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       1                 :            : /* Linux kernel image support for libdwfl.
       2                 :            :    Copyright (C) 2009-2011 Red Hat, Inc.
       3                 :            :    Copyright (C) 2022, 2024 Mark J. Wielaard <mark@klomp.org>
       4                 :            :    This file is part of elfutils.
       5                 :            : 
       6                 :            :    This file is free software; you can redistribute it and/or modify
       7                 :            :    it under the terms of either
       8                 :            : 
       9                 :            :      * the GNU Lesser General Public License as published by the Free
      10                 :            :        Software Foundation; either version 3 of the License, or (at
      11                 :            :        your option) any later version
      12                 :            : 
      13                 :            :    or
      14                 :            : 
      15                 :            :      * the GNU General Public License as published by the Free
      16                 :            :        Software Foundation; either version 2 of the License, or (at
      17                 :            :        your option) any later version
      18                 :            : 
      19                 :            :    or both in parallel, as here.
      20                 :            : 
      21                 :            :    elfutils is distributed in the hope that it will be useful, but
      22                 :            :    WITHOUT ANY WARRANTY; without even the implied warranty of
      23                 :            :    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      24                 :            :    General Public License for more details.
      25                 :            : 
      26                 :            :    You should have received copies of the GNU General Public License and
      27                 :            :    the GNU Lesser General Public License along with this program.  If
      28                 :            :    not, see <http://www.gnu.org/licenses/>.  */
      29                 :            : 
      30                 :            : #ifdef HAVE_CONFIG_H
      31                 :            : # include <config.h>
      32                 :            : #endif
      33                 :            : 
      34                 :            : #include "libdwflP.h"
      35                 :            : 
      36                 :            : #if BYTE_ORDER == LITTLE_ENDIAN
      37                 :            : # define LE16(x)        (x)
      38                 :            : #else
      39                 :            : # define LE16(x)        bswap_16 (x)
      40                 :            : #endif
      41                 :            : 
      42                 :            : /* See Documentation/x86/boot.txt in Linux kernel sources
      43                 :            :    for an explanation of these format details.  */
      44                 :            : 
      45                 :            : #define MAGIC1                  0xaa55
      46                 :            : #define MAGIC2                  0x53726448 /* "HdrS" little-endian */
      47                 :            : #define MIN_VERSION             0x0208
      48                 :            : 
      49                 :            : #define H_START                 (H_SETUP_SECTS & -4)
      50                 :            : #define H_SETUP_SECTS           0x1f1
      51                 :            : #define H_MAGIC1                0x1fe
      52                 :            : #define H_MAGIC2                0x202
      53                 :            : #define H_VERSION               0x206
      54                 :            : #define H_PAYLOAD_OFFSET        0x248
      55                 :            : #define H_PAYLOAD_LENGTH        0x24c
      56                 :            : #define H_END                   0x250
      57                 :            : #define H_READ_SIZE             (H_END - H_START)
      58                 :            : 
      59                 :            : Dwfl_Error
      60                 :            : internal_function
      61                 :          0 : __libdw_image_header (int fd, off_t *start_offset,
      62                 :            :                       void *mapped, size_t mapped_size)
      63                 :            : {
      64         [ #  # ]:          0 :   if (likely (mapped_size > H_END))
      65                 :            :     {
      66                 :          0 :       const void *header = mapped;
      67                 :          0 :       char header_buffer[H_READ_SIZE + H_START];
      68         [ #  # ]:          0 :       if (header == NULL)
      69                 :            :         {
      70                 :          0 :           ssize_t n = pread_retry (fd, header_buffer + H_START, H_READ_SIZE,
      71                 :          0 :                                    *start_offset + H_START);
      72         [ #  # ]:          0 :           if (n < 0)
      73                 :          0 :             return DWFL_E_ERRNO;
      74         [ #  # ]:          0 :           if (n < H_READ_SIZE)
      75                 :            :             return DWFL_E_BADELF;
      76                 :            : 
      77                 :            :           header = header_buffer;
      78                 :            :         }
      79                 :            : 
      80                 :          0 :       uint16_t magic1;
      81                 :          0 :       uint32_t magic2;
      82                 :          0 :       uint16_t version;
      83         [ #  # ]:          0 :       memcpy (&magic1, header + H_MAGIC1, sizeof (uint16_t));
      84                 :          0 :       memcpy (&magic2, header + H_MAGIC2, sizeof (uint32_t));
      85                 :          0 :       memcpy (&version, header + H_VERSION, sizeof (uint16_t));
      86   [ #  #  #  # ]:          0 :       if (magic1 == LE16 (MAGIC1) && magic2 == LE32 (MAGIC2)
      87         [ #  # ]:          0 :           && LE16 (version) >= MIN_VERSION)
      88                 :            :         {
      89                 :            :           /* The magic numbers match and the version field is sufficient.
      90                 :            :              Extract the payload bounds.  */
      91                 :            : 
      92                 :          0 :           uint32_t offset;
      93                 :          0 :           uint32_t length;
      94                 :          0 :           uint8_t sects;
      95         [ #  # ]:          0 :           memcpy (&offset, header + H_PAYLOAD_OFFSET, sizeof (uint32_t));
      96                 :          0 :           memcpy (&length, header + H_PAYLOAD_LENGTH, sizeof (uint32_t));
      97                 :          0 :           memcpy (&sects, header + H_SETUP_SECTS, sizeof (uint8_t));
      98                 :          0 :           offset = LE32 (offset);
      99                 :          0 :           length = LE32 (length);
     100                 :            : 
     101         [ #  # ]:          0 :           offset += ((sects ?: 4) + 1) * 512;
     102                 :            : 
     103   [ #  #  #  # ]:          0 :           if (offset > H_END && offset < mapped_size
     104         [ #  # ]:          0 :               && mapped_size - offset >= length)
     105                 :            :             {
     106                 :            :               /* It looks kosher.  Use it!  */
     107                 :          0 :               *start_offset += offset;
     108                 :          0 :               return DWFL_E_NOERROR;
     109                 :            :             }
     110                 :            :         }
     111                 :            :     }
     112                 :            :   return DWFL_E_BADELF;
     113                 :            : }