elf.c

早期freebsd实现

  case SHT_PROGBITS:
  case SHT_NOBITS:
    /* Bits that get saved. This one is real. */
    if (! hdr->rawdata ) 
      {
	newsect = bfd_make_section (abfd, name);
	newsect->vma = hdr->sh_addr;
	newsect->_raw_size = hdr->sh_size;
	newsect->filepos = hdr->sh_offset; /* so we can read back the bits */
	newsect->flags |= SEC_HAS_CONTENTS;
	
	if (hdr->sh_flags & SHF_ALLOC)
	  {
	    newsect->flags |= SEC_ALLOC;
	    if (hdr->sh_type != SHT_NOBITS)
	      newsect->flags |= SEC_LOAD;
	  }
	
	if (!(hdr->sh_flags & SHF_WRITE))
	  newsect->flags |= SEC_READONLY;
	
	if (hdr->sh_flags & SHF_EXECINSTR)
	  newsect->flags |= SEC_CODE;	/* FIXME: may only contain SOME code */
	else
	  newsect->flags |= SEC_DATA;
	
	hdr->rawdata = (void*)newsect;
      }
    return true;
    break;

  case SHT_SYMTAB:			/* A symbol table */
    BFD_ASSERT (hdr->sh_entsize == sizeof (Elf_External_Sym));
    elf_onesymtab (abfd) = shindex;
    abfd->flags |= HAS_SYMS;
    return true;

  case SHT_STRTAB:			/* A string table */
    return true;

  case SHT_REL:
  case SHT_RELA:
    /* *these* do a lot of work -- but build no sections! */
    /* the spec says there can be multiple strtabs, but only one symtab */
    /* but there can be lots of REL* sections. */
    /* FIXME:  The above statement is wrong!  There are typically at least
       two symbol tables in a dynamically linked executable, ".dynsym"
       which is the dynamic linkage symbol table and ".symtab", which is
       the "traditional" symbol table.  -fnf */
       
    {
      asection		*target_sect;
      
      bfd_section_from_shdr (abfd, hdr->sh_link); /* symbol table */
      bfd_section_from_shdr (abfd, hdr->sh_info); /* target */
      target_sect = section_from_elf_index (abfd, hdr->sh_info);
      if (target_sect == NULL)
	  return false;

#if 0
      /* FIXME:  We are only prepared to read one symbol table, so
	 do NOT read the dynamic symbol table since it is only a
	 subset of the full symbol table.  Also see comment above. -fnf */
      if (!elf_slurp_symbol_table(abfd, i_shdrp + hdr->sh_link))
	return false;
#endif

      target_sect->reloc_count = hdr->sh_size / hdr->sh_entsize;
      target_sect->flags |= SEC_RELOC;
      target_sect->relocation = 0;
      target_sect->rel_filepos = hdr->sh_offset;
      return true;
    }
    break;

  case SHT_HASH:
  case SHT_DYNAMIC:
  case SHT_DYNSYM:		/* could treat this like symtab... */
#if 0
    fprintf(stderr, "Dynamic Linking sections not yet supported.\n");
    abort ();
#endif
    break;

  case SHT_NOTE:
#if 0
    fprintf(stderr, "Note Sections not yet supported.\n");
    abort ();
#endif
    break;

  case SHT_SHLIB:
#if 0
    fprintf(stderr, "SHLIB Sections not supported (and non conforming.)\n");
#endif
    return true;

  default:
    break;
  }
  
  return (true);
}




struct strtab {
  char *tab;
  int nentries;
  int length;
};


static struct strtab *
DEFUN(bfd_new_strtab, (abfd),
      bfd		*abfd)
{
  struct strtab *ss;

  ss = (struct strtab *)malloc(sizeof(struct strtab));
  ss->tab = malloc(1);
  BFD_ASSERT(ss->tab != 0);
  *ss->tab = 0;
  ss->nentries = 0;
  ss->length = 1;

  return ss;
}

static int
DEFUN(bfd_add_to_strtab, (abfd, ss, str),
      bfd		*abfd AND
      struct strtab	*ss AND
      CONST char	*str)
{
  /* should search first, but for now: */
  /* include the trailing NUL */
  int ln = strlen(str)+1;
  
  /* should this be using obstacks? */
  ss->tab = realloc(ss->tab, ss->length + ln);

  BFD_ASSERT(ss->tab != 0);
  strcpy(ss->tab + ss->length, str);
  ss->nentries++;
  ss->length += ln;

  return ss->length - ln;
}

static int
DEFUN(bfd_add_2_to_strtab, (abfd, ss, str, str2),
      bfd		*abfd AND
      struct strtab	*ss AND
      char		*str AND
      CONST char	*str2)
{
  /* should search first, but for now: */
  /* include the trailing NUL */
  int ln = strlen(str)+strlen(str2)+1;
  
  /* should this be using obstacks? */
  if (ss->length)
    ss->tab = realloc(ss->tab, ss->length + ln);
  else 
    ss->tab = malloc(ln);

  BFD_ASSERT(ss->tab != 0);
  strcpy(ss->tab + ss->length, str);
  strcpy(ss->tab + ss->length + strlen(str), str2);
  ss->nentries++;
  ss->length += ln;

  return ss->length - ln;
}

/* Create a new ELF section from a bfd section. */

static boolean
DEFUN(bfd_shdr_from_section, (abfd, hdr, shstrtab, indx),
      bfd               *abfd AND
      Elf_Internal_Shdr *hdr AND
      struct strtab	*shstrtab AND
      int		indx)
{
  asection *sect;
  int ndx;
  
  /* figure out out to write the section name from the bfd section name. MWE */
  	      
  sect = abfd->sections;
  for (ndx = indx; --ndx; )
    {
      sect = sect->next;
    }
  hdr[indx].sh_name = bfd_add_to_strtab(abfd, shstrtab,
					bfd_section_name(abfd, sect));
  hdr[indx].sh_addr = sect->vma;
  hdr[indx].sh_size = sect->_raw_size;
  hdr[indx].sh_flags = 0;
  /* these need to be preserved on */
  hdr[indx].sh_link = 0;
  hdr[indx].sh_info = 0;
  hdr[indx].sh_addralign = 0;
  hdr[indx].sh_entsize = 0;

  hdr[indx].sh_type = 0;
  if (sect->flags & SEC_RELOC) {
    hdr[indx].sh_type = SHT_RELA; /* FIXME -- sparc specific */
  }
  
  if (sect->flags & SEC_HAS_CONTENTS)
    {
      hdr[indx].sh_offset = sect->filepos;
      hdr[indx].sh_size = sect->_raw_size;
    }
  if (sect->flags & SEC_ALLOC)
    {
      hdr[indx].sh_flags |= SHF_ALLOC;
      if (sect->flags & SEC_LOAD)
	{
	  /* do something with sh_type ? */
	}
    }
  if (!(sect->flags & SEC_READONLY)) 
    hdr[indx].sh_flags |= SHF_WRITE;

  if (sect->flags & SEC_CODE)
    hdr[indx].sh_flags |= SHF_EXECINSTR;

  return (true);
}

/* Create a new bfd section from an ELF program header.

   Since program segments have no names, we generate a synthetic name
   of the form segment<NUM>, where NUM is generally the index in the
   program header table.  For segments that are split (see below) we
   generate the names segment<NUM>a and segment<NUM>b.

   Note that some program segments may have a file size that is different than
   (less than) the memory size.  All this means is that at execution the
   system must allocate the amount of memory specified by the memory size,
   but only initialize it with the first "file size" bytes read from the
   file.  This would occur for example, with program segments consisting
   of combined data+bss.

   To handle the above situation, this routine generates TWO bfd sections
   for the single program segment.  The first has the length specified by
   the file size of the segment, and the second has the length specified
   by the difference between the two sizes.  In effect, the segment is split
   into it's initialized and uninitialized parts.

 */

static boolean
DEFUN(bfd_section_from_phdr, (abfd, hdr, index),
      bfd               *abfd AND
      Elf_Internal_Phdr *hdr AND
      int		 index)
{
  asection *newsect;
  char *name;
  char namebuf[64];
  int split;

  split = ((hdr -> p_memsz > 0) &&
	   (hdr -> p_filesz > 0) &&
	   (hdr -> p_memsz > hdr -> p_filesz));
  sprintf (namebuf, split ? "segment%da" : "segment%d", index);
  name = bfd_alloc (abfd, strlen (namebuf) + 1);
  strcpy (name, namebuf);
  newsect = bfd_make_section (abfd, name);
  newsect -> vma = hdr -> p_vaddr;
  newsect -> _raw_size = hdr -> p_filesz;
  newsect -> filepos = hdr -> p_offset;
  newsect -> flags |= SEC_HAS_CONTENTS;
  if (hdr -> p_type == PT_LOAD)
    {
      newsect -> flags |= SEC_ALLOC;
      newsect -> flags |= SEC_LOAD;
      if (hdr -> p_flags & PF_X)
	{
	  /* FIXME: all we known is that it has execute PERMISSION,
	     may be data. */
	  newsect -> flags |= SEC_CODE;
	}
    }
  if (!(hdr -> p_flags & PF_W))
    {
      newsect -> flags |= SEC_READONLY;
    }

  if (split)
    {
      sprintf (namebuf, "segment%db", index);
      name = bfd_alloc (abfd, strlen (namebuf) + 1);
      strcpy (name, namebuf);
      newsect = bfd_make_section (abfd, name);
      newsect -> vma = hdr -> p_vaddr + hdr -> p_filesz;
      newsect -> _raw_size = hdr -> p_memsz - hdr -> p_filesz;
      if (hdr -> p_type == PT_LOAD)
	{
	  newsect -> flags |= SEC_ALLOC;
	  if (hdr -> p_flags & PF_X)
	    newsect -> flags |= SEC_CODE;
	}
      if (!(hdr -> p_flags & PF_W))
	newsect -> flags |= SEC_READONLY;
    }

  return (true);
}

#ifdef HAVE_PROCFS

static void
DEFUN(bfd_prstatus,(abfd, descdata, descsz, filepos),
      bfd	*abfd AND
      char	*descdata AND
      int	 descsz AND
      long	 filepos)
{
  asection *newsect;
  prstatus_t *status = (prstatus_t *)0;

  if (descsz == sizeof (prstatus_t))
    {
      newsect = bfd_make_section (abfd, ".reg");
      newsect -> _raw_size = sizeof (status->pr_reg);
      newsect -> filepos = filepos + (long) &status->pr_reg;
      newsect -> flags = SEC_ALLOC | SEC_HAS_CONTENTS;
      newsect -> alignment_power = 2;
      if ((core_prstatus (abfd) = bfd_alloc (abfd, descsz)) != NULL)
	{
	  memcpy (core_prstatus (abfd), descdata, descsz);
	}
    }
}

/* Stash a copy of the prpsinfo structure away for future use. */

static void
DEFUN(bfd_prpsinfo,(abfd, descdata, descsz, filepos),
      bfd	*abfd AND
      char	*descdata AND
      int	 descsz AND
      long	 filepos)
{
  asection *newsect;

  if (descsz == sizeof (prpsinfo_t))
    {
      if ((core_prpsinfo (abfd) = bfd_alloc (abfd, descsz)) != NULL)
	{
	  memcpy (core_prpsinfo (abfd), descdata, descsz);
	}
    }
}

static void
DEFUN(bfd_fpregset,(abfd, descdata, descsz, filepos),
      bfd	*abfd AND
      char	*descdata AND
      int	 descsz AND
      long	 filepos)
{
  asection *newsect;

  newsect = bfd_make_section (abfd, ".reg2");
  newsect -> _raw_size = descsz;
  newsect -> filepos = filepos;
  newsect -> flags = SEC_ALLOC | SEC_HAS_CONTENTS;
  newsect -> alignment_power = 2;
}

#endif	/* HAVE_PROCFS */

/* Return a pointer to the args (including the command name) that were
   seen by the program that generated the core dump.  Note that for
   some reason, a spurious space is tacked onto the end of the args
   in some (at least one anyway) implementations, so strip it off if
   it exists. */

char *
DEFUN(elf_core_file_failing_command, (abfd),
     bfd *abfd)
{
#ifdef HAVE_PROCFS
  if (core_prpsinfo (abfd))
    {
      prpsinfo_t *p = core_prpsinfo (abfd);
      char *scan = p -> pr_psargs;
      while (*scan++) {;}
      scan -= 2;
      if ((scan > p -> pr_psargs) && (*scan == ' '))
	{
	  *scan = '\000';
	}
      return (p -> pr_psargs);
    }
#endif
  return (NULL);
}

/* Return the number of the signal that caused the core dump.  Presumably,
   since we have a core file, we got a signal of some kind, so don't bother
   checking the other process status fields, just return the signal number.
   */

static int
DEFUN(elf_core_file_failing_signal, (abfd),
      bfd *abfd)
{
#ifdef HAVE_PROCFS
  if (core_prstatus (abfd))
    {
      return (((prstatus_t *)(core_prstatus (abfd))) -> pr_cursig);
    }
#endif
  return (-1);
}