kernel/arch/arm/probes/kprobes/core.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 #include <asm/patch.h>
  34
  35 #include "../decode-arm.h"
  36 #include "../decode-thumb.h"
  37 #include "core.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         const struct decode_checker **checkers;
  65
  66         if (in_exception_text(addr))
  67                 return -EINVAL;
  68
  69 #ifdef CONFIG_THUMB2_KERNEL
  70         thumb = true;
  71         addr &= ~1; /* Bit 0 would normally be set to indicate Thumb code */
  72         insn = __mem_to_opcode_thumb16(((u16 *)addr)[0]);
  73         if (is_wide_instruction(insn)) {
  74                 u16 inst2 = __mem_to_opcode_thumb16(((u16 *)addr)[1]);
  75                 insn = __opcode_thumb32_compose(insn, inst2);
  76                 decode_insn = thumb32_probes_decode_insn;
  77                 actions = kprobes_t32_actions;
  78                 checkers = kprobes_t32_checkers;
  79         } else {
  80                 decode_insn = thumb16_probes_decode_insn;
  81                 actions = kprobes_t16_actions;
  82                 checkers = kprobes_t16_checkers;
  83         }
  84 #else /* !CONFIG_THUMB2_KERNEL */
  85         thumb = false;
  86         if (addr & 0x3)
  87                 return -EINVAL;
  88         insn = __mem_to_opcode_arm(*p->addr);
  89         decode_insn = arm_probes_decode_insn;
  90         actions = kprobes_arm_actions;
  91         checkers = kprobes_arm_checkers;
  92 #endif
  93
  94         p->opcode = insn;
  95         p->ainsn.insn = tmp_insn;
  96
  97         switch ((*decode_insn)(insn, &p->ainsn, true, actions, checkers)) {
  98         case INSN_REJECTED:     /* not supported */
  99                 return -EINVAL;
 100
 101         case INSN_GOOD:         /* instruction uses slot */
 102                 p->ainsn.insn = get_insn_slot();
 103                 if (!p->ainsn.insn)
 104                         return -ENOMEM;
 105                 for (is = 0; is < MAX_INSN_SIZE; ++is)
 106                         p->ainsn.insn[is] = tmp_insn[is];
 107                 flush_insns(p->ainsn.insn,
 108                                 sizeof(p->ainsn.insn[0]) * MAX_INSN_SIZE);
 109                 p->ainsn.insn_fn = (probes_insn_fn_t *)
 110                                         ((uintptr_t)p->ainsn.insn | thumb);
 111                 break;
 112
 113         case INSN_GOOD_NO_SLOT: /* instruction doesn't need insn slot */
 114                 p->ainsn.insn = NULL;
 115                 break;
 116         }
 117
 118         /*
 119          * Never instrument insn like 'str r0, [sp, +/-r1]'. Also, insn likes
 120          * 'str r0, [sp, #-68]' should also be prohibited.
 121          * See __und_svc.
 122          */
 123         if ((p->ainsn.stack_space < 0) ||
 124                         (p->ainsn.stack_space > MAX_STACK_SIZE))
 125                 return -EINVAL;
 126
 127         return 0;
 128 }
 129
 130 void __kprobes arch_arm_kprobe(struct kprobe *p)
 131 {
 132         unsigned int brkp;
 133         void *addr;
 134
 135         if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
 136                 /* Remove any Thumb flag */
 137                 addr = (void *)((uintptr_t)p->addr & ~1);
 138
 139                 if (is_wide_instruction(p->opcode))
 140                         brkp = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION;
 141                 else
 142                         brkp = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION;
 143         } else {
 144                 kprobe_opcode_t insn = p->opcode;
 145
 146                 addr = p->addr;
 147                 brkp = KPROBE_ARM_BREAKPOINT_INSTRUCTION;
 148
 149                 if (insn >= 0xe0000000)
 150                         brkp |= 0xe0000000;  /* Unconditional instruction */
 151                 else
 152                         brkp |= insn & 0xf0000000;  /* Copy condition from insn */
 153         }
 154
 155         patch_text(addr, brkp);
 156 }
 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 struct patch {
 167         void *addr;
 168         unsigned int insn;
 169 };
 170
 171 static int __kprobes_remove_breakpoint(void *data)
 172 {
 173         struct patch *p = data;
 174         __patch_text(p->addr, p->insn);
 175         return 0;
 176 }
 177
 178 void __kprobes kprobes_remove_breakpoint(void *addr, unsigned int insn)
 179 {
 180         struct patch p = {
 181                 .addr = addr,
 182                 .insn = insn,
 183         };
 184         stop_machine(__kprobes_remove_breakpoint, &p, cpu_online_mask);
 185 }
 186
 187 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 188 {
 189         kprobes_remove_breakpoint((void *)((uintptr_t)p->addr & ~1),
 190                         p->opcode);
 191 }
 192
 193 void __kprobes arch_remove_kprobe(struct kprobe *p)
 194 {
 195         if (p->ainsn.insn) {
 196                 free_insn_slot(p->ainsn.insn, 0);
 197                 p->ainsn.insn = NULL;
 198         }
 199 }
 200
 201 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 202 {
 203         kcb->prev_kprobe.kp = kprobe_running();
 204         kcb->prev_kprobe.status = kcb->kprobe_status;
 205 }
 206
 207 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 208 {
 209         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 210         kcb->kprobe_status = kcb->prev_kprobe.status;
 211 }
 212
 213 static void __kprobes set_current_kprobe(struct kprobe *p)
 214 {
 215         __this_cpu_write(current_kprobe, p);
 216 }
 217
 218 static void __kprobes
 219 singlestep_skip(struct kprobe *p, struct pt_regs *regs)
 220 {
 221 #ifdef CONFIG_THUMB2_KERNEL
 222         regs->ARM_cpsr = it_advance(regs->ARM_cpsr);
 223         if (is_wide_instruction(p->opcode))
 224                 regs->ARM_pc += 4;
 225         else
 226                 regs->ARM_pc += 2;
 227 #else
 228         regs->ARM_pc += 4;
 229 #endif
 230 }
 231
 232 static inline void __kprobes
 233 singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 234 {
 235         p->ainsn.insn_singlestep(p->opcode, &p->ainsn, regs);
 236 }
 237
 238 /*
 239  * Called with IRQs disabled. IRQs must remain disabled from that point
 240  * all the way until processing this kprobe is complete.  The current
 241  * kprobes implementation cannot process more than one nested level of
 242  * kprobe, and that level is reserved for user kprobe handlers, so we can't
 243  * risk encountering a new kprobe in an interrupt handler.
 244  */
 245 void __kprobes kprobe_handler(struct pt_regs *regs)
 246 {
 247         struct kprobe *p, *cur;
 248         struct kprobe_ctlblk *kcb;
 249
 250         kcb = get_kprobe_ctlblk();
 251         cur = kprobe_running();
 252
 253 #ifdef CONFIG_THUMB2_KERNEL
 254         /*
 255          * First look for a probe which was registered using an address with
 256          * bit 0 set, this is the usual situation for pointers to Thumb code.
 257          * If not found, fallback to looking for one with bit 0 clear.
 258          */
 259         p = get_kprobe((kprobe_opcode_t *)(regs->ARM_pc | 1));
 260         if (!p)
 261                 p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
 262
 263 #else /* ! CONFIG_THUMB2_KERNEL */
 264         p = get_kprobe((kprobe_opcode_t *)regs->ARM_pc);
 265 #endif
 266
 267         if (p) {
 268                 if (cur) {
 269                         /* Kprobe is pending, so we're recursing. */
 270                         switch (kcb->kprobe_status) {
 271                         case KPROBE_HIT_ACTIVE:
 272                         case KPROBE_HIT_SSDONE:
 273                                 /* A pre- or post-handler probe got us here. */
 274                                 kprobes_inc_nmissed_count(p);
 275                                 save_previous_kprobe(kcb);
 276                                 set_current_kprobe(p);
 277                                 kcb->kprobe_status = KPROBE_REENTER;
 278                                 singlestep(p, regs, kcb);
 279                                 restore_previous_kprobe(kcb);
 280                                 break;
 281                         default:
 282                                 /* impossible cases */
 283                                 BUG();
 284                         }
 285                 } else if (p->ainsn.insn_check_cc(regs->ARM_cpsr)) {
 286                         /* Probe hit and conditional execution check ok. */
 287                         set_current_kprobe(p);
 288                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 289
 290                         /*
 291                          * If we have no pre-handler or it returned 0, we
 292                          * continue with normal processing.  If we have a
 293                          * pre-handler and it returned non-zero, it prepped
 294                          * for calling the break_handler below on re-entry,
 295                          * so get out doing nothing more here.
 296                          */
 297                         if (!p->pre_handler || !p->pre_handler(p, regs)) {
 298                                 kcb->kprobe_status = KPROBE_HIT_SS;
 299                                 singlestep(p, regs, kcb);
 300                                 if (p->post_handler) {
 301                                         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 302                                         p->post_handler(p, regs, 0);
 303                                 }
 304                                 reset_current_kprobe();
 305                         }
 306                 } else {
 307                         /*
 308                          * Probe hit but conditional execution check failed,
 309                          * so just skip the instruction and continue as if
 310                          * nothing had happened.
 311                          */
 312                         singlestep_skip(p, regs);
 313                 }
 314         } else if (cur) {
 315                 /* We probably hit a jprobe.  Call its break handler. */
 316                 if (cur->break_handler && cur->break_handler(cur, regs)) {
 317                         kcb->kprobe_status = KPROBE_HIT_SS;
 318                         singlestep(cur, regs, kcb);
 319                         if (cur->post_handler) {
 320                                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 321                                 cur->post_handler(cur, regs, 0);
 322                         }
 323                 }
 324                 reset_current_kprobe();
 325         } else {
 326                 /*
 327                  * The probe was removed and a race is in progress.
 328                  * There is nothing we can do about it.  Let's restart
 329                  * the instruction.  By the time we can restart, the
 330                  * real instruction will be there.
 331                  */
 332         }
 333 }
 334
 335 static int __kprobes kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
 336 {
 337         unsigned long flags;
 338         local_irq_save(flags);
 339         kprobe_handler(regs);
 340         local_irq_restore(flags);
 341         return 0;
 342 }
 343
 344 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
 345 {
 346         struct kprobe *cur = kprobe_running();
 347         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 348
 349         switch (kcb->kprobe_status) {
 350         case KPROBE_HIT_SS:
 351         case KPROBE_REENTER:
 352                 /*
 353                  * We are here because the instruction being single
 354                  * stepped caused a page fault. We reset the current
 355                  * kprobe and the PC to point back to the probe address
 356                  * and allow the page fault handler to continue as a
 357                  * normal page fault.
 358                  */
 359                 regs->ARM_pc = (long)cur->addr;
 360                 if (kcb->kprobe_status == KPROBE_REENTER) {
 361                         restore_previous_kprobe(kcb);
 362                 } else {
 363                         reset_current_kprobe();
 364                 }
 365                 break;
 366
 367         case KPROBE_HIT_ACTIVE:
 368         case KPROBE_HIT_SSDONE:
 369                 /*
 370                  * We increment the nmissed count for accounting,
 371                  * we can also use npre/npostfault count for accounting
 372                  * these specific fault cases.
 373                  */
 374                 kprobes_inc_nmissed_count(cur);
 375
 376                 /*
 377                  * We come here because instructions in the pre/post
 378                  * handler caused the page_fault, this could happen
 379                  * if handler tries to access user space by
 380                  * copy_from_user(), get_user() etc. Let the
 381                  * user-specified handler try to fix it.
 382                  */
 383                 if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
 384                         return 1;
 385                 break;
 386
 387         default:
 388                 break;
 389         }
 390
 391         return 0;
 392 }
 393
 394 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 395                                        unsigned long val, void *data)
 396 {
 397         /*
 398          * notify_die() is currently never called on ARM,
 399          * so this callback is currently empty.
 400          */
 401         return NOTIFY_DONE;
 402 }
 403
 404 /*
 405  * When a retprobed function returns, trampoline_handler() is called,
 406  * calling the kretprobe's handler. We construct a struct pt_regs to
 407  * give a view of registers r0-r11 to the user return-handler.  This is
 408  * not a complete pt_regs structure, but that should be plenty sufficient
 409  * for kretprobe handlers which should normally be interested in r0 only
 410  * anyway.
 411  */
 412 void __naked __kprobes kretprobe_trampoline(void)
 413 {
 414         __asm__ __volatile__ (
 415                 "stmdb  sp!, {r0 - r11}         \n\t"
 416                 "mov    r0, sp                  \n\t"
 417                 "bl     trampoline_handler      \n\t"
 418                 "mov    lr, r0                  \n\t"
 419                 "ldmia  sp!, {r0 - r11}         \n\t"
 420 #ifdef CONFIG_THUMB2_KERNEL
 421                 "bx     lr                      \n\t"
 422 #else
 423                 "mov    pc, lr                  \n\t"
 424 #endif
 425                 : : : "memory");
 426 }
 427
 428 /* Called from kretprobe_trampoline */
 429 static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
 430 {
 431         struct kretprobe_instance *ri = NULL;
 432         struct hlist_head *head, empty_rp;
 433         struct hlist_node *tmp;
 434         unsigned long flags, orig_ret_address = 0;
 435         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 436
 437         INIT_HLIST_HEAD(&empty_rp);
 438         kretprobe_hash_lock(current, &head, &flags);
 439
 440         /*
 441          * It is possible to have multiple instances associated with a given
 442          * task either because multiple functions in the call path have
 443          * a return probe installed on them, and/or more than one return
 444          * probe was registered for a target function.
 445          *
 446          * We can handle this because:
 447          *     - instances are always inserted at the head of the list
 448          *     - when multiple return probes are registered for the same
 449          *       function, the first instance's ret_addr will point to the
 450          *       real return address, and all the rest will point to
 451          *       kretprobe_trampoline
 452          */
 453         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 454                 if (ri->task != current)
 455                         /* another task is sharing our hash bucket */
 456                         continue;
 457
 458                 if (ri->rp && ri->rp->handler) {
 459                         __this_cpu_write(current_kprobe, &ri->rp->kp);
 460                         get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
 461                         ri->rp->handler(ri, regs);
 462                         __this_cpu_write(current_kprobe, NULL);
 463                 }
 464
 465                 orig_ret_address = (unsigned long)ri->ret_addr;
 466                 recycle_rp_inst(ri, &empty_rp);
 467
 468                 if (orig_ret_address != trampoline_address)
 469                         /*
 470                          * This is the real return address. Any other
 471                          * instances associated with this task are for
 472                          * other calls deeper on the call stack
 473                          */
 474                         break;
 475         }
 476
 477         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 478         kretprobe_hash_unlock(current, &flags);
 479
 480         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 481                 hlist_del(&ri->hlist);
 482                 kfree(ri);
 483         }
 484
 485         return (void *)orig_ret_address;
 486 }
 487
 488 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 489                                       struct pt_regs *regs)
 490 {
 491         ri->ret_addr = (kprobe_opcode_t *)regs->ARM_lr;
 492
 493         /* Replace the return addr with trampoline addr. */
 494         regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
 495 }
 496
 497 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 498 {
 499         struct jprobe *jp = container_of(p, struct jprobe, kp);
 500         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 501         long sp_addr = regs->ARM_sp;
 502         long cpsr;
 503
 504         kcb->jprobe_saved_regs = *regs;
 505         memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
 506         regs->ARM_pc = (long)jp->entry;
 507
 508         cpsr = regs->ARM_cpsr | PSR_I_BIT;
 509 #ifdef CONFIG_THUMB2_KERNEL
 510         /* Set correct Thumb state in cpsr */
 511         if (regs->ARM_pc & 1)
 512                 cpsr |= PSR_T_BIT;
 513         else
 514                 cpsr &= ~PSR_T_BIT;
 515 #endif
 516         regs->ARM_cpsr = cpsr;
 517
 518         preempt_disable();
 519         return 1;
 520 }
 521
 522 void __kprobes jprobe_return(void)
 523 {
 524         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 525
 526         __asm__ __volatile__ (
 527                 /*
 528                  * Setup an empty pt_regs. Fill SP and PC fields as
 529                  * they're needed by longjmp_break_handler.
 530                  *
 531                  * We allocate some slack between the original SP and start of
 532                  * our fabricated regs. To be precise we want to have worst case
 533                  * covered which is STMFD with all 16 regs so we allocate 2 *
 534                  * sizeof(struct_pt_regs)).
 535                  *
 536                  * This is to prevent any simulated instruction from writing
 537                  * over the regs when they are accessing the stack.
 538                  */
 539 #ifdef CONFIG_THUMB2_KERNEL
 540                 "sub    r0, %0, %1              \n\t"
 541                 "mov    sp, r0                  \n\t"
 542 #else
 543                 "sub    sp, %0, %1              \n\t"
 544 #endif
 545                 "ldr    r0, ="__stringify(JPROBE_MAGIC_ADDR)"\n\t"
 546                 "str    %0, [sp, %2]            \n\t"
 547                 "str    r0, [sp, %3]            \n\t"
 548                 "mov    r0, sp                  \n\t"
 549                 "bl     kprobe_handler          \n\t"
 550
 551                 /*
 552                  * Return to the context saved by setjmp_pre_handler
 553                  * and restored by longjmp_break_handler.
 554                  */
 555 #ifdef CONFIG_THUMB2_KERNEL
 556                 "ldr    lr, [sp, %2]            \n\t" /* lr = saved sp */
 557                 "ldrd   r0, r1, [sp, %5]        \n\t" /* r0,r1 = saved lr,pc */
 558                 "ldr    r2, [sp, %4]            \n\t" /* r2 = saved psr */
 559                 "stmdb  lr!, {r0, r1, r2}       \n\t" /* push saved lr and */
 560                                                       /* rfe context */
 561                 "ldmia  sp, {r0 - r12}          \n\t"
 562                 "mov    sp, lr                  \n\t"
 563                 "ldr    lr, [sp], #4            \n\t"
 564                 "rfeia  sp!                     \n\t"
 565 #else
 566                 "ldr    r0, [sp, %4]            \n\t"
 567                 "msr    cpsr_cxsf, r0           \n\t"
 568                 "ldmia  sp, {r0 - pc}           \n\t"
 569 #endif
 570                 :
 571                 : "r" (kcb->jprobe_saved_regs.ARM_sp),
 572                   "I" (sizeof(struct pt_regs) * 2),
 573                   "J" (offsetof(struct pt_regs, ARM_sp)),
 574                   "J" (offsetof(struct pt_regs, ARM_pc)),
 575                   "J" (offsetof(struct pt_regs, ARM_cpsr)),
 576                   "J" (offsetof(struct pt_regs, ARM_lr))
 577                 : "memory", "cc");
 578 }
 579
 580 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 581 {
 582         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 583         long stack_addr = kcb->jprobe_saved_regs.ARM_sp;
 584         long orig_sp = regs->ARM_sp;
 585         struct jprobe *jp = container_of(p, struct jprobe, kp);
 586
 587         if (regs->ARM_pc == JPROBE_MAGIC_ADDR) {
 588                 if (orig_sp != stack_addr) {
 589                         struct pt_regs *saved_regs =
 590                                 (struct pt_regs *)kcb->jprobe_saved_regs.ARM_sp;
 591                         printk("current sp %lx does not match saved sp %lx\n",
 592                                orig_sp, stack_addr);
 593                         printk("Saved registers for jprobe %p\n", jp);
 594                         show_regs(saved_regs);
 595                         printk("Current registers\n");
 596                         show_regs(regs);
 597                         BUG();
 598                 }
 599                 *regs = kcb->jprobe_saved_regs;
 600                 memcpy((void *)stack_addr, kcb->jprobes_stack,
 601                        MIN_STACK_SIZE(stack_addr));
 602                 preempt_enable_no_resched();
 603                 return 1;
 604         }
 605         return 0;
 606 }
 607
 608 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 609 {
 610         return 0;
 611 }
 612
 613 #ifdef CONFIG_THUMB2_KERNEL
 614
 615 static struct undef_hook kprobes_thumb16_break_hook = {
 616         .instr_mask     = 0xffff,
 617         .instr_val      = KPROBE_THUMB16_BREAKPOINT_INSTRUCTION,
 618         .cpsr_mask      = MODE_MASK,
 619         .cpsr_val       = SVC_MODE,
 620         .fn             = kprobe_trap_handler,
 621 };
 622
 623 static struct undef_hook kprobes_thumb32_break_hook = {
 624         .instr_mask     = 0xffffffff,
 625         .instr_val      = KPROBE_THUMB32_BREAKPOINT_INSTRUCTION,
 626         .cpsr_mask      = MODE_MASK,
 627         .cpsr_val       = SVC_MODE,
 628         .fn             = kprobe_trap_handler,
 629 };
 630
 631 #else  /* !CONFIG_THUMB2_KERNEL */
 632
 633 static struct undef_hook kprobes_arm_break_hook = {
 634         .instr_mask     = 0x0fffffff,
 635         .instr_val      = KPROBE_ARM_BREAKPOINT_INSTRUCTION,
 636         .cpsr_mask      = MODE_MASK,
 637         .cpsr_val       = SVC_MODE,
 638         .fn             = kprobe_trap_handler,
 639 };
 640
 641 #endif /* !CONFIG_THUMB2_KERNEL */
 642
 643 int __init arch_init_kprobes()
 644 {
 645         arm_probes_decode_init();
 646 #ifdef CONFIG_THUMB2_KERNEL
 647         register_undef_hook(&kprobes_thumb16_break_hook);
 648         register_undef_hook(&kprobes_thumb32_break_hook);
 649 #else
 650         register_undef_hook(&kprobes_arm_break_hook);
 651 #endif
 652         return 0;
 653 }