arch/sparc/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 <linux/slab.h>
  11 #include <linux/context_tracking.h>
  12 #include <asm/signal.h>
  13 #include <asm/cacheflush.h>
  14 #include <asm/uaccess.h>
  15
  16 /* We do not have hardware single-stepping on sparc64.
  17  * So we implement software single-stepping with breakpoint
  18  * traps.  The top-level scheme is similar to that used
  19  * in the x86 kprobes implementation.
  20  *
  21  * In the kprobe->ainsn.insn[] array we store the original
  22  * instruction at index zero and a break instruction at
  23  * index one.
  24  *
  25  * When we hit a kprobe we:
  26  * - Run the pre-handler
  27  * - Remember "regs->tnpc" and interrupt level stored in
  28  *   "regs->tstate" so we can restore them later
  29  * - Disable PIL interrupts
  30  * - Set regs->tpc to point to kprobe->ainsn.insn[0]
  31  * - Set regs->tnpc to point to kprobe->ainsn.insn[1]
  32  * - Mark that we are actively in a kprobe
  33  *
  34  * At this point we wait for the second breakpoint at
  35  * kprobe->ainsn.insn[1] to hit.  When it does we:
  36  * - Run the post-handler
  37  * - Set regs->tpc to "remembered" regs->tnpc stored above,
  38  *   restore the PIL interrupt level in "regs->tstate" as well
  39  * - Make any adjustments necessary to regs->tnpc in order
  40  *   to handle relative branches correctly.  See below.
  41  * - Mark that we are no longer actively in a kprobe.
  42  */
  43
  44 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  45 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  46
  47 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
  48
  49 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  50 {
  51         if ((unsigned long) p->addr & 0x3UL)
  52                 return -EILSEQ;
  53
  54         p->ainsn.insn[0] = *p->addr;
  55         flushi(&p->ainsn.insn[0]);
  56
  57         p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
  58         flushi(&p->ainsn.insn[1]);
  59
  60         p->opcode = *p->addr;
  61         return 0;
  62 }
  63
  64 void __kprobes arch_arm_kprobe(struct kprobe *p)
  65 {
  66         *p->addr = BREAKPOINT_INSTRUCTION;
  67         flushi(p->addr);
  68 }
  69
  70 void __kprobes arch_disarm_kprobe(struct kprobe *p)
  71 {
  72         *p->addr = p->opcode;
  73         flushi(p->addr);
  74 }
  75
  76 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
  77 {
  78         kcb->prev_kprobe.kp = kprobe_running();
  79         kcb->prev_kprobe.status = kcb->kprobe_status;
  80         kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc;
  81         kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil;
  82 }
  83
  84 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
  85 {
  86         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
  87         kcb->kprobe_status = kcb->prev_kprobe.status;
  88         kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc;
  89         kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil;
  90 }
  91
  92 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
  93                                 struct kprobe_ctlblk *kcb)
  94 {
  95         __get_cpu_var(current_kprobe) = p;
  96         kcb->kprobe_orig_tnpc = regs->tnpc;
  97         kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
  98 }
  99
 100 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
 101                         struct kprobe_ctlblk *kcb)
 102 {
 103         regs->tstate |= TSTATE_PIL;
 104
 105         /*single step inline, if it a breakpoint instruction*/
 106         if (p->opcode == BREAKPOINT_INSTRUCTION) {
 107                 regs->tpc = (unsigned long) p->addr;
 108                 regs->tnpc = kcb->kprobe_orig_tnpc;
 109         } else {
 110                 regs->tpc = (unsigned long) &p->ainsn.insn[0];
 111                 regs->tnpc = (unsigned long) &p->ainsn.insn[1];
 112         }
 113 }
 114
 115 static int __kprobes kprobe_handler(struct pt_regs *regs)
 116 {
 117         struct kprobe *p;
 118         void *addr = (void *) regs->tpc;
 119         int ret = 0;
 120         struct kprobe_ctlblk *kcb;
 121
 122         /*
 123          * We don't want to be preempted for the entire
 124          * duration of kprobe processing
 125          */
 126         preempt_disable();
 127         kcb = get_kprobe_ctlblk();
 128
 129         if (kprobe_running()) {
 130                 p = get_kprobe(addr);
 131                 if (p) {
 132                         if (kcb->kprobe_status == KPROBE_HIT_SS) {
 133                                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 134                                         kcb->kprobe_orig_tstate_pil);
 135                                 goto no_kprobe;
 136                         }
 137                         /* We have reentered the kprobe_handler(), since
 138                          * another probe was hit while within the handler.
 139                          * We here save the original kprobes variables and
 140                          * just single step on the instruction of the new probe
 141                          * without calling any user handlers.
 142                          */
 143                         save_previous_kprobe(kcb);
 144                         set_current_kprobe(p, regs, kcb);
 145                         kprobes_inc_nmissed_count(p);
 146                         kcb->kprobe_status = KPROBE_REENTER;
 147                         prepare_singlestep(p, regs, kcb);
 148                         return 1;
 149                 } else {
 150                         if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
 151                         /* The breakpoint instruction was removed by
 152                          * another cpu right after we hit, no further
 153                          * handling of this interrupt is appropriate
 154                          */
 155                                 ret = 1;
 156                                 goto no_kprobe;
 157                         }
 158                         p = __get_cpu_var(current_kprobe);
 159                         if (p->break_handler && p->break_handler(p, regs))
 160                                 goto ss_probe;
 161                 }
 162                 goto no_kprobe;
 163         }
 164
 165         p = get_kprobe(addr);
 166         if (!p) {
 167                 if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
 168                         /*
 169                          * The breakpoint instruction was removed right
 170                          * after we hit it.  Another cpu has removed
 171                          * either a probepoint or a debugger breakpoint
 172                          * at this address.  In either case, no further
 173                          * handling of this interrupt is appropriate.
 174                          */
 175                         ret = 1;
 176                 }
 177                 /* Not one of ours: let kernel handle it */
 178                 goto no_kprobe;
 179         }
 180
 181         set_current_kprobe(p, regs, kcb);
 182         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 183         if (p->pre_handler && p->pre_handler(p, regs))
 184                 return 1;
 185
 186 ss_probe:
 187         prepare_singlestep(p, regs, kcb);
 188         kcb->kprobe_status = KPROBE_HIT_SS;
 189         return 1;
 190
 191 no_kprobe:
 192         preempt_enable_no_resched();
 193         return ret;
 194 }
 195
 196 /* If INSN is a relative control transfer instruction,
 197  * return the corrected branch destination value.
 198  *
 199  * regs->tpc and regs->tnpc still hold the values of the
 200  * program counters at the time of trap due to the execution
 201  * of the BREAKPOINT_INSTRUCTION_2 at p->ainsn.insn[1]
 202  *
 203  */
 204 static unsigned long __kprobes relbranch_fixup(u32 insn, struct kprobe *p,
 205                                                struct pt_regs *regs)
 206 {
 207         unsigned long real_pc = (unsigned long) p->addr;
 208
 209         /* Branch not taken, no mods necessary.  */
 210         if (regs->tnpc == regs->tpc + 0x4UL)
 211                 return real_pc + 0x8UL;
 212
 213         /* The three cases are call, branch w/prediction,
 214          * and traditional branch.
 215          */
 216         if ((insn & 0xc0000000) == 0x40000000 ||
 217             (insn & 0xc1c00000) == 0x00400000 ||
 218             (insn & 0xc1c00000) == 0x00800000) {
 219                 unsigned long ainsn_addr;
 220
 221                 ainsn_addr = (unsigned long) &p->ainsn.insn[0];
 222
 223                 /* The instruction did all the work for us
 224                  * already, just apply the offset to the correct
 225                  * instruction location.
 226                  */
 227                 return (real_pc + (regs->tnpc - ainsn_addr));
 228         }
 229
 230         /* It is jmpl or some other absolute PC modification instruction,
 231          * leave NPC as-is.
 232          */
 233         return regs->tnpc;
 234 }
 235
 236 /* If INSN is an instruction which writes it's PC location
 237  * into a destination register, fix that up.
 238  */
 239 static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn,
 240                                   unsigned long real_pc)
 241 {
 242         unsigned long *slot = NULL;
 243
 244         /* Simplest case is 'call', which always uses %o7 */
 245         if ((insn & 0xc0000000) == 0x40000000) {
 246                 slot = &regs->u_regs[UREG_I7];
 247         }
 248
 249         /* 'jmpl' encodes the register inside of the opcode */
 250         if ((insn & 0xc1f80000) == 0x81c00000) {
 251                 unsigned long rd = ((insn >> 25) & 0x1f);
 252
 253                 if (rd <= 15) {
 254                         slot = &regs->u_regs[rd];
 255                 } else {
 256                         /* Hard case, it goes onto the stack. */
 257                         flushw_all();
 258
 259                         rd -= 16;
 260                         slot = (unsigned long *)
 261                                 (regs->u_regs[UREG_FP] + STACK_BIAS);
 262                         slot += rd;
 263                 }
 264         }
 265         if (slot != NULL)
 266                 *slot = real_pc;
 267 }
 268
 269 /*
 270  * Called after single-stepping.  p->addr is the address of the
 271  * instruction which has been replaced by the breakpoint
 272  * instruction.  To avoid the SMP problems that can occur when we
 273  * temporarily put back the original opcode to single-step, we
 274  * single-stepped a copy of the instruction.  The address of this
 275  * copy is &p->ainsn.insn[0].
 276  *
 277  * This function prepares to return from the post-single-step
 278  * breakpoint trap.
 279  */
 280 static void __kprobes resume_execution(struct kprobe *p,
 281                 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 282 {
 283         u32 insn = p->ainsn.insn[0];
 284
 285         regs->tnpc = relbranch_fixup(insn, p, regs);
 286
 287         /* This assignment must occur after relbranch_fixup() */
 288         regs->tpc = kcb->kprobe_orig_tnpc;
 289
 290         retpc_fixup(regs, insn, (unsigned long) p->addr);
 291
 292         regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 293                         kcb->kprobe_orig_tstate_pil);
 294 }
 295
 296 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 297 {
 298         struct kprobe *cur = kprobe_running();
 299         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 300
 301         if (!cur)
 302                 return 0;
 303
 304         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 305                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 306                 cur->post_handler(cur, regs, 0);
 307         }
 308
 309         resume_execution(cur, regs, kcb);
 310
 311         /*Restore back the original saved kprobes variables and continue. */
 312         if (kcb->kprobe_status == KPROBE_REENTER) {
 313                 restore_previous_kprobe(kcb);
 314                 goto out;
 315         }
 316         reset_current_kprobe();
 317 out:
 318         preempt_enable_no_resched();
 319
 320         return 1;
 321 }
 322
 323 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 324 {
 325         struct kprobe *cur = kprobe_running();
 326         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 327         const struct exception_table_entry *entry;
 328
 329         switch(kcb->kprobe_status) {
 330         case KPROBE_HIT_SS:
 331         case KPROBE_REENTER:
 332                 /*
 333                  * We are here because the instruction being single
 334                  * stepped caused a page fault. We reset the current
 335                  * kprobe and the tpc points back to the probe address
 336                  * and allow the page fault handler to continue as a
 337                  * normal page fault.
 338                  */
 339                 regs->tpc = (unsigned long)cur->addr;
 340                 regs->tnpc = kcb->kprobe_orig_tnpc;
 341                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 342                                 kcb->kprobe_orig_tstate_pil);
 343                 if (kcb->kprobe_status == KPROBE_REENTER)
 344                         restore_previous_kprobe(kcb);
 345                 else
 346                         reset_current_kprobe();
 347                 preempt_enable_no_resched();
 348                 break;
 349         case KPROBE_HIT_ACTIVE:
 350         case KPROBE_HIT_SSDONE:
 351                 /*
 352                  * We increment the nmissed count for accounting,
 353                  * we can also use npre/npostfault count for accounting
 354                  * these specific fault cases.
 355                  */
 356                 kprobes_inc_nmissed_count(cur);
 357
 358                 /*
 359                  * We come here because instructions in the pre/post
 360                  * handler caused the page_fault, this could happen
 361                  * if handler tries to access user space by
 362                  * copy_from_user(), get_user() etc. Let the
 363                  * user-specified handler try to fix it first.
 364                  */
 365                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 366                         return 1;
 367
 368                 /*
 369                  * In case the user-specified fault handler returned
 370                  * zero, try to fix up.
 371                  */
 372
 373                 entry = search_exception_tables(regs->tpc);
 374                 if (entry) {
 375                         regs->tpc = entry->fixup;
 376                         regs->tnpc = regs->tpc + 4;
 377                         return 1;
 378                 }
 379
 380                 /*
 381                  * fixup_exception() could not handle it,
 382                  * Let do_page_fault() fix it.
 383                  */
 384                 break;
 385         default:
 386                 break;
 387         }
 388
 389         return 0;
 390 }
 391
 392 /*
 393  * Wrapper routine to for handling exceptions.
 394  */
 395 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 396                                        unsigned long val, void *data)
 397 {
 398         struct die_args *args = (struct die_args *)data;
 399         int ret = NOTIFY_DONE;
 400
 401         if (args->regs && user_mode(args->regs))
 402                 return ret;
 403
 404         switch (val) {
 405         case DIE_DEBUG:
 406                 if (kprobe_handler(args->regs))
 407                         ret = NOTIFY_STOP;
 408                 break;
 409         case DIE_DEBUG_2:
 410                 if (post_kprobe_handler(args->regs))
 411                         ret = NOTIFY_STOP;
 412                 break;
 413         default:
 414                 break;
 415         }
 416         return ret;
 417 }
 418
 419 asmlinkage void __kprobes kprobe_trap(unsigned long trap_level,
 420                                       struct pt_regs *regs)
 421 {
 422         enum ctx_state prev_state = exception_enter();
 423
 424         BUG_ON(trap_level != 0x170 && trap_level != 0x171);
 425
 426         if (user_mode(regs)) {
 427                 local_irq_enable();
 428                 bad_trap(regs, trap_level);
 429                 goto out;
 430         }
 431
 432         /* trap_level == 0x170 --> ta 0x70
 433          * trap_level == 0x171 --> ta 0x71
 434          */
 435         if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
 436                        (trap_level == 0x170) ? "debug" : "debug_2",
 437                        regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
 438                 bad_trap(regs, trap_level);
 439 out:
 440         exception_exit(prev_state);
 441 }
 442
 443 /* Jprobes support.  */
 444 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 445 {
 446         struct jprobe *jp = container_of(p, struct jprobe, kp);
 447         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 448
 449         memcpy(&(kcb->jprobe_saved_regs), regs, sizeof(*regs));
 450
 451         regs->tpc  = (unsigned long) jp->entry;
 452         regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
 453         regs->tstate |= TSTATE_PIL;
 454
 455         return 1;
 456 }
 457
 458 void __kprobes jprobe_return(void)
 459 {
 460         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 461         register unsigned long orig_fp asm("g1");
 462
 463         orig_fp = kcb->jprobe_saved_regs.u_regs[UREG_FP];
 464         __asm__ __volatile__("\n"
 465 "1:     cmp             %%sp, %0\n\t"
 466         "blu,a,pt       %%xcc, 1b\n\t"
 467         " restore\n\t"
 468         ".globl         jprobe_return_trap_instruction\n"
 469 "jprobe_return_trap_instruction:\n\t"
 470         "ta             0x70"
 471         : /* no outputs */
 472         : "r" (orig_fp));
 473 }
 474
 475 extern void jprobe_return_trap_instruction(void);
 476
 477 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 478 {
 479         u32 *addr = (u32 *) regs->tpc;
 480         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 481
 482         if (addr == (u32 *) jprobe_return_trap_instruction) {
 483                 memcpy(regs, &(kcb->jprobe_saved_regs), sizeof(*regs));
 484                 preempt_enable_no_resched();
 485                 return 1;
 486         }
 487         return 0;
 488 }
 489
 490 /* The value stored in the return address register is actually 2
 491  * instructions before where the callee will return to.
 492  * Sequences usually look something like this
 493  *
 494  *              call    some_function   <--- return register points here
 495  *               nop                    <--- call delay slot
 496  *              whatever                <--- where callee returns to
 497  *
 498  * To keep trampoline_probe_handler logic simpler, we normalize the
 499  * value kept in ri->ret_addr so we don't need to keep adjusting it
 500  * back and forth.
 501  */
 502 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 503                                       struct pt_regs *regs)
 504 {
 505         ri->ret_addr = (kprobe_opcode_t *)(regs->u_regs[UREG_RETPC] + 8);
 506
 507         /* Replace the return addr with trampoline addr */
 508         regs->u_regs[UREG_RETPC] =
 509                 ((unsigned long)kretprobe_trampoline) - 8;
 510 }
 511
 512 /*
 513  * Called when the probe at kretprobe trampoline is hit
 514  */
 515 static int __kprobes trampoline_probe_handler(struct kprobe *p,
 516                                               struct pt_regs *regs)
 517 {
 518         struct kretprobe_instance *ri = NULL;
 519         struct hlist_head *head, empty_rp;
 520         struct hlist_node *tmp;
 521         unsigned long flags, orig_ret_address = 0;
 522         unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
 523
 524         INIT_HLIST_HEAD(&empty_rp);
 525         kretprobe_hash_lock(current, &head, &flags);
 526
 527         /*
 528          * It is possible to have multiple instances associated with a given
 529          * task either because an multiple functions in the call path
 530          * have a return probe installed on them, and/or more than one return
 531          * return probe was registered for a target function.
 532          *
 533          * We can handle this because:
 534          *     - instances are always inserted at the head of the list
 535          *     - when multiple return probes are registered for the same
 536          *       function, the first instance's ret_addr will point to the
 537          *       real return address, and all the rest will point to
 538          *       kretprobe_trampoline
 539          */
 540         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 541                 if (ri->task != current)
 542                         /* another task is sharing our hash bucket */
 543                         continue;
 544
 545                 if (ri->rp && ri->rp->handler)
 546                         ri->rp->handler(ri, regs);
 547
 548                 orig_ret_address = (unsigned long)ri->ret_addr;
 549                 recycle_rp_inst(ri, &empty_rp);
 550
 551                 if (orig_ret_address != trampoline_address)
 552                         /*
 553                          * This is the real return address. Any other
 554                          * instances associated with this task are for
 555                          * other calls deeper on the call stack
 556                          */
 557                         break;
 558         }
 559
 560         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 561         regs->tpc = orig_ret_address;
 562         regs->tnpc = orig_ret_address + 4;
 563
 564         reset_current_kprobe();
 565         kretprobe_hash_unlock(current, &flags);
 566         preempt_enable_no_resched();
 567
 568         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 569                 hlist_del(&ri->hlist);
 570                 kfree(ri);
 571         }
 572         /*
 573          * By returning a non-zero value, we are telling
 574          * kprobe_handler() that we don't want the post_handler
 575          * to run (and have re-enabled preemption)
 576          */
 577         return 1;
 578 }
 579
 580 static void __used kretprobe_trampoline_holder(void)
 581 {
 582         asm volatile(".global kretprobe_trampoline\n"
 583                      "kretprobe_trampoline:\n"
 584                      "\tnop\n"
 585                      "\tnop\n");
 586 }
 587 static struct kprobe trampoline_p = {
 588         .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
 589         .pre_handler = trampoline_probe_handler
 590 };
 591
 592 int __init arch_init_kprobes(void)
 593 {
 594         return register_kprobe(&trampoline_p);
 595 }
 596
 597 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 598 {
 599         if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
 600                 return 1;
 601
 602         return 0;
 603 }