elf/dl-support.c

   1 /* Support for dynamic linking code in static libc.
   2    Copyright (C) 1996-2005, 2006, 2007 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 <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
  36 extern char *__progname;
  37 char **_dl_argv = &__progname;  /* This is checked for some error messages.  */
  38
  39 /* Name of the architecture.  */
  40 const char *_dl_platform;
  41 size_t _dl_platformlen;
  42
  43 int _dl_debug_mask;
  44 int _dl_lazy;
  45 ElfW(Addr) _dl_use_load_bias = -2;
  46 int _dl_dynamic_weak;
  47
  48 /* If nonzero print warnings about problematic situations.  */
  49 int _dl_verbose;
  50
  51 /* We never do profiling.  */
  52 const char *_dl_profile;
  53 const char *_dl_profile_output;
  54
  55 /* Names of shared object for which the RUNPATHs and RPATHs should be
  56    ignored.  */
  57 const char *_dl_inhibit_rpath;
  58
  59 /* The map for the object we will profile.  */
  60 struct link_map *_dl_profile_map;
  61
  62 /* This is the address of the last stack address ever used.  */
  63 void *__libc_stack_end;
  64
  65 /* Path where the binary is found.  */
  66 const char *_dl_origin_path;
  67
  68 /* Nonzero if runtime lookup should not update the .got/.plt.  */
  69 int _dl_bind_not;
  70
  71 /* Namespace information.  */
  72 struct link_namespaces _dl_ns[DL_NNS];
  73
  74 /* Incremented whenever something may have been added to dl_loaded. */
  75 unsigned long long _dl_load_adds;
  76
  77 /* Fake scope.  In dynamically linked binaries this is the scope of the
  78    main application but here we don't have something like this.  So
  79    create a fake scope containing nothing.  */
  80 struct r_scope_elem _dl_initial_searchlist;
  81
  82 #ifndef HAVE_INLINED_SYSCALLS
  83 /* Nonzero during startup.  */
  84 int _dl_starting_up = 1;
  85 #endif
  86
  87 /* Get architecture specific initializer.  */
  88 #include <dl-procinfo.c>
  89
  90 /* We expect less than a second for relocation.  */
  91 #ifdef HP_SMALL_TIMING_AVAIL
  92 # undef HP_TIMING_AVAIL
  93 # define HP_TIMING_AVAIL HP_SMALL_TIMING_AVAIL
  94 #endif
  95
  96 /* Initial value of the CPU clock.  */
  97 #ifndef HP_TIMING_NONAVAIL
  98 hp_timing_t _dl_cpuclock_offset;
  99 #endif
 100
 101 #ifdef USE_TLS
 102 void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
 103 #endif
 104
 105 size_t _dl_pagesize;
 106
 107 unsigned int _dl_osversion;
 108
 109 /* All known directories in sorted order.  */
 110 struct r_search_path_elem *_dl_all_dirs;
 111
 112 /* All directories after startup.  */
 113 struct r_search_path_elem *_dl_init_all_dirs;
 114
 115 /* The object to be initialized first.  */
 116 struct link_map *_dl_initfirst;
 117
 118 /* Descriptor to write debug messages to.  */
 119 int _dl_debug_fd = STDERR_FILENO;
 120
 121 int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
 122
 123 ElfW(Phdr) *_dl_phdr;
 124 size_t _dl_phnum;
 125 uint64_t _dl_hwcap __attribute__ ((nocommon));
 126
 127 /* Prevailing state of the stack, PF_X indicating it's executable.  */
 128 ElfW(Word) _dl_stack_flags = PF_R|PF_W|PF_X;
 129
 130 /* If loading a shared object requires that we make the stack executable
 131    when it was not, we do it by calling this function.
 132    It returns an errno code or zero on success.  */
 133 int (*_dl_make_stack_executable_hook) (void **) internal_function
 134   = _dl_make_stack_executable;
 135
 136
 137 /* Function in libpthread to wait for termination of lookups.  */
 138 void (*_dl_wait_lookup_done) (void);
 139
 140 struct dl_scope_free_list *_dl_scope_free_list;
 141
 142 #ifdef NEED_DL_SYSINFO
 143 /* Needed for improved syscall handling on at least x86/Linux.  */
 144 uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
 145 #endif
 146 #if defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO
 147 /* Address of the ELF headers in the vsyscall page.  */
 148 const ElfW(Ehdr) *_dl_sysinfo_dso;
 149 #endif
 150
 151 /* During the program run we must not modify the global data of
 152    loaded shared object simultanously in two threads.  Therefore we
 153    protect `_dl_open' and `_dl_close' in dl-close.c.
 154
 155    This must be a recursive lock since the initializer function of
 156    the loaded object might as well require a call to this function.
 157    At this time it is not anymore a problem to modify the tables.  */
 158 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 159
 160
 161 #ifdef HAVE_AUX_VECTOR
 162 int _dl_clktck;
 163
 164 void
 165 internal_function
 166 _dl_aux_init (ElfW(auxv_t) *av)
 167 {
 168   int seen = 0;
 169   uid_t uid = 0;
 170   gid_t gid = 0;
 171
 172   for (; av->a_type != AT_NULL; ++av)
 173     switch (av->a_type)
 174       {
 175       case AT_PAGESZ:
 176         GLRO(dl_pagesize) = av->a_un.a_val;
 177         break;
 178       case AT_CLKTCK:
 179         GLRO(dl_clktck) = av->a_un.a_val;
 180         break;
 181       case AT_PHDR:
 182         GL(dl_phdr) = (void *) av->a_un.a_val;
 183         break;
 184       case AT_PHNUM:
 185         GL(dl_phnum) = av->a_un.a_val;
 186         break;
 187       case AT_HWCAP:
 188         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 189         break;
 190 #ifdef NEED_DL_SYSINFO
 191       case AT_SYSINFO:
 192         GL(dl_sysinfo) = av->a_un.a_val;
 193         break;
 194 #endif
 195 #if defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO
 196       case AT_SYSINFO_EHDR:
 197         GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 198         break;
 199 #endif
 200       case AT_UID:
 201         uid ^= av->a_un.a_val;
 202         seen |= 1;
 203         break;
 204       case AT_EUID:
 205         uid ^= av->a_un.a_val;
 206         seen |= 2;
 207         break;
 208       case AT_GID:
 209         gid ^= av->a_un.a_val;
 210         seen |= 4;
 211         break;
 212       case AT_EGID:
 213         gid ^= av->a_un.a_val;
 214         seen |= 8;
 215         break;
 216       case AT_SECURE:
 217         seen = -1;
 218         __libc_enable_secure = av->a_un.a_val;
 219         __libc_enable_secure_decided = 1;
 220         break;
 221       }
 222   if (seen == 0xf)
 223     {
 224       __libc_enable_secure = uid != 0 || gid != 0;
 225       __libc_enable_secure_decided = 1;
 226     }
 227 }
 228 #endif
 229
 230
 231 void
 232 internal_function
 233 _dl_non_dynamic_init (void)
 234 {
 235   if (HP_TIMING_AVAIL)
 236     HP_TIMING_NOW (_dl_cpuclock_offset);
 237
 238   if (!_dl_pagesize)
 239     _dl_pagesize = __getpagesize ();
 240
 241   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 242
 243   /* Initialize the data structures for the search paths for shared
 244      objects.  */
 245   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 246
 247   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 248
 249   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 250
 251   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 252
 253   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 254   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 255     _dl_profile_output
 256       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 257
 258   if (__libc_enable_secure)
 259     {
 260       static const char unsecure_envvars[] =
 261         UNSECURE_ENVVARS
 262 #ifdef EXTRA_UNSECURE_ENVVARS
 263         EXTRA_UNSECURE_ENVVARS
 264 #endif
 265         ;
 266       const char *cp = unsecure_envvars;
 267
 268       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 269         {
 270           __unsetenv (cp);
 271           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 272         }
 273
 274       if (__access ("/etc/suid-debug", F_OK) != 0)
 275         __unsetenv ("MALLOC_CHECK_");
 276     }
 277
 278 #ifdef DL_PLATFORM_INIT
 279   DL_PLATFORM_INIT;
 280 #endif
 281
 282 #ifdef DL_OSVERSION_INIT
 283   DL_OSVERSION_INIT;
 284 #endif
 285
 286   /* Now determine the length of the platform string.  */
 287   if (_dl_platform != NULL)
 288     _dl_platformlen = strlen (_dl_platform);
 289
 290   /* Scan for a program header telling us the stack is nonexecutable.  */
 291   if (_dl_phdr != NULL)
 292     for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
 293       if (_dl_phdr[i].p_type == PT_GNU_STACK)
 294         {
 295           _dl_stack_flags = _dl_phdr[i].p_flags;
 296           break;
 297         }
 298 }
 299
 300
 301 const struct r_strlenpair *
 302 internal_function
 303 _dl_important_hwcaps (const char *platform, size_t platform_len, size_t *sz,
 304                       size_t *max_capstrlen)
 305 {
 306   static struct r_strlenpair result;
 307   static char buf[1];
 308
 309   result.str = buf;     /* Does not really matter.  */
 310   result.len = 0;
 311
 312   *sz = 1;
 313   return &result;
 314 }
 315
 316
 317 #ifdef DL_SYSINFO_IMPLEMENTATION
 318 DL_SYSINFO_IMPLEMENTATION
 319 #endif