linux-user/s390x: Implement setup_sigtramp

Create and record the two signal trampolines.
Use them when the guest does not use SA_RESTORER.

Cc: qemu-s390x@nongnu.org
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20210929130553.121567-22-richard.henderson@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
2 files changed