elf/dl-support.c

   1 /* Support for dynamic linking code in static libc.
   2    Copyright (C) 1996-2002, 2003, 2004 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 /* This file defines some things that for the dynamic linker are defined in
  21    rtld.c and dl-sysdep.c in ways appropriate to bootstrap dynamic linking.  */
  22
  23 #include <errno.h>
  24 #include <libintl.h>
  25 #include <stdlib.h>
  26 #include <unistd.h>
  27 #include <ldsodefs.h>
  28 #include <dl-machine.h>
  29 #include <bits/libc-lock.h>
  30 #include <dl-cache.h>
  31 #include <dl-librecon.h>
  32 #include <unsecvars.h>
  33 #include <hp-timing.h>
  34
  35 extern char *__progname;
  36 char **_dl_argv = &__progname;  /* This is checked for some error messages.  */
  37
  38 /* Name of the architecture.  */
  39 const char *_dl_platform;
  40 size_t _dl_platformlen;
  41
  42 int _dl_debug_mask;
  43 int _dl_lazy;
  44 ElfW(Addr) _dl_use_load_bias = -2;
  45 int _dl_dynamic_weak;
  46
  47 /* If nonzero print warnings about problematic situations.  */
  48 int _dl_verbose;
  49
  50 /* We never do profiling.  */
  51 const char *_dl_profile;
  52 const char *_dl_profile_output;
  53
  54 /* Names of shared object for which the RUNPATHs and RPATHs should be
  55    ignored.  */
  56 const char *_dl_inhibit_rpath;
  57
  58 /* The map for the object we will profile.  */
  59 struct link_map *_dl_profile_map;
  60
  61 /* This is the address of the last stack address ever used.  */
  62 void *__libc_stack_end;
  63
  64 /* Path where the binary is found.  */
  65 const char *_dl_origin_path;
  66
  67 /* Nonzero if runtime lookup should not update the .got/.plt.  */
  68 int _dl_bind_not;
  69
  70 /* Initially empty list of loaded objects.  */
  71 struct link_map *_dl_loaded;
  72 /* Number of object in the _dl_loaded list.  */
  73 unsigned int _dl_nloaded;
  74
  75 /* Incremented whenever something may have been added to dl_loaded. */
  76 unsigned long long _dl_load_adds;
  77
  78 /* Fake scope.  In dynamically linked binaries this is the scope of the
  79    main application but here we don't have something like this.  So
  80    create a fake scope containing nothing.  */
  81 struct r_scope_elem _dl_initial_searchlist;
  82 /* Variable which can be used in lookup to process the global scope.  */
  83 struct r_scope_elem *_dl_global_scope[2] = { &_dl_initial_searchlist, NULL };
  84 /* This is a global pointer to this structure which is public.  It is
  85    used by dlopen/dlclose to add and remove objects from what is regarded
  86    to be the global scope.  */
  87 struct r_scope_elem *_dl_main_searchlist = &_dl_initial_searchlist;
  88
  89 #ifndef HAVE_INLINED_SYSCALLS
  90 /* Nonzero during startup.  */
  91 int _dl_starting_up = 1;
  92 #endif
  93
  94 /* Get architecture specific initializer.  */
  95 #include <dl-procinfo.c>
  96
  97 /* We expect less than a second for relocation.  */
  98 #ifdef HP_SMALL_TIMING_AVAIL
  99 # undef HP_TIMING_AVAIL
 100 # define HP_TIMING_AVAIL HP_SMALL_TIMING_AVAIL
 101 #endif
 102
 103 /* Initial value of the CPU clock.  */
 104 #ifndef HP_TIMING_NONAVAIL
 105 hp_timing_t _dl_cpuclock_offset;
 106 #endif
 107
 108 #ifdef USE_TLS
 109 void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
 110 #endif
 111
 112 /* This is zero at program start to signal that the global scope map is
 113    allocated by rtld.  Later it keeps the size of the map.  It might be
 114    reset if in _dl_close if the last global object is removed.  */
 115 size_t _dl_global_scope_alloc;
 116
 117 size_t _dl_pagesize;
 118
 119 unsigned int _dl_osversion;
 120
 121 /* All known directories in sorted order.  */
 122 struct r_search_path_elem *_dl_all_dirs;
 123
 124 /* All directories after startup.  */
 125 struct r_search_path_elem *_dl_init_all_dirs;
 126
 127 /* The object to be initialized first.  */
 128 struct link_map *_dl_initfirst;
 129
 130 /* Descriptor to write debug messages to.  */
 131 int _dl_debug_fd = STDERR_FILENO;
 132
 133 int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
 134
 135 ElfW(Phdr) *_dl_phdr;
 136 size_t _dl_phnum;
 137 unsigned long int _dl_hwcap __attribute__ ((nocommon));
 138
 139 /* Prevailing state of the stack, PF_X indicating it's executable.  */
 140 ElfW(Word) _dl_stack_flags = PF_R|PF_W|PF_X;
 141
 142 /* If loading a shared object requires that we make the stack executable
 143    when it was not, we do it by calling this function.
 144    It returns an errno code or zero on success.  */
 145 int (*_dl_make_stack_executable_hook) (void **) internal_function
 146   = _dl_make_stack_executable;
 147
 148
 149 #ifdef NEED_DL_SYSINFO
 150 /* Needed for improved syscall handling on at least x86/Linux.  */
 151 uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT;
 152 /* Address of the ELF headers in the vsyscall page.  */
 153 const ElfW(Ehdr) *_dl_sysinfo_dso;
 154 #endif
 155
 156 /* During the program run we must not modify the global data of
 157    loaded shared object simultanously in two threads.  Therefore we
 158    protect `_dl_open' and `_dl_close' in dl-close.c.
 159
 160    This must be a recursive lock since the initializer function of
 161    the loaded object might as well require a call to this function.
 162    At this time it is not anymore a problem to modify the tables.  */
 163 __rtld_lock_define_initialized_recursive (, _dl_load_lock)
 164
 165
 166 #ifdef HAVE_AUX_VECTOR
 167 int _dl_clktck;
 168
 169 void
 170 internal_function
 171 _dl_aux_init (ElfW(auxv_t) *av)
 172 {
 173   int seen = 0;
 174   uid_t uid = 0;
 175   gid_t gid = 0;
 176
 177   for (; av->a_type != AT_NULL; ++av)
 178     switch (av->a_type)
 179       {
 180       case AT_PAGESZ:
 181         GLRO(dl_pagesize) = av->a_un.a_val;
 182         break;
 183       case AT_CLKTCK:
 184         GLRO(dl_clktck) = av->a_un.a_val;
 185         break;
 186       case AT_PHDR:
 187         GL(dl_phdr) = av->a_un.a_ptr;
 188         break;
 189       case AT_PHNUM:
 190         GL(dl_phnum) = av->a_un.a_val;
 191         break;
 192       case AT_HWCAP:
 193         GLRO(dl_hwcap) = av->a_un.a_val;
 194         break;
 195 #ifdef NEED_DL_SYSINFO
 196       case AT_SYSINFO:
 197         GL(dl_sysinfo) = av->a_un.a_val;
 198         break;
 199 #endif
 200       case AT_UID:
 201         uid ^= av->a_un.a_val;
 202         seen |= 1;
 203         break;
 204       case AT_EUID:
 205         uid ^= av->a_un.a_val;
 206         seen |= 2;
 207         break;
 208       case AT_GID:
 209         gid ^= av->a_un.a_val;
 210         seen |= 4;
 211         break;
 212       case AT_EGID:
 213         gid ^= av->a_un.a_val;
 214         seen |= 8;
 215         break;
 216       case AT_SECURE:
 217         seen = -1;
 218         __libc_enable_secure = av->a_un.a_val;
 219         __libc_enable_secure_decided = 1;
 220         break;
 221       }
 222   if (seen == 0xf)
 223     {
 224       __libc_enable_secure = uid != 0 || gid != 0;
 225       __libc_enable_secure_decided = 1;
 226     }
 227 }
 228 #endif
 229
 230
 231 void
 232 internal_function
 233 _dl_non_dynamic_init (void)
 234 {
 235   if (HP_TIMING_AVAIL)
 236     HP_TIMING_NOW (_dl_cpuclock_offset);
 237
 238   if (!_dl_pagesize)
 239     _dl_pagesize = __getpagesize ();
 240
 241   _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
 242
 243   /* Initialize the data structures for the search paths for shared
 244      objects.  */
 245   _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
 246
 247   _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
 248
 249   _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
 250
 251   _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
 252
 253   _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
 254   if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
 255     _dl_profile_output
 256       = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 257
 258   if (__libc_enable_secure)
 259     {
 260       static const char unsecure_envvars[] =
 261         UNSECURE_ENVVARS
 262 #ifdef EXTRA_UNSECURE_ENVVARS
 263         EXTRA_UNSECURE_ENVVARS
 264 #endif
 265         ;
 266       const char *cp = unsecure_envvars;
 267
 268       while (cp < unsecure_envvars + sizeof (unsecure_envvars))
 269         {
 270           __unsetenv (cp);
 271           cp = (const char *) __rawmemchr (cp, '\0') + 1;
 272         }
 273
 274       if (__access ("/etc/suid-debug", F_OK) != 0)
 275         __unsetenv ("MALLOC_CHECK_");
 276     }
 277
 278 #ifdef DL_PLATFORM_INIT
 279   DL_PLATFORM_INIT;
 280 #endif
 281
 282 #ifdef DL_OSVERSION_INIT
 283   DL_OSVERSION_INIT;
 284 #endif
 285
 286   /* Now determine the length of the platform string.  */
 287   if (_dl_platform != NULL)
 288     _dl_platformlen = strlen (_dl_platform);
 289
 290 #if defined (__i386__) && !defined (USE_TLS)
 291   /* Load libs not using TLS.  */
 292   _dl_osversion = 0x20205;
 293 #endif
 294
 295   /* Scan for a program header telling us the stack is nonexecutable.  */
 296   if (_dl_phdr != NULL)
 297     for (uint_fast16_t i = 0; i < _dl_phnum; ++i)
 298       if (_dl_phdr[i].p_type == PT_GNU_STACK)
 299         {
 300           _dl_stack_flags = _dl_phdr[i].p_flags;
 301           break;
 302         }
 303 }
 304
 305
 306 const struct r_strlenpair *
 307 internal_function
 308 _dl_important_hwcaps (const char *platform, size_t platform_len, size_t *sz,
 309                       size_t *max_capstrlen)
 310 {
 311   static struct r_strlenpair result;
 312   static char buf[1];
 313
 314   result.str = buf;     /* Does not really matter.  */
 315   result.len = 0;
 316
 317   *sz = 1;
 318   return &result;
 319 }
 320
 321
 322 #ifdef DL_SYSINFO_IMPLEMENTATION
 323 DL_SYSINFO_IMPLEMENTATION
 324 #endif