elf/dl-support.c

   1 /* Support for dynamic linking code in static libc.
   2    Copyright (C) 1996-2008, 2009 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 <dl-procinfo.h>
  33 #include <unsecvars.h>
  34 #include <hp-timing.h>
  35
  36 extern char *__progname;
  37 char **_dl_argv = &__progname;  /* This is checked for some error messages.  */
  38
  39 /* Name of the architecture.  */
  40 const char *_dl_platform;
  41 size_t _dl_platformlen;
  42
  43 int _dl_debug_mask;
  44 int _dl_lazy;
  45 ElfW(Addr) _dl_use_load_bias = -2;
  46 int _dl_dynamic_weak;
  47
  48 /* If nonzero print warnings about problematic situations.  */
  49 int _dl_verbose;
  50
  51 /* We never do profiling.  */
  52 const char *_dl_profile;
  53 const char *_dl_profile_output;
  54
  55 /* Names of shared object for which the RUNPATHs and RPATHs should be
  56    ignored.  */
  57 const char *_dl_inhibit_rpath;
  58
  59 /* The map for the object we will profile.  */
  60 struct link_map *_dl_profile_map;
  61
  62 /* This is the address of the last stack address ever used.  */
  63 void *__libc_stack_end;
  64
  65 /* Path where the binary is found.  */
  66 const char *_dl_origin_path;
  67
  68 /* Nonzero if runtime lookup should not update the .got/.plt.  */
  69 int _dl_bind_not;
  70
  71 /* Namespace information.  */
  72 struct link_namespaces _dl_ns[DL_NNS];
  73 size_t _dl_nns;
  74
  75 /* Incremented whenever something may have been added to dl_loaded. */
  76 unsigned long long _dl_load_adds;
  77
  78 /* Fake scope.  In dynamically linked binaries this is the scope of the
  79    main application but here we don't have something like this.  So
  80    create a fake scope containing nothing.  */
  81 struct r_scope_elem _dl_initial_searchlist;
  82
  83 #ifndef HAVE_INLINED_SYSCALLS
  84 /* Nonzero during startup.  */
  85 int _dl_starting_up = 1;
  86 #endif
  87
  88 /* Random data provided by the kernel.  */
  89 void *_dl_random;
  90
  91 /* Get architecture specific initializer.  */
  92 #include <dl-procinfo.c>
  93
  94 /* We expect less than a second for relocation.  */
  95 #ifdef HP_SMALL_TIMING_AVAIL
  96 # undef HP_TIMING_AVAIL
  97 # define HP_TIMING_AVAIL HP_SMALL_TIMING_AVAIL
  98 #endif
  99
 100 /* Initial value of the CPU clock.  */
 101 #ifndef HP_TIMING_NONAVAIL
 102 hp_timing_t _dl_cpuclock_offset;
 103 #endif
 104
 105 void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
 106
 107 size_t _dl_pagesize;
 108
 109 unsigned int _dl_osversion;
 110
 111 /* All known directories in sorted order.  */
 112 struct r_search_path_elem *_dl_all_dirs;
 113
 114 /* All directories after startup.  */
 115 struct r_search_path_elem *_dl_init_all_dirs;
 116
 117 /* The object to be initialized first.  */
 118 struct link_map *_dl_initfirst;
 119
 120 /* Descriptor to write debug messages to.  */
 121 int _dl_debug_fd = STDERR_FILENO;
 122
 123 int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
 124
 125 ElfW(Phdr) *_dl_phdr;
 126 size_t _dl_phnum;
 127 uint64_t _dl_hwcap __attribute__ ((nocommon));
 128
 129 /* Prevailing state of the stack, PF_X indicating it's executable.  */
 130 ElfW(Word) _dl_stack_flags = PF_R|PF_W|PF_X;
 131
 132 /* If loading a shared object requires that we make the stack executable
 133    when it was not, we do it by calling this function.
 134    It returns an errno code or zero on success.  */
 135 int (*_dl_make_stack_executable_hook) (void **) internal_function
 136   = _dl_make_stack_executable;
 137
 138
 139 /* Function in libpthread to wait for termination of lookups.  */
 140 void (*_dl_wait_lookup_done) (void);
 141
 142 struct dl_scope_free_list *_dl_scope_free_list;
 143
 144 #ifdef NEED_DL_SYSINFO
 145 /* Needed for improved syscall handling on at least x86/Linux.  */
 146 uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
 147 #endif
 148 #if defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO
 149 /* Address of the ELF headers in the vsyscall page.  */
 150 const ElfW(Ehdr) *_dl_sysinfo_dso;
 151 #endif
 152
 153 /* During the program run we must not modify the global data of
 154    loaded shared object simultanously in two threads.  Therefore we
 155    protect `_dl_open' and `_dl_close' in dl-close.c.
 156
 157    This must be a recursive lock since the initializer function of
 158    the loaded object might as well require a call to this function.
 159    At this time it is not anymore a problem to modify the tables.  */
 160 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 161
 162
 163 #ifdef HAVE_AUX_VECTOR
 164 int _dl_clktck;
 165
 166 void
 167 internal_function
 168 _dl_aux_init (ElfW(auxv_t) *av)
 169 {
 170   int seen = 0;
 171   uid_t uid = 0;
 172   gid_t gid = 0;
 173
 174   for (; av->a_type != AT_NULL; ++av)
 175     switch (av->a_type)
 176       {
 177       case AT_PAGESZ:
 178         GLRO(dl_pagesize) = av->a_un.a_val;
 179         break;
 180       case AT_CLKTCK:
 181         GLRO(dl_clktck) = av->a_un.a_val;
 182         break;
 183       case AT_PHDR:
 184         GL(dl_phdr) = (void *) av->a_un.a_val;
 185         break;
 186       case AT_PHNUM:
 187         GL(dl_phnum) = av->a_un.a_val;
 188         break;
 189       case AT_HWCAP:
 190         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 191         break;
 192 #ifdef NEED_DL_SYSINFO
 193       case AT_SYSINFO:
 194         GL(dl_sysinfo) = av->a_un.a_val;
 195         break;
 196 #endif
 197 #if defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO
 198       case AT_SYSINFO_EHDR:
 199         GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 200         break;
 201 #endif
 202       case AT_UID:
 203         uid ^= av->a_un.a_val;
 204         seen |= 1;
 205         break;
 206       case AT_EUID:
 207         uid ^= av->a_un.a_val;
 208         seen |= 2;
 209         break;
 210       case AT_GID:
 211         gid ^= av->a_un.a_val;
 212         seen |= 4;
 213         break;
 214       case AT_EGID:
 215         gid ^= av->a_un.a_val;
 216         seen |= 8;
 217         break;
 218       case AT_SECURE:
 219         seen = -1;
 220         __libc_enable_secure = av->a_un.a_val;
 221         __libc_enable_secure_decided = 1;
 222         break;
 223       case AT_RANDOM:
 224         _dl_random = (void *) av->a_un.a_val;
 225         break;
 226 # ifdef DL_PLATFORM_AUXV
 227       DL_PLATFORM_AUXV
 228 # endif
 229       }
 230   if (seen == 0xf)
 231     {
 232       __libc_enable_secure = uid != 0 || gid != 0;
 233       __libc_enable_secure_decided = 1;
 234     }
 235 }
 236 #endif
 237
 238
 239 void
 240 internal_function
 241 _dl_non_dynamic_init (void)
 242 {
 243   if (HP_TIMING_AVAIL)
 244     HP_TIMING_NOW (_dl_cpuclock_offset);
 245
 246   if (!_dl_pagesize)
 247     _dl_pagesize = __getpagesize ();
 248
 249   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 250
 251   /* Initialize the data structures for the search paths for shared
 252      objects.  */
 253   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 254
 255   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 256
 257   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 258
 259   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 260
 261   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 262   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 263     _dl_profile_output
 264       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 265
 266   if (__libc_enable_secure)
 267     {
 268       static const char unsecure_envvars[] =
 269         UNSECURE_ENVVARS
 270 #ifdef EXTRA_UNSECURE_ENVVARS
 271         EXTRA_UNSECURE_ENVVARS
 272 #endif
 273         ;
 274       const char *cp = unsecure_envvars;
 275
 276       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 277         {
 278           __unsetenv (cp);
 279           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 280         }
 281
 282       if (__access ("/etc/suid-debug", F_OK) != 0)
 283         __unsetenv ("MALLOC_CHECK_");
 284     }
 285
 286 #ifdef DL_PLATFORM_INIT
 287   DL_PLATFORM_INIT;
 288 #endif
 289
 290 #ifdef DL_OSVERSION_INIT
 291   DL_OSVERSION_INIT;
 292 #endif
 293
 294   /* Now determine the length of the platform string.  */
 295   if (_dl_platform != NULL)
 296     _dl_platformlen = strlen (_dl_platform);
 297
 298   /* Scan for a program header telling us the stack is nonexecutable.  */
 299   if (_dl_phdr != NULL)
 300     for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
 301       if (_dl_phdr[i].p_type == PT_GNU_STACK)
 302         {
 303           _dl_stack_flags = _dl_phdr[i].p_flags;
 304           break;
 305         }
 306 }
 307
 308
 309 const struct r_strlenpair *
 310 internal_function
 311 _dl_important_hwcaps (const char *platform, size_t platform_len, size_t *sz,
 312                       size_t *max_capstrlen)
 313 {
 314   static struct r_strlenpair result;
 315   static char buf[1];
 316
 317   result.str = buf;     /* Does not really matter.  */
 318   result.len = 0;
 319
 320   *sz = 1;
 321   return &result;
 322 }
 323
 324
 325 #ifdef DL_SYSINFO_IMPLEMENTATION
 326 DL_SYSINFO_IMPLEMENTATION
 327 #endif