elf/dl-sysdep.c

   1 /* Operating system support for run-time dynamic linker.  Generic Unix version.
   2    Copyright (C) 1995-2013 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 INTVARDEF(__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, INTUSE(_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         INTUSE(__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_CLKTCK:
 160         GLRO(dl_clktck) = av->a_un.a_val;
 161         break;
 162       case AT_FPUCW:
 163         GLRO(dl_fpu_control) = av->a_un.a_val;
 164         break;
 165 #ifdef NEED_DL_SYSINFO
 166       case AT_SYSINFO:
 167         new_sysinfo = av->a_un.a_val;
 168         break;
 169 #endif
 170 #ifdef NEED_DL_SYSINFO_DSO
 171       case AT_SYSINFO_EHDR:
 172         GLRO(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 173         break;
 174 #endif
 175       case AT_RANDOM:
 176         _dl_random = (void *) av->a_un.a_val;
 177         break;
 178 #ifdef DL_PLATFORM_AUXV
 179       DL_PLATFORM_AUXV
 180 #endif
 181       }
 182
 183 #ifndef HAVE_AUX_SECURE
 184   if (seen != -1)
 185     {
 186       /* Fill in the values we have not gotten from the kernel through the
 187          auxiliary vector.  */
 188 # ifndef HAVE_AUX_XID
 189 #  define SEE(UID, var, uid) \
 190    if ((seen & M (AT_##UID)) == 0) var ^= __get##uid ()
 191       SEE (UID, uid, uid);
 192       SEE (EUID, uid, euid);
 193       SEE (GID, gid, gid);
 194       SEE (EGID, gid, egid);
 195 # endif
 196
 197       /* If one of the two pairs of IDs does not match this is a setuid
 198          or setgid run.  */
 199       INTUSE(__libc_enable_secure) = uid | gid;
 200     }
 201 #endif
 202
 203 #ifndef HAVE_AUX_PAGESIZE
 204   if (GLRO(dl_pagesize) == 0)
 205     GLRO(dl_pagesize) = __getpagesize ();
 206 #endif
 207
 208 #ifdef NEED_DL_SYSINFO
 209   if (new_sysinfo != 0)
 210     {
 211 # ifdef NEED_DL_SYSINFO_DSO
 212       /* Only set the sysinfo value if we also have the vsyscall DSO.  */
 213       if (GLRO(dl_sysinfo_dso) != 0)
 214 # endif
 215         GLRO(dl_sysinfo) = new_sysinfo;
 216     }
 217 #endif
 218
 219 #ifdef DL_SYSDEP_INIT
 220   DL_SYSDEP_INIT;
 221 #endif
 222
 223 #ifdef DL_PLATFORM_INIT
 224   DL_PLATFORM_INIT;
 225 #endif
 226
 227   /* Determine the length of the platform name.  */
 228   if (GLRO(dl_platform) != NULL)
 229     GLRO(dl_platformlen) = strlen (GLRO(dl_platform));
 230
 231   if (__sbrk (0) == _end)
 232     /* The dynamic linker was run as a program, and so the initial break
 233        starts just after our bss, at &_end.  The malloc in dl-minimal.c
 234        will consume the rest of this page, so tell the kernel to move the
 235        break up that far.  When the user program examines its break, it
 236        will see this new value and not clobber our data.  */
 237     __sbrk (GLRO(dl_pagesize)
 238             - ((_end - (char *) 0) & (GLRO(dl_pagesize) - 1)));
 239
 240   /* If this is a SUID program we make sure that FDs 0, 1, and 2 are
 241      allocated.  If necessary we are doing it ourself.  If it is not
 242      possible we stop the program.  */
 243   if (__builtin_expect (INTUSE(__libc_enable_secure), 0))
 244     __libc_check_standard_fds ();
 245
 246   (*dl_main) (phdr, phnum, &user_entry, GLRO(dl_auxv));
 247   return user_entry;
 248 }
 249
 250 void
 251 internal_function
 252 _dl_sysdep_start_cleanup (void)
 253 {
 254 }
 255
 256 void
 257 internal_function
 258 _dl_show_auxv (void)
 259 {
 260   char buf[64];
 261   ElfW(auxv_t) *av;
 262
 263   /* Terminate string.  */
 264   buf[63] = '\0';
 265
 266   /* The following code assumes that the AT_* values are encoded
 267      starting from 0 with AT_NULL, 1 for AT_IGNORE, and all other values
 268      close by (otherwise the array will be too large).  In case we have
 269      to support a platform where these requirements are not fulfilled
 270      some alternative implementation has to be used.  */
 271   for (av = GLRO(dl_auxv); av->a_type != AT_NULL; ++av)
 272     {
 273       static const struct
 274       {
 275         const char label[17];
 276         enum { unknown = 0, dec, hex, str, ignore } form : 8;
 277       } auxvars[] =
 278         {
 279           [AT_EXECFD - 2] =             { "EXECFD:       ", dec },
 280           [AT_EXECFN - 2] =             { "EXECFN:       ", str },
 281           [AT_PHDR - 2] =               { "PHDR:         0x", hex },
 282           [AT_PHENT - 2] =              { "PHENT:        ", dec },
 283           [AT_PHNUM - 2] =              { "PHNUM:        ", dec },
 284           [AT_PAGESZ - 2] =             { "PAGESZ:       ", dec },
 285           [AT_BASE - 2] =               { "BASE:         0x", hex },
 286           [AT_FLAGS - 2] =              { "FLAGS:        0x", hex },
 287           [AT_ENTRY - 2] =              { "ENTRY:        0x", hex },
 288           [AT_NOTELF - 2] =             { "NOTELF:       ", hex },
 289           [AT_UID - 2] =                { "UID:          ", dec },
 290           [AT_EUID - 2] =               { "EUID:         ", dec },
 291           [AT_GID - 2] =                { "GID:          ", dec },
 292           [AT_EGID - 2] =               { "EGID:         ", dec },
 293           [AT_PLATFORM - 2] =           { "PLATFORM:     ", str },
 294           [AT_HWCAP - 2] =              { "HWCAP:        ", hex },
 295           [AT_CLKTCK - 2] =             { "CLKTCK:       ", dec },
 296           [AT_FPUCW - 2] =              { "FPUCW:        ", hex },
 297           [AT_DCACHEBSIZE - 2] =        { "DCACHEBSIZE:  0x", hex },
 298           [AT_ICACHEBSIZE - 2] =        { "ICACHEBSIZE:  0x", hex },
 299           [AT_UCACHEBSIZE - 2] =        { "UCACHEBSIZE:  0x", hex },
 300           [AT_IGNOREPPC - 2] =          { "IGNOREPPC", ignore },
 301           [AT_SECURE - 2] =             { "SECURE:       ", dec },
 302           [AT_BASE_PLATFORM - 2] =      { "BASE_PLATFORM:", str },
 303           [AT_SYSINFO - 2] =            { "SYSINFO:      0x", hex },
 304           [AT_SYSINFO_EHDR - 2] =       { "SYSINFO_EHDR: 0x", hex },
 305           [AT_RANDOM - 2] =             { "RANDOM:       0x", hex },
 306         };
 307       unsigned int idx = (unsigned int) (av->a_type - 2);
 308
 309       if ((unsigned int) av->a_type < 2u
 310           || (idx < sizeof (auxvars) / sizeof (auxvars[0])
 311               && auxvars[idx].form == ignore))
 312         continue;
 313
 314       assert (AT_NULL == 0);
 315       assert (AT_IGNORE == 1);
 316
 317       if (av->a_type == AT_HWCAP)
 318         {
 319           /* This is handled special.  */
 320           if (_dl_procinfo (av->a_un.a_val) == 0)
 321             continue;
 322         }
 323
 324       if (idx < sizeof (auxvars) / sizeof (auxvars[0])
 325           && auxvars[idx].form != unknown)
 326         {
 327           const char *val = (char *) av->a_un.a_val;
 328
 329           if (__builtin_expect (auxvars[idx].form, dec) == dec)
 330             val = _itoa ((unsigned long int) av->a_un.a_val,
 331                          buf + sizeof buf - 1, 10, 0);
 332           else if (__builtin_expect (auxvars[idx].form, hex) == hex)
 333             val = _itoa ((unsigned long int) av->a_un.a_val,
 334                          buf + sizeof buf - 1, 16, 0);
 335
 336           _dl_printf ("AT_%s%s\n", auxvars[idx].label, val);
 337
 338           continue;
 339         }
 340
 341       /* Unknown value: print a generic line.  */
 342       char buf2[17];
 343       buf2[sizeof (buf2) - 1] = '\0';
 344       const char *val2 = _itoa ((unsigned long int) av->a_un.a_val,
 345                                 buf2 + sizeof buf2 - 1, 16, 0);
 346       const char *val =  _itoa ((unsigned long int) av->a_type,
 347                                 buf + sizeof buf - 1, 16, 0);
 348       _dl_printf ("AT_??? (0x%s): 0x%s\n", val, val2);
 349     }
 350 }
 351
 352 #endif