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 /* The "objstats" structure provides a place for gdb to record some
 163    interesting information about its internal state at runtime, on a
 164    per objfile basis, such as information about the number of symbols
 165    read, size of string table (if any), etc. */
 166
 167 #if MAINTENANCE_CMDS
 168
 169 struct objstats {
 170   int n_minsyms;        /* Number of minimal symbols read */
 171   int n_psyms;          /* Number of partial symbols read */
 172   int n_syms;           /* Number of full symbols read */
 173   int n_stabs;          /* Number of ".stabs" read (if applicable) */
 174   int n_types;          /* Number of types */
 175   int sz_strtab;        /* Size of stringtable, (if applicable) */
 176 };
 177
 178 #define OBJSTAT(objfile, expr) (objfile -> stats.expr)
 179 #define OBJSTATS struct objstats stats
 180 extern void print_objfile_statistics PARAMS ((void));
 181 extern void print_symbol_bcache_statistics PARAMS ((void));
 182
 183 #else
 184
 185 #define OBJSTAT(objfile, expr)  /* Nothing */
 186 #define OBJSTATS                /* Nothing */
 187
 188 #endif  /* MAINTENANCE_CMDS */
 189
 190 /* Master structure for keeping track of each file from which
 191    gdb reads symbols.  There are several ways these get allocated: 1.
 192    The main symbol file, symfile_objfile, set by the symbol-file command,
 193    2.  Additional symbol files added by the add-symbol-file command,
 194    3.  Shared library objfiles, added by ADD_SOLIB,  4.  symbol files
 195    for modules that were loaded when GDB attached to a remote system
 196    (see remote-vx.c).  */
 197
 198 struct objfile
 199 {
 200
 201   /* All struct objfile's are chained together by their next pointers.
 202      The global variable "object_files" points to the first link in this
 203      chain.
 204
 205      FIXME:  There is a problem here if the objfile is reusable, and if
 206      multiple users are to be supported.  The problem is that the objfile
 207      list is linked through a member of the objfile struct itself, which
 208      is only valid for one gdb process.  The list implementation needs to
 209      be changed to something like:
 210
 211      struct list {struct list *next; struct objfile *objfile};
 212
 213      where the list structure is completely maintained separately within
 214      each gdb process. */
 215
 216   struct objfile *next;
 217
 218   /* The object file's name.  Malloc'd; free it if you free this struct.  */
 219
 220   char *name;
 221
 222   /* Some flag bits for this objfile. */
 223
 224   unsigned short flags;
 225
 226   /* Each objfile points to a linked list of symtabs derived from this file,
 227      one symtab structure for each compilation unit (source file).  Each link
 228      in the symtab list contains a backpointer to this objfile. */
 229
 230   struct symtab *symtabs;
 231
 232   /* Each objfile points to a linked list of partial symtabs derived from
 233      this file, one partial symtab structure for each compilation unit
 234      (source file). */
 235
 236   struct partial_symtab *psymtabs;
 237
 238   /* List of freed partial symtabs, available for re-use */
 239
 240   struct partial_symtab *free_psymtabs;
 241
 242   /* The object file's BFD.  Can be null if the objfile contains only
 243      minimal symbols, e.g. the run time common symbols for SunOS4.  */
 244
 245   bfd *obfd;
 246
 247   /* The modification timestamp of the object file, as of the last time
 248      we read its symbols.  */
 249
 250   long mtime;
 251
 252   /* Obstacks to hold objects that should be freed when we load a new symbol
 253      table from this object file. */
 254
 255   struct obstack psymbol_obstack;       /* Partial symbols */
 256   struct obstack symbol_obstack;        /* Full symbols */
 257   struct obstack type_obstack;          /* Types */
 258
 259   /* A byte cache where we can stash arbitrary "chunks" of bytes that
 260      will not change. */
 261
 262   struct bcache psymbol_cache;          /* Byte cache for partial syms */
 263
 264   /* Vectors of all partial symbols read in from file.  The actual data
 265      is stored in the psymbol_obstack. */
 266
 267   struct psymbol_allocation_list global_psymbols;
 268   struct psymbol_allocation_list static_psymbols;
 269
 270   /* Each file contains a pointer to an array of minimal symbols for all
 271      global symbols that are defined within the file.  The array is terminated
 272      by a "null symbol", one that has a NULL pointer for the name and a zero
 273      value for the address.  This makes it easy to walk through the array
 274      when passed a pointer to somewhere in the middle of it.  There is also
 275      a count of the number of symbols, which does not include the terminating
 276      null symbol.  The array itself, as well as all the data that it points
 277      to, should be allocated on the symbol_obstack for this file. */
 278
 279   struct minimal_symbol *msymbols;
 280   int minimal_symbol_count;
 281
 282   /* For object file formats which don't specify fundamental types, gdb
 283      can create such types.  For now, it maintains a vector of pointers
 284      to these internally created fundamental types on a per objfile basis,
 285      however it really should ultimately keep them on a per-compilation-unit
 286      basis, to account for linkage-units that consist of a number of
 287      compilation units that may have different fundamental types, such as
 288      linking C modules with ADA modules, or linking C modules that are
 289      compiled with 32-bit ints with C modules that are compiled with 64-bit
 290      ints (not inherently evil with a smarter linker). */
 291
 292   struct type **fundamental_types;
 293
 294   /* The mmalloc() malloc-descriptor for this objfile if we are using
 295      the memory mapped malloc() package to manage storage for this objfile's
 296      data.  NULL if we are not. */
 297
 298   PTR md;
 299
 300   /* The file descriptor that was used to obtain the mmalloc descriptor
 301      for this objfile.  If we call mmalloc_detach with the malloc descriptor
 302      we should then close this file descriptor. */
 303
 304   int mmfd;
 305
 306   /* Structure which keeps track of functions that manipulate objfile's
 307      of the same type as this objfile.  I.E. the function to read partial
 308      symbols for example.  Note that this structure is in statically
 309      allocated memory, and is shared by all objfiles that use the
 310      object module reader of this type. */
 311
 312   struct sym_fns *sf;
 313
 314   /* The per-objfile information about the entry point, the scope (file/func)
 315      containing the entry point, and the scope of the user's main() func. */
 316
 317   struct entry_info ei;
 318
 319   /* Information about stabs.  Will be filled in with a dbx_symfile_info
 320      struct by those readers that need it. */
 321
 322   struct dbx_symfile_info *sym_stab_info;
 323
 324   /* Hook for information for use by the symbol reader (currently used
 325      for information shared by sym_init and sym_read).  It is
 326      typically a pointer to malloc'd memory.  The symbol reader's finish
 327      function is responsible for freeing the memory thusly allocated.  */
 328
 329   PTR sym_private;
 330
 331   /* Hook for target-architecture-specific information.  This must
 332      point to memory allocated on one of the obstacks in this objfile,
 333      so that it gets freed automatically when reading a new object
 334      file. */
 335
 336   PTR obj_private;
 337
 338   /* Set of relocation offsets to apply to each section.
 339      Currently on the psymbol_obstack (which makes no sense, but I'm
 340      not sure it's harming anything).
 341
 342      These offsets indicate that all symbols (including partial and
 343      minimal symbols) which have been read have been relocated by this
 344      much.  Symbols which are yet to be read need to be relocated by
 345      it.  */
 346
 347   struct section_offsets *section_offsets;
 348   int num_sections;
 349
 350   /* set of section begin and end addresses used to map pc addresses
 351      into sections.  Currently on the psymbol_obstack (which makes no
 352      sense, but I'm not sure it's harming anything).  */
 353
 354   struct obj_section
 355     *sections,
 356     *sections_end;
 357
 358   /* two auxiliary fields, used to hold the fp of separate symbol files */
 359   FILE *auxf1, *auxf2;
 360
 361   /* Place to stash various statistics about this objfile */
 362   OBJSTATS;
 363 };
 364
 365 /* Defines for the objfile flag word. */
 366
 367 /* Gdb can arrange to allocate storage for all objects related to a
 368    particular objfile in a designated section of its address space,
 369    managed at a low level by mmap() and using a special version of
 370    malloc that handles malloc/free/realloc on top of the mmap() interface.
 371    This allows the "internal gdb state" for a particular objfile to be
 372    dumped to a gdb state file and subsequently reloaded at a later time. */
 373
 374 #define OBJF_MAPPED     (1 << 0)        /* Objfile data is mmap'd */
 375
 376 /* When using mapped/remapped predigested gdb symbol information, we need
 377    a flag that indicates that we have previously done an initial symbol
 378    table read from this particular objfile.  We can't just look for the
 379    absence of any of the three symbol tables (msymbols, psymtab, symtab)
 380    because if the file has no symbols for example, none of these will
 381    exist. */
 382
 383 #define OBJF_SYMS       (1 << 1)        /* Have tried to read symbols */
 384
 385 /* When an object file has its functions reordered (currently Irix-5.2
 386    shared libraries exhibit this behaviour), we will need an expensive
 387    algorithm to locate a partial symtab or symtab via an address.
 388    To avoid this penalty for normal object files, we use this flag,
 389    whose setting is determined upon symbol table read in.  */
 390
 391 #define OBJF_REORDERED  (1 << 2)        /* Functions are reordered */
 392
 393 /* Distinguish between an objfile for a shared library and a
 394    "vanilla" objfile. */
 395
 396 #define OBJF_SHARED     (1 << 3)        /* From a shared library */
 397
 398 /* The object file that the main symbol table was loaded from (e.g. the
 399    argument to the "symbol-file" or "file" command).  */
 400
 401 extern struct objfile *symfile_objfile;
 402
 403 /* The object file that contains the runtime common minimal symbols
 404    for SunOS4. Note that this objfile has no associated BFD.  */
 405
 406 extern struct objfile *rt_common_objfile;
 407
 408 /* When we need to allocate a new type, we need to know which type_obstack
 409    to allocate the type on, since there is one for each objfile.  The places
 410    where types are allocated are deeply buried in function call hierarchies
 411    which know nothing about objfiles, so rather than trying to pass a
 412    particular objfile down to them, we just do an end run around them and
 413    set current_objfile to be whatever objfile we expect to be using at the
 414    time types are being allocated.  For instance, when we start reading
 415    symbols for a particular objfile, we set current_objfile to point to that
 416    objfile, and when we are done, we set it back to NULL, to ensure that we
 417    never put a type someplace other than where we are expecting to put it.
 418    FIXME:  Maybe we should review the entire type handling system and
 419    see if there is a better way to avoid this problem. */
 420
 421 extern struct objfile *current_objfile;
 422
 423 /* All known objfiles are kept in a linked list.  This points to the
 424    root of this list. */
 425
 426 extern struct objfile *object_files;
 427
 428 /* Declarations for functions defined in objfiles.c */
 429
 430 extern struct objfile *
 431 allocate_objfile PARAMS ((bfd *, int));
 432
 433 extern int
 434 build_objfile_section_table PARAMS ((struct objfile *));
 435
 436 extern void objfile_to_front PARAMS ((struct objfile *));
 437
 438 extern void
 439 unlink_objfile PARAMS ((struct objfile *));
 440
 441 extern void
 442 free_objfile PARAMS ((struct objfile *));
 443
 444 extern void
 445 free_all_objfiles PARAMS ((void));
 446
 447 extern void
 448 objfile_relocate PARAMS ((struct objfile *, struct section_offsets *));
 449
 450 extern int
 451 have_partial_symbols PARAMS ((void));
 452
 453 extern int
 454 have_full_symbols PARAMS ((void));
 455
 456 /* Functions for dealing with the minimal symbol table, really a misc
 457    address<->symbol mapping for things we don't have debug symbols for.  */
 458
 459 extern int
 460 have_minimal_symbols PARAMS ((void));
 461
 462 extern struct obj_section *
 463 find_pc_section PARAMS((CORE_ADDR pc));
 464
 465 extern struct obj_section *
 466 find_pc_sect_section PARAMS((CORE_ADDR pc, asection *section));
 467
 468 extern int
 469 in_plt_section PARAMS ((CORE_ADDR, char *));
 470
 471 /* Traverse all object files.  ALL_OBJFILES_SAFE works even if you delete
 472    the objfile during the traversal.  */
 473
 474 #define ALL_OBJFILES(obj) \
 475   for ((obj) = object_files; (obj) != NULL; (obj) = (obj)->next)
 476
 477 #define ALL_OBJFILES_SAFE(obj,nxt) \
 478   for ((obj) = object_files;       \
 479        (obj) != NULL? ((nxt)=(obj)->next,1) :0; \
 480        (obj) = (nxt))
 481
 482 /* Traverse all symtabs in one objfile.  */
 483
 484 #define ALL_OBJFILE_SYMTABS(objfile, s) \
 485     for ((s) = (objfile) -> symtabs; (s) != NULL; (s) = (s) -> next)
 486
 487 /* Traverse all psymtabs in one objfile.  */
 488
 489 #define ALL_OBJFILE_PSYMTABS(objfile, p) \
 490     for ((p) = (objfile) -> psymtabs; (p) != NULL; (p) = (p) -> next)
 491
 492 /* Traverse all minimal symbols in one objfile.  */
 493
 494 #define ALL_OBJFILE_MSYMBOLS(objfile, m) \
 495     for ((m) = (objfile) -> msymbols; SYMBOL_NAME(m) != NULL; (m)++)
 496
 497 /* Traverse all symtabs in all objfiles.  */
 498
 499 #define ALL_SYMTABS(objfile, s) \
 500   ALL_OBJFILES (objfile)         \
 501     ALL_OBJFILE_SYMTABS (objfile, s)
 502
 503 /* Traverse all psymtabs in all objfiles.  */
 504
 505 #define ALL_PSYMTABS(objfile, p) \
 506   ALL_OBJFILES (objfile)         \
 507     ALL_OBJFILE_PSYMTABS (objfile, p)
 508
 509 /* Traverse all minimal symbols in all objfiles.  */
 510
 511 #define ALL_MSYMBOLS(objfile, m) \
 512   ALL_OBJFILES (objfile)         \
 513     if ((objfile)->msymbols)     \
 514       ALL_OBJFILE_MSYMBOLS (objfile, m)
 515
 516 #define ALL_OBJFILE_OSECTIONS(objfile, osect)   \
 517   for (osect = objfile->sections; osect < objfile->sections_end; osect++)
 518
 519 #define ALL_OBJSECTIONS(objfile, osect)         \
 520   ALL_OBJFILES (objfile)                        \
 521     ALL_OBJFILE_OSECTIONS (objfile, osect)
 522
 523 #endif  /* !defined (OBJFILES_H) */