elf/dl-support.c

   1 /* Support for dynamic linking code in static libc.
   2    Copyright (C) 1996-2008,2009,2010 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 #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;
 109
 110 unsigned int _dl_osversion;
 111
 112 /* All known directories in sorted order.  */
 113 struct r_search_path_elem *_dl_all_dirs;
 114
 115 /* All directories after startup.  */
 116 struct r_search_path_elem *_dl_init_all_dirs;
 117
 118 /* The object to be initialized first.  */
 119 struct link_map *_dl_initfirst;
 120
 121 /* Descriptor to write debug messages to.  */
 122 int _dl_debug_fd = STDERR_FILENO;
 123
 124 int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
 125
 126 ElfW(Phdr) *_dl_phdr;
 127 size_t _dl_phnum;
 128 uint64_t _dl_hwcap __attribute__ ((nocommon));
 129
 130 /* This is not initialized to HWCAP_IMPORTANT, matching the definition
 131    of _dl_important_hwcaps, below, where no hwcap strings are ever
 132    used.  This mask is still used to mediate the lookups in the cache
 133    file.  Since there is no way to set this nonzero (we don't grok the
 134    LD_HWCAP_MASK environment variable here), there is no real point in
 135    setting _dl_hwcap nonzero below, but we do anyway.  */
 136 uint64_t _dl_hwcap_mask __attribute__ ((nocommon));
 137
 138 /* Prevailing state of the stack.  Generally this includes PF_X, indicating it's
 139  * executable but this isn't true for all platforms.  */
 140 ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
 141
 142 /* If loading a shared object requires that we make the stack executable
 143    when it was not, we do it by calling this function.
 144    It returns an errno code or zero on success.  */
 145 int (*_dl_make_stack_executable_hook) (void **) internal_function
 146   = _dl_make_stack_executable;
 147
 148
 149 /* Function in libpthread to wait for termination of lookups.  */
 150 void (*_dl_wait_lookup_done) (void);
 151
 152 struct dl_scope_free_list *_dl_scope_free_list;
 153
 154 #ifdef NEED_DL_SYSINFO
 155 /* Needed for improved syscall handling on at least x86/Linux.  */
 156 uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
 157 #endif
 158 #if defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO
 159 /* Address of the ELF headers in the vsyscall page.  */
 160 const ElfW(Ehdr) *_dl_sysinfo_dso;
 161 #endif
 162
 163 /* During the program run we must not modify the global data of
 164    loaded shared object simultanously in two threads.  Therefore we
 165    protect `_dl_open' and `_dl_close' in dl-close.c.
 166
 167    This must be a recursive lock since the initializer function of
 168    the loaded object might as well require a call to this function.
 169    At this time it is not anymore a problem to modify the tables.  */
 170 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 171 /* This lock is used to keep __dl_iterate_phdr from inspecting the
 172    list of loaded objects while an object is added to or removed from
 173    that list.  */
 174 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
 175
 176
 177 #ifdef HAVE_AUX_VECTOR
 178 int _dl_clktck;
 179
 180 void
 181 internal_function
 182 _dl_aux_init (ElfW(auxv_t) *av)
 183 {
 184   int seen = 0;
 185   uid_t uid = 0;
 186   gid_t gid = 0;
 187
 188   for (; av->a_type != AT_NULL; ++av)
 189     switch (av->a_type)
 190       {
 191       case AT_PAGESZ:
 192         GLRO(dl_pagesize) = av->a_un.a_val;
 193         break;
 194       case AT_CLKTCK:
 195         GLRO(dl_clktck) = av->a_un.a_val;
 196         break;
 197       case AT_PHDR:
 198         GL(dl_phdr) = (void *) av->a_un.a_val;
 199         break;
 200       case AT_PHNUM:
 201         GL(dl_phnum) = av->a_un.a_val;
 202         break;
 203       case AT_HWCAP:
 204         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 205         break;
 206 #ifdef NEED_DL_SYSINFO
 207       case AT_SYSINFO:
 208         GL(dl_sysinfo) = av->a_un.a_val;
 209         break;
 210 #endif
 211 #if defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO
 212       case AT_SYSINFO_EHDR:
 213         GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 214         break;
 215 #endif
 216       case AT_UID:
 217         uid ^= av->a_un.a_val;
 218         seen |= 1;
 219         break;
 220       case AT_EUID:
 221         uid ^= av->a_un.a_val;
 222         seen |= 2;
 223         break;
 224       case AT_GID:
 225         gid ^= av->a_un.a_val;
 226         seen |= 4;
 227         break;
 228       case AT_EGID:
 229         gid ^= av->a_un.a_val;
 230         seen |= 8;
 231         break;
 232       case AT_SECURE:
 233         seen = -1;
 234         __libc_enable_secure = av->a_un.a_val;
 235         __libc_enable_secure_decided = 1;
 236         break;
 237       case AT_RANDOM:
 238         _dl_random = (void *) av->a_un.a_val;
 239         break;
 240 # ifdef DL_PLATFORM_AUXV
 241       DL_PLATFORM_AUXV
 242 # endif
 243       }
 244   if (seen == 0xf)
 245     {
 246       __libc_enable_secure = uid != 0 || gid != 0;
 247       __libc_enable_secure_decided = 1;
 248     }
 249 }
 250 #endif
 251
 252
 253 void
 254 internal_function
 255 _dl_non_dynamic_init (void)
 256 {
 257   if (HP_TIMING_AVAIL)
 258     HP_TIMING_NOW (_dl_cpuclock_offset);
 259
 260   if (!_dl_pagesize)
 261     _dl_pagesize = __getpagesize ();
 262
 263   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 264
 265   /* Initialize the data structures for the search paths for shared
 266      objects.  */
 267   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 268
 269   /* Remember the last search directory added at startup.  */
 270   _dl_init_all_dirs = GL(dl_all_dirs);
 271
 272   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 273
 274   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 275
 276   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 277
 278   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 279   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 280     _dl_profile_output
 281       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 282
 283   if (__libc_enable_secure)
 284     {
 285       static const char unsecure_envvars[] =
 286         UNSECURE_ENVVARS
 287 #ifdef EXTRA_UNSECURE_ENVVARS
 288         EXTRA_UNSECURE_ENVVARS
 289 #endif
 290         ;
 291       const char *cp = unsecure_envvars;
 292
 293       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 294         {
 295           __unsetenv (cp);
 296           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 297         }
 298
 299       if (__access ("/etc/suid-debug", F_OK) != 0)
 300         __unsetenv ("MALLOC_CHECK_");
 301     }
 302
 303 #ifdef DL_PLATFORM_INIT
 304   DL_PLATFORM_INIT;
 305 #endif
 306
 307 #ifdef DL_OSVERSION_INIT
 308   DL_OSVERSION_INIT;
 309 #endif
 310
 311   /* Now determine the length of the platform string.  */
 312   if (_dl_platform != NULL)
 313     _dl_platformlen = strlen (_dl_platform);
 314
 315   /* Scan for a program header telling us the stack is nonexecutable.  */
 316   if (_dl_phdr != NULL)
 317     for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
 318       if (_dl_phdr[i].p_type == PT_GNU_STACK)
 319         {
 320           _dl_stack_flags = _dl_phdr[i].p_flags;
 321           break;
 322         }
 323 }
 324
 325
 326 const struct r_strlenpair *
 327 internal_function
 328 _dl_important_hwcaps (const char *platform, size_t platform_len, size_t *sz,
 329                       size_t *max_capstrlen)
 330 {
 331   static struct r_strlenpair result;
 332   static char buf[1];
 333
 334   result.str = buf;     /* Does not really matter.  */
 335   result.len = 0;
 336
 337   *sz = 1;
 338   return &result;
 339 }
 340
 341
 342 #ifdef DL_SYSINFO_IMPLEMENTATION
 343 DL_SYSINFO_IMPLEMENTATION
 344 #endif