1 /* GDB routines for manipulating the minimal symbol tables.
2 Copyright 1992, 1993, 1994 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. */
48 /* Accumulate the minimal symbols for each objfile in bunches of BUNCH_SIZE.
49 At the end, copy them all into one newly allocated location on an objfile's
52 #define BUNCH_SIZE 127
56 struct msym_bunch
*next
;
57 struct minimal_symbol contents
[BUNCH_SIZE
];
60 /* Bunch currently being filled up.
61 The next field points to chain of filled bunches. */
63 static struct msym_bunch
*msym_bunch
;
65 /* Number of slots filled in current bunch. */
67 static int msym_bunch_index
;
69 /* Total number of minimal symbols recorded so far for the objfile. */
71 static int msym_count
;
73 /* Prototypes for local functions. */
76 compare_minimal_symbols
PARAMS ((const void *, const void *));
79 compact_minimal_symbols
PARAMS ((struct minimal_symbol
*, int));
81 /* Look through all the current minimal symbol tables and find the first
82 minimal symbol that matches NAME. If OBJF is non-NULL, it specifies a
83 particular objfile and the search is limited to that objfile. Returns
84 a pointer to the minimal symbol that matches, or NULL if no match is found.
86 Note: One instance where there may be duplicate minimal symbols with
87 the same name is when the symbol tables for a shared library and the
88 symbol tables for an executable contain global symbols with the same
89 names (the dynamic linker deals with the duplication). */
91 struct minimal_symbol
*
92 lookup_minimal_symbol (name
, objf
)
93 register const char *name
;
96 struct objfile
*objfile
;
97 struct minimal_symbol
*msymbol
;
98 struct minimal_symbol
*found_symbol
= NULL
;
99 struct minimal_symbol
*found_file_symbol
= NULL
;
100 struct minimal_symbol
*trampoline_symbol
= NULL
;
102 for (objfile
= object_files
;
103 objfile
!= NULL
&& found_symbol
== NULL
;
104 objfile
= objfile
-> next
)
106 if (objf
== NULL
|| objf
== objfile
)
108 for (msymbol
= objfile
-> msymbols
;
109 msymbol
!= NULL
&& SYMBOL_NAME (msymbol
) != NULL
&&
110 found_symbol
== NULL
;
113 if (SYMBOL_MATCHES_NAME (msymbol
, name
))
115 switch (MSYMBOL_TYPE (msymbol
))
120 /* It is file-local. If we find more than one, just
121 return the latest one (the user can't expect
122 useful behavior in that case). */
123 found_file_symbol
= msymbol
;
126 case mst_solib_trampoline
:
128 /* If a trampoline symbol is found, we prefer to
129 keep looking for the *real* symbol. If the
130 actual symbol is not found, then we'll use the
132 if (trampoline_symbol
== NULL
)
133 trampoline_symbol
= msymbol
;
138 found_symbol
= msymbol
;
145 /* External symbols are best. */
149 /* File-local symbols are next best. */
150 if (found_file_symbol
)
151 return found_file_symbol
;
153 /* Symbols for shared library trampolines are next best. */
154 if (trampoline_symbol
)
155 return trampoline_symbol
;
161 /* Search through the minimal symbol table for each objfile and find the
162 symbol whose address is the largest address that is still less than or
163 equal to PC. Returns a pointer to the minimal symbol if such a symbol
164 is found, or NULL if PC is not in a suitable range. Note that we need
165 to look through ALL the minimal symbol tables before deciding on the
166 symbol that comes closest to the specified PC. This is because objfiles
167 can overlap, for example objfile A has .text at 0x100 and .data at 0x40000
168 and objfile B has .text at 0x234 and .data at 0x40048. */
170 struct minimal_symbol
*
171 lookup_minimal_symbol_by_pc (pc
)
172 register CORE_ADDR pc
;
177 register struct objfile
*objfile
;
178 register struct minimal_symbol
*msymbol
;
179 register struct minimal_symbol
*best_symbol
= NULL
;
181 for (objfile
= object_files
;
183 objfile
= objfile
-> next
)
185 /* If this objfile has a minimal symbol table, go search it using
186 a binary search. Note that a minimal symbol table always consists
187 of at least two symbols, a "real" symbol and the terminating
188 "null symbol". If there are no real symbols, then there is no
189 minimal symbol table at all. */
191 if ((msymbol
= objfile
-> msymbols
) != NULL
)
194 hi
= objfile
-> minimal_symbol_count
- 1;
196 /* This code assumes that the minimal symbols are sorted by
197 ascending address values. If the pc value is greater than or
198 equal to the first symbol's address, then some symbol in this
199 minimal symbol table is a suitable candidate for being the
200 "best" symbol. This includes the last real symbol, for cases
201 where the pc value is larger than any address in this vector.
203 By iterating until the address associated with the current
204 hi index (the endpoint of the test interval) is less than
205 or equal to the desired pc value, we accomplish two things:
206 (1) the case where the pc value is larger than any minimal
207 symbol address is trivially solved, (2) the address associated
208 with the hi index is always the one we want when the interation
209 terminates. In essence, we are iterating the test interval
210 down until the pc value is pushed out of it from the high end.
212 Warning: this code is trickier than it would appear at first. */
214 /* Should also requires that pc is <= end of objfile. FIXME! */
215 if (pc
>= SYMBOL_VALUE_ADDRESS (&msymbol
[lo
]))
217 while (SYMBOL_VALUE_ADDRESS (&msymbol
[hi
]) > pc
)
219 /* pc is still strictly less than highest address */
220 /* Note "new" will always be >= lo */
222 if ((SYMBOL_VALUE_ADDRESS (&msymbol
[new]) >= pc
) ||
232 /* The minimal symbol indexed by hi now is the best one in this
233 objfile's minimal symbol table. See if it is the best one
236 /* Skip any absolute symbols. This is apparently what adb
237 and dbx do, and is needed for the CM-5. There are two
238 known possible problems: (1) on ELF, apparently end, edata,
239 etc. are absolute. Not sure ignoring them here is a big
240 deal, but if we want to use them, the fix would go in
241 elfread.c. (2) I think shared library entry points on the
242 NeXT are absolute. If we want special handling for this
243 it probably should be triggered by a special
244 mst_abs_or_lib or some such. */
246 && msymbol
[hi
].type
== mst_abs
)
250 && ((best_symbol
== NULL
) ||
251 (SYMBOL_VALUE_ADDRESS (best_symbol
) <
252 SYMBOL_VALUE_ADDRESS (&msymbol
[hi
]))))
254 best_symbol
= &msymbol
[hi
];
259 return (best_symbol
);
262 /* Prepare to start collecting minimal symbols. Note that presetting
263 msym_bunch_index to BUNCH_SIZE causes the first call to save a minimal
264 symbol to allocate the memory for the first bunch. */
267 init_minimal_symbol_collection ()
271 msym_bunch_index
= BUNCH_SIZE
;
275 prim_record_minimal_symbol (name
, address
, ms_type
, objfile
)
278 enum minimal_symbol_type ms_type
;
279 struct objfile
*objfile
;
281 prim_record_minimal_symbol_and_info (name
, address
, ms_type
,
286 prim_record_minimal_symbol_and_info (name
, address
, ms_type
, info
, section
,
290 enum minimal_symbol_type ms_type
;
293 struct objfile
*objfile
;
295 register struct msym_bunch
*new;
296 register struct minimal_symbol
*msymbol
;
298 if (ms_type
== mst_file_text
)
300 /* Don't put gcc_compiled, __gnu_compiled_cplus, and friends into
301 the minimal symbols, because if there is also another symbol
302 at the same address (e.g. the first function of the file),
303 lookup_minimal_symbol_by_pc would have no way of getting the
306 && (strcmp (name
, GCC_COMPILED_FLAG_SYMBOL
) == 0
307 || strcmp (name
, GCC2_COMPILED_FLAG_SYMBOL
) == 0))
311 const char *tempstring
= name
;
312 if (tempstring
[0] == bfd_get_symbol_leading_char (objfile
->obfd
))
314 if (STREQN (tempstring
, "__gnu_compiled", 14))
319 if (msym_bunch_index
== BUNCH_SIZE
)
321 new = (struct msym_bunch
*) xmalloc (sizeof (struct msym_bunch
));
322 msym_bunch_index
= 0;
323 new -> next
= msym_bunch
;
326 msymbol
= &msym_bunch
-> contents
[msym_bunch_index
];
327 SYMBOL_NAME (msymbol
) = (char *) name
;
328 SYMBOL_INIT_LANGUAGE_SPECIFIC (msymbol
, language_unknown
);
329 SYMBOL_VALUE_ADDRESS (msymbol
) = address
;
330 SYMBOL_SECTION (msymbol
) = section
;
331 MSYMBOL_TYPE (msymbol
) = ms_type
;
332 /* FIXME: This info, if it remains, needs its own field. */
333 MSYMBOL_INFO (msymbol
) = info
; /* FIXME! */
338 /* Compare two minimal symbols by address and return a signed result based
339 on unsigned comparisons, so that we sort into unsigned numeric order. */
342 compare_minimal_symbols (fn1p
, fn2p
)
346 register const struct minimal_symbol
*fn1
;
347 register const struct minimal_symbol
*fn2
;
349 fn1
= (const struct minimal_symbol
*) fn1p
;
350 fn2
= (const struct minimal_symbol
*) fn2p
;
352 if (SYMBOL_VALUE_ADDRESS (fn1
) < SYMBOL_VALUE_ADDRESS (fn2
))
356 else if (SYMBOL_VALUE_ADDRESS (fn1
) > SYMBOL_VALUE_ADDRESS (fn2
))
366 /* Discard the currently collected minimal symbols, if any. If we wish
367 to save them for later use, we must have already copied them somewhere
368 else before calling this function.
370 FIXME: We could allocate the minimal symbol bunches on their own
371 obstack and then simply blow the obstack away when we are done with
372 it. Is it worth the extra trouble though? */
376 discard_minimal_symbols (foo
)
379 register struct msym_bunch
*next
;
381 while (msym_bunch
!= NULL
)
383 next
= msym_bunch
-> next
;
384 free ((PTR
)msym_bunch
);
389 /* Compact duplicate entries out of a minimal symbol table by walking
390 through the table and compacting out entries with duplicate addresses
391 and matching names. Return the number of entries remaining.
393 On entry, the table resides between msymbol[0] and msymbol[mcount].
394 On exit, it resides between msymbol[0] and msymbol[result_count].
396 When files contain multiple sources of symbol information, it is
397 possible for the minimal symbol table to contain many duplicate entries.
398 As an example, SVR4 systems use ELF formatted object files, which
399 usually contain at least two different types of symbol tables (a
400 standard ELF one and a smaller dynamic linking table), as well as
401 DWARF debugging information for files compiled with -g.
403 Without compacting, the minimal symbol table for gdb itself contains
404 over a 1000 duplicates, about a third of the total table size. Aside
405 from the potential trap of not noticing that two successive entries
406 identify the same location, this duplication impacts the time required
407 to linearly scan the table, which is done in a number of places. So we
408 just do one linear scan here and toss out the duplicates.
410 Note that we are not concerned here about recovering the space that
411 is potentially freed up, because the strings themselves are allocated
412 on the symbol_obstack, and will get automatically freed when the symbol
413 table is freed. The caller can free up the unused minimal symbols at
414 the end of the compacted region if their allocation strategy allows it.
416 Also note we only go up to the next to last entry within the loop
417 and then copy the last entry explicitly after the loop terminates.
419 Since the different sources of information for each symbol may
420 have different levels of "completeness", we may have duplicates
421 that have one entry with type "mst_unknown" and the other with a
422 known type. So if the one we are leaving alone has type mst_unknown,
423 overwrite its type with the type from the one we are compacting out. */
426 compact_minimal_symbols (msymbol
, mcount
)
427 struct minimal_symbol
*msymbol
;
430 struct minimal_symbol
*copyfrom
;
431 struct minimal_symbol
*copyto
;
435 copyfrom
= copyto
= msymbol
;
436 while (copyfrom
< msymbol
+ mcount
- 1)
438 if (SYMBOL_VALUE_ADDRESS (copyfrom
) ==
439 SYMBOL_VALUE_ADDRESS ((copyfrom
+ 1)) &&
440 (STREQ (SYMBOL_NAME (copyfrom
), SYMBOL_NAME ((copyfrom
+ 1)))))
442 if (MSYMBOL_TYPE((copyfrom
+ 1)) == mst_unknown
)
444 MSYMBOL_TYPE ((copyfrom
+ 1)) = MSYMBOL_TYPE (copyfrom
);
450 *copyto
++ = *copyfrom
++;
453 *copyto
++ = *copyfrom
++;
454 mcount
= copyto
- msymbol
;
459 /* Add the minimal symbols in the existing bunches to the objfile's official
460 minimal symbol table. In most cases there is no minimal symbol table yet
461 for this objfile, and the existing bunches are used to create one. Once
462 in a while (for shared libraries for example), we add symbols (e.g. common
463 symbols) to an existing objfile.
465 Because of the way minimal symbols are collected, we generally have no way
466 of knowing what source language applies to any particular minimal symbol.
467 Specifically, we have no way of knowing if the minimal symbol comes from a
468 C++ compilation unit or not. So for the sake of supporting cached
469 demangled C++ names, we have no choice but to try and demangle each new one
470 that comes in. If the demangling succeeds, then we assume it is a C++
471 symbol and set the symbol's language and demangled name fields
472 appropriately. Note that in order to avoid unnecessary demanglings, and
473 allocating obstack space that subsequently can't be freed for the demangled
474 names, we mark all newly added symbols with language_auto. After
475 compaction of the minimal symbols, we go back and scan the entire minimal
476 symbol table looking for these new symbols. For each new symbol we attempt
477 to demangle it, and if successful, record it as a language_cplus symbol
478 and cache the demangled form on the symbol obstack. Symbols which don't
479 demangle are marked as language_unknown symbols, which inhibits future
480 attempts to demangle them if we later add more minimal symbols. */
483 install_minimal_symbols (objfile
)
484 struct objfile
*objfile
;
488 register struct msym_bunch
*bunch
;
489 register struct minimal_symbol
*msymbols
;
491 register char leading_char
;
495 /* Allocate enough space in the obstack, into which we will gather the
496 bunches of new and existing minimal symbols, sort them, and then
497 compact out the duplicate entries. Once we have a final table,
498 we will give back the excess space. */
500 alloc_count
= msym_count
+ objfile
->minimal_symbol_count
+ 1;
501 obstack_blank (&objfile
->symbol_obstack
,
502 alloc_count
* sizeof (struct minimal_symbol
));
503 msymbols
= (struct minimal_symbol
*)
504 obstack_base (&objfile
->symbol_obstack
);
506 /* Copy in the existing minimal symbols, if there are any. */
508 if (objfile
->minimal_symbol_count
)
509 memcpy ((char *)msymbols
, (char *)objfile
->msymbols
,
510 objfile
->minimal_symbol_count
* sizeof (struct minimal_symbol
));
512 /* Walk through the list of minimal symbol bunches, adding each symbol
513 to the new contiguous array of symbols. Note that we start with the
514 current, possibly partially filled bunch (thus we use the current
515 msym_bunch_index for the first bunch we copy over), and thereafter
516 each bunch is full. */
518 mcount
= objfile
->minimal_symbol_count
;
519 leading_char
= bfd_get_symbol_leading_char (objfile
->obfd
);
521 for (bunch
= msym_bunch
; bunch
!= NULL
; bunch
= bunch
-> next
)
523 for (bindex
= 0; bindex
< msym_bunch_index
; bindex
++, mcount
++)
525 msymbols
[mcount
] = bunch
-> contents
[bindex
];
526 SYMBOL_LANGUAGE (&msymbols
[mcount
]) = language_auto
;
527 if (SYMBOL_NAME (&msymbols
[mcount
])[0] == leading_char
)
529 SYMBOL_NAME(&msymbols
[mcount
])++;
532 msym_bunch_index
= BUNCH_SIZE
;
535 /* Sort the minimal symbols by address. */
537 qsort (msymbols
, mcount
, sizeof (struct minimal_symbol
),
538 compare_minimal_symbols
);
540 /* Compact out any duplicates, and free up whatever space we are
543 mcount
= compact_minimal_symbols (msymbols
, mcount
);
545 obstack_blank (&objfile
->symbol_obstack
,
546 (mcount
+ 1 - alloc_count
) * sizeof (struct minimal_symbol
));
547 msymbols
= (struct minimal_symbol
*)
548 obstack_finish (&objfile
->symbol_obstack
);
550 /* We also terminate the minimal symbol table with a "null symbol",
551 which is *not* included in the size of the table. This makes it
552 easier to find the end of the table when we are handed a pointer
553 to some symbol in the middle of it. Zero out the fields in the
554 "null symbol" allocated at the end of the array. Note that the
555 symbol count does *not* include this null symbol, which is why it
556 is indexed by mcount and not mcount-1. */
558 SYMBOL_NAME (&msymbols
[mcount
]) = NULL
;
559 SYMBOL_VALUE_ADDRESS (&msymbols
[mcount
]) = 0;
560 MSYMBOL_INFO (&msymbols
[mcount
]) = NULL
;
561 MSYMBOL_TYPE (&msymbols
[mcount
]) = mst_unknown
;
562 SYMBOL_INIT_LANGUAGE_SPECIFIC (&msymbols
[mcount
], language_unknown
);
564 /* Attach the minimal symbol table to the specified objfile.
565 The strings themselves are also located in the symbol_obstack
568 objfile
-> minimal_symbol_count
= mcount
;
569 objfile
-> msymbols
= msymbols
;
571 /* Now walk through all the minimal symbols, selecting the newly added
572 ones and attempting to cache their C++ demangled names. */
574 for ( ; mcount
-- > 0 ; msymbols
++)
576 SYMBOL_INIT_DEMANGLED_NAME (msymbols
, &objfile
->symbol_obstack
);