arch/mips/kernel/kprobes.c

   1 /*
   2  *  Kernel Probes (KProbes)
   3  *  arch/mips/kernel/kprobes.c
   4  *
   5  *  Copyright 2006 Sony Corp.
   6  *  Copyright 2010 Cavium Networks
   7  *
   8  *  Some portions copied from the powerpc version.
   9  *
  10  *   Copyright (C) IBM Corporation, 2002, 2004
  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 as published by
  14  *  the Free Software Foundation; version 2 of the License.
  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
  19  *  GNU General Public License for more details.
  20  *
  21  *  You should have received a copy of the GNU General Public License
  22  *  along with this program; if not, write to the Free Software
  23  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  24  */
  25
  26 #include <linux/kprobes.h>
  27 #include <linux/preempt.h>
  28 #include <linux/uaccess.h>
  29 #include <linux/kdebug.h>
  30 #include <linux/slab.h>
  31
  32 #include <asm/ptrace.h>
  33 #include <asm/branch.h>
  34 #include <asm/break.h>
  35 #include <asm/inst.h>
  36
  37 static const union mips_instruction breakpoint_insn = {
  38         .b_format = {
  39                 .opcode = spec_op,
  40                 .code = BRK_KPROBE_BP,
  41                 .func = break_op
  42         }
  43 };
  44
  45 static const union mips_instruction breakpoint2_insn = {
  46         .b_format = {
  47                 .opcode = spec_op,
  48                 .code = BRK_KPROBE_SSTEPBP,
  49                 .func = break_op
  50         }
  51 };
  52
  53 DEFINE_PER_CPU(struct kprobe *, current_kprobe);
  54 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  55
  56 static int __kprobes insn_has_delayslot(union mips_instruction insn)
  57 {
  58         switch (insn.i_format.opcode) {
  59
  60                 /*
  61                  * This group contains:
  62                  * jr and jalr are in r_format format.
  63                  */
  64         case spec_op:
  65                 switch (insn.r_format.func) {
  66                 case jr_op:
  67                 case jalr_op:
  68                         break;
  69                 default:
  70                         goto insn_ok;
  71                 }
  72
  73                 /*
  74                  * This group contains:
  75                  * bltz_op, bgez_op, bltzl_op, bgezl_op,
  76                  * bltzal_op, bgezal_op, bltzall_op, bgezall_op.
  77                  */
  78         case bcond_op:
  79
  80                 /*
  81                  * These are unconditional and in j_format.
  82                  */
  83         case jal_op:
  84         case j_op:
  85
  86                 /*
  87                  * These are conditional and in i_format.
  88                  */
  89         case beq_op:
  90         case beql_op:
  91         case bne_op:
  92         case bnel_op:
  93         case blez_op:
  94         case blezl_op:
  95         case bgtz_op:
  96         case bgtzl_op:
  97
  98                 /*
  99                  * These are the FPA/cp1 branch instructions.
 100                  */
 101         case cop1_op:
 102
 103 #ifdef CONFIG_CPU_CAVIUM_OCTEON
 104         case lwc2_op: /* This is bbit0 on Octeon */
 105         case ldc2_op: /* This is bbit032 on Octeon */
 106         case swc2_op: /* This is bbit1 on Octeon */
 107         case sdc2_op: /* This is bbit132 on Octeon */
 108 #endif
 109                 return 1;
 110         default:
 111                 break;
 112         }
 113 insn_ok:
 114         return 0;
 115 }
 116
 117 /*
 118  * insn_has_ll_or_sc function checks whether instruction is ll or sc
 119  * one; putting breakpoint on top of atomic ll/sc pair is bad idea;
 120  * so we need to prevent it and refuse kprobes insertion for such
 121  * instructions; cannot do much about breakpoint in the middle of
 122  * ll/sc pair; it is upto user to avoid those places
 123  */
 124 static int __kprobes insn_has_ll_or_sc(union mips_instruction insn)
 125 {
 126         int ret = 0;
 127
 128         switch (insn.i_format.opcode) {
 129         case ll_op:
 130         case lld_op:
 131         case sc_op:
 132         case scd_op:
 133                 ret = 1;
 134                 break;
 135         default:
 136                 break;
 137         }
 138         return ret;
 139 }
 140
 141 int __kprobes arch_prepare_kprobe(struct kprobe *p)
 142 {
 143         union mips_instruction insn;
 144         union mips_instruction prev_insn;
 145         int ret = 0;
 146
 147         insn = p->addr[0];
 148
 149         if (insn_has_ll_or_sc(insn)) {
 150                 pr_notice("Kprobes for ll and sc instructions are not"
 151                           "supported\n");
 152                 ret = -EINVAL;
 153                 goto out;
 154         }
 155
 156         if ((probe_kernel_read(&prev_insn, p->addr - 1,
 157                                 sizeof(mips_instruction)) == 0) &&
 158                                 insn_has_delayslot(prev_insn)) {
 159                 pr_notice("Kprobes for branch delayslot are not supported\n");
 160                 ret = -EINVAL;
 161                 goto out;
 162         }
 163
 164         /* insn: must be on special executable page on mips. */
 165         p->ainsn.insn = get_insn_slot();
 166         if (!p->ainsn.insn) {
 167                 ret = -ENOMEM;
 168                 goto out;
 169         }
 170
 171         /*
 172          * In the kprobe->ainsn.insn[] array we store the original
 173          * instruction at index zero and a break trap instruction at
 174          * index one.
 175          *
 176          * On MIPS arch if the instruction at probed address is a
 177          * branch instruction, we need to execute the instruction at
 178          * Branch Delayslot (BD) at the time of probe hit. As MIPS also
 179          * doesn't have single stepping support, the BD instruction can
 180          * not be executed in-line and it would be executed on SSOL slot
 181          * using a normal breakpoint instruction in the next slot.
 182          * So, read the instruction and save it for later execution.
 183          */
 184         if (insn_has_delayslot(insn))
 185                 memcpy(&p->ainsn.insn[0], p->addr + 1, sizeof(kprobe_opcode_t));
 186         else
 187                 memcpy(&p->ainsn.insn[0], p->addr, sizeof(kprobe_opcode_t));
 188
 189         p->ainsn.insn[1] = breakpoint2_insn;
 190         p->opcode = *p->addr;
 191
 192 out:
 193         return ret;
 194 }
 195
 196 void __kprobes arch_arm_kprobe(struct kprobe *p)
 197 {
 198         *p->addr = breakpoint_insn;
 199         flush_insn_slot(p);
 200 }
 201
 202 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 203 {
 204         *p->addr = p->opcode;
 205         flush_insn_slot(p);
 206 }
 207
 208 void __kprobes arch_remove_kprobe(struct kprobe *p)
 209 {
 210         if (p->ainsn.insn) {
 211                 free_insn_slot(p->ainsn.insn, 0);
 212                 p->ainsn.insn = NULL;
 213         }
 214 }
 215
 216 static void save_previous_kprobe(struct kprobe_ctlblk *kcb)
 217 {
 218         kcb->prev_kprobe.kp = kprobe_running();
 219         kcb->prev_kprobe.status = kcb->kprobe_status;
 220         kcb->prev_kprobe.old_SR = kcb->kprobe_old_SR;
 221         kcb->prev_kprobe.saved_SR = kcb->kprobe_saved_SR;
 222         kcb->prev_kprobe.saved_epc = kcb->kprobe_saved_epc;
 223 }
 224
 225 static void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 226 {
 227         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 228         kcb->kprobe_status = kcb->prev_kprobe.status;
 229         kcb->kprobe_old_SR = kcb->prev_kprobe.old_SR;
 230         kcb->kprobe_saved_SR = kcb->prev_kprobe.saved_SR;
 231         kcb->kprobe_saved_epc = kcb->prev_kprobe.saved_epc;
 232 }
 233
 234 static void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 235                                struct kprobe_ctlblk *kcb)
 236 {
 237         __this_cpu_write(current_kprobe, p);
 238         kcb->kprobe_saved_SR = kcb->kprobe_old_SR = (regs->cp0_status & ST0_IE);
 239         kcb->kprobe_saved_epc = regs->cp0_epc;
 240 }
 241
 242 /**
 243  * evaluate_branch_instrucion -
 244  *
 245  * Evaluate the branch instruction at probed address during probe hit. The
 246  * result of evaluation would be the updated epc. The insturction in delayslot
 247  * would actually be single stepped using a normal breakpoint) on SSOL slot.
 248  *
 249  * The result is also saved in the kprobe control block for later use,
 250  * in case we need to execute the delayslot instruction. The latter will be
 251  * false for NOP instruction in dealyslot and the branch-likely instructions
 252  * when the branch is taken. And for those cases we set a flag as
 253  * SKIP_DELAYSLOT in the kprobe control block
 254  */
 255 static int evaluate_branch_instruction(struct kprobe *p, struct pt_regs *regs,
 256                                         struct kprobe_ctlblk *kcb)
 257 {
 258         union mips_instruction insn = p->opcode;
 259         long epc;
 260         int ret = 0;
 261
 262         epc = regs->cp0_epc;
 263         if (epc & 3)
 264                 goto unaligned;
 265
 266         if (p->ainsn.insn->word == 0)
 267                 kcb->flags |= SKIP_DELAYSLOT;
 268         else
 269                 kcb->flags &= ~SKIP_DELAYSLOT;
 270
 271         ret = __compute_return_epc_for_insn(regs, insn);
 272         if (ret < 0)
 273                 return ret;
 274
 275         if (ret == BRANCH_LIKELY_TAKEN)
 276                 kcb->flags |= SKIP_DELAYSLOT;
 277
 278         kcb->target_epc = regs->cp0_epc;
 279
 280         return 0;
 281
 282 unaligned:
 283         pr_notice("%s: unaligned epc - sending SIGBUS.\n", current->comm);
 284         force_sig(SIGBUS, current);
 285         return -EFAULT;
 286
 287 }
 288
 289 static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
 290                                                 struct kprobe_ctlblk *kcb)
 291 {
 292         int ret = 0;
 293
 294         regs->cp0_status &= ~ST0_IE;
 295
 296         /* single step inline if the instruction is a break */
 297         if (p->opcode.word == breakpoint_insn.word ||
 298             p->opcode.word == breakpoint2_insn.word)
 299                 regs->cp0_epc = (unsigned long)p->addr;
 300         else if (insn_has_delayslot(p->opcode)) {
 301                 ret = evaluate_branch_instruction(p, regs, kcb);
 302                 if (ret < 0) {
 303                         pr_notice("Kprobes: Error in evaluating branch\n");
 304                         return;
 305                 }
 306         }
 307         regs->cp0_epc = (unsigned long)&p->ainsn.insn[0];
 308 }
 309
 310 /*
 311  * Called after single-stepping.  p->addr is the address of the
 312  * instruction whose first byte has been replaced by the "break 0"
 313  * instruction.  To avoid the SMP problems that can occur when we
 314  * temporarily put back the original opcode to single-step, we
 315  * single-stepped a copy of the instruction.  The address of this
 316  * copy is p->ainsn.insn.
 317  *
 318  * This function prepares to return from the post-single-step
 319  * breakpoint trap. In case of branch instructions, the target
 320  * epc to be restored.
 321  */
 322 static void __kprobes resume_execution(struct kprobe *p,
 323                                        struct pt_regs *regs,
 324                                        struct kprobe_ctlblk *kcb)
 325 {
 326         if (insn_has_delayslot(p->opcode))
 327                 regs->cp0_epc = kcb->target_epc;
 328         else {
 329                 unsigned long orig_epc = kcb->kprobe_saved_epc;
 330                 regs->cp0_epc = orig_epc + 4;
 331         }
 332 }
 333
 334 static int __kprobes kprobe_handler(struct pt_regs *regs)
 335 {
 336         struct kprobe *p;
 337         int ret = 0;
 338         kprobe_opcode_t *addr;
 339         struct kprobe_ctlblk *kcb;
 340
 341         addr = (kprobe_opcode_t *) regs->cp0_epc;
 342
 343         /*
 344          * We don't want to be preempted for the entire
 345          * duration of kprobe processing
 346          */
 347         preempt_disable();
 348         kcb = get_kprobe_ctlblk();
 349
 350         /* Check we're not actually recursing */
 351         if (kprobe_running()) {
 352                 p = get_kprobe(addr);
 353                 if (p) {
 354                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
 355                             p->ainsn.insn->word == breakpoint_insn.word) {
 356                                 regs->cp0_status &= ~ST0_IE;
 357                                 regs->cp0_status |= kcb->kprobe_saved_SR;
 358                                 goto no_kprobe;
 359                         }
 360                         /*
 361                          * We have reentered the kprobe_handler(), since
 362                          * another probe was hit while within the handler.
 363                          * We here save the original kprobes variables and
 364                          * just single step on the instruction of the new probe
 365                          * without calling any user handlers.
 366                          */
 367                         save_previous_kprobe(kcb);
 368                         set_current_kprobe(p, regs, kcb);
 369                         kprobes_inc_nmissed_count(p);
 370                         prepare_singlestep(p, regs, kcb);
 371                         kcb->kprobe_status = KPROBE_REENTER;
 372                         if (kcb->flags & SKIP_DELAYSLOT) {
 373                                 resume_execution(p, regs, kcb);
 374                                 restore_previous_kprobe(kcb);
 375                                 preempt_enable_no_resched();
 376                         }
 377                         return 1;
 378                 } else {
 379                         if (addr->word != breakpoint_insn.word) {
 380                                 /*
 381                                  * The breakpoint instruction was removed by
 382                                  * another cpu right after we hit, no further
 383                                  * handling of this interrupt is appropriate
 384                                  */
 385                                 ret = 1;
 386                                 goto no_kprobe;
 387                         }
 388                         p = __this_cpu_read(current_kprobe);
 389                         if (p->break_handler && p->break_handler(p, regs))
 390                                 goto ss_probe;
 391                 }
 392                 goto no_kprobe;
 393         }
 394
 395         p = get_kprobe(addr);
 396         if (!p) {
 397                 if (addr->word != breakpoint_insn.word) {
 398                         /*
 399                          * The breakpoint instruction was removed right
 400                          * after we hit it.  Another cpu has removed
 401                          * either a probepoint or a debugger breakpoint
 402                          * at this address.  In either case, no further
 403                          * handling of this interrupt is appropriate.
 404                          */
 405                         ret = 1;
 406                 }
 407                 /* Not one of ours: let kernel handle it */
 408                 goto no_kprobe;
 409         }
 410
 411         set_current_kprobe(p, regs, kcb);
 412         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 413
 414         if (p->pre_handler && p->pre_handler(p, regs)) {
 415                 /* handler has already set things up, so skip ss setup */
 416                 return 1;
 417         }
 418
 419 ss_probe:
 420         prepare_singlestep(p, regs, kcb);
 421         if (kcb->flags & SKIP_DELAYSLOT) {
 422                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 423                 if (p->post_handler)
 424                         p->post_handler(p, regs, 0);
 425                 resume_execution(p, regs, kcb);
 426                 preempt_enable_no_resched();
 427         } else
 428                 kcb->kprobe_status = KPROBE_HIT_SS;
 429
 430         return 1;
 431
 432 no_kprobe:
 433         preempt_enable_no_resched();
 434         return ret;
 435
 436 }
 437
 438 static inline int post_kprobe_handler(struct pt_regs *regs)
 439 {
 440         struct kprobe *cur = kprobe_running();
 441         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 442
 443         if (!cur)
 444                 return 0;
 445
 446         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 447                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 448                 cur->post_handler(cur, regs, 0);
 449         }
 450
 451         resume_execution(cur, regs, kcb);
 452
 453         regs->cp0_status |= kcb->kprobe_saved_SR;
 454
 455         /* Restore back the original saved kprobes variables and continue. */
 456         if (kcb->kprobe_status == KPROBE_REENTER) {
 457                 restore_previous_kprobe(kcb);
 458                 goto out;
 459         }
 460         reset_current_kprobe();
 461 out:
 462         preempt_enable_no_resched();
 463
 464         return 1;
 465 }
 466
 467 static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 468 {
 469         struct kprobe *cur = kprobe_running();
 470         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 471
 472         if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 473                 return 1;
 474
 475         if (kcb->kprobe_status & KPROBE_HIT_SS) {
 476                 resume_execution(cur, regs, kcb);
 477                 regs->cp0_status |= kcb->kprobe_old_SR;
 478
 479                 reset_current_kprobe();
 480                 preempt_enable_no_resched();
 481         }
 482         return 0;
 483 }
 484
 485 /*
 486  * Wrapper routine for handling exceptions.
 487  */
 488 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 489                                        unsigned long val, void *data)
 490 {
 491
 492         struct die_args *args = (struct die_args *)data;
 493         int ret = NOTIFY_DONE;
 494
 495         switch (val) {
 496         case DIE_BREAK:
 497                 if (kprobe_handler(args->regs))
 498                         ret = NOTIFY_STOP;
 499                 break;
 500         case DIE_SSTEPBP:
 501                 if (post_kprobe_handler(args->regs))
 502                         ret = NOTIFY_STOP;
 503                 break;
 504
 505         case DIE_PAGE_FAULT:
 506                 /* kprobe_running() needs smp_processor_id() */
 507                 preempt_disable();
 508
 509                 if (kprobe_running()
 510                     && kprobe_fault_handler(args->regs, args->trapnr))
 511                         ret = NOTIFY_STOP;
 512                 preempt_enable();
 513                 break;
 514         default:
 515                 break;
 516         }
 517         return ret;
 518 }
 519
 520 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 521 {
 522         struct jprobe *jp = container_of(p, struct jprobe, kp);
 523         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 524
 525         kcb->jprobe_saved_regs = *regs;
 526         kcb->jprobe_saved_sp = regs->regs[29];
 527
 528         memcpy(kcb->jprobes_stack, (void *)kcb->jprobe_saved_sp,
 529                MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp));
 530
 531         regs->cp0_epc = (unsigned long)(jp->entry);
 532
 533         return 1;
 534 }
 535
 536 /* Defined in the inline asm below. */
 537 void jprobe_return_end(void);
 538
 539 void __kprobes jprobe_return(void)
 540 {
 541         /* Assembler quirk necessitates this '0,code' business.  */
 542         asm volatile(
 543                 "break 0,%0\n\t"
 544                 ".globl jprobe_return_end\n"
 545                 "jprobe_return_end:\n"
 546                 : : "n" (BRK_KPROBE_BP) : "memory");
 547 }
 548
 549 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 550 {
 551         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 552
 553         if (regs->cp0_epc >= (unsigned long)jprobe_return &&
 554             regs->cp0_epc <= (unsigned long)jprobe_return_end) {
 555                 *regs = kcb->jprobe_saved_regs;
 556                 memcpy((void *)kcb->jprobe_saved_sp, kcb->jprobes_stack,
 557                        MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp));
 558                 preempt_enable_no_resched();
 559
 560                 return 1;
 561         }
 562         return 0;
 563 }
 564
 565 /*
 566  * Function return probe trampoline:
 567  *      - init_kprobes() establishes a probepoint here
 568  *      - When the probed function returns, this probe causes the
 569  *        handlers to fire
 570  */
 571 static void __used kretprobe_trampoline_holder(void)
 572 {
 573         asm volatile(
 574                 ".set push\n\t"
 575                 /* Keep the assembler from reordering and placing JR here. */
 576                 ".set noreorder\n\t"
 577                 "nop\n\t"
 578                 ".global kretprobe_trampoline\n"
 579                 "kretprobe_trampoline:\n\t"
 580                 "nop\n\t"
 581                 ".set pop"
 582                 : : : "memory");
 583 }
 584
 585 void kretprobe_trampoline(void);
 586
 587 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 588                                       struct pt_regs *regs)
 589 {
 590         ri->ret_addr = (kprobe_opcode_t *) regs->regs[31];
 591
 592         /* Replace the return addr with trampoline addr */
 593         regs->regs[31] = (unsigned long)kretprobe_trampoline;
 594 }
 595
 596 /*
 597  * Called when the probe at kretprobe trampoline is hit
 598  */
 599 static int __kprobes trampoline_probe_handler(struct kprobe *p,
 600                                                 struct pt_regs *regs)
 601 {
 602         struct kretprobe_instance *ri = NULL;
 603         struct hlist_head *head, empty_rp;
 604         struct hlist_node *tmp;
 605         unsigned long flags, orig_ret_address = 0;
 606         unsigned long trampoline_address = (unsigned long)kretprobe_trampoline;
 607
 608         INIT_HLIST_HEAD(&empty_rp);
 609         kretprobe_hash_lock(current, &head, &flags);
 610
 611         /*
 612          * It is possible to have multiple instances associated with a given
 613          * task either because an multiple functions in the call path
 614          * have a return probe installed on them, and/or more than one return
 615          * return probe was registered for a target function.
 616          *
 617          * We can handle this because:
 618          *     - instances are always inserted at the head of the list
 619          *     - when multiple return probes are registered for the same
 620          *       function, the first instance's ret_addr will point to the
 621          *       real return address, and all the rest will point to
 622          *       kretprobe_trampoline
 623          */
 624         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 625                 if (ri->task != current)
 626                         /* another task is sharing our hash bucket */
 627                         continue;
 628
 629                 if (ri->rp && ri->rp->handler)
 630                         ri->rp->handler(ri, regs);
 631
 632                 orig_ret_address = (unsigned long)ri->ret_addr;
 633                 recycle_rp_inst(ri, &empty_rp);
 634
 635                 if (orig_ret_address != trampoline_address)
 636                         /*
 637                          * This is the real return address. Any other
 638                          * instances associated with this task are for
 639                          * other calls deeper on the call stack
 640                          */
 641                         break;
 642         }
 643
 644         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 645         instruction_pointer(regs) = orig_ret_address;
 646
 647         reset_current_kprobe();
 648         kretprobe_hash_unlock(current, &flags);
 649         preempt_enable_no_resched();
 650
 651         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 652                 hlist_del(&ri->hlist);
 653                 kfree(ri);
 654         }
 655         /*
 656          * By returning a non-zero value, we are telling
 657          * kprobe_handler() that we don't want the post_handler
 658          * to run (and have re-enabled preemption)
 659          */
 660         return 1;
 661 }
 662
 663 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 664 {
 665         if (p->addr == (kprobe_opcode_t *)kretprobe_trampoline)
 666                 return 1;
 667
 668         return 0;
 669 }
 670
 671 static struct kprobe trampoline_p = {
 672         .addr = (kprobe_opcode_t *)kretprobe_trampoline,
 673         .pre_handler = trampoline_probe_handler
 674 };
 675
 676 int __init arch_init_kprobes(void)
 677 {
 678         return register_kprobe(&trampoline_p);
 679 }