arch/s390/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, 2006
  19  *
  20  * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
  21  */
  22
  23 #include <linux/kprobes.h>
  24 #include <linux/ptrace.h>
  25 #include <linux/preempt.h>
  26 #include <linux/stop_machine.h>
  27 #include <linux/kdebug.h>
  28 #include <linux/uaccess.h>
  29 #include <asm/cacheflush.h>
  30 #include <asm/sections.h>
  31 #include <linux/module.h>
  32
  33 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  34 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  35
  36 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
  37
  38 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  39 {
  40         /* Make sure the probe isn't going on a difficult instruction */
  41         if (is_prohibited_opcode((kprobe_opcode_t *) p->addr))
  42                 return -EINVAL;
  43
  44         if ((unsigned long)p->addr & 0x01)
  45                 return -EINVAL;
  46
  47         /* Use the get_insn_slot() facility for correctness */
  48         if (!(p->ainsn.insn = get_insn_slot()))
  49                 return -ENOMEM;
  50
  51         memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
  52
  53         get_instruction_type(&p->ainsn);
  54         p->opcode = *p->addr;
  55         return 0;
  56 }
  57
  58 int __kprobes is_prohibited_opcode(kprobe_opcode_t *instruction)
  59 {
  60         switch (*(__u8 *) instruction) {
  61         case 0x0c:      /* bassm */
  62         case 0x0b:      /* bsm   */
  63         case 0x83:      /* diag  */
  64         case 0x44:      /* ex    */
  65                 return -EINVAL;
  66         }
  67         switch (*(__u16 *) instruction) {
  68         case 0x0101:    /* pr    */
  69         case 0xb25a:    /* bsa   */
  70         case 0xb240:    /* bakr  */
  71         case 0xb258:    /* bsg   */
  72         case 0xb218:    /* pc    */
  73         case 0xb228:    /* pt    */
  74                 return -EINVAL;
  75         }
  76         return 0;
  77 }
  78
  79 void __kprobes get_instruction_type(struct arch_specific_insn *ainsn)
  80 {
  81         /* default fixup method */
  82         ainsn->fixup = FIXUP_PSW_NORMAL;
  83
  84         /* save r1 operand */
  85         ainsn->reg = (*ainsn->insn & 0xf0) >> 4;
  86
  87         /* save the instruction length (pop 5-5) in bytes */
  88         switch (*(__u8 *) (ainsn->insn) >> 6) {
  89         case 0:
  90                 ainsn->ilen = 2;
  91                 break;
  92         case 1:
  93         case 2:
  94                 ainsn->ilen = 4;
  95                 break;
  96         case 3:
  97                 ainsn->ilen = 6;
  98                 break;
  99         }
 100
 101         switch (*(__u8 *) ainsn->insn) {
 102         case 0x05:      /* balr */
 103         case 0x0d:      /* basr */
 104                 ainsn->fixup = FIXUP_RETURN_REGISTER;
 105                 /* if r2 = 0, no branch will be taken */
 106                 if ((*ainsn->insn & 0x0f) == 0)
 107                         ainsn->fixup |= FIXUP_BRANCH_NOT_TAKEN;
 108                 break;
 109         case 0x06:      /* bctr */
 110         case 0x07:      /* bcr  */
 111                 ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
 112                 break;
 113         case 0x45:      /* bal  */
 114         case 0x4d:      /* bas  */
 115                 ainsn->fixup = FIXUP_RETURN_REGISTER;
 116                 break;
 117         case 0x47:      /* bc   */
 118         case 0x46:      /* bct  */
 119         case 0x86:      /* bxh  */
 120         case 0x87:      /* bxle */
 121                 ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
 122                 break;
 123         case 0x82:      /* lpsw */
 124                 ainsn->fixup = FIXUP_NOT_REQUIRED;
 125                 break;
 126         case 0xb2:      /* lpswe */
 127                 if (*(((__u8 *) ainsn->insn) + 1) == 0xb2) {
 128                         ainsn->fixup = FIXUP_NOT_REQUIRED;
 129                 }
 130                 break;
 131         case 0xa7:      /* bras */
 132                 if ((*ainsn->insn & 0x0f) == 0x05) {
 133                         ainsn->fixup |= FIXUP_RETURN_REGISTER;
 134                 }
 135                 break;
 136         case 0xc0:
 137                 if ((*ainsn->insn & 0x0f) == 0x00  /* larl  */
 138                         || (*ainsn->insn & 0x0f) == 0x05) /* brasl */
 139                 ainsn->fixup |= FIXUP_RETURN_REGISTER;
 140                 break;
 141         case 0xeb:
 142                 if (*(((__u8 *) ainsn->insn) + 5 ) == 0x44 ||   /* bxhg  */
 143                         *(((__u8 *) ainsn->insn) + 5) == 0x45) {/* bxleg */
 144                         ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
 145                 }
 146                 break;
 147         case 0xe3:      /* bctg */
 148                 if (*(((__u8 *) ainsn->insn) + 5) == 0x46) {
 149                         ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
 150                 }
 151                 break;
 152         }
 153 }
 154
 155 static int __kprobes swap_instruction(void *aref)
 156 {
 157         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 158         unsigned long status = kcb->kprobe_status;
 159         struct ins_replace_args *args = aref;
 160         int rc;
 161
 162         kcb->kprobe_status = KPROBE_SWAP_INST;
 163         rc = probe_kernel_write(args->ptr, &args->new, sizeof(args->new));
 164         kcb->kprobe_status = status;
 165         return rc;
 166 }
 167
 168 void __kprobes arch_arm_kprobe(struct kprobe *p)
 169 {
 170         struct ins_replace_args args;
 171
 172         args.ptr = p->addr;
 173         args.old = p->opcode;
 174         args.new = BREAKPOINT_INSTRUCTION;
 175         stop_machine(swap_instruction, &args, NULL);
 176 }
 177
 178 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 179 {
 180         struct ins_replace_args args;
 181
 182         args.ptr = p->addr;
 183         args.old = BREAKPOINT_INSTRUCTION;
 184         args.new = p->opcode;
 185         stop_machine(swap_instruction, &args, NULL);
 186 }
 187
 188 void __kprobes arch_remove_kprobe(struct kprobe *p)
 189 {
 190         if (p->ainsn.insn) {
 191                 free_insn_slot(p->ainsn.insn, 0);
 192                 p->ainsn.insn = NULL;
 193         }
 194 }
 195
 196 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 197 {
 198         per_cr_bits kprobe_per_regs[1];
 199
 200         memset(kprobe_per_regs, 0, sizeof(per_cr_bits));
 201         regs->psw.addr = (unsigned long)p->ainsn.insn | PSW_ADDR_AMODE;
 202
 203         /* Set up the per control reg info, will pass to lctl */
 204         kprobe_per_regs[0].em_instruction_fetch = 1;
 205         kprobe_per_regs[0].starting_addr = (unsigned long)p->ainsn.insn;
 206         kprobe_per_regs[0].ending_addr = (unsigned long)p->ainsn.insn + 1;
 207
 208         /* Set the PER control regs, turns on single step for this address */
 209         __ctl_load(kprobe_per_regs, 9, 11);
 210         regs->psw.mask |= PSW_MASK_PER;
 211         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK);
 212 }
 213
 214 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 215 {
 216         kcb->prev_kprobe.kp = kprobe_running();
 217         kcb->prev_kprobe.status = kcb->kprobe_status;
 218         kcb->prev_kprobe.kprobe_saved_imask = kcb->kprobe_saved_imask;
 219         memcpy(kcb->prev_kprobe.kprobe_saved_ctl, kcb->kprobe_saved_ctl,
 220                                         sizeof(kcb->kprobe_saved_ctl));
 221 }
 222
 223 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 224 {
 225         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
 226         kcb->kprobe_status = kcb->prev_kprobe.status;
 227         kcb->kprobe_saved_imask = kcb->prev_kprobe.kprobe_saved_imask;
 228         memcpy(kcb->kprobe_saved_ctl, kcb->prev_kprobe.kprobe_saved_ctl,
 229                                         sizeof(kcb->kprobe_saved_ctl));
 230 }
 231
 232 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 233                                                 struct kprobe_ctlblk *kcb)
 234 {
 235         __get_cpu_var(current_kprobe) = p;
 236         /* Save the interrupt and per flags */
 237         kcb->kprobe_saved_imask = regs->psw.mask &
 238             (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK);
 239         /* Save the control regs that govern PER */
 240         __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
 241 }
 242
 243 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 244                                         struct pt_regs *regs)
 245 {
 246         ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
 247
 248         /* Replace the return addr with trampoline addr */
 249         regs->gprs[14] = (unsigned long)&kretprobe_trampoline;
 250 }
 251
 252 static int __kprobes kprobe_handler(struct pt_regs *regs)
 253 {
 254         struct kprobe *p;
 255         int ret = 0;
 256         unsigned long *addr = (unsigned long *)
 257                 ((regs->psw.addr & PSW_ADDR_INSN) - 2);
 258         struct kprobe_ctlblk *kcb;
 259
 260         /*
 261          * We don't want to be preempted for the entire
 262          * duration of kprobe processing
 263          */
 264         preempt_disable();
 265         kcb = get_kprobe_ctlblk();
 266
 267         /* Check we're not actually recursing */
 268         if (kprobe_running()) {
 269                 p = get_kprobe(addr);
 270                 if (p) {
 271                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
 272                             *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
 273                                 regs->psw.mask &= ~PSW_MASK_PER;
 274                                 regs->psw.mask |= kcb->kprobe_saved_imask;
 275                                 goto no_kprobe;
 276                         }
 277                         /* We have reentered the kprobe_handler(), since
 278                          * another probe was hit while within the handler.
 279                          * We here save the original kprobes variables and
 280                          * just single step on the instruction of the new probe
 281                          * without calling any user handlers.
 282                          */
 283                         save_previous_kprobe(kcb);
 284                         set_current_kprobe(p, regs, kcb);
 285                         kprobes_inc_nmissed_count(p);
 286                         prepare_singlestep(p, regs);
 287                         kcb->kprobe_status = KPROBE_REENTER;
 288                         return 1;
 289                 } else {
 290                         p = __get_cpu_var(current_kprobe);
 291                         if (p->break_handler && p->break_handler(p, regs)) {
 292                                 goto ss_probe;
 293                         }
 294                 }
 295                 goto no_kprobe;
 296         }
 297
 298         p = get_kprobe(addr);
 299         if (!p)
 300                 /*
 301                  * No kprobe at this address. The fault has not been
 302                  * caused by a kprobe breakpoint. The race of breakpoint
 303                  * vs. kprobe remove does not exist because on s390 we
 304                  * use stop_machine to arm/disarm the breakpoints.
 305                  */
 306                 goto no_kprobe;
 307
 308         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 309         set_current_kprobe(p, regs, kcb);
 310         if (p->pre_handler && p->pre_handler(p, regs))
 311                 /* handler has already set things up, so skip ss setup */
 312                 return 1;
 313
 314 ss_probe:
 315         prepare_singlestep(p, regs);
 316         kcb->kprobe_status = KPROBE_HIT_SS;
 317         return 1;
 318
 319 no_kprobe:
 320         preempt_enable_no_resched();
 321         return ret;
 322 }
 323
 324 /*
 325  * Function return probe trampoline:
 326  *      - init_kprobes() establishes a probepoint here
 327  *      - When the probed function returns, this probe
 328  *              causes the handlers to fire
 329  */
 330 static void __used kretprobe_trampoline_holder(void)
 331 {
 332         asm volatile(".global kretprobe_trampoline\n"
 333                      "kretprobe_trampoline: bcr 0,0\n");
 334 }
 335
 336 /*
 337  * Called when the probe at kretprobe trampoline is hit
 338  */
 339 static int __kprobes trampoline_probe_handler(struct kprobe *p,
 340                                               struct pt_regs *regs)
 341 {
 342         struct kretprobe_instance *ri = NULL;
 343         struct hlist_head *head, empty_rp;
 344         struct hlist_node *node, *tmp;
 345         unsigned long flags, orig_ret_address = 0;
 346         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 347
 348         INIT_HLIST_HEAD(&empty_rp);
 349         kretprobe_hash_lock(current, &head, &flags);
 350
 351         /*
 352          * It is possible to have multiple instances associated with a given
 353          * task either because an multiple functions in the call path
 354          * have a return probe installed on them, and/or more than one return
 355          * return probe was registered for a target function.
 356          *
 357          * We can handle this because:
 358          *     - instances are always inserted at the head of the list
 359          *     - when multiple return probes are registered for the same
 360          *       function, the first instance's ret_addr will point to the
 361          *       real return address, and all the rest will point to
 362          *       kretprobe_trampoline
 363          */
 364         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
 365                 if (ri->task != current)
 366                         /* another task is sharing our hash bucket */
 367                         continue;
 368
 369                 if (ri->rp && ri->rp->handler)
 370                         ri->rp->handler(ri, regs);
 371
 372                 orig_ret_address = (unsigned long)ri->ret_addr;
 373                 recycle_rp_inst(ri, &empty_rp);
 374
 375                 if (orig_ret_address != trampoline_address) {
 376                         /*
 377                          * This is the real return address. Any other
 378                          * instances associated with this task are for
 379                          * other calls deeper on the call stack
 380                          */
 381                         break;
 382                 }
 383         }
 384         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 385         regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE;
 386
 387         reset_current_kprobe();
 388         kretprobe_hash_unlock(current, &flags);
 389         preempt_enable_no_resched();
 390
 391         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
 392                 hlist_del(&ri->hlist);
 393                 kfree(ri);
 394         }
 395         /*
 396          * By returning a non-zero value, we are telling
 397          * kprobe_handler() that we don't want the post_handler
 398          * to run (and have re-enabled preemption)
 399          */
 400         return 1;
 401 }
 402
 403 /*
 404  * Called after single-stepping.  p->addr is the address of the
 405  * instruction whose first byte has been replaced by the "breakpoint"
 406  * instruction.  To avoid the SMP problems that can occur when we
 407  * temporarily put back the original opcode to single-step, we
 408  * single-stepped a copy of the instruction.  The address of this
 409  * copy is p->ainsn.insn.
 410  */
 411 static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
 412 {
 413         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 414
 415         regs->psw.addr &= PSW_ADDR_INSN;
 416
 417         if (p->ainsn.fixup & FIXUP_PSW_NORMAL)
 418                 regs->psw.addr = (unsigned long)p->addr +
 419                                 ((unsigned long)regs->psw.addr -
 420                                  (unsigned long)p->ainsn.insn);
 421
 422         if (p->ainsn.fixup & FIXUP_BRANCH_NOT_TAKEN)
 423                 if ((unsigned long)regs->psw.addr -
 424                     (unsigned long)p->ainsn.insn == p->ainsn.ilen)
 425                         regs->psw.addr = (unsigned long)p->addr + p->ainsn.ilen;
 426
 427         if (p->ainsn.fixup & FIXUP_RETURN_REGISTER)
 428                 regs->gprs[p->ainsn.reg] = ((unsigned long)p->addr +
 429                                                 (regs->gprs[p->ainsn.reg] -
 430                                                 (unsigned long)p->ainsn.insn))
 431                                                 | PSW_ADDR_AMODE;
 432
 433         regs->psw.addr |= PSW_ADDR_AMODE;
 434         /* turn off PER mode */
 435         regs->psw.mask &= ~PSW_MASK_PER;
 436         /* Restore the original per control regs */
 437         __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
 438         regs->psw.mask |= kcb->kprobe_saved_imask;
 439 }
 440
 441 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 442 {
 443         struct kprobe *cur = kprobe_running();
 444         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 445
 446         if (!cur)
 447                 return 0;
 448
 449         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 450                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 451                 cur->post_handler(cur, regs, 0);
 452         }
 453
 454         resume_execution(cur, regs);
 455
 456         /*Restore back the original saved kprobes variables and continue. */
 457         if (kcb->kprobe_status == KPROBE_REENTER) {
 458                 restore_previous_kprobe(kcb);
 459                 goto out;
 460         }
 461         reset_current_kprobe();
 462 out:
 463         preempt_enable_no_resched();
 464
 465         /*
 466          * if somebody else is singlestepping across a probe point, psw mask
 467          * will have PER set, in which case, continue the remaining processing
 468          * of do_single_step, as if this is not a probe hit.
 469          */
 470         if (regs->psw.mask & PSW_MASK_PER) {
 471                 return 0;
 472         }
 473
 474         return 1;
 475 }
 476
 477 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 478 {
 479         struct kprobe *cur = kprobe_running();
 480         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 481         const struct exception_table_entry *entry;
 482
 483         switch(kcb->kprobe_status) {
 484         case KPROBE_SWAP_INST:
 485                 /* We are here because the instruction replacement failed */
 486                 return 0;
 487         case KPROBE_HIT_SS:
 488         case KPROBE_REENTER:
 489                 /*
 490                  * We are here because the instruction being single
 491                  * stepped caused a page fault. We reset the current
 492                  * kprobe and the nip points back to the probe address
 493                  * and allow the page fault handler to continue as a
 494                  * normal page fault.
 495                  */
 496                 regs->psw.addr = (unsigned long)cur->addr | PSW_ADDR_AMODE;
 497                 regs->psw.mask &= ~PSW_MASK_PER;
 498                 regs->psw.mask |= kcb->kprobe_saved_imask;
 499                 if (kcb->kprobe_status == KPROBE_REENTER)
 500                         restore_previous_kprobe(kcb);
 501                 else
 502                         reset_current_kprobe();
 503                 preempt_enable_no_resched();
 504                 break;
 505         case KPROBE_HIT_ACTIVE:
 506         case KPROBE_HIT_SSDONE:
 507                 /*
 508                  * We increment the nmissed count for accounting,
 509                  * we can also use npre/npostfault count for accouting
 510                  * these specific fault cases.
 511                  */
 512                 kprobes_inc_nmissed_count(cur);
 513
 514                 /*
 515                  * We come here because instructions in the pre/post
 516                  * handler caused the page_fault, this could happen
 517                  * if handler tries to access user space by
 518                  * copy_from_user(), get_user() etc. Let the
 519                  * user-specified handler try to fix it first.
 520                  */
 521                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 522                         return 1;
 523
 524                 /*
 525                  * In case the user-specified fault handler returned
 526                  * zero, try to fix up.
 527                  */
 528                 entry = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
 529                 if (entry) {
 530                         regs->psw.addr = entry->fixup | PSW_ADDR_AMODE;
 531                         return 1;
 532                 }
 533
 534                 /*
 535                  * fixup_exception() could not handle it,
 536                  * Let do_page_fault() fix it.
 537                  */
 538                 break;
 539         default:
 540                 break;
 541         }
 542         return 0;
 543 }
 544
 545 /*
 546  * Wrapper routine to for handling exceptions.
 547  */
 548 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 549                                        unsigned long val, void *data)
 550 {
 551         struct die_args *args = (struct die_args *)data;
 552         int ret = NOTIFY_DONE;
 553
 554         switch (val) {
 555         case DIE_BPT:
 556                 if (kprobe_handler(args->regs))
 557                         ret = NOTIFY_STOP;
 558                 break;
 559         case DIE_SSTEP:
 560                 if (post_kprobe_handler(args->regs))
 561                         ret = NOTIFY_STOP;
 562                 break;
 563         case DIE_TRAP:
 564                 /* kprobe_running() needs smp_processor_id() */
 565                 preempt_disable();
 566                 if (kprobe_running() &&
 567                     kprobe_fault_handler(args->regs, args->trapnr))
 568                         ret = NOTIFY_STOP;
 569                 preempt_enable();
 570                 break;
 571         default:
 572                 break;
 573         }
 574         return ret;
 575 }
 576
 577 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 578 {
 579         struct jprobe *jp = container_of(p, struct jprobe, kp);
 580         unsigned long addr;
 581         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 582
 583         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
 584
 585         /* setup return addr to the jprobe handler routine */
 586         regs->psw.addr = (unsigned long)(jp->entry) | PSW_ADDR_AMODE;
 587
 588         /* r14 is the function return address */
 589         kcb->jprobe_saved_r14 = (unsigned long)regs->gprs[14];
 590         /* r15 is the stack pointer */
 591         kcb->jprobe_saved_r15 = (unsigned long)regs->gprs[15];
 592         addr = (unsigned long)kcb->jprobe_saved_r15;
 593
 594         memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr,
 595                MIN_STACK_SIZE(addr));
 596         return 1;
 597 }
 598
 599 void __kprobes jprobe_return(void)
 600 {
 601         asm volatile(".word 0x0002");
 602 }
 603
 604 void __kprobes jprobe_return_end(void)
 605 {
 606         asm volatile("bcr 0,0");
 607 }
 608
 609 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 610 {
 611         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 612         unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_r15);
 613
 614         /* Put the regs back */
 615         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
 616         /* put the stack back */
 617         memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
 618                MIN_STACK_SIZE(stack_addr));
 619         preempt_enable_no_resched();
 620         return 1;
 621 }
 622
 623 static struct kprobe trampoline_p = {
 624         .addr = (kprobe_opcode_t *) & kretprobe_trampoline,
 625         .pre_handler = trampoline_probe_handler
 626 };
 627
 628 int __init arch_init_kprobes(void)
 629 {
 630         return register_kprobe(&trampoline_p);
 631 }
 632
 633 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 634 {
 635         if (p->addr == (kprobe_opcode_t *) & kretprobe_trampoline)
 636                 return 1;
 637         return 0;
 638 }