Re: Non-static variables and nested function pointers [bug #28392]

[Seth Goldberg]

Quoting Grégoire Sutre, who wrote the following on Thu, 24 Dec 2009:

> Seth Goldberg wrote:
>
> >  Exactly -- the presence of the execstack attribute in the segment is 
> > merely a request -- the kernel is free to discard it, and many OSes do, as 
> > you've found :).
>
> The problem is more complex: I tried a simple example with a pointer to a 
> nested function, and it runs without any segfault on NetBSD/i386.
> This would suggest that, by default, the stack is executable -- at least if 
> trampolines are used?

 It depends how the page tables are configured on that kernel -- if the NX bit 
isn't being set in page table entries on that platform, then the hardware 
support for execute-protection isn't enabled and you won't get any faults.

 --S