elf/dl-support.c

   1 /* Support for dynamic linking code in static libc.
   2    Copyright (C) 1996-2019 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-procruntime.c>
 130 #include <dl-procinfo.c>
 131
 132 void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
 133
 134 size_t _dl_pagesize = EXEC_PAGESIZE;
 135
 136 int _dl_inhibit_cache;
 137
 138 unsigned int _dl_osversion;
 139
 140 /* All known directories in sorted order.  */
 141 struct r_search_path_elem *_dl_all_dirs;
 142
 143 /* All directories after startup.  */
 144 struct r_search_path_elem *_dl_init_all_dirs;
 145
 146 /* The object to be initialized first.  */
 147 struct link_map *_dl_initfirst;
 148
 149 /* Descriptor to write debug messages to.  */
 150 int _dl_debug_fd = STDERR_FILENO;
 151
 152 int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
 153
 154 ElfW(auxv_t) *_dl_auxv;
 155 const ElfW(Phdr) *_dl_phdr;
 156 size_t _dl_phnum;
 157 uint64_t _dl_hwcap __attribute__ ((nocommon));
 158 uint64_t _dl_hwcap2 __attribute__ ((nocommon));
 159
 160 /* The value of the FPU control word the kernel will preset in hardware.  */
 161 fpu_control_t _dl_fpu_control = _FPU_DEFAULT;
 162
 163 #if !HAVE_TUNABLES
 164 /* This is not initialized to HWCAP_IMPORTANT, matching the definition
 165    of _dl_important_hwcaps, below, where no hwcap strings are ever
 166    used.  This mask is still used to mediate the lookups in the cache
 167    file.  Since there is no way to set this nonzero (we don't grok the
 168    LD_HWCAP_MASK environment variable here), there is no real point in
 169    setting _dl_hwcap nonzero below, but we do anyway.  */
 170 uint64_t _dl_hwcap_mask __attribute__ ((nocommon));
 171 #endif
 172
 173 /* Prevailing state of the stack.  Generally this includes PF_X, indicating it's
 174  * executable but this isn't true for all platforms.  */
 175 ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
 176
 177 /* If loading a shared object requires that we make the stack executable
 178    when it was not, we do it by calling this function.
 179    It returns an errno code or zero on success.  */
 180 int (*_dl_make_stack_executable_hook) (void **) = _dl_make_stack_executable;
 181
 182
 183 /* Function in libpthread to wait for termination of lookups.  */
 184 void (*_dl_wait_lookup_done) (void);
 185
 186 #if !THREAD_GSCOPE_IN_TCB
 187 int _dl_thread_gscope_count;
 188 #endif
 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 _dl_aux_init (ElfW(auxv_t) *av)
 224 {
 225   int seen = 0;
 226   uid_t uid = 0;
 227   gid_t gid = 0;
 228
 229   _dl_auxv = av;
 230   for (; av->a_type != AT_NULL; ++av)
 231     switch (av->a_type)
 232       {
 233       case AT_PAGESZ:
 234         if (av->a_un.a_val != 0)
 235           GLRO(dl_pagesize) = av->a_un.a_val;
 236         break;
 237       case AT_CLKTCK:
 238         GLRO(dl_clktck) = av->a_un.a_val;
 239         break;
 240       case AT_PHDR:
 241         GL(dl_phdr) = (const void *) av->a_un.a_val;
 242         break;
 243       case AT_PHNUM:
 244         GL(dl_phnum) = av->a_un.a_val;
 245         break;
 246       case AT_PLATFORM:
 247         GLRO(dl_platform) = (void *) av->a_un.a_val;
 248         break;
 249       case AT_HWCAP:
 250         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 251         break;
 252       case AT_HWCAP2:
 253         GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
 254         break;
 255       case AT_FPUCW:
 256         GLRO(dl_fpu_control) = av->a_un.a_val;
 257         break;
 258 #ifdef NEED_DL_SYSINFO
 259       case AT_SYSINFO:
 260         GL(dl_sysinfo) = av->a_un.a_val;
 261         break;
 262 #endif
 263 #ifdef NEED_DL_SYSINFO_DSO
 264       case AT_SYSINFO_EHDR:
 265         GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 266         break;
 267 #endif
 268       case AT_UID:
 269         uid ^= av->a_un.a_val;
 270         seen |= 1;
 271         break;
 272       case AT_EUID:
 273         uid ^= av->a_un.a_val;
 274         seen |= 2;
 275         break;
 276       case AT_GID:
 277         gid ^= av->a_un.a_val;
 278         seen |= 4;
 279         break;
 280       case AT_EGID:
 281         gid ^= av->a_un.a_val;
 282         seen |= 8;
 283         break;
 284       case AT_SECURE:
 285         seen = -1;
 286         __libc_enable_secure = av->a_un.a_val;
 287         __libc_enable_secure_decided = 1;
 288         break;
 289       case AT_RANDOM:
 290         _dl_random = (void *) av->a_un.a_val;
 291         break;
 292 # ifdef DL_PLATFORM_AUXV
 293       DL_PLATFORM_AUXV
 294 # endif
 295       }
 296   if (seen == 0xf)
 297     {
 298       __libc_enable_secure = uid != 0 || gid != 0;
 299       __libc_enable_secure_decided = 1;
 300     }
 301 }
 302 #endif
 303
 304
 305 void
 306 _dl_non_dynamic_init (void)
 307 {
 308   _dl_main_map.l_origin = _dl_get_origin ();
 309   _dl_main_map.l_phdr = GL(dl_phdr);
 310   _dl_main_map.l_phnum = GL(dl_phnum);
 311
 312   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 313
 314   /* Set up the data structures for the system-supplied DSO early,
 315      so they can influence _dl_init_paths.  */
 316   setup_vdso (NULL, NULL);
 317
 318   /* Initialize the data structures for the search paths for shared
 319      objects.  */
 320   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 321
 322   /* Remember the last search directory added at startup.  */
 323   _dl_init_all_dirs = GL(dl_all_dirs);
 324
 325   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 326
 327   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 328
 329   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 330
 331   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 332   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 333     _dl_profile_output
 334       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 335
 336   if (__libc_enable_secure)
 337     {
 338       static const char unsecure_envvars[] =
 339         UNSECURE_ENVVARS
 340 #ifdef EXTRA_UNSECURE_ENVVARS
 341         EXTRA_UNSECURE_ENVVARS
 342 #endif
 343         ;
 344       const char *cp = unsecure_envvars;
 345
 346       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 347         {
 348           __unsetenv (cp);
 349           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 350         }
 351
 352 #if !HAVE_TUNABLES
 353       if (__access ("/etc/suid-debug", F_OK) != 0)
 354         __unsetenv ("MALLOC_CHECK_");
 355 #endif
 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
 383
 384 #if ENABLE_STATIC_PIE
 385 /* Since relocation to hidden _dl_main_map causes relocation overflow on
 386    aarch64, a function is used to get the address of _dl_main_map.  */
 387
 388 struct link_map *
 389 _dl_get_dl_main_map (void)
 390 {
 391   return &_dl_main_map;
 392 }
 393 #endif