elf/dl-error.c

   1 /* Error handling for runtime dynamic linker.
   2    Copyright (C) 1995-2016 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 #include <libintl.h>
  20 #include <setjmp.h>
  21 #include <stdbool.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <unistd.h>
  25 #include <ldsodefs.h>
  26
  27 /* This structure communicates state between _dl_catch_error and
  28    _dl_signal_error.  */
  29 struct catch
  30   {
  31     const char **objname;       /* Object/File name.  */
  32     const char **errstring;     /* Error detail filled in here.  */
  33     bool *malloced;             /* Nonzero if the string is malloced
  34                                    by the libc malloc.  */
  35     volatile int *errcode;      /* Return value of _dl_signal_error.  */
  36     jmp_buf env;                /* longjmp here on error.  */
  37   };
  38
  39 /* Multiple threads at once can use the `_dl_catch_error' function.  The
  40    calls can come from `_dl_map_object_deps', `_dlerror_run', or from
  41    any of the libc functionality which loads dynamic objects (NSS, iconv).
  42    Therefore we have to be prepared to save the state in thread-local
  43    memory.  The _dl_error_catch_tsd function pointer is reset by the thread
  44    library so that it returns the address of a thread-local variable.  */
  45
  46
  47 /* This message we return as a last resort.  We define the string in a
  48    variable since we have to avoid freeing it and so have to enable
  49    a pointer comparison.  See below and in dlfcn/dlerror.c.  */
  50 static const char _dl_out_of_memory[] = "out of memory";
  51
  52
  53 /* This points to a function which is called when an continuable error is
  54    received.  Unlike the handling of `catch' this function may return.
  55    The arguments will be the `errstring' and `objname'.
  56
  57    Since this functionality is not used in normal programs (only in ld.so)
  58    we do not care about multi-threaded programs here.  We keep this as a
  59    global variable.  */
  60 static receiver_fct receiver;
  61
  62 #ifdef _LIBC_REENTRANT
  63 # define CATCH_HOOK     (*(struct catch **) (*GL(dl_error_catch_tsd)) ())
  64 #else
  65 static struct catch *catch_hook;
  66 # define CATCH_HOOK     catch_hook
  67 #endif
  68
  69 void
  70 internal_function
  71 _dl_signal_error (int errcode, const char *objname, const char *occation,
  72                   const char *errstring)
  73 {
  74   struct catch *lcatch;
  75
  76   if (! errstring)
  77     errstring = N_("DYNAMIC LINKER BUG!!!");
  78
  79   lcatch = CATCH_HOOK;
  80   if (objname == NULL)
  81     objname = "";
  82   if (lcatch != NULL)
  83     {
  84       /* We are inside _dl_catch_error.  Return to it.  We have to
  85          duplicate the error string since it might be allocated on the
  86          stack.  The object name is always a string constant.  */
  87       size_t len_objname = strlen (objname) + 1;
  88       size_t len_errstring = strlen (errstring) + 1;
  89
  90       char *errstring_copy = malloc (len_objname + len_errstring);
  91       if (errstring_copy != NULL)
  92         {
  93           /* Make a copy of the object file name and the error string.  */
  94           *lcatch->objname = memcpy (__mempcpy (errstring_copy,
  95                                                 errstring, len_errstring),
  96                                      objname, len_objname);
  97           *lcatch->errstring = errstring_copy;
  98
  99           /* If the main executable is relocated it means the libc's malloc
 100              is used.  */
 101           bool malloced = true;
 102 #ifdef SHARED
 103           malloced = (GL(dl_ns)[LM_ID_BASE]._ns_loaded != NULL
 104                       && (GL(dl_ns)[LM_ID_BASE]._ns_loaded->l_relocated != 0));
 105 #endif
 106           *lcatch->malloced = malloced;
 107         }
 108       else
 109         {
 110           /* This is better than nothing.  */
 111           *lcatch->objname = "";
 112           *lcatch->errstring = _dl_out_of_memory;
 113           *lcatch->malloced = false;
 114         }
 115
 116       *lcatch->errcode = errcode;
 117
 118       /* We do not restore the signal mask because none was saved.  */
 119       __longjmp (lcatch->env[0].__jmpbuf, 1);
 120     }
 121   else
 122     {
 123       /* Lossage while resolving the program's own symbols is always fatal.  */
 124       char buffer[1024];
 125       _dl_fatal_printf ("%s: %s: %s%s%s%s%s\n",
 126                         RTLD_PROGNAME,
 127                         occation ?: N_("error while loading shared libraries"),
 128                         objname, *objname ? ": " : "",
 129                         errstring, errcode ? ": " : "",
 130                         (errcode
 131                          ? __strerror_r (errcode, buffer, sizeof buffer)
 132                          : ""));
 133     }
 134 }
 135
 136
 137 void
 138 internal_function
 139 _dl_signal_cerror (int errcode, const char *objname, const char *occation,
 140                    const char *errstring)
 141 {
 142   if (__builtin_expect (GLRO(dl_debug_mask)
 143                         & ~(DL_DEBUG_STATISTICS|DL_DEBUG_PRELINK), 0))
 144     _dl_debug_printf ("%s: error: %s: %s (%s)\n", objname, occation,
 145                       errstring, receiver ? "continued" : "fatal");
 146
 147   if (receiver)
 148     {
 149       /* We are inside _dl_receive_error.  Call the user supplied
 150          handler and resume the work.  The receiver will still be
 151          installed.  */
 152       (*receiver) (errcode, objname, errstring);
 153     }
 154   else
 155     _dl_signal_error (errcode, objname, occation, errstring);
 156 }
 157
 158
 159 int
 160 internal_function
 161 _dl_catch_error (const char **objname, const char **errstring,
 162                  bool *mallocedp, void (*operate) (void *), void *args)
 163 {
 164   /* We need not handle `receiver' since setting a `catch' is handled
 165      before it.  */
 166
 167   /* Only this needs to be marked volatile, because it is the only local
 168      variable that gets changed between the setjmp invocation and the
 169      longjmp call.  All others are just set here (before setjmp) and read
 170      in _dl_signal_error (before longjmp).  */
 171   volatile int errcode;
 172
 173   struct catch c;
 174   /* Don't use an initializer since we don't need to clear C.env.  */
 175   c.objname = objname;
 176   c.errstring = errstring;
 177   c.malloced = mallocedp;
 178   c.errcode = &errcode;
 179
 180   struct catch **const catchp = &CATCH_HOOK;
 181   struct catch *const old = *catchp;
 182   *catchp = &c;
 183
 184   /* Do not save the signal mask.  */
 185   if (__builtin_expect (__sigsetjmp (c.env, 0), 0) == 0)
 186     {
 187       (*operate) (args);
 188       *catchp = old;
 189       *objname = NULL;
 190       *errstring = NULL;
 191       *mallocedp = false;
 192       return 0;
 193     }
 194
 195   /* We get here only if we longjmp'd out of OPERATE.  _dl_signal_error has
 196      already stored values into *OBJNAME, *ERRSTRING, and *MALLOCEDP.  */
 197   *catchp = old;
 198   return errcode;
 199 }
 200
 201
 202 void
 203 internal_function
 204 _dl_receive_error (receiver_fct fct, void (*operate) (void *), void *args)
 205 {
 206   struct catch **const catchp = &CATCH_HOOK;
 207   struct catch *old_catch;
 208   receiver_fct old_receiver;
 209
 210   old_catch = *catchp;
 211   old_receiver = receiver;
 212
 213   /* Set the new values.  */
 214   *catchp = NULL;
 215   receiver = fct;
 216
 217   (*operate) (args);
 218
 219   *catchp = old_catch;
 220   receiver = old_receiver;
 221 }