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 <dl-hwcap2.h>
  35 #include <unsecvars.h>
  36 #include <hp-timing.h>
  37 #include <stackinfo.h>
  38
  39 extern char *__progname;
  40 char **_dl_argv = &__progname;  /* This is checked for some error messages.  */
  41
  42 /* Name of the architecture.  */
  43 const char *_dl_platform;
  44 size_t _dl_platformlen;
  45
  46 int _dl_debug_mask;
  47 int _dl_lazy;
  48 ElfW(Addr) _dl_use_load_bias = -2;
  49 int _dl_dynamic_weak;
  50
  51 /* If nonzero print warnings about problematic situations.  */
  52 int _dl_verbose;
  53
  54 /* We never do profiling.  */
  55 const char *_dl_profile;
  56 const char *_dl_profile_output;
  57
  58 /* Names of shared object for which the RUNPATHs and RPATHs should be
  59    ignored.  */
  60 const char *_dl_inhibit_rpath;
  61
  62 /* The map for the object we will profile.  */
  63 struct link_map *_dl_profile_map;
  64
  65 /* This is the address of the last stack address ever used.  */
  66 void *__libc_stack_end;
  67
  68 /* Path where the binary is found.  */
  69 const char *_dl_origin_path;
  70
  71 /* Nonzero if runtime lookup should not update the .got/.plt.  */
  72 int _dl_bind_not;
  73
  74 /* Namespace information.  */
  75 struct link_namespaces _dl_ns[DL_NNS];
  76 size_t _dl_nns;
  77
  78 /* Incremented whenever something may have been added to dl_loaded. */
  79 unsigned long long _dl_load_adds;
  80
  81 /* Fake scope.  In dynamically linked binaries this is the scope of the
  82    main application but here we don't have something like this.  So
  83    create a fake scope containing nothing.  */
  84 struct r_scope_elem _dl_initial_searchlist;
  85
  86 #ifndef HAVE_INLINED_SYSCALLS
  87 /* Nonzero during startup.  */
  88 int _dl_starting_up = 1;
  89 #endif
  90
  91 /* Random data provided by the kernel.  */
  92 void *_dl_random;
  93
  94 /* Get architecture specific initializer.  */
  95 #include <dl-procinfo.c>
  96
  97 /* We expect less than a second for relocation.  */
  98 #ifdef HP_SMALL_TIMING_AVAIL
  99 # undef HP_TIMING_AVAIL
 100 # define HP_TIMING_AVAIL HP_SMALL_TIMING_AVAIL
 101 #endif
 102
 103 /* Initial value of the CPU clock.  */
 104 #ifndef HP_TIMING_NONAVAIL
 105 hp_timing_t _dl_cpuclock_offset;
 106 #endif
 107
 108 void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
 109
 110 size_t _dl_pagesize = EXEC_PAGESIZE;
 111
 112 int _dl_inhibit_cache;
 113
 114 unsigned int _dl_osversion;
 115
 116 /* All known directories in sorted order.  */
 117 struct r_search_path_elem *_dl_all_dirs;
 118
 119 /* All directories after startup.  */
 120 struct r_search_path_elem *_dl_init_all_dirs;
 121
 122 /* The object to be initialized first.  */
 123 struct link_map *_dl_initfirst;
 124
 125 /* Descriptor to write debug messages to.  */
 126 int _dl_debug_fd = STDERR_FILENO;
 127
 128 int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
 129
 130 ElfW(auxv_t) *_dl_auxv;
 131 const ElfW(Phdr) *_dl_phdr;
 132 size_t _dl_phnum;
 133 uint64_t _dl_hwcap __attribute__ ((nocommon));
 134
 135 #if HWCAP2_AVAIL
 136 uint64_t _dl_hwcap2 __attribute__ ((nocommon));
 137 #endif
 138
 139 /* This is not initialized to HWCAP_IMPORTANT, matching the definition
 140    of _dl_important_hwcaps, below, where no hwcap strings are ever
 141    used.  This mask is still used to mediate the lookups in the cache
 142    file.  Since there is no way to set this nonzero (we don't grok the
 143    LD_HWCAP_MASK environment variable here), there is no real point in
 144    setting _dl_hwcap nonzero below, but we do anyway.  */
 145 uint64_t _dl_hwcap_mask __attribute__ ((nocommon));
 146
 147 /* Prevailing state of the stack.  Generally this includes PF_X, indicating it's
 148  * executable but this isn't true for all platforms.  */
 149 ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
 150
 151 /* If loading a shared object requires that we make the stack executable
 152    when it was not, we do it by calling this function.
 153    It returns an errno code or zero on success.  */
 154 int (*_dl_make_stack_executable_hook) (void **) internal_function
 155   = _dl_make_stack_executable;
 156
 157
 158 /* Function in libpthread to wait for termination of lookups.  */
 159 void (*_dl_wait_lookup_done) (void);
 160
 161 struct dl_scope_free_list *_dl_scope_free_list;
 162
 163 #ifdef NEED_DL_SYSINFO
 164 /* Needed for improved syscall handling on at least x86/Linux.  */
 165 uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
 166 #endif
 167 #ifdef NEED_DL_SYSINFO_DSO
 168 /* Address of the ELF headers in the vsyscall page.  */
 169 const ElfW(Ehdr) *_dl_sysinfo_dso;
 170
 171 struct link_map *_dl_sysinfo_map;
 172
 173 # include "get-dynamic-info.h"
 174 #endif
 175 #include "setup-vdso.h"
 176
 177 /* During the program run we must not modify the global data of
 178    loaded shared object simultanously in two threads.  Therefore we
 179    protect `_dl_open' and `_dl_close' in dl-close.c.
 180
 181    This must be a recursive lock since the initializer function of
 182    the loaded object might as well require a call to this function.
 183    At this time it is not anymore a problem to modify the tables.  */
 184 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 185 /* This lock is used to keep __dl_iterate_phdr from inspecting the
 186    list of loaded objects while an object is added to or removed from
 187    that list.  */
 188 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
 189
 190
 191 #ifdef HAVE_AUX_VECTOR
 192 int _dl_clktck;
 193
 194 void
 195 internal_function
 196 _dl_aux_init (ElfW(auxv_t) *av)
 197 {
 198   int seen = 0;
 199   uid_t uid = 0;
 200   gid_t gid = 0;
 201
 202   _dl_auxv = av;
 203   for (; av->a_type != AT_NULL; ++av)
 204     switch (av->a_type)
 205       {
 206       case AT_PAGESZ:
 207         if (av->a_un.a_val != 0)
 208           GLRO(dl_pagesize) = av->a_un.a_val;
 209         break;
 210       case AT_CLKTCK:
 211         GLRO(dl_clktck) = av->a_un.a_val;
 212         break;
 213       case AT_PHDR:
 214         GL(dl_phdr) = (const void *) av->a_un.a_val;
 215         break;
 216       case AT_PHNUM:
 217         GL(dl_phnum) = av->a_un.a_val;
 218         break;
 219       case AT_HWCAP:
 220         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 221         break;
 222 #if HWCAP2_AVAIL
 223       case AT_HWCAP2:
 224         GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
 225         break;
 226 #endif
 227 #ifdef NEED_DL_SYSINFO
 228       case AT_SYSINFO:
 229         GL(dl_sysinfo) = av->a_un.a_val;
 230         break;
 231 #endif
 232 #ifdef NEED_DL_SYSINFO_DSO
 233       case AT_SYSINFO_EHDR:
 234         GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 235         break;
 236 #endif
 237       case AT_UID:
 238         uid ^= av->a_un.a_val;
 239         seen |= 1;
 240         break;
 241       case AT_EUID:
 242         uid ^= av->a_un.a_val;
 243         seen |= 2;
 244         break;
 245       case AT_GID:
 246         gid ^= av->a_un.a_val;
 247         seen |= 4;
 248         break;
 249       case AT_EGID:
 250         gid ^= av->a_un.a_val;
 251         seen |= 8;
 252         break;
 253       case AT_SECURE:
 254         seen = -1;
 255         __libc_enable_secure = av->a_un.a_val;
 256         __libc_enable_secure_decided = 1;
 257         break;
 258       case AT_RANDOM:
 259         _dl_random = (void *) av->a_un.a_val;
 260         break;
 261 # ifdef DL_PLATFORM_AUXV
 262       DL_PLATFORM_AUXV
 263 # endif
 264       }
 265   if (seen == 0xf)
 266     {
 267       __libc_enable_secure = uid != 0 || gid != 0;
 268       __libc_enable_secure_decided = 1;
 269     }
 270 }
 271 #endif
 272
 273
 274 void
 275 internal_function
 276 _dl_non_dynamic_init (void)
 277 {
 278   if (HP_TIMING_AVAIL)
 279     HP_TIMING_NOW (_dl_cpuclock_offset);
 280
 281   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 282
 283   /* Set up the data structures for the system-supplied DSO early,
 284      so they can influence _dl_init_paths.  */
 285   setup_vdso (NULL, NULL);
 286
 287   /* Initialize the data structures for the search paths for shared
 288      objects.  */
 289   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 290
 291   /* Remember the last search directory added at startup.  */
 292   _dl_init_all_dirs = GL(dl_all_dirs);
 293
 294   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 295
 296   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 297
 298   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 299
 300   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 301   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 302     _dl_profile_output
 303       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 304
 305   if (__libc_enable_secure)
 306     {
 307       static const char unsecure_envvars[] =
 308         UNSECURE_ENVVARS
 309 #ifdef EXTRA_UNSECURE_ENVVARS
 310         EXTRA_UNSECURE_ENVVARS
 311 #endif
 312         ;
 313       const char *cp = unsecure_envvars;
 314
 315       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 316         {
 317           __unsetenv (cp);
 318           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 319         }
 320
 321       if (__access ("/etc/suid-debug", F_OK) != 0)
 322         __unsetenv ("MALLOC_CHECK_");
 323     }
 324
 325 #ifdef DL_PLATFORM_INIT
 326   DL_PLATFORM_INIT;
 327 #endif
 328
 329 #ifdef DL_OSVERSION_INIT
 330   DL_OSVERSION_INIT;
 331 #endif
 332
 333   /* Now determine the length of the platform string.  */
 334   if (_dl_platform != NULL)
 335     _dl_platformlen = strlen (_dl_platform);
 336
 337   /* Scan for a program header telling us the stack is nonexecutable.  */
 338   if (_dl_phdr != NULL)
 339     for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
 340       if (_dl_phdr[i].p_type == PT_GNU_STACK)
 341         {
 342           _dl_stack_flags = _dl_phdr[i].p_flags;
 343           break;
 344         }
 345 }
 346
 347 #ifdef DL_SYSINFO_IMPLEMENTATION
 348 DL_SYSINFO_IMPLEMENTATION
 349 #endif