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       case AT_EXECFN:
 177         GLRO(dl_execfn) = (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 - (void *) 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);
 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 = _dl_auxv; av->a_type != AT_NULL; ++av)
 268     {
 269       static const struct
 270       {
 271         const char label[20];
 272         enum { unknown = 0, dec, hex, str, ignore } form;
 273       } auxvars[] =
 274         {
 275           [AT_EXECFD - 2] =             { "AT_EXECFD:       ", dec },
 276           [AT_PHDR - 2] =               { "AT_PHDR:         0x", hex },
 277           [AT_PHENT - 2] =              { "AT_PHENT:        ", dec },
 278           [AT_PHNUM - 2] =              { "AT_PHNUM:        ", dec },
 279           [AT_PAGESZ - 2] =             { "AT_PAGESZ:       ", dec },
 280           [AT_BASE - 2] =               { "AT_BASE:         0x", hex },
 281           [AT_FLAGS - 2] =              { "AT_FLAGS:        0x", hex },
 282           [AT_ENTRY - 2] =              { "AT_ENTRY:        0x", hex },
 283           [AT_NOTELF - 2] =             { "AT_NOTELF:       ", hex },
 284           [AT_UID - 2] =                { "AT_UID:          ", dec },
 285           [AT_EUID - 2] =               { "AT_EUID:         ", dec },
 286           [AT_GID - 2] =                { "AT_GID:          ", dec },
 287           [AT_EGID - 2] =               { "AT_EGID:         ", dec },
 288           [AT_PLATFORM - 2] =           { "AT_PLATFORM:     ", str },
 289           [AT_HWCAP - 2] =              { "AT_HWCAP:        ", hex },
 290           [AT_CLKTCK - 2] =             { "AT_CLKTCK:       ", dec },
 291           [AT_FPUCW - 2] =              { "AT_FPUCW:        ", hex },
 292           [AT_DCACHEBSIZE - 2] =        { "AT_DCACHEBSIZE:  0x", hex },
 293           [AT_ICACHEBSIZE - 2] =        { "AT_ICACHEBSIZE:  0x", hex },
 294           [AT_UCACHEBSIZE - 2] =        { "AT_UCACHEBSIZE:  0x", hex },
 295           [AT_IGNOREPPC - 2] =          { "AT_IGNOREPPC", ignore },
 296           [AT_SECURE - 2] =             { "AT_SECURE:       ", dec },
 297           [AT_SYSINFO - 2] =            { "AT_SYSINFO:      0x", hex },
 298           [AT_SYSINFO_EHDR - 2] =       { "AT_SYSINFO_EHDR: 0x", hex },
 299         };
 300       unsigned int idx = (unsigned int) (av->a_type - 2);
 301
 302       if ((unsigned int) av->a_type < 2u || auxvars[idx].form == ignore)
 303         continue;
 304
 305       assert (AT_NULL == 0);
 306       assert (AT_IGNORE == 1);
 307
 308       if (av->a_type == AT_HWCAP)
 309         {
 310           /* This is handled special.  */
 311           if (_dl_procinfo (av->a_un.a_val) == 0)
 312             continue;
 313         }
 314
 315       if (idx < sizeof (auxvars) / sizeof (auxvars[0])
 316           && auxvars[idx].form != unknown)
 317         {
 318           const char *val = (char *) av->a_un.a_val;
 319
 320           if (__builtin_expect (auxvars[idx].form, dec) == dec)
 321             val = _itoa ((unsigned long int) av->a_un.a_val,
 322                          buf + sizeof buf - 1, 10, 0);
 323           else if (__builtin_expect (auxvars[idx].form, hex) == hex)
 324             val = _itoa ((unsigned long int) av->a_un.a_val,
 325                          buf + sizeof buf - 1, 16, 0);
 326
 327           _dl_printf ("%s%s\n", auxvars[idx].label, val);
 328
 329           continue;
 330         }
 331
 332       /* Unknown value: print a generic line.  */
 333       char buf2[17];
 334       buf[sizeof (buf2) - 1] = '\0';
 335       const char *val2 = _itoa ((unsigned long int) av->a_un.a_val,
 336                                 buf2 + sizeof buf2 - 1, 16, 0);
 337       const char *val =  _itoa ((unsigned long int) av->a_type,
 338                                 buf + sizeof buf - 1, 16, 0);
 339       _dl_printf ("AT_??? (0x%s): 0x%s\n", val, val2);
 340     }
 341 }
 342
 343
 344 /* Return an array of useful/necessary hardware capability names.  */
 345 const struct r_strlenpair *
 346 internal_function
 347 _dl_important_hwcaps (const char *platform, size_t platform_len, size_t *sz,
 348                       size_t *max_capstrlen)
 349 {
 350   /* Determine how many important bits are set.  */
 351   uint64_t masked = GLRO(dl_hwcap) & GLRO(dl_hwcap_mask);
 352   size_t cnt = platform != NULL;
 353   size_t n, m;
 354   size_t total;
 355   struct r_strlenpair *temp;
 356   struct r_strlenpair *result;
 357   struct r_strlenpair *rp;
 358   char *cp;
 359
 360   /* Count the number of bits set in the masked value.  */
 361   for (n = 0; (~((1ULL << n) - 1) & masked) != 0; ++n)
 362     if ((masked & (1ULL << n)) != 0)
 363       ++cnt;
 364
 365 #if (defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO) && defined SHARED
 366   /* The system-supplied DSO can contain a note of type 2, vendor "GNU".
 367      This gives us a list of names to treat as fake hwcap bits.  */
 368
 369   const char *dsocaps = NULL;
 370   size_t dsocapslen = 0;
 371   if (GLRO(dl_sysinfo_map) != NULL)
 372     {
 373       const ElfW(Phdr) *const phdr = GLRO(dl_sysinfo_map)->l_phdr;
 374       const ElfW(Word) phnum = GLRO(dl_sysinfo_map)->l_phnum;
 375       for (uint_fast16_t i = 0; i < phnum; ++i)
 376         if (phdr[i].p_type == PT_NOTE)
 377           {
 378             const ElfW(Addr) start = (phdr[i].p_vaddr
 379                                       + GLRO(dl_sysinfo_map)->l_addr);
 380             const struct
 381             {
 382               ElfW(Word) vendorlen;
 383               ElfW(Word) datalen;
 384               ElfW(Word) type;
 385             } *note = (const void *) start;
 386             while ((ElfW(Addr)) (note + 1) - start < phdr[i].p_memsz)
 387               {
 388 #define ROUND(len) (((len) + sizeof (ElfW(Word)) - 1) & -sizeof (ElfW(Word)))
 389                 if (note->type == 2
 390                     && note->vendorlen == sizeof "GNU"
 391                     && !memcmp ((note + 1), "GNU", sizeof "GNU")
 392                     && note->datalen > 2 * sizeof (ElfW(Word)) + 2)
 393                   {
 394                     const ElfW(Word) *p = ((const void *) (note + 1)
 395                                            + ROUND (sizeof "GNU"));
 396                     cnt += *p++;
 397                     ++p;        /* Skip mask word.  */
 398                     dsocaps = (const char *) p;
 399                     dsocapslen = note->datalen - sizeof *p * 2;
 400                     break;
 401                   }
 402                 note = ((const void *) (note + 1)
 403                         + ROUND (note->vendorlen) + ROUND (note->datalen));
 404 #undef ROUND
 405               }
 406             if (dsocaps != NULL)
 407               break;
 408           }
 409     }
 410 #endif
 411
 412   /* For TLS enabled builds always add 'tls'.  */
 413   ++cnt;
 414
 415   /* Create temporary data structure to generate result table.  */
 416   temp = (struct r_strlenpair *) alloca (cnt * sizeof (*temp));
 417   m = 0;
 418 #if defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO
 419   if (dsocaps != NULL)
 420     {
 421       const ElfW(Word) mask = ((const ElfW(Word) *) dsocaps)[-1];
 422       GLRO(dl_hwcap) |= (uint64_t) mask << _DL_FIRST_EXTRA;
 423       size_t len;
 424       for (const char *p = dsocaps; p < dsocaps + dsocapslen; p += len + 1)
 425         {
 426           uint_fast8_t bit = *p++;
 427           len = strlen (p);
 428
 429           /* Skip entries that are not enabled in the mask word.  */
 430           if (__builtin_expect (mask & ((ElfW(Word)) 1 << bit), 1))
 431             {
 432               temp[m].str = p;
 433               temp[m].len = len;
 434               ++m;
 435             }
 436           else
 437             --cnt;
 438         }
 439     }
 440 #endif
 441   for (n = 0; masked != 0; ++n)
 442     if ((masked & (1ULL << n)) != 0)
 443       {
 444         temp[m].str = _dl_hwcap_string (n);
 445         temp[m].len = strlen (temp[m].str);
 446         masked ^= 1ULL << n;
 447         ++m;
 448       }
 449   if (platform != NULL)
 450     {
 451       temp[m].str = platform;
 452       temp[m].len = platform_len;
 453       ++m;
 454     }
 455
 456   temp[m].str = "tls";
 457   temp[m].len = 3;
 458   ++m;
 459
 460   assert (m == cnt);
 461
 462   /* Determine the total size of all strings together.  */
 463   if (cnt == 1)
 464     total = temp[0].len + 1;
 465   else
 466     {
 467       total = temp[0].len + temp[cnt - 1].len + 2;
 468       if (cnt > 2)
 469         {
 470           total <<= 1;
 471           for (n = 1; n + 1 < cnt; ++n)
 472             total += temp[n].len + 1;
 473           if (cnt > 3
 474               && (cnt >= sizeof (size_t) * 8
 475                   || total + (sizeof (*result) << 3)
 476                      >= (1UL << (sizeof (size_t) * 8 - cnt + 3))))
 477             _dl_signal_error (ENOMEM, NULL, NULL,
 478                               N_("cannot create capability list"));
 479
 480           total <<= cnt - 3;
 481         }
 482     }
 483
 484   /* The result structure: we use a very compressed way to store the
 485      various combinations of capability names.  */
 486   *sz = 1 << cnt;
 487   result = (struct r_strlenpair *) malloc (*sz * sizeof (*result) + total);
 488   if (result == NULL)
 489     _dl_signal_error (ENOMEM, NULL, NULL,
 490                       N_("cannot create capability list"));
 491
 492   if (cnt == 1)
 493     {
 494       result[0].str = (char *) (result + *sz);
 495       result[0].len = temp[0].len + 1;
 496       result[1].str = (char *) (result + *sz);
 497       result[1].len = 0;
 498       cp = __mempcpy ((char *) (result + *sz), temp[0].str, temp[0].len);
 499       *cp = '/';
 500       *sz = 2;
 501       *max_capstrlen = result[0].len;
 502
 503       return result;
 504     }
 505
 506   /* Fill in the information.  This follows the following scheme
 507      (indeces from TEMP for four strings):
 508         entry #0: 0, 1, 2, 3    binary: 1111
 509               #1: 0, 1, 3               1101
 510               #2: 0, 2, 3               1011
 511               #3: 0, 3                  1001
 512      This allows the representation of all possible combinations of
 513      capability names in the string.  First generate the strings.  */
 514   result[1].str = result[0].str = cp = (char *) (result + *sz);
 515 #define add(idx) \
 516       cp = __mempcpy (__mempcpy (cp, temp[idx].str, temp[idx].len), "/", 1);
 517   if (cnt == 2)
 518     {
 519       add (1);
 520       add (0);
 521     }
 522   else
 523     {
 524       n = 1 << (cnt - 1);
 525       do
 526         {
 527           n -= 2;
 528
 529           /* We always add the last string.  */
 530           add (cnt - 1);
 531
 532           /* Add the strings which have the bit set in N.  */
 533           for (m = cnt - 2; m > 0; --m)
 534             if ((n & (1 << m)) != 0)
 535               add (m);
 536
 537           /* Always add the first string.  */
 538           add (0);
 539         }
 540       while (n != 0);
 541     }
 542 #undef add
 543
 544   /* Now we are ready to install the string pointers and length.  */
 545   for (n = 0; n < (1UL << cnt); ++n)
 546     result[n].len = 0;
 547   n = cnt;
 548   do
 549     {
 550       size_t mask = 1 << --n;
 551
 552       rp = result;
 553       for (m = 1 << cnt; m > 0; ++rp)
 554         if ((--m & mask) != 0)
 555           rp->len += temp[n].len + 1;
 556     }
 557   while (n != 0);
 558
 559   /* The first half of the strings all include the first string.  */
 560   n = (1 << cnt) - 2;
 561   rp = &result[2];
 562   while (n != (1UL << (cnt - 1)))
 563     {
 564       if ((--n & 1) != 0)
 565         rp[0].str = rp[-2].str + rp[-2].len;
 566       else
 567         rp[0].str = rp[-1].str;
 568       ++rp;
 569     }
 570
 571   /* The second half starts right after the first part of the string of
 572      the corresponding entry in the first half.  */
 573   do
 574     {
 575       rp[0].str = rp[-(1 << (cnt - 1))].str + temp[cnt - 1].len + 1;
 576       ++rp;
 577     }
 578   while (--n != 0);
 579
 580   /* The maximum string length.  */
 581   *max_capstrlen = result[0].len;
 582
 583   return result;
 584 }