reloc.c

早期freebsd实现

  }

  /* 
    Work out which section the relocation is targetted at and the
    initial relocation command value.
    */


  if (symbol->section == &bfd_com_section) {
    relocation = 0;
  }
  else {
    relocation = symbol->value;
  }


  reloc_target_output_section = symbol->section->output_section;

  if (output_bfd && howto->partial_inplace==false) {
    output_base = 0;
  }
  else {
    output_base = reloc_target_output_section->vma;

  }

  relocation += output_base +   symbol->section->output_offset;
  

  relocation += reloc_entry->addend ;


  if(reloc_entry->address > input_section->_cooked_size)
  {
    return bfd_reloc_outofrange;
  }
          

  if (howto->pc_relative == true)
  {
    /*
      Anything which started out as pc relative should end up that
      way too. 
      
      There are two ways we can see a pcrel instruction. Sometimes
      the pcrel displacement has been partially calculated, it
      includes the distance from the start of the section to the
      instruction in it (eg sun3), and sometimes the field is
      totally blank - eg m88kbcs.
      */

        
    relocation -= 
     input_section->output_section->vma + input_section->output_offset;

    if (howto->pcrel_offset == true) {
      relocation -= reloc_entry->address;
    }

  }

  if (output_bfd!= (bfd *)NULL) {
    if ( howto->partial_inplace == false)  {
      /*
	This is a partial relocation, and we want to apply the relocation
	to the reloc entry rather than the raw data. Modify the reloc
	inplace to reflect what we now know.
	*/
      reloc_entry->addend = relocation  ;
      reloc_entry->address +=  input_section->output_offset;
      return flag;
    }
    else 
    {
      /* This is a partial relocation, but inplace, so modify the
	 reloc record a bit. 
	 
	 If we've relocated with a symbol with a section, change
	 into a ref to  the section belonging to the symbol
	 */
      reloc_entry->addend = relocation  ;
      reloc_entry->address +=  input_section->output_offset;


    }
  }
  else 
  {
    
    reloc_entry->addend = 0;
  }
  


  /* 
    Either we are relocating all the way, or we don't want to apply
    the relocation to the reloc entry (probably because there isn't
    any room in the output format to describe addends to relocs)
    */
  relocation >>= howto->rightshift;

  /* Shift everything up to where it's going to be used */
   
  relocation <<= howto->bitpos;

  /* Wait for the day when all have the mask in them */

  /* What we do:
     i instruction to be left alone
     o offset within instruction
     r relocation offset to apply
     S src mask
     D dst mask
     N ~dst mask
     A part 1
     B part 2
     R result
     
     Do this:
     i i i i i o o o o o        from bfd_get<size>
     and           S S S S S    to get the size offset we want
     +   r r r r r r r r r r  to get the final value to place
     and           D D D D D  to chop to right size
     -----------------------
     A A A A A 
     And this:
     ...   i i i i i o o o o o  from bfd_get<size>
     and   N N N N N            get instruction
     -----------------------
     ...   B B B B B
     
     And then:       
     B B B B B       
     or              A A A A A     
     -----------------------
     R R R R R R R R R R        put into bfd_put<size>
     */

#define DOIT(x) \
  x = ( (x & ~howto->dst_mask) | (((x & howto->src_mask) +  relocation) & howto->dst_mask))

   switch (howto->size)
   {
    case 0:
    {
      char x = bfd_get_8(abfd, (char *)data + addr);
      DOIT(x);
      bfd_put_8(abfd,x, (unsigned char *) data + addr);
    }
     break;

    case 1:
    { 
      short x = bfd_get_16(abfd, (bfd_byte *)data + addr);
      DOIT(x);
      bfd_put_16(abfd, x,   (unsigned char *)data + addr);
    }
     break;
    case 2:
    {
      long  x = bfd_get_32(abfd, (bfd_byte *) data + addr);
      DOIT(x);
      bfd_put_32(abfd,x,    (bfd_byte *)data + addr);
    }      
     break;
    case -2:
    {
      long  x = bfd_get_32(abfd, (bfd_byte *) data + addr);
      relocation = -relocation;
      DOIT(x);
      bfd_put_32(abfd,x,    (bfd_byte *)data + addr);
    }      
     break;

    case 3:

     /* Do nothing */
     break;
    default:
     return bfd_reloc_other;
   }

  return flag;
}



/*
DOCDD
INODE
	howto manager,  , typedef arelent, Relocations

SECTION
	The howto manager 

	When an application wants to create a relocation, but doesn't
	know what the target machine might call it, it can find out by
	using this bit of code.

*/

/*
TYPEDEF
	bfd_reloc_code_type

DESCRIPTION
	The insides of a reloc code

CODE_FRAGMENT
.
.typedef enum bfd_reloc_code_real 
.
.{
.       {* 16 bits wide, simple reloc *}
.  BFD_RELOC_16,        
.
.       {* 8 bits wide, but used to form an address like 0xffnn *}
.  BFD_RELOC_8_FFnn,
.
.       {* 8 bits wide, simple *}
.  BFD_RELOC_8,
.
.       {* 8 bits wide, pc relative *}
.  BFD_RELOC_8_PCREL,
.
.       {* The type of reloc used to build a contructor table - at the
.          moment probably a 32 bit wide abs address, but the cpu can
.          choose. *}
.
.  BFD_RELOC_CTOR,
.
.       {* 32 bits wide, simple reloc *}
.  BFD_RELOC_32,
.	{* 32 bits, PC-relative *}
.  BFD_RELOC_32_PCREL,
.
.	{* High 22 bits of 32-bit value; simple reloc.  *}
.  BFD_RELOC_HI22,
.	{* Low 10 bits.  *}
.  BFD_RELOC_LO10,
.
.	{* Reloc types used for i960/b.out.  *}
.  BFD_RELOC_24_PCREL,
.  BFD_RELOC_I960_CALLJ,
.
.  BFD_RELOC_16_PCREL,
.	{* 32-bit pc-relative, shifted right 2 bits (i.e., 30-bit
.	   word displacement, e.g. for SPARC) *}
.  BFD_RELOC_32_PCREL_S2,
.
.  {* now for the sparc/elf codes *}
.  BFD_RELOC_NONE,		{* actually used *}
.  BFD_RELOC_SPARC_WDISP22,
.  BFD_RELOC_SPARC22,
.  BFD_RELOC_SPARC13,
.  BFD_RELOC_SPARC_BASE13,
.  BFD_RELOC_SPARC_GOT10,
.  BFD_RELOC_SPARC_GOT13,
.  BFD_RELOC_SPARC_GOT22,
.  BFD_RELOC_SPARC_PC10,
.  BFD_RELOC_SPARC_PC22,
.  BFD_RELOC_SPARC_WPLT30,
.  BFD_RELOC_SPARC_COPY,
.  BFD_RELOC_SPARC_GLOB_DAT,
.  BFD_RELOC_SPARC_JMP_SLOT,
.  BFD_RELOC_SPARC_RELATIVE,
.  BFD_RELOC_SPARC_UA32,
.
.  {* this one is a.out specific? *}
.  BFD_RELOC_SPARC_BASE22,
.
.  {* this must be the highest numeric value *}
.  BFD_RELOC_UNUSED
. } bfd_reloc_code_real_type;
*/



/*
SECTION
	bfd_reloc_type_lookup

SYNOPSIS
	CONST struct reloc_howto_struct *
	bfd_reloc_type_lookup (bfd *abfd, bfd_reloc_code_real_type code);

DESCRIPTION
	This routine returns a pointer to a howto struct which when
	invoked, will perform the supplied relocation on data from the
	architecture noted.

*/


CONST struct reloc_howto_struct *
DEFUN(bfd_reloc_type_lookup,(abfd, code),
      bfd *abfd AND
      bfd_reloc_code_real_type code)
{
  return BFD_SEND (abfd, reloc_type_lookup, (abfd, code));
}

static reloc_howto_type bfd_howto_32 =
 HOWTO(0, 00,2,32,false,0,false,true,0,"VRT32", false,0xffffffff,0xffffffff,true);


/*
INTERNAL_FUNCTION
	bfd_default_reloc_type_lookup

SYNOPSIS
	CONST struct reloc_howto_struct *bfd_default_reloc_type_lookup
	(CONST struct bfd_arch_info *,
         bfd_reloc_code_real_type  code);

DESCRIPTION
	Provides a default relocation lookuperer for any architectue 


*/
CONST struct reloc_howto_struct *
DEFUN(bfd_default_reloc_type_lookup,(arch,  code),
     CONST struct bfd_arch_info *arch AND
      bfd_reloc_code_real_type  code)
{
    switch (code) 
    {
       case BFD_RELOC_CTOR:
	/* The type of reloc used in a ctor, which will be as wide as the
	   address - so either a 64, 32, or 16 bitter.. */
	switch (arch->bits_per_address) {
	   case 64:
	    BFD_FAIL();
	   case 32:
	    return &bfd_howto_32;
	   case 16:
	    BFD_FAIL();
	   default:
	    BFD_FAIL();
	}
       default:
	BFD_FAIL();
    }
return (CONST struct reloc_howto_struct *)NULL;
}


/*
INTERNAL_FUNCTION
	bfd_generic_relax_section

SYNOPSIS
	boolean bfd_generic_relax_section
	 (bfd *abfd,
	  asection *section,
	  asymbol **symbols);

DESCRIPTION
	Provides default handling for relaxing for back ends which
	don't do relaxing -- i.e., does nothing.
*/

boolean
DEFUN(bfd_generic_relax_section,(abfd, section, symbols),
      bfd *abfd AND
      asection *section AND
      asymbol **symbols)
{
  
  return false;
  
}

		
/*
INTERNAL_FUNCTION
	bfd_generic_get_relocated_section_contents

SYNOPSIS
	bfd_byte *
	   bfd_generic_get_relocated_section_contents(bfd *abfd,
	     struct bfd_seclet_struct  *seclet,
	     bfd_byte *data)

DESCRIPTION
	Provides default handling of relocation effort for back ends
	which can't be bothered to do it efficiently.

*/

bfd_byte *
DEFUN(bfd_generic_get_relocated_section_contents,(abfd, seclet, data),
      bfd *abfd AND
      struct bfd_seclet_struct *seclet AND
      bfd_byte *data)
{
  extern bfd_error_vector_type bfd_error_vector;

  /* Get enough memory to hold the stuff */
  bfd *input_bfd = seclet->u.indirect.section->owner;
  asection *input_section = seclet->u.indirect.section;



  bfd_size_type reloc_size = bfd_get_reloc_upper_bound(input_bfd,
						       input_section);
  arelent **reloc_vector = (arelent **) alloca(reloc_size);
  
  /* read in the section */
  bfd_get_section_contents(input_bfd,
			   input_section,
			   data,
			   0,
			   input_section->_raw_size);
  
/* We're not relaxing the section, so just copy the size info */
  input_section->_cooked_size = input_section->_raw_size;
  input_section->reloc_done = true;
  

  if (bfd_canonicalize_reloc(input_bfd, 
			     input_section,
			     reloc_vector,
			     seclet->u.indirect.symbols) )
  {
    arelent **parent;
    for (parent = reloc_vector;  * parent != (arelent *)NULL;
	 parent++) 
    { 
      bfd_reloc_status_type r=
       bfd_perform_relocation(input_bfd,
			      *parent,
			      data,
			      input_section, 0);
      

      if (r != bfd_reloc_ok) 
      {
	switch (r)
	{
	case bfd_reloc_undefined:
	  bfd_error_vector.undefined_symbol(*parent, seclet);
	  break;
	case bfd_reloc_dangerous: 
	  bfd_error_vector.reloc_dangerous(*parent, seclet);
	  break;
	case bfd_reloc_outofrange:
	case bfd_reloc_overflow:
	  bfd_error_vector.reloc_value_truncated(*parent, seclet);
	  break;
	default:
	  abort();
	  break;
	}

      }
    }    
  }


  return data;

  
}