| 1 | /* DWARF 2 location expression support for GDB. |
| 2 | |
| 3 | Copyright (C) 2003, 2005, 2007 Free Software Foundation, Inc. |
| 4 | |
| 5 | Contributed by Daniel Jacobowitz, MontaVista Software, 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 2 of the License, or (at |
| 12 | your option) any later version. |
| 13 | |
| 14 | This program is distributed in the hope that it will be useful, but |
| 15 | WITHOUT ANY WARRANTY; without even the implied warranty of |
| 16 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 17 | 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, write to the Free Software |
| 21 | Foundation, Inc., 51 Franklin Street, Fifth Floor, |
| 22 | Boston, MA 02110-1301, USA. */ |
| 23 | |
| 24 | #include "defs.h" |
| 25 | #include "ui-out.h" |
| 26 | #include "value.h" |
| 27 | #include "frame.h" |
| 28 | #include "gdbcore.h" |
| 29 | #include "target.h" |
| 30 | #include "inferior.h" |
| 31 | #include "ax.h" |
| 32 | #include "ax-gdb.h" |
| 33 | #include "regcache.h" |
| 34 | #include "objfiles.h" |
| 35 | #include "exceptions.h" |
| 36 | |
| 37 | #include "elf/dwarf2.h" |
| 38 | #include "dwarf2expr.h" |
| 39 | #include "dwarf2loc.h" |
| 40 | |
| 41 | #include "gdb_string.h" |
| 42 | |
| 43 | #ifndef DWARF2_REG_TO_REGNUM |
| 44 | #define DWARF2_REG_TO_REGNUM(REG) (REG) |
| 45 | #endif |
| 46 | |
| 47 | /* A helper function for dealing with location lists. Given a |
| 48 | symbol baton (BATON) and a pc value (PC), find the appropriate |
| 49 | location expression, set *LOCEXPR_LENGTH, and return a pointer |
| 50 | to the beginning of the expression. Returns NULL on failure. |
| 51 | |
| 52 | For now, only return the first matching location expression; there |
| 53 | can be more than one in the list. */ |
| 54 | |
| 55 | static gdb_byte * |
| 56 | find_location_expression (struct dwarf2_loclist_baton *baton, |
| 57 | size_t *locexpr_length, CORE_ADDR pc) |
| 58 | { |
| 59 | CORE_ADDR low, high; |
| 60 | gdb_byte *loc_ptr, *buf_end; |
| 61 | int length; |
| 62 | unsigned int addr_size = TARGET_ADDR_BIT / TARGET_CHAR_BIT; |
| 63 | CORE_ADDR base_mask = ~(~(CORE_ADDR)1 << (addr_size * 8 - 1)); |
| 64 | /* Adjust base_address for relocatable objects. */ |
| 65 | CORE_ADDR base_offset = ANOFFSET (baton->objfile->section_offsets, |
| 66 | SECT_OFF_TEXT (baton->objfile)); |
| 67 | CORE_ADDR base_address = baton->base_address + base_offset; |
| 68 | |
| 69 | loc_ptr = baton->data; |
| 70 | buf_end = baton->data + baton->size; |
| 71 | |
| 72 | while (1) |
| 73 | { |
| 74 | low = dwarf2_read_address (loc_ptr, buf_end, &length); |
| 75 | loc_ptr += length; |
| 76 | high = dwarf2_read_address (loc_ptr, buf_end, &length); |
| 77 | loc_ptr += length; |
| 78 | |
| 79 | /* An end-of-list entry. */ |
| 80 | if (low == 0 && high == 0) |
| 81 | return NULL; |
| 82 | |
| 83 | /* A base-address-selection entry. */ |
| 84 | if ((low & base_mask) == base_mask) |
| 85 | { |
| 86 | base_address = high; |
| 87 | continue; |
| 88 | } |
| 89 | |
| 90 | /* Otherwise, a location expression entry. */ |
| 91 | low += base_address; |
| 92 | high += base_address; |
| 93 | |
| 94 | length = extract_unsigned_integer (loc_ptr, 2); |
| 95 | loc_ptr += 2; |
| 96 | |
| 97 | if (pc >= low && pc < high) |
| 98 | { |
| 99 | *locexpr_length = length; |
| 100 | return loc_ptr; |
| 101 | } |
| 102 | |
| 103 | loc_ptr += length; |
| 104 | } |
| 105 | } |
| 106 | |
| 107 | /* This is the baton used when performing dwarf2 expression |
| 108 | evaluation. */ |
| 109 | struct dwarf_expr_baton |
| 110 | { |
| 111 | struct frame_info *frame; |
| 112 | struct objfile *objfile; |
| 113 | }; |
| 114 | |
| 115 | /* Helper functions for dwarf2_evaluate_loc_desc. */ |
| 116 | |
| 117 | /* Using the frame specified in BATON, return the value of register |
| 118 | REGNUM, treated as a pointer. */ |
| 119 | static CORE_ADDR |
| 120 | dwarf_expr_read_reg (void *baton, int dwarf_regnum) |
| 121 | { |
| 122 | struct dwarf_expr_baton *debaton = (struct dwarf_expr_baton *) baton; |
| 123 | CORE_ADDR result; |
| 124 | int regnum; |
| 125 | |
| 126 | regnum = DWARF2_REG_TO_REGNUM (dwarf_regnum); |
| 127 | result = address_from_register (builtin_type_void_data_ptr, |
| 128 | regnum, debaton->frame); |
| 129 | return result; |
| 130 | } |
| 131 | |
| 132 | /* Read memory at ADDR (length LEN) into BUF. */ |
| 133 | |
| 134 | static void |
| 135 | dwarf_expr_read_mem (void *baton, gdb_byte *buf, CORE_ADDR addr, size_t len) |
| 136 | { |
| 137 | read_memory (addr, buf, len); |
| 138 | } |
| 139 | |
| 140 | /* Using the frame specified in BATON, find the location expression |
| 141 | describing the frame base. Return a pointer to it in START and |
| 142 | its length in LENGTH. */ |
| 143 | static void |
| 144 | dwarf_expr_frame_base (void *baton, gdb_byte **start, size_t * length) |
| 145 | { |
| 146 | /* FIXME: cagney/2003-03-26: This code should be using |
| 147 | get_frame_base_address(), and then implement a dwarf2 specific |
| 148 | this_base method. */ |
| 149 | struct symbol *framefunc; |
| 150 | struct dwarf_expr_baton *debaton = (struct dwarf_expr_baton *) baton; |
| 151 | |
| 152 | framefunc = get_frame_function (debaton->frame); |
| 153 | |
| 154 | if (SYMBOL_OPS (framefunc) == &dwarf2_loclist_funcs) |
| 155 | { |
| 156 | struct dwarf2_loclist_baton *symbaton; |
| 157 | struct frame_info *frame = debaton->frame; |
| 158 | |
| 159 | symbaton = SYMBOL_LOCATION_BATON (framefunc); |
| 160 | *start = find_location_expression (symbaton, length, |
| 161 | get_frame_address_in_block (frame)); |
| 162 | } |
| 163 | else |
| 164 | { |
| 165 | struct dwarf2_locexpr_baton *symbaton; |
| 166 | symbaton = SYMBOL_LOCATION_BATON (framefunc); |
| 167 | *length = symbaton->size; |
| 168 | *start = symbaton->data; |
| 169 | } |
| 170 | |
| 171 | if (*start == NULL) |
| 172 | error (_("Could not find the frame base for \"%s\"."), |
| 173 | SYMBOL_NATURAL_NAME (framefunc)); |
| 174 | } |
| 175 | |
| 176 | /* Using the objfile specified in BATON, find the address for the |
| 177 | current thread's thread-local storage with offset OFFSET. */ |
| 178 | static CORE_ADDR |
| 179 | dwarf_expr_tls_address (void *baton, CORE_ADDR offset) |
| 180 | { |
| 181 | struct dwarf_expr_baton *debaton = (struct dwarf_expr_baton *) baton; |
| 182 | |
| 183 | return target_translate_tls_address (debaton->objfile, offset); |
| 184 | } |
| 185 | |
| 186 | /* Evaluate a location description, starting at DATA and with length |
| 187 | SIZE, to find the current location of variable VAR in the context |
| 188 | of FRAME. */ |
| 189 | static struct value * |
| 190 | dwarf2_evaluate_loc_desc (struct symbol *var, struct frame_info *frame, |
| 191 | gdb_byte *data, unsigned short size, |
| 192 | struct objfile *objfile) |
| 193 | { |
| 194 | struct gdbarch *arch = get_frame_arch (frame); |
| 195 | struct value *retval; |
| 196 | struct dwarf_expr_baton baton; |
| 197 | struct dwarf_expr_context *ctx; |
| 198 | |
| 199 | if (size == 0) |
| 200 | { |
| 201 | retval = allocate_value (SYMBOL_TYPE (var)); |
| 202 | VALUE_LVAL (retval) = not_lval; |
| 203 | set_value_optimized_out (retval, 1); |
| 204 | return retval; |
| 205 | } |
| 206 | |
| 207 | baton.frame = frame; |
| 208 | baton.objfile = objfile; |
| 209 | |
| 210 | ctx = new_dwarf_expr_context (); |
| 211 | ctx->baton = &baton; |
| 212 | ctx->read_reg = dwarf_expr_read_reg; |
| 213 | ctx->read_mem = dwarf_expr_read_mem; |
| 214 | ctx->get_frame_base = dwarf_expr_frame_base; |
| 215 | ctx->get_tls_address = dwarf_expr_tls_address; |
| 216 | |
| 217 | dwarf_expr_eval (ctx, data, size); |
| 218 | if (ctx->num_pieces > 0) |
| 219 | { |
| 220 | int i; |
| 221 | long offset = 0; |
| 222 | bfd_byte *contents; |
| 223 | |
| 224 | retval = allocate_value (SYMBOL_TYPE (var)); |
| 225 | contents = value_contents_raw (retval); |
| 226 | for (i = 0; i < ctx->num_pieces; i++) |
| 227 | { |
| 228 | struct dwarf_expr_piece *p = &ctx->pieces[i]; |
| 229 | if (p->in_reg) |
| 230 | { |
| 231 | bfd_byte regval[MAX_REGISTER_SIZE]; |
| 232 | int gdb_regnum = DWARF2_REG_TO_REGNUM (p->value); |
| 233 | get_frame_register (frame, gdb_regnum, regval); |
| 234 | memcpy (contents + offset, regval, p->size); |
| 235 | } |
| 236 | else /* In memory? */ |
| 237 | { |
| 238 | read_memory (p->value, contents + offset, p->size); |
| 239 | } |
| 240 | offset += p->size; |
| 241 | } |
| 242 | } |
| 243 | else if (ctx->in_reg) |
| 244 | { |
| 245 | CORE_ADDR dwarf_regnum = dwarf_expr_fetch (ctx, 0); |
| 246 | int gdb_regnum = DWARF2_REG_TO_REGNUM (dwarf_regnum); |
| 247 | retval = value_from_register (SYMBOL_TYPE (var), gdb_regnum, frame); |
| 248 | } |
| 249 | else |
| 250 | { |
| 251 | CORE_ADDR address = dwarf_expr_fetch (ctx, 0); |
| 252 | |
| 253 | retval = allocate_value (SYMBOL_TYPE (var)); |
| 254 | VALUE_LVAL (retval) = lval_memory; |
| 255 | set_value_lazy (retval, 1); |
| 256 | VALUE_ADDRESS (retval) = address; |
| 257 | } |
| 258 | |
| 259 | free_dwarf_expr_context (ctx); |
| 260 | |
| 261 | return retval; |
| 262 | } |
| 263 | |
| 264 | |
| 265 | |
| 266 | |
| 267 | \f |
| 268 | /* Helper functions and baton for dwarf2_loc_desc_needs_frame. */ |
| 269 | |
| 270 | struct needs_frame_baton |
| 271 | { |
| 272 | int needs_frame; |
| 273 | }; |
| 274 | |
| 275 | /* Reads from registers do require a frame. */ |
| 276 | static CORE_ADDR |
| 277 | needs_frame_read_reg (void *baton, int regnum) |
| 278 | { |
| 279 | struct needs_frame_baton *nf_baton = baton; |
| 280 | nf_baton->needs_frame = 1; |
| 281 | return 1; |
| 282 | } |
| 283 | |
| 284 | /* Reads from memory do not require a frame. */ |
| 285 | static void |
| 286 | needs_frame_read_mem (void *baton, gdb_byte *buf, CORE_ADDR addr, size_t len) |
| 287 | { |
| 288 | memset (buf, 0, len); |
| 289 | } |
| 290 | |
| 291 | /* Frame-relative accesses do require a frame. */ |
| 292 | static void |
| 293 | needs_frame_frame_base (void *baton, gdb_byte **start, size_t * length) |
| 294 | { |
| 295 | static gdb_byte lit0 = DW_OP_lit0; |
| 296 | struct needs_frame_baton *nf_baton = baton; |
| 297 | |
| 298 | *start = &lit0; |
| 299 | *length = 1; |
| 300 | |
| 301 | nf_baton->needs_frame = 1; |
| 302 | } |
| 303 | |
| 304 | /* Thread-local accesses do require a frame. */ |
| 305 | static CORE_ADDR |
| 306 | needs_frame_tls_address (void *baton, CORE_ADDR offset) |
| 307 | { |
| 308 | struct needs_frame_baton *nf_baton = baton; |
| 309 | nf_baton->needs_frame = 1; |
| 310 | return 1; |
| 311 | } |
| 312 | |
| 313 | /* Return non-zero iff the location expression at DATA (length SIZE) |
| 314 | requires a frame to evaluate. */ |
| 315 | |
| 316 | static int |
| 317 | dwarf2_loc_desc_needs_frame (gdb_byte *data, unsigned short size) |
| 318 | { |
| 319 | struct needs_frame_baton baton; |
| 320 | struct dwarf_expr_context *ctx; |
| 321 | int in_reg; |
| 322 | |
| 323 | baton.needs_frame = 0; |
| 324 | |
| 325 | ctx = new_dwarf_expr_context (); |
| 326 | ctx->baton = &baton; |
| 327 | ctx->read_reg = needs_frame_read_reg; |
| 328 | ctx->read_mem = needs_frame_read_mem; |
| 329 | ctx->get_frame_base = needs_frame_frame_base; |
| 330 | ctx->get_tls_address = needs_frame_tls_address; |
| 331 | |
| 332 | dwarf_expr_eval (ctx, data, size); |
| 333 | |
| 334 | in_reg = ctx->in_reg; |
| 335 | |
| 336 | if (ctx->num_pieces > 0) |
| 337 | { |
| 338 | int i; |
| 339 | |
| 340 | /* If the location has several pieces, and any of them are in |
| 341 | registers, then we will need a frame to fetch them from. */ |
| 342 | for (i = 0; i < ctx->num_pieces; i++) |
| 343 | if (ctx->pieces[i].in_reg) |
| 344 | in_reg = 1; |
| 345 | } |
| 346 | |
| 347 | free_dwarf_expr_context (ctx); |
| 348 | |
| 349 | return baton.needs_frame || in_reg; |
| 350 | } |
| 351 | |
| 352 | static void |
| 353 | dwarf2_tracepoint_var_ref (struct symbol *symbol, struct agent_expr *ax, |
| 354 | struct axs_value *value, gdb_byte *data, |
| 355 | int size) |
| 356 | { |
| 357 | if (size == 0) |
| 358 | error (_("Symbol \"%s\" has been optimized out."), |
| 359 | SYMBOL_PRINT_NAME (symbol)); |
| 360 | |
| 361 | if (size == 1 |
| 362 | && data[0] >= DW_OP_reg0 |
| 363 | && data[0] <= DW_OP_reg31) |
| 364 | { |
| 365 | value->kind = axs_lvalue_register; |
| 366 | value->u.reg = data[0] - DW_OP_reg0; |
| 367 | } |
| 368 | else if (data[0] == DW_OP_regx) |
| 369 | { |
| 370 | ULONGEST reg; |
| 371 | read_uleb128 (data + 1, data + size, ®); |
| 372 | value->kind = axs_lvalue_register; |
| 373 | value->u.reg = reg; |
| 374 | } |
| 375 | else if (data[0] == DW_OP_fbreg) |
| 376 | { |
| 377 | /* And this is worse than just minimal; we should honor the frame base |
| 378 | as above. */ |
| 379 | int frame_reg; |
| 380 | LONGEST frame_offset; |
| 381 | gdb_byte *buf_end; |
| 382 | |
| 383 | buf_end = read_sleb128 (data + 1, data + size, &frame_offset); |
| 384 | if (buf_end != data + size) |
| 385 | error (_("Unexpected opcode after DW_OP_fbreg for symbol \"%s\"."), |
| 386 | SYMBOL_PRINT_NAME (symbol)); |
| 387 | |
| 388 | TARGET_VIRTUAL_FRAME_POINTER (ax->scope, &frame_reg, &frame_offset); |
| 389 | ax_reg (ax, frame_reg); |
| 390 | ax_const_l (ax, frame_offset); |
| 391 | ax_simple (ax, aop_add); |
| 392 | |
| 393 | value->kind = axs_lvalue_memory; |
| 394 | } |
| 395 | else if (data[0] >= DW_OP_breg0 |
| 396 | && data[0] <= DW_OP_breg31) |
| 397 | { |
| 398 | unsigned int reg; |
| 399 | LONGEST offset; |
| 400 | gdb_byte *buf_end; |
| 401 | |
| 402 | reg = data[0] - DW_OP_breg0; |
| 403 | buf_end = read_sleb128 (data + 1, data + size, &offset); |
| 404 | if (buf_end != data + size) |
| 405 | error (_("Unexpected opcode after DW_OP_breg%u for symbol \"%s\"."), |
| 406 | reg, SYMBOL_PRINT_NAME (symbol)); |
| 407 | |
| 408 | ax_reg (ax, reg); |
| 409 | ax_const_l (ax, offset); |
| 410 | ax_simple (ax, aop_add); |
| 411 | |
| 412 | value->kind = axs_lvalue_memory; |
| 413 | } |
| 414 | else |
| 415 | error (_("Unsupported DWARF opcode 0x%x in the location of \"%s\"."), |
| 416 | data[0], SYMBOL_PRINT_NAME (symbol)); |
| 417 | } |
| 418 | \f |
| 419 | /* Return the value of SYMBOL in FRAME using the DWARF-2 expression |
| 420 | evaluator to calculate the location. */ |
| 421 | static struct value * |
| 422 | locexpr_read_variable (struct symbol *symbol, struct frame_info *frame) |
| 423 | { |
| 424 | struct dwarf2_locexpr_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); |
| 425 | struct value *val; |
| 426 | val = dwarf2_evaluate_loc_desc (symbol, frame, dlbaton->data, dlbaton->size, |
| 427 | dlbaton->objfile); |
| 428 | |
| 429 | return val; |
| 430 | } |
| 431 | |
| 432 | /* Return non-zero iff we need a frame to evaluate SYMBOL. */ |
| 433 | static int |
| 434 | locexpr_read_needs_frame (struct symbol *symbol) |
| 435 | { |
| 436 | struct dwarf2_locexpr_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); |
| 437 | return dwarf2_loc_desc_needs_frame (dlbaton->data, dlbaton->size); |
| 438 | } |
| 439 | |
| 440 | /* Print a natural-language description of SYMBOL to STREAM. */ |
| 441 | static int |
| 442 | locexpr_describe_location (struct symbol *symbol, struct ui_file *stream) |
| 443 | { |
| 444 | /* FIXME: be more extensive. */ |
| 445 | struct dwarf2_locexpr_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); |
| 446 | |
| 447 | if (dlbaton->size == 1 |
| 448 | && dlbaton->data[0] >= DW_OP_reg0 |
| 449 | && dlbaton->data[0] <= DW_OP_reg31) |
| 450 | { |
| 451 | int regno = DWARF2_REG_TO_REGNUM (dlbaton->data[0] - DW_OP_reg0); |
| 452 | fprintf_filtered (stream, |
| 453 | "a variable in register %s", REGISTER_NAME (regno)); |
| 454 | return 1; |
| 455 | } |
| 456 | |
| 457 | /* The location expression for a TLS variable looks like this (on a |
| 458 | 64-bit LE machine): |
| 459 | |
| 460 | DW_AT_location : 10 byte block: 3 4 0 0 0 0 0 0 0 e0 |
| 461 | (DW_OP_addr: 4; DW_OP_GNU_push_tls_address) |
| 462 | |
| 463 | 0x3 is the encoding for DW_OP_addr, which has an operand as long |
| 464 | as the size of an address on the target machine (here is 8 |
| 465 | bytes). 0xe0 is the encoding for DW_OP_GNU_push_tls_address. |
| 466 | The operand represents the offset at which the variable is within |
| 467 | the thread local storage. */ |
| 468 | |
| 469 | if (dlbaton->size > 1 |
| 470 | && dlbaton->data[dlbaton->size - 1] == DW_OP_GNU_push_tls_address) |
| 471 | if (dlbaton->data[0] == DW_OP_addr) |
| 472 | { |
| 473 | int bytes_read; |
| 474 | CORE_ADDR offset = dwarf2_read_address (&dlbaton->data[1], |
| 475 | &dlbaton->data[dlbaton->size - 1], |
| 476 | &bytes_read); |
| 477 | fprintf_filtered (stream, |
| 478 | "a thread-local variable at offset %s in the " |
| 479 | "thread-local storage for `%s'", |
| 480 | paddr_nz (offset), dlbaton->objfile->name); |
| 481 | return 1; |
| 482 | } |
| 483 | |
| 484 | |
| 485 | fprintf_filtered (stream, |
| 486 | "a variable with complex or multiple locations (DWARF2)"); |
| 487 | return 1; |
| 488 | } |
| 489 | |
| 490 | |
| 491 | /* Describe the location of SYMBOL as an agent value in VALUE, generating |
| 492 | any necessary bytecode in AX. |
| 493 | |
| 494 | NOTE drow/2003-02-26: This function is extremely minimal, because |
| 495 | doing it correctly is extremely complicated and there is no |
| 496 | publicly available stub with tracepoint support for me to test |
| 497 | against. When there is one this function should be revisited. */ |
| 498 | |
| 499 | static void |
| 500 | locexpr_tracepoint_var_ref (struct symbol * symbol, struct agent_expr * ax, |
| 501 | struct axs_value * value) |
| 502 | { |
| 503 | struct dwarf2_locexpr_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); |
| 504 | |
| 505 | dwarf2_tracepoint_var_ref (symbol, ax, value, dlbaton->data, dlbaton->size); |
| 506 | } |
| 507 | |
| 508 | /* The set of location functions used with the DWARF-2 expression |
| 509 | evaluator. */ |
| 510 | const struct symbol_ops dwarf2_locexpr_funcs = { |
| 511 | locexpr_read_variable, |
| 512 | locexpr_read_needs_frame, |
| 513 | locexpr_describe_location, |
| 514 | locexpr_tracepoint_var_ref |
| 515 | }; |
| 516 | |
| 517 | |
| 518 | /* Wrapper functions for location lists. These generally find |
| 519 | the appropriate location expression and call something above. */ |
| 520 | |
| 521 | /* Return the value of SYMBOL in FRAME using the DWARF-2 expression |
| 522 | evaluator to calculate the location. */ |
| 523 | static struct value * |
| 524 | loclist_read_variable (struct symbol *symbol, struct frame_info *frame) |
| 525 | { |
| 526 | struct dwarf2_loclist_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); |
| 527 | struct value *val; |
| 528 | gdb_byte *data; |
| 529 | size_t size; |
| 530 | |
| 531 | data = find_location_expression (dlbaton, &size, |
| 532 | frame ? get_frame_address_in_block (frame) |
| 533 | : 0); |
| 534 | if (data == NULL) |
| 535 | { |
| 536 | val = allocate_value (SYMBOL_TYPE (symbol)); |
| 537 | VALUE_LVAL (val) = not_lval; |
| 538 | set_value_optimized_out (val, 1); |
| 539 | } |
| 540 | else |
| 541 | val = dwarf2_evaluate_loc_desc (symbol, frame, data, size, |
| 542 | dlbaton->objfile); |
| 543 | |
| 544 | return val; |
| 545 | } |
| 546 | |
| 547 | /* Return non-zero iff we need a frame to evaluate SYMBOL. */ |
| 548 | static int |
| 549 | loclist_read_needs_frame (struct symbol *symbol) |
| 550 | { |
| 551 | /* If there's a location list, then assume we need to have a frame |
| 552 | to choose the appropriate location expression. With tracking of |
| 553 | global variables this is not necessarily true, but such tracking |
| 554 | is disabled in GCC at the moment until we figure out how to |
| 555 | represent it. */ |
| 556 | |
| 557 | return 1; |
| 558 | } |
| 559 | |
| 560 | /* Print a natural-language description of SYMBOL to STREAM. */ |
| 561 | static int |
| 562 | loclist_describe_location (struct symbol *symbol, struct ui_file *stream) |
| 563 | { |
| 564 | /* FIXME: Could print the entire list of locations. */ |
| 565 | fprintf_filtered (stream, "a variable with multiple locations"); |
| 566 | return 1; |
| 567 | } |
| 568 | |
| 569 | /* Describe the location of SYMBOL as an agent value in VALUE, generating |
| 570 | any necessary bytecode in AX. */ |
| 571 | static void |
| 572 | loclist_tracepoint_var_ref (struct symbol * symbol, struct agent_expr * ax, |
| 573 | struct axs_value * value) |
| 574 | { |
| 575 | struct dwarf2_loclist_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); |
| 576 | gdb_byte *data; |
| 577 | size_t size; |
| 578 | |
| 579 | data = find_location_expression (dlbaton, &size, ax->scope); |
| 580 | if (data == NULL) |
| 581 | error (_("Variable \"%s\" is not available."), SYMBOL_NATURAL_NAME (symbol)); |
| 582 | |
| 583 | dwarf2_tracepoint_var_ref (symbol, ax, value, data, size); |
| 584 | } |
| 585 | |
| 586 | /* The set of location functions used with the DWARF-2 expression |
| 587 | evaluator and location lists. */ |
| 588 | const struct symbol_ops dwarf2_loclist_funcs = { |
| 589 | loclist_read_variable, |
| 590 | loclist_read_needs_frame, |
| 591 | loclist_describe_location, |
| 592 | loclist_tracepoint_var_ref |
| 593 | }; |