arch/powerpc/kernel/kprobes.c

   1 /*
   2  *  Kernel Probes (KProbes)
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17  *
  18  * Copyright (C) IBM Corporation, 2002, 2004
  19  *
  20  * 2002-Oct     Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
  21  *              Probes initial implementation ( includes contributions from
  22  *              Rusty Russell).
  23  * 2004-July    Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
  24  *              interface to access function arguments.
  25  * 2004-Nov     Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
  26  *              for PPC64
  27  */
  28
  29 #include <linux/kprobes.h>
  30 #include <linux/ptrace.h>
  31 #include <linux/preempt.h>
  32 #include <linux/extable.h>
  33 #include <linux/kdebug.h>
  34 #include <linux/slab.h>
  35 #include <asm/code-patching.h>
  36 #include <asm/cacheflush.h>
  37 #include <asm/sstep.h>
  38 #include <asm/sections.h>
  39 #include <linux/uaccess.h>
  40
  41 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  42 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  43
  44 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
  45
  46 bool arch_within_kprobe_blacklist(unsigned long addr)
  47 {
  48         return  (addr >= (unsigned long)__kprobes_text_start &&
  49                  addr < (unsigned long)__kprobes_text_end) ||
  50                 (addr >= (unsigned long)_stext &&
  51                  addr < (unsigned long)__head_end);
  52 }
  53
  54 kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
  55 {
  56         kprobe_opcode_t *addr;
  57
  58 #ifdef PPC64_ELF_ABI_v2
  59         /* PPC64 ABIv2 needs local entry point */
  60         addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
  61         if (addr && !offset) {
  62 #ifdef CONFIG_KPROBES_ON_FTRACE
  63                 unsigned long faddr;
  64                 /*
  65                  * Per livepatch.h, ftrace location is always within the first
  66                  * 16 bytes of a function on powerpc with -mprofile-kernel.
  67                  */
  68                 faddr = ftrace_location_range((unsigned long)addr,
  69                                               (unsigned long)addr + 16);
  70                 if (faddr)
  71                         addr = (kprobe_opcode_t *)faddr;
  72                 else
  73 #endif
  74                         addr = (kprobe_opcode_t *)ppc_function_entry(addr);
  75         }
  76 #elif defined(PPC64_ELF_ABI_v1)
  77         /*
  78          * 64bit powerpc ABIv1 uses function descriptors:
  79          * - Check for the dot variant of the symbol first.
  80          * - If that fails, try looking up the symbol provided.
  81          *
  82          * This ensures we always get to the actual symbol and not
  83          * the descriptor.
  84          *
  85          * Also handle <module:symbol> format.
  86          */
  87         char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
  88         const char *modsym;
  89         bool dot_appended = false;
  90         if ((modsym = strchr(name, ':')) != NULL) {
  91                 modsym++;
  92                 if (*modsym != '\0' && *modsym != '.') {
  93                         /* Convert to <module:.symbol> */
  94                         strncpy(dot_name, name, modsym - name);
  95                         dot_name[modsym - name] = '.';
  96                         dot_name[modsym - name + 1] = '\0';
  97                         strncat(dot_name, modsym,
  98                                 sizeof(dot_name) - (modsym - name) - 2);
  99                         dot_appended = true;
 100                 } else {
 101                         dot_name[0] = '\0';
 102                         strncat(dot_name, name, sizeof(dot_name) - 1);
 103                 }
 104         } else if (name[0] != '.') {
 105                 dot_name[0] = '.';
 106                 dot_name[1] = '\0';
 107                 strncat(dot_name, name, KSYM_NAME_LEN - 2);
 108                 dot_appended = true;
 109         } else {
 110                 dot_name[0] = '\0';
 111                 strncat(dot_name, name, KSYM_NAME_LEN - 1);
 112         }
 113         addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name);
 114         if (!addr && dot_appended) {
 115                 /* Let's try the original non-dot symbol lookup */
 116                 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
 117         }
 118 #else
 119         addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
 120 #endif
 121
 122         return addr;
 123 }
 124
 125 int arch_prepare_kprobe(struct kprobe *p)
 126 {
 127         int ret = 0;
 128         kprobe_opcode_t insn = *p->addr;
 129
 130         if ((unsigned long)p->addr & 0x03) {
 131                 printk("Attempt to register kprobe at an unaligned address\n");
 132                 ret = -EINVAL;
 133         } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
 134                 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
 135                 ret = -EINVAL;
 136         }
 137
 138         /* insn must be on a special executable page on ppc64.  This is
 139          * not explicitly required on ppc32 (right now), but it doesn't hurt */
 140         if (!ret) {
 141                 p->ainsn.insn = get_insn_slot();
 142                 if (!p->ainsn.insn)
 143                         ret = -ENOMEM;
 144         }
 145
 146         if (!ret) {
 147                 memcpy(p->ainsn.insn, p->addr,
 148                                 MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
 149                 p->opcode = *p->addr;
 150                 flush_icache_range((unsigned long)p->ainsn.insn,
 151                         (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
 152         }
 153
 154         p->ainsn.boostable = 0;
 155         return ret;
 156 }
 157 NOKPROBE_SYMBOL(arch_prepare_kprobe);
 158
 159 void arch_arm_kprobe(struct kprobe *p)
 160 {
 161         *p->addr = BREAKPOINT_INSTRUCTION;
 162         flush_icache_range((unsigned long) p->addr,
 163                            (unsigned long) p->addr + sizeof(kprobe_opcode_t));
 164 }
 165 NOKPROBE_SYMBOL(arch_arm_kprobe);
 166
 167 void arch_disarm_kprobe(struct kprobe *p)
 168 {
 169         *p->addr = p->opcode;
 170         flush_icache_range((unsigned long) p->addr,
 171                            (unsigned long) p->addr + sizeof(kprobe_opcode_t));
 172 }
 173 NOKPROBE_SYMBOL(arch_disarm_kprobe);
 174
 175 void arch_remove_kprobe(struct kprobe *p)
 176 {
 177         if (p->ainsn.insn) {
 178                 free_insn_slot(p->ainsn.insn, 0);
 179                 p->ainsn.insn = NULL;
 180         }
 181 }
 182 NOKPROBE_SYMBOL(arch_remove_kprobe);
 183
 184 static nokprobe_inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 185 {
 186         enable_single_step(regs);
 187
 188         /*
 189          * On powerpc we should single step on the original
 190          * instruction even if the probed insn is a trap
 191          * variant as values in regs could play a part in
 192          * if the trap is taken or not
 193          */
 194         regs->nip = (unsigned long)p->ainsn.insn;
 195 }
 196
 197 static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
 198 {
 199         kcb->prev_kprobe.kp = kprobe_running();
 200         kcb->prev_kprobe.status = kcb->kprobe_status;
 201         kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
 202 }
 203
 204 static nokprobe_inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 205 {
 206         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 207         kcb->kprobe_status = kcb->prev_kprobe.status;
 208         kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
 209 }
 210
 211 static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 212                                 struct kprobe_ctlblk *kcb)
 213 {
 214         __this_cpu_write(current_kprobe, p);
 215         kcb->kprobe_saved_msr = regs->msr;
 216 }
 217
 218 bool arch_function_offset_within_entry(unsigned long offset)
 219 {
 220 #ifdef PPC64_ELF_ABI_v2
 221 #ifdef CONFIG_KPROBES_ON_FTRACE
 222         return offset <= 16;
 223 #else
 224         return offset <= 8;
 225 #endif
 226 #else
 227         return !offset;
 228 #endif
 229 }
 230
 231 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
 232 {
 233         ri->ret_addr = (kprobe_opcode_t *)regs->link;
 234
 235         /* Replace the return addr with trampoline addr */
 236         regs->link = (unsigned long)kretprobe_trampoline;
 237 }
 238 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
 239
 240 int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
 241 {
 242         int ret;
 243         unsigned int insn = *p->ainsn.insn;
 244
 245         /* regs->nip is also adjusted if emulate_step returns 1 */
 246         ret = emulate_step(regs, insn);
 247         if (ret > 0) {
 248                 /*
 249                  * Once this instruction has been boosted
 250                  * successfully, set the boostable flag
 251                  */
 252                 if (unlikely(p->ainsn.boostable == 0))
 253                         p->ainsn.boostable = 1;
 254         } else if (ret < 0) {
 255                 /*
 256                  * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
 257                  * So, we should never get here... but, its still
 258                  * good to catch them, just in case...
 259                  */
 260                 printk("Can't step on instruction %x\n", insn);
 261                 BUG();
 262         } else if (ret == 0)
 263                 /* This instruction can't be boosted */
 264                 p->ainsn.boostable = -1;
 265
 266         return ret;
 267 }
 268 NOKPROBE_SYMBOL(try_to_emulate);
 269
 270 int kprobe_handler(struct pt_regs *regs)
 271 {
 272         struct kprobe *p;
 273         int ret = 0;
 274         unsigned int *addr = (unsigned int *)regs->nip;
 275         struct kprobe_ctlblk *kcb;
 276
 277         if (user_mode(regs))
 278                 return 0;
 279
 280         /*
 281          * We don't want to be preempted for the entire
 282          * duration of kprobe processing
 283          */
 284         preempt_disable();
 285         kcb = get_kprobe_ctlblk();
 286
 287         /* Check we're not actually recursing */
 288         if (kprobe_running()) {
 289                 p = get_kprobe(addr);
 290                 if (p) {
 291                         kprobe_opcode_t insn = *p->ainsn.insn;
 292                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
 293                                         is_trap(insn)) {
 294                                 /* Turn off 'trace' bits */
 295                                 regs->msr &= ~MSR_SINGLESTEP;
 296                                 regs->msr |= kcb->kprobe_saved_msr;
 297                                 goto no_kprobe;
 298                         }
 299                         /* We have reentered the kprobe_handler(), since
 300                          * another probe was hit while within the handler.
 301                          * We here save the original kprobes variables and
 302                          * just single step on the instruction of the new probe
 303                          * without calling any user handlers.
 304                          */
 305                         save_previous_kprobe(kcb);
 306                         set_current_kprobe(p, regs, kcb);
 307                         kprobes_inc_nmissed_count(p);
 308                         kcb->kprobe_status = KPROBE_REENTER;
 309                         if (p->ainsn.boostable >= 0) {
 310                                 ret = try_to_emulate(p, regs);
 311
 312                                 if (ret > 0) {
 313                                         restore_previous_kprobe(kcb);
 314                                         preempt_enable_no_resched();
 315                                         return 1;
 316                                 }
 317                         }
 318                         prepare_singlestep(p, regs);
 319                         return 1;
 320                 } else {
 321                         if (*addr != BREAKPOINT_INSTRUCTION) {
 322                                 /* If trap variant, then it belongs not to us */
 323                                 kprobe_opcode_t cur_insn = *addr;
 324                                 if (is_trap(cur_insn))
 325                                         goto no_kprobe;
 326                                 /* The breakpoint instruction was removed by
 327                                  * another cpu right after we hit, no further
 328                                  * handling of this interrupt is appropriate
 329                                  */
 330                                 ret = 1;
 331                                 goto no_kprobe;
 332                         }
 333                         p = __this_cpu_read(current_kprobe);
 334                         if (p->break_handler && p->break_handler(p, regs)) {
 335                                 if (!skip_singlestep(p, regs, kcb))
 336                                         goto ss_probe;
 337                                 ret = 1;
 338                         }
 339                 }
 340                 goto no_kprobe;
 341         }
 342
 343         p = get_kprobe(addr);
 344         if (!p) {
 345                 if (*addr != BREAKPOINT_INSTRUCTION) {
 346                         /*
 347                          * PowerPC has multiple variants of the "trap"
 348                          * instruction. If the current instruction is a
 349                          * trap variant, it could belong to someone else
 350                          */
 351                         kprobe_opcode_t cur_insn = *addr;
 352                         if (is_trap(cur_insn))
 353                                 goto no_kprobe;
 354                         /*
 355                          * The breakpoint instruction was removed right
 356                          * after we hit it.  Another cpu has removed
 357                          * either a probepoint or a debugger breakpoint
 358                          * at this address.  In either case, no further
 359                          * handling of this interrupt is appropriate.
 360                          */
 361                         ret = 1;
 362                 }
 363                 /* Not one of ours: let kernel handle it */
 364                 goto no_kprobe;
 365         }
 366
 367         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 368         set_current_kprobe(p, regs, kcb);
 369         if (p->pre_handler && p->pre_handler(p, regs))
 370                 /* handler has already set things up, so skip ss setup */
 371                 return 1;
 372
 373 ss_probe:
 374         if (p->ainsn.boostable >= 0) {
 375                 ret = try_to_emulate(p, regs);
 376
 377                 if (ret > 0) {
 378                         if (p->post_handler)
 379                                 p->post_handler(p, regs, 0);
 380
 381                         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 382                         reset_current_kprobe();
 383                         preempt_enable_no_resched();
 384                         return 1;
 385                 }
 386         }
 387         prepare_singlestep(p, regs);
 388         kcb->kprobe_status = KPROBE_HIT_SS;
 389         return 1;
 390
 391 no_kprobe:
 392         preempt_enable_no_resched();
 393         return ret;
 394 }
 395 NOKPROBE_SYMBOL(kprobe_handler);
 396
 397 /*
 398  * Function return probe trampoline:
 399  *      - init_kprobes() establishes a probepoint here
 400  *      - When the probed function returns, this probe
 401  *              causes the handlers to fire
 402  */
 403 asm(".global kretprobe_trampoline\n"
 404         ".type kretprobe_trampoline, @function\n"
 405         "kretprobe_trampoline:\n"
 406         "nop\n"
 407         "blr\n"
 408         ".size kretprobe_trampoline, .-kretprobe_trampoline\n");
 409
 410 /*
 411  * Called when the probe at kretprobe trampoline is hit
 412  */
 413 static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 414 {
 415         struct kretprobe_instance *ri = NULL;
 416         struct hlist_head *head, empty_rp;
 417         struct hlist_node *tmp;
 418         unsigned long flags, orig_ret_address = 0;
 419         unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
 420
 421         INIT_HLIST_HEAD(&empty_rp);
 422         kretprobe_hash_lock(current, &head, &flags);
 423
 424         /*
 425          * It is possible to have multiple instances associated with a given
 426          * task either because an multiple functions in the call path
 427          * have a return probe installed on them, and/or more than one return
 428          * return probe was registered for a target function.
 429          *
 430          * We can handle this because:
 431          *     - instances are always inserted at the head of the list
 432          *     - when multiple return probes are registered for the same
 433          *       function, the first instance's ret_addr will point to the
 434          *       real return address, and all the rest will point to
 435          *       kretprobe_trampoline
 436          */
 437         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 438                 if (ri->task != current)
 439                         /* another task is sharing our hash bucket */
 440                         continue;
 441
 442                 if (ri->rp && ri->rp->handler)
 443                         ri->rp->handler(ri, regs);
 444
 445                 orig_ret_address = (unsigned long)ri->ret_addr;
 446                 recycle_rp_inst(ri, &empty_rp);
 447
 448                 if (orig_ret_address != trampoline_address)
 449                         /*
 450                          * This is the real return address. Any other
 451                          * instances associated with this task are for
 452                          * other calls deeper on the call stack
 453                          */
 454                         break;
 455         }
 456
 457         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 458         regs->nip = orig_ret_address;
 459         /*
 460          * Make LR point to the orig_ret_address.
 461          * When the 'nop' inside the kretprobe_trampoline
 462          * is optimized, we can do a 'blr' after executing the
 463          * detour buffer code.
 464          */
 465         regs->link = orig_ret_address;
 466
 467         reset_current_kprobe();
 468         kretprobe_hash_unlock(current, &flags);
 469         preempt_enable_no_resched();
 470
 471         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 472                 hlist_del(&ri->hlist);
 473                 kfree(ri);
 474         }
 475         /*
 476          * By returning a non-zero value, we are telling
 477          * kprobe_handler() that we don't want the post_handler
 478          * to run (and have re-enabled preemption)
 479          */
 480         return 1;
 481 }
 482 NOKPROBE_SYMBOL(trampoline_probe_handler);
 483
 484 /*
 485  * Called after single-stepping.  p->addr is the address of the
 486  * instruction whose first byte has been replaced by the "breakpoint"
 487  * instruction.  To avoid the SMP problems that can occur when we
 488  * temporarily put back the original opcode to single-step, we
 489  * single-stepped a copy of the instruction.  The address of this
 490  * copy is p->ainsn.insn.
 491  */
 492 int kprobe_post_handler(struct pt_regs *regs)
 493 {
 494         struct kprobe *cur = kprobe_running();
 495         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 496
 497         if (!cur || user_mode(regs))
 498                 return 0;
 499
 500         /* make sure we got here for instruction we have a kprobe on */
 501         if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
 502                 return 0;
 503
 504         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 505                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 506                 cur->post_handler(cur, regs, 0);
 507         }
 508
 509         /* Adjust nip to after the single-stepped instruction */
 510         regs->nip = (unsigned long)cur->addr + 4;
 511         regs->msr |= kcb->kprobe_saved_msr;
 512
 513         /*Restore back the original saved kprobes variables and continue. */
 514         if (kcb->kprobe_status == KPROBE_REENTER) {
 515                 restore_previous_kprobe(kcb);
 516                 goto out;
 517         }
 518         reset_current_kprobe();
 519 out:
 520         preempt_enable_no_resched();
 521
 522         /*
 523          * if somebody else is singlestepping across a probe point, msr
 524          * will have DE/SE set, in which case, continue the remaining processing
 525          * of do_debug, as if this is not a probe hit.
 526          */
 527         if (regs->msr & MSR_SINGLESTEP)
 528                 return 0;
 529
 530         return 1;
 531 }
 532 NOKPROBE_SYMBOL(kprobe_post_handler);
 533
 534 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 535 {
 536         struct kprobe *cur = kprobe_running();
 537         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 538         const struct exception_table_entry *entry;
 539
 540         switch(kcb->kprobe_status) {
 541         case KPROBE_HIT_SS:
 542         case KPROBE_REENTER:
 543                 /*
 544                  * We are here because the instruction being single
 545                  * stepped caused a page fault. We reset the current
 546                  * kprobe and the nip points back to the probe address
 547                  * and allow the page fault handler to continue as a
 548                  * normal page fault.
 549                  */
 550                 regs->nip = (unsigned long)cur->addr;
 551                 regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
 552                 regs->msr |= kcb->kprobe_saved_msr;
 553                 if (kcb->kprobe_status == KPROBE_REENTER)
 554                         restore_previous_kprobe(kcb);
 555                 else
 556                         reset_current_kprobe();
 557                 preempt_enable_no_resched();
 558                 break;
 559         case KPROBE_HIT_ACTIVE:
 560         case KPROBE_HIT_SSDONE:
 561                 /*
 562                  * We increment the nmissed count for accounting,
 563                  * we can also use npre/npostfault count for accounting
 564                  * these specific fault cases.
 565                  */
 566                 kprobes_inc_nmissed_count(cur);
 567
 568                 /*
 569                  * We come here because instructions in the pre/post
 570                  * handler caused the page_fault, this could happen
 571                  * if handler tries to access user space by
 572                  * copy_from_user(), get_user() etc. Let the
 573                  * user-specified handler try to fix it first.
 574                  */
 575                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 576                         return 1;
 577
 578                 /*
 579                  * In case the user-specified fault handler returned
 580                  * zero, try to fix up.
 581                  */
 582                 if ((entry = search_exception_tables(regs->nip)) != NULL) {
 583                         regs->nip = extable_fixup(entry);
 584                         return 1;
 585                 }
 586
 587                 /*
 588                  * fixup_exception() could not handle it,
 589                  * Let do_page_fault() fix it.
 590                  */
 591                 break;
 592         default:
 593                 break;
 594         }
 595         return 0;
 596 }
 597 NOKPROBE_SYMBOL(kprobe_fault_handler);
 598
 599 unsigned long arch_deref_entry_point(void *entry)
 600 {
 601         return ppc_global_function_entry(entry);
 602 }
 603 NOKPROBE_SYMBOL(arch_deref_entry_point);
 604
 605 int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 606 {
 607         struct jprobe *jp = container_of(p, struct jprobe, kp);
 608         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 609
 610         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
 611
 612         /* setup return addr to the jprobe handler routine */
 613         regs->nip = arch_deref_entry_point(jp->entry);
 614 #ifdef PPC64_ELF_ABI_v2
 615         regs->gpr[12] = (unsigned long)jp->entry;
 616 #elif defined(PPC64_ELF_ABI_v1)
 617         regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
 618 #endif
 619
 620         return 1;
 621 }
 622 NOKPROBE_SYMBOL(setjmp_pre_handler);
 623
 624 void __used jprobe_return(void)
 625 {
 626         asm volatile("trap" ::: "memory");
 627 }
 628 NOKPROBE_SYMBOL(jprobe_return);
 629
 630 static void __used jprobe_return_end(void)
 631 {
 632 }
 633 NOKPROBE_SYMBOL(jprobe_return_end);
 634
 635 int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 636 {
 637         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 638
 639         /*
 640          * FIXME - we should ideally be validating that we got here 'cos
 641          * of the "trap" in jprobe_return() above, before restoring the
 642          * saved regs...
 643          */
 644         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
 645         preempt_enable_no_resched();
 646         return 1;
 647 }
 648 NOKPROBE_SYMBOL(longjmp_break_handler);
 649
 650 static struct kprobe trampoline_p = {
 651         .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
 652         .pre_handler = trampoline_probe_handler
 653 };
 654
 655 int __init arch_init_kprobes(void)
 656 {
 657         return register_kprobe(&trampoline_p);
 658 }
 659
 660 int arch_trampoline_kprobe(struct kprobe *p)
 661 {
 662         if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
 663                 return 1;
 664
 665         return 0;
 666 }
 667 NOKPROBE_SYMBOL(arch_trampoline_kprobe);