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.
5 This file is part of GDB.
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.
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.
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. */
22 /* This file contains support routines for creating, manipulating, and
23 destroying minimal symbol tables.
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.
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.
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. */
47 /* Accumulate the minimal symbols for each objfile in bunches of BUNCH_SIZE.
48 At the end, copy them all into one newly allocated location on an objfile's
51 #define BUNCH_SIZE 127
55 struct msym_bunch *next;
56 struct minimal_symbol contents[BUNCH_SIZE];
59 /* Bunch currently being filled up.
60 The next field points to chain of filled bunches. */
62 static struct msym_bunch *msym_bunch;
64 /* Number of slots filled in current bunch. */
66 static int msym_bunch_index;
68 /* Total number of minimal symbols recorded so far for the objfile. */
70 static int msym_count;
72 /* Prototypes for local functions. */
75 compare_minimal_symbols PARAMS ((const void *, const void *));
78 compact_minimal_symbols PARAMS ((struct minimal_symbol *, int));
80 /* Look through all the current minimal symbol tables and find the first
81 minimal symbol that matches NAME. If OBJF is non-NULL, it specifies a
82 particular objfile and the search is limited to that objfile. Returns
83 a pointer to the minimal symbol that matches, or NULL if no match is found.
85 Note: One instance where there may be duplicate minimal symbols with
86 the same name is when the symbol tables for a shared library and the
87 symbol tables for an executable contain global symbols with the same
88 names (the dynamic linker deals with the duplication). */
90 struct minimal_symbol *
91 lookup_minimal_symbol (name, objf)
92 register const char *name;
95 struct objfile *objfile;
96 struct minimal_symbol *msymbol;
97 struct minimal_symbol *found_symbol = NULL;
98 struct minimal_symbol *found_file_symbol = NULL;
100 struct minimal_symbol *trampoline_symbol = NULL;
103 for (objfile = object_files;
104 objfile != NULL && found_symbol == NULL;
105 objfile = objfile -> next)
107 if (objf == NULL || objf == objfile)
109 for (msymbol = objfile -> msymbols;
110 msymbol != NULL && SYMBOL_NAME (msymbol) != NULL &&
111 found_symbol == NULL;
114 if (SYMBOL_MATCHES_NAME (msymbol, name))
116 switch (MSYMBOL_TYPE (msymbol))
121 /* It is file-local. If we find more than one, just
122 return the latest one (the user can't expect
123 useful behavior in that case). */
124 found_file_symbol = msymbol;
128 #ifdef IBM6000_TARGET
129 /* I *think* all platforms using shared
130 libraries (and trampoline code) will suffer
131 this problem. Consider a case where there are
132 5 shared libraries, each referencing `foo'
133 with a trampoline entry. When someone wants
134 to put a breakpoint on `foo' and the only
135 info we have is minimal symbol vector, we
136 want to use the real `foo', rather than one
137 of those trampoline entries. MGO */
139 /* If a trampoline symbol is found, we prefer to
140 keep looking for the *real* symbol. If the
141 actual symbol not found, then we'll use the
142 trampoline entry. Sorry for the machine
143 dependent code here, but I hope this will
144 benefit other platforms as well. For
145 trampoline entries, we used mst_unknown
146 earlier. Perhaps we should define a
147 `mst_trampoline' type?? */
149 if (trampoline_symbol == NULL)
150 trampoline_symbol = msymbol;
156 found_symbol = msymbol;
163 /* External symbols are best. */
167 /* File-local symbols are next best. */
168 if (found_file_symbol)
169 return found_file_symbol;
171 /* Symbols for IBM shared library trampolines are next best. */
172 #ifdef IBM6000_TARGET
173 if (trampoline_symbol)
174 return trampoline_symbol;
181 /* Search through the minimal symbol table for each objfile and find the
182 symbol whose address is the largest address that is still less than or
183 equal to PC. Returns a pointer to the minimal symbol if such a symbol
184 is found, or NULL if PC is not in a suitable range. Note that we need
185 to look through ALL the minimal symbol tables before deciding on the
186 symbol that comes closest to the specified PC. This is because objfiles
187 can overlap, for example objfile A has .text at 0x100 and .data at 0x40000
188 and objfile B has .text at 0x234 and .data at 0x40048. */
190 struct minimal_symbol *
191 lookup_minimal_symbol_by_pc (pc)
192 register CORE_ADDR pc;
197 register struct objfile *objfile;
198 register struct minimal_symbol *msymbol;
199 register struct minimal_symbol *best_symbol = NULL;
201 for (objfile = object_files;
203 objfile = objfile -> next)
205 /* If this objfile has a minimal symbol table, go search it using
206 a binary search. Note that a minimal symbol table always consists
207 of at least two symbols, a "real" symbol and the terminating
208 "null symbol". If there are no real symbols, then there is no
209 minimal symbol table at all. */
211 if ((msymbol = objfile -> msymbols) != NULL)
214 hi = objfile -> minimal_symbol_count - 1;
216 /* This code assumes that the minimal symbols are sorted by
217 ascending address values. If the pc value is greater than or
218 equal to the first symbol's address, then some symbol in this
219 minimal symbol table is a suitable candidate for being the
220 "best" symbol. This includes the last real symbol, for cases
221 where the pc value is larger than any address in this vector.
223 By iterating until the address associated with the current
224 hi index (the endpoint of the test interval) is less than
225 or equal to the desired pc value, we accomplish two things:
226 (1) the case where the pc value is larger than any minimal
227 symbol address is trivially solved, (2) the address associated
228 with the hi index is always the one we want when the interation
229 terminates. In essence, we are iterating the test interval
230 down until the pc value is pushed out of it from the high end.
232 Warning: this code is trickier than it would appear at first. */
234 /* Should also requires that pc is <= end of objfile. FIXME! */
235 if (pc >= SYMBOL_VALUE_ADDRESS (&msymbol[lo]))
237 while (SYMBOL_VALUE_ADDRESS (&msymbol[hi]) > pc)
239 /* pc is still strictly less than highest address */
240 /* Note "new" will always be >= lo */
242 if ((SYMBOL_VALUE_ADDRESS (&msymbol[new]) >= pc) ||
252 /* The minimal symbol indexed by hi now is the best one in this
253 objfile's minimal symbol table. See if it is the best one
256 if ((best_symbol == NULL) ||
257 (SYMBOL_VALUE_ADDRESS (best_symbol) <
258 SYMBOL_VALUE_ADDRESS (&msymbol[hi])))
260 best_symbol = &msymbol[hi];
265 return (best_symbol);
268 /* Just like lookup_minimal_symbol_by_pc, but look up the closest minimal
269 symbol > PC, not the one <= PC. */
271 struct minimal_symbol *
272 lookup_next_minimal_symbol (pc)
278 register struct objfile *objfile;
279 register struct minimal_symbol *msymbol;
280 register struct minimal_symbol *best_symbol = NULL;
282 for (objfile = object_files;
284 objfile = objfile -> next)
286 /* If this objfile has a minimal symbol table, go search it using
287 a binary search. Note that a minimal symbol table always consists
288 of at least two symbols, a "real" symbol and the terminating
289 "null symbol". If there are no real symbols, then there is no
290 minimal symbol table at all. */
292 if ((msymbol = objfile -> msymbols) != NULL)
295 hi = objfile -> minimal_symbol_count - 1;
297 /* This code assumes that the minimal symbols are sorted by
298 ascending address values. If the pc value is greater than or
299 equal to the first symbol's address, then some symbol in this
300 minimal symbol table is a suitable candidate for being the
301 "best" symbol. This includes the last real symbol, for cases
302 where the pc value is larger than any address in this vector.
304 By iterating until the address associated with the current
305 hi index (the endpoint of the test interval) is less than
306 or equal to the desired pc value, we accomplish two things:
307 (1) the case where the pc value is larger than any minimal
308 symbol address is trivially solved, (2) the address associated
309 with the hi index is always the one we want when the interation
310 terminates. In essence, we are iterating the test interval
311 down until the pc value is pushed out of it from the high end.
313 Warning: this code is trickier than it would appear at first. */
315 /* Intentionally does not check that pc <= start of objfile.
316 dbxread.c:process_one_symbol wants to call this with zero and
317 get the first minimal symbol. */
318 if (pc < SYMBOL_VALUE_ADDRESS (&msymbol[hi]))
320 while (SYMBOL_VALUE_ADDRESS (&msymbol[lo]) <= pc)
322 /* pc is still strictly less than highest address */
323 /* Note "new" will always be >= lo */
325 if ((SYMBOL_VALUE_ADDRESS (&msymbol[new]) < pc) ||
335 /* The minimal symbol indexed by hi now is the best one in this
336 objfile's minimal symbol table. See if it is the best one
339 if ((best_symbol == NULL) ||
340 (SYMBOL_VALUE_ADDRESS (best_symbol) >
341 SYMBOL_VALUE_ADDRESS (&msymbol[lo])))
343 best_symbol = &msymbol[lo];
348 return (best_symbol);
351 /* Prepare to start collecting minimal symbols. Note that presetting
352 msym_bunch_index to BUNCH_SIZE causes the first call to save a minimal
353 symbol to allocate the memory for the first bunch. */
356 init_minimal_symbol_collection ()
360 msym_bunch_index = BUNCH_SIZE;
364 prim_record_minimal_symbol (name, address, ms_type)
367 enum minimal_symbol_type ms_type;
369 register struct msym_bunch *new;
370 register struct minimal_symbol *msymbol;
372 if (msym_bunch_index == BUNCH_SIZE)
374 new = (struct msym_bunch *) xmalloc (sizeof (struct msym_bunch));
375 msym_bunch_index = 0;
376 new -> next = msym_bunch;
379 msymbol = &msym_bunch -> contents[msym_bunch_index];
380 SYMBOL_NAME (msymbol) = (char *) name;
381 SYMBOL_INIT_LANGUAGE_SPECIFIC (msymbol, language_unknown);
382 SYMBOL_VALUE_ADDRESS (msymbol) = address;
383 SYMBOL_SECTION (msymbol) = -1;
384 MSYMBOL_TYPE (msymbol) = ms_type;
385 /* FIXME: This info, if it remains, needs its own field. */
386 MSYMBOL_INFO (msymbol) = NULL; /* FIXME! */
391 /* FIXME: Why don't we just combine this function with the one above
392 and pass it a NULL info pointer value if info is not needed? */
395 prim_record_minimal_symbol_and_info (name, address, ms_type, info, section)
398 enum minimal_symbol_type ms_type;
402 register struct msym_bunch *new;
403 register struct minimal_symbol *msymbol;
405 if (msym_bunch_index == BUNCH_SIZE)
407 new = (struct msym_bunch *) xmalloc (sizeof (struct msym_bunch));
408 msym_bunch_index = 0;
409 new -> next = msym_bunch;
412 msymbol = &msym_bunch -> contents[msym_bunch_index];
413 SYMBOL_NAME (msymbol) = (char *) name;
414 SYMBOL_INIT_LANGUAGE_SPECIFIC (msymbol, language_unknown);
415 SYMBOL_VALUE_ADDRESS (msymbol) = address;
416 SYMBOL_SECTION (msymbol) = section;
417 MSYMBOL_TYPE (msymbol) = ms_type;
418 /* FIXME: This info, if it remains, needs its own field. */
419 MSYMBOL_INFO (msymbol) = info; /* FIXME! */
424 /* Compare two minimal symbols by address and return a signed result based
425 on unsigned comparisons, so that we sort into unsigned numeric order. */
428 compare_minimal_symbols (fn1p, fn2p)
432 register const struct minimal_symbol *fn1;
433 register const struct minimal_symbol *fn2;
435 fn1 = (const struct minimal_symbol *) fn1p;
436 fn2 = (const struct minimal_symbol *) fn2p;
438 if (SYMBOL_VALUE_ADDRESS (fn1) < SYMBOL_VALUE_ADDRESS (fn2))
442 else if (SYMBOL_VALUE_ADDRESS (fn1) > SYMBOL_VALUE_ADDRESS (fn2))
452 /* Discard the currently collected minimal symbols, if any. If we wish
453 to save them for later use, we must have already copied them somewhere
454 else before calling this function.
456 FIXME: We could allocate the minimal symbol bunches on their own
457 obstack and then simply blow the obstack away when we are done with
458 it. Is it worth the extra trouble though? */
462 discard_minimal_symbols (foo)
465 register struct msym_bunch *next;
467 while (msym_bunch != NULL)
469 next = msym_bunch -> next;
470 free ((PTR)msym_bunch);
475 /* Compact duplicate entries out of a minimal symbol table by walking
476 through the table and compacting out entries with duplicate addresses
477 and matching names. Return the number of entries remaining.
479 On entry, the table resides between msymbol[0] and msymbol[mcount].
480 On exit, it resides between msymbol[0] and msymbol[result_count].
482 When files contain multiple sources of symbol information, it is
483 possible for the minimal symbol table to contain many duplicate entries.
484 As an example, SVR4 systems use ELF formatted object files, which
485 usually contain at least two different types of symbol tables (a
486 standard ELF one and a smaller dynamic linking table), as well as
487 DWARF debugging information for files compiled with -g.
489 Without compacting, the minimal symbol table for gdb itself contains
490 over a 1000 duplicates, about a third of the total table size. Aside
491 from the potential trap of not noticing that two successive entries
492 identify the same location, this duplication impacts the time required
493 to linearly scan the table, which is done in a number of places. So we
494 just do one linear scan here and toss out the duplicates.
496 Note that we are not concerned here about recovering the space that
497 is potentially freed up, because the strings themselves are allocated
498 on the symbol_obstack, and will get automatically freed when the symbol
499 table is freed. The caller can free up the unused minimal symbols at
500 the end of the compacted region if their allocation strategy allows it.
502 Also note we only go up to the next to last entry within the loop
503 and then copy the last entry explicitly after the loop terminates.
505 Since the different sources of information for each symbol may
506 have different levels of "completeness", we may have duplicates
507 that have one entry with type "mst_unknown" and the other with a
508 known type. So if the one we are leaving alone has type mst_unknown,
509 overwrite its type with the type from the one we are compacting out. */
512 compact_minimal_symbols (msymbol, mcount)
513 struct minimal_symbol *msymbol;
516 struct minimal_symbol *copyfrom;
517 struct minimal_symbol *copyto;
521 copyfrom = copyto = msymbol;
522 while (copyfrom < msymbol + mcount - 1)
524 if (SYMBOL_VALUE_ADDRESS (copyfrom) ==
525 SYMBOL_VALUE_ADDRESS ((copyfrom + 1)) &&
526 (STREQ (SYMBOL_NAME (copyfrom), SYMBOL_NAME ((copyfrom + 1)))))
528 if (MSYMBOL_TYPE((copyfrom + 1)) == mst_unknown)
530 MSYMBOL_TYPE ((copyfrom + 1)) = MSYMBOL_TYPE (copyfrom);
536 *copyto++ = *copyfrom++;
539 *copyto++ = *copyfrom++;
540 mcount = copyto - msymbol;
545 /* Add the minimal symbols in the existing bunches to the objfile's official
546 minimal symbol table. In most cases there is no minimal symbol table yet
547 for this objfile, and the existing bunches are used to create one. Once
548 in a while (for shared libraries for example), we add symbols (e.g. common
549 symbols) to an existing objfile.
551 Because of the way minimal symbols are collected, we generally have no way
552 of knowing what source language applies to any particular minimal symbol.
553 Specifically, we have no way of knowing if the minimal symbol comes from a
554 C++ compilation unit or not. So for the sake of supporting cached
555 demangled C++ names, we have no choice but to try and demangle each new one
556 that comes in. If the demangling succeeds, then we assume it is a C++
557 symbol and set the symbol's language and demangled name fields
558 appropriately. Note that in order to avoid unnecessary demanglings, and
559 allocating obstack space that subsequently can't be freed for the demangled
560 names, we mark all newly added symbols with language_auto. After
561 compaction of the minimal symbols, we go back and scan the entire minimal
562 symbol table looking for these new symbols. For each new symbol we attempt
563 to demangle it, and if successful, record it as a language_cplus symbol
564 and cache the demangled form on the symbol obstack. Symbols which don't
565 demangle are marked as language_unknown symbols, which inhibits future
566 attempts to demangle them if we later add more minimal symbols. */
569 install_minimal_symbols (objfile)
570 struct objfile *objfile;
574 register struct msym_bunch *bunch;
575 register struct minimal_symbol *msymbols;
577 register char leading_char;
581 /* Allocate enough space in the obstack, into which we will gather the
582 bunches of new and existing minimal symbols, sort them, and then
583 compact out the duplicate entries. Once we have a final table,
584 we will give back the excess space. */
586 alloc_count = msym_count + objfile->minimal_symbol_count + 1;
587 obstack_blank (&objfile->symbol_obstack,
588 alloc_count * sizeof (struct minimal_symbol));
589 msymbols = (struct minimal_symbol *)
590 obstack_base (&objfile->symbol_obstack);
592 /* Copy in the existing minimal symbols, if there are any. */
594 if (objfile->minimal_symbol_count)
595 memcpy ((char *)msymbols, (char *)objfile->msymbols,
596 objfile->minimal_symbol_count * sizeof (struct minimal_symbol));
598 /* Walk through the list of minimal symbol bunches, adding each symbol
599 to the new contiguous array of symbols. Note that we start with the
600 current, possibly partially filled bunch (thus we use the current
601 msym_bunch_index for the first bunch we copy over), and thereafter
602 each bunch is full. */
604 mcount = objfile->minimal_symbol_count;
605 leading_char = bfd_get_symbol_leading_char (objfile->obfd);
607 for (bunch = msym_bunch; bunch != NULL; bunch = bunch -> next)
609 for (bindex = 0; bindex < msym_bunch_index; bindex++, mcount++)
611 msymbols[mcount] = bunch -> contents[bindex];
612 SYMBOL_LANGUAGE (&msymbols[mcount]) = language_auto;
613 if (SYMBOL_NAME (&msymbols[mcount])[0] == leading_char)
615 SYMBOL_NAME(&msymbols[mcount])++;
618 msym_bunch_index = BUNCH_SIZE;
621 /* Sort the minimal symbols by address. */
623 qsort (msymbols, mcount, sizeof (struct minimal_symbol),
624 compare_minimal_symbols);
626 /* Compact out any duplicates, and free up whatever space we are
629 mcount = compact_minimal_symbols (msymbols, mcount);
631 obstack_blank (&objfile->symbol_obstack,
632 (mcount + 1 - alloc_count) * sizeof (struct minimal_symbol));
633 msymbols = (struct minimal_symbol *)
634 obstack_finish (&objfile->symbol_obstack);
636 /* We also terminate the minimal symbol table with a "null symbol",
637 which is *not* included in the size of the table. This makes it
638 easier to find the end of the table when we are handed a pointer
639 to some symbol in the middle of it. Zero out the fields in the
640 "null symbol" allocated at the end of the array. Note that the
641 symbol count does *not* include this null symbol, which is why it
642 is indexed by mcount and not mcount-1. */
644 SYMBOL_NAME (&msymbols[mcount]) = NULL;
645 SYMBOL_VALUE_ADDRESS (&msymbols[mcount]) = 0;
646 MSYMBOL_INFO (&msymbols[mcount]) = NULL;
647 MSYMBOL_TYPE (&msymbols[mcount]) = mst_unknown;
648 SYMBOL_INIT_LANGUAGE_SPECIFIC (&msymbols[mcount], language_unknown);
650 /* Attach the minimal symbol table to the specified objfile.
651 The strings themselves are also located in the symbol_obstack
654 objfile -> minimal_symbol_count = mcount;
655 objfile -> msymbols = msymbols;
657 /* Now walk through all the minimal symbols, selecting the newly added
658 ones and attempting to cache their C++ demangled names. */
660 for ( ; mcount-- > 0 ; msymbols++)
662 SYMBOL_INIT_DEMANGLED_NAME (msymbols, &objfile->symbol_obstack);