arch/sparc64/kernel/kprobes.c

   1 /* arch/sparc64/kernel/kprobes.c
   2  *
   3  * Copyright (C) 2004 David S. Miller <davem@davemloft.net>
   4  */
   5
   6 #include <linux/kernel.h>
   7 #include <linux/kprobes.h>
   8 #include <linux/module.h>
   9 #include <linux/kdebug.h>
  10 #include <asm/signal.h>
  11 #include <asm/cacheflush.h>
  12 #include <asm/uaccess.h>
  13
  14 /* We do not have hardware single-stepping on sparc64.
  15  * So we implement software single-stepping with breakpoint
  16  * traps.  The top-level scheme is similar to that used
  17  * in the x86 kprobes implementation.
  18  *
  19  * In the kprobe->ainsn.insn[] array we store the original
  20  * instruction at index zero and a break instruction at
  21  * index one.
  22  *
  23  * When we hit a kprobe we:
  24  * - Run the pre-handler
  25  * - Remember "regs->tnpc" and interrupt level stored in
  26  *   "regs->tstate" so we can restore them later
  27  * - Disable PIL interrupts
  28  * - Set regs->tpc to point to kprobe->ainsn.insn[0]
  29  * - Set regs->tnpc to point to kprobe->ainsn.insn[1]
  30  * - Mark that we are actively in a kprobe
  31  *
  32  * At this point we wait for the second breakpoint at
  33  * kprobe->ainsn.insn[1] to hit.  When it does we:
  34  * - Run the post-handler
  35  * - Set regs->tpc to "remembered" regs->tnpc stored above,
  36  *   restore the PIL interrupt level in "regs->tstate" as well
  37  * - Make any adjustments necessary to regs->tnpc in order
  38  *   to handle relative branches correctly.  See below.
  39  * - Mark that we are no longer actively in a kprobe.
  40  */
  41
  42 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  43 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  44
  45 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
  46
  47 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  48 {
  49         p->ainsn.insn[0] = *p->addr;
  50         flushi(&p->ainsn.insn[0]);
  51
  52         p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
  53         flushi(&p->ainsn.insn[1]);
  54
  55         p->opcode = *p->addr;
  56         return 0;
  57 }
  58
  59 void __kprobes arch_arm_kprobe(struct kprobe *p)
  60 {
  61         *p->addr = BREAKPOINT_INSTRUCTION;
  62         flushi(p->addr);
  63 }
  64
  65 void __kprobes arch_disarm_kprobe(struct kprobe *p)
  66 {
  67         *p->addr = p->opcode;
  68         flushi(p->addr);
  69 }
  70
  71 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
  72 {
  73         kcb->prev_kprobe.kp = kprobe_running();
  74         kcb->prev_kprobe.status = kcb->kprobe_status;
  75         kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc;
  76         kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil;
  77 }
  78
  79 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
  80 {
  81         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
  82         kcb->kprobe_status = kcb->prev_kprobe.status;
  83         kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc;
  84         kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil;
  85 }
  86
  87 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
  88                                 struct kprobe_ctlblk *kcb)
  89 {
  90         __get_cpu_var(current_kprobe) = p;
  91         kcb->kprobe_orig_tnpc = regs->tnpc;
  92         kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
  93 }
  94
  95 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
  96                         struct kprobe_ctlblk *kcb)
  97 {
  98         regs->tstate |= TSTATE_PIL;
  99
 100         /*single step inline, if it a breakpoint instruction*/
 101         if (p->opcode == BREAKPOINT_INSTRUCTION) {
 102                 regs->tpc = (unsigned long) p->addr;
 103                 regs->tnpc = kcb->kprobe_orig_tnpc;
 104         } else {
 105                 regs->tpc = (unsigned long) &p->ainsn.insn[0];
 106                 regs->tnpc = (unsigned long) &p->ainsn.insn[1];
 107         }
 108 }
 109
 110 static int __kprobes kprobe_handler(struct pt_regs *regs)
 111 {
 112         struct kprobe *p;
 113         void *addr = (void *) regs->tpc;
 114         int ret = 0;
 115         struct kprobe_ctlblk *kcb;
 116
 117         /*
 118          * We don't want to be preempted for the entire
 119          * duration of kprobe processing
 120          */
 121         preempt_disable();
 122         kcb = get_kprobe_ctlblk();
 123
 124         if (kprobe_running()) {
 125                 p = get_kprobe(addr);
 126                 if (p) {
 127                         if (kcb->kprobe_status == KPROBE_HIT_SS) {
 128                                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 129                                         kcb->kprobe_orig_tstate_pil);
 130                                 goto no_kprobe;
 131                         }
 132                         /* We have reentered the kprobe_handler(), since
 133                          * another probe was hit while within the handler.
 134                          * We here save the original kprobes variables and
 135                          * just single step on the instruction of the new probe
 136                          * without calling any user handlers.
 137                          */
 138                         save_previous_kprobe(kcb);
 139                         set_current_kprobe(p, regs, kcb);
 140                         kprobes_inc_nmissed_count(p);
 141                         kcb->kprobe_status = KPROBE_REENTER;
 142                         prepare_singlestep(p, regs, kcb);
 143                         return 1;
 144                 } else {
 145                         if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
 146                         /* The breakpoint instruction was removed by
 147                          * another cpu right after we hit, no further
 148                          * handling of this interrupt is appropriate
 149                          */
 150                                 ret = 1;
 151                                 goto no_kprobe;
 152                         }
 153                         p = __get_cpu_var(current_kprobe);
 154                         if (p->break_handler && p->break_handler(p, regs))
 155                                 goto ss_probe;
 156                 }
 157                 goto no_kprobe;
 158         }
 159
 160         p = get_kprobe(addr);
 161         if (!p) {
 162                 if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
 163                         /*
 164                          * The breakpoint instruction was removed right
 165                          * after we hit it.  Another cpu has removed
 166                          * either a probepoint or a debugger breakpoint
 167                          * at this address.  In either case, no further
 168                          * handling of this interrupt is appropriate.
 169                          */
 170                         ret = 1;
 171                 }
 172                 /* Not one of ours: let kernel handle it */
 173                 goto no_kprobe;
 174         }
 175
 176         set_current_kprobe(p, regs, kcb);
 177         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 178         if (p->pre_handler && p->pre_handler(p, regs))
 179                 return 1;
 180
 181 ss_probe:
 182         prepare_singlestep(p, regs, kcb);
 183         kcb->kprobe_status = KPROBE_HIT_SS;
 184         return 1;
 185
 186 no_kprobe:
 187         preempt_enable_no_resched();
 188         return ret;
 189 }
 190
 191 /* If INSN is a relative control transfer instruction,
 192  * return the corrected branch destination value.
 193  *
 194  * regs->tpc and regs->tnpc still hold the values of the
 195  * program counters at the time of trap due to the execution
 196  * of the BREAKPOINT_INSTRUCTION_2 at p->ainsn.insn[1]
 197  *
 198  */
 199 static unsigned long __kprobes relbranch_fixup(u32 insn, struct kprobe *p,
 200                                                struct pt_regs *regs)
 201 {
 202         unsigned long real_pc = (unsigned long) p->addr;
 203
 204         /* Branch not taken, no mods necessary.  */
 205         if (regs->tnpc == regs->tpc + 0x4UL)
 206                 return real_pc + 0x8UL;
 207
 208         /* The three cases are call, branch w/prediction,
 209          * and traditional branch.
 210          */
 211         if ((insn & 0xc0000000) == 0x40000000 ||
 212             (insn & 0xc1c00000) == 0x00400000 ||
 213             (insn & 0xc1c00000) == 0x00800000) {
 214                 unsigned long ainsn_addr;
 215
 216                 ainsn_addr = (unsigned long) &p->ainsn.insn[0];
 217
 218                 /* The instruction did all the work for us
 219                  * already, just apply the offset to the correct
 220                  * instruction location.
 221                  */
 222                 return (real_pc + (regs->tnpc - ainsn_addr));
 223         }
 224
 225         /* It is jmpl or some other absolute PC modification instruction,
 226          * leave NPC as-is.
 227          */
 228         return regs->tnpc;
 229 }
 230
 231 /* If INSN is an instruction which writes it's PC location
 232  * into a destination register, fix that up.
 233  */
 234 static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn,
 235                                   unsigned long real_pc)
 236 {
 237         unsigned long *slot = NULL;
 238
 239         /* Simplest case is 'call', which always uses %o7 */
 240         if ((insn & 0xc0000000) == 0x40000000) {
 241                 slot = &regs->u_regs[UREG_I7];
 242         }
 243
 244         /* 'jmpl' encodes the register inside of the opcode */
 245         if ((insn & 0xc1f80000) == 0x81c00000) {
 246                 unsigned long rd = ((insn >> 25) & 0x1f);
 247
 248                 if (rd <= 15) {
 249                         slot = &regs->u_regs[rd];
 250                 } else {
 251                         /* Hard case, it goes onto the stack. */
 252                         flushw_all();
 253
 254                         rd -= 16;
 255                         slot = (unsigned long *)
 256                                 (regs->u_regs[UREG_FP] + STACK_BIAS);
 257                         slot += rd;
 258                 }
 259         }
 260         if (slot != NULL)
 261                 *slot = real_pc;
 262 }
 263
 264 /*
 265  * Called after single-stepping.  p->addr is the address of the
 266  * instruction which has been replaced by the breakpoint
 267  * instruction.  To avoid the SMP problems that can occur when we
 268  * temporarily put back the original opcode to single-step, we
 269  * single-stepped a copy of the instruction.  The address of this
 270  * copy is &p->ainsn.insn[0].
 271  *
 272  * This function prepares to return from the post-single-step
 273  * breakpoint trap.
 274  */
 275 static void __kprobes resume_execution(struct kprobe *p,
 276                 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 277 {
 278         u32 insn = p->ainsn.insn[0];
 279
 280         regs->tnpc = relbranch_fixup(insn, p, regs);
 281
 282         /* This assignment must occur after relbranch_fixup() */
 283         regs->tpc = kcb->kprobe_orig_tnpc;
 284
 285         retpc_fixup(regs, insn, (unsigned long) p->addr);
 286
 287         regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 288                         kcb->kprobe_orig_tstate_pil);
 289 }
 290
 291 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 292 {
 293         struct kprobe *cur = kprobe_running();
 294         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 295
 296         if (!cur)
 297                 return 0;
 298
 299         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 300                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 301                 cur->post_handler(cur, regs, 0);
 302         }
 303
 304         resume_execution(cur, regs, kcb);
 305
 306         /*Restore back the original saved kprobes variables and continue. */
 307         if (kcb->kprobe_status == KPROBE_REENTER) {
 308                 restore_previous_kprobe(kcb);
 309                 goto out;
 310         }
 311         reset_current_kprobe();
 312 out:
 313         preempt_enable_no_resched();
 314
 315         return 1;
 316 }
 317
 318 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 319 {
 320         struct kprobe *cur = kprobe_running();
 321         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 322         const struct exception_table_entry *entry;
 323
 324         switch(kcb->kprobe_status) {
 325         case KPROBE_HIT_SS:
 326         case KPROBE_REENTER:
 327                 /*
 328                  * We are here because the instruction being single
 329                  * stepped caused a page fault. We reset the current
 330                  * kprobe and the tpc points back to the probe address
 331                  * and allow the page fault handler to continue as a
 332                  * normal page fault.
 333                  */
 334                 regs->tpc = (unsigned long)cur->addr;
 335                 regs->tnpc = kcb->kprobe_orig_tnpc;
 336                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 337                                 kcb->kprobe_orig_tstate_pil);
 338                 if (kcb->kprobe_status == KPROBE_REENTER)
 339                         restore_previous_kprobe(kcb);
 340                 else
 341                         reset_current_kprobe();
 342                 preempt_enable_no_resched();
 343                 break;
 344         case KPROBE_HIT_ACTIVE:
 345         case KPROBE_HIT_SSDONE:
 346                 /*
 347                  * We increment the nmissed count for accounting,
 348                  * we can also use npre/npostfault count for accouting
 349                  * these specific fault cases.
 350                  */
 351                 kprobes_inc_nmissed_count(cur);
 352
 353                 /*
 354                  * We come here because instructions in the pre/post
 355                  * handler caused the page_fault, this could happen
 356                  * if handler tries to access user space by
 357                  * copy_from_user(), get_user() etc. Let the
 358                  * user-specified handler try to fix it first.
 359                  */
 360                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 361                         return 1;
 362
 363                 /*
 364                  * In case the user-specified fault handler returned
 365                  * zero, try to fix up.
 366                  */
 367
 368                 entry = search_exception_tables(regs->tpc);
 369                 if (entry) {
 370                         regs->tpc = entry->fixup;
 371                         regs->tnpc = regs->tpc + 4;
 372                         return 1;
 373                 }
 374
 375                 /*
 376                  * fixup_exception() could not handle it,
 377                  * Let do_page_fault() fix it.
 378                  */
 379                 break;
 380         default:
 381                 break;
 382         }
 383
 384         return 0;
 385 }
 386
 387 /*
 388  * Wrapper routine to for handling exceptions.
 389  */
 390 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 391                                        unsigned long val, void *data)
 392 {
 393         struct die_args *args = (struct die_args *)data;
 394         int ret = NOTIFY_DONE;
 395
 396         if (args->regs && user_mode(args->regs))
 397                 return ret;
 398
 399         switch (val) {
 400         case DIE_DEBUG:
 401                 if (kprobe_handler(args->regs))
 402                         ret = NOTIFY_STOP;
 403                 break;
 404         case DIE_DEBUG_2:
 405                 if (post_kprobe_handler(args->regs))
 406                         ret = NOTIFY_STOP;
 407                 break;
 408         default:
 409                 break;
 410         }
 411         return ret;
 412 }
 413
 414 asmlinkage void __kprobes kprobe_trap(unsigned long trap_level,
 415                                       struct pt_regs *regs)
 416 {
 417         BUG_ON(trap_level != 0x170 && trap_level != 0x171);
 418
 419         if (user_mode(regs)) {
 420                 local_irq_enable();
 421                 bad_trap(regs, trap_level);
 422                 return;
 423         }
 424
 425         /* trap_level == 0x170 --> ta 0x70
 426          * trap_level == 0x171 --> ta 0x71
 427          */
 428         if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
 429                        (trap_level == 0x170) ? "debug" : "debug_2",
 430                        regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
 431                 bad_trap(regs, trap_level);
 432 }
 433
 434 /* Jprobes support.  */
 435 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 436 {
 437         struct jprobe *jp = container_of(p, struct jprobe, kp);
 438         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 439
 440         memcpy(&(kcb->jprobe_saved_regs), regs, sizeof(*regs));
 441
 442         regs->tpc  = (unsigned long) jp->entry;
 443         regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
 444         regs->tstate |= TSTATE_PIL;
 445
 446         return 1;
 447 }
 448
 449 void __kprobes jprobe_return(void)
 450 {
 451         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 452         register unsigned long orig_fp asm("g1");
 453
 454         orig_fp = kcb->jprobe_saved_regs.u_regs[UREG_FP];
 455         __asm__ __volatile__("\n"
 456 "1:     cmp             %%sp, %0\n\t"
 457         "blu,a,pt       %%xcc, 1b\n\t"
 458         " restore\n\t"
 459         ".globl         jprobe_return_trap_instruction\n"
 460 "jprobe_return_trap_instruction:\n\t"
 461         "ta             0x70"
 462         : /* no outputs */
 463         : "r" (orig_fp));
 464 }
 465
 466 extern void jprobe_return_trap_instruction(void);
 467
 468 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 469 {
 470         u32 *addr = (u32 *) regs->tpc;
 471         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 472
 473         if (addr == (u32 *) jprobe_return_trap_instruction) {
 474                 memcpy(regs, &(kcb->jprobe_saved_regs), sizeof(*regs));
 475                 preempt_enable_no_resched();
 476                 return 1;
 477         }
 478         return 0;
 479 }
 480
 481 /* The value stored in the return address register is actually 2
 482  * instructions before where the callee will return to.
 483  * Sequences usually look something like this
 484  *
 485  *              call    some_function   <--- return register points here
 486  *               nop                    <--- call delay slot
 487  *              whatever                <--- where callee returns to
 488  *
 489  * To keep trampoline_probe_handler logic simpler, we normalize the
 490  * value kept in ri->ret_addr so we don't need to keep adjusting it
 491  * back and forth.
 492  */
 493 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 494                                       struct pt_regs *regs)
 495 {
 496         ri->ret_addr = (kprobe_opcode_t *)(regs->u_regs[UREG_RETPC] + 8);
 497
 498         /* Replace the return addr with trampoline addr */
 499         regs->u_regs[UREG_RETPC] =
 500                 ((unsigned long)kretprobe_trampoline) - 8;
 501 }
 502
 503 /*
 504  * Called when the probe at kretprobe trampoline is hit
 505  */
 506 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 507 {
 508         struct kretprobe_instance *ri = NULL;
 509         struct hlist_head *head, empty_rp;
 510         struct hlist_node *node, *tmp;
 511         unsigned long flags, orig_ret_address = 0;
 512         unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
 513
 514         INIT_HLIST_HEAD(&empty_rp);
 515         kretprobe_hash_lock(current, &head, &flags);
 516
 517         /*
 518          * It is possible to have multiple instances associated with a given
 519          * task either because an multiple functions in the call path
 520          * have a return probe installed on them, and/or more then one return
 521          * return probe was registered for a target function.
 522          *
 523          * We can handle this because:
 524          *     - instances are always inserted at the head of the list
 525          *     - when multiple return probes are registered for the same
 526          *       function, the first instance's ret_addr will point to the
 527          *       real return address, and all the rest will point to
 528          *       kretprobe_trampoline
 529          */
 530         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
 531                 if (ri->task != current)
 532                         /* another task is sharing our hash bucket */
 533                         continue;
 534
 535                 if (ri->rp && ri->rp->handler)
 536                         ri->rp->handler(ri, regs);
 537
 538                 orig_ret_address = (unsigned long)ri->ret_addr;
 539                 recycle_rp_inst(ri, &empty_rp);
 540
 541                 if (orig_ret_address != trampoline_address)
 542                         /*
 543                          * This is the real return address. Any other
 544                          * instances associated with this task are for
 545                          * other calls deeper on the call stack
 546                          */
 547                         break;
 548         }
 549
 550         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 551         regs->tpc = orig_ret_address;
 552         regs->tnpc = orig_ret_address + 4;
 553
 554         reset_current_kprobe();
 555         kretprobe_hash_unlock(current, &flags);
 556         preempt_enable_no_resched();
 557
 558         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
 559                 hlist_del(&ri->hlist);
 560                 kfree(ri);
 561         }
 562         /*
 563          * By returning a non-zero value, we are telling
 564          * kprobe_handler() that we don't want the post_handler
 565          * to run (and have re-enabled preemption)
 566          */
 567         return 1;
 568 }
 569
 570 void kretprobe_trampoline_holder(void)
 571 {
 572         asm volatile(".global kretprobe_trampoline\n"
 573                      "kretprobe_trampoline:\n"
 574                      "\tnop\n"
 575                      "\tnop\n");
 576 }
 577 static struct kprobe trampoline_p = {
 578         .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
 579         .pre_handler = trampoline_probe_handler
 580 };
 581
 582 int __init arch_init_kprobes(void)
 583 {
 584         return register_kprobe(&trampoline_p);
 585 }
 586
 587 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 588 {
 589         if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
 590                 return 1;
 591
 592         return 0;
 593 }