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                 printk("Attempt to register kprobe at an unaligned address\n");
  46                 return -EINVAL;
  47                 }
  48
  49         /* Use the get_insn_slot() facility for correctness */
  50         if (!(p->ainsn.insn = get_insn_slot()))
  51                 return -ENOMEM;
  52
  53         memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
  54
  55         get_instruction_type(&p->ainsn);
  56         p->opcode = *p->addr;
  57         return 0;
  58 }
  59
  60 int __kprobes is_prohibited_opcode(kprobe_opcode_t *instruction)
  61 {
  62         switch (*(__u8 *) instruction) {
  63         case 0x0c:      /* bassm */
  64         case 0x0b:      /* bsm   */
  65         case 0x83:      /* diag  */
  66         case 0x44:      /* ex    */
  67                 return -EINVAL;
  68         }
  69         switch (*(__u16 *) instruction) {
  70         case 0x0101:    /* pr    */
  71         case 0xb25a:    /* bsa   */
  72         case 0xb240:    /* bakr  */
  73         case 0xb258:    /* bsg   */
  74         case 0xb218:    /* pc    */
  75         case 0xb228:    /* pt    */
  76                 return -EINVAL;
  77         }
  78         return 0;
  79 }
  80
  81 void __kprobes get_instruction_type(struct arch_specific_insn *ainsn)
  82 {
  83         /* default fixup method */
  84         ainsn->fixup = FIXUP_PSW_NORMAL;
  85
  86         /* save r1 operand */
  87         ainsn->reg = (*ainsn->insn & 0xf0) >> 4;
  88
  89         /* save the instruction length (pop 5-5) in bytes */
  90         switch (*(__u8 *) (ainsn->insn) >> 6) {
  91         case 0:
  92                 ainsn->ilen = 2;
  93                 break;
  94         case 1:
  95         case 2:
  96                 ainsn->ilen = 4;
  97                 break;
  98         case 3:
  99                 ainsn->ilen = 6;
 100                 break;
 101         }
 102
 103         switch (*(__u8 *) ainsn->insn) {
 104         case 0x05:      /* balr */
 105         case 0x0d:      /* basr */
 106                 ainsn->fixup = FIXUP_RETURN_REGISTER;
 107                 /* if r2 = 0, no branch will be taken */
 108                 if ((*ainsn->insn & 0x0f) == 0)
 109                         ainsn->fixup |= FIXUP_BRANCH_NOT_TAKEN;
 110                 break;
 111         case 0x06:      /* bctr */
 112         case 0x07:      /* bcr  */
 113                 ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
 114                 break;
 115         case 0x45:      /* bal  */
 116         case 0x4d:      /* bas  */
 117                 ainsn->fixup = FIXUP_RETURN_REGISTER;
 118                 break;
 119         case 0x47:      /* bc   */
 120         case 0x46:      /* bct  */
 121         case 0x86:      /* bxh  */
 122         case 0x87:      /* bxle */
 123                 ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
 124                 break;
 125         case 0x82:      /* lpsw */
 126                 ainsn->fixup = FIXUP_NOT_REQUIRED;
 127                 break;
 128         case 0xb2:      /* lpswe */
 129                 if (*(((__u8 *) ainsn->insn) + 1) == 0xb2) {
 130                         ainsn->fixup = FIXUP_NOT_REQUIRED;
 131                 }
 132                 break;
 133         case 0xa7:      /* bras */
 134                 if ((*ainsn->insn & 0x0f) == 0x05) {
 135                         ainsn->fixup |= FIXUP_RETURN_REGISTER;
 136                 }
 137                 break;
 138         case 0xc0:
 139                 if ((*ainsn->insn & 0x0f) == 0x00  /* larl  */
 140                         || (*ainsn->insn & 0x0f) == 0x05) /* brasl */
 141                 ainsn->fixup |= FIXUP_RETURN_REGISTER;
 142                 break;
 143         case 0xeb:
 144                 if (*(((__u8 *) ainsn->insn) + 5 ) == 0x44 ||   /* bxhg  */
 145                         *(((__u8 *) ainsn->insn) + 5) == 0x45) {/* bxleg */
 146                         ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
 147                 }
 148                 break;
 149         case 0xe3:      /* bctg */
 150                 if (*(((__u8 *) ainsn->insn) + 5) == 0x46) {
 151                         ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
 152                 }
 153                 break;
 154         }
 155 }
 156
 157 static int __kprobes swap_instruction(void *aref)
 158 {
 159         struct ins_replace_args *args = aref;
 160         u32 *addr;
 161         u32 instr;
 162         int err = -EFAULT;
 163
 164         /*
 165          * Text segment is read-only, hence we use stura to bypass dynamic
 166          * address translation to exchange the instruction. Since stura
 167          * always operates on four bytes, but we only want to exchange two
 168          * bytes do some calculations to get things right. In addition we
 169          * shall not cross any page boundaries (vmalloc area!) when writing
 170          * the new instruction.
 171          */
 172         addr = (u32 *)((unsigned long)args->ptr & -4UL);
 173         if ((unsigned long)args->ptr & 2)
 174                 instr = ((*addr) & 0xffff0000) | args->new;
 175         else
 176                 instr = ((*addr) & 0x0000ffff) | args->new << 16;
 177
 178         asm volatile(
 179                 "       lra     %1,0(%1)\n"
 180                 "0:     stura   %2,%1\n"
 181                 "1:     la      %0,0\n"
 182                 "2:\n"
 183                 EX_TABLE(0b,2b)
 184                 : "+d" (err)
 185                 : "a" (addr), "d" (instr)
 186                 : "memory", "cc");
 187
 188         return err;
 189 }
 190
 191 void __kprobes arch_arm_kprobe(struct kprobe *p)
 192 {
 193         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 194         unsigned long status = kcb->kprobe_status;
 195         struct ins_replace_args args;
 196
 197         args.ptr = p->addr;
 198         args.old = p->opcode;
 199         args.new = BREAKPOINT_INSTRUCTION;
 200
 201         kcb->kprobe_status = KPROBE_SWAP_INST;
 202         stop_machine_run(swap_instruction, &args, NR_CPUS);
 203         kcb->kprobe_status = status;
 204 }
 205
 206 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 207 {
 208         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 209         unsigned long status = kcb->kprobe_status;
 210         struct ins_replace_args args;
 211
 212         args.ptr = p->addr;
 213         args.old = BREAKPOINT_INSTRUCTION;
 214         args.new = p->opcode;
 215
 216         kcb->kprobe_status = KPROBE_SWAP_INST;
 217         stop_machine_run(swap_instruction, &args, NR_CPUS);
 218         kcb->kprobe_status = status;
 219 }
 220
 221 void __kprobes arch_remove_kprobe(struct kprobe *p)
 222 {
 223         mutex_lock(&kprobe_mutex);
 224         free_insn_slot(p->ainsn.insn, 0);
 225         mutex_unlock(&kprobe_mutex);
 226 }
 227
 228 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 229 {
 230         per_cr_bits kprobe_per_regs[1];
 231
 232         memset(kprobe_per_regs, 0, sizeof(per_cr_bits));
 233         regs->psw.addr = (unsigned long)p->ainsn.insn | PSW_ADDR_AMODE;
 234
 235         /* Set up the per control reg info, will pass to lctl */
 236         kprobe_per_regs[0].em_instruction_fetch = 1;
 237         kprobe_per_regs[0].starting_addr = (unsigned long)p->ainsn.insn;
 238         kprobe_per_regs[0].ending_addr = (unsigned long)p->ainsn.insn + 1;
 239
 240         /* Set the PER control regs, turns on single step for this address */
 241         __ctl_load(kprobe_per_regs, 9, 11);
 242         regs->psw.mask |= PSW_MASK_PER;
 243         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK);
 244 }
 245
 246 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 247 {
 248         kcb->prev_kprobe.kp = kprobe_running();
 249         kcb->prev_kprobe.status = kcb->kprobe_status;
 250         kcb->prev_kprobe.kprobe_saved_imask = kcb->kprobe_saved_imask;
 251         memcpy(kcb->prev_kprobe.kprobe_saved_ctl, kcb->kprobe_saved_ctl,
 252                                         sizeof(kcb->kprobe_saved_ctl));
 253 }
 254
 255 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 256 {
 257         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
 258         kcb->kprobe_status = kcb->prev_kprobe.status;
 259         kcb->kprobe_saved_imask = kcb->prev_kprobe.kprobe_saved_imask;
 260         memcpy(kcb->kprobe_saved_ctl, kcb->prev_kprobe.kprobe_saved_ctl,
 261                                         sizeof(kcb->kprobe_saved_ctl));
 262 }
 263
 264 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 265                                                 struct kprobe_ctlblk *kcb)
 266 {
 267         __get_cpu_var(current_kprobe) = p;
 268         /* Save the interrupt and per flags */
 269         kcb->kprobe_saved_imask = regs->psw.mask &
 270             (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK);
 271         /* Save the control regs that govern PER */
 272         __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
 273 }
 274
 275 /* Called with kretprobe_lock held */
 276 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 277                                         struct pt_regs *regs)
 278 {
 279         ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
 280
 281         /* Replace the return addr with trampoline addr */
 282         regs->gprs[14] = (unsigned long)&kretprobe_trampoline;
 283 }
 284
 285 static int __kprobes kprobe_handler(struct pt_regs *regs)
 286 {
 287         struct kprobe *p;
 288         int ret = 0;
 289         unsigned long *addr = (unsigned long *)
 290                 ((regs->psw.addr & PSW_ADDR_INSN) - 2);
 291         struct kprobe_ctlblk *kcb;
 292
 293         /*
 294          * We don't want to be preempted for the entire
 295          * duration of kprobe processing
 296          */
 297         preempt_disable();
 298         kcb = get_kprobe_ctlblk();
 299
 300         /* Check we're not actually recursing */
 301         if (kprobe_running()) {
 302                 p = get_kprobe(addr);
 303                 if (p) {
 304                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
 305                             *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
 306                                 regs->psw.mask &= ~PSW_MASK_PER;
 307                                 regs->psw.mask |= kcb->kprobe_saved_imask;
 308                                 goto no_kprobe;
 309                         }
 310                         /* We have reentered the kprobe_handler(), since
 311                          * another probe was hit while within the handler.
 312                          * We here save the original kprobes variables and
 313                          * just single step on the instruction of the new probe
 314                          * without calling any user handlers.
 315                          */
 316                         save_previous_kprobe(kcb);
 317                         set_current_kprobe(p, regs, kcb);
 318                         kprobes_inc_nmissed_count(p);
 319                         prepare_singlestep(p, regs);
 320                         kcb->kprobe_status = KPROBE_REENTER;
 321                         return 1;
 322                 } else {
 323                         p = __get_cpu_var(current_kprobe);
 324                         if (p->break_handler && p->break_handler(p, regs)) {
 325                                 goto ss_probe;
 326                         }
 327                 }
 328                 goto no_kprobe;
 329         }
 330
 331         p = get_kprobe(addr);
 332         if (!p)
 333                 /*
 334                  * No kprobe at this address. The fault has not been
 335                  * caused by a kprobe breakpoint. The race of breakpoint
 336                  * vs. kprobe remove does not exist because on s390 we
 337                  * use stop_machine_run to arm/disarm the breakpoints.
 338                  */
 339                 goto no_kprobe;
 340
 341         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 342         set_current_kprobe(p, regs, kcb);
 343         if (p->pre_handler && p->pre_handler(p, regs))
 344                 /* handler has already set things up, so skip ss setup */
 345                 return 1;
 346
 347 ss_probe:
 348         prepare_singlestep(p, regs);
 349         kcb->kprobe_status = KPROBE_HIT_SS;
 350         return 1;
 351
 352 no_kprobe:
 353         preempt_enable_no_resched();
 354         return ret;
 355 }
 356
 357 /*
 358  * Function return probe trampoline:
 359  *      - init_kprobes() establishes a probepoint here
 360  *      - When the probed function returns, this probe
 361  *              causes the handlers to fire
 362  */
 363 void kretprobe_trampoline_holder(void)
 364 {
 365         asm volatile(".global kretprobe_trampoline\n"
 366                      "kretprobe_trampoline: bcr 0,0\n");
 367 }
 368
 369 /*
 370  * Called when the probe at kretprobe trampoline is hit
 371  */
 372 static int __kprobes trampoline_probe_handler(struct kprobe *p,
 373                                               struct pt_regs *regs)
 374 {
 375         struct kretprobe_instance *ri = NULL;
 376         struct hlist_head *head, empty_rp;
 377         struct hlist_node *node, *tmp;
 378         unsigned long flags, orig_ret_address = 0;
 379         unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 380
 381         INIT_HLIST_HEAD(&empty_rp);
 382         spin_lock_irqsave(&kretprobe_lock, flags);
 383         head = kretprobe_inst_table_head(current);
 384
 385         /*
 386          * It is possible to have multiple instances associated with a given
 387          * task either because an multiple functions in the call path
 388          * have a return probe installed on them, and/or more then one return
 389          * return probe was registered for a target function.
 390          *
 391          * We can handle this because:
 392          *     - instances are always inserted at the head of the list
 393          *     - when multiple return probes are registered for the same
 394          *       function, the first instance's ret_addr will point to the
 395          *       real return address, and all the rest will point to
 396          *       kretprobe_trampoline
 397          */
 398         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
 399                 if (ri->task != current)
 400                         /* another task is sharing our hash bucket */
 401                         continue;
 402
 403                 if (ri->rp && ri->rp->handler)
 404                         ri->rp->handler(ri, regs);
 405
 406                 orig_ret_address = (unsigned long)ri->ret_addr;
 407                 recycle_rp_inst(ri, &empty_rp);
 408
 409                 if (orig_ret_address != trampoline_address) {
 410                         /*
 411                          * This is the real return address. Any other
 412                          * instances associated with this task are for
 413                          * other calls deeper on the call stack
 414                          */
 415                         break;
 416                 }
 417         }
 418         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 419         regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE;
 420
 421         reset_current_kprobe();
 422         spin_unlock_irqrestore(&kretprobe_lock, flags);
 423         preempt_enable_no_resched();
 424
 425         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
 426                 hlist_del(&ri->hlist);
 427                 kfree(ri);
 428         }
 429         /*
 430          * By returning a non-zero value, we are telling
 431          * kprobe_handler() that we don't want the post_handler
 432          * to run (and have re-enabled preemption)
 433          */
 434         return 1;
 435 }
 436
 437 /*
 438  * Called after single-stepping.  p->addr is the address of the
 439  * instruction whose first byte has been replaced by the "breakpoint"
 440  * instruction.  To avoid the SMP problems that can occur when we
 441  * temporarily put back the original opcode to single-step, we
 442  * single-stepped a copy of the instruction.  The address of this
 443  * copy is p->ainsn.insn.
 444  */
 445 static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
 446 {
 447         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 448
 449         regs->psw.addr &= PSW_ADDR_INSN;
 450
 451         if (p->ainsn.fixup & FIXUP_PSW_NORMAL)
 452                 regs->psw.addr = (unsigned long)p->addr +
 453                                 ((unsigned long)regs->psw.addr -
 454                                  (unsigned long)p->ainsn.insn);
 455
 456         if (p->ainsn.fixup & FIXUP_BRANCH_NOT_TAKEN)
 457                 if ((unsigned long)regs->psw.addr -
 458                     (unsigned long)p->ainsn.insn == p->ainsn.ilen)
 459                         regs->psw.addr = (unsigned long)p->addr + p->ainsn.ilen;
 460
 461         if (p->ainsn.fixup & FIXUP_RETURN_REGISTER)
 462                 regs->gprs[p->ainsn.reg] = ((unsigned long)p->addr +
 463                                                 (regs->gprs[p->ainsn.reg] -
 464                                                 (unsigned long)p->ainsn.insn))
 465                                                 | PSW_ADDR_AMODE;
 466
 467         regs->psw.addr |= PSW_ADDR_AMODE;
 468         /* turn off PER mode */
 469         regs->psw.mask &= ~PSW_MASK_PER;
 470         /* Restore the original per control regs */
 471         __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
 472         regs->psw.mask |= kcb->kprobe_saved_imask;
 473 }
 474
 475 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 476 {
 477         struct kprobe *cur = kprobe_running();
 478         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 479
 480         if (!cur)
 481                 return 0;
 482
 483         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 484                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 485                 cur->post_handler(cur, regs, 0);
 486         }
 487
 488         resume_execution(cur, regs);
 489
 490         /*Restore back the original saved kprobes variables and continue. */
 491         if (kcb->kprobe_status == KPROBE_REENTER) {
 492                 restore_previous_kprobe(kcb);
 493                 goto out;
 494         }
 495         reset_current_kprobe();
 496 out:
 497         preempt_enable_no_resched();
 498
 499         /*
 500          * if somebody else is singlestepping across a probe point, psw mask
 501          * will have PER set, in which case, continue the remaining processing
 502          * of do_single_step, as if this is not a probe hit.
 503          */
 504         if (regs->psw.mask & PSW_MASK_PER) {
 505                 return 0;
 506         }
 507
 508         return 1;
 509 }
 510
 511 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 512 {
 513         struct kprobe *cur = kprobe_running();
 514         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 515         const struct exception_table_entry *entry;
 516
 517         switch(kcb->kprobe_status) {
 518         case KPROBE_SWAP_INST:
 519                 /* We are here because the instruction replacement failed */
 520                 return 0;
 521         case KPROBE_HIT_SS:
 522         case KPROBE_REENTER:
 523                 /*
 524                  * We are here because the instruction being single
 525                  * stepped caused a page fault. We reset the current
 526                  * kprobe and the nip points back to the probe address
 527                  * and allow the page fault handler to continue as a
 528                  * normal page fault.
 529                  */
 530                 regs->psw.addr = (unsigned long)cur->addr | PSW_ADDR_AMODE;
 531                 regs->psw.mask &= ~PSW_MASK_PER;
 532                 regs->psw.mask |= kcb->kprobe_saved_imask;
 533                 if (kcb->kprobe_status == KPROBE_REENTER)
 534                         restore_previous_kprobe(kcb);
 535                 else
 536                         reset_current_kprobe();
 537                 preempt_enable_no_resched();
 538                 break;
 539         case KPROBE_HIT_ACTIVE:
 540         case KPROBE_HIT_SSDONE:
 541                 /*
 542                  * We increment the nmissed count for accounting,
 543                  * we can also use npre/npostfault count for accouting
 544                  * these specific fault cases.
 545                  */
 546                 kprobes_inc_nmissed_count(cur);
 547
 548                 /*
 549                  * We come here because instructions in the pre/post
 550                  * handler caused the page_fault, this could happen
 551                  * if handler tries to access user space by
 552                  * copy_from_user(), get_user() etc. Let the
 553                  * user-specified handler try to fix it first.
 554                  */
 555                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 556                         return 1;
 557
 558                 /*
 559                  * In case the user-specified fault handler returned
 560                  * zero, try to fix up.
 561                  */
 562                 entry = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
 563                 if (entry) {
 564                         regs->psw.addr = entry->fixup | PSW_ADDR_AMODE;
 565                         return 1;
 566                 }
 567
 568                 /*
 569                  * fixup_exception() could not handle it,
 570                  * Let do_page_fault() fix it.
 571                  */
 572                 break;
 573         default:
 574                 break;
 575         }
 576         return 0;
 577 }
 578
 579 /*
 580  * Wrapper routine to for handling exceptions.
 581  */
 582 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 583                                        unsigned long val, void *data)
 584 {
 585         struct die_args *args = (struct die_args *)data;
 586         int ret = NOTIFY_DONE;
 587
 588         switch (val) {
 589         case DIE_BPT:
 590                 if (kprobe_handler(args->regs))
 591                         ret = NOTIFY_STOP;
 592                 break;
 593         case DIE_SSTEP:
 594                 if (post_kprobe_handler(args->regs))
 595                         ret = NOTIFY_STOP;
 596                 break;
 597         case DIE_TRAP:
 598                 /* kprobe_running() needs smp_processor_id() */
 599                 preempt_disable();
 600                 if (kprobe_running() &&
 601                     kprobe_fault_handler(args->regs, args->trapnr))
 602                         ret = NOTIFY_STOP;
 603                 preempt_enable();
 604                 break;
 605         default:
 606                 break;
 607         }
 608         return ret;
 609 }
 610
 611 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 612 {
 613         struct jprobe *jp = container_of(p, struct jprobe, kp);
 614         unsigned long addr;
 615         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 616
 617         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
 618
 619         /* setup return addr to the jprobe handler routine */
 620         regs->psw.addr = (unsigned long)(jp->entry) | PSW_ADDR_AMODE;
 621
 622         /* r14 is the function return address */
 623         kcb->jprobe_saved_r14 = (unsigned long)regs->gprs[14];
 624         /* r15 is the stack pointer */
 625         kcb->jprobe_saved_r15 = (unsigned long)regs->gprs[15];
 626         addr = (unsigned long)kcb->jprobe_saved_r15;
 627
 628         memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr,
 629                MIN_STACK_SIZE(addr));
 630         return 1;
 631 }
 632
 633 void __kprobes jprobe_return(void)
 634 {
 635         asm volatile(".word 0x0002");
 636 }
 637
 638 void __kprobes jprobe_return_end(void)
 639 {
 640         asm volatile("bcr 0,0");
 641 }
 642
 643 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 644 {
 645         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 646         unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_r15);
 647
 648         /* Put the regs back */
 649         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
 650         /* put the stack back */
 651         memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
 652                MIN_STACK_SIZE(stack_addr));
 653         preempt_enable_no_resched();
 654         return 1;
 655 }
 656
 657 static struct kprobe trampoline_p = {
 658         .addr = (kprobe_opcode_t *) & kretprobe_trampoline,
 659         .pre_handler = trampoline_probe_handler
 660 };
 661
 662 int __init arch_init_kprobes(void)
 663 {
 664         return register_kprobe(&trampoline_p);
 665 }
 666
 667 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 668 {
 669         if (p->addr == (kprobe_opcode_t *) & kretprobe_trampoline)
 670                 return 1;
 671         return 0;
 672 }