The sigpage is currently placed alongside shared libraries etc in the
address space.  Similar to what x86_64 does for its VDSO, place the
sigpage at a randomized offset above the stack so that learning the
base address of the sigpage doesn't help expose where shared libraries
are loaded in the address space (and vice versa).
Signed-off-by: NNathan Lynch <nathan_lynch@mentor.com>
Reviewed-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>