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 <linux/ftrace.h>
  33 #include <asm/cacheflush.h>
  34 #include <asm/sections.h>
  35 #include <asm/dis.h>
  36
  37 DEFINE_PER_CPU(struct kprobe *, current_kprobe);
  38 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  39
  40 struct kretprobe_blackpoint kretprobe_blacklist[] = { };
  41
  42 DEFINE_INSN_CACHE_OPS(dmainsn);
  43
  44 static void *alloc_dmainsn_page(void)
  45 {
  46         return (void *)__get_free_page(GFP_KERNEL | GFP_DMA);
  47 }
  48
  49 static void free_dmainsn_page(void *page)
  50 {
  51         free_page((unsigned long)page);
  52 }
  53
  54 struct kprobe_insn_cache kprobe_dmainsn_slots = {
  55         .mutex = __MUTEX_INITIALIZER(kprobe_dmainsn_slots.mutex),
  56         .alloc = alloc_dmainsn_page,
  57         .free = free_dmainsn_page,
  58         .pages = LIST_HEAD_INIT(kprobe_dmainsn_slots.pages),
  59         .insn_size = MAX_INSN_SIZE,
  60 };
  61
  62 static void copy_instruction(struct kprobe *p)
  63 {
  64         unsigned long ip = (unsigned long) p->addr;
  65         s64 disp, new_disp;
  66         u64 addr, new_addr;
  67
  68         if (ftrace_location(ip) == ip) {
  69                 /*
  70                  * If kprobes patches the instruction that is morphed by
  71                  * ftrace make sure that kprobes always sees the branch
  72                  * "jg .+24" that skips the mcount block
  73                  */
  74                 ftrace_generate_nop_insn((struct ftrace_insn *)p->ainsn.insn);
  75                 p->ainsn.is_ftrace_insn = 1;
  76         } else
  77                 memcpy(p->ainsn.insn, p->addr, insn_length(*p->addr >> 8));
  78         p->opcode = p->ainsn.insn[0];
  79         if (!probe_is_insn_relative_long(p->ainsn.insn))
  80                 return;
  81         /*
  82          * For pc-relative instructions in RIL-b or RIL-c format patch the
  83          * RI2 displacement field. We have already made sure that the insn
  84          * slot for the patched instruction is within the same 2GB area
  85          * as the original instruction (either kernel image or module area).
  86          * Therefore the new displacement will always fit.
  87          */
  88         disp = *(s32 *)&p->ainsn.insn[1];
  89         addr = (u64)(unsigned long)p->addr;
  90         new_addr = (u64)(unsigned long)p->ainsn.insn;
  91         new_disp = ((addr + (disp * 2)) - new_addr) / 2;
  92         *(s32 *)&p->ainsn.insn[1] = new_disp;
  93 }
  94 NOKPROBE_SYMBOL(copy_instruction);
  95
  96 static inline int is_kernel_addr(void *addr)
  97 {
  98         return addr < (void *)_end;
  99 }
 100
 101 static int s390_get_insn_slot(struct kprobe *p)
 102 {
 103         /*
 104          * Get an insn slot that is within the same 2GB area like the original
 105          * instruction. That way instructions with a 32bit signed displacement
 106          * field can be patched and executed within the insn slot.
 107          */
 108         p->ainsn.insn = NULL;
 109         if (is_kernel_addr(p->addr))
 110                 p->ainsn.insn = get_dmainsn_slot();
 111         else if (is_module_addr(p->addr))
 112                 p->ainsn.insn = get_insn_slot();
 113         return p->ainsn.insn ? 0 : -ENOMEM;
 114 }
 115 NOKPROBE_SYMBOL(s390_get_insn_slot);
 116
 117 static void s390_free_insn_slot(struct kprobe *p)
 118 {
 119         if (!p->ainsn.insn)
 120                 return;
 121         if (is_kernel_addr(p->addr))
 122                 free_dmainsn_slot(p->ainsn.insn, 0);
 123         else
 124                 free_insn_slot(p->ainsn.insn, 0);
 125         p->ainsn.insn = NULL;
 126 }
 127 NOKPROBE_SYMBOL(s390_free_insn_slot);
 128
 129 int arch_prepare_kprobe(struct kprobe *p)
 130 {
 131         if ((unsigned long) p->addr & 0x01)
 132                 return -EINVAL;
 133         /* Make sure the probe isn't going on a difficult instruction */
 134         if (probe_is_prohibited_opcode(p->addr))
 135                 return -EINVAL;
 136         if (s390_get_insn_slot(p))
 137                 return -ENOMEM;
 138         copy_instruction(p);
 139         return 0;
 140 }
 141 NOKPROBE_SYMBOL(arch_prepare_kprobe);
 142
 143 int arch_check_ftrace_location(struct kprobe *p)
 144 {
 145         return 0;
 146 }
 147
 148 struct swap_insn_args {
 149         struct kprobe *p;
 150         unsigned int arm_kprobe : 1;
 151 };
 152
 153 static int swap_instruction(void *data)
 154 {
 155         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 156         unsigned long status = kcb->kprobe_status;
 157         struct swap_insn_args *args = data;
 158         struct ftrace_insn new_insn, *insn;
 159         struct kprobe *p = args->p;
 160         size_t len;
 161
 162         new_insn.opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
 163         len = sizeof(new_insn.opc);
 164         if (!p->ainsn.is_ftrace_insn)
 165                 goto skip_ftrace;
 166         len = sizeof(new_insn);
 167         insn = (struct ftrace_insn *) p->addr;
 168         if (args->arm_kprobe) {
 169                 if (is_ftrace_nop(insn))
 170                         new_insn.disp = KPROBE_ON_FTRACE_NOP;
 171                 else
 172                         new_insn.disp = KPROBE_ON_FTRACE_CALL;
 173         } else {
 174                 ftrace_generate_call_insn(&new_insn, (unsigned long)p->addr);
 175                 if (insn->disp == KPROBE_ON_FTRACE_NOP)
 176                         ftrace_generate_nop_insn(&new_insn);
 177         }
 178 skip_ftrace:
 179         kcb->kprobe_status = KPROBE_SWAP_INST;
 180         probe_kernel_write(p->addr, &new_insn, len);
 181         kcb->kprobe_status = status;
 182         return 0;
 183 }
 184 NOKPROBE_SYMBOL(swap_instruction);
 185
 186 void arch_arm_kprobe(struct kprobe *p)
 187 {
 188         struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
 189
 190         stop_machine(swap_instruction, &args, NULL);
 191 }
 192 NOKPROBE_SYMBOL(arch_arm_kprobe);
 193
 194 void arch_disarm_kprobe(struct kprobe *p)
 195 {
 196         struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
 197
 198         stop_machine(swap_instruction, &args, NULL);
 199 }
 200 NOKPROBE_SYMBOL(arch_disarm_kprobe);
 201
 202 void arch_remove_kprobe(struct kprobe *p)
 203 {
 204         s390_free_insn_slot(p);
 205 }
 206 NOKPROBE_SYMBOL(arch_remove_kprobe);
 207
 208 static void enable_singlestep(struct kprobe_ctlblk *kcb,
 209                               struct pt_regs *regs,
 210                               unsigned long ip)
 211 {
 212         struct per_regs per_kprobe;
 213
 214         /* Set up the PER control registers %cr9-%cr11 */
 215         per_kprobe.control = PER_EVENT_IFETCH;
 216         per_kprobe.start = ip;
 217         per_kprobe.end = ip;
 218
 219         /* Save control regs and psw mask */
 220         __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
 221         kcb->kprobe_saved_imask = regs->psw.mask &
 222                 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
 223
 224         /* Set PER control regs, turns on single step for the given address */
 225         __ctl_load(per_kprobe, 9, 11);
 226         regs->psw.mask |= PSW_MASK_PER;
 227         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
 228         regs->psw.addr = ip | PSW_ADDR_AMODE;
 229 }
 230 NOKPROBE_SYMBOL(enable_singlestep);
 231
 232 static void disable_singlestep(struct kprobe_ctlblk *kcb,
 233                                struct pt_regs *regs,
 234                                unsigned long ip)
 235 {
 236         /* Restore control regs and psw mask, set new psw address */
 237         __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
 238         regs->psw.mask &= ~PSW_MASK_PER;
 239         regs->psw.mask |= kcb->kprobe_saved_imask;
 240         regs->psw.addr = ip | PSW_ADDR_AMODE;
 241 }
 242 NOKPROBE_SYMBOL(disable_singlestep);
 243
 244 /*
 245  * Activate a kprobe by storing its pointer to current_kprobe. The
 246  * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
 247  * two kprobes can be active, see KPROBE_REENTER.
 248  */
 249 static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
 250 {
 251         kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
 252         kcb->prev_kprobe.status = kcb->kprobe_status;
 253         __this_cpu_write(current_kprobe, p);
 254 }
 255 NOKPROBE_SYMBOL(push_kprobe);
 256
 257 /*
 258  * Deactivate a kprobe by backing up to the previous state. If the
 259  * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
 260  * for any other state prev_kprobe.kp will be NULL.
 261  */
 262 static void pop_kprobe(struct kprobe_ctlblk *kcb)
 263 {
 264         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 265         kcb->kprobe_status = kcb->prev_kprobe.status;
 266 }
 267 NOKPROBE_SYMBOL(pop_kprobe);
 268
 269 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
 270 {
 271         ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
 272
 273         /* Replace the return addr with trampoline addr */
 274         regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
 275 }
 276 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
 277
 278 static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
 279 {
 280         switch (kcb->kprobe_status) {
 281         case KPROBE_HIT_SSDONE:
 282         case KPROBE_HIT_ACTIVE:
 283                 kprobes_inc_nmissed_count(p);
 284                 break;
 285         case KPROBE_HIT_SS:
 286         case KPROBE_REENTER:
 287         default:
 288                 /*
 289                  * A kprobe on the code path to single step an instruction
 290                  * is a BUG. The code path resides in the .kprobes.text
 291                  * section and is executed with interrupts disabled.
 292                  */
 293                 printk(KERN_EMERG "Invalid kprobe detected at %p.\n", p->addr);
 294                 dump_kprobe(p);
 295                 BUG();
 296         }
 297 }
 298 NOKPROBE_SYMBOL(kprobe_reenter_check);
 299
 300 static int kprobe_handler(struct pt_regs *regs)
 301 {
 302         struct kprobe_ctlblk *kcb;
 303         struct kprobe *p;
 304
 305         /*
 306          * We want to disable preemption for the entire duration of kprobe
 307          * processing. That includes the calls to the pre/post handlers
 308          * and single stepping the kprobe instruction.
 309          */
 310         preempt_disable();
 311         kcb = get_kprobe_ctlblk();
 312         p = get_kprobe((void *)((regs->psw.addr & PSW_ADDR_INSN) - 2));
 313
 314         if (p) {
 315                 if (kprobe_running()) {
 316                         /*
 317                          * We have hit a kprobe while another is still
 318                          * active. This can happen in the pre and post
 319                          * handler. Single step the instruction of the
 320                          * new probe but do not call any handler function
 321                          * of this secondary kprobe.
 322                          * push_kprobe and pop_kprobe saves and restores
 323                          * the currently active kprobe.
 324                          */
 325                         kprobe_reenter_check(kcb, p);
 326                         push_kprobe(kcb, p);
 327                         kcb->kprobe_status = KPROBE_REENTER;
 328                 } else {
 329                         /*
 330                          * If we have no pre-handler or it returned 0, we
 331                          * continue with single stepping. If we have a
 332                          * pre-handler and it returned non-zero, it prepped
 333                          * for calling the break_handler below on re-entry
 334                          * for jprobe processing, so get out doing nothing
 335                          * more here.
 336                          */
 337                         push_kprobe(kcb, p);
 338                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 339                         if (p->pre_handler && p->pre_handler(p, regs))
 340                                 return 1;
 341                         kcb->kprobe_status = KPROBE_HIT_SS;
 342                 }
 343                 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
 344                 return 1;
 345         } else if (kprobe_running()) {
 346                 p = __this_cpu_read(current_kprobe);
 347                 if (p->break_handler && p->break_handler(p, regs)) {
 348                         /*
 349                          * Continuation after the jprobe completed and
 350                          * caused the jprobe_return trap. The jprobe
 351                          * break_handler "returns" to the original
 352                          * function that still has the kprobe breakpoint
 353                          * installed. We continue with single stepping.
 354                          */
 355                         kcb->kprobe_status = KPROBE_HIT_SS;
 356                         enable_singlestep(kcb, regs,
 357                                           (unsigned long) p->ainsn.insn);
 358                         return 1;
 359                 } /* else:
 360                    * No kprobe at this address and the current kprobe
 361                    * has no break handler (no jprobe!). The kernel just
 362                    * exploded, let the standard trap handler pick up the
 363                    * pieces.
 364                    */
 365         } /* else:
 366            * No kprobe at this address and no active kprobe. The trap has
 367            * not been caused by a kprobe breakpoint. The race of breakpoint
 368            * vs. kprobe remove does not exist because on s390 as we use
 369            * stop_machine to arm/disarm the breakpoints.
 370            */
 371         preempt_enable_no_resched();
 372         return 0;
 373 }
 374 NOKPROBE_SYMBOL(kprobe_handler);
 375
 376 /*
 377  * Function return probe trampoline:
 378  *      - init_kprobes() establishes a probepoint here
 379  *      - When the probed function returns, this probe
 380  *              causes the handlers to fire
 381  */
 382 static void __used kretprobe_trampoline_holder(void)
 383 {
 384         asm volatile(".global kretprobe_trampoline\n"
 385                      "kretprobe_trampoline: bcr 0,0\n");
 386 }
 387
 388 /*
 389  * Called when the probe at kretprobe trampoline is hit
 390  */
 391 static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 392 {
 393         struct kretprobe_instance *ri;
 394         struct hlist_head *head, empty_rp;
 395         struct hlist_node *tmp;
 396         unsigned long flags, orig_ret_address;
 397         unsigned long trampoline_address;
 398         kprobe_opcode_t *correct_ret_addr;
 399
 400         INIT_HLIST_HEAD(&empty_rp);
 401         kretprobe_hash_lock(current, &head, &flags);
 402
 403         /*
 404          * It is possible to have multiple instances associated with a given
 405          * task either because an multiple functions in the call path
 406          * have a return probe installed on them, and/or more than one return
 407          * return probe was registered for a target function.
 408          *
 409          * We can handle this because:
 410          *     - instances are always inserted at the head of the list
 411          *     - when multiple return probes are registered for the same
 412          *       function, the first instance's ret_addr will point to the
 413          *       real return address, and all the rest will point to
 414          *       kretprobe_trampoline
 415          */
 416         ri = NULL;
 417         orig_ret_address = 0;
 418         correct_ret_addr = NULL;
 419         trampoline_address = (unsigned long) &kretprobe_trampoline;
 420         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 421                 if (ri->task != current)
 422                         /* another task is sharing our hash bucket */
 423                         continue;
 424
 425                 orig_ret_address = (unsigned long) ri->ret_addr;
 426
 427                 if (orig_ret_address != trampoline_address)
 428                         /*
 429                          * This is the real return address. Any other
 430                          * instances associated with this task are for
 431                          * other calls deeper on the call stack
 432                          */
 433                         break;
 434         }
 435
 436         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 437
 438         correct_ret_addr = ri->ret_addr;
 439         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 440                 if (ri->task != current)
 441                         /* another task is sharing our hash bucket */
 442                         continue;
 443
 444                 orig_ret_address = (unsigned long) ri->ret_addr;
 445
 446                 if (ri->rp && ri->rp->handler) {
 447                         ri->ret_addr = correct_ret_addr;
 448                         ri->rp->handler(ri, regs);
 449                 }
 450
 451                 recycle_rp_inst(ri, &empty_rp);
 452
 453                 if (orig_ret_address != trampoline_address)
 454                         /*
 455                          * This is the real return address. Any other
 456                          * instances associated with this task are for
 457                          * other calls deeper on the call stack
 458                          */
 459                         break;
 460         }
 461
 462         regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE;
 463
 464         pop_kprobe(get_kprobe_ctlblk());
 465         kretprobe_hash_unlock(current, &flags);
 466         preempt_enable_no_resched();
 467
 468         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 469                 hlist_del(&ri->hlist);
 470                 kfree(ri);
 471         }
 472         /*
 473          * By returning a non-zero value, we are telling
 474          * kprobe_handler() that we don't want the post_handler
 475          * to run (and have re-enabled preemption)
 476          */
 477         return 1;
 478 }
 479 NOKPROBE_SYMBOL(trampoline_probe_handler);
 480
 481 /*
 482  * Called after single-stepping.  p->addr is the address of the
 483  * instruction whose first byte has been replaced by the "breakpoint"
 484  * instruction.  To avoid the SMP problems that can occur when we
 485  * temporarily put back the original opcode to single-step, we
 486  * single-stepped a copy of the instruction.  The address of this
 487  * copy is p->ainsn.insn.
 488  */
 489 static void resume_execution(struct kprobe *p, struct pt_regs *regs)
 490 {
 491         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 492         unsigned long ip = regs->psw.addr & PSW_ADDR_INSN;
 493         int fixup = probe_get_fixup_type(p->ainsn.insn);
 494
 495         /* Check if the kprobes location is an enabled ftrace caller */
 496         if (p->ainsn.is_ftrace_insn) {
 497                 struct ftrace_insn *insn = (struct ftrace_insn *) p->addr;
 498                 struct ftrace_insn call_insn;
 499
 500                 ftrace_generate_call_insn(&call_insn, (unsigned long) p->addr);
 501                 /*
 502                  * A kprobe on an enabled ftrace call site actually single
 503                  * stepped an unconditional branch (ftrace nop equivalent).
 504                  * Now we need to fixup things and pretend that a brasl r0,...
 505                  * was executed instead.
 506                  */
 507                 if (insn->disp == KPROBE_ON_FTRACE_CALL) {
 508                         ip += call_insn.disp * 2 - MCOUNT_INSN_SIZE;
 509                         regs->gprs[0] = (unsigned long)p->addr + sizeof(*insn);
 510                 }
 511         }
 512
 513         if (fixup & FIXUP_PSW_NORMAL)
 514                 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
 515
 516         if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
 517                 int ilen = insn_length(p->ainsn.insn[0] >> 8);
 518                 if (ip - (unsigned long) p->ainsn.insn == ilen)
 519                         ip = (unsigned long) p->addr + ilen;
 520         }
 521
 522         if (fixup & FIXUP_RETURN_REGISTER) {
 523                 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
 524                 regs->gprs[reg] += (unsigned long) p->addr -
 525                                    (unsigned long) p->ainsn.insn;
 526         }
 527
 528         disable_singlestep(kcb, regs, ip);
 529 }
 530 NOKPROBE_SYMBOL(resume_execution);
 531
 532 static int post_kprobe_handler(struct pt_regs *regs)
 533 {
 534         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 535         struct kprobe *p = kprobe_running();
 536
 537         if (!p)
 538                 return 0;
 539
 540         if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
 541                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 542                 p->post_handler(p, regs, 0);
 543         }
 544
 545         resume_execution(p, regs);
 546         pop_kprobe(kcb);
 547         preempt_enable_no_resched();
 548
 549         /*
 550          * if somebody else is singlestepping across a probe point, psw mask
 551          * will have PER set, in which case, continue the remaining processing
 552          * of do_single_step, as if this is not a probe hit.
 553          */
 554         if (regs->psw.mask & PSW_MASK_PER)
 555                 return 0;
 556
 557         return 1;
 558 }
 559 NOKPROBE_SYMBOL(post_kprobe_handler);
 560
 561 static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
 562 {
 563         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 564         struct kprobe *p = kprobe_running();
 565         const struct exception_table_entry *entry;
 566
 567         switch(kcb->kprobe_status) {
 568         case KPROBE_SWAP_INST:
 569                 /* We are here because the instruction replacement failed */
 570                 return 0;
 571         case KPROBE_HIT_SS:
 572         case KPROBE_REENTER:
 573                 /*
 574                  * We are here because the instruction being single
 575                  * stepped caused a page fault. We reset the current
 576                  * kprobe and the nip points back to the probe address
 577                  * and allow the page fault handler to continue as a
 578                  * normal page fault.
 579                  */
 580                 disable_singlestep(kcb, regs, (unsigned long) p->addr);
 581                 pop_kprobe(kcb);
 582                 preempt_enable_no_resched();
 583                 break;
 584         case KPROBE_HIT_ACTIVE:
 585         case KPROBE_HIT_SSDONE:
 586                 /*
 587                  * We increment the nmissed count for accounting,
 588                  * we can also use npre/npostfault count for accounting
 589                  * these specific fault cases.
 590                  */
 591                 kprobes_inc_nmissed_count(p);
 592
 593                 /*
 594                  * We come here because instructions in the pre/post
 595                  * handler caused the page_fault, this could happen
 596                  * if handler tries to access user space by
 597                  * copy_from_user(), get_user() etc. Let the
 598                  * user-specified handler try to fix it first.
 599                  */
 600                 if (p->fault_handler && p->fault_handler(p, regs, trapnr))
 601                         return 1;
 602
 603                 /*
 604                  * In case the user-specified fault handler returned
 605                  * zero, try to fix up.
 606                  */
 607                 entry = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
 608                 if (entry) {
 609                         regs->psw.addr = extable_fixup(entry) | PSW_ADDR_AMODE;
 610                         return 1;
 611                 }
 612
 613                 /*
 614                  * fixup_exception() could not handle it,
 615                  * Let do_page_fault() fix it.
 616                  */
 617                 break;
 618         default:
 619                 break;
 620         }
 621         return 0;
 622 }
 623 NOKPROBE_SYMBOL(kprobe_trap_handler);
 624
 625 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 626 {
 627         int ret;
 628
 629         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 630                 local_irq_disable();
 631         ret = kprobe_trap_handler(regs, trapnr);
 632         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 633                 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
 634         return ret;
 635 }
 636 NOKPROBE_SYMBOL(kprobe_fault_handler);
 637
 638 /*
 639  * Wrapper routine to for handling exceptions.
 640  */
 641 int kprobe_exceptions_notify(struct notifier_block *self,
 642                              unsigned long val, void *data)
 643 {
 644         struct die_args *args = (struct die_args *) data;
 645         struct pt_regs *regs = args->regs;
 646         int ret = NOTIFY_DONE;
 647
 648         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 649                 local_irq_disable();
 650
 651         switch (val) {
 652         case DIE_BPT:
 653                 if (kprobe_handler(regs))
 654                         ret = NOTIFY_STOP;
 655                 break;
 656         case DIE_SSTEP:
 657                 if (post_kprobe_handler(regs))
 658                         ret = NOTIFY_STOP;
 659                 break;
 660         case DIE_TRAP:
 661                 if (!preemptible() && kprobe_running() &&
 662                     kprobe_trap_handler(regs, args->trapnr))
 663                         ret = NOTIFY_STOP;
 664                 break;
 665         default:
 666                 break;
 667         }
 668
 669         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 670                 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
 671
 672         return ret;
 673 }
 674 NOKPROBE_SYMBOL(kprobe_exceptions_notify);
 675
 676 int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 677 {
 678         struct jprobe *jp = container_of(p, struct jprobe, kp);
 679         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 680         unsigned long stack;
 681
 682         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
 683
 684         /* setup return addr to the jprobe handler routine */
 685         regs->psw.addr = (unsigned long) jp->entry | PSW_ADDR_AMODE;
 686         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
 687
 688         /* r15 is the stack pointer */
 689         stack = (unsigned long) regs->gprs[15];
 690
 691         memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack));
 692         return 1;
 693 }
 694 NOKPROBE_SYMBOL(setjmp_pre_handler);
 695
 696 void jprobe_return(void)
 697 {
 698         asm volatile(".word 0x0002");
 699 }
 700 NOKPROBE_SYMBOL(jprobe_return);
 701
 702 int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 703 {
 704         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 705         unsigned long stack;
 706
 707         stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15];
 708
 709         /* Put the regs back */
 710         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
 711         /* put the stack back */
 712         memcpy((void *) stack, kcb->jprobes_stack, MIN_STACK_SIZE(stack));
 713         preempt_enable_no_resched();
 714         return 1;
 715 }
 716 NOKPROBE_SYMBOL(longjmp_break_handler);
 717
 718 static struct kprobe trampoline = {
 719         .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
 720         .pre_handler = trampoline_probe_handler
 721 };
 722
 723 int __init arch_init_kprobes(void)
 724 {
 725         return register_kprobe(&trampoline);
 726 }
 727
 728 int arch_trampoline_kprobe(struct kprobe *p)
 729 {
 730         return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
 731 }
 732 NOKPROBE_SYMBOL(arch_trampoline_kprobe);