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, or (at your option)
   8    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, write to the Free Software Foundation,
  17    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  18
  19 #ifndef _MSC_VER
  20 # include <config.h>
  21 #endif
  22
  23 #include "sigsegv.h"
  24
  25 #if HAVE_SIGSEGV_RECOVERY
  26
  27 /* Cygwin uses faults for internal purposes, i.e. even when the user passes
  28    valid pointers to all system calls.
  29
  30    An example is pthread_attr_init.  POSIX:2001 states pthread_attr_init may
  31    fail with EBUSY if an object was previously initialized.  Recognizing
  32    whether an object was previously initialized can be done with a magic
  33    cookie.  If the type pthread_attr_t is defined as
  34      struct { int magic; ... other_data; }
  35    it is easy.  But in Cygwin, pthread_attr_t is defined as a pointer type.
  36    Cygwin implements the check by testing whether the pthread_attr_t contains
  37    a pointer to a memory region that contains a particular magic cookie.
  38    This indirection may fault.  (Search for pthread_attr_init and
  39    verifyable_object_isvalid in the Cygwin sources.)  In this example we trick
  40    Cygwin into dereferencing the address 0x01010101.  */
  41
  42 #include <pthread.h>
  43 #include <stdlib.h>
  44 #include <string.h>
  45
  46 static int
  47 handler (void *fault_address, int serious)
  48 {
  49   exit (2);
  50 }
  51
  52 int
  53 main ()
  54 {
  55   pthread_attr_t a;
  56
  57   sigsegv_install_handler (handler);
  58
  59   /* Set up a pthread_attr_t that contains a pointer to address 0x01010101.  */
  60   memset (&a, 1, sizeof (a));
  61
  62   /* Make a system call to initialize it.  It should succeed and not invoke
  63      the handler.  */
  64   pthread_attr_init (&a);
  65
  66   return 0;
  67 }
  68
  69 #endif