elf/dl-support.c

   1 /* Support for dynamic linking code in static libc.
   2    Copyright (C) 1996-2016 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-procinfo.c>
 130
 131 /* Initial value of the CPU clock.  */
 132 #ifndef HP_TIMING_NONAVAIL
 133 hp_timing_t _dl_cpuclock_offset;
 134 #endif
 135
 136 void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
 137
 138 size_t _dl_pagesize = EXEC_PAGESIZE;
 139
 140 int _dl_inhibit_cache;
 141
 142 unsigned int _dl_osversion;
 143
 144 /* All known directories in sorted order.  */
 145 struct r_search_path_elem *_dl_all_dirs;
 146
 147 /* All directories after startup.  */
 148 struct r_search_path_elem *_dl_init_all_dirs;
 149
 150 /* The object to be initialized first.  */
 151 struct link_map *_dl_initfirst;
 152
 153 /* Descriptor to write debug messages to.  */
 154 int _dl_debug_fd = STDERR_FILENO;
 155
 156 int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
 157
 158 ElfW(auxv_t) *_dl_auxv;
 159 const ElfW(Phdr) *_dl_phdr;
 160 size_t _dl_phnum;
 161 uint64_t _dl_hwcap __attribute__ ((nocommon));
 162 uint64_t _dl_hwcap2 __attribute__ ((nocommon));
 163
 164 /* The value of the FPU control word the kernel will preset in hardware.  */
 165 fpu_control_t _dl_fpu_control = _FPU_DEFAULT;
 166
 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
 175 /* Prevailing state of the stack.  Generally this includes PF_X, indicating it's
 176  * executable but this isn't true for all platforms.  */
 177 ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
 178
 179 /* If loading a shared object requires that we make the stack executable
 180    when it was not, we do it by calling this function.
 181    It returns an errno code or zero on success.  */
 182 int (*_dl_make_stack_executable_hook) (void **) internal_function
 183   = _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 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 internal_function
 224 _dl_aux_init (ElfW(auxv_t) *av)
 225 {
 226   int seen = 0;
 227   uid_t uid = 0;
 228   gid_t gid = 0;
 229
 230   _dl_auxv = av;
 231   for (; av->a_type != AT_NULL; ++av)
 232     switch (av->a_type)
 233       {
 234       case AT_PAGESZ:
 235         if (av->a_un.a_val != 0)
 236           GLRO(dl_pagesize) = av->a_un.a_val;
 237         break;
 238       case AT_CLKTCK:
 239         GLRO(dl_clktck) = av->a_un.a_val;
 240         break;
 241       case AT_PHDR:
 242         GL(dl_phdr) = (const void *) av->a_un.a_val;
 243         break;
 244       case AT_PHNUM:
 245         GL(dl_phnum) = av->a_un.a_val;
 246         break;
 247       case AT_PLATFORM:
 248         GLRO(dl_platform) = (void *) av->a_un.a_val;
 249         break;
 250       case AT_HWCAP:
 251         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 252         break;
 253       case AT_HWCAP2:
 254         GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
 255         break;
 256       case AT_FPUCW:
 257         GLRO(dl_fpu_control) = av->a_un.a_val;
 258         break;
 259 #ifdef NEED_DL_SYSINFO
 260       case AT_SYSINFO:
 261         GL(dl_sysinfo) = av->a_un.a_val;
 262         break;
 263 #endif
 264 #ifdef NEED_DL_SYSINFO_DSO
 265       case AT_SYSINFO_EHDR:
 266         GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 267         break;
 268 #endif
 269       case AT_UID:
 270         uid ^= av->a_un.a_val;
 271         seen |= 1;
 272         break;
 273       case AT_EUID:
 274         uid ^= av->a_un.a_val;
 275         seen |= 2;
 276         break;
 277       case AT_GID:
 278         gid ^= av->a_un.a_val;
 279         seen |= 4;
 280         break;
 281       case AT_EGID:
 282         gid ^= av->a_un.a_val;
 283         seen |= 8;
 284         break;
 285       case AT_SECURE:
 286         seen = -1;
 287         __libc_enable_secure = av->a_un.a_val;
 288         __libc_enable_secure_decided = 1;
 289         break;
 290       case AT_RANDOM:
 291         _dl_random = (void *) av->a_un.a_val;
 292         break;
 293 # ifdef DL_PLATFORM_AUXV
 294       DL_PLATFORM_AUXV
 295 # endif
 296       }
 297   if (seen == 0xf)
 298     {
 299       __libc_enable_secure = uid != 0 || gid != 0;
 300       __libc_enable_secure_decided = 1;
 301     }
 302 }
 303 #endif
 304
 305
 306 void
 307 internal_function
 308 _dl_non_dynamic_init (void)
 309 {
 310   _dl_main_map.l_origin = _dl_get_origin ();
 311   _dl_main_map.l_phdr = GL(dl_phdr);
 312   _dl_main_map.l_phnum = GL(dl_phnum);
 313
 314   if (HP_SMALL_TIMING_AVAIL)
 315     HP_TIMING_NOW (_dl_cpuclock_offset);
 316
 317   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 318
 319   /* Set up the data structures for the system-supplied DSO early,
 320      so they can influence _dl_init_paths.  */
 321   setup_vdso (NULL, NULL);
 322
 323   /* Initialize the data structures for the search paths for shared
 324      objects.  */
 325   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 326
 327   /* Remember the last search directory added at startup.  */
 328   _dl_init_all_dirs = GL(dl_all_dirs);
 329
 330   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 331
 332   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 333
 334   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 335
 336   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 337   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 338     _dl_profile_output
 339       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 340
 341   if (__libc_enable_secure)
 342     {
 343       static const char unsecure_envvars[] =
 344         UNSECURE_ENVVARS
 345 #ifdef EXTRA_UNSECURE_ENVVARS
 346         EXTRA_UNSECURE_ENVVARS
 347 #endif
 348         ;
 349       const char *cp = unsecure_envvars;
 350
 351       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 352         {
 353           __unsetenv (cp);
 354           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 355         }
 356
 357       if (__access ("/etc/suid-debug", F_OK) != 0)
 358         __unsetenv ("MALLOC_CHECK_");
 359     }
 360
 361 #ifdef DL_PLATFORM_INIT
 362   DL_PLATFORM_INIT;
 363 #endif
 364
 365 #ifdef DL_OSVERSION_INIT
 366   DL_OSVERSION_INIT;
 367 #endif
 368
 369   /* Now determine the length of the platform string.  */
 370   if (_dl_platform != NULL)
 371     _dl_platformlen = strlen (_dl_platform);
 372
 373   /* Scan for a program header telling us the stack is nonexecutable.  */
 374   if (_dl_phdr != NULL)
 375     for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
 376       if (_dl_phdr[i].p_type == PT_GNU_STACK)
 377         {
 378           _dl_stack_flags = _dl_phdr[i].p_flags;
 379           break;
 380         }
 381 }
 382
 383 #ifdef DL_SYSINFO_IMPLEMENTATION
 384 DL_SYSINFO_IMPLEMENTATION
 385 #endif