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