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. */
45 /* Accumulate the minimal symbols for each objfile in bunches of BUNCH_SIZE.
46 At the end, copy them all into one newly allocated location on an objfile's
49 #define BUNCH_SIZE 127
53 struct msym_bunch *next;
54 struct minimal_symbol contents[BUNCH_SIZE];
57 /* Bunch currently being filled up.
58 The next field points to chain of filled bunches. */
60 static struct msym_bunch *msym_bunch;
62 /* Number of slots filled in current bunch. */
64 static int msym_bunch_index;
66 /* Total number of minimal symbols recorded so far for the objfile. */
68 static int msym_count;
70 /* Prototypes for local functions. */
73 compare_minimal_symbols PARAMS ((const void *, const void *));
76 compact_minimal_symbols PARAMS ((struct minimal_symbol *, int));
78 /* Call the function specified by FUNC for each currently available minimal
79 symbol, for as long as this function continues to return NULL. If the
80 function ever returns non-NULL, then the iteration over the minimal
81 symbols is terminated and the result is returned to the caller.
83 The function called has full control over the form and content of the
84 information returned via the non-NULL result, which may be as simple as a
85 pointer to the minimal symbol that the iteration terminated on, or as
86 complex as a pointer to a private structure containing multiple results. */
89 iterate_over_msymbols (func, arg1, arg2, arg3)
90 PTR (*func) PARAMS ((struct objfile *, struct minimal_symbol *,
96 register struct objfile *objfile;
97 register struct minimal_symbol *msymbol;
100 for (objfile = object_files;
101 objfile != NULL && result == NULL;
102 objfile = objfile -> next)
104 for (msymbol = objfile -> msymbols;
105 msymbol != NULL && msymbol -> name != NULL && result == NULL;
108 result = (*func)(objfile, msymbol, arg1, arg2, arg3);
114 /* Look through all the current minimal symbol tables and find the first
115 minimal symbol that matches NAME. If OBJF is non-NULL, it specifies a
116 particular objfile and the search is limited to that objfile. Returns
117 a pointer to the minimal symbol that matches, or NULL if no match is found.
119 Note: One instance where there may be duplicate minimal symbols with
120 the same name is when the symbol tables for a shared library and the
121 symbol tables for an executable contain global symbols with the same
122 names (the dynamic linker deals with the duplication). */
124 struct minimal_symbol *
125 lookup_minimal_symbol (name, objf)
126 register const char *name;
127 struct objfile *objf;
129 struct objfile *objfile;
130 struct minimal_symbol *msymbol;
131 struct minimal_symbol *found_symbol = NULL;
133 struct minimal_symbol *trampoline_symbol = NULL;
136 for (objfile = object_files;
137 objfile != NULL && found_symbol == NULL;
138 objfile = objfile -> next)
140 if (objf == NULL || objf == objfile)
142 for (msymbol = objfile -> msymbols;
143 msymbol != NULL && msymbol -> name != NULL &&
144 found_symbol == NULL;
147 if (strcmp (msymbol -> name, name) == 0)
149 /* I *think* all platforms using shared libraries (and trampoline code)
150 * will suffer this problem. Consider a case where there are 5 shared
151 * libraries, each referencing `foo' with a trampoline entry. When someone
152 * wants to put a breakpoint on `foo' and the only info we have is minimal
153 * symbol vector, we want to use the real `foo', rather than one of those
154 * trampoline entries. MGO */
156 /* If a trampoline symbol is found, we prefer to keep looking
157 for the *real* symbol. If the actual symbol not found,
158 then we'll use the trampoline entry. Sorry for the machine
159 dependent code here, but I hope this will benefit other
160 platforms as well. For trampoline entries, we used mst_unknown
161 earlier. Perhaps we should define a `mst_trampoline' type?? */
163 if (msymbol->type != mst_unknown)
164 found_symbol = msymbol;
165 else if (msymbol->type == mst_unknown && !trampoline_symbol)
166 trampoline_symbol = msymbol;
169 found_symbol = msymbol;
176 return found_symbol ? found_symbol : trampoline_symbol;
179 return (found_symbol);
183 /* Search through the minimal symbol table for each objfile and find the
184 symbol whose address is the largest address that is still less than or
185 equal to PC. Returns a pointer to the minimal symbol if such a symbol
186 is found, or NULL if PC is not in a suitable range. Note that we need
187 to look through ALL the minimal symbol tables before deciding on the
188 symbol that comes closest to the specified PC. */
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 - 2;
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 if (pc >= msymbol[lo].address)
236 while (msymbol[hi].address > pc)
238 /* pc is still strictly less than highest address */
239 /* Note "new" will always be >= lo */
241 if ((msymbol[new].address >= pc) || (lo == new))
250 /* The minimal symbol indexed by hi now is the best one in this
251 objfile's minimal symbol table. See if it is the best one
254 if ((best_symbol == NULL) ||
255 (best_symbol -> address < msymbol[hi].address))
257 best_symbol = &msymbol[hi];
262 return (best_symbol);
265 /* Prepare to start collecting minimal symbols. Note that presetting
266 msym_bunch_index to BUNCH_SIZE causes the first call to save a minimal
267 symbol to allocate the memory for the first bunch. */
270 init_minimal_symbol_collection ()
274 msym_bunch_index = BUNCH_SIZE;
278 prim_record_minimal_symbol (name, address, ms_type)
281 enum minimal_symbol_type ms_type;
283 register struct msym_bunch *new;
285 if (msym_bunch_index == BUNCH_SIZE)
287 new = (struct msym_bunch *) xmalloc (sizeof (struct msym_bunch));
288 msym_bunch_index = 0;
289 new -> next = msym_bunch;
292 msym_bunch -> contents[msym_bunch_index].name = (char *) name;
293 msym_bunch -> contents[msym_bunch_index].address = address;
294 msym_bunch -> contents[msym_bunch_index].info = NULL;
295 msym_bunch -> contents[msym_bunch_index].type = ms_type;
300 /* Compare two minimal symbols by address and return a signed result based
301 on unsigned comparisons, so that we sort into unsigned numeric order. */
304 compare_minimal_symbols (fn1p, fn2p)
308 register const struct minimal_symbol *fn1;
309 register const struct minimal_symbol *fn2;
311 fn1 = (const struct minimal_symbol *) fn1p;
312 fn2 = (const struct minimal_symbol *) fn2p;
314 if (fn1 -> address < fn2 -> address)
318 else if (fn1 -> address > fn2 -> address)
328 /* Discard the currently collected minimal symbols, if any. If we wish
329 to save them for later use, we must have already copied them somewhere
330 else before calling this function.
332 FIXME: We could allocate the minimal symbol bunches on their own
333 obstack and then simply blow the obstack away when we are done with
334 it. Is it worth the extra trouble though? */
338 discard_minimal_symbols (foo)
341 register struct msym_bunch *next;
343 while (msym_bunch != NULL)
345 next = msym_bunch -> next;
351 /* Compact duplicate entries out of a minimal symbol table by walking
352 through the table and compacting out entries with duplicate addresses
353 and matching names. Return the number of entries remaining.
355 On entry, the table resides between msymbol[0] and msymbol[mcount].
356 On exit, it resides between msymbol[0] and msymbol[result_count].
358 When files contain multiple sources of symbol information, it is
359 possible for the minimal symbol table to contain many duplicate entries.
360 As an example, SVR4 systems use ELF formatted object files, which
361 usually contain at least two different types of symbol tables (a
362 standard ELF one and a smaller dynamic linking table), as well as
363 DWARF debugging information for files compiled with -g.
365 Without compacting, the minimal symbol table for gdb itself contains
366 over a 1000 duplicates, about a third of the total table size. Aside
367 from the potential trap of not noticing that two successive entries
368 identify the same location, this duplication impacts the time required
369 to linearly scan the table, which is done in a number of places. So we
370 just do one linear scan here and toss out the duplicates.
372 Note that we are not concerned here about recovering the space that
373 is potentially freed up, because the strings themselves are allocated
374 on the symbol_obstack, and will get automatically freed when the symbol
375 table is freed. The caller can free up the unused minimal symbols at
376 the end of the compacted region if their allocation strategy allows it.
378 Also note we only go up to the next to last entry within the loop
379 and then copy the last entry explicitly after the loop terminates.
381 Since the different sources of information for each symbol may
382 have different levels of "completeness", we may have duplicates
383 that have one entry with type "mst_unknown" and the other with a
384 known type. So if the one we are leaving alone has type mst_unknown,
385 overwrite its type with the type from the one we are compacting out. */
388 compact_minimal_symbols (msymbol, mcount)
389 struct minimal_symbol *msymbol;
392 struct minimal_symbol *copyfrom;
393 struct minimal_symbol *copyto;
397 copyfrom = copyto = msymbol;
398 while (copyfrom < msymbol + mcount - 1)
400 if (copyfrom -> address == (copyfrom + 1) -> address
401 && (strcmp (copyfrom -> name, (copyfrom + 1) -> name) == 0))
403 if ((copyfrom + 1) -> type == mst_unknown)
405 (copyfrom + 1) -> type = copyfrom -> type;
411 *copyto++ = *copyfrom++;
414 *copyto++ = *copyfrom++;
415 mcount = copyto - msymbol;
420 /* Add the minimal symbols in the existing bunches to the objfile's
421 official minimal symbol table. 99% of the time, this adds the
422 bunches to NO existing symbols. Once in a while for shared
423 libraries, we add symbols (e.g. common symbols) to an existing
427 install_minimal_symbols (objfile)
428 struct objfile *objfile;
432 register struct msym_bunch *bunch;
433 register struct minimal_symbol *msymbols;
438 /* Allocate enough space in the obstack, into which we will gather the
439 bunches of new and existing minimal symbols, sort them, and then
440 compact out the duplicate entries. Once we have a final table,
441 we will give back the excess space. */
443 alloc_count = msym_count + objfile->minimal_symbol_count + 1;
444 obstack_blank (&objfile->symbol_obstack,
445 alloc_count * sizeof (struct minimal_symbol));
446 msymbols = (struct minimal_symbol *)
447 obstack_base (&objfile->symbol_obstack);
449 /* Copy in the existing minimal symbols, if there are any. */
451 if (objfile->minimal_symbol_count)
452 memcpy ((char *)msymbols, (char *)objfile->msymbols,
453 objfile->minimal_symbol_count * sizeof (struct minimal_symbol));
455 /* Walk through the list of minimal symbol bunches, adding each symbol
456 to the new contiguous array of symbols. Note that we start with the
457 current, possibly partially filled bunch (thus we use the current
458 msym_bunch_index for the first bunch we copy over), and thereafter
459 each bunch is full. */
461 mcount = objfile->minimal_symbol_count;
463 for (bunch = msym_bunch; bunch != NULL; bunch = bunch -> next)
465 for (bindex = 0; bindex < msym_bunch_index; bindex++, mcount++)
467 msymbols[mcount] = bunch -> contents[bindex];
468 #ifdef NAMES_HAVE_UNDERSCORE
469 if (msymbols[mcount].name[0] == '_')
471 msymbols[mcount].name++;
474 #ifdef SOME_NAMES_HAVE_DOT
475 if (msymbols[mcount].name[0] == '.')
477 msymbols[mcount].name++;
481 msym_bunch_index = BUNCH_SIZE;
484 /* Sort the minimal symbols by address. */
486 qsort (msymbols, mcount, sizeof (struct minimal_symbol),
487 compare_minimal_symbols);
489 /* Compact out any duplicates, and free up whatever space we are
492 mcount = compact_minimal_symbols (msymbols, mcount);
494 obstack_blank (&objfile->symbol_obstack,
495 (mcount + 1 - alloc_count) * sizeof (struct minimal_symbol));
496 msymbols = (struct minimal_symbol *)
497 obstack_finish (&objfile->symbol_obstack);
499 /* We also terminate the minimal symbol table
500 with a "null symbol", which is *not* included in the size of
501 the table. This makes it easier to find the end of the table
502 when we are handed a pointer to some symbol in the middle of it.
503 Zero out the fields in the "null symbol" allocated at the end
504 of the array. Note that the symbol count does *not* include
505 this null symbol, which is why it is indexed by mcount and not
508 msymbols[mcount].name = NULL;
509 msymbols[mcount].address = 0;
510 msymbols[mcount].info = NULL;
511 msymbols[mcount].type = mst_unknown;
513 /* Attach the minimal symbol table to the specified objfile.
514 The strings themselves are also located in the symbol_obstack
517 objfile -> minimal_symbol_count = mcount;
518 objfile -> msymbols = msymbols;