gdb/objfiles.h

   1 /* Definitions for symbol file management in GDB.
   2    Copyright (C) 1992, 1993, 1994, 1995 Free Software Foundation, Inc.
   3
   4 This file is part of GDB.
   5
   6 This program is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2 of the License, or
   9 (at your option) any later version.
  10
  11 This program is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with this program; if not, write to the Free Software
  18 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  19
  20 #if !defined (OBJFILES_H)
  21 #define OBJFILES_H
  22
  23 /* This structure maintains information on a per-objfile basis about the
  24    "entry point" of the objfile, and the scope within which the entry point
  25    exists.  It is possible that gdb will see more than one objfile that is
  26    executable, each with its own entry point.
  27
  28    For example, for dynamically linked executables in SVR4, the dynamic linker
  29    code is contained within the shared C library, which is actually executable
  30    and is run by the kernel first when an exec is done of a user executable
  31    that is dynamically linked.  The dynamic linker within the shared C library
  32    then maps in the various program segments in the user executable and jumps
  33    to the user executable's recorded entry point, as if the call had been made
  34    directly by the kernel.
  35
  36    The traditional gdb method of using this info is to use the recorded entry
  37    point to set the variables entry_file_lowpc and entry_file_highpc from
  38    the debugging information, where these values are the starting address
  39    (inclusive) and ending address (exclusive) of the instruction space in the
  40    executable which correspond to the "startup file", I.E. crt0.o in most
  41    cases.  This file is assumed to be a startup file and frames with pc's
  42    inside it are treated as nonexistent.  Setting these variables is necessary
  43    so that backtraces do not fly off the bottom of the stack.
  44
  45    Gdb also supports an alternate method to avoid running off the bottom
  46    of the stack.
  47
  48    There are two frames that are "special", the frame for the function
  49    containing the process entry point, since it has no predecessor frame,
  50    and the frame for the function containing the user code entry point
  51    (the main() function), since all the predecessor frames are for the
  52    process startup code.  Since we have no guarantee that the linked
  53    in startup modules have any debugging information that gdb can use,
  54    we need to avoid following frame pointers back into frames that might
  55    have been built in the startup code, as we might get hopelessly
  56    confused.  However, we almost always have debugging information
  57    available for main().
  58
  59    These variables are used to save the range of PC values which are valid
  60    within the main() function and within the function containing the process
  61    entry point.  If we always consider the frame for main() as the outermost
  62    frame when debugging user code, and the frame for the process entry
  63    point function as the outermost frame when debugging startup code, then
  64    all we have to do is have FRAME_CHAIN_VALID return false whenever a
  65    frame's current PC is within the range specified by these variables.
  66    In essence, we set "ceilings" in the frame chain beyond which we will
  67    not proceed when following the frame chain back up the stack.
  68
  69    A nice side effect is that we can still debug startup code without
  70    running off the end of the frame chain, assuming that we have usable
  71    debugging information in the startup modules, and if we choose to not
  72    use the block at main, or can't find it for some reason, everything
  73    still works as before.  And if we have no startup code debugging
  74    information but we do have usable information for main(), backtraces
  75    from user code don't go wandering off into the startup code.
  76
  77    To use this method, define your FRAME_CHAIN_VALID macro like:
  78
  79         #define FRAME_CHAIN_VALID(chain, thisframe)     \
  80           (chain != 0                                   \
  81            && !(inside_main_func ((thisframe)->pc))     \
  82            && !(inside_entry_func ((thisframe)->pc)))
  83
  84    and add initializations of the four scope controlling variables inside
  85    the object file / debugging information processing modules.  */
  86
  87 struct entry_info
  88 {
  89
  90   /* The value we should use for this objects entry point.
  91      The illegal/unknown value needs to be something other than 0, ~0
  92      for instance, which is much less likely than 0. */
  93
  94   CORE_ADDR entry_point;
  95
  96 #define INVALID_ENTRY_POINT (~0) /* ~0 will not be in any file, we hope.  */
  97
  98   /* Start (inclusive) and end (exclusive) of function containing the
  99      entry point. */
 100
 101   CORE_ADDR entry_func_lowpc;
 102   CORE_ADDR entry_func_highpc;
 103
 104   /* Start (inclusive) and end (exclusive) of object file containing the
 105      entry point. */
 106
 107   CORE_ADDR entry_file_lowpc;
 108   CORE_ADDR entry_file_highpc;
 109
 110   /* Start (inclusive) and end (exclusive) of the user code main() function. */
 111
 112   CORE_ADDR main_func_lowpc;
 113   CORE_ADDR main_func_highpc;
 114
 115 /* Use these values when any of the above ranges is invalid.  */
 116
 117 /* We use these values because it guarantees that there is no number that is
 118    both >= LOWPC && < HIGHPC.  It is also highly unlikely that 3 is a valid
 119    module or function start address (as opposed to 0).  */
 120
 121 #define INVALID_ENTRY_LOWPC (3)
 122 #define INVALID_ENTRY_HIGHPC (1)
 123
 124 };
 125
 126 /* Sections in an objfile.
 127
 128    It is strange that we have both this notion of "sections"
 129    and the one used by section_offsets.  Section as used
 130    here, (currently at least) means a BFD section, and the sections
 131    are set up from the BFD sections in allocate_objfile.
 132
 133    The sections in section_offsets have their meaning determined by
 134    the symbol format, and they are set up by the sym_offsets function
 135    for that symbol file format.
 136
 137    I'm not sure this could or should be changed, however.  */
 138
 139 struct obj_section {
 140   CORE_ADDR     addr;    /* lowest address in section */
 141   CORE_ADDR     endaddr; /* 1+highest address in section */
 142
 143   /* This field is being used for nefarious purposes by syms_from_objfile.
 144      It is said to be redundant with section_offsets; it's not really being
 145      used that way, however, it's some sort of hack I don't understand
 146      and am not going to try to eliminate (yet, anyway).  FIXME.
 147
 148      It was documented as "offset between (end)addr and actual memory
 149      addresses", but that's not true; addr & endaddr are actual memory
 150      addresses.  */
 151   CORE_ADDR offset;
 152
 153   sec_ptr the_bfd_section; /* BFD section pointer */
 154
 155   /* Objfile this section is part of.  */
 156   struct objfile *objfile;
 157
 158   /* True if this "overlay section" is mapped into an "overlay region". */
 159   int ovly_mapped;
 160 };
 161
 162 /* An import entry contains information about a symbol that
 163    is used in this objfile but not defined in it, and so needs
 164    to be imported from some other objfile */
 165 /* Currently we just store the name; no attributes. 1997-08-05 */
 166 typedef char * ImportEntry;
 167
 168
 169 /* An export entry contains information about a symbol that
 170    is defined in this objfile and available for use in other
 171    objfiles */
 172 typedef struct {
 173   char * name; /* name of exported symbol */
 174   int address; /* offset subject to relocation */
 175   /* Currently no other attributes 1997-08-05 */
 176 } ExportEntry;
 177
 178
 179 /* The "objstats" structure provides a place for gdb to record some
 180    interesting information about its internal state at runtime, on a
 181    per objfile basis, such as information about the number of symbols
 182    read, size of string table (if any), etc. */
 183
 184 struct objstats {
 185   int n_minsyms;        /* Number of minimal symbols read */
 186   int n_psyms;          /* Number of partial symbols read */
 187   int n_syms;           /* Number of full symbols read */
 188   int n_stabs;          /* Number of ".stabs" read (if applicable) */
 189   int n_types;          /* Number of types */
 190   int sz_strtab;        /* Size of stringtable, (if applicable) */
 191 };
 192
 193 #define OBJSTAT(objfile, expr) (objfile -> stats.expr)
 194 #define OBJSTATS struct objstats stats
 195 extern void print_objfile_statistics PARAMS ((void));
 196 extern void print_symbol_bcache_statistics PARAMS ((void));
 197
 198 /* Master structure for keeping track of each file from which
 199    gdb reads symbols.  There are several ways these get allocated: 1.
 200    The main symbol file, symfile_objfile, set by the symbol-file command,
 201    2.  Additional symbol files added by the add-symbol-file command,
 202    3.  Shared library objfiles, added by ADD_SOLIB,  4.  symbol files
 203    for modules that were loaded when GDB attached to a remote system
 204    (see remote-vx.c).  */
 205
 206 struct objfile
 207 {
 208
 209   /* All struct objfile's are chained together by their next pointers.
 210      The global variable "object_files" points to the first link in this
 211      chain.
 212
 213      FIXME:  There is a problem here if the objfile is reusable, and if
 214      multiple users are to be supported.  The problem is that the objfile
 215      list is linked through a member of the objfile struct itself, which
 216      is only valid for one gdb process.  The list implementation needs to
 217      be changed to something like:
 218
 219      struct list {struct list *next; struct objfile *objfile};
 220
 221      where the list structure is completely maintained separately within
 222      each gdb process. */
 223
 224   struct objfile *next;
 225
 226   /* The object file's name.  Malloc'd; free it if you free this struct.  */
 227
 228   char *name;
 229
 230   /* TRUE if this objfile was created because the user explicitly caused
 231      it (e.g., used the add-symbol-file command).
 232      */
 233   int  user_loaded;
 234
 235   /* TRUE if this objfile was explicitly created to represent a solib.
 236
 237      (If FALSE, the objfile may actually be a solib.  This can happen if
 238      the user created the objfile by using the add-symbol-file command.
 239      GDB doesn't in that situation actually check whether the file is a
 240      solib.  Rather, the target's implementation of the solib interface
 241      is responsible for setting this flag when noticing solibs used by
 242      an inferior.)
 243      */
 244   int  is_solib;
 245
 246   /* Some flag bits for this objfile. */
 247
 248   unsigned short flags;
 249
 250   /* Each objfile points to a linked list of symtabs derived from this file,
 251      one symtab structure for each compilation unit (source file).  Each link
 252      in the symtab list contains a backpointer to this objfile. */
 253
 254   struct symtab *symtabs;
 255
 256   /* Each objfile points to a linked list of partial symtabs derived from
 257      this file, one partial symtab structure for each compilation unit
 258      (source file). */
 259
 260   struct partial_symtab *psymtabs;
 261
 262   /* List of freed partial symtabs, available for re-use */
 263
 264   struct partial_symtab *free_psymtabs;
 265
 266   /* The object file's BFD.  Can be null if the objfile contains only
 267      minimal symbols, e.g. the run time common symbols for SunOS4.  */
 268
 269   bfd *obfd;
 270
 271   /* The modification timestamp of the object file, as of the last time
 272      we read its symbols.  */
 273
 274   long mtime;
 275
 276   /* Obstacks to hold objects that should be freed when we load a new symbol
 277      table from this object file. */
 278
 279   struct obstack psymbol_obstack;       /* Partial symbols */
 280   struct obstack symbol_obstack;        /* Full symbols */
 281   struct obstack type_obstack;          /* Types */
 282
 283   /* A byte cache where we can stash arbitrary "chunks" of bytes that
 284      will not change. */
 285
 286   struct bcache psymbol_cache;          /* Byte cache for partial syms */
 287
 288   /* Vectors of all partial symbols read in from file.  The actual data
 289      is stored in the psymbol_obstack. */
 290
 291   struct psymbol_allocation_list global_psymbols;
 292   struct psymbol_allocation_list static_psymbols;
 293
 294   /* Each file contains a pointer to an array of minimal symbols for all
 295      global symbols that are defined within the file.  The array is terminated
 296      by a "null symbol", one that has a NULL pointer for the name and a zero
 297      value for the address.  This makes it easy to walk through the array
 298      when passed a pointer to somewhere in the middle of it.  There is also
 299      a count of the number of symbols, which does not include the terminating
 300      null symbol.  The array itself, as well as all the data that it points
 301      to, should be allocated on the symbol_obstack for this file. */
 302
 303   struct minimal_symbol *msymbols;
 304   int minimal_symbol_count;
 305
 306   /* For object file formats which don't specify fundamental types, gdb
 307      can create such types.  For now, it maintains a vector of pointers
 308      to these internally created fundamental types on a per objfile basis,
 309      however it really should ultimately keep them on a per-compilation-unit
 310      basis, to account for linkage-units that consist of a number of
 311      compilation units that may have different fundamental types, such as
 312      linking C modules with ADA modules, or linking C modules that are
 313      compiled with 32-bit ints with C modules that are compiled with 64-bit
 314      ints (not inherently evil with a smarter linker). */
 315
 316   struct type **fundamental_types;
 317
 318   /* The mmalloc() malloc-descriptor for this objfile if we are using
 319      the memory mapped malloc() package to manage storage for this objfile's
 320      data.  NULL if we are not. */
 321
 322   PTR md;
 323
 324   /* The file descriptor that was used to obtain the mmalloc descriptor
 325      for this objfile.  If we call mmalloc_detach with the malloc descriptor
 326      we should then close this file descriptor. */
 327
 328   int mmfd;
 329
 330   /* Structure which keeps track of functions that manipulate objfile's
 331      of the same type as this objfile.  I.E. the function to read partial
 332      symbols for example.  Note that this structure is in statically
 333      allocated memory, and is shared by all objfiles that use the
 334      object module reader of this type. */
 335
 336   struct sym_fns *sf;
 337
 338   /* The per-objfile information about the entry point, the scope (file/func)
 339      containing the entry point, and the scope of the user's main() func. */
 340
 341   struct entry_info ei;
 342
 343   /* Information about stabs.  Will be filled in with a dbx_symfile_info
 344      struct by those readers that need it. */
 345
 346   struct dbx_symfile_info *sym_stab_info;
 347
 348   /* Hook for information for use by the symbol reader (currently used
 349      for information shared by sym_init and sym_read).  It is
 350      typically a pointer to malloc'd memory.  The symbol reader's finish
 351      function is responsible for freeing the memory thusly allocated.  */
 352
 353   PTR sym_private;
 354
 355   /* Hook for target-architecture-specific information.  This must
 356      point to memory allocated on one of the obstacks in this objfile,
 357      so that it gets freed automatically when reading a new object
 358      file. */
 359
 360   PTR obj_private;
 361
 362   /* Set of relocation offsets to apply to each section.
 363      Currently on the psymbol_obstack (which makes no sense, but I'm
 364      not sure it's harming anything).
 365
 366      These offsets indicate that all symbols (including partial and
 367      minimal symbols) which have been read have been relocated by this
 368      much.  Symbols which are yet to be read need to be relocated by
 369      it.  */
 370
 371   struct section_offsets *section_offsets;
 372   int num_sections;
 373
 374   /* set of section begin and end addresses used to map pc addresses
 375      into sections.  Currently on the psymbol_obstack (which makes no
 376      sense, but I'm not sure it's harming anything).  */
 377
 378   struct obj_section
 379     *sections,
 380     *sections_end;
 381
 382   /* two auxiliary fields, used to hold the fp of separate symbol files */
 383   FILE *auxf1, *auxf2;
 384
 385   /* Imported symbols */
 386   ImportEntry * import_list;
 387   int import_list_size;
 388
 389   /* Exported symbols */
 390   ExportEntry * export_list;
 391   int export_list_size;
 392
 393   /* Place to stash various statistics about this objfile */
 394   OBJSTATS;
 395 };
 396
 397 /* Defines for the objfile flag word. */
 398
 399 /* Gdb can arrange to allocate storage for all objects related to a
 400    particular objfile in a designated section of its address space,
 401    managed at a low level by mmap() and using a special version of
 402    malloc that handles malloc/free/realloc on top of the mmap() interface.
 403    This allows the "internal gdb state" for a particular objfile to be
 404    dumped to a gdb state file and subsequently reloaded at a later time. */
 405
 406 #define OBJF_MAPPED     (1 << 0)        /* Objfile data is mmap'd */
 407
 408 /* When using mapped/remapped predigested gdb symbol information, we need
 409    a flag that indicates that we have previously done an initial symbol
 410    table read from this particular objfile.  We can't just look for the
 411    absence of any of the three symbol tables (msymbols, psymtab, symtab)
 412    because if the file has no symbols for example, none of these will
 413    exist. */
 414
 415 #define OBJF_SYMS       (1 << 1)        /* Have tried to read symbols */
 416
 417 /* When an object file has its functions reordered (currently Irix-5.2
 418    shared libraries exhibit this behaviour), we will need an expensive
 419    algorithm to locate a partial symtab or symtab via an address.
 420    To avoid this penalty for normal object files, we use this flag,
 421    whose setting is determined upon symbol table read in.  */
 422
 423 #define OBJF_REORDERED  (1 << 2)        /* Functions are reordered */
 424
 425 /* Distinguish between an objfile for a shared library and a
 426    "vanilla" objfile. */
 427
 428 #define OBJF_SHARED     (1 << 3)        /* From a shared library */
 429
 430 /* The object file that the main symbol table was loaded from (e.g. the
 431    argument to the "symbol-file" or "file" command).  */
 432
 433 extern struct objfile *symfile_objfile;
 434
 435 /* The object file that contains the runtime common minimal symbols
 436    for SunOS4. Note that this objfile has no associated BFD.  */
 437
 438 extern struct objfile *rt_common_objfile;
 439
 440 /* When we need to allocate a new type, we need to know which type_obstack
 441    to allocate the type on, since there is one for each objfile.  The places
 442    where types are allocated are deeply buried in function call hierarchies
 443    which know nothing about objfiles, so rather than trying to pass a
 444    particular objfile down to them, we just do an end run around them and
 445    set current_objfile to be whatever objfile we expect to be using at the
 446    time types are being allocated.  For instance, when we start reading
 447    symbols for a particular objfile, we set current_objfile to point to that
 448    objfile, and when we are done, we set it back to NULL, to ensure that we
 449    never put a type someplace other than where we are expecting to put it.
 450    FIXME:  Maybe we should review the entire type handling system and
 451    see if there is a better way to avoid this problem. */
 452
 453 extern struct objfile *current_objfile;
 454
 455 /* All known objfiles are kept in a linked list.  This points to the
 456    root of this list. */
 457
 458 extern struct objfile *object_files;
 459
 460 /* Declarations for functions defined in objfiles.c */
 461
 462 extern struct objfile *
 463 allocate_objfile PARAMS ((bfd *, int, int, int));
 464
 465 extern int
 466 build_objfile_section_table PARAMS ((struct objfile *));
 467
 468 extern void objfile_to_front PARAMS ((struct objfile *));
 469
 470 extern void
 471 unlink_objfile PARAMS ((struct objfile *));
 472
 473 extern void
 474 free_objfile PARAMS ((struct objfile *));
 475
 476 extern void
 477 free_all_objfiles PARAMS ((void));
 478
 479 extern void
 480 objfile_relocate PARAMS ((struct objfile *, struct section_offsets *));
 481
 482 extern int
 483 have_partial_symbols PARAMS ((void));
 484
 485 extern int
 486 have_full_symbols PARAMS ((void));
 487
 488 /* This operation deletes all objfile entries that represent solibs that
 489    weren't explicitly loaded by the user, via e.g., the add-symbol-file
 490    command.
 491    */
 492 extern void
 493 objfile_purge_solibs PARAMS ((void));
 494
 495 /* Functions for dealing with the minimal symbol table, really a misc
 496    address<->symbol mapping for things we don't have debug symbols for.  */
 497
 498 extern int
 499 have_minimal_symbols PARAMS ((void));
 500
 501 extern struct obj_section *
 502 find_pc_section PARAMS((CORE_ADDR pc));
 503
 504 extern struct obj_section *
 505 find_pc_sect_section PARAMS((CORE_ADDR pc, asection *section));
 506
 507 extern int
 508 in_plt_section PARAMS ((CORE_ADDR, char *));
 509
 510 /* Traverse all object files.  ALL_OBJFILES_SAFE works even if you delete
 511    the objfile during the traversal.  */
 512
 513 #define ALL_OBJFILES(obj) \
 514   for ((obj) = object_files; (obj) != NULL; (obj) = (obj)->next)
 515
 516 #define ALL_OBJFILES_SAFE(obj,nxt) \
 517   for ((obj) = object_files;       \
 518        (obj) != NULL? ((nxt)=(obj)->next,1) :0; \
 519        (obj) = (nxt))
 520
 521 /* Traverse all symtabs in one objfile.  */
 522
 523 #define ALL_OBJFILE_SYMTABS(objfile, s) \
 524     for ((s) = (objfile) -> symtabs; (s) != NULL; (s) = (s) -> next)
 525
 526 /* Traverse all psymtabs in one objfile.  */
 527
 528 #define ALL_OBJFILE_PSYMTABS(objfile, p) \
 529     for ((p) = (objfile) -> psymtabs; (p) != NULL; (p) = (p) -> next)
 530
 531 /* Traverse all minimal symbols in one objfile.  */
 532
 533 #define ALL_OBJFILE_MSYMBOLS(objfile, m) \
 534     for ((m) = (objfile) -> msymbols; SYMBOL_NAME(m) != NULL; (m)++)
 535
 536 /* Traverse all symtabs in all objfiles.  */
 537
 538 #define ALL_SYMTABS(objfile, s) \
 539   ALL_OBJFILES (objfile)         \
 540     ALL_OBJFILE_SYMTABS (objfile, s)
 541
 542 /* Traverse all psymtabs in all objfiles.  */
 543
 544 #define ALL_PSYMTABS(objfile, p) \
 545   ALL_OBJFILES (objfile)         \
 546     ALL_OBJFILE_PSYMTABS (objfile, p)
 547
 548 /* Traverse all minimal symbols in all objfiles.  */
 549
 550 #define ALL_MSYMBOLS(objfile, m) \
 551   ALL_OBJFILES (objfile)         \
 552     if ((objfile)->msymbols)     \
 553       ALL_OBJFILE_MSYMBOLS (objfile, m)
 554
 555 #define ALL_OBJFILE_OSECTIONS(objfile, osect)   \
 556   for (osect = objfile->sections; osect < objfile->sections_end; osect++)
 557
 558 #define ALL_OBJSECTIONS(objfile, osect)         \
 559   ALL_OBJFILES (objfile)                        \
 560     ALL_OBJFILE_OSECTIONS (objfile, osect)
 561
 562 #endif  /* !defined (OBJFILES_H) */