On 06/20/2011 07:01 AM, H.J. Lu wrote:
> On Mon, Jun 20, 2011 at 6:53 AM, Bernd Schmidt <[email protected]>
> wrote:
>> On 06/20/2011 03:51 PM, H.J. Lu wrote:
>>> Promote pointers to Pmode when passing/returning in registers is
>>> a security concern.
No. Promoting *NON*-pointers (or rather, requiring non-pointers to
having already been zero extended) is a security concern. I thought I'd
made that point clear already. This is a hideously critical distinction.
> Peter, do you think it is safe to assume upper 32bits are zero in
> user space for x32? Kernel isn't a problem since pointer is 64bit
> in kernel and we don't pass pointers on stack to kernel.
As I have already stated, if we *cannot* require pointers to be
zero-extended on entry to the kernel, we're going to have to have
special entry points for all the x32 system calls except the ones that
don't take pointers.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
