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/kernel.h>
  20 #include <linux/kprobes.h>
  21 #include <linux/module.h>
  22 #include <linux/slab.h>
  23 #include <linux/stop_machine.h>
  24 #include <linux/stringify.h>
  25 #include <asm/traps.h>
  26 #include <asm/ptrace.h>
  27 #include <asm/cacheflush.h>
  28 #include <asm/debug-monitors.h>
  29 #include <asm/system_misc.h>
  30 #include <asm/insn.h>
  31 #include <asm/uaccess.h>
  32 #include <asm/irq.h>
  33 #include <asm-generic/sections.h>
  34
  35 #include "decode-insn.h"
  36
  37 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  38 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  39
  40 static void __kprobes
  41 post_kprobe_handler(struct kprobe_ctlblk *, struct pt_regs *);
  42
  43 static inline unsigned long min_stack_size(unsigned long addr)
  44 {
  45         unsigned long size;
  46
  47         size = (unsigned long)current_thread_info() + THREAD_START_SP - addr;
  48
  49         return min(size, FIELD_SIZEOF(struct kprobe_ctlblk, jprobes_stack));
  50 }
  51
  52 static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
  53 {
  54         /* prepare insn slot */
  55         p->ainsn.insn[0] = cpu_to_le32(p->opcode);
  56
  57         flush_icache_range((uintptr_t) (p->ainsn.insn),
  58                            (uintptr_t) (p->ainsn.insn) +
  59                            MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
  60
  61         /*
  62          * Needs restoring of return address after stepping xol.
  63          */
  64         p->ainsn.restore = (unsigned long) p->addr +
  65           sizeof(kprobe_opcode_t);
  66 }
  67
  68 static void __kprobes arch_prepare_simulate(struct kprobe *p)
  69 {
  70         /* This instructions is not executed xol. No need to adjust the PC */
  71         p->ainsn.restore = 0;
  72 }
  73
  74 static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
  75 {
  76         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
  77
  78         if (p->ainsn.handler)
  79                 p->ainsn.handler((u32)p->opcode, (long)p->addr, regs);
  80
  81         /* single step simulated, now go for post processing */
  82         post_kprobe_handler(kcb, regs);
  83 }
  84
  85 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  86 {
  87         unsigned long probe_addr = (unsigned long)p->addr;
  88         extern char __start_rodata[];
  89         extern char __end_rodata[];
  90
  91         if (probe_addr & 0x3)
  92                 return -EINVAL;
  93
  94         /* copy instruction */
  95         p->opcode = le32_to_cpu(*p->addr);
  96
  97         if (in_exception_text(probe_addr))
  98                 return -EINVAL;
  99         if (probe_addr >= (unsigned long) __start_rodata &&
 100             probe_addr <= (unsigned long) __end_rodata)
 101                 return -EINVAL;
 102
 103         /* decode instruction */
 104         switch (arm_kprobe_decode_insn(p->addr, &p->ainsn)) {
 105         case INSN_REJECTED:     /* insn not supported */
 106                 return -EINVAL;
 107
 108         case INSN_GOOD_NO_SLOT: /* insn need simulation */
 109                 p->ainsn.insn = NULL;
 110                 break;
 111
 112         case INSN_GOOD: /* instruction uses slot */
 113                 p->ainsn.insn = get_insn_slot();
 114                 if (!p->ainsn.insn)
 115                         return -ENOMEM;
 116                 break;
 117         };
 118
 119         /* prepare the instruction */
 120         if (p->ainsn.insn)
 121                 arch_prepare_ss_slot(p);
 122         else
 123                 arch_prepare_simulate(p);
 124
 125         return 0;
 126 }
 127
 128 static int __kprobes patch_text(kprobe_opcode_t *addr, u32 opcode)
 129 {
 130         void *addrs[1];
 131         u32 insns[1];
 132
 133         addrs[0] = (void *)addr;
 134         insns[0] = (u32)opcode;
 135
 136         return aarch64_insn_patch_text(addrs, insns, 1);
 137 }
 138
 139 /* arm kprobe: install breakpoint in text */
 140 void __kprobes arch_arm_kprobe(struct kprobe *p)
 141 {
 142         patch_text(p->addr, BRK64_OPCODE_KPROBES);
 143 }
 144
 145 /* disarm kprobe: remove breakpoint from text */
 146 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 147 {
 148         patch_text(p->addr, p->opcode);
 149 }
 150
 151 void __kprobes arch_remove_kprobe(struct kprobe *p)
 152 {
 153         if (p->ainsn.insn) {
 154                 free_insn_slot(p->ainsn.insn, 0);
 155                 p->ainsn.insn = NULL;
 156         }
 157 }
 158
 159 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 160 {
 161         kcb->prev_kprobe.kp = kprobe_running();
 162         kcb->prev_kprobe.status = kcb->kprobe_status;
 163 }
 164
 165 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 166 {
 167         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 168         kcb->kprobe_status = kcb->prev_kprobe.status;
 169 }
 170
 171 static void __kprobes set_current_kprobe(struct kprobe *p)
 172 {
 173         __this_cpu_write(current_kprobe, p);
 174 }
 175
 176 /*
 177  * The D-flag (Debug mask) is set (masked) upon debug exception entry.
 178  * Kprobes needs to clear (unmask) D-flag -ONLY- in case of recursive
 179  * probe i.e. when probe hit from kprobe handler context upon
 180  * executing the pre/post handlers. In this case we return with
 181  * D-flag clear so that single-stepping can be carried-out.
 182  *
 183  * Leave D-flag set in all other cases.
 184  */
 185 static void __kprobes
 186 spsr_set_debug_flag(struct pt_regs *regs, int mask)
 187 {
 188         unsigned long spsr = regs->pstate;
 189
 190         if (mask)
 191                 spsr |= PSR_D_BIT;
 192         else
 193                 spsr &= ~PSR_D_BIT;
 194
 195         regs->pstate = spsr;
 196 }
 197
 198 /*
 199  * Interrupts need to be disabled before single-step mode is set, and not
 200  * reenabled until after single-step mode ends.
 201  * Without disabling interrupt on local CPU, there is a chance of
 202  * interrupt occurrence in the period of exception return and  start of
 203  * out-of-line single-step, that result in wrongly single stepping
 204  * into the interrupt handler.
 205  */
 206 static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb,
 207                                                 struct pt_regs *regs)
 208 {
 209         kcb->saved_irqflag = regs->pstate;
 210         regs->pstate |= PSR_I_BIT;
 211 }
 212
 213 static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
 214                                                 struct pt_regs *regs)
 215 {
 216         if (kcb->saved_irqflag & PSR_I_BIT)
 217                 regs->pstate |= PSR_I_BIT;
 218         else
 219                 regs->pstate &= ~PSR_I_BIT;
 220 }
 221
 222 static void __kprobes
 223 set_ss_context(struct kprobe_ctlblk *kcb, unsigned long addr)
 224 {
 225         kcb->ss_ctx.ss_pending = true;
 226         kcb->ss_ctx.match_addr = addr + sizeof(kprobe_opcode_t);
 227 }
 228
 229 static void __kprobes clear_ss_context(struct kprobe_ctlblk *kcb)
 230 {
 231         kcb->ss_ctx.ss_pending = false;
 232         kcb->ss_ctx.match_addr = 0;
 233 }
 234
 235 static void __kprobes setup_singlestep(struct kprobe *p,
 236                                        struct pt_regs *regs,
 237                                        struct kprobe_ctlblk *kcb, int reenter)
 238 {
 239         unsigned long slot;
 240
 241         if (reenter) {
 242                 save_previous_kprobe(kcb);
 243                 set_current_kprobe(p);
 244                 kcb->kprobe_status = KPROBE_REENTER;
 245         } else {
 246                 kcb->kprobe_status = KPROBE_HIT_SS;
 247         }
 248
 249
 250         if (p->ainsn.insn) {
 251                 /* prepare for single stepping */
 252                 slot = (unsigned long)p->ainsn.insn;
 253
 254                 set_ss_context(kcb, slot);      /* mark pending ss */
 255
 256                 if (kcb->kprobe_status == KPROBE_REENTER)
 257                         spsr_set_debug_flag(regs, 0);
 258                 else
 259                         WARN_ON(regs->pstate & PSR_D_BIT);
 260
 261                 /* IRQs and single stepping do not mix well. */
 262                 kprobes_save_local_irqflag(kcb, regs);
 263                 kernel_enable_single_step(regs);
 264                 instruction_pointer_set(regs, slot);
 265         } else {
 266                 /* insn simulation */
 267                 arch_simulate_insn(p, regs);
 268         }
 269 }
 270
 271 static int __kprobes reenter_kprobe(struct kprobe *p,
 272                                     struct pt_regs *regs,
 273                                     struct kprobe_ctlblk *kcb)
 274 {
 275         switch (kcb->kprobe_status) {
 276         case KPROBE_HIT_SSDONE:
 277         case KPROBE_HIT_ACTIVE:
 278                 kprobes_inc_nmissed_count(p);
 279                 setup_singlestep(p, regs, kcb, 1);
 280                 break;
 281         case KPROBE_HIT_SS:
 282         case KPROBE_REENTER:
 283                 pr_warn("Unrecoverable kprobe detected at %p.\n", p->addr);
 284                 dump_kprobe(p);
 285                 BUG();
 286                 break;
 287         default:
 288                 WARN_ON(1);
 289                 return 0;
 290         }
 291
 292         return 1;
 293 }
 294
 295 static void __kprobes
 296 post_kprobe_handler(struct kprobe_ctlblk *kcb, struct pt_regs *regs)
 297 {
 298         struct kprobe *cur = kprobe_running();
 299
 300         if (!cur)
 301                 return;
 302
 303         /* return addr restore if non-branching insn */
 304         if (cur->ainsn.restore != 0)
 305                 instruction_pointer_set(regs, cur->ainsn.restore);
 306
 307         /* restore back original saved kprobe variables and continue */
 308         if (kcb->kprobe_status == KPROBE_REENTER) {
 309                 restore_previous_kprobe(kcb);
 310                 return;
 311         }
 312         /* call post handler */
 313         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 314         if (cur->post_handler)  {
 315                 /* post_handler can hit breakpoint and single step
 316                  * again, so we enable D-flag for recursive exception.
 317                  */
 318                 cur->post_handler(cur, regs, 0);
 319         }
 320
 321         reset_current_kprobe();
 322 }
 323
 324 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
 325 {
 326         struct kprobe *cur = kprobe_running();
 327         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 328
 329         switch (kcb->kprobe_status) {
 330         case KPROBE_HIT_SS:
 331         case KPROBE_REENTER:
 332                 /*
 333                  * We are here because the instruction being single
 334                  * stepped caused a page fault. We reset the current
 335                  * kprobe and the ip points back to the probe address
 336                  * and allow the page fault handler to continue as a
 337                  * normal page fault.
 338                  */
 339                 instruction_pointer_set(regs, (unsigned long) cur->addr);
 340                 if (!instruction_pointer(regs))
 341                         BUG();
 342
 343                 kernel_disable_single_step();
 344                 if (kcb->kprobe_status == KPROBE_REENTER)
 345                         spsr_set_debug_flag(regs, 1);
 346
 347                 if (kcb->kprobe_status == KPROBE_REENTER)
 348                         restore_previous_kprobe(kcb);
 349                 else
 350                         reset_current_kprobe();
 351
 352                 break;
 353         case KPROBE_HIT_ACTIVE:
 354         case KPROBE_HIT_SSDONE:
 355                 /*
 356                  * We increment the nmissed count for accounting,
 357                  * we can also use npre/npostfault count for accounting
 358                  * these specific fault cases.
 359                  */
 360                 kprobes_inc_nmissed_count(cur);
 361
 362                 /*
 363                  * We come here because instructions in the pre/post
 364                  * handler caused the page_fault, this could happen
 365                  * if handler tries to access user space by
 366                  * copy_from_user(), get_user() etc. Let the
 367                  * user-specified handler try to fix it first.
 368                  */
 369                 if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
 370                         return 1;
 371
 372                 /*
 373                  * In case the user-specified fault handler returned
 374                  * zero, try to fix up.
 375                  */
 376                 if (fixup_exception(regs))
 377                         return 1;
 378         }
 379         return 0;
 380 }
 381
 382 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 383                                        unsigned long val, void *data)
 384 {
 385         return NOTIFY_DONE;
 386 }
 387
 388 static void __kprobes kprobe_handler(struct pt_regs *regs)
 389 {
 390         struct kprobe *p, *cur_kprobe;
 391         struct kprobe_ctlblk *kcb;
 392         unsigned long addr = instruction_pointer(regs);
 393
 394         kcb = get_kprobe_ctlblk();
 395         cur_kprobe = kprobe_running();
 396
 397         p = get_kprobe((kprobe_opcode_t *) addr);
 398
 399         if (p) {
 400                 if (cur_kprobe) {
 401                         if (reenter_kprobe(p, regs, kcb))
 402                                 return;
 403                 } else {
 404                         /* Probe hit */
 405                         set_current_kprobe(p);
 406                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 407
 408                         /*
 409                          * If we have no pre-handler or it returned 0, we
 410                          * continue with normal processing.  If we have a
 411                          * pre-handler and it returned non-zero, it prepped
 412                          * for calling the break_handler below on re-entry,
 413                          * so get out doing nothing more here.
 414                          *
 415                          * pre_handler can hit a breakpoint and can step thru
 416                          * before return, keep PSTATE D-flag enabled until
 417                          * pre_handler return back.
 418                          */
 419                         if (!p->pre_handler || !p->pre_handler(p, regs)) {
 420                                 setup_singlestep(p, regs, kcb, 0);
 421                                 return;
 422                         }
 423                 }
 424         } else if ((le32_to_cpu(*(kprobe_opcode_t *) addr) ==
 425             BRK64_OPCODE_KPROBES) && cur_kprobe) {
 426                 /* We probably hit a jprobe.  Call its break handler. */
 427                 if (cur_kprobe->break_handler  &&
 428                      cur_kprobe->break_handler(cur_kprobe, regs)) {
 429                         setup_singlestep(cur_kprobe, regs, kcb, 0);
 430                         return;
 431                 }
 432         }
 433         /*
 434          * The breakpoint instruction was removed right
 435          * after we hit it.  Another cpu has removed
 436          * either a probepoint or a debugger breakpoint
 437          * at this address.  In either case, no further
 438          * handling of this interrupt is appropriate.
 439          * Return back to original instruction, and continue.
 440          */
 441 }
 442
 443 static int __kprobes
 444 kprobe_ss_hit(struct kprobe_ctlblk *kcb, unsigned long addr)
 445 {
 446         if ((kcb->ss_ctx.ss_pending)
 447             && (kcb->ss_ctx.match_addr == addr)) {
 448                 clear_ss_context(kcb);  /* clear pending ss */
 449                 return DBG_HOOK_HANDLED;
 450         }
 451         /* not ours, kprobes should ignore it */
 452         return DBG_HOOK_ERROR;
 453 }
 454
 455 int __kprobes
 456 kprobe_single_step_handler(struct pt_regs *regs, unsigned int esr)
 457 {
 458         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 459         int retval;
 460
 461         /* return error if this is not our step */
 462         retval = kprobe_ss_hit(kcb, instruction_pointer(regs));
 463
 464         if (retval == DBG_HOOK_HANDLED) {
 465                 kprobes_restore_local_irqflag(kcb, regs);
 466                 kernel_disable_single_step();
 467
 468                 if (kcb->kprobe_status == KPROBE_REENTER)
 469                         spsr_set_debug_flag(regs, 1);
 470
 471                 post_kprobe_handler(kcb, regs);
 472         }
 473
 474         return retval;
 475 }
 476
 477 int __kprobes
 478 kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr)
 479 {
 480         kprobe_handler(regs);
 481         return DBG_HOOK_HANDLED;
 482 }
 483
 484 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 485 {
 486         struct jprobe *jp = container_of(p, struct jprobe, kp);
 487         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 488         long stack_ptr = kernel_stack_pointer(regs);
 489
 490         kcb->jprobe_saved_regs = *regs;
 491         /*
 492          * As Linus pointed out, gcc assumes that the callee
 493          * owns the argument space and could overwrite it, e.g.
 494          * tailcall optimization. So, to be absolutely safe
 495          * we also save and restore enough stack bytes to cover
 496          * the argument area.
 497          */
 498         memcpy(kcb->jprobes_stack, (void *)stack_ptr,
 499                min_stack_size(stack_ptr));
 500
 501         instruction_pointer_set(regs, (unsigned long) jp->entry);
 502         preempt_disable();
 503         pause_graph_tracing();
 504         return 1;
 505 }
 506
 507 void __kprobes jprobe_return(void)
 508 {
 509         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 510
 511         /*
 512          * Jprobe handler return by entering break exception,
 513          * encoded same as kprobe, but with following conditions
 514          * -a special PC to identify it from the other kprobes.
 515          * -restore stack addr to original saved pt_regs
 516          */
 517         asm volatile("                          mov sp, %0      \n"
 518                      "jprobe_return_break:      brk %1          \n"
 519                      :
 520                      : "r" (kcb->jprobe_saved_regs.sp),
 521                        "I" (BRK64_ESR_KPROBES)
 522                      : "memory");
 523
 524         unreachable();
 525 }
 526
 527 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 528 {
 529         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 530         long stack_addr = kcb->jprobe_saved_regs.sp;
 531         long orig_sp = kernel_stack_pointer(regs);
 532         struct jprobe *jp = container_of(p, struct jprobe, kp);
 533         extern const char jprobe_return_break[];
 534
 535         if (instruction_pointer(regs) != (u64) jprobe_return_break)
 536                 return 0;
 537
 538         if (orig_sp != stack_addr) {
 539                 struct pt_regs *saved_regs =
 540                     (struct pt_regs *)kcb->jprobe_saved_regs.sp;
 541                 pr_err("current sp %lx does not match saved sp %lx\n",
 542                        orig_sp, stack_addr);
 543                 pr_err("Saved registers for jprobe %p\n", jp);
 544                 show_regs(saved_regs);
 545                 pr_err("Current registers\n");
 546                 show_regs(regs);
 547                 BUG();
 548         }
 549         unpause_graph_tracing();
 550         *regs = kcb->jprobe_saved_regs;
 551         memcpy((void *)stack_addr, kcb->jprobes_stack,
 552                min_stack_size(stack_addr));
 553         preempt_enable_no_resched();
 554         return 1;
 555 }
 556
 557 bool arch_within_kprobe_blacklist(unsigned long addr)
 558 {
 559         extern char __idmap_text_start[], __idmap_text_end[];
 560
 561         if ((addr >= (unsigned long)__kprobes_text_start &&
 562             addr < (unsigned long)__kprobes_text_end) ||
 563             (addr >= (unsigned long)__entry_text_start &&
 564             addr < (unsigned long)__entry_text_end) ||
 565             (addr >= (unsigned long)__idmap_text_start &&
 566             addr < (unsigned long)__idmap_text_end) ||
 567             !!search_exception_tables(addr))
 568                 return true;
 569
 570
 571         return false;
 572 }
 573
 574 void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
 575 {
 576         struct kretprobe_instance *ri = NULL;
 577         struct hlist_head *head, empty_rp;
 578         struct hlist_node *tmp;
 579         unsigned long flags, orig_ret_address = 0;
 580         unsigned long trampoline_address =
 581                 (unsigned long)&kretprobe_trampoline;
 582         kprobe_opcode_t *correct_ret_addr = NULL;
 583
 584         INIT_HLIST_HEAD(&empty_rp);
 585         kretprobe_hash_lock(current, &head, &flags);
 586
 587         /*
 588          * It is possible to have multiple instances associated with a given
 589          * task either because multiple functions in the call path have
 590          * return probes installed on them, and/or more than one
 591          * return probe was registered for a target function.
 592          *
 593          * We can handle this because:
 594          *     - instances are always pushed into the head of the list
 595          *     - when multiple return probes are registered for the same
 596          *       function, the (chronologically) first instance's ret_addr
 597          *       will be the real return address, and all the rest will
 598          *       point to kretprobe_trampoline.
 599          */
 600         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 601                 if (ri->task != current)
 602                         /* another task is sharing our hash bucket */
 603                         continue;
 604
 605                 orig_ret_address = (unsigned long)ri->ret_addr;
 606
 607                 if (orig_ret_address != trampoline_address)
 608                         /*
 609                          * This is the real return address. Any other
 610                          * instances associated with this task are for
 611                          * other calls deeper on the call stack
 612                          */
 613                         break;
 614         }
 615
 616         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 617
 618         correct_ret_addr = ri->ret_addr;
 619         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 620                 if (ri->task != current)
 621                         /* another task is sharing our hash bucket */
 622                         continue;
 623
 624                 orig_ret_address = (unsigned long)ri->ret_addr;
 625                 if (ri->rp && ri->rp->handler) {
 626                         __this_cpu_write(current_kprobe, &ri->rp->kp);
 627                         get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
 628                         ri->ret_addr = correct_ret_addr;
 629                         ri->rp->handler(ri, regs);
 630                         __this_cpu_write(current_kprobe, NULL);
 631                 }
 632
 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_hash_unlock(current, &flags);
 645
 646         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 647                 hlist_del(&ri->hlist);
 648                 kfree(ri);
 649         }
 650         return (void *)orig_ret_address;
 651 }
 652
 653 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 654                                       struct pt_regs *regs)
 655 {
 656         ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];
 657
 658         /* replace return addr (x30) with trampoline */
 659         regs->regs[30] = (long)&kretprobe_trampoline;
 660 }
 661
 662 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 663 {
 664         return 0;
 665 }
 666
 667 int __init arch_init_kprobes(void)
 668 {
 669         return 0;
 670 }