Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/cddl/contrib/opensolaris/uts/powerpc/dtrace/fasttrap_isa.c
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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 2013 Justin Hibbits */ 22 /* 23 * Copyright 2007 Sun Microsystems, Inc. All rights reserved. 24 * Use is subject to license terms. 25 */ 26 27 #include <sys/fasttrap_isa.h> 28 #include <sys/fasttrap_impl.h> 29 #include <sys/dtrace.h> 30 #include <sys/dtrace_impl.h> 31 #include <cddl/dev/dtrace/dtrace_cddl.h> 32 #include <sys/proc.h> 33 #include <sys/types.h> 34 #include <sys/uio.h> 35 #include <sys/ptrace.h> 36 #include <sys/rmlock.h> 37 #include <sys/sysent.h> 38 39 #define OP(x) ((x) >> 26) 40 #define OPX(x) (((x) >> 2) & 0x3FF) 41 #define OP_BO(x) (((x) & 0x03E00000) >> 21) 42 #define OP_BI(x) (((x) & 0x001F0000) >> 16) 43 #define OP_RS(x) (((x) & 0x03E00000) >> 21) 44 #define OP_RA(x) (((x) & 0x001F0000) >> 16) 45 #define OP_RB(x) (((x) & 0x0000F100) >> 11) 46 47 int 48 fasttrap_tracepoint_install(proc_t *p, fasttrap_tracepoint_t *tp) 49 { 50 fasttrap_instr_t instr = FASTTRAP_INSTR; 51 52 if (uwrite(p, &instr, 4, tp->ftt_pc) != 0) 53 return (-1); 54 55 return (0); 56 } 57 58 int 59 fasttrap_tracepoint_remove(proc_t *p, fasttrap_tracepoint_t *tp) 60 { 61 uint32_t instr; 62 63 /* 64 * Distinguish between read or write failures and a changed 65 * instruction. 66 */ 67 if (uread(p, &instr, 4, tp->ftt_pc) != 0) 68 return (0); 69 if (instr != FASTTRAP_INSTR) 70 return (0); 71 if (uwrite(p, &tp->ftt_instr, 4, tp->ftt_pc) != 0) 72 return (-1); 73 74 return (0); 75 } 76 77 int 78 fasttrap_tracepoint_init(proc_t *p, fasttrap_tracepoint_t *tp, uintptr_t pc, 79 fasttrap_probe_type_t type) 80 { 81 uint32_t instr; 82 //int32_t disp; 83 84 /* 85 * Read the instruction at the given address out of the process's 86 * address space. We don't have to worry about a debugger 87 * changing this instruction before we overwrite it with our trap 88 * instruction since P_PR_LOCK is set. 89 */ 90 if (uread(p, &instr, 4, pc) != 0) 91 return (-1); 92 93 /* 94 * Decode the instruction to fill in the probe flags. We can have 95 * the process execute most instructions on its own using a pc/npc 96 * trick, but pc-relative control transfer present a problem since 97 * we're relocating the instruction. We emulate these instructions 98 * in the kernel. We assume a default type and over-write that as 99 * needed. 100 * 101 * pc-relative instructions must be emulated for correctness; 102 * other instructions (which represent a large set of commonly traced 103 * instructions) are emulated or otherwise optimized for performance. 104 */ 105 tp->ftt_type = FASTTRAP_T_COMMON; 106 tp->ftt_instr = instr; 107 108 switch (OP(instr)) { 109 /* The following are invalid for trapping (invalid opcodes, tw/twi). */ 110 case 0: 111 case 1: 112 case 2: 113 case 4: 114 case 5: 115 case 6: 116 case 30: 117 case 39: 118 case 58: 119 case 62: 120 case 3: /* twi */ 121 return (-1); 122 case 31: /* tw */ 123 if (OPX(instr) == 4) 124 return (-1); 125 else if (OPX(instr) == 444 && OP_RS(instr) == OP_RA(instr) && 126 OP_RS(instr) == OP_RB(instr)) 127 tp->ftt_type = FASTTRAP_T_NOP; 128 break; 129 case 16: 130 tp->ftt_type = FASTTRAP_T_BC; 131 tp->ftt_dest = instr & 0x0000FFFC; /* Extract target address */ 132 if (instr & 0x00008000) 133 tp->ftt_dest |= 0xFFFF0000; 134 /* Use as offset if not absolute address. */ 135 if (!(instr & 0x02)) 136 tp->ftt_dest += pc; 137 tp->ftt_bo = OP_BO(instr); 138 tp->ftt_bi = OP_BI(instr); 139 break; 140 case 18: 141 tp->ftt_type = FASTTRAP_T_B; 142 tp->ftt_dest = instr & 0x03FFFFFC; /* Extract target address */ 143 if (instr & 0x02000000) 144 tp->ftt_dest |= 0xFC000000; 145 /* Use as offset if not absolute address. */ 146 if (!(instr & 0x02)) 147 tp->ftt_dest += pc; 148 break; 149 case 19: 150 switch (OPX(instr)) { 151 case 528: /* bcctr */ 152 tp->ftt_type = FASTTRAP_T_BCTR; 153 tp->ftt_bo = OP_BO(instr); 154 tp->ftt_bi = OP_BI(instr); 155 break; 156 case 16: /* bclr */ 157 tp->ftt_type = FASTTRAP_T_BCTR; 158 tp->ftt_bo = OP_BO(instr); 159 tp->ftt_bi = OP_BI(instr); 160 break; 161 }; 162 break; 163 case 24: 164 if (OP_RS(instr) == OP_RA(instr) && 165 (instr & 0x0000FFFF) == 0) 166 tp->ftt_type = FASTTRAP_T_NOP; 167 break; 168 }; 169 170 /* 171 * We don't know how this tracepoint is going to be used, but in case 172 * it's used as part of a function return probe, we need to indicate 173 * whether it's always a return site or only potentially a return 174 * site. If it's part of a return probe, it's always going to be a 175 * return from that function if it's a restore instruction or if 176 * the previous instruction was a return. If we could reliably 177 * distinguish jump tables from return sites, this wouldn't be 178 * necessary. 179 */ 180 #if 0 181 if (tp->ftt_type != FASTTRAP_T_RESTORE && 182 (uread(p, &instr, 4, pc - sizeof (instr)) != 0 || 183 !(OP(instr) == 2 && OP3(instr) == OP3_RETURN))) 184 tp->ftt_flags |= FASTTRAP_F_RETMAYBE; 185 #endif 186 187 return (0); 188 } 189 190 static uint64_t 191 fasttrap_anarg(struct reg *rp, int argno) 192 { 193 uint64_t value; 194 proc_t *p = curproc; 195 196 /* The first 8 arguments are in registers. */ 197 if (argno < 8) 198 return rp->fixreg[argno + 3]; 199 200 /* Arguments on stack start after SP+LR (2 register slots). */ 201 if (SV_PROC_FLAG(p, SV_ILP32)) { 202 DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT); 203 value = dtrace_fuword32((void *)(rp->fixreg[1] + 8 + 204 ((argno - 8) * sizeof(uint32_t)))); 205 DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT | CPU_DTRACE_BADADDR); 206 } else { 207 DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT); 208 value = dtrace_fuword64((void *)(rp->fixreg[1] + 48 + 209 ((argno - 8) * sizeof(uint64_t)))); 210 DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT | CPU_DTRACE_BADADDR); 211 } 212 return value; 213 } 214 215 uint64_t 216 fasttrap_pid_getarg(void *arg, dtrace_id_t id, void *parg, int argno, 217 int aframes) 218 { 219 struct reg r; 220 221 fill_regs(curthread, &r); 222 223 return (fasttrap_anarg(&r, argno)); 224 } 225 226 uint64_t 227 fasttrap_usdt_getarg(void *arg, dtrace_id_t id, void *parg, int argno, 228 int aframes) 229 { 230 struct reg r; 231 232 fill_regs(curthread, &r); 233 234 return (fasttrap_anarg(&r, argno)); 235 } 236 237 static void 238 fasttrap_usdt_args(fasttrap_probe_t *probe, struct reg *rp, int argc, 239 uintptr_t *argv) 240 { 241 int i, x, cap = MIN(argc, probe->ftp_nargs); 242 243 for (i = 0; i < cap; i++) { 244 x = probe->ftp_argmap[i]; 245 246 if (x < 8) 247 argv[i] = rp->fixreg[x]; 248 else 249 #ifdef __powerpc64__ 250 if (SV_PROC_FLAG(curproc, SV_ILP32)) 251 #endif 252 argv[i] = fuword32((void *)(rp->fixreg[1] + 8 + 253 (x * sizeof(uint32_t)))); 254 #ifdef __powerpc64__ 255 else 256 argv[i] = fuword64((void *)(rp->fixreg[1] + 48 + 257 (x * sizeof(uint64_t)))); 258 #endif 259 } 260 261 for (; i < argc; i++) { 262 argv[i] = 0; 263 } 264 } 265 266 static void 267 fasttrap_return_common(struct reg *rp, uintptr_t pc, pid_t pid, 268 uintptr_t new_pc) 269 { 270 struct rm_priotracker tracker; 271 fasttrap_tracepoint_t *tp; 272 fasttrap_bucket_t *bucket; 273 fasttrap_id_t *id; 274 275 rm_rlock(&fasttrap_tp_lock, &tracker); 276 bucket = &fasttrap_tpoints.fth_table[FASTTRAP_TPOINTS_INDEX(pid, pc)]; 277 278 for (tp = bucket->ftb_data; tp != NULL; tp = tp->ftt_next) { 279 if (pid == tp->ftt_pid && pc == tp->ftt_pc && 280 tp->ftt_proc->ftpc_acount != 0) 281 break; 282 } 283 284 /* 285 * Don't sweat it if we can't find the tracepoint again; unlike 286 * when we're in fasttrap_pid_probe(), finding the tracepoint here 287 * is not essential to the correct execution of the process. 288 */ 289 if (tp == NULL) { 290 rm_runlock(&fasttrap_tp_lock, &tracker); 291 return; 292 } 293 294 for (id = tp->ftt_retids; id != NULL; id = id->fti_next) { 295 /* 296 * If there's a branch that could act as a return site, we 297 * need to trace it, and check here if the program counter is 298 * external to the function. 299 */ 300 /* Skip function-local branches. */ 301 if ((new_pc - id->fti_probe->ftp_faddr) < id->fti_probe->ftp_fsize) 302 continue; 303 304 dtrace_probe(id->fti_probe->ftp_id, 305 pc - id->fti_probe->ftp_faddr, 306 rp->fixreg[3], rp->fixreg[4], 0, 0); 307 } 308 rm_runlock(&fasttrap_tp_lock, &tracker); 309 } 310 311 312 static int 313 fasttrap_branch_taken(int bo, int bi, struct reg *regs) 314 { 315 int crzero = 0; 316 317 /* Branch always? */ 318 if ((bo & 0x14) == 0x14) 319 return 1; 320 321 /* Handle decrementing ctr */ 322 if (!(bo & 0x04)) { 323 --regs->ctr; 324 crzero = (regs->ctr == 0); 325 if (bo & 0x10) { 326 return (!(crzero ^ (bo >> 1))); 327 } 328 } 329 330 return (crzero | (((regs->cr >> (31 - bi)) ^ (bo >> 3)) ^ 1)); 331 } 332 333 334 int 335 fasttrap_pid_probe(struct trapframe *frame) 336 { 337 struct reg reg, *rp; 338 struct rm_priotracker tracker; 339 proc_t *p = curproc; 340 uintptr_t pc; 341 uintptr_t new_pc = 0; 342 fasttrap_bucket_t *bucket; 343 fasttrap_tracepoint_t *tp, tp_local; 344 pid_t pid; 345 dtrace_icookie_t cookie; 346 uint_t is_enabled = 0; 347 348 fill_regs(curthread, ®); 349 rp = ® 350 pc = rp->pc; 351 352 /* 353 * It's possible that a user (in a veritable orgy of bad planning) 354 * could redirect this thread's flow of control before it reached the 355 * return probe fasttrap. In this case we need to kill the process 356 * since it's in a unrecoverable state. 357 */ 358 if (curthread->t_dtrace_step) { 359 ASSERT(curthread->t_dtrace_on); 360 fasttrap_sigtrap(p, curthread, pc); 361 return (0); 362 } 363 364 /* 365 * Clear all user tracing flags. 366 */ 367 curthread->t_dtrace_ft = 0; 368 curthread->t_dtrace_pc = 0; 369 curthread->t_dtrace_npc = 0; 370 curthread->t_dtrace_scrpc = 0; 371 curthread->t_dtrace_astpc = 0; 372 373 rm_rlock(&fasttrap_tp_lock, &tracker); 374 pid = p->p_pid; 375 bucket = &fasttrap_tpoints.fth_table[FASTTRAP_TPOINTS_INDEX(pid, pc)]; 376 377 /* 378 * Lookup the tracepoint that the process just hit. 379 */ 380 for (tp = bucket->ftb_data; tp != NULL; tp = tp->ftt_next) { 381 if (pid == tp->ftt_pid && pc == tp->ftt_pc && 382 tp->ftt_proc->ftpc_acount != 0) 383 break; 384 } 385 386 /* 387 * If we couldn't find a matching tracepoint, either a tracepoint has 388 * been inserted without using the pid<pid> ioctl interface (see 389 * fasttrap_ioctl), or somehow we have mislaid this tracepoint. 390 */ 391 if (tp == NULL) { 392 rm_runlock(&fasttrap_tp_lock, &tracker); 393 return (-1); 394 } 395 396 if (tp->ftt_ids != NULL) { 397 fasttrap_id_t *id; 398 399 for (id = tp->ftt_ids; id != NULL; id = id->fti_next) { 400 fasttrap_probe_t *probe = id->fti_probe; 401 402 if (id->fti_ptype == DTFTP_ENTRY) { 403 /* 404 * We note that this was an entry 405 * probe to help ustack() find the 406 * first caller. 407 */ 408 cookie = dtrace_interrupt_disable(); 409 DTRACE_CPUFLAG_SET(CPU_DTRACE_ENTRY); 410 dtrace_probe(probe->ftp_id, rp->fixreg[3], 411 rp->fixreg[4], rp->fixreg[5], rp->fixreg[6], 412 rp->fixreg[7]); 413 DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_ENTRY); 414 dtrace_interrupt_enable(cookie); 415 } else if (id->fti_ptype == DTFTP_IS_ENABLED) { 416 /* 417 * Note that in this case, we don't 418 * call dtrace_probe() since it's only 419 * an artificial probe meant to change 420 * the flow of control so that it 421 * encounters the true probe. 422 */ 423 is_enabled = 1; 424 } else if (probe->ftp_argmap == NULL) { 425 dtrace_probe(probe->ftp_id, rp->fixreg[3], 426 rp->fixreg[4], rp->fixreg[5], rp->fixreg[6], 427 rp->fixreg[7]); 428 } else { 429 uintptr_t t[5]; 430 431 fasttrap_usdt_args(probe, rp, 432 sizeof (t) / sizeof (t[0]), t); 433 434 dtrace_probe(probe->ftp_id, t[0], t[1], 435 t[2], t[3], t[4]); 436 } 437 } 438 } 439 440 /* 441 * We're about to do a bunch of work so we cache a local copy of 442 * the tracepoint to emulate the instruction, and then find the 443 * tracepoint again later if we need to light up any return probes. 444 */ 445 tp_local = *tp; 446 rm_runlock(&fasttrap_tp_lock, &tracker); 447 tp = &tp_local; 448 449 /* 450 * If there's an is-enabled probe connected to this tracepoint it 451 * means that there was a 'xor r3, r3, r3' 452 * instruction that was placed there by DTrace when the binary was 453 * linked. As this probe is, in fact, enabled, we need to stuff 1 454 * into R3. Accordingly, we can bypass all the instruction 455 * emulation logic since we know the inevitable result. It's possible 456 * that a user could construct a scenario where the 'is-enabled' 457 * probe was on some other instruction, but that would be a rather 458 * exotic way to shoot oneself in the foot. 459 */ 460 if (is_enabled) { 461 rp->fixreg[3] = 1; 462 new_pc = rp->pc + 4; 463 goto done; 464 } 465 466 467 switch (tp->ftt_type) { 468 case FASTTRAP_T_NOP: 469 new_pc = rp->pc + 4; 470 break; 471 case FASTTRAP_T_BC: 472 if (!fasttrap_branch_taken(tp->ftt_bo, tp->ftt_bi, rp)) 473 break; 474 /* FALLTHROUGH */ 475 case FASTTRAP_T_B: 476 if (tp->ftt_instr & 0x01) 477 rp->lr = rp->pc + 4; 478 new_pc = tp->ftt_dest; 479 break; 480 case FASTTRAP_T_BLR: 481 case FASTTRAP_T_BCTR: 482 if (!fasttrap_branch_taken(tp->ftt_bo, tp->ftt_bi, rp)) 483 break; 484 /* FALLTHROUGH */ 485 if (tp->ftt_type == FASTTRAP_T_BCTR) 486 new_pc = rp->ctr; 487 else 488 new_pc = rp->lr; 489 if (tp->ftt_instr & 0x01) 490 rp->lr = rp->pc + 4; 491 break; 492 case FASTTRAP_T_COMMON: 493 curthread->t_dtrace_pc = pc; 494 curthread->t_dtrace_npc = pc + 4; 495 curthread->t_dtrace_on = 1; 496 new_pc = pc; 497 break; 498 }; 499 done: 500 /* 501 * If there were no return probes when we first found the tracepoint, 502 * we should feel no obligation to honor any return probes that were 503 * subsequently enabled -- they'll just have to wait until the next 504 * time around. 505 */ 506 if (tp->ftt_retids != NULL) { 507 /* 508 * We need to wait until the results of the instruction are 509 * apparent before invoking any return probes. If this 510 * instruction was emulated we can just call 511 * fasttrap_return_common(); if it needs to be executed, we 512 * need to wait until the user thread returns to the kernel. 513 */ 514 if (tp->ftt_type != FASTTRAP_T_COMMON) { 515 fasttrap_return_common(rp, pc, pid, new_pc); 516 } else { 517 ASSERT(curthread->t_dtrace_ret != 0); 518 ASSERT(curthread->t_dtrace_pc == pc); 519 ASSERT(curthread->t_dtrace_scrpc != 0); 520 ASSERT(new_pc == curthread->t_dtrace_astpc); 521 } 522 } 523 524 rp->pc = new_pc; 525 set_regs(curthread, rp); 526 527 return (0); 528 } 529 530 int 531 fasttrap_return_probe(struct trapframe *tf) 532 { 533 struct reg reg, *rp; 534 proc_t *p = curproc; 535 uintptr_t pc = curthread->t_dtrace_pc; 536 uintptr_t npc = curthread->t_dtrace_npc; 537 538 curthread->t_dtrace_pc = 0; 539 curthread->t_dtrace_npc = 0; 540 curthread->t_dtrace_scrpc = 0; 541 curthread->t_dtrace_astpc = 0; 542 543 fill_regs(curthread, ®); 544 rp = ® 545 546 /* 547 * We set rp->pc to the address of the traced instruction so 548 * that it appears to dtrace_probe() that we're on the original 549 * instruction. 550 */ 551 rp->pc = pc; 552 553 fasttrap_return_common(rp, pc, p->p_pid, npc); 554 555 return (0); 556 }
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