elf/dl-support.c

   1 /* Support for dynamic linking code in static libc.
   2    Copyright (C) 1996-2008,2009,2010,2011 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 /* This file defines some things that for the dynamic linker are defined in
  21    rtld.c and dl-sysdep.c in ways appropriate to bootstrap dynamic linking.  */
  22
  23 #include <errno.h>
  24 #include <libintl.h>
  25 #include <stdlib.h>
  26 #include <unistd.h>
  27 #include <sys/param.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 unsigned int _dl_osversion;
 112
 113 /* All known directories in sorted order.  */
 114 struct r_search_path_elem *_dl_all_dirs;
 115
 116 /* All directories after startup.  */
 117 struct r_search_path_elem *_dl_init_all_dirs;
 118
 119 /* The object to be initialized first.  */
 120 struct link_map *_dl_initfirst;
 121
 122 /* Descriptor to write debug messages to.  */
 123 int _dl_debug_fd = STDERR_FILENO;
 124
 125 int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
 126
 127 ElfW(Phdr) *_dl_phdr;
 128 size_t _dl_phnum;
 129 uint64_t _dl_hwcap __attribute__ ((nocommon));
 130
 131 /* This is not initialized to HWCAP_IMPORTANT, matching the definition
 132    of _dl_important_hwcaps, below, where no hwcap strings are ever
 133    used.  This mask is still used to mediate the lookups in the cache
 134    file.  Since there is no way to set this nonzero (we don't grok the
 135    LD_HWCAP_MASK environment variable here), there is no real point in
 136    setting _dl_hwcap nonzero below, but we do anyway.  */
 137 uint64_t _dl_hwcap_mask __attribute__ ((nocommon));
 138
 139 /* Prevailing state of the stack.  Generally this includes PF_X, indicating it's
 140  * executable but this isn't true for all platforms.  */
 141 ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
 142
 143 /* If loading a shared object requires that we make the stack executable
 144    when it was not, we do it by calling this function.
 145    It returns an errno code or zero on success.  */
 146 int (*_dl_make_stack_executable_hook) (void **) internal_function
 147   = _dl_make_stack_executable;
 148
 149
 150 /* Function in libpthread to wait for termination of lookups.  */
 151 void (*_dl_wait_lookup_done) (void);
 152
 153 struct dl_scope_free_list *_dl_scope_free_list;
 154
 155 #ifdef NEED_DL_SYSINFO
 156 /* Needed for improved syscall handling on at least x86/Linux.  */
 157 uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
 158 #endif
 159 #if defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO
 160 /* Address of the ELF headers in the vsyscall page.  */
 161 const ElfW(Ehdr) *_dl_sysinfo_dso;
 162 #endif
 163
 164 /* During the program run we must not modify the global data of
 165    loaded shared object simultanously in two threads.  Therefore we
 166    protect `_dl_open' and `_dl_close' in dl-close.c.
 167
 168    This must be a recursive lock since the initializer function of
 169    the loaded object might as well require a call to this function.
 170    At this time it is not anymore a problem to modify the tables.  */
 171 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 172 /* This lock is used to keep __dl_iterate_phdr from inspecting the
 173    list of loaded objects while an object is added to or removed from
 174    that list.  */
 175 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
 176
 177
 178 #ifdef HAVE_AUX_VECTOR
 179 int _dl_clktck;
 180
 181 void
 182 internal_function
 183 _dl_aux_init (ElfW(auxv_t) *av)
 184 {
 185   int seen = 0;
 186   uid_t uid = 0;
 187   gid_t gid = 0;
 188
 189   for (; av->a_type != AT_NULL; ++av)
 190     switch (av->a_type)
 191       {
 192       case AT_PAGESZ:
 193         GLRO(dl_pagesize) = av->a_un.a_val;
 194         break;
 195       case AT_CLKTCK:
 196         GLRO(dl_clktck) = av->a_un.a_val;
 197         break;
 198       case AT_PHDR:
 199         GL(dl_phdr) = (void *) av->a_un.a_val;
 200         break;
 201       case AT_PHNUM:
 202         GL(dl_phnum) = av->a_un.a_val;
 203         break;
 204       case AT_HWCAP:
 205         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 206         break;
 207 #ifdef NEED_DL_SYSINFO
 208       case AT_SYSINFO:
 209         GL(dl_sysinfo) = av->a_un.a_val;
 210         break;
 211 #endif
 212 #if defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO
 213       case AT_SYSINFO_EHDR:
 214         GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 215         break;
 216 #endif
 217       case AT_UID:
 218         uid ^= av->a_un.a_val;
 219         seen |= 1;
 220         break;
 221       case AT_EUID:
 222         uid ^= av->a_un.a_val;
 223         seen |= 2;
 224         break;
 225       case AT_GID:
 226         gid ^= av->a_un.a_val;
 227         seen |= 4;
 228         break;
 229       case AT_EGID:
 230         gid ^= av->a_un.a_val;
 231         seen |= 8;
 232         break;
 233       case AT_SECURE:
 234         seen = -1;
 235         __libc_enable_secure = av->a_un.a_val;
 236         __libc_enable_secure_decided = 1;
 237         break;
 238       case AT_RANDOM:
 239         _dl_random = (void *) av->a_un.a_val;
 240         break;
 241 # ifdef DL_PLATFORM_AUXV
 242       DL_PLATFORM_AUXV
 243 # endif
 244       }
 245   if (seen == 0xf)
 246     {
 247       __libc_enable_secure = uid != 0 || gid != 0;
 248       __libc_enable_secure_decided = 1;
 249     }
 250 }
 251 #endif
 252
 253
 254 void
 255 internal_function
 256 _dl_non_dynamic_init (void)
 257 {
 258   if (HP_TIMING_AVAIL)
 259     HP_TIMING_NOW (_dl_cpuclock_offset);
 260
 261   if (!_dl_pagesize)
 262     _dl_pagesize = __getpagesize ();
 263
 264   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 265
 266   /* Initialize the data structures for the search paths for shared
 267      objects.  */
 268   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 269
 270   /* Remember the last search directory added at startup.  */
 271   _dl_init_all_dirs = GL(dl_all_dirs);
 272
 273   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 274
 275   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 276
 277   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 278
 279   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 280   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 281     _dl_profile_output
 282       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 283
 284   if (__libc_enable_secure)
 285     {
 286       static const char unsecure_envvars[] =
 287         UNSECURE_ENVVARS
 288 #ifdef EXTRA_UNSECURE_ENVVARS
 289         EXTRA_UNSECURE_ENVVARS
 290 #endif
 291         ;
 292       const char *cp = unsecure_envvars;
 293
 294       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 295         {
 296           __unsetenv (cp);
 297           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 298         }
 299
 300       if (__access ("/etc/suid-debug", F_OK) != 0)
 301         __unsetenv ("MALLOC_CHECK_");
 302     }
 303
 304 #ifdef DL_PLATFORM_INIT
 305   DL_PLATFORM_INIT;
 306 #endif
 307
 308 #ifdef DL_OSVERSION_INIT
 309   DL_OSVERSION_INIT;
 310 #endif
 311
 312   /* Now determine the length of the platform string.  */
 313   if (_dl_platform != NULL)
 314     _dl_platformlen = strlen (_dl_platform);
 315
 316   /* Scan for a program header telling us the stack is nonexecutable.  */
 317   if (_dl_phdr != NULL)
 318     for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
 319       if (_dl_phdr[i].p_type == PT_GNU_STACK)
 320         {
 321           _dl_stack_flags = _dl_phdr[i].p_flags;
 322           break;
 323         }
 324 }
 325
 326
 327 const struct r_strlenpair *
 328 internal_function
 329 _dl_important_hwcaps (const char *platform, size_t platform_len, size_t *sz,
 330                       size_t *max_capstrlen)
 331 {
 332   static struct r_strlenpair result;
 333   static char buf[1];
 334
 335   result.str = buf;     /* Does not really matter.  */
 336   result.len = 0;
 337
 338   *sz = 1;
 339   return &result;
 340 }
 341
 342
 343 #ifdef DL_SYSINFO_IMPLEMENTATION
 344 DL_SYSINFO_IMPLEMENTATION
 345 #endif