elf/dl-sysdep.c

   1 /* Operating system support for run-time dynamic linker.  Generic Unix version.
   2    Copyright (C) 1995-1998,2000-2010,2012
   3         Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <assert.h>
  21 #include <elf.h>
  22 #include <errno.h>
  23 #include <fcntl.h>
  24 #include <libintl.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <unistd.h>
  28 #include <sys/types.h>
  29 #include <sys/stat.h>
  30 #include <sys/mman.h>
  31 #include <ldsodefs.h>
  32 #include <_itoa.h>
  33 #include <fpu_control.h>
  34
  35 #include <entry.h>
  36 #include <dl-machine.h>
  37 #include <dl-procinfo.h>
  38 #include <dl-osinfo.h>
  39 #include <hp-timing.h>
  40 #include <tls.h>
  41
  42 #ifdef _DL_FIRST_PLATFORM
  43 # define _DL_FIRST_EXTRA (_DL_FIRST_PLATFORM + _DL_PLATFORMS_COUNT)
  44 #else
  45 # define _DL_FIRST_EXTRA _DL_HWCAP_COUNT
  46 #endif
  47
  48 extern char **_environ attribute_hidden;
  49 extern char _end[] attribute_hidden;
  50
  51 /* Protect SUID program against misuse of file descriptors.  */
  52 extern void __libc_check_standard_fds (void);
  53
  54 #ifdef NEED_DL_BASE_ADDR
  55 ElfW(Addr) _dl_base_addr;
  56 #endif
  57 int __libc_enable_secure attribute_relro = 0;
  58 INTVARDEF(__libc_enable_secure)
  59 int __libc_multiple_libcs = 0;  /* Defining this here avoids the inclusion
  60                                    of init-first.  */
  61 /* This variable contains the lowest stack address ever used.  */
  62 void *__libc_stack_end attribute_relro = NULL;
  63 rtld_hidden_data_def(__libc_stack_end)
  64 void *_dl_random attribute_relro = NULL;
  65
  66 #ifndef DL_FIND_ARG_COMPONENTS
  67 # define DL_FIND_ARG_COMPONENTS(cookie, argc, argv, envp, auxp) \
  68   do {                                                                        \
  69     void **_tmp;                                                              \
  70     (argc) = *(long int *) cookie;                                            \
  71     (argv) = (char **) ((long int *) cookie + 1);                             \
  72     (envp) = (argv) + (argc) + 1;                                             \
  73     for (_tmp = (void **) (envp); *_tmp; ++_tmp)                              \
  74       continue;                                                               \
  75     (auxp) = (void *) ++_tmp;                                                 \
  76   } while (0)
  77 #endif
  78
  79 #ifndef DL_STACK_END
  80 # define DL_STACK_END(cookie) ((void *) (cookie))
  81 #endif
  82
  83 ElfW(Addr)
  84 _dl_sysdep_start (void **start_argptr,
  85                   void (*dl_main) (const ElfW(Phdr) *phdr, ElfW(Word) phnum,
  86                                    ElfW(Addr) *user_entry, ElfW(auxv_t) *auxv))
  87 {
  88   const ElfW(Phdr) *phdr = NULL;
  89   ElfW(Word) phnum = 0;
  90   ElfW(Addr) user_entry;
  91   ElfW(auxv_t) *av;
  92 #ifdef HAVE_AUX_SECURE
  93 # define set_seen(tag) (tag)    /* Evaluate for the side effects.  */
  94 # define set_seen_secure() ((void) 0)
  95 #else
  96   uid_t uid = 0;
  97   gid_t gid = 0;
  98   unsigned int seen = 0;
  99 # define set_seen_secure() (seen = -1)
 100 # ifdef HAVE_AUX_XID
 101 #  define set_seen(tag) (tag)   /* Evaluate for the side effects.  */
 102 # else
 103 #  define M(type) (1 << (type))
 104 #  define set_seen(tag) seen |= M ((tag)->a_type)
 105 # endif
 106 #endif
 107 #ifdef NEED_DL_SYSINFO
 108   uintptr_t new_sysinfo = 0;
 109 #endif
 110
 111   __libc_stack_end = DL_STACK_END (start_argptr);
 112   DL_FIND_ARG_COMPONENTS (start_argptr, _dl_argc, INTUSE(_dl_argv), _environ,
 113                           GLRO(dl_auxv));
 114
 115   user_entry = (ElfW(Addr)) ENTRY_POINT;
 116   GLRO(dl_platform) = NULL; /* Default to nothing known about the platform.  */
 117
 118   for (av = GLRO(dl_auxv); av->a_type != AT_NULL; set_seen (av++))
 119     switch (av->a_type)
 120       {
 121       case AT_PHDR:
 122         phdr = (void *) av->a_un.a_val;
 123         break;
 124       case AT_PHNUM:
 125         phnum = av->a_un.a_val;
 126         break;
 127       case AT_PAGESZ:
 128         GLRO(dl_pagesize) = av->a_un.a_val;
 129         break;
 130       case AT_ENTRY:
 131         user_entry = av->a_un.a_val;
 132         break;
 133 #ifdef NEED_DL_BASE_ADDR
 134       case AT_BASE:
 135         _dl_base_addr = av->a_un.a_val;
 136         break;
 137 #endif
 138 #ifndef HAVE_AUX_SECURE
 139       case AT_UID:
 140       case AT_EUID:
 141         uid ^= av->a_un.a_val;
 142         break;
 143       case AT_GID:
 144       case AT_EGID:
 145         gid ^= av->a_un.a_val;
 146         break;
 147 #endif
 148       case AT_SECURE:
 149 #ifndef HAVE_AUX_SECURE
 150         seen = -1;
 151 #endif
 152         INTUSE(__libc_enable_secure) = av->a_un.a_val;
 153         break;
 154       case AT_PLATFORM:
 155         GLRO(dl_platform) = (void *) av->a_un.a_val;
 156         break;
 157       case AT_HWCAP:
 158         GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
 159         break;
 160       case AT_CLKTCK:
 161         GLRO(dl_clktck) = av->a_un.a_val;
 162         break;
 163       case AT_FPUCW:
 164         GLRO(dl_fpu_control) = av->a_un.a_val;
 165         break;
 166 #ifdef NEED_DL_SYSINFO
 167       case AT_SYSINFO:
 168         new_sysinfo = av->a_un.a_val;
 169         break;
 170 #endif
 171 #if defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO
 172       case AT_SYSINFO_EHDR:
 173         GLRO(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 174         break;
 175 #endif
 176       case AT_RANDOM:
 177         _dl_random = (void *) av->a_un.a_val;
 178         break;
 179 #ifdef DL_PLATFORM_AUXV
 180       DL_PLATFORM_AUXV
 181 #endif
 182       }
 183
 184 #ifndef HAVE_AUX_SECURE
 185   if (seen != -1)
 186     {
 187       /* Fill in the values we have not gotten from the kernel through the
 188          auxiliary vector.  */
 189 # ifndef HAVE_AUX_XID
 190 #  define SEE(UID, var, uid) \
 191    if ((seen & M (AT_##UID)) == 0) var ^= __get##uid ()
 192       SEE (UID, uid, uid);
 193       SEE (EUID, uid, euid);
 194       SEE (GID, gid, gid);
 195       SEE (EGID, gid, egid);
 196 # endif
 197
 198       /* If one of the two pairs of IDs does not match this is a setuid
 199          or setgid run.  */
 200       INTUSE(__libc_enable_secure) = uid | gid;
 201     }
 202 #endif
 203
 204 #ifndef HAVE_AUX_PAGESIZE
 205   if (GLRO(dl_pagesize) == 0)
 206     GLRO(dl_pagesize) = __getpagesize ();
 207 #endif
 208
 209 #if defined NEED_DL_SYSINFO
 210   /* Only set the sysinfo value if we also have the vsyscall DSO.  */
 211   if (GLRO(dl_sysinfo_dso) != 0 && new_sysinfo)
 212     GLRO(dl_sysinfo) = new_sysinfo;
 213 #endif
 214
 215 #ifdef DL_SYSDEP_INIT
 216   DL_SYSDEP_INIT;
 217 #endif
 218
 219 #ifdef DL_PLATFORM_INIT
 220   DL_PLATFORM_INIT;
 221 #endif
 222
 223   /* Determine the length of the platform name.  */
 224   if (GLRO(dl_platform) != NULL)
 225     GLRO(dl_platformlen) = strlen (GLRO(dl_platform));
 226
 227   if (__sbrk (0) == _end)
 228     /* The dynamic linker was run as a program, and so the initial break
 229        starts just after our bss, at &_end.  The malloc in dl-minimal.c
 230        will consume the rest of this page, so tell the kernel to move the
 231        break up that far.  When the user program examines its break, it
 232        will see this new value and not clobber our data.  */
 233     __sbrk (GLRO(dl_pagesize)
 234             - ((_end - (char *) 0) & (GLRO(dl_pagesize) - 1)));
 235
 236   /* If this is a SUID program we make sure that FDs 0, 1, and 2 are
 237      allocated.  If necessary we are doing it ourself.  If it is not
 238      possible we stop the program.  */
 239   if (__builtin_expect (INTUSE(__libc_enable_secure), 0))
 240     __libc_check_standard_fds ();
 241
 242   (*dl_main) (phdr, phnum, &user_entry, GLRO(dl_auxv));
 243   return user_entry;
 244 }
 245
 246 void
 247 internal_function
 248 _dl_sysdep_start_cleanup (void)
 249 {
 250 }
 251
 252 void
 253 internal_function
 254 _dl_show_auxv (void)
 255 {
 256   char buf[64];
 257   ElfW(auxv_t) *av;
 258
 259   /* Terminate string.  */
 260   buf[63] = '\0';
 261
 262   /* The following code assumes that the AT_* values are encoded
 263      starting from 0 with AT_NULL, 1 for AT_IGNORE, and all other values
 264      close by (otherwise the array will be too large).  In case we have
 265      to support a platform where these requirements are not fulfilled
 266      some alternative implementation has to be used.  */
 267   for (av = GLRO(dl_auxv); av->a_type != AT_NULL; ++av)
 268     {
 269       static const struct
 270       {
 271         const char label[17];
 272         enum { unknown = 0, dec, hex, str, ignore } form : 8;
 273       } auxvars[] =
 274         {
 275           [AT_EXECFD - 2] =             { "EXECFD:       ", dec },
 276           [AT_EXECFN - 2] =             { "EXECFN:       ", str },
 277           [AT_PHDR - 2] =               { "PHDR:         0x", hex },
 278           [AT_PHENT - 2] =              { "PHENT:        ", dec },
 279           [AT_PHNUM - 2] =              { "PHNUM:        ", dec },
 280           [AT_PAGESZ - 2] =             { "PAGESZ:       ", dec },
 281           [AT_BASE - 2] =               { "BASE:         0x", hex },
 282           [AT_FLAGS - 2] =              { "FLAGS:        0x", hex },
 283           [AT_ENTRY - 2] =              { "ENTRY:        0x", hex },
 284           [AT_NOTELF - 2] =             { "NOTELF:       ", hex },
 285           [AT_UID - 2] =                { "UID:          ", dec },
 286           [AT_EUID - 2] =               { "EUID:         ", dec },
 287           [AT_GID - 2] =                { "GID:          ", dec },
 288           [AT_EGID - 2] =               { "EGID:         ", dec },
 289           [AT_PLATFORM - 2] =           { "PLATFORM:     ", str },
 290           [AT_HWCAP - 2] =              { "HWCAP:        ", hex },
 291           [AT_CLKTCK - 2] =             { "CLKTCK:       ", dec },
 292           [AT_FPUCW - 2] =              { "FPUCW:        ", hex },
 293           [AT_DCACHEBSIZE - 2] =        { "DCACHEBSIZE:  0x", hex },
 294           [AT_ICACHEBSIZE - 2] =        { "ICACHEBSIZE:  0x", hex },
 295           [AT_UCACHEBSIZE - 2] =        { "UCACHEBSIZE:  0x", hex },
 296           [AT_IGNOREPPC - 2] =          { "IGNOREPPC", ignore },
 297           [AT_SECURE - 2] =             { "SECURE:       ", dec },
 298           [AT_BASE_PLATFORM - 2] =      { "BASE_PLATFORM:", str },
 299           [AT_SYSINFO - 2] =            { "SYSINFO:      0x", hex },
 300           [AT_SYSINFO_EHDR - 2] =       { "SYSINFO_EHDR: 0x", hex },
 301           [AT_RANDOM - 2] =             { "RANDOM:       0x", hex },
 302         };
 303       unsigned int idx = (unsigned int) (av->a_type - 2);
 304
 305       if ((unsigned int) av->a_type < 2u
 306           || (idx < sizeof (auxvars) / sizeof (auxvars[0])
 307               && auxvars[idx].form == ignore))
 308         continue;
 309
 310       assert (AT_NULL == 0);
 311       assert (AT_IGNORE == 1);
 312
 313       if (av->a_type == AT_HWCAP)
 314         {
 315           /* This is handled special.  */
 316           if (_dl_procinfo (av->a_un.a_val) == 0)
 317             continue;
 318         }
 319
 320       if (idx < sizeof (auxvars) / sizeof (auxvars[0])
 321           && auxvars[idx].form != unknown)
 322         {
 323           const char *val = (char *) av->a_un.a_val;
 324
 325           if (__builtin_expect (auxvars[idx].form, dec) == dec)
 326             val = _itoa ((unsigned long int) av->a_un.a_val,
 327                          buf + sizeof buf - 1, 10, 0);
 328           else if (__builtin_expect (auxvars[idx].form, hex) == hex)
 329             val = _itoa ((unsigned long int) av->a_un.a_val,
 330                          buf + sizeof buf - 1, 16, 0);
 331
 332           _dl_printf ("AT_%s%s\n", auxvars[idx].label, val);
 333
 334           continue;
 335         }
 336
 337       /* Unknown value: print a generic line.  */
 338       char buf2[17];
 339       buf2[sizeof (buf2) - 1] = '\0';
 340       const char *val2 = _itoa ((unsigned long int) av->a_un.a_val,
 341                                 buf2 + sizeof buf2 - 1, 16, 0);
 342       const char *val =  _itoa ((unsigned long int) av->a_type,
 343                                 buf + sizeof buf - 1, 16, 0);
 344       _dl_printf ("AT_??? (0x%s): 0x%s\n", val, val2);
 345     }
 346 }
 347
 348
 349 /* Return an array of useful/necessary hardware capability names.  */
 350 const struct r_strlenpair *
 351 internal_function
 352 _dl_important_hwcaps (const char *platform, size_t platform_len, size_t *sz,
 353                       size_t *max_capstrlen)
 354 {
 355   /* Determine how many important bits are set.  */
 356   uint64_t masked = GLRO(dl_hwcap) & GLRO(dl_hwcap_mask);
 357   size_t cnt = platform != NULL;
 358   size_t n, m;
 359   size_t total;
 360   struct r_strlenpair *temp;
 361   struct r_strlenpair *result;
 362   struct r_strlenpair *rp;
 363   char *cp;
 364
 365   /* Count the number of bits set in the masked value.  */
 366   for (n = 0; (~((1ULL << n) - 1) & masked) != 0; ++n)
 367     if ((masked & (1ULL << n)) != 0)
 368       ++cnt;
 369
 370 #if (defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO) && defined SHARED
 371   /* The system-supplied DSO can contain a note of type 2, vendor "GNU".
 372      This gives us a list of names to treat as fake hwcap bits.  */
 373
 374   const char *dsocaps = NULL;
 375   size_t dsocapslen = 0;
 376   if (GLRO(dl_sysinfo_map) != NULL)
 377     {
 378       const ElfW(Phdr) *const phdr = GLRO(dl_sysinfo_map)->l_phdr;
 379       const ElfW(Word) phnum = GLRO(dl_sysinfo_map)->l_phnum;
 380       for (uint_fast16_t i = 0; i < phnum; ++i)
 381         if (phdr[i].p_type == PT_NOTE)
 382           {
 383             const ElfW(Addr) start = (phdr[i].p_vaddr
 384                                       + GLRO(dl_sysinfo_map)->l_addr);
 385             const struct
 386             {
 387               ElfW(Word) vendorlen;
 388               ElfW(Word) datalen;
 389               ElfW(Word) type;
 390             } *note = (const void *) start;
 391             while ((ElfW(Addr)) (note + 1) - start < phdr[i].p_memsz)
 392               {
 393 #define ROUND(len) (((len) + sizeof (ElfW(Word)) - 1) & -sizeof (ElfW(Word)))
 394                 if (note->type == NT_GNU_HWCAP
 395                     && note->vendorlen == sizeof "GNU"
 396                     && !memcmp ((note + 1), "GNU", sizeof "GNU")
 397                     && note->datalen > 2 * sizeof (ElfW(Word)) + 2)
 398                   {
 399                     const ElfW(Word) *p = ((const void *) (note + 1)
 400                                            + ROUND (sizeof "GNU"));
 401                     cnt += *p++;
 402                     ++p;        /* Skip mask word.  */
 403                     dsocaps = (const char *) p;
 404                     dsocapslen = note->datalen - sizeof *p * 2;
 405                     break;
 406                   }
 407                 note = ((const void *) (note + 1)
 408                         + ROUND (note->vendorlen) + ROUND (note->datalen));
 409 #undef ROUND
 410               }
 411             if (dsocaps != NULL)
 412               break;
 413           }
 414     }
 415 #endif
 416
 417   /* For TLS enabled builds always add 'tls'.  */
 418   ++cnt;
 419
 420   /* Create temporary data structure to generate result table.  */
 421   temp = (struct r_strlenpair *) alloca (cnt * sizeof (*temp));
 422   m = 0;
 423 #if (defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO) && defined SHARED
 424   if (dsocaps != NULL)
 425     {
 426       const ElfW(Word) mask = ((const ElfW(Word) *) dsocaps)[-1];
 427       GLRO(dl_hwcap) |= (uint64_t) mask << _DL_FIRST_EXTRA;
 428       /* Note that we add the dsocaps to the set already chosen by the
 429          LD_HWCAP_MASK environment variable (or default HWCAP_IMPORTANT).
 430          So there is no way to request ignoring an OS-supplied dsocap
 431          string and bit like you can ignore an OS-supplied HWCAP bit.  */
 432       GLRO(dl_hwcap_mask) |= (uint64_t) mask << _DL_FIRST_EXTRA;
 433       size_t len;
 434       for (const char *p = dsocaps; p < dsocaps + dsocapslen; p += len + 1)
 435         {
 436           uint_fast8_t bit = *p++;
 437           len = strlen (p);
 438
 439           /* Skip entries that are not enabled in the mask word.  */
 440           if (__builtin_expect (mask & ((ElfW(Word)) 1 << bit), 1))
 441             {
 442               temp[m].str = p;
 443               temp[m].len = len;
 444               ++m;
 445             }
 446           else
 447             --cnt;
 448         }
 449     }
 450 #endif
 451   for (n = 0; masked != 0; ++n)
 452     if ((masked & (1ULL << n)) != 0)
 453       {
 454         temp[m].str = _dl_hwcap_string (n);
 455         temp[m].len = strlen (temp[m].str);
 456         masked ^= 1ULL << n;
 457         ++m;
 458       }
 459   if (platform != NULL)
 460     {
 461       temp[m].str = platform;
 462       temp[m].len = platform_len;
 463       ++m;
 464     }
 465
 466   temp[m].str = "tls";
 467   temp[m].len = 3;
 468   ++m;
 469
 470   assert (m == cnt);
 471
 472   /* Determine the total size of all strings together.  */
 473   if (cnt == 1)
 474     total = temp[0].len + 1;
 475   else
 476     {
 477       total = temp[0].len + temp[cnt - 1].len + 2;
 478       if (cnt > 2)
 479         {
 480           total <<= 1;
 481           for (n = 1; n + 1 < cnt; ++n)
 482             total += temp[n].len + 1;
 483           if (cnt > 3
 484               && (cnt >= sizeof (size_t) * 8
 485                   || total + (sizeof (*result) << 3)
 486                      >= (1UL << (sizeof (size_t) * 8 - cnt + 3))))
 487             _dl_signal_error (ENOMEM, NULL, NULL,
 488                               N_("cannot create capability list"));
 489
 490           total <<= cnt - 3;
 491         }
 492     }
 493
 494   /* The result structure: we use a very compressed way to store the
 495      various combinations of capability names.  */
 496   *sz = 1 << cnt;
 497   result = (struct r_strlenpair *) malloc (*sz * sizeof (*result) + total);
 498   if (result == NULL)
 499     _dl_signal_error (ENOMEM, NULL, NULL,
 500                       N_("cannot create capability list"));
 501
 502   if (cnt == 1)
 503     {
 504       result[0].str = (char *) (result + *sz);
 505       result[0].len = temp[0].len + 1;
 506       result[1].str = (char *) (result + *sz);
 507       result[1].len = 0;
 508       cp = __mempcpy ((char *) (result + *sz), temp[0].str, temp[0].len);
 509       *cp = '/';
 510       *sz = 2;
 511       *max_capstrlen = result[0].len;
 512
 513       return result;
 514     }
 515
 516   /* Fill in the information.  This follows the following scheme
 517      (indeces from TEMP for four strings):
 518         entry #0: 0, 1, 2, 3    binary: 1111
 519               #1: 0, 1, 3               1101
 520               #2: 0, 2, 3               1011
 521               #3: 0, 3                  1001
 522      This allows the representation of all possible combinations of
 523      capability names in the string.  First generate the strings.  */
 524   result[1].str = result[0].str = cp = (char *) (result + *sz);
 525 #define add(idx) \
 526       cp = __mempcpy (__mempcpy (cp, temp[idx].str, temp[idx].len), "/", 1);
 527   if (cnt == 2)
 528     {
 529       add (1);
 530       add (0);
 531     }
 532   else
 533     {
 534       n = 1 << (cnt - 1);
 535       do
 536         {
 537           n -= 2;
 538
 539           /* We always add the last string.  */
 540           add (cnt - 1);
 541
 542           /* Add the strings which have the bit set in N.  */
 543           for (m = cnt - 2; m > 0; --m)
 544             if ((n & (1 << m)) != 0)
 545               add (m);
 546
 547           /* Always add the first string.  */
 548           add (0);
 549         }
 550       while (n != 0);
 551     }
 552 #undef add
 553
 554   /* Now we are ready to install the string pointers and length.  */
 555   for (n = 0; n < (1UL << cnt); ++n)
 556     result[n].len = 0;
 557   n = cnt;
 558   do
 559     {
 560       size_t mask = 1 << --n;
 561
 562       rp = result;
 563       for (m = 1 << cnt; m > 0; ++rp)
 564         if ((--m & mask) != 0)
 565           rp->len += temp[n].len + 1;
 566     }
 567   while (n != 0);
 568
 569   /* The first half of the strings all include the first string.  */
 570   n = (1 << cnt) - 2;
 571   rp = &result[2];
 572   while (n != (1UL << (cnt - 1)))
 573     {
 574       if ((--n & 1) != 0)
 575         rp[0].str = rp[-2].str + rp[-2].len;
 576       else
 577         rp[0].str = rp[-1].str;
 578       ++rp;
 579     }
 580
 581   /* The second half starts right after the first part of the string of
 582      the corresponding entry in the first half.  */
 583   do
 584     {
 585       rp[0].str = rp[-(1 << (cnt - 1))].str + temp[cnt - 1].len + 1;
 586       ++rp;
 587     }
 588   while (--n != 0);
 589
 590   /* The maximum string length.  */
 591   *max_capstrlen = result[0].len;
 592
 593   return result;
 594 }