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
 165 struct link_map *_dl_sysinfo_map;
 166
 167 # include "get-dynamic-info.h"
 168 # include "setup-vdso.h"
 169 #endif
 170
 171 /* During the program run we must not modify the global data of
 172    loaded shared object simultanously in two threads.  Therefore we
 173    protect `_dl_open' and `_dl_close' in dl-close.c.
 174
 175    This must be a recursive lock since the initializer function of
 176    the loaded object might as well require a call to this function.
 177    At this time it is not anymore a problem to modify the tables.  */
 178 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 179 /* This lock is used to keep __dl_iterate_phdr from inspecting the
 180    list of loaded objects while an object is added to or removed from
 181    that list.  */
 182 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
 183
 184
 185 #ifdef HAVE_AUX_VECTOR
 186 int _dl_clktck;
 187
 188 void
 189 internal_function
 190 _dl_aux_init (ElfW(auxv_t) *av)
 191 {
 192   int seen = 0;
 193   uid_t uid = 0;
 194   gid_t gid = 0;
 195
 196   _dl_auxv = av;
 197   for (; av->a_type != AT_NULL; ++av)
 198     switch (av->a_type)
 199       {
 200       case AT_PAGESZ:
 201         GLRO(dl_pagesize) = av->a_un.a_val;
 202         break;
 203       case AT_CLKTCK:
 204         GLRO(dl_clktck) = av->a_un.a_val;
 205         break;
 206       case AT_PHDR:
 207         GL(dl_phdr) = (void *) av->a_un.a_val;
 208         break;
 209       case AT_PHNUM:
 210         GL(dl_phnum) = av->a_un.a_val;
 211         break;
 212       case AT_HWCAP:
 213         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 214         break;
 215 #ifdef NEED_DL_SYSINFO
 216       case AT_SYSINFO:
 217         GL(dl_sysinfo) = av->a_un.a_val;
 218         break;
 219 #endif
 220 #if defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO
 221       case AT_SYSINFO_EHDR:
 222         GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 223         break;
 224 #endif
 225       case AT_UID:
 226         uid ^= av->a_un.a_val;
 227         seen |= 1;
 228         break;
 229       case AT_EUID:
 230         uid ^= av->a_un.a_val;
 231         seen |= 2;
 232         break;
 233       case AT_GID:
 234         gid ^= av->a_un.a_val;
 235         seen |= 4;
 236         break;
 237       case AT_EGID:
 238         gid ^= av->a_un.a_val;
 239         seen |= 8;
 240         break;
 241       case AT_SECURE:
 242         seen = -1;
 243         __libc_enable_secure = av->a_un.a_val;
 244         __libc_enable_secure_decided = 1;
 245         break;
 246       case AT_RANDOM:
 247         _dl_random = (void *) av->a_un.a_val;
 248         break;
 249 # ifdef DL_PLATFORM_AUXV
 250       DL_PLATFORM_AUXV
 251 # endif
 252       }
 253   if (seen == 0xf)
 254     {
 255       __libc_enable_secure = uid != 0 || gid != 0;
 256       __libc_enable_secure_decided = 1;
 257     }
 258 }
 259 #endif
 260
 261
 262 void
 263 internal_function
 264 _dl_non_dynamic_init (void)
 265 {
 266   if (HP_TIMING_AVAIL)
 267     HP_TIMING_NOW (_dl_cpuclock_offset);
 268
 269   if (!_dl_pagesize)
 270     _dl_pagesize = __getpagesize ();
 271
 272   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 273
 274   /* Set up the data structures for the system-supplied DSO early,
 275      so they can influence _dl_init_paths.  */
 276   setup_vdso (NULL, NULL);
 277
 278   /* Initialize the data structures for the search paths for shared
 279      objects.  */
 280   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 281
 282   /* Remember the last search directory added at startup.  */
 283   _dl_init_all_dirs = GL(dl_all_dirs);
 284
 285   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 286
 287   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 288
 289   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 290
 291   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 292   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 293     _dl_profile_output
 294       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 295
 296   if (__libc_enable_secure)
 297     {
 298       static const char unsecure_envvars[] =
 299         UNSECURE_ENVVARS
 300 #ifdef EXTRA_UNSECURE_ENVVARS
 301         EXTRA_UNSECURE_ENVVARS
 302 #endif
 303         ;
 304       const char *cp = unsecure_envvars;
 305
 306       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 307         {
 308           __unsetenv (cp);
 309           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 310         }
 311
 312       if (__access ("/etc/suid-debug", F_OK) != 0)
 313         __unsetenv ("MALLOC_CHECK_");
 314     }
 315
 316 #ifdef DL_PLATFORM_INIT
 317   DL_PLATFORM_INIT;
 318 #endif
 319
 320 #ifdef DL_OSVERSION_INIT
 321   DL_OSVERSION_INIT;
 322 #endif
 323
 324   /* Now determine the length of the platform string.  */
 325   if (_dl_platform != NULL)
 326     _dl_platformlen = strlen (_dl_platform);
 327
 328   /* Scan for a program header telling us the stack is nonexecutable.  */
 329   if (_dl_phdr != NULL)
 330     for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
 331       if (_dl_phdr[i].p_type == PT_GNU_STACK)
 332         {
 333           _dl_stack_flags = _dl_phdr[i].p_flags;
 334           break;
 335         }
 336 }
 337
 338 #ifdef DL_SYSINFO_IMPLEMENTATION
 339 DL_SYSINFO_IMPLEMENTATION
 340 #endif