arch/arm64/kernel/probes/kprobes.c

   1 /*
   2  * arch/arm64/kernel/probes/kprobes.c
   3  *
   4  * Kprobes support for ARM64
   5  *
   6  * Copyright (C) 2013 Linaro Limited.
   7  * Author: Sandeepa Prabhu <sandeepa.prabhu@linaro.org>
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * General Public License for more details.
  17  *
  18  */
  19 #include <linux/kasan.h>
  20 #include <linux/kernel.h>
  21 #include <linux/kprobes.h>
  22 #include <linux/extable.h>
  23 #include <linux/slab.h>
  24 #include <linux/stop_machine.h>
  25 #include <linux/stringify.h>
  26 #include <asm/traps.h>
  27 #include <asm/ptrace.h>
  28 #include <asm/cacheflush.h>
  29 #include <asm/debug-monitors.h>
  30 #include <asm/system_misc.h>
  31 #include <asm/insn.h>
  32 #include <asm/uaccess.h>
  33 #include <asm/irq.h>
  34 #include <asm/sections.h>
  35
  36 #include "decode-insn.h"
  37
  38 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  39 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  40
  41 static void __kprobes
  42 post_kprobe_handler(struct kprobe_ctlblk *, struct pt_regs *);
  43
  44 static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
  45 {
  46         /* prepare insn slot */
  47         p->ainsn.insn[0] = cpu_to_le32(p->opcode);
  48
  49         flush_icache_range((uintptr_t) (p->ainsn.insn),
  50                            (uintptr_t) (p->ainsn.insn) +
  51                            MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
  52
  53         /*
  54          * Needs restoring of return address after stepping xol.
  55          */
  56         p->ainsn.restore = (unsigned long) p->addr +
  57           sizeof(kprobe_opcode_t);
  58 }
  59
  60 static void __kprobes arch_prepare_simulate(struct kprobe *p)
  61 {
  62         /* This instructions is not executed xol. No need to adjust the PC */
  63         p->ainsn.restore = 0;
  64 }
  65
  66 static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
  67 {
  68         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
  69
  70         if (p->ainsn.handler)
  71                 p->ainsn.handler((u32)p->opcode, (long)p->addr, regs);
  72
  73         /* single step simulated, now go for post processing */
  74         post_kprobe_handler(kcb, regs);
  75 }
  76
  77 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  78 {
  79         unsigned long probe_addr = (unsigned long)p->addr;
  80         extern char __start_rodata[];
  81         extern char __end_rodata[];
  82
  83         if (probe_addr & 0x3)
  84                 return -EINVAL;
  85
  86         /* copy instruction */
  87         p->opcode = le32_to_cpu(*p->addr);
  88
  89         if (in_exception_text(probe_addr))
  90                 return -EINVAL;
  91         if (probe_addr >= (unsigned long) __start_rodata &&
  92             probe_addr <= (unsigned long) __end_rodata)
  93                 return -EINVAL;
  94
  95         /* decode instruction */
  96         switch (arm_kprobe_decode_insn(p->addr, &p->ainsn)) {
  97         case INSN_REJECTED:     /* insn not supported */
  98                 return -EINVAL;
  99
 100         case INSN_GOOD_NO_SLOT: /* insn need simulation */
 101                 p->ainsn.insn = NULL;
 102                 break;
 103
 104         case INSN_GOOD: /* instruction uses slot */
 105                 p->ainsn.insn = get_insn_slot();
 106                 if (!p->ainsn.insn)
 107                         return -ENOMEM;
 108                 break;
 109         };
 110
 111         /* prepare the instruction */
 112         if (p->ainsn.insn)
 113                 arch_prepare_ss_slot(p);
 114         else
 115                 arch_prepare_simulate(p);
 116
 117         return 0;
 118 }
 119
 120 static int __kprobes patch_text(kprobe_opcode_t *addr, u32 opcode)
 121 {
 122         void *addrs[1];
 123         u32 insns[1];
 124
 125         addrs[0] = (void *)addr;
 126         insns[0] = (u32)opcode;
 127
 128         return aarch64_insn_patch_text(addrs, insns, 1);
 129 }
 130
 131 /* arm kprobe: install breakpoint in text */
 132 void __kprobes arch_arm_kprobe(struct kprobe *p)
 133 {
 134         patch_text(p->addr, BRK64_OPCODE_KPROBES);
 135 }
 136
 137 /* disarm kprobe: remove breakpoint from text */
 138 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 139 {
 140         patch_text(p->addr, p->opcode);
 141 }
 142
 143 void __kprobes arch_remove_kprobe(struct kprobe *p)
 144 {
 145         if (p->ainsn.insn) {
 146                 free_insn_slot(p->ainsn.insn, 0);
 147                 p->ainsn.insn = NULL;
 148         }
 149 }
 150
 151 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 152 {
 153         kcb->prev_kprobe.kp = kprobe_running();
 154         kcb->prev_kprobe.status = kcb->kprobe_status;
 155 }
 156
 157 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 158 {
 159         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 160         kcb->kprobe_status = kcb->prev_kprobe.status;
 161 }
 162
 163 static void __kprobes set_current_kprobe(struct kprobe *p)
 164 {
 165         __this_cpu_write(current_kprobe, p);
 166 }
 167
 168 /*
 169  * When PSTATE.D is set (masked), then software step exceptions can not be
 170  * generated.
 171  * SPSR's D bit shows the value of PSTATE.D immediately before the
 172  * exception was taken. PSTATE.D is set while entering into any exception
 173  * mode, however software clears it for any normal (none-debug-exception)
 174  * mode in the exception entry. Therefore, when we are entering into kprobe
 175  * breakpoint handler from any normal mode then SPSR.D bit is already
 176  * cleared, however it is set when we are entering from any debug exception
 177  * mode.
 178  * Since we always need to generate single step exception after a kprobe
 179  * breakpoint exception therefore we need to clear it unconditionally, when
 180  * we become sure that the current breakpoint exception is for kprobe.
 181  */
 182 static void __kprobes
 183 spsr_set_debug_flag(struct pt_regs *regs, int mask)
 184 {
 185         unsigned long spsr = regs->pstate;
 186
 187         if (mask)
 188                 spsr |= PSR_D_BIT;
 189         else
 190                 spsr &= ~PSR_D_BIT;
 191
 192         regs->pstate = spsr;
 193 }
 194
 195 /*
 196  * Interrupts need to be disabled before single-step mode is set, and not
 197  * reenabled until after single-step mode ends.
 198  * Without disabling interrupt on local CPU, there is a chance of
 199  * interrupt occurrence in the period of exception return and  start of
 200  * out-of-line single-step, that result in wrongly single stepping
 201  * into the interrupt handler.
 202  */
 203 static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb,
 204                                                 struct pt_regs *regs)
 205 {
 206         kcb->saved_irqflag = regs->pstate;
 207         regs->pstate |= PSR_I_BIT;
 208 }
 209
 210 static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
 211                                                 struct pt_regs *regs)
 212 {
 213         if (kcb->saved_irqflag & PSR_I_BIT)
 214                 regs->pstate |= PSR_I_BIT;
 215         else
 216                 regs->pstate &= ~PSR_I_BIT;
 217 }
 218
 219 static void __kprobes
 220 set_ss_context(struct kprobe_ctlblk *kcb, unsigned long addr)
 221 {
 222         kcb->ss_ctx.ss_pending = true;
 223         kcb->ss_ctx.match_addr = addr + sizeof(kprobe_opcode_t);
 224 }
 225
 226 static void __kprobes clear_ss_context(struct kprobe_ctlblk *kcb)
 227 {
 228         kcb->ss_ctx.ss_pending = false;
 229         kcb->ss_ctx.match_addr = 0;
 230 }
 231
 232 static void __kprobes setup_singlestep(struct kprobe *p,
 233                                        struct pt_regs *regs,
 234                                        struct kprobe_ctlblk *kcb, int reenter)
 235 {
 236         unsigned long slot;
 237
 238         if (reenter) {
 239                 save_previous_kprobe(kcb);
 240                 set_current_kprobe(p);
 241                 kcb->kprobe_status = KPROBE_REENTER;
 242         } else {
 243                 kcb->kprobe_status = KPROBE_HIT_SS;
 244         }
 245
 246
 247         if (p->ainsn.insn) {
 248                 /* prepare for single stepping */
 249                 slot = (unsigned long)p->ainsn.insn;
 250
 251                 set_ss_context(kcb, slot);      /* mark pending ss */
 252
 253                 spsr_set_debug_flag(regs, 0);
 254
 255                 /* IRQs and single stepping do not mix well. */
 256                 kprobes_save_local_irqflag(kcb, regs);
 257                 kernel_enable_single_step(regs);
 258                 instruction_pointer_set(regs, slot);
 259         } else {
 260                 /* insn simulation */
 261                 arch_simulate_insn(p, regs);
 262         }
 263 }
 264
 265 static int __kprobes reenter_kprobe(struct kprobe *p,
 266                                     struct pt_regs *regs,
 267                                     struct kprobe_ctlblk *kcb)
 268 {
 269         switch (kcb->kprobe_status) {
 270         case KPROBE_HIT_SSDONE:
 271         case KPROBE_HIT_ACTIVE:
 272                 kprobes_inc_nmissed_count(p);
 273                 setup_singlestep(p, regs, kcb, 1);
 274                 break;
 275         case KPROBE_HIT_SS:
 276         case KPROBE_REENTER:
 277                 pr_warn("Unrecoverable kprobe detected.\n");
 278                 dump_kprobe(p);
 279                 BUG();
 280                 break;
 281         default:
 282                 WARN_ON(1);
 283                 return 0;
 284         }
 285
 286         return 1;
 287 }
 288
 289 static void __kprobes
 290 post_kprobe_handler(struct kprobe_ctlblk *kcb, struct pt_regs *regs)
 291 {
 292         struct kprobe *cur = kprobe_running();
 293
 294         if (!cur)
 295                 return;
 296
 297         /* return addr restore if non-branching insn */
 298         if (cur->ainsn.restore != 0)
 299                 instruction_pointer_set(regs, cur->ainsn.restore);
 300
 301         /* restore back original saved kprobe variables and continue */
 302         if (kcb->kprobe_status == KPROBE_REENTER) {
 303                 restore_previous_kprobe(kcb);
 304                 return;
 305         }
 306         /* call post handler */
 307         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 308         if (cur->post_handler)  {
 309                 /* post_handler can hit breakpoint and single step
 310                  * again, so we enable D-flag for recursive exception.
 311                  */
 312                 cur->post_handler(cur, regs, 0);
 313         }
 314
 315         reset_current_kprobe();
 316 }
 317
 318 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
 319 {
 320         struct kprobe *cur = kprobe_running();
 321         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 322
 323         switch (kcb->kprobe_status) {
 324         case KPROBE_HIT_SS:
 325         case KPROBE_REENTER:
 326                 /*
 327                  * We are here because the instruction being single
 328                  * stepped caused a page fault. We reset the current
 329                  * kprobe and the ip points back to the probe address
 330                  * and allow the page fault handler to continue as a
 331                  * normal page fault.
 332                  */
 333                 instruction_pointer_set(regs, (unsigned long) cur->addr);
 334                 if (!instruction_pointer(regs))
 335                         BUG();
 336
 337                 kernel_disable_single_step();
 338
 339                 if (kcb->kprobe_status == KPROBE_REENTER)
 340                         restore_previous_kprobe(kcb);
 341                 else
 342                         reset_current_kprobe();
 343
 344                 break;
 345         case KPROBE_HIT_ACTIVE:
 346         case KPROBE_HIT_SSDONE:
 347                 /*
 348                  * We increment the nmissed count for accounting,
 349                  * we can also use npre/npostfault count for accounting
 350                  * these specific fault cases.
 351                  */
 352                 kprobes_inc_nmissed_count(cur);
 353
 354                 /*
 355                  * We come here because instructions in the pre/post
 356                  * handler caused the page_fault, this could happen
 357                  * if handler tries to access user space by
 358                  * copy_from_user(), get_user() etc. Let the
 359                  * user-specified handler try to fix it first.
 360                  */
 361                 if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
 362                         return 1;
 363
 364                 /*
 365                  * In case the user-specified fault handler returned
 366                  * zero, try to fix up.
 367                  */
 368                 if (fixup_exception(regs))
 369                         return 1;
 370         }
 371         return 0;
 372 }
 373
 374 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 375                                        unsigned long val, void *data)
 376 {
 377         return NOTIFY_DONE;
 378 }
 379
 380 static void __kprobes kprobe_handler(struct pt_regs *regs)
 381 {
 382         struct kprobe *p, *cur_kprobe;
 383         struct kprobe_ctlblk *kcb;
 384         unsigned long addr = instruction_pointer(regs);
 385
 386         kcb = get_kprobe_ctlblk();
 387         cur_kprobe = kprobe_running();
 388
 389         p = get_kprobe((kprobe_opcode_t *) addr);
 390
 391         if (p) {
 392                 if (cur_kprobe) {
 393                         if (reenter_kprobe(p, regs, kcb))
 394                                 return;
 395                 } else {
 396                         /* Probe hit */
 397                         set_current_kprobe(p);
 398                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 399
 400                         /*
 401                          * If we have no pre-handler or it returned 0, we
 402                          * continue with normal processing.  If we have a
 403                          * pre-handler and it returned non-zero, it prepped
 404                          * for calling the break_handler below on re-entry,
 405                          * so get out doing nothing more here.
 406                          *
 407                          * pre_handler can hit a breakpoint and can step thru
 408                          * before return, keep PSTATE D-flag enabled until
 409                          * pre_handler return back.
 410                          */
 411                         if (!p->pre_handler || !p->pre_handler(p, regs)) {
 412                                 setup_singlestep(p, regs, kcb, 0);
 413                                 return;
 414                         }
 415                 }
 416         } else if ((le32_to_cpu(*(kprobe_opcode_t *) addr) ==
 417             BRK64_OPCODE_KPROBES) && cur_kprobe) {
 418                 /* We probably hit a jprobe.  Call its break handler. */
 419                 if (cur_kprobe->break_handler  &&
 420                      cur_kprobe->break_handler(cur_kprobe, regs)) {
 421                         setup_singlestep(cur_kprobe, regs, kcb, 0);
 422                         return;
 423                 }
 424         }
 425         /*
 426          * The breakpoint instruction was removed right
 427          * after we hit it.  Another cpu has removed
 428          * either a probepoint or a debugger breakpoint
 429          * at this address.  In either case, no further
 430          * handling of this interrupt is appropriate.
 431          * Return back to original instruction, and continue.
 432          */
 433 }
 434
 435 static int __kprobes
 436 kprobe_ss_hit(struct kprobe_ctlblk *kcb, unsigned long addr)
 437 {
 438         if ((kcb->ss_ctx.ss_pending)
 439             && (kcb->ss_ctx.match_addr == addr)) {
 440                 clear_ss_context(kcb);  /* clear pending ss */
 441                 return DBG_HOOK_HANDLED;
 442         }
 443         /* not ours, kprobes should ignore it */
 444         return DBG_HOOK_ERROR;
 445 }
 446
 447 int __kprobes
 448 kprobe_single_step_handler(struct pt_regs *regs, unsigned int esr)
 449 {
 450         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 451         int retval;
 452
 453         if (user_mode(regs))
 454                 return DBG_HOOK_ERROR;
 455
 456         /* return error if this is not our step */
 457         retval = kprobe_ss_hit(kcb, instruction_pointer(regs));
 458
 459         if (retval == DBG_HOOK_HANDLED) {
 460                 kprobes_restore_local_irqflag(kcb, regs);
 461                 kernel_disable_single_step();
 462
 463                 post_kprobe_handler(kcb, regs);
 464         }
 465
 466         return retval;
 467 }
 468
 469 int __kprobes
 470 kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr)
 471 {
 472         if (user_mode(regs))
 473                 return DBG_HOOK_ERROR;
 474
 475         kprobe_handler(regs);
 476         return DBG_HOOK_HANDLED;
 477 }
 478
 479 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 480 {
 481         struct jprobe *jp = container_of(p, struct jprobe, kp);
 482         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 483
 484         kcb->jprobe_saved_regs = *regs;
 485         /*
 486          * Since we can't be sure where in the stack frame "stacked"
 487          * pass-by-value arguments are stored we just don't try to
 488          * duplicate any of the stack. Do not use jprobes on functions that
 489          * use more than 64 bytes (after padding each to an 8 byte boundary)
 490          * of arguments, or pass individual arguments larger than 16 bytes.
 491          */
 492
 493         instruction_pointer_set(regs, (unsigned long) jp->entry);
 494         preempt_disable();
 495         pause_graph_tracing();
 496         return 1;
 497 }
 498
 499 void __kprobes jprobe_return(void)
 500 {
 501         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 502
 503         /*
 504          * Jprobe handler return by entering break exception,
 505          * encoded same as kprobe, but with following conditions
 506          * -a special PC to identify it from the other kprobes.
 507          * -restore stack addr to original saved pt_regs
 508          */
 509         asm volatile("                          mov sp, %0      \n"
 510                      "jprobe_return_break:      brk %1          \n"
 511                      :
 512                      : "r" (kcb->jprobe_saved_regs.sp),
 513                        "I" (BRK64_ESR_KPROBES)
 514                      : "memory");
 515
 516         unreachable();
 517 }
 518
 519 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 520 {
 521         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 522         long stack_addr = kcb->jprobe_saved_regs.sp;
 523         long orig_sp = kernel_stack_pointer(regs);
 524         struct jprobe *jp = container_of(p, struct jprobe, kp);
 525         extern const char jprobe_return_break[];
 526
 527         if (instruction_pointer(regs) != (u64) jprobe_return_break)
 528                 return 0;
 529
 530         if (orig_sp != stack_addr) {
 531                 struct pt_regs *saved_regs =
 532                     (struct pt_regs *)kcb->jprobe_saved_regs.sp;
 533                 pr_err("current sp %lx does not match saved sp %lx\n",
 534                        orig_sp, stack_addr);
 535                 pr_err("Saved registers for jprobe %p\n", jp);
 536                 show_regs(saved_regs);
 537                 pr_err("Current registers\n");
 538                 show_regs(regs);
 539                 BUG();
 540         }
 541         unpause_graph_tracing();
 542         *regs = kcb->jprobe_saved_regs;
 543         preempt_enable_no_resched();
 544         return 1;
 545 }
 546
 547 bool arch_within_kprobe_blacklist(unsigned long addr)
 548 {
 549         if ((addr >= (unsigned long)__kprobes_text_start &&
 550             addr < (unsigned long)__kprobes_text_end) ||
 551             (addr >= (unsigned long)__entry_text_start &&
 552             addr < (unsigned long)__entry_text_end) ||
 553             (addr >= (unsigned long)__idmap_text_start &&
 554             addr < (unsigned long)__idmap_text_end) ||
 555             (addr >= (unsigned long)__hyp_text_start &&
 556             addr < (unsigned long)__hyp_text_end) ||
 557             !!search_exception_tables(addr))
 558                 return true;
 559
 560         if (!is_kernel_in_hyp_mode()) {
 561                 if ((addr >= (unsigned long)__hyp_idmap_text_start &&
 562                     addr < (unsigned long)__hyp_idmap_text_end))
 563                         return true;
 564         }
 565
 566         return false;
 567 }
 568
 569 void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
 570 {
 571         struct kretprobe_instance *ri = NULL;
 572         struct hlist_head *head, empty_rp;
 573         struct hlist_node *tmp;
 574         unsigned long flags, orig_ret_address = 0;
 575         unsigned long trampoline_address =
 576                 (unsigned long)&kretprobe_trampoline;
 577         kprobe_opcode_t *correct_ret_addr = NULL;
 578
 579         INIT_HLIST_HEAD(&empty_rp);
 580         kretprobe_hash_lock(current, &head, &flags);
 581
 582         /*
 583          * It is possible to have multiple instances associated with a given
 584          * task either because multiple functions in the call path have
 585          * return probes installed on them, and/or more than one
 586          * return probe was registered for a target function.
 587          *
 588          * We can handle this because:
 589          *     - instances are always pushed into the head of the list
 590          *     - when multiple return probes are registered for the same
 591          *       function, the (chronologically) first instance's ret_addr
 592          *       will be the real return address, and all the rest will
 593          *       point to kretprobe_trampoline.
 594          */
 595         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 596                 if (ri->task != current)
 597                         /* another task is sharing our hash bucket */
 598                         continue;
 599
 600                 orig_ret_address = (unsigned long)ri->ret_addr;
 601
 602                 if (orig_ret_address != trampoline_address)
 603                         /*
 604                          * This is the real return address. Any other
 605                          * instances associated with this task are for
 606                          * other calls deeper on the call stack
 607                          */
 608                         break;
 609         }
 610
 611         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 612
 613         correct_ret_addr = ri->ret_addr;
 614         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 615                 if (ri->task != current)
 616                         /* another task is sharing our hash bucket */
 617                         continue;
 618
 619                 orig_ret_address = (unsigned long)ri->ret_addr;
 620                 if (ri->rp && ri->rp->handler) {
 621                         __this_cpu_write(current_kprobe, &ri->rp->kp);
 622                         get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
 623                         ri->ret_addr = correct_ret_addr;
 624                         ri->rp->handler(ri, regs);
 625                         __this_cpu_write(current_kprobe, NULL);
 626                 }
 627
 628                 recycle_rp_inst(ri, &empty_rp);
 629
 630                 if (orig_ret_address != trampoline_address)
 631                         /*
 632                          * This is the real return address. Any other
 633                          * instances associated with this task are for
 634                          * other calls deeper on the call stack
 635                          */
 636                         break;
 637         }
 638
 639         kretprobe_hash_unlock(current, &flags);
 640
 641         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 642                 hlist_del(&ri->hlist);
 643                 kfree(ri);
 644         }
 645         return (void *)orig_ret_address;
 646 }
 647
 648 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 649                                       struct pt_regs *regs)
 650 {
 651         ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];
 652
 653         /* replace return addr (x30) with trampoline */
 654         regs->regs[30] = (long)&kretprobe_trampoline;
 655 }
 656
 657 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 658 {
 659         return 0;
 660 }
 661
 662 int __init arch_init_kprobes(void)
 663 {
 664         return 0;
 665 }