elf/dl-support.c

   1 /* Support for dynamic linking code in static libc.
   2    Copyright (C) 1996-2013 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 <stdint.h>
  28 #include <ldsodefs.h>
  29 #include <dl-machine.h>
  30 #include <bits/libc-lock.h>
  31 #include <dl-cache.h>
  32 #include <dl-librecon.h>
  33 #include <dl-procinfo.h>
  34 #include <unsecvars.h>
  35 #include <hp-timing.h>
  36 #include <stackinfo.h>
  37
  38 extern char *__progname;
  39 char **_dl_argv = &__progname;  /* This is checked for some error messages.  */
  40
  41 /* Name of the architecture.  */
  42 const char *_dl_platform;
  43 size_t _dl_platformlen;
  44
  45 int _dl_debug_mask;
  46 int _dl_lazy;
  47 ElfW(Addr) _dl_use_load_bias = -2;
  48 int _dl_dynamic_weak;
  49
  50 /* If nonzero print warnings about problematic situations.  */
  51 int _dl_verbose;
  52
  53 /* We never do profiling.  */
  54 const char *_dl_profile;
  55 const char *_dl_profile_output;
  56
  57 /* Names of shared object for which the RUNPATHs and RPATHs should be
  58    ignored.  */
  59 const char *_dl_inhibit_rpath;
  60
  61 /* The map for the object we will profile.  */
  62 struct link_map *_dl_profile_map;
  63
  64 /* This is the address of the last stack address ever used.  */
  65 void *__libc_stack_end;
  66
  67 /* Path where the binary is found.  */
  68 const char *_dl_origin_path;
  69
  70 /* Nonzero if runtime lookup should not update the .got/.plt.  */
  71 int _dl_bind_not;
  72
  73 /* A dummy link map for the executable, used by dlopen to access the global
  74    scope.  We don't export any symbols ourselves, so this can be minimal.  */
  75 static struct link_map _dl_main_map =
  76   {
  77     .l_name = (char *) "",
  78     .l_real = &_dl_main_map,
  79     .l_ns = LM_ID_BASE,
  80     .l_libname = &(struct libname_list) { .name = "", .dont_free = 1 },
  81     .l_searchlist =
  82       {
  83         .r_list = &(struct link_map *) { &_dl_main_map },
  84         .r_nlist = 1,
  85       },
  86     .l_symbolic_searchlist = { .r_list = &(struct link_map *) { NULL } },
  87     .l_type = lt_executable,
  88     .l_scope_mem = { &_dl_main_map.l_searchlist },
  89     .l_scope_max = (sizeof (_dl_main_map.l_scope_mem)
  90                     / sizeof (_dl_main_map.l_scope_mem[0])),
  91     .l_scope = _dl_main_map.l_scope_mem,
  92     .l_local_scope = { &_dl_main_map.l_searchlist },
  93     .l_used = 1,
  94     .l_tls_offset = NO_TLS_OFFSET,
  95     .l_serial = 1,
  96   };
  97
  98 /* Namespace information.  */
  99 struct link_namespaces _dl_ns[DL_NNS] =
 100   {
 101     [LM_ID_BASE] =
 102       {
 103         ._ns_loaded = &_dl_main_map,
 104         ._ns_nloaded = 1,
 105         ._ns_main_searchlist = &_dl_main_map.l_searchlist,
 106       }
 107   };
 108 size_t _dl_nns = 1;
 109
 110 /* Incremented whenever something may have been added to dl_loaded. */
 111 unsigned long long _dl_load_adds = 1;
 112
 113 /* Fake scope of the main application.  */
 114 struct r_scope_elem _dl_initial_searchlist =
 115   {
 116     .r_list = &(struct link_map *) { &_dl_main_map },
 117     .r_nlist = 1,
 118   };
 119
 120 #ifndef HAVE_INLINED_SYSCALLS
 121 /* Nonzero during startup.  */
 122 int _dl_starting_up = 1;
 123 #endif
 124
 125 /* Random data provided by the kernel.  */
 126 void *_dl_random;
 127
 128 /* Get architecture specific initializer.  */
 129 #include <dl-procinfo.c>
 130
 131 /* We expect less than a second for relocation.  */
 132 #ifdef HP_SMALL_TIMING_AVAIL
 133 # undef HP_TIMING_AVAIL
 134 # define HP_TIMING_AVAIL HP_SMALL_TIMING_AVAIL
 135 #endif
 136
 137 /* Initial value of the CPU clock.  */
 138 #ifndef HP_TIMING_NONAVAIL
 139 hp_timing_t _dl_cpuclock_offset;
 140 #endif
 141
 142 void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
 143
 144 size_t _dl_pagesize = EXEC_PAGESIZE;
 145
 146 int _dl_inhibit_cache;
 147
 148 unsigned int _dl_osversion;
 149
 150 /* All known directories in sorted order.  */
 151 struct r_search_path_elem *_dl_all_dirs;
 152
 153 /* All directories after startup.  */
 154 struct r_search_path_elem *_dl_init_all_dirs;
 155
 156 /* The object to be initialized first.  */
 157 struct link_map *_dl_initfirst;
 158
 159 /* Descriptor to write debug messages to.  */
 160 int _dl_debug_fd = STDERR_FILENO;
 161
 162 int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
 163
 164 ElfW(auxv_t) *_dl_auxv;
 165 const ElfW(Phdr) *_dl_phdr;
 166 size_t _dl_phnum;
 167 uint64_t _dl_hwcap __attribute__ ((nocommon));
 168 uint64_t _dl_hwcap2 __attribute__ ((nocommon));
 169
 170 /* This is not initialized to HWCAP_IMPORTANT, matching the definition
 171    of _dl_important_hwcaps, below, where no hwcap strings are ever
 172    used.  This mask is still used to mediate the lookups in the cache
 173    file.  Since there is no way to set this nonzero (we don't grok the
 174    LD_HWCAP_MASK environment variable here), there is no real point in
 175    setting _dl_hwcap nonzero below, but we do anyway.  */
 176 uint64_t _dl_hwcap_mask __attribute__ ((nocommon));
 177
 178 /* Prevailing state of the stack.  Generally this includes PF_X, indicating it's
 179  * executable but this isn't true for all platforms.  */
 180 ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
 181
 182 /* If loading a shared object requires that we make the stack executable
 183    when it was not, we do it by calling this function.
 184    It returns an errno code or zero on success.  */
 185 int (*_dl_make_stack_executable_hook) (void **) internal_function
 186   = _dl_make_stack_executable;
 187
 188
 189 /* Function in libpthread to wait for termination of lookups.  */
 190 void (*_dl_wait_lookup_done) (void);
 191
 192 struct dl_scope_free_list *_dl_scope_free_list;
 193
 194 #ifdef NEED_DL_SYSINFO
 195 /* Needed for improved syscall handling on at least x86/Linux.  */
 196 uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
 197 #endif
 198 #ifdef NEED_DL_SYSINFO_DSO
 199 /* Address of the ELF headers in the vsyscall page.  */
 200 const ElfW(Ehdr) *_dl_sysinfo_dso;
 201
 202 struct link_map *_dl_sysinfo_map;
 203
 204 # include "get-dynamic-info.h"
 205 #endif
 206 #include "setup-vdso.h"
 207
 208 /* During the program run we must not modify the global data of
 209    loaded shared object simultanously in two threads.  Therefore we
 210    protect `_dl_open' and `_dl_close' in dl-close.c.
 211
 212    This must be a recursive lock since the initializer function of
 213    the loaded object might as well require a call to this function.
 214    At this time it is not anymore a problem to modify the tables.  */
 215 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 216 /* This lock is used to keep __dl_iterate_phdr from inspecting the
 217    list of loaded objects while an object is added to or removed from
 218    that list.  */
 219 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
 220
 221
 222 #ifdef HAVE_AUX_VECTOR
 223 int _dl_clktck;
 224
 225 void
 226 internal_function
 227 _dl_aux_init (ElfW(auxv_t) *av)
 228 {
 229   int seen = 0;
 230   uid_t uid = 0;
 231   gid_t gid = 0;
 232
 233   _dl_auxv = av;
 234   for (; av->a_type != AT_NULL; ++av)
 235     switch (av->a_type)
 236       {
 237       case AT_PAGESZ:
 238         if (av->a_un.a_val != 0)
 239           GLRO(dl_pagesize) = av->a_un.a_val;
 240         break;
 241       case AT_CLKTCK:
 242         GLRO(dl_clktck) = av->a_un.a_val;
 243         break;
 244       case AT_PHDR:
 245         GL(dl_phdr) = (const void *) av->a_un.a_val;
 246         break;
 247       case AT_PHNUM:
 248         GL(dl_phnum) = av->a_un.a_val;
 249         break;
 250       case AT_HWCAP:
 251         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 252         break;
 253       case AT_HWCAP2:
 254         GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
 255         break;
 256 #ifdef NEED_DL_SYSINFO
 257       case AT_SYSINFO:
 258         GL(dl_sysinfo) = av->a_un.a_val;
 259         break;
 260 #endif
 261 #ifdef NEED_DL_SYSINFO_DSO
 262       case AT_SYSINFO_EHDR:
 263         GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 264         break;
 265 #endif
 266       case AT_UID:
 267         uid ^= av->a_un.a_val;
 268         seen |= 1;
 269         break;
 270       case AT_EUID:
 271         uid ^= av->a_un.a_val;
 272         seen |= 2;
 273         break;
 274       case AT_GID:
 275         gid ^= av->a_un.a_val;
 276         seen |= 4;
 277         break;
 278       case AT_EGID:
 279         gid ^= av->a_un.a_val;
 280         seen |= 8;
 281         break;
 282       case AT_SECURE:
 283         seen = -1;
 284         __libc_enable_secure = av->a_un.a_val;
 285         __libc_enable_secure_decided = 1;
 286         break;
 287       case AT_RANDOM:
 288         _dl_random = (void *) av->a_un.a_val;
 289         break;
 290 # ifdef DL_PLATFORM_AUXV
 291       DL_PLATFORM_AUXV
 292 # endif
 293       }
 294   if (seen == 0xf)
 295     {
 296       __libc_enable_secure = uid != 0 || gid != 0;
 297       __libc_enable_secure_decided = 1;
 298     }
 299 }
 300 #endif
 301
 302
 303 void
 304 internal_function
 305 _dl_non_dynamic_init (void)
 306 {
 307   _dl_main_map.l_origin = _dl_get_origin ();
 308
 309   if (HP_TIMING_AVAIL)
 310     HP_TIMING_NOW (_dl_cpuclock_offset);
 311
 312   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 313
 314   /* Set up the data structures for the system-supplied DSO early,
 315      so they can influence _dl_init_paths.  */
 316   setup_vdso (NULL, NULL);
 317
 318   /* Initialize the data structures for the search paths for shared
 319      objects.  */
 320   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 321
 322   /* Remember the last search directory added at startup.  */
 323   _dl_init_all_dirs = GL(dl_all_dirs);
 324
 325   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 326
 327   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 328
 329   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 330
 331   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 332   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 333     _dl_profile_output
 334       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 335
 336   if (__libc_enable_secure)
 337     {
 338       static const char unsecure_envvars[] =
 339         UNSECURE_ENVVARS
 340 #ifdef EXTRA_UNSECURE_ENVVARS
 341         EXTRA_UNSECURE_ENVVARS
 342 #endif
 343         ;
 344       const char *cp = unsecure_envvars;
 345
 346       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 347         {
 348           __unsetenv (cp);
 349           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 350         }
 351
 352       if (__access ("/etc/suid-debug", F_OK) != 0)
 353         __unsetenv ("MALLOC_CHECK_");
 354     }
 355
 356 #ifdef DL_PLATFORM_INIT
 357   DL_PLATFORM_INIT;
 358 #endif
 359
 360 #ifdef DL_OSVERSION_INIT
 361   DL_OSVERSION_INIT;
 362 #endif
 363
 364   /* Now determine the length of the platform string.  */
 365   if (_dl_platform != NULL)
 366     _dl_platformlen = strlen (_dl_platform);
 367
 368   /* Scan for a program header telling us the stack is nonexecutable.  */
 369   if (_dl_phdr != NULL)
 370     for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
 371       if (_dl_phdr[i].p_type == PT_GNU_STACK)
 372         {
 373           _dl_stack_flags = _dl_phdr[i].p_flags;
 374           break;
 375         }
 376 }
 377
 378 #ifdef DL_SYSINFO_IMPLEMENTATION
 379 DL_SYSINFO_IMPLEMENTATION
 380 #endif