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 #ifdef IBM6000_TARGET
101 struct minimal_symbol
*trampoline_symbol
= NULL
;
104 for (objfile
= object_files
;
105 objfile
!= NULL
&& found_symbol
== NULL
;
106 objfile
= objfile
-> next
)
108 if (objf
== NULL
|| objf
== objfile
)
110 for (msymbol
= objfile
-> msymbols
;
111 msymbol
!= NULL
&& SYMBOL_NAME (msymbol
) != NULL
&&
112 found_symbol
== NULL
;
115 if (SYMBOL_MATCHES_NAME (msymbol
, name
))
117 switch (MSYMBOL_TYPE (msymbol
))
122 /* It is file-local. If we find more than one, just
123 return the latest one (the user can't expect
124 useful behavior in that case). */
125 found_file_symbol
= msymbol
;
129 #ifdef IBM6000_TARGET
130 /* I *think* all platforms using shared
131 libraries (and trampoline code) will suffer
132 this problem. Consider a case where there are
133 5 shared libraries, each referencing `foo'
134 with a trampoline entry. When someone wants
135 to put a breakpoint on `foo' and the only
136 info we have is minimal symbol vector, we
137 want to use the real `foo', rather than one
138 of those trampoline entries. MGO */
140 /* If a trampoline symbol is found, we prefer to
141 keep looking for the *real* symbol. If the
142 actual symbol not found, then we'll use the
143 trampoline entry. Sorry for the machine
144 dependent code here, but I hope this will
145 benefit other platforms as well. For
146 trampoline entries, we used mst_unknown
147 earlier. Perhaps we should define a
148 `mst_trampoline' type?? */
150 if (trampoline_symbol
== NULL
)
151 trampoline_symbol
= msymbol
;
157 found_symbol
= msymbol
;
164 /* External symbols are best. */
168 /* File-local symbols are next best. */
169 if (found_file_symbol
)
170 return found_file_symbol
;
172 /* Symbols for IBM shared library trampolines are next best. */
173 #ifdef IBM6000_TARGET
174 if (trampoline_symbol
)
175 return trampoline_symbol
;
182 /* Search through the minimal symbol table for each objfile and find the
183 symbol whose address is the largest address that is still less than or
184 equal to PC. Returns a pointer to the minimal symbol if such a symbol
185 is found, or NULL if PC is not in a suitable range. Note that we need
186 to look through ALL the minimal symbol tables before deciding on the
187 symbol that comes closest to the specified PC. This is because objfiles
188 can overlap, for example objfile A has .text at 0x100 and .data at 0x40000
189 and objfile B has .text at 0x234 and .data at 0x40048. */
191 struct minimal_symbol
*
192 lookup_minimal_symbol_by_pc (pc
)
193 register CORE_ADDR pc
;
198 register struct objfile
*objfile
;
199 register struct minimal_symbol
*msymbol
;
200 register struct minimal_symbol
*best_symbol
= NULL
;
202 for (objfile
= object_files
;
204 objfile
= objfile
-> next
)
206 /* If this objfile has a minimal symbol table, go search it using
207 a binary search. Note that a minimal symbol table always consists
208 of at least two symbols, a "real" symbol and the terminating
209 "null symbol". If there are no real symbols, then there is no
210 minimal symbol table at all. */
212 if ((msymbol
= objfile
-> msymbols
) != NULL
)
215 hi
= objfile
-> minimal_symbol_count
- 1;
217 /* This code assumes that the minimal symbols are sorted by
218 ascending address values. If the pc value is greater than or
219 equal to the first symbol's address, then some symbol in this
220 minimal symbol table is a suitable candidate for being the
221 "best" symbol. This includes the last real symbol, for cases
222 where the pc value is larger than any address in this vector.
224 By iterating until the address associated with the current
225 hi index (the endpoint of the test interval) is less than
226 or equal to the desired pc value, we accomplish two things:
227 (1) the case where the pc value is larger than any minimal
228 symbol address is trivially solved, (2) the address associated
229 with the hi index is always the one we want when the interation
230 terminates. In essence, we are iterating the test interval
231 down until the pc value is pushed out of it from the high end.
233 Warning: this code is trickier than it would appear at first. */
235 /* Should also requires that pc is <= end of objfile. FIXME! */
236 if (pc
>= SYMBOL_VALUE_ADDRESS (&msymbol
[lo
]))
238 while (SYMBOL_VALUE_ADDRESS (&msymbol
[hi
]) > pc
)
240 /* pc is still strictly less than highest address */
241 /* Note "new" will always be >= lo */
243 if ((SYMBOL_VALUE_ADDRESS (&msymbol
[new]) >= pc
) ||
253 /* The minimal symbol indexed by hi now is the best one in this
254 objfile's minimal symbol table. See if it is the best one
257 /* Skip any absolute symbols. This is apparently what adb
258 and dbx do, and is needed for the CM-5. There are two
259 known possible problems: (1) on ELF, apparently end, edata,
260 etc. are absolute. Not sure ignoring them here is a big
261 deal, but if we want to use them, the fix would go in
262 elfread.c. (2) I think shared library entry points on the
263 NeXT are absolute. If we want special handling for this
264 it probably should be triggered by a special
265 mst_abs_or_lib or some such. */
267 && msymbol
[hi
].type
== mst_abs
)
271 && ((best_symbol
== NULL
) ||
272 (SYMBOL_VALUE_ADDRESS (best_symbol
) <
273 SYMBOL_VALUE_ADDRESS (&msymbol
[hi
]))))
275 best_symbol
= &msymbol
[hi
];
280 return (best_symbol
);
283 /* Prepare to start collecting minimal symbols. Note that presetting
284 msym_bunch_index to BUNCH_SIZE causes the first call to save a minimal
285 symbol to allocate the memory for the first bunch. */
288 init_minimal_symbol_collection ()
292 msym_bunch_index
= BUNCH_SIZE
;
296 prim_record_minimal_symbol (name
, address
, ms_type
, objfile
)
299 enum minimal_symbol_type ms_type
;
300 struct objfile
*objfile
;
302 prim_record_minimal_symbol_and_info (name
, address
, ms_type
,
307 prim_record_minimal_symbol_and_info (name
, address
, ms_type
, info
, section
,
311 enum minimal_symbol_type ms_type
;
314 struct objfile
*objfile
;
316 register struct msym_bunch
*new;
317 register struct minimal_symbol
*msymbol
;
319 if (ms_type
== mst_file_text
)
321 /* Don't put gcc_compiled, __gnu_compiled_cplus, and friends into
322 the minimal symbols, because if there is also another symbol
323 at the same address (e.g. the first function of the file),
324 lookup_minimal_symbol_by_pc would have no way of getting the
327 && (strcmp (name
, GCC_COMPILED_FLAG_SYMBOL
) == 0
328 || strcmp (name
, GCC2_COMPILED_FLAG_SYMBOL
) == 0))
332 const char *tempstring
= name
;
333 if (tempstring
[0] == bfd_get_symbol_leading_char (objfile
->obfd
))
335 if (STREQN (tempstring
, "__gnu_compiled", 14))
340 if (msym_bunch_index
== BUNCH_SIZE
)
342 new = (struct msym_bunch
*) xmalloc (sizeof (struct msym_bunch
));
343 msym_bunch_index
= 0;
344 new -> next
= msym_bunch
;
347 msymbol
= &msym_bunch
-> contents
[msym_bunch_index
];
348 SYMBOL_NAME (msymbol
) = (char *) name
;
349 SYMBOL_INIT_LANGUAGE_SPECIFIC (msymbol
, language_unknown
);
350 SYMBOL_VALUE_ADDRESS (msymbol
) = address
;
351 SYMBOL_SECTION (msymbol
) = section
;
352 MSYMBOL_TYPE (msymbol
) = ms_type
;
353 /* FIXME: This info, if it remains, needs its own field. */
354 MSYMBOL_INFO (msymbol
) = info
; /* FIXME! */
359 /* Compare two minimal symbols by address and return a signed result based
360 on unsigned comparisons, so that we sort into unsigned numeric order. */
363 compare_minimal_symbols (fn1p
, fn2p
)
367 register const struct minimal_symbol
*fn1
;
368 register const struct minimal_symbol
*fn2
;
370 fn1
= (const struct minimal_symbol
*) fn1p
;
371 fn2
= (const struct minimal_symbol
*) fn2p
;
373 if (SYMBOL_VALUE_ADDRESS (fn1
) < SYMBOL_VALUE_ADDRESS (fn2
))
377 else if (SYMBOL_VALUE_ADDRESS (fn1
) > SYMBOL_VALUE_ADDRESS (fn2
))
387 /* Discard the currently collected minimal symbols, if any. If we wish
388 to save them for later use, we must have already copied them somewhere
389 else before calling this function.
391 FIXME: We could allocate the minimal symbol bunches on their own
392 obstack and then simply blow the obstack away when we are done with
393 it. Is it worth the extra trouble though? */
397 discard_minimal_symbols (foo
)
400 register struct msym_bunch
*next
;
402 while (msym_bunch
!= NULL
)
404 next
= msym_bunch
-> next
;
405 free ((PTR
)msym_bunch
);
410 /* Compact duplicate entries out of a minimal symbol table by walking
411 through the table and compacting out entries with duplicate addresses
412 and matching names. Return the number of entries remaining.
414 On entry, the table resides between msymbol[0] and msymbol[mcount].
415 On exit, it resides between msymbol[0] and msymbol[result_count].
417 When files contain multiple sources of symbol information, it is
418 possible for the minimal symbol table to contain many duplicate entries.
419 As an example, SVR4 systems use ELF formatted object files, which
420 usually contain at least two different types of symbol tables (a
421 standard ELF one and a smaller dynamic linking table), as well as
422 DWARF debugging information for files compiled with -g.
424 Without compacting, the minimal symbol table for gdb itself contains
425 over a 1000 duplicates, about a third of the total table size. Aside
426 from the potential trap of not noticing that two successive entries
427 identify the same location, this duplication impacts the time required
428 to linearly scan the table, which is done in a number of places. So we
429 just do one linear scan here and toss out the duplicates.
431 Note that we are not concerned here about recovering the space that
432 is potentially freed up, because the strings themselves are allocated
433 on the symbol_obstack, and will get automatically freed when the symbol
434 table is freed. The caller can free up the unused minimal symbols at
435 the end of the compacted region if their allocation strategy allows it.
437 Also note we only go up to the next to last entry within the loop
438 and then copy the last entry explicitly after the loop terminates.
440 Since the different sources of information for each symbol may
441 have different levels of "completeness", we may have duplicates
442 that have one entry with type "mst_unknown" and the other with a
443 known type. So if the one we are leaving alone has type mst_unknown,
444 overwrite its type with the type from the one we are compacting out. */
447 compact_minimal_symbols (msymbol
, mcount
)
448 struct minimal_symbol
*msymbol
;
451 struct minimal_symbol
*copyfrom
;
452 struct minimal_symbol
*copyto
;
456 copyfrom
= copyto
= msymbol
;
457 while (copyfrom
< msymbol
+ mcount
- 1)
459 if (SYMBOL_VALUE_ADDRESS (copyfrom
) ==
460 SYMBOL_VALUE_ADDRESS ((copyfrom
+ 1)) &&
461 (STREQ (SYMBOL_NAME (copyfrom
), SYMBOL_NAME ((copyfrom
+ 1)))))
463 if (MSYMBOL_TYPE((copyfrom
+ 1)) == mst_unknown
)
465 MSYMBOL_TYPE ((copyfrom
+ 1)) = MSYMBOL_TYPE (copyfrom
);
471 *copyto
++ = *copyfrom
++;
474 *copyto
++ = *copyfrom
++;
475 mcount
= copyto
- msymbol
;
480 /* Add the minimal symbols in the existing bunches to the objfile's official
481 minimal symbol table. In most cases there is no minimal symbol table yet
482 for this objfile, and the existing bunches are used to create one. Once
483 in a while (for shared libraries for example), we add symbols (e.g. common
484 symbols) to an existing objfile.
486 Because of the way minimal symbols are collected, we generally have no way
487 of knowing what source language applies to any particular minimal symbol.
488 Specifically, we have no way of knowing if the minimal symbol comes from a
489 C++ compilation unit or not. So for the sake of supporting cached
490 demangled C++ names, we have no choice but to try and demangle each new one
491 that comes in. If the demangling succeeds, then we assume it is a C++
492 symbol and set the symbol's language and demangled name fields
493 appropriately. Note that in order to avoid unnecessary demanglings, and
494 allocating obstack space that subsequently can't be freed for the demangled
495 names, we mark all newly added symbols with language_auto. After
496 compaction of the minimal symbols, we go back and scan the entire minimal
497 symbol table looking for these new symbols. For each new symbol we attempt
498 to demangle it, and if successful, record it as a language_cplus symbol
499 and cache the demangled form on the symbol obstack. Symbols which don't
500 demangle are marked as language_unknown symbols, which inhibits future
501 attempts to demangle them if we later add more minimal symbols. */
504 install_minimal_symbols (objfile
)
505 struct objfile
*objfile
;
509 register struct msym_bunch
*bunch
;
510 register struct minimal_symbol
*msymbols
;
512 register char leading_char
;
516 /* Allocate enough space in the obstack, into which we will gather the
517 bunches of new and existing minimal symbols, sort them, and then
518 compact out the duplicate entries. Once we have a final table,
519 we will give back the excess space. */
521 alloc_count
= msym_count
+ objfile
->minimal_symbol_count
+ 1;
522 obstack_blank (&objfile
->symbol_obstack
,
523 alloc_count
* sizeof (struct minimal_symbol
));
524 msymbols
= (struct minimal_symbol
*)
525 obstack_base (&objfile
->symbol_obstack
);
527 /* Copy in the existing minimal symbols, if there are any. */
529 if (objfile
->minimal_symbol_count
)
530 memcpy ((char *)msymbols
, (char *)objfile
->msymbols
,
531 objfile
->minimal_symbol_count
* sizeof (struct minimal_symbol
));
533 /* Walk through the list of minimal symbol bunches, adding each symbol
534 to the new contiguous array of symbols. Note that we start with the
535 current, possibly partially filled bunch (thus we use the current
536 msym_bunch_index for the first bunch we copy over), and thereafter
537 each bunch is full. */
539 mcount
= objfile
->minimal_symbol_count
;
540 leading_char
= bfd_get_symbol_leading_char (objfile
->obfd
);
542 for (bunch
= msym_bunch
; bunch
!= NULL
; bunch
= bunch
-> next
)
544 for (bindex
= 0; bindex
< msym_bunch_index
; bindex
++, mcount
++)
546 msymbols
[mcount
] = bunch
-> contents
[bindex
];
547 SYMBOL_LANGUAGE (&msymbols
[mcount
]) = language_auto
;
548 if (SYMBOL_NAME (&msymbols
[mcount
])[0] == leading_char
)
550 SYMBOL_NAME(&msymbols
[mcount
])++;
553 msym_bunch_index
= BUNCH_SIZE
;
556 /* Sort the minimal symbols by address. */
558 qsort (msymbols
, mcount
, sizeof (struct minimal_symbol
),
559 compare_minimal_symbols
);
561 /* Compact out any duplicates, and free up whatever space we are
564 mcount
= compact_minimal_symbols (msymbols
, mcount
);
566 obstack_blank (&objfile
->symbol_obstack
,
567 (mcount
+ 1 - alloc_count
) * sizeof (struct minimal_symbol
));
568 msymbols
= (struct minimal_symbol
*)
569 obstack_finish (&objfile
->symbol_obstack
);
571 /* We also terminate the minimal symbol table with a "null symbol",
572 which is *not* included in the size of the table. This makes it
573 easier to find the end of the table when we are handed a pointer
574 to some symbol in the middle of it. Zero out the fields in the
575 "null symbol" allocated at the end of the array. Note that the
576 symbol count does *not* include this null symbol, which is why it
577 is indexed by mcount and not mcount-1. */
579 SYMBOL_NAME (&msymbols
[mcount
]) = NULL
;
580 SYMBOL_VALUE_ADDRESS (&msymbols
[mcount
]) = 0;
581 MSYMBOL_INFO (&msymbols
[mcount
]) = NULL
;
582 MSYMBOL_TYPE (&msymbols
[mcount
]) = mst_unknown
;
583 SYMBOL_INIT_LANGUAGE_SPECIFIC (&msymbols
[mcount
], language_unknown
);
585 /* Attach the minimal symbol table to the specified objfile.
586 The strings themselves are also located in the symbol_obstack
589 objfile
-> minimal_symbol_count
= mcount
;
590 objfile
-> msymbols
= msymbols
;
592 /* Now walk through all the minimal symbols, selecting the newly added
593 ones and attempting to cache their C++ demangled names. */
595 for ( ; mcount
-- > 0 ; msymbols
++)
597 SYMBOL_INIT_DEMANGLED_NAME (msymbols
, &objfile
->symbol_obstack
);