gdb/objfiles.h

   1 /* Definitions for symbol file management in GDB.
   2    Copyright (C) 1992 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., 675 Mass Ave, Cambridge, MA 02139, 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 it's 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   /* Start (inclusive) and end (exclusive) of function containing the
  97      entry point. */
  98
  99   CORE_ADDR entry_func_lowpc;
 100   CORE_ADDR entry_func_highpc;
 101
 102   /* Start (inclusive) and end (exclusive) of object file containing the
 103      entry point. */
 104
 105   CORE_ADDR entry_file_lowpc;
 106   CORE_ADDR entry_file_highpc;
 107
 108   /* Start (inclusive) and end (exclusive) of the user code main() function. */
 109
 110   CORE_ADDR main_func_lowpc;
 111   CORE_ADDR main_func_highpc;
 112
 113 };
 114
 115
 116 /* Sections in an objfile.
 117
 118    It is strange that we have both this notion of "sections"
 119    and the one used by section_offsets.  Section as used
 120    here, (currently at least) means a BFD section, and the sections
 121    are set up from the BFD sections in allocate_objfile.
 122
 123    The sections in section_offsets have their meaning determined by
 124    the symbol format, and they are set up by the sym_offsets function
 125    for that symbol file format.
 126
 127    I'm not sure this could or should be changed, however.  */
 128
 129 struct obj_section {
 130   CORE_ADDR     addr;    /* lowest address in section */
 131   CORE_ADDR     endaddr; /* 1+highest address in section */
 132
 133   /* This field is being used for nefarious purposes by syms_from_objfile.
 134      It is said to be redundant with section_offsets; it's not really being
 135      used that way, however, it's some sort of hack I don't understand
 136      and am not going to try to eliminate (yet, anyway).  FIXME.
 137
 138      It was documented as "offset between (end)addr and actual memory
 139      addresses", but that's not true; addr & endaddr are actual memory
 140      addresses.  */
 141   CORE_ADDR offset;
 142
 143   sec_ptr the_bfd_section; /* BFD section pointer */
 144
 145   /* Objfile this section is part of.  */
 146   struct objfile *objfile;
 147 };
 148
 149 /* Master structure for keeping track of each file from which
 150    gdb reads symbols.  There are several ways these get allocated: 1.
 151    The main symbol file, symfile_objfile, set by the symbol-file command,
 152    2.  Additional symbol files added by the add-symbol-file command,
 153    3.  Shared library objfiles, added by ADD_SOLIB,  4.  symbol files
 154    for modules that were loaded when GDB attached to a remote system
 155    (see remote-vx.c).  */
 156
 157 struct objfile
 158 {
 159
 160   /* All struct objfile's are chained together by their next pointers.
 161      The global variable "object_files" points to the first link in this
 162      chain.
 163
 164      FIXME:  There is a problem here if the objfile is reusable, and if
 165      multiple users are to be supported.  The problem is that the objfile
 166      list is linked through a member of the objfile struct itself, which
 167      is only valid for one gdb process.  The list implementation needs to
 168      be changed to something like:
 169
 170      struct list {struct list *next; struct objfile *objfile};
 171
 172      where the list structure is completely maintained separately within
 173      each gdb process. */
 174
 175   struct objfile *next;
 176
 177   /* The object file's name.  Malloc'd; free it if you free this struct.  */
 178
 179   char *name;
 180
 181   /* Some flag bits for this objfile. */
 182
 183   unsigned short flags;
 184
 185   /* Each objfile points to a linked list of symtabs derived from this file,
 186      one symtab structure for each compilation unit (source file).  Each link
 187      in the symtab list contains a backpointer to this objfile. */
 188
 189   struct symtab *symtabs;
 190
 191   /* Each objfile points to a linked list of partial symtabs derived from
 192      this file, one partial symtab structure for each compilation unit
 193      (source file). */
 194
 195   struct partial_symtab *psymtabs;
 196
 197   /* List of freed partial symtabs, available for re-use */
 198
 199   struct partial_symtab *free_psymtabs;
 200
 201   /* The object file's BFD.  Can be null, in which case bfd_open (name) and
 202      put the result here.  */
 203
 204   bfd *obfd;
 205
 206   /* The modification timestamp of the object file, as of the last time
 207      we read its symbols.  */
 208
 209   long mtime;
 210
 211   /* Obstacks to hold objects that should be freed when we load a new symbol
 212      table from this object file. */
 213
 214   struct obstack psymbol_obstack;       /* Partial symbols */
 215   struct obstack symbol_obstack;        /* Full symbols */
 216   struct obstack type_obstack;          /* Types */
 217
 218   /* Vectors of all partial symbols read in from file.  The actual data
 219      is stored in the psymbol_obstack. */
 220
 221   struct psymbol_allocation_list global_psymbols;
 222   struct psymbol_allocation_list static_psymbols;
 223
 224   /* Each file contains a pointer to an array of minimal symbols for all
 225      global symbols that are defined within the file.  The array is terminated
 226      by a "null symbol", one that has a NULL pointer for the name and a zero
 227      value for the address.  This makes it easy to walk through the array
 228      when passed a pointer to somewhere in the middle of it.  There is also
 229      a count of the number of symbols, which does include the terminating
 230      null symbol.  The array itself, as well as all the data that it points
 231      to, should be allocated on the symbol_obstack for this file. */
 232
 233   struct minimal_symbol *msymbols;
 234   int minimal_symbol_count;
 235
 236   /* For object file formats which don't specify fundamental types, gdb
 237      can create such types.  For now, it maintains a vector of pointers
 238      to these internally created fundamental types on a per objfile basis,
 239      however it really should ultimately keep them on a per-compilation-unit
 240      basis, to account for linkage-units that consist of a number of
 241      compilation units that may have different fundamental types, such as
 242      linking C modules with ADA modules, or linking C modules that are
 243      compiled with 32-bit ints with C modules that are compiled with 64-bit
 244      ints (not inherently evil with a smarter linker). */
 245
 246   struct type **fundamental_types;
 247
 248   /* The mmalloc() malloc-descriptor for this objfile if we are using
 249      the memory mapped malloc() package to manage storage for this objfile's
 250      data.  NULL if we are not. */
 251
 252   PTR md;
 253
 254   /* The file descriptor that was used to obtain the mmalloc descriptor
 255      for this objfile.  If we call mmalloc_detach with the malloc descriptor
 256      we should then close this file descriptor. */
 257
 258   int mmfd;
 259
 260   /* Structure which keeps track of functions that manipulate objfile's
 261      of the same type as this objfile.  I.E. the function to read partial
 262      symbols for example.  Note that this structure is in statically
 263      allocated memory, and is shared by all objfiles that use the
 264      object module reader of this type. */
 265
 266   struct sym_fns *sf;
 267
 268   /* The per-objfile information about the entry point, the scope (file/func)
 269      containing the entry point, and the scope of the user's main() func. */
 270
 271   struct entry_info ei;
 272
 273   /* Information about stabs.  Will be filled in with a dbx_symfile_info
 274      struct by those readers that need it. */
 275
 276   PTR sym_stab_info;
 277
 278   /* Hook for information for use by the symbol reader (currently used
 279      for information shared by sym_init and sym_read).  It is
 280      typically a pointer to malloc'd memory.  The symbol reader's finish
 281      function is responsible for freeing the memory thusly allocated.  */
 282
 283   PTR sym_private;
 284
 285   /* Hook for target-architecture-specific information.  This must
 286      point to memory allocated on one of the obstacks in this objfile,
 287      so that it gets freed automatically when reading a new object
 288      file. */
 289
 290   PTR obj_private;
 291
 292   /* Set of relocation offsets to apply to each section.
 293      Currently on the psymbol_obstack (which makes no sense, but I'm
 294      not sure it's harming anything).
 295
 296      These offsets indicate that all symbols (including partial and
 297      minimal symbols) which have been read have been relocated by this
 298      much.  Symbols which are yet to be read need to be relocated by
 299      it.  */
 300
 301   struct section_offsets *section_offsets;
 302   int num_sections;
 303
 304   /* set of section begin and end addresses used to map pc addresses
 305      into sections.  Currently on the psymbol_obstack (which makes no
 306      sense, but I'm not sure it's harming anything).  */
 307
 308   struct obj_section
 309     *sections,
 310     *sections_end;
 311
 312   /* two auxiliary fields, used to hold the fp of separate symbol files */
 313   FILE *auxf1, *auxf2;
 314 };
 315
 316 /* Defines for the objfile flag word. */
 317
 318 /* Gdb can arrange to allocate storage for all objects related to a
 319    particular objfile in a designated section of it's address space,
 320    managed at a low level by mmap() and using a special version of
 321    malloc that handles malloc/free/realloc on top of the mmap() interface.
 322    This allows the "internal gdb state" for a particular objfile to be
 323    dumped to a gdb state file and subsequently reloaded at a later time. */
 324
 325 #define OBJF_MAPPED     (1 << 0)        /* Objfile data is mmap'd */
 326
 327 /* When using mapped/remapped predigested gdb symbol information, we need
 328    a flag that indicates that we have previously done an initial symbol
 329    table read from this particular objfile.  We can't just look for the
 330    absence of any of the three symbol tables (msymbols, psymtab, symtab)
 331    because if the file has no symbols for example, none of these will
 332    exist. */
 333
 334 #define OBJF_SYMS       (1 << 1)        /* Have tried to read symbols */
 335
 336 /* The object file that the main symbol table was loaded from (e.g. the
 337    argument to the "symbol-file" or "file" command).  */
 338
 339 extern struct objfile *symfile_objfile;
 340
 341 /* When we need to allocate a new type, we need to know which type_obstack
 342    to allocate the type on, since there is one for each objfile.  The places
 343    where types are allocated are deeply buried in function call hierarchies
 344    which know nothing about objfiles, so rather than trying to pass a
 345    particular objfile down to them, we just do an end run around them and
 346    set current_objfile to be whatever objfile we expect to be using at the
 347    time types are being allocated.  For instance, when we start reading
 348    symbols for a particular objfile, we set current_objfile to point to that
 349    objfile, and when we are done, we set it back to NULL, to ensure that we
 350    never put a type someplace other than where we are expecting to put it.
 351    FIXME:  Maybe we should review the entire type handling system and
 352    see if there is a better way to avoid this problem. */
 353
 354 extern struct objfile *current_objfile;
 355
 356 /* All known objfiles are kept in a linked list.  This points to the
 357    root of this list. */
 358
 359 extern struct objfile *object_files;
 360
 361 /* Declarations for functions defined in objfiles.c */
 362
 363 extern struct objfile *allocate_objfile PARAMS ((bfd *, int));
 364
 365 int build_objfile_section_table PARAMS ((struct objfile *));
 366
 367 extern void unlink_objfile PARAMS ((struct objfile *));
 368
 369 extern void free_objfile PARAMS ((struct objfile *));
 370
 371 extern void
 372 free_all_objfiles PARAMS ((void));
 373
 374 extern void
 375 objfile_relocate PARAMS ((struct objfile *, struct section_offsets *));
 376
 377 extern int
 378 have_partial_symbols PARAMS ((void));
 379
 380 extern int
 381 have_full_symbols PARAMS ((void));
 382
 383 /* Functions for dealing with the minimal symbol table, really a misc
 384    address<->symbol mapping for things we don't have debug symbols for.  */
 385
 386 extern int
 387 have_minimal_symbols PARAMS ((void));
 388
 389 extern struct obj_section *
 390 find_pc_section PARAMS((CORE_ADDR pc));
 391
 392 /* Traverse all object files.  ALL_OBJFILES_SAFE works even if you delete
 393    the objfile during the traversal.  */
 394
 395 #define ALL_OBJFILES(obj) \
 396   for ((obj) = object_files; (obj) != NULL; (obj) = (obj)->next)
 397
 398 #define ALL_OBJFILES_SAFE(obj,nxt) \
 399   for ((obj) = object_files;       \
 400        (obj) != NULL? ((nxt)=(obj)->next,1) :0; \
 401        (obj) = (nxt))
 402
 403
 404 /* Traverse all symtabs in one objfile.  */
 405
 406 #define ALL_OBJFILE_SYMTABS(objfile, s) \
 407     for ((s) = (objfile) -> symtabs; (s) != NULL; (s) = (s) -> next)
 408
 409 /* Traverse all psymtabs in one objfile.  */
 410
 411 #define ALL_OBJFILE_PSYMTABS(objfile, p) \
 412     for ((p) = (objfile) -> psymtabs; (p) != NULL; (p) = (p) -> next)
 413
 414 /* Traverse all minimal symbols in one objfile.  */
 415
 416 #define ALL_OBJFILE_MSYMBOLS(objfile, m) \
 417     for ((m) = (objfile) -> msymbols; SYMBOL_NAME(m) != NULL; (m)++)
 418
 419
 420 /* Traverse all symtabs in all objfiles.  */
 421
 422 #define ALL_SYMTABS(objfile, s) \
 423   ALL_OBJFILES (objfile)         \
 424     ALL_OBJFILE_SYMTABS (objfile, s)
 425
 426 /* Traverse all psymtabs in all objfiles.  */
 427
 428 #define ALL_PSYMTABS(objfile, p) \
 429   ALL_OBJFILES (objfile)         \
 430     ALL_OBJFILE_PSYMTABS (objfile, p)
 431
 432 /* Traverse all minimal symbols in all objfiles.  */
 433
 434 #define ALL_MSYMBOLS(objfile, m) \
 435   ALL_OBJFILES (objfile)         \
 436     if ((objfile)->msymbols)     \
 437       ALL_OBJFILE_MSYMBOLS (objfile, m)
 438
 439 #endif  /* !defined (OBJFILES_H) */