1 /* Functions for manipulating expressions designed to be executed on the agent 2 Copyright (C) 1998-2015 Free Software Foundation, Inc. 3 4 This file is part of GDB. 5 6 This program is free software; you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 3 of the License, or 9 (at your option) any later version. 10 11 This program is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 GNU General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 18 19 /* Despite what the above comment says about this file being part of 20 GDB, we would like to keep these functions free of GDB 21 dependencies, since we want to be able to use them in contexts 22 outside of GDB (test suites, the stub, etc.) */ 23 24 #include "defs.h" 25 #include "ax.h" 26 27 #include "value.h" 28 #include "user-regs.h" 29 30 static void grow_expr (struct agent_expr *x, int n); 31 32 static void append_const (struct agent_expr *x, LONGEST val, int n); 33 34 static LONGEST read_const (struct agent_expr *x, int o, int n); 35 36 static void generic_ext (struct agent_expr *x, enum agent_op op, int n); 37 38 /* Functions for building expressions. */ 39 40 /* Allocate a new, empty agent expression. */ 41 struct agent_expr * 42 new_agent_expr (struct gdbarch *gdbarch, CORE_ADDR scope) 43 { 44 struct agent_expr *x = xmalloc (sizeof (*x)); 45 46 x->len = 0; 47 x->size = 1; /* Change this to a larger value once 48 reallocation code is tested. */ 49 x->buf = xmalloc (x->size); 50 51 x->gdbarch = gdbarch; 52 x->scope = scope; 53 54 /* Bit vector for registers used. */ 55 x->reg_mask_len = 1; 56 x->reg_mask = xmalloc (x->reg_mask_len * sizeof (x->reg_mask[0])); 57 memset (x->reg_mask, 0, x->reg_mask_len * sizeof (x->reg_mask[0])); 58 59 x->tracing = 0; 60 x->trace_string = 0; 61 62 return x; 63 } 64 65 /* Free a agent expression. */ 66 void 67 free_agent_expr (struct agent_expr *x) 68 { 69 xfree (x->buf); 70 xfree (x->reg_mask); 71 xfree (x); 72 } 73 74 static void 75 do_free_agent_expr_cleanup (void *x) 76 { 77 free_agent_expr (x); 78 } 79 80 struct cleanup * 81 make_cleanup_free_agent_expr (struct agent_expr *x) 82 { 83 return make_cleanup (do_free_agent_expr_cleanup, x); 84 } 85 86 87 /* Make sure that X has room for at least N more bytes. This doesn't 88 affect the length, just the allocated size. */ 89 static void 90 grow_expr (struct agent_expr *x, int n) 91 { 92 if (x->len + n > x->size) 93 { 94 x->size *= 2; 95 if (x->size < x->len + n) 96 x->size = x->len + n + 10; 97 x->buf = xrealloc (x->buf, x->size); 98 } 99 } 100 101 102 /* Append the low N bytes of VAL as an N-byte integer to the 103 expression X, in big-endian order. */ 104 static void 105 append_const (struct agent_expr *x, LONGEST val, int n) 106 { 107 int i; 108 109 grow_expr (x, n); 110 for (i = n - 1; i >= 0; i--) 111 { 112 x->buf[x->len + i] = val & 0xff; 113 val >>= 8; 114 } 115 x->len += n; 116 } 117 118 119 /* Extract an N-byte big-endian unsigned integer from expression X at 120 offset O. */ 121 static LONGEST 122 read_const (struct agent_expr *x, int o, int n) 123 { 124 int i; 125 LONGEST accum = 0; 126 127 /* Make sure we're not reading off the end of the expression. */ 128 if (o + n > x->len) 129 error (_("GDB bug: ax-general.c (read_const): incomplete constant")); 130 131 for (i = 0; i < n; i++) 132 accum = (accum << 8) | x->buf[o + i]; 133 134 return accum; 135 } 136 137 138 /* Append a simple operator OP to EXPR. */ 139 void 140 ax_simple (struct agent_expr *x, enum agent_op op) 141 { 142 grow_expr (x, 1); 143 x->buf[x->len++] = op; 144 } 145 146 /* Append a pick operator to EXPR. DEPTH is the stack item to pick, 147 with 0 being top of stack. */ 148 149 void 150 ax_pick (struct agent_expr *x, int depth) 151 { 152 if (depth < 0 || depth > 255) 153 error (_("GDB bug: ax-general.c (ax_pick): stack depth out of range")); 154 ax_simple (x, aop_pick); 155 append_const (x, 1, depth); 156 } 157 158 159 /* Append a sign-extension or zero-extension instruction to EXPR, to 160 extend an N-bit value. */ 161 static void 162 generic_ext (struct agent_expr *x, enum agent_op op, int n) 163 { 164 /* N must fit in a byte. */ 165 if (n < 0 || n > 255) 166 error (_("GDB bug: ax-general.c (generic_ext): bit count out of range")); 167 /* That had better be enough range. */ 168 if (sizeof (LONGEST) * 8 > 255) 169 error (_("GDB bug: ax-general.c (generic_ext): " 170 "opcode has inadequate range")); 171 172 grow_expr (x, 2); 173 x->buf[x->len++] = op; 174 x->buf[x->len++] = n; 175 } 176 177 178 /* Append a sign-extension instruction to EXPR, to extend an N-bit value. */ 179 void 180 ax_ext (struct agent_expr *x, int n) 181 { 182 generic_ext (x, aop_ext, n); 183 } 184 185 186 /* Append a zero-extension instruction to EXPR, to extend an N-bit value. */ 187 void 188 ax_zero_ext (struct agent_expr *x, int n) 189 { 190 generic_ext (x, aop_zero_ext, n); 191 } 192 193 194 /* Append a trace_quick instruction to EXPR, to record N bytes. */ 195 void 196 ax_trace_quick (struct agent_expr *x, int n) 197 { 198 /* N must fit in a byte. */ 199 if (n < 0 || n > 255) 200 error (_("GDB bug: ax-general.c (ax_trace_quick): " 201 "size out of range for trace_quick")); 202 203 grow_expr (x, 2); 204 x->buf[x->len++] = aop_trace_quick; 205 x->buf[x->len++] = n; 206 } 207 208 209 /* Append a goto op to EXPR. OP is the actual op (must be aop_goto or 210 aop_if_goto). We assume we don't know the target offset yet, 211 because it's probably a forward branch, so we leave space in EXPR 212 for the target, and return the offset in EXPR of that space, so we 213 can backpatch it once we do know the target offset. Use ax_label 214 to do the backpatching. */ 215 int 216 ax_goto (struct agent_expr *x, enum agent_op op) 217 { 218 grow_expr (x, 3); 219 x->buf[x->len + 0] = op; 220 x->buf[x->len + 1] = 0xff; 221 x->buf[x->len + 2] = 0xff; 222 x->len += 3; 223 return x->len - 2; 224 } 225 226 /* Suppose a given call to ax_goto returns some value PATCH. When you 227 know the offset TARGET that goto should jump to, call 228 ax_label (EXPR, PATCH, TARGET) 229 to patch TARGET into the ax_goto instruction. */ 230 void 231 ax_label (struct agent_expr *x, int patch, int target) 232 { 233 /* Make sure the value is in range. Don't accept 0xffff as an 234 offset; that's our magic sentinel value for unpatched branches. */ 235 if (target < 0 || target >= 0xffff) 236 error (_("GDB bug: ax-general.c (ax_label): label target out of range")); 237 238 x->buf[patch] = (target >> 8) & 0xff; 239 x->buf[patch + 1] = target & 0xff; 240 } 241 242 243 /* Assemble code to push a constant on the stack. */ 244 void 245 ax_const_l (struct agent_expr *x, LONGEST l) 246 { 247 static enum agent_op ops[] 248 = 249 {aop_const8, aop_const16, aop_const32, aop_const64}; 250 int size; 251 int op; 252 253 /* How big is the number? 'op' keeps track of which opcode to use. 254 Notice that we don't really care whether the original number was 255 signed or unsigned; we always reproduce the value exactly, and 256 use the shortest representation. */ 257 for (op = 0, size = 8; size < 64; size *= 2, op++) 258 { 259 LONGEST lim = ((LONGEST) 1) << (size - 1); 260 261 if (-lim <= l && l <= lim - 1) 262 break; 263 } 264 265 /* Emit the right opcode... */ 266 ax_simple (x, ops[op]); 267 268 /* Emit the low SIZE bytes as an unsigned number. We know that 269 sign-extending this will yield l. */ 270 append_const (x, l, size / 8); 271 272 /* Now, if it was negative, and not full-sized, sign-extend it. */ 273 if (l < 0 && size < 64) 274 ax_ext (x, size); 275 } 276 277 278 void 279 ax_const_d (struct agent_expr *x, LONGEST d) 280 { 281 /* FIXME: floating-point support not present yet. */ 282 error (_("GDB bug: ax-general.c (ax_const_d): " 283 "floating point not supported yet")); 284 } 285 286 287 /* Assemble code to push the value of register number REG on the 288 stack. */ 289 void 290 ax_reg (struct agent_expr *x, int reg) 291 { 292 if (reg >= gdbarch_num_regs (x->gdbarch)) 293 { 294 /* This is a pseudo-register. */ 295 if (!gdbarch_ax_pseudo_register_push_stack_p (x->gdbarch)) 296 error (_("'%s' is a pseudo-register; " 297 "GDB cannot yet trace its contents."), 298 user_reg_map_regnum_to_name (x->gdbarch, reg)); 299 if (gdbarch_ax_pseudo_register_push_stack (x->gdbarch, x, reg)) 300 error (_("Trace '%s' failed."), 301 user_reg_map_regnum_to_name (x->gdbarch, reg)); 302 } 303 else 304 { 305 /* Make sure the register number is in range. */ 306 if (reg < 0 || reg > 0xffff) 307 error (_("GDB bug: ax-general.c (ax_reg): " 308 "register number out of range")); 309 grow_expr (x, 3); 310 x->buf[x->len] = aop_reg; 311 x->buf[x->len + 1] = (reg >> 8) & 0xff; 312 x->buf[x->len + 2] = (reg) & 0xff; 313 x->len += 3; 314 } 315 } 316 317 /* Assemble code to operate on a trace state variable. */ 318 319 void 320 ax_tsv (struct agent_expr *x, enum agent_op op, int num) 321 { 322 /* Make sure the tsv number is in range. */ 323 if (num < 0 || num > 0xffff) 324 internal_error (__FILE__, __LINE__, 325 _("ax-general.c (ax_tsv): variable " 326 "number is %d, out of range"), num); 327 328 grow_expr (x, 3); 329 x->buf[x->len] = op; 330 x->buf[x->len + 1] = (num >> 8) & 0xff; 331 x->buf[x->len + 2] = (num) & 0xff; 332 x->len += 3; 333 } 334 335 /* Append a string to the expression. Note that the string is going 336 into the bytecodes directly, not on the stack. As a precaution, 337 include both length as prefix, and terminate with a NUL. (The NUL 338 is counted in the length.) */ 339 340 void 341 ax_string (struct agent_expr *x, const char *str, int slen) 342 { 343 int i; 344 345 /* Make sure the string length is reasonable. */ 346 if (slen < 0 || slen > 0xffff) 347 internal_error (__FILE__, __LINE__, 348 _("ax-general.c (ax_string): string " 349 "length is %d, out of allowed range"), slen); 350 351 grow_expr (x, 2 + slen + 1); 352 x->buf[x->len++] = ((slen + 1) >> 8) & 0xff; 353 x->buf[x->len++] = (slen + 1) & 0xff; 354 for (i = 0; i < slen; ++i) 355 x->buf[x->len++] = str[i]; 356 x->buf[x->len++] = '\0'; 357 } 358 359 360 361 /* Functions for disassembling agent expressions, and otherwise 362 debugging the expression compiler. */ 363 364 struct aop_map aop_map[] = 365 { 366 {0, 0, 0, 0, 0} 367 #define DEFOP(NAME, SIZE, DATA_SIZE, CONSUMED, PRODUCED, VALUE) \ 368 , { # NAME, SIZE, DATA_SIZE, CONSUMED, PRODUCED } 369 #include "ax.def" 370 #undef DEFOP 371 }; 372 373 374 /* Disassemble the expression EXPR, writing to F. */ 375 void 376 ax_print (struct ui_file *f, struct agent_expr *x) 377 { 378 int i; 379 380 fprintf_filtered (f, _("Scope: %s\n"), paddress (x->gdbarch, x->scope)); 381 fprintf_filtered (f, _("Reg mask:")); 382 for (i = 0; i < x->reg_mask_len; ++i) 383 fprintf_filtered (f, _(" %02x"), x->reg_mask[i]); 384 fprintf_filtered (f, _("\n")); 385 386 /* Check the size of the name array against the number of entries in 387 the enum, to catch additions that people didn't sync. */ 388 if ((sizeof (aop_map) / sizeof (aop_map[0])) 389 != aop_last) 390 error (_("GDB bug: ax-general.c (ax_print): opcode map out of sync")); 391 392 for (i = 0; i < x->len;) 393 { 394 enum agent_op op = x->buf[i]; 395 396 if (op >= (sizeof (aop_map) / sizeof (aop_map[0])) 397 || !aop_map[op].name) 398 { 399 fprintf_filtered (f, _("%3d <bad opcode %02x>\n"), i, op); 400 i++; 401 continue; 402 } 403 if (i + 1 + aop_map[op].op_size > x->len) 404 { 405 fprintf_filtered (f, _("%3d <incomplete opcode %s>\n"), 406 i, aop_map[op].name); 407 break; 408 } 409 410 fprintf_filtered (f, "%3d %s", i, aop_map[op].name); 411 if (aop_map[op].op_size > 0) 412 { 413 fputs_filtered (" ", f); 414 415 print_longest (f, 'd', 0, 416 read_const (x, i + 1, aop_map[op].op_size)); 417 } 418 /* Handle the complicated printf arguments specially. */ 419 else if (op == aop_printf) 420 { 421 int slen, nargs; 422 423 i++; 424 nargs = x->buf[i++]; 425 slen = x->buf[i++]; 426 slen = slen * 256 + x->buf[i++]; 427 fprintf_filtered (f, _(" \"%s\", %d args"), 428 &(x->buf[i]), nargs); 429 i += slen - 1; 430 } 431 fprintf_filtered (f, "\n"); 432 i += 1 + aop_map[op].op_size; 433 } 434 } 435 436 /* Add register REG to the register mask for expression AX. */ 437 void 438 ax_reg_mask (struct agent_expr *ax, int reg) 439 { 440 if (reg >= gdbarch_num_regs (ax->gdbarch)) 441 { 442 /* This is a pseudo-register. */ 443 if (!gdbarch_ax_pseudo_register_collect_p (ax->gdbarch)) 444 error (_("'%s' is a pseudo-register; " 445 "GDB cannot yet trace its contents."), 446 user_reg_map_regnum_to_name (ax->gdbarch, reg)); 447 if (gdbarch_ax_pseudo_register_collect (ax->gdbarch, ax, reg)) 448 error (_("Trace '%s' failed."), 449 user_reg_map_regnum_to_name (ax->gdbarch, reg)); 450 } 451 else 452 { 453 int byte = reg / 8; 454 455 /* Grow the bit mask if necessary. */ 456 if (byte >= ax->reg_mask_len) 457 { 458 /* It's not appropriate to double here. This isn't a 459 string buffer. */ 460 int new_len = byte + 1; 461 unsigned char *new_reg_mask = xrealloc (ax->reg_mask, 462 new_len 463 * sizeof (ax->reg_mask[0])); 464 memset (new_reg_mask + ax->reg_mask_len, 0, 465 (new_len - ax->reg_mask_len) * sizeof (ax->reg_mask[0])); 466 ax->reg_mask_len = new_len; 467 ax->reg_mask = new_reg_mask; 468 } 469 470 ax->reg_mask[byte] |= 1 << (reg % 8); 471 } 472 } 473 474 /* Given an agent expression AX, fill in requirements and other descriptive 475 bits. */ 476 void 477 ax_reqs (struct agent_expr *ax) 478 { 479 int i; 480 int height; 481 482 /* Jump target table. targets[i] is non-zero iff we have found a 483 jump to offset i. */ 484 char *targets = (char *) alloca (ax->len * sizeof (targets[0])); 485 486 /* Instruction boundary table. boundary[i] is non-zero iff our scan 487 has reached an instruction starting at offset i. */ 488 char *boundary = (char *) alloca (ax->len * sizeof (boundary[0])); 489 490 /* Stack height record. If either targets[i] or boundary[i] is 491 non-zero, heights[i] is the height the stack should have before 492 executing the bytecode at that point. */ 493 int *heights = (int *) alloca (ax->len * sizeof (heights[0])); 494 495 /* Pointer to a description of the present op. */ 496 struct aop_map *op; 497 498 memset (targets, 0, ax->len * sizeof (targets[0])); 499 memset (boundary, 0, ax->len * sizeof (boundary[0])); 500 501 ax->max_height = ax->min_height = height = 0; 502 ax->flaw = agent_flaw_none; 503 ax->max_data_size = 0; 504 505 for (i = 0; i < ax->len; i += 1 + op->op_size) 506 { 507 if (ax->buf[i] > (sizeof (aop_map) / sizeof (aop_map[0]))) 508 { 509 ax->flaw = agent_flaw_bad_instruction; 510 return; 511 } 512 513 op = &aop_map[ax->buf[i]]; 514 515 if (!op->name) 516 { 517 ax->flaw = agent_flaw_bad_instruction; 518 return; 519 } 520 521 if (i + 1 + op->op_size > ax->len) 522 { 523 ax->flaw = agent_flaw_incomplete_instruction; 524 return; 525 } 526 527 /* If this instruction is a forward jump target, does the 528 current stack height match the stack height at the jump 529 source? */ 530 if (targets[i] && (heights[i] != height)) 531 { 532 ax->flaw = agent_flaw_height_mismatch; 533 return; 534 } 535 536 boundary[i] = 1; 537 heights[i] = height; 538 539 height -= op->consumed; 540 if (height < ax->min_height) 541 ax->min_height = height; 542 height += op->produced; 543 if (height > ax->max_height) 544 ax->max_height = height; 545 546 if (op->data_size > ax->max_data_size) 547 ax->max_data_size = op->data_size; 548 549 /* For jump instructions, check that the target is a valid 550 offset. If it is, record the fact that that location is a 551 jump target, and record the height we expect there. */ 552 if (aop_goto == op - aop_map 553 || aop_if_goto == op - aop_map) 554 { 555 int target = read_const (ax, i + 1, 2); 556 if (target < 0 || target >= ax->len) 557 { 558 ax->flaw = agent_flaw_bad_jump; 559 return; 560 } 561 562 /* Do we have any information about what the stack height 563 should be at the target? */ 564 if (targets[target] || boundary[target]) 565 { 566 if (heights[target] != height) 567 { 568 ax->flaw = agent_flaw_height_mismatch; 569 return; 570 } 571 } 572 573 /* Record the target, along with the stack height we expect. */ 574 targets[target] = 1; 575 heights[target] = height; 576 } 577 578 /* For unconditional jumps with a successor, check that the 579 successor is a target, and pick up its stack height. */ 580 if (aop_goto == op - aop_map 581 && i + 3 < ax->len) 582 { 583 if (!targets[i + 3]) 584 { 585 ax->flaw = agent_flaw_hole; 586 return; 587 } 588 589 height = heights[i + 3]; 590 } 591 592 /* For reg instructions, record the register in the bit mask. */ 593 if (aop_reg == op - aop_map) 594 { 595 int reg = read_const (ax, i + 1, 2); 596 597 ax_reg_mask (ax, reg); 598 } 599 } 600 601 /* Check that all the targets are on boundaries. */ 602 for (i = 0; i < ax->len; i++) 603 if (targets[i] && !boundary[i]) 604 { 605 ax->flaw = agent_flaw_bad_jump; 606 return; 607 } 608 609 ax->final_height = height; 610 } 611