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