elf/dl-support.c

   1 /* Support for dynamic linking code in static libc.
   2    Copyright (C) 1996-2014 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 <bits/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_flags_1 = DF_1_NODEFLIB,
  95     .l_tls_offset = NO_TLS_OFFSET,
  96     .l_serial = 1,
  97   };
  98
  99 /* Namespace information.  */
 100 struct link_namespaces _dl_ns[DL_NNS] =
 101   {
 102     [LM_ID_BASE] =
 103       {
 104         ._ns_loaded = &_dl_main_map,
 105         ._ns_nloaded = 1,
 106         ._ns_main_searchlist = &_dl_main_map.l_searchlist,
 107       }
 108   };
 109 size_t _dl_nns = 1;
 110
 111 /* Incremented whenever something may have been added to dl_loaded. */
 112 unsigned long long _dl_load_adds = 1;
 113
 114 /* Fake scope of the main application.  */
 115 struct r_scope_elem _dl_initial_searchlist =
 116   {
 117     .r_list = &(struct link_map *) { &_dl_main_map },
 118     .r_nlist = 1,
 119   };
 120
 121 #ifndef HAVE_INLINED_SYSCALLS
 122 /* Nonzero during startup.  */
 123 int _dl_starting_up = 1;
 124 #endif
 125
 126 /* Random data provided by the kernel.  */
 127 void *_dl_random;
 128
 129 /* Get architecture specific initializer.  */
 130 #include <dl-procinfo.c>
 131
 132 /* We expect less than a second for relocation.  */
 133 #ifdef HP_SMALL_TIMING_AVAIL
 134 # undef HP_TIMING_AVAIL
 135 # define HP_TIMING_AVAIL HP_SMALL_TIMING_AVAIL
 136 #endif
 137
 138 /* Initial value of the CPU clock.  */
 139 #ifndef HP_TIMING_NONAVAIL
 140 hp_timing_t _dl_cpuclock_offset;
 141 #endif
 142
 143 void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
 144
 145 size_t _dl_pagesize = EXEC_PAGESIZE;
 146
 147 int _dl_inhibit_cache;
 148
 149 unsigned int _dl_osversion;
 150
 151 /* All known directories in sorted order.  */
 152 struct r_search_path_elem *_dl_all_dirs;
 153
 154 /* All directories after startup.  */
 155 struct r_search_path_elem *_dl_init_all_dirs;
 156
 157 /* The object to be initialized first.  */
 158 struct link_map *_dl_initfirst;
 159
 160 /* Descriptor to write debug messages to.  */
 161 int _dl_debug_fd = STDERR_FILENO;
 162
 163 int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
 164
 165 ElfW(auxv_t) *_dl_auxv;
 166 const ElfW(Phdr) *_dl_phdr;
 167 size_t _dl_phnum;
 168 uint64_t _dl_hwcap __attribute__ ((nocommon));
 169 uint64_t _dl_hwcap2 __attribute__ ((nocommon));
 170
 171 /* The value of the FPU control word the kernel will preset in hardware.  */
 172 fpu_control_t _dl_fpu_control = _FPU_DEFAULT;
 173
 174 /* This is not initialized to HWCAP_IMPORTANT, matching the definition
 175    of _dl_important_hwcaps, below, where no hwcap strings are ever
 176    used.  This mask is still used to mediate the lookups in the cache
 177    file.  Since there is no way to set this nonzero (we don't grok the
 178    LD_HWCAP_MASK environment variable here), there is no real point in
 179    setting _dl_hwcap nonzero below, but we do anyway.  */
 180 uint64_t _dl_hwcap_mask __attribute__ ((nocommon));
 181
 182 /* Prevailing state of the stack.  Generally this includes PF_X, indicating it's
 183  * executable but this isn't true for all platforms.  */
 184 ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
 185
 186 /* If loading a shared object requires that we make the stack executable
 187    when it was not, we do it by calling this function.
 188    It returns an errno code or zero on success.  */
 189 int (*_dl_make_stack_executable_hook) (void **) internal_function
 190   = _dl_make_stack_executable;
 191
 192
 193 /* Function in libpthread to wait for termination of lookups.  */
 194 void (*_dl_wait_lookup_done) (void);
 195
 196 struct dl_scope_free_list *_dl_scope_free_list;
 197
 198 #ifdef NEED_DL_SYSINFO
 199 /* Needed for improved syscall handling on at least x86/Linux.  */
 200 uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
 201 #endif
 202 #ifdef NEED_DL_SYSINFO_DSO
 203 /* Address of the ELF headers in the vsyscall page.  */
 204 const ElfW(Ehdr) *_dl_sysinfo_dso;
 205
 206 struct link_map *_dl_sysinfo_map;
 207
 208 # include "get-dynamic-info.h"
 209 #endif
 210 #include "setup-vdso.h"
 211
 212 /* During the program run we must not modify the global data of
 213    loaded shared object simultanously in two threads.  Therefore we
 214    protect `_dl_open' and `_dl_close' in dl-close.c.
 215
 216    This must be a recursive lock since the initializer function of
 217    the loaded object might as well require a call to this function.
 218    At this time it is not anymore a problem to modify the tables.  */
 219 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 220 /* This lock is used to keep __dl_iterate_phdr from inspecting the
 221    list of loaded objects while an object is added to or removed from
 222    that list.  */
 223 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
 224
 225
 226 #ifdef HAVE_AUX_VECTOR
 227 int _dl_clktck;
 228
 229 void
 230 internal_function
 231 _dl_aux_init (ElfW(auxv_t) *av)
 232 {
 233   int seen = 0;
 234   uid_t uid = 0;
 235   gid_t gid = 0;
 236
 237   _dl_auxv = av;
 238   for (; av->a_type != AT_NULL; ++av)
 239     switch (av->a_type)
 240       {
 241       case AT_PAGESZ:
 242         if (av->a_un.a_val != 0)
 243           GLRO(dl_pagesize) = av->a_un.a_val;
 244         break;
 245       case AT_CLKTCK:
 246         GLRO(dl_clktck) = av->a_un.a_val;
 247         break;
 248       case AT_PHDR:
 249         GL(dl_phdr) = (const void *) av->a_un.a_val;
 250         break;
 251       case AT_PHNUM:
 252         GL(dl_phnum) = 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 # ifdef DL_PLATFORM_AUXV
 298       DL_PLATFORM_AUXV
 299 # endif
 300       }
 301   if (seen == 0xf)
 302     {
 303       __libc_enable_secure = uid != 0 || gid != 0;
 304       __libc_enable_secure_decided = 1;
 305     }
 306 }
 307 #endif
 308
 309
 310 void
 311 internal_function
 312 _dl_non_dynamic_init (void)
 313 {
 314   _dl_main_map.l_origin = _dl_get_origin ();
 315   _dl_main_map.l_phdr = GL(dl_phdr);
 316   _dl_main_map.l_phnum = GL(dl_phnum);
 317
 318   if (HP_TIMING_AVAIL)
 319     HP_TIMING_NOW (_dl_cpuclock_offset);
 320
 321   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 322
 323   /* Set up the data structures for the system-supplied DSO early,
 324      so they can influence _dl_init_paths.  */
 325   setup_vdso (NULL, NULL);
 326
 327   /* Initialize the data structures for the search paths for shared
 328      objects.  */
 329   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 330
 331   /* Remember the last search directory added at startup.  */
 332   _dl_init_all_dirs = GL(dl_all_dirs);
 333
 334   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 335
 336   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 337
 338   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 339
 340   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 341   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 342     _dl_profile_output
 343       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 344
 345   if (__libc_enable_secure)
 346     {
 347       static const char unsecure_envvars[] =
 348         UNSECURE_ENVVARS
 349 #ifdef EXTRA_UNSECURE_ENVVARS
 350         EXTRA_UNSECURE_ENVVARS
 351 #endif
 352         ;
 353       const char *cp = unsecure_envvars;
 354
 355       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 356         {
 357           __unsetenv (cp);
 358           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 359         }
 360
 361       if (__access ("/etc/suid-debug", F_OK) != 0)
 362         __unsetenv ("MALLOC_CHECK_");
 363     }
 364
 365 #ifdef DL_PLATFORM_INIT
 366   DL_PLATFORM_INIT;
 367 #endif
 368
 369 #ifdef DL_OSVERSION_INIT
 370   DL_OSVERSION_INIT;
 371 #endif
 372
 373   /* Now determine the length of the platform string.  */
 374   if (_dl_platform != NULL)
 375     _dl_platformlen = strlen (_dl_platform);
 376
 377   /* Scan for a program header telling us the stack is nonexecutable.  */
 378   if (_dl_phdr != NULL)
 379     for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
 380       if (_dl_phdr[i].p_type == PT_GNU_STACK)
 381         {
 382           _dl_stack_flags = _dl_phdr[i].p_flags;
 383           break;
 384         }
 385 }
 386
 387 #ifdef DL_SYSINFO_IMPLEMENTATION
 388 DL_SYSINFO_IMPLEMENTATION
 389 #endif