| 1 | /* GDB routines for manipulating the minimal symbol tables. |
| 2 | Copyright 1992 Free Software Foundation, Inc. |
| 3 | Contributed by Cygnus Support, using pieces from other GDB modules. |
| 4 | |
| 5 | This file is part of GDB. |
| 6 | |
| 7 | This program is free software; you can redistribute it and/or modify |
| 8 | it under the terms of the GNU General Public License as published by |
| 9 | the Free Software Foundation; either version 2 of the License, or |
| 10 | (at your option) any later version. |
| 11 | |
| 12 | This program is distributed in the hope that it will be useful, |
| 13 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 15 | GNU General Public License for more details. |
| 16 | |
| 17 | You should have received a copy of the GNU General Public License |
| 18 | along with this program; if not, write to the Free Software |
| 19 | Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ |
| 20 | |
| 21 | |
| 22 | /* This file contains support routines for creating, manipulating, and |
| 23 | destroying minimal symbol tables. |
| 24 | |
| 25 | Minimal symbol tables are used to hold some very basic information about |
| 26 | all defined global symbols (text, data, bss, abs, etc). The only two |
| 27 | required pieces of information are the symbol's name and the address |
| 28 | associated with that symbol. |
| 29 | |
| 30 | In many cases, even if a file was compiled with no special options for |
| 31 | debugging at all, as long as was not stripped it will contain sufficient |
| 32 | information to build useful minimal symbol tables using this structure. |
| 33 | |
| 34 | Even when a file contains enough debugging information to build a full |
| 35 | symbol table, these minimal symbols are still useful for quickly mapping |
| 36 | between names and addresses, and vice versa. They are also sometimes used |
| 37 | to figure out what full symbol table entries need to be read in. */ |
| 38 | |
| 39 | |
| 40 | #include "defs.h" |
| 41 | #include "symtab.h" |
| 42 | #include "bfd.h" |
| 43 | #include "symfile.h" |
| 44 | #include "objfiles.h" |
| 45 | |
| 46 | /* Accumulate the minimal symbols for each objfile in bunches of BUNCH_SIZE. |
| 47 | At the end, copy them all into one newly allocated location on an objfile's |
| 48 | symbol obstack. */ |
| 49 | |
| 50 | #define BUNCH_SIZE 127 |
| 51 | |
| 52 | struct msym_bunch |
| 53 | { |
| 54 | struct msym_bunch *next; |
| 55 | struct minimal_symbol contents[BUNCH_SIZE]; |
| 56 | }; |
| 57 | |
| 58 | /* Bunch currently being filled up. |
| 59 | The next field points to chain of filled bunches. */ |
| 60 | |
| 61 | static struct msym_bunch *msym_bunch; |
| 62 | |
| 63 | /* Number of slots filled in current bunch. */ |
| 64 | |
| 65 | static int msym_bunch_index; |
| 66 | |
| 67 | /* Total number of minimal symbols recorded so far for the objfile. */ |
| 68 | |
| 69 | static int msym_count; |
| 70 | |
| 71 | /* Prototypes for local functions. */ |
| 72 | |
| 73 | static int |
| 74 | compare_minimal_symbols PARAMS ((const void *, const void *)); |
| 75 | |
| 76 | static int |
| 77 | compact_minimal_symbols PARAMS ((struct minimal_symbol *, int)); |
| 78 | |
| 79 | /* Look through all the current minimal symbol tables and find the first |
| 80 | minimal symbol that matches NAME. If OBJF is non-NULL, it specifies a |
| 81 | particular objfile and the search is limited to that objfile. Returns |
| 82 | a pointer to the minimal symbol that matches, or NULL if no match is found. |
| 83 | |
| 84 | Note: One instance where there may be duplicate minimal symbols with |
| 85 | the same name is when the symbol tables for a shared library and the |
| 86 | symbol tables for an executable contain global symbols with the same |
| 87 | names (the dynamic linker deals with the duplication). */ |
| 88 | |
| 89 | struct minimal_symbol * |
| 90 | lookup_minimal_symbol (name, objf) |
| 91 | register const char *name; |
| 92 | struct objfile *objf; |
| 93 | { |
| 94 | struct objfile *objfile; |
| 95 | struct minimal_symbol *msymbol; |
| 96 | struct minimal_symbol *found_symbol = NULL; |
| 97 | #ifdef IBM6000_TARGET |
| 98 | struct minimal_symbol *trampoline_symbol = NULL; |
| 99 | #endif |
| 100 | |
| 101 | for (objfile = object_files; |
| 102 | objfile != NULL && found_symbol == NULL; |
| 103 | objfile = objfile -> next) |
| 104 | { |
| 105 | if (objf == NULL || objf == objfile) |
| 106 | { |
| 107 | for (msymbol = objfile -> msymbols; |
| 108 | msymbol != NULL && msymbol -> name != NULL && |
| 109 | found_symbol == NULL; |
| 110 | msymbol++) |
| 111 | { |
| 112 | if (strcmp (msymbol -> name, name) == 0) |
| 113 | { |
| 114 | #ifdef IBM6000_TARGET |
| 115 | /* I *think* all platforms using shared libraries (and trampoline code) |
| 116 | * will suffer this problem. Consider a case where there are 5 shared |
| 117 | * libraries, each referencing `foo' with a trampoline entry. When someone |
| 118 | * wants to put a breakpoint on `foo' and the only info we have is minimal |
| 119 | * symbol vector, we want to use the real `foo', rather than one of those |
| 120 | * trampoline entries. MGO */ |
| 121 | /* If a trampoline symbol is found, we prefer to keep looking |
| 122 | for the *real* symbol. If the actual symbol not found, |
| 123 | then we'll use the trampoline entry. Sorry for the machine |
| 124 | dependent code here, but I hope this will benefit other |
| 125 | platforms as well. For trampoline entries, we used mst_unknown |
| 126 | earlier. Perhaps we should define a `mst_trampoline' type?? */ |
| 127 | |
| 128 | if (msymbol->type != mst_unknown) |
| 129 | found_symbol = msymbol; |
| 130 | else if (msymbol->type == mst_unknown && !trampoline_symbol) |
| 131 | trampoline_symbol = msymbol; |
| 132 | |
| 133 | #else |
| 134 | found_symbol = msymbol; |
| 135 | #endif |
| 136 | } |
| 137 | } |
| 138 | } |
| 139 | } |
| 140 | #ifdef IBM6000_TARGET |
| 141 | return found_symbol ? found_symbol : trampoline_symbol; |
| 142 | #endif |
| 143 | |
| 144 | return (found_symbol); |
| 145 | } |
| 146 | |
| 147 | |
| 148 | /* Search through the minimal symbol table for each objfile and find the |
| 149 | symbol whose address is the largest address that is still less than or |
| 150 | equal to PC. Returns a pointer to the minimal symbol if such a symbol |
| 151 | is found, or NULL if PC is not in a suitable range. Note that we need |
| 152 | to look through ALL the minimal symbol tables before deciding on the |
| 153 | symbol that comes closest to the specified PC. */ |
| 154 | |
| 155 | struct minimal_symbol * |
| 156 | lookup_minimal_symbol_by_pc (pc) |
| 157 | register CORE_ADDR pc; |
| 158 | { |
| 159 | register int lo; |
| 160 | register int hi; |
| 161 | register int new; |
| 162 | register struct objfile *objfile; |
| 163 | register struct minimal_symbol *msymbol; |
| 164 | register struct minimal_symbol *best_symbol = NULL; |
| 165 | |
| 166 | for (objfile = object_files; |
| 167 | objfile != NULL; |
| 168 | objfile = objfile -> next) |
| 169 | { |
| 170 | /* If this objfile has a minimal symbol table, go search it using |
| 171 | a binary search. Note that a minimal symbol table always consists |
| 172 | of at least two symbols, a "real" symbol and the terminating |
| 173 | "null symbol". If there are no real symbols, then there is no |
| 174 | minimal symbol table at all. */ |
| 175 | |
| 176 | if ((msymbol = objfile -> msymbols) != NULL) |
| 177 | { |
| 178 | lo = 0; |
| 179 | hi = objfile -> minimal_symbol_count - 2; |
| 180 | |
| 181 | /* This code assumes that the minimal symbols are sorted by |
| 182 | ascending address values. If the pc value is greater than or |
| 183 | equal to the first symbol's address, then some symbol in this |
| 184 | minimal symbol table is a suitable candidate for being the |
| 185 | "best" symbol. This includes the last real symbol, for cases |
| 186 | where the pc value is larger than any address in this vector. |
| 187 | |
| 188 | By iterating until the address associated with the current |
| 189 | hi index (the endpoint of the test interval) is less than |
| 190 | or equal to the desired pc value, we accomplish two things: |
| 191 | (1) the case where the pc value is larger than any minimal |
| 192 | symbol address is trivially solved, (2) the address associated |
| 193 | with the hi index is always the one we want when the interation |
| 194 | terminates. In essence, we are iterating the test interval |
| 195 | down until the pc value is pushed out of it from the high end. |
| 196 | |
| 197 | Warning: this code is trickier than it would appear at first. */ |
| 198 | |
| 199 | /* Should also requires that pc is <= end of objfile. FIXME! */ |
| 200 | if (pc >= msymbol[lo].address) |
| 201 | { |
| 202 | while (msymbol[hi].address > pc) |
| 203 | { |
| 204 | /* pc is still strictly less than highest address */ |
| 205 | /* Note "new" will always be >= lo */ |
| 206 | new = (lo + hi) / 2; |
| 207 | if ((msymbol[new].address >= pc) || (lo == new)) |
| 208 | { |
| 209 | hi = new; |
| 210 | } |
| 211 | else |
| 212 | { |
| 213 | lo = new; |
| 214 | } |
| 215 | } |
| 216 | /* The minimal symbol indexed by hi now is the best one in this |
| 217 | objfile's minimal symbol table. See if it is the best one |
| 218 | overall. */ |
| 219 | |
| 220 | if ((best_symbol == NULL) || |
| 221 | (best_symbol -> address < msymbol[hi].address)) |
| 222 | { |
| 223 | best_symbol = &msymbol[hi]; |
| 224 | } |
| 225 | } |
| 226 | } |
| 227 | } |
| 228 | return (best_symbol); |
| 229 | } |
| 230 | |
| 231 | /* Prepare to start collecting minimal symbols. Note that presetting |
| 232 | msym_bunch_index to BUNCH_SIZE causes the first call to save a minimal |
| 233 | symbol to allocate the memory for the first bunch. */ |
| 234 | |
| 235 | void |
| 236 | init_minimal_symbol_collection () |
| 237 | { |
| 238 | msym_count = 0; |
| 239 | msym_bunch = NULL; |
| 240 | msym_bunch_index = BUNCH_SIZE; |
| 241 | } |
| 242 | |
| 243 | void |
| 244 | prim_record_minimal_symbol (name, address, ms_type) |
| 245 | const char *name; |
| 246 | CORE_ADDR address; |
| 247 | enum minimal_symbol_type ms_type; |
| 248 | { |
| 249 | register struct msym_bunch *new; |
| 250 | |
| 251 | if (msym_bunch_index == BUNCH_SIZE) |
| 252 | { |
| 253 | new = (struct msym_bunch *) xmalloc (sizeof (struct msym_bunch)); |
| 254 | msym_bunch_index = 0; |
| 255 | new -> next = msym_bunch; |
| 256 | msym_bunch = new; |
| 257 | } |
| 258 | msym_bunch -> contents[msym_bunch_index].name = (char *) name; |
| 259 | msym_bunch -> contents[msym_bunch_index].address = address; |
| 260 | msym_bunch -> contents[msym_bunch_index].info = NULL; |
| 261 | msym_bunch -> contents[msym_bunch_index].type = ms_type; |
| 262 | msym_bunch_index++; |
| 263 | msym_count++; |
| 264 | } |
| 265 | |
| 266 | void |
| 267 | prim_record_minimal_symbol_and_info (name, address, ms_type, info) |
| 268 | const char *name; |
| 269 | CORE_ADDR address; |
| 270 | enum minimal_symbol_type ms_type; |
| 271 | char *info; |
| 272 | { |
| 273 | register struct msym_bunch *new; |
| 274 | |
| 275 | if (msym_bunch_index == BUNCH_SIZE) |
| 276 | { |
| 277 | new = (struct msym_bunch *) xmalloc (sizeof (struct msym_bunch)); |
| 278 | msym_bunch_index = 0; |
| 279 | new -> next = msym_bunch; |
| 280 | msym_bunch = new; |
| 281 | } |
| 282 | msym_bunch -> contents[msym_bunch_index].name = (char *) name; |
| 283 | msym_bunch -> contents[msym_bunch_index].address = address; |
| 284 | msym_bunch -> contents[msym_bunch_index].info = NULL; |
| 285 | msym_bunch -> contents[msym_bunch_index].type = ms_type; |
| 286 | /* FIXME: This info, if it remains, needs its own field. */ |
| 287 | msym_bunch -> contents[msym_bunch_index].info = info; /* FIXME! */ |
| 288 | msym_bunch_index++; |
| 289 | msym_count++; |
| 290 | } |
| 291 | |
| 292 | /* Compare two minimal symbols by address and return a signed result based |
| 293 | on unsigned comparisons, so that we sort into unsigned numeric order. */ |
| 294 | |
| 295 | static int |
| 296 | compare_minimal_symbols (fn1p, fn2p) |
| 297 | const PTR fn1p; |
| 298 | const PTR fn2p; |
| 299 | { |
| 300 | register const struct minimal_symbol *fn1; |
| 301 | register const struct minimal_symbol *fn2; |
| 302 | |
| 303 | fn1 = (const struct minimal_symbol *) fn1p; |
| 304 | fn2 = (const struct minimal_symbol *) fn2p; |
| 305 | |
| 306 | if (fn1 -> address < fn2 -> address) |
| 307 | { |
| 308 | return (-1); |
| 309 | } |
| 310 | else if (fn1 -> address > fn2 -> address) |
| 311 | { |
| 312 | return (1); |
| 313 | } |
| 314 | else |
| 315 | { |
| 316 | return (0); |
| 317 | } |
| 318 | } |
| 319 | |
| 320 | /* Discard the currently collected minimal symbols, if any. If we wish |
| 321 | to save them for later use, we must have already copied them somewhere |
| 322 | else before calling this function. |
| 323 | |
| 324 | FIXME: We could allocate the minimal symbol bunches on their own |
| 325 | obstack and then simply blow the obstack away when we are done with |
| 326 | it. Is it worth the extra trouble though? */ |
| 327 | |
| 328 | /* ARGSUSED */ |
| 329 | void |
| 330 | discard_minimal_symbols (foo) |
| 331 | int foo; |
| 332 | { |
| 333 | register struct msym_bunch *next; |
| 334 | |
| 335 | while (msym_bunch != NULL) |
| 336 | { |
| 337 | next = msym_bunch -> next; |
| 338 | free ((PTR)msym_bunch); |
| 339 | msym_bunch = next; |
| 340 | } |
| 341 | } |
| 342 | |
| 343 | /* Compact duplicate entries out of a minimal symbol table by walking |
| 344 | through the table and compacting out entries with duplicate addresses |
| 345 | and matching names. Return the number of entries remaining. |
| 346 | |
| 347 | On entry, the table resides between msymbol[0] and msymbol[mcount]. |
| 348 | On exit, it resides between msymbol[0] and msymbol[result_count]. |
| 349 | |
| 350 | When files contain multiple sources of symbol information, it is |
| 351 | possible for the minimal symbol table to contain many duplicate entries. |
| 352 | As an example, SVR4 systems use ELF formatted object files, which |
| 353 | usually contain at least two different types of symbol tables (a |
| 354 | standard ELF one and a smaller dynamic linking table), as well as |
| 355 | DWARF debugging information for files compiled with -g. |
| 356 | |
| 357 | Without compacting, the minimal symbol table for gdb itself contains |
| 358 | over a 1000 duplicates, about a third of the total table size. Aside |
| 359 | from the potential trap of not noticing that two successive entries |
| 360 | identify the same location, this duplication impacts the time required |
| 361 | to linearly scan the table, which is done in a number of places. So we |
| 362 | just do one linear scan here and toss out the duplicates. |
| 363 | |
| 364 | Note that we are not concerned here about recovering the space that |
| 365 | is potentially freed up, because the strings themselves are allocated |
| 366 | on the symbol_obstack, and will get automatically freed when the symbol |
| 367 | table is freed. The caller can free up the unused minimal symbols at |
| 368 | the end of the compacted region if their allocation strategy allows it. |
| 369 | |
| 370 | Also note we only go up to the next to last entry within the loop |
| 371 | and then copy the last entry explicitly after the loop terminates. |
| 372 | |
| 373 | Since the different sources of information for each symbol may |
| 374 | have different levels of "completeness", we may have duplicates |
| 375 | that have one entry with type "mst_unknown" and the other with a |
| 376 | known type. So if the one we are leaving alone has type mst_unknown, |
| 377 | overwrite its type with the type from the one we are compacting out. */ |
| 378 | |
| 379 | static int |
| 380 | compact_minimal_symbols (msymbol, mcount) |
| 381 | struct minimal_symbol *msymbol; |
| 382 | int mcount; |
| 383 | { |
| 384 | struct minimal_symbol *copyfrom; |
| 385 | struct minimal_symbol *copyto; |
| 386 | |
| 387 | if (mcount > 0) |
| 388 | { |
| 389 | copyfrom = copyto = msymbol; |
| 390 | while (copyfrom < msymbol + mcount - 1) |
| 391 | { |
| 392 | if (copyfrom -> address == (copyfrom + 1) -> address |
| 393 | && (strcmp (copyfrom -> name, (copyfrom + 1) -> name) == 0)) |
| 394 | { |
| 395 | if ((copyfrom + 1) -> type == mst_unknown) |
| 396 | { |
| 397 | (copyfrom + 1) -> type = copyfrom -> type; |
| 398 | } |
| 399 | copyfrom++; |
| 400 | } |
| 401 | else |
| 402 | { |
| 403 | *copyto++ = *copyfrom++; |
| 404 | } |
| 405 | } |
| 406 | *copyto++ = *copyfrom++; |
| 407 | mcount = copyto - msymbol; |
| 408 | } |
| 409 | return (mcount); |
| 410 | } |
| 411 | |
| 412 | /* Add the minimal symbols in the existing bunches to the objfile's |
| 413 | official minimal symbol table. 99% of the time, this adds the |
| 414 | bunches to NO existing symbols. Once in a while for shared |
| 415 | libraries, we add symbols (e.g. common symbols) to an existing |
| 416 | objfile. */ |
| 417 | |
| 418 | void |
| 419 | install_minimal_symbols (objfile) |
| 420 | struct objfile *objfile; |
| 421 | { |
| 422 | register int bindex; |
| 423 | register int mcount; |
| 424 | register struct msym_bunch *bunch; |
| 425 | register struct minimal_symbol *msymbols; |
| 426 | int alloc_count; |
| 427 | |
| 428 | if (msym_count > 0) |
| 429 | { |
| 430 | /* Allocate enough space in the obstack, into which we will gather the |
| 431 | bunches of new and existing minimal symbols, sort them, and then |
| 432 | compact out the duplicate entries. Once we have a final table, |
| 433 | we will give back the excess space. */ |
| 434 | |
| 435 | alloc_count = msym_count + objfile->minimal_symbol_count + 1; |
| 436 | obstack_blank (&objfile->symbol_obstack, |
| 437 | alloc_count * sizeof (struct minimal_symbol)); |
| 438 | msymbols = (struct minimal_symbol *) |
| 439 | obstack_base (&objfile->symbol_obstack); |
| 440 | |
| 441 | /* Copy in the existing minimal symbols, if there are any. */ |
| 442 | |
| 443 | if (objfile->minimal_symbol_count) |
| 444 | memcpy ((char *)msymbols, (char *)objfile->msymbols, |
| 445 | objfile->minimal_symbol_count * sizeof (struct minimal_symbol)); |
| 446 | |
| 447 | /* Walk through the list of minimal symbol bunches, adding each symbol |
| 448 | to the new contiguous array of symbols. Note that we start with the |
| 449 | current, possibly partially filled bunch (thus we use the current |
| 450 | msym_bunch_index for the first bunch we copy over), and thereafter |
| 451 | each bunch is full. */ |
| 452 | |
| 453 | mcount = objfile->minimal_symbol_count; |
| 454 | |
| 455 | for (bunch = msym_bunch; bunch != NULL; bunch = bunch -> next) |
| 456 | { |
| 457 | for (bindex = 0; bindex < msym_bunch_index; bindex++, mcount++) |
| 458 | { |
| 459 | msymbols[mcount] = bunch -> contents[bindex]; |
| 460 | #ifdef NAMES_HAVE_UNDERSCORE |
| 461 | if (msymbols[mcount].name[0] == '_') |
| 462 | { |
| 463 | msymbols[mcount].name++; |
| 464 | } |
| 465 | #endif |
| 466 | #ifdef SOME_NAMES_HAVE_DOT |
| 467 | if (msymbols[mcount].name[0] == '.') |
| 468 | { |
| 469 | msymbols[mcount].name++; |
| 470 | } |
| 471 | #endif |
| 472 | } |
| 473 | msym_bunch_index = BUNCH_SIZE; |
| 474 | } |
| 475 | |
| 476 | /* Sort the minimal symbols by address. */ |
| 477 | |
| 478 | qsort (msymbols, mcount, sizeof (struct minimal_symbol), |
| 479 | compare_minimal_symbols); |
| 480 | |
| 481 | /* Compact out any duplicates, and free up whatever space we are |
| 482 | no longer using. */ |
| 483 | |
| 484 | mcount = compact_minimal_symbols (msymbols, mcount); |
| 485 | |
| 486 | obstack_blank (&objfile->symbol_obstack, |
| 487 | (mcount + 1 - alloc_count) * sizeof (struct minimal_symbol)); |
| 488 | msymbols = (struct minimal_symbol *) |
| 489 | obstack_finish (&objfile->symbol_obstack); |
| 490 | |
| 491 | /* We also terminate the minimal symbol table |
| 492 | with a "null symbol", which is *not* included in the size of |
| 493 | the table. This makes it easier to find the end of the table |
| 494 | when we are handed a pointer to some symbol in the middle of it. |
| 495 | Zero out the fields in the "null symbol" allocated at the end |
| 496 | of the array. Note that the symbol count does *not* include |
| 497 | this null symbol, which is why it is indexed by mcount and not |
| 498 | mcount-1. */ |
| 499 | |
| 500 | msymbols[mcount].name = NULL; |
| 501 | msymbols[mcount].address = 0; |
| 502 | msymbols[mcount].info = NULL; |
| 503 | msymbols[mcount].type = mst_unknown; |
| 504 | |
| 505 | /* Attach the minimal symbol table to the specified objfile. |
| 506 | The strings themselves are also located in the symbol_obstack |
| 507 | of this objfile. */ |
| 508 | |
| 509 | objfile -> minimal_symbol_count = mcount; |
| 510 | objfile -> msymbols = msymbols; |
| 511 | } |
| 512 | } |
| 513 | |