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 <asm/cacheflush.h>
  30 #include <asm/sections.h>
  31 #include <linux/module.h>
  32 #include <linux/slab.h>
  33 #include <linux/hardirq.h>
  34
  35 DEFINE_PER_CPU(struct kprobe *, current_kprobe);
  36 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  37
  38 struct kretprobe_blackpoint kretprobe_blacklist[] = { };
  39
  40 DEFINE_INSN_CACHE_OPS(dmainsn);
  41
  42 static void *alloc_dmainsn_page(void)
  43 {
  44         return (void *)__get_free_page(GFP_KERNEL | GFP_DMA);
  45 }
  46
  47 static void free_dmainsn_page(void *page)
  48 {
  49         free_page((unsigned long)page);
  50 }
  51
  52 struct kprobe_insn_cache kprobe_dmainsn_slots = {
  53         .mutex = __MUTEX_INITIALIZER(kprobe_dmainsn_slots.mutex),
  54         .alloc = alloc_dmainsn_page,
  55         .free = free_dmainsn_page,
  56         .pages = LIST_HEAD_INIT(kprobe_dmainsn_slots.pages),
  57         .insn_size = MAX_INSN_SIZE,
  58 };
  59
  60 static int __kprobes is_prohibited_opcode(kprobe_opcode_t *insn)
  61 {
  62         switch (insn[0] >> 8) {
  63         case 0x0c:      /* bassm */
  64         case 0x0b:      /* bsm   */
  65         case 0x83:      /* diag  */
  66         case 0x44:      /* ex    */
  67         case 0xac:      /* stnsm */
  68         case 0xad:      /* stosm */
  69                 return -EINVAL;
  70         case 0xc6:
  71                 switch (insn[0] & 0x0f) {
  72                 case 0x00: /* exrl   */
  73                         return -EINVAL;
  74                 }
  75         }
  76         switch (insn[0]) {
  77         case 0x0101:    /* pr    */
  78         case 0xb25a:    /* bsa   */
  79         case 0xb240:    /* bakr  */
  80         case 0xb258:    /* bsg   */
  81         case 0xb218:    /* pc    */
  82         case 0xb228:    /* pt    */
  83         case 0xb98d:    /* epsw  */
  84                 return -EINVAL;
  85         }
  86         return 0;
  87 }
  88
  89 static int __kprobes get_fixup_type(kprobe_opcode_t *insn)
  90 {
  91         /* default fixup method */
  92         int fixup = FIXUP_PSW_NORMAL;
  93
  94         switch (insn[0] >> 8) {
  95         case 0x05:      /* balr */
  96         case 0x0d:      /* basr */
  97                 fixup = FIXUP_RETURN_REGISTER;
  98                 /* if r2 = 0, no branch will be taken */
  99                 if ((insn[0] & 0x0f) == 0)
 100                         fixup |= FIXUP_BRANCH_NOT_TAKEN;
 101                 break;
 102         case 0x06:      /* bctr */
 103         case 0x07:      /* bcr  */
 104                 fixup = FIXUP_BRANCH_NOT_TAKEN;
 105                 break;
 106         case 0x45:      /* bal  */
 107         case 0x4d:      /* bas  */
 108                 fixup = FIXUP_RETURN_REGISTER;
 109                 break;
 110         case 0x47:      /* bc   */
 111         case 0x46:      /* bct  */
 112         case 0x86:      /* bxh  */
 113         case 0x87:      /* bxle */
 114                 fixup = FIXUP_BRANCH_NOT_TAKEN;
 115                 break;
 116         case 0x82:      /* lpsw */
 117                 fixup = FIXUP_NOT_REQUIRED;
 118                 break;
 119         case 0xb2:      /* lpswe */
 120                 if ((insn[0] & 0xff) == 0xb2)
 121                         fixup = FIXUP_NOT_REQUIRED;
 122                 break;
 123         case 0xa7:      /* bras */
 124                 if ((insn[0] & 0x0f) == 0x05)
 125                         fixup |= FIXUP_RETURN_REGISTER;
 126                 break;
 127         case 0xc0:
 128                 if ((insn[0] & 0x0f) == 0x05)   /* brasl */
 129                         fixup |= FIXUP_RETURN_REGISTER;
 130                 break;
 131         case 0xeb:
 132                 switch (insn[2] & 0xff) {
 133                 case 0x44: /* bxhg  */
 134                 case 0x45: /* bxleg */
 135                         fixup = FIXUP_BRANCH_NOT_TAKEN;
 136                         break;
 137                 }
 138                 break;
 139         case 0xe3:      /* bctg */
 140                 if ((insn[2] & 0xff) == 0x46)
 141                         fixup = FIXUP_BRANCH_NOT_TAKEN;
 142                 break;
 143         case 0xec:
 144                 switch (insn[2] & 0xff) {
 145                 case 0xe5: /* clgrb */
 146                 case 0xe6: /* cgrb  */
 147                 case 0xf6: /* crb   */
 148                 case 0xf7: /* clrb  */
 149                 case 0xfc: /* cgib  */
 150                 case 0xfd: /* cglib */
 151                 case 0xfe: /* cib   */
 152                 case 0xff: /* clib  */
 153                         fixup = FIXUP_BRANCH_NOT_TAKEN;
 154                         break;
 155                 }
 156                 break;
 157         }
 158         return fixup;
 159 }
 160
 161 static int __kprobes is_insn_relative_long(kprobe_opcode_t *insn)
 162 {
 163         /* Check if we have a RIL-b or RIL-c format instruction which
 164          * we need to modify in order to avoid instruction emulation. */
 165         switch (insn[0] >> 8) {
 166         case 0xc0:
 167                 if ((insn[0] & 0x0f) == 0x00) /* larl */
 168                         return true;
 169                 break;
 170         case 0xc4:
 171                 switch (insn[0] & 0x0f) {
 172                 case 0x02: /* llhrl  */
 173                 case 0x04: /* lghrl  */
 174                 case 0x05: /* lhrl   */
 175                 case 0x06: /* llghrl */
 176                 case 0x07: /* sthrl  */
 177                 case 0x08: /* lgrl   */
 178                 case 0x0b: /* stgrl  */
 179                 case 0x0c: /* lgfrl  */
 180                 case 0x0d: /* lrl    */
 181                 case 0x0e: /* llgfrl */
 182                 case 0x0f: /* strl   */
 183                         return true;
 184                 }
 185                 break;
 186         case 0xc6:
 187                 switch (insn[0] & 0x0f) {
 188                 case 0x02: /* pfdrl  */
 189                 case 0x04: /* cghrl  */
 190                 case 0x05: /* chrl   */
 191                 case 0x06: /* clghrl */
 192                 case 0x07: /* clhrl  */
 193                 case 0x08: /* cgrl   */
 194                 case 0x0a: /* clgrl  */
 195                 case 0x0c: /* cgfrl  */
 196                 case 0x0d: /* crl    */
 197                 case 0x0e: /* clgfrl */
 198                 case 0x0f: /* clrl   */
 199                         return true;
 200                 }
 201                 break;
 202         }
 203         return false;
 204 }
 205
 206 static void __kprobes copy_instruction(struct kprobe *p)
 207 {
 208         s64 disp, new_disp;
 209         u64 addr, new_addr;
 210
 211         memcpy(p->ainsn.insn, p->addr, ((p->opcode >> 14) + 3) & -2);
 212         if (!is_insn_relative_long(p->ainsn.insn))
 213                 return;
 214         /*
 215          * For pc-relative instructions in RIL-b or RIL-c format patch the
 216          * RI2 displacement field. We have already made sure that the insn
 217          * slot for the patched instruction is within the same 2GB area
 218          * as the original instruction (either kernel image or module area).
 219          * Therefore the new displacement will always fit.
 220          */
 221         disp = *(s32 *)&p->ainsn.insn[1];
 222         addr = (u64)(unsigned long)p->addr;
 223         new_addr = (u64)(unsigned long)p->ainsn.insn;
 224         new_disp = ((addr + (disp * 2)) - new_addr) / 2;
 225         *(s32 *)&p->ainsn.insn[1] = new_disp;
 226 }
 227
 228 static inline int is_kernel_addr(void *addr)
 229 {
 230         return addr < (void *)_end;
 231 }
 232
 233 static inline int is_module_addr(void *addr)
 234 {
 235 #ifdef CONFIG_64BIT
 236         BUILD_BUG_ON(MODULES_LEN > (1UL << 31));
 237         if (addr < (void *)MODULES_VADDR)
 238                 return 0;
 239         if (addr > (void *)MODULES_END)
 240                 return 0;
 241 #endif
 242         return 1;
 243 }
 244
 245 static int __kprobes s390_get_insn_slot(struct kprobe *p)
 246 {
 247         /*
 248          * Get an insn slot that is within the same 2GB area like the original
 249          * instruction. That way instructions with a 32bit signed displacement
 250          * field can be patched and executed within the insn slot.
 251          */
 252         p->ainsn.insn = NULL;
 253         if (is_kernel_addr(p->addr))
 254                 p->ainsn.insn = get_dmainsn_slot();
 255         if (is_module_addr(p->addr))
 256                 p->ainsn.insn = get_insn_slot();
 257         return p->ainsn.insn ? 0 : -ENOMEM;
 258 }
 259
 260 static void __kprobes s390_free_insn_slot(struct kprobe *p)
 261 {
 262         if (!p->ainsn.insn)
 263                 return;
 264         if (is_kernel_addr(p->addr))
 265                 free_dmainsn_slot(p->ainsn.insn, 0);
 266         else
 267                 free_insn_slot(p->ainsn.insn, 0);
 268         p->ainsn.insn = NULL;
 269 }
 270
 271 int __kprobes arch_prepare_kprobe(struct kprobe *p)
 272 {
 273         if ((unsigned long) p->addr & 0x01)
 274                 return -EINVAL;
 275         /* Make sure the probe isn't going on a difficult instruction */
 276         if (is_prohibited_opcode(p->addr))
 277                 return -EINVAL;
 278         if (s390_get_insn_slot(p))
 279                 return -ENOMEM;
 280         p->opcode = *p->addr;
 281         copy_instruction(p);
 282         return 0;
 283 }
 284
 285 struct ins_replace_args {
 286         kprobe_opcode_t *ptr;
 287         kprobe_opcode_t opcode;
 288 };
 289
 290 static int __kprobes swap_instruction(void *aref)
 291 {
 292         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 293         unsigned long status = kcb->kprobe_status;
 294         struct ins_replace_args *args = aref;
 295
 296         kcb->kprobe_status = KPROBE_SWAP_INST;
 297         probe_kernel_write(args->ptr, &args->opcode, sizeof(args->opcode));
 298         kcb->kprobe_status = status;
 299         return 0;
 300 }
 301
 302 void __kprobes arch_arm_kprobe(struct kprobe *p)
 303 {
 304         struct ins_replace_args args;
 305
 306         args.ptr = p->addr;
 307         args.opcode = BREAKPOINT_INSTRUCTION;
 308         stop_machine(swap_instruction, &args, NULL);
 309 }
 310
 311 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 312 {
 313         struct ins_replace_args args;
 314
 315         args.ptr = p->addr;
 316         args.opcode = p->opcode;
 317         stop_machine(swap_instruction, &args, NULL);
 318 }
 319
 320 void __kprobes arch_remove_kprobe(struct kprobe *p)
 321 {
 322         s390_free_insn_slot(p);
 323 }
 324
 325 static void __kprobes enable_singlestep(struct kprobe_ctlblk *kcb,
 326                                         struct pt_regs *regs,
 327                                         unsigned long ip)
 328 {
 329         struct per_regs per_kprobe;
 330
 331         /* Set up the PER control registers %cr9-%cr11 */
 332         per_kprobe.control = PER_EVENT_IFETCH;
 333         per_kprobe.start = ip;
 334         per_kprobe.end = ip;
 335
 336         /* Save control regs and psw mask */
 337         __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
 338         kcb->kprobe_saved_imask = regs->psw.mask &
 339                 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
 340
 341         /* Set PER control regs, turns on single step for the given address */
 342         __ctl_load(per_kprobe, 9, 11);
 343         regs->psw.mask |= PSW_MASK_PER;
 344         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
 345         regs->psw.addr = ip | PSW_ADDR_AMODE;
 346 }
 347
 348 static void __kprobes disable_singlestep(struct kprobe_ctlblk *kcb,
 349                                          struct pt_regs *regs,
 350                                          unsigned long ip)
 351 {
 352         /* Restore control regs and psw mask, set new psw address */
 353         __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
 354         regs->psw.mask &= ~PSW_MASK_PER;
 355         regs->psw.mask |= kcb->kprobe_saved_imask;
 356         regs->psw.addr = ip | PSW_ADDR_AMODE;
 357 }
 358
 359 /*
 360  * Activate a kprobe by storing its pointer to current_kprobe. The
 361  * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
 362  * two kprobes can be active, see KPROBE_REENTER.
 363  */
 364 static void __kprobes push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
 365 {
 366         kcb->prev_kprobe.kp = __get_cpu_var(current_kprobe);
 367         kcb->prev_kprobe.status = kcb->kprobe_status;
 368         __get_cpu_var(current_kprobe) = p;
 369 }
 370
 371 /*
 372  * Deactivate a kprobe by backing up to the previous state. If the
 373  * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
 374  * for any other state prev_kprobe.kp will be NULL.
 375  */
 376 static void __kprobes pop_kprobe(struct kprobe_ctlblk *kcb)
 377 {
 378         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
 379         kcb->kprobe_status = kcb->prev_kprobe.status;
 380 }
 381
 382 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 383                                         struct pt_regs *regs)
 384 {
 385         ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
 386
 387         /* Replace the return addr with trampoline addr */
 388         regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
 389 }
 390
 391 static void __kprobes kprobe_reenter_check(struct kprobe_ctlblk *kcb,
 392                                            struct kprobe *p)
 393 {
 394         switch (kcb->kprobe_status) {
 395         case KPROBE_HIT_SSDONE:
 396         case KPROBE_HIT_ACTIVE:
 397                 kprobes_inc_nmissed_count(p);
 398                 break;
 399         case KPROBE_HIT_SS:
 400         case KPROBE_REENTER:
 401         default:
 402                 /*
 403                  * A kprobe on the code path to single step an instruction
 404                  * is a BUG. The code path resides in the .kprobes.text
 405                  * section and is executed with interrupts disabled.
 406                  */
 407                 printk(KERN_EMERG "Invalid kprobe detected at %p.\n", p->addr);
 408                 dump_kprobe(p);
 409                 BUG();
 410         }
 411 }
 412
 413 static int __kprobes kprobe_handler(struct pt_regs *regs)
 414 {
 415         struct kprobe_ctlblk *kcb;
 416         struct kprobe *p;
 417
 418         /*
 419          * We want to disable preemption for the entire duration of kprobe
 420          * processing. That includes the calls to the pre/post handlers
 421          * and single stepping the kprobe instruction.
 422          */
 423         preempt_disable();
 424         kcb = get_kprobe_ctlblk();
 425         p = get_kprobe((void *)((regs->psw.addr & PSW_ADDR_INSN) - 2));
 426
 427         if (p) {
 428                 if (kprobe_running()) {
 429                         /*
 430                          * We have hit a kprobe while another is still
 431                          * active. This can happen in the pre and post
 432                          * handler. Single step the instruction of the
 433                          * new probe but do not call any handler function
 434                          * of this secondary kprobe.
 435                          * push_kprobe and pop_kprobe saves and restores
 436                          * the currently active kprobe.
 437                          */
 438                         kprobe_reenter_check(kcb, p);
 439                         push_kprobe(kcb, p);
 440                         kcb->kprobe_status = KPROBE_REENTER;
 441                 } else {
 442                         /*
 443                          * If we have no pre-handler or it returned 0, we
 444                          * continue with single stepping. If we have a
 445                          * pre-handler and it returned non-zero, it prepped
 446                          * for calling the break_handler below on re-entry
 447                          * for jprobe processing, so get out doing nothing
 448                          * more here.
 449                          */
 450                         push_kprobe(kcb, p);
 451                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 452                         if (p->pre_handler && p->pre_handler(p, regs))
 453                                 return 1;
 454                         kcb->kprobe_status = KPROBE_HIT_SS;
 455                 }
 456                 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
 457                 return 1;
 458         } else if (kprobe_running()) {
 459                 p = __get_cpu_var(current_kprobe);
 460                 if (p->break_handler && p->break_handler(p, regs)) {
 461                         /*
 462                          * Continuation after the jprobe completed and
 463                          * caused the jprobe_return trap. The jprobe
 464                          * break_handler "returns" to the original
 465                          * function that still has the kprobe breakpoint
 466                          * installed. We continue with single stepping.
 467                          */
 468                         kcb->kprobe_status = KPROBE_HIT_SS;
 469                         enable_singlestep(kcb, regs,
 470                                           (unsigned long) p->ainsn.insn);
 471                         return 1;
 472                 } /* else:
 473                    * No kprobe at this address and the current kprobe
 474                    * has no break handler (no jprobe!). The kernel just
 475                    * exploded, let the standard trap handler pick up the
 476                    * pieces.
 477                    */
 478         } /* else:
 479            * No kprobe at this address and no active kprobe. The trap has
 480            * not been caused by a kprobe breakpoint. The race of breakpoint
 481            * vs. kprobe remove does not exist because on s390 as we use
 482            * stop_machine to arm/disarm the breakpoints.
 483            */
 484         preempt_enable_no_resched();
 485         return 0;
 486 }
 487
 488 /*
 489  * Function return probe trampoline:
 490  *      - init_kprobes() establishes a probepoint here
 491  *      - When the probed function returns, this probe
 492  *              causes the handlers to fire
 493  */
 494 static void __used kretprobe_trampoline_holder(void)
 495 {
 496         asm volatile(".global kretprobe_trampoline\n"
 497                      "kretprobe_trampoline: bcr 0,0\n");
 498 }
 499
 500 /*
 501  * Called when the probe at kretprobe trampoline is hit
 502  */
 503 static int __kprobes trampoline_probe_handler(struct kprobe *p,
 504                                               struct pt_regs *regs)
 505 {
 506         struct kretprobe_instance *ri;
 507         struct hlist_head *head, empty_rp;
 508         struct hlist_node *tmp;
 509         unsigned long flags, orig_ret_address;
 510         unsigned long trampoline_address;
 511         kprobe_opcode_t *correct_ret_addr;
 512
 513         INIT_HLIST_HEAD(&empty_rp);
 514         kretprobe_hash_lock(current, &head, &flags);
 515
 516         /*
 517          * It is possible to have multiple instances associated with a given
 518          * task either because an multiple functions in the call path
 519          * have a return probe installed on them, and/or more than one return
 520          * return probe was registered for a target function.
 521          *
 522          * We can handle this because:
 523          *     - instances are always inserted at the head of the list
 524          *     - when multiple return probes are registered for the same
 525          *       function, the first instance's ret_addr will point to the
 526          *       real return address, and all the rest will point to
 527          *       kretprobe_trampoline
 528          */
 529         ri = NULL;
 530         orig_ret_address = 0;
 531         correct_ret_addr = NULL;
 532         trampoline_address = (unsigned long) &kretprobe_trampoline;
 533         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 534                 if (ri->task != current)
 535                         /* another task is sharing our hash bucket */
 536                         continue;
 537
 538                 orig_ret_address = (unsigned long) ri->ret_addr;
 539
 540                 if (orig_ret_address != trampoline_address)
 541                         /*
 542                          * This is the real return address. Any other
 543                          * instances associated with this task are for
 544                          * other calls deeper on the call stack
 545                          */
 546                         break;
 547         }
 548
 549         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 550
 551         correct_ret_addr = ri->ret_addr;
 552         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 553                 if (ri->task != current)
 554                         /* another task is sharing our hash bucket */
 555                         continue;
 556
 557                 orig_ret_address = (unsigned long) ri->ret_addr;
 558
 559                 if (ri->rp && ri->rp->handler) {
 560                         ri->ret_addr = correct_ret_addr;
 561                         ri->rp->handler(ri, regs);
 562                 }
 563
 564                 recycle_rp_inst(ri, &empty_rp);
 565
 566                 if (orig_ret_address != trampoline_address)
 567                         /*
 568                          * This is the real return address. Any other
 569                          * instances associated with this task are for
 570                          * other calls deeper on the call stack
 571                          */
 572                         break;
 573         }
 574
 575         regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE;
 576
 577         pop_kprobe(get_kprobe_ctlblk());
 578         kretprobe_hash_unlock(current, &flags);
 579         preempt_enable_no_resched();
 580
 581         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 582                 hlist_del(&ri->hlist);
 583                 kfree(ri);
 584         }
 585         /*
 586          * By returning a non-zero value, we are telling
 587          * kprobe_handler() that we don't want the post_handler
 588          * to run (and have re-enabled preemption)
 589          */
 590         return 1;
 591 }
 592
 593 /*
 594  * Called after single-stepping.  p->addr is the address of the
 595  * instruction whose first byte has been replaced by the "breakpoint"
 596  * instruction.  To avoid the SMP problems that can occur when we
 597  * temporarily put back the original opcode to single-step, we
 598  * single-stepped a copy of the instruction.  The address of this
 599  * copy is p->ainsn.insn.
 600  */
 601 static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
 602 {
 603         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 604         unsigned long ip = regs->psw.addr & PSW_ADDR_INSN;
 605         int fixup = get_fixup_type(p->ainsn.insn);
 606
 607         if (fixup & FIXUP_PSW_NORMAL)
 608                 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
 609
 610         if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
 611                 int ilen = ((p->ainsn.insn[0] >> 14) + 3) & -2;
 612                 if (ip - (unsigned long) p->ainsn.insn == ilen)
 613                         ip = (unsigned long) p->addr + ilen;
 614         }
 615
 616         if (fixup & FIXUP_RETURN_REGISTER) {
 617                 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
 618                 regs->gprs[reg] += (unsigned long) p->addr -
 619                                    (unsigned long) p->ainsn.insn;
 620         }
 621
 622         disable_singlestep(kcb, regs, ip);
 623 }
 624
 625 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 626 {
 627         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 628         struct kprobe *p = kprobe_running();
 629
 630         if (!p)
 631                 return 0;
 632
 633         if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
 634                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 635                 p->post_handler(p, regs, 0);
 636         }
 637
 638         resume_execution(p, regs);
 639         pop_kprobe(kcb);
 640         preempt_enable_no_resched();
 641
 642         /*
 643          * if somebody else is singlestepping across a probe point, psw mask
 644          * will have PER set, in which case, continue the remaining processing
 645          * of do_single_step, as if this is not a probe hit.
 646          */
 647         if (regs->psw.mask & PSW_MASK_PER)
 648                 return 0;
 649
 650         return 1;
 651 }
 652
 653 static int __kprobes kprobe_trap_handler(struct pt_regs *regs, int trapnr)
 654 {
 655         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 656         struct kprobe *p = kprobe_running();
 657         const struct exception_table_entry *entry;
 658
 659         switch(kcb->kprobe_status) {
 660         case KPROBE_SWAP_INST:
 661                 /* We are here because the instruction replacement failed */
 662                 return 0;
 663         case KPROBE_HIT_SS:
 664         case KPROBE_REENTER:
 665                 /*
 666                  * We are here because the instruction being single
 667                  * stepped caused a page fault. We reset the current
 668                  * kprobe and the nip points back to the probe address
 669                  * and allow the page fault handler to continue as a
 670                  * normal page fault.
 671                  */
 672                 disable_singlestep(kcb, regs, (unsigned long) p->addr);
 673                 pop_kprobe(kcb);
 674                 preempt_enable_no_resched();
 675                 break;
 676         case KPROBE_HIT_ACTIVE:
 677         case KPROBE_HIT_SSDONE:
 678                 /*
 679                  * We increment the nmissed count for accounting,
 680                  * we can also use npre/npostfault count for accouting
 681                  * these specific fault cases.
 682                  */
 683                 kprobes_inc_nmissed_count(p);
 684
 685                 /*
 686                  * We come here because instructions in the pre/post
 687                  * handler caused the page_fault, this could happen
 688                  * if handler tries to access user space by
 689                  * copy_from_user(), get_user() etc. Let the
 690                  * user-specified handler try to fix it first.
 691                  */
 692                 if (p->fault_handler && p->fault_handler(p, regs, trapnr))
 693                         return 1;
 694
 695                 /*
 696                  * In case the user-specified fault handler returned
 697                  * zero, try to fix up.
 698                  */
 699                 entry = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
 700                 if (entry) {
 701                         regs->psw.addr = extable_fixup(entry) | PSW_ADDR_AMODE;
 702                         return 1;
 703                 }
 704
 705                 /*
 706                  * fixup_exception() could not handle it,
 707                  * Let do_page_fault() fix it.
 708                  */
 709                 break;
 710         default:
 711                 break;
 712         }
 713         return 0;
 714 }
 715
 716 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 717 {
 718         int ret;
 719
 720         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 721                 local_irq_disable();
 722         ret = kprobe_trap_handler(regs, trapnr);
 723         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 724                 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
 725         return ret;
 726 }
 727
 728 /*
 729  * Wrapper routine to for handling exceptions.
 730  */
 731 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 732                                        unsigned long val, void *data)
 733 {
 734         struct die_args *args = (struct die_args *) data;
 735         struct pt_regs *regs = args->regs;
 736         int ret = NOTIFY_DONE;
 737
 738         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 739                 local_irq_disable();
 740
 741         switch (val) {
 742         case DIE_BPT:
 743                 if (kprobe_handler(regs))
 744                         ret = NOTIFY_STOP;
 745                 break;
 746         case DIE_SSTEP:
 747                 if (post_kprobe_handler(regs))
 748                         ret = NOTIFY_STOP;
 749                 break;
 750         case DIE_TRAP:
 751                 if (!preemptible() && kprobe_running() &&
 752                     kprobe_trap_handler(regs, args->trapnr))
 753                         ret = NOTIFY_STOP;
 754                 break;
 755         default:
 756                 break;
 757         }
 758
 759         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 760                 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
 761
 762         return ret;
 763 }
 764
 765 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 766 {
 767         struct jprobe *jp = container_of(p, struct jprobe, kp);
 768         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 769         unsigned long stack;
 770
 771         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
 772
 773         /* setup return addr to the jprobe handler routine */
 774         regs->psw.addr = (unsigned long) jp->entry | PSW_ADDR_AMODE;
 775         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
 776
 777         /* r15 is the stack pointer */
 778         stack = (unsigned long) regs->gprs[15];
 779
 780         memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack));
 781         return 1;
 782 }
 783
 784 void __kprobes jprobe_return(void)
 785 {
 786         asm volatile(".word 0x0002");
 787 }
 788
 789 static void __used __kprobes jprobe_return_end(void)
 790 {
 791         asm volatile("bcr 0,0");
 792 }
 793
 794 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 795 {
 796         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 797         unsigned long stack;
 798
 799         stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15];
 800
 801         /* Put the regs back */
 802         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
 803         /* put the stack back */
 804         memcpy((void *) stack, kcb->jprobes_stack, MIN_STACK_SIZE(stack));
 805         preempt_enable_no_resched();
 806         return 1;
 807 }
 808
 809 static struct kprobe trampoline = {
 810         .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
 811         .pre_handler = trampoline_probe_handler
 812 };
 813
 814 int __init arch_init_kprobes(void)
 815 {
 816         return register_kprobe(&trampoline);
 817 }
 818
 819 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 820 {
 821         return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
 822 }