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