1 /* Find a variable's value in memory, for GDB, the GNU debugger. 2 3 Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 4 1996, 1997, 1998, 1999, 2000, 2001, 2003, 2004, 2005, 2007, 2008, 2009 5 Free Software Foundation, Inc. 6 7 This file is part of GDB. 8 9 This program is free software; you can redistribute it and/or modify 10 it under the terms of the GNU General Public License as published by 11 the Free Software Foundation; either version 3 of the License, or 12 (at your option) any later version. 13 14 This program is distributed in the hope that it will be useful, 15 but WITHOUT ANY WARRANTY; without even the implied warranty of 16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 17 GNU General Public License for more details. 18 19 You should have received a copy of the GNU General Public License 20 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 21 22 #include "defs.h" 23 #include "symtab.h" 24 #include "gdbtypes.h" 25 #include "frame.h" 26 #include "value.h" 27 #include "gdbcore.h" 28 #include "inferior.h" 29 #include "target.h" 30 #include "gdb_string.h" 31 #include "gdb_assert.h" 32 #include "floatformat.h" 33 #include "symfile.h" /* for overlay functions */ 34 #include "regcache.h" 35 #include "user-regs.h" 36 #include "block.h" 37 #include "objfiles.h" 38 39 /* Basic byte-swapping routines. GDB has needed these for a long time... 40 All extract a target-format integer at ADDR which is LEN bytes long. */ 41 42 #if TARGET_CHAR_BIT != 8 || HOST_CHAR_BIT != 8 43 /* 8 bit characters are a pretty safe assumption these days, so we 44 assume it throughout all these swapping routines. If we had to deal with 45 9 bit characters, we would need to make len be in bits and would have 46 to re-write these routines... */ 47 you lose 48 #endif 49 50 LONGEST 51 extract_signed_integer (const gdb_byte *addr, int len, 52 enum bfd_endian byte_order) 53 { 54 LONGEST retval; 55 const unsigned char *p; 56 const unsigned char *startaddr = addr; 57 const unsigned char *endaddr = startaddr + len; 58 59 if (len > (int) sizeof (LONGEST)) 60 error (_("\ 61 That operation is not available on integers of more than %d bytes."), 62 (int) sizeof (LONGEST)); 63 64 /* Start at the most significant end of the integer, and work towards 65 the least significant. */ 66 if (byte_order == BFD_ENDIAN_BIG) 67 { 68 p = startaddr; 69 /* Do the sign extension once at the start. */ 70 retval = ((LONGEST) * p ^ 0x80) - 0x80; 71 for (++p; p < endaddr; ++p) 72 retval = (retval << 8) | *p; 73 } 74 else 75 { 76 p = endaddr - 1; 77 /* Do the sign extension once at the start. */ 78 retval = ((LONGEST) * p ^ 0x80) - 0x80; 79 for (--p; p >= startaddr; --p) 80 retval = (retval << 8) | *p; 81 } 82 return retval; 83 } 84 85 ULONGEST 86 extract_unsigned_integer (const gdb_byte *addr, int len, 87 enum bfd_endian byte_order) 88 { 89 ULONGEST retval; 90 const unsigned char *p; 91 const unsigned char *startaddr = addr; 92 const unsigned char *endaddr = startaddr + len; 93 94 if (len > (int) sizeof (ULONGEST)) 95 error (_("\ 96 That operation is not available on integers of more than %d bytes."), 97 (int) sizeof (ULONGEST)); 98 99 /* Start at the most significant end of the integer, and work towards 100 the least significant. */ 101 retval = 0; 102 if (byte_order == BFD_ENDIAN_BIG) 103 { 104 for (p = startaddr; p < endaddr; ++p) 105 retval = (retval << 8) | *p; 106 } 107 else 108 { 109 for (p = endaddr - 1; p >= startaddr; --p) 110 retval = (retval << 8) | *p; 111 } 112 return retval; 113 } 114 115 /* Sometimes a long long unsigned integer can be extracted as a 116 LONGEST value. This is done so that we can print these values 117 better. If this integer can be converted to a LONGEST, this 118 function returns 1 and sets *PVAL. Otherwise it returns 0. */ 119 120 int 121 extract_long_unsigned_integer (const gdb_byte *addr, int orig_len, 122 enum bfd_endian byte_order, LONGEST *pval) 123 { 124 const gdb_byte *p; 125 const gdb_byte *first_addr; 126 int len; 127 128 len = orig_len; 129 if (byte_order == BFD_ENDIAN_BIG) 130 { 131 for (p = addr; 132 len > (int) sizeof (LONGEST) && p < addr + orig_len; 133 p++) 134 { 135 if (*p == 0) 136 len--; 137 else 138 break; 139 } 140 first_addr = p; 141 } 142 else 143 { 144 first_addr = addr; 145 for (p = addr + orig_len - 1; 146 len > (int) sizeof (LONGEST) && p >= addr; 147 p--) 148 { 149 if (*p == 0) 150 len--; 151 else 152 break; 153 } 154 } 155 156 if (len <= (int) sizeof (LONGEST)) 157 { 158 *pval = (LONGEST) extract_unsigned_integer (first_addr, 159 sizeof (LONGEST), 160 byte_order); 161 return 1; 162 } 163 164 return 0; 165 } 166 167 168 /* Treat the bytes at BUF as a pointer of type TYPE, and return the 169 address it represents. */ 170 CORE_ADDR 171 extract_typed_address (const gdb_byte *buf, struct type *type) 172 { 173 if (TYPE_CODE (type) != TYPE_CODE_PTR 174 && TYPE_CODE (type) != TYPE_CODE_REF) 175 internal_error (__FILE__, __LINE__, 176 _("extract_typed_address: " 177 "type is not a pointer or reference")); 178 179 return gdbarch_pointer_to_address (get_type_arch (type), type, buf); 180 } 181 182 183 void 184 store_signed_integer (gdb_byte *addr, int len, 185 enum bfd_endian byte_order, LONGEST val) 186 { 187 gdb_byte *p; 188 gdb_byte *startaddr = addr; 189 gdb_byte *endaddr = startaddr + len; 190 191 /* Start at the least significant end of the integer, and work towards 192 the most significant. */ 193 if (byte_order == BFD_ENDIAN_BIG) 194 { 195 for (p = endaddr - 1; p >= startaddr; --p) 196 { 197 *p = val & 0xff; 198 val >>= 8; 199 } 200 } 201 else 202 { 203 for (p = startaddr; p < endaddr; ++p) 204 { 205 *p = val & 0xff; 206 val >>= 8; 207 } 208 } 209 } 210 211 void 212 store_unsigned_integer (gdb_byte *addr, int len, 213 enum bfd_endian byte_order, ULONGEST val) 214 { 215 unsigned char *p; 216 unsigned char *startaddr = (unsigned char *) addr; 217 unsigned char *endaddr = startaddr + len; 218 219 /* Start at the least significant end of the integer, and work towards 220 the most significant. */ 221 if (byte_order == BFD_ENDIAN_BIG) 222 { 223 for (p = endaddr - 1; p >= startaddr; --p) 224 { 225 *p = val & 0xff; 226 val >>= 8; 227 } 228 } 229 else 230 { 231 for (p = startaddr; p < endaddr; ++p) 232 { 233 *p = val & 0xff; 234 val >>= 8; 235 } 236 } 237 } 238 239 /* Store the address ADDR as a pointer of type TYPE at BUF, in target 240 form. */ 241 void 242 store_typed_address (gdb_byte *buf, struct type *type, CORE_ADDR addr) 243 { 244 if (TYPE_CODE (type) != TYPE_CODE_PTR 245 && TYPE_CODE (type) != TYPE_CODE_REF) 246 internal_error (__FILE__, __LINE__, 247 _("store_typed_address: " 248 "type is not a pointer or reference")); 249 250 gdbarch_address_to_pointer (get_type_arch (type), type, buf, addr); 251 } 252 253 254 255 /* Return a `value' with the contents of (virtual or cooked) register 256 REGNUM as found in the specified FRAME. The register's type is 257 determined by register_type(). */ 258 259 struct value * 260 value_of_register (int regnum, struct frame_info *frame) 261 { 262 struct gdbarch *gdbarch = get_frame_arch (frame); 263 CORE_ADDR addr; 264 int optim; 265 struct value *reg_val; 266 int realnum; 267 gdb_byte raw_buffer[MAX_REGISTER_SIZE]; 268 enum lval_type lval; 269 270 /* User registers lie completely outside of the range of normal 271 registers. Catch them early so that the target never sees them. */ 272 if (regnum >= gdbarch_num_regs (gdbarch) 273 + gdbarch_num_pseudo_regs (gdbarch)) 274 return value_of_user_reg (regnum, frame); 275 276 frame_register (frame, regnum, &optim, &lval, &addr, &realnum, raw_buffer); 277 278 reg_val = allocate_value (register_type (gdbarch, regnum)); 279 280 memcpy (value_contents_raw (reg_val), raw_buffer, 281 register_size (gdbarch, regnum)); 282 VALUE_LVAL (reg_val) = lval; 283 set_value_address (reg_val, addr); 284 VALUE_REGNUM (reg_val) = regnum; 285 set_value_optimized_out (reg_val, optim); 286 VALUE_FRAME_ID (reg_val) = get_frame_id (frame); 287 return reg_val; 288 } 289 290 /* Return a `value' with the contents of (virtual or cooked) register 291 REGNUM as found in the specified FRAME. The register's type is 292 determined by register_type(). The value is not fetched. */ 293 294 struct value * 295 value_of_register_lazy (struct frame_info *frame, int regnum) 296 { 297 struct gdbarch *gdbarch = get_frame_arch (frame); 298 struct value *reg_val; 299 300 gdb_assert (regnum < (gdbarch_num_regs (gdbarch) 301 + gdbarch_num_pseudo_regs (gdbarch))); 302 303 /* We should have a valid (i.e. non-sentinel) frame. */ 304 gdb_assert (frame_id_p (get_frame_id (frame))); 305 306 reg_val = allocate_value (register_type (gdbarch, regnum)); 307 VALUE_LVAL (reg_val) = lval_register; 308 VALUE_REGNUM (reg_val) = regnum; 309 VALUE_FRAME_ID (reg_val) = get_frame_id (frame); 310 set_value_lazy (reg_val, 1); 311 return reg_val; 312 } 313 314 /* Given a pointer of type TYPE in target form in BUF, return the 315 address it represents. */ 316 CORE_ADDR 317 unsigned_pointer_to_address (struct gdbarch *gdbarch, 318 struct type *type, const gdb_byte *buf) 319 { 320 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch); 321 return extract_unsigned_integer (buf, TYPE_LENGTH (type), byte_order); 322 } 323 324 CORE_ADDR 325 signed_pointer_to_address (struct gdbarch *gdbarch, 326 struct type *type, const gdb_byte *buf) 327 { 328 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch); 329 return extract_signed_integer (buf, TYPE_LENGTH (type), byte_order); 330 } 331 332 /* Given an address, store it as a pointer of type TYPE in target 333 format in BUF. */ 334 void 335 unsigned_address_to_pointer (struct gdbarch *gdbarch, struct type *type, 336 gdb_byte *buf, CORE_ADDR addr) 337 { 338 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch); 339 store_unsigned_integer (buf, TYPE_LENGTH (type), byte_order, addr); 340 } 341 342 void 343 address_to_signed_pointer (struct gdbarch *gdbarch, struct type *type, 344 gdb_byte *buf, CORE_ADDR addr) 345 { 346 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch); 347 store_signed_integer (buf, TYPE_LENGTH (type), byte_order, addr); 348 } 349 350 /* Will calling read_var_value or locate_var_value on SYM end 351 up caring what frame it is being evaluated relative to? SYM must 352 be non-NULL. */ 353 int 354 symbol_read_needs_frame (struct symbol *sym) 355 { 356 switch (SYMBOL_CLASS (sym)) 357 { 358 /* All cases listed explicitly so that gcc -Wall will detect it if 359 we failed to consider one. */ 360 case LOC_COMPUTED: 361 /* FIXME: cagney/2004-01-26: It should be possible to 362 unconditionally call the SYMBOL_COMPUTED_OPS method when available. 363 Unfortunately DWARF 2 stores the frame-base (instead of the 364 function) location in a function's symbol. Oops! For the 365 moment enable this when/where applicable. */ 366 return SYMBOL_COMPUTED_OPS (sym)->read_needs_frame (sym); 367 368 case LOC_REGISTER: 369 case LOC_ARG: 370 case LOC_REF_ARG: 371 case LOC_REGPARM_ADDR: 372 case LOC_LOCAL: 373 return 1; 374 375 case LOC_UNDEF: 376 case LOC_CONST: 377 case LOC_STATIC: 378 case LOC_TYPEDEF: 379 380 case LOC_LABEL: 381 /* Getting the address of a label can be done independently of the block, 382 even if some *uses* of that address wouldn't work so well without 383 the right frame. */ 384 385 case LOC_BLOCK: 386 case LOC_CONST_BYTES: 387 case LOC_UNRESOLVED: 388 case LOC_OPTIMIZED_OUT: 389 return 0; 390 } 391 return 1; 392 } 393 394 /* Given a struct symbol for a variable, 395 and a stack frame id, read the value of the variable 396 and return a (pointer to a) struct value containing the value. 397 If the variable cannot be found, return a zero pointer. */ 398 399 struct value * 400 read_var_value (struct symbol *var, struct frame_info *frame) 401 { 402 struct value *v; 403 struct type *type = SYMBOL_TYPE (var); 404 CORE_ADDR addr; 405 int len; 406 407 if (SYMBOL_CLASS (var) == LOC_COMPUTED 408 || SYMBOL_CLASS (var) == LOC_REGISTER) 409 /* These cases do not use V. */ 410 v = NULL; 411 else 412 { 413 v = allocate_value (type); 414 VALUE_LVAL (v) = lval_memory; /* The most likely possibility. */ 415 } 416 417 len = TYPE_LENGTH (type); 418 419 if (symbol_read_needs_frame (var)) 420 gdb_assert (frame); 421 422 switch (SYMBOL_CLASS (var)) 423 { 424 case LOC_CONST: 425 /* Put the constant back in target format. */ 426 store_signed_integer (value_contents_raw (v), len, 427 gdbarch_byte_order (get_type_arch (type)), 428 (LONGEST) SYMBOL_VALUE (var)); 429 VALUE_LVAL (v) = not_lval; 430 return v; 431 432 case LOC_LABEL: 433 /* Put the constant back in target format. */ 434 if (overlay_debugging) 435 { 436 CORE_ADDR addr 437 = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var), 438 SYMBOL_OBJ_SECTION (var)); 439 store_typed_address (value_contents_raw (v), type, addr); 440 } 441 else 442 store_typed_address (value_contents_raw (v), type, 443 SYMBOL_VALUE_ADDRESS (var)); 444 VALUE_LVAL (v) = not_lval; 445 return v; 446 447 case LOC_CONST_BYTES: 448 { 449 memcpy (value_contents_raw (v), SYMBOL_VALUE_BYTES (var), len); 450 VALUE_LVAL (v) = not_lval; 451 return v; 452 } 453 454 case LOC_STATIC: 455 if (overlay_debugging) 456 addr = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var), 457 SYMBOL_OBJ_SECTION (var)); 458 else 459 addr = SYMBOL_VALUE_ADDRESS (var); 460 break; 461 462 case LOC_ARG: 463 addr = get_frame_args_address (frame); 464 if (!addr) 465 return 0; 466 addr += SYMBOL_VALUE (var); 467 break; 468 469 case LOC_REF_ARG: 470 { 471 struct value *ref; 472 CORE_ADDR argref; 473 argref = get_frame_args_address (frame); 474 if (!argref) 475 return 0; 476 argref += SYMBOL_VALUE (var); 477 ref = value_at (lookup_pointer_type (type), argref); 478 addr = value_as_address (ref); 479 break; 480 } 481 482 case LOC_LOCAL: 483 addr = get_frame_locals_address (frame); 484 addr += SYMBOL_VALUE (var); 485 break; 486 487 case LOC_TYPEDEF: 488 error (_("Cannot look up value of a typedef")); 489 break; 490 491 case LOC_BLOCK: 492 if (overlay_debugging) 493 set_value_address (v, symbol_overlayed_address 494 (BLOCK_START (SYMBOL_BLOCK_VALUE (var)), SYMBOL_OBJ_SECTION (var))); 495 else 496 set_value_address (v, BLOCK_START (SYMBOL_BLOCK_VALUE (var))); 497 return v; 498 499 case LOC_REGISTER: 500 case LOC_REGPARM_ADDR: 501 { 502 int regno = SYMBOL_REGISTER_OPS (var) 503 ->register_number (var, get_frame_arch (frame)); 504 struct value *regval; 505 506 if (SYMBOL_CLASS (var) == LOC_REGPARM_ADDR) 507 { 508 regval = value_from_register (lookup_pointer_type (type), 509 regno, 510 frame); 511 512 if (regval == NULL) 513 error (_("Value of register variable not available.")); 514 515 addr = value_as_address (regval); 516 VALUE_LVAL (v) = lval_memory; 517 } 518 else 519 { 520 regval = value_from_register (type, regno, frame); 521 522 if (regval == NULL) 523 error (_("Value of register variable not available.")); 524 return regval; 525 } 526 } 527 break; 528 529 case LOC_COMPUTED: 530 /* FIXME: cagney/2004-01-26: It should be possible to 531 unconditionally call the SYMBOL_COMPUTED_OPS method when available. 532 Unfortunately DWARF 2 stores the frame-base (instead of the 533 function) location in a function's symbol. Oops! For the 534 moment enable this when/where applicable. */ 535 return SYMBOL_COMPUTED_OPS (var)->read_variable (var, frame); 536 537 case LOC_UNRESOLVED: 538 { 539 struct minimal_symbol *msym; 540 struct obj_section *obj_section; 541 542 msym = lookup_minimal_symbol (SYMBOL_LINKAGE_NAME (var), NULL, NULL); 543 if (msym == NULL) 544 return 0; 545 if (overlay_debugging) 546 addr = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (msym), 547 SYMBOL_OBJ_SECTION (msym)); 548 else 549 addr = SYMBOL_VALUE_ADDRESS (msym); 550 551 obj_section = SYMBOL_OBJ_SECTION (msym); 552 if (obj_section 553 && (obj_section->the_bfd_section->flags & SEC_THREAD_LOCAL) != 0) 554 addr = target_translate_tls_address (obj_section->objfile, addr); 555 } 556 break; 557 558 case LOC_OPTIMIZED_OUT: 559 VALUE_LVAL (v) = not_lval; 560 set_value_optimized_out (v, 1); 561 return v; 562 563 default: 564 error (_("Cannot look up value of a botched symbol.")); 565 break; 566 } 567 568 set_value_address (v, addr); 569 set_value_lazy (v, 1); 570 return v; 571 } 572 573 /* Install default attributes for register values. */ 574 575 struct value * 576 default_value_from_register (struct type *type, int regnum, 577 struct frame_info *frame) 578 { 579 struct gdbarch *gdbarch = get_frame_arch (frame); 580 int len = TYPE_LENGTH (type); 581 struct value *value = allocate_value (type); 582 583 VALUE_LVAL (value) = lval_register; 584 VALUE_FRAME_ID (value) = get_frame_id (frame); 585 VALUE_REGNUM (value) = regnum; 586 587 /* Any structure stored in more than one register will always be 588 an integral number of registers. Otherwise, you need to do 589 some fiddling with the last register copied here for little 590 endian machines. */ 591 if (gdbarch_byte_order (gdbarch) == BFD_ENDIAN_BIG 592 && len < register_size (gdbarch, regnum)) 593 /* Big-endian, and we want less than full size. */ 594 set_value_offset (value, register_size (gdbarch, regnum) - len); 595 else 596 set_value_offset (value, 0); 597 598 return value; 599 } 600 601 /* Return a value of type TYPE, stored in register REGNUM, in frame FRAME. */ 602 603 struct value * 604 value_from_register (struct type *type, int regnum, struct frame_info *frame) 605 { 606 struct gdbarch *gdbarch = get_frame_arch (frame); 607 struct type *type1 = check_typedef (type); 608 struct value *v; 609 610 if (gdbarch_convert_register_p (gdbarch, regnum, type1)) 611 { 612 /* The ISA/ABI need to something weird when obtaining the 613 specified value from this register. It might need to 614 re-order non-adjacent, starting with REGNUM (see MIPS and 615 i386). It might need to convert the [float] register into 616 the corresponding [integer] type (see Alpha). The assumption 617 is that gdbarch_register_to_value populates the entire value 618 including the location. */ 619 v = allocate_value (type); 620 VALUE_LVAL (v) = lval_register; 621 VALUE_FRAME_ID (v) = get_frame_id (frame); 622 VALUE_REGNUM (v) = regnum; 623 gdbarch_register_to_value (gdbarch, 624 frame, regnum, type1, value_contents_raw (v)); 625 } 626 else 627 { 628 int len = TYPE_LENGTH (type); 629 630 /* Construct the value. */ 631 v = gdbarch_value_from_register (gdbarch, type, regnum, frame); 632 633 /* Get the data. */ 634 if (!get_frame_register_bytes (frame, regnum, value_offset (v), len, 635 value_contents_raw (v))) 636 set_value_optimized_out (v, 1); 637 } 638 return v; 639 } 640 641 /* Return contents of register REGNUM in frame FRAME as address, 642 interpreted as value of type TYPE. Will abort if register 643 value is not available. */ 644 645 CORE_ADDR 646 address_from_register (struct type *type, int regnum, struct frame_info *frame) 647 { 648 struct value *value; 649 CORE_ADDR result; 650 651 value = value_from_register (type, regnum, frame); 652 gdb_assert (value); 653 654 result = value_as_address (value); 655 release_value (value); 656 value_free (value); 657 658 return result; 659 } 660