elf/readlib.c

   1 /* Copyright (C) 1999-2022 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published
   6    by the Free Software Foundation; version 2 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* The code in this file and in readelflib is a heavily simplified
  18    version of the readelf program that's part of the current binutils
  19    development version.  Besides the simplification, it has also been
  20    modified to read some other file formats.  */
  21
  22 #include <a.out.h>
  23 #include <elf.h>
  24 #include <error.h>
  25 #include <libintl.h>
  26 #include <link.h>
  27 #include <stdio.h>
  28 #include <string.h>
  29 #include <unistd.h>
  30 #include <sys/mman.h>
  31 #include <sys/param.h>
  32 #include <sys/stat.h>
  33 #include <gnu/lib-names.h>
  34
  35 #include <ldconfig.h>
  36
  37 #define Elf32_CLASS ELFCLASS32
  38 #define Elf64_CLASS ELFCLASS64
  39
  40 struct known_names
  41 {
  42   const char *soname;
  43   int flag;
  44 };
  45
  46 static struct known_names interpreters[] =
  47 {
  48   { "/lib/" LD_SO, FLAG_ELF_LIBC6 },
  49 #ifdef SYSDEP_KNOWN_INTERPRETER_NAMES
  50   SYSDEP_KNOWN_INTERPRETER_NAMES
  51 #endif
  52 };
  53
  54 static struct known_names known_libs[] =
  55 {
  56   { LIBC_SO, FLAG_ELF_LIBC6 },
  57   { LIBM_SO, FLAG_ELF_LIBC6 },
  58 #ifdef SYSDEP_KNOWN_LIBRARY_NAMES
  59   SYSDEP_KNOWN_LIBRARY_NAMES
  60 #endif
  61 };
  62
  63
  64 /* Check if string corresponds to a GDB Python file.  */
  65 static bool
  66 is_gdb_python_file (const char *name)
  67 {
  68   size_t len = strlen (name);
  69   return len > 7 && strcmp (name + len - 7, "-gdb.py") == 0;
  70 }
  71
  72 /* Returns 0 if everything is ok, != 0 in case of error.  */
  73 int
  74 process_file (const char *real_file_name, const char *file_name,
  75               const char *lib, int *flag, unsigned int *isa_level,
  76               char **soname, int is_link, struct stat *stat_buf)
  77 {
  78   FILE *file;
  79   struct stat statbuf;
  80   void *file_contents;
  81   int ret;
  82   ElfW(Ehdr) *elf_header;
  83   struct exec *aout_header;
  84
  85   ret = 0;
  86   *flag = FLAG_ANY;
  87   *soname = NULL;
  88
  89   file = fopen (real_file_name, "rb");
  90   if (file == NULL)
  91     {
  92       /* No error for stale symlink.  */
  93       if (is_link && strstr (file_name, ".so") != NULL)
  94         return 1;
  95       error (0, 0, _("Input file %s not found.\n"), file_name);
  96       return 1;
  97     }
  98
  99   if (fstat (fileno (file), &statbuf) < 0)
 100     {
 101       error (0, 0, _("Cannot fstat file %s.\n"), file_name);
 102       fclose (file);
 103       return 1;
 104     }
 105
 106   /* Check that the file is large enough so that we can access the
 107      information.  We're only checking the size of the headers here.  */
 108   if ((size_t) statbuf.st_size < sizeof (struct exec)
 109       || (size_t) statbuf.st_size < sizeof (ElfW(Ehdr)))
 110     {
 111       if (statbuf.st_size == 0)
 112         error (0, 0, _("File %s is empty, not checked."), file_name);
 113       else
 114         {
 115           char buf[SELFMAG];
 116           size_t n = MIN (statbuf.st_size, SELFMAG);
 117           if (fread (buf, n, 1, file) == 1 && memcmp (buf, ELFMAG, n) == 0)
 118             error (0, 0, _("File %s is too small, not checked."), file_name);
 119         }
 120       fclose (file);
 121       return 1;
 122     }
 123
 124   file_contents = mmap (0, statbuf.st_size, PROT_READ, MAP_SHARED,
 125                         fileno (file), 0);
 126   if (file_contents == MAP_FAILED)
 127     {
 128       error (0, 0, _("Cannot mmap file %s.\n"), file_name);
 129       fclose (file);
 130       return 1;
 131     }
 132
 133   /* First check if this is an aout file.  */
 134   aout_header = (struct exec *) file_contents;
 135   if (N_MAGIC (*aout_header) == ZMAGIC
 136 #ifdef QMAGIC                   /* Linuxism.  */
 137       || N_MAGIC (*aout_header) == QMAGIC
 138 #endif
 139       )
 140     {
 141       /* Aout files don't have a soname, just return the name
 142          including the major number.  */
 143       char *copy, *major, *dot;
 144       copy = xstrdup (lib);
 145       major = strstr (copy, ".so.");
 146       if (major)
 147         {
 148           dot = strstr (major + 4, ".");
 149           if (dot)
 150             *dot = '\0';
 151         }
 152       *soname = copy;
 153       *flag = FLAG_LIBC4;
 154       goto done;
 155     }
 156
 157   elf_header = (ElfW(Ehdr) *) file_contents;
 158   if (memcmp (elf_header->e_ident, ELFMAG, SELFMAG) != 0)
 159     {
 160       /* The file is neither ELF nor aout.  Check if it's a linker
 161          script, like libc.so - otherwise complain.  Only search the
 162          beginning of the file.  */
 163       size_t len = MIN (statbuf.st_size, 512);
 164       if (memmem (file_contents, len, "GROUP", 5) == NULL
 165           && memmem (file_contents, len, "GNU ld script", 13) == NULL
 166           && !is_gdb_python_file (file_name))
 167         error (0, 0, _("%s is not an ELF file - it has the wrong magic bytes at the start.\n"),
 168                file_name);
 169       ret = 1;
 170     }
 171   /* Libraries have to be shared object files.  */
 172   else if (elf_header->e_type != ET_DYN)
 173     ret = 1;
 174   else if (process_elf_file (file_name, lib, flag, isa_level, soname,
 175                              file_contents, statbuf.st_size))
 176     ret = 1;
 177
 178  done:
 179   /* Clean up allocated memory and resources.  */
 180   munmap (file_contents, statbuf.st_size);
 181   fclose (file);
 182
 183   *stat_buf = statbuf;
 184   return ret;
 185 }
 186
 187 /* Returns made up soname if lib doesn't have explicit DT_SONAME.  */
 188
 189 char *
 190 implicit_soname (const char *lib, int flag)
 191 {
 192   char *soname = xstrdup (lib);
 193
 194   if ((flag & FLAG_TYPE_MASK) != FLAG_LIBC4)
 195     return soname;
 196
 197   /* Aout files don't have a soname, just return the name
 198      including the major number.  */
 199   char *major = strstr (soname, ".so.");
 200   if (major)
 201     {
 202       char *dot = strstr (major + 4, ".");
 203       if (dot)
 204         *dot = '\0';
 205     }
 206   return soname;
 207 }
 208
 209 /* Get architecture specific version of process_elf_file.  */
 210 #include <readelflib.c>