arch/powerpc/kernel/kprobes.c

   1 /*
   2  *  Kernel Probes (KProbes)
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17  *
  18  * Copyright (C) IBM Corporation, 2002, 2004
  19  *
  20  * 2002-Oct     Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
  21  *              Probes initial implementation ( includes contributions from
  22  *              Rusty Russell).
  23  * 2004-July    Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
  24  *              interface to access function arguments.
  25  * 2004-Nov     Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
  26  *              for PPC64
  27  */
  28
  29 #include <linux/kprobes.h>
  30 #include <linux/ptrace.h>
  31 #include <linux/preempt.h>
  32 #include <linux/extable.h>
  33 #include <linux/kdebug.h>
  34 #include <linux/slab.h>
  35 #include <asm/code-patching.h>
  36 #include <asm/cacheflush.h>
  37 #include <asm/sstep.h>
  38 #include <asm/sections.h>
  39 #include <linux/uaccess.h>
  40
  41 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  42 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  43
  44 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
  45
  46 bool arch_within_kprobe_blacklist(unsigned long addr)
  47 {
  48         return  (addr >= (unsigned long)__kprobes_text_start &&
  49                  addr < (unsigned long)__kprobes_text_end) ||
  50                 (addr >= (unsigned long)_stext &&
  51                  addr < (unsigned long)__head_end);
  52 }
  53
  54 kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
  55 {
  56         kprobe_opcode_t *addr;
  57
  58 #ifdef PPC64_ELF_ABI_v2
  59         /* PPC64 ABIv2 needs local entry point */
  60         addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
  61         if (addr && !offset) {
  62 #ifdef CONFIG_KPROBES_ON_FTRACE
  63                 unsigned long faddr;
  64                 /*
  65                  * Per livepatch.h, ftrace location is always within the first
  66                  * 16 bytes of a function on powerpc with -mprofile-kernel.
  67                  */
  68                 faddr = ftrace_location_range((unsigned long)addr,
  69                                               (unsigned long)addr + 16);
  70                 if (faddr)
  71                         addr = (kprobe_opcode_t *)faddr;
  72                 else
  73 #endif
  74                         addr = (kprobe_opcode_t *)ppc_function_entry(addr);
  75         }
  76 #elif defined(PPC64_ELF_ABI_v1)
  77         /*
  78          * 64bit powerpc ABIv1 uses function descriptors:
  79          * - Check for the dot variant of the symbol first.
  80          * - If that fails, try looking up the symbol provided.
  81          *
  82          * This ensures we always get to the actual symbol and not
  83          * the descriptor.
  84          *
  85          * Also handle <module:symbol> format.
  86          */
  87         char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
  88         const char *modsym;
  89         bool dot_appended = false;
  90         if ((modsym = strchr(name, ':')) != NULL) {
  91                 modsym++;
  92                 if (*modsym != '\0' && *modsym != '.') {
  93                         /* Convert to <module:.symbol> */
  94                         strncpy(dot_name, name, modsym - name);
  95                         dot_name[modsym - name] = '.';
  96                         dot_name[modsym - name + 1] = '\0';
  97                         strncat(dot_name, modsym,
  98                                 sizeof(dot_name) - (modsym - name) - 2);
  99                         dot_appended = true;
 100                 } else {
 101                         dot_name[0] = '\0';
 102                         strncat(dot_name, name, sizeof(dot_name) - 1);
 103                 }
 104         } else if (name[0] != '.') {
 105                 dot_name[0] = '.';
 106                 dot_name[1] = '\0';
 107                 strncat(dot_name, name, KSYM_NAME_LEN - 2);
 108                 dot_appended = true;
 109         } else {
 110                 dot_name[0] = '\0';
 111                 strncat(dot_name, name, KSYM_NAME_LEN - 1);
 112         }
 113         addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name);
 114         if (!addr && dot_appended) {
 115                 /* Let's try the original non-dot symbol lookup */
 116                 addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
 117         }
 118 #else
 119         addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
 120 #endif
 121
 122         return addr;
 123 }
 124
 125 int arch_prepare_kprobe(struct kprobe *p)
 126 {
 127         int ret = 0;
 128         kprobe_opcode_t insn = *p->addr;
 129
 130         if ((unsigned long)p->addr & 0x03) {
 131                 printk("Attempt to register kprobe at an unaligned address\n");
 132                 ret = -EINVAL;
 133         } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
 134                 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
 135                 ret = -EINVAL;
 136         }
 137
 138         /* insn must be on a special executable page on ppc64.  This is
 139          * not explicitly required on ppc32 (right now), but it doesn't hurt */
 140         if (!ret) {
 141                 p->ainsn.insn = get_insn_slot();
 142                 if (!p->ainsn.insn)
 143                         ret = -ENOMEM;
 144         }
 145
 146         if (!ret) {
 147                 memcpy(p->ainsn.insn, p->addr,
 148                                 MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
 149                 p->opcode = *p->addr;
 150                 flush_icache_range((unsigned long)p->ainsn.insn,
 151                         (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
 152         }
 153
 154         p->ainsn.boostable = 0;
 155         return ret;
 156 }
 157 NOKPROBE_SYMBOL(arch_prepare_kprobe);
 158
 159 void arch_arm_kprobe(struct kprobe *p)
 160 {
 161         patch_instruction(p->addr, BREAKPOINT_INSTRUCTION);
 162 }
 163 NOKPROBE_SYMBOL(arch_arm_kprobe);
 164
 165 void arch_disarm_kprobe(struct kprobe *p)
 166 {
 167         patch_instruction(p->addr, p->opcode);
 168 }
 169 NOKPROBE_SYMBOL(arch_disarm_kprobe);
 170
 171 void arch_remove_kprobe(struct kprobe *p)
 172 {
 173         if (p->ainsn.insn) {
 174                 free_insn_slot(p->ainsn.insn, 0);
 175                 p->ainsn.insn = NULL;
 176         }
 177 }
 178 NOKPROBE_SYMBOL(arch_remove_kprobe);
 179
 180 static nokprobe_inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 181 {
 182         enable_single_step(regs);
 183
 184         /*
 185          * On powerpc we should single step on the original
 186          * instruction even if the probed insn is a trap
 187          * variant as values in regs could play a part in
 188          * if the trap is taken or not
 189          */
 190         regs->nip = (unsigned long)p->ainsn.insn;
 191 }
 192
 193 static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
 194 {
 195         kcb->prev_kprobe.kp = kprobe_running();
 196         kcb->prev_kprobe.status = kcb->kprobe_status;
 197         kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
 198 }
 199
 200 static nokprobe_inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 201 {
 202         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 203         kcb->kprobe_status = kcb->prev_kprobe.status;
 204         kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
 205 }
 206
 207 static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 208                                 struct kprobe_ctlblk *kcb)
 209 {
 210         __this_cpu_write(current_kprobe, p);
 211         kcb->kprobe_saved_msr = regs->msr;
 212 }
 213
 214 bool arch_kprobe_on_func_entry(unsigned long offset)
 215 {
 216 #ifdef PPC64_ELF_ABI_v2
 217 #ifdef CONFIG_KPROBES_ON_FTRACE
 218         return offset <= 16;
 219 #else
 220         return offset <= 8;
 221 #endif
 222 #else
 223         return !offset;
 224 #endif
 225 }
 226
 227 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
 228 {
 229         ri->ret_addr = (kprobe_opcode_t *)regs->link;
 230
 231         /* Replace the return addr with trampoline addr */
 232         regs->link = (unsigned long)kretprobe_trampoline;
 233 }
 234 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
 235
 236 static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
 237 {
 238         int ret;
 239         unsigned int insn = *p->ainsn.insn;
 240
 241         /* regs->nip is also adjusted if emulate_step returns 1 */
 242         ret = emulate_step(regs, insn);
 243         if (ret > 0) {
 244                 /*
 245                  * Once this instruction has been boosted
 246                  * successfully, set the boostable flag
 247                  */
 248                 if (unlikely(p->ainsn.boostable == 0))
 249                         p->ainsn.boostable = 1;
 250         } else if (ret < 0) {
 251                 /*
 252                  * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
 253                  * So, we should never get here... but, its still
 254                  * good to catch them, just in case...
 255                  */
 256                 printk("Can't step on instruction %x\n", insn);
 257                 BUG();
 258         } else {
 259                 /*
 260                  * If we haven't previously emulated this instruction, then it
 261                  * can't be boosted. Note it down so we don't try to do so again.
 262                  *
 263                  * If, however, we had emulated this instruction in the past,
 264                  * then this is just an error with the current run (for
 265                  * instance, exceptions due to a load/store). We return 0 so
 266                  * that this is now single-stepped, but continue to try
 267                  * emulating it in subsequent probe hits.
 268                  */
 269                 if (unlikely(p->ainsn.boostable != 1))
 270                         p->ainsn.boostable = -1;
 271         }
 272
 273         return ret;
 274 }
 275 NOKPROBE_SYMBOL(try_to_emulate);
 276
 277 int kprobe_handler(struct pt_regs *regs)
 278 {
 279         struct kprobe *p;
 280         int ret = 0;
 281         unsigned int *addr = (unsigned int *)regs->nip;
 282         struct kprobe_ctlblk *kcb;
 283
 284         if (user_mode(regs))
 285                 return 0;
 286
 287         /*
 288          * We don't want to be preempted for the entire
 289          * duration of kprobe processing
 290          */
 291         preempt_disable();
 292         kcb = get_kprobe_ctlblk();
 293
 294         /* Check we're not actually recursing */
 295         if (kprobe_running()) {
 296                 p = get_kprobe(addr);
 297                 if (p) {
 298                         kprobe_opcode_t insn = *p->ainsn.insn;
 299                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
 300                                         is_trap(insn)) {
 301                                 /* Turn off 'trace' bits */
 302                                 regs->msr &= ~MSR_SINGLESTEP;
 303                                 regs->msr |= kcb->kprobe_saved_msr;
 304                                 goto no_kprobe;
 305                         }
 306                         /* We have reentered the kprobe_handler(), since
 307                          * another probe was hit while within the handler.
 308                          * We here save the original kprobes variables and
 309                          * just single step on the instruction of the new probe
 310                          * without calling any user handlers.
 311                          */
 312                         save_previous_kprobe(kcb);
 313                         set_current_kprobe(p, regs, kcb);
 314                         kprobes_inc_nmissed_count(p);
 315                         kcb->kprobe_status = KPROBE_REENTER;
 316                         if (p->ainsn.boostable >= 0) {
 317                                 ret = try_to_emulate(p, regs);
 318
 319                                 if (ret > 0) {
 320                                         restore_previous_kprobe(kcb);
 321                                         preempt_enable_no_resched();
 322                                         return 1;
 323                                 }
 324                         }
 325                         prepare_singlestep(p, regs);
 326                         return 1;
 327                 } else {
 328                         if (*addr != BREAKPOINT_INSTRUCTION) {
 329                                 /* If trap variant, then it belongs not to us */
 330                                 kprobe_opcode_t cur_insn = *addr;
 331                                 if (is_trap(cur_insn))
 332                                         goto no_kprobe;
 333                                 /* The breakpoint instruction was removed by
 334                                  * another cpu right after we hit, no further
 335                                  * handling of this interrupt is appropriate
 336                                  */
 337                                 ret = 1;
 338                                 goto no_kprobe;
 339                         }
 340                         p = __this_cpu_read(current_kprobe);
 341                         if (p->break_handler && p->break_handler(p, regs)) {
 342                                 if (!skip_singlestep(p, regs, kcb))
 343                                         goto ss_probe;
 344                                 ret = 1;
 345                         }
 346                 }
 347                 goto no_kprobe;
 348         }
 349
 350         p = get_kprobe(addr);
 351         if (!p) {
 352                 if (*addr != BREAKPOINT_INSTRUCTION) {
 353                         /*
 354                          * PowerPC has multiple variants of the "trap"
 355                          * instruction. If the current instruction is a
 356                          * trap variant, it could belong to someone else
 357                          */
 358                         kprobe_opcode_t cur_insn = *addr;
 359                         if (is_trap(cur_insn))
 360                                 goto no_kprobe;
 361                         /*
 362                          * The breakpoint instruction was removed right
 363                          * after we hit it.  Another cpu has removed
 364                          * either a probepoint or a debugger breakpoint
 365                          * at this address.  In either case, no further
 366                          * handling of this interrupt is appropriate.
 367                          */
 368                         ret = 1;
 369                 }
 370                 /* Not one of ours: let kernel handle it */
 371                 goto no_kprobe;
 372         }
 373
 374         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 375         set_current_kprobe(p, regs, kcb);
 376         if (p->pre_handler && p->pre_handler(p, regs))
 377                 /* handler has already set things up, so skip ss setup */
 378                 return 1;
 379
 380 ss_probe:
 381         if (p->ainsn.boostable >= 0) {
 382                 ret = try_to_emulate(p, regs);
 383
 384                 if (ret > 0) {
 385                         if (p->post_handler)
 386                                 p->post_handler(p, regs, 0);
 387
 388                         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 389                         reset_current_kprobe();
 390                         preempt_enable_no_resched();
 391                         return 1;
 392                 }
 393         }
 394         prepare_singlestep(p, regs);
 395         kcb->kprobe_status = KPROBE_HIT_SS;
 396         return 1;
 397
 398 no_kprobe:
 399         preempt_enable_no_resched();
 400         return ret;
 401 }
 402 NOKPROBE_SYMBOL(kprobe_handler);
 403
 404 /*
 405  * Function return probe trampoline:
 406  *      - init_kprobes() establishes a probepoint here
 407  *      - When the probed function returns, this probe
 408  *              causes the handlers to fire
 409  */
 410 asm(".global kretprobe_trampoline\n"
 411         ".type kretprobe_trampoline, @function\n"
 412         "kretprobe_trampoline:\n"
 413         "nop\n"
 414         "blr\n"
 415         ".size kretprobe_trampoline, .-kretprobe_trampoline\n");
 416
 417 /*
 418  * Called when the probe at kretprobe trampoline is hit
 419  */
 420 static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 421 {
 422         struct kretprobe_instance *ri = NULL;
 423         struct hlist_head *head, empty_rp;
 424         struct hlist_node *tmp;
 425         unsigned long flags, orig_ret_address = 0;
 426         unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
 427
 428         INIT_HLIST_HEAD(&empty_rp);
 429         kretprobe_hash_lock(current, &head, &flags);
 430
 431         /*
 432          * It is possible to have multiple instances associated with a given
 433          * task either because an multiple functions in the call path
 434          * have a return probe installed on them, and/or more than one return
 435          * return probe was registered for a target function.
 436          *
 437          * We can handle this because:
 438          *     - instances are always inserted at the head of the list
 439          *     - when multiple return probes are registered for the same
 440          *       function, the first instance's ret_addr will point to the
 441          *       real return address, and all the rest will point to
 442          *       kretprobe_trampoline
 443          */
 444         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 445                 if (ri->task != current)
 446                         /* another task is sharing our hash bucket */
 447                         continue;
 448
 449                 if (ri->rp && ri->rp->handler)
 450                         ri->rp->handler(ri, regs);
 451
 452                 orig_ret_address = (unsigned long)ri->ret_addr;
 453                 recycle_rp_inst(ri, &empty_rp);
 454
 455                 if (orig_ret_address != trampoline_address)
 456                         /*
 457                          * This is the real return address. Any other
 458                          * instances associated with this task are for
 459                          * other calls deeper on the call stack
 460                          */
 461                         break;
 462         }
 463
 464         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 465         regs->nip = orig_ret_address;
 466         /*
 467          * Make LR point to the orig_ret_address.
 468          * When the 'nop' inside the kretprobe_trampoline
 469          * is optimized, we can do a 'blr' after executing the
 470          * detour buffer code.
 471          */
 472         regs->link = orig_ret_address;
 473
 474         reset_current_kprobe();
 475         kretprobe_hash_unlock(current, &flags);
 476         preempt_enable_no_resched();
 477
 478         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 479                 hlist_del(&ri->hlist);
 480                 kfree(ri);
 481         }
 482         /*
 483          * By returning a non-zero value, we are telling
 484          * kprobe_handler() that we don't want the post_handler
 485          * to run (and have re-enabled preemption)
 486          */
 487         return 1;
 488 }
 489 NOKPROBE_SYMBOL(trampoline_probe_handler);
 490
 491 /*
 492  * Called after single-stepping.  p->addr is the address of the
 493  * instruction whose first byte has been replaced by the "breakpoint"
 494  * instruction.  To avoid the SMP problems that can occur when we
 495  * temporarily put back the original opcode to single-step, we
 496  * single-stepped a copy of the instruction.  The address of this
 497  * copy is p->ainsn.insn.
 498  */
 499 int kprobe_post_handler(struct pt_regs *regs)
 500 {
 501         struct kprobe *cur = kprobe_running();
 502         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 503
 504         if (!cur || user_mode(regs))
 505                 return 0;
 506
 507         /* make sure we got here for instruction we have a kprobe on */
 508         if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
 509                 return 0;
 510
 511         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 512                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 513                 cur->post_handler(cur, regs, 0);
 514         }
 515
 516         /* Adjust nip to after the single-stepped instruction */
 517         regs->nip = (unsigned long)cur->addr + 4;
 518         regs->msr |= kcb->kprobe_saved_msr;
 519
 520         /*Restore back the original saved kprobes variables and continue. */
 521         if (kcb->kprobe_status == KPROBE_REENTER) {
 522                 restore_previous_kprobe(kcb);
 523                 goto out;
 524         }
 525         reset_current_kprobe();
 526 out:
 527         preempt_enable_no_resched();
 528
 529         /*
 530          * if somebody else is singlestepping across a probe point, msr
 531          * will have DE/SE set, in which case, continue the remaining processing
 532          * of do_debug, as if this is not a probe hit.
 533          */
 534         if (regs->msr & MSR_SINGLESTEP)
 535                 return 0;
 536
 537         return 1;
 538 }
 539 NOKPROBE_SYMBOL(kprobe_post_handler);
 540
 541 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 542 {
 543         struct kprobe *cur = kprobe_running();
 544         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 545         const struct exception_table_entry *entry;
 546
 547         switch(kcb->kprobe_status) {
 548         case KPROBE_HIT_SS:
 549         case KPROBE_REENTER:
 550                 /*
 551                  * We are here because the instruction being single
 552                  * stepped caused a page fault. We reset the current
 553                  * kprobe and the nip points back to the probe address
 554                  * and allow the page fault handler to continue as a
 555                  * normal page fault.
 556                  */
 557                 regs->nip = (unsigned long)cur->addr;
 558                 regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
 559                 regs->msr |= kcb->kprobe_saved_msr;
 560                 if (kcb->kprobe_status == KPROBE_REENTER)
 561                         restore_previous_kprobe(kcb);
 562                 else
 563                         reset_current_kprobe();
 564                 preempt_enable_no_resched();
 565                 break;
 566         case KPROBE_HIT_ACTIVE:
 567         case KPROBE_HIT_SSDONE:
 568                 /*
 569                  * We increment the nmissed count for accounting,
 570                  * we can also use npre/npostfault count for accounting
 571                  * these specific fault cases.
 572                  */
 573                 kprobes_inc_nmissed_count(cur);
 574
 575                 /*
 576                  * We come here because instructions in the pre/post
 577                  * handler caused the page_fault, this could happen
 578                  * if handler tries to access user space by
 579                  * copy_from_user(), get_user() etc. Let the
 580                  * user-specified handler try to fix it first.
 581                  */
 582                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 583                         return 1;
 584
 585                 /*
 586                  * In case the user-specified fault handler returned
 587                  * zero, try to fix up.
 588                  */
 589                 if ((entry = search_exception_tables(regs->nip)) != NULL) {
 590                         regs->nip = extable_fixup(entry);
 591                         return 1;
 592                 }
 593
 594                 /*
 595                  * fixup_exception() could not handle it,
 596                  * Let do_page_fault() fix it.
 597                  */
 598                 break;
 599         default:
 600                 break;
 601         }
 602         return 0;
 603 }
 604 NOKPROBE_SYMBOL(kprobe_fault_handler);
 605
 606 unsigned long arch_deref_entry_point(void *entry)
 607 {
 608         return ppc_global_function_entry(entry);
 609 }
 610 NOKPROBE_SYMBOL(arch_deref_entry_point);
 611
 612 int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 613 {
 614         struct jprobe *jp = container_of(p, struct jprobe, kp);
 615         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 616
 617         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
 618
 619         /* setup return addr to the jprobe handler routine */
 620         regs->nip = arch_deref_entry_point(jp->entry);
 621 #ifdef PPC64_ELF_ABI_v2
 622         regs->gpr[12] = (unsigned long)jp->entry;
 623 #elif defined(PPC64_ELF_ABI_v1)
 624         regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
 625 #endif
 626
 627         /*
 628          * jprobes use jprobe_return() which skips the normal return
 629          * path of the function, and this messes up the accounting of the
 630          * function graph tracer.
 631          *
 632          * Pause function graph tracing while performing the jprobe function.
 633          */
 634         pause_graph_tracing();
 635
 636         return 1;
 637 }
 638 NOKPROBE_SYMBOL(setjmp_pre_handler);
 639
 640 void __used jprobe_return(void)
 641 {
 642         asm volatile("jprobe_return_trap:\n"
 643                      "trap\n"
 644                      ::: "memory");
 645 }
 646 NOKPROBE_SYMBOL(jprobe_return);
 647
 648 int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 649 {
 650         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 651
 652         if (regs->nip != ppc_kallsyms_lookup_name("jprobe_return_trap")) {
 653                 pr_debug("longjmp_break_handler NIP (0x%lx) does not match jprobe_return_trap (0x%lx)\n",
 654                                 regs->nip, ppc_kallsyms_lookup_name("jprobe_return_trap"));
 655                 return 0;
 656         }
 657
 658         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
 659         /* It's OK to start function graph tracing again */
 660         unpause_graph_tracing();
 661         preempt_enable_no_resched();
 662         return 1;
 663 }
 664 NOKPROBE_SYMBOL(longjmp_break_handler);
 665
 666 static struct kprobe trampoline_p = {
 667         .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
 668         .pre_handler = trampoline_probe_handler
 669 };
 670
 671 int __init arch_init_kprobes(void)
 672 {
 673         return register_kprobe(&trampoline_p);
 674 }
 675
 676 int arch_trampoline_kprobe(struct kprobe *p)
 677 {
 678         if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
 679                 return 1;
 680
 681         return 0;
 682 }
 683 NOKPROBE_SYMBOL(arch_trampoline_kprobe);