elf/dl-support.c

   1 /* Support for dynamic linking code in static libc.
   2    Copyright (C) 1996-2015 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 /* Initial value of the CPU clock.  */
 133 #ifndef HP_TIMING_NONAVAIL
 134 hp_timing_t _dl_cpuclock_offset;
 135 #endif
 136
 137 void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
 138
 139 size_t _dl_pagesize = EXEC_PAGESIZE;
 140
 141 int _dl_inhibit_cache;
 142
 143 unsigned int _dl_osversion;
 144
 145 /* All known directories in sorted order.  */
 146 struct r_search_path_elem *_dl_all_dirs;
 147
 148 /* All directories after startup.  */
 149 struct r_search_path_elem *_dl_init_all_dirs;
 150
 151 /* The object to be initialized first.  */
 152 struct link_map *_dl_initfirst;
 153
 154 /* Descriptor to write debug messages to.  */
 155 int _dl_debug_fd = STDERR_FILENO;
 156
 157 int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
 158
 159 ElfW(auxv_t) *_dl_auxv;
 160 const ElfW(Phdr) *_dl_phdr;
 161 size_t _dl_phnum;
 162 uint64_t _dl_hwcap __attribute__ ((nocommon));
 163 uint64_t _dl_hwcap2 __attribute__ ((nocommon));
 164
 165 /* The value of the FPU control word the kernel will preset in hardware.  */
 166 fpu_control_t _dl_fpu_control = _FPU_DEFAULT;
 167
 168 /* This is not initialized to HWCAP_IMPORTANT, matching the definition
 169    of _dl_important_hwcaps, below, where no hwcap strings are ever
 170    used.  This mask is still used to mediate the lookups in the cache
 171    file.  Since there is no way to set this nonzero (we don't grok the
 172    LD_HWCAP_MASK environment variable here), there is no real point in
 173    setting _dl_hwcap nonzero below, but we do anyway.  */
 174 uint64_t _dl_hwcap_mask __attribute__ ((nocommon));
 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 **) internal_function
 184   = _dl_make_stack_executable;
 185
 186
 187 /* Function in libpthread to wait for termination of lookups.  */
 188 void (*_dl_wait_lookup_done) (void);
 189
 190 struct dl_scope_free_list *_dl_scope_free_list;
 191
 192 #ifdef NEED_DL_SYSINFO
 193 /* Needed for improved syscall handling on at least x86/Linux.  */
 194 uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
 195 #endif
 196 #ifdef NEED_DL_SYSINFO_DSO
 197 /* Address of the ELF headers in the vsyscall page.  */
 198 const ElfW(Ehdr) *_dl_sysinfo_dso;
 199
 200 struct link_map *_dl_sysinfo_map;
 201
 202 # include "get-dynamic-info.h"
 203 #endif
 204 #include "setup-vdso.h"
 205
 206 /* During the program run we must not modify the global data of
 207    loaded shared object simultanously in two threads.  Therefore we
 208    protect `_dl_open' and `_dl_close' in dl-close.c.
 209
 210    This must be a recursive lock since the initializer function of
 211    the loaded object might as well require a call to this function.
 212    At this time it is not anymore a problem to modify the tables.  */
 213 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 214 /* This lock is used to keep __dl_iterate_phdr from inspecting the
 215    list of loaded objects while an object is added to or removed from
 216    that list.  */
 217 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
 218
 219
 220 #ifdef HAVE_AUX_VECTOR
 221 int _dl_clktck;
 222
 223 void
 224 internal_function
 225 _dl_aux_init (ElfW(auxv_t) *av)
 226 {
 227   int seen = 0;
 228   uid_t uid = 0;
 229   gid_t gid = 0;
 230
 231   _dl_auxv = av;
 232   for (; av->a_type != AT_NULL; ++av)
 233     switch (av->a_type)
 234       {
 235       case AT_PAGESZ:
 236         if (av->a_un.a_val != 0)
 237           GLRO(dl_pagesize) = av->a_un.a_val;
 238         break;
 239       case AT_CLKTCK:
 240         GLRO(dl_clktck) = av->a_un.a_val;
 241         break;
 242       case AT_PHDR:
 243         GL(dl_phdr) = (const void *) av->a_un.a_val;
 244         break;
 245       case AT_PHNUM:
 246         GL(dl_phnum) = av->a_un.a_val;
 247         break;
 248       case AT_HWCAP:
 249         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 250         break;
 251       case AT_HWCAP2:
 252         GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
 253         break;
 254       case AT_FPUCW:
 255         GLRO(dl_fpu_control) = av->a_un.a_val;
 256         break;
 257 #ifdef NEED_DL_SYSINFO
 258       case AT_SYSINFO:
 259         GL(dl_sysinfo) = av->a_un.a_val;
 260         break;
 261 #endif
 262 #ifdef NEED_DL_SYSINFO_DSO
 263       case AT_SYSINFO_EHDR:
 264         GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 265         break;
 266 #endif
 267       case AT_UID:
 268         uid ^= av->a_un.a_val;
 269         seen |= 1;
 270         break;
 271       case AT_EUID:
 272         uid ^= av->a_un.a_val;
 273         seen |= 2;
 274         break;
 275       case AT_GID:
 276         gid ^= av->a_un.a_val;
 277         seen |= 4;
 278         break;
 279       case AT_EGID:
 280         gid ^= av->a_un.a_val;
 281         seen |= 8;
 282         break;
 283       case AT_SECURE:
 284         seen = -1;
 285         __libc_enable_secure = av->a_un.a_val;
 286         __libc_enable_secure_decided = 1;
 287         break;
 288       case AT_RANDOM:
 289         _dl_random = (void *) av->a_un.a_val;
 290         break;
 291 # ifdef DL_PLATFORM_AUXV
 292       DL_PLATFORM_AUXV
 293 # endif
 294       }
 295   if (seen == 0xf)
 296     {
 297       __libc_enable_secure = uid != 0 || gid != 0;
 298       __libc_enable_secure_decided = 1;
 299     }
 300 }
 301 #endif
 302
 303
 304 void
 305 internal_function
 306 _dl_non_dynamic_init (void)
 307 {
 308   _dl_main_map.l_origin = _dl_get_origin ();
 309   _dl_main_map.l_phdr = GL(dl_phdr);
 310   _dl_main_map.l_phnum = GL(dl_phnum);
 311
 312   if (HP_SMALL_TIMING_AVAIL)
 313     HP_TIMING_NOW (_dl_cpuclock_offset);
 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   /* Initialize the data structures for the search paths for shared
 322      objects.  */
 323   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 324
 325   /* Remember the last search directory added at startup.  */
 326   _dl_init_all_dirs = GL(dl_all_dirs);
 327
 328   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 329
 330   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 331
 332   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 333
 334   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 335   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 336     _dl_profile_output
 337       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 338
 339   if (__libc_enable_secure)
 340     {
 341       static const char unsecure_envvars[] =
 342         UNSECURE_ENVVARS
 343 #ifdef EXTRA_UNSECURE_ENVVARS
 344         EXTRA_UNSECURE_ENVVARS
 345 #endif
 346         ;
 347       const char *cp = unsecure_envvars;
 348
 349       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 350         {
 351           __unsetenv (cp);
 352           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 353         }
 354
 355       if (__access ("/etc/suid-debug", F_OK) != 0)
 356         __unsetenv ("MALLOC_CHECK_");
 357     }
 358
 359 #ifdef DL_PLATFORM_INIT
 360   DL_PLATFORM_INIT;
 361 #endif
 362
 363 #ifdef DL_OSVERSION_INIT
 364   DL_OSVERSION_INIT;
 365 #endif
 366
 367   /* Now determine the length of the platform string.  */
 368   if (_dl_platform != NULL)
 369     _dl_platformlen = strlen (_dl_platform);
 370
 371   /* Scan for a program header telling us the stack is nonexecutable.  */
 372   if (_dl_phdr != NULL)
 373     for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
 374       if (_dl_phdr[i].p_type == PT_GNU_STACK)
 375         {
 376           _dl_stack_flags = _dl_phdr[i].p_flags;
 377           break;
 378         }
 379 }
 380
 381 #ifdef DL_SYSINFO_IMPLEMENTATION
 382 DL_SYSINFO_IMPLEMENTATION
 383 #endif