elf/dl-support.c

   1 /* Support for dynamic linking code in static libc.
   2    Copyright (C) 1996-2012 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 /* This file defines some things that for the dynamic linker are defined in
  20    rtld.c and dl-sysdep.c in ways appropriate to bootstrap dynamic linking.  */
  21
  22 #include <errno.h>
  23 #include <libintl.h>
  24 #include <stdlib.h>
  25 #include <unistd.h>
  26 #include <sys/param.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 #include <stackinfo.h>
  36
  37 extern char *__progname;
  38 char **_dl_argv = &__progname;  /* This is checked for some error messages.  */
  39
  40 /* Name of the architecture.  */
  41 const char *_dl_platform;
  42 size_t _dl_platformlen;
  43
  44 int _dl_debug_mask;
  45 int _dl_lazy;
  46 ElfW(Addr) _dl_use_load_bias = -2;
  47 int _dl_dynamic_weak;
  48
  49 /* If nonzero print warnings about problematic situations.  */
  50 int _dl_verbose;
  51
  52 /* We never do profiling.  */
  53 const char *_dl_profile;
  54 const char *_dl_profile_output;
  55
  56 /* Names of shared object for which the RUNPATHs and RPATHs should be
  57    ignored.  */
  58 const char *_dl_inhibit_rpath;
  59
  60 /* The map for the object we will profile.  */
  61 struct link_map *_dl_profile_map;
  62
  63 /* This is the address of the last stack address ever used.  */
  64 void *__libc_stack_end;
  65
  66 /* Path where the binary is found.  */
  67 const char *_dl_origin_path;
  68
  69 /* Nonzero if runtime lookup should not update the .got/.plt.  */
  70 int _dl_bind_not;
  71
  72 /* Namespace information.  */
  73 struct link_namespaces _dl_ns[DL_NNS];
  74 size_t _dl_nns;
  75
  76 /* Incremented whenever something may have been added to dl_loaded. */
  77 unsigned long long _dl_load_adds;
  78
  79 /* Fake scope.  In dynamically linked binaries this is the scope of the
  80    main application but here we don't have something like this.  So
  81    create a fake scope containing nothing.  */
  82 struct r_scope_elem _dl_initial_searchlist;
  83
  84 #ifndef HAVE_INLINED_SYSCALLS
  85 /* Nonzero during startup.  */
  86 int _dl_starting_up = 1;
  87 #endif
  88
  89 /* Random data provided by the kernel.  */
  90 void *_dl_random;
  91
  92 /* Get architecture specific initializer.  */
  93 #include <dl-procinfo.c>
  94
  95 /* We expect less than a second for relocation.  */
  96 #ifdef HP_SMALL_TIMING_AVAIL
  97 # undef HP_TIMING_AVAIL
  98 # define HP_TIMING_AVAIL HP_SMALL_TIMING_AVAIL
  99 #endif
 100
 101 /* Initial value of the CPU clock.  */
 102 #ifndef HP_TIMING_NONAVAIL
 103 hp_timing_t _dl_cpuclock_offset;
 104 #endif
 105
 106 void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
 107
 108 size_t _dl_pagesize = EXEC_PAGESIZE;
 109
 110 int _dl_inhibit_cache;
 111
 112 unsigned int _dl_osversion;
 113
 114 /* All known directories in sorted order.  */
 115 struct r_search_path_elem *_dl_all_dirs;
 116
 117 /* All directories after startup.  */
 118 struct r_search_path_elem *_dl_init_all_dirs;
 119
 120 /* The object to be initialized first.  */
 121 struct link_map *_dl_initfirst;
 122
 123 /* Descriptor to write debug messages to.  */
 124 int _dl_debug_fd = STDERR_FILENO;
 125
 126 int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
 127
 128 ElfW(auxv_t) *_dl_auxv;
 129 ElfW(Phdr) *_dl_phdr;
 130 size_t _dl_phnum;
 131 uint64_t _dl_hwcap __attribute__ ((nocommon));
 132
 133 /* This is not initialized to HWCAP_IMPORTANT, matching the definition
 134    of _dl_important_hwcaps, below, where no hwcap strings are ever
 135    used.  This mask is still used to mediate the lookups in the cache
 136    file.  Since there is no way to set this nonzero (we don't grok the
 137    LD_HWCAP_MASK environment variable here), there is no real point in
 138    setting _dl_hwcap nonzero below, but we do anyway.  */
 139 uint64_t _dl_hwcap_mask __attribute__ ((nocommon));
 140
 141 /* Prevailing state of the stack.  Generally this includes PF_X, indicating it's
 142  * executable but this isn't true for all platforms.  */
 143 ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
 144
 145 /* If loading a shared object requires that we make the stack executable
 146    when it was not, we do it by calling this function.
 147    It returns an errno code or zero on success.  */
 148 int (*_dl_make_stack_executable_hook) (void **) internal_function
 149   = _dl_make_stack_executable;
 150
 151
 152 /* Function in libpthread to wait for termination of lookups.  */
 153 void (*_dl_wait_lookup_done) (void);
 154
 155 struct dl_scope_free_list *_dl_scope_free_list;
 156
 157 #ifdef NEED_DL_SYSINFO
 158 /* Needed for improved syscall handling on at least x86/Linux.  */
 159 uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
 160 #endif
 161 #if defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO
 162 /* Address of the ELF headers in the vsyscall page.  */
 163 const ElfW(Ehdr) *_dl_sysinfo_dso;
 164 #endif
 165
 166 /* During the program run we must not modify the global data of
 167    loaded shared object simultanously in two threads.  Therefore we
 168    protect `_dl_open' and `_dl_close' in dl-close.c.
 169
 170    This must be a recursive lock since the initializer function of
 171    the loaded object might as well require a call to this function.
 172    At this time it is not anymore a problem to modify the tables.  */
 173 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 174 /* This lock is used to keep __dl_iterate_phdr from inspecting the
 175    list of loaded objects while an object is added to or removed from
 176    that list.  */
 177 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
 178
 179
 180 #ifdef HAVE_AUX_VECTOR
 181 int _dl_clktck;
 182
 183 void
 184 internal_function
 185 _dl_aux_init (ElfW(auxv_t) *av)
 186 {
 187   int seen = 0;
 188   uid_t uid = 0;
 189   gid_t gid = 0;
 190
 191   _dl_auxv = av;
 192   for (; av->a_type != AT_NULL; ++av)
 193     switch (av->a_type)
 194       {
 195       case AT_PAGESZ:
 196         GLRO(dl_pagesize) = av->a_un.a_val;
 197         break;
 198       case AT_CLKTCK:
 199         GLRO(dl_clktck) = av->a_un.a_val;
 200         break;
 201       case AT_PHDR:
 202         GL(dl_phdr) = (void *) av->a_un.a_val;
 203         break;
 204       case AT_PHNUM:
 205         GL(dl_phnum) = av->a_un.a_val;
 206         break;
 207       case AT_HWCAP:
 208         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 209         break;
 210 #ifdef NEED_DL_SYSINFO
 211       case AT_SYSINFO:
 212         GL(dl_sysinfo) = av->a_un.a_val;
 213         break;
 214 #endif
 215 #if defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO
 216       case AT_SYSINFO_EHDR:
 217         GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 218         break;
 219 #endif
 220       case AT_UID:
 221         uid ^= av->a_un.a_val;
 222         seen |= 1;
 223         break;
 224       case AT_EUID:
 225         uid ^= av->a_un.a_val;
 226         seen |= 2;
 227         break;
 228       case AT_GID:
 229         gid ^= av->a_un.a_val;
 230         seen |= 4;
 231         break;
 232       case AT_EGID:
 233         gid ^= av->a_un.a_val;
 234         seen |= 8;
 235         break;
 236       case AT_SECURE:
 237         seen = -1;
 238         __libc_enable_secure = av->a_un.a_val;
 239         __libc_enable_secure_decided = 1;
 240         break;
 241       case AT_RANDOM:
 242         _dl_random = (void *) av->a_un.a_val;
 243         break;
 244 # ifdef DL_PLATFORM_AUXV
 245       DL_PLATFORM_AUXV
 246 # endif
 247       }
 248   if (seen == 0xf)
 249     {
 250       __libc_enable_secure = uid != 0 || gid != 0;
 251       __libc_enable_secure_decided = 1;
 252     }
 253 }
 254 #endif
 255
 256
 257 void
 258 internal_function
 259 _dl_non_dynamic_init (void)
 260 {
 261   if (HP_TIMING_AVAIL)
 262     HP_TIMING_NOW (_dl_cpuclock_offset);
 263
 264   if (!_dl_pagesize)
 265     _dl_pagesize = __getpagesize ();
 266
 267   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 268
 269   /* Initialize the data structures for the search paths for shared
 270      objects.  */
 271   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 272
 273   /* Remember the last search directory added at startup.  */
 274   _dl_init_all_dirs = GL(dl_all_dirs);
 275
 276   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 277
 278   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 279
 280   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 281
 282   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 283   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 284     _dl_profile_output
 285       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 286
 287   if (__libc_enable_secure)
 288     {
 289       static const char unsecure_envvars[] =
 290         UNSECURE_ENVVARS
 291 #ifdef EXTRA_UNSECURE_ENVVARS
 292         EXTRA_UNSECURE_ENVVARS
 293 #endif
 294         ;
 295       const char *cp = unsecure_envvars;
 296
 297       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 298         {
 299           __unsetenv (cp);
 300           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 301         }
 302
 303       if (__access ("/etc/suid-debug", F_OK) != 0)
 304         __unsetenv ("MALLOC_CHECK_");
 305     }
 306
 307 #ifdef DL_PLATFORM_INIT
 308   DL_PLATFORM_INIT;
 309 #endif
 310
 311 #ifdef DL_OSVERSION_INIT
 312   DL_OSVERSION_INIT;
 313 #endif
 314
 315   /* Now determine the length of the platform string.  */
 316   if (_dl_platform != NULL)
 317     _dl_platformlen = strlen (_dl_platform);
 318
 319   /* Scan for a program header telling us the stack is nonexecutable.  */
 320   if (_dl_phdr != NULL)
 321     for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
 322       if (_dl_phdr[i].p_type == PT_GNU_STACK)
 323         {
 324           _dl_stack_flags = _dl_phdr[i].p_flags;
 325           break;
 326         }
 327 }
 328
 329
 330 const struct r_strlenpair *
 331 internal_function
 332 _dl_important_hwcaps (const char *platform, size_t platform_len, size_t *sz,
 333                       size_t *max_capstrlen)
 334 {
 335   static struct r_strlenpair result;
 336   static char buf[1];
 337
 338   result.str = buf;     /* Does not really matter.  */
 339   result.len = 0;
 340
 341   *sz = 1;
 342   return &result;
 343 }
 344
 345
 346 #ifdef DL_SYSINFO_IMPLEMENTATION
 347 DL_SYSINFO_IMPLEMENTATION
 348 #endif