elf/dl-sysdep.c

   1 /* Operating system support for run-time dynamic linker.  Generic Unix version.
   2    Copyright (C) 1995-1998, 2000-2007, 2008 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 #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 <stdio-common/_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 void _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 static ElfW(auxv_t) *_dl_auxv attribute_relro;
  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))
  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                           _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 = _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 #ifdef DL_PLATFORM_AUXV
 177       DL_PLATFORM_AUXV
 178 #endif
 179       }
 180
 181 #ifndef HAVE_AUX_SECURE
 182   if (seen != -1)
 183     {
 184       /* Fill in the values we have not gotten from the kernel through the
 185          auxiliary vector.  */
 186 # ifndef HAVE_AUX_XID
 187 #  define SEE(UID, var, uid) \
 188    if ((seen & M (AT_##UID)) == 0) var ^= __get##uid ()
 189       SEE (UID, uid, uid);
 190       SEE (EUID, uid, euid);
 191       SEE (GID, gid, gid);
 192       SEE (EGID, gid, egid);
 193 # endif
 194
 195       /* If one of the two pairs of IDs does not match this is a setuid
 196          or setgid run.  */
 197       INTUSE(__libc_enable_secure) = uid | gid;
 198     }
 199 #endif
 200
 201 #ifndef HAVE_AUX_PAGESIZE
 202   if (GLRO(dl_pagesize) == 0)
 203     GLRO(dl_pagesize) = __getpagesize ();
 204 #endif
 205
 206 #if defined NEED_DL_SYSINFO
 207   /* Only set the sysinfo value if we also have the vsyscall DSO.  */
 208   if (GLRO(dl_sysinfo_dso) != 0 && new_sysinfo)
 209     GLRO(dl_sysinfo) = new_sysinfo;
 210 #endif
 211
 212 #ifdef DL_SYSDEP_INIT
 213   DL_SYSDEP_INIT;
 214 #endif
 215
 216 #ifdef DL_PLATFORM_INIT
 217   DL_PLATFORM_INIT;
 218 #endif
 219
 220   /* Determine the length of the platform name.  */
 221   if (GLRO(dl_platform) != NULL)
 222     GLRO(dl_platformlen) = strlen (GLRO(dl_platform));
 223
 224   if (__sbrk (0) == &_end)
 225     /* The dynamic linker was run as a program, and so the initial break
 226        starts just after our bss, at &_end.  The malloc in dl-minimal.c
 227        will consume the rest of this page, so tell the kernel to move the
 228        break up that far.  When the user program examines its break, it
 229        will see this new value and not clobber our data.  */
 230     __sbrk (GLRO(dl_pagesize)
 231             - ((&_end - (void *) 0) & (GLRO(dl_pagesize) - 1)));
 232
 233   /* If this is a SUID program we make sure that FDs 0, 1, and 2 are
 234      allocated.  If necessary we are doing it ourself.  If it is not
 235      possible we stop the program.  */
 236   if (__builtin_expect (INTUSE(__libc_enable_secure), 0))
 237     __libc_check_standard_fds ();
 238
 239   (*dl_main) (phdr, phnum, &user_entry);
 240   return user_entry;
 241 }
 242
 243 void
 244 internal_function
 245 _dl_sysdep_start_cleanup (void)
 246 {
 247 }
 248
 249 void
 250 internal_function
 251 _dl_show_auxv (void)
 252 {
 253   char buf[64];
 254   ElfW(auxv_t) *av;
 255
 256   /* Terminate string.  */
 257   buf[63] = '\0';
 258
 259   /* The following code assumes that the AT_* values are encoded
 260      starting from 0 with AT_NULL, 1 for AT_IGNORE, and all other values
 261      close by (otherwise the array will be too large).  In case we have
 262      to support a platform where these requirements are not fulfilled
 263      some alternative implementation has to be used.  */
 264   for (av = _dl_auxv; av->a_type != AT_NULL; ++av)
 265     {
 266       static const struct
 267       {
 268         const char label[20];
 269         enum { unknown = 0, dec, hex, str, ignore } form;
 270       } auxvars[] =
 271         {
 272           [AT_EXECFD - 2] =             { "AT_EXECFD:       ", dec },
 273           [AT_EXECFN - 2] =             { "AT_EXECFN:       ", str },
 274           [AT_PHDR - 2] =               { "AT_PHDR:         0x", hex },
 275           [AT_PHENT - 2] =              { "AT_PHENT:        ", dec },
 276           [AT_PHNUM - 2] =              { "AT_PHNUM:        ", dec },
 277           [AT_PAGESZ - 2] =             { "AT_PAGESZ:       ", dec },
 278           [AT_BASE - 2] =               { "AT_BASE:         0x", hex },
 279           [AT_FLAGS - 2] =              { "AT_FLAGS:        0x", hex },
 280           [AT_ENTRY - 2] =              { "AT_ENTRY:        0x", hex },
 281           [AT_NOTELF - 2] =             { "AT_NOTELF:       ", hex },
 282           [AT_UID - 2] =                { "AT_UID:          ", dec },
 283           [AT_EUID - 2] =               { "AT_EUID:         ", dec },
 284           [AT_GID - 2] =                { "AT_GID:          ", dec },
 285           [AT_EGID - 2] =               { "AT_EGID:         ", dec },
 286           [AT_PLATFORM - 2] =           { "AT_PLATFORM:     ", str },
 287           [AT_HWCAP - 2] =              { "AT_HWCAP:        ", hex },
 288           [AT_CLKTCK - 2] =             { "AT_CLKTCK:       ", dec },
 289           [AT_FPUCW - 2] =              { "AT_FPUCW:        ", hex },
 290           [AT_DCACHEBSIZE - 2] =        { "AT_DCACHEBSIZE:  0x", hex },
 291           [AT_ICACHEBSIZE - 2] =        { "AT_ICACHEBSIZE:  0x", hex },
 292           [AT_UCACHEBSIZE - 2] =        { "AT_UCACHEBSIZE:  0x", hex },
 293           [AT_IGNOREPPC - 2] =          { "AT_IGNOREPPC", ignore },
 294           [AT_SECURE - 2] =             { "AT_SECURE:       ", dec },
 295           [AT_SYSINFO - 2] =            { "AT_SYSINFO:      0x", hex },
 296           [AT_SYSINFO_EHDR - 2] =       { "AT_SYSINFO_EHDR: 0x", hex },
 297         };
 298       unsigned int idx = (unsigned int) (av->a_type - 2);
 299
 300       if ((unsigned int) av->a_type < 2u || auxvars[idx].form == ignore)
 301         continue;
 302
 303       assert (AT_NULL == 0);
 304       assert (AT_IGNORE == 1);
 305
 306       if (av->a_type == AT_HWCAP)
 307         {
 308           /* This is handled special.  */
 309           if (_dl_procinfo (av->a_un.a_val) == 0)
 310             continue;
 311         }
 312
 313       if (idx < sizeof (auxvars) / sizeof (auxvars[0])
 314           && auxvars[idx].form != unknown)
 315         {
 316           const char *val = (char *) av->a_un.a_val;
 317
 318           if (__builtin_expect (auxvars[idx].form, dec) == dec)
 319             val = _itoa ((unsigned long int) av->a_un.a_val,
 320                          buf + sizeof buf - 1, 10, 0);
 321           else if (__builtin_expect (auxvars[idx].form, hex) == hex)
 322             val = _itoa ((unsigned long int) av->a_un.a_val,
 323                          buf + sizeof buf - 1, 16, 0);
 324
 325           _dl_printf ("%s%s\n", auxvars[idx].label, val);
 326
 327           continue;
 328         }
 329
 330       /* Unknown value: print a generic line.  */
 331       char buf2[17];
 332       buf[sizeof (buf2) - 1] = '\0';
 333       const char *val2 = _itoa ((unsigned long int) av->a_un.a_val,
 334                                 buf2 + sizeof buf2 - 1, 16, 0);
 335       const char *val =  _itoa ((unsigned long int) av->a_type,
 336                                 buf + sizeof buf - 1, 16, 0);
 337       _dl_printf ("AT_??? (0x%s): 0x%s\n", val, val2);
 338     }
 339 }
 340
 341
 342 /* Return an array of useful/necessary hardware capability names.  */
 343 const struct r_strlenpair *
 344 internal_function
 345 _dl_important_hwcaps (const char *platform, size_t platform_len, size_t *sz,
 346                       size_t *max_capstrlen)
 347 {
 348   /* Determine how many important bits are set.  */
 349   uint64_t masked = GLRO(dl_hwcap) & GLRO(dl_hwcap_mask);
 350   size_t cnt = platform != NULL;
 351   size_t n, m;
 352   size_t total;
 353   struct r_strlenpair *temp;
 354   struct r_strlenpair *result;
 355   struct r_strlenpair *rp;
 356   char *cp;
 357
 358   /* Count the number of bits set in the masked value.  */
 359   for (n = 0; (~((1ULL << n) - 1) & masked) != 0; ++n)
 360     if ((masked & (1ULL << n)) != 0)
 361       ++cnt;
 362
 363 #if (defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO) && defined SHARED
 364   /* The system-supplied DSO can contain a note of type 2, vendor "GNU".
 365      This gives us a list of names to treat as fake hwcap bits.  */
 366
 367   const char *dsocaps = NULL;
 368   size_t dsocapslen = 0;
 369   if (GLRO(dl_sysinfo_map) != NULL)
 370     {
 371       const ElfW(Phdr) *const phdr = GLRO(dl_sysinfo_map)->l_phdr;
 372       const ElfW(Word) phnum = GLRO(dl_sysinfo_map)->l_phnum;
 373       for (uint_fast16_t i = 0; i < phnum; ++i)
 374         if (phdr[i].p_type == PT_NOTE)
 375           {
 376             const ElfW(Addr) start = (phdr[i].p_vaddr
 377                                       + GLRO(dl_sysinfo_map)->l_addr);
 378             const struct
 379             {
 380               ElfW(Word) vendorlen;
 381               ElfW(Word) datalen;
 382               ElfW(Word) type;
 383             } *note = (const void *) start;
 384             while ((ElfW(Addr)) (note + 1) - start < phdr[i].p_memsz)
 385               {
 386 #define ROUND(len) (((len) + sizeof (ElfW(Word)) - 1) & -sizeof (ElfW(Word)))
 387                 if (note->type == 2
 388                     && note->vendorlen == sizeof "GNU"
 389                     && !memcmp ((note + 1), "GNU", sizeof "GNU")
 390                     && note->datalen > 2 * sizeof (ElfW(Word)) + 2)
 391                   {
 392                     const ElfW(Word) *p = ((const void *) (note + 1)
 393                                            + ROUND (sizeof "GNU"));
 394                     cnt += *p++;
 395                     ++p;        /* Skip mask word.  */
 396                     dsocaps = (const char *) p;
 397                     dsocapslen = note->datalen - sizeof *p * 2;
 398                     break;
 399                   }
 400                 note = ((const void *) (note + 1)
 401                         + ROUND (note->vendorlen) + ROUND (note->datalen));
 402 #undef ROUND
 403               }
 404             if (dsocaps != NULL)
 405               break;
 406           }
 407     }
 408 #endif
 409
 410   /* For TLS enabled builds always add 'tls'.  */
 411   ++cnt;
 412
 413   /* Create temporary data structure to generate result table.  */
 414   temp = (struct r_strlenpair *) alloca (cnt * sizeof (*temp));
 415   m = 0;
 416 #if defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO
 417   if (dsocaps != NULL)
 418     {
 419       const ElfW(Word) mask = ((const ElfW(Word) *) dsocaps)[-1];
 420       GLRO(dl_hwcap) |= (uint64_t) mask << _DL_FIRST_EXTRA;
 421       size_t len;
 422       for (const char *p = dsocaps; p < dsocaps + dsocapslen; p += len + 1)
 423         {
 424           uint_fast8_t bit = *p++;
 425           len = strlen (p);
 426
 427           /* Skip entries that are not enabled in the mask word.  */
 428           if (__builtin_expect (mask & ((ElfW(Word)) 1 << bit), 1))
 429             {
 430               temp[m].str = p;
 431               temp[m].len = len;
 432               ++m;
 433             }
 434           else
 435             --cnt;
 436         }
 437     }
 438 #endif
 439   for (n = 0; masked != 0; ++n)
 440     if ((masked & (1ULL << n)) != 0)
 441       {
 442         temp[m].str = _dl_hwcap_string (n);
 443         temp[m].len = strlen (temp[m].str);
 444         masked ^= 1ULL << n;
 445         ++m;
 446       }
 447   if (platform != NULL)
 448     {
 449       temp[m].str = platform;
 450       temp[m].len = platform_len;
 451       ++m;
 452     }
 453
 454   temp[m].str = "tls";
 455   temp[m].len = 3;
 456   ++m;
 457
 458   assert (m == cnt);
 459
 460   /* Determine the total size of all strings together.  */
 461   if (cnt == 1)
 462     total = temp[0].len + 1;
 463   else
 464     {
 465       total = temp[0].len + temp[cnt - 1].len + 2;
 466       if (cnt > 2)
 467         {
 468           total <<= 1;
 469           for (n = 1; n + 1 < cnt; ++n)
 470             total += temp[n].len + 1;
 471           if (cnt > 3
 472               && (cnt >= sizeof (size_t) * 8
 473                   || total + (sizeof (*result) << 3)
 474                      >= (1UL << (sizeof (size_t) * 8 - cnt + 3))))
 475             _dl_signal_error (ENOMEM, NULL, NULL,
 476                               N_("cannot create capability list"));
 477
 478           total <<= cnt - 3;
 479         }
 480     }
 481
 482   /* The result structure: we use a very compressed way to store the
 483      various combinations of capability names.  */
 484   *sz = 1 << cnt;
 485   result = (struct r_strlenpair *) malloc (*sz * sizeof (*result) + total);
 486   if (result == NULL)
 487     _dl_signal_error (ENOMEM, NULL, NULL,
 488                       N_("cannot create capability list"));
 489
 490   if (cnt == 1)
 491     {
 492       result[0].str = (char *) (result + *sz);
 493       result[0].len = temp[0].len + 1;
 494       result[1].str = (char *) (result + *sz);
 495       result[1].len = 0;
 496       cp = __mempcpy ((char *) (result + *sz), temp[0].str, temp[0].len);
 497       *cp = '/';
 498       *sz = 2;
 499       *max_capstrlen = result[0].len;
 500
 501       return result;
 502     }
 503
 504   /* Fill in the information.  This follows the following scheme
 505      (indeces from TEMP for four strings):
 506         entry #0: 0, 1, 2, 3    binary: 1111
 507               #1: 0, 1, 3               1101
 508               #2: 0, 2, 3               1011
 509               #3: 0, 3                  1001
 510      This allows the representation of all possible combinations of
 511      capability names in the string.  First generate the strings.  */
 512   result[1].str = result[0].str = cp = (char *) (result + *sz);
 513 #define add(idx) \
 514       cp = __mempcpy (__mempcpy (cp, temp[idx].str, temp[idx].len), "/", 1);
 515   if (cnt == 2)
 516     {
 517       add (1);
 518       add (0);
 519     }
 520   else
 521     {
 522       n = 1 << (cnt - 1);
 523       do
 524         {
 525           n -= 2;
 526
 527           /* We always add the last string.  */
 528           add (cnt - 1);
 529
 530           /* Add the strings which have the bit set in N.  */
 531           for (m = cnt - 2; m > 0; --m)
 532             if ((n & (1 << m)) != 0)
 533               add (m);
 534
 535           /* Always add the first string.  */
 536           add (0);
 537         }
 538       while (n != 0);
 539     }
 540 #undef add
 541
 542   /* Now we are ready to install the string pointers and length.  */
 543   for (n = 0; n < (1UL << cnt); ++n)
 544     result[n].len = 0;
 545   n = cnt;
 546   do
 547     {
 548       size_t mask = 1 << --n;
 549
 550       rp = result;
 551       for (m = 1 << cnt; m > 0; ++rp)
 552         if ((--m & mask) != 0)
 553           rp->len += temp[n].len + 1;
 554     }
 555   while (n != 0);
 556
 557   /* The first half of the strings all include the first string.  */
 558   n = (1 << cnt) - 2;
 559   rp = &result[2];
 560   while (n != (1UL << (cnt - 1)))
 561     {
 562       if ((--n & 1) != 0)
 563         rp[0].str = rp[-2].str + rp[-2].len;
 564       else
 565         rp[0].str = rp[-1].str;
 566       ++rp;
 567     }
 568
 569   /* The second half starts right after the first part of the string of
 570      the corresponding entry in the first half.  */
 571   do
 572     {
 573       rp[0].str = rp[-(1 << (cnt - 1))].str + temp[cnt - 1].len + 1;
 574       ++rp;
 575     }
 576   while (--n != 0);
 577
 578   /* The maximum string length.  */
 579   *max_capstrlen = result[0].len;
 580
 581   return result;
 582 }