sys/cddl/contrib/opensolaris/uts/intel/dtrace/fasttrap_isa.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  *
  21  * Portions Copyright 2010 The FreeBSD Foundation
  22  *
  23  * $FreeBSD$
  24  */
  25
  26 /*
  27  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  28  * Use is subject to license terms.
  29  */
  30
  31 #if defined(sun)
  32 #pragma ident   "%Z%%M% %I%     %E% SMI"
  33 #endif
  34
  35 #include <sys/fasttrap_isa.h>
  36 #include <sys/fasttrap_impl.h>
  37 #include <sys/dtrace.h>
  38 #include <sys/dtrace_impl.h>
  39 #include <sys/cmn_err.h>
  40 #if defined(sun)
  41 #include <sys/regset.h>
  42 #include <sys/privregs.h>
  43 #include <sys/segments.h>
  44 #include <sys/x86_archext.h>
  45 #else
  46 #include <cddl/dev/dtrace/dtrace_cddl.h>
  47 #include <sys/types.h>
  48 #include <sys/proc.h>
  49 #include <sys/dtrace_bsd.h>
  50 #include <cddl/dev/dtrace/i386/regset.h>
  51 #include <machine/segments.h>
  52 #include <machine/reg.h>
  53 #include <machine/pcb.h>
  54 #endif
  55 #include <sys/sysmacros.h>
  56 #if defined(sun)
  57 #include <sys/trap.h>
  58 #include <sys/archsystm.h>
  59 #else
  60 #include <sys/ptrace.h>
  61
  62 static int
  63 proc_ops(int op, proc_t *p, void *kaddr, off_t uaddr, size_t len)
  64 {
  65         struct iovec iov;
  66         struct uio uio;
  67
  68         iov.iov_base = kaddr;
  69         iov.iov_len = len;
  70         uio.uio_offset = uaddr;
  71         uio.uio_iov = &iov;
  72         uio.uio_resid = len;
  73         uio.uio_iovcnt = 1;
  74         uio.uio_segflg = UIO_SYSSPACE;
  75         uio.uio_td = curthread;
  76         uio.uio_rw = op;
  77         PHOLD(p);
  78         if (proc_rwmem(p, &uio) < 0) {
  79                 PRELE(p);
  80                 return (-1);
  81         }
  82         PRELE(p);
  83
  84         return (0);
  85 }
  86
  87 static int
  88 uread(proc_t *p, void *kaddr, size_t len, uintptr_t uaddr)
  89 {
  90
  91         return (proc_ops(UIO_READ, p, kaddr, uaddr, len));
  92 }
  93
  94 static int
  95 uwrite(proc_t *p, void *kaddr, size_t len, uintptr_t uaddr)
  96 {
  97
  98         return (proc_ops(UIO_WRITE, p, kaddr, uaddr, len));
  99 }
 100 #endif /* sun */
 101 #ifdef __i386__
 102 #define r_rax   r_eax
 103 #define r_rbx   r_ebx
 104 #define r_rip   r_eip
 105 #define r_rflags r_eflags
 106 #define r_rsp   r_esp
 107 #define r_rbp   r_ebp
 108 #endif
 109
 110 /*
 111  * Lossless User-Land Tracing on x86
 112  * ---------------------------------
 113  *
 114  * The execution of most instructions is not dependent on the address; for
 115  * these instructions it is sufficient to copy them into the user process's
 116  * address space and execute them. To effectively single-step an instruction
 117  * in user-land, we copy out the following sequence of instructions to scratch
 118  * space in the user thread's ulwp_t structure.
 119  *
 120  * We then set the program counter (%eip or %rip) to point to this scratch
 121  * space. Once execution resumes, the original instruction is executed and
 122  * then control flow is redirected to what was originally the subsequent
 123  * instruction. If the kernel attemps to deliver a signal while single-
 124  * stepping, the signal is deferred and the program counter is moved into the
 125  * second sequence of instructions. The second sequence ends in a trap into
 126  * the kernel where the deferred signal is then properly handled and delivered.
 127  *
 128  * For instructions whose execute is position dependent, we perform simple
 129  * emulation. These instructions are limited to control transfer
 130  * instructions in 32-bit mode, but in 64-bit mode there's the added wrinkle
 131  * of %rip-relative addressing that means that almost any instruction can be
 132  * position dependent. For all the details on how we emulate generic
 133  * instructions included %rip-relative instructions, see the code in
 134  * fasttrap_pid_probe() below where we handle instructions of type
 135  * FASTTRAP_T_COMMON (under the header: Generic Instruction Tracing).
 136  */
 137
 138 #define FASTTRAP_MODRM_MOD(modrm)       (((modrm) >> 6) & 0x3)
 139 #define FASTTRAP_MODRM_REG(modrm)       (((modrm) >> 3) & 0x7)
 140 #define FASTTRAP_MODRM_RM(modrm)        ((modrm) & 0x7)
 141 #define FASTTRAP_MODRM(mod, reg, rm)    (((mod) << 6) | ((reg) << 3) | (rm))
 142
 143 #define FASTTRAP_SIB_SCALE(sib)         (((sib) >> 6) & 0x3)
 144 #define FASTTRAP_SIB_INDEX(sib)         (((sib) >> 3) & 0x7)
 145 #define FASTTRAP_SIB_BASE(sib)          ((sib) & 0x7)
 146
 147 #define FASTTRAP_REX_W(rex)             (((rex) >> 3) & 1)
 148 #define FASTTRAP_REX_R(rex)             (((rex) >> 2) & 1)
 149 #define FASTTRAP_REX_X(rex)             (((rex) >> 1) & 1)
 150 #define FASTTRAP_REX_B(rex)             ((rex) & 1)
 151 #define FASTTRAP_REX(w, r, x, b)        \
 152         (0x40 | ((w) << 3) | ((r) << 2) | ((x) << 1) | (b))
 153
 154 /*
 155  * Single-byte op-codes.
 156  */
 157 #define FASTTRAP_PUSHL_EBP      0x55
 158
 159 #define FASTTRAP_JO             0x70
 160 #define FASTTRAP_JNO            0x71
 161 #define FASTTRAP_JB             0x72
 162 #define FASTTRAP_JAE            0x73
 163 #define FASTTRAP_JE             0x74
 164 #define FASTTRAP_JNE            0x75
 165 #define FASTTRAP_JBE            0x76
 166 #define FASTTRAP_JA             0x77
 167 #define FASTTRAP_JS             0x78
 168 #define FASTTRAP_JNS            0x79
 169 #define FASTTRAP_JP             0x7a
 170 #define FASTTRAP_JNP            0x7b
 171 #define FASTTRAP_JL             0x7c
 172 #define FASTTRAP_JGE            0x7d
 173 #define FASTTRAP_JLE            0x7e
 174 #define FASTTRAP_JG             0x7f
 175
 176 #define FASTTRAP_NOP            0x90
 177
 178 #define FASTTRAP_MOV_EAX        0xb8
 179 #define FASTTRAP_MOV_ECX        0xb9
 180
 181 #define FASTTRAP_RET16          0xc2
 182 #define FASTTRAP_RET            0xc3
 183
 184 #define FASTTRAP_LOOPNZ         0xe0
 185 #define FASTTRAP_LOOPZ          0xe1
 186 #define FASTTRAP_LOOP           0xe2
 187 #define FASTTRAP_JCXZ           0xe3
 188
 189 #define FASTTRAP_CALL           0xe8
 190 #define FASTTRAP_JMP32          0xe9
 191 #define FASTTRAP_JMP8           0xeb
 192
 193 #define FASTTRAP_INT3           0xcc
 194 #define FASTTRAP_INT            0xcd
 195
 196 #define FASTTRAP_2_BYTE_OP      0x0f
 197 #define FASTTRAP_GROUP5_OP      0xff
 198
 199 /*
 200  * Two-byte op-codes (second byte only).
 201  */
 202 #define FASTTRAP_0F_JO          0x80
 203 #define FASTTRAP_0F_JNO         0x81
 204 #define FASTTRAP_0F_JB          0x82
 205 #define FASTTRAP_0F_JAE         0x83
 206 #define FASTTRAP_0F_JE          0x84
 207 #define FASTTRAP_0F_JNE         0x85
 208 #define FASTTRAP_0F_JBE         0x86
 209 #define FASTTRAP_0F_JA          0x87
 210 #define FASTTRAP_0F_JS          0x88
 211 #define FASTTRAP_0F_JNS         0x89
 212 #define FASTTRAP_0F_JP          0x8a
 213 #define FASTTRAP_0F_JNP         0x8b
 214 #define FASTTRAP_0F_JL          0x8c
 215 #define FASTTRAP_0F_JGE         0x8d
 216 #define FASTTRAP_0F_JLE         0x8e
 217 #define FASTTRAP_0F_JG          0x8f
 218
 219 #define FASTTRAP_EFLAGS_OF      0x800
 220 #define FASTTRAP_EFLAGS_DF      0x400
 221 #define FASTTRAP_EFLAGS_SF      0x080
 222 #define FASTTRAP_EFLAGS_ZF      0x040
 223 #define FASTTRAP_EFLAGS_AF      0x010
 224 #define FASTTRAP_EFLAGS_PF      0x004
 225 #define FASTTRAP_EFLAGS_CF      0x001
 226
 227 /*
 228  * Instruction prefixes.
 229  */
 230 #define FASTTRAP_PREFIX_OPERAND 0x66
 231 #define FASTTRAP_PREFIX_ADDRESS 0x67
 232 #define FASTTRAP_PREFIX_CS      0x2E
 233 #define FASTTRAP_PREFIX_DS      0x3E
 234 #define FASTTRAP_PREFIX_ES      0x26
 235 #define FASTTRAP_PREFIX_FS      0x64
 236 #define FASTTRAP_PREFIX_GS      0x65
 237 #define FASTTRAP_PREFIX_SS      0x36
 238 #define FASTTRAP_PREFIX_LOCK    0xF0
 239 #define FASTTRAP_PREFIX_REP     0xF3
 240 #define FASTTRAP_PREFIX_REPNE   0xF2
 241
 242 #define FASTTRAP_NOREG  0xff
 243
 244 /*
 245  * Map between instruction register encodings and the kernel constants which
 246  * correspond to indicies into struct regs.
 247  */
 248 #ifdef __amd64
 249 static const uint8_t regmap[16] = {
 250         REG_RAX, REG_RCX, REG_RDX, REG_RBX, REG_RSP, REG_RBP, REG_RSI, REG_RDI,
 251         REG_R8, REG_R9, REG_R10, REG_R11, REG_R12, REG_R13, REG_R14, REG_R15,
 252 };
 253 #else
 254 static const uint8_t regmap[8] = {
 255         EAX, ECX, EDX, EBX, UESP, EBP, ESI, EDI
 256 };
 257 #endif
 258
 259 static ulong_t fasttrap_getreg(struct reg *, uint_t);
 260
 261 static uint64_t
 262 fasttrap_anarg(struct reg *rp, int function_entry, int argno)
 263 {
 264         uint64_t value = 0;
 265         int shift = function_entry ? 1 : 0;
 266
 267 #ifdef __amd64
 268         if (curproc->p_model == DATAMODEL_LP64) {
 269                 uintptr_t *stack;
 270
 271                 /*
 272                  * In 64-bit mode, the first six arguments are stored in
 273                  * registers.
 274                  */
 275                 if (argno < 6)
 276                         return ((&rp->r_rdi)[argno]);
 277
 278                 stack = (uintptr_t *)rp->r_rsp;
 279                 DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
 280                 value = dtrace_fulword(&stack[argno - 6 + shift]);
 281                 DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT | CPU_DTRACE_BADADDR);
 282         } else {
 283 #endif
 284 #ifdef __i386
 285                 uint32_t *stack = (uint32_t *)rp->r_esp;
 286                 DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
 287                 value = dtrace_fuword32(&stack[argno + shift]);
 288                 DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT | CPU_DTRACE_BADADDR);
 289 #endif
 290 #ifdef __amd64
 291         }
 292 #endif
 293
 294         return (value);
 295 }
 296
 297 /*ARGSUSED*/
 298 int
 299 fasttrap_tracepoint_init(proc_t *p, fasttrap_tracepoint_t *tp, uintptr_t pc,
 300     fasttrap_probe_type_t type)
 301 {
 302         uint8_t instr[FASTTRAP_MAX_INSTR_SIZE + 10];
 303         size_t len = FASTTRAP_MAX_INSTR_SIZE;
 304         size_t first = MIN(len, PAGESIZE - (pc & PAGEOFFSET));
 305         uint_t start = 0;
 306         int rmindex, size;
 307         uint8_t seg, rex = 0;
 308
 309         /*
 310          * Read the instruction at the given address out of the process's
 311          * address space. We don't have to worry about a debugger
 312          * changing this instruction before we overwrite it with our trap
 313          * instruction since P_PR_LOCK is set. Since instructions can span
 314          * pages, we potentially read the instruction in two parts. If the
 315          * second part fails, we just zero out that part of the instruction.
 316          */
 317         if (uread(p, &instr[0], first, pc) != 0)
 318                 return (-1);
 319         if (len > first &&
 320             uread(p, &instr[first], len - first, pc + first) != 0) {
 321                 bzero(&instr[first], len - first);
 322                 len = first;
 323         }
 324
 325         /*
 326          * If the disassembly fails, then we have a malformed instruction.
 327          */
 328         if ((size = dtrace_instr_size_isa(instr, p->p_model, &rmindex)) <= 0)
 329                 return (-1);
 330
 331         /*
 332          * Make sure the disassembler isn't completely broken.
 333          */
 334         ASSERT(-1 <= rmindex && rmindex < size);
 335
 336         /*
 337          * If the computed size is greater than the number of bytes read,
 338          * then it was a malformed instruction possibly because it fell on a
 339          * page boundary and the subsequent page was missing or because of
 340          * some malicious user.
 341          */
 342         if (size > len)
 343                 return (-1);
 344
 345         tp->ftt_size = (uint8_t)size;
 346         tp->ftt_segment = FASTTRAP_SEG_NONE;
 347
 348         /*
 349          * Find the start of the instruction's opcode by processing any
 350          * legacy prefixes.
 351          */
 352         for (;;) {
 353                 seg = 0;
 354                 switch (instr[start]) {
 355                 case FASTTRAP_PREFIX_SS:
 356                         seg++;
 357                         /*FALLTHRU*/
 358                 case FASTTRAP_PREFIX_GS:
 359                         seg++;
 360                         /*FALLTHRU*/
 361                 case FASTTRAP_PREFIX_FS:
 362                         seg++;
 363                         /*FALLTHRU*/
 364                 case FASTTRAP_PREFIX_ES:
 365                         seg++;
 366                         /*FALLTHRU*/
 367                 case FASTTRAP_PREFIX_DS:
 368                         seg++;
 369                         /*FALLTHRU*/
 370                 case FASTTRAP_PREFIX_CS:
 371                         seg++;
 372                         /*FALLTHRU*/
 373                 case FASTTRAP_PREFIX_OPERAND:
 374                 case FASTTRAP_PREFIX_ADDRESS:
 375                 case FASTTRAP_PREFIX_LOCK:
 376                 case FASTTRAP_PREFIX_REP:
 377                 case FASTTRAP_PREFIX_REPNE:
 378                         if (seg != 0) {
 379                                 /*
 380                                  * It's illegal for an instruction to specify
 381                                  * two segment prefixes -- give up on this
 382                                  * illegal instruction.
 383                                  */
 384                                 if (tp->ftt_segment != FASTTRAP_SEG_NONE)
 385                                         return (-1);
 386
 387                                 tp->ftt_segment = seg;
 388                         }
 389                         start++;
 390                         continue;
 391                 }
 392                 break;
 393         }
 394
 395 #ifdef __amd64
 396         /*
 397          * Identify the REX prefix on 64-bit processes.
 398          */
 399         if (p->p_model == DATAMODEL_LP64 && (instr[start] & 0xf0) == 0x40)
 400                 rex = instr[start++];
 401 #endif
 402
 403         /*
 404          * Now that we're pretty sure that the instruction is okay, copy the
 405          * valid part to the tracepoint.
 406          */
 407         bcopy(instr, tp->ftt_instr, FASTTRAP_MAX_INSTR_SIZE);
 408
 409         tp->ftt_type = FASTTRAP_T_COMMON;
 410         if (instr[start] == FASTTRAP_2_BYTE_OP) {
 411                 switch (instr[start + 1]) {
 412                 case FASTTRAP_0F_JO:
 413                 case FASTTRAP_0F_JNO:
 414                 case FASTTRAP_0F_JB:
 415                 case FASTTRAP_0F_JAE:
 416                 case FASTTRAP_0F_JE:
 417                 case FASTTRAP_0F_JNE:
 418                 case FASTTRAP_0F_JBE:
 419                 case FASTTRAP_0F_JA:
 420                 case FASTTRAP_0F_JS:
 421                 case FASTTRAP_0F_JNS:
 422                 case FASTTRAP_0F_JP:
 423                 case FASTTRAP_0F_JNP:
 424                 case FASTTRAP_0F_JL:
 425                 case FASTTRAP_0F_JGE:
 426                 case FASTTRAP_0F_JLE:
 427                 case FASTTRAP_0F_JG:
 428                         tp->ftt_type = FASTTRAP_T_JCC;
 429                         tp->ftt_code = (instr[start + 1] & 0x0f) | FASTTRAP_JO;
 430                         tp->ftt_dest = pc + tp->ftt_size +
 431                             /* LINTED - alignment */
 432                             *(int32_t *)&instr[start + 2];
 433                         break;
 434                 }
 435         } else if (instr[start] == FASTTRAP_GROUP5_OP) {
 436                 uint_t mod = FASTTRAP_MODRM_MOD(instr[start + 1]);
 437                 uint_t reg = FASTTRAP_MODRM_REG(instr[start + 1]);
 438                 uint_t rm = FASTTRAP_MODRM_RM(instr[start + 1]);
 439
 440                 if (reg == 2 || reg == 4) {
 441                         uint_t i, sz;
 442
 443                         if (reg == 2)
 444                                 tp->ftt_type = FASTTRAP_T_CALL;
 445                         else
 446                                 tp->ftt_type = FASTTRAP_T_JMP;
 447
 448                         if (mod == 3)
 449                                 tp->ftt_code = 2;
 450                         else
 451                                 tp->ftt_code = 1;
 452
 453                         ASSERT(p->p_model == DATAMODEL_LP64 || rex == 0);
 454
 455                         /*
 456                          * See AMD x86-64 Architecture Programmer's Manual
 457                          * Volume 3, Section 1.2.7, Table 1-12, and
 458                          * Appendix A.3.1, Table A-15.
 459                          */
 460                         if (mod != 3 && rm == 4) {
 461                                 uint8_t sib = instr[start + 2];
 462                                 uint_t index = FASTTRAP_SIB_INDEX(sib);
 463                                 uint_t base = FASTTRAP_SIB_BASE(sib);
 464
 465                                 tp->ftt_scale = FASTTRAP_SIB_SCALE(sib);
 466
 467                                 tp->ftt_index = (index == 4) ?
 468                                     FASTTRAP_NOREG :
 469                                     regmap[index | (FASTTRAP_REX_X(rex) << 3)];
 470                                 tp->ftt_base = (mod == 0 && base == 5) ?
 471                                     FASTTRAP_NOREG :
 472                                     regmap[base | (FASTTRAP_REX_B(rex) << 3)];
 473
 474                                 i = 3;
 475                                 sz = mod == 1 ? 1 : 4;
 476                         } else {
 477                                 /*
 478                                  * In 64-bit mode, mod == 0 and r/m == 5
 479                                  * denotes %rip-relative addressing; in 32-bit
 480                                  * mode, the base register isn't used. In both
 481                                  * modes, there is a 32-bit operand.
 482                                  */
 483                                 if (mod == 0 && rm == 5) {
 484 #ifdef __amd64
 485                                         if (p->p_model == DATAMODEL_LP64)
 486                                                 tp->ftt_base = REG_RIP;
 487                                         else
 488 #endif
 489                                                 tp->ftt_base = FASTTRAP_NOREG;
 490                                         sz = 4;
 491                                 } else  {
 492                                         uint8_t base = rm |
 493                                             (FASTTRAP_REX_B(rex) << 3);
 494
 495                                         tp->ftt_base = regmap[base];
 496                                         sz = mod == 1 ? 1 : mod == 2 ? 4 : 0;
 497                                 }
 498                                 tp->ftt_index = FASTTRAP_NOREG;
 499                                 i = 2;
 500                         }
 501
 502                         if (sz == 1) {
 503                                 tp->ftt_dest = *(int8_t *)&instr[start + i];
 504                         } else if (sz == 4) {
 505                                 /* LINTED - alignment */
 506                                 tp->ftt_dest = *(int32_t *)&instr[start + i];
 507                         } else {
 508                                 tp->ftt_dest = 0;
 509                         }
 510                 }
 511         } else {
 512                 switch (instr[start]) {
 513                 case FASTTRAP_RET:
 514                         tp->ftt_type = FASTTRAP_T_RET;
 515                         break;
 516
 517                 case FASTTRAP_RET16:
 518                         tp->ftt_type = FASTTRAP_T_RET16;
 519                         /* LINTED - alignment */
 520                         tp->ftt_dest = *(uint16_t *)&instr[start + 1];
 521                         break;
 522
 523                 case FASTTRAP_JO:
 524                 case FASTTRAP_JNO:
 525                 case FASTTRAP_JB:
 526                 case FASTTRAP_JAE:
 527                 case FASTTRAP_JE:
 528                 case FASTTRAP_JNE:
 529                 case FASTTRAP_JBE:
 530                 case FASTTRAP_JA:
 531                 case FASTTRAP_JS:
 532                 case FASTTRAP_JNS:
 533                 case FASTTRAP_JP:
 534                 case FASTTRAP_JNP:
 535                 case FASTTRAP_JL:
 536                 case FASTTRAP_JGE:
 537                 case FASTTRAP_JLE:
 538                 case FASTTRAP_JG:
 539                         tp->ftt_type = FASTTRAP_T_JCC;
 540                         tp->ftt_code = instr[start];
 541                         tp->ftt_dest = pc + tp->ftt_size +
 542                             (int8_t)instr[start + 1];
 543                         break;
 544
 545                 case FASTTRAP_LOOPNZ:
 546                 case FASTTRAP_LOOPZ:
 547                 case FASTTRAP_LOOP:
 548                         tp->ftt_type = FASTTRAP_T_LOOP;
 549                         tp->ftt_code = instr[start];
 550                         tp->ftt_dest = pc + tp->ftt_size +
 551                             (int8_t)instr[start + 1];
 552                         break;
 553
 554                 case FASTTRAP_JCXZ:
 555                         tp->ftt_type = FASTTRAP_T_JCXZ;
 556                         tp->ftt_dest = pc + tp->ftt_size +
 557                             (int8_t)instr[start + 1];
 558                         break;
 559
 560                 case FASTTRAP_CALL:
 561                         tp->ftt_type = FASTTRAP_T_CALL;
 562                         tp->ftt_dest = pc + tp->ftt_size +
 563                             /* LINTED - alignment */
 564                             *(int32_t *)&instr[start + 1];
 565                         tp->ftt_code = 0;
 566                         break;
 567
 568                 case FASTTRAP_JMP32:
 569                         tp->ftt_type = FASTTRAP_T_JMP;
 570                         tp->ftt_dest = pc + tp->ftt_size +
 571                             /* LINTED - alignment */
 572                             *(int32_t *)&instr[start + 1];
 573                         break;
 574                 case FASTTRAP_JMP8:
 575                         tp->ftt_type = FASTTRAP_T_JMP;
 576                         tp->ftt_dest = pc + tp->ftt_size +
 577                             (int8_t)instr[start + 1];
 578                         break;
 579
 580                 case FASTTRAP_PUSHL_EBP:
 581                         if (start == 0)
 582                                 tp->ftt_type = FASTTRAP_T_PUSHL_EBP;
 583                         break;
 584
 585                 case FASTTRAP_NOP:
 586 #ifdef __amd64
 587                         ASSERT(p->p_model == DATAMODEL_LP64 || rex == 0);
 588
 589                         /*
 590                          * On amd64 we have to be careful not to confuse a nop
 591                          * (actually xchgl %eax, %eax) with an instruction using
 592                          * the same opcode, but that does something different
 593                          * (e.g. xchgl %r8d, %eax or xcghq %r8, %rax).
 594                          */
 595                         if (FASTTRAP_REX_B(rex) == 0)
 596 #endif
 597                                 tp->ftt_type = FASTTRAP_T_NOP;
 598                         break;
 599
 600                 case FASTTRAP_INT3:
 601                         /*
 602                          * The pid provider shares the int3 trap with debugger
 603                          * breakpoints so we can't instrument them.
 604                          */
 605                         ASSERT(instr[start] == FASTTRAP_INSTR);
 606                         return (-1);
 607
 608                 case FASTTRAP_INT:
 609                         /*
 610                          * Interrupts seem like they could be traced with
 611                          * no negative implications, but it's possible that
 612                          * a thread could be redirected by the trap handling
 613                          * code which would eventually return to the
 614                          * instruction after the interrupt. If the interrupt
 615                          * were in our scratch space, the subsequent
 616                          * instruction might be overwritten before we return.
 617                          * Accordingly we refuse to instrument any interrupt.
 618                          */
 619                         return (-1);
 620                 }
 621         }
 622
 623 #ifdef __amd64
 624         if (p->p_model == DATAMODEL_LP64 && tp->ftt_type == FASTTRAP_T_COMMON) {
 625                 /*
 626                  * If the process is 64-bit and the instruction type is still
 627                  * FASTTRAP_T_COMMON -- meaning we're going to copy it out an
 628                  * execute it -- we need to watch for %rip-relative
 629                  * addressing mode. See the portion of fasttrap_pid_probe()
 630                  * below where we handle tracepoints with type
 631                  * FASTTRAP_T_COMMON for how we emulate instructions that
 632                  * employ %rip-relative addressing.
 633                  */
 634                 if (rmindex != -1) {
 635                         uint_t mod = FASTTRAP_MODRM_MOD(instr[rmindex]);
 636                         uint_t reg = FASTTRAP_MODRM_REG(instr[rmindex]);
 637                         uint_t rm = FASTTRAP_MODRM_RM(instr[rmindex]);
 638
 639                         ASSERT(rmindex > start);
 640
 641                         if (mod == 0 && rm == 5) {
 642                                 /*
 643                                  * We need to be sure to avoid other
 644                                  * registers used by this instruction. While
 645                                  * the reg field may determine the op code
 646                                  * rather than denoting a register, assuming
 647                                  * that it denotes a register is always safe.
 648                                  * We leave the REX field intact and use
 649                                  * whatever value's there for simplicity.
 650                                  */
 651                                 if (reg != 0) {
 652                                         tp->ftt_ripmode = FASTTRAP_RIP_1 |
 653                                             (FASTTRAP_RIP_X *
 654                                             FASTTRAP_REX_B(rex));
 655                                         rm = 0;
 656                                 } else {
 657                                         tp->ftt_ripmode = FASTTRAP_RIP_2 |
 658                                             (FASTTRAP_RIP_X *
 659                                             FASTTRAP_REX_B(rex));
 660                                         rm = 1;
 661                                 }
 662
 663                                 tp->ftt_modrm = tp->ftt_instr[rmindex];
 664                                 tp->ftt_instr[rmindex] =
 665                                     FASTTRAP_MODRM(2, reg, rm);
 666                         }
 667                 }
 668         }
 669 #endif
 670
 671         return (0);
 672 }
 673
 674 int
 675 fasttrap_tracepoint_install(proc_t *p, fasttrap_tracepoint_t *tp)
 676 {
 677         fasttrap_instr_t instr = FASTTRAP_INSTR;
 678
 679         if (uwrite(p, &instr, 1, tp->ftt_pc) != 0)
 680                 return (-1);
 681
 682         return (0);
 683 }
 684
 685 int
 686 fasttrap_tracepoint_remove(proc_t *p, fasttrap_tracepoint_t *tp)
 687 {
 688         uint8_t instr;
 689
 690         /*
 691          * Distinguish between read or write failures and a changed
 692          * instruction.
 693          */
 694         if (uread(p, &instr, 1, tp->ftt_pc) != 0)
 695                 return (0);
 696         if (instr != FASTTRAP_INSTR)
 697                 return (0);
 698         if (uwrite(p, &tp->ftt_instr[0], 1, tp->ftt_pc) != 0)
 699                 return (-1);
 700
 701         return (0);
 702 }
 703
 704 #ifdef __amd64
 705 static uintptr_t
 706 fasttrap_fulword_noerr(const void *uaddr)
 707 {
 708         uintptr_t ret;
 709
 710         if ((ret = fasttrap_fulword(uaddr)) != -1)
 711                 return (ret);
 712
 713         return (0);
 714 }
 715 #endif
 716
 717 #ifdef __i386__
 718 static uint32_t
 719 fasttrap_fuword32_noerr(const void *uaddr)
 720 {
 721         uint32_t ret;
 722
 723         if ((ret = fasttrap_fuword32(uaddr)) != -1)
 724                 return (ret);
 725
 726         return (0);
 727 }
 728 #endif
 729
 730 static void
 731 fasttrap_return_common(struct reg *rp, uintptr_t pc, pid_t pid,
 732     uintptr_t new_pc)
 733 {
 734         fasttrap_tracepoint_t *tp;
 735         fasttrap_bucket_t *bucket;
 736         fasttrap_id_t *id;
 737 #if defined(sun)
 738         kmutex_t *pid_mtx;
 739 #endif
 740
 741 #if defined(sun)
 742         pid_mtx = &cpu_core[CPU->cpu_id].cpuc_pid_lock;
 743         mutex_enter(pid_mtx);
 744 #endif
 745         bucket = &fasttrap_tpoints.fth_table[FASTTRAP_TPOINTS_INDEX(pid, pc)];
 746
 747         for (tp = bucket->ftb_data; tp != NULL; tp = tp->ftt_next) {
 748                 if (pid == tp->ftt_pid && pc == tp->ftt_pc &&
 749                     tp->ftt_proc->ftpc_acount != 0)
 750                         break;
 751         }
 752
 753         /*
 754          * Don't sweat it if we can't find the tracepoint again; unlike
 755          * when we're in fasttrap_pid_probe(), finding the tracepoint here
 756          * is not essential to the correct execution of the process.
 757          */
 758         if (tp == NULL) {
 759 #if defined(sun)
 760                 mutex_exit(pid_mtx);
 761 #endif
 762                 return;
 763         }
 764
 765         for (id = tp->ftt_retids; id != NULL; id = id->fti_next) {
 766                 /*
 767                  * If there's a branch that could act as a return site, we
 768                  * need to trace it, and check here if the program counter is
 769                  * external to the function.
 770                  */
 771                 if (tp->ftt_type != FASTTRAP_T_RET &&
 772                     tp->ftt_type != FASTTRAP_T_RET16 &&
 773                     new_pc - id->fti_probe->ftp_faddr <
 774                     id->fti_probe->ftp_fsize)
 775                         continue;
 776
 777                 dtrace_probe(id->fti_probe->ftp_id,
 778                     pc - id->fti_probe->ftp_faddr,
 779                     rp->r_rax, rp->r_rbx, 0, 0);
 780         }
 781
 782 #if defined(sun)
 783         mutex_exit(pid_mtx);
 784 #endif
 785 }
 786
 787 static void
 788 fasttrap_sigsegv(proc_t *p, kthread_t *t, uintptr_t addr)
 789 {
 790 #if defined(sun)
 791         sigqueue_t *sqp = kmem_zalloc(sizeof (sigqueue_t), KM_SLEEP);
 792
 793         sqp->sq_info.si_signo = SIGSEGV;
 794         sqp->sq_info.si_code = SEGV_MAPERR;
 795         sqp->sq_info.si_addr = (caddr_t)addr;
 796
 797         mutex_enter(&p->p_lock);
 798         sigaddqa(p, t, sqp);
 799         mutex_exit(&p->p_lock);
 800
 801         if (t != NULL)
 802                 aston(t);
 803 #else
 804         ksiginfo_t *ksi = kmem_zalloc(sizeof (ksiginfo_t), KM_SLEEP);
 805
 806         ksiginfo_init(ksi);
 807         ksi->ksi_signo = SIGSEGV;
 808         ksi->ksi_code = SEGV_MAPERR;
 809         ksi->ksi_addr = (caddr_t)addr;
 810         (void) tdksignal(t, SIGSEGV, ksi);
 811 #endif
 812 }
 813
 814 #ifdef __amd64
 815 static void
 816 fasttrap_usdt_args64(fasttrap_probe_t *probe, struct reg *rp, int argc,
 817     uintptr_t *argv)
 818 {
 819         int i, x, cap = MIN(argc, probe->ftp_nargs);
 820         uintptr_t *stack = (uintptr_t *)rp->r_rsp;
 821
 822         for (i = 0; i < cap; i++) {
 823                 x = probe->ftp_argmap[i];
 824
 825                 if (x < 6)
 826                         argv[i] = (&rp->r_rdi)[x];
 827                 else
 828                         argv[i] = fasttrap_fulword_noerr(&stack[x]);
 829         }
 830
 831         for (; i < argc; i++) {
 832                 argv[i] = 0;
 833         }
 834 }
 835 #endif
 836
 837 #ifdef __i386__
 838 static void
 839 fasttrap_usdt_args32(fasttrap_probe_t *probe, struct reg *rp, int argc,
 840     uint32_t *argv)
 841 {
 842         int i, x, cap = MIN(argc, probe->ftp_nargs);
 843         uint32_t *stack = (uint32_t *)rp->r_rsp;
 844
 845         for (i = 0; i < cap; i++) {
 846                 x = probe->ftp_argmap[i];
 847
 848                 argv[i] = fasttrap_fuword32_noerr(&stack[x]);
 849         }
 850
 851         for (; i < argc; i++) {
 852                 argv[i] = 0;
 853         }
 854 }
 855 #endif
 856
 857 static int
 858 fasttrap_do_seg(fasttrap_tracepoint_t *tp, struct reg *rp, uintptr_t *addr)
 859 {
 860         proc_t *p = curproc;
 861 #ifdef __i386__
 862         struct segment_descriptor *desc;
 863 #else
 864         struct user_segment_descriptor *desc;
 865 #endif
 866         uint16_t sel = 0, ndx, type;
 867         uintptr_t limit;
 868
 869         switch (tp->ftt_segment) {
 870         case FASTTRAP_SEG_CS:
 871                 sel = rp->r_cs;
 872                 break;
 873         case FASTTRAP_SEG_DS:
 874                 sel = rp->r_ds;
 875                 break;
 876         case FASTTRAP_SEG_ES:
 877                 sel = rp->r_es;
 878                 break;
 879         case FASTTRAP_SEG_FS:
 880                 sel = rp->r_fs;
 881                 break;
 882         case FASTTRAP_SEG_GS:
 883                 sel = rp->r_gs;
 884                 break;
 885         case FASTTRAP_SEG_SS:
 886                 sel = rp->r_ss;
 887                 break;
 888         }
 889
 890         /*
 891          * Make sure the given segment register specifies a user priority
 892          * selector rather than a kernel selector.
 893          */
 894         if (ISPL(sel) != SEL_UPL)
 895                 return (-1);
 896
 897         ndx = IDXSEL(sel);
 898
 899         /*
 900          * Check the bounds and grab the descriptor out of the specified
 901          * descriptor table.
 902          */
 903         if (ISLDT(sel)) {
 904 #ifdef __i386__
 905                 if (ndx > p->p_md.md_ldt->ldt_len)
 906                         return (-1);
 907
 908                 desc = (struct segment_descriptor *)
 909                     p->p_md.md_ldt[ndx].ldt_base;
 910 #else
 911                 if (ndx > max_ldt_segment)
 912                         return (-1);
 913
 914                 desc = (struct user_segment_descriptor *)
 915                     p->p_md.md_ldt[ndx].ldt_base;
 916 #endif
 917
 918         } else {
 919                 if (ndx >= NGDT)
 920                         return (-1);
 921
 922 #ifdef __i386__
 923                 desc = &gdt[ndx].sd;
 924 #else
 925                 desc = &gdt[ndx];
 926 #endif
 927         }
 928
 929         /*
 930          * The descriptor must have user privilege level and it must be
 931          * present in memory.
 932          */
 933         if (desc->sd_dpl != SEL_UPL || desc->sd_p != 1)
 934                 return (-1);
 935
 936         type = desc->sd_type;
 937
 938         /*
 939          * If the S bit in the type field is not set, this descriptor can
 940          * only be used in system context.
 941          */
 942         if ((type & 0x10) != 0x10)
 943                 return (-1);
 944
 945         limit = USD_GETLIMIT(desc) * (desc->sd_gran ? PAGESIZE : 1);
 946
 947         if (tp->ftt_segment == FASTTRAP_SEG_CS) {
 948                 /*
 949                  * The code/data bit and readable bit must both be set.
 950                  */
 951                 if ((type & 0xa) != 0xa)
 952                         return (-1);
 953
 954                 if (*addr > limit)
 955                         return (-1);
 956         } else {
 957                 /*
 958                  * The code/data bit must be clear.
 959                  */
 960                 if ((type & 0x8) != 0)
 961                         return (-1);
 962
 963                 /*
 964                  * If the expand-down bit is clear, we just check the limit as
 965                  * it would naturally be applied. Otherwise, we need to check
 966                  * that the address is the range [limit + 1 .. 0xffff] or
 967                  * [limit + 1 ... 0xffffffff] depending on if the default
 968                  * operand size bit is set.
 969                  */
 970                 if ((type & 0x4) == 0) {
 971                         if (*addr > limit)
 972                                 return (-1);
 973                 } else if (desc->sd_def32) {
 974                         if (*addr < limit + 1 || 0xffff < *addr)
 975                                 return (-1);
 976                 } else {
 977                         if (*addr < limit + 1 || 0xffffffff < *addr)
 978                                 return (-1);
 979                 }
 980         }
 981
 982         *addr += USD_GETBASE(desc);
 983
 984         return (0);
 985 }
 986
 987 int
 988 fasttrap_pid_probe(struct reg *rp)
 989 {
 990         proc_t *p = curproc;
 991         uintptr_t pc = rp->r_rip - 1;
 992         uintptr_t new_pc = 0;
 993         fasttrap_bucket_t *bucket;
 994 #if defined(sun)
 995         kmutex_t *pid_mtx;
 996 #endif
 997         fasttrap_tracepoint_t *tp, tp_local;
 998         pid_t pid;
 999         dtrace_icookie_t cookie;
1000         uint_t is_enabled = 0;
1001
1002         /*
1003          * It's possible that a user (in a veritable orgy of bad planning)
1004          * could redirect this thread's flow of control before it reached the
1005          * return probe fasttrap. In this case we need to kill the process
1006          * since it's in a unrecoverable state.
1007          */
1008         if (curthread->t_dtrace_step) {
1009                 ASSERT(curthread->t_dtrace_on);
1010                 fasttrap_sigtrap(p, curthread, pc);
1011                 return (0);
1012         }
1013
1014         /*
1015          * Clear all user tracing flags.
1016          */
1017         curthread->t_dtrace_ft = 0;
1018         curthread->t_dtrace_pc = 0;
1019         curthread->t_dtrace_npc = 0;
1020         curthread->t_dtrace_scrpc = 0;
1021         curthread->t_dtrace_astpc = 0;
1022 #ifdef __amd64
1023         curthread->t_dtrace_regv = 0;
1024 #endif
1025
1026 #if defined(sun)
1027         /*
1028          * Treat a child created by a call to vfork(2) as if it were its
1029          * parent. We know that there's only one thread of control in such a
1030          * process: this one.
1031          */
1032         while (p->p_flag & SVFORK) {
1033                 p = p->p_parent;
1034         }
1035 #endif
1036
1037         PROC_LOCK(p);
1038         _PHOLD(p);
1039         pid = p->p_pid;
1040 #if defined(sun)
1041         pid_mtx = &cpu_core[CPU->cpu_id].cpuc_pid_lock;
1042         mutex_enter(pid_mtx);
1043 #endif
1044         bucket = &fasttrap_tpoints.fth_table[FASTTRAP_TPOINTS_INDEX(pid, pc)];
1045
1046         /*
1047          * Lookup the tracepoint that the process just hit.
1048          */
1049         for (tp = bucket->ftb_data; tp != NULL; tp = tp->ftt_next) {
1050                 if (pid == tp->ftt_pid && pc == tp->ftt_pc &&
1051                     tp->ftt_proc->ftpc_acount != 0)
1052                         break;
1053         }
1054
1055         /*
1056          * If we couldn't find a matching tracepoint, either a tracepoint has
1057          * been inserted without using the pid<pid> ioctl interface (see
1058          * fasttrap_ioctl), or somehow we have mislaid this tracepoint.
1059          */
1060         if (tp == NULL) {
1061 #if defined(sun)
1062                 mutex_exit(pid_mtx);
1063 #endif
1064                 _PRELE(p);
1065                 PROC_UNLOCK(p);
1066                 return (-1);
1067         }
1068
1069         /*
1070          * Set the program counter to the address of the traced instruction
1071          * so that it looks right in ustack() output.
1072          */
1073         rp->r_rip = pc;
1074
1075         if (tp->ftt_ids != NULL) {
1076                 fasttrap_id_t *id;
1077
1078 #ifdef __amd64
1079                 if (p->p_model == DATAMODEL_LP64) {
1080                         for (id = tp->ftt_ids; id != NULL; id = id->fti_next) {
1081                                 fasttrap_probe_t *probe = id->fti_probe;
1082
1083                                 if (id->fti_ptype == DTFTP_ENTRY) {
1084                                         /*
1085                                          * We note that this was an entry
1086                                          * probe to help ustack() find the
1087                                          * first caller.
1088                                          */
1089                                         cookie = dtrace_interrupt_disable();
1090                                         DTRACE_CPUFLAG_SET(CPU_DTRACE_ENTRY);
1091                                         dtrace_probe(probe->ftp_id, rp->r_rdi,
1092                                             rp->r_rsi, rp->r_rdx, rp->r_rcx,
1093                                             rp->r_r8);
1094                                         DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_ENTRY);
1095                                         dtrace_interrupt_enable(cookie);
1096                                 } else if (id->fti_ptype == DTFTP_IS_ENABLED) {
1097                                         /*
1098                                          * Note that in this case, we don't
1099                                          * call dtrace_probe() since it's only
1100                                          * an artificial probe meant to change
1101                                          * the flow of control so that it
1102                                          * encounters the true probe.
1103                                          */
1104                                         is_enabled = 1;
1105                                 } else if (probe->ftp_argmap == NULL) {
1106                                         dtrace_probe(probe->ftp_id, rp->r_rdi,
1107                                             rp->r_rsi, rp->r_rdx, rp->r_rcx,
1108                                             rp->r_r8);
1109                                 } else {
1110                                         uintptr_t t[5];
1111
1112                                         fasttrap_usdt_args64(probe, rp,
1113                                             sizeof (t) / sizeof (t[0]), t);
1114
1115                                         dtrace_probe(probe->ftp_id, t[0], t[1],
1116                                             t[2], t[3], t[4]);
1117                                 }
1118                         }
1119                 } else {
1120 #else /* __amd64 */
1121                         uintptr_t s0, s1, s2, s3, s4, s5;
1122                         uint32_t *stack = (uint32_t *)rp->r_esp;
1123
1124                         /*
1125                          * In 32-bit mode, all arguments are passed on the
1126                          * stack. If this is a function entry probe, we need
1127                          * to skip the first entry on the stack as it
1128                          * represents the return address rather than a
1129                          * parameter to the function.
1130                          */
1131                         s0 = fasttrap_fuword32_noerr(&stack[0]);
1132                         s1 = fasttrap_fuword32_noerr(&stack[1]);
1133                         s2 = fasttrap_fuword32_noerr(&stack[2]);
1134                         s3 = fasttrap_fuword32_noerr(&stack[3]);
1135                         s4 = fasttrap_fuword32_noerr(&stack[4]);
1136                         s5 = fasttrap_fuword32_noerr(&stack[5]);
1137
1138                         for (id = tp->ftt_ids; id != NULL; id = id->fti_next) {
1139                                 fasttrap_probe_t *probe = id->fti_probe;
1140
1141                                 if (id->fti_ptype == DTFTP_ENTRY) {
1142                                         /*
1143                                          * We note that this was an entry
1144                                          * probe to help ustack() find the
1145                                          * first caller.
1146                                          */
1147                                         cookie = dtrace_interrupt_disable();
1148                                         DTRACE_CPUFLAG_SET(CPU_DTRACE_ENTRY);
1149                                         dtrace_probe(probe->ftp_id, s1, s2,
1150                                             s3, s4, s5);
1151                                         DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_ENTRY);
1152                                         dtrace_interrupt_enable(cookie);
1153                                 } else if (id->fti_ptype == DTFTP_IS_ENABLED) {
1154                                         /*
1155                                          * Note that in this case, we don't
1156                                          * call dtrace_probe() since it's only
1157                                          * an artificial probe meant to change
1158                                          * the flow of control so that it
1159                                          * encounters the true probe.
1160                                          */
1161                                         is_enabled = 1;
1162                                 } else if (probe->ftp_argmap == NULL) {
1163                                         dtrace_probe(probe->ftp_id, s0, s1,
1164                                             s2, s3, s4);
1165                                 } else {
1166                                         uint32_t t[5];
1167
1168                                         fasttrap_usdt_args32(probe, rp,
1169                                             sizeof (t) / sizeof (t[0]), t);
1170
1171                                         dtrace_probe(probe->ftp_id, t[0], t[1],
1172                                             t[2], t[3], t[4]);
1173                                 }
1174                         }
1175 #endif /* __amd64 */
1176 #ifdef __amd64
1177                 }
1178 #endif
1179         }
1180
1181         /*
1182          * We're about to do a bunch of work so we cache a local copy of
1183          * the tracepoint to emulate the instruction, and then find the
1184          * tracepoint again later if we need to light up any return probes.
1185          */
1186         tp_local = *tp;
1187         PROC_UNLOCK(p);
1188 #if defined(sun)
1189         mutex_exit(pid_mtx);
1190 #endif
1191         tp = &tp_local;
1192
1193         /*
1194          * Set the program counter to appear as though the traced instruction
1195          * had completely executed. This ensures that fasttrap_getreg() will
1196          * report the expected value for REG_RIP.
1197          */
1198         rp->r_rip = pc + tp->ftt_size;
1199
1200         /*
1201          * If there's an is-enabled probe connected to this tracepoint it
1202          * means that there was a 'xorl %eax, %eax' or 'xorq %rax, %rax'
1203          * instruction that was placed there by DTrace when the binary was
1204          * linked. As this probe is, in fact, enabled, we need to stuff 1
1205          * into %eax or %rax. Accordingly, we can bypass all the instruction
1206          * emulation logic since we know the inevitable result. It's possible
1207          * that a user could construct a scenario where the 'is-enabled'
1208          * probe was on some other instruction, but that would be a rather
1209          * exotic way to shoot oneself in the foot.
1210          */
1211         if (is_enabled) {
1212                 rp->r_rax = 1;
1213                 new_pc = rp->r_rip;
1214                 goto done;
1215         }
1216
1217         /*
1218          * We emulate certain types of instructions to ensure correctness
1219          * (in the case of position dependent instructions) or optimize
1220          * common cases. The rest we have the thread execute back in user-
1221          * land.
1222          */
1223         switch (tp->ftt_type) {
1224         case FASTTRAP_T_RET:
1225         case FASTTRAP_T_RET16:
1226         {
1227                 uintptr_t dst = 0;
1228                 uintptr_t addr = 0;
1229                 int ret = 0;
1230
1231                 /*
1232                  * We have to emulate _every_ facet of the behavior of a ret
1233                  * instruction including what happens if the load from %esp
1234                  * fails; in that case, we send a SIGSEGV.
1235                  */
1236 #ifdef __amd64
1237                 if (p->p_model == DATAMODEL_NATIVE) {
1238                         ret = dst = fasttrap_fulword((void *)rp->r_rsp);
1239                         addr = rp->r_rsp + sizeof (uintptr_t);
1240                 } else {
1241 #endif
1242 #ifdef __i386__
1243                         uint32_t dst32;
1244                         ret = dst32 = fasttrap_fuword32((void *)rp->r_esp);
1245                         dst = dst32;
1246                         addr = rp->r_esp + sizeof (uint32_t);
1247 #endif
1248 #ifdef __amd64
1249                 }
1250 #endif
1251
1252                 if (ret == -1) {
1253                         fasttrap_sigsegv(p, curthread, rp->r_rsp);
1254                         new_pc = pc;
1255                         break;
1256                 }
1257
1258                 if (tp->ftt_type == FASTTRAP_T_RET16)
1259                         addr += tp->ftt_dest;
1260
1261                 rp->r_rsp = addr;
1262                 new_pc = dst;
1263                 break;
1264         }
1265
1266         case FASTTRAP_T_JCC:
1267         {
1268                 uint_t taken = 0;
1269
1270                 switch (tp->ftt_code) {
1271                 case FASTTRAP_JO:
1272                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_OF) != 0;
1273                         break;
1274                 case FASTTRAP_JNO:
1275                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_OF) == 0;
1276                         break;
1277                 case FASTTRAP_JB:
1278                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_CF) != 0;
1279                         break;
1280                 case FASTTRAP_JAE:
1281                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_CF) == 0;
1282                         break;
1283                 case FASTTRAP_JE:
1284                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_ZF) != 0;
1285                         break;
1286                 case FASTTRAP_JNE:
1287                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_ZF) == 0;
1288                         break;
1289                 case FASTTRAP_JBE:
1290                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_CF) != 0 ||
1291                             (rp->r_rflags & FASTTRAP_EFLAGS_ZF) != 0;
1292                         break;
1293                 case FASTTRAP_JA:
1294                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_CF) == 0 &&
1295                             (rp->r_rflags & FASTTRAP_EFLAGS_ZF) == 0;
1296                         break;
1297                 case FASTTRAP_JS:
1298                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_SF) != 0;
1299                         break;
1300                 case FASTTRAP_JNS:
1301                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_SF) == 0;
1302                         break;
1303                 case FASTTRAP_JP:
1304                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_PF) != 0;
1305                         break;
1306                 case FASTTRAP_JNP:
1307                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_PF) == 0;
1308                         break;
1309                 case FASTTRAP_JL:
1310                         taken = ((rp->r_rflags & FASTTRAP_EFLAGS_SF) == 0) !=
1311                             ((rp->r_rflags & FASTTRAP_EFLAGS_OF) == 0);
1312                         break;
1313                 case FASTTRAP_JGE:
1314                         taken = ((rp->r_rflags & FASTTRAP_EFLAGS_SF) == 0) ==
1315                             ((rp->r_rflags & FASTTRAP_EFLAGS_OF) == 0);
1316                         break;
1317                 case FASTTRAP_JLE:
1318                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_ZF) != 0 ||
1319                             ((rp->r_rflags & FASTTRAP_EFLAGS_SF) == 0) !=
1320                             ((rp->r_rflags & FASTTRAP_EFLAGS_OF) == 0);
1321                         break;
1322                 case FASTTRAP_JG:
1323                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_ZF) == 0 &&
1324                             ((rp->r_rflags & FASTTRAP_EFLAGS_SF) == 0) ==
1325                             ((rp->r_rflags & FASTTRAP_EFLAGS_OF) == 0);
1326                         break;
1327
1328                 }
1329
1330                 if (taken)
1331                         new_pc = tp->ftt_dest;
1332                 else
1333                         new_pc = pc + tp->ftt_size;
1334                 break;
1335         }
1336
1337         case FASTTRAP_T_LOOP:
1338         {
1339                 uint_t taken = 0;
1340 #ifdef __amd64
1341                 greg_t cx = rp->r_rcx--;
1342 #else
1343                 greg_t cx = rp->r_ecx--;
1344 #endif
1345
1346                 switch (tp->ftt_code) {
1347                 case FASTTRAP_LOOPNZ:
1348                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_ZF) == 0 &&
1349                             cx != 0;
1350                         break;
1351                 case FASTTRAP_LOOPZ:
1352                         taken = (rp->r_rflags & FASTTRAP_EFLAGS_ZF) != 0 &&
1353                             cx != 0;
1354                         break;
1355                 case FASTTRAP_LOOP:
1356                         taken = (cx != 0);
1357                         break;
1358                 }
1359
1360                 if (taken)
1361                         new_pc = tp->ftt_dest;
1362                 else
1363                         new_pc = pc + tp->ftt_size;
1364                 break;
1365         }
1366
1367         case FASTTRAP_T_JCXZ:
1368         {
1369 #ifdef __amd64
1370                 greg_t cx = rp->r_rcx;
1371 #else
1372                 greg_t cx = rp->r_ecx;
1373 #endif
1374
1375                 if (cx == 0)
1376                         new_pc = tp->ftt_dest;
1377                 else
1378                         new_pc = pc + tp->ftt_size;
1379                 break;
1380         }
1381
1382         case FASTTRAP_T_PUSHL_EBP:
1383         {
1384                 int ret = 0;
1385
1386 #ifdef __amd64
1387                 if (p->p_model == DATAMODEL_NATIVE) {
1388                         rp->r_rsp -= sizeof (uintptr_t);
1389                         ret = fasttrap_sulword((void *)rp->r_rsp, rp->r_rbp);
1390                 } else {
1391 #endif
1392 #ifdef __i386__
1393                         rp->r_rsp -= sizeof (uint32_t);
1394                         ret = fasttrap_suword32((void *)rp->r_rsp, rp->r_rbp);
1395 #endif
1396 #ifdef __amd64
1397                 }
1398 #endif
1399
1400                 if (ret == -1) {
1401                         fasttrap_sigsegv(p, curthread, rp->r_rsp);
1402                         new_pc = pc;
1403                         break;
1404                 }
1405
1406                 new_pc = pc + tp->ftt_size;
1407                 break;
1408         }
1409
1410         case FASTTRAP_T_NOP:
1411                 new_pc = pc + tp->ftt_size;
1412                 break;
1413
1414         case FASTTRAP_T_JMP:
1415         case FASTTRAP_T_CALL:
1416                 if (tp->ftt_code == 0) {
1417                         new_pc = tp->ftt_dest;
1418                 } else {
1419 #ifdef __amd64
1420                         uintptr_t value;
1421 #endif
1422                         uintptr_t addr = tp->ftt_dest;
1423
1424                         if (tp->ftt_base != FASTTRAP_NOREG)
1425                                 addr += fasttrap_getreg(rp, tp->ftt_base);
1426                         if (tp->ftt_index != FASTTRAP_NOREG)
1427                                 addr += fasttrap_getreg(rp, tp->ftt_index) <<
1428                                     tp->ftt_scale;
1429
1430                         if (tp->ftt_code == 1) {
1431                                 /*
1432                                  * If there's a segment prefix for this
1433                                  * instruction, we'll need to check permissions
1434                                  * and bounds on the given selector, and adjust
1435                                  * the address accordingly.
1436                                  */
1437                                 if (tp->ftt_segment != FASTTRAP_SEG_NONE &&
1438                                     fasttrap_do_seg(tp, rp, &addr) != 0) {
1439                                         fasttrap_sigsegv(p, curthread, addr);
1440                                         new_pc = pc;
1441                                         break;
1442                                 }
1443
1444 #ifdef __amd64
1445                                 if (p->p_model == DATAMODEL_NATIVE) {
1446                                         if ((value = fasttrap_fulword((void *)addr))
1447                                              == -1) {
1448                                                 fasttrap_sigsegv(p, curthread,
1449                                                     addr);
1450                                                 new_pc = pc;
1451                                                 break;
1452                                         }
1453                                         new_pc = value;
1454                                 } else {
1455 #endif
1456 #ifdef __i386__
1457                                         uint32_t value32;
1458                                         addr = (uintptr_t)(uint32_t)addr;
1459                                         if ((value32 = fasttrap_fuword32((void *)addr))
1460                                             == -1) {
1461                                                 fasttrap_sigsegv(p, curthread,
1462                                                     addr);
1463                                                 new_pc = pc;
1464                                                 break;
1465                                         }
1466                                         new_pc = value32;
1467 #endif
1468                                 }
1469 #ifdef __amd64
1470                         } else {
1471                                 new_pc = addr;
1472                         }
1473 #endif
1474                 }
1475
1476                 /*
1477                  * If this is a call instruction, we need to push the return
1478                  * address onto the stack. If this fails, we send the process
1479                  * a SIGSEGV and reset the pc to emulate what would happen if
1480                  * this instruction weren't traced.
1481                  */
1482                 if (tp->ftt_type == FASTTRAP_T_CALL) {
1483                         int ret = 0;
1484                         uintptr_t addr = 0, pcps;
1485 #ifdef __amd64
1486                         if (p->p_model == DATAMODEL_NATIVE) {
1487                                 addr = rp->r_rsp - sizeof (uintptr_t);
1488                                 pcps = pc + tp->ftt_size;
1489                                 ret = fasttrap_sulword((void *)addr, pcps);
1490                         } else {
1491 #endif
1492 #ifdef __i386__
1493                                 addr = rp->r_rsp - sizeof (uint32_t);
1494                                 pcps = (uint32_t)(pc + tp->ftt_size);
1495                                 ret = fasttrap_suword32((void *)addr, pcps);
1496 #endif
1497 #ifdef __amd64
1498                         }
1499 #endif
1500
1501                         if (ret == -1) {
1502                                 fasttrap_sigsegv(p, curthread, addr);
1503                                 new_pc = pc;
1504                                 break;
1505                         }
1506
1507                         rp->r_rsp = addr;
1508                 }
1509
1510                 break;
1511
1512         case FASTTRAP_T_COMMON:
1513         {
1514                 uintptr_t addr;
1515 #if defined(__amd64)
1516                 uint8_t scratch[2 * FASTTRAP_MAX_INSTR_SIZE + 22];
1517 #else
1518                 uint8_t scratch[2 * FASTTRAP_MAX_INSTR_SIZE + 7];
1519 #endif
1520                 uint_t i = 0;
1521 #if defined(sun)
1522                 klwp_t *lwp = ttolwp(curthread);
1523 #endif
1524
1525                 /*
1526                  * Compute the address of the ulwp_t and step over the
1527                  * ul_self pointer. The method used to store the user-land
1528                  * thread pointer is very different on 32- and 64-bit
1529                  * kernels.
1530                  */
1531 #if defined(sun)
1532 #if defined(__amd64)
1533                 if (p->p_model == DATAMODEL_LP64) {
1534                         addr = lwp->lwp_pcb.pcb_fsbase;
1535                         addr += sizeof (void *);
1536                 } else {
1537                         addr = lwp->lwp_pcb.pcb_gsbase;
1538                         addr += sizeof (caddr32_t);
1539                 }
1540 #else
1541                 addr = USD_GETBASE(&lwp->lwp_pcb.pcb_gsdesc);
1542                 addr += sizeof (void *);
1543 #endif
1544 #endif /* sun */
1545 #ifdef __i386__
1546                 addr = USD_GETBASE(&curthread->td_pcb->pcb_gsd);
1547 #else
1548                 addr = curthread->td_pcb->pcb_gsbase;
1549 #endif
1550                 addr += sizeof (void *);
1551
1552                 /*
1553                  * Generic Instruction Tracing
1554                  * ---------------------------
1555                  *
1556                  * This is the layout of the scratch space in the user-land
1557                  * thread structure for our generated instructions.
1558                  *
1559                  *      32-bit mode                     bytes
1560                  *      ------------------------        -----
1561                  * a:   <original instruction>          <= 15
1562                  *      jmp     <pc + tp->ftt_size>         5
1563                  * b:   <original instruction>          <= 15
1564                  *      int     T_DTRACE_RET                2
1565                  *                                      -----
1566                  *                                      <= 37
1567                  *
1568                  *      64-bit mode                     bytes
1569                  *      ------------------------        -----
1570                  * a:   <original instruction>          <= 15
1571                  *      jmp     0(%rip)                     6
1572                  *      <pc + tp->ftt_size>                 8
1573                  * b:   <original instruction>          <= 15
1574                  *      int     T_DTRACE_RET                2
1575                  *                                      -----
1576                  *                                      <= 46
1577                  *
1578                  * The %pc is set to a, and curthread->t_dtrace_astpc is set
1579                  * to b. If we encounter a signal on the way out of the
1580                  * kernel, trap() will set %pc to curthread->t_dtrace_astpc
1581                  * so that we execute the original instruction and re-enter
1582                  * the kernel rather than redirecting to the next instruction.
1583                  *
1584                  * If there are return probes (so we know that we're going to
1585                  * need to reenter the kernel after executing the original
1586                  * instruction), the scratch space will just contain the
1587                  * original instruction followed by an interrupt -- the same
1588                  * data as at b.
1589                  *
1590                  * %rip-relative Addressing
1591                  * ------------------------
1592                  *
1593                  * There's a further complication in 64-bit mode due to %rip-
1594                  * relative addressing. While this is clearly a beneficial
1595                  * architectural decision for position independent code, it's
1596                  * hard not to see it as a personal attack against the pid
1597                  * provider since before there was a relatively small set of
1598                  * instructions to emulate; with %rip-relative addressing,
1599                  * almost every instruction can potentially depend on the
1600                  * address at which it's executed. Rather than emulating
1601                  * the broad spectrum of instructions that can now be
1602                  * position dependent, we emulate jumps and others as in
1603                  * 32-bit mode, and take a different tack for instructions
1604                  * using %rip-relative addressing.
1605                  *
1606                  * For every instruction that uses the ModRM byte, the
1607                  * in-kernel disassembler reports its location. We use the
1608                  * ModRM byte to identify that an instruction uses
1609                  * %rip-relative addressing and to see what other registers
1610                  * the instruction uses. To emulate those instructions,
1611                  * we modify the instruction to be %rax-relative rather than
1612                  * %rip-relative (or %rcx-relative if the instruction uses
1613                  * %rax; or %r8- or %r9-relative if the REX.B is present so
1614                  * we don't have to rewrite the REX prefix). We then load
1615                  * the value that %rip would have been into the scratch
1616                  * register and generate an instruction to reset the scratch
1617                  * register back to its original value. The instruction
1618                  * sequence looks like this:
1619                  *
1620                  *      64-mode %rip-relative           bytes
1621                  *      ------------------------        -----
1622                  * a:   <modified instruction>          <= 15
1623                  *      movq    $<value>, %<scratch>        6
1624                  *      jmp     0(%rip)                     6
1625                  *      <pc + tp->ftt_size>                 8
1626                  * b:   <modified instruction>          <= 15
1627                  *      int     T_DTRACE_RET                2
1628                  *                                      -----
1629                  *                                         52
1630                  *
1631                  * We set curthread->t_dtrace_regv so that upon receiving
1632                  * a signal we can reset the value of the scratch register.
1633                  */
1634
1635                 ASSERT(tp->ftt_size < FASTTRAP_MAX_INSTR_SIZE);
1636
1637                 curthread->t_dtrace_scrpc = addr;
1638                 bcopy(tp->ftt_instr, &scratch[i], tp->ftt_size);
1639                 i += tp->ftt_size;
1640
1641 #ifdef __amd64
1642                 if (tp->ftt_ripmode != 0) {
1643                         greg_t *reg = NULL;
1644
1645                         ASSERT(p->p_model == DATAMODEL_LP64);
1646                         ASSERT(tp->ftt_ripmode &
1647                             (FASTTRAP_RIP_1 | FASTTRAP_RIP_2));
1648
1649                         /*
1650                          * If this was a %rip-relative instruction, we change
1651                          * it to be either a %rax- or %rcx-relative
1652                          * instruction (depending on whether those registers
1653                          * are used as another operand; or %r8- or %r9-
1654                          * relative depending on the value of REX.B). We then
1655                          * set that register and generate a movq instruction
1656                          * to reset the value.
1657                          */
1658                         if (tp->ftt_ripmode & FASTTRAP_RIP_X)
1659                                 scratch[i++] = FASTTRAP_REX(1, 0, 0, 1);
1660                         else
1661                                 scratch[i++] = FASTTRAP_REX(1, 0, 0, 0);
1662
1663                         if (tp->ftt_ripmode & FASTTRAP_RIP_1)
1664                                 scratch[i++] = FASTTRAP_MOV_EAX;
1665                         else
1666                                 scratch[i++] = FASTTRAP_MOV_ECX;
1667
1668                         switch (tp->ftt_ripmode) {
1669                         case FASTTRAP_RIP_1:
1670                                 reg = &rp->r_rax;
1671                                 curthread->t_dtrace_reg = REG_RAX;
1672                                 break;
1673                         case FASTTRAP_RIP_2:
1674                                 reg = &rp->r_rcx;
1675                                 curthread->t_dtrace_reg = REG_RCX;
1676                                 break;
1677                         case FASTTRAP_RIP_1 | FASTTRAP_RIP_X:
1678                                 reg = &rp->r_r8;
1679                                 curthread->t_dtrace_reg = REG_R8;
1680                                 break;
1681                         case FASTTRAP_RIP_2 | FASTTRAP_RIP_X:
1682                                 reg = &rp->r_r9;
1683                                 curthread->t_dtrace_reg = REG_R9;
1684                                 break;
1685                         }
1686
1687                         /* LINTED - alignment */
1688                         *(uint64_t *)&scratch[i] = *reg;
1689                         curthread->t_dtrace_regv = *reg;
1690                         *reg = pc + tp->ftt_size;
1691                         i += sizeof (uint64_t);
1692                 }
1693 #endif
1694
1695                 /*
1696                  * Generate the branch instruction to what would have
1697                  * normally been the subsequent instruction. In 32-bit mode,
1698                  * this is just a relative branch; in 64-bit mode this is a
1699                  * %rip-relative branch that loads the 64-bit pc value
1700                  * immediately after the jmp instruction.
1701                  */
1702 #ifdef __amd64
1703                 if (p->p_model == DATAMODEL_LP64) {
1704                         scratch[i++] = FASTTRAP_GROUP5_OP;
1705                         scratch[i++] = FASTTRAP_MODRM(0, 4, 5);
1706                         /* LINTED - alignment */
1707                         *(uint32_t *)&scratch[i] = 0;
1708                         i += sizeof (uint32_t);
1709                         /* LINTED - alignment */
1710                         *(uint64_t *)&scratch[i] = pc + tp->ftt_size;
1711                         i += sizeof (uint64_t);
1712                 } else {
1713 #endif
1714 #ifdef __i386__
1715                         /*
1716                          * Set up the jmp to the next instruction; note that
1717                          * the size of the traced instruction cancels out.
1718                          */
1719                         scratch[i++] = FASTTRAP_JMP32;
1720                         /* LINTED - alignment */
1721                         *(uint32_t *)&scratch[i] = pc - addr - 5;
1722                         i += sizeof (uint32_t);
1723 #endif
1724 #ifdef __amd64
1725                 }
1726 #endif
1727
1728                 curthread->t_dtrace_astpc = addr + i;
1729                 bcopy(tp->ftt_instr, &scratch[i], tp->ftt_size);
1730                 i += tp->ftt_size;
1731                 scratch[i++] = FASTTRAP_INT;
1732                 scratch[i++] = T_DTRACE_RET;
1733
1734                 ASSERT(i <= sizeof (scratch));
1735
1736 #if defined(sun)
1737                 if (fasttrap_copyout(scratch, (char *)addr, i)) {
1738 #else
1739                 if (uwrite(curproc, scratch, i, addr)) {
1740 #endif
1741                         fasttrap_sigtrap(p, curthread, pc);
1742                         new_pc = pc;
1743                         break;
1744                 }
1745                 if (tp->ftt_retids != NULL) {
1746                         curthread->t_dtrace_step = 1;
1747                         curthread->t_dtrace_ret = 1;
1748                         new_pc = curthread->t_dtrace_astpc;
1749                 } else {
1750                         new_pc = curthread->t_dtrace_scrpc;
1751                 }
1752
1753                 curthread->t_dtrace_pc = pc;
1754                 curthread->t_dtrace_npc = pc + tp->ftt_size;
1755                 curthread->t_dtrace_on = 1;
1756                 break;
1757         }
1758
1759         default:
1760                 panic("fasttrap: mishandled an instruction");
1761         }
1762
1763 done:
1764         /*
1765          * If there were no return probes when we first found the tracepoint,
1766          * we should feel no obligation to honor any return probes that were
1767          * subsequently enabled -- they'll just have to wait until the next
1768          * time around.
1769          */
1770         if (tp->ftt_retids != NULL) {
1771                 /*
1772                  * We need to wait until the results of the instruction are
1773                  * apparent before invoking any return probes. If this
1774                  * instruction was emulated we can just call
1775                  * fasttrap_return_common(); if it needs to be executed, we
1776                  * need to wait until the user thread returns to the kernel.
1777                  */
1778                 if (tp->ftt_type != FASTTRAP_T_COMMON) {
1779                         /*
1780                          * Set the program counter to the address of the traced
1781                          * instruction so that it looks right in ustack()
1782                          * output. We had previously set it to the end of the
1783                          * instruction to simplify %rip-relative addressing.
1784                          */
1785                         rp->r_rip = pc;
1786
1787                         fasttrap_return_common(rp, pc, pid, new_pc);
1788                 } else {
1789                         ASSERT(curthread->t_dtrace_ret != 0);
1790                         ASSERT(curthread->t_dtrace_pc == pc);
1791                         ASSERT(curthread->t_dtrace_scrpc != 0);
1792                         ASSERT(new_pc == curthread->t_dtrace_astpc);
1793                 }
1794         }
1795
1796         rp->r_rip = new_pc;
1797
1798         PROC_LOCK(p);
1799         proc_write_regs(curthread, rp);
1800         _PRELE(p);
1801         PROC_UNLOCK(p);
1802
1803         return (0);
1804 }
1805
1806 int
1807 fasttrap_return_probe(struct reg *rp)
1808 {
1809         proc_t *p = curproc;
1810         uintptr_t pc = curthread->t_dtrace_pc;
1811         uintptr_t npc = curthread->t_dtrace_npc;
1812
1813         curthread->t_dtrace_pc = 0;
1814         curthread->t_dtrace_npc = 0;
1815         curthread->t_dtrace_scrpc = 0;
1816         curthread->t_dtrace_astpc = 0;
1817
1818 #if defined(sun)
1819         /*
1820          * Treat a child created by a call to vfork(2) as if it were its
1821          * parent. We know that there's only one thread of control in such a
1822          * process: this one.
1823          */
1824         while (p->p_flag & SVFORK) {
1825                 p = p->p_parent;
1826         }
1827 #endif
1828
1829         /*
1830          * We set rp->r_rip to the address of the traced instruction so
1831          * that it appears to dtrace_probe() that we're on the original
1832          * instruction, and so that the user can't easily detect our
1833          * complex web of lies. dtrace_return_probe() (our caller)
1834          * will correctly set %pc after we return.
1835          */
1836         rp->r_rip = pc;
1837
1838         fasttrap_return_common(rp, pc, p->p_pid, npc);
1839
1840         return (0);
1841 }
1842
1843 /*ARGSUSED*/
1844 uint64_t
1845 fasttrap_pid_getarg(void *arg, dtrace_id_t id, void *parg, int argno,
1846     int aframes)
1847 {
1848         struct reg r;
1849
1850         fill_regs(curthread, &r);
1851
1852         return (fasttrap_anarg(&r, 1, argno));
1853 }
1854
1855 /*ARGSUSED*/
1856 uint64_t
1857 fasttrap_usdt_getarg(void *arg, dtrace_id_t id, void *parg, int argno,
1858     int aframes)
1859 {
1860         struct reg r;
1861
1862         fill_regs(curthread, &r);
1863
1864         return (fasttrap_anarg(&r, 0, argno));
1865 }
1866
1867 static ulong_t
1868 fasttrap_getreg(struct reg *rp, uint_t reg)
1869 {
1870 #ifdef __amd64
1871         switch (reg) {
1872         case REG_R15:           return (rp->r_r15);
1873         case REG_R14:           return (rp->r_r14);
1874         case REG_R13:           return (rp->r_r13);
1875         case REG_R12:           return (rp->r_r12);
1876         case REG_R11:           return (rp->r_r11);
1877         case REG_R10:           return (rp->r_r10);
1878         case REG_R9:            return (rp->r_r9);
1879         case REG_R8:            return (rp->r_r8);
1880         case REG_RDI:           return (rp->r_rdi);
1881         case REG_RSI:           return (rp->r_rsi);
1882         case REG_RBP:           return (rp->r_rbp);
1883         case REG_RBX:           return (rp->r_rbx);
1884         case REG_RDX:           return (rp->r_rdx);
1885         case REG_RCX:           return (rp->r_rcx);
1886         case REG_RAX:           return (rp->r_rax);
1887         case REG_TRAPNO:        return (rp->r_trapno);
1888         case REG_ERR:           return (rp->r_err);
1889         case REG_RIP:           return (rp->r_rip);
1890         case REG_CS:            return (rp->r_cs);
1891 #if defined(sun)
1892         case REG_RFL:           return (rp->r_rfl);
1893 #endif
1894         case REG_RSP:           return (rp->r_rsp);
1895         case REG_SS:            return (rp->r_ss);
1896         case REG_FS:            return (rp->r_fs);
1897         case REG_GS:            return (rp->r_gs);
1898         case REG_DS:            return (rp->r_ds);
1899         case REG_ES:            return (rp->r_es);
1900         case REG_FSBASE:        return (rdmsr(MSR_FSBASE));
1901         case REG_GSBASE:        return (rdmsr(MSR_GSBASE));
1902         }
1903
1904         panic("dtrace: illegal register constant");
1905         /*NOTREACHED*/
1906 #else
1907 #define _NGREG 19
1908         if (reg >= _NGREG)
1909                 panic("dtrace: illegal register constant");
1910
1911         return (((greg_t *)&rp->r_gs)[reg]);
1912 #endif
1913 }