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