elf/dl-support.c

   1 /* Support for dynamic linking code in static libc.
   2    Copyright (C) 1996-2017 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 #if !HAVE_TUNABLES
 168 /* This is not initialized to HWCAP_IMPORTANT, matching the definition
 169    of _dl_important_hwcaps, below, where no hwcap strings are ever
 170    used.  This mask is still used to mediate the lookups in the cache
 171    file.  Since there is no way to set this nonzero (we don't grok the
 172    LD_HWCAP_MASK environment variable here), there is no real point in
 173    setting _dl_hwcap nonzero below, but we do anyway.  */
 174 uint64_t _dl_hwcap_mask __attribute__ ((nocommon));
 175 #endif
 176
 177 /* Prevailing state of the stack.  Generally this includes PF_X, indicating it's
 178  * executable but this isn't true for all platforms.  */
 179 ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
 180
 181 /* If loading a shared object requires that we make the stack executable
 182    when it was not, we do it by calling this function.
 183    It returns an errno code or zero on success.  */
 184 int (*_dl_make_stack_executable_hook) (void **) internal_function
 185   = _dl_make_stack_executable;
 186
 187
 188 /* Function in libpthread to wait for termination of lookups.  */
 189 void (*_dl_wait_lookup_done) (void);
 190
 191 struct dl_scope_free_list *_dl_scope_free_list;
 192
 193 #ifdef NEED_DL_SYSINFO
 194 /* Needed for improved syscall handling on at least x86/Linux.  */
 195 uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
 196 #endif
 197 #ifdef NEED_DL_SYSINFO_DSO
 198 /* Address of the ELF headers in the vsyscall page.  */
 199 const ElfW(Ehdr) *_dl_sysinfo_dso;
 200
 201 struct link_map *_dl_sysinfo_map;
 202
 203 # include "get-dynamic-info.h"
 204 #endif
 205 #include "setup-vdso.h"
 206
 207 /* During the program run we must not modify the global data of
 208    loaded shared object simultanously in two threads.  Therefore we
 209    protect `_dl_open' and `_dl_close' in dl-close.c.
 210
 211    This must be a recursive lock since the initializer function of
 212    the loaded object might as well require a call to this function.
 213    At this time it is not anymore a problem to modify the tables.  */
 214 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 215 /* This lock is used to keep __dl_iterate_phdr from inspecting the
 216    list of loaded objects while an object is added to or removed from
 217    that list.  */
 218 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
 219
 220
 221 #ifdef HAVE_AUX_VECTOR
 222 int _dl_clktck;
 223
 224 void
 225 internal_function
 226 _dl_aux_init (ElfW(auxv_t) *av)
 227 {
 228   int seen = 0;
 229   uid_t uid = 0;
 230   gid_t gid = 0;
 231
 232   _dl_auxv = av;
 233   for (; av->a_type != AT_NULL; ++av)
 234     switch (av->a_type)
 235       {
 236       case AT_PAGESZ:
 237         if (av->a_un.a_val != 0)
 238           GLRO(dl_pagesize) = av->a_un.a_val;
 239         break;
 240       case AT_CLKTCK:
 241         GLRO(dl_clktck) = av->a_un.a_val;
 242         break;
 243       case AT_PHDR:
 244         GL(dl_phdr) = (const void *) av->a_un.a_val;
 245         break;
 246       case AT_PHNUM:
 247         GL(dl_phnum) = av->a_un.a_val;
 248         break;
 249       case AT_PLATFORM:
 250         GLRO(dl_platform) = (void *) av->a_un.a_val;
 251         break;
 252       case AT_HWCAP:
 253         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 254         break;
 255       case AT_HWCAP2:
 256         GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
 257         break;
 258       case AT_FPUCW:
 259         GLRO(dl_fpu_control) = av->a_un.a_val;
 260         break;
 261 #ifdef NEED_DL_SYSINFO
 262       case AT_SYSINFO:
 263         GL(dl_sysinfo) = av->a_un.a_val;
 264         break;
 265 #endif
 266 #ifdef NEED_DL_SYSINFO_DSO
 267       case AT_SYSINFO_EHDR:
 268         GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 269         break;
 270 #endif
 271       case AT_UID:
 272         uid ^= av->a_un.a_val;
 273         seen |= 1;
 274         break;
 275       case AT_EUID:
 276         uid ^= av->a_un.a_val;
 277         seen |= 2;
 278         break;
 279       case AT_GID:
 280         gid ^= av->a_un.a_val;
 281         seen |= 4;
 282         break;
 283       case AT_EGID:
 284         gid ^= av->a_un.a_val;
 285         seen |= 8;
 286         break;
 287       case AT_SECURE:
 288         seen = -1;
 289         __libc_enable_secure = av->a_un.a_val;
 290         __libc_enable_secure_decided = 1;
 291         break;
 292       case AT_RANDOM:
 293         _dl_random = (void *) av->a_un.a_val;
 294         break;
 295 # ifdef DL_PLATFORM_AUXV
 296       DL_PLATFORM_AUXV
 297 # endif
 298       }
 299   if (seen == 0xf)
 300     {
 301       __libc_enable_secure = uid != 0 || gid != 0;
 302       __libc_enable_secure_decided = 1;
 303     }
 304 }
 305 #endif
 306
 307
 308 void
 309 internal_function
 310 _dl_non_dynamic_init (void)
 311 {
 312   _dl_main_map.l_origin = _dl_get_origin ();
 313   _dl_main_map.l_phdr = GL(dl_phdr);
 314   _dl_main_map.l_phnum = GL(dl_phnum);
 315
 316   if (HP_SMALL_TIMING_AVAIL)
 317     HP_TIMING_NOW (_dl_cpuclock_offset);
 318
 319   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 320
 321   /* Set up the data structures for the system-supplied DSO early,
 322      so they can influence _dl_init_paths.  */
 323   setup_vdso (NULL, NULL);
 324
 325   /* Initialize the data structures for the search paths for shared
 326      objects.  */
 327   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 328
 329   /* Remember the last search directory added at startup.  */
 330   _dl_init_all_dirs = GL(dl_all_dirs);
 331
 332   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 333
 334   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 335
 336   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 337
 338   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 339   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 340     _dl_profile_output
 341       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 342
 343   if (__libc_enable_secure)
 344     {
 345       static const char unsecure_envvars[] =
 346         UNSECURE_ENVVARS
 347 #ifdef EXTRA_UNSECURE_ENVVARS
 348         EXTRA_UNSECURE_ENVVARS
 349 #endif
 350         ;
 351       const char *cp = unsecure_envvars;
 352
 353       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 354         {
 355           __unsetenv (cp);
 356           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 357         }
 358
 359 #if !HAVE_TUNABLES
 360       if (__access ("/etc/suid-debug", F_OK) != 0)
 361         __unsetenv ("MALLOC_CHECK_");
 362 #endif
 363     }
 364
 365 #ifdef DL_PLATFORM_INIT
 366   DL_PLATFORM_INIT;
 367 #endif
 368
 369 #ifdef DL_OSVERSION_INIT
 370   DL_OSVERSION_INIT;
 371 #endif
 372
 373   /* Now determine the length of the platform string.  */
 374   if (_dl_platform != NULL)
 375     _dl_platformlen = strlen (_dl_platform);
 376
 377   /* Scan for a program header telling us the stack is nonexecutable.  */
 378   if (_dl_phdr != NULL)
 379     for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
 380       if (_dl_phdr[i].p_type == PT_GNU_STACK)
 381         {
 382           _dl_stack_flags = _dl_phdr[i].p_flags;
 383           break;
 384         }
 385 }
 386
 387 #ifdef DL_SYSINFO_IMPLEMENTATION
 388 DL_SYSINFO_IMPLEMENTATION
 389 #endif