Re: MIT discovered issue with gcc

[Florian Weimer <fw@deneb.enyo.de>]

* Bob Proulx:

> In those systems the zero page is initially bit-zero and reading from
> the zero point will return zero values from the contents there.  If
> the program writes to the zero page then subsequent reads will return
> whatever was written there.  This is bad behavior that was the default
> due to bugs in much legacy software.  Unmapping the zero page will
> cause those programs to segfault and therefore the vendors default to
> having the page mapped to avoid support calls from their customers.

There is also an optimization which allows better code generation for
loops over linked lists.  But for that, a read-only mapping is
sufficient.