elf/dl-support.c

   1 /* Support for dynamic linking code in static libc.
   2    Copyright (C) 1996-2022 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 <string.h>
  23 /* Mark symbols hidden in static PIE for early self relocation to work.
  24    Note: string.h may have ifuncs which cannot be hidden on i686.  */
  25 #if BUILD_PIE_DEFAULT
  26 # pragma GCC visibility push(hidden)
  27 #endif
  28 #include <errno.h>
  29 #include <libintl.h>
  30 #include <stdlib.h>
  31 #include <unistd.h>
  32 #include <sys/param.h>
  33 #include <stdint.h>
  34 #include <ldsodefs.h>
  35 #include <dl-machine.h>
  36 #include <libc-lock.h>
  37 #include <dl-cache.h>
  38 #include <dl-librecon.h>
  39 #include <dl-procinfo.h>
  40 #include <unsecvars.h>
  41 #include <hp-timing.h>
  42 #include <stackinfo.h>
  43 #include <dl-vdso.h>
  44 #include <dl-vdso-setup.h>
  45 #include <dl-auxv.h>
  46 #include <dl-find_object.h>
  47 #include <array_length.h>
  48
  49 extern char *__progname;
  50 char **_dl_argv = &__progname;  /* This is checked for some error messages.  */
  51
  52 /* Name of the architecture.  */
  53 const char *_dl_platform;
  54 size_t _dl_platformlen;
  55
  56 int _dl_debug_mask;
  57 int _dl_lazy;
  58 int _dl_dynamic_weak;
  59
  60 /* If nonzero print warnings about problematic situations.  */
  61 int _dl_verbose;
  62
  63 /* We never do profiling.  */
  64 const char *_dl_profile;
  65 const char *_dl_profile_output;
  66
  67 /* Names of shared object for which the RUNPATHs and RPATHs should be
  68    ignored.  */
  69 const char *_dl_inhibit_rpath;
  70
  71 /* The map for the object we will profile.  */
  72 struct link_map *_dl_profile_map;
  73
  74 /* This is the address of the last stack address ever used.  */
  75 void *__libc_stack_end;
  76
  77 /* Path where the binary is found.  */
  78 const char *_dl_origin_path;
  79
  80 /* Nonzero if runtime lookup should not update the .got/.plt.  */
  81 int _dl_bind_not;
  82
  83 /* A dummy link map for the executable, used by dlopen to access the global
  84    scope.  We don't export any symbols ourselves, so this can be minimal.  */
  85 static struct link_map _dl_main_map =
  86   {
  87     .l_name = (char *) "",
  88     .l_real = &_dl_main_map,
  89     .l_ns = LM_ID_BASE,
  90     .l_libname = &(struct libname_list) { .name = "", .dont_free = 1 },
  91     .l_searchlist =
  92       {
  93         .r_list = &(struct link_map *) { &_dl_main_map },
  94         .r_nlist = 1,
  95       },
  96     .l_symbolic_searchlist = { .r_list = &(struct link_map *) { NULL } },
  97     .l_type = lt_executable,
  98     .l_scope_mem = { &_dl_main_map.l_searchlist },
  99     .l_scope_max = (sizeof (_dl_main_map.l_scope_mem)
 100                     / sizeof (_dl_main_map.l_scope_mem[0])),
 101     .l_scope = _dl_main_map.l_scope_mem,
 102     .l_local_scope = { &_dl_main_map.l_searchlist },
 103     .l_used = 1,
 104     .l_tls_offset = NO_TLS_OFFSET,
 105     .l_serial = 1,
 106   };
 107
 108 /* Namespace information.  */
 109 struct link_namespaces _dl_ns[DL_NNS] =
 110   {
 111     [LM_ID_BASE] =
 112       {
 113         ._ns_loaded = &_dl_main_map,
 114         ._ns_nloaded = 1,
 115         ._ns_main_searchlist = &_dl_main_map.l_searchlist,
 116       }
 117   };
 118 size_t _dl_nns = 1;
 119
 120 /* Incremented whenever something may have been added to dl_loaded. */
 121 unsigned long long _dl_load_adds = 1;
 122
 123 /* Fake scope of the main application.  */
 124 struct r_scope_elem _dl_initial_searchlist =
 125   {
 126     .r_list = &(struct link_map *) { &_dl_main_map },
 127     .r_nlist = 1,
 128   };
 129
 130 #ifndef HAVE_INLINED_SYSCALLS
 131 /* Nonzero during startup.  */
 132 int _dl_starting_up = 1;
 133 #endif
 134
 135 /* Random data provided by the kernel.  */
 136 void *_dl_random;
 137
 138 /* Get architecture specific initializer.  */
 139 #include <dl-procruntime.c>
 140 #include <dl-procinfo.c>
 141
 142 size_t _dl_pagesize = EXEC_PAGESIZE;
 143
 144 size_t _dl_minsigstacksize = CONSTANT_MINSIGSTKSZ;
 145
 146 int _dl_inhibit_cache;
 147
 148 unsigned int _dl_osversion;
 149
 150 /* All known directories in sorted order.  */
 151 struct r_search_path_elem *_dl_all_dirs;
 152
 153 /* All directories after startup.  */
 154 struct r_search_path_elem *_dl_init_all_dirs;
 155
 156 /* The object to be initialized first.  */
 157 struct link_map *_dl_initfirst;
 158
 159 /* Descriptor to write debug messages to.  */
 160 int _dl_debug_fd = STDERR_FILENO;
 161
 162 int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
 163
 164 ElfW(auxv_t) *_dl_auxv;
 165 const ElfW(Phdr) *_dl_phdr;
 166 size_t _dl_phnum;
 167 uint64_t _dl_hwcap;
 168 uint64_t _dl_hwcap2;
 169
 170 enum dso_sort_algorithm _dl_dso_sort_algo;
 171
 172 /* The value of the FPU control word the kernel will preset in hardware.  */
 173 fpu_control_t _dl_fpu_control = _FPU_DEFAULT;
 174
 175 #if !HAVE_TUNABLES
 176 /* This is not initialized to HWCAP_IMPORTANT, matching the definition
 177    of _dl_important_hwcaps, below, where no hwcap strings are ever
 178    used.  This mask is still used to mediate the lookups in the cache
 179    file.  Since there is no way to set this nonzero (we don't grok the
 180    LD_HWCAP_MASK environment variable here), there is no real point in
 181    setting _dl_hwcap nonzero below, but we do anyway.  */
 182 uint64_t _dl_hwcap_mask;
 183 #endif
 184
 185 /* Prevailing state of the stack.  Generally this includes PF_X, indicating it's
 186  * executable but this isn't true for all platforms.  */
 187 ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
 188
 189 #if PTHREAD_IN_LIBC
 190 list_t _dl_stack_used;
 191 list_t _dl_stack_user;
 192 list_t _dl_stack_cache;
 193 size_t _dl_stack_cache_actsize;
 194 uintptr_t _dl_in_flight_stack;
 195 int _dl_stack_cache_lock;
 196 #else
 197 /* If loading a shared object requires that we make the stack executable
 198    when it was not, we do it by calling this function.
 199    It returns an errno code or zero on success.  */
 200 int (*_dl_make_stack_executable_hook) (void **) = _dl_make_stack_executable;
 201 void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
 202 #endif
 203 struct dl_scope_free_list *_dl_scope_free_list;
 204
 205 #ifdef NEED_DL_SYSINFO
 206 /* Needed for improved syscall handling on at least x86/Linux.  NB: Don't
 207    initialize it here to avoid RELATIVE relocation in static PIE.  */
 208 uintptr_t _dl_sysinfo;
 209 #endif
 210 #ifdef NEED_DL_SYSINFO_DSO
 211 /* Address of the ELF headers in the vsyscall page.  */
 212 const ElfW(Ehdr) *_dl_sysinfo_dso;
 213
 214 struct link_map *_dl_sysinfo_map;
 215
 216 # include "get-dynamic-info.h"
 217 #endif
 218 #include "setup-vdso.h"
 219 /* Define the vDSO function pointers.  */
 220 #include <dl-vdso-setup.c>
 221
 222 /* During the program run we must not modify the global data of
 223    loaded shared object simultanously in two threads.  Therefore we
 224    protect `_dl_open' and `_dl_close' in dl-close.c.
 225
 226    This must be a recursive lock since the initializer function of
 227    the loaded object might as well require a call to this function.
 228    At this time it is not anymore a problem to modify the tables.  */
 229 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 230 /* This lock is used to keep __dl_iterate_phdr from inspecting the
 231    list of loaded objects while an object is added to or removed from
 232    that list.  */
 233 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
 234   /* This lock protects global and module specific TLS related data.
 235      E.g. it is held in dlopen and dlclose when GL(dl_tls_generation),
 236      GL(dl_tls_max_dtv_idx) or GL(dl_tls_dtv_slotinfo_list) are
 237      accessed and when TLS related relocations are processed for a
 238      module.  It was introduced to keep pthread_create accessing TLS
 239      state that is being set up.  */
 240 __rtld_lock_define_initialized_recursive (, _dl_load_tls_lock)
 241
 242
 243 #ifdef HAVE_AUX_VECTOR
 244 #include <dl-parse_auxv.h>
 245
 246 int _dl_clktck;
 247
 248 void
 249 _dl_aux_init (ElfW(auxv_t) *av)
 250 {
 251 #ifdef NEED_DL_SYSINFO
 252   /* NB: Avoid RELATIVE relocation in static PIE.  */
 253   GL(dl_sysinfo) = DL_SYSINFO_DEFAULT;
 254 #endif
 255
 256   _dl_auxv = av;
 257   dl_parse_auxv_t auxv_values;
 258   /* Use an explicit initialization loop here because memset may not
 259      be available yet.  */
 260   for (int i = 0; i < array_length (auxv_values); ++i)
 261     auxv_values[i] = 0;
 262   _dl_parse_auxv (av, auxv_values);
 263 }
 264 #endif
 265
 266
 267 void
 268 _dl_non_dynamic_init (void)
 269 {
 270   _dl_main_map.l_origin = _dl_get_origin ();
 271   _dl_main_map.l_phdr = GL(dl_phdr);
 272   _dl_main_map.l_phnum = GL(dl_phnum);
 273
 274   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 275
 276   /* Set up the data structures for the system-supplied DSO early,
 277      so they can influence _dl_init_paths.  */
 278   setup_vdso (NULL, NULL);
 279
 280   /* With vDSO setup we can initialize the function pointers.  */
 281   setup_vdso_pointers ();
 282
 283   /* Initialize the data structures for the search paths for shared
 284      objects.  */
 285   _dl_init_paths (getenv ("LD_LIBRARY_PATH"), "LD_LIBRARY_PATH",
 286                   /* No glibc-hwcaps selection support in statically
 287                      linked binaries.  */
 288                   NULL, NULL);
 289
 290   /* Remember the last search directory added at startup.  */
 291   _dl_init_all_dirs = GL(dl_all_dirs);
 292
 293   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 294
 295   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 296
 297   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 298
 299   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 300   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 301     _dl_profile_output
 302       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 303
 304   if (__libc_enable_secure)
 305     {
 306       static const char unsecure_envvars[] =
 307         UNSECURE_ENVVARS
 308 #ifdef EXTRA_UNSECURE_ENVVARS
 309         EXTRA_UNSECURE_ENVVARS
 310 #endif
 311         ;
 312       const char *cp = unsecure_envvars;
 313
 314       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 315         {
 316           __unsetenv (cp);
 317           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 318         }
 319
 320 #if !HAVE_TUNABLES
 321       if (__access ("/etc/suid-debug", F_OK) != 0)
 322         __unsetenv ("MALLOC_CHECK_");
 323 #endif
 324     }
 325
 326 #ifdef DL_PLATFORM_INIT
 327   DL_PLATFORM_INIT;
 328 #endif
 329
 330 #ifdef DL_OSVERSION_INIT
 331   DL_OSVERSION_INIT;
 332 #endif
 333
 334   /* Now determine the length of the platform string.  */
 335   if (_dl_platform != NULL)
 336     _dl_platformlen = strlen (_dl_platform);
 337
 338   if (_dl_phdr != NULL)
 339     for (const ElfW(Phdr) *ph = _dl_phdr; ph < &_dl_phdr[_dl_phnum]; ++ph)
 340       switch (ph->p_type)
 341         {
 342         /* Check if the stack is nonexecutable.  */
 343         case PT_GNU_STACK:
 344           _dl_stack_flags = ph->p_flags;
 345           break;
 346
 347         case PT_GNU_RELRO:
 348           _dl_main_map.l_relro_addr = ph->p_vaddr;
 349           _dl_main_map.l_relro_size = ph->p_memsz;
 350           break;
 351         }
 352
 353   call_function_static_weak (_dl_find_object_init);
 354
 355   /* Setup relro on the binary itself.  */
 356   if (_dl_main_map.l_relro_size != 0)
 357     _dl_protect_relro (&_dl_main_map);
 358 }
 359
 360 #ifdef DL_SYSINFO_IMPLEMENTATION
 361 DL_SYSINFO_IMPLEMENTATION
 362 #endif
 363
 364 #if ENABLE_STATIC_PIE
 365 /* Since relocation to hidden _dl_main_map causes relocation overflow on
 366    aarch64, a function is used to get the address of _dl_main_map.  */
 367
 368 struct link_map *
 369 _dl_get_dl_main_map (void)
 370 {
 371   return &_dl_main_map;
 372 }
 373 #endif
 374
 375 /* This is used by _dl_runtime_profile, not used on static code.  */
 376 void
 377 DL_ARCH_FIXUP_ATTRIBUTE
 378 _dl_audit_pltexit (struct link_map *l, ElfW(Word) reloc_arg,
 379                    const void *inregs, void *outregs)
 380 {
 381 }