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 /* Skip any absolute symbols. This is apparently what adb
257 and dbx do, and is needed for the CM-5. There are two
258 known possible problems: (1) on ELF, apparently end, edata,
259 etc. are absolute. Not sure ignoring them here is a big
260 deal, but if we want to use them, the fix would go in
261 elfread.c. (2) I think shared library entry points on the
262 NeXT are absolute. If we want special handling for this
263 it probably should be triggered by a special
264 mst_abs_or_lib or some such. */
266 && msymbol
[hi
].type
== mst_abs
)
270 && ((best_symbol
== NULL
) ||
271 (SYMBOL_VALUE_ADDRESS (best_symbol
) <
272 SYMBOL_VALUE_ADDRESS (&msymbol
[hi
]))))
274 best_symbol
= &msymbol
[hi
];
279 return (best_symbol
);
282 /* Prepare to start collecting minimal symbols. Note that presetting
283 msym_bunch_index to BUNCH_SIZE causes the first call to save a minimal
284 symbol to allocate the memory for the first bunch. */
287 init_minimal_symbol_collection ()
291 msym_bunch_index
= BUNCH_SIZE
;
295 prim_record_minimal_symbol (name
, address
, ms_type
)
298 enum minimal_symbol_type ms_type
;
300 prim_record_minimal_symbol (name
, address
, ms_type
, NULL
, -1);
304 prim_record_minimal_symbol_and_info (name
, address
, ms_type
, info
, section
)
307 enum minimal_symbol_type ms_type
;
311 register struct msym_bunch
*new;
312 register struct minimal_symbol
*msymbol
;
314 if (ms_type
== mst_file_text
)
316 /* Don't put gcc_compiled, __gnu_compiled_cplus, and friends into
317 the minimal symbols, because if there is also another symbol
318 at the same address (e.g. the first function of the file),
319 lookup_minimal_symbol_by_pc would have no way of getting the
322 && (strcmp (name
, GCC_COMPILED_FLAG_SYMBOL
) == 0
323 || strcmp (name
, GCC2_COMPILED_FLAG_SYMBOL
) == 0))
327 char *tempstring
= name
;
328 if (tempstring
[0] == bfd_get_symbol_leading_char (objfile
->obfd
))
330 if (STREQN (tempstring
, "__gnu_compiled", 14))
335 if (msym_bunch_index
== BUNCH_SIZE
)
337 new = (struct msym_bunch
*) xmalloc (sizeof (struct msym_bunch
));
338 msym_bunch_index
= 0;
339 new -> next
= msym_bunch
;
342 msymbol
= &msym_bunch
-> contents
[msym_bunch_index
];
343 SYMBOL_NAME (msymbol
) = (char *) name
;
344 SYMBOL_INIT_LANGUAGE_SPECIFIC (msymbol
, language_unknown
);
345 SYMBOL_VALUE_ADDRESS (msymbol
) = address
;
346 SYMBOL_SECTION (msymbol
) = section
;
347 MSYMBOL_TYPE (msymbol
) = ms_type
;
348 /* FIXME: This info, if it remains, needs its own field. */
349 MSYMBOL_INFO (msymbol
) = info
; /* FIXME! */
354 /* Compare two minimal symbols by address and return a signed result based
355 on unsigned comparisons, so that we sort into unsigned numeric order. */
358 compare_minimal_symbols (fn1p
, fn2p
)
362 register const struct minimal_symbol
*fn1
;
363 register const struct minimal_symbol
*fn2
;
365 fn1
= (const struct minimal_symbol
*) fn1p
;
366 fn2
= (const struct minimal_symbol
*) fn2p
;
368 if (SYMBOL_VALUE_ADDRESS (fn1
) < SYMBOL_VALUE_ADDRESS (fn2
))
372 else if (SYMBOL_VALUE_ADDRESS (fn1
) > SYMBOL_VALUE_ADDRESS (fn2
))
382 /* Discard the currently collected minimal symbols, if any. If we wish
383 to save them for later use, we must have already copied them somewhere
384 else before calling this function.
386 FIXME: We could allocate the minimal symbol bunches on their own
387 obstack and then simply blow the obstack away when we are done with
388 it. Is it worth the extra trouble though? */
392 discard_minimal_symbols (foo
)
395 register struct msym_bunch
*next
;
397 while (msym_bunch
!= NULL
)
399 next
= msym_bunch
-> next
;
400 free ((PTR
)msym_bunch
);
405 /* Compact duplicate entries out of a minimal symbol table by walking
406 through the table and compacting out entries with duplicate addresses
407 and matching names. Return the number of entries remaining.
409 On entry, the table resides between msymbol[0] and msymbol[mcount].
410 On exit, it resides between msymbol[0] and msymbol[result_count].
412 When files contain multiple sources of symbol information, it is
413 possible for the minimal symbol table to contain many duplicate entries.
414 As an example, SVR4 systems use ELF formatted object files, which
415 usually contain at least two different types of symbol tables (a
416 standard ELF one and a smaller dynamic linking table), as well as
417 DWARF debugging information for files compiled with -g.
419 Without compacting, the minimal symbol table for gdb itself contains
420 over a 1000 duplicates, about a third of the total table size. Aside
421 from the potential trap of not noticing that two successive entries
422 identify the same location, this duplication impacts the time required
423 to linearly scan the table, which is done in a number of places. So we
424 just do one linear scan here and toss out the duplicates.
426 Note that we are not concerned here about recovering the space that
427 is potentially freed up, because the strings themselves are allocated
428 on the symbol_obstack, and will get automatically freed when the symbol
429 table is freed. The caller can free up the unused minimal symbols at
430 the end of the compacted region if their allocation strategy allows it.
432 Also note we only go up to the next to last entry within the loop
433 and then copy the last entry explicitly after the loop terminates.
435 Since the different sources of information for each symbol may
436 have different levels of "completeness", we may have duplicates
437 that have one entry with type "mst_unknown" and the other with a
438 known type. So if the one we are leaving alone has type mst_unknown,
439 overwrite its type with the type from the one we are compacting out. */
442 compact_minimal_symbols (msymbol
, mcount
)
443 struct minimal_symbol
*msymbol
;
446 struct minimal_symbol
*copyfrom
;
447 struct minimal_symbol
*copyto
;
451 copyfrom
= copyto
= msymbol
;
452 while (copyfrom
< msymbol
+ mcount
- 1)
454 if (SYMBOL_VALUE_ADDRESS (copyfrom
) ==
455 SYMBOL_VALUE_ADDRESS ((copyfrom
+ 1)) &&
456 (STREQ (SYMBOL_NAME (copyfrom
), SYMBOL_NAME ((copyfrom
+ 1)))))
458 if (MSYMBOL_TYPE((copyfrom
+ 1)) == mst_unknown
)
460 MSYMBOL_TYPE ((copyfrom
+ 1)) = MSYMBOL_TYPE (copyfrom
);
466 *copyto
++ = *copyfrom
++;
469 *copyto
++ = *copyfrom
++;
470 mcount
= copyto
- msymbol
;
475 /* Add the minimal symbols in the existing bunches to the objfile's official
476 minimal symbol table. In most cases there is no minimal symbol table yet
477 for this objfile, and the existing bunches are used to create one. Once
478 in a while (for shared libraries for example), we add symbols (e.g. common
479 symbols) to an existing objfile.
481 Because of the way minimal symbols are collected, we generally have no way
482 of knowing what source language applies to any particular minimal symbol.
483 Specifically, we have no way of knowing if the minimal symbol comes from a
484 C++ compilation unit or not. So for the sake of supporting cached
485 demangled C++ names, we have no choice but to try and demangle each new one
486 that comes in. If the demangling succeeds, then we assume it is a C++
487 symbol and set the symbol's language and demangled name fields
488 appropriately. Note that in order to avoid unnecessary demanglings, and
489 allocating obstack space that subsequently can't be freed for the demangled
490 names, we mark all newly added symbols with language_auto. After
491 compaction of the minimal symbols, we go back and scan the entire minimal
492 symbol table looking for these new symbols. For each new symbol we attempt
493 to demangle it, and if successful, record it as a language_cplus symbol
494 and cache the demangled form on the symbol obstack. Symbols which don't
495 demangle are marked as language_unknown symbols, which inhibits future
496 attempts to demangle them if we later add more minimal symbols. */
499 install_minimal_symbols (objfile
)
500 struct objfile
*objfile
;
504 register struct msym_bunch
*bunch
;
505 register struct minimal_symbol
*msymbols
;
507 register char leading_char
;
511 /* Allocate enough space in the obstack, into which we will gather the
512 bunches of new and existing minimal symbols, sort them, and then
513 compact out the duplicate entries. Once we have a final table,
514 we will give back the excess space. */
516 alloc_count
= msym_count
+ objfile
->minimal_symbol_count
+ 1;
517 obstack_blank (&objfile
->symbol_obstack
,
518 alloc_count
* sizeof (struct minimal_symbol
));
519 msymbols
= (struct minimal_symbol
*)
520 obstack_base (&objfile
->symbol_obstack
);
522 /* Copy in the existing minimal symbols, if there are any. */
524 if (objfile
->minimal_symbol_count
)
525 memcpy ((char *)msymbols
, (char *)objfile
->msymbols
,
526 objfile
->minimal_symbol_count
* sizeof (struct minimal_symbol
));
528 /* Walk through the list of minimal symbol bunches, adding each symbol
529 to the new contiguous array of symbols. Note that we start with the
530 current, possibly partially filled bunch (thus we use the current
531 msym_bunch_index for the first bunch we copy over), and thereafter
532 each bunch is full. */
534 mcount
= objfile
->minimal_symbol_count
;
535 leading_char
= bfd_get_symbol_leading_char (objfile
->obfd
);
537 for (bunch
= msym_bunch
; bunch
!= NULL
; bunch
= bunch
-> next
)
539 for (bindex
= 0; bindex
< msym_bunch_index
; bindex
++, mcount
++)
541 msymbols
[mcount
] = bunch
-> contents
[bindex
];
542 SYMBOL_LANGUAGE (&msymbols
[mcount
]) = language_auto
;
543 if (SYMBOL_NAME (&msymbols
[mcount
])[0] == leading_char
)
545 SYMBOL_NAME(&msymbols
[mcount
])++;
548 msym_bunch_index
= BUNCH_SIZE
;
551 /* Sort the minimal symbols by address. */
553 qsort (msymbols
, mcount
, sizeof (struct minimal_symbol
),
554 compare_minimal_symbols
);
556 /* Compact out any duplicates, and free up whatever space we are
559 mcount
= compact_minimal_symbols (msymbols
, mcount
);
561 obstack_blank (&objfile
->symbol_obstack
,
562 (mcount
+ 1 - alloc_count
) * sizeof (struct minimal_symbol
));
563 msymbols
= (struct minimal_symbol
*)
564 obstack_finish (&objfile
->symbol_obstack
);
566 /* We also terminate the minimal symbol table with a "null symbol",
567 which is *not* included in the size of the table. This makes it
568 easier to find the end of the table when we are handed a pointer
569 to some symbol in the middle of it. Zero out the fields in the
570 "null symbol" allocated at the end of the array. Note that the
571 symbol count does *not* include this null symbol, which is why it
572 is indexed by mcount and not mcount-1. */
574 SYMBOL_NAME (&msymbols
[mcount
]) = NULL
;
575 SYMBOL_VALUE_ADDRESS (&msymbols
[mcount
]) = 0;
576 MSYMBOL_INFO (&msymbols
[mcount
]) = NULL
;
577 MSYMBOL_TYPE (&msymbols
[mcount
]) = mst_unknown
;
578 SYMBOL_INIT_LANGUAGE_SPECIFIC (&msymbols
[mcount
], language_unknown
);
580 /* Attach the minimal symbol table to the specified objfile.
581 The strings themselves are also located in the symbol_obstack
584 objfile
-> minimal_symbol_count
= mcount
;
585 objfile
-> msymbols
= msymbols
;
587 /* Now walk through all the minimal symbols, selecting the newly added
588 ones and attempting to cache their C++ demangled names. */
590 for ( ; mcount
-- > 0 ; msymbols
++)
592 SYMBOL_INIT_DEMANGLED_NAME (msymbols
, &objfile
->symbol_obstack
);