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   1 /*
   2  *  Kernel Probes (KProbes)
   3  *  arch/i386/kernel/kprobes.c
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  18  *
  19  * Copyright (C) IBM Corporation, 2002, 2004
  20  *
  21  * 2002-Oct     Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
  22  *              Probes initial implementation ( includes contributions from
  23  *              Rusty Russell).
  24  * 2004-July    Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
  25  *              interface to access function arguments.
  26  * 2005-May     Hien Nguyen <hien@us.ibm.com>, Jim Keniston
  27  *              <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
  28  *              <prasanna@in.ibm.com> added function-return probes.
  29  */
  30
  31 #include <linux/config.h>
  32 #include <linux/kprobes.h>
  33 #include <linux/ptrace.h>
  34 #include <linux/preempt.h>
  35 #include <asm/cacheflush.h>
  36 #include <asm/kdebug.h>
  37 #include <asm/desc.h>
  38 #include <asm/uaccess.h>
  39
  40 void jprobe_return_end(void);
  41
  42 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  43 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  44
  45 /* insert a jmp code */
  46 static __always_inline void set_jmp_op(void *from, void *to)
  47 {
  48         struct __arch_jmp_op {
  49                 char op;
  50                 long raddr;
  51         } __attribute__((packed)) *jop;
  52         jop = (struct __arch_jmp_op *)from;
  53         jop->raddr = (long)(to) - ((long)(from) + 5);
  54         jop->op = RELATIVEJUMP_INSTRUCTION;
  55 }
  56
  57 /*
  58  * returns non-zero if opcodes can be boosted.
  59  */
  60 static __always_inline int can_boost(kprobe_opcode_t opcode)
  61 {
  62         switch (opcode & 0xf0 ) {
  63         case 0x70:
  64                 return 0; /* can't boost conditional jump */
  65         case 0x90:
  66                 /* can't boost call and pushf */
  67                 return opcode != 0x9a && opcode != 0x9c;
  68         case 0xc0:
  69                 /* can't boost undefined opcodes and soft-interruptions */
  70                 return (0xc1 < opcode && opcode < 0xc6) ||
  71                         (0xc7 < opcode && opcode < 0xcc) || opcode == 0xcf;
  72         case 0xd0:
  73                 /* can boost AA* and XLAT */
  74                 return (opcode == 0xd4 || opcode == 0xd5 || opcode == 0xd7);
  75         case 0xe0:
  76                 /* can boost in/out and (may be) jmps */
  77                 return (0xe3 < opcode && opcode != 0xe8);
  78         case 0xf0:
  79                 /* clear and set flags can be boost */
  80                 return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));
  81         default:
  82                 /* currently, can't boost 2 bytes opcodes */
  83                 return opcode != 0x0f;
  84         }
  85 }
  86
  87
  88 /*
  89  * returns non-zero if opcode modifies the interrupt flag.
  90  */
  91 static int __kprobes is_IF_modifier(kprobe_opcode_t opcode)
  92 {
  93         switch (opcode) {
  94         case 0xfa:              /* cli */
  95         case 0xfb:              /* sti */
  96         case 0xcf:              /* iret/iretd */
  97         case 0x9d:              /* popf/popfd */
  98                 return 1;
  99         }
 100         return 0;
 101 }
 102
 103 int __kprobes arch_prepare_kprobe(struct kprobe *p)
 104 {
 105         /* insn: must be on special executable page on i386. */
 106         p->ainsn.insn = get_insn_slot();
 107         if (!p->ainsn.insn)
 108                 return -ENOMEM;
 109
 110         memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
 111         p->opcode = *p->addr;
 112         if (can_boost(p->opcode)) {
 113                 p->ainsn.boostable = 0;
 114         } else {
 115                 p->ainsn.boostable = -1;
 116         }
 117         return 0;
 118 }
 119
 120 void __kprobes arch_arm_kprobe(struct kprobe *p)
 121 {
 122         *p->addr = BREAKPOINT_INSTRUCTION;
 123         flush_icache_range((unsigned long) p->addr,
 124                            (unsigned long) p->addr + sizeof(kprobe_opcode_t));
 125 }
 126
 127 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 128 {
 129         *p->addr = p->opcode;
 130         flush_icache_range((unsigned long) p->addr,
 131                            (unsigned long) p->addr + sizeof(kprobe_opcode_t));
 132 }
 133
 134 void __kprobes arch_remove_kprobe(struct kprobe *p)
 135 {
 136         mutex_lock(&kprobe_mutex);
 137         free_insn_slot(p->ainsn.insn);
 138         mutex_unlock(&kprobe_mutex);
 139 }
 140
 141 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 142 {
 143         kcb->prev_kprobe.kp = kprobe_running();
 144         kcb->prev_kprobe.status = kcb->kprobe_status;
 145         kcb->prev_kprobe.old_eflags = kcb->kprobe_old_eflags;
 146         kcb->prev_kprobe.saved_eflags = kcb->kprobe_saved_eflags;
 147 }
 148
 149 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 150 {
 151         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
 152         kcb->kprobe_status = kcb->prev_kprobe.status;
 153         kcb->kprobe_old_eflags = kcb->prev_kprobe.old_eflags;
 154         kcb->kprobe_saved_eflags = kcb->prev_kprobe.saved_eflags;
 155 }
 156
 157 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 158                                 struct kprobe_ctlblk *kcb)
 159 {
 160         __get_cpu_var(current_kprobe) = p;
 161         kcb->kprobe_saved_eflags = kcb->kprobe_old_eflags
 162                 = (regs->eflags & (TF_MASK | IF_MASK));
 163         if (is_IF_modifier(p->opcode))
 164                 kcb->kprobe_saved_eflags &= ~IF_MASK;
 165 }
 166
 167 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 168 {
 169         regs->eflags |= TF_MASK;
 170         regs->eflags &= ~IF_MASK;
 171         /*single step inline if the instruction is an int3*/
 172         if (p->opcode == BREAKPOINT_INSTRUCTION)
 173                 regs->eip = (unsigned long)p->addr;
 174         else
 175                 regs->eip = (unsigned long)p->ainsn.insn;
 176 }
 177
 178 /* Called with kretprobe_lock held */
 179 void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
 180                                       struct pt_regs *regs)
 181 {
 182         unsigned long *sara = (unsigned long *)&regs->esp;
 183         struct kretprobe_instance *ri;
 184
 185         if ((ri = get_free_rp_inst(rp)) != NULL) {
 186                 ri->rp = rp;
 187                 ri->task = current;
 188                 ri->ret_addr = (kprobe_opcode_t *) *sara;
 189
 190                 /* Replace the return addr with trampoline addr */
 191                 *sara = (unsigned long) &kretprobe_trampoline;
 192
 193                 add_rp_inst(ri);
 194         } else {
 195                 rp->nmissed++;
 196         }
 197 }
 198
 199 /*
 200  * Interrupts are disabled on entry as trap3 is an interrupt gate and they
 201  * remain disabled thorough out this function.
 202  */
 203 static int __kprobes kprobe_handler(struct pt_regs *regs)
 204 {
 205         struct kprobe *p;
 206         int ret = 0;
 207         kprobe_opcode_t *addr;
 208         struct kprobe_ctlblk *kcb;
 209 #ifdef CONFIG_PREEMPT
 210         unsigned pre_preempt_count = preempt_count();
 211 #endif /* CONFIG_PREEMPT */
 212
 213         addr = (kprobe_opcode_t *)(regs->eip - sizeof(kprobe_opcode_t));
 214
 215         /*
 216          * We don't want to be preempted for the entire
 217          * duration of kprobe processing
 218          */
 219         preempt_disable();
 220         kcb = get_kprobe_ctlblk();
 221
 222         /* Check we're not actually recursing */
 223         if (kprobe_running()) {
 224                 p = get_kprobe(addr);
 225                 if (p) {
 226                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
 227                                 *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
 228                                 regs->eflags &= ~TF_MASK;
 229                                 regs->eflags |= kcb->kprobe_saved_eflags;
 230                                 goto no_kprobe;
 231                         }
 232                         /* We have reentered the kprobe_handler(), since
 233                          * another probe was hit while within the handler.
 234                          * We here save the original kprobes variables and
 235                          * just single step on the instruction of the new probe
 236                          * without calling any user handlers.
 237                          */
 238                         save_previous_kprobe(kcb);
 239                         set_current_kprobe(p, regs, kcb);
 240                         kprobes_inc_nmissed_count(p);
 241                         prepare_singlestep(p, regs);
 242                         kcb->kprobe_status = KPROBE_REENTER;
 243                         return 1;
 244                 } else {
 245                         if (regs->eflags & VM_MASK) {
 246                         /* We are in virtual-8086 mode. Return 0 */
 247                                 goto no_kprobe;
 248                         }
 249                         if (*addr != BREAKPOINT_INSTRUCTION) {
 250                         /* The breakpoint instruction was removed by
 251                          * another cpu right after we hit, no further
 252                          * handling of this interrupt is appropriate
 253                          */
 254                                 regs->eip -= sizeof(kprobe_opcode_t);
 255                                 ret = 1;
 256                                 goto no_kprobe;
 257                         }
 258                         p = __get_cpu_var(current_kprobe);
 259                         if (p->break_handler && p->break_handler(p, regs)) {
 260                                 goto ss_probe;
 261                         }
 262                 }
 263                 goto no_kprobe;
 264         }
 265
 266         p = get_kprobe(addr);
 267         if (!p) {
 268                 if (regs->eflags & VM_MASK) {
 269                         /* We are in virtual-8086 mode. Return 0 */
 270                         goto no_kprobe;
 271                 }
 272
 273                 if (*addr != BREAKPOINT_INSTRUCTION) {
 274                         /*
 275                          * The breakpoint instruction was removed right
 276                          * after we hit it.  Another cpu has removed
 277                          * either a probepoint or a debugger breakpoint
 278                          * at this address.  In either case, no further
 279                          * handling of this interrupt is appropriate.
 280                          * Back up over the (now missing) int3 and run
 281                          * the original instruction.
 282                          */
 283                         regs->eip -= sizeof(kprobe_opcode_t);
 284                         ret = 1;
 285                 }
 286                 /* Not one of ours: let kernel handle it */
 287                 goto no_kprobe;
 288         }
 289
 290         set_current_kprobe(p, regs, kcb);
 291         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 292
 293         if (p->pre_handler && p->pre_handler(p, regs))
 294                 /* handler has already set things up, so skip ss setup */
 295                 return 1;
 296
 297         if (p->ainsn.boostable == 1 &&
 298 #ifdef CONFIG_PREEMPT
 299             !(pre_preempt_count) && /*
 300                                        * This enables booster when the direct
 301                                        * execution path aren't preempted.
 302                                        */
 303 #endif /* CONFIG_PREEMPT */
 304             !p->post_handler && !p->break_handler ) {
 305                 /* Boost up -- we can execute copied instructions directly */
 306                 reset_current_kprobe();
 307                 regs->eip = (unsigned long)p->ainsn.insn;
 308                 preempt_enable_no_resched();
 309                 return 1;
 310         }
 311
 312 ss_probe:
 313         prepare_singlestep(p, regs);
 314         kcb->kprobe_status = KPROBE_HIT_SS;
 315         return 1;
 316
 317 no_kprobe:
 318         preempt_enable_no_resched();
 319         return ret;
 320 }
 321
 322 /*
 323  * For function-return probes, init_kprobes() establishes a probepoint
 324  * here. When a retprobed function returns, this probe is hit and
 325  * trampoline_probe_handler() runs, calling the kretprobe's handler.
 326  */
 327  void __kprobes kretprobe_trampoline_holder(void)
 328  {
 329         asm volatile ( ".global kretprobe_trampoline\n"
 330                         "kretprobe_trampoline: \n"
 331                         "       pushf\n"
 332                         /* skip cs, eip, orig_eax, es, ds */
 333                         "       subl $20, %esp\n"
 334                         "       pushl %eax\n"
 335                         "       pushl %ebp\n"
 336                         "       pushl %edi\n"
 337                         "       pushl %esi\n"
 338                         "       pushl %edx\n"
 339                         "       pushl %ecx\n"
 340                         "       pushl %ebx\n"
 341                         "       movl %esp, %eax\n"
 342                         "       call trampoline_handler\n"
 343                         /* move eflags to cs */
 344                         "       movl 48(%esp), %edx\n"
 345                         "       movl %edx, 44(%esp)\n"
 346                         /* save true return address on eflags */
 347                         "       movl %eax, 48(%esp)\n"
 348                         "       popl %ebx\n"
 349                         "       popl %ecx\n"
 350                         "       popl %edx\n"
 351                         "       popl %esi\n"
 352                         "       popl %edi\n"
 353                         "       popl %ebp\n"
 354                         "       popl %eax\n"
 355                         /* skip eip, orig_eax, es, ds */
 356                         "       addl $16, %esp\n"
 357                         "       popf\n"
 358                         "       ret\n");
 359 }
 360
 361 /*
 362  * Called from kretprobe_trampoline
 363  */
 364 fastcall void *__kprobes trampoline_handler(struct pt_regs *regs)
 365 {
 366         struct kretprobe_instance *ri = NULL;
 367         struct hlist_head *head;
 368         struct hlist_node *node, *tmp;
 369         unsigned long flags, orig_ret_address = 0;
 370         unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
 371
 372         spin_lock_irqsave(&kretprobe_lock, flags);
 373         head = kretprobe_inst_table_head(current);
 374
 375         /*
 376          * It is possible to have multiple instances associated with a given
 377          * task either because an multiple functions in the call path
 378          * have a return probe installed on them, and/or more then one return
 379          * return probe was registered for a target function.
 380          *
 381          * We can handle this because:
 382          *     - instances are always inserted at the head of the list
 383          *     - when multiple return probes are registered for the same
 384          *       function, the first instance's ret_addr will point to the
 385          *       real return address, and all the rest will point to
 386          *       kretprobe_trampoline
 387          */
 388         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
 389                 if (ri->task != current)
 390                         /* another task is sharing our hash bucket */
 391                         continue;
 392
 393                 if (ri->rp && ri->rp->handler){
 394                         __get_cpu_var(current_kprobe) = &ri->rp->kp;
 395                         ri->rp->handler(ri, regs);
 396                         __get_cpu_var(current_kprobe) = NULL;
 397                 }
 398
 399                 orig_ret_address = (unsigned long)ri->ret_addr;
 400                 recycle_rp_inst(ri);
 401
 402                 if (orig_ret_address != trampoline_address)
 403                         /*
 404                          * This is the real return address. Any other
 405                          * instances associated with this task are for
 406                          * other calls deeper on the call stack
 407                          */
 408                         break;
 409         }
 410
 411         BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
 412
 413         spin_unlock_irqrestore(&kretprobe_lock, flags);
 414
 415         return (void*)orig_ret_address;
 416 }
 417
 418 /*
 419  * Called after single-stepping.  p->addr is the address of the
 420  * instruction whose first byte has been replaced by the "int 3"
 421  * instruction.  To avoid the SMP problems that can occur when we
 422  * temporarily put back the original opcode to single-step, we
 423  * single-stepped a copy of the instruction.  The address of this
 424  * copy is p->ainsn.insn.
 425  *
 426  * This function prepares to return from the post-single-step
 427  * interrupt.  We have to fix up the stack as follows:
 428  *
 429  * 0) Except in the case of absolute or indirect jump or call instructions,
 430  * the new eip is relative to the copied instruction.  We need to make
 431  * it relative to the original instruction.
 432  *
 433  * 1) If the single-stepped instruction was pushfl, then the TF and IF
 434  * flags are set in the just-pushed eflags, and may need to be cleared.
 435  *
 436  * 2) If the single-stepped instruction was a call, the return address
 437  * that is atop the stack is the address following the copied instruction.
 438  * We need to make it the address following the original instruction.
 439  *
 440  * This function also checks instruction size for preparing direct execution.
 441  */
 442 static void __kprobes resume_execution(struct kprobe *p,
 443                 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 444 {
 445         unsigned long *tos = (unsigned long *)&regs->esp;
 446         unsigned long copy_eip = (unsigned long)p->ainsn.insn;
 447         unsigned long orig_eip = (unsigned long)p->addr;
 448
 449         regs->eflags &= ~TF_MASK;
 450         switch (p->ainsn.insn[0]) {
 451         case 0x9c:              /* pushfl */
 452                 *tos &= ~(TF_MASK | IF_MASK);
 453                 *tos |= kcb->kprobe_old_eflags;
 454                 break;
 455         case 0xc3:              /* ret/lret */
 456         case 0xcb:
 457         case 0xc2:
 458         case 0xca:
 459         case 0xea:              /* jmp absolute -- eip is correct */
 460                 /* eip is already adjusted, no more changes required */
 461                 p->ainsn.boostable = 1;
 462                 goto no_change;
 463         case 0xe8:              /* call relative - Fix return addr */
 464                 *tos = orig_eip + (*tos - copy_eip);
 465                 break;
 466         case 0xff:
 467                 if ((p->ainsn.insn[1] & 0x30) == 0x10) {
 468                         /* call absolute, indirect */
 469                         /*
 470                          * Fix return addr; eip is correct.
 471                          * But this is not boostable
 472                          */
 473                         *tos = orig_eip + (*tos - copy_eip);
 474                         goto no_change;
 475                 } else if (((p->ainsn.insn[1] & 0x31) == 0x20) ||       /* jmp near, absolute indirect */
 476                            ((p->ainsn.insn[1] & 0x31) == 0x21)) {       /* jmp far, absolute indirect */
 477                         /* eip is correct. And this is boostable */
 478                         p->ainsn.boostable = 1;
 479                         goto no_change;
 480                 }
 481         default:
 482                 break;
 483         }
 484
 485         if (p->ainsn.boostable == 0) {
 486                 if ((regs->eip > copy_eip) &&
 487                     (regs->eip - copy_eip) + 5 < MAX_INSN_SIZE) {
 488                         /*
 489                          * These instructions can be executed directly if it
 490                          * jumps back to correct address.
 491                          */
 492                         set_jmp_op((void *)regs->eip,
 493                                    (void *)orig_eip + (regs->eip - copy_eip));
 494                         p->ainsn.boostable = 1;
 495                 } else {
 496                         p->ainsn.boostable = -1;
 497                 }
 498         }
 499
 500         regs->eip = orig_eip + (regs->eip - copy_eip);
 501
 502 no_change:
 503         return;
 504 }
 505
 506 /*
 507  * Interrupts are disabled on entry as trap1 is an interrupt gate and they
 508  * remain disabled thoroughout this function.
 509  */
 510 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 511 {
 512         struct kprobe *cur = kprobe_running();
 513         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 514
 515         if (!cur)
 516                 return 0;
 517
 518         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 519                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 520                 cur->post_handler(cur, regs, 0);
 521         }
 522
 523         resume_execution(cur, regs, kcb);
 524         regs->eflags |= kcb->kprobe_saved_eflags;
 525
 526         /*Restore back the original saved kprobes variables and continue. */
 527         if (kcb->kprobe_status == KPROBE_REENTER) {
 528                 restore_previous_kprobe(kcb);
 529                 goto out;
 530         }
 531         reset_current_kprobe();
 532 out:
 533         preempt_enable_no_resched();
 534
 535         /*
 536          * if somebody else is singlestepping across a probe point, eflags
 537          * will have TF set, in which case, continue the remaining processing
 538          * of do_debug, as if this is not a probe hit.
 539          */
 540         if (regs->eflags & TF_MASK)
 541                 return 0;
 542
 543         return 1;
 544 }
 545
 546 static int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 547 {
 548         struct kprobe *cur = kprobe_running();
 549         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 550
 551         switch(kcb->kprobe_status) {
 552         case KPROBE_HIT_SS:
 553         case KPROBE_REENTER:
 554                 /*
 555                  * We are here because the instruction being single
 556                  * stepped caused a page fault. We reset the current
 557                  * kprobe and the eip points back to the probe address
 558                  * and allow the page fault handler to continue as a
 559                  * normal page fault.
 560                  */
 561                 regs->eip = (unsigned long)cur->addr;
 562                 regs->eflags |= kcb->kprobe_old_eflags;
 563                 if (kcb->kprobe_status == KPROBE_REENTER)
 564                         restore_previous_kprobe(kcb);
 565                 else
 566                         reset_current_kprobe();
 567                 preempt_enable_no_resched();
 568                 break;
 569         case KPROBE_HIT_ACTIVE:
 570         case KPROBE_HIT_SSDONE:
 571                 /*
 572                  * We increment the nmissed count for accounting,
 573                  * we can also use npre/npostfault count for accouting
 574                  * these specific fault cases.
 575                  */
 576                 kprobes_inc_nmissed_count(cur);
 577
 578                 /*
 579                  * We come here because instructions in the pre/post
 580                  * handler caused the page_fault, this could happen
 581                  * if handler tries to access user space by
 582                  * copy_from_user(), get_user() etc. Let the
 583                  * user-specified handler try to fix it first.
 584                  */
 585                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 586                         return 1;
 587
 588                 /*
 589                  * In case the user-specified fault handler returned
 590                  * zero, try to fix up.
 591                  */
 592                 if (fixup_exception(regs))
 593                         return 1;
 594
 595                 /*
 596                  * fixup_exception() could not handle it,
 597                  * Let do_page_fault() fix it.
 598                  */
 599                 break;
 600         default:
 601                 break;
 602         }
 603         return 0;
 604 }
 605
 606 /*
 607  * Wrapper routine to for handling exceptions.
 608  */
 609 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 610                                        unsigned long val, void *data)
 611 {
 612         struct die_args *args = (struct die_args *)data;
 613         int ret = NOTIFY_DONE;
 614
 615         if (args->regs && user_mode(args->regs))
 616                 return ret;
 617
 618         switch (val) {
 619         case DIE_INT3:
 620                 if (kprobe_handler(args->regs))
 621                         ret = NOTIFY_STOP;
 622                 break;
 623         case DIE_DEBUG:
 624                 if (post_kprobe_handler(args->regs))
 625                         ret = NOTIFY_STOP;
 626                 break;
 627         case DIE_GPF:
 628         case DIE_PAGE_FAULT:
 629                 /* kprobe_running() needs smp_processor_id() */
 630                 preempt_disable();
 631                 if (kprobe_running() &&
 632                     kprobe_fault_handler(args->regs, args->trapnr))
 633                         ret = NOTIFY_STOP;
 634                 preempt_enable();
 635                 break;
 636         default:
 637                 break;
 638         }
 639         return ret;
 640 }
 641
 642 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 643 {
 644         struct jprobe *jp = container_of(p, struct jprobe, kp);
 645         unsigned long addr;
 646         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 647
 648         kcb->jprobe_saved_regs = *regs;
 649         kcb->jprobe_saved_esp = &regs->esp;
 650         addr = (unsigned long)(kcb->jprobe_saved_esp);
 651
 652         /*
 653          * TBD: As Linus pointed out, gcc assumes that the callee
 654          * owns the argument space and could overwrite it, e.g.
 655          * tailcall optimization. So, to be absolutely safe
 656          * we also save and restore enough stack bytes to cover
 657          * the argument area.
 658          */
 659         memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr,
 660                         MIN_STACK_SIZE(addr));
 661         regs->eflags &= ~IF_MASK;
 662         regs->eip = (unsigned long)(jp->entry);
 663         return 1;
 664 }
 665
 666 void __kprobes jprobe_return(void)
 667 {
 668         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 669
 670         asm volatile ("       xchgl   %%ebx,%%esp     \n"
 671                       "       int3                      \n"
 672                       "       .globl jprobe_return_end  \n"
 673                       "       jprobe_return_end:        \n"
 674                       "       nop                       \n"::"b"
 675                       (kcb->jprobe_saved_esp):"memory");
 676 }
 677
 678 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 679 {
 680         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 681         u8 *addr = (u8 *) (regs->eip - 1);
 682         unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_esp);
 683         struct jprobe *jp = container_of(p, struct jprobe, kp);
 684
 685         if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
 686                 if (&regs->esp != kcb->jprobe_saved_esp) {
 687                         struct pt_regs *saved_regs =
 688                             container_of(kcb->jprobe_saved_esp,
 689                                             struct pt_regs, esp);
 690                         printk("current esp %p does not match saved esp %p\n",
 691                                &regs->esp, kcb->jprobe_saved_esp);
 692                         printk("Saved registers for jprobe %p\n", jp);
 693                         show_registers(saved_regs);
 694                         printk("Current registers\n");
 695                         show_registers(regs);
 696                         BUG();
 697                 }
 698                 *regs = kcb->jprobe_saved_regs;
 699                 memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
 700                        MIN_STACK_SIZE(stack_addr));
 701                 preempt_enable_no_resched();
 702                 return 1;
 703         }
 704         return 0;
 705 }
 706
 707 int __init arch_init_kprobes(void)
 708 {
 709         return 0;
 710 }