dwarfread.c

早期freebsd实现

DESCRIPTION

	Translate the DWARF line number information to gdb form.

	The ".line" section contains one or more line number tables, one for
	each ".line" section from the objects that were linked.

	The AT_stmt_list attribute for each TAG_source_file entry in the
	".debug" section contains the offset into the ".line" section for the
	start of the table for that file.

	The table itself has the following structure:

	<table length><base address><source statement entry>
	4 bytes       4 bytes       10 bytes

	The table length is the total size of the table, including the 4 bytes
	for the length information.

	The base address is the address of the first instruction generated
	for the source file.

	Each source statement entry has the following structure:

	<line number><statement position><address delta>
	4 bytes      2 bytes             4 bytes

	The line number is relative to the start of the file, starting with
	line 1.

	The statement position either -1 (0xFFFF) or the number of characters
	from the beginning of the line to the beginning of the statement.

	The address delta is the difference between the base address and
	the address of the first instruction for the statement.

	Note that we must copy the bytes from the packed table to our local
	variables before attempting to use them, to avoid alignment problems
	on some machines, particularly RISC processors.

BUGS

	Does gdb expect the line numbers to be sorted?  They are now by
	chance/luck, but are not required to be.  (FIXME)

	The line with number 0 is unused, gdb apparently can discover the
	span of the last line some other way. How?  (FIXME)
 */

static void
decode_line_numbers (linetable)
     char *linetable;
{
  char *tblscan;
  char *tblend;
  unsigned long length;
  unsigned long base;
  unsigned long line;
  unsigned long pc;
  
  if (linetable != NULL)
    {
      tblscan = tblend = linetable;
      length = target_to_host (tblscan, SIZEOF_LINETBL_LENGTH, GET_UNSIGNED,
			       current_objfile);
      tblscan += SIZEOF_LINETBL_LENGTH;
      tblend += length;
      base = target_to_host (tblscan, TARGET_FT_POINTER_SIZE (objfile),
			     GET_UNSIGNED, current_objfile);
      tblscan += TARGET_FT_POINTER_SIZE (objfile);
      base += baseaddr;
      while (tblscan < tblend)
	{
	  line = target_to_host (tblscan, SIZEOF_LINETBL_LINENO, GET_UNSIGNED,
				 current_objfile);
	  tblscan += SIZEOF_LINETBL_LINENO + SIZEOF_LINETBL_STMT;
	  pc = target_to_host (tblscan, SIZEOF_LINETBL_DELTA, GET_UNSIGNED,
			       current_objfile);
	  tblscan += SIZEOF_LINETBL_DELTA;
	  pc += base;
	  if (line != 0)
	    {
	      record_line (current_subfile, line, pc);
	    }
	}
    }
}

/*

LOCAL FUNCTION

	locval -- compute the value of a location attribute

SYNOPSIS

	static int locval (char *loc)

DESCRIPTION

	Given pointer to a string of bytes that define a location, compute
	the location and return the value.

	When computing values involving the current value of the frame pointer,
	the value zero is used, which results in a value relative to the frame
	pointer, rather than the absolute value.  This is what GDB wants
	anyway.
    
	When the result is a register number, the global isreg flag is set,
	otherwise it is cleared.  This is a kludge until we figure out a better
	way to handle the problem.  Gdb's design does not mesh well with the
	DWARF notion of a location computing interpreter, which is a shame
	because the flexibility goes unused.

NOTES

	Note that stack[0] is unused except as a default error return.
	Note that stack overflow is not yet handled.
 */

static int
locval (loc)
     char *loc;
{
  unsigned short nbytes;
  unsigned short locsize;
  auto long stack[64];
  int stacki;
  char *end;
  long regno;
  int loc_atom_code;
  int loc_value_size;
  
  nbytes = attribute_size (AT_location);
  locsize = target_to_host (loc, nbytes, GET_UNSIGNED, current_objfile);
  loc += nbytes;
  end = loc + locsize;
  stacki = 0;
  stack[stacki] = 0;
  isreg = 0;
  offreg = 0;
  loc_value_size = TARGET_FT_LONG_SIZE (current_objfile);
  while (loc < end)
    {
      loc_atom_code = target_to_host (loc, SIZEOF_LOC_ATOM_CODE, GET_UNSIGNED,
				      current_objfile);
      loc += SIZEOF_LOC_ATOM_CODE;
      switch (loc_atom_code)
	{
	  case 0:
	    /* error */
	    loc = end;
	    break;
	  case OP_REG:
	    /* push register (number) */
	    stack[++stacki] = target_to_host (loc, loc_value_size,
					      GET_UNSIGNED, current_objfile);
	    loc += loc_value_size;
	    isreg = 1;
	    break;
	  case OP_BASEREG:
	    /* push value of register (number) */
	    /* Actually, we compute the value as if register has 0 */
	    offreg = 1;
	    regno = target_to_host (loc, loc_value_size, GET_UNSIGNED,
				    current_objfile);
	    loc += loc_value_size;
	    if (regno == R_FP)
	      {
		stack[++stacki] = 0;
	      }
	    else
	      {
		stack[++stacki] = 0;
		SQUAWK (("BASEREG %d not handled!", regno));
	      }
	    break;
	  case OP_ADDR:
	    /* push address (relocated address) */
	    stack[++stacki] = target_to_host (loc, loc_value_size,
					      GET_UNSIGNED, current_objfile);
	    loc += loc_value_size;
	    break;
	  case OP_CONST:
	    /* push constant (number)   FIXME: signed or unsigned! */
	    stack[++stacki] = target_to_host (loc, loc_value_size,
					      GET_SIGNED, current_objfile);
	    loc += loc_value_size;
	    break;
	  case OP_DEREF2:
	    /* pop, deref and push 2 bytes (as a long) */
	    SQUAWK (("OP_DEREF2 address 0x%x not handled", stack[stacki]));
	    break;
	  case OP_DEREF4:	/* pop, deref and push 4 bytes (as a long) */
	    SQUAWK (("OP_DEREF4 address 0x%x not handled", stack[stacki]));
	    break;
	  case OP_ADD:	/* pop top 2 items, add, push result */
	    stack[stacki - 1] += stack[stacki];
	    stacki--;
	    break;
	}
    }
  return (stack[stacki]);
}

/*

LOCAL FUNCTION

	read_ofile_symtab -- build a full symtab entry from chunk of DIE's

SYNOPSIS

	static struct symtab *read_ofile_symtab (struct partial_symtab *pst)

DESCRIPTION

	When expanding a partial symbol table entry to a full symbol table
	entry, this is the function that gets called to read in the symbols
	for the compilation unit.

	Returns a pointer to the newly constructed symtab (which is now
	the new first one on the objfile's symtab list).
 */

static struct symtab *
read_ofile_symtab (pst)
     struct partial_symtab *pst;
{
  struct cleanup *back_to;
  unsigned long lnsize;
  file_ptr foffset;
  bfd *abfd;
  char lnsizedata[SIZEOF_LINETBL_LENGTH];

  abfd = pst -> objfile -> obfd;
  current_objfile = pst -> objfile;

  /* Allocate a buffer for the entire chunk of DIE's for this compilation
     unit, seek to the location in the file, and read in all the DIE's. */

  diecount = 0;
  dbsize = DBLENGTH (pst);
  dbbase = xmalloc (dbsize);
  dbroff = DBROFF(pst);
  foffset = DBFOFF(pst) + dbroff;
  base_section_offsets = pst->section_offsets;
  baseaddr = ANOFFSET (pst->section_offsets, 0);
  if (bfd_seek (abfd, foffset, L_SET) ||
      (bfd_read (dbbase, dbsize, 1, abfd) != dbsize))
    {
      free (dbbase);
      error ("can't read DWARF data");
    }
  back_to = make_cleanup (free, dbbase);

  /* If there is a line number table associated with this compilation unit
     then read the size of this fragment in bytes, from the fragment itself.
     Allocate a buffer for the fragment and read it in for future 
     processing. */

  lnbase = NULL;
  if (LNFOFF (pst))
    {
      if (bfd_seek (abfd, LNFOFF (pst), L_SET) ||
	  (bfd_read ((PTR) lnsizedata, sizeof (lnsizedata), 1, abfd) !=
	   sizeof (lnsizedata)))
	{
	  error ("can't read DWARF line number table size");
	}
      lnsize = target_to_host (lnsizedata, SIZEOF_LINETBL_LENGTH,
			       GET_UNSIGNED, pst -> objfile);
      lnbase = xmalloc (lnsize);
      if (bfd_seek (abfd, LNFOFF (pst), L_SET) ||
	  (bfd_read (lnbase, lnsize, 1, abfd) != lnsize))
	{
	  free (lnbase);
	  error ("can't read DWARF line numbers");
	}
      make_cleanup (free, lnbase);
    }

  process_dies (dbbase, dbbase + dbsize, pst -> objfile);
  do_cleanups (back_to);
  current_objfile = NULL;
  return (pst -> objfile -> symtabs);
}

/*

LOCAL FUNCTION

	psymtab_to_symtab_1 -- do grunt work for building a full symtab entry

SYNOPSIS

	static void psymtab_to_symtab_1 (struct partial_symtab *pst)

DESCRIPTION

	Called once for each partial symbol table entry that needs to be
	expanded into a full symbol table entry.

*/

static void
psymtab_to_symtab_1 (pst)
     struct partial_symtab *pst;
{
  int i;
  struct cleanup *old_chain;
  
  if (pst != NULL)
    {
      if (pst->readin)
	{
	  warning ("psymtab for %s already read in.  Shouldn't happen.",
		   pst -> filename);
	}
      else
	{
	  /* Read in all partial symtabs on which this one is dependent */
	  for (i = 0; i < pst -> number_of_dependencies; i++)
	    {
	      if (!pst -> dependencies[i] -> readin)
		{
		  /* Inform about additional files that need to be read in. */
		  if (info_verbose)
		    {
		      fputs_filtered (" ", stdout);
		      wrap_here ("");
		      fputs_filtered ("and ", stdout);
		      wrap_here ("");
		      printf_filtered ("%s...",
				       pst -> dependencies[i] -> filename);
		      wrap_here ("");
		      fflush (stdout);		/* Flush output */
		    }
		  psymtab_to_symtab_1 (pst -> dependencies[i]);
		}
	    }	  
	  if (DBLENGTH (pst))		/* Otherwise it's a dummy */
	    {
	      buildsym_init ();
	      old_chain = make_cleanup (really_free_pendings, 0);
	      pst -> symtab = read_ofile_symtab (pst);
	      if (info_verbose)
		{
		  printf_filtered ("%d DIE's, sorting...", diecount);
		  wrap_here ("");
		  fflush (stdout);
		}
	      sort_symtab_syms (pst -> symtab);
	      do_cleanups (old_chain);
	    }
	  pst -> readin = 1;
	}
    }
}

/*

LOCAL FUNCTION

	dwarf_psymtab_to_symtab -- build a full symtab entry from partial one

SYNOPSIS

	static void dwarf_psymtab_to_symtab (struct partial_symtab *pst)

DESCRIPTION

	This is the DWARF support entry point for building a full symbol
	table entry from a partial symbol table entry.  We are passed a
	pointer to the partial symbol table entry that needs to be expanded.

*/

static void
dwarf_psymtab_to_symtab (pst)
     struct partial_symtab *pst;
{

  if (pst != NULL)
    {
      if (pst -> readin)
	{
	  warning ("psymtab for %s already read in.  Shouldn't happen.",
		   pst -> filename);
	}
      else
	{
	  if (DBLENGTH (pst) || pst -> number_of_dependencies)
	    {
	      /* Print the message now, before starting serious work, to avoid
		 disconcerting pauses.  */
	      if (info_verbose)
		{
		  printf_filtered ("Reading in symbols for %s...",
				   pst -> filename);
		  fflush (stdout);
		}
	      
	      psymtab_to_symtab_1 (pst);
	      
#if 0	      /* FIXME:  Check to see what dbxread is doing here and see if
		 we need to do an equivalent or is this something peculiar to
		 stabs/a.out format.
		 Match with global symbols.  This only needs to be done once,
		 after all of the symtabs and dependencies have been read in.
		 */
	      scan_file_globals (pst -> objfile);
#endif
	      
	      /* Finish up the verbose info message.  */
	      if (info_verbose)
		{
		  printf_filtered ("done.\n");
		  fflush (stdout);
		}
	    }
	}
    }
}

/*

LOCAL FUNCTION

	init_psymbol_list -- initialize storage for partial symbols

SYNOPSIS

	static void init_psymbol_list (struct objfile *objfile, int total_symbols)

DESCRIPTION

	Initializes storage for all of the partial symbols that will be
	created by dwarf_build_psymtabs and subsidiaries.
 */

static void
init_psymbol_list (objfile, total_symbols)
     struct objfile *objfile;
     int total_symbols;
{
  /* Free any previously allocated psymbol lists.  */
  
  if (objfile -> global_psymbols.list)
    {
      mfree (objfile -> md, (PTR)objfile -> global_psymbols.list);
    }
  if (objfile -> static_psymbols.list)
    {
      mfree (objfile -> md, (PTR)objfile -> static_psymbols.list);
    }
  
  /* Current best guess is that there are approximately a twentieth
     of the total symbols (in a debugging file) are global or static
     oriented symbols */
  
  objfile -> global_psymbols.size = total_symbols / 10;
  objfile -> static_psymbols.size = total_symbols / 10;
  objfile -> global_psymbols.next =
    objfile -> global_psymbols.list = (stru