elf/dl-support.c

   1 /* Support for dynamic linking code in static libc.
   2    Copyright (C) 1996-2015 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 <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 /* A dummy link map for the executable, used by dlopen to access the global
  74    scope.  We don't export any symbols ourselves, so this can be minimal.  */
  75 static struct link_map _dl_main_map =
  76   {
  77     .l_name = (char *) "",
  78     .l_real = &_dl_main_map,
  79     .l_ns = LM_ID_BASE,
  80     .l_libname = &(struct libname_list) { .name = "", .dont_free = 1 },
  81     .l_searchlist =
  82       {
  83         .r_list = &(struct link_map *) { &_dl_main_map },
  84         .r_nlist = 1,
  85       },
  86     .l_symbolic_searchlist = { .r_list = &(struct link_map *) { NULL } },
  87     .l_type = lt_executable,
  88     .l_scope_mem = { &_dl_main_map.l_searchlist },
  89     .l_scope_max = (sizeof (_dl_main_map.l_scope_mem)
  90                     / sizeof (_dl_main_map.l_scope_mem[0])),
  91     .l_scope = _dl_main_map.l_scope_mem,
  92     .l_local_scope = { &_dl_main_map.l_searchlist },
  93     .l_used = 1,
  94     .l_tls_offset = NO_TLS_OFFSET,
  95     .l_serial = 1,
  96   };
  97
  98 /* Namespace information.  */
  99 struct link_namespaces _dl_ns[DL_NNS] =
 100   {
 101     [LM_ID_BASE] =
 102       {
 103         ._ns_loaded = &_dl_main_map,
 104         ._ns_nloaded = 1,
 105         ._ns_main_searchlist = &_dl_main_map.l_searchlist,
 106       }
 107   };
 108 size_t _dl_nns = 1;
 109
 110 /* Incremented whenever something may have been added to dl_loaded. */
 111 unsigned long long _dl_load_adds = 1;
 112
 113 /* Fake scope of the main application.  */
 114 struct r_scope_elem _dl_initial_searchlist =
 115   {
 116     .r_list = &(struct link_map *) { &_dl_main_map },
 117     .r_nlist = 1,
 118   };
 119
 120 #ifndef HAVE_INLINED_SYSCALLS
 121 /* Nonzero during startup.  */
 122 int _dl_starting_up = 1;
 123 #endif
 124
 125 /* Random data provided by the kernel.  */
 126 void *_dl_random;
 127
 128 /* Get architecture specific initializer.  */
 129 #include <dl-procinfo.c>
 130
 131 /* Initial value of the CPU clock.  */
 132 #ifndef HP_TIMING_NONAVAIL
 133 hp_timing_t _dl_cpuclock_offset;
 134 #endif
 135
 136 void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
 137
 138 size_t _dl_pagesize = EXEC_PAGESIZE;
 139
 140 int _dl_inhibit_cache;
 141
 142 unsigned int _dl_osversion;
 143
 144 /* All known directories in sorted order.  */
 145 struct r_search_path_elem *_dl_all_dirs;
 146
 147 /* All directories after startup.  */
 148 struct r_search_path_elem *_dl_init_all_dirs;
 149
 150 /* The object to be initialized first.  */
 151 struct link_map *_dl_initfirst;
 152
 153 /* Descriptor to write debug messages to.  */
 154 int _dl_debug_fd = STDERR_FILENO;
 155
 156 int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
 157
 158 ElfW(auxv_t) *_dl_auxv;
 159 const ElfW(Phdr) *_dl_phdr;
 160 size_t _dl_phnum;
 161 uint64_t _dl_hwcap __attribute__ ((nocommon));
 162 uint64_t _dl_hwcap2 __attribute__ ((nocommon));
 163
 164 /* The value of the FPU control word the kernel will preset in hardware.  */
 165 fpu_control_t _dl_fpu_control = _FPU_DEFAULT;
 166
 167 /* This is not initialized to HWCAP_IMPORTANT, matching the definition
 168    of _dl_important_hwcaps, below, where no hwcap strings are ever
 169    used.  This mask is still used to mediate the lookups in the cache
 170    file.  Since there is no way to set this nonzero (we don't grok the
 171    LD_HWCAP_MASK environment variable here), there is no real point in
 172    setting _dl_hwcap nonzero below, but we do anyway.  */
 173 uint64_t _dl_hwcap_mask __attribute__ ((nocommon));
 174
 175 /* Prevailing state of the stack.  Generally this includes PF_X, indicating it's
 176  * executable but this isn't true for all platforms.  */
 177 ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
 178
 179 /* If loading a shared object requires that we make the stack executable
 180    when it was not, we do it by calling this function.
 181    It returns an errno code or zero on success.  */
 182 int (*_dl_make_stack_executable_hook) (void **) internal_function
 183   = _dl_make_stack_executable;
 184
 185
 186 /* Function in libpthread to wait for termination of lookups.  */
 187 void (*_dl_wait_lookup_done) (void);
 188
 189 struct dl_scope_free_list *_dl_scope_free_list;
 190
 191 #ifdef NEED_DL_SYSINFO
 192 /* Needed for improved syscall handling on at least x86/Linux.  */
 193 uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
 194 #endif
 195 #ifdef NEED_DL_SYSINFO_DSO
 196 /* Address of the ELF headers in the vsyscall page.  */
 197 const ElfW(Ehdr) *_dl_sysinfo_dso;
 198
 199 struct link_map *_dl_sysinfo_map;
 200
 201 # include "get-dynamic-info.h"
 202 #endif
 203 #include "setup-vdso.h"
 204
 205 /* During the program run we must not modify the global data of
 206    loaded shared object simultanously in two threads.  Therefore we
 207    protect `_dl_open' and `_dl_close' in dl-close.c.
 208
 209    This must be a recursive lock since the initializer function of
 210    the loaded object might as well require a call to this function.
 211    At this time it is not anymore a problem to modify the tables.  */
 212 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 213 /* This lock is used to keep __dl_iterate_phdr from inspecting the
 214    list of loaded objects while an object is added to or removed from
 215    that list.  */
 216 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
 217
 218
 219 #ifdef HAVE_AUX_VECTOR
 220 int _dl_clktck;
 221
 222 void
 223 internal_function
 224 _dl_aux_init (ElfW(auxv_t) *av)
 225 {
 226   int seen = 0;
 227   uid_t uid = 0;
 228   gid_t gid = 0;
 229
 230   _dl_auxv = av;
 231   for (; av->a_type != AT_NULL; ++av)
 232     switch (av->a_type)
 233       {
 234       case AT_PAGESZ:
 235         if (av->a_un.a_val != 0)
 236           GLRO(dl_pagesize) = av->a_un.a_val;
 237         break;
 238       case AT_CLKTCK:
 239         GLRO(dl_clktck) = av->a_un.a_val;
 240         break;
 241       case AT_PHDR:
 242         GL(dl_phdr) = (const void *) av->a_un.a_val;
 243         break;
 244       case AT_PHNUM:
 245         GL(dl_phnum) = av->a_un.a_val;
 246         break;
 247       case AT_HWCAP:
 248         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 249         break;
 250       case AT_HWCAP2:
 251         GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
 252         break;
 253       case AT_FPUCW:
 254         GLRO(dl_fpu_control) = av->a_un.a_val;
 255         break;
 256 #ifdef NEED_DL_SYSINFO
 257       case AT_SYSINFO:
 258         GL(dl_sysinfo) = av->a_un.a_val;
 259         break;
 260 #endif
 261 #ifdef NEED_DL_SYSINFO_DSO
 262       case AT_SYSINFO_EHDR:
 263         GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 264         break;
 265 #endif
 266       case AT_UID:
 267         uid ^= av->a_un.a_val;
 268         seen |= 1;
 269         break;
 270       case AT_EUID:
 271         uid ^= av->a_un.a_val;
 272         seen |= 2;
 273         break;
 274       case AT_GID:
 275         gid ^= av->a_un.a_val;
 276         seen |= 4;
 277         break;
 278       case AT_EGID:
 279         gid ^= av->a_un.a_val;
 280         seen |= 8;
 281         break;
 282       case AT_SECURE:
 283         seen = -1;
 284         __libc_enable_secure = av->a_un.a_val;
 285         __libc_enable_secure_decided = 1;
 286         break;
 287       case AT_RANDOM:
 288         _dl_random = (void *) av->a_un.a_val;
 289         break;
 290 # ifdef DL_PLATFORM_AUXV
 291       DL_PLATFORM_AUXV
 292 # endif
 293       }
 294   if (seen == 0xf)
 295     {
 296       __libc_enable_secure = uid != 0 || gid != 0;
 297       __libc_enable_secure_decided = 1;
 298     }
 299 }
 300 #endif
 301
 302
 303 void
 304 internal_function
 305 _dl_non_dynamic_init (void)
 306 {
 307   _dl_main_map.l_origin = _dl_get_origin ();
 308   _dl_main_map.l_phdr = GL(dl_phdr);
 309   _dl_main_map.l_phnum = GL(dl_phnum);
 310
 311   if (HP_SMALL_TIMING_AVAIL)
 312     HP_TIMING_NOW (_dl_cpuclock_offset);
 313
 314   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 315
 316   /* Set up the data structures for the system-supplied DSO early,
 317      so they can influence _dl_init_paths.  */
 318   setup_vdso (NULL, NULL);
 319
 320   /* Initialize the data structures for the search paths for shared
 321      objects.  */
 322   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 323
 324   /* Remember the last search directory added at startup.  */
 325   _dl_init_all_dirs = GL(dl_all_dirs);
 326
 327   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 328
 329   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 330
 331   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 332
 333   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 334   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 335     _dl_profile_output
 336       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 337
 338   if (__libc_enable_secure)
 339     {
 340       static const char unsecure_envvars[] =
 341         UNSECURE_ENVVARS
 342 #ifdef EXTRA_UNSECURE_ENVVARS
 343         EXTRA_UNSECURE_ENVVARS
 344 #endif
 345         ;
 346       const char *cp = unsecure_envvars;
 347
 348       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 349         {
 350           __unsetenv (cp);
 351           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 352         }
 353
 354       if (__access ("/etc/suid-debug", F_OK) != 0)
 355         __unsetenv ("MALLOC_CHECK_");
 356     }
 357
 358 #ifdef DL_PLATFORM_INIT
 359   DL_PLATFORM_INIT;
 360 #endif
 361
 362 #ifdef DL_OSVERSION_INIT
 363   DL_OSVERSION_INIT;
 364 #endif
 365
 366   /* Now determine the length of the platform string.  */
 367   if (_dl_platform != NULL)
 368     _dl_platformlen = strlen (_dl_platform);
 369
 370   /* Scan for a program header telling us the stack is nonexecutable.  */
 371   if (_dl_phdr != NULL)
 372     for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
 373       if (_dl_phdr[i].p_type == PT_GNU_STACK)
 374         {
 375           _dl_stack_flags = _dl_phdr[i].p_flags;
 376           break;
 377         }
 378 }
 379
 380 #ifdef DL_SYSINFO_IMPLEMENTATION
 381 DL_SYSINFO_IMPLEMENTATION
 382 #endif