Line data    Source code

       1             : /* Linux kernel image support for libdwfl.
       2             :    Copyright (C) 2009-2011 Red Hat, Inc.
       3             :    This file is part of elfutils.
       4             : 
       5             :    This file is free software; you can redistribute it and/or modify
       6             :    it under the terms of either
       7             : 
       8             :      * the GNU Lesser General Public License as published by the Free
       9             :        Software Foundation; either version 3 of the License, or (at
      10             :        your option) any later version
      11             : 
      12             :    or
      13             : 
      14             :      * the GNU General Public License as published by the Free
      15             :        Software Foundation; either version 2 of the License, or (at
      16             :        your option) any later version
      17             : 
      18             :    or both in parallel, as here.
      19             : 
      20             :    elfutils is distributed in the hope that it will be useful, but
      21             :    WITHOUT ANY WARRANTY; without even the implied warranty of
      22             :    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      23             :    General Public License for more details.
      24             : 
      25             :    You should have received copies of the GNU General Public License and
      26             :    the GNU Lesser General Public License along with this program.  If
      27             :    not, see <http://www.gnu.org/licenses/>.  */
      28             : 
      29             : #ifdef HAVE_CONFIG_H
      30             : # include <config.h>
      31             : #endif
      32             : 
      33             : #include "libdwflP.h"
      34             : #include "system.h"
      35             : 
      36             : #include <unistd.h>
      37             : #include <endian.h>
      38             : 
      39             : #if BYTE_ORDER == LITTLE_ENDIAN
      40             : # define LE16(x)        (x)
      41             : #else
      42             : # define LE16(x)        bswap_16 (x)
      43             : #endif
      44             : 
      45             : /* See Documentation/x86/boot.txt in Linux kernel sources
      46             :    for an explanation of these format details.  */
      47             : 
      48             : #define MAGIC1                  0xaa55
      49             : #define MAGIC2                  0x53726448 /* "HdrS" little-endian */
      50             : #define MIN_VERSION             0x0208
      51             : 
      52             : #define H_START                 (H_SETUP_SECTS & -4)
      53             : #define H_SETUP_SECTS           0x1f1
      54             : #define H_MAGIC1                0x1fe
      55             : #define H_MAGIC2                0x202
      56             : #define H_VERSION               0x206
      57             : #define H_PAYLOAD_OFFSET        0x248
      58             : #define H_PAYLOAD_LENGTH        0x24c
      59             : #define H_END                   0x250
      60             : #define H_READ_SIZE             (H_END - H_START)
      61             : 
      62             : Dwfl_Error
      63             : internal_function
      64           0 : __libdw_image_header (int fd, off_t *start_offset,
      65             :                       void *mapped, size_t mapped_size)
      66             : {
      67           0 :   if (likely (mapped_size > H_END))
      68             :     {
      69           0 :       const void *header = mapped;
      70           0 :       char header_buffer[H_READ_SIZE];
      71           0 :       if (header == NULL)
      72             :         {
      73           0 :           ssize_t n = pread_retry (fd, header_buffer, H_READ_SIZE,
      74           0 :                                    *start_offset + H_START);
      75           0 :           if (n < 0)
      76           0 :             return DWFL_E_ERRNO;
      77           0 :           if (n < H_READ_SIZE)
      78             :             return DWFL_E_BADELF;
      79             : 
      80             :           header = header_buffer - H_START;
      81             :         }
      82             : 
      83           0 :       if (*(uint16_t *) (header + H_MAGIC1) == LE16 (MAGIC1)
      84           0 :           && *(uint32_t *) (header + H_MAGIC2) == LE32 (MAGIC2)
      85           0 :           && LE16 (*(uint16_t *) (header + H_VERSION)) >= MIN_VERSION)
      86             :         {
      87             :           /* The magic numbers match and the version field is sufficient.
      88             :              Extract the payload bounds.  */
      89             : 
      90           0 :           uint32_t offset = LE32 (*(uint32_t *) (header + H_PAYLOAD_OFFSET));
      91           0 :           uint32_t length = LE32 (*(uint32_t *) (header + H_PAYLOAD_LENGTH));
      92             : 
      93           0 :           offset += ((*(uint8_t *) (header + H_SETUP_SECTS) ?: 4) + 1) * 512;
      94             : 
      95           0 :           if (offset > H_END && offset < mapped_size
      96           0 :               && mapped_size - offset >= length)
      97             :             {
      98             :               /* It looks kosher.  Use it!  */
      99           0 :               *start_offset += offset;
     100           0 :               return DWFL_E_NOERROR;
     101             :             }
     102             :         }
     103             :     }
     104             :   return DWFL_E_BADELF;
     105             : }