elf/readlib.c

   1 /* Copyright (C) 1999-2014 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Andreas Jaeger <aj@suse.de>, 1999 and
   4                   Jakub Jelinek <jakub@redhat.com>, 1999.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published
   8    by the Free Software Foundation; version 2 of the License, or
   9    (at your option) any later version.
  10
  11    This program 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
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, see <http://www.gnu.org/licenses/>.  */
  18
  19 /* The code in this file and in readelflib is a heavily simplified
  20    version of the readelf program that's part of the current binutils
  21    development version.  Besides the simplification, it has also been
  22    modified to read some other file formats.  */
  23
  24 #include <a.out.h>
  25 #include <elf.h>
  26 #include <error.h>
  27 #include <libintl.h>
  28 #include <link.h>
  29 #include <stdio.h>
  30 #include <string.h>
  31 #include <unistd.h>
  32 #include <sys/mman.h>
  33 #include <sys/param.h>
  34 #include <sys/stat.h>
  35 #include <gnu/lib-names.h>
  36
  37 #include <ldconfig.h>
  38
  39 #define Elf32_CLASS ELFCLASS32
  40 #define Elf64_CLASS ELFCLASS64
  41
  42 struct known_names
  43 {
  44   const char *soname;
  45   int flag;
  46 };
  47
  48 static struct known_names interpreters[] =
  49 {
  50   { "/lib/" LD_SO, FLAG_ELF_LIBC6 },
  51 #ifdef SYSDEP_KNOWN_INTERPRETER_NAMES
  52   SYSDEP_KNOWN_INTERPRETER_NAMES
  53 #endif
  54 };
  55
  56 static struct known_names known_libs[] =
  57 {
  58   { LIBC_SO, FLAG_ELF_LIBC6 },
  59   { LIBM_SO, FLAG_ELF_LIBC6 },
  60 #ifdef SYSDEP_KNOWN_LIBRARY_NAMES
  61   SYSDEP_KNOWN_LIBRARY_NAMES
  62 #endif
  63 };
  64
  65
  66
  67 /* Returns 0 if everything is ok, != 0 in case of error.  */
  68 int
  69 process_file (const char *real_file_name, const char *file_name,
  70               const char *lib, int *flag, unsigned int *osversion,
  71               char **soname, int is_link, struct stat64 *stat_buf)
  72 {
  73   FILE *file;
  74   struct stat64 statbuf;
  75   void *file_contents;
  76   int ret;
  77   ElfW(Ehdr) *elf_header;
  78   struct exec *aout_header;
  79
  80   ret = 0;
  81   *flag = FLAG_ANY;
  82   *soname = NULL;
  83
  84   file = fopen (real_file_name, "rb");
  85   if (file == NULL)
  86     {
  87       /* No error for stale symlink.  */
  88       if (is_link && strstr (file_name, ".so") != NULL)
  89         return 1;
  90       error (0, 0, _("Input file %s not found.\n"), file_name);
  91       return 1;
  92     }
  93
  94   if (fstat64 (fileno (file), &statbuf) < 0)
  95     {
  96       error (0, 0, _("Cannot fstat file %s.\n"), file_name);
  97       fclose (file);
  98       return 1;
  99     }
 100
 101   /* Check that the file is large enough so that we can access the
 102      information.  We're only checking the size of the headers here.  */
 103   if ((size_t) statbuf.st_size < sizeof (struct exec)
 104       || (size_t) statbuf.st_size < sizeof (ElfW(Ehdr)))
 105     {
 106       if (statbuf.st_size == 0)
 107         error (0, 0, _("File %s is empty, not checked."), file_name);
 108       else
 109         {
 110           char buf[SELFMAG];
 111           size_t n = MIN (statbuf.st_size, SELFMAG);
 112           if (fread (buf, n, 1, file) == 1 && memcmp (buf, ELFMAG, n) == 0)
 113             error (0, 0, _("File %s is too small, not checked."), file_name);
 114         }
 115       fclose (file);
 116       return 1;
 117     }
 118
 119   file_contents = mmap (0, statbuf.st_size, PROT_READ, MAP_SHARED,
 120                         fileno (file), 0);
 121   if (file_contents == MAP_FAILED)
 122     {
 123       error (0, 0, _("Cannot mmap file %s.\n"), file_name);
 124       fclose (file);
 125       return 1;
 126     }
 127
 128   /* First check if this is an aout file.  */
 129   aout_header = (struct exec *) file_contents;
 130   if (N_MAGIC (*aout_header) == ZMAGIC
 131 #ifdef QMAGIC                   /* Linuxism.  */
 132       || N_MAGIC (*aout_header) == QMAGIC
 133 #endif
 134       )
 135     {
 136       /* Aout files don't have a soname, just return the name
 137          including the major number.  */
 138       char *copy, *major, *dot;
 139       copy = xstrdup (lib);
 140       major = strstr (copy, ".so.");
 141       if (major)
 142         {
 143           dot = strstr (major + 4, ".");
 144           if (dot)
 145             *dot = '\0';
 146         }
 147       *soname = copy;
 148       *flag = FLAG_LIBC4;
 149       goto done;
 150     }
 151
 152   elf_header = (ElfW(Ehdr) *) file_contents;
 153   if (memcmp (elf_header->e_ident, ELFMAG, SELFMAG) != 0)
 154     {
 155       /* The file is neither ELF nor aout.  Check if it's a linker
 156          script, like libc.so - otherwise complain.  Only search the
 157          beginning of the file.  */
 158       size_t len = MIN (statbuf.st_size, 512);
 159       if (memmem (file_contents, len, "GROUP", 5) == NULL
 160           && memmem (file_contents, len, "GNU ld script", 13) == NULL)
 161         error (0, 0, _("%s is not an ELF file - it has the wrong magic bytes at the start.\n"),
 162                file_name);
 163       ret = 1;
 164     }
 165   /* Libraries have to be shared object files.  */
 166   else if (elf_header->e_type != ET_DYN)
 167     ret = 1;
 168   else if (process_elf_file (file_name, lib, flag, osversion, soname,
 169                              file_contents, statbuf.st_size))
 170     ret = 1;
 171
 172  done:
 173   /* Clean up allocated memory and resources.  */
 174   munmap (file_contents, statbuf.st_size);
 175   fclose (file);
 176
 177   *stat_buf = statbuf;
 178   return ret;
 179 }
 180
 181 /* Returns made up soname if lib doesn't have explicit DT_SONAME.  */
 182
 183 char *
 184 implicit_soname (const char *lib, int flag)
 185 {
 186   char *soname = xstrdup (lib);
 187
 188   if ((flag & FLAG_TYPE_MASK) != FLAG_LIBC4)
 189     return soname;
 190
 191   /* Aout files don't have a soname, just return the name
 192      including the major number.  */
 193   char *major = strstr (soname, ".so.");
 194   if (major)
 195     {
 196       char *dot = strstr (major + 4, ".");
 197       if (dot)
 198         *dot = '\0';
 199     }
 200   return soname;
 201 }
 202
 203 /* Get architecture specific version of process_elf_file.  */
 204 #include <readelflib.c>