git.oblomov.eu Git - linux-2.6/blob - 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 <asm/cacheflush.h>
  28 #include <asm/kdebug.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 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  37 {
  38         /* Make sure the probe isn't going on a difficult instruction */
  39         if (is_prohibited_opcode((kprobe_opcode_t *) p->addr))
  40                 return -EINVAL;
  41
  42         if ((unsigned long)p->addr & 0x01) {
  43                 printk("Attempt to register kprobe at an unaligned address\n");
  44                 return -EINVAL;
  45                 }
  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) >> 4) {
  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 *)ALIGN((unsigned long)args->ptr, 4);
 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_run(swap_instruction, &args, NR_CPUS);
 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_run(swap_instruction, &args, NR_CPUS);
 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 /* Called with kretprobe_lock held */
 274 void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
 275                                         struct pt_regs *regs)
 276 {
 277         struct kretprobe_instance *ri;
 278
 279         if ((ri = get_free_rp_inst(rp)) != NULL) {
 280                 ri->rp = rp;
 281                 ri->task = current;
 282                 ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
 283
 284                 /* Replace the return addr with trampoline addr */
 285                 regs->gprs[14] = (unsigned long)&kretprobe_trampoline;
 286
 287                 add_rp_inst(ri);
 288         } else {
 289                 rp->nmissed++;
 290         }
 291 }
 292
 293 static int __kprobes kprobe_handler(struct pt_regs *regs)
 294 {
 295         struct kprobe *p;
 296         int ret = 0;
 297         unsigned long *addr = (unsigned long *)
 298                 ((regs->psw.addr & PSW_ADDR_INSN) - 2);
 299         struct kprobe_ctlblk *kcb;
 300
 301         /*
 302          * We don't want to be preempted for the entire
 303          * duration of kprobe processing
 304          */
 305         preempt_disable();
 306         kcb = get_kprobe_ctlblk();
 307
 308         /* Check we're not actually recursing */
 309         if (kprobe_running()) {
 310                 p = get_kprobe(addr);
 311                 if (p) {
 312                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
 313                             *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
 314                                 regs->psw.mask &= ~PSW_MASK_PER;
 315                                 regs->psw.mask |= kcb->kprobe_saved_imask;
 316                                 goto no_kprobe;
 317                         }
 318                         /* We have reentered the kprobe_handler(), since
 319                          * another probe was hit while within the handler.
 320                          * We here save the original kprobes variables and
 321                          * just single step on the instruction of the new probe
 322                          * without calling any user handlers.
 323                          */
 324                         save_previous_kprobe(kcb);
 325                         set_current_kprobe(p, regs, kcb);
 326                         kprobes_inc_nmissed_count(p);
 327                         prepare_singlestep(p, regs);
 328                         kcb->kprobe_status = KPROBE_REENTER;
 329                         return 1;
 330                 } else {
 331                         p = __get_cpu_var(current_kprobe);
 332                         if (p->break_handler && p->break_handler(p, regs)) {
 333                                 goto ss_probe;
 334                         }
 335                 }
 336                 goto no_kprobe;
 337         }
 338
 339         p = get_kprobe(addr);
 340         if (!p) {
 341                 if (*addr != BREAKPOINT_INSTRUCTION) {
 342                         /*
 343                          * The breakpoint instruction was removed right
 344                          * after we hit it.  Another cpu has removed
 345                          * either a probepoint or a debugger breakpoint
 346                          * at this address.  In either case, no further
 347                          * handling of this interrupt is appropriate.
 348                          *
 349                          */
 350                         ret = 1;
 351                 }
 352                 /* Not one of ours: let kernel handle it */
 353                 goto no_kprobe;
 354         }
 355
 356         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 357         set_current_kprobe(p, regs, kcb);
 358         if (p->pre_handler && p->pre_handler(p, regs))
 359                 /* handler has already set things up, so skip ss setup */
 360                 return 1;
 361
 362 ss_probe:
 363         prepare_singlestep(p, regs);
 364         kcb->kprobe_status = KPROBE_HIT_SS;
 365         return 1;
 366
 367 no_kprobe:
 368         preempt_enable_no_resched();
 369         return ret;
 370 }
 371
 372 /*
 373  * Function return probe trampoline:
 374  *      - init_kprobes() establishes a probepoint here
 375  *      - When the probed function returns, this probe
 376  *              causes the handlers to fire
 377  */
 378 void kretprobe_trampoline_holder(void)
 379 {
 380         asm volatile(".global kretprobe_trampoline\n"
 381                      "kretprobe_trampoline: bcr 0,0\n");
 382 }
 383
 384 /*
 385  * Called when the probe at kretprobe trampoline is hit
 386  */
 387 static int __kprobes trampoline_probe_handler(struct kprobe *p,
 388                                               struct pt_regs *regs)
 389 {
 390         struct kretprobe_instance *ri = NULL;
 391         struct hlist_head *head, empty_rp;
 392         struct hlist_node *node, *tmp;
 393         unsigned long flags, orig_ret_address = 0;
 394         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 395
 396         INIT_HLIST_HEAD(&empty_rp);
 397         spin_lock_irqsave(&kretprobe_lock, flags);
 398         head = kretprobe_inst_table_head(current);
 399
 400         /*
 401          * It is possible to have multiple instances associated with a given
 402          * task either because an multiple functions in the call path
 403          * have a return probe installed on them, and/or more then one return
 404          * return probe was registered for a target function.
 405          *
 406          * We can handle this because:
 407          *     - instances are always inserted at the head of the list
 408          *     - when multiple return probes are registered for the same
 409          *       function, the first instance's ret_addr will point to the
 410          *       real return address, and all the rest will point to
 411          *       kretprobe_trampoline
 412          */
 413         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
 414                 if (ri->task != current)
 415                         /* another task is sharing our hash bucket */
 416                         continue;
 417
 418                 if (ri->rp && ri->rp->handler)
 419                         ri->rp->handler(ri, regs);
 420
 421                 orig_ret_address = (unsigned long)ri->ret_addr;
 422                 recycle_rp_inst(ri, &empty_rp);
 423
 424                 if (orig_ret_address != trampoline_address) {
 425                         /*
 426                          * This is the real return address. Any other
 427                          * instances associated with this task are for
 428                          * other calls deeper on the call stack
 429                          */
 430                         break;
 431                 }
 432         }
 433         BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
 434         regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE;
 435
 436         reset_current_kprobe();
 437         spin_unlock_irqrestore(&kretprobe_lock, flags);
 438         preempt_enable_no_resched();
 439
 440         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
 441                 hlist_del(&ri->hlist);
 442                 kfree(ri);
 443         }
 444         /*
 445          * By returning a non-zero value, we are telling
 446          * kprobe_handler() that we don't want the post_handler
 447          * to run (and have re-enabled preemption)
 448          */
 449         return 1;
 450 }
 451
 452 /*
 453  * Called after single-stepping.  p->addr is the address of the
 454  * instruction whose first byte has been replaced by the "breakpoint"
 455  * instruction.  To avoid the SMP problems that can occur when we
 456  * temporarily put back the original opcode to single-step, we
 457  * single-stepped a copy of the instruction.  The address of this
 458  * copy is p->ainsn.insn.
 459  */
 460 static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
 461 {
 462         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 463
 464         regs->psw.addr &= PSW_ADDR_INSN;
 465
 466         if (p->ainsn.fixup & FIXUP_PSW_NORMAL)
 467                 regs->psw.addr = (unsigned long)p->addr +
 468                                 ((unsigned long)regs->psw.addr -
 469                                  (unsigned long)p->ainsn.insn);
 470
 471         if (p->ainsn.fixup & FIXUP_BRANCH_NOT_TAKEN)
 472                 if ((unsigned long)regs->psw.addr -
 473                     (unsigned long)p->ainsn.insn == p->ainsn.ilen)
 474                         regs->psw.addr = (unsigned long)p->addr + p->ainsn.ilen;
 475
 476         if (p->ainsn.fixup & FIXUP_RETURN_REGISTER)
 477                 regs->gprs[p->ainsn.reg] = ((unsigned long)p->addr +
 478                                                 (regs->gprs[p->ainsn.reg] -
 479                                                 (unsigned long)p->ainsn.insn))
 480                                                 | PSW_ADDR_AMODE;
 481
 482         regs->psw.addr |= PSW_ADDR_AMODE;
 483         /* turn off PER mode */
 484         regs->psw.mask &= ~PSW_MASK_PER;
 485         /* Restore the original per control regs */
 486         __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
 487         regs->psw.mask |= kcb->kprobe_saved_imask;
 488 }
 489
 490 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 491 {
 492         struct kprobe *cur = kprobe_running();
 493         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 494
 495         if (!cur)
 496                 return 0;
 497
 498         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 499                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 500                 cur->post_handler(cur, regs, 0);
 501         }
 502
 503         resume_execution(cur, regs);
 504
 505         /*Restore back the original saved kprobes variables and continue. */
 506         if (kcb->kprobe_status == KPROBE_REENTER) {
 507                 restore_previous_kprobe(kcb);
 508                 goto out;
 509         }
 510         reset_current_kprobe();
 511 out:
 512         preempt_enable_no_resched();
 513
 514         /*
 515          * if somebody else is singlestepping across a probe point, psw mask
 516          * will have PER set, in which case, continue the remaining processing
 517          * of do_single_step, as if this is not a probe hit.
 518          */
 519         if (regs->psw.mask & PSW_MASK_PER) {
 520                 return 0;
 521         }
 522
 523         return 1;
 524 }
 525
 526 static int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 527 {
 528         struct kprobe *cur = kprobe_running();
 529         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 530         const struct exception_table_entry *entry;
 531
 532         switch(kcb->kprobe_status) {
 533         case KPROBE_SWAP_INST:
 534                 /* We are here because the instruction replacement failed */
 535                 return 0;
 536         case KPROBE_HIT_SS:
 537         case KPROBE_REENTER:
 538                 /*
 539                  * We are here because the instruction being single
 540                  * stepped caused a page fault. We reset the current
 541                  * kprobe and the nip points back to the probe address
 542                  * and allow the page fault handler to continue as a
 543                  * normal page fault.
 544                  */
 545                 regs->psw.addr = (unsigned long)cur->addr | PSW_ADDR_AMODE;
 546                 regs->psw.mask &= ~PSW_MASK_PER;
 547                 regs->psw.mask |= kcb->kprobe_saved_imask;
 548                 if (kcb->kprobe_status == KPROBE_REENTER)
 549                         restore_previous_kprobe(kcb);
 550                 else
 551                         reset_current_kprobe();
 552                 preempt_enable_no_resched();
 553                 break;
 554         case KPROBE_HIT_ACTIVE:
 555         case KPROBE_HIT_SSDONE:
 556                 /*
 557                  * We increment the nmissed count for accounting,
 558                  * we can also use npre/npostfault count for accouting
 559                  * these specific fault cases.
 560                  */
 561                 kprobes_inc_nmissed_count(cur);
 562
 563                 /*
 564                  * We come here because instructions in the pre/post
 565                  * handler caused the page_fault, this could happen
 566                  * if handler tries to access user space by
 567                  * copy_from_user(), get_user() etc. Let the
 568                  * user-specified handler try to fix it first.
 569                  */
 570                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 571                         return 1;
 572
 573                 /*
 574                  * In case the user-specified fault handler returned
 575                  * zero, try to fix up.
 576                  */
 577                 entry = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
 578                 if (entry) {
 579                         regs->psw.addr = entry->fixup | PSW_ADDR_AMODE;
 580                         return 1;
 581                 }
 582
 583                 /*
 584                  * fixup_exception() could not handle it,
 585                  * Let do_page_fault() fix it.
 586                  */
 587                 break;
 588         default:
 589                 break;
 590         }
 591         return 0;
 592 }
 593
 594 /*
 595  * Wrapper routine to for handling exceptions.
 596  */
 597 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 598                                        unsigned long val, void *data)
 599 {
 600         struct die_args *args = (struct die_args *)data;
 601         int ret = NOTIFY_DONE;
 602
 603         switch (val) {
 604         case DIE_BPT:
 605                 if (kprobe_handler(args->regs))
 606                         ret = NOTIFY_STOP;
 607                 break;
 608         case DIE_SSTEP:
 609                 if (post_kprobe_handler(args->regs))
 610                         ret = NOTIFY_STOP;
 611                 break;
 612         case DIE_TRAP:
 613         case DIE_PAGE_FAULT:
 614                 /* kprobe_running() needs smp_processor_id() */
 615                 preempt_disable();
 616                 if (kprobe_running() &&
 617                     kprobe_fault_handler(args->regs, args->trapnr))
 618                         ret = NOTIFY_STOP;
 619                 preempt_enable();
 620                 break;
 621         default:
 622                 break;
 623         }
 624         return ret;
 625 }
 626
 627 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 628 {
 629         struct jprobe *jp = container_of(p, struct jprobe, kp);
 630         unsigned long addr;
 631         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 632
 633         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
 634
 635         /* setup return addr to the jprobe handler routine */
 636         regs->psw.addr = (unsigned long)(jp->entry) | PSW_ADDR_AMODE;
 637
 638         /* r14 is the function return address */
 639         kcb->jprobe_saved_r14 = (unsigned long)regs->gprs[14];
 640         /* r15 is the stack pointer */
 641         kcb->jprobe_saved_r15 = (unsigned long)regs->gprs[15];
 642         addr = (unsigned long)kcb->jprobe_saved_r15;
 643
 644         memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr,
 645                MIN_STACK_SIZE(addr));
 646         return 1;
 647 }
 648
 649 void __kprobes jprobe_return(void)
 650 {
 651         asm volatile(".word 0x0002");
 652 }
 653
 654 void __kprobes jprobe_return_end(void)
 655 {
 656         asm volatile("bcr 0,0");
 657 }
 658
 659 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 660 {
 661         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 662         unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_r15);
 663
 664         /* Put the regs back */
 665         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
 666         /* put the stack back */
 667         memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
 668                MIN_STACK_SIZE(stack_addr));
 669         preempt_enable_no_resched();
 670         return 1;
 671 }
 672
 673 static struct kprobe trampoline_p = {
 674         .addr = (kprobe_opcode_t *) & kretprobe_trampoline,
 675         .pre_handler = trampoline_probe_handler
 676 };
 677
 678 int __init arch_init_kprobes(void)
 679 {
 680         return register_kprobe(&trampoline_p);
 681 }