elf32-m68k.c

来自「基于4个mips核的noc设计」· C语言 代码 · 共 2,163 行 · 第 1/5 页

      switch (ELF32_R_TYPE (rel->r_info))
	{
	case R_68K_GOT8:
	case R_68K_GOT16:
	case R_68K_GOT32:
	case R_68K_GOT8O:
	case R_68K_GOT16O:
	case R_68K_GOT32O:
	  r_symndx = ELF32_R_SYM (rel->r_info);
	  if (r_symndx >= symtab_hdr->sh_info)
	    {
	      h = sym_hashes[r_symndx - symtab_hdr->sh_info];
	      if (h->got.refcount > 0)
		{
		  --h->got.refcount;
		  if (h->got.refcount == 0)
		    {
		      /* We don't need the .got entry any more.  */
		      sgot->_raw_size -= 4;
		      srelgot->_raw_size -= sizeof (Elf32_External_Rela);
		    }
		}
	    }
	  else if (local_got_refcounts != NULL)
	    {
	      if (local_got_refcounts[r_symndx] > 0)
		{
		  --local_got_refcounts[r_symndx];
		  if (local_got_refcounts[r_symndx] == 0)
		    {
		      /* We don't need the .got entry any more.  */
		      sgot->_raw_size -= 4;
		      if (info->shared)
			srelgot->_raw_size -= sizeof (Elf32_External_Rela);
		    }
		}
	    }
	  break;

	case R_68K_PLT8:
	case R_68K_PLT16:
	case R_68K_PLT32:
	case R_68K_PLT8O:
	case R_68K_PLT16O:
	case R_68K_PLT32O:
	case R_68K_PC8:
	case R_68K_PC16:
	case R_68K_PC32:
	case R_68K_8:
	case R_68K_16:
	case R_68K_32:
	  r_symndx = ELF32_R_SYM (rel->r_info);
	  if (r_symndx >= symtab_hdr->sh_info)
	    {
	      h = sym_hashes[r_symndx - symtab_hdr->sh_info];
	      if (h->plt.refcount > 0)
		--h->plt.refcount;
	    }
	  break;

	default:
	  break;
	}
    }

  return true;
}

/* Adjust a symbol defined by a dynamic object and referenced by a
   regular object.  The current definition is in some section of the
   dynamic object, but we're not including those sections.  We have to
   change the definition to something the rest of the link can
   understand.  */

static boolean
elf_m68k_adjust_dynamic_symbol (info, h)
     struct bfd_link_info *info;
     struct elf_link_hash_entry *h;
{
  bfd *dynobj;
  asection *s;
  unsigned int power_of_two;

  dynobj = elf_hash_table (info)->dynobj;

  /* Make sure we know what is going on here.  */
  BFD_ASSERT (dynobj != NULL
	      && ((h->elf_link_hash_flags & ELF_LINK_HASH_NEEDS_PLT)
		  || h->weakdef != NULL
		  || ((h->elf_link_hash_flags
		       & ELF_LINK_HASH_DEF_DYNAMIC) != 0
		      && (h->elf_link_hash_flags
			  & ELF_LINK_HASH_REF_REGULAR) != 0
		      && (h->elf_link_hash_flags
			  & ELF_LINK_HASH_DEF_REGULAR) == 0)));

  /* If this is a function, put it in the procedure linkage table.  We
     will fill in the contents of the procedure linkage table later,
     when we know the address of the .got section.  */
  if (h->type == STT_FUNC
      || (h->elf_link_hash_flags & ELF_LINK_HASH_NEEDS_PLT) != 0)
    {
      if (! info->shared
	  && (h->elf_link_hash_flags & ELF_LINK_HASH_DEF_DYNAMIC) == 0
	  && (h->elf_link_hash_flags & ELF_LINK_HASH_REF_DYNAMIC) == 0
	  /* We must always create the plt entry if it was referenced
	     by a PLTxxO relocation.  In this case we already recorded
	     it as a dynamic symbol.  */
	  && h->dynindx == -1)
	{
	  /* This case can occur if we saw a PLTxx reloc in an input
	     file, but the symbol was never referred to by a dynamic
	     object.  In such a case, we don't actually need to build
	     a procedure linkage table, and we can just do a PCxx
	     reloc instead.  */
	  BFD_ASSERT ((h->elf_link_hash_flags & ELF_LINK_HASH_NEEDS_PLT) != 0);
	  h->plt.offset = (bfd_vma) -1;
	  return true;
	}

      /* GC may have rendered this entry unused.  */
      if (h->plt.refcount <= 0)
	{
	  h->elf_link_hash_flags &= ~ELF_LINK_HASH_NEEDS_PLT;
	  h->plt.offset = (bfd_vma) -1;
	  return true;
	}

      /* Make sure this symbol is output as a dynamic symbol.  */
      if (h->dynindx == -1)
	{
	  if (! bfd_elf32_link_record_dynamic_symbol (info, h))
	    return false;
	}

      s = bfd_get_section_by_name (dynobj, ".plt");
      BFD_ASSERT (s != NULL);

      /* If this is the first .plt entry, make room for the special
	 first entry.  */
      if (s->_raw_size == 0)
	{
	  if (CPU32_FLAG (dynobj))
	    s->_raw_size += PLT_CPU32_ENTRY_SIZE;
	  else
	    s->_raw_size += PLT_ENTRY_SIZE;
	}

      /* If this symbol is not defined in a regular file, and we are
	 not generating a shared library, then set the symbol to this
	 location in the .plt.  This is required to make function
	 pointers compare as equal between the normal executable and
	 the shared library.  */
      if (!info->shared
	  && (h->elf_link_hash_flags & ELF_LINK_HASH_DEF_REGULAR) == 0)
	{
	  h->root.u.def.section = s;
	  h->root.u.def.value = s->_raw_size;
	}

      h->plt.offset = s->_raw_size;

      /* Make room for this entry.  */
      if (CPU32_FLAG (dynobj))
        s->_raw_size += PLT_CPU32_ENTRY_SIZE;
      else
        s->_raw_size += PLT_ENTRY_SIZE;

      /* We also need to make an entry in the .got.plt section, which
	 will be placed in the .got section by the linker script.  */

      s = bfd_get_section_by_name (dynobj, ".got.plt");
      BFD_ASSERT (s != NULL);
      s->_raw_size += 4;

      /* We also need to make an entry in the .rela.plt section.  */

      s = bfd_get_section_by_name (dynobj, ".rela.plt");
      BFD_ASSERT (s != NULL);
      s->_raw_size += sizeof (Elf32_External_Rela);

      return true;
    }

  /* Reinitialize the plt offset now that it is not used as a reference
     count any more.  */
  h->plt.offset = (bfd_vma) -1;

  /* If this is a weak symbol, and there is a real definition, the
     processor independent code will have arranged for us to see the
     real definition first, and we can just use the same value.  */
  if (h->weakdef != NULL)
    {
      BFD_ASSERT (h->weakdef->root.type == bfd_link_hash_defined
		  || h->weakdef->root.type == bfd_link_hash_defweak);
      h->root.u.def.section = h->weakdef->root.u.def.section;
      h->root.u.def.value = h->weakdef->root.u.def.value;
      return true;
    }

  /* This is a reference to a symbol defined by a dynamic object which
     is not a function.  */

  /* If we are creating a shared library, we must presume that the
     only references to the symbol are via the global offset table.
     For such cases we need not do anything here; the relocations will
     be handled correctly by relocate_section.  */
  if (info->shared)
    return true;

  /* We must allocate the symbol in our .dynbss section, which will
     become part of the .bss section of the executable.  There will be
     an entry for this symbol in the .dynsym section.  The dynamic
     object will contain position independent code, so all references
     from the dynamic object to this symbol will go through the global
     offset table.  The dynamic linker will use the .dynsym entry to
     determine the address it must put in the global offset table, so
     both the dynamic object and the regular object will refer to the
     same memory location for the variable.  */

  s = bfd_get_section_by_name (dynobj, ".dynbss");
  BFD_ASSERT (s != NULL);

  /* We must generate a R_68K_COPY reloc to tell the dynamic linker to
     copy the initial value out of the dynamic object and into the
     runtime process image.  We need to remember the offset into the
     .rela.bss section we are going to use.  */
  if ((h->root.u.def.section->flags & SEC_ALLOC) != 0)
    {
      asection *srel;

      srel = bfd_get_section_by_name (dynobj, ".rela.bss");
      BFD_ASSERT (srel != NULL);
      srel->_raw_size += sizeof (Elf32_External_Rela);
      h->elf_link_hash_flags |= ELF_LINK_HASH_NEEDS_COPY;
    }

  /* We need to figure out the alignment required for this symbol.  I
     have no idea how ELF linkers handle this.  */
  power_of_two = bfd_log2 (h->size);
  if (power_of_two > 3)
    power_of_two = 3;

  /* Apply the required alignment.  */
  s->_raw_size = BFD_ALIGN (s->_raw_size,
			    (bfd_size_type) (1 << power_of_two));
  if (power_of_two > bfd_get_section_alignment (dynobj, s))
    {
      if (!bfd_set_section_alignment (dynobj, s, power_of_two))
	return false;
    }

  /* Define the symbol as being at this point in the section.  */
  h->root.u.def.section = s;
  h->root.u.def.value = s->_raw_size;

  /* Increment the section size to make room for the symbol.  */
  s->_raw_size += h->size;

  return true;
}

/* Set the sizes of the dynamic sections.  */

static boolean
elf_m68k_size_dynamic_sections (output_bfd, info)
     bfd *output_bfd;
     struct bfd_link_info *info;
{
  bfd *dynobj;
  asection *s;
  boolean plt;
  boolean relocs;
  boolean reltext;

  dynobj = elf_hash_table (info)->dynobj;
  BFD_ASSERT (dynobj != NULL);

  if (elf_hash_table (info)->dynamic_sections_created)
    {
      /* Set the contents of the .interp section to the interpreter.  */
      if (!info->shared)
	{
	  s = bfd_get_section_by_name (dynobj, ".interp");
	  BFD_ASSERT (s != NULL);
	  s->_raw_size = sizeof ELF_DYNAMIC_INTERPRETER;
	  s->contents = (unsigned char *) ELF_DYNAMIC_INTERPRETER;
	}
    }
  else
    {
      /* We may have created entries in the .rela.got section.
	 However, if we are not creating the dynamic sections, we will
	 not actually use these entries.  Reset the size of .rela.got,
	 which will cause it to get stripped from the output file
	 below.  */
      s = bfd_get_section_by_name (dynobj, ".rela.got");
      if (s != NULL)
	s->_raw_size = 0;
    }

  /* If this is a -Bsymbolic shared link, then we need to discard all PC
     relative relocs against symbols defined in a regular object.  We
     allocated space for them in the check_relocs routine, but we will not
     fill them in in the relocate_section routine.  */
  if (info->shared && info->symbolic)
    elf_m68k_link_hash_traverse (elf_m68k_hash_table (info),
				 elf_m68k_discard_copies,
				 (PTR) NULL);

  /* The check_relocs and adjust_dynamic_symbol entry points have
     determined the sizes of the various dynamic sections.  Allocate
     memory for them.  */
  plt = false;
  relocs = false;
  reltext = false;
  for (s = dynobj->sections; s != NULL; s = s->next)
    {
      const char *name;
      boolean strip;

      if ((s->flags & SEC_LINKER_CREATED) == 0)
	continue;

      /* It's OK to base decisions on the section name, because none
	 of the dynobj section names depend upon the input files.  */
      name = bfd_get_section_name (dynobj, s);

      strip = false;

      if (strcmp (name, ".plt") == 0)
	{
	  if (s->_raw_size == 0)
	    {
	      /* Strip this section if we don't need it; see the
                 comment below.  */
	      strip = true;
	    }
	  else
	    {
	      /* Remember whether there is a PLT.  */
	      plt = true;
	    }
	}
      else if (strncmp (name, ".rela", 5) == 0)
	{
	  if (s->_raw_size == 0)
	    {
	      /* If we don't need this section, strip it from the
		 output file.  This is mostly to handle .rela.bss and
		 .rela.plt.  We must create both sections in
		 create_dynamic_sections, because they must be created
		 before the linker maps input sections to output
		 sections.  The linker does that before
		 adjust_dynamic_symbol is called, and it is that
		 function which decides whether anything needs to go
		 into these sections.  */
	      strip = true;
	    }
	  else
	    {
	      asection *target;

	      /* Remember whether there are any reloc sections other
                 than .rela.plt.  */
	      if (strcmp (name, ".rela.plt") != 0)
		{
		  const char *outname;

		  relocs = true;

		  /* If this relocation section applies to a read only
		     section, then we probably need a DT_TEXTREL
		     entry.  .rela.plt is actually associated with
		     .got.plt, which is never readonly.  */
		  outname = bfd_get_section_name (output_bfd,
						  s->output_section);
		  target = bfd_get_section_by_name (output_bfd, outname + 5);
		  if (target != NULL
		      && (target->flags & SEC_READONLY) != 0
		      && (target->flags & SEC_ALLOC) != 0)
		    reltext = true;
		}

	      /* We use the reloc_count field as a counter if we need
		 to copy relocs into the output file.  */
	      s->reloc_count = 0;
	    }
	}
      else if (strncmp (name, ".got", 4) != 0)
	{
	  /* It's not one of our sections, so don't allocate space.  */
	  continue;
	}

      if (strip)
	{
	  _bfd_strip_section_from_output (info, s);
	  continue;
	}

      /* Allocate memory for the section contents.  */
      /* FIXME: This should be a call to bfd_alloc not bfd_zalloc.
	 Unused entries should be reclaimed before the section's contents
	 are written out, but at the moment this does not happen.  Thus in
	 order to prevent writing out garbage, we initialise the section's
	 contents to zero.  */
      s->contents = (bfd_byte *) bfd_zalloc (dynobj, s->_raw_size);
      if (s->contents == NULL && s->_raw_size != 0)
	return false;
    }

  if (elf_hash_table (info)->dynamic_sections_created)
    {
      /* Add some entries to the .dynamic section.  We fill in the
	 values later, in elf_m68k_finish_dynamic_sections, but we
	 must add the entries now so that we get the correct size for
	 the .dynamic section.  The DT_DEBUG entry is filled in by the
	 dynamic linker and used by the debugger.  */
      if (!info->shared)
	{
	  if (!bfd_elf32_add_dynamic_entry (info, DT_DEBUG, 0))
	    return false;
	}

      if (plt)
	{
	  if (!bfd_elf32_add_dynamic_entry (info, DT_PLTGOT, 0)
	      || !bfd_elf32_add_dynamic_entry (info, DT_PLTRELSZ, 0)
	      || !bfd_elf32_add_dynamic_entry (info, DT_PLTREL, DT_RELA)
	      || !bfd_elf32_add_dynamic_entry (info, DT_JMPREL, 0))
	    return false;
	}