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 IBM Corp. 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 <linux/module.h>
  30 #include <linux/slab.h>
  31 #include <linux/hardirq.h>
  32 #include <asm/cacheflush.h>
  33 #include <asm/sections.h>
  34 #include <asm/dis.h>
  35
  36 DEFINE_PER_CPU(struct kprobe *, current_kprobe);
  37 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  38
  39 struct kretprobe_blackpoint kretprobe_blacklist[] = { };
  40
  41 DEFINE_INSN_CACHE_OPS(dmainsn);
  42
  43 static void *alloc_dmainsn_page(void)
  44 {
  45         return (void *)__get_free_page(GFP_KERNEL | GFP_DMA);
  46 }
  47
  48 static void free_dmainsn_page(void *page)
  49 {
  50         free_page((unsigned long)page);
  51 }
  52
  53 struct kprobe_insn_cache kprobe_dmainsn_slots = {
  54         .mutex = __MUTEX_INITIALIZER(kprobe_dmainsn_slots.mutex),
  55         .alloc = alloc_dmainsn_page,
  56         .free = free_dmainsn_page,
  57         .pages = LIST_HEAD_INIT(kprobe_dmainsn_slots.pages),
  58         .insn_size = MAX_INSN_SIZE,
  59 };
  60
  61 static int __kprobes is_prohibited_opcode(kprobe_opcode_t *insn)
  62 {
  63         if (!is_known_insn((unsigned char *)insn))
  64                 return -EINVAL;
  65         switch (insn[0] >> 8) {
  66         case 0x0c:      /* bassm */
  67         case 0x0b:      /* bsm   */
  68         case 0x83:      /* diag  */
  69         case 0x44:      /* ex    */
  70         case 0xac:      /* stnsm */
  71         case 0xad:      /* stosm */
  72                 return -EINVAL;
  73         case 0xc6:
  74                 switch (insn[0] & 0x0f) {
  75                 case 0x00: /* exrl   */
  76                         return -EINVAL;
  77                 }
  78         }
  79         switch (insn[0]) {
  80         case 0x0101:    /* pr    */
  81         case 0xb25a:    /* bsa   */
  82         case 0xb240:    /* bakr  */
  83         case 0xb258:    /* bsg   */
  84         case 0xb218:    /* pc    */
  85         case 0xb228:    /* pt    */
  86         case 0xb98d:    /* epsw  */
  87                 return -EINVAL;
  88         }
  89         return 0;
  90 }
  91
  92 static int __kprobes get_fixup_type(kprobe_opcode_t *insn)
  93 {
  94         /* default fixup method */
  95         int fixup = FIXUP_PSW_NORMAL;
  96
  97         switch (insn[0] >> 8) {
  98         case 0x05:      /* balr */
  99         case 0x0d:      /* basr */
 100                 fixup = FIXUP_RETURN_REGISTER;
 101                 /* if r2 = 0, no branch will be taken */
 102                 if ((insn[0] & 0x0f) == 0)
 103                         fixup |= FIXUP_BRANCH_NOT_TAKEN;
 104                 break;
 105         case 0x06:      /* bctr */
 106         case 0x07:      /* bcr  */
 107                 fixup = FIXUP_BRANCH_NOT_TAKEN;
 108                 break;
 109         case 0x45:      /* bal  */
 110         case 0x4d:      /* bas  */
 111                 fixup = FIXUP_RETURN_REGISTER;
 112                 break;
 113         case 0x47:      /* bc   */
 114         case 0x46:      /* bct  */
 115         case 0x86:      /* bxh  */
 116         case 0x87:      /* bxle */
 117                 fixup = FIXUP_BRANCH_NOT_TAKEN;
 118                 break;
 119         case 0x82:      /* lpsw */
 120                 fixup = FIXUP_NOT_REQUIRED;
 121                 break;
 122         case 0xb2:      /* lpswe */
 123                 if ((insn[0] & 0xff) == 0xb2)
 124                         fixup = FIXUP_NOT_REQUIRED;
 125                 break;
 126         case 0xa7:      /* bras */
 127                 if ((insn[0] & 0x0f) == 0x05)
 128                         fixup |= FIXUP_RETURN_REGISTER;
 129                 break;
 130         case 0xc0:
 131                 if ((insn[0] & 0x0f) == 0x05)   /* brasl */
 132                         fixup |= FIXUP_RETURN_REGISTER;
 133                 break;
 134         case 0xeb:
 135                 switch (insn[2] & 0xff) {
 136                 case 0x44: /* bxhg  */
 137                 case 0x45: /* bxleg */
 138                         fixup = FIXUP_BRANCH_NOT_TAKEN;
 139                         break;
 140                 }
 141                 break;
 142         case 0xe3:      /* bctg */
 143                 if ((insn[2] & 0xff) == 0x46)
 144                         fixup = FIXUP_BRANCH_NOT_TAKEN;
 145                 break;
 146         case 0xec:
 147                 switch (insn[2] & 0xff) {
 148                 case 0xe5: /* clgrb */
 149                 case 0xe6: /* cgrb  */
 150                 case 0xf6: /* crb   */
 151                 case 0xf7: /* clrb  */
 152                 case 0xfc: /* cgib  */
 153                 case 0xfd: /* cglib */
 154                 case 0xfe: /* cib   */
 155                 case 0xff: /* clib  */
 156                         fixup = FIXUP_BRANCH_NOT_TAKEN;
 157                         break;
 158                 }
 159                 break;
 160         }
 161         return fixup;
 162 }
 163
 164 static int __kprobes is_insn_relative_long(kprobe_opcode_t *insn)
 165 {
 166         /* Check if we have a RIL-b or RIL-c format instruction which
 167          * we need to modify in order to avoid instruction emulation. */
 168         switch (insn[0] >> 8) {
 169         case 0xc0:
 170                 if ((insn[0] & 0x0f) == 0x00) /* larl */
 171                         return true;
 172                 break;
 173         case 0xc4:
 174                 switch (insn[0] & 0x0f) {
 175                 case 0x02: /* llhrl  */
 176                 case 0x04: /* lghrl  */
 177                 case 0x05: /* lhrl   */
 178                 case 0x06: /* llghrl */
 179                 case 0x07: /* sthrl  */
 180                 case 0x08: /* lgrl   */
 181                 case 0x0b: /* stgrl  */
 182                 case 0x0c: /* lgfrl  */
 183                 case 0x0d: /* lrl    */
 184                 case 0x0e: /* llgfrl */
 185                 case 0x0f: /* strl   */
 186                         return true;
 187                 }
 188                 break;
 189         case 0xc6:
 190                 switch (insn[0] & 0x0f) {
 191                 case 0x02: /* pfdrl  */
 192                 case 0x04: /* cghrl  */
 193                 case 0x05: /* chrl   */
 194                 case 0x06: /* clghrl */
 195                 case 0x07: /* clhrl  */
 196                 case 0x08: /* cgrl   */
 197                 case 0x0a: /* clgrl  */
 198                 case 0x0c: /* cgfrl  */
 199                 case 0x0d: /* crl    */
 200                 case 0x0e: /* clgfrl */
 201                 case 0x0f: /* clrl   */
 202                         return true;
 203                 }
 204                 break;
 205         }
 206         return false;
 207 }
 208
 209 static void __kprobes copy_instruction(struct kprobe *p)
 210 {
 211         s64 disp, new_disp;
 212         u64 addr, new_addr;
 213
 214         memcpy(p->ainsn.insn, p->addr, insn_length(p->opcode >> 8));
 215         if (!is_insn_relative_long(p->ainsn.insn))
 216                 return;
 217         /*
 218          * For pc-relative instructions in RIL-b or RIL-c format patch the
 219          * RI2 displacement field. We have already made sure that the insn
 220          * slot for the patched instruction is within the same 2GB area
 221          * as the original instruction (either kernel image or module area).
 222          * Therefore the new displacement will always fit.
 223          */
 224         disp = *(s32 *)&p->ainsn.insn[1];
 225         addr = (u64)(unsigned long)p->addr;
 226         new_addr = (u64)(unsigned long)p->ainsn.insn;
 227         new_disp = ((addr + (disp * 2)) - new_addr) / 2;
 228         *(s32 *)&p->ainsn.insn[1] = new_disp;
 229 }
 230
 231 static inline int is_kernel_addr(void *addr)
 232 {
 233         return addr < (void *)_end;
 234 }
 235
 236 static inline int is_module_addr(void *addr)
 237 {
 238 #ifdef CONFIG_64BIT
 239         BUILD_BUG_ON(MODULES_LEN > (1UL << 31));
 240         if (addr < (void *)MODULES_VADDR)
 241                 return 0;
 242         if (addr > (void *)MODULES_END)
 243                 return 0;
 244 #endif
 245         return 1;
 246 }
 247
 248 static int __kprobes s390_get_insn_slot(struct kprobe *p)
 249 {
 250         /*
 251          * Get an insn slot that is within the same 2GB area like the original
 252          * instruction. That way instructions with a 32bit signed displacement
 253          * field can be patched and executed within the insn slot.
 254          */
 255         p->ainsn.insn = NULL;
 256         if (is_kernel_addr(p->addr))
 257                 p->ainsn.insn = get_dmainsn_slot();
 258         else if (is_module_addr(p->addr))
 259                 p->ainsn.insn = get_insn_slot();
 260         return p->ainsn.insn ? 0 : -ENOMEM;
 261 }
 262
 263 static void __kprobes s390_free_insn_slot(struct kprobe *p)
 264 {
 265         if (!p->ainsn.insn)
 266                 return;
 267         if (is_kernel_addr(p->addr))
 268                 free_dmainsn_slot(p->ainsn.insn, 0);
 269         else
 270                 free_insn_slot(p->ainsn.insn, 0);
 271         p->ainsn.insn = NULL;
 272 }
 273
 274 int __kprobes arch_prepare_kprobe(struct kprobe *p)
 275 {
 276         if ((unsigned long) p->addr & 0x01)
 277                 return -EINVAL;
 278         /* Make sure the probe isn't going on a difficult instruction */
 279         if (is_prohibited_opcode(p->addr))
 280                 return -EINVAL;
 281         if (s390_get_insn_slot(p))
 282                 return -ENOMEM;
 283         p->opcode = *p->addr;
 284         copy_instruction(p);
 285         return 0;
 286 }
 287
 288 struct ins_replace_args {
 289         kprobe_opcode_t *ptr;
 290         kprobe_opcode_t opcode;
 291 };
 292
 293 static int __kprobes swap_instruction(void *aref)
 294 {
 295         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 296         unsigned long status = kcb->kprobe_status;
 297         struct ins_replace_args *args = aref;
 298
 299         kcb->kprobe_status = KPROBE_SWAP_INST;
 300         probe_kernel_write(args->ptr, &args->opcode, sizeof(args->opcode));
 301         kcb->kprobe_status = status;
 302         return 0;
 303 }
 304
 305 void __kprobes arch_arm_kprobe(struct kprobe *p)
 306 {
 307         struct ins_replace_args args;
 308
 309         args.ptr = p->addr;
 310         args.opcode = BREAKPOINT_INSTRUCTION;
 311         stop_machine(swap_instruction, &args, NULL);
 312 }
 313
 314 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 315 {
 316         struct ins_replace_args args;
 317
 318         args.ptr = p->addr;
 319         args.opcode = p->opcode;
 320         stop_machine(swap_instruction, &args, NULL);
 321 }
 322
 323 void __kprobes arch_remove_kprobe(struct kprobe *p)
 324 {
 325         s390_free_insn_slot(p);
 326 }
 327
 328 static void __kprobes enable_singlestep(struct kprobe_ctlblk *kcb,
 329                                         struct pt_regs *regs,
 330                                         unsigned long ip)
 331 {
 332         struct per_regs per_kprobe;
 333
 334         /* Set up the PER control registers %cr9-%cr11 */
 335         per_kprobe.control = PER_EVENT_IFETCH;
 336         per_kprobe.start = ip;
 337         per_kprobe.end = ip;
 338
 339         /* Save control regs and psw mask */
 340         __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
 341         kcb->kprobe_saved_imask = regs->psw.mask &
 342                 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
 343
 344         /* Set PER control regs, turns on single step for the given address */
 345         __ctl_load(per_kprobe, 9, 11);
 346         regs->psw.mask |= PSW_MASK_PER;
 347         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
 348         regs->psw.addr = ip | PSW_ADDR_AMODE;
 349 }
 350
 351 static void __kprobes disable_singlestep(struct kprobe_ctlblk *kcb,
 352                                          struct pt_regs *regs,
 353                                          unsigned long ip)
 354 {
 355         /* Restore control regs and psw mask, set new psw address */
 356         __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
 357         regs->psw.mask &= ~PSW_MASK_PER;
 358         regs->psw.mask |= kcb->kprobe_saved_imask;
 359         regs->psw.addr = ip | PSW_ADDR_AMODE;
 360 }
 361
 362 /*
 363  * Activate a kprobe by storing its pointer to current_kprobe. The
 364  * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
 365  * two kprobes can be active, see KPROBE_REENTER.
 366  */
 367 static void __kprobes push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
 368 {
 369         kcb->prev_kprobe.kp = __get_cpu_var(current_kprobe);
 370         kcb->prev_kprobe.status = kcb->kprobe_status;
 371         __get_cpu_var(current_kprobe) = p;
 372 }
 373
 374 /*
 375  * Deactivate a kprobe by backing up to the previous state. If the
 376  * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
 377  * for any other state prev_kprobe.kp will be NULL.
 378  */
 379 static void __kprobes pop_kprobe(struct kprobe_ctlblk *kcb)
 380 {
 381         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
 382         kcb->kprobe_status = kcb->prev_kprobe.status;
 383 }
 384
 385 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 386                                         struct pt_regs *regs)
 387 {
 388         ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
 389
 390         /* Replace the return addr with trampoline addr */
 391         regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
 392 }
 393
 394 static void __kprobes kprobe_reenter_check(struct kprobe_ctlblk *kcb,
 395                                            struct kprobe *p)
 396 {
 397         switch (kcb->kprobe_status) {
 398         case KPROBE_HIT_SSDONE:
 399         case KPROBE_HIT_ACTIVE:
 400                 kprobes_inc_nmissed_count(p);
 401                 break;
 402         case KPROBE_HIT_SS:
 403         case KPROBE_REENTER:
 404         default:
 405                 /*
 406                  * A kprobe on the code path to single step an instruction
 407                  * is a BUG. The code path resides in the .kprobes.text
 408                  * section and is executed with interrupts disabled.
 409                  */
 410                 printk(KERN_EMERG "Invalid kprobe detected at %p.\n", p->addr);
 411                 dump_kprobe(p);
 412                 BUG();
 413         }
 414 }
 415
 416 static int __kprobes kprobe_handler(struct pt_regs *regs)
 417 {
 418         struct kprobe_ctlblk *kcb;
 419         struct kprobe *p;
 420
 421         /*
 422          * We want to disable preemption for the entire duration of kprobe
 423          * processing. That includes the calls to the pre/post handlers
 424          * and single stepping the kprobe instruction.
 425          */
 426         preempt_disable();
 427         kcb = get_kprobe_ctlblk();
 428         p = get_kprobe((void *)((regs->psw.addr & PSW_ADDR_INSN) - 2));
 429
 430         if (p) {
 431                 if (kprobe_running()) {
 432                         /*
 433                          * We have hit a kprobe while another is still
 434                          * active. This can happen in the pre and post
 435                          * handler. Single step the instruction of the
 436                          * new probe but do not call any handler function
 437                          * of this secondary kprobe.
 438                          * push_kprobe and pop_kprobe saves and restores
 439                          * the currently active kprobe.
 440                          */
 441                         kprobe_reenter_check(kcb, p);
 442                         push_kprobe(kcb, p);
 443                         kcb->kprobe_status = KPROBE_REENTER;
 444                 } else {
 445                         /*
 446                          * If we have no pre-handler or it returned 0, we
 447                          * continue with single stepping. If we have a
 448                          * pre-handler and it returned non-zero, it prepped
 449                          * for calling the break_handler below on re-entry
 450                          * for jprobe processing, so get out doing nothing
 451                          * more here.
 452                          */
 453                         push_kprobe(kcb, p);
 454                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 455                         if (p->pre_handler && p->pre_handler(p, regs))
 456                                 return 1;
 457                         kcb->kprobe_status = KPROBE_HIT_SS;
 458                 }
 459                 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
 460                 return 1;
 461         } else if (kprobe_running()) {
 462                 p = __get_cpu_var(current_kprobe);
 463                 if (p->break_handler && p->break_handler(p, regs)) {
 464                         /*
 465                          * Continuation after the jprobe completed and
 466                          * caused the jprobe_return trap. The jprobe
 467                          * break_handler "returns" to the original
 468                          * function that still has the kprobe breakpoint
 469                          * installed. We continue with single stepping.
 470                          */
 471                         kcb->kprobe_status = KPROBE_HIT_SS;
 472                         enable_singlestep(kcb, regs,
 473                                           (unsigned long) p->ainsn.insn);
 474                         return 1;
 475                 } /* else:
 476                    * No kprobe at this address and the current kprobe
 477                    * has no break handler (no jprobe!). The kernel just
 478                    * exploded, let the standard trap handler pick up the
 479                    * pieces.
 480                    */
 481         } /* else:
 482            * No kprobe at this address and no active kprobe. The trap has
 483            * not been caused by a kprobe breakpoint. The race of breakpoint
 484            * vs. kprobe remove does not exist because on s390 as we use
 485            * stop_machine to arm/disarm the breakpoints.
 486            */
 487         preempt_enable_no_resched();
 488         return 0;
 489 }
 490
 491 /*
 492  * Function return probe trampoline:
 493  *      - init_kprobes() establishes a probepoint here
 494  *      - When the probed function returns, this probe
 495  *              causes the handlers to fire
 496  */
 497 static void __used kretprobe_trampoline_holder(void)
 498 {
 499         asm volatile(".global kretprobe_trampoline\n"
 500                      "kretprobe_trampoline: bcr 0,0\n");
 501 }
 502
 503 /*
 504  * Called when the probe at kretprobe trampoline is hit
 505  */
 506 static int __kprobes trampoline_probe_handler(struct kprobe *p,
 507                                               struct pt_regs *regs)
 508 {
 509         struct kretprobe_instance *ri;
 510         struct hlist_head *head, empty_rp;
 511         struct hlist_node *tmp;
 512         unsigned long flags, orig_ret_address;
 513         unsigned long trampoline_address;
 514         kprobe_opcode_t *correct_ret_addr;
 515
 516         INIT_HLIST_HEAD(&empty_rp);
 517         kretprobe_hash_lock(current, &head, &flags);
 518
 519         /*
 520          * It is possible to have multiple instances associated with a given
 521          * task either because an multiple functions in the call path
 522          * have a return probe installed on them, and/or more than one return
 523          * return probe was registered for a target function.
 524          *
 525          * We can handle this because:
 526          *     - instances are always inserted at the head of the list
 527          *     - when multiple return probes are registered for the same
 528          *       function, the first instance's ret_addr will point to the
 529          *       real return address, and all the rest will point to
 530          *       kretprobe_trampoline
 531          */
 532         ri = NULL;
 533         orig_ret_address = 0;
 534         correct_ret_addr = NULL;
 535         trampoline_address = (unsigned long) &kretprobe_trampoline;
 536         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 537                 if (ri->task != current)
 538                         /* another task is sharing our hash bucket */
 539                         continue;
 540
 541                 orig_ret_address = (unsigned long) ri->ret_addr;
 542
 543                 if (orig_ret_address != trampoline_address)
 544                         /*
 545                          * This is the real return address. Any other
 546                          * instances associated with this task are for
 547                          * other calls deeper on the call stack
 548                          */
 549                         break;
 550         }
 551
 552         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 553
 554         correct_ret_addr = ri->ret_addr;
 555         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 556                 if (ri->task != current)
 557                         /* another task is sharing our hash bucket */
 558                         continue;
 559
 560                 orig_ret_address = (unsigned long) ri->ret_addr;
 561
 562                 if (ri->rp && ri->rp->handler) {
 563                         ri->ret_addr = correct_ret_addr;
 564                         ri->rp->handler(ri, regs);
 565                 }
 566
 567                 recycle_rp_inst(ri, &empty_rp);
 568
 569                 if (orig_ret_address != trampoline_address)
 570                         /*
 571                          * This is the real return address. Any other
 572                          * instances associated with this task are for
 573                          * other calls deeper on the call stack
 574                          */
 575                         break;
 576         }
 577
 578         regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE;
 579
 580         pop_kprobe(get_kprobe_ctlblk());
 581         kretprobe_hash_unlock(current, &flags);
 582         preempt_enable_no_resched();
 583
 584         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 585                 hlist_del(&ri->hlist);
 586                 kfree(ri);
 587         }
 588         /*
 589          * By returning a non-zero value, we are telling
 590          * kprobe_handler() that we don't want the post_handler
 591          * to run (and have re-enabled preemption)
 592          */
 593         return 1;
 594 }
 595
 596 /*
 597  * Called after single-stepping.  p->addr is the address of the
 598  * instruction whose first byte has been replaced by the "breakpoint"
 599  * instruction.  To avoid the SMP problems that can occur when we
 600  * temporarily put back the original opcode to single-step, we
 601  * single-stepped a copy of the instruction.  The address of this
 602  * copy is p->ainsn.insn.
 603  */
 604 static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
 605 {
 606         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 607         unsigned long ip = regs->psw.addr & PSW_ADDR_INSN;
 608         int fixup = get_fixup_type(p->ainsn.insn);
 609
 610         if (fixup & FIXUP_PSW_NORMAL)
 611                 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
 612
 613         if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
 614                 int ilen = insn_length(p->ainsn.insn[0] >> 8);
 615                 if (ip - (unsigned long) p->ainsn.insn == ilen)
 616                         ip = (unsigned long) p->addr + ilen;
 617         }
 618
 619         if (fixup & FIXUP_RETURN_REGISTER) {
 620                 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
 621                 regs->gprs[reg] += (unsigned long) p->addr -
 622                                    (unsigned long) p->ainsn.insn;
 623         }
 624
 625         disable_singlestep(kcb, regs, ip);
 626 }
 627
 628 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 629 {
 630         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 631         struct kprobe *p = kprobe_running();
 632
 633         if (!p)
 634                 return 0;
 635
 636         if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
 637                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 638                 p->post_handler(p, regs, 0);
 639         }
 640
 641         resume_execution(p, regs);
 642         pop_kprobe(kcb);
 643         preempt_enable_no_resched();
 644
 645         /*
 646          * if somebody else is singlestepping across a probe point, psw mask
 647          * will have PER set, in which case, continue the remaining processing
 648          * of do_single_step, as if this is not a probe hit.
 649          */
 650         if (regs->psw.mask & PSW_MASK_PER)
 651                 return 0;
 652
 653         return 1;
 654 }
 655
 656 static int __kprobes kprobe_trap_handler(struct pt_regs *regs, int trapnr)
 657 {
 658         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 659         struct kprobe *p = kprobe_running();
 660         const struct exception_table_entry *entry;
 661
 662         switch(kcb->kprobe_status) {
 663         case KPROBE_SWAP_INST:
 664                 /* We are here because the instruction replacement failed */
 665                 return 0;
 666         case KPROBE_HIT_SS:
 667         case KPROBE_REENTER:
 668                 /*
 669                  * We are here because the instruction being single
 670                  * stepped caused a page fault. We reset the current
 671                  * kprobe and the nip points back to the probe address
 672                  * and allow the page fault handler to continue as a
 673                  * normal page fault.
 674                  */
 675                 disable_singlestep(kcb, regs, (unsigned long) p->addr);
 676                 pop_kprobe(kcb);
 677                 preempt_enable_no_resched();
 678                 break;
 679         case KPROBE_HIT_ACTIVE:
 680         case KPROBE_HIT_SSDONE:
 681                 /*
 682                  * We increment the nmissed count for accounting,
 683                  * we can also use npre/npostfault count for accounting
 684                  * these specific fault cases.
 685                  */
 686                 kprobes_inc_nmissed_count(p);
 687
 688                 /*
 689                  * We come here because instructions in the pre/post
 690                  * handler caused the page_fault, this could happen
 691                  * if handler tries to access user space by
 692                  * copy_from_user(), get_user() etc. Let the
 693                  * user-specified handler try to fix it first.
 694                  */
 695                 if (p->fault_handler && p->fault_handler(p, regs, trapnr))
 696                         return 1;
 697
 698                 /*
 699                  * In case the user-specified fault handler returned
 700                  * zero, try to fix up.
 701                  */
 702                 entry = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
 703                 if (entry) {
 704                         regs->psw.addr = extable_fixup(entry) | PSW_ADDR_AMODE;
 705                         return 1;
 706                 }
 707
 708                 /*
 709                  * fixup_exception() could not handle it,
 710                  * Let do_page_fault() fix it.
 711                  */
 712                 break;
 713         default:
 714                 break;
 715         }
 716         return 0;
 717 }
 718
 719 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 720 {
 721         int ret;
 722
 723         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 724                 local_irq_disable();
 725         ret = kprobe_trap_handler(regs, trapnr);
 726         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 727                 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
 728         return ret;
 729 }
 730
 731 /*
 732  * Wrapper routine to for handling exceptions.
 733  */
 734 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 735                                        unsigned long val, void *data)
 736 {
 737         struct die_args *args = (struct die_args *) data;
 738         struct pt_regs *regs = args->regs;
 739         int ret = NOTIFY_DONE;
 740
 741         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 742                 local_irq_disable();
 743
 744         switch (val) {
 745         case DIE_BPT:
 746                 if (kprobe_handler(regs))
 747                         ret = NOTIFY_STOP;
 748                 break;
 749         case DIE_SSTEP:
 750                 if (post_kprobe_handler(regs))
 751                         ret = NOTIFY_STOP;
 752                 break;
 753         case DIE_TRAP:
 754                 if (!preemptible() && kprobe_running() &&
 755                     kprobe_trap_handler(regs, args->trapnr))
 756                         ret = NOTIFY_STOP;
 757                 break;
 758         default:
 759                 break;
 760         }
 761
 762         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 763                 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
 764
 765         return ret;
 766 }
 767
 768 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 769 {
 770         struct jprobe *jp = container_of(p, struct jprobe, kp);
 771         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 772         unsigned long stack;
 773
 774         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
 775
 776         /* setup return addr to the jprobe handler routine */
 777         regs->psw.addr = (unsigned long) jp->entry | PSW_ADDR_AMODE;
 778         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
 779
 780         /* r15 is the stack pointer */
 781         stack = (unsigned long) regs->gprs[15];
 782
 783         memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack));
 784         return 1;
 785 }
 786
 787 void __kprobes jprobe_return(void)
 788 {
 789         asm volatile(".word 0x0002");
 790 }
 791
 792 static void __used __kprobes jprobe_return_end(void)
 793 {
 794         asm volatile("bcr 0,0");
 795 }
 796
 797 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 798 {
 799         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 800         unsigned long stack;
 801
 802         stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15];
 803
 804         /* Put the regs back */
 805         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
 806         /* put the stack back */
 807         memcpy((void *) stack, kcb->jprobes_stack, MIN_STACK_SIZE(stack));
 808         preempt_enable_no_resched();
 809         return 1;
 810 }
 811
 812 static struct kprobe trampoline = {
 813         .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
 814         .pre_handler = trampoline_probe_handler
 815 };
 816
 817 int __init arch_init_kprobes(void)
 818 {
 819         return register_kprobe(&trampoline);
 820 }
 821
 822 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 823 {
 824         return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
 825 }