elf/dl-support.c

   1 /* Support for dynamic linking code in static libc.
   2    Copyright (C) 1996-2020 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    <https://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 #include <dl-vdso.h>
  38 #include <dl-vdso-setup.h>
  39 #include <dl-auxv.h>
  40
  41 extern char *__progname;
  42 char **_dl_argv = &__progname;  /* This is checked for some error messages.  */
  43
  44 /* Name of the architecture.  */
  45 const char *_dl_platform;
  46 size_t _dl_platformlen;
  47
  48 int _dl_debug_mask;
  49 int _dl_lazy;
  50 ElfW(Addr) _dl_use_load_bias = -2;
  51 int _dl_dynamic_weak;
  52
  53 /* If nonzero print warnings about problematic situations.  */
  54 int _dl_verbose;
  55
  56 /* We never do profiling.  */
  57 const char *_dl_profile;
  58 const char *_dl_profile_output;
  59
  60 /* Names of shared object for which the RUNPATHs and RPATHs should be
  61    ignored.  */
  62 const char *_dl_inhibit_rpath;
  63
  64 /* The map for the object we will profile.  */
  65 struct link_map *_dl_profile_map;
  66
  67 /* This is the address of the last stack address ever used.  */
  68 void *__libc_stack_end;
  69
  70 /* Path where the binary is found.  */
  71 const char *_dl_origin_path;
  72
  73 /* Nonzero if runtime lookup should not update the .got/.plt.  */
  74 int _dl_bind_not;
  75
  76 /* A dummy link map for the executable, used by dlopen to access the global
  77    scope.  We don't export any symbols ourselves, so this can be minimal.  */
  78 static struct link_map _dl_main_map =
  79   {
  80     .l_name = (char *) "",
  81     .l_real = &_dl_main_map,
  82     .l_ns = LM_ID_BASE,
  83     .l_libname = &(struct libname_list) { .name = "", .dont_free = 1 },
  84     .l_searchlist =
  85       {
  86         .r_list = &(struct link_map *) { &_dl_main_map },
  87         .r_nlist = 1,
  88       },
  89     .l_symbolic_searchlist = { .r_list = &(struct link_map *) { NULL } },
  90     .l_type = lt_executable,
  91     .l_scope_mem = { &_dl_main_map.l_searchlist },
  92     .l_scope_max = (sizeof (_dl_main_map.l_scope_mem)
  93                     / sizeof (_dl_main_map.l_scope_mem[0])),
  94     .l_scope = _dl_main_map.l_scope_mem,
  95     .l_local_scope = { &_dl_main_map.l_searchlist },
  96     .l_used = 1,
  97     .l_tls_offset = NO_TLS_OFFSET,
  98     .l_serial = 1,
  99   };
 100
 101 /* Namespace information.  */
 102 struct link_namespaces _dl_ns[DL_NNS] =
 103   {
 104     [LM_ID_BASE] =
 105       {
 106         ._ns_loaded = &_dl_main_map,
 107         ._ns_nloaded = 1,
 108         ._ns_main_searchlist = &_dl_main_map.l_searchlist,
 109       }
 110   };
 111 size_t _dl_nns = 1;
 112
 113 /* Incremented whenever something may have been added to dl_loaded. */
 114 unsigned long long _dl_load_adds = 1;
 115
 116 /* Fake scope of the main application.  */
 117 struct r_scope_elem _dl_initial_searchlist =
 118   {
 119     .r_list = &(struct link_map *) { &_dl_main_map },
 120     .r_nlist = 1,
 121   };
 122
 123 #ifndef HAVE_INLINED_SYSCALLS
 124 /* Nonzero during startup.  */
 125 int _dl_starting_up = 1;
 126 #endif
 127
 128 /* Random data provided by the kernel.  */
 129 void *_dl_random;
 130
 131 /* Get architecture specific initializer.  */
 132 #include <dl-procruntime.c>
 133 #include <dl-procinfo.c>
 134
 135 void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
 136
 137 size_t _dl_pagesize = EXEC_PAGESIZE;
 138
 139 int _dl_inhibit_cache;
 140
 141 unsigned int _dl_osversion;
 142
 143 /* All known directories in sorted order.  */
 144 struct r_search_path_elem *_dl_all_dirs;
 145
 146 /* All directories after startup.  */
 147 struct r_search_path_elem *_dl_init_all_dirs;
 148
 149 /* The object to be initialized first.  */
 150 struct link_map *_dl_initfirst;
 151
 152 /* Descriptor to write debug messages to.  */
 153 int _dl_debug_fd = STDERR_FILENO;
 154
 155 int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
 156
 157 ElfW(auxv_t) *_dl_auxv;
 158 const ElfW(Phdr) *_dl_phdr;
 159 size_t _dl_phnum;
 160 uint64_t _dl_hwcap __attribute__ ((nocommon));
 161 uint64_t _dl_hwcap2 __attribute__ ((nocommon));
 162
 163 /* The value of the FPU control word the kernel will preset in hardware.  */
 164 fpu_control_t _dl_fpu_control = _FPU_DEFAULT;
 165
 166 #if !HAVE_TUNABLES
 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 #endif
 175
 176 /* Prevailing state of the stack.  Generally this includes PF_X, indicating it's
 177  * executable but this isn't true for all platforms.  */
 178 ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
 179
 180 /* If loading a shared object requires that we make the stack executable
 181    when it was not, we do it by calling this function.
 182    It returns an errno code or zero on success.  */
 183 int (*_dl_make_stack_executable_hook) (void **) = _dl_make_stack_executable;
 184
 185
 186 #if THREAD_GSCOPE_IN_TCB
 187 list_t _dl_stack_used;
 188 list_t _dl_stack_user;
 189 int _dl_stack_cache_lock;
 190 #else
 191 int _dl_thread_gscope_count;
 192 #endif
 193 struct dl_scope_free_list *_dl_scope_free_list;
 194
 195 #ifdef NEED_DL_SYSINFO
 196 /* Needed for improved syscall handling on at least x86/Linux.  */
 197 uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
 198 #endif
 199 #ifdef NEED_DL_SYSINFO_DSO
 200 /* Address of the ELF headers in the vsyscall page.  */
 201 const ElfW(Ehdr) *_dl_sysinfo_dso;
 202
 203 struct link_map *_dl_sysinfo_map;
 204
 205 # include "get-dynamic-info.h"
 206 #endif
 207 #include "setup-vdso.h"
 208 /* Define the vDSO function pointers.  */
 209 #include <dl-vdso-setup.c>
 210
 211 /* During the program run we must not modify the global data of
 212    loaded shared object simultanously in two threads.  Therefore we
 213    protect `_dl_open' and `_dl_close' in dl-close.c.
 214
 215    This must be a recursive lock since the initializer function of
 216    the loaded object might as well require a call to this function.
 217    At this time it is not anymore a problem to modify the tables.  */
 218 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 219 /* This lock is used to keep __dl_iterate_phdr from inspecting the
 220    list of loaded objects while an object is added to or removed from
 221    that list.  */
 222 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
 223
 224
 225 #ifdef HAVE_AUX_VECTOR
 226 int _dl_clktck;
 227
 228 void
 229 _dl_aux_init (ElfW(auxv_t) *av)
 230 {
 231   int seen = 0;
 232   uid_t uid = 0;
 233   gid_t gid = 0;
 234
 235   _dl_auxv = av;
 236   for (; av->a_type != AT_NULL; ++av)
 237     switch (av->a_type)
 238       {
 239       case AT_PAGESZ:
 240         if (av->a_un.a_val != 0)
 241           GLRO(dl_pagesize) = av->a_un.a_val;
 242         break;
 243       case AT_CLKTCK:
 244         GLRO(dl_clktck) = av->a_un.a_val;
 245         break;
 246       case AT_PHDR:
 247         GL(dl_phdr) = (const void *) av->a_un.a_val;
 248         break;
 249       case AT_PHNUM:
 250         GL(dl_phnum) = av->a_un.a_val;
 251         break;
 252       case AT_PLATFORM:
 253         GLRO(dl_platform) = (void *) av->a_un.a_val;
 254         break;
 255       case AT_HWCAP:
 256         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 257         break;
 258       case AT_HWCAP2:
 259         GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
 260         break;
 261       case AT_FPUCW:
 262         GLRO(dl_fpu_control) = av->a_un.a_val;
 263         break;
 264 #ifdef NEED_DL_SYSINFO
 265       case AT_SYSINFO:
 266         GL(dl_sysinfo) = av->a_un.a_val;
 267         break;
 268 #endif
 269 #ifdef NEED_DL_SYSINFO_DSO
 270       case AT_SYSINFO_EHDR:
 271         GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 272         break;
 273 #endif
 274       case AT_UID:
 275         uid ^= av->a_un.a_val;
 276         seen |= 1;
 277         break;
 278       case AT_EUID:
 279         uid ^= av->a_un.a_val;
 280         seen |= 2;
 281         break;
 282       case AT_GID:
 283         gid ^= av->a_un.a_val;
 284         seen |= 4;
 285         break;
 286       case AT_EGID:
 287         gid ^= av->a_un.a_val;
 288         seen |= 8;
 289         break;
 290       case AT_SECURE:
 291         seen = -1;
 292         __libc_enable_secure = av->a_un.a_val;
 293         __libc_enable_secure_decided = 1;
 294         break;
 295       case AT_RANDOM:
 296         _dl_random = (void *) av->a_un.a_val;
 297         break;
 298       DL_PLATFORM_AUXV
 299       }
 300   if (seen == 0xf)
 301     {
 302       __libc_enable_secure = uid != 0 || gid != 0;
 303       __libc_enable_secure_decided = 1;
 304     }
 305 }
 306 #endif
 307
 308
 309 void
 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   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 317
 318   /* Set up the data structures for the system-supplied DSO early,
 319      so they can influence _dl_init_paths.  */
 320   setup_vdso (NULL, NULL);
 321
 322   /* With vDSO setup we can initialize the function pointers.  */
 323   setup_vdso_pointers ();
 324
 325   /* Initialize the data structures for the search paths for shared
 326      objects.  */
 327   _dl_init_paths (getenv ("LD_LIBRARY_PATH"), "LD_LIBRARY_PATH",
 328                   /* No glibc-hwcaps selection support in statically
 329                      linked binaries.  */
 330                   NULL, NULL);
 331
 332   /* Remember the last search directory added at startup.  */
 333   _dl_init_all_dirs = GL(dl_all_dirs);
 334
 335   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 336
 337   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 338
 339   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 340
 341   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 342   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 343     _dl_profile_output
 344       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 345
 346   if (__libc_enable_secure)
 347     {
 348       static const char unsecure_envvars[] =
 349         UNSECURE_ENVVARS
 350 #ifdef EXTRA_UNSECURE_ENVVARS
 351         EXTRA_UNSECURE_ENVVARS
 352 #endif
 353         ;
 354       const char *cp = unsecure_envvars;
 355
 356       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 357         {
 358           __unsetenv (cp);
 359           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 360         }
 361
 362 #if !HAVE_TUNABLES
 363       if (__access ("/etc/suid-debug", F_OK) != 0)
 364         __unsetenv ("MALLOC_CHECK_");
 365 #endif
 366     }
 367
 368 #ifdef DL_PLATFORM_INIT
 369   DL_PLATFORM_INIT;
 370 #endif
 371
 372 #ifdef DL_OSVERSION_INIT
 373   DL_OSVERSION_INIT;
 374 #endif
 375
 376   /* Now determine the length of the platform string.  */
 377   if (_dl_platform != NULL)
 378     _dl_platformlen = strlen (_dl_platform);
 379
 380   if (_dl_phdr != NULL)
 381     for (const ElfW(Phdr) *ph = _dl_phdr; ph < &_dl_phdr[_dl_phnum]; ++ph)
 382       switch (ph->p_type)
 383         {
 384         /* Check if the stack is nonexecutable.  */
 385         case PT_GNU_STACK:
 386           _dl_stack_flags = ph->p_flags;
 387           break;
 388
 389         case PT_GNU_RELRO:
 390           _dl_main_map.l_relro_addr = ph->p_vaddr;
 391           _dl_main_map.l_relro_size = ph->p_memsz;
 392           break;
 393         }
 394
 395   /* Setup relro on the binary itself.  */
 396   if (_dl_main_map.l_relro_size != 0)
 397     _dl_protect_relro (&_dl_main_map);
 398 }
 399
 400 #ifdef DL_SYSINFO_IMPLEMENTATION
 401 DL_SYSINFO_IMPLEMENTATION
 402 #endif
 403
 404 #if ENABLE_STATIC_PIE
 405 /* Since relocation to hidden _dl_main_map causes relocation overflow on
 406    aarch64, a function is used to get the address of _dl_main_map.  */
 407
 408 struct link_map *
 409 _dl_get_dl_main_map (void)
 410 {
 411   return &_dl_main_map;
 412 }
 413 #endif