coff-mips.c

基于4个mips核的noc设计

		    {
		      /* This symbol is not being written out.  */
		      if (! ((*info->callbacks->unattached_reloc)
			     (info, h->root.root.string, input_bfd,
			      input_section,
			      int_rel.r_vaddr - input_section->vma)))
			return false;
		      int_rel.r_symndx = 0;
		    }
		  relocation = 0;
		}
	    }
	  else
	    {
	      /* This is a relocation against a section.  Adjust the
		 value by the amount the section moved.  */
	      relocation = (s->output_section->vma
			    + s->output_offset
			    - s->vma);
	    }

	  relocation += addend;
	  addend = 0;

	  /* Adjust a PC relative relocation by removing the reference
	     to the original address in the section and including the
	     reference to the new address.  However, external RELHI
	     and RELLO relocs are PC relative, but don't include any
	     reference to the address.  The addend is merely an
	     addend.  */
	  if (howto->pc_relative
	      && (! int_rel.r_extern
		  || (int_rel.r_type != MIPS_R_RELHI
		      && int_rel.r_type != MIPS_R_RELLO)))
	    relocation -= (input_section->output_section->vma
			   + input_section->output_offset
			   - input_section->vma);

	  /* Adjust the contents.  */
	  if (relocation == 0)
	    r = bfd_reloc_ok;
	  else
	    {
	      if (int_rel.r_type != MIPS_R_REFHI
		  && int_rel.r_type != MIPS_R_RELHI)
		r = _bfd_relocate_contents (howto, input_bfd, relocation,
					    (contents
					     + adjust
					     + int_rel.r_vaddr
					     - input_section->vma));
	      else
		{
		  mips_relocate_hi (&int_rel,
				    use_lo ? &lo_int_rel : NULL,
				    input_bfd, input_section, contents,
				    adjust, relocation,
				    int_rel.r_type == MIPS_R_RELHI);
		  r = bfd_reloc_ok;
		}
	    }

	  /* Adjust the reloc address.  */
	  int_rel.r_vaddr += (input_section->output_section->vma
			      + input_section->output_offset
			      - input_section->vma);

	  /* Save the changed reloc information.  */
	  mips_ecoff_swap_reloc_out (input_bfd, &int_rel, (PTR) ext_rel);
	}
      else
	{
	  /* We are producing a final executable.  */
	  if (int_rel.r_extern)
	    {
	      /* This is a reloc against a symbol.  */
	      if (h->root.type == bfd_link_hash_defined
		  || h->root.type == bfd_link_hash_defweak)
		{
		  asection *hsec;

		  hsec = h->root.u.def.section;
		  relocation = (h->root.u.def.value
				+ hsec->output_section->vma
				+ hsec->output_offset);
		}
	      else
		{
		  if (! ((*info->callbacks->undefined_symbol)
			 (info, h->root.root.string, input_bfd,
			  input_section,
			  int_rel.r_vaddr - input_section->vma, true)))
		    return false;
		  relocation = 0;
		}
	    }
	  else
	    {
	      /* This is a reloc against a section.  */
	      relocation = (s->output_section->vma
			    + s->output_offset
			    - s->vma);

	      /* A PC relative reloc is already correct in the object
		 file.  Make it look like a pcrel_offset relocation by
		 adding in the start address.  */
	      if (howto->pc_relative)
		{
		  if (int_rel.r_type != MIPS_R_RELHI || ! use_lo)
		    relocation += int_rel.r_vaddr + adjust;
		  else
		    relocation += lo_int_rel.r_vaddr + adjust;
		}
	    }

	  if (int_rel.r_type != MIPS_R_REFHI
	      && int_rel.r_type != MIPS_R_RELHI)
	    r = _bfd_final_link_relocate (howto,
					  input_bfd,
					  input_section,
					  contents,
					  (int_rel.r_vaddr
					   - input_section->vma
					   + adjust),
					  relocation,
					  addend);
	  else
	    {
	      mips_relocate_hi (&int_rel,
				use_lo ? &lo_int_rel : NULL,
				input_bfd, input_section, contents, adjust,
				relocation,
				int_rel.r_type == MIPS_R_RELHI);
	      r = bfd_reloc_ok;
	    }
	}

      /* MIPS_R_JMPADDR requires peculiar overflow detection.  The
	 instruction provides a 28 bit address (the two lower bits are
	 implicit zeroes) which is combined with the upper four bits
	 of the instruction address.  */
      if (r == bfd_reloc_ok
	  && int_rel.r_type == MIPS_R_JMPADDR
	  && (((relocation
		+ addend
		+ (int_rel.r_extern ? 0 : s->vma))
	       & 0xf0000000)
	      != ((input_section->output_section->vma
		   + input_section->output_offset
		   + (int_rel.r_vaddr - input_section->vma)
		   + adjust)
		  & 0xf0000000)))
	r = bfd_reloc_overflow;

      if (r != bfd_reloc_ok)
	{
	  switch (r)
	    {
	    default:
	    case bfd_reloc_outofrange:
	      abort ();
	    case bfd_reloc_overflow:
	      {
		const char *name;

		if (int_rel.r_extern)
		  name = h->root.root.string;
		else
		  name = bfd_section_name (input_bfd, s);
		if (! ((*info->callbacks->reloc_overflow)
		       (info, name, howto->name, (bfd_vma) 0,
			input_bfd, input_section,
			int_rel.r_vaddr - input_section->vma)))
		  return false;
	      }
	      break;
	    }
	}
    }

  return true;
}

/* Read in the relocs for a section.  */

static boolean
mips_read_relocs (abfd, sec)
     bfd *abfd;
     asection *sec;
{
  struct ecoff_section_tdata *section_tdata;

  section_tdata = ecoff_section_data (abfd, sec);
  if (section_tdata == (struct ecoff_section_tdata *) NULL)
    {
      sec->used_by_bfd =
	(PTR) bfd_alloc (abfd, sizeof (struct ecoff_section_tdata));
      if (sec->used_by_bfd == NULL)
	return false;

      section_tdata = ecoff_section_data (abfd, sec);
      section_tdata->external_relocs = NULL;
      section_tdata->contents = NULL;
      section_tdata->offsets = NULL;
    }

  if (section_tdata->external_relocs == NULL)
    {
      bfd_size_type external_relocs_size;

      external_relocs_size = (ecoff_backend (abfd)->external_reloc_size
			      * sec->reloc_count);

      section_tdata->external_relocs =
	(PTR) bfd_alloc (abfd, external_relocs_size);
      if (section_tdata->external_relocs == NULL && external_relocs_size != 0)
	return false;

      if (bfd_seek (abfd, sec->rel_filepos, SEEK_SET) != 0
	  || (bfd_read (section_tdata->external_relocs, 1,
			external_relocs_size, abfd)
	      != external_relocs_size))
	return false;
    }

  return true;
}

/* Relax a section when linking a MIPS ECOFF file.  This is used for
   embedded PIC code, which always uses PC relative branches which
   only have an 18 bit range on MIPS.  If a branch is not in range, we
   generate a long instruction sequence to compensate.  Each time we
   find a branch to expand, we have to check all the others again to
   make sure they are still in range.  This is slow, but it only has
   to be done when -relax is passed to the linker.

   This routine figures out which branches need to expand; the actual
   expansion is done in mips_relocate_section when the section
   contents are relocated.  The information is stored in the offsets
   field of the ecoff_section_tdata structure.  An offset of 1 means
   that the branch must be expanded into a multi-instruction PC
   relative branch (such an offset will only occur for a PC relative
   branch to an external symbol).  Any other offset must be a multiple
   of four, and is the amount to change the branch by (such an offset
   will only occur for a PC relative branch within the same section).

   We do not modify the section relocs or contents themselves so that
   if memory usage becomes an issue we can discard them and read them
   again.  The only information we must save in memory between this
   routine and the mips_relocate_section routine is the table of
   offsets.  */

static boolean
mips_relax_section (abfd, sec, info, again)
     bfd *abfd;
     asection *sec;
     struct bfd_link_info *info;
     boolean *again;
{
  struct ecoff_section_tdata *section_tdata;
  bfd_byte *contents = NULL;
  long *offsets;
  struct external_reloc *ext_rel;
  struct external_reloc *ext_rel_end;
  unsigned int i;

  /* Assume we are not going to need another pass.  */
  *again = false;

  /* If we are not generating an ECOFF file, this is much too
     confusing to deal with.  */
  if (info->hash->creator->flavour != bfd_get_flavour (abfd))
    return true;

  /* If there are no relocs, there is nothing to do.  */
  if (sec->reloc_count == 0)
    return true;

  /* We are only interested in PC relative relocs, and why would there
     ever be one from anything but the .text section?  */
  if (strcmp (bfd_get_section_name (abfd, sec), ".text") != 0)
    return true;

  /* Read in the relocs, if we haven't already got them.  */
  section_tdata = ecoff_section_data (abfd, sec);
  if (section_tdata == (struct ecoff_section_tdata *) NULL
      || section_tdata->external_relocs == NULL)
    {
      if (! mips_read_relocs (abfd, sec))
	goto error_return;
      section_tdata = ecoff_section_data (abfd, sec);
    }

  if (sec->_cooked_size == 0)
    {
      /* We must initialize _cooked_size only the first time we are
	 called.  */
      sec->_cooked_size = sec->_raw_size;
    }

  contents = section_tdata->contents;
  offsets = section_tdata->offsets;

  /* Look for any external PC relative relocs.  Internal PC relative
     relocs are already correct in the object file, so they certainly
     can not overflow.  */
  ext_rel = (struct external_reloc *) section_tdata->external_relocs;
  ext_rel_end = ext_rel + sec->reloc_count;
  for (i = 0; ext_rel < ext_rel_end; ext_rel++, i++)
    {
      struct internal_reloc int_rel;
      struct ecoff_link_hash_entry *h;
      asection *hsec;
      bfd_signed_vma relocation;
      struct external_reloc *adj_ext_rel;
      unsigned int adj_i;
      unsigned long ext_count;
      struct ecoff_link_hash_entry **adj_h_ptr;
      struct ecoff_link_hash_entry **adj_h_ptr_end;
      struct ecoff_value_adjust *adjust;

      /* If we have already expanded this reloc, we certainly don't
	 need to do it again.  */
      if (offsets != (long *) NULL && offsets[i] == 1)
	continue;

      /* Quickly check that this reloc is external PCREL16.  */
      if (bfd_header_big_endian (abfd))
	{
	  if ((ext_rel->r_bits[3] & RELOC_BITS3_EXTERN_BIG) == 0
	      || (((ext_rel->r_bits[3] & RELOC_BITS3_TYPE_BIG)
		   >> RELOC_BITS3_TYPE_SH_BIG)
		  != MIPS_R_PCREL16))
	    continue;
	}
      else
	{
	  if ((ext_rel->r_bits[3] & RELOC_BITS3_EXTERN_LITTLE) == 0
	      || (((ext_rel->r_bits[3] & RELOC_BITS3_TYPE_LITTLE)
		   >> RELOC_BITS3_TYPE_SH_LITTLE)
		  != MIPS_R_PCREL16))
	    continue;
	}

      mips_ecoff_swap_reloc_in (abfd, (PTR) ext_rel, &int_rel);

      h = ecoff_data (abfd)->sym_hashes[int_rel.r_symndx];
      if (h == (struct ecoff_link_hash_entry *) NULL)
	abort ();

      if (h->root.type != bfd_link_hash_defined
	  && h->root.type != bfd_link_hash_defweak)
	{
	  /* Just ignore undefined symbols.  These will presumably
	     generate an error later in the link.  */
	  continue;
	}

      /* Get the value of the symbol.  */
      hsec = h->root.u.def.section;
      relocation = (h->root.u.def.value
		    + hsec->output_section->vma
		    + hsec->output_offset);

      /* Subtract out the current address.  */
      relocation -= (sec->output_section->vma
		     + sec->output_offset
		     + (int_rel.r_vaddr - sec->vma));

      /* The addend is stored in the object file.  In the normal case
	 of ``bal symbol'', the addend will be -4.  It will only be
	 different in the case of ``bal symbol+constant''.  To avoid
	 always reading in the section contents, we don't check the
	 addend in the object file (we could easily check the contents
	 if we happen to have already read them in, but I fear that
	 this could be confusing).  This means we will screw up if
	 there is a branch to a symbol that is in range, but added to
	 a constant which puts it out of range; in such a case the
	 link will fail with a reloc overflow error.  Since the
	 compiler will never generate such code, it should be easy
	 enough to work around it by changing the assembly code in the
	 source file.  */
      relocation -= 4;

      /* Now RELOCATION is the number we want to put in the object
	 file.  See whether it fits.  */
      if (relocation >= -0x20000 && relocation < 0x20000)
	continue;

      /* Now that we know this reloc needs work, which will rarely
	 happen, go ahead and grab the section contents.  */
      if (contents == (bfd_byte *) NULL)
	{
	  if (info->keep_memory)
	    contents = (bfd_byte *) bfd_alloc (abfd, sec->_raw_size);
	  else
	    contents = (bfd_byte *) bfd_malloc ((size_t) sec->_raw_size);
	  if (contents == (bfd_byte *) NULL)
	    goto error_return;
	  if (! bfd_get_section_contents (abfd, sec, (PTR) contents,
					  (file_ptr) 0, sec->_raw_size))
	    goto error_return;
	  if (info->keep_memory)
	    section_tdata->contents = contents;
	}

      /* We only support changing the bal instruction.  It would be
	 possible to handle other PC relative branches, but some of
	 them (the conditional branches) would require a different
	 length instruction sequence which would complicate both this
	 routine and mips_relax_pcrel16.  It could be written if
	 somebody felt it were important.  Ignoring this reloc will
	 presumably cause a reloc overflow error later on.  */
      if (bfd_get_32 (abfd, contents + int_rel.r_vaddr - sec->vma)
	  != 0x0411ffff) /* bgezal $0,. == bal .  */
	continue;

      /* Bother.  We need to expand this reloc, and we will need to
	 make another relaxation pass since this change may put other
	 relocs out of range.  We need to examine the local branches
	 and we need to allocate memory to hold the offsets we must
	 add to them.  We also need to adjust the values of all
	 symbols in the object file following this locati