elf.c

早期freebsd实现

    }

  /* Switch xvec to match the specified byte order.  */
  switch (x_ehdr.e_ident[EI_DATA])
    {
    case ELFDATA2MSB:		/* Big-endian */ 
      abfd->xvec = &elf_big_vec;
      break;
    case ELFDATA2LSB:		/* Little-endian */
      abfd->xvec = &elf_little_vec;
      break;
    case ELFDATANONE:		/* No data encoding specified */
    default:			/* Unknown data encoding specified */
      goto wrong;
    }
  
  /* Allocate an instance of the elf_obj_tdata structure and hook it up to
     the tdata pointer in the bfd. */

  elf_tdata (abfd) =
    (struct elf_obj_tdata *) bfd_zalloc (abfd, sizeof (struct elf_obj_tdata));
  if (elf_tdata (abfd) == NULL)
    {
      bfd_error = no_memory;
      return (NULL);
    }

  /* FIXME, `wrong' returns from this point onward, leak memory.  */

  /* Now that we know the byte order, swap in the rest of the header */
  i_ehdrp = elf_elfheader (abfd);
  elf_swap_ehdr_in (abfd, &x_ehdr, i_ehdrp);

  /* If there is no program header, or the type is not a core file, then
     we are hosed. */
  if (i_ehdrp->e_phoff == 0 || i_ehdrp->e_type != ET_CORE)
    goto wrong;

  /* Allocate space for a copy of the program header table in 
     internal form, seek to the program header table in the file,
     read it in, and convert it to internal form.  As a simple sanity
     check, verify that the what BFD thinks is the size of each program
     header table entry actually matches the size recorded in the file. */

  if (i_ehdrp->e_phentsize != sizeof (x_phdr))
    goto wrong;
  i_phdrp = (Elf_Internal_Phdr *)
    bfd_alloc (abfd, sizeof (*i_phdrp) * i_ehdrp->e_phnum);
  if (! i_phdrp)
    {
      bfd_error = no_memory;
      return (NULL);
    }
  if (bfd_seek (abfd, i_ehdrp->e_phoff, SEEK_SET) == -1)
    {
      bfd_error = system_call_error;
      return (NULL);
    }
  for (phindex = 0; phindex < i_ehdrp->e_phnum; phindex++)
    {
      if (bfd_read ((PTR) &x_phdr, sizeof (x_phdr), 1, abfd)
	  != sizeof (x_phdr))
	{
	  bfd_error = system_call_error;
	  return (NULL);
	}
      elf_swap_phdr_in (abfd, &x_phdr, i_phdrp + phindex);
    }

  /* Once all of the program headers have been read and converted, we
     can start processing them. */

  for (phindex = 0; phindex < i_ehdrp->e_phnum; phindex++)
    {
      bfd_section_from_phdr (abfd, i_phdrp + phindex, phindex);
      if ((i_phdrp + phindex) -> p_type == PT_NOTE)
	{
	  elf_corefile_note (abfd, i_phdrp + phindex);
	}
    }

  /* Remember the entry point specified in the ELF file header. */

  bfd_get_start_address (abfd) = i_ehdrp->e_entry;

  return (abfd->xvec);
}

static boolean
DEFUN (elf_mkobject, (abfd), bfd *abfd)
{
  /* this just does initialization */
  /* coff_mkobject zalloc's space for tdata.coff_obj_data ... */
  elf_tdata(abfd) = (struct elf_obj_tdata *)
    bfd_zalloc (abfd, sizeof(struct elf_obj_tdata));
  if (elf_tdata(abfd) == 0) {
    bfd_error = no_memory;
    return false;
  }
  /* since everything is done at close time, do we need any
     initialization? */
  
  return (true);
}

/*
  Create ELF output from BFD sections.
  
  Essentially, just create the section header and forget about the program
  header for now.   
  
*/

/* lacking nested functions and nested types, set up for mapping over
   BFD sections to produce ELF sections */

typedef struct {
  Elf_Internal_Ehdr	*i_ehdr;
  Elf_Internal_Shdr	*i_shdrp;
  struct strtab		*shstrtab;
  int			symtab_section;
} elf_sect_thunk;



static void
DEFUN (elf_make_sections, (abfd, asect, obj),
       bfd		*abfd AND
       asection		*asect AND
       PTR		obj)
{
  elf_sect_thunk *thunk = (elf_sect_thunk*)obj;
  /* most of what is in bfd_shdr_from_section goes in here... */
  /* and all of these sections generate at *least* one ELF section. */
  int this_section;
  int idx;
  
  /* check if we're making a PROGBITS section... */
  /* if ((asect->flags & SEC_ALLOC) && (asect->flags & SEC_LOAD)) */
  /* this was too strict... what *do* we want to check here? */
  if(1)
    {
      Elf_Internal_Shdr *this_hdr;
      this_section = elf_section_from_bfd_section (abfd, asect);
      this_hdr = &thunk->i_shdrp[this_section];

      this_hdr->sh_addr = asect->vma;
      this_hdr->sh_size = asect->_raw_size;
      /* contents already set by elf_set_section_contents */

      if (asect->flags & SEC_RELOC)
	{
	  /* emit a reloc section, and thus strtab and symtab... */
	  Elf_Internal_Shdr *rela_hdr;
	  Elf_Internal_Shdr *symtab_hdr;
	  Elf_Internal_Shdr *symstrtab_hdr;
	  Elf_External_Rela *outbound_relocs;
	  Elf_External_Sym *outbound_syms;
	  int rela_section;
	  int symstrtab_section;
	  
	  symtab_hdr = &thunk->i_shdrp[thunk->symtab_section];

	  if (thunk->symtab_section == this_section + 1)
	    rela_section = thunk->symtab_section + 2; /* symtab + symstrtab */
	  else
	    rela_section = this_section + 1;
	  rela_hdr = &thunk->i_shdrp[rela_section];
	  rela_hdr->sh_type = SHT_RELA;
	  rela_hdr->sh_link = thunk->symtab_section;
	  rela_hdr->sh_info = this_section;
	  rela_hdr->sh_entsize = sizeof (Elf_External_Rela);
	  /* orelocation has the data, reloc_count has the count... */
	  rela_hdr->sh_size = rela_hdr->sh_entsize * asect->reloc_count;
	  outbound_relocs = (Elf_External_Rela *)
	    bfd_alloc(abfd, asect->reloc_count * sizeof(Elf_External_Rela));
	  for (idx = 0; idx < asect->reloc_count; idx++)
	    {
	      Elf_Internal_Rela dst;
	      arelent        *ptr;
	      Elf_External_Rela  *src;
	      
	      ptr = asect->orelocation[idx];
	      src = outbound_relocs + idx;
	      if (asect->flags & SEC_RELOC)
		dst.r_offset = ptr->address - asect->vma;
	      else
		dst.r_offset = ptr->address;

	      dst.r_info = ELF_R_INFO(1 /*ptr->sym_ptr_ptr*/, /* needs index into symtab (FIXME) */
				      ptr->howto->type);

	      dst.r_addend = ptr->addend;
	      elf_swap_reloca_out(abfd, &dst, src);
	    }
	  rela_hdr->contents = (void*)outbound_relocs;
	}
    }
}

static void
DEFUN (elf_fake_sections, (abfd, asect, obj),
       bfd		*abfd AND
       asection		*asect AND
       PTR		obj)
{
  elf_sect_thunk *thunk = (elf_sect_thunk*)obj;
  /* most of what is in bfd_shdr_from_section goes in here... */
  /* and all of these sections generate at *least* one ELF section. */
  int this_section;
  int idx;
  
  /* check if we're making a PROGBITS section... */
  /* if ((asect->flags & SEC_ALLOC) && (asect->flags & SEC_LOAD)) */
  /* this was too strict... what *do* we want to check here? */
  if(1)
    {
      Elf_Internal_Shdr *this_hdr;
      this_section = thunk->i_ehdr->e_shnum++;
      this_hdr = &thunk->i_shdrp[this_section];
      this_hdr->sh_name = 
	bfd_add_to_strtab (abfd, thunk->shstrtab, asect->name);
      /* we need to log the type *now* so that elf_section_from_bfd_section
	 can find us... have to set rawdata too. */
      this_hdr->rawdata = (void*)asect;
      if ((asect->flags & SEC_ALLOC) && (asect->flags & SEC_LOAD))
	this_hdr->sh_type = SHT_PROGBITS;
      else
	/* what *do* we put here? */
	this_hdr->sh_type = SHT_PROGBITS;


      if (asect->flags & SEC_RELOC)
	{
	  /* emit a reloc section, and thus strtab and symtab... */
	  Elf_Internal_Shdr *rela_hdr;
	  Elf_Internal_Shdr *symtab_hdr;
	  Elf_Internal_Shdr *symstrtab_hdr;
	  Elf_External_Rela *outbound_relocs;
	  Elf_External_Sym *outbound_syms;
	  int rela_section;
	  int symstrtab_section;
	  
	  /* note that only one symtab is used, so just remember it
	     for now */
	  if (! thunk->symtab_section)
	    {
	      thunk->symtab_section = thunk->i_ehdr->e_shnum++;
	      symtab_hdr = &thunk->i_shdrp[thunk->symtab_section];
	      symtab_hdr->sh_name =
		bfd_add_to_strtab (abfd, thunk->shstrtab, ".symtab");
	      symtab_hdr->sh_type = SHT_SYMTAB;
	      symtab_hdr->sh_entsize = sizeof (Elf_External_Sym);

	      symstrtab_section = thunk->i_ehdr->e_shnum++;
	      BFD_ASSERT(symstrtab_section == thunk->symtab_section+1);
	      symstrtab_hdr = &thunk->i_shdrp[symstrtab_section];
	      symtab_hdr->sh_link = symstrtab_section;
	      symstrtab_hdr->sh_name =
		bfd_add_to_strtab (abfd, thunk->shstrtab, ".strtab");
	      symstrtab_hdr->sh_type = SHT_STRTAB;

	      symtab_hdr->contents = 0;
	      symstrtab_hdr->contents = 0;
	      symstrtab_hdr->sh_size = 0;
	    } 
	  else
	    symtab_hdr = &thunk->i_shdrp[thunk->symtab_section];

	  rela_section = thunk->i_ehdr->e_shnum++;
	  rela_hdr = &thunk->i_shdrp[rela_section];
	  rela_hdr->sh_name =
	    bfd_add_2_to_strtab (abfd, thunk->shstrtab, ".rela", asect->name);
	  rela_hdr->sh_type = SHT_RELA;
	  rela_hdr->sh_link = thunk->symtab_section;
	  rela_hdr->sh_info = this_section;
	  rela_hdr->sh_entsize = sizeof (Elf_External_Rela);
	}
    }
}


static boolean
DEFUN (elf_compute_section_file_positions, (abfd), bfd *abfd)
{
  Elf_Internal_Ehdr *i_ehdrp;	/* Elf file header, internal form */
  Elf_Internal_Shdr *i_shdrp;	/* Section header table, internal form */
  struct strtab *shstrtab;
  int count, maxsections;
  int outbase;
  elf_sect_thunk est;

  if (! elf_shstrtab (abfd)) {
    i_ehdrp = elf_elfheader (abfd);	/* build new header in tdata memory */
    shstrtab = bfd_new_strtab(abfd);
    
    i_ehdrp->e_ident[EI_MAG0] = ELFMAG0;
    i_ehdrp->e_ident[EI_MAG1] = ELFMAG1;
    i_ehdrp->e_ident[EI_MAG2] = ELFMAG2;
    i_ehdrp->e_ident[EI_MAG3] = ELFMAG3;

    i_ehdrp->e_ident[EI_CLASS] = ELFCLASS32; /* FIXME: find out from bfd */
    i_ehdrp->e_ident[EI_DATA] =
      abfd->xvec->byteorder_big_p ? ELFDATA2MSB : ELFDATA2LSB;
    i_ehdrp->e_ident[EI_VERSION] = EV_CURRENT;

    for(count = EI_PAD; count < EI_NIDENT; count ++)
      i_ehdrp->e_ident[count] = 0;
      
    i_ehdrp->e_type = (abfd->flags & EXEC_P)? ET_EXEC : ET_REL;
    switch(bfd_get_arch(abfd))
      {
      case bfd_arch_unknown:
	i_ehdrp->e_machine = EM_NONE;
	break;
      case bfd_arch_sparc:
	i_ehdrp->e_machine = EM_SPARC;
	break;
      case bfd_arch_i386:
	i_ehdrp->e_machine = EM_386;
	break;
      case bfd_arch_m68k:
	i_ehdrp->e_machine = EM_68K;
	break;
      case bfd_arch_m88k:
	i_ehdrp->e_machine = EM_88K;
	break;
      case bfd_arch_i860:
	i_ehdrp->e_machine = EM_860;
	break;
      case bfd_arch_mips:		  /* MIPS Rxxxx */
	i_ehdrp->e_machine = EM_MIPS; /* only MIPS R3000 */
	break;
	/* also note that EM_M32, AT&T WE32100 is unknown to bfd */
      default:
	i_ehdrp->e_machine = EM_NONE;
      }
    i_ehdrp->e_version = EV_CURRENT;
    i_ehdrp->e_ehsize = sizeof(Elf_External_Ehdr);
    
    /* no program header, for now. */
    i_ehdrp->e_phoff = 0;
    i_ehdrp->e_phentsize = 0;
    i_ehdrp->e_phnum = 0;

    /* each bfd section is section header entry */
    i_ehdrp->e_entry = bfd_get_start_address (abfd);
    i_ehdrp->e_shentsize = sizeof (Elf_External_Shdr);

    /* figure at most each section can have a rel, strtab, symtab */
    maxsections = 4*bfd_count_sections(abfd)+2;

    i_ehdrp->e_shoff = i_ehdrp->e_ehsize;

    /* and we'll just have to fix up the offsets later. */
    /* outbase += i_ehdr.e_shentsize * i_ehdr.e_shnum; */
    
    i_shdrp = (Elf_Internal_Shdr *)
      bfd_alloc (abfd, sizeof (*i_shdrp) * maxsections);
    if (! i_shdrp)
      {
	bfd_error = no_memory;
	return (false);
      }
    for (count=0; count < maxsections; count++) 
      {
	i_shdrp[count].rawdata = 0;
	i_shdrp[count].contents = 0;
      }
    
    
    i_shdrp[0].sh_name = 0;
    i_shdrp[0].sh_type = SHT_NULL;
    i_shdrp[0].sh_flags = 0;
    i_shdrp[0].sh_addr = 0;
    i_shdrp[0].sh_offset = 0;
    i_shdrp[0].sh_size = 0;
    i_shdrp[0].sh_link = SHN_UNDEF;
    i_shdrp[0].sh_info = 0;
    i_shdrp[0].sh_addralign = 0;
    i_shdrp[0].sh_entsize = 0;

    i_ehdrp->e_shnum = 1;

    elf_elfsections (abfd) = i_shdrp;
    elf_shstrtab (abfd) = shstrtab;
  }
  est.i_ehdr = elf_elfheader(abfd);
  est.i_shdrp = elf_elfsections(abfd);
  est.shstrtab = elf_shstrtab(abfd);
  est.symtab_section = 0;	/* elf_fake_sections fils it in */

  bfd_map_over_sections(abfd, elf_fake_sections, &est);
  elf_onesymtab (abfd) = est.symtab_section;
  return (true);
}

static boolean
DEFUN (elf_write_object_contents, (abfd), bfd *abfd)
{
  Elf_External_Ehdr x_ehdr;	/* Elf file header, external form */
  Elf_Internal_Ehdr *i_ehdrp;	/* Elf file header, internal form */
  Elf_External_Phdr *x_phdrp;	/* Program header table, external form */
  Elf_Internal_Phdr *i_phdrp;	/* Program header table, internal form */
  Elf_External_Shdr *x_shdrp;	/* Section header table, external form */
  Elf_Internal_Shdr *i_shdrp;	/* Section header table, internal form */
  asection *nsect;
  int maxsections;
  elf_sect_thunk est;
  
  int outbase = 0;
  int count;
  struct strtab *shstrtab;
  
  if(abfd->output_has_begun == false) 
    elf_compute_section_file_positions(abfd);

  i_ehdrp = elf_elfheader (abfd);
  i_shdrp = elf_elfsections (abfd);
  shstrtab = elf_shstrtab (abfd);

  est.i_ehdr = i_ehdrp;
  est.i_shdrp = i_shdrp;
  est.shstrtab = shstrtab;
  est.symtab_section = elf_onesymtab (abfd); /* filled in by elf_fake */