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 /* Check if string corresponds to a GDB Python file.  */
  47 static bool
  48 is_gdb_python_file (const char *name)
  49 {
  50   size_t len = strlen (name);
  51   return len > 7 && strcmp (name + len - 7, "-gdb.py") == 0;
  52 }
  53
  54 /* Returns 0 if everything is ok, != 0 in case of error.  */
  55 int
  56 process_file (const char *real_file_name, const char *file_name,
  57               const char *lib, int *flag, unsigned int *isa_level,
  58               char **soname, int is_link, struct stat *stat_buf)
  59 {
  60   FILE *file;
  61   struct stat statbuf;
  62   void *file_contents;
  63   int ret;
  64   ElfW(Ehdr) *elf_header;
  65   struct exec *aout_header;
  66
  67   ret = 0;
  68   /* Just set FLAG_ELF_LIBC6 as old formats are not supported anymore.  */
  69   *flag = FLAG_ELF_LIBC6;
  70   *soname = NULL;
  71
  72   file = fopen (real_file_name, "rb");
  73   if (file == NULL)
  74     {
  75       /* No error for stale symlink.  */
  76       if (is_link && strstr (file_name, ".so") != NULL)
  77         return 1;
  78       error (0, 0, _("Input file %s not found.\n"), file_name);
  79       return 1;
  80     }
  81
  82   if (fstat (fileno (file), &statbuf) < 0)
  83     {
  84       error (0, 0, _("Cannot fstat file %s.\n"), file_name);
  85       fclose (file);
  86       return 1;
  87     }
  88
  89   /* Check that the file is large enough so that we can access the
  90      information.  We're only checking the size of the headers here.  */
  91   if ((size_t) statbuf.st_size < sizeof (struct exec)
  92       || (size_t) statbuf.st_size < sizeof (ElfW(Ehdr)))
  93     {
  94       if (statbuf.st_size == 0)
  95         error (0, 0, _("File %s is empty, not checked."), file_name);
  96       else
  97         {
  98           char buf[SELFMAG];
  99           size_t n = MIN (statbuf.st_size, SELFMAG);
 100           if (fread (buf, n, 1, file) == 1 && memcmp (buf, ELFMAG, n) == 0)
 101             error (0, 0, _("File %s is too small, not checked."), file_name);
 102         }
 103       fclose (file);
 104       return 1;
 105     }
 106
 107   file_contents = mmap (0, statbuf.st_size, PROT_READ, MAP_SHARED,
 108                         fileno (file), 0);
 109   if (file_contents == MAP_FAILED)
 110     {
 111       error (0, 0, _("Cannot mmap file %s.\n"), file_name);
 112       fclose (file);
 113       return 1;
 114     }
 115
 116   /* First check if this is an aout file.  */
 117   aout_header = (struct exec *) file_contents;
 118   if (N_MAGIC (*aout_header) == ZMAGIC
 119 #ifdef QMAGIC                   /* Linuxism.  */
 120       || N_MAGIC (*aout_header) == QMAGIC
 121 #endif
 122       )
 123     {
 124       /* Aout files don't have a soname, just return the name
 125          including the major number.  */
 126       char *copy, *major, *dot;
 127       copy = xstrdup (lib);
 128       major = strstr (copy, ".so.");
 129       if (major)
 130         {
 131           dot = strstr (major + 4, ".");
 132           if (dot)
 133             *dot = '\0';
 134         }
 135       *soname = copy;
 136       goto done;
 137     }
 138
 139   elf_header = (ElfW(Ehdr) *) file_contents;
 140   if (memcmp (elf_header->e_ident, ELFMAG, SELFMAG) != 0)
 141     {
 142       /* The file is neither ELF nor aout.  Check if it's a linker
 143          script, like libc.so - otherwise complain.  Only search the
 144          beginning of the file.  */
 145       size_t len = MIN (statbuf.st_size, 512);
 146       if (memmem (file_contents, len, "GROUP", 5) == NULL
 147           && memmem (file_contents, len, "GNU ld script", 13) == NULL
 148           && !is_gdb_python_file (file_name))
 149         error (0, 0, _("%s is not an ELF file - it has the wrong magic bytes at the start.\n"),
 150                file_name);
 151       ret = 1;
 152     }
 153   /* Libraries have to be shared object files.  */
 154   else if (elf_header->e_type != ET_DYN)
 155     ret = 1;
 156   else if (process_elf_file (file_name, lib, flag, isa_level, soname,
 157                              file_contents, statbuf.st_size))
 158     ret = 1;
 159
 160  done:
 161   /* Clean up allocated memory and resources.  */
 162   munmap (file_contents, statbuf.st_size);
 163   fclose (file);
 164
 165   *stat_buf = statbuf;
 166   return ret;
 167 }
 168
 169 /* Returns made up soname if lib doesn't have explicit DT_SONAME.  */
 170
 171 char *
 172 implicit_soname (const char *lib, int flag)
 173 {
 174   char *soname = xstrdup (lib);
 175
 176   /* Aout files don't have a soname, just return the name
 177      including the major number.  */
 178   char *major = strstr (soname, ".so.");
 179   if (major)
 180     {
 181       char *dot = strstr (major + 4, ".");
 182       if (dot)
 183         *dot = '\0';
 184     }
 185   return soname;
 186 }
 187
 188 /* Get architecture specific version of process_elf_file.  */
 189 #include <readelflib.c>