Re: mprotect PROT_SIGNAL

[Florian Weimer <fweimer@redhat.com>]

* Soni L.:

> we'd like an mprotect PROT_SIGNAL flag for a compiler we're making
>
> PROT_SIGNAL - marks the pages as unmapped while running signal handlers
>
> this would be very useful, do you think you could provide it?
>
> (not much more to say about it, it's supposed to do what it says on
> the tin, we want to unmap pages in signal handlers so as to catch bugs
> without causing memory corruption.)

The challenge is going to be to detect abnormal exit from the signal
handler.

You can already get some of this behavior to today with memory
protection keys, on x86-64 at least.  (I consider this a glitch in the
implementation, it makes it less useful.)  Access is revoked
automatically when the hander is invoked.  However, access is not
restored if you jump out of the handler using longjmp or by throwing an
exception.

Thanks,
Florian