elf/dl-sysdep.c

   1 /* Operating system support for run-time dynamic linker.  Generic Unix version.
   2    Copyright (C) 1995-2014 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 /* We conditionalize the whole of this file rather than simply eliding it
  20    from the static build, because other sysdeps/ versions of this file
  21    might define things needed by a static build.  */
  22
  23 #ifdef SHARED
  24
  25 #include <assert.h>
  26 #include <elf.h>
  27 #include <errno.h>
  28 #include <fcntl.h>
  29 #include <libintl.h>
  30 #include <stdlib.h>
  31 #include <string.h>
  32 #include <unistd.h>
  33 #include <sys/types.h>
  34 #include <sys/stat.h>
  35 #include <sys/mman.h>
  36 #include <ldsodefs.h>
  37 #include <_itoa.h>
  38 #include <fpu_control.h>
  39
  40 #include <entry.h>
  41 #include <dl-machine.h>
  42 #include <dl-procinfo.h>
  43 #include <dl-osinfo.h>
  44 #include <hp-timing.h>
  45 #include <tls.h>
  46
  47 extern char **_environ attribute_hidden;
  48 extern char _end[] attribute_hidden;
  49
  50 /* Protect SUID program against misuse of file descriptors.  */
  51 extern void __libc_check_standard_fds (void);
  52
  53 #ifdef NEED_DL_BASE_ADDR
  54 ElfW(Addr) _dl_base_addr;
  55 #endif
  56 int __libc_enable_secure attribute_relro = 0;
  57 rtld_hidden_data_def (__libc_enable_secure)
  58 int __libc_multiple_libcs = 0;  /* Defining this here avoids the inclusion
  59                                    of init-first.  */
  60 /* This variable contains the lowest stack address ever used.  */
  61 void *__libc_stack_end attribute_relro = NULL;
  62 rtld_hidden_data_def(__libc_stack_end)
  63 void *_dl_random attribute_relro = NULL;
  64
  65 #ifndef DL_FIND_ARG_COMPONENTS
  66 # define DL_FIND_ARG_COMPONENTS(cookie, argc, argv, envp, auxp) \
  67   do {                                                                        \
  68     void **_tmp;                                                              \
  69     (argc) = *(long int *) cookie;                                            \
  70     (argv) = (char **) ((long int *) cookie + 1);                             \
  71     (envp) = (argv) + (argc) + 1;                                             \
  72     for (_tmp = (void **) (envp); *_tmp; ++_tmp)                              \
  73       continue;                                                               \
  74     (auxp) = (void *) ++_tmp;                                                 \
  75   } while (0)
  76 #endif
  77
  78 #ifndef DL_STACK_END
  79 # define DL_STACK_END(cookie) ((void *) (cookie))
  80 #endif
  81
  82 ElfW(Addr)
  83 _dl_sysdep_start (void **start_argptr,
  84                   void (*dl_main) (const ElfW(Phdr) *phdr, ElfW(Word) phnum,
  85                                    ElfW(Addr) *user_entry, ElfW(auxv_t) *auxv))
  86 {
  87   const ElfW(Phdr) *phdr = NULL;
  88   ElfW(Word) phnum = 0;
  89   ElfW(Addr) user_entry;
  90   ElfW(auxv_t) *av;
  91 #ifdef HAVE_AUX_SECURE
  92 # define set_seen(tag) (tag)    /* Evaluate for the side effects.  */
  93 # define set_seen_secure() ((void) 0)
  94 #else
  95   uid_t uid = 0;
  96   gid_t gid = 0;
  97   unsigned int seen = 0;
  98 # define set_seen_secure() (seen = -1)
  99 # ifdef HAVE_AUX_XID
 100 #  define set_seen(tag) (tag)   /* Evaluate for the side effects.  */
 101 # else
 102 #  define M(type) (1 << (type))
 103 #  define set_seen(tag) seen |= M ((tag)->a_type)
 104 # endif
 105 #endif
 106 #ifdef NEED_DL_SYSINFO
 107   uintptr_t new_sysinfo = 0;
 108 #endif
 109
 110   __libc_stack_end = DL_STACK_END (start_argptr);
 111   DL_FIND_ARG_COMPONENTS (start_argptr, _dl_argc, _dl_argv, _environ,
 112                           GLRO(dl_auxv));
 113
 114   user_entry = (ElfW(Addr)) ENTRY_POINT;
 115   GLRO(dl_platform) = NULL; /* Default to nothing known about the platform.  */
 116
 117   for (av = GLRO(dl_auxv); av->a_type != AT_NULL; set_seen (av++))
 118     switch (av->a_type)
 119       {
 120       case AT_PHDR:
 121         phdr = (void *) av->a_un.a_val;
 122         break;
 123       case AT_PHNUM:
 124         phnum = av->a_un.a_val;
 125         break;
 126       case AT_PAGESZ:
 127         GLRO(dl_pagesize) = av->a_un.a_val;
 128         break;
 129       case AT_ENTRY:
 130         user_entry = av->a_un.a_val;
 131         break;
 132 #ifdef NEED_DL_BASE_ADDR
 133       case AT_BASE:
 134         _dl_base_addr = av->a_un.a_val;
 135         break;
 136 #endif
 137 #ifndef HAVE_AUX_SECURE
 138       case AT_UID:
 139       case AT_EUID:
 140         uid ^= av->a_un.a_val;
 141         break;
 142       case AT_GID:
 143       case AT_EGID:
 144         gid ^= av->a_un.a_val;
 145         break;
 146 #endif
 147       case AT_SECURE:
 148 #ifndef HAVE_AUX_SECURE
 149         seen = -1;
 150 #endif
 151         __libc_enable_secure = av->a_un.a_val;
 152         break;
 153       case AT_PLATFORM:
 154         GLRO(dl_platform) = (void *) av->a_un.a_val;
 155         break;
 156       case AT_HWCAP:
 157         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 158         break;
 159       case AT_HWCAP2:
 160         GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
 161         break;
 162       case AT_CLKTCK:
 163         GLRO(dl_clktck) = av->a_un.a_val;
 164         break;
 165       case AT_FPUCW:
 166         GLRO(dl_fpu_control) = av->a_un.a_val;
 167         break;
 168 #ifdef NEED_DL_SYSINFO
 169       case AT_SYSINFO:
 170         new_sysinfo = av->a_un.a_val;
 171         break;
 172 #endif
 173 #ifdef NEED_DL_SYSINFO_DSO
 174       case AT_SYSINFO_EHDR:
 175         GLRO(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 176         break;
 177 #endif
 178       case AT_RANDOM:
 179         _dl_random = (void *) av->a_un.a_val;
 180         break;
 181 #ifdef DL_PLATFORM_AUXV
 182       DL_PLATFORM_AUXV
 183 #endif
 184       }
 185
 186 #ifndef HAVE_AUX_SECURE
 187   if (seen != -1)
 188     {
 189       /* Fill in the values we have not gotten from the kernel through the
 190          auxiliary vector.  */
 191 # ifndef HAVE_AUX_XID
 192 #  define SEE(UID, var, uid) \
 193    if ((seen & M (AT_##UID)) == 0) var ^= __get##uid ()
 194       SEE (UID, uid, uid);
 195       SEE (EUID, uid, euid);
 196       SEE (GID, gid, gid);
 197       SEE (EGID, gid, egid);
 198 # endif
 199
 200       /* If one of the two pairs of IDs does not match this is a setuid
 201          or setgid run.  */
 202       __libc_enable_secure = uid | gid;
 203     }
 204 #endif
 205
 206 #ifndef HAVE_AUX_PAGESIZE
 207   if (GLRO(dl_pagesize) == 0)
 208     GLRO(dl_pagesize) = __getpagesize ();
 209 #endif
 210
 211 #ifdef NEED_DL_SYSINFO
 212   if (new_sysinfo != 0)
 213     {
 214 # ifdef NEED_DL_SYSINFO_DSO
 215       /* Only set the sysinfo value if we also have the vsyscall DSO.  */
 216       if (GLRO(dl_sysinfo_dso) != 0)
 217 # endif
 218         GLRO(dl_sysinfo) = new_sysinfo;
 219     }
 220 #endif
 221
 222 #ifdef DL_SYSDEP_INIT
 223   DL_SYSDEP_INIT;
 224 #endif
 225
 226 #ifdef DL_PLATFORM_INIT
 227   DL_PLATFORM_INIT;
 228 #endif
 229
 230   /* Determine the length of the platform name.  */
 231   if (GLRO(dl_platform) != NULL)
 232     GLRO(dl_platformlen) = strlen (GLRO(dl_platform));
 233
 234   if (__sbrk (0) == _end)
 235     /* The dynamic linker was run as a program, and so the initial break
 236        starts just after our bss, at &_end.  The malloc in dl-minimal.c
 237        will consume the rest of this page, so tell the kernel to move the
 238        break up that far.  When the user program examines its break, it
 239        will see this new value and not clobber our data.  */
 240     __sbrk (GLRO(dl_pagesize)
 241             - ((_end - (char *) 0) & (GLRO(dl_pagesize) - 1)));
 242
 243   /* If this is a SUID program we make sure that FDs 0, 1, and 2 are
 244      allocated.  If necessary we are doing it ourself.  If it is not
 245      possible we stop the program.  */
 246   if (__builtin_expect (__libc_enable_secure, 0))
 247     __libc_check_standard_fds ();
 248
 249   (*dl_main) (phdr, phnum, &user_entry, GLRO(dl_auxv));
 250   return user_entry;
 251 }
 252
 253 void
 254 internal_function
 255 _dl_sysdep_start_cleanup (void)
 256 {
 257 }
 258
 259 void
 260 internal_function
 261 _dl_show_auxv (void)
 262 {
 263   char buf[64];
 264   ElfW(auxv_t) *av;
 265
 266   /* Terminate string.  */
 267   buf[63] = '\0';
 268
 269   /* The following code assumes that the AT_* values are encoded
 270      starting from 0 with AT_NULL, 1 for AT_IGNORE, and all other values
 271      close by (otherwise the array will be too large).  In case we have
 272      to support a platform where these requirements are not fulfilled
 273      some alternative implementation has to be used.  */
 274   for (av = GLRO(dl_auxv); av->a_type != AT_NULL; ++av)
 275     {
 276       static const struct
 277       {
 278         const char label[17];
 279         enum { unknown = 0, dec, hex, str, ignore } form : 8;
 280       } auxvars[] =
 281         {
 282           [AT_EXECFD - 2] =             { "EXECFD:       ", dec },
 283           [AT_EXECFN - 2] =             { "EXECFN:       ", str },
 284           [AT_PHDR - 2] =               { "PHDR:         0x", hex },
 285           [AT_PHENT - 2] =              { "PHENT:        ", dec },
 286           [AT_PHNUM - 2] =              { "PHNUM:        ", dec },
 287           [AT_PAGESZ - 2] =             { "PAGESZ:       ", dec },
 288           [AT_BASE - 2] =               { "BASE:         0x", hex },
 289           [AT_FLAGS - 2] =              { "FLAGS:        0x", hex },
 290           [AT_ENTRY - 2] =              { "ENTRY:        0x", hex },
 291           [AT_NOTELF - 2] =             { "NOTELF:       ", hex },
 292           [AT_UID - 2] =                { "UID:          ", dec },
 293           [AT_EUID - 2] =               { "EUID:         ", dec },
 294           [AT_GID - 2] =                { "GID:          ", dec },
 295           [AT_EGID - 2] =               { "EGID:         ", dec },
 296           [AT_PLATFORM - 2] =           { "PLATFORM:     ", str },
 297           [AT_HWCAP - 2] =              { "HWCAP:        ", hex },
 298           [AT_CLKTCK - 2] =             { "CLKTCK:       ", dec },
 299           [AT_FPUCW - 2] =              { "FPUCW:        ", hex },
 300           [AT_DCACHEBSIZE - 2] =        { "DCACHEBSIZE:  0x", hex },
 301           [AT_ICACHEBSIZE - 2] =        { "ICACHEBSIZE:  0x", hex },
 302           [AT_UCACHEBSIZE - 2] =        { "UCACHEBSIZE:  0x", hex },
 303           [AT_IGNOREPPC - 2] =          { "IGNOREPPC", ignore },
 304           [AT_SECURE - 2] =             { "SECURE:       ", dec },
 305           [AT_BASE_PLATFORM - 2] =      { "BASE_PLATFORM:", str },
 306           [AT_SYSINFO - 2] =            { "SYSINFO:      0x", hex },
 307           [AT_SYSINFO_EHDR - 2] =       { "SYSINFO_EHDR: 0x", hex },
 308           [AT_RANDOM - 2] =             { "RANDOM:       0x", hex },
 309           [AT_HWCAP2 - 2] =             { "HWCAP2:       0x", hex },
 310         };
 311       unsigned int idx = (unsigned int) (av->a_type - 2);
 312
 313       if ((unsigned int) av->a_type < 2u
 314           || (idx < sizeof (auxvars) / sizeof (auxvars[0])
 315               && auxvars[idx].form == ignore))
 316         continue;
 317
 318       assert (AT_NULL == 0);
 319       assert (AT_IGNORE == 1);
 320
 321       if (av->a_type == AT_HWCAP || av->a_type == AT_HWCAP2)
 322         {
 323           /* These are handled in a special way per platform.  */
 324           if (_dl_procinfo (av->a_type, av->a_un.a_val) == 0)
 325             continue;
 326         }
 327
 328       if (idx < sizeof (auxvars) / sizeof (auxvars[0])
 329           && auxvars[idx].form != unknown)
 330         {
 331           const char *val = (char *) av->a_un.a_val;
 332
 333           if (__builtin_expect (auxvars[idx].form, dec) == dec)
 334             val = _itoa ((unsigned long int) av->a_un.a_val,
 335                          buf + sizeof buf - 1, 10, 0);
 336           else if (__builtin_expect (auxvars[idx].form, hex) == hex)
 337             val = _itoa ((unsigned long int) av->a_un.a_val,
 338                          buf + sizeof buf - 1, 16, 0);
 339
 340           _dl_printf ("AT_%s%s\n", auxvars[idx].label, val);
 341
 342           continue;
 343         }
 344
 345       /* Unknown value: print a generic line.  */
 346       char buf2[17];
 347       buf2[sizeof (buf2) - 1] = '\0';
 348       const char *val2 = _itoa ((unsigned long int) av->a_un.a_val,
 349                                 buf2 + sizeof buf2 - 1, 16, 0);
 350       const char *val =  _itoa ((unsigned long int) av->a_type,
 351                                 buf + sizeof buf - 1, 16, 0);
 352       _dl_printf ("AT_??? (0x%s): 0x%s\n", val, val2);
 353     }
 354 }
 355
 356 #endif