sysdeps/unix/sysv/linux/dl-osinfo.h

   1 /* Operating system specific code for generic dynamic loader functions.  Linux.
   2    Copyright (C) 2000-2002,2004-2008, 2009 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 <kernel-features.h>
  21 #include <dl-sysdep.h>
  22 #include <fcntl.h>
  23 #include <stdint.h>
  24
  25 #ifndef MIN
  26 # define MIN(a,b) (((a)<(b))?(a):(b))
  27 #endif
  28
  29 #ifdef SHARED
  30 /* This is the function used in the dynamic linker to print the fatal error
  31    message.  */
  32 static void
  33 __attribute__ ((__noreturn__))
  34 dl_fatal (const char *str)
  35 {
  36   _dl_dprintf (2, str);
  37   _exit (1);
  38 }
  39 #endif
  40
  41 #define DL_SYSDEP_OSCHECK(FATAL)                                              \
  42   do {                                                                        \
  43     /* Test whether the kernel is new enough.  This test is only performed    \
  44        if the library is not compiled to run on all kernels.  */              \
  45                                                                               \
  46     int version = _dl_discover_osversion ();                                  \
  47     if (__builtin_expect (version >= 0, 1))                                   \
  48       {                                                                       \
  49         if (__builtin_expect (GLRO(dl_osversion) == 0, 1)                     \
  50             || GLRO(dl_osversion) > version)                                  \
  51           GLRO(dl_osversion) = version;                                       \
  52                                                                               \
  53         /* Now we can test with the required version.  */                     \
  54         if (__LINUX_KERNEL_VERSION > 0 && version < __LINUX_KERNEL_VERSION)   \
  55           /* Not sufficent.  */                                               \
  56           FATAL ("FATAL: kernel too old\n");                                  \
  57       }                                                                       \
  58     else if (__LINUX_KERNEL_VERSION > 0)                                      \
  59       FATAL ("FATAL: cannot determine kernel version\n");                     \
  60   } while (0)
  61
  62 static inline uintptr_t __attribute__ ((always_inline))
  63 _dl_setup_stack_chk_guard (void *dl_random)
  64 {
  65   uintptr_t ret;
  66 #ifndef __ASSUME_AT_RANDOM
  67   if (__builtin_expect (dl_random == NULL, 0))
  68     {
  69 # ifdef ENABLE_STACKGUARD_RANDOMIZE
  70       int fd = __open ("/dev/urandom", O_RDONLY);
  71       if (fd >= 0)
  72         {
  73           ssize_t reslen = __read (fd, &ret, sizeof (ret));
  74           __close (fd);
  75           if (reslen == (ssize_t) sizeof (ret))
  76             return ret;
  77         }
  78 # endif
  79       ret = 0;
  80       unsigned char *p = (unsigned char *) &ret;
  81       p[sizeof (ret) - 1] = 255;
  82       p[sizeof (ret) - 2] = '\n';
  83     }
  84   else
  85 #endif
  86     /* We need in the moment only 8 bytes on 32-bit platforms and 16
  87        bytes on 64-bit platforms.  Therefore we can use the data
  88        directly and not use the kernel-provided data to seed a PRNG.  */
  89     memcpy (&ret, dl_random, sizeof (ret));
  90   return ret;
  91 }
  92
  93 static inline uintptr_t __attribute__ ((always_inline))
  94 _dl_setup_pointer_guard (void *dl_random, uintptr_t stack_chk_guard)
  95 {
  96   uintptr_t ret;
  97 #ifndef __ASSUME_AT_RANDOM
  98   if (dl_random == NULL)
  99     {
 100       ret = stack_chk_guard;
 101 # ifndef HP_TIMING_NONAVAIL
 102       hp_timing_t now;
 103       HP_TIMING_NOW (now);
 104       ret ^= now;
 105 # endif
 106     }
 107   else
 108 #endif
 109     memcpy (&ret, (char *) dl_random + sizeof (ret), sizeof (ret));
 110   return ret;
 111 }