kselftest/arm64: Allow larger buffers in get_signal_context()

In order to allow testing of signal contexts that overflow the base signal
frame allow callers to pass the buffer size for the user context into
get_signal_context(). No functional change.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220829160703.874492-10-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

kselftest/arm64: signal: Skip SVE signal test if not enough VLs supported

On platform where SVE is supported but there are less than 2 VLs available
the signal SVE change test should be skipped instead of failing.

Reported-by: Andre Przywara <andre.przywara@arm.com>
Tested-by: Andre Przywara <andre.przywara@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220524103149.2802-1-cristian.marussi@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

kselftest/arm64: signal: Verify that signals can't change the SVE vector length

We do not support changing the SVE vector length as part of signal return,
verify that this is the case if the system supports multiple vector lengths.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20210819134245.13935-5-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>