git.oblomov.eu Git - linux-2.6/blob - 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/module.h>
  33 #include <linux/kdebug.h>
  34 #include <asm/cacheflush.h>
  35 #include <asm/sstep.h>
  36 #include <asm/uaccess.h>
  37
  38 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  39 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  40
  41 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
  42
  43 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  44 {
  45         int ret = 0;
  46         kprobe_opcode_t insn = *p->addr;
  47
  48         if ((unsigned long)p->addr & 0x03) {
  49                 printk("Attempt to register kprobe at an unaligned address\n");
  50                 ret = -EINVAL;
  51         } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
  52                 printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
  53                 ret = -EINVAL;
  54         }
  55
  56         /* insn must be on a special executable page on ppc64 */
  57         if (!ret) {
  58                 p->ainsn.insn = get_insn_slot();
  59                 if (!p->ainsn.insn)
  60                         ret = -ENOMEM;
  61         }
  62
  63         if (!ret) {
  64                 memcpy(p->ainsn.insn, p->addr,
  65                                 MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
  66                 p->opcode = *p->addr;
  67                 flush_icache_range((unsigned long)p->ainsn.insn,
  68                         (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
  69         }
  70
  71         p->ainsn.boostable = 0;
  72         return ret;
  73 }
  74
  75 void __kprobes arch_arm_kprobe(struct kprobe *p)
  76 {
  77         *p->addr = BREAKPOINT_INSTRUCTION;
  78         flush_icache_range((unsigned long) p->addr,
  79                            (unsigned long) p->addr + sizeof(kprobe_opcode_t));
  80 }
  81
  82 void __kprobes arch_disarm_kprobe(struct kprobe *p)
  83 {
  84         *p->addr = p->opcode;
  85         flush_icache_range((unsigned long) p->addr,
  86                            (unsigned long) p->addr + sizeof(kprobe_opcode_t));
  87 }
  88
  89 void __kprobes arch_remove_kprobe(struct kprobe *p)
  90 {
  91         mutex_lock(&kprobe_mutex);
  92         free_insn_slot(p->ainsn.insn, 0);
  93         mutex_unlock(&kprobe_mutex);
  94 }
  95
  96 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
  97 {
  98         regs->msr |= MSR_SE;
  99
 100         /*
 101          * On powerpc we should single step on the original
 102          * instruction even if the probed insn is a trap
 103          * variant as values in regs could play a part in
 104          * if the trap is taken or not
 105          */
 106         regs->nip = (unsigned long)p->ainsn.insn;
 107 }
 108
 109 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 110 {
 111         kcb->prev_kprobe.kp = kprobe_running();
 112         kcb->prev_kprobe.status = kcb->kprobe_status;
 113         kcb->prev_kprobe.saved_msr = kcb->kprobe_saved_msr;
 114 }
 115
 116 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 117 {
 118         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
 119         kcb->kprobe_status = kcb->prev_kprobe.status;
 120         kcb->kprobe_saved_msr = kcb->prev_kprobe.saved_msr;
 121 }
 122
 123 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 124                                 struct kprobe_ctlblk *kcb)
 125 {
 126         __get_cpu_var(current_kprobe) = p;
 127         kcb->kprobe_saved_msr = regs->msr;
 128 }
 129
 130 /* Called with kretprobe_lock held */
 131 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 132                                       struct pt_regs *regs)
 133 {
 134         ri->ret_addr = (kprobe_opcode_t *)regs->link;
 135
 136         /* Replace the return addr with trampoline addr */
 137         regs->link = (unsigned long)kretprobe_trampoline;
 138 }
 139
 140 static int __kprobes kprobe_handler(struct pt_regs *regs)
 141 {
 142         struct kprobe *p;
 143         int ret = 0;
 144         unsigned int *addr = (unsigned int *)regs->nip;
 145         struct kprobe_ctlblk *kcb;
 146
 147         /*
 148          * We don't want to be preempted for the entire
 149          * duration of kprobe processing
 150          */
 151         preempt_disable();
 152         kcb = get_kprobe_ctlblk();
 153
 154         /* Check we're not actually recursing */
 155         if (kprobe_running()) {
 156                 p = get_kprobe(addr);
 157                 if (p) {
 158                         kprobe_opcode_t insn = *p->ainsn.insn;
 159                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
 160                                         is_trap(insn)) {
 161                                 regs->msr &= ~MSR_SE;
 162                                 regs->msr |= kcb->kprobe_saved_msr;
 163                                 goto no_kprobe;
 164                         }
 165                         /* We have reentered the kprobe_handler(), since
 166                          * another probe was hit while within the handler.
 167                          * We here save the original kprobes variables and
 168                          * just single step on the instruction of the new probe
 169                          * without calling any user handlers.
 170                          */
 171                         save_previous_kprobe(kcb);
 172                         set_current_kprobe(p, regs, kcb);
 173                         kcb->kprobe_saved_msr = regs->msr;
 174                         kprobes_inc_nmissed_count(p);
 175                         prepare_singlestep(p, regs);
 176                         kcb->kprobe_status = KPROBE_REENTER;
 177                         return 1;
 178                 } else {
 179                         if (*addr != BREAKPOINT_INSTRUCTION) {
 180                                 /* If trap variant, then it belongs not to us */
 181                                 kprobe_opcode_t cur_insn = *addr;
 182                                 if (is_trap(cur_insn))
 183                                         goto no_kprobe;
 184                                 /* The breakpoint instruction was removed by
 185                                  * another cpu right after we hit, no further
 186                                  * handling of this interrupt is appropriate
 187                                  */
 188                                 ret = 1;
 189                                 goto no_kprobe;
 190                         }
 191                         p = __get_cpu_var(current_kprobe);
 192                         if (p->break_handler && p->break_handler(p, regs)) {
 193                                 goto ss_probe;
 194                         }
 195                 }
 196                 goto no_kprobe;
 197         }
 198
 199         p = get_kprobe(addr);
 200         if (!p) {
 201                 if (*addr != BREAKPOINT_INSTRUCTION) {
 202                         /*
 203                          * PowerPC has multiple variants of the "trap"
 204                          * instruction. If the current instruction is a
 205                          * trap variant, it could belong to someone else
 206                          */
 207                         kprobe_opcode_t cur_insn = *addr;
 208                         if (is_trap(cur_insn))
 209                                 goto no_kprobe;
 210                         /*
 211                          * The breakpoint instruction was removed right
 212                          * after we hit it.  Another cpu has removed
 213                          * either a probepoint or a debugger breakpoint
 214                          * at this address.  In either case, no further
 215                          * handling of this interrupt is appropriate.
 216                          */
 217                         ret = 1;
 218                 }
 219                 /* Not one of ours: let kernel handle it */
 220                 goto no_kprobe;
 221         }
 222
 223         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 224         set_current_kprobe(p, regs, kcb);
 225         if (p->pre_handler && p->pre_handler(p, regs))
 226                 /* handler has already set things up, so skip ss setup */
 227                 return 1;
 228
 229 ss_probe:
 230         if (p->ainsn.boostable >= 0) {
 231                 unsigned int insn = *p->ainsn.insn;
 232
 233                 /* regs->nip is also adjusted if emulate_step returns 1 */
 234                 ret = emulate_step(regs, insn);
 235                 if (ret > 0) {
 236                         /*
 237                          * Once this instruction has been boosted
 238                          * successfully, set the boostable flag
 239                          */
 240                         if (unlikely(p->ainsn.boostable == 0))
 241                                 p->ainsn.boostable = 1;
 242
 243                         if (p->post_handler)
 244                                 p->post_handler(p, regs, 0);
 245
 246                         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 247                         reset_current_kprobe();
 248                         preempt_enable_no_resched();
 249                         return 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 if (ret == 0)
 259                         /* This instruction can't be boosted */
 260                         p->ainsn.boostable = -1;
 261         }
 262         prepare_singlestep(p, regs);
 263         kcb->kprobe_status = KPROBE_HIT_SS;
 264         return 1;
 265
 266 no_kprobe:
 267         preempt_enable_no_resched();
 268         return ret;
 269 }
 270
 271 /*
 272  * Function return probe trampoline:
 273  *      - init_kprobes() establishes a probepoint here
 274  *      - When the probed function returns, this probe
 275  *              causes the handlers to fire
 276  */
 277 static void __used kretprobe_trampoline_holder(void)
 278 {
 279         asm volatile(".global kretprobe_trampoline\n"
 280                         "kretprobe_trampoline:\n"
 281                         "nop\n");
 282 }
 283
 284 /*
 285  * Called when the probe at kretprobe trampoline is hit
 286  */
 287 static int __kprobes trampoline_probe_handler(struct kprobe *p,
 288                                                 struct pt_regs *regs)
 289 {
 290         struct kretprobe_instance *ri = NULL;
 291         struct hlist_head *head, empty_rp;
 292         struct hlist_node *node, *tmp;
 293         unsigned long flags, orig_ret_address = 0;
 294         unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
 295
 296         INIT_HLIST_HEAD(&empty_rp);
 297         spin_lock_irqsave(&kretprobe_lock, flags);
 298         head = kretprobe_inst_table_head(current);
 299
 300         /*
 301          * It is possible to have multiple instances associated with a given
 302          * task either because an multiple functions in the call path
 303          * have a return probe installed on them, and/or more then one return
 304          * return probe was registered for a target function.
 305          *
 306          * We can handle this because:
 307          *     - instances are always inserted at the head of the list
 308          *     - when multiple return probes are registered for the same
 309          *       function, the first instance's ret_addr will point to the
 310          *       real return address, and all the rest will point to
 311          *       kretprobe_trampoline
 312          */
 313         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
 314                 if (ri->task != current)
 315                         /* another task is sharing our hash bucket */
 316                         continue;
 317
 318                 if (ri->rp && ri->rp->handler)
 319                         ri->rp->handler(ri, regs);
 320
 321                 orig_ret_address = (unsigned long)ri->ret_addr;
 322                 recycle_rp_inst(ri, &empty_rp);
 323
 324                 if (orig_ret_address != trampoline_address)
 325                         /*
 326                          * This is the real return address. Any other
 327                          * instances associated with this task are for
 328                          * other calls deeper on the call stack
 329                          */
 330                         break;
 331         }
 332
 333         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 334         regs->nip = orig_ret_address;
 335
 336         reset_current_kprobe();
 337         spin_unlock_irqrestore(&kretprobe_lock, flags);
 338         preempt_enable_no_resched();
 339
 340         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
 341                 hlist_del(&ri->hlist);
 342                 kfree(ri);
 343         }
 344         /*
 345          * By returning a non-zero value, we are telling
 346          * kprobe_handler() that we don't want the post_handler
 347          * to run (and have re-enabled preemption)
 348          */
 349         return 1;
 350 }
 351
 352 /*
 353  * Called after single-stepping.  p->addr is the address of the
 354  * instruction whose first byte has been replaced by the "breakpoint"
 355  * instruction.  To avoid the SMP problems that can occur when we
 356  * temporarily put back the original opcode to single-step, we
 357  * single-stepped a copy of the instruction.  The address of this
 358  * copy is p->ainsn.insn.
 359  */
 360 static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
 361 {
 362         int ret;
 363         unsigned int insn = *p->ainsn.insn;
 364
 365         regs->nip = (unsigned long)p->addr;
 366         ret = emulate_step(regs, insn);
 367         if (ret == 0)
 368                 regs->nip = (unsigned long)p->addr + 4;
 369 }
 370
 371 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 372 {
 373         struct kprobe *cur = kprobe_running();
 374         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 375
 376         if (!cur)
 377                 return 0;
 378
 379         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 380                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 381                 cur->post_handler(cur, regs, 0);
 382         }
 383
 384         resume_execution(cur, regs);
 385         regs->msr |= kcb->kprobe_saved_msr;
 386
 387         /*Restore back the original saved kprobes variables and continue. */
 388         if (kcb->kprobe_status == KPROBE_REENTER) {
 389                 restore_previous_kprobe(kcb);
 390                 goto out;
 391         }
 392         reset_current_kprobe();
 393 out:
 394         preempt_enable_no_resched();
 395
 396         /*
 397          * if somebody else is singlestepping across a probe point, msr
 398          * will have SE set, in which case, continue the remaining processing
 399          * of do_debug, as if this is not a probe hit.
 400          */
 401         if (regs->msr & MSR_SE)
 402                 return 0;
 403
 404         return 1;
 405 }
 406
 407 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 408 {
 409         struct kprobe *cur = kprobe_running();
 410         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 411         const struct exception_table_entry *entry;
 412
 413         switch(kcb->kprobe_status) {
 414         case KPROBE_HIT_SS:
 415         case KPROBE_REENTER:
 416                 /*
 417                  * We are here because the instruction being single
 418                  * stepped caused a page fault. We reset the current
 419                  * kprobe and the nip points back to the probe address
 420                  * and allow the page fault handler to continue as a
 421                  * normal page fault.
 422                  */
 423                 regs->nip = (unsigned long)cur->addr;
 424                 regs->msr &= ~MSR_SE;
 425                 regs->msr |= kcb->kprobe_saved_msr;
 426                 if (kcb->kprobe_status == KPROBE_REENTER)
 427                         restore_previous_kprobe(kcb);
 428                 else
 429                         reset_current_kprobe();
 430                 preempt_enable_no_resched();
 431                 break;
 432         case KPROBE_HIT_ACTIVE:
 433         case KPROBE_HIT_SSDONE:
 434                 /*
 435                  * We increment the nmissed count for accounting,
 436                  * we can also use npre/npostfault count for accouting
 437                  * these specific fault cases.
 438                  */
 439                 kprobes_inc_nmissed_count(cur);
 440
 441                 /*
 442                  * We come here because instructions in the pre/post
 443                  * handler caused the page_fault, this could happen
 444                  * if handler tries to access user space by
 445                  * copy_from_user(), get_user() etc. Let the
 446                  * user-specified handler try to fix it first.
 447                  */
 448                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 449                         return 1;
 450
 451                 /*
 452                  * In case the user-specified fault handler returned
 453                  * zero, try to fix up.
 454                  */
 455                 if ((entry = search_exception_tables(regs->nip)) != NULL) {
 456                         regs->nip = entry->fixup;
 457                         return 1;
 458                 }
 459
 460                 /*
 461                  * fixup_exception() could not handle it,
 462                  * Let do_page_fault() fix it.
 463                  */
 464                 break;
 465         default:
 466                 break;
 467         }
 468         return 0;
 469 }
 470
 471 /*
 472  * Wrapper routine to for handling exceptions.
 473  */
 474 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 475                                        unsigned long val, void *data)
 476 {
 477         struct die_args *args = (struct die_args *)data;
 478         int ret = NOTIFY_DONE;
 479
 480         if (args->regs && user_mode(args->regs))
 481                 return ret;
 482
 483         switch (val) {
 484         case DIE_BPT:
 485                 if (kprobe_handler(args->regs))
 486                         ret = NOTIFY_STOP;
 487                 break;
 488         case DIE_SSTEP:
 489                 if (post_kprobe_handler(args->regs))
 490                         ret = NOTIFY_STOP;
 491                 break;
 492         default:
 493                 break;
 494         }
 495         return ret;
 496 }
 497
 498 #ifdef CONFIG_PPC64
 499 unsigned long arch_deref_entry_point(void *entry)
 500 {
 501         return (unsigned long)(((func_descr_t *)entry)->entry);
 502 }
 503 #endif
 504
 505 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 506 {
 507         struct jprobe *jp = container_of(p, struct jprobe, kp);
 508         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 509
 510         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
 511
 512         /* setup return addr to the jprobe handler routine */
 513         regs->nip = arch_deref_entry_point(jp->entry);
 514 #ifdef CONFIG_PPC64
 515         regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
 516 #endif
 517
 518         return 1;
 519 }
 520
 521 void __used __kprobes jprobe_return(void)
 522 {
 523         asm volatile("trap" ::: "memory");
 524 }
 525
 526 static void __used __kprobes jprobe_return_end(void)
 527 {
 528 };
 529
 530 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 531 {
 532         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 533
 534         /*
 535          * FIXME - we should ideally be validating that we got here 'cos
 536          * of the "trap" in jprobe_return() above, before restoring the
 537          * saved regs...
 538          */
 539         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
 540         preempt_enable_no_resched();
 541         return 1;
 542 }
 543
 544 static struct kprobe trampoline_p = {
 545         .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
 546         .pre_handler = trampoline_probe_handler
 547 };
 548
 549 int __init arch_init_kprobes(void)
 550 {
 551         return register_kprobe(&trampoline_p);
 552 }
 553
 554 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 555 {
 556         if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
 557                 return 1;
 558
 559         return 0;
 560 }