elf/readlib.c

   1 /* Copyright (C) 1999-2020 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 <https://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 /* Check if string corresponds to a GDB Python file.  */
  67 static bool
  68 is_gdb_python_file (const char *name)
  69 {
  70   size_t len = strlen (name);
  71   return len > 7 && strcmp (name + len - 7, "-gdb.py") == 0;
  72 }
  73
  74 /* Returns 0 if everything is ok, != 0 in case of error.  */
  75 int
  76 process_file (const char *real_file_name, const char *file_name,
  77               const char *lib, int *flag, unsigned int *osversion,
  78               char **soname, int is_link, struct stat64 *stat_buf)
  79 {
  80   FILE *file;
  81   struct stat64 statbuf;
  82   void *file_contents;
  83   int ret;
  84   ElfW(Ehdr) *elf_header;
  85   struct exec *aout_header;
  86
  87   ret = 0;
  88   *flag = FLAG_ANY;
  89   *soname = NULL;
  90
  91   file = fopen (real_file_name, "rb");
  92   if (file == NULL)
  93     {
  94       /* No error for stale symlink.  */
  95       if (is_link && strstr (file_name, ".so") != NULL)
  96         return 1;
  97       error (0, 0, _("Input file %s not found.\n"), file_name);
  98       return 1;
  99     }
 100
 101   if (fstat64 (fileno (file), &statbuf) < 0)
 102     {
 103       error (0, 0, _("Cannot fstat file %s.\n"), file_name);
 104       fclose (file);
 105       return 1;
 106     }
 107
 108   /* Check that the file is large enough so that we can access the
 109      information.  We're only checking the size of the headers here.  */
 110   if ((size_t) statbuf.st_size < sizeof (struct exec)
 111       || (size_t) statbuf.st_size < sizeof (ElfW(Ehdr)))
 112     {
 113       if (statbuf.st_size == 0)
 114         error (0, 0, _("File %s is empty, not checked."), file_name);
 115       else
 116         {
 117           char buf[SELFMAG];
 118           size_t n = MIN (statbuf.st_size, SELFMAG);
 119           if (fread (buf, n, 1, file) == 1 && memcmp (buf, ELFMAG, n) == 0)
 120             error (0, 0, _("File %s is too small, not checked."), file_name);
 121         }
 122       fclose (file);
 123       return 1;
 124     }
 125
 126   file_contents = mmap (0, statbuf.st_size, PROT_READ, MAP_SHARED,
 127                         fileno (file), 0);
 128   if (file_contents == MAP_FAILED)
 129     {
 130       error (0, 0, _("Cannot mmap file %s.\n"), file_name);
 131       fclose (file);
 132       return 1;
 133     }
 134
 135   /* First check if this is an aout file.  */
 136   aout_header = (struct exec *) file_contents;
 137   if (N_MAGIC (*aout_header) == ZMAGIC
 138 #ifdef QMAGIC                   /* Linuxism.  */
 139       || N_MAGIC (*aout_header) == QMAGIC
 140 #endif
 141       )
 142     {
 143       /* Aout files don't have a soname, just return the name
 144          including the major number.  */
 145       char *copy, *major, *dot;
 146       copy = xstrdup (lib);
 147       major = strstr (copy, ".so.");
 148       if (major)
 149         {
 150           dot = strstr (major + 4, ".");
 151           if (dot)
 152             *dot = '\0';
 153         }
 154       *soname = copy;
 155       *flag = FLAG_LIBC4;
 156       goto done;
 157     }
 158
 159   elf_header = (ElfW(Ehdr) *) file_contents;
 160   if (memcmp (elf_header->e_ident, ELFMAG, SELFMAG) != 0)
 161     {
 162       /* The file is neither ELF nor aout.  Check if it's a linker
 163          script, like libc.so - otherwise complain.  Only search the
 164          beginning of the file.  */
 165       size_t len = MIN (statbuf.st_size, 512);
 166       if (memmem (file_contents, len, "GROUP", 5) == NULL
 167           && memmem (file_contents, len, "GNU ld script", 13) == NULL
 168           && !is_gdb_python_file (file_name))
 169         error (0, 0, _("%s is not an ELF file - it has the wrong magic bytes at the start.\n"),
 170                file_name);
 171       ret = 1;
 172     }
 173   /* Libraries have to be shared object files.  */
 174   else if (elf_header->e_type != ET_DYN)
 175     ret = 1;
 176   else if (process_elf_file (file_name, lib, flag, osversion, soname,
 177                              file_contents, statbuf.st_size))
 178     ret = 1;
 179
 180  done:
 181   /* Clean up allocated memory and resources.  */
 182   munmap (file_contents, statbuf.st_size);
 183   fclose (file);
 184
 185   *stat_buf = statbuf;
 186   return ret;
 187 }
 188
 189 /* Returns made up soname if lib doesn't have explicit DT_SONAME.  */
 190
 191 char *
 192 implicit_soname (const char *lib, int flag)
 193 {
 194   char *soname = xstrdup (lib);
 195
 196   if ((flag & FLAG_TYPE_MASK) != FLAG_LIBC4)
 197     return soname;
 198
 199   /* Aout files don't have a soname, just return the name
 200      including the major number.  */
 201   char *major = strstr (soname, ".so.");
 202   if (major)
 203     {
 204       char *dot = strstr (major + 4, ".");
 205       if (dot)
 206         *dot = '\0';
 207     }
 208   return soname;
 209 }
 210
 211 /* Get architecture specific version of process_elf_file.  */
 212 #include <readelflib.c>