elf/dl-dst.h

   1 /* Handling of dynamic sring tokens.
   2    Copyright (C) 1999-2016 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 "trusted-dirs.h"
  20
  21 /* Determine the number of DST elements in the name.  Only if IS_PATH is
  22    nonzero paths are recognized (i.e., multiple, ':' separated filenames).  */
  23 #define DL_DST_COUNT(name, is_path) \
  24   ({                                                                          \
  25     size_t __cnt = 0;                                                         \
  26     const char *__sf = strchr (name, '$');                                    \
  27                                                                               \
  28     if (__glibc_unlikely (__sf != NULL))                                      \
  29       __cnt = _dl_dst_count (__sf, is_path);                          \
  30                                                                               \
  31     __cnt; })
  32
  33
  34 #ifdef SHARED
  35 # define IS_RTLD(l) (l) == &GL(dl_rtld_map)
  36 #else
  37 # define IS_RTLD(l) 0
  38 #endif
  39 /* Guess from the number of DSTs the length of the result string.  */
  40 #define DL_DST_REQUIRED(l, name, len, cnt) \
  41   ({                                                                          \
  42     size_t __len = (len);                                                     \
  43     size_t __cnt = (cnt);                                                     \
  44                                                                               \
  45     if (__cnt > 0)                                                            \
  46       {                                                                       \
  47         size_t dst_len;                                                       \
  48         /* Now we make a guess how many extra characters on top of the        \
  49            length of S we need to represent the result.  We know that         \
  50            we have CNT replacements.  Each at most can use                    \
  51              MAX (MAX (strlen (ORIGIN), strlen (_dl_platform)),               \
  52                   strlen (DL_DST_LIB))                                        \
  53            minus 4 (which is the length of "$LIB").                           \
  54                                                                               \
  55            First get the origin string if it is not available yet.            \
  56            This can only happen for the map of the executable or, when        \
  57            auditing, in ld.so.  */                                            \
  58         if ((l)->l_origin == NULL)                                            \
  59           {                                                                   \
  60             assert ((l)->l_name[0] == '\0' || IS_RTLD (l));                   \
  61             (l)->l_origin = _dl_get_origin ();                                \
  62             dst_len = ((l)->l_origin && (l)->l_origin != (char *) -1          \
  63                           ? strlen ((l)->l_origin) : 0);                      \
  64           }                                                                   \
  65         else                                                                  \
  66           dst_len = (l)->l_origin == (char *) -1                              \
  67             ? 0 : strlen ((l)->l_origin);                                     \
  68         dst_len = MAX (MAX (dst_len, GLRO(dl_platformlen)),                   \
  69                        strlen (DL_DST_LIB));                                  \
  70         if (dst_len > 4)                                                      \
  71           __len += __cnt * (dst_len - 4);                                     \
  72       }                                                                       \
  73                                                                               \
  74     __len; })