elf/dl-sysdep.c

   1 /* Operating system support for run-time dynamic linker.  Generic Unix version.
   2    Copyright (C) 1995-2012 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 #if defined NEED_DL_SYSINFO || defined 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 #if defined NEED_DL_SYSINFO
 209   /* Only set the sysinfo value if we also have the vsyscall DSO.  */
 210   if (GLRO(dl_sysinfo_dso) != 0 && new_sysinfo)
 211     GLRO(dl_sysinfo) = new_sysinfo;
 212 #endif
 213
 214 #ifdef DL_SYSDEP_INIT
 215   DL_SYSDEP_INIT;
 216 #endif
 217
 218 #ifdef DL_PLATFORM_INIT
 219   DL_PLATFORM_INIT;
 220 #endif
 221
 222   /* Determine the length of the platform name.  */
 223   if (GLRO(dl_platform) != NULL)
 224     GLRO(dl_platformlen) = strlen (GLRO(dl_platform));
 225
 226   if (__sbrk (0) == _end)
 227     /* The dynamic linker was run as a program, and so the initial break
 228        starts just after our bss, at &_end.  The malloc in dl-minimal.c
 229        will consume the rest of this page, so tell the kernel to move the
 230        break up that far.  When the user program examines its break, it
 231        will see this new value and not clobber our data.  */
 232     __sbrk (GLRO(dl_pagesize)
 233             - ((_end - (char *) 0) & (GLRO(dl_pagesize) - 1)));
 234
 235   /* If this is a SUID program we make sure that FDs 0, 1, and 2 are
 236      allocated.  If necessary we are doing it ourself.  If it is not
 237      possible we stop the program.  */
 238   if (__builtin_expect (INTUSE(__libc_enable_secure), 0))
 239     __libc_check_standard_fds ();
 240
 241   (*dl_main) (phdr, phnum, &user_entry, GLRO(dl_auxv));
 242   return user_entry;
 243 }
 244
 245 void
 246 internal_function
 247 _dl_sysdep_start_cleanup (void)
 248 {
 249 }
 250
 251 void
 252 internal_function
 253 _dl_show_auxv (void)
 254 {
 255   char buf[64];
 256   ElfW(auxv_t) *av;
 257
 258   /* Terminate string.  */
 259   buf[63] = '\0';
 260
 261   /* The following code assumes that the AT_* values are encoded
 262      starting from 0 with AT_NULL, 1 for AT_IGNORE, and all other values
 263      close by (otherwise the array will be too large).  In case we have
 264      to support a platform where these requirements are not fulfilled
 265      some alternative implementation has to be used.  */
 266   for (av = GLRO(dl_auxv); av->a_type != AT_NULL; ++av)
 267     {
 268       static const struct
 269       {
 270         const char label[17];
 271         enum { unknown = 0, dec, hex, str, ignore } form : 8;
 272       } auxvars[] =
 273         {
 274           [AT_EXECFD - 2] =             { "EXECFD:       ", dec },
 275           [AT_EXECFN - 2] =             { "EXECFN:       ", str },
 276           [AT_PHDR - 2] =               { "PHDR:         0x", hex },
 277           [AT_PHENT - 2] =              { "PHENT:        ", dec },
 278           [AT_PHNUM - 2] =              { "PHNUM:        ", dec },
 279           [AT_PAGESZ - 2] =             { "PAGESZ:       ", dec },
 280           [AT_BASE - 2] =               { "BASE:         0x", hex },
 281           [AT_FLAGS - 2] =              { "FLAGS:        0x", hex },
 282           [AT_ENTRY - 2] =              { "ENTRY:        0x", hex },
 283           [AT_NOTELF - 2] =             { "NOTELF:       ", hex },
 284           [AT_UID - 2] =                { "UID:          ", dec },
 285           [AT_EUID - 2] =               { "EUID:         ", dec },
 286           [AT_GID - 2] =                { "GID:          ", dec },
 287           [AT_EGID - 2] =               { "EGID:         ", dec },
 288           [AT_PLATFORM - 2] =           { "PLATFORM:     ", str },
 289           [AT_HWCAP - 2] =              { "HWCAP:        ", hex },
 290           [AT_CLKTCK - 2] =             { "CLKTCK:       ", dec },
 291           [AT_FPUCW - 2] =              { "FPUCW:        ", hex },
 292           [AT_DCACHEBSIZE - 2] =        { "DCACHEBSIZE:  0x", hex },
 293           [AT_ICACHEBSIZE - 2] =        { "ICACHEBSIZE:  0x", hex },
 294           [AT_UCACHEBSIZE - 2] =        { "UCACHEBSIZE:  0x", hex },
 295           [AT_IGNOREPPC - 2] =          { "IGNOREPPC", ignore },
 296           [AT_SECURE - 2] =             { "SECURE:       ", dec },
 297           [AT_BASE_PLATFORM - 2] =      { "BASE_PLATFORM:", str },
 298           [AT_SYSINFO - 2] =            { "SYSINFO:      0x", hex },
 299           [AT_SYSINFO_EHDR - 2] =       { "SYSINFO_EHDR: 0x", hex },
 300           [AT_RANDOM - 2] =             { "RANDOM:       0x", hex },
 301         };
 302       unsigned int idx = (unsigned int) (av->a_type - 2);
 303
 304       if ((unsigned int) av->a_type < 2u
 305           || (idx < sizeof (auxvars) / sizeof (auxvars[0])
 306               && auxvars[idx].form == ignore))
 307         continue;
 308
 309       assert (AT_NULL == 0);
 310       assert (AT_IGNORE == 1);
 311
 312       if (av->a_type == AT_HWCAP)
 313         {
 314           /* This is handled special.  */
 315           if (_dl_procinfo (av->a_un.a_val) == 0)
 316             continue;
 317         }
 318
 319       if (idx < sizeof (auxvars) / sizeof (auxvars[0])
 320           && auxvars[idx].form != unknown)
 321         {
 322           const char *val = (char *) av->a_un.a_val;
 323
 324           if (__builtin_expect (auxvars[idx].form, dec) == dec)
 325             val = _itoa ((unsigned long int) av->a_un.a_val,
 326                          buf + sizeof buf - 1, 10, 0);
 327           else if (__builtin_expect (auxvars[idx].form, hex) == hex)
 328             val = _itoa ((unsigned long int) av->a_un.a_val,
 329                          buf + sizeof buf - 1, 16, 0);
 330
 331           _dl_printf ("AT_%s%s\n", auxvars[idx].label, val);
 332
 333           continue;
 334         }
 335
 336       /* Unknown value: print a generic line.  */
 337       char buf2[17];
 338       buf2[sizeof (buf2) - 1] = '\0';
 339       const char *val2 = _itoa ((unsigned long int) av->a_un.a_val,
 340                                 buf2 + sizeof buf2 - 1, 16, 0);
 341       const char *val =  _itoa ((unsigned long int) av->a_type,
 342                                 buf + sizeof buf - 1, 16, 0);
 343       _dl_printf ("AT_??? (0x%s): 0x%s\n", val, val2);
 344     }
 345 }
 346
 347 #endif