reloc.c

来自「基于4个mips核的noc设计」· C语言 代码 · 共 2,228 行 · 第 1/5 页

   relocateable link depends upon how the object format defines
   relocations.

   FIXME: This routine ignores any special_function in the HOWTO,
   since the existing special_function values have been written for
   bfd_perform_relocation.

   HOWTO is the reloc howto information.
   INPUT_BFD is the BFD which the reloc applies to.
   INPUT_SECTION is the section which the reloc applies to.
   CONTENTS is the contents of the section.
   ADDRESS is the address of the reloc within INPUT_SECTION.
   VALUE is the value of the symbol the reloc refers to.
   ADDEND is the addend of the reloc.  */

bfd_reloc_status_type
_bfd_final_link_relocate (howto, input_bfd, input_section, contents, address,
			  value, addend)
     reloc_howto_type *howto;
     bfd *input_bfd;
     asection *input_section;
     bfd_byte *contents;
     bfd_vma address;
     bfd_vma value;
     bfd_vma addend;
{
  bfd_vma relocation;

  /* Sanity check the address.  */
  if (address > input_section->_raw_size)
    return bfd_reloc_outofrange;

  /* This function assumes that we are dealing with a basic relocation
     against a symbol.  We want to compute the value of the symbol to
     relocate to.  This is just VALUE, the value of the symbol, plus
     ADDEND, any addend associated with the reloc.  */
  relocation = value + addend;

  /* If the relocation is PC relative, we want to set RELOCATION to
     the distance between the symbol (currently in RELOCATION) and the
     location we are relocating.  Some targets (e.g., i386-aout)
     arrange for the contents of the section to be the negative of the
     offset of the location within the section; for such targets
     pcrel_offset is false.  Other targets (e.g., m88kbcs or ELF)
     simply leave the contents of the section as zero; for such
     targets pcrel_offset is true.  If pcrel_offset is false we do not
     need to subtract out the offset of the location within the
     section (which is just ADDRESS).  */
  if (howto->pc_relative)
    {
      relocation -= (input_section->output_section->vma
		     + input_section->output_offset);
      if (howto->pcrel_offset)
	relocation -= address;
    }

  return _bfd_relocate_contents (howto, input_bfd, relocation,
				 contents + address);
}

/* Relocate a given location using a given value and howto.  */

bfd_reloc_status_type
_bfd_relocate_contents (howto, input_bfd, relocation, location)
     reloc_howto_type *howto;
     bfd *input_bfd;
     bfd_vma relocation;
     bfd_byte *location;
{
  int size;
  bfd_vma x = 0;
  bfd_reloc_status_type flag;
  unsigned int rightshift = howto->rightshift;
  unsigned int bitpos = howto->bitpos;

  /* If the size is negative, negate RELOCATION.  This isn't very
     general.  */
  if (howto->size < 0)
    relocation = -relocation;

  /* Get the value we are going to relocate.  */
  size = bfd_get_reloc_size (howto);
  switch (size)
    {
    default:
    case 0:
      abort ();
    case 1:
      x = bfd_get_8 (input_bfd, location);
      break;
    case 2:
      x = bfd_get_16 (input_bfd, location);
      break;
    case 4:
      x = bfd_get_32 (input_bfd, location);
      break;
    case 8:
#ifdef BFD64
      x = bfd_get_64 (input_bfd, location);
#else
      abort ();
#endif
      break;
    }

  /* Check for overflow.  FIXME: We may drop bits during the addition
     which we don't check for.  We must either check at every single
     operation, which would be tedious, or we must do the computations
     in a type larger than bfd_vma, which would be inefficient.  */
  flag = bfd_reloc_ok;
  if (howto->complain_on_overflow != complain_overflow_dont)
    {
      bfd_vma addrmask, fieldmask, signmask, ss;
      bfd_vma a, b, sum;

      /* Get the values to be added together.  For signed and unsigned
         relocations, we assume that all values should be truncated to
         the size of an address.  For bitfields, all the bits matter.
         See also bfd_check_overflow.  */
      fieldmask = N_ONES (howto->bitsize);
      addrmask = N_ONES (bfd_arch_bits_per_address (input_bfd)) | fieldmask;
      a = relocation;
      b = x & howto->src_mask;

      switch (howto->complain_on_overflow)
	{
	case complain_overflow_signed:
	  a = (a & addrmask) >> rightshift;

	  /* If any sign bits are set, all sign bits must be set.
	     That is, A must be a valid negative address after
	     shifting.  */
	  signmask = ~ (fieldmask >> 1);
	  ss = a & signmask;
	  if (ss != 0 && ss != ((addrmask >> rightshift) & signmask))
	    flag = bfd_reloc_overflow;

	  /* We only need this next bit of code if the sign bit of B
             is below the sign bit of A.  This would only happen if
             SRC_MASK had fewer bits than BITSIZE.  Note that if
             SRC_MASK has more bits than BITSIZE, we can get into
             trouble; we would need to verify that B is in range, as
             we do for A above.  */
	  signmask = ((~ howto->src_mask) >> 1) & howto->src_mask;

	  /* Set all the bits above the sign bit.  */
	  b = (b ^ signmask) - signmask;

	  b = (b & addrmask) >> bitpos;

	  /* Now we can do the addition.  */
	  sum = a + b;

	  /* See if the result has the correct sign.  Bits above the
             sign bit are junk now; ignore them.  If the sum is
             positive, make sure we did not have all negative inputs;
             if the sum is negative, make sure we did not have all
             positive inputs.  The test below looks only at the sign
             bits, and it really just
	         SIGN (A) == SIGN (B) && SIGN (A) != SIGN (SUM)
	     */
	  signmask = (fieldmask >> 1) + 1;
	  if (((~ (a ^ b)) & (a ^ sum)) & signmask)
	    flag = bfd_reloc_overflow;

	  break;

	case complain_overflow_unsigned:
	  /* Checking for an unsigned overflow is relatively easy:
             trim the addresses and add, and trim the result as well.
             Overflow is normally indicated when the result does not
             fit in the field.  However, we also need to consider the
             case when, e.g., fieldmask is 0x7fffffff or smaller, an
             input is 0x80000000, and bfd_vma is only 32 bits; then we
             will get sum == 0, but there is an overflow, since the
             inputs did not fit in the field.  Instead of doing a
             separate test, we can check for this by or-ing in the
             operands when testing for the sum overflowing its final
             field.  */
	  a = (a & addrmask) >> rightshift;
	  b = (b & addrmask) >> bitpos;
	  sum = (a + b) & addrmask;
	  if ((a | b | sum) & ~ fieldmask)
	    flag = bfd_reloc_overflow;

	  break;

	case complain_overflow_bitfield:
	  /* Much like the signed check, but for a field one bit
	     wider, and no trimming inputs with addrmask.  We allow a
	     bitfield to represent numbers in the range -2**n to
	     2**n-1, where n is the number of bits in the field.
	     Note that when bfd_vma is 32 bits, a 32-bit reloc can't
	     overflow, which is exactly what we want.  */
	  a >>= rightshift;

	  signmask = ~ fieldmask;
	  ss = a & signmask;
	  if (ss != 0 && ss != (((bfd_vma) -1 >> rightshift) & signmask))
	    flag = bfd_reloc_overflow;

	  signmask = ((~ howto->src_mask) >> 1) & howto->src_mask;
	  b = (b ^ signmask) - signmask;

	  b >>= bitpos;

	  sum = a + b;

	  /* We mask with addrmask here to explicitly allow an address
	     wrap-around.  The Linux kernel relies on it, and it is
	     the only way to write assembler code which can run when
	     loaded at a location 0x80000000 away from the location at
	     which it is linked.  */
	  signmask = fieldmask + 1;
	  if (((~ (a ^ b)) & (a ^ sum)) & signmask & addrmask)
	    flag = bfd_reloc_overflow;

	  break;

	default:
	  abort ();
	}
    }

  /* Put RELOCATION in the right bits.  */
  relocation >>= (bfd_vma) rightshift;
  relocation <<= (bfd_vma) bitpos;

  /* Add RELOCATION to the right bits of X.  */
  x = ((x & ~howto->dst_mask)
       | (((x & howto->src_mask) + relocation) & howto->dst_mask));

  /* Put the relocated value back in the object file.  */
  switch (size)
    {
    default:
    case 0:
      abort ();
    case 1:
      bfd_put_8 (input_bfd, x, location);
      break;
    case 2:
      bfd_put_16 (input_bfd, x, location);
      break;
    case 4:
      bfd_put_32 (input_bfd, x, location);
      break;
    case 8:
#ifdef BFD64
      bfd_put_64 (input_bfd, x, location);
#else
      abort ();
#endif
      break;
    }

  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.  The idea is that, eventually, there
	will be one enumerator for every type of relocation we ever do.
	Pass one of these values to <<bfd_reloc_type_lookup>>, and it'll
	return a howto pointer.

	This does mean that the application must determine the correct
	enumerator value; you can't get a howto pointer from a random set
	of attributes.

SENUM
   bfd_reloc_code_real

ENUM
  BFD_RELOC_64
ENUMX
  BFD_RELOC_32
ENUMX
  BFD_RELOC_26
ENUMX
  BFD_RELOC_24
ENUMX
  BFD_RELOC_16
ENUMX
  BFD_RELOC_14
ENUMX
  BFD_RELOC_8
ENUMDOC
  Basic absolute relocations of N bits.

ENUM
  BFD_RELOC_64_PCREL
ENUMX
  BFD_RELOC_32_PCREL
ENUMX
  BFD_RELOC_24_PCREL
ENUMX
  BFD_RELOC_16_PCREL
ENUMX
  BFD_RELOC_12_PCREL
ENUMX
  BFD_RELOC_8_PCREL
ENUMDOC
  PC-relative relocations.  Sometimes these are relative to the address
of the relocation itself; sometimes they are relative to the start of
the section containing the relocation.  It depends on the specific target.

The 24-bit relocation is used in some Intel 960 configurations.

ENUM
  BFD_RELOC_32_GOT_PCREL
ENUMX
  BFD_RELOC_16_GOT_PCREL
ENUMX
  BFD_RELOC_8_GOT_PCREL
ENUMX
  BFD_RELOC_32_GOTOFF
ENUMX
  BFD_RELOC_16_GOTOFF
ENUMX
  BFD_RELOC_LO16_GOTOFF
ENUMX
  BFD_RELOC_HI16_GOTOFF
ENUMX
  BFD_RELOC_HI16_S_GOTOFF
ENUMX
  BFD_RELOC_8_GOTOFF
ENUMX
  BFD_RELOC_32_PLT_PCREL
ENUMX
  BFD_RELOC_24_PLT_PCREL
ENUMX
  BFD_RELOC_16_PLT_PCREL
ENUMX
  BFD_RELOC_8_PLT_PCREL
ENUMX
  BFD_RELOC_32_PLTOFF
ENUMX
  BFD_RELOC_16_PLTOFF
ENUMX
  BFD_RELOC_LO16_PLTOFF
ENUMX
  BFD_RELOC_HI16_PLTOFF
ENUMX
  BFD_RELOC_HI16_S_PLTOFF
ENUMX
  BFD_RELOC_8_PLTOFF
ENUMDOC
  For ELF.

ENUM
  BFD_RELOC_68K_GLOB_DAT
ENUMX
  BFD_RELOC_68K_JMP_SLOT
ENUMX
  BFD_RELOC_68K_RELATIVE
ENUMDOC
  Relocations used by 68K ELF.

ENUM
  BFD_RELOC_32_BASEREL
ENUMX
  BFD_RELOC_16_BASEREL
ENUMX
  BFD_RELOC_LO16_BASEREL
ENUMX
  BFD_RELOC_HI16_BASEREL
ENUMX
  BFD_RELOC_HI16_S_BASEREL
ENUMX
  BFD_RELOC_8_BASEREL
ENUMX
  BFD_RELOC_RVA
ENUMDOC
  Linkage-table relative.

ENUM
  BFD_RELOC_8_FFnn
ENUMDOC
  Absolute 8-bit relocation, but used to form an address like 0xFFnn.

ENUM
  BFD_RELOC_32_PCREL_S2
ENUMX
  BFD_RELOC_16_PCREL_S2
ENUMX
  BFD_RELOC_23_PCREL_S2
ENUMDOC
  These PC-relative relocations are stored as word displacements --
i.e., byte displacements shifted right two bits.  The 30-bit word
displacement (<<32_PCREL_S2>> -- 32 bits, shifted 2) is used on the
SPARC.  (SPARC tools generally refer to this as <<WDISP30>>.)  The
signed 16-bit displacement is used on the MIPS, and the 23-bit
displacement is used on the Alpha.

ENUM
  BFD_RELOC_HI22
ENUMX
  BFD_RELOC_LO10
ENUMDOC
  High 22 bits and low 10 bits of 32-bit value, placed into lower bits of
the target word.  These are used on the SPARC.

ENUM
  BFD_RELOC_GPREL16
ENUMX
  BFD_RELOC_GPREL32
ENUMDOC
  For systems that allocate a Global Pointer register, these are
displacements off that register.  These relocation types are
handled specially, because the value the register will have is
decided relatively late.

ENUM
  BFD_RELOC_I960_CALLJ
ENUMDOC
  Reloc types used for i960/b.out.

ENUM
  BFD_RELOC_NONE
ENUMX
  BFD_RELOC_SPARC_WDISP22
ENUMX
  BFD_RELOC_SPARC22
ENUMX
  BFD_RELOC_SPARC13
ENUMX
  BFD_RELOC_SPARC_GOT10
ENUMX