elf/dl-support.c

   1 /* Support for dynamic linking code in static libc.
   2    Copyright (C) 1996-2014 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 /* The value of the FPU control word the kernel will preset in hardware.  */
 171 fpu_control_t _dl_fpu_control = _FPU_DEFAULT;
 172
 173 /* This is not initialized to HWCAP_IMPORTANT, matching the definition
 174    of _dl_important_hwcaps, below, where no hwcap strings are ever
 175    used.  This mask is still used to mediate the lookups in the cache
 176    file.  Since there is no way to set this nonzero (we don't grok the
 177    LD_HWCAP_MASK environment variable here), there is no real point in
 178    setting _dl_hwcap nonzero below, but we do anyway.  */
 179 uint64_t _dl_hwcap_mask __attribute__ ((nocommon));
 180
 181 /* Prevailing state of the stack.  Generally this includes PF_X, indicating it's
 182  * executable but this isn't true for all platforms.  */
 183 ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
 184
 185 /* If loading a shared object requires that we make the stack executable
 186    when it was not, we do it by calling this function.
 187    It returns an errno code or zero on success.  */
 188 int (*_dl_make_stack_executable_hook) (void **) internal_function
 189   = _dl_make_stack_executable;
 190
 191
 192 /* Function in libpthread to wait for termination of lookups.  */
 193 void (*_dl_wait_lookup_done) (void);
 194
 195 struct dl_scope_free_list *_dl_scope_free_list;
 196
 197 #ifdef NEED_DL_SYSINFO
 198 /* Needed for improved syscall handling on at least x86/Linux.  */
 199 uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
 200 #endif
 201 #ifdef NEED_DL_SYSINFO_DSO
 202 /* Address of the ELF headers in the vsyscall page.  */
 203 const ElfW(Ehdr) *_dl_sysinfo_dso;
 204
 205 struct link_map *_dl_sysinfo_map;
 206
 207 # include "get-dynamic-info.h"
 208 #endif
 209 #include "setup-vdso.h"
 210
 211 /* During the program run we must not modify the global data of
 212    loaded shared object simultanously in two threads.  Therefore we
 213    protect `_dl_open' and `_dl_close' in dl-close.c.
 214
 215    This must be a recursive lock since the initializer function of
 216    the loaded object might as well require a call to this function.
 217    At this time it is not anymore a problem to modify the tables.  */
 218 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 219 /* This lock is used to keep __dl_iterate_phdr from inspecting the
 220    list of loaded objects while an object is added to or removed from
 221    that list.  */
 222 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
 223
 224
 225 #ifdef HAVE_AUX_VECTOR
 226 int _dl_clktck;
 227
 228 void
 229 internal_function
 230 _dl_aux_init (ElfW(auxv_t) *av)
 231 {
 232   int seen = 0;
 233   uid_t uid = 0;
 234   gid_t gid = 0;
 235
 236   _dl_auxv = av;
 237   for (; av->a_type != AT_NULL; ++av)
 238     switch (av->a_type)
 239       {
 240       case AT_PAGESZ:
 241         if (av->a_un.a_val != 0)
 242           GLRO(dl_pagesize) = av->a_un.a_val;
 243         break;
 244       case AT_CLKTCK:
 245         GLRO(dl_clktck) = av->a_un.a_val;
 246         break;
 247       case AT_PHDR:
 248         GL(dl_phdr) = (const void *) av->a_un.a_val;
 249         break;
 250       case AT_PHNUM:
 251         GL(dl_phnum) = av->a_un.a_val;
 252         break;
 253       case AT_HWCAP:
 254         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 255         break;
 256       case AT_HWCAP2:
 257         GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
 258         break;
 259       case AT_FPUCW:
 260         GLRO(dl_fpu_control) = av->a_un.a_val;
 261         break;
 262 #ifdef NEED_DL_SYSINFO
 263       case AT_SYSINFO:
 264         GL(dl_sysinfo) = av->a_un.a_val;
 265         break;
 266 #endif
 267 #ifdef NEED_DL_SYSINFO_DSO
 268       case AT_SYSINFO_EHDR:
 269         GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 270         break;
 271 #endif
 272       case AT_UID:
 273         uid ^= av->a_un.a_val;
 274         seen |= 1;
 275         break;
 276       case AT_EUID:
 277         uid ^= av->a_un.a_val;
 278         seen |= 2;
 279         break;
 280       case AT_GID:
 281         gid ^= av->a_un.a_val;
 282         seen |= 4;
 283         break;
 284       case AT_EGID:
 285         gid ^= av->a_un.a_val;
 286         seen |= 8;
 287         break;
 288       case AT_SECURE:
 289         seen = -1;
 290         __libc_enable_secure = av->a_un.a_val;
 291         __libc_enable_secure_decided = 1;
 292         break;
 293       case AT_RANDOM:
 294         _dl_random = (void *) av->a_un.a_val;
 295         break;
 296 # ifdef DL_PLATFORM_AUXV
 297       DL_PLATFORM_AUXV
 298 # endif
 299       }
 300   if (seen == 0xf)
 301     {
 302       __libc_enable_secure = uid != 0 || gid != 0;
 303       __libc_enable_secure_decided = 1;
 304     }
 305 }
 306 #endif
 307
 308
 309 void
 310 internal_function
 311 _dl_non_dynamic_init (void)
 312 {
 313   _dl_main_map.l_origin = _dl_get_origin ();
 314
 315   if (HP_TIMING_AVAIL)
 316     HP_TIMING_NOW (_dl_cpuclock_offset);
 317
 318   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 319
 320   /* Set up the data structures for the system-supplied DSO early,
 321      so they can influence _dl_init_paths.  */
 322   setup_vdso (NULL, NULL);
 323
 324   /* Initialize the data structures for the search paths for shared
 325      objects.  */
 326   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 327
 328   /* Remember the last search directory added at startup.  */
 329   _dl_init_all_dirs = GL(dl_all_dirs);
 330
 331   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 332
 333   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 334
 335   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 336
 337   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 338   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 339     _dl_profile_output
 340       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 341
 342   if (__libc_enable_secure)
 343     {
 344       static const char unsecure_envvars[] =
 345         UNSECURE_ENVVARS
 346 #ifdef EXTRA_UNSECURE_ENVVARS
 347         EXTRA_UNSECURE_ENVVARS
 348 #endif
 349         ;
 350       const char *cp = unsecure_envvars;
 351
 352       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 353         {
 354           __unsetenv (cp);
 355           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 356         }
 357
 358       if (__access ("/etc/suid-debug", F_OK) != 0)
 359         __unsetenv ("MALLOC_CHECK_");
 360     }
 361
 362 #ifdef DL_PLATFORM_INIT
 363   DL_PLATFORM_INIT;
 364 #endif
 365
 366 #ifdef DL_OSVERSION_INIT
 367   DL_OSVERSION_INIT;
 368 #endif
 369
 370   /* Now determine the length of the platform string.  */
 371   if (_dl_platform != NULL)
 372     _dl_platformlen = strlen (_dl_platform);
 373
 374   /* Scan for a program header telling us the stack is nonexecutable.  */
 375   if (_dl_phdr != NULL)
 376     for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
 377       if (_dl_phdr[i].p_type == PT_GNU_STACK)
 378         {
 379           _dl_stack_flags = _dl_phdr[i].p_flags;
 380           break;
 381         }
 382 }
 383
 384 #ifdef DL_SYSINFO_IMPLEMENTATION
 385 DL_SYSINFO_IMPLEMENTATION
 386 #endif