On Tue, Feb 21, 2012 at 11:03 AM, H. Peter Anvin [off-list ref] wrote:

On 02/21/2012 10:54 AM, Andrew Lutomirski wrote:

quoted

uclibc hardcodes a call to the vsyscall gettimeofday implementation in
its locking primitives, which probably gives terrible performance, but
that's a separate issue.  I think do_emulate_vsyscall should send a
segfault if called by an x32 task -- there's some security benefit to
doing so, and there's unlikely to be any downside.

The vsyscall page shouldn't be mapped for x32 tasks...

How is that possible?  It lives in the fixmap and is presumably
visible from any 64-bit code.

Admittedly, x32 tasks are probably somewhat difficult to trick into
calling addresses with high bits set, but it's not necessarily
impossible.

--Andy