Re: [PATCH RFC 0/9] PKS write protected page tables

[Peter Zijlstra]

On Tue, May 04, 2021 at 11:25:31PM -0700, Kees Cook wrote:

> It looks like PKS-protected page tables would be much like the
> RO-protected text pages in the sense that there is already code in
> the kernel to do things to make it writable, change text, and set it
> read-only again (alternatives, ftrace, etc).

We don't actually modify text by changing the mapping at all. We modify
through a writable (but not executable) temporary alias on the page (on
x86).

Once a mapping is RX it will *never* be writable again (until we tear it
all down).