[Xen-devel] Re: [PATCH]: xl: poison data objects in auto-generated destructors

[Gianni Tedesco <gianni.tedesco@xxxxxxxxxx>]

On Fri, 2010-08-20 at 16:05 +0100, Ian Campbell wrote:
> On Fri, 2010-08-20 at 15:49 +0100, Gianni Tedesco (3P) wrote:
> > Increase the probability of blowing up badly up during any
> > use-after-destroy scenarios.
> > 
> > Signed-off-by: Gianni Tedesco <gianni.tedesco@xxxxxxxxxx>
> 
> I'd suggest perhaps only for debug=y builds but we don't seem to
> propagate that concept into tools/ and it's probably not worth it
> anyhow.

The other approach would be to teach valgrind about such things but not
sure if it has a concept of freeing-in-two-stages. Same could be said
about gc pointers but I suspect sparse or something would work well to
catch those 'return gc allocated pointers' etc. bugs.

> So:
> 
> Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> 
> 
> > diff -r f68726cdf357 tools/libxl/gentypes.py
> > --- a/tools/libxl/gentypes.py       Thu Aug 19 18:24:12 2010 +0100
> > +++ b/tools/libxl/gentypes.py       Fri Aug 20 15:51:35 2010 +0100
> > @@ -145,15 +145,19 @@ if __name__ == '__main__':
> >  
> >  #include <stdint.h>
> >  #include <stdlib.h>
> > +#include <string.h>
> >  
> >  #include "libxl.h"
> >  
> > +#define LIBXL_DTOR_POISON 0xa5
> > +
> >  """ % " ".join(sys.argv))
> >  
> >      for ty in [t for t in types if t.destructor_fn is not None and 
> > t.autogenerate_destructor]:
> >          f.write("void %s(%s *p)\n" % (ty.destructor_fn, ty.typename))
> >          f.write("{\n")
> >          f.write(libxl_C_type_destroy(ty, "p", True))
> > +        f.write("\tmemset(p, LIBXL_DTOR_POISON, sizeof(*p));\n")
> >          f.write("}\n")
> >          f.write("\n")
> >      f.close()
> > 
> > 
> 
> 



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel