Blame libdwfl/image-header.c

Packit Service 97d2fb
/* Linux kernel image support for libdwfl.
Packit Service 97d2fb
   Copyright (C) 2009-2011 Red Hat, Inc.
Packit Service 97d2fb
   This file is part of elfutils.
Packit Service 97d2fb
Packit Service 97d2fb
   This file is free software; you can redistribute it and/or modify
Packit Service 97d2fb
   it under the terms of either
Packit Service 97d2fb
Packit Service 97d2fb
     * the GNU Lesser General Public License as published by the Free
Packit Service 97d2fb
       Software Foundation; either version 3 of the License, or (at
Packit Service 97d2fb
       your option) any later version
Packit Service 97d2fb
Packit Service 97d2fb
   or
Packit Service 97d2fb
Packit Service 97d2fb
     * the GNU General Public License as published by the Free
Packit Service 97d2fb
       Software Foundation; either version 2 of the License, or (at
Packit Service 97d2fb
       your option) any later version
Packit Service 97d2fb
Packit Service 97d2fb
   or both in parallel, as here.
Packit Service 97d2fb
Packit Service 97d2fb
   elfutils is distributed in the hope that it will be useful, but
Packit Service 97d2fb
   WITHOUT ANY WARRANTY; without even the implied warranty of
Packit Service 97d2fb
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Packit Service 97d2fb
   General Public License for more details.
Packit Service 97d2fb
Packit Service 97d2fb
   You should have received copies of the GNU General Public License and
Packit Service 97d2fb
   the GNU Lesser General Public License along with this program.  If
Packit Service 97d2fb
   not, see <http://www.gnu.org/licenses/>.  */
Packit Service 97d2fb
Packit Service 97d2fb
#ifdef HAVE_CONFIG_H
Packit Service 97d2fb
# include <config.h>
Packit Service 97d2fb
#endif
Packit Service 97d2fb
Packit Service 97d2fb
#include "libdwflP.h"
Packit Service 97d2fb
#include "system.h"
Packit Service 97d2fb
Packit Service 97d2fb
#include <unistd.h>
Packit Service 97d2fb
#include <endian.h>
Packit Service 97d2fb
Packit Service 97d2fb
#if BYTE_ORDER == LITTLE_ENDIAN
Packit Service 97d2fb
# define LE16(x)	(x)
Packit Service 97d2fb
#else
Packit Service 97d2fb
# define LE16(x)	bswap_16 (x)
Packit Service 97d2fb
#endif
Packit Service 97d2fb
Packit Service 97d2fb
/* See Documentation/x86/boot.txt in Linux kernel sources
Packit Service 97d2fb
   for an explanation of these format details.  */
Packit Service 97d2fb
Packit Service 97d2fb
#define MAGIC1			0xaa55
Packit Service 97d2fb
#define MAGIC2			0x53726448 /* "HdrS" little-endian */
Packit Service 97d2fb
#define MIN_VERSION		0x0208
Packit Service 97d2fb
Packit Service 97d2fb
#define H_START			(H_SETUP_SECTS & -4)
Packit Service 97d2fb
#define H_SETUP_SECTS		0x1f1
Packit Service 97d2fb
#define H_MAGIC1		0x1fe
Packit Service 97d2fb
#define H_MAGIC2		0x202
Packit Service 97d2fb
#define H_VERSION		0x206
Packit Service 97d2fb
#define H_PAYLOAD_OFFSET	0x248
Packit Service 97d2fb
#define H_PAYLOAD_LENGTH	0x24c
Packit Service 97d2fb
#define H_END			0x250
Packit Service 97d2fb
#define H_READ_SIZE		(H_END - H_START)
Packit Service 97d2fb
Packit Service 97d2fb
Dwfl_Error
Packit Service 97d2fb
internal_function
Packit Service 97d2fb
__libdw_image_header (int fd, off_t *start_offset,
Packit Service 97d2fb
		      void *mapped, size_t mapped_size)
Packit Service 97d2fb
{
Packit Service 97d2fb
  if (likely (mapped_size > H_END))
Packit Service 97d2fb
    {
Packit Service 97d2fb
      const void *header = mapped;
Packit Service 97d2fb
      char header_buffer[H_READ_SIZE];
Packit Service 97d2fb
      if (header == NULL)
Packit Service 97d2fb
	{
Packit Service 97d2fb
	  ssize_t n = pread_retry (fd, header_buffer, H_READ_SIZE,
Packit Service 97d2fb
				   *start_offset + H_START);
Packit Service 97d2fb
	  if (n < 0)
Packit Service 97d2fb
	    return DWFL_E_ERRNO;
Packit Service 97d2fb
	  if (n < H_READ_SIZE)
Packit Service 97d2fb
	    return DWFL_E_BADELF;
Packit Service 97d2fb
Packit Service 97d2fb
	  header = header_buffer - H_START;
Packit Service 97d2fb
	}
Packit Service 97d2fb
Packit Service 97d2fb
      if (*(uint16_t *) (header + H_MAGIC1) == LE16 (MAGIC1)
Packit Service 97d2fb
	  && *(uint32_t *) (header + H_MAGIC2) == LE32 (MAGIC2)
Packit Service 97d2fb
	  && LE16 (*(uint16_t *) (header + H_VERSION)) >= MIN_VERSION)
Packit Service 97d2fb
	{
Packit Service 97d2fb
	  /* The magic numbers match and the version field is sufficient.
Packit Service 97d2fb
	     Extract the payload bounds.  */
Packit Service 97d2fb
Packit Service 97d2fb
	  uint32_t offset = LE32 (*(uint32_t *) (header + H_PAYLOAD_OFFSET));
Packit Service 97d2fb
	  uint32_t length = LE32 (*(uint32_t *) (header + H_PAYLOAD_LENGTH));
Packit Service 97d2fb
Packit Service 97d2fb
	  offset += ((*(uint8_t *) (header + H_SETUP_SECTS) ?: 4) + 1) * 512;
Packit Service 97d2fb
Packit Service 97d2fb
	  if (offset > H_END && offset < mapped_size
Packit Service 97d2fb
	      && mapped_size - offset >= length)
Packit Service 97d2fb
	    {
Packit Service 97d2fb
	      /* It looks kosher.  Use it!  */
Packit Service 97d2fb
	      *start_offset += offset;
Packit Service 97d2fb
	      return DWFL_E_NOERROR;
Packit Service 97d2fb
	    }
Packit Service 97d2fb
	}
Packit Service 97d2fb
    }
Packit Service 97d2fb
  return DWFL_E_BADELF;
Packit Service 97d2fb
}