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 #include <linux/slab.h>
  33
  34 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  35 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  36
  37 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
  38
  39 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  40 {
  41         /* Make sure the probe isn't going on a difficult instruction */
  42         if (is_prohibited_opcode((kprobe_opcode_t *) p->addr))
  43                 return -EINVAL;
  44
  45         if ((unsigned long)p->addr & 0x01)
  46                 return -EINVAL;
  47
  48         /* Use the get_insn_slot() facility for correctness */
  49         if (!(p->ainsn.insn = get_insn_slot()))
  50                 return -ENOMEM;
  51
  52         memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
  53
  54         get_instruction_type(&p->ainsn);
  55         p->opcode = *p->addr;
  56         return 0;
  57 }
  58
  59 int __kprobes is_prohibited_opcode(kprobe_opcode_t *instruction)
  60 {
  61         switch (*(__u8 *) instruction) {
  62         case 0x0c:      /* bassm */
  63         case 0x0b:      /* bsm   */
  64         case 0x83:      /* diag  */
  65         case 0x44:      /* ex    */
  66         case 0xac:      /* stnsm */
  67         case 0xad:      /* stosm */
  68                 return -EINVAL;
  69         }
  70         switch (*(__u16 *) instruction) {
  71         case 0x0101:    /* pr    */
  72         case 0xb25a:    /* bsa   */
  73         case 0xb240:    /* bakr  */
  74         case 0xb258:    /* bsg   */
  75         case 0xb218:    /* pc    */
  76         case 0xb228:    /* pt    */
  77         case 0xb98d:    /* epsw  */
  78                 return -EINVAL;
  79         }
  80         return 0;
  81 }
  82
  83 void __kprobes get_instruction_type(struct arch_specific_insn *ainsn)
  84 {
  85         /* default fixup method */
  86         ainsn->fixup = FIXUP_PSW_NORMAL;
  87
  88         /* save r1 operand */
  89         ainsn->reg = (*ainsn->insn & 0xf0) >> 4;
  90
  91         /* save the instruction length (pop 5-5) in bytes */
  92         switch (*(__u8 *) (ainsn->insn) >> 6) {
  93         case 0:
  94                 ainsn->ilen = 2;
  95                 break;
  96         case 1:
  97         case 2:
  98                 ainsn->ilen = 4;
  99                 break;
 100         case 3:
 101                 ainsn->ilen = 6;
 102                 break;
 103         }
 104
 105         switch (*(__u8 *) ainsn->insn) {
 106         case 0x05:      /* balr */
 107         case 0x0d:      /* basr */
 108                 ainsn->fixup = FIXUP_RETURN_REGISTER;
 109                 /* if r2 = 0, no branch will be taken */
 110                 if ((*ainsn->insn & 0x0f) == 0)
 111                         ainsn->fixup |= FIXUP_BRANCH_NOT_TAKEN;
 112                 break;
 113         case 0x06:      /* bctr */
 114         case 0x07:      /* bcr  */
 115                 ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
 116                 break;
 117         case 0x45:      /* bal  */
 118         case 0x4d:      /* bas  */
 119                 ainsn->fixup = FIXUP_RETURN_REGISTER;
 120                 break;
 121         case 0x47:      /* bc   */
 122         case 0x46:      /* bct  */
 123         case 0x86:      /* bxh  */
 124         case 0x87:      /* bxle */
 125                 ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
 126                 break;
 127         case 0x82:      /* lpsw */
 128                 ainsn->fixup = FIXUP_NOT_REQUIRED;
 129                 break;
 130         case 0xb2:      /* lpswe */
 131                 if (*(((__u8 *) ainsn->insn) + 1) == 0xb2) {
 132                         ainsn->fixup = FIXUP_NOT_REQUIRED;
 133                 }
 134                 break;
 135         case 0xa7:      /* bras */
 136                 if ((*ainsn->insn & 0x0f) == 0x05) {
 137                         ainsn->fixup |= FIXUP_RETURN_REGISTER;
 138                 }
 139                 break;
 140         case 0xc0:
 141                 if ((*ainsn->insn & 0x0f) == 0x00  /* larl  */
 142                         || (*ainsn->insn & 0x0f) == 0x05) /* brasl */
 143                 ainsn->fixup |= FIXUP_RETURN_REGISTER;
 144                 break;
 145         case 0xeb:
 146                 if (*(((__u8 *) ainsn->insn) + 5 ) == 0x44 ||   /* bxhg  */
 147                         *(((__u8 *) ainsn->insn) + 5) == 0x45) {/* bxleg */
 148                         ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
 149                 }
 150                 break;
 151         case 0xe3:      /* bctg */
 152                 if (*(((__u8 *) ainsn->insn) + 5) == 0x46) {
 153                         ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
 154                 }
 155                 break;
 156         }
 157 }
 158
 159 static int __kprobes swap_instruction(void *aref)
 160 {
 161         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 162         unsigned long status = kcb->kprobe_status;
 163         struct ins_replace_args *args = aref;
 164         int rc;
 165
 166         kcb->kprobe_status = KPROBE_SWAP_INST;
 167         rc = probe_kernel_write(args->ptr, &args->new, sizeof(args->new));
 168         kcb->kprobe_status = status;
 169         return rc;
 170 }
 171
 172 void __kprobes arch_arm_kprobe(struct kprobe *p)
 173 {
 174         struct ins_replace_args args;
 175
 176         args.ptr = p->addr;
 177         args.old = p->opcode;
 178         args.new = BREAKPOINT_INSTRUCTION;
 179         stop_machine(swap_instruction, &args, NULL);
 180 }
 181
 182 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 183 {
 184         struct ins_replace_args args;
 185
 186         args.ptr = p->addr;
 187         args.old = BREAKPOINT_INSTRUCTION;
 188         args.new = p->opcode;
 189         stop_machine(swap_instruction, &args, NULL);
 190 }
 191
 192 void __kprobes arch_remove_kprobe(struct kprobe *p)
 193 {
 194         if (p->ainsn.insn) {
 195                 free_insn_slot(p->ainsn.insn, 0);
 196                 p->ainsn.insn = NULL;
 197         }
 198 }
 199
 200 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 201 {
 202         per_cr_bits kprobe_per_regs[1];
 203
 204         memset(kprobe_per_regs, 0, sizeof(per_cr_bits));
 205         regs->psw.addr = (unsigned long)p->ainsn.insn | PSW_ADDR_AMODE;
 206
 207         /* Set up the per control reg info, will pass to lctl */
 208         kprobe_per_regs[0].em_instruction_fetch = 1;
 209         kprobe_per_regs[0].starting_addr = (unsigned long)p->ainsn.insn;
 210         kprobe_per_regs[0].ending_addr = (unsigned long)p->ainsn.insn + 1;
 211
 212         /* Set the PER control regs, turns on single step for this address */
 213         __ctl_load(kprobe_per_regs, 9, 11);
 214         regs->psw.mask |= PSW_MASK_PER;
 215         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK);
 216 }
 217
 218 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 219 {
 220         kcb->prev_kprobe.kp = kprobe_running();
 221         kcb->prev_kprobe.status = kcb->kprobe_status;
 222         kcb->prev_kprobe.kprobe_saved_imask = kcb->kprobe_saved_imask;
 223         memcpy(kcb->prev_kprobe.kprobe_saved_ctl, kcb->kprobe_saved_ctl,
 224                                         sizeof(kcb->kprobe_saved_ctl));
 225 }
 226
 227 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 228 {
 229         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
 230         kcb->kprobe_status = kcb->prev_kprobe.status;
 231         kcb->kprobe_saved_imask = kcb->prev_kprobe.kprobe_saved_imask;
 232         memcpy(kcb->kprobe_saved_ctl, kcb->prev_kprobe.kprobe_saved_ctl,
 233                                         sizeof(kcb->kprobe_saved_ctl));
 234 }
 235
 236 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 237                                                 struct kprobe_ctlblk *kcb)
 238 {
 239         __get_cpu_var(current_kprobe) = p;
 240         /* Save the interrupt and per flags */
 241         kcb->kprobe_saved_imask = regs->psw.mask &
 242             (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK);
 243         /* Save the control regs that govern PER */
 244         __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
 245 }
 246
 247 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 248                                         struct pt_regs *regs)
 249 {
 250         ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
 251
 252         /* Replace the return addr with trampoline addr */
 253         regs->gprs[14] = (unsigned long)&kretprobe_trampoline;
 254 }
 255
 256 static int __kprobes kprobe_handler(struct pt_regs *regs)
 257 {
 258         struct kprobe *p;
 259         int ret = 0;
 260         unsigned long *addr = (unsigned long *)
 261                 ((regs->psw.addr & PSW_ADDR_INSN) - 2);
 262         struct kprobe_ctlblk *kcb;
 263
 264         /*
 265          * We don't want to be preempted for the entire
 266          * duration of kprobe processing
 267          */
 268         preempt_disable();
 269         kcb = get_kprobe_ctlblk();
 270
 271         /* Check we're not actually recursing */
 272         if (kprobe_running()) {
 273                 p = get_kprobe(addr);
 274                 if (p) {
 275                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
 276                             *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
 277                                 regs->psw.mask &= ~PSW_MASK_PER;
 278                                 regs->psw.mask |= kcb->kprobe_saved_imask;
 279                                 goto no_kprobe;
 280                         }
 281                         /* We have reentered the kprobe_handler(), since
 282                          * another probe was hit while within the handler.
 283                          * We here save the original kprobes variables and
 284                          * just single step on the instruction of the new probe
 285                          * without calling any user handlers.
 286                          */
 287                         save_previous_kprobe(kcb);
 288                         set_current_kprobe(p, regs, kcb);
 289                         kprobes_inc_nmissed_count(p);
 290                         prepare_singlestep(p, regs);
 291                         kcb->kprobe_status = KPROBE_REENTER;
 292                         return 1;
 293                 } else {
 294                         p = __get_cpu_var(current_kprobe);
 295                         if (p->break_handler && p->break_handler(p, regs)) {
 296                                 goto ss_probe;
 297                         }
 298                 }
 299                 goto no_kprobe;
 300         }
 301
 302         p = get_kprobe(addr);
 303         if (!p)
 304                 /*
 305                  * No kprobe at this address. The fault has not been
 306                  * caused by a kprobe breakpoint. The race of breakpoint
 307                  * vs. kprobe remove does not exist because on s390 we
 308                  * use stop_machine to arm/disarm the breakpoints.
 309                  */
 310                 goto no_kprobe;
 311
 312         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 313         set_current_kprobe(p, regs, kcb);
 314         if (p->pre_handler && p->pre_handler(p, regs))
 315                 /* handler has already set things up, so skip ss setup */
 316                 return 1;
 317
 318 ss_probe:
 319         prepare_singlestep(p, regs);
 320         kcb->kprobe_status = KPROBE_HIT_SS;
 321         return 1;
 322
 323 no_kprobe:
 324         preempt_enable_no_resched();
 325         return ret;
 326 }
 327
 328 /*
 329  * Function return probe trampoline:
 330  *      - init_kprobes() establishes a probepoint here
 331  *      - When the probed function returns, this probe
 332  *              causes the handlers to fire
 333  */
 334 static void __used kretprobe_trampoline_holder(void)
 335 {
 336         asm volatile(".global kretprobe_trampoline\n"
 337                      "kretprobe_trampoline: bcr 0,0\n");
 338 }
 339
 340 /*
 341  * Called when the probe at kretprobe trampoline is hit
 342  */
 343 static int __kprobes trampoline_probe_handler(struct kprobe *p,
 344                                               struct pt_regs *regs)
 345 {
 346         struct kretprobe_instance *ri = NULL;
 347         struct hlist_head *head, empty_rp;
 348         struct hlist_node *node, *tmp;
 349         unsigned long flags, orig_ret_address = 0;
 350         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 351
 352         INIT_HLIST_HEAD(&empty_rp);
 353         kretprobe_hash_lock(current, &head, &flags);
 354
 355         /*
 356          * It is possible to have multiple instances associated with a given
 357          * task either because an multiple functions in the call path
 358          * have a return probe installed on them, and/or more than one return
 359          * return probe was registered for a target function.
 360          *
 361          * We can handle this because:
 362          *     - instances are always inserted at the head of the list
 363          *     - when multiple return probes are registered for the same
 364          *       function, the first instance's ret_addr will point to the
 365          *       real return address, and all the rest will point to
 366          *       kretprobe_trampoline
 367          */
 368         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
 369                 if (ri->task != current)
 370                         /* another task is sharing our hash bucket */
 371                         continue;
 372
 373                 if (ri->rp && ri->rp->handler)
 374                         ri->rp->handler(ri, regs);
 375
 376                 orig_ret_address = (unsigned long)ri->ret_addr;
 377                 recycle_rp_inst(ri, &empty_rp);
 378
 379                 if (orig_ret_address != trampoline_address) {
 380                         /*
 381                          * This is the real return address. Any other
 382                          * instances associated with this task are for
 383                          * other calls deeper on the call stack
 384                          */
 385                         break;
 386                 }
 387         }
 388         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 389         regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE;
 390
 391         reset_current_kprobe();
 392         kretprobe_hash_unlock(current, &flags);
 393         preempt_enable_no_resched();
 394
 395         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
 396                 hlist_del(&ri->hlist);
 397                 kfree(ri);
 398         }
 399         /*
 400          * By returning a non-zero value, we are telling
 401          * kprobe_handler() that we don't want the post_handler
 402          * to run (and have re-enabled preemption)
 403          */
 404         return 1;
 405 }
 406
 407 /*
 408  * Called after single-stepping.  p->addr is the address of the
 409  * instruction whose first byte has been replaced by the "breakpoint"
 410  * instruction.  To avoid the SMP problems that can occur when we
 411  * temporarily put back the original opcode to single-step, we
 412  * single-stepped a copy of the instruction.  The address of this
 413  * copy is p->ainsn.insn.
 414  */
 415 static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
 416 {
 417         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 418
 419         regs->psw.addr &= PSW_ADDR_INSN;
 420
 421         if (p->ainsn.fixup & FIXUP_PSW_NORMAL)
 422                 regs->psw.addr = (unsigned long)p->addr +
 423                                 ((unsigned long)regs->psw.addr -
 424                                  (unsigned long)p->ainsn.insn);
 425
 426         if (p->ainsn.fixup & FIXUP_BRANCH_NOT_TAKEN)
 427                 if ((unsigned long)regs->psw.addr -
 428                     (unsigned long)p->ainsn.insn == p->ainsn.ilen)
 429                         regs->psw.addr = (unsigned long)p->addr + p->ainsn.ilen;
 430
 431         if (p->ainsn.fixup & FIXUP_RETURN_REGISTER)
 432                 regs->gprs[p->ainsn.reg] = ((unsigned long)p->addr +
 433                                                 (regs->gprs[p->ainsn.reg] -
 434                                                 (unsigned long)p->ainsn.insn))
 435                                                 | PSW_ADDR_AMODE;
 436
 437         regs->psw.addr |= PSW_ADDR_AMODE;
 438         /* turn off PER mode */
 439         regs->psw.mask &= ~PSW_MASK_PER;
 440         /* Restore the original per control regs */
 441         __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
 442         regs->psw.mask |= kcb->kprobe_saved_imask;
 443 }
 444
 445 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 446 {
 447         struct kprobe *cur = kprobe_running();
 448         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 449
 450         if (!cur)
 451                 return 0;
 452
 453         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 454                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 455                 cur->post_handler(cur, regs, 0);
 456         }
 457
 458         resume_execution(cur, regs);
 459
 460         /*Restore back the original saved kprobes variables and continue. */
 461         if (kcb->kprobe_status == KPROBE_REENTER) {
 462                 restore_previous_kprobe(kcb);
 463                 goto out;
 464         }
 465         reset_current_kprobe();
 466 out:
 467         preempt_enable_no_resched();
 468
 469         /*
 470          * if somebody else is singlestepping across a probe point, psw mask
 471          * will have PER set, in which case, continue the remaining processing
 472          * of do_single_step, as if this is not a probe hit.
 473          */
 474         if (regs->psw.mask & PSW_MASK_PER) {
 475                 return 0;
 476         }
 477
 478         return 1;
 479 }
 480
 481 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 482 {
 483         struct kprobe *cur = kprobe_running();
 484         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 485         const struct exception_table_entry *entry;
 486
 487         switch(kcb->kprobe_status) {
 488         case KPROBE_SWAP_INST:
 489                 /* We are here because the instruction replacement failed */
 490                 return 0;
 491         case KPROBE_HIT_SS:
 492         case KPROBE_REENTER:
 493                 /*
 494                  * We are here because the instruction being single
 495                  * stepped caused a page fault. We reset the current
 496                  * kprobe and the nip points back to the probe address
 497                  * and allow the page fault handler to continue as a
 498                  * normal page fault.
 499                  */
 500                 regs->psw.addr = (unsigned long)cur->addr | PSW_ADDR_AMODE;
 501                 regs->psw.mask &= ~PSW_MASK_PER;
 502                 regs->psw.mask |= kcb->kprobe_saved_imask;
 503                 if (kcb->kprobe_status == KPROBE_REENTER)
 504                         restore_previous_kprobe(kcb);
 505                 else
 506                         reset_current_kprobe();
 507                 preempt_enable_no_resched();
 508                 break;
 509         case KPROBE_HIT_ACTIVE:
 510         case KPROBE_HIT_SSDONE:
 511                 /*
 512                  * We increment the nmissed count for accounting,
 513                  * we can also use npre/npostfault count for accouting
 514                  * these specific fault cases.
 515                  */
 516                 kprobes_inc_nmissed_count(cur);
 517
 518                 /*
 519                  * We come here because instructions in the pre/post
 520                  * handler caused the page_fault, this could happen
 521                  * if handler tries to access user space by
 522                  * copy_from_user(), get_user() etc. Let the
 523                  * user-specified handler try to fix it first.
 524                  */
 525                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 526                         return 1;
 527
 528                 /*
 529                  * In case the user-specified fault handler returned
 530                  * zero, try to fix up.
 531                  */
 532                 entry = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
 533                 if (entry) {
 534                         regs->psw.addr = entry->fixup | PSW_ADDR_AMODE;
 535                         return 1;
 536                 }
 537
 538                 /*
 539                  * fixup_exception() could not handle it,
 540                  * Let do_page_fault() fix it.
 541                  */
 542                 break;
 543         default:
 544                 break;
 545         }
 546         return 0;
 547 }
 548
 549 /*
 550  * Wrapper routine to for handling exceptions.
 551  */
 552 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 553                                        unsigned long val, void *data)
 554 {
 555         struct die_args *args = (struct die_args *)data;
 556         int ret = NOTIFY_DONE;
 557
 558         switch (val) {
 559         case DIE_BPT:
 560                 if (kprobe_handler(args->regs))
 561                         ret = NOTIFY_STOP;
 562                 break;
 563         case DIE_SSTEP:
 564                 if (post_kprobe_handler(args->regs))
 565                         ret = NOTIFY_STOP;
 566                 break;
 567         case DIE_TRAP:
 568                 /* kprobe_running() needs smp_processor_id() */
 569                 preempt_disable();
 570                 if (kprobe_running() &&
 571                     kprobe_fault_handler(args->regs, args->trapnr))
 572                         ret = NOTIFY_STOP;
 573                 preempt_enable();
 574                 break;
 575         default:
 576                 break;
 577         }
 578         return ret;
 579 }
 580
 581 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 582 {
 583         struct jprobe *jp = container_of(p, struct jprobe, kp);
 584         unsigned long addr;
 585         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 586
 587         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
 588
 589         /* setup return addr to the jprobe handler routine */
 590         regs->psw.addr = (unsigned long)(jp->entry) | PSW_ADDR_AMODE;
 591
 592         /* r14 is the function return address */
 593         kcb->jprobe_saved_r14 = (unsigned long)regs->gprs[14];
 594         /* r15 is the stack pointer */
 595         kcb->jprobe_saved_r15 = (unsigned long)regs->gprs[15];
 596         addr = (unsigned long)kcb->jprobe_saved_r15;
 597
 598         memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr,
 599                MIN_STACK_SIZE(addr));
 600         return 1;
 601 }
 602
 603 void __kprobes jprobe_return(void)
 604 {
 605         asm volatile(".word 0x0002");
 606 }
 607
 608 void __kprobes jprobe_return_end(void)
 609 {
 610         asm volatile("bcr 0,0");
 611 }
 612
 613 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 614 {
 615         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 616         unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_r15);
 617
 618         /* Put the regs back */
 619         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
 620         /* put the stack back */
 621         memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
 622                MIN_STACK_SIZE(stack_addr));
 623         preempt_enable_no_resched();
 624         return 1;
 625 }
 626
 627 static struct kprobe trampoline_p = {
 628         .addr = (kprobe_opcode_t *) & kretprobe_trampoline,
 629         .pre_handler = trampoline_probe_handler
 630 };
 631
 632 int __init arch_init_kprobes(void)
 633 {
 634         return register_kprobe(&trampoline_p);
 635 }
 636
 637 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 638 {
 639         if (p->addr == (kprobe_opcode_t *) & kretprobe_trampoline)
 640                 return 1;
 641         return 0;
 642 }