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 <asm/cacheflush.h>
  29 #include <asm/sections.h>
  30 #include <asm/uaccess.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 ins_replace_args *args = aref;
 158         u32 *addr;
 159         u32 instr;
 160         int err = -EFAULT;
 161
 162         /*
 163          * Text segment is read-only, hence we use stura to bypass dynamic
 164          * address translation to exchange the instruction. Since stura
 165          * always operates on four bytes, but we only want to exchange two
 166          * bytes do some calculations to get things right. In addition we
 167          * shall not cross any page boundaries (vmalloc area!) when writing
 168          * the new instruction.
 169          */
 170         addr = (u32 *)((unsigned long)args->ptr & -4UL);
 171         if ((unsigned long)args->ptr & 2)
 172                 instr = ((*addr) & 0xffff0000) | args->new;
 173         else
 174                 instr = ((*addr) & 0x0000ffff) | args->new << 16;
 175
 176         asm volatile(
 177                 "       lra     %1,0(%1)\n"
 178                 "0:     stura   %2,%1\n"
 179                 "1:     la      %0,0\n"
 180                 "2:\n"
 181                 EX_TABLE(0b,2b)
 182                 : "+d" (err)
 183                 : "a" (addr), "d" (instr)
 184                 : "memory", "cc");
 185
 186         return err;
 187 }
 188
 189 void __kprobes arch_arm_kprobe(struct kprobe *p)
 190 {
 191         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 192         unsigned long status = kcb->kprobe_status;
 193         struct ins_replace_args args;
 194
 195         args.ptr = p->addr;
 196         args.old = p->opcode;
 197         args.new = BREAKPOINT_INSTRUCTION;
 198
 199         kcb->kprobe_status = KPROBE_SWAP_INST;
 200         stop_machine(swap_instruction, &args, NULL);
 201         kcb->kprobe_status = status;
 202 }
 203
 204 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 205 {
 206         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 207         unsigned long status = kcb->kprobe_status;
 208         struct ins_replace_args args;
 209
 210         args.ptr = p->addr;
 211         args.old = BREAKPOINT_INSTRUCTION;
 212         args.new = p->opcode;
 213
 214         kcb->kprobe_status = KPROBE_SWAP_INST;
 215         stop_machine(swap_instruction, &args, NULL);
 216         kcb->kprobe_status = status;
 217 }
 218
 219 void __kprobes arch_remove_kprobe(struct kprobe *p)
 220 {
 221         mutex_lock(&kprobe_mutex);
 222         free_insn_slot(p->ainsn.insn, 0);
 223         mutex_unlock(&kprobe_mutex);
 224 }
 225
 226 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 227 {
 228         per_cr_bits kprobe_per_regs[1];
 229
 230         memset(kprobe_per_regs, 0, sizeof(per_cr_bits));
 231         regs->psw.addr = (unsigned long)p->ainsn.insn | PSW_ADDR_AMODE;
 232
 233         /* Set up the per control reg info, will pass to lctl */
 234         kprobe_per_regs[0].em_instruction_fetch = 1;
 235         kprobe_per_regs[0].starting_addr = (unsigned long)p->ainsn.insn;
 236         kprobe_per_regs[0].ending_addr = (unsigned long)p->ainsn.insn + 1;
 237
 238         /* Set the PER control regs, turns on single step for this address */
 239         __ctl_load(kprobe_per_regs, 9, 11);
 240         regs->psw.mask |= PSW_MASK_PER;
 241         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK);
 242 }
 243
 244 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 245 {
 246         kcb->prev_kprobe.kp = kprobe_running();
 247         kcb->prev_kprobe.status = kcb->kprobe_status;
 248         kcb->prev_kprobe.kprobe_saved_imask = kcb->kprobe_saved_imask;
 249         memcpy(kcb->prev_kprobe.kprobe_saved_ctl, kcb->kprobe_saved_ctl,
 250                                         sizeof(kcb->kprobe_saved_ctl));
 251 }
 252
 253 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 254 {
 255         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
 256         kcb->kprobe_status = kcb->prev_kprobe.status;
 257         kcb->kprobe_saved_imask = kcb->prev_kprobe.kprobe_saved_imask;
 258         memcpy(kcb->kprobe_saved_ctl, kcb->prev_kprobe.kprobe_saved_ctl,
 259                                         sizeof(kcb->kprobe_saved_ctl));
 260 }
 261
 262 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 263                                                 struct kprobe_ctlblk *kcb)
 264 {
 265         __get_cpu_var(current_kprobe) = p;
 266         /* Save the interrupt and per flags */
 267         kcb->kprobe_saved_imask = regs->psw.mask &
 268             (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK);
 269         /* Save the control regs that govern PER */
 270         __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
 271 }
 272
 273 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 274                                         struct pt_regs *regs)
 275 {
 276         ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
 277
 278         /* Replace the return addr with trampoline addr */
 279         regs->gprs[14] = (unsigned long)&kretprobe_trampoline;
 280 }
 281
 282 static int __kprobes kprobe_handler(struct pt_regs *regs)
 283 {
 284         struct kprobe *p;
 285         int ret = 0;
 286         unsigned long *addr = (unsigned long *)
 287                 ((regs->psw.addr & PSW_ADDR_INSN) - 2);
 288         struct kprobe_ctlblk *kcb;
 289
 290         /*
 291          * We don't want to be preempted for the entire
 292          * duration of kprobe processing
 293          */
 294         preempt_disable();
 295         kcb = get_kprobe_ctlblk();
 296
 297         /* Check we're not actually recursing */
 298         if (kprobe_running()) {
 299                 p = get_kprobe(addr);
 300                 if (p) {
 301                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
 302                             *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
 303                                 regs->psw.mask &= ~PSW_MASK_PER;
 304                                 regs->psw.mask |= kcb->kprobe_saved_imask;
 305                                 goto no_kprobe;
 306                         }
 307                         /* We have reentered the kprobe_handler(), since
 308                          * another probe was hit while within the handler.
 309                          * We here save the original kprobes variables and
 310                          * just single step on the instruction of the new probe
 311                          * without calling any user handlers.
 312                          */
 313                         save_previous_kprobe(kcb);
 314                         set_current_kprobe(p, regs, kcb);
 315                         kprobes_inc_nmissed_count(p);
 316                         prepare_singlestep(p, regs);
 317                         kcb->kprobe_status = KPROBE_REENTER;
 318                         return 1;
 319                 } else {
 320                         p = __get_cpu_var(current_kprobe);
 321                         if (p->break_handler && p->break_handler(p, regs)) {
 322                                 goto ss_probe;
 323                         }
 324                 }
 325                 goto no_kprobe;
 326         }
 327
 328         p = get_kprobe(addr);
 329         if (!p)
 330                 /*
 331                  * No kprobe at this address. The fault has not been
 332                  * caused by a kprobe breakpoint. The race of breakpoint
 333                  * vs. kprobe remove does not exist because on s390 we
 334                  * use stop_machine to arm/disarm the breakpoints.
 335                  */
 336                 goto no_kprobe;
 337
 338         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 339         set_current_kprobe(p, regs, kcb);
 340         if (p->pre_handler && p->pre_handler(p, regs))
 341                 /* handler has already set things up, so skip ss setup */
 342                 return 1;
 343
 344 ss_probe:
 345         prepare_singlestep(p, regs);
 346         kcb->kprobe_status = KPROBE_HIT_SS;
 347         return 1;
 348
 349 no_kprobe:
 350         preempt_enable_no_resched();
 351         return ret;
 352 }
 353
 354 /*
 355  * Function return probe trampoline:
 356  *      - init_kprobes() establishes a probepoint here
 357  *      - When the probed function returns, this probe
 358  *              causes the handlers to fire
 359  */
 360 static void __used kretprobe_trampoline_holder(void)
 361 {
 362         asm volatile(".global kretprobe_trampoline\n"
 363                      "kretprobe_trampoline: bcr 0,0\n");
 364 }
 365
 366 /*
 367  * Called when the probe at kretprobe trampoline is hit
 368  */
 369 static int __kprobes trampoline_probe_handler(struct kprobe *p,
 370                                               struct pt_regs *regs)
 371 {
 372         struct kretprobe_instance *ri = NULL;
 373         struct hlist_head *head, empty_rp;
 374         struct hlist_node *node, *tmp;
 375         unsigned long flags, orig_ret_address = 0;
 376         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 377
 378         INIT_HLIST_HEAD(&empty_rp);
 379         kretprobe_hash_lock(current, &head, &flags);
 380
 381         /*
 382          * It is possible to have multiple instances associated with a given
 383          * task either because an multiple functions in the call path
 384          * have a return probe installed on them, and/or more then one return
 385          * return probe was registered for a target function.
 386          *
 387          * We can handle this because:
 388          *     - instances are always inserted at the head of the list
 389          *     - when multiple return probes are registered for the same
 390          *       function, the first instance's ret_addr will point to the
 391          *       real return address, and all the rest will point to
 392          *       kretprobe_trampoline
 393          */
 394         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
 395                 if (ri->task != current)
 396                         /* another task is sharing our hash bucket */
 397                         continue;
 398
 399                 if (ri->rp && ri->rp->handler)
 400                         ri->rp->handler(ri, regs);
 401
 402                 orig_ret_address = (unsigned long)ri->ret_addr;
 403                 recycle_rp_inst(ri, &empty_rp);
 404
 405                 if (orig_ret_address != trampoline_address) {
 406                         /*
 407                          * This is the real return address. Any other
 408                          * instances associated with this task are for
 409                          * other calls deeper on the call stack
 410                          */
 411                         break;
 412                 }
 413         }
 414         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 415         regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE;
 416
 417         reset_current_kprobe();
 418         kretprobe_hash_unlock(current, &flags);
 419         preempt_enable_no_resched();
 420
 421         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
 422                 hlist_del(&ri->hlist);
 423                 kfree(ri);
 424         }
 425         /*
 426          * By returning a non-zero value, we are telling
 427          * kprobe_handler() that we don't want the post_handler
 428          * to run (and have re-enabled preemption)
 429          */
 430         return 1;
 431 }
 432
 433 /*
 434  * Called after single-stepping.  p->addr is the address of the
 435  * instruction whose first byte has been replaced by the "breakpoint"
 436  * instruction.  To avoid the SMP problems that can occur when we
 437  * temporarily put back the original opcode to single-step, we
 438  * single-stepped a copy of the instruction.  The address of this
 439  * copy is p->ainsn.insn.
 440  */
 441 static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
 442 {
 443         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 444
 445         regs->psw.addr &= PSW_ADDR_INSN;
 446
 447         if (p->ainsn.fixup & FIXUP_PSW_NORMAL)
 448                 regs->psw.addr = (unsigned long)p->addr +
 449                                 ((unsigned long)regs->psw.addr -
 450                                  (unsigned long)p->ainsn.insn);
 451
 452         if (p->ainsn.fixup & FIXUP_BRANCH_NOT_TAKEN)
 453                 if ((unsigned long)regs->psw.addr -
 454                     (unsigned long)p->ainsn.insn == p->ainsn.ilen)
 455                         regs->psw.addr = (unsigned long)p->addr + p->ainsn.ilen;
 456
 457         if (p->ainsn.fixup & FIXUP_RETURN_REGISTER)
 458                 regs->gprs[p->ainsn.reg] = ((unsigned long)p->addr +
 459                                                 (regs->gprs[p->ainsn.reg] -
 460                                                 (unsigned long)p->ainsn.insn))
 461                                                 | PSW_ADDR_AMODE;
 462
 463         regs->psw.addr |= PSW_ADDR_AMODE;
 464         /* turn off PER mode */
 465         regs->psw.mask &= ~PSW_MASK_PER;
 466         /* Restore the original per control regs */
 467         __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
 468         regs->psw.mask |= kcb->kprobe_saved_imask;
 469 }
 470
 471 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 472 {
 473         struct kprobe *cur = kprobe_running();
 474         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 475
 476         if (!cur)
 477                 return 0;
 478
 479         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 480                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 481                 cur->post_handler(cur, regs, 0);
 482         }
 483
 484         resume_execution(cur, regs);
 485
 486         /*Restore back the original saved kprobes variables and continue. */
 487         if (kcb->kprobe_status == KPROBE_REENTER) {
 488                 restore_previous_kprobe(kcb);
 489                 goto out;
 490         }
 491         reset_current_kprobe();
 492 out:
 493         preempt_enable_no_resched();
 494
 495         /*
 496          * if somebody else is singlestepping across a probe point, psw mask
 497          * will have PER set, in which case, continue the remaining processing
 498          * of do_single_step, as if this is not a probe hit.
 499          */
 500         if (regs->psw.mask & PSW_MASK_PER) {
 501                 return 0;
 502         }
 503
 504         return 1;
 505 }
 506
 507 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 508 {
 509         struct kprobe *cur = kprobe_running();
 510         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 511         const struct exception_table_entry *entry;
 512
 513         switch(kcb->kprobe_status) {
 514         case KPROBE_SWAP_INST:
 515                 /* We are here because the instruction replacement failed */
 516                 return 0;
 517         case KPROBE_HIT_SS:
 518         case KPROBE_REENTER:
 519                 /*
 520                  * We are here because the instruction being single
 521                  * stepped caused a page fault. We reset the current
 522                  * kprobe and the nip points back to the probe address
 523                  * and allow the page fault handler to continue as a
 524                  * normal page fault.
 525                  */
 526                 regs->psw.addr = (unsigned long)cur->addr | PSW_ADDR_AMODE;
 527                 regs->psw.mask &= ~PSW_MASK_PER;
 528                 regs->psw.mask |= kcb->kprobe_saved_imask;
 529                 if (kcb->kprobe_status == KPROBE_REENTER)
 530                         restore_previous_kprobe(kcb);
 531                 else
 532                         reset_current_kprobe();
 533                 preempt_enable_no_resched();
 534                 break;
 535         case KPROBE_HIT_ACTIVE:
 536         case KPROBE_HIT_SSDONE:
 537                 /*
 538                  * We increment the nmissed count for accounting,
 539                  * we can also use npre/npostfault count for accouting
 540                  * these specific fault cases.
 541                  */
 542                 kprobes_inc_nmissed_count(cur);
 543
 544                 /*
 545                  * We come here because instructions in the pre/post
 546                  * handler caused the page_fault, this could happen
 547                  * if handler tries to access user space by
 548                  * copy_from_user(), get_user() etc. Let the
 549                  * user-specified handler try to fix it first.
 550                  */
 551                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 552                         return 1;
 553
 554                 /*
 555                  * In case the user-specified fault handler returned
 556                  * zero, try to fix up.
 557                  */
 558                 entry = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
 559                 if (entry) {
 560                         regs->psw.addr = entry->fixup | PSW_ADDR_AMODE;
 561                         return 1;
 562                 }
 563
 564                 /*
 565                  * fixup_exception() could not handle it,
 566                  * Let do_page_fault() fix it.
 567                  */
 568                 break;
 569         default:
 570                 break;
 571         }
 572         return 0;
 573 }
 574
 575 /*
 576  * Wrapper routine to for handling exceptions.
 577  */
 578 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 579                                        unsigned long val, void *data)
 580 {
 581         struct die_args *args = (struct die_args *)data;
 582         int ret = NOTIFY_DONE;
 583
 584         switch (val) {
 585         case DIE_BPT:
 586                 if (kprobe_handler(args->regs))
 587                         ret = NOTIFY_STOP;
 588                 break;
 589         case DIE_SSTEP:
 590                 if (post_kprobe_handler(args->regs))
 591                         ret = NOTIFY_STOP;
 592                 break;
 593         case DIE_TRAP:
 594                 /* kprobe_running() needs smp_processor_id() */
 595                 preempt_disable();
 596                 if (kprobe_running() &&
 597                     kprobe_fault_handler(args->regs, args->trapnr))
 598                         ret = NOTIFY_STOP;
 599                 preempt_enable();
 600                 break;
 601         default:
 602                 break;
 603         }
 604         return ret;
 605 }
 606
 607 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 608 {
 609         struct jprobe *jp = container_of(p, struct jprobe, kp);
 610         unsigned long addr;
 611         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 612
 613         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
 614
 615         /* setup return addr to the jprobe handler routine */
 616         regs->psw.addr = (unsigned long)(jp->entry) | PSW_ADDR_AMODE;
 617
 618         /* r14 is the function return address */
 619         kcb->jprobe_saved_r14 = (unsigned long)regs->gprs[14];
 620         /* r15 is the stack pointer */
 621         kcb->jprobe_saved_r15 = (unsigned long)regs->gprs[15];
 622         addr = (unsigned long)kcb->jprobe_saved_r15;
 623
 624         memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr,
 625                MIN_STACK_SIZE(addr));
 626         return 1;
 627 }
 628
 629 void __kprobes jprobe_return(void)
 630 {
 631         asm volatile(".word 0x0002");
 632 }
 633
 634 void __kprobes jprobe_return_end(void)
 635 {
 636         asm volatile("bcr 0,0");
 637 }
 638
 639 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 640 {
 641         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 642         unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_r15);
 643
 644         /* Put the regs back */
 645         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
 646         /* put the stack back */
 647         memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
 648                MIN_STACK_SIZE(stack_addr));
 649         preempt_enable_no_resched();
 650         return 1;
 651 }
 652
 653 static struct kprobe trampoline_p = {
 654         .addr = (kprobe_opcode_t *) & kretprobe_trampoline,
 655         .pre_handler = trampoline_probe_handler
 656 };
 657
 658 int __init arch_init_kprobes(void)
 659 {
 660         return register_kprobe(&trampoline_p);
 661 }
 662
 663 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 664 {
 665         if (p->addr == (kprobe_opcode_t *) & kretprobe_trampoline)
 666                 return 1;
 667         return 0;
 668 }