elf/dl-object.c

   1 /* Storage management for the chain of loaded shared objects.
   2    Copyright (C) 1995-2022 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    <https://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 _dl_add_to_namespace_list (struct link_map *new, Lmid_t nsid)
  31 {
  32   /* We modify the list of loaded objects.  */
  33   __rtld_lock_lock_recursive (GL(dl_load_write_lock));
  34
  35   if (GL(dl_ns)[nsid]._ns_loaded != NULL)
  36     {
  37       struct link_map *l = GL(dl_ns)[nsid]._ns_loaded;
  38       while (l->l_next != NULL)
  39         l = l->l_next;
  40       new->l_prev = l;
  41       /* new->l_next = NULL;   Would be necessary but we use calloc.  */
  42       l->l_next = new;
  43     }
  44   else
  45     GL(dl_ns)[nsid]._ns_loaded = new;
  46   ++GL(dl_ns)[nsid]._ns_nloaded;
  47   new->l_serial = GL(dl_load_adds);
  48   ++GL(dl_load_adds);
  49
  50   __rtld_lock_unlock_recursive (GL(dl_load_write_lock));
  51 }
  52
  53
  54 /* Allocate a `struct link_map' for a new object being loaded,
  55    and enter it into the _dl_loaded list.  */
  56 struct link_map *
  57 _dl_new_object (char *realname, const char *libname, int type,
  58                 struct link_map *loader, int mode, Lmid_t nsid)
  59 {
  60 #ifdef SHARED
  61   unsigned int naudit;
  62   if (__glibc_unlikely ((mode & (__RTLD_OPENEXEC | __RTLD_VDSO)) != 0))
  63     {
  64       if (mode & __RTLD_OPENEXEC)
  65         {
  66           assert (type == lt_executable);
  67           assert (nsid == LM_ID_BASE);
  68
  69           /* Ignore the specified libname for the main executable.  It is
  70              only known with an explicit loader invocation.  */
  71           libname = "";
  72         }
  73
  74       /* We create the map for the executable and vDSO before we know whether
  75          we have auditing libraries and if yes, how many.  Assume the
  76          worst.  */
  77       naudit = DL_NNS;
  78     }
  79   else
  80     naudit = GLRO (dl_naudit);
  81 #endif
  82
  83   size_t libname_len = strlen (libname) + 1;
  84   struct link_map *new;
  85   struct libname_list *newname;
  86 #ifdef SHARED
  87   size_t audit_space = naudit * sizeof (struct auditstate);
  88 #else
  89 # define audit_space 0
  90 #endif
  91
  92   new = (struct link_map *) calloc (sizeof (*new) + audit_space
  93                                     + sizeof (struct link_map *)
  94                                     + sizeof (*newname) + libname_len, 1);
  95   if (new == NULL)
  96     return NULL;
  97
  98   new->l_real = new;
  99   new->l_symbolic_searchlist.r_list = (struct link_map **) ((char *) (new + 1)
 100                                                             + audit_space);
 101
 102   new->l_libname = newname
 103     = (struct libname_list *) (new->l_symbolic_searchlist.r_list + 1);
 104   newname->name = (char *) memcpy (newname + 1, libname, libname_len);
 105   /* newname->next = NULL;      We use calloc therefore not necessary.  */
 106   newname->dont_free = 1;
 107
 108   /* When we create the executable link map, or a VDSO link map, we start
 109      with "" for the l_name. In these cases "" points to ld.so rodata
 110      and won't get dumped during core file generation. Therefore to assist
 111      gdb and to create more self-contained core files we adjust l_name to
 112      point at the newly allocated copy (which will get dumped) instead of
 113      the ld.so rodata copy.
 114
 115      Furthermore, in case of explicit loader invocation, discard the
 116      name of the main executable, to match the regular behavior, where
 117      name of the executable is not known.  */
 118 #ifdef SHARED
 119   if (*realname != '\0' && (mode & __RTLD_OPENEXEC) == 0)
 120 #else
 121   if (*realname != '\0')
 122 #endif
 123     new->l_name = realname;
 124   else
 125     new->l_name = (char *) newname->name + libname_len - 1;
 126
 127   new->l_type = type;
 128   /* If we set the bit now since we know it is never used we avoid
 129      dirtying the cache line later.  */
 130   if ((GLRO(dl_debug_mask) & DL_DEBUG_UNUSED) == 0)
 131     new->l_used = 1;
 132   new->l_loader = loader;
 133 #if NO_TLS_OFFSET != 0
 134   new->l_tls_offset = NO_TLS_OFFSET;
 135 #endif
 136   new->l_ns = nsid;
 137
 138 #ifdef SHARED
 139   for (unsigned int cnt = 0; cnt < naudit; ++cnt)
 140     /* No need to initialize bindflags due to calloc.  */
 141     link_map_audit_state (new, cnt)->cookie = (uintptr_t) new;
 142 #endif
 143
 144   /* new->l_global = 0; We use calloc therefore not necessary.  */
 145
 146   /* Use the 'l_scope_mem' array by default for the 'l_scope'
 147      information.  If we need more entries we will allocate a large
 148      array dynamically.  */
 149   new->l_scope = new->l_scope_mem;
 150   new->l_scope_max = sizeof (new->l_scope_mem) / sizeof (new->l_scope_mem[0]);
 151
 152   /* Counter for the scopes we have to handle.  */
 153   int idx = 0;
 154
 155   if (GL(dl_ns)[nsid]._ns_loaded != NULL)
 156     /* Add the global scope.  */
 157     new->l_scope[idx++] = &GL(dl_ns)[nsid]._ns_loaded->l_searchlist;
 158
 159   /* If we have no loader the new object acts as it.  */
 160   if (loader == NULL)
 161     loader = new;
 162   else
 163     /* Determine the local scope.  */
 164     while (loader->l_loader != NULL)
 165       loader = loader->l_loader;
 166
 167   /* Insert the scope if it isn't the global scope we already added.  */
 168   if (idx == 0 || &loader->l_searchlist != new->l_scope[0])
 169     {
 170       if ((mode & RTLD_DEEPBIND) != 0 && idx != 0)
 171         {
 172           new->l_scope[1] = new->l_scope[0];
 173           idx = 0;
 174         }
 175
 176       new->l_scope[idx] = &loader->l_searchlist;
 177     }
 178
 179   new->l_local_scope[0] = &new->l_searchlist;
 180
 181   /* Determine the origin.  If allocating the link map for the main
 182      executable, the realname is not known and "".  In this case, the
 183      origin needs to be determined by other means.  However, in case
 184      of an explicit loader invocation, the pathname of the main
 185      executable is known and needs to be processed here: From the
 186      point of view of the kernel, the main executable is the
 187      dynamic loader, and this would lead to a computation of the wrong
 188      origin.  */
 189   if (realname[0] != '\0')
 190     {
 191       size_t realname_len = strlen (realname) + 1;
 192       char *origin;
 193       char *cp;
 194
 195       if (realname[0] == '/')
 196         {
 197           /* It is an absolute path.  Use it.  But we have to make a
 198              copy since we strip out the trailing slash.  */
 199           cp = origin = (char *) malloc (realname_len);
 200           if (origin == NULL)
 201             {
 202               origin = (char *) -1;
 203               goto out;
 204             }
 205         }
 206       else
 207         {
 208           size_t len = realname_len;
 209           char *result = NULL;
 210
 211           /* Get the current directory name.  */
 212           origin = NULL;
 213           do
 214             {
 215               char *new_origin;
 216
 217               len += 128;
 218               new_origin = (char *) realloc (origin, len);
 219               if (new_origin == NULL)
 220                 /* We exit the loop.  Note that result == NULL.  */
 221                 break;
 222               origin = new_origin;
 223             }
 224           while ((result = __getcwd (origin, len - realname_len)) == NULL
 225                  && errno == ERANGE);
 226
 227           if (result == NULL)
 228             {
 229               /* We were not able to determine the current directory.
 230                  Note that free(origin) is OK if origin == NULL.  */
 231               free (origin);
 232               origin = (char *) -1;
 233               goto out;
 234             }
 235
 236           /* Find the end of the path and see whether we have to add a
 237              slash.  We could use rawmemchr but this need not be
 238              fast.  */
 239           cp = (strchr) (origin, '\0');
 240           if (cp[-1] != '/')
 241             *cp++ = '/';
 242         }
 243
 244       /* Add the real file name.  */
 245       cp = __mempcpy (cp, realname, realname_len);
 246
 247       /* Now remove the filename and the slash.  Leave the slash if
 248          the name is something like "/foo".  */
 249       do
 250         --cp;
 251       while (*cp != '/');
 252
 253       if (cp == origin)
 254         /* Keep the only slash which is the first character.  */
 255         ++cp;
 256       *cp = '\0';
 257
 258     out:
 259       new->l_origin = origin;
 260     }
 261
 262   return new;
 263 }