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-procinfo.h>
  39 #include <unsecvars.h>
  40 #include <hp-timing.h>
  41 #include <stackinfo.h>
  42 #include <dl-vdso.h>
  43 #include <dl-vdso-setup.h>
  44 #include <dl-auxv.h>
  45 #include <dl-find_object.h>
  46 #include <array_length.h>
  47 #include <dl-symbol-redir-ifunc.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 /* All known directories in sorted order.  */
 149 struct r_search_path_elem *_dl_all_dirs;
 150
 151 /* All directories after startup.  */
 152 struct r_search_path_elem *_dl_init_all_dirs;
 153
 154 /* The object to be initialized first.  */
 155 struct link_map *_dl_initfirst;
 156
 157 /* Descriptor to write debug messages to.  */
 158 int _dl_debug_fd = STDERR_FILENO;
 159
 160 ElfW(auxv_t) *_dl_auxv;
 161 const ElfW(Phdr) *_dl_phdr;
 162 size_t _dl_phnum;
 163 uint64_t _dl_hwcap;
 164 uint64_t _dl_hwcap2;
 165
 166 enum dso_sort_algorithm _dl_dso_sort_algo;
 167
 168 /* The value of the FPU control word the kernel will preset in hardware.  */
 169 fpu_control_t _dl_fpu_control = _FPU_DEFAULT;
 170
 171 #if !HAVE_TUNABLES
 172 /* This is not initialized to HWCAP_IMPORTANT, matching the definition
 173    of _dl_important_hwcaps, below, where no hwcap strings are ever
 174    used.  This mask is still used to mediate the lookups in the cache
 175    file.  Since there is no way to set this nonzero (we don't grok the
 176    LD_HWCAP_MASK environment variable here), there is no real point in
 177    setting _dl_hwcap nonzero below, but we do anyway.  */
 178 uint64_t _dl_hwcap_mask;
 179 #endif
 180
 181 /* Prevailing state of the stack.  Generally this includes PF_X, indicating it's
 182  * executable but this isn't true for all platforms.  */
 183 ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
 184
 185 #if PTHREAD_IN_LIBC
 186 list_t _dl_stack_used;
 187 list_t _dl_stack_user;
 188 list_t _dl_stack_cache;
 189 size_t _dl_stack_cache_actsize;
 190 uintptr_t _dl_in_flight_stack;
 191 int _dl_stack_cache_lock;
 192 #else
 193 /* If loading a shared object requires that we make the stack executable
 194    when it was not, we do it by calling this function.
 195    It returns an errno code or zero on success.  */
 196 int (*_dl_make_stack_executable_hook) (void **) = _dl_make_stack_executable;
 197 void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
 198 #endif
 199 struct dl_scope_free_list *_dl_scope_free_list;
 200
 201 #ifdef NEED_DL_SYSINFO
 202 /* Needed for improved syscall handling on at least x86/Linux.  NB: Don't
 203    initialize it here to avoid RELATIVE relocation in static PIE.  */
 204 uintptr_t _dl_sysinfo;
 205 #endif
 206 #ifdef NEED_DL_SYSINFO_DSO
 207 /* Address of the ELF headers in the vsyscall page.  */
 208 const ElfW(Ehdr) *_dl_sysinfo_dso;
 209
 210 struct link_map *_dl_sysinfo_map;
 211
 212 # include "get-dynamic-info.h"
 213 #endif
 214 #include "setup-vdso.h"
 215 /* Define the vDSO function pointers.  */
 216 #include <dl-vdso-setup.c>
 217
 218 /* During the program run we must not modify the global data of
 219    loaded shared object simultanously in two threads.  Therefore we
 220    protect `_dl_open' and `_dl_close' in dl-close.c.
 221
 222    This must be a recursive lock since the initializer function of
 223    the loaded object might as well require a call to this function.
 224    At this time it is not anymore a problem to modify the tables.  */
 225 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 226 /* This lock is used to keep __dl_iterate_phdr from inspecting the
 227    list of loaded objects while an object is added to or removed from
 228    that list.  */
 229 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
 230   /* This lock protects global and module specific TLS related data.
 231      E.g. it is held in dlopen and dlclose when GL(dl_tls_generation),
 232      GL(dl_tls_max_dtv_idx) or GL(dl_tls_dtv_slotinfo_list) are
 233      accessed and when TLS related relocations are processed for a
 234      module.  It was introduced to keep pthread_create accessing TLS
 235      state that is being set up.  */
 236 __rtld_lock_define_initialized_recursive (, _dl_load_tls_lock)
 237
 238
 239 #ifdef HAVE_AUX_VECTOR
 240 #include <dl-parse_auxv.h>
 241
 242 int _dl_clktck;
 243
 244 void
 245 _dl_aux_init (ElfW(auxv_t) *av)
 246 {
 247 #ifdef NEED_DL_SYSINFO
 248   /* NB: Avoid RELATIVE relocation in static PIE.  */
 249   GL(dl_sysinfo) = DL_SYSINFO_DEFAULT;
 250 #endif
 251
 252   _dl_auxv = av;
 253   dl_parse_auxv_t auxv_values;
 254   /* Use an explicit initialization loop here because memset may not
 255      be available yet.  */
 256   for (int i = 0; i < array_length (auxv_values); ++i)
 257     auxv_values[i] = 0;
 258   _dl_parse_auxv (av, auxv_values);
 259 }
 260 #endif
 261
 262
 263 void
 264 _dl_non_dynamic_init (void)
 265 {
 266   _dl_main_map.l_origin = _dl_get_origin ();
 267   _dl_main_map.l_phdr = GL(dl_phdr);
 268   _dl_main_map.l_phnum = GL(dl_phnum);
 269
 270   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 271
 272   /* Set up the data structures for the system-supplied DSO early,
 273      so they can influence _dl_init_paths.  */
 274   setup_vdso (NULL, NULL);
 275
 276   /* With vDSO setup we can initialize the function pointers.  */
 277   setup_vdso_pointers ();
 278
 279   /* Initialize the data structures for the search paths for shared
 280      objects.  */
 281   _dl_init_paths (getenv ("LD_LIBRARY_PATH"), "LD_LIBRARY_PATH",
 282                   /* No glibc-hwcaps selection support in statically
 283                      linked binaries.  */
 284                   NULL, NULL);
 285
 286   /* Remember the last search directory added at startup.  */
 287   _dl_init_all_dirs = GL(dl_all_dirs);
 288
 289   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 290
 291   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 292
 293   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 294
 295   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 296   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 297     _dl_profile_output
 298       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 299
 300   if (__libc_enable_secure)
 301     {
 302       static const char unsecure_envvars[] =
 303         UNSECURE_ENVVARS
 304         ;
 305       const char *cp = unsecure_envvars;
 306
 307       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 308         {
 309           __unsetenv (cp);
 310           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 311         }
 312
 313 #if !HAVE_TUNABLES
 314       if (__access ("/etc/suid-debug", F_OK) != 0)
 315         __unsetenv ("MALLOC_CHECK_");
 316 #endif
 317     }
 318
 319 #ifdef DL_PLATFORM_INIT
 320   DL_PLATFORM_INIT;
 321 #endif
 322
 323   /* Now determine the length of the platform string.  */
 324   if (_dl_platform != NULL)
 325     _dl_platformlen = strlen (_dl_platform);
 326
 327   if (_dl_phdr != NULL)
 328     for (const ElfW(Phdr) *ph = _dl_phdr; ph < &_dl_phdr[_dl_phnum]; ++ph)
 329       switch (ph->p_type)
 330         {
 331         /* Check if the stack is nonexecutable.  */
 332         case PT_GNU_STACK:
 333           _dl_stack_flags = ph->p_flags;
 334           break;
 335
 336         case PT_GNU_RELRO:
 337           _dl_main_map.l_relro_addr = ph->p_vaddr;
 338           _dl_main_map.l_relro_size = ph->p_memsz;
 339           break;
 340         }
 341
 342   call_function_static_weak (_dl_find_object_init);
 343
 344   /* Setup relro on the binary itself.  */
 345   if (_dl_main_map.l_relro_size != 0)
 346     _dl_protect_relro (&_dl_main_map);
 347 }
 348
 349 #ifdef DL_SYSINFO_IMPLEMENTATION
 350 DL_SYSINFO_IMPLEMENTATION
 351 #endif
 352
 353 #if ENABLE_STATIC_PIE
 354 /* Since relocation to hidden _dl_main_map causes relocation overflow on
 355    aarch64, a function is used to get the address of _dl_main_map.  */
 356
 357 struct link_map *
 358 _dl_get_dl_main_map (void)
 359 {
 360   return &_dl_main_map;
 361 }
 362 #endif
 363
 364 /* This is used by _dl_runtime_profile, not used on static code.  */
 365 void
 366 DL_ARCH_FIXUP_ATTRIBUTE
 367 _dl_audit_pltexit (struct link_map *l, ElfW(Word) reloc_arg,
 368                    const void *inregs, void *outregs)
 369 {
 370 }