elf/check-textrel.c

   1 /* Check for text relocations in DSOs.
   2    Copyright (C) 2002 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contribute by Ulrich Drepper <drepper@redhat.com>. 2002.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <byteswap.h>
  22 #include <elf.h>
  23 #include <endian.h>
  24 #include <fcntl.h>
  25 #include <stdio.h>
  26 #include <stdlib.h>
  27 #include <string.h>
  28 #include <unistd.h>
  29
  30
  31 #ifdef BITS
  32
  33 # define AB(name) _AB (name, BITS)
  34 # define _AB(name, bits) __AB (name, bits)
  35 # define __AB(name, bits) name##bits
  36 # define E(name) _E (name, BITS)
  37 # define _E(name, bits) __E (name, bits)
  38 # define __E(name, bits) Elf##bits##_##name
  39 # define SWAP(val) \
  40   ({ __typeof (val) __res;                                                    \
  41      if ((ehdr.e_ident[EI_DATA] == ELFDATA2MSB && BYTE_ORDER == LITTLE_ENDIAN \
  42           || ehdr.e_ident[EI_DATA] == ELFDATA2LSB && BYTE_ORDER == BIG_ENDIAN)\
  43          && sizeof (val) != 1)                                                \
  44        {                                                                      \
  45          if (sizeof (val) == 2)                                               \
  46            __res = bswap_16 (val);                                            \
  47          else if (sizeof (val) == 4)                                          \
  48            __res = bswap_32 (val);                                            \
  49          else                                                                 \
  50            __res = bswap_64 (val);                                            \
  51        }                                                                      \
  52      else                                                                     \
  53        __res = (val);                                                         \
  54      __res; })
  55
  56
  57 static int
  58 AB(handle_file) (const char *fname, int fd)
  59 {
  60   E(Ehdr) ehdr;
  61
  62   if (pread (fd, &ehdr, sizeof (ehdr), 0) != sizeof (ehdr))
  63     {
  64     read_error:
  65       printf ("%s: read error: %m\n", fname);
  66       return 1;
  67     }
  68
  69   const size_t phnum = SWAP (ehdr.e_phnum);
  70   const size_t phentsize = SWAP (ehdr.e_phentsize);
  71
  72   /* Read the program header.  */
  73   E(Phdr) *phdr = alloca (phentsize * phnum);
  74   if (pread (fd, phdr, phentsize * phnum, SWAP (ehdr.e_phoff))
  75       != phentsize * phnum)
  76     goto read_error;
  77
  78   /* Search for the PT_DYNAMIC entry.  */
  79   size_t cnt;
  80   for (cnt = 0; cnt < phnum; ++cnt)
  81     if (SWAP (phdr[cnt].p_type) == PT_DYNAMIC)
  82       break;
  83
  84   if (cnt == phnum)
  85     {
  86       printf ("%s: no DYNAMIC segment found\n", fname);
  87       return 1;
  88     }
  89
  90   /* Read the dynamic segment.  */
  91   size_t pmemsz = SWAP(phdr[cnt].p_memsz);
  92   E(Dyn) *dyn = alloca (pmemsz);
  93   if (pread (fd, dyn, pmemsz, SWAP(phdr[cnt].p_offset)) != pmemsz)
  94     goto read_error;
  95
  96   /* Search for an DT_TEXTREL entry of DT_FLAGS with the DF_TEXTREL
  97      bit set.  */
  98   for (cnt = 0; (cnt + 1) * sizeof (E(Dyn)) - 1 < pmemsz; ++cnt)
  99     {
 100       unsigned int tag = SWAP (dyn[cnt].d_tag);
 101
 102       if (tag == DT_NULL)
 103         /* We reached the end.  */
 104         break;
 105
 106       if (tag == DT_TEXTREL
 107           || (tag == DT_FLAGS
 108               && (SWAP (dyn[cnt].d_un.d_val) & DF_TEXTREL) != 0))
 109         {
 110           /* Urgh!  The DSO has text relocations.  */
 111           printf ("%s: text relocations used\n", fname);
 112           return 1;
 113         }
 114     }
 115
 116   printf ("%s: OK\n", fname);
 117
 118   return 0;
 119 }
 120
 121 # undef BITS
 122 #else
 123
 124 # define BITS 32
 125 # include "check-textrel.c"
 126
 127 # define BITS 64
 128 # include "check-textrel.c"
 129
 130
 131 static int
 132 handle_file (const char *fname)
 133 {
 134   int fd = open (fname, O_RDONLY);
 135   if (fd == -1)
 136     {
 137       printf ("cannot open %s: %m\n", fname);
 138       return 1;
 139     }
 140
 141   /* Read was is supposed to be the ELF header.  Read the initial
 142      bytes to determine whether this is a 32 or 64 bit file.  */
 143   char ident[EI_NIDENT];
 144   if (read (fd, ident, EI_NIDENT) != EI_NIDENT)
 145     {
 146       printf ("%s: read error: %m\n", fname);
 147       close (fd);
 148       return 1;
 149     }
 150
 151   if (memcmp (&ident[EI_MAG0], ELFMAG, SELFMAG) != 0)
 152     {
 153       printf ("%s: not an ELF file\n", fname);
 154       close (fd);
 155       return 1;
 156     }
 157
 158   int result;
 159   if (ident[EI_CLASS] == ELFCLASS64)
 160     result = handle_file64 (fname, fd);
 161   else
 162     result = handle_file32 (fname, fd);
 163
 164   close (fd);
 165
 166   return result;
 167 }
 168
 169
 170 int
 171 main (int argc, char *argv[])
 172 {
 173   int cnt;
 174   int result = 0;
 175
 176   for (cnt = 1; cnt < argc; ++cnt)
 177     result |= handle_file (argv[cnt]);
 178
 179   return result;
 180 }
 181 #endif