objfiles.c

早期freebsd实现

/* GDB routines for manipulating objfiles.
   Copyright 1992 Free Software Foundation, Inc.
   Contributed by Cygnus Support, using pieces from other GDB modules.

This file is part of GDB.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */

/* This file contains support routines for creating, manipulating, and
   destroying objfile structures. */

#include "defs.h"
#include "bfd.h"		/* Binary File Description */
#include "symtab.h"
#include "symfile.h"
#include "objfiles.h"

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <obstack.h>

/* Prototypes for local functions */

#if !defined(NO_MMALLOC) && defined(HAVE_MMAP)

static int
open_existing_mapped_file PARAMS ((char *, long, int));

static int
open_mapped_file PARAMS ((char *filename, long mtime, int mapped));

static CORE_ADDR
map_to_address PARAMS ((void));

#endif  /* !defined(NO_MMALLOC) && defined(HAVE_MMAP) */

/* Message to be printed before the error message, when an error occurs.  */

extern char *error_pre_print;

/* Externally visible variables that are owned by this module.
   See declarations in objfile.h for more info. */

struct objfile *object_files;		/* Linked list of all objfiles */
struct objfile *current_objfile;	/* For symbol file being read in */
struct objfile *symfile_objfile;	/* Main symbol table loaded from */

int mapped_symbol_files;		/* Try to use mapped symbol files */

/* Given a pointer to an initialized bfd (ABFD) and a flag that indicates
   whether or not an objfile is to be mapped (MAPPED), allocate a new objfile
   struct, fill it in as best we can, link it into the list of all known
   objfiles, and return a pointer to the new objfile struct. */

struct objfile *
allocate_objfile (abfd, mapped)
     bfd *abfd;
     int mapped;
{
  struct objfile *objfile = NULL;
  int fd;
  void *md;
  CORE_ADDR mapto;

  mapped |= mapped_symbol_files;

#if !defined(NO_MMALLOC) && defined(HAVE_MMAP)

  /* If we can support mapped symbol files, try to open/reopen the mapped file
     that corresponds to the file from which we wish to read symbols.  If the
     objfile is to be mapped, we must malloc the structure itself using the
     mmap version, and arrange that all memory allocation for the objfile uses
     the mmap routines.  If we are reusing an existing mapped file, from which
     we get our objfile pointer, we have to make sure that we update the
     pointers to the alloc/free functions in the obstack, in case these
     functions have moved within the current gdb. */

  fd = open_mapped_file (bfd_get_filename (abfd), bfd_get_mtime (abfd),
			 mapped);
  if (fd >= 0)
    {
      if (((mapto = map_to_address ()) == 0) ||
	  ((md = mmalloc_attach (fd, (void *) mapto)) == NULL))
	{
	  close (fd);
	}
      else if ((objfile = (struct objfile *) mmalloc_getkey (md, 0)) != NULL)
	{
	  /* Update memory corruption handler function addresses. */
	  init_malloc (md);
	  objfile -> md = md;
	  objfile -> mmfd = fd;
	  /* Update pointers to functions to *our* copies */
	  obstack_chunkfun (&objfile -> psymbol_obstack, xmmalloc);
	  obstack_freefun (&objfile -> psymbol_obstack, mfree);
	  obstack_chunkfun (&objfile -> symbol_obstack, xmmalloc);
	  obstack_freefun (&objfile -> symbol_obstack, mfree);
	  obstack_chunkfun (&objfile -> type_obstack, xmmalloc);
	  obstack_freefun (&objfile -> type_obstack, mfree);
	  /* If already in objfile list, unlink it. */
	  unlink_objfile (objfile);
	  /* Forget things specific to a particular gdb, may have changed. */
	  objfile -> sf = NULL;
	}
      else
	{
	  /* Set up to detect internal memory corruption.  MUST be done before
	     the first malloc.  See comments in init_malloc() and mmcheck(). */
	  init_malloc (md);
	  objfile = (struct objfile *) xmmalloc (md, sizeof (struct objfile));
	  memset (objfile, 0, sizeof (struct objfile));
	  objfile -> md = md;
	  objfile -> mmfd = fd;
	  objfile -> flags |= OBJF_MAPPED;
	  mmalloc_setkey (objfile -> md, 0, objfile);
	  obstack_specify_allocation_with_arg (&objfile -> psymbol_obstack,
					       0, 0, xmmalloc, mfree,
					       objfile -> md);
	  obstack_specify_allocation_with_arg (&objfile -> symbol_obstack,
					       0, 0, xmmalloc, mfree,
					       objfile -> md);
	  obstack_specify_allocation_with_arg (&objfile -> type_obstack,
					       0, 0, xmmalloc, mfree,
					       objfile -> md);
	}
    }

  if (mapped && (objfile == NULL))
    {
      warning ("symbol table for '%s' will not be mapped",
	       bfd_get_filename (abfd));
    }

#else	/* defined(NO_MMALLOC) || !defined(HAVE_MMAP) */

  if (mapped)
    {
      warning ("this version of gdb does not support mapped symbol tables.");

      /* Turn off the global flag so we don't try to do mapped symbol tables
	 any more, which shuts up gdb unless the user specifically gives the
	 "mapped" keyword again. */

      mapped_symbol_files = 0;
    }

#endif	/* !defined(NO_MMALLOC) && defined(HAVE_MMAP) */

  /* If we don't support mapped symbol files, didn't ask for the file to be
     mapped, or failed to open the mapped file for some reason, then revert
     back to an unmapped objfile. */

  if (objfile == NULL)
    {
      objfile = (struct objfile *) xmalloc (sizeof (struct objfile));
      memset (objfile, 0, sizeof (struct objfile));
      objfile -> md = NULL;
      obstack_specify_allocation (&objfile -> psymbol_obstack, 0, 0, xmalloc,
				  free);
      obstack_specify_allocation (&objfile -> symbol_obstack, 0, 0, xmalloc,
				  free);
      obstack_specify_allocation (&objfile -> type_obstack, 0, 0, xmalloc,
				  free);
    }

  /* Update the per-objfile information that comes from the bfd, ensuring
     that any data that is reference is saved in the per-objfile data
     region. */

  objfile -> obfd = abfd;
  if (objfile -> name != NULL)
    {
      mfree (objfile -> md, objfile -> name);
    }
  objfile -> name = mstrsave (objfile -> md, bfd_get_filename (abfd));
  objfile -> mtime = bfd_get_mtime (abfd);

  /* Push this file onto the head of the linked list of other such files. */

  objfile -> next = object_files;
  object_files = objfile;

  return (objfile);
}

/* Unlink OBJFILE from the list of known objfiles, if it is found in the
   list.

   It is not a bug, or error, to call this function if OBJFILE is not known
   to be in the current list.  This is done in the case of mapped objfiles,
   for example, just to ensure that the mapped objfile doesn't appear twice
   in the list.  Since the list is threaded, linking in a mapped objfile
   twice would create a circular list.

   If OBJFILE turns out to be in the list, we zap it's NEXT pointer after
   unlinking it, just to ensure that we have completely severed any linkages
   between the OBJFILE and the list. */

void
unlink_objfile (objfile)
     struct objfile *objfile;
{
  struct objfile** objpp;

  for (objpp = &object_files; *objpp != NULL; objpp = &((*objpp) -> next))
    {
      if (*objpp == objfile) 
	{
	  *objpp = (*objpp) -> next;
	  objfile -> next = NULL;
	  break;
	}
    }
}


/* Destroy an objfile and all the symtabs and psymtabs under it.  Note
   that as much as possible is allocated on the symbol_obstack and
   psymbol_obstack, so that the memory can be efficiently freed.

   Things which we do NOT free because they are not in malloc'd memory
   or not in memory specific to the objfile include:

   	objfile -> sf

   FIXME:  If the objfile is using reusable symbol information (via mmalloc),
   then we need to take into account the fact that more than one process
   may be using the symbol information at the same time (when mmalloc is
   extended to support cooperative locking).  When more than one process
   is using the mapped symbol info, we need to be more careful about when
   we free objects in the reusable area. */

void
free_objfile (objfile)
     struct objfile *objfile;
{
  int mmfd;

  /* First do any symbol file specific actions required when we are
     finished with a particular symbol file.  Note that if the objfile
     is using reusable symbol information (via mmalloc) then each of
     these routines is responsible for doing the correct thing, either
     freeing things which are valid only during this particular gdb
     execution, or leaving them to be reused during the next one. */

  if (objfile -> sf != NULL)
    {
      (*objfile -> sf -> sym_finish) (objfile);
    }

  /* We always close the bfd. */

  if (objfile -> obfd != NULL)
    {
      char *name = bfd_get_filename (objfile->obfd);
      bfd_close (objfile -> obfd);
      free (name);
    }

  /* Remove it from the chain of all objfiles. */

  unlink_objfile (objfile);

  /* Before the symbol table code was redone to make it easier to
     selectively load and remove information particular to a specific
     linkage unit, gdb used to do these things whenever the monolithic
     symbol table was blown away.  How much still needs to be done
     is unknown, but we play it safe for now and keep each action until
     it is shown to be no longer needed. */
     
  clear_symtab_users_once ();
#if defined (CLEAR_SOLIB)
  CLEAR_SOLIB ();