elf/dl-object.c

   1 /* Storage management for the chain of loaded shared objects.
   2    Copyright (C) 1995-2017 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <string.h>
  21 #include <stdlib.h>
  22 #include <unistd.h>
  23 #include <ldsodefs.h>
  24
  25 #include <assert.h>
  26
  27
  28 /* Add the new link_map NEW to the end of the namespace list.  */
  29 void
  30 internal_function
  31 _dl_add_to_namespace_list (struct link_map *new, Lmid_t nsid)
  32 {
  33   /* We modify the list of loaded objects.  */
  34   __rtld_lock_lock_recursive (GL(dl_load_write_lock));
  35
  36   if (GL(dl_ns)[nsid]._ns_loaded != NULL)
  37     {
  38       struct link_map *l = GL(dl_ns)[nsid]._ns_loaded;
  39       while (l->l_next != NULL)
  40         l = l->l_next;
  41       new->l_prev = l;
  42       /* new->l_next = NULL;   Would be necessary but we use calloc.  */
  43       l->l_next = new;
  44     }
  45   else
  46     GL(dl_ns)[nsid]._ns_loaded = new;
  47   ++GL(dl_ns)[nsid]._ns_nloaded;
  48   new->l_serial = GL(dl_load_adds);
  49   ++GL(dl_load_adds);
  50
  51   __rtld_lock_unlock_recursive (GL(dl_load_write_lock));
  52 }
  53
  54
  55 /* Allocate a `struct link_map' for a new object being loaded,
  56    and enter it into the _dl_loaded list.  */
  57 struct link_map *
  58 internal_function
  59 _dl_new_object (char *realname, const char *libname, int type,
  60                 struct link_map *loader, int mode, Lmid_t nsid)
  61 {
  62   size_t libname_len = strlen (libname) + 1;
  63   struct link_map *new;
  64   struct libname_list *newname;
  65 #ifdef SHARED
  66   /* We create the map for the executable before we know whether we have
  67      auditing libraries and if yes, how many.  Assume the worst.  */
  68   unsigned int naudit = GLRO(dl_naudit) ?: ((mode & __RTLD_OPENEXEC)
  69                                             ? DL_NNS : 0);
  70   size_t audit_space = naudit * sizeof (new->l_audit[0]);
  71 #else
  72 # define audit_space 0
  73 #endif
  74
  75   new = (struct link_map *) calloc (sizeof (*new) + audit_space
  76                                     + sizeof (struct link_map *)
  77                                     + sizeof (*newname) + libname_len, 1);
  78   if (new == NULL)
  79     return NULL;
  80
  81   new->l_real = new;
  82   new->l_symbolic_searchlist.r_list = (struct link_map **) ((char *) (new + 1)
  83                                                             + audit_space);
  84
  85   new->l_libname = newname
  86     = (struct libname_list *) (new->l_symbolic_searchlist.r_list + 1);
  87   newname->name = (char *) memcpy (newname + 1, libname, libname_len);
  88   /* newname->next = NULL;      We use calloc therefore not necessary.  */
  89   newname->dont_free = 1;
  90
  91   /* When we create the executable link map, or a VDSO link map, we start
  92      with "" for the l_name. In these cases "" points to ld.so rodata
  93      and won't get dumped during core file generation. Therefore to assist
  94      gdb and to create more self-contained core files we adjust l_name to
  95      point at the newly allocated copy (which will get dumped) instead of
  96      the ld.so rodata copy.  */
  97   new->l_name = *realname ? realname : (char *) newname->name + libname_len - 1;
  98   new->l_type = type;
  99   /* If we set the bit now since we know it is never used we avoid
 100      dirtying the cache line later.  */
 101   if ((GLRO(dl_debug_mask) & DL_DEBUG_UNUSED) == 0)
 102     new->l_used = 1;
 103   new->l_loader = loader;
 104 #if NO_TLS_OFFSET != 0
 105   new->l_tls_offset = NO_TLS_OFFSET;
 106 #endif
 107   new->l_ns = nsid;
 108
 109 #ifdef SHARED
 110   for (unsigned int cnt = 0; cnt < naudit; ++cnt)
 111     {
 112       new->l_audit[cnt].cookie = (uintptr_t) new;
 113       /* new->l_audit[cnt].bindflags = 0; */
 114     }
 115 #endif
 116
 117   /* new->l_global = 0; We use calloc therefore not necessary.  */
 118
 119   /* Use the 'l_scope_mem' array by default for the 'l_scope'
 120      information.  If we need more entries we will allocate a large
 121      array dynamically.  */
 122   new->l_scope = new->l_scope_mem;
 123   new->l_scope_max = sizeof (new->l_scope_mem) / sizeof (new->l_scope_mem[0]);
 124
 125   /* Counter for the scopes we have to handle.  */
 126   int idx = 0;
 127
 128   if (GL(dl_ns)[nsid]._ns_loaded != NULL)
 129     /* Add the global scope.  */
 130     new->l_scope[idx++] = &GL(dl_ns)[nsid]._ns_loaded->l_searchlist;
 131
 132   /* If we have no loader the new object acts as it.  */
 133   if (loader == NULL)
 134     loader = new;
 135   else
 136     /* Determine the local scope.  */
 137     while (loader->l_loader != NULL)
 138       loader = loader->l_loader;
 139
 140   /* Insert the scope if it isn't the global scope we already added.  */
 141   if (idx == 0 || &loader->l_searchlist != new->l_scope[0])
 142     {
 143       if ((mode & RTLD_DEEPBIND) != 0 && idx != 0)
 144         {
 145           new->l_scope[1] = new->l_scope[0];
 146           idx = 0;
 147         }
 148
 149       new->l_scope[idx] = &loader->l_searchlist;
 150     }
 151
 152   new->l_local_scope[0] = &new->l_searchlist;
 153
 154   /* Don't try to find the origin for the main map which has the name "".  */
 155   if (realname[0] != '\0')
 156     {
 157       size_t realname_len = strlen (realname) + 1;
 158       char *origin;
 159       char *cp;
 160
 161       if (realname[0] == '/')
 162         {
 163           /* It is an absolute path.  Use it.  But we have to make a
 164              copy since we strip out the trailing slash.  */
 165           cp = origin = (char *) malloc (realname_len);
 166           if (origin == NULL)
 167             {
 168               origin = (char *) -1;
 169               goto out;
 170             }
 171         }
 172       else
 173         {
 174           size_t len = realname_len;
 175           char *result = NULL;
 176
 177           /* Get the current directory name.  */
 178           origin = NULL;
 179           do
 180             {
 181               char *new_origin;
 182
 183               len += 128;
 184               new_origin = (char *) realloc (origin, len);
 185               if (new_origin == NULL)
 186                 /* We exit the loop.  Note that result == NULL.  */
 187                 break;
 188               origin = new_origin;
 189             }
 190           while ((result = __getcwd (origin, len - realname_len)) == NULL
 191                  && errno == ERANGE);
 192
 193           if (result == NULL)
 194             {
 195               /* We were not able to determine the current directory.
 196                  Note that free(origin) is OK if origin == NULL.  */
 197               free (origin);
 198               origin = (char *) -1;
 199               goto out;
 200             }
 201
 202           /* Find the end of the path and see whether we have to add a
 203              slash.  We could use rawmemchr but this need not be
 204              fast.  */
 205           cp = (strchr) (origin, '\0');
 206           if (cp[-1] != '/')
 207             *cp++ = '/';
 208         }
 209
 210       /* Add the real file name.  */
 211       cp = __mempcpy (cp, realname, realname_len);
 212
 213       /* Now remove the filename and the slash.  Leave the slash if
 214          the name is something like "/foo".  */
 215       do
 216         --cp;
 217       while (*cp != '/');
 218
 219       if (cp == origin)
 220         /* Keep the only slash which is the first character.  */
 221         ++cp;
 222       *cp = '\0';
 223
 224     out:
 225       new->l_origin = origin;
 226     }
 227
 228   return new;
 229 }