path: root/bfd/elf.c

/* ELF support for BFD.
   Copyright (C) 1991 Free Software Foundation, Inc.

   Written by Fred Fish @ Cygnus Support, from information published
   in "UNIX System V Release 4, Programmers Guide: ANSI C and
   Programming Support Tools".

This file is part of BFD, the Binary File Descriptor library.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */


	/****************************************

	  		WARNING

	This is only a partial ELF implementation,
	incorporating only those parts that are
	required to get gdb up and running.  It is
	expected that it will be expanded to a full
	ELF implementation at some future date.

	Unimplemented stubs call abort() to ensure
	that they get proper attention if they are
	ever called.  The stubs are here since
	this version was hacked from the COFF
	version, and thus they will probably
	go away or get expanded appropriately in a
	future version.

	fnf@cygnus.com

	*****************************************/


/* Problems and other issues to resolve.

   (1)	BFD expects there to be some fixed number of "sections" in
        the object file.  I.E. there is a "section_count" variable in the
	bfd structure which contains the number of sections.  However, ELF
	supports multiple "views" of a file.  In particular, with current
	implementations, executable files typically have two tables, a
	program header table and a section header table, both of which
	partition the executable.

	In ELF-speak, the "linking view" of the file uses the section header
	table to access "sections" within the file, and the "execution view"
	uses the program header table to access "segments" within the file.
	"Segments" typically may contain all the data from one or more
	"sections".

	Note that the section header table is optional in ELF executables,
	but it is this information that is most useful to gdb.  If the
	section header table is missing, then gdb should probably try
	to make do with the program header table.  (FIXME)

*/

#include <ansidecl.h>
#include <sysdep.h>
#include "bfd.h"
#include "libbfd.h"
#include "obstack.h"
#include "elf-common.h"
#include "elf-internal.h"
#include "elf-external.h"

/* Forward data declarations */
extern bfd_target elf_little_vec, elf_big_vec;

/* Translate an ELF header in external format into an ELF header in internal
   format. */

static void
DEFUN(bfd_swap_ehdr_in,(abfd, src, dst),
      bfd               *abfd AND
      Elf_External_Ehdr *src AND
      Elf_Internal_Ehdr *dst)
{
  bcopy (src -> e_ident, dst -> e_ident, EI_NIDENT);
  dst -> e_type = bfd_h_get_16 (abfd, (bfd_byte *) src -> e_type);
  dst -> e_machine = bfd_h_get_16 (abfd, (bfd_byte *) src -> e_machine);
  dst -> e_version = bfd_h_get_32 (abfd, (bfd_byte *) src -> e_version);
  dst -> e_entry = bfd_h_get_32 (abfd, (bfd_byte *) src -> e_entry);
  dst -> e_phoff = bfd_h_get_32 (abfd, (bfd_byte *) src -> e_phoff);
  dst -> e_shoff = bfd_h_get_32 (abfd, (bfd_byte *) src -> e_shoff);
  dst -> e_flags = bfd_h_get_32 (abfd, (bfd_byte *) src -> e_flags);
  dst -> e_ehsize = bfd_h_get_16 (abfd, (bfd_byte *) src -> e_ehsize);
  dst -> e_phentsize = bfd_h_get_16 (abfd, (bfd_byte *) src -> e_phentsize);
  dst -> e_phnum = bfd_h_get_16 (abfd, (bfd_byte *) src -> e_phnum);
  dst -> e_shentsize = bfd_h_get_16 (abfd, (bfd_byte *) src -> e_shentsize);
  dst -> e_shnum = bfd_h_get_16 (abfd, (bfd_byte *) src -> e_shnum);
  dst -> e_shstrndx = bfd_h_get_16 (abfd, (bfd_byte *) src -> e_shstrndx);
}


/* Translate an ELF section header table entry in external format into an
   ELF section header table entry in internal format. */

static void
DEFUN(bfd_swap_shdr_in,(abfd, src, dst),
      bfd               *abfd AND
      Elf_External_Shdr *src AND
      Elf_Internal_Shdr *dst)
{
  dst -> sh_name = bfd_h_get_32 (abfd, (bfd_byte *) src -> sh_name);
  dst -> sh_type = bfd_h_get_32 (abfd, (bfd_byte *) src -> sh_type);
  dst -> sh_flags = bfd_h_get_32 (abfd, (bfd_byte *) src -> sh_flags);
  dst -> sh_addr = bfd_h_get_32 (abfd, (bfd_byte *) src -> sh_addr);
  dst -> sh_offset = bfd_h_get_32 (abfd, (bfd_byte *) src -> sh_offset);
  dst -> sh_size = bfd_h_get_32 (abfd, (bfd_byte *) src -> sh_size);
  dst -> sh_link = bfd_h_get_32 (abfd, (bfd_byte *) src -> sh_link);
  dst -> sh_info = bfd_h_get_32 (abfd, (bfd_byte *) src -> sh_info);
  dst -> sh_addralign = bfd_h_get_32 (abfd, (bfd_byte *) src -> sh_addralign);
  dst -> sh_entsize = bfd_h_get_32 (abfd, (bfd_byte *) src -> sh_entsize);
}


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

static boolean
DEFUN(bfd_section_from_shdr, (abfd, hdr, shstrtab),
      bfd               *abfd AND
      Elf_Internal_Shdr *hdr AND
      char		*shstrtab)
{
  asection *newsect;
  char *name;

  name = hdr -> sh_name ? shstrtab + hdr -> sh_name : "unnamed";
  newsect = bfd_make_section (abfd, name);
  newsect -> vma = hdr -> sh_addr;
  newsect -> size = hdr -> sh_size;
  if (!(hdr -> sh_type == SHT_NOBITS))
    {
      newsect -> filepos = hdr -> sh_offset;
      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 */
    }
  if (hdr -> sh_type == SHT_SYMTAB)
    {
      abfd -> flags |= HAS_SYMS;
    }

  return (true);
}

/* Begin processing a given object.

   First we validate the file by reading in the ELF header and checking
   the magic number.

   */

static bfd_target *
DEFUN (elf_object_p, (abfd), bfd *abfd)
{
  Elf_External_Ehdr x_ehdr;	/* Elf file header, external form */
  Elf_Internal_Ehdr i_ehdr;	/* Elf file header, internal form */
  Elf_External_Shdr *x_shdr;	/* Section header table, external form */
  Elf_Internal_Shdr *i_shdr;	/* Section header table, internal form */
  int shindex;
  char *shstrtab;		/* Internal copy of section header stringtab */
  int shstrtabsize;		/* Size of section header string table */
  
  /* Read in the ELF header in external format.  */

  if (bfd_read ((PTR) &x_ehdr, sizeof (x_ehdr), 1, abfd) != sizeof (x_ehdr))
    {
      bfd_error = system_call_error;
      return (NULL);
    }

  /* Now check to see if we have a valid ELF file, and one that BFD can
     make use of.  The magic number must match, the address size ('class')
     and byte-swapping must match our XVEC entry, and it must have a
     section header table (FIXME: See comments re sections at top of this
     file). */

  if (x_ehdr.e_ident[EI_MAG0] != ELFMAG0 ||
      x_ehdr.e_ident[EI_MAG1] != ELFMAG1 ||
      x_ehdr.e_ident[EI_MAG2] != ELFMAG2 ||
      x_ehdr.e_ident[EI_MAG3] != ELFMAG3)
    {
wrong:
      bfd_error = wrong_format;
      return (NULL);
    }

  /* FIXME, Check EI_VERSION here !  */

  switch (x_ehdr.e_ident[EI_CLASS]) {
  case ELFCLASSNONE:			/* address size not specified */
    goto wrong;			/* No support if can't tell address size */
  case ELFCLASS32:			/* 32-bit addresses */
    break;
  case ELFCLASS64:			/* 64-bit addresses */
    goto wrong;			/* FIXME: 64 bits not yet supported */
  default:
    goto wrong;			/* No support if unknown address class */
  }

  /* 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;
  case ELFDATANONE:			/* No data encoding specified */
  default:				/* Unknown data encoding specified */
    goto wrong;
  }
  
  /* Now that we know the byte order, swap in the rest of the header */
  bfd_swap_ehdr_in (abfd, &x_ehdr, &i_ehdr);
  if (x_ehdr.e_shoff == 0)
    goto wrong;

  if (i_ehdr.e_type == ET_EXEC || i_ehdr.e_type == ET_DYN)
    {
      abfd -> flags |= EXEC_P;
    }

  /* Allocate space for copies of the section header table in external
     and internal form, seek to the section 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 section
     header table entry actually matches the size recorded in the file. */

  if (i_ehdr.e_shentsize != sizeof (*x_shdr))
    goto wrong;
  if ((x_shdr = (Elf_External_Shdr *)
	bfd_alloc (abfd, sizeof (*x_shdr) * i_ehdr.e_shnum)) == NULL)
    {
      bfd_error = no_memory;
      return (NULL);
    }
  if ((i_shdr = (Elf_Internal_Shdr *)
	bfd_alloc (abfd, sizeof (*i_shdr) * i_ehdr.e_shnum)) == NULL)
    {
      bfd_error = no_memory;
      return (NULL);
    }
  if (bfd_seek (abfd, i_ehdr.e_shoff, SEEK_SET) == -1)
    {
      bfd_error = system_call_error;
      return (NULL);
    }
  for (shindex = 0; shindex < i_ehdr.e_shnum; shindex++)
    {
      if (bfd_read ((PTR) (x_shdr + shindex), sizeof (*x_shdr), 1, abfd)
	  != sizeof (*x_shdr))
	{
	  bfd_error = system_call_error;
	  return (NULL);
	}
      bfd_swap_shdr_in (abfd, x_shdr + shindex, i_shdr + shindex);
    }

  /* Read in the string table containing the names of the sections.  We
     will need the base pointer to this table later. */

  shstrtabsize = i_shdr[i_ehdr.e_shstrndx].sh_size;
  if ((shstrtab = bfd_alloc (abfd, shstrtabsize)) == NULL)
    {
      bfd_error = no_memory;
      return (NULL);
    }
  if (bfd_seek (abfd, i_shdr[i_ehdr.e_shstrndx].sh_offset, SEEK_SET) == -1)
    {
      bfd_error = system_call_error;
      return (NULL);
    }
  if (bfd_read ((PTR) shstrtab, shstrtabsize, 1, abfd) != shstrtabsize)
    {
      bfd_error = system_call_error;
      return (NULL);
    }
  
  /* Once all of the section headers have been read and converted, we
     can start processing them. */

  for (shindex = 0; shindex < i_ehdr.e_shnum; shindex++)
    {
      bfd_section_from_shdr (abfd, i_shdr + shindex, shstrtab);
    }

  return (abfd->xvec);
}

static boolean
DEFUN (elf_mkobject, (abfd), bfd *abfd)
{
  fprintf (stderr, "elf_mkobject unimplemented\n");
  fflush (stderr);
  abort ();
  return (false);
}

static boolean
DEFUN (elf_write_object_contents, (abfd), bfd *abfd)
{
  fprintf (stderr, "elf_write_object_contents unimplemented\n");
  fflush (stderr);
  abort ();
  return (false);
}

static boolean
DEFUN (elf_set_section_contents, (abfd, section, location, offset, count),
      bfd            *abfd AND
      sec_ptr         section AND
      PTR             location AND
      file_ptr        offset AND
      bfd_size_type   count)
{
  fprintf (stderr, "elf_set_section_contents unimplemented\n");
  fflush (stderr);
  abort ();
  return (false);
}

#define elf_new_section_hook		_bfd_dummy_new_section_hook
#define elf_core_file_failing_command	_bfd_dummy_core_file_failing_command
#define elf_core_file_failing_signal	_bfd_dummy_core_file_failing_signal
#define elf_core_file_matches_executable_p	_bfd_dummy_core_file_matches_executable_p
#define elf_slurp_armap			bfd_false
#define elf_slurp_extended_name_table	_bfd_slurp_extended_name_table
#define elf_truncate_arname		bfd_dont_truncate_arname
#define elf_openr_next_archived_file	bfd_generic_openr_next_archived_file
#define elf_generic_stat_arch_elt	bfd_generic_stat_arch_elt
#define	elf_get_section_contents	bfd_generic_get_section_contents
#define	elf_close_and_cleanup		bfd_generic_close_and_cleanup

#define elf_bfd_debug_info_start	bfd_void
#define elf_bfd_debug_info_end		bfd_void
#define elf_bfd_debug_info_accumulate	(PROTO(void,(*),(bfd*, struct sec *))) bfd_void

#define elf_write_armap			bfd_false


static unsigned int
elf_get_symtab_upper_bound(abfd)
bfd *abfd;
{
  fprintf (stderr, "elf_get_symtab_upper_bound unimplemented\n");
  fflush (stderr);
  abort ();
  return (0);
}

static unsigned int
elf_get_reloc_upper_bound (abfd, asect)
bfd            *abfd;
sec_ptr         asect;
{
  fprintf (stderr, "elf_get_reloc_upper_bound unimplemented\n");
  fflush (stderr);
  abort ();
  return (0);
}

static unsigned int
elf_canonicalize_reloc (abfd, section, relptr, symbols)
bfd            *abfd;
sec_ptr         section;
arelent       **relptr;
asymbol       **symbols;
{
  fprintf (stderr, "elf_canonicalize_reloc unimplemented\n");
  fflush (stderr);
  abort ();
  return (0);
}

static unsigned int
elf_get_symtab (abfd, alocation)
bfd            *abfd;
asymbol       **alocation;
{
  fprintf (stderr, "elf_get_symtab unimplemented\n");
  fflush (stderr);
  abort ();
  return (0);
}

static asymbol *
elf_make_empty_symbol(abfd)
bfd            *abfd;
{
  fprintf (stderr, "elf_make_empty_symbol unimplemented\n");
  fflush (stderr);
  abort ();
  return (NULL);
}

static void 
DEFUN (elf_print_symbol,(ignore_abfd, filep, symbol, how),
      bfd            *ignore_abfd AND
      PTR           filep AND
      asymbol        *symbol AND
      bfd_print_symbol_enum_type how)
{
  fprintf (stderr, "elf_print_symbol unimplemented\n");
  fflush (stderr);
  abort ();
}

static alent *
DEFUN (elf_get_lineno,(ignore_abfd, symbol),
      bfd            *ignore_abfd AND
      asymbol        *symbol)
{
  fprintf (stderr, "elf_get_lineno unimplemented\n");
  fflush (stderr);
  abort ();
  return (NULL);
}

static boolean
DEFUN (elf_set_arch_mach,(abfd, arch, machine),
      bfd            *abfd AND
      enum bfd_architecture arch AND
      unsigned long   machine)
{
  fprintf (stderr, "elf_set_arch_mach unimplemented\n");
  fflush (stderr);
  /* Allow any architecture to be supported by the elf backend */
  return  bfd_default_set_arch_mach(abfd, arch, machine);
}

static boolean
DEFUN (elf_find_nearest_line,(abfd,
			      section,
			      symbols,
			      offset,
			      filename_ptr,
			      functionname_ptr,
			      line_ptr),
      bfd            *abfd AND
      asection       *section AND
      asymbol       **symbols AND
      bfd_vma         offset AND
      CONST char      **filename_ptr AND
      CONST char       **functionname_ptr AND
      unsigned int   *line_ptr)
{
  fprintf (stderr, "elf_find_nearest_line unimplemented\n");
  fflush (stderr);
  abort ();
  return (false);
}

static int 
DEFUN (elf_sizeof_headers, (abfd, reloc),
      bfd *abfd AND
      boolean reloc)
{
  fprintf (stderr, "elf_sizeof_headers unimplemented\n");
  fflush (stderr);
  abort ();
  return (0);
}

/* This structure contains everything that BFD knows about a target.
   It includes things like its byte order, name, what routines to call
   to do various operations, etc.  Every BFD points to a target structure
   with its "xvec" member.

   There are two such structures here:  one for big-endian machines and
   one for little-endian machines.   */

bfd_target elf_big_vec =
{
  /* name: identify kind of target */
  "elf-big",

  /* flavour: general indication about file */
  bfd_target_elf_flavour_enum,

  /* byteorder_big_p: data is big endian */
  true,

  /* header_byteorder_big_p: header is also big endian */
  true,

  /* object_flags: mask of all file flags */
  (HAS_RELOC | EXEC_P | HAS_LINENO | HAS_DEBUG | HAS_SYMS | HAS_LOCALS |
   DYNAMIC | WP_TEXT),
  
  /* section_flags: mask of all section flags */
  (SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD | SEC_RELOC | SEC_READONLY |
   SEC_DATA), 

  /* ar_pad_char: pad character for filenames within an archive header
     FIXME:  this really has nothing to do with ELF, this is a characteristic
     of the archiver and/or os and should be independently tunable */
  '/',

  /* ar_max_namelen: maximum number of characters in an archive header
     FIXME:  this really has nothing to do with ELF, this is a characteristic
     of the archiver and should be independently tunable.  This value is
     a WAG (wild a** guess) */
  15,

  /* align_power_min: minimum alignment restriction for any section
     FIXME:  this value may be target machine dependent */
  3,

  /* Routines to byte-swap various sized integers from the data sections */
  _do_getb64, _do_putb64, _do_getb32, _do_putb32, _do_getb16, _do_putb16,

  /* Routines to byte-swap various sized integers from the file headers */
  _do_getb64, _do_putb64, _do_getb32, _do_putb32, _do_getb16, _do_putb16,

  /* bfd_check_format: check the format of a file being read */
  { _bfd_dummy_target,
    elf_object_p,
    bfd_generic_archive_p,
    _bfd_dummy_target
  },

  /* bfd_set_format: set the format of a file being written */
  { bfd_false,
    elf_mkobject,
    _bfd_generic_mkarchive,
    bfd_false
  },

  /* bfd_write_contents: write cached information into a file being written */
  { bfd_false,
    elf_write_object_contents,
    _bfd_write_archive_contents,
    bfd_false
  },

  /* Initialize a jump table with the standard macro.  All names start
     with "elf" */
  JUMP_TABLE(elf),

  /* SWAP_TABLE */
  NULL, NULL, NULL
};

bfd_target elf_little_vec =
{
  /* name: identify kind of target */
  "elf-little",

  /* flavour: general indication about file */
  bfd_target_elf_flavour_enum,

  /* byteorder_big_p: data is big endian */
  false,		/* Nope -- this one's little endian */

  /* header_byteorder_big_p: header is also big endian */
  false,		/* Nope -- this one's little endian */

  /* object_flags: mask of all file flags */
  (HAS_RELOC | EXEC_P | HAS_LINENO | HAS_DEBUG | HAS_SYMS | HAS_LOCALS |
   DYNAMIC | WP_TEXT),
  
  /* section_flags: mask of all section flags */
  (SEC_HAS_CONTENTS | SEC_ALLOC | SEC_LOAD | SEC_RELOC | SEC_READONLY |
   SEC_DATA), 

  /* ar_pad_char: pad character for filenames within an archive header
     FIXME:  this really has nothing to do with ELF, this is a characteristic
     of the archiver and/or os and should be independently tunable */
  '/',

  /* ar_max_namelen: maximum number of characters in an archive header
     FIXME:  this really has nothing to do with ELF, this is a characteristic
     of the archiver and should be independently tunable.  This value is
     a WAG (wild a** guess) */
  15,

  /* align_power_min: minimum alignment restriction for any section
     FIXME:  this value may be target machine dependent */
  3,

  /* Routines to byte-swap various sized integers from the data sections */
  _do_getl64, _do_putl64, _do_getl32, _do_putl32, _do_getl16, _do_putl16,

  /* Routines to byte-swap various sized integers from the file headers */
  _do_getl64, _do_putl64, _do_getl32, _do_putl32, _do_getl16, _do_putl16,

  /* bfd_check_format: check the format of a file being read */
  { _bfd_dummy_target,
    elf_object_p,
    bfd_generic_archive_p,
    _bfd_dummy_target
  },

  /* bfd_set_format: set the format of a file being written */
  { bfd_false,
    elf_mkobject,
    _bfd_generic_mkarchive,
    bfd_false
  },

  /* bfd_write_contents: write cached information into a file being written */
  { bfd_false,
    elf_write_object_contents,
    _bfd_write_archive_contents,
    bfd_false
  },

  /* Initialize a jump table with the standard macro.  All names start
     with "elf" */
  JUMP_TABLE(elf),

  /* SWAP_TABLE */
  NULL, NULL, NULL
};