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
;
99 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 #ifdef IBM6000_TARGET
116 /* I *think* all platforms using shared libraries (and
117 trampoline code) will suffer this problem. Consider a
118 case where there are 5 shared libraries, each referencing
119 `foo' with a trampoline entry. When someone wants to put
120 a breakpoint on `foo' and the only info we have is minimal
121 symbol vector, we want to use the real `foo', rather than
122 one of those trampoline entries. MGO */
123 /* If a trampoline symbol is found, we prefer to keep looking
124 for the *real* symbol. If the actual symbol not found,
125 then we'll use the trampoline entry. Sorry for the machine
126 dependent code here, but I hope this will benefit other
127 platforms as well. For trampoline entries, we used
128 mst_unknown earlier. Perhaps we should define a
129 `mst_trampoline' type?? */
131 if (MSYMBOL_TYPE (msymbol
) != mst_unknown
)
132 found_symbol
= msymbol
;
133 else if (MSYMBOL_TYPE (msymbol
) == mst_unknown
&&
135 trampoline_symbol
= msymbol
;
138 found_symbol
= msymbol
;
144 #ifdef IBM6000_TARGET
145 return found_symbol
? found_symbol
: trampoline_symbol
;
148 return (found_symbol
);
152 /* Search through the minimal symbol table for each objfile and find the
153 symbol whose address is the largest address that is still less than or
154 equal to PC. Returns a pointer to the minimal symbol if such a symbol
155 is found, or NULL if PC is not in a suitable range. Note that we need
156 to look through ALL the minimal symbol tables before deciding on the
157 symbol that comes closest to the specified PC. */
159 struct minimal_symbol
*
160 lookup_minimal_symbol_by_pc (pc
)
161 register CORE_ADDR pc
;
166 register struct objfile
*objfile
;
167 register struct minimal_symbol
*msymbol
;
168 register struct minimal_symbol
*best_symbol
= NULL
;
170 for (objfile
= object_files
;
172 objfile
= objfile
-> next
)
174 /* If this objfile has a minimal symbol table, go search it using
175 a binary search. Note that a minimal symbol table always consists
176 of at least two symbols, a "real" symbol and the terminating
177 "null symbol". If there are no real symbols, then there is no
178 minimal symbol table at all. */
180 if ((msymbol
= objfile
-> msymbols
) != NULL
)
183 hi
= objfile
-> minimal_symbol_count
- 1;
185 /* This code assumes that the minimal symbols are sorted by
186 ascending address values. If the pc value is greater than or
187 equal to the first symbol's address, then some symbol in this
188 minimal symbol table is a suitable candidate for being the
189 "best" symbol. This includes the last real symbol, for cases
190 where the pc value is larger than any address in this vector.
192 By iterating until the address associated with the current
193 hi index (the endpoint of the test interval) is less than
194 or equal to the desired pc value, we accomplish two things:
195 (1) the case where the pc value is larger than any minimal
196 symbol address is trivially solved, (2) the address associated
197 with the hi index is always the one we want when the interation
198 terminates. In essence, we are iterating the test interval
199 down until the pc value is pushed out of it from the high end.
201 Warning: this code is trickier than it would appear at first. */
203 /* Should also requires that pc is <= end of objfile. FIXME! */
204 if (pc
>= SYMBOL_VALUE_ADDRESS (&msymbol
[lo
]))
206 while (SYMBOL_VALUE_ADDRESS (&msymbol
[hi
]) > pc
)
208 /* pc is still strictly less than highest address */
209 /* Note "new" will always be >= lo */
211 if ((SYMBOL_VALUE_ADDRESS (&msymbol
[new]) >= pc
) ||
221 /* The minimal symbol indexed by hi now is the best one in this
222 objfile's minimal symbol table. See if it is the best one
225 if ((best_symbol
== NULL
) ||
226 (SYMBOL_VALUE_ADDRESS (best_symbol
) <
227 SYMBOL_VALUE_ADDRESS (&msymbol
[hi
])))
229 best_symbol
= &msymbol
[hi
];
234 return (best_symbol
);
237 /* Prepare to start collecting minimal symbols. Note that presetting
238 msym_bunch_index to BUNCH_SIZE causes the first call to save a minimal
239 symbol to allocate the memory for the first bunch. */
242 init_minimal_symbol_collection ()
246 msym_bunch_index
= BUNCH_SIZE
;
250 prim_record_minimal_symbol (name
, address
, ms_type
)
253 enum minimal_symbol_type ms_type
;
255 register struct msym_bunch
*new;
256 register struct minimal_symbol
*msymbol
;
258 if (msym_bunch_index
== BUNCH_SIZE
)
260 new = (struct msym_bunch
*) xmalloc (sizeof (struct msym_bunch
));
261 msym_bunch_index
= 0;
262 new -> next
= msym_bunch
;
265 msymbol
= &msym_bunch
-> contents
[msym_bunch_index
];
266 SYMBOL_NAME (msymbol
) = (char *) name
;
267 /* Note that SYMBOL_LANGUAGE and SYMBOL_DEMANGLED_NAME are not initialized
268 to their final values until the minimal symbols are actually added to
269 the minimal symbol table. We just set them to a known state here so
270 random values won't confuse anyone debugging the debugger. */
271 SYMBOL_LANGUAGE (msymbol
) = language_unknown
;
272 SYMBOL_DEMANGLED_NAME (msymbol
) = NULL
;
273 SYMBOL_VALUE_ADDRESS (msymbol
) = address
;
274 MSYMBOL_TYPE (msymbol
) = ms_type
;
275 /* FIXME: This info, if it remains, needs its own field. */
276 MSYMBOL_INFO (msymbol
) = NULL
; /* FIXME! */
281 /* FIXME: Why don't we just combine this function with the one above
282 and pass it a NULL info pointer value if info is not needed? */
285 prim_record_minimal_symbol_and_info (name
, address
, ms_type
, info
)
288 enum minimal_symbol_type ms_type
;
291 register struct msym_bunch
*new;
292 register struct minimal_symbol
*msymbol
;
294 if (msym_bunch_index
== BUNCH_SIZE
)
296 new = (struct msym_bunch
*) xmalloc (sizeof (struct msym_bunch
));
297 msym_bunch_index
= 0;
298 new -> next
= msym_bunch
;
301 msymbol
= &msym_bunch
-> contents
[msym_bunch_index
];
302 SYMBOL_NAME (msymbol
) = (char *) name
;
303 /* Note that SYMBOL_LANGUAGE and SYMBOL_DEMANGLED_NAME are not initialized
304 to their final values until the minimal symbols are actually added to
305 the minimal symbol table. We just set them to a known state here so
306 random values won't confuse anyone debugging the debugger. */
307 SYMBOL_LANGUAGE (msymbol
) = language_unknown
;
308 SYMBOL_DEMANGLED_NAME (msymbol
) = NULL
;
309 SYMBOL_VALUE_ADDRESS (msymbol
) = address
;
310 MSYMBOL_TYPE (msymbol
) = ms_type
;
311 /* FIXME: This info, if it remains, needs its own field. */
312 MSYMBOL_INFO (msymbol
) = info
; /* FIXME! */
317 /* Compare two minimal symbols by address and return a signed result based
318 on unsigned comparisons, so that we sort into unsigned numeric order. */
321 compare_minimal_symbols (fn1p
, fn2p
)
325 register const struct minimal_symbol
*fn1
;
326 register const struct minimal_symbol
*fn2
;
328 fn1
= (const struct minimal_symbol
*) fn1p
;
329 fn2
= (const struct minimal_symbol
*) fn2p
;
331 if (SYMBOL_VALUE_ADDRESS (fn1
) < SYMBOL_VALUE_ADDRESS (fn2
))
335 else if (SYMBOL_VALUE_ADDRESS (fn1
) > SYMBOL_VALUE_ADDRESS (fn2
))
345 /* Discard the currently collected minimal symbols, if any. If we wish
346 to save them for later use, we must have already copied them somewhere
347 else before calling this function.
349 FIXME: We could allocate the minimal symbol bunches on their own
350 obstack and then simply blow the obstack away when we are done with
351 it. Is it worth the extra trouble though? */
355 discard_minimal_symbols (foo
)
358 register struct msym_bunch
*next
;
360 while (msym_bunch
!= NULL
)
362 next
= msym_bunch
-> next
;
363 free ((PTR
)msym_bunch
);
368 /* Compact duplicate entries out of a minimal symbol table by walking
369 through the table and compacting out entries with duplicate addresses
370 and matching names. Return the number of entries remaining.
372 On entry, the table resides between msymbol[0] and msymbol[mcount].
373 On exit, it resides between msymbol[0] and msymbol[result_count].
375 When files contain multiple sources of symbol information, it is
376 possible for the minimal symbol table to contain many duplicate entries.
377 As an example, SVR4 systems use ELF formatted object files, which
378 usually contain at least two different types of symbol tables (a
379 standard ELF one and a smaller dynamic linking table), as well as
380 DWARF debugging information for files compiled with -g.
382 Without compacting, the minimal symbol table for gdb itself contains
383 over a 1000 duplicates, about a third of the total table size. Aside
384 from the potential trap of not noticing that two successive entries
385 identify the same location, this duplication impacts the time required
386 to linearly scan the table, which is done in a number of places. So we
387 just do one linear scan here and toss out the duplicates.
389 Note that we are not concerned here about recovering the space that
390 is potentially freed up, because the strings themselves are allocated
391 on the symbol_obstack, and will get automatically freed when the symbol
392 table is freed. The caller can free up the unused minimal symbols at
393 the end of the compacted region if their allocation strategy allows it.
395 Also note we only go up to the next to last entry within the loop
396 and then copy the last entry explicitly after the loop terminates.
398 Since the different sources of information for each symbol may
399 have different levels of "completeness", we may have duplicates
400 that have one entry with type "mst_unknown" and the other with a
401 known type. So if the one we are leaving alone has type mst_unknown,
402 overwrite its type with the type from the one we are compacting out. */
405 compact_minimal_symbols (msymbol
, mcount
)
406 struct minimal_symbol
*msymbol
;
409 struct minimal_symbol
*copyfrom
;
410 struct minimal_symbol
*copyto
;
414 copyfrom
= copyto
= msymbol
;
415 while (copyfrom
< msymbol
+ mcount
- 1)
417 if (SYMBOL_VALUE_ADDRESS (copyfrom
) ==
418 SYMBOL_VALUE_ADDRESS ((copyfrom
+ 1)) &&
419 (STREQ (SYMBOL_NAME (copyfrom
), SYMBOL_NAME ((copyfrom
+ 1)))))
421 if (MSYMBOL_TYPE((copyfrom
+ 1)) == mst_unknown
)
423 MSYMBOL_TYPE ((copyfrom
+ 1)) = MSYMBOL_TYPE (copyfrom
);
429 *copyto
++ = *copyfrom
++;
432 *copyto
++ = *copyfrom
++;
433 mcount
= copyto
- msymbol
;
438 /* Add the minimal symbols in the existing bunches to the objfile's official
439 minimal symbol table. In most cases there is no minimal symbol table yet
440 for this objfile, and the existing bunches are used to create one. Once
441 in a while (for shared libraries for example), we add symbols (e.g. common
442 symbols) to an existing objfile.
444 Because of the way minimal symbols are collected, we generally have no way
445 of knowing what source language applies to any particular minimal symbol.
446 Specifically, we have no way of knowing if the minimal symbol comes from a
447 C++ compilation unit or not. So for the sake of supporting cached
448 demangled C++ names, we have no choice but to try and demangle each new one
449 that comes in. If the demangling succeeds, then we assume it is a C++
450 symbol and set the symbol's language and demangled name fields
451 appropriately. Note that in order to avoid unnecessary demanglings, and
452 allocating obstack space that subsequently can't be freed for the demangled
453 names, we mark all newly added symbols with language_auto. After
454 compaction of the minimal symbols, we go back and scan the entire minimal
455 symbol table looking for these new symbols. For each new symbol we attempt
456 to demangle it, and if successful, record it as a language_cplus symbol
457 and cache the demangled form on the symbol obstack. Symbols which don't
458 demangle are marked as language_unknown symbols, which inhibits future
459 attempts to demangle them if we later add more minimal symbols. */
462 install_minimal_symbols (objfile
)
463 struct objfile
*objfile
;
467 register struct msym_bunch
*bunch
;
468 register struct minimal_symbol
*msymbols
;
470 register char leading_char
;
471 char *demangled_name
;
475 /* Allocate enough space in the obstack, into which we will gather the
476 bunches of new and existing minimal symbols, sort them, and then
477 compact out the duplicate entries. Once we have a final table,
478 we will give back the excess space. */
480 alloc_count
= msym_count
+ objfile
->minimal_symbol_count
+ 1;
481 obstack_blank (&objfile
->symbol_obstack
,
482 alloc_count
* sizeof (struct minimal_symbol
));
483 msymbols
= (struct minimal_symbol
*)
484 obstack_base (&objfile
->symbol_obstack
);
486 /* Copy in the existing minimal symbols, if there are any. */
488 if (objfile
->minimal_symbol_count
)
489 memcpy ((char *)msymbols
, (char *)objfile
->msymbols
,
490 objfile
->minimal_symbol_count
* sizeof (struct minimal_symbol
));
492 /* Walk through the list of minimal symbol bunches, adding each symbol
493 to the new contiguous array of symbols. Note that we start with the
494 current, possibly partially filled bunch (thus we use the current
495 msym_bunch_index for the first bunch we copy over), and thereafter
496 each bunch is full. */
498 mcount
= objfile
->minimal_symbol_count
;
499 leading_char
= bfd_get_symbol_leading_char (objfile
->obfd
);
501 for (bunch
= msym_bunch
; bunch
!= NULL
; bunch
= bunch
-> next
)
503 for (bindex
= 0; bindex
< msym_bunch_index
; bindex
++, mcount
++)
505 msymbols
[mcount
] = bunch
-> contents
[bindex
];
506 SYMBOL_LANGUAGE (&msymbols
[mcount
]) = language_auto
;
507 if (SYMBOL_NAME (&msymbols
[mcount
])[0] == leading_char
)
509 SYMBOL_NAME(&msymbols
[mcount
])++;
512 msym_bunch_index
= BUNCH_SIZE
;
515 /* Sort the minimal symbols by address. */
517 qsort (msymbols
, mcount
, sizeof (struct minimal_symbol
),
518 compare_minimal_symbols
);
520 /* Compact out any duplicates, and free up whatever space we are
523 mcount
= compact_minimal_symbols (msymbols
, mcount
);
525 obstack_blank (&objfile
->symbol_obstack
,
526 (mcount
+ 1 - alloc_count
) * sizeof (struct minimal_symbol
));
527 msymbols
= (struct minimal_symbol
*)
528 obstack_finish (&objfile
->symbol_obstack
);
530 /* We also terminate the minimal symbol table with a "null symbol",
531 which is *not* included in the size of the table. This makes it
532 easier to find the end of the table when we are handed a pointer
533 to some symbol in the middle of it. Zero out the fields in the
534 "null symbol" allocated at the end of the array. Note that the
535 symbol count does *not* include this null symbol, which is why it
536 is indexed by mcount and not mcount-1. */
538 SYMBOL_NAME (&msymbols
[mcount
]) = NULL
;
539 SYMBOL_VALUE_ADDRESS (&msymbols
[mcount
]) = 0;
540 MSYMBOL_INFO (&msymbols
[mcount
]) = NULL
;
541 MSYMBOL_TYPE (&msymbols
[mcount
]) = mst_unknown
;
542 SYMBOL_LANGUAGE (&msymbols
[mcount
]) = language_unknown
;
543 SYMBOL_DEMANGLED_NAME (&msymbols
[mcount
]) = NULL
;
545 /* Attach the minimal symbol table to the specified objfile.
546 The strings themselves are also located in the symbol_obstack
549 objfile
-> minimal_symbol_count
= mcount
;
550 objfile
-> msymbols
= msymbols
;
552 /* Now walk through all the minimal symbols, selecting the newly added
553 ones and attempting to cache their C++ demangled names. */
555 for ( ; mcount
-- > 0 ; msymbols
++)
557 if (SYMBOL_LANGUAGE (msymbols
) == language_auto
)
559 demangled_name
= cplus_demangle (SYMBOL_NAME (msymbols
),
560 DMGL_PARAMS
| DMGL_ANSI
);
561 if (demangled_name
== NULL
)
563 SYMBOL_LANGUAGE (msymbols
) = language_unknown
;
567 SYMBOL_LANGUAGE (msymbols
) = language_cplus
;
568 SYMBOL_DEMANGLED_NAME (msymbols
) =
569 obsavestring (demangled_name
, strlen (demangled_name
),
570 &objfile
->symbol_obstack
);
572 free (demangled_name
);