src/libdwfl/open.c

/* Decompression support for libdwfl: zlib (gzip) and/or bzlib (bzip2).
   Copyright (C) 2009 Red Hat, Inc.
   This file is part of Red Hat elfutils.

   Red Hat elfutils 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; version 2 of the License.

   Red Hat elfutils 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 Red Hat elfutils; if not, write to the Free Software Foundation,
   Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA.

   In addition, as a special exception, Red Hat, Inc. gives You the
   additional right to link the code of Red Hat elfutils with code licensed
   under any Open Source Initiative certified open source license
   (http://www.opensource.org/licenses/index.php) which requires the
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   distribute linked combinations of the two.  Non-GPL Code permitted under
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   those well defined interfaces identified in the file named EXCEPTION
   found in the source code files (the "Approved Interfaces").  The files
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   Red Hat's grant of this exception is conditioned upon your not adding
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   exception, please contact Red Hat.  You must obey the GNU General Public
   License in all respects for all of the Red Hat elfutils code and other
   code used in conjunction with Red Hat elfutils except the Non-GPL Code
   covered by this exception.  If you modify this file, you may extend this
   exception to your version of the file, but you are not obligated to do
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   you must delete this exception statement from your version and license
   this file solely under the GPL without exception.

   Red Hat elfutils is an included package of the Open Invention Network.
   An included package of the Open Invention Network is a package for which
   Open Invention Network licensees cross-license their patents.  No patent
   license is granted, either expressly or impliedly, by designation as an
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#include "../libelf/libelfP.h"
#undef	_
#include "libdwflP.h"

#include <unistd.h>

#if !USE_ZLIB
# define __libdw_gunzip(...)	false
#endif

#if !USE_BZLIB
# define __libdw_bunzip2(...)	false
#endif

#if !USE_LZMA
# define __libdw_unlzma(...)	false
#endif

/* Consumes and replaces *ELF only on success.  */
static Dwfl_Error
decompress (int fd __attribute__ ((unused)), Elf **elf)
{
  Dwfl_Error error = DWFL_E_BADELF;
  void *buffer = NULL;
  size_t size = 0;

#if USE_ZLIB || USE_BZLIB || USE_LZMA
  const off64_t offset = (*elf)->start_offset;
  void *const mapped = ((*elf)->map_address == NULL ? NULL
			: (*elf)->map_address + offset);
  const size_t mapped_size = (*elf)->maximum_size;
  if (mapped_size == 0)
    return error;

  error = __libdw_gunzip (fd, offset, mapped, mapped_size, &buffer, &size);
  if (error == DWFL_E_BADELF)
    error = __libdw_bunzip2 (fd, offset, mapped, mapped_size, &buffer, &size);
  if (error == DWFL_E_BADELF)
    error = __libdw_unlzma (fd, offset, mapped, mapped_size, &buffer, &size);
#endif

  if (error == DWFL_E_NOERROR)
    {
      if (unlikely (size == 0))
	{
	  error = DWFL_E_BADELF;
	  free (buffer);
	}
      else
	{
	  Elf *memelf = elf_memory (buffer, size);
	  if (memelf == NULL)
	    {
	      error = DWFL_E_LIBELF;
	      free (buffer);
	    }
	  else
	    {
	      memelf->flags |= ELF_F_MALLOCED;
	      elf_end (*elf);
	      *elf = memelf;
	    }
	}
    }
  else
    free (buffer);

  return error;
}

static Dwfl_Error
what_kind (int fd, Elf **elfp, Elf_Kind *kind, bool *close_fd)
{
  Dwfl_Error error = DWFL_E_NOERROR;
  *kind = elf_kind (*elfp);
  if (unlikely (*kind == ELF_K_NONE))
    {
      if (unlikely (*elfp == NULL))
	error = DWFL_E_LIBELF;
      else
	{
	  error = decompress (fd, elfp);
	  if (error == DWFL_E_NOERROR)
	    {
	      *close_fd = true;
	      *kind = elf_kind (*elfp);
	    }
	}
    }
  return error;
}

Dwfl_Error internal_function
__libdw_open_file (int *fdp, Elf **elfp, bool close_on_fail, bool archive_ok)
{
  bool close_fd = false;

  Elf *elf = elf_begin (*fdp, ELF_C_READ_MMAP_PRIVATE, NULL);

  Elf_Kind kind;
  Dwfl_Error error = what_kind (*fdp, &elf, &kind, &close_fd);
  if (error == DWFL_E_BADELF)
    {
      /* It's not an ELF file or a compressed file.
	 See if it's an image with a header preceding the real file.  */

      off64_t offset = elf->start_offset;
      error = __libdw_image_header (*fdp, &offset,
				    (elf->map_address == NULL ? NULL
				     : elf->map_address + offset),
				    elf->maximum_size);
      if (error == DWFL_E_NOERROR)
	{
	  /* Pure evil.  libelf needs some better interfaces.  */
	  elf->kind = ELF_K_AR;
	  elf->state.ar.elf_ar_hdr.ar_name = "libdwfl is faking you out";
	  elf->state.ar.elf_ar_hdr.ar_size = elf->maximum_size - offset;
	  elf->state.ar.offset = offset - sizeof (struct ar_hdr);
	  Elf *subelf = elf_begin (-1, ELF_C_READ_MMAP_PRIVATE, elf);
	  elf->kind = ELF_K_NONE;
	  if (unlikely (subelf == NULL))
	    error = DWFL_E_LIBELF;
	  else
	    {
	      subelf->parent = NULL;
	      subelf->flags |= elf->flags & (ELF_F_MMAPPED | ELF_F_MALLOCED);
	      elf->flags &= ~(ELF_F_MMAPPED | ELF_F_MALLOCED);
	      elf_end (elf);
	      elf = subelf;
	      error = what_kind (*fdp, &elf, &kind, &close_fd);
	    }
	}
    }

  if (error == DWFL_E_NOERROR
      && kind != ELF_K_ELF
      && !(archive_ok && kind == ELF_K_AR))
    error = DWFL_E_BADELF;

  if (error != DWFL_E_NOERROR)
    {
      elf_end (elf);
      elf = NULL;
    }

  if (error == DWFL_E_NOERROR ? close_fd : close_on_fail)
    {
      close (*fdp);
      *fdp = -1;
    }

  *elfp = elf;
  return error;
}