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