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(Phdr) *_dl_phdr;
 129 size_t _dl_phnum;
 130 uint64_t _dl_hwcap __attribute__ ((nocommon));
 131
 132 /* This is not initialized to HWCAP_IMPORTANT, matching the definition
 133    of _dl_important_hwcaps, below, where no hwcap strings are ever
 134    used.  This mask is still used to mediate the lookups in the cache
 135    file.  Since there is no way to set this nonzero (we don't grok the
 136    LD_HWCAP_MASK environment variable here), there is no real point in
 137    setting _dl_hwcap nonzero below, but we do anyway.  */
 138 uint64_t _dl_hwcap_mask __attribute__ ((nocommon));
 139
 140 /* Prevailing state of the stack.  Generally this includes PF_X, indicating it's
 141  * executable but this isn't true for all platforms.  */
 142 ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
 143
 144 /* If loading a shared object requires that we make the stack executable
 145    when it was not, we do it by calling this function.
 146    It returns an errno code or zero on success.  */
 147 int (*_dl_make_stack_executable_hook) (void **) internal_function
 148   = _dl_make_stack_executable;
 149
 150
 151 /* Function in libpthread to wait for termination of lookups.  */
 152 void (*_dl_wait_lookup_done) (void);
 153
 154 struct dl_scope_free_list *_dl_scope_free_list;
 155
 156 #ifdef NEED_DL_SYSINFO
 157 /* Needed for improved syscall handling on at least x86/Linux.  */
 158 uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
 159 #endif
 160 #if defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO
 161 /* Address of the ELF headers in the vsyscall page.  */
 162 const ElfW(Ehdr) *_dl_sysinfo_dso;
 163 #endif
 164
 165 /* During the program run we must not modify the global data of
 166    loaded shared object simultanously in two threads.  Therefore we
 167    protect `_dl_open' and `_dl_close' in dl-close.c.
 168
 169    This must be a recursive lock since the initializer function of
 170    the loaded object might as well require a call to this function.
 171    At this time it is not anymore a problem to modify the tables.  */
 172 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 173 /* This lock is used to keep __dl_iterate_phdr from inspecting the
 174    list of loaded objects while an object is added to or removed from
 175    that list.  */
 176 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
 177
 178
 179 #ifdef HAVE_AUX_VECTOR
 180 int _dl_clktck;
 181
 182 void
 183 internal_function
 184 _dl_aux_init (ElfW(auxv_t) *av)
 185 {
 186   int seen = 0;
 187   uid_t uid = 0;
 188   gid_t gid = 0;
 189
 190   for (; av->a_type != AT_NULL; ++av)
 191     switch (av->a_type)
 192       {
 193       case AT_PAGESZ:
 194         GLRO(dl_pagesize) = av->a_un.a_val;
 195         break;
 196       case AT_CLKTCK:
 197         GLRO(dl_clktck) = av->a_un.a_val;
 198         break;
 199       case AT_PHDR:
 200         GL(dl_phdr) = (void *) av->a_un.a_val;
 201         break;
 202       case AT_PHNUM:
 203         GL(dl_phnum) = av->a_un.a_val;
 204         break;
 205       case AT_HWCAP:
 206         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 207         break;
 208 #ifdef NEED_DL_SYSINFO
 209       case AT_SYSINFO:
 210         GL(dl_sysinfo) = av->a_un.a_val;
 211         break;
 212 #endif
 213 #if defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO
 214       case AT_SYSINFO_EHDR:
 215         GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 216         break;
 217 #endif
 218       case AT_UID:
 219         uid ^= av->a_un.a_val;
 220         seen |= 1;
 221         break;
 222       case AT_EUID:
 223         uid ^= av->a_un.a_val;
 224         seen |= 2;
 225         break;
 226       case AT_GID:
 227         gid ^= av->a_un.a_val;
 228         seen |= 4;
 229         break;
 230       case AT_EGID:
 231         gid ^= av->a_un.a_val;
 232         seen |= 8;
 233         break;
 234       case AT_SECURE:
 235         seen = -1;
 236         __libc_enable_secure = av->a_un.a_val;
 237         __libc_enable_secure_decided = 1;
 238         break;
 239       case AT_RANDOM:
 240         _dl_random = (void *) av->a_un.a_val;
 241         break;
 242 # ifdef DL_PLATFORM_AUXV
 243       DL_PLATFORM_AUXV
 244 # endif
 245       }
 246   if (seen == 0xf)
 247     {
 248       __libc_enable_secure = uid != 0 || gid != 0;
 249       __libc_enable_secure_decided = 1;
 250     }
 251 }
 252 #endif
 253
 254
 255 void
 256 internal_function
 257 _dl_non_dynamic_init (void)
 258 {
 259   if (HP_TIMING_AVAIL)
 260     HP_TIMING_NOW (_dl_cpuclock_offset);
 261
 262   if (!_dl_pagesize)
 263     _dl_pagesize = __getpagesize ();
 264
 265   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 266
 267   /* Initialize the data structures for the search paths for shared
 268      objects.  */
 269   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 270
 271   /* Remember the last search directory added at startup.  */
 272   _dl_init_all_dirs = GL(dl_all_dirs);
 273
 274   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 275
 276   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 277
 278   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 279
 280   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 281   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 282     _dl_profile_output
 283       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 284
 285   if (__libc_enable_secure)
 286     {
 287       static const char unsecure_envvars[] =
 288         UNSECURE_ENVVARS
 289 #ifdef EXTRA_UNSECURE_ENVVARS
 290         EXTRA_UNSECURE_ENVVARS
 291 #endif
 292         ;
 293       const char *cp = unsecure_envvars;
 294
 295       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 296         {
 297           __unsetenv (cp);
 298           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 299         }
 300
 301       if (__access ("/etc/suid-debug", F_OK) != 0)
 302         __unsetenv ("MALLOC_CHECK_");
 303     }
 304
 305 #ifdef DL_PLATFORM_INIT
 306   DL_PLATFORM_INIT;
 307 #endif
 308
 309 #ifdef DL_OSVERSION_INIT
 310   DL_OSVERSION_INIT;
 311 #endif
 312
 313   /* Now determine the length of the platform string.  */
 314   if (_dl_platform != NULL)
 315     _dl_platformlen = strlen (_dl_platform);
 316
 317   /* Scan for a program header telling us the stack is nonexecutable.  */
 318   if (_dl_phdr != NULL)
 319     for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
 320       if (_dl_phdr[i].p_type == PT_GNU_STACK)
 321         {
 322           _dl_stack_flags = _dl_phdr[i].p_flags;
 323           break;
 324         }
 325 }
 326
 327
 328 const struct r_strlenpair *
 329 internal_function
 330 _dl_important_hwcaps (const char *platform, size_t platform_len, size_t *sz,
 331                       size_t *max_capstrlen)
 332 {
 333   static struct r_strlenpair result;
 334   static char buf[1];
 335
 336   result.str = buf;     /* Does not really matter.  */
 337   result.len = 0;
 338
 339   *sz = 1;
 340   return &result;
 341 }
 342
 343
 344 #ifdef DL_SYSINFO_IMPLEMENTATION
 345 DL_SYSINFO_IMPLEMENTATION
 346 #endif