[x32] PATCH: Remove ix86_promote_function_mode

H. Peter Anvin hpa@zytor.com
Mon Jun 20 14:41:00 GMT 2011

On 06/20/2011 07:01 AM, H.J. Lu wrote:
> On Mon, Jun 20, 2011 at 6:53 AM, Bernd Schmidt <bernds@codesourcery.com> 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.


H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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