elf/readlib.c

   1 /* Copyright (C) 1999-2021 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               unsigned int *isa_level, char **soname, int is_link,
  79               struct stat64 *stat_buf)
  80 {
  81   FILE *file;
  82   struct stat64 statbuf;
  83   void *file_contents;
  84   int ret;
  85   ElfW(Ehdr) *elf_header;
  86   struct exec *aout_header;
  87
  88   ret = 0;
  89   *flag = FLAG_ANY;
  90   *soname = NULL;
  91
  92   file = fopen (real_file_name, "rb");
  93   if (file == NULL)
  94     {
  95       /* No error for stale symlink.  */
  96       if (is_link && strstr (file_name, ".so") != NULL)
  97         return 1;
  98       error (0, 0, _("Input file %s not found.\n"), file_name);
  99       return 1;
 100     }
 101
 102   if (fstat64 (fileno (file), &statbuf) < 0)
 103     {
 104       error (0, 0, _("Cannot fstat file %s.\n"), file_name);
 105       fclose (file);
 106       return 1;
 107     }
 108
 109   /* Check that the file is large enough so that we can access the
 110      information.  We're only checking the size of the headers here.  */
 111   if ((size_t) statbuf.st_size < sizeof (struct exec)
 112       || (size_t) statbuf.st_size < sizeof (ElfW(Ehdr)))
 113     {
 114       if (statbuf.st_size == 0)
 115         error (0, 0, _("File %s is empty, not checked."), file_name);
 116       else
 117         {
 118           char buf[SELFMAG];
 119           size_t n = MIN (statbuf.st_size, SELFMAG);
 120           if (fread (buf, n, 1, file) == 1 && memcmp (buf, ELFMAG, n) == 0)
 121             error (0, 0, _("File %s is too small, not checked."), file_name);
 122         }
 123       fclose (file);
 124       return 1;
 125     }
 126
 127   file_contents = mmap (0, statbuf.st_size, PROT_READ, MAP_SHARED,
 128                         fileno (file), 0);
 129   if (file_contents == MAP_FAILED)
 130     {
 131       error (0, 0, _("Cannot mmap file %s.\n"), file_name);
 132       fclose (file);
 133       return 1;
 134     }
 135
 136   /* First check if this is an aout file.  */
 137   aout_header = (struct exec *) file_contents;
 138   if (N_MAGIC (*aout_header) == ZMAGIC
 139 #ifdef QMAGIC                   /* Linuxism.  */
 140       || N_MAGIC (*aout_header) == QMAGIC
 141 #endif
 142       )
 143     {
 144       /* Aout files don't have a soname, just return the name
 145          including the major number.  */
 146       char *copy, *major, *dot;
 147       copy = xstrdup (lib);
 148       major = strstr (copy, ".so.");
 149       if (major)
 150         {
 151           dot = strstr (major + 4, ".");
 152           if (dot)
 153             *dot = '\0';
 154         }
 155       *soname = copy;
 156       *flag = FLAG_LIBC4;
 157       goto done;
 158     }
 159
 160   elf_header = (ElfW(Ehdr) *) file_contents;
 161   if (memcmp (elf_header->e_ident, ELFMAG, SELFMAG) != 0)
 162     {
 163       /* The file is neither ELF nor aout.  Check if it's a linker
 164          script, like libc.so - otherwise complain.  Only search the
 165          beginning of the file.  */
 166       size_t len = MIN (statbuf.st_size, 512);
 167       if (memmem (file_contents, len, "GROUP", 5) == NULL
 168           && memmem (file_contents, len, "GNU ld script", 13) == NULL
 169           && !is_gdb_python_file (file_name))
 170         error (0, 0, _("%s is not an ELF file - it has the wrong magic bytes at the start.\n"),
 171                file_name);
 172       ret = 1;
 173     }
 174   /* Libraries have to be shared object files.  */
 175   else if (elf_header->e_type != ET_DYN)
 176     ret = 1;
 177   else if (process_elf_file (file_name, lib, flag, osversion, isa_level,
 178                              soname, file_contents, statbuf.st_size))
 179     ret = 1;
 180
 181  done:
 182   /* Clean up allocated memory and resources.  */
 183   munmap (file_contents, statbuf.st_size);
 184   fclose (file);
 185
 186   *stat_buf = statbuf;
 187   return ret;
 188 }
 189
 190 /* Returns made up soname if lib doesn't have explicit DT_SONAME.  */
 191
 192 char *
 193 implicit_soname (const char *lib, int flag)
 194 {
 195   char *soname = xstrdup (lib);
 196
 197   if ((flag & FLAG_TYPE_MASK) != FLAG_LIBC4)
 198     return soname;
 199
 200   /* Aout files don't have a soname, just return the name
 201      including the major number.  */
 202   char *major = strstr (soname, ".so.");
 203   if (major)
 204     {
 205       char *dot = strstr (major + 4, ".");
 206       if (dot)
 207         *dot = '\0';
 208     }
 209   return soname;
 210 }
 211
 212 /* Get architecture specific version of process_elf_file.  */
 213 #include <readelflib.c>