tests/cygwin1.c

   1 /* Test that libsigsegv does not interfere with internal fault handling
   2    inside system calls.
   3    Copyright (C) 2009  Eric Blake <ebb9@byu.net>
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2 of the License, or
   8    (at your option) any later version.
   9
  10    This program 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
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 #ifndef _MSC_VER
  19 # include <config.h>
  20 #endif
  21
  22 #include "sigsegv.h"
  23
  24 #if HAVE_SIGSEGV_RECOVERY
  25
  26 /* Cygwin uses faults for internal purposes, i.e. even when the user passes
  27    valid pointers to all system calls.
  28
  29    An example is pthread_attr_init.  POSIX:2001 states pthread_attr_init may
  30    fail with EBUSY if an object was previously initialized.  Recognizing
  31    whether an object was previously initialized can be done with a magic
  32    cookie.  If the type pthread_attr_t is defined as
  33      struct { int magic; ... other_data; }
  34    it is easy.  But in Cygwin, pthread_attr_t is defined as a pointer type.
  35    Cygwin implements the check by testing whether the pthread_attr_t contains
  36    a pointer to a memory region that contains a particular magic cookie.
  37    This indirection may fault.  (Search for pthread_attr_init and
  38    verifyable_object_isvalid in the Cygwin sources.)  In this example we trick
  39    Cygwin into dereferencing the address 0x01010101.  */
  40
  41 #include <pthread.h>
  42 #include <stdlib.h>
  43 #include <string.h>
  44
  45 static int
  46 handler (void *fault_address, int serious)
  47 {
  48   exit (2);
  49 }
  50
  51 int
  52 main ()
  53 {
  54   pthread_attr_t a;
  55
  56   sigsegv_install_handler (handler);
  57
  58   /* Set up a pthread_attr_t that contains a pointer to address 0x01010101.  */
  59   memset (&a, 1, sizeof (a));
  60
  61   /* Make a system call to initialize it.  It should succeed and not invoke
  62      the handler.  */
  63   pthread_attr_init (&a);
  64
  65   return 0;
  66 }
  67
  68 #endif