Re: Query regarding Linux Arm pagetable setup

On Thu, May 05, 2016 at 06:00:38PM +0100, Russell King - ARM Linux wrote:
> On Thu, May 05, 2016 at 05:59:01PM +0100, Catalin Marinas wrote:
> > On Thu, May 05, 2016 at 05:04:57PM +0100, Russell King - ARM Linux wrote:
> > > On Thu, May 05, 2016 at 04:17:08PM +0530, Dushyant Behl wrote:
> > > > Also are there any other kernel pages which are marked with similar
> > > > user bit and read only permissions in the pagetables with possible
> > > > aliasing in the kernel's address space too?
> > > 
> > > No.
> > 
> > Actually, most read-only user pages (e.g. mmap'ed code) have an alias in
> > the kernel linear mapping or temporarily in highmem (after kmap).
> 
> If you want to be strict about it, all pages can end up in that state.
> 
> I assumed, however, that the OP was asking about pages similar to the
> special vector page.

That was my first thought as well but given that we don't know the
background to this question, I think it's better to state the other
cases (maybe OP is trying to work around a hardware bug affecting page
permission, you never know; I hope not).

-- 
Catalin