user-exec: Don't reextract sigmask from usercontext pointer

user-exec: Don't reextract sigmask from usercontext pointer

Extracting the old signal mask from the usercontext pointer passed to
a signal handler is a pain because it is OS and CPU dependent.
Since we've already done it once and passed it to handle_cpu_signal(),
there's no need to do it again in cpu_exit_tb_from_sighandler().
This then means we don't need to pass a usercontext pointer in to
handle_cpu_signal() at all.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Sergey Fedorov <sergey.fedorov@linaro.org>
Acked-by: Eduardo Habkost <ehabkost@redhat.com>
Acked-by: Riku Voipio <riku.voipio@linaro.org>
Message-id: 1463494687-25947-5-git-send-email-peter.maydell@linaro.org