elf/dl-error.c

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