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 /* Namespace information.  */
  74 struct link_namespaces _dl_ns[DL_NNS];
  75 size_t _dl_nns;
  76
  77 /* Incremented whenever something may have been added to dl_loaded. */
  78 unsigned long long _dl_load_adds;
  79
  80 /* Fake scope.  In dynamically linked binaries this is the scope of the
  81    main application but here we don't have something like this.  So
  82    create a fake scope containing nothing.  */
  83 struct r_scope_elem _dl_initial_searchlist;
  84
  85 #ifndef HAVE_INLINED_SYSCALLS
  86 /* Nonzero during startup.  */
  87 int _dl_starting_up = 1;
  88 #endif
  89
  90 /* Random data provided by the kernel.  */
  91 void *_dl_random;
  92
  93 /* Get architecture specific initializer.  */
  94 #include <dl-procinfo.c>
  95
  96 /* We expect less than a second for relocation.  */
  97 #ifdef HP_SMALL_TIMING_AVAIL
  98 # undef HP_TIMING_AVAIL
  99 # define HP_TIMING_AVAIL HP_SMALL_TIMING_AVAIL
 100 #endif
 101
 102 /* Initial value of the CPU clock.  */
 103 #ifndef HP_TIMING_NONAVAIL
 104 hp_timing_t _dl_cpuclock_offset;
 105 #endif
 106
 107 void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
 108
 109 size_t _dl_pagesize = EXEC_PAGESIZE;
 110
 111 int _dl_inhibit_cache;
 112
 113 unsigned int _dl_osversion;
 114
 115 /* All known directories in sorted order.  */
 116 struct r_search_path_elem *_dl_all_dirs;
 117
 118 /* All directories after startup.  */
 119 struct r_search_path_elem *_dl_init_all_dirs;
 120
 121 /* The object to be initialized first.  */
 122 struct link_map *_dl_initfirst;
 123
 124 /* Descriptor to write debug messages to.  */
 125 int _dl_debug_fd = STDERR_FILENO;
 126
 127 int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
 128
 129 ElfW(auxv_t) *_dl_auxv;
 130 const ElfW(Phdr) *_dl_phdr;
 131 size_t _dl_phnum;
 132 uint64_t _dl_hwcap __attribute__ ((nocommon));
 133
 134 /* This is not initialized to HWCAP_IMPORTANT, matching the definition
 135    of _dl_important_hwcaps, below, where no hwcap strings are ever
 136    used.  This mask is still used to mediate the lookups in the cache
 137    file.  Since there is no way to set this nonzero (we don't grok the
 138    LD_HWCAP_MASK environment variable here), there is no real point in
 139    setting _dl_hwcap nonzero below, but we do anyway.  */
 140 uint64_t _dl_hwcap_mask __attribute__ ((nocommon));
 141
 142 /* Prevailing state of the stack.  Generally this includes PF_X, indicating it's
 143  * executable but this isn't true for all platforms.  */
 144 ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
 145
 146 /* If loading a shared object requires that we make the stack executable
 147    when it was not, we do it by calling this function.
 148    It returns an errno code or zero on success.  */
 149 int (*_dl_make_stack_executable_hook) (void **) internal_function
 150   = _dl_make_stack_executable;
 151
 152
 153 /* Function in libpthread to wait for termination of lookups.  */
 154 void (*_dl_wait_lookup_done) (void);
 155
 156 struct dl_scope_free_list *_dl_scope_free_list;
 157
 158 #ifdef NEED_DL_SYSINFO
 159 /* Needed for improved syscall handling on at least x86/Linux.  */
 160 uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
 161 #endif
 162 #ifdef NEED_DL_SYSINFO_DSO
 163 /* Address of the ELF headers in the vsyscall page.  */
 164 const ElfW(Ehdr) *_dl_sysinfo_dso;
 165
 166 struct link_map *_dl_sysinfo_map;
 167
 168 # include "get-dynamic-info.h"
 169 #endif
 170 #include "setup-vdso.h"
 171
 172 /* During the program run we must not modify the global data of
 173    loaded shared object simultanously in two threads.  Therefore we
 174    protect `_dl_open' and `_dl_close' in dl-close.c.
 175
 176    This must be a recursive lock since the initializer function of
 177    the loaded object might as well require a call to this function.
 178    At this time it is not anymore a problem to modify the tables.  */
 179 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 180 /* This lock is used to keep __dl_iterate_phdr from inspecting the
 181    list of loaded objects while an object is added to or removed from
 182    that list.  */
 183 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
 184
 185
 186 #ifdef HAVE_AUX_VECTOR
 187 int _dl_clktck;
 188
 189 void
 190 internal_function
 191 _dl_aux_init (ElfW(auxv_t) *av)
 192 {
 193   int seen = 0;
 194   uid_t uid = 0;
 195   gid_t gid = 0;
 196
 197   _dl_auxv = av;
 198   for (; av->a_type != AT_NULL; ++av)
 199     switch (av->a_type)
 200       {
 201       case AT_PAGESZ:
 202         if (av->a_un.a_val != 0)
 203           GLRO(dl_pagesize) = av->a_un.a_val;
 204         break;
 205       case AT_CLKTCK:
 206         GLRO(dl_clktck) = av->a_un.a_val;
 207         break;
 208       case AT_PHDR:
 209         GL(dl_phdr) = (const void *) av->a_un.a_val;
 210         break;
 211       case AT_PHNUM:
 212         GL(dl_phnum) = av->a_un.a_val;
 213         break;
 214       case AT_HWCAP:
 215         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 216         break;
 217 #ifdef NEED_DL_SYSINFO
 218       case AT_SYSINFO:
 219         GL(dl_sysinfo) = av->a_un.a_val;
 220         break;
 221 #endif
 222 #ifdef NEED_DL_SYSINFO_DSO
 223       case AT_SYSINFO_EHDR:
 224         GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 225         break;
 226 #endif
 227       case AT_UID:
 228         uid ^= av->a_un.a_val;
 229         seen |= 1;
 230         break;
 231       case AT_EUID:
 232         uid ^= av->a_un.a_val;
 233         seen |= 2;
 234         break;
 235       case AT_GID:
 236         gid ^= av->a_un.a_val;
 237         seen |= 4;
 238         break;
 239       case AT_EGID:
 240         gid ^= av->a_un.a_val;
 241         seen |= 8;
 242         break;
 243       case AT_SECURE:
 244         seen = -1;
 245         __libc_enable_secure = av->a_un.a_val;
 246         __libc_enable_secure_decided = 1;
 247         break;
 248       case AT_RANDOM:
 249         _dl_random = (void *) av->a_un.a_val;
 250         break;
 251 # ifdef DL_PLATFORM_AUXV
 252       DL_PLATFORM_AUXV
 253 # endif
 254       }
 255   if (seen == 0xf)
 256     {
 257       __libc_enable_secure = uid != 0 || gid != 0;
 258       __libc_enable_secure_decided = 1;
 259     }
 260 }
 261 #endif
 262
 263
 264 void
 265 internal_function
 266 _dl_non_dynamic_init (void)
 267 {
 268   if (HP_TIMING_AVAIL)
 269     HP_TIMING_NOW (_dl_cpuclock_offset);
 270
 271   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 272
 273   /* Set up the data structures for the system-supplied DSO early,
 274      so they can influence _dl_init_paths.  */
 275   setup_vdso (NULL, NULL);
 276
 277   /* Initialize the data structures for the search paths for shared
 278      objects.  */
 279   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 280
 281   /* Remember the last search directory added at startup.  */
 282   _dl_init_all_dirs = GL(dl_all_dirs);
 283
 284   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 285
 286   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 287
 288   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 289
 290   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 291   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 292     _dl_profile_output
 293       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 294
 295   if (__libc_enable_secure)
 296     {
 297       static const char unsecure_envvars[] =
 298         UNSECURE_ENVVARS
 299 #ifdef EXTRA_UNSECURE_ENVVARS
 300         EXTRA_UNSECURE_ENVVARS
 301 #endif
 302         ;
 303       const char *cp = unsecure_envvars;
 304
 305       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 306         {
 307           __unsetenv (cp);
 308           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 309         }
 310
 311       if (__access ("/etc/suid-debug", F_OK) != 0)
 312         __unsetenv ("MALLOC_CHECK_");
 313     }
 314
 315 #ifdef DL_PLATFORM_INIT
 316   DL_PLATFORM_INIT;
 317 #endif
 318
 319 #ifdef DL_OSVERSION_INIT
 320   DL_OSVERSION_INIT;
 321 #endif
 322
 323   /* Now determine the length of the platform string.  */
 324   if (_dl_platform != NULL)
 325     _dl_platformlen = strlen (_dl_platform);
 326
 327   /* Scan for a program header telling us the stack is nonexecutable.  */
 328   if (_dl_phdr != NULL)
 329     for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
 330       if (_dl_phdr[i].p_type == PT_GNU_STACK)
 331         {
 332           _dl_stack_flags = _dl_phdr[i].p_flags;
 333           break;
 334         }
 335 }
 336
 337 #ifdef DL_SYSINFO_IMPLEMENTATION
 338 DL_SYSINFO_IMPLEMENTATION
 339 #endif