section.c

早期freebsd实现

asection *
DEFUN(bfd_get_section_by_name,(abfd, name),
      bfd *abfd AND
      CONST char *name)
{
  asection *sect;

  for (sect = abfd->sections; sect != NULL; sect = sect->next)
    if (!strcmp (sect->name, name)) return sect;
  return NULL;
}


/*
FUNCTION
	bfd_make_section_old_way

SYNOPSIS
	asection *bfd_make_section_old_way(bfd *, CONST char *name);

DESCRIPTION
	This function creates a new empty section called @var{name}
	and attaches it to the end of the chain of sections for the
	BFD supplied. An attempt to create a section with a name which
	is already in use, returns its pointer without changing the
	section chain.

	It has the funny name since this is the way it used to be
	before is was rewritten...

	Possible errors are:
	o invalid_operation -
	If output has already started for this BFD.
	o no_memory -
	If obstack alloc fails.

*/


asection *
DEFUN(bfd_make_section_old_way,(abfd, name),
      bfd *abfd AND
      CONST char * name)
{
  asection *sec = bfd_get_section_by_name(abfd, name);
  if (sec == (asection *)NULL) 
    {
      sec = bfd_make_section(abfd, name);
    }
  return sec;
}


/*
FUNCTION
	bfd_make_section

SYNOPSIS
	asection * bfd_make_section(bfd *, CONST char *name);

DESCRIPTION
	This function creates a new empty section called @var{name}
	and attaches it to the end of the chain of sections for the
	BFD supplied. An attempt to create a section with a name which
	is already in use, returns NULL without changing the section
	chain.

	Possible errors are:
	o invalid_operation - If output has already started for this BFD.
	o no_memory - If obstack alloc fails.
*/



sec_ptr
DEFUN(bfd_make_section,(abfd, name),
      bfd *abfd AND
      CONST char * name)
{
  asection *newsect;  
  asection **  prev = &abfd->sections;
  asection * sect = abfd->sections;
  
  if (abfd->output_has_begun) {
    bfd_error = invalid_operation;
    return NULL;
  }

  if (strcmp(name, BFD_ABS_SECTION_NAME) == 0) 
  {
    return &bfd_abs_section;
  }
  if (strcmp(name, BFD_COM_SECTION_NAME) == 0) 
  {
    return &bfd_com_section;
  }
  if (strcmp(name, BFD_UND_SECTION_NAME) == 0) 
  {
    return &bfd_und_section;
  }
  
  while (sect) {
    if (!strcmp(sect->name, name)) return NULL;
    prev = &sect->next;
    sect = sect->next;
  }

  newsect = (asection *) bfd_zalloc(abfd, sizeof (asection));
  if (newsect == NULL) {
    bfd_error = no_memory;
    return NULL;
  }

  newsect->name = name;
  newsect->index = abfd->section_count++;
  newsect->flags = SEC_NO_FLAGS;

  newsect->userdata = 0;
  newsect->next = (asection *)NULL;
  newsect->relocation = (arelent *)NULL;
  newsect->reloc_count = 0;
  newsect->line_filepos =0;
  newsect->owner = abfd;

  /* Create a symbol whos only job is to point to this section. This is
     useful for things like relocs which are relative to the base of a
     section.  */
  newsect->symbol = bfd_make_empty_symbol(abfd);
  newsect->symbol->name = name;
  newsect->symbol->value = 0;
  newsect->symbol->section = newsect;
  newsect->symbol->flags = BSF_SECTION_SYM;
  

  newsect->symbol_ptr_ptr = &newsect->symbol;
  
  if (BFD_SEND (abfd, _new_section_hook, (abfd, newsect)) != true) {
    free (newsect);
    return NULL;
  }

  *prev = newsect;
  return newsect;
}


/*
FUNCTION
	bfd_set_section_flags

SYNOPSIS
	boolean bfd_set_section_flags(bfd *, asection *, flagword);

DESCRIPTION
	Attempts to set the attributes of the section named in the BFD
	supplied to the value. Returns true on success, false on
	error. Possible error returns are:

	o invalid operation -
	The section cannot have one or more of the attributes
	requested. For example, a .bss section in <<a.out>> may not
	have the <<SEC_HAS_CONTENTS>> field set.

*/

boolean
DEFUN(bfd_set_section_flags,(abfd, section, flags),
     bfd *abfd AND
     sec_ptr section AND
     flagword flags)
{
#if 0
  /* If you try to copy a text section from an input file (where it
     has the SEC_CODE flag set) to an output file, this loses big if
     the bfd_applicable_section_flags (abfd) doesn't have the SEC_CODE
     set - which it doesn't, at least not for a.out.  FIXME */

  if ((flags & bfd_applicable_section_flags (abfd)) != flags) {
    bfd_error = invalid_operation;
    return false;
  }
#endif

  section->flags = flags;
  return true;
}


/*
FUNCTION
	bfd_map_over_sections

SYNOPSIS
	void bfd_map_over_sections(bfd *abfd,
				   void (*func)(bfd *abfd,
						asection *sect,
						PTR obj),
				   PTR obj);

DESCRIPTION
	Calls the provided function @var{func} for each section
	attached to the BFD @var{abfd}, passing @var{obj} as an
	argument. The function will be called as if by 

|	func(abfd, the_section, obj);

	This is the prefered method for iterating over sections, an
	alternative would be to use a loop:

|	   section *p;
|	   for (p = abfd->sections; p != NULL; p = p->next)
|	      func(abfd, p, ...)


*/

/*VARARGS2*/
void
DEFUN(bfd_map_over_sections,(abfd, operation, user_storage),
      bfd *abfd AND
      void EXFUN((*operation), (bfd *abfd,
				asection *sect,
				PTR obj)) AND
      PTR user_storage)
{
  asection *sect;
  int i = 0;
  
  for (sect = abfd->sections; sect != NULL; i++, sect = sect->next)
    (*operation) (abfd, sect, user_storage);

  if (i != abfd->section_count)         /* Debugging */
    abort();
}


/*
FUNCTION
	bfd_set_section_size

SYNOPSIS
	boolean bfd_set_section_size(bfd *, asection *, bfd_size_type val);

DESCRIPTION
	Sets @var{section} to the size @var{val}. If the operation is
	ok, then <<true>> is returned, else <<false>>. 

	Possible error returns:
	o invalid_operation -
	Writing has started to the BFD, so setting the size is invalid

*/

boolean
DEFUN(bfd_set_section_size,(abfd, ptr, val),
      bfd *abfd AND
      sec_ptr ptr AND
      bfd_size_type val)
{
  /* Once you've started writing to any section you cannot create or change
     the size of any others. */

  if (abfd->output_has_begun) {
    bfd_error = invalid_operation;
    return false;
  }

  ptr->_cooked_size = val;
  ptr->_raw_size = val;
  
  return true;
}

/*
FUNCTION
	bfd_set_section_contents

SYNOPSIS
	boolean bfd_set_section_contents
         (bfd *abfd,        
         asection *section,
         PTR data,
         file_ptr offset,
         bfd_size_type count);


DESCRIPTION
	Sets the contents of the section @var{section} in BFD
	@var{abfd} to the data starting in memory at @var{data}. The
	data is written to the output section starting at offset
	@var{offset} for @var{count} bytes. 



	Normally <<true>> is returned, else <<false>>. Possible error
	returns are:
	o no_contents -
	The output section does not have the <<SEC_HAS_CONTENTS>>
	attribute, so nothing can be written to it.
	o and some more too

	This routine is front end to the back end function
	<<_bfd_set_section_contents>>.


*/

#define bfd_get_section_size_now(abfd,sec) \
(sec->reloc_done \
 ? bfd_get_section_size_after_reloc (sec) \
 : bfd_get_section_size_before_reloc (sec))

boolean
DEFUN(bfd_set_section_contents,(abfd, section, location, offset, count),
      bfd *abfd AND
      sec_ptr section AND
      PTR location AND
      file_ptr offset AND
      bfd_size_type count)
{
  bfd_size_type sz;

  if (!(bfd_get_section_flags(abfd, section) & SEC_HAS_CONTENTS)) 
      {
        bfd_error = no_contents;
        return(false);
      }

  if (offset < 0 || count < 0)
    {
    bad_val:
      bfd_error = bad_value;
      return false;
    }
  sz = bfd_get_section_size_now (abfd, section);
  if (offset > sz
      || count > sz
      || offset + count > sz)
    goto bad_val;

  if (BFD_SEND (abfd, _bfd_set_section_contents,
                (abfd, section, location, offset, count))) 
      {
        abfd->output_has_begun = true;
        return true;
      }

  return false;
}

/*
FUNCTION
	bfd_get_section_contents

SYNOPSIS
	boolean bfd_get_section_contents 
        (bfd *abfd, asection *section, PTR location,
         file_ptr offset, bfd_size_type count);

DESCRIPTION
	This function reads data from @var{section} in BFD @var{abfd}
	into memory starting at @var{location}. The data is read at an
	offset of @var{offset} from the start of the input section,
	and is read for @var{count} bytes.

	If the contents of a constuctor with the <<SEC_CONSTUCTOR>>
	flag set are requested, then the @var{location} is filled with
	zeroes. If no errors occur, <<true>> is returned, else
	<<false>>.



*/
boolean
DEFUN(bfd_get_section_contents,(abfd, section, location, offset, count),
      bfd *abfd AND
      sec_ptr section AND
      PTR location AND
      file_ptr offset AND
      bfd_size_type count)
{
  bfd_size_type sz;

  if (section->flags & SEC_CONSTRUCTOR) 
    {
      memset(location, 0, (unsigned)count);
      return true;
    }

  if (offset < 0 || count < 0)
    {
    bad_val:
      bfd_error = bad_value;
      return false;
    }
  sz = bfd_get_section_size_now (abfd, section);
  if (offset > sz
      || count > sz
      || offset + count > sz)
    goto bad_val;

  if (count == 0)
    /* Don't bother.  */
    return true;

  return BFD_SEND (abfd, _bfd_get_section_contents,
		   (abfd, section, location, offset, count));
}