elf/dl-support.c

   1 /* Support for dynamic linking code in static libc.
   2    Copyright (C) 1996-2002, 2003 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 /* This file defines some things that for the dynamic linker are defined in
  21    rtld.c and dl-sysdep.c in ways appropriate to bootstrap dynamic linking.  */
  22
  23 #include <errno.h>
  24 #include <libintl.h>
  25 #include <stdlib.h>
  26 #include <unistd.h>
  27 #include <ldsodefs.h>
  28 #include <dl-machine.h>
  29 #include <bits/libc-lock.h>
  30 #include <dl-cache.h>
  31 #include <dl-librecon.h>
  32 #include <unsecvars.h>
  33 #include <hp-timing.h>
  34
  35 extern char *__progname;
  36 char **_dl_argv = &__progname;  /* This is checked for some error messages.  */
  37
  38 /* Name of the architecture.  */
  39 const char *_dl_platform;
  40 size_t _dl_platformlen;
  41
  42 int _dl_debug_mask;
  43 int _dl_lazy;
  44 int _dl_dynamic_weak;
  45
  46 /* If nonzero print warnings about problematic situations.  */
  47 int _dl_verbose;
  48
  49 /* We never do profiling.  */
  50 const char *_dl_profile;
  51
  52 /* Names of shared object for which the RUNPATHs and RPATHs should be
  53    ignored.  */
  54 const char *_dl_inhibit_rpath;
  55
  56 /* The map for the object we will profile.  */
  57 struct link_map *_dl_profile_map;
  58
  59 /* This is the address of the last stack address ever used.  */
  60 void *__libc_stack_end;
  61
  62 /* Path where the binary is found.  */
  63 const char *_dl_origin_path;
  64
  65 /* Nonzero if runtime lookup should not update the .got/.plt.  */
  66 int _dl_bind_not;
  67
  68 /* Initially empty list of loaded objects.  */
  69 struct link_map *_dl_loaded;
  70 /* Number of object in the _dl_loaded list.  */
  71 unsigned int _dl_nloaded;
  72
  73 /* Fake scope.  In dynamically linked binaries this is the scope of the
  74    main application but here we don't have something like this.  So
  75    create a fake scope containing nothing.  */
  76 struct r_scope_elem _dl_initial_searchlist;
  77 /* Variable which can be used in lookup to process the global scope.  */
  78 struct r_scope_elem *_dl_global_scope[2] = { &_dl_initial_searchlist, NULL };
  79 /* This is a global pointer to this structure which is public.  It is
  80    used by dlopen/dlclose to add and remove objects from what is regarded
  81    to be the global scope.  */
  82 struct r_scope_elem *_dl_main_searchlist = &_dl_initial_searchlist;
  83
  84 /* Nonzero during startup.  */
  85 int _dl_starting_up = 1;
  86
  87 /* Get architecture specific initializer.  */
  88 #include <dl-procinfo.c>
  89
  90 /* We expect less than a second for relocation.  */
  91 #ifdef HP_SMALL_TIMING_AVAIL
  92 # undef HP_TIMING_AVAIL
  93 # define HP_TIMING_AVAIL HP_SMALL_TIMING_AVAIL
  94 #endif
  95
  96 /* Initial value of the CPU clock.  */
  97 #ifndef HP_TIMING_NONAVAIL
  98 hp_timing_t _dl_cpuclock_offset;
  99 #endif
 100
 101 /* This is zero at program start to signal that the global scope map is
 102    allocated by rtld.  Later it keeps the size of the map.  It might be
 103    reset if in _dl_close if the last global object is removed.  */
 104 size_t _dl_global_scope_alloc;
 105
 106 size_t _dl_pagesize;
 107
 108 unsigned int _dl_osversion;
 109
 110 /* All known directories in sorted order.  */
 111 struct r_search_path_elem *_dl_all_dirs;
 112
 113 /* All directories after startup.  */
 114 struct r_search_path_elem *_dl_init_all_dirs;
 115
 116 /* The object to be initialized first.  */
 117 struct link_map *_dl_initfirst;
 118
 119 /* Descriptor to write debug messages to.  */
 120 int _dl_debug_fd = STDERR_FILENO;
 121
 122 int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
 123
 124 ElfW(Phdr) *_dl_phdr;
 125 size_t _dl_phnum;
 126 unsigned long int _dl_hwcap __attribute__ ((nocommon));
 127
 128 /* Prevailing state of the stack, PF_X indicating it's executable.  */
 129 ElfW(Word) _dl_stack_flags = PF_R|PF_W|PF_X;
 130
 131 /* If loading a shared object requires that we make the stack executable
 132    when it was not, we do it by calling this function.
 133    It returns an errno code or zero on success.  */
 134 int (*_dl_make_stack_executable_hook) (void) internal_function
 135   = _dl_make_stack_executable;
 136
 137
 138 #ifdef NEED_DL_SYSINFO
 139 /* Needed for improved syscall handling on at least x86/Linux.  */
 140 uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
 141 /* Address of the ELF headers in the vsyscall page.  */
 142 const ElfW(Ehdr) *_dl_sysinfo_dso;
 143 #endif
 144
 145 /* During the program run we must not modify the global data of
 146    loaded shared object simultanously in two threads.  Therefore we
 147    protect `_dl_open' and `_dl_close' in dl-close.c.
 148
 149    This must be a recursive lock since the initializer function of
 150    the loaded object might as well require a call to this function.
 151    At this time it is not anymore a problem to modify the tables.  */
 152 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 153
 154
 155 #ifdef HAVE_AUX_VECTOR
 156 int _dl_clktck;
 157
 158 void
 159 internal_function
 160 _dl_aux_init (ElfW(auxv_t) *av)
 161 {
 162   int seen = 0;
 163   uid_t uid = 0;
 164   gid_t gid = 0;
 165
 166   for (; av->a_type != AT_NULL; ++av)
 167     switch (av->a_type)
 168       {
 169       case AT_PAGESZ:
 170         GL(dl_pagesize) = av->a_un.a_val;
 171         break;
 172       case AT_CLKTCK:
 173         GL(dl_clktck) = av->a_un.a_val;
 174         break;
 175       case AT_PHDR:
 176         GL(dl_phdr) = av->a_un.a_ptr;
 177         break;
 178       case AT_PHNUM:
 179         GL(dl_phnum) = av->a_un.a_val;
 180         break;
 181       case AT_HWCAP:
 182         GL(dl_hwcap) = av->a_un.a_val;
 183         break;
 184 #ifdef NEED_DL_SYSINFO
 185       case AT_SYSINFO:
 186         GL(dl_sysinfo) = av->a_un.a_val;
 187         break;
 188 #endif
 189       case AT_UID:
 190         uid ^= av->a_un.a_val;
 191         seen |= 1;
 192         break;
 193       case AT_EUID:
 194         uid ^= av->a_un.a_val;
 195         seen |= 2;
 196         break;
 197       case AT_GID:
 198         gid ^= av->a_un.a_val;
 199         seen |= 4;
 200         break;
 201       case AT_EGID:
 202         gid ^= av->a_un.a_val;
 203         seen |= 8;
 204         break;
 205       case AT_SECURE:
 206         seen = -1;
 207         __libc_enable_secure = av->a_un.a_val;
 208         __libc_enable_secure_decided = 1;
 209         break;
 210       }
 211   if (seen == 0xf)
 212     {
 213       __libc_enable_secure = uid != 0 || gid != 0;
 214       __libc_enable_secure_decided = 1;
 215     }
 216 }
 217 #endif
 218
 219
 220 void
 221 internal_function
 222 _dl_non_dynamic_init (void)
 223 {
 224   if (HP_TIMING_AVAIL)
 225     HP_TIMING_NOW (_dl_cpuclock_offset);
 226
 227   if (!_dl_pagesize)
 228     _dl_pagesize = __getpagesize ();
 229
 230   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 231
 232   /* Initialize the data structures for the search paths for shared
 233      objects.  */
 234   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 235
 236   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 237
 238   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 239
 240   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 241
 242   if (__libc_enable_secure)
 243     {
 244       static const char *unsecure_envvars[] =
 245       {
 246         UNSECURE_ENVVARS,
 247 #ifdef EXTRA_UNSECURE_ENVVARS
 248         EXTRA_UNSECURE_ENVVARS
 249 #endif
 250       };
 251       size_t cnt;
 252
 253       for (cnt = 0;
 254            cnt < sizeof (unsecure_envvars) / sizeof (unsecure_envvars[0]);
 255            ++cnt)
 256         unsetenv (unsecure_envvars[cnt]);
 257
 258       if (__access ("/etc/suid-debug", F_OK) != 0)
 259         unsetenv ("MALLOC_CHECK_");
 260     }
 261
 262 #ifdef DL_PLATFORM_INIT
 263   DL_PLATFORM_INIT;
 264 #endif
 265
 266 #ifdef DL_OSVERSION_INIT
 267   DL_OSVERSION_INIT;
 268 #endif
 269
 270   /* Now determine the length of the platform string.  */
 271   if (_dl_platform != NULL)
 272     _dl_platformlen = strlen (_dl_platform);
 273
 274   /* Scan for a program header telling us the stack is nonexecutable.  */
 275   if (_dl_phdr != NULL)
 276     for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
 277       if (_dl_phdr[i].p_type == PT_GNU_STACK)
 278         {
 279           _dl_stack_flags = _dl_phdr[i].p_flags;
 280           break;
 281         }
 282 }
 283
 284
 285 const struct r_strlenpair *
 286 internal_function
 287 _dl_important_hwcaps (const char *platform, size_t platform_len, size_t *sz,
 288                       size_t *max_capstrlen)
 289 {
 290   static struct r_strlenpair result;
 291   static char buf[1];
 292
 293   result.str = buf;     /* Does not really matter.  */
 294   result.len = 0;
 295
 296   *sz = 1;
 297   return &result;
 298 }
 299
 300
 301 #ifdef DL_SYSINFO_IMPLEMENTATION
 302 DL_SYSINFO_IMPLEMENTATION
 303 #endif