
 428                 : : : "memory");
 429 }
 430
 431 /* Called from kretprobe_trampoline */
 432 static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
 433 {
 434         struct kretprobe_instance *ri = NULL;
 435         struct hlist_head *head, empty_rp;
 436         struct hlist_node *node, *tmp;
 437         unsigned long flags, orig_ret_address = 0;
 438         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 439
 440         INIT_HLIST_HEAD(&empty_rp);
 441         kretprobe_hash_lock(current, &head, &flags);
 442
 443         /*
 444          * It is possible to have multiple instances associated with a given
 445          * task either because multiple functions in the call path have
 446          * a return probe installed on them, and/or more than one return
 447          * probe was registered for a target function.
 448          *
 449          * We can handle this because:
 450          *     - instances are always inserted at the head of the list
 451          *     - when multiple return probes are registered for the same
 452          *       function, the first instance's ret_addr will point to the
 453          *       real return address, and all the rest will point to
 454          *       kretprobe_trampoline
 455          */
 456         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
 457                 if (ri->task != current)
 458                         /* another task is sharing our hash bucket */
 459                         continue;
 460
 461                 if (ri->rp && ri->rp->handler) {
 462                         __get_cpu_var(current_kprobe) = &ri->rp->kp;
 463                         get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
 464                         ri->rp->handler(ri, regs);
 465                         __get_cpu_var(current_kprobe) = NULL;
 466                 }
 467
 468                 orig_ret_address = (unsigned long)ri->ret_addr;
 469                 recycle_rp_inst(ri, &empty_rp);
 470
 471                 if (orig_ret_address != trampoline_address)
 472                         /*
 473                          * This is the real return address. Any other
 474                          * instances associated with this task are for
 475                          * other calls deeper on the call stack
 476                          */
 477                         break;
 478         }
 479
 480         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 481         kretprobe_hash_unlock(current, &flags);
 482
 483         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
 484                 hlist_del(&ri->hlist);
 485                 kfree(ri);
 486         }
 487
 488         return (void *)orig_ret_address;
 489 }
 490
 491 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 492                                       struct pt_regs *regs)
 493 {
 494         ri->ret_addr = (kprobe_opcode_t *)regs->ARM_lr;
 495
 496         /* Replace the return addr with trampoline addr. */
 497         regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
 498 }
 499
 500 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 501 {
 502         struct jprobe *jp = container_of(p, struct jprobe, kp);
 503         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 504         long sp_addr = regs->ARM_sp;
 505         long cpsr;
 506
 507         kcb->jprobe_saved_regs = *regs;
 508         memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
 509         regs->ARM_pc = (long)jp->entry;
 510
 511         cpsr = regs->ARM_cpsr | PSR_I_BIT;
 512 #ifdef CONFIG_THUMB2_KERNEL
 513         /* Set correct Thumb state in cpsr */
 514         if (regs->ARM_pc & 1)
 515                 cpsr |= PSR_T_BIT;
 516         else
 517                 cpsr &= ~PSR_T_BIT;
 518 #endif
 519         regs->ARM_cpsr = cpsr;
 520
 521         preempt_disable();
 522         return 1;
 523 }
 524
 525 void __kprobes jprobe_return(void)
 526 {
 527         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 528
 529         __asm__ __volatile__ (
 530                 /*
 531                  * Setup an empty pt_regs. Fill SP and PC fields as
 532                  * they're needed by longjmp_break_handler.
 533                  *
 534                  * We allocate some slack between the original SP and start of
 535                  * our fabricated regs. To be precise we want to have worst case
 536                  * covered which is STMFD with all 16 regs so we allocate 2 *
 537                  * sizeof(struct_pt_regs)).
 538                  *
 539                  * This is to prevent any simulated instruction from writing
 540                  * over the regs when they are accessing the stack.
 541                  */
 542 #ifdef CONFIG_THUMB2_KERNEL
 543                 "sub    r0, %0, %1              \n\t"
 544                 "mov    sp, r0                  \n\t"
 545 #else
 546                 "sub    sp, %0, %1              \n\t"
 547 #endif
 548                 "ldr    r0, ="__stringify(JPROBE_MAGIC_ADDR)"\n\t"
 549                 "str    %0, [sp, %2]            \n\t"
 550                 "str    r0, [sp, %3]            \n\t"
 551                 "mov    r0, sp                  \n\t"
 552                 "bl     kprobe_handler          \n\t"
 553
 554                 /*
 555                  * Return to the context saved by setjmp_pre_handler
 556                  * and restored by longjmp_break_handler.
 557                  */
 558 #ifdef CONFIG_THUMB2_KERNEL
 559                 "ldr    lr, [sp, %2]            \n\t" /* lr = saved sp */
 560                 "ldrd   r0, r1, [sp, %5]        \n\t" /* r0,r1 = saved lr,pc */
 561                 "ldr    r2, [sp, %4]            \n\t" /* r2 = saved psr */
 562                 "stmdb  lr!, {r0, r1, r2}       \n\t" /* push saved lr and */
 563                                                       /* rfe context */
 564                 "ldmia  sp, {r0 - r12}          \n\t"
 565                 "mov    sp, lr                  \n\t"
 566                 "ldr    lr, [sp], #4            \n\t"
 567                 "rfeia  sp!                     \n\t"
 568 #else
 569                 "ldr    r0, [sp, %4]            \n\t"
 570                 "msr    cpsr_cxsf, r0           \n\t"
 571                 "ldmia  sp, {r0 - pc}           \n\t"
 572 #endif
 573                 :
 574                 : "r" (kcb->jprobe_saved_regs.ARM_sp),
 575                   "I" (sizeof(struct pt_regs) * 2),
 576                   "J" (offsetof(struct pt_regs, ARM_sp)),
 577                   "J" (offsetof(struct pt_regs, ARM_pc)),
 578                   "J" (offsetof(struct pt_regs, ARM_cpsr)),
 579                   "J" (offsetof(struct pt_regs, ARM_lr))
 580                 : "memory", "cc");
 581 }
 582
 583 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 584 {
 585         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 586         long stack_addr = kcb->jprobe_saved_regs.ARM_sp;
 587         long orig_sp = regs->ARM_sp;
 588         struct jprobe *jp = container_of(p, struct jprobe, kp);
 589
 590         if (regs->ARM_pc == JPROBE_MAGIC_ADDR) {
 591                 if (orig_sp != stack_addr) {
 592                         struct pt_regs *saved_regs =
 593                                 (struct pt_regs *)kcb->jprobe_saved_regs.ARM_sp;
 594                         printk("current sp %lx does not match saved sp %lx\n",
 595                                orig_sp, stack_addr);
 596                         printk("Saved registers for jprobe %p\n", jp);
 597                         show_regs(saved_regs);
 598                         printk("Current registers\n");
 599                         show_regs(regs);
 600                         BUG();
 601                 }
 602                 *regs = kcb->jprobe_saved_regs;
 603                 memcpy((void *)stack_addr, kcb->jprobes_stack,
 604                        MIN_STACK_SIZE(stack_addr));
 605                 preempt_enable_no_resched();
 606                 return 1;
 607         }
 608         return 0;
 609 }
 610
 611 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 612 {
 613         return 0;
 614 }
 615
 616 #ifdef CONFIG_THUMB2_KERNEL
 617
 618 static struct undef_hook kprobes_thumb16_break_hook = {
 619         .instr_mask     = 0xffff,
 620         .instr_val      = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION,
 621         .cpsr_mask      = MODE_MASK,
 622         .cpsr_val       = SVC_MODE,
 623         .fn             = kprobe_trap_handler,
 624 };
 625
 626 static struct undef_hook kprobes_thumb32_break_hook = {
 627         .instr_mask     = 0xffffffff,
 628         .instr_val      = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION,
 629         .cpsr_mask      = MODE_MASK,
 630         .cpsr_val       = SVC_MODE,
 631         .fn             = kprobe_trap_handler,
 632 };
 633
 634 #else  /* !CONFIG_THUMB2_KERNEL */
 635
 636 static struct undef_hook kprobes_arm_break_hook = {
 637         .instr_mask     = 0x0fffffff,
 638         .instr_val      = KPROBE_ARM_BREAKPOINT_INSTRUCTION,
 639         .cpsr_mask      = MODE_MASK,
 640         .cpsr_val       = SVC_MODE,
 641         .fn             = kprobe_trap_handler,
 642 };
 643
 644 #endif /* !CONFIG_THUMB2_KERNEL */
 645
 646 int __init arch_init_kprobes()
 647 {
 648         arm_kprobe_decode_init();
 649 #ifdef CONFIG_THUMB2_KERNEL
 650         register_undef_hook(&kprobes_thumb16_break_hook);
 651         register_undef_hook(&kprobes_thumb32_break_hook);
 652 #else
 653         register_undef_hook(&kprobes_arm_break_hook);
 654 #endif
 655         return 0;
 656 }