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 /* Function in libpthread to wait for termination of lookups.  */
 187 void (*_dl_wait_lookup_done) (void);
 188
 189 #if !THREAD_GSCOPE_IN_TCB
 190 int _dl_thread_gscope_count;
 191 #endif
 192 struct dl_scope_free_list *_dl_scope_free_list;
 193
 194 #ifdef NEED_DL_SYSINFO
 195 /* Needed for improved syscall handling on at least x86/Linux.  */
 196 uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
 197 #endif
 198 #ifdef NEED_DL_SYSINFO_DSO
 199 /* Address of the ELF headers in the vsyscall page.  */
 200 const ElfW(Ehdr) *_dl_sysinfo_dso;
 201
 202 struct link_map *_dl_sysinfo_map;
 203
 204 # include "get-dynamic-info.h"
 205 #endif
 206 #include "setup-vdso.h"
 207 /* Define the vDSO function pointers.  */
 208 #include <dl-vdso-setup.c>
 209
 210 /* During the program run we must not modify the global data of
 211    loaded shared object simultanously in two threads.  Therefore we
 212    protect `_dl_open' and `_dl_close' in dl-close.c.
 213
 214    This must be a recursive lock since the initializer function of
 215    the loaded object might as well require a call to this function.
 216    At this time it is not anymore a problem to modify the tables.  */
 217 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 218 /* This lock is used to keep __dl_iterate_phdr from inspecting the
 219    list of loaded objects while an object is added to or removed from
 220    that list.  */
 221 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
 222
 223
 224 #ifdef HAVE_AUX_VECTOR
 225 int _dl_clktck;
 226
 227 void
 228 _dl_aux_init (ElfW(auxv_t) *av)
 229 {
 230   int seen = 0;
 231   uid_t uid = 0;
 232   gid_t gid = 0;
 233
 234   _dl_auxv = av;
 235   for (; av->a_type != AT_NULL; ++av)
 236     switch (av->a_type)
 237       {
 238       case AT_PAGESZ:
 239         if (av->a_un.a_val != 0)
 240           GLRO(dl_pagesize) = av->a_un.a_val;
 241         break;
 242       case AT_CLKTCK:
 243         GLRO(dl_clktck) = av->a_un.a_val;
 244         break;
 245       case AT_PHDR:
 246         GL(dl_phdr) = (const void *) av->a_un.a_val;
 247         break;
 248       case AT_PHNUM:
 249         GL(dl_phnum) = av->a_un.a_val;
 250         break;
 251       case AT_PLATFORM:
 252         GLRO(dl_platform) = (void *) av->a_un.a_val;
 253         break;
 254       case AT_HWCAP:
 255         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 256         break;
 257       case AT_HWCAP2:
 258         GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
 259         break;
 260       case AT_FPUCW:
 261         GLRO(dl_fpu_control) = av->a_un.a_val;
 262         break;
 263 #ifdef NEED_DL_SYSINFO
 264       case AT_SYSINFO:
 265         GL(dl_sysinfo) = av->a_un.a_val;
 266         break;
 267 #endif
 268 #ifdef NEED_DL_SYSINFO_DSO
 269       case AT_SYSINFO_EHDR:
 270         GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 271         break;
 272 #endif
 273       case AT_UID:
 274         uid ^= av->a_un.a_val;
 275         seen |= 1;
 276         break;
 277       case AT_EUID:
 278         uid ^= av->a_un.a_val;
 279         seen |= 2;
 280         break;
 281       case AT_GID:
 282         gid ^= av->a_un.a_val;
 283         seen |= 4;
 284         break;
 285       case AT_EGID:
 286         gid ^= av->a_un.a_val;
 287         seen |= 8;
 288         break;
 289       case AT_SECURE:
 290         seen = -1;
 291         __libc_enable_secure = av->a_un.a_val;
 292         __libc_enable_secure_decided = 1;
 293         break;
 294       case AT_RANDOM:
 295         _dl_random = (void *) av->a_un.a_val;
 296         break;
 297       DL_PLATFORM_AUXV
 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 _dl_non_dynamic_init (void)
 310 {
 311   _dl_main_map.l_origin = _dl_get_origin ();
 312   _dl_main_map.l_phdr = GL(dl_phdr);
 313   _dl_main_map.l_phnum = GL(dl_phnum);
 314
 315   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 316
 317   /* Set up the data structures for the system-supplied DSO early,
 318      so they can influence _dl_init_paths.  */
 319   setup_vdso (NULL, NULL);
 320
 321   /* With vDSO setup we can initialize the function pointers.  */
 322   setup_vdso_pointers ();
 323
 324   /* Initialize the data structures for the search paths for shared
 325      objects.  */
 326   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 327
 328   /* Remember the last search directory added at startup.  */
 329   _dl_init_all_dirs = GL(dl_all_dirs);
 330
 331   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 332
 333   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 334
 335   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 336
 337   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 338   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 339     _dl_profile_output
 340       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 341
 342   if (__libc_enable_secure)
 343     {
 344       static const char unsecure_envvars[] =
 345         UNSECURE_ENVVARS
 346 #ifdef EXTRA_UNSECURE_ENVVARS
 347         EXTRA_UNSECURE_ENVVARS
 348 #endif
 349         ;
 350       const char *cp = unsecure_envvars;
 351
 352       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 353         {
 354           __unsetenv (cp);
 355           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 356         }
 357
 358 #if !HAVE_TUNABLES
 359       if (__access ("/etc/suid-debug", F_OK) != 0)
 360         __unsetenv ("MALLOC_CHECK_");
 361 #endif
 362     }
 363
 364 #ifdef DL_PLATFORM_INIT
 365   DL_PLATFORM_INIT;
 366 #endif
 367
 368 #ifdef DL_OSVERSION_INIT
 369   DL_OSVERSION_INIT;
 370 #endif
 371
 372   /* Now determine the length of the platform string.  */
 373   if (_dl_platform != NULL)
 374     _dl_platformlen = strlen (_dl_platform);
 375
 376   if (_dl_phdr != NULL)
 377     for (const ElfW(Phdr) *ph = _dl_phdr; ph < &_dl_phdr[_dl_phnum]; ++ph)
 378       switch (ph->p_type)
 379         {
 380         /* Check if the stack is nonexecutable.  */
 381         case PT_GNU_STACK:
 382           _dl_stack_flags = ph->p_flags;
 383           break;
 384
 385         case PT_GNU_RELRO:
 386           _dl_main_map.l_relro_addr = ph->p_vaddr;
 387           _dl_main_map.l_relro_size = ph->p_memsz;
 388           break;
 389         }
 390
 391   /* Setup relro on the binary itself.  */
 392   if (_dl_main_map.l_relro_size != 0)
 393     _dl_protect_relro (&_dl_main_map);
 394 }
 395
 396 #ifdef DL_SYSINFO_IMPLEMENTATION
 397 DL_SYSINFO_IMPLEMENTATION
 398 #endif
 399
 400 #if ENABLE_STATIC_PIE
 401 /* Since relocation to hidden _dl_main_map causes relocation overflow on
 402    aarch64, a function is used to get the address of _dl_main_map.  */
 403
 404 struct link_map *
 405 _dl_get_dl_main_map (void)
 406 {
 407   return &_dl_main_map;
 408 }
 409 #endif