On 02/22/2012 03:51 PM, Andrew Lutomirski wrote:

On Wed, Feb 22, 2012 at 3:46 PM, Indan Zupancic [off-list ref] wrote:

quoted

On Wed, February 22, 2012 20:47, Will Drewry wrote:

quoted

On Wed, Feb 22, 2012 at 8:23 AM, Ben Hutchings

quoted

I would have thought the way to make sure the architecture is always
checked is to pack it together with the syscall number.

I missed that suggestion, putting the syscall number and arch in one
data field would indeed make it harder to not check the arch.

Is there enough room?  On x86-64 at least, rax could conceivably be
extended to 64 bits some day.  Bit 30 is already spoken for by x32.

No it couldn't, because we mask off the high 32 bits and thus it could
(theoretically) break user space.

	-hpa


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