symfile.c

早期freebsd实现

/* Generic symbol file reading for the GNU debugger, GDB.
   Copyright 1990, 1991, 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.  */

#include "defs.h"
#include "symtab.h"
#include "gdbtypes.h"
#include "gdbcore.h"
#include "frame.h"
#include "target.h"
#include "value.h"
#include "symfile.h"
#include "objfiles.h"
#include "gdbcmd.h"
#include "breakpoint.h"
#include "language.h"

#include <obstack.h>
#include <assert.h>

#include <sys/types.h>
#include <fcntl.h>
#include <string.h>
#include <sys/stat.h>
#include <ctype.h>

/* Global variables owned by this file */

int readnow_symbol_files;		/* Read full symbols immediately */

/* External variables and functions referenced. */

extern int info_verbose;

/* Functions this file defines */

static void
set_initial_language PARAMS ((void));

static void
load_command PARAMS ((char *, int));

static void
add_symbol_file_command PARAMS ((char *, int));

static void
cashier_psymtab PARAMS ((struct partial_symtab *));

static int
compare_psymbols PARAMS ((const void *, const void *));

static int
compare_symbols PARAMS ((const void *, const void *));

static bfd *
symfile_bfd_open PARAMS ((char *));

static void
find_sym_fns PARAMS ((struct objfile *));

void
clear_symtab_users_once PARAMS ((void));

/* List of all available sym_fns.  On gdb startup, each object file reader
   calls add_symtab_fns() to register information on each format it is
   prepared to read. */

static struct sym_fns *symtab_fns = NULL;

/* Structures with which to manage partial symbol allocation.  */

struct psymbol_allocation_list global_psymbols = {0}, static_psymbols = {0};

/* Flag for whether user will be reloading symbols multiple times.
   Defaults to ON for VxWorks, otherwise OFF.  */

#ifdef SYMBOL_RELOADING_DEFAULT
int symbol_reloading = SYMBOL_RELOADING_DEFAULT;
#else
int symbol_reloading = 0;
#endif

/* Structure to manage complaints about symbol file contents.  */

struct complaint complaint_root[1] = {
  {(char *) 0, 0, complaint_root},
};

/* Some actual complaints.  */

struct complaint oldsyms_complaint = {
	"Replacing old symbols for `%s'", 0, 0 };

struct complaint empty_symtab_complaint = {
	"Empty symbol table found for `%s'", 0, 0 };


/* In the following sort, we always make sure that
   register debug symbol declarations always come before regular
   debug symbol declarations (as might happen when parameters are
   then put into registers by the compiler).

   Since this function is called from within qsort, in an ANSI environment
   it must conform to the prototype for qsort, which specifies that the
   comparison function takes two "void *" pointers. */

static int
compare_symbols (s1p, s2p)
     const PTR s1p;
     const PTR s2p;
{
  register struct symbol **s1, **s2;
  register int namediff;

  s1 = (struct symbol **) s1p;
  s2 = (struct symbol **) s2p;

  /* Compare the initial characters.  */
  namediff = SYMBOL_NAME (*s1)[0] - SYMBOL_NAME (*s2)[0];
  if (namediff != 0) return namediff;

  /* If they match, compare the rest of the names.  */
  namediff = strcmp (SYMBOL_NAME (*s1), SYMBOL_NAME (*s2));
  if (namediff != 0) return namediff;

  /* For symbols of the same name, registers should come first.  */
  return ((SYMBOL_CLASS (*s2) == LOC_REGISTER)
	  - (SYMBOL_CLASS (*s1) == LOC_REGISTER));
}

/*

LOCAL FUNCTION

	compare_psymbols -- compare two partial symbols by name

DESCRIPTION

	Given pointer to two partial symbol table entries, compare
	them by name and return -N, 0, or +N (ala strcmp).  Typically
	used by sorting routines like qsort().

NOTES

	Does direct compare of first two characters before punting
	and passing to strcmp for longer compares.  Note that the
	original version had a bug whereby two null strings or two
	identically named one character strings would return the
	comparison of memory following the null byte.

 */

static int
compare_psymbols (s1p, s2p)
     const PTR s1p;
     const PTR s2p;
{
  register char *st1 = SYMBOL_NAME ((struct partial_symbol *) s1p);
  register char *st2 = SYMBOL_NAME ((struct partial_symbol *) s2p);

  if ((st1[0] - st2[0]) || !st1[0])
    {
      return (st1[0] - st2[0]);
    }
  else if ((st1[1] - st2[1]) || !st1[1])
    {
      return (st1[1] - st2[1]);
    }
  else
    {
      return (strcmp (st1 + 2, st2 + 2));
    }
}

void
sort_pst_symbols (pst)
     struct partial_symtab *pst;
{
  /* Sort the global list; don't sort the static list */

  qsort (pst -> objfile -> global_psymbols.list + pst -> globals_offset,
	 pst -> n_global_syms, sizeof (struct partial_symbol),
	 compare_psymbols);
}

/* Call sort_block_syms to sort alphabetically the symbols of one block.  */

void
sort_block_syms (b)
     register struct block *b;
{
  qsort (&BLOCK_SYM (b, 0), BLOCK_NSYMS (b),
	 sizeof (struct symbol *), compare_symbols);
}

/* Call sort_symtab_syms to sort alphabetically
   the symbols of each block of one symtab.  */

void
sort_symtab_syms (s)
     register struct symtab *s;
{
  register struct blockvector *bv;
  int nbl;
  int i;
  register struct block *b;

  if (s == 0)
    return;
  bv = BLOCKVECTOR (s);
  nbl = BLOCKVECTOR_NBLOCKS (bv);
  for (i = 0; i < nbl; i++)
    {
      b = BLOCKVECTOR_BLOCK (bv, i);
      if (BLOCK_SHOULD_SORT (b))
	sort_block_syms (b);
    }
}

void
sort_all_symtab_syms ()
{
  register struct symtab *s;
  register struct objfile *objfile;

  for (objfile = object_files; objfile != NULL; objfile = objfile -> next)
    {
      for (s = objfile -> symtabs; s != NULL; s = s -> next)
	{
	  sort_symtab_syms (s);
	}
    }
}

/* Make a copy of the string at PTR with SIZE characters in the symbol obstack
   (and add a null character at the end in the copy).
   Returns the address of the copy.  */

char *
obsavestring (ptr, size, obstackp)
     char *ptr;
     int size;
     struct obstack *obstackp;
{
  register char *p = (char *) obstack_alloc (obstackp, size + 1);
  /* Open-coded bcopy--saves function call time.
     These strings are usually short.  */
  {
    register char *p1 = ptr;
    register char *p2 = p;
    char *end = ptr + size;
    while (p1 != end)
      *p2++ = *p1++;
  }
  p[size] = 0;
  return p;
}

/* Concatenate strings S1, S2 and S3; return the new string.
   Space is found in the symbol_obstack.  */

char *
obconcat (obstackp, s1, s2, s3)
     struct obstack *obstackp;
     const char *s1, *s2, *s3;
{
  register int len = strlen (s1) + strlen (s2) + strlen (s3) + 1;
  register char *val = (char *) obstack_alloc (obstackp, len);
  strcpy (val, s1);
  strcat (val, s2);
  strcat (val, s3);
  return val;
}

/* Get the symbol table that corresponds to a partial_symtab.
   This is fast after the first time you do it.  In fact, there
   is an even faster macro PSYMTAB_TO_SYMTAB that does the fast
   case inline.  */

struct symtab *
psymtab_to_symtab (pst)
     register struct partial_symtab *pst;
{
  /* If it's been looked up before, return it. */
  if (pst->symtab)
    return pst->symtab;

  /* If it has not yet been read in, read it.  */
  if (!pst->readin)
    { 
      (*pst->read_symtab) (pst);
    }

  return pst->symtab;
}

/* Initialize entry point information for this objfile. */

void
init_entry_point_info (objfile)
     struct objfile *objfile;
{
  /* Save startup file's range of PC addresses to help blockframe.c
     decide where the bottom of the stack is.  */

  if (bfd_get_file_flags (objfile -> obfd) & EXEC_P)
    {
      /* Executable file -- record its entry point so we'll recognize
	 the startup file because it contains the entry point.  */
      objfile -> ei.entry_point = bfd_get_start_address (objfile -> obfd);
    }
  else
    {
      /* Examination of non-executable.o files.  Short-circuit this stuff.  */
      /* ~0 will not be in any file, we hope.  */
      objfile -> ei.entry_point = ~0;
      /* set the startup file to be an empty range.  */
      objfile -> ei.entry_file_lowpc = 0;
      objfile -> ei.entry_file_highpc = 0;
    }
}

/* Remember the lowest-addressed loadable section we've seen.  
   This function is called via bfd_map_over_sections.  */

#if 0 	/* Not used yet */
static void
find_lowest_section (abfd, sect, obj)
     bfd *abfd;
     asection *sect;
     PTR obj;
{
  asection **lowest = (asection **)obj;

  if (0 == (bfd_get_section_flags (abfd, sect) & SEC_LOAD))
    return;
  if (!*lowest)
    *lowest = sect;		/* First loadable section */
  else if (bfd_section_vma (abfd, *lowest) >= bfd_section_vma (abfd, sect))
    *lowest = sect;		/* A lower loadable section */
}
#endif 

/* Process a symbol file, as either the main file or as a dynamically
   loaded file.

   NAME is the file name (which will be tilde-expanded and made
   absolute herein) (but we don't free or modify NAME itself).
   FROM_TTY says how verbose to be.  MAINLINE specifies whether this
   is the main symbol file, or whether it's an extra symbol file such
   as dynamically loaded code.  If !mainline, ADDR is the address
   where the text segment was loaded.  If VERBO, the caller has printed
   a verbose message about the symbol reading (and complaints can be
   more terse about it).  */

void
syms_from_objfile (objfile, addr, mainline, verbo)
     struct objfile *objfile;
     CORE_ADDR addr;
     int mainline;
     int verbo;
{
  struct section_offsets *section_offsets;
  asection *lowest_sect;

  /* There is a distinction between having no symbol table
     (we refuse to read the file, leaving the old set of symbols around)
     and having no debugging symbols in your symbol table (we read
     the file and end up with a mostly empty symbol table).

     FIXME:  This strategy works correctly when the debugging symbols are
     intermixed with "normal" symbols.  However, when the debugging symbols
     are separate, such as with ELF/DWARF, it is perfectly plausible for
     the symbol table to be missing but still have all the DWARF info
     intact.  Thus in general it is wrong to assume that having no symbol
     table implies no debugging information. */

  if (!(bfd_get_file_flags (objfile -> obfd) & HAS_SYMS))
    return;

  init_entry_point_info (objfile);
  find_sym_fns (objfile);

  if (mainline) 
    {
      /* Since no error yet, throw away the old symbol table.  */

      if (symfile_objfile != NULL)
	{
	  free_objfile (symfile_objfile);
	  symfile_objfile = NULL;
	}

      (*objfile -> sf -> sym_new_init) (objfile);
    }

  /* Convert addr into an offset rather than an absolute address.
     We find the lowest address of a loaded segment in the objfile,
     and assume that <addr> is where that got loaded.  Due to historical
     precedent, we warn if that doesn't happen to be the ".text"
     segment.  */

  if (mainline)
    {
      addr = 0;		/* No offset from objfile addresses.  */
    }
  else
    {
      lowest_sect = bfd_get_section_by_name (objfile->obfd, ".text");
#if 0
      lowest_sect = 0;
      bfd_map_over_sections (objfile->obfd, find_lowest_section,
			     (PTR) &lowest_sect);
#endif

      if (lowest_sect == 0)
	warning ("no loadable sections found in added symbol-file %s",
		 objfile->name);
      else if (0 == bfd_get_section_name (objfile->obfd, lowest_sect)
	       || 0 != strcmp(".text",
			      bfd_get_section_name (objfile->obfd, lowest_sect)))
	warning ("Lowest section in %s is %s at 0x%x",
		 objfile->name,
		 bfd_section_name (objfile->obfd, lowest_sect),
		 bfd_section_vma (objfile->obfd, lowest_sect));

      if (lowest_sect)
	addr -= bfd_section_vma (objfile->obfd, lowest_sect);
    }

  /* Initialize symbol reading routines for this objfile, allow complaints to
     appear for this new file, and record how verbose to be, then do the
     initial symbol reading for this file. */

  (*objfile -> sf -> sym_init) (objfile);
  clear_complaints (1, verbo);
  section_offsets = (*objfile -> sf -> sym_offsets) (objfile, addr);
  (*objfile -> sf -> sym_read) (objfile, section_offsets, mainline);

  /* Don't allow char * to have a typename (else would get caddr_t.)  */
  /* Ditto void *.  FIXME should do this for all the builtin types.  */

  TYPE_NAME (lookup_pointer_type (builtin_type_char)) = 0;
  TYPE_NAME (lookup_pointer_type (builtin_type_void)) = 0;

  /* Mark the objfile has having had initial symbol read attempted.  Note
     that this does not mean we found any symbols... */

  objfile -> flags |= OBJF_SYMS;
}

/* Perform required actions immediately after either reading in the initial
   symbols for a new objfile, or mapping in the symbols from a reusable
   objfile. */
   
void
new_symfile_objfile (objfile, mainline, verbo)
     struct objfile *objfile;
     int mainline;
     int verbo;
{
  if (mainline)
    {
      /* OK, make it the "real" symbol file.  */