kselftest/arm64: Log SVCR when the SME tests barf

On failure we log the actual and expected value of the register we detect
a mismatch in. For SME one obvious potential source of corruption would be
if we had corrupted SVCR since changes in streaming mode will reset the
register values, log the value to aid in understanding issues.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20231205-arm64-kselftest-log-svcr-v1-1-b77abd9ee7f3@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

kselftest/arm64: Remove redundant _start labels from FP tests

There are a number of freestanding static executables used in floating
point testing that have no runtime at all. These all define the main entry
point as:

.globl _start
function _start
_start:

but clang's integrated assembler complains that:

error: symbol '_start' is already defined

due to having both a label and function directive. Remove the label to
allow building with clang.

No functional change.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/r/20230111-arm64-kselftest-clang-v1-2-89c69d377727@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

kselftest/arm64: Install signal handlers before output in FP stress tests

To interface more robustly with other processes install the signal handers
in the floating point stress tests before we produce any output, this
means that a parent process can know that if it has seen any output from
the test then the test is ready to handle incoming signals.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220906220056.820295-1-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

kselftest/arm64: Count SIGUSR2 deliveries in FP stress tests

Currently the floating point stress tests mostly support testing that the
data they are checking can be disrupted from a signal handler triggered by
SIGUSR1. This is not properly implemented for all the tests and in testing
is frequently modified to just handle the signal without corrupting data in
order to ensure that signal handling does not corrupt data. Directly support
this usage by installing a SIGUSR2 handler which simply counts the signal
delivery.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220829154452.824870-3-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

kselftest/arm64: Always encourage preemption for za-test

Since we now have an explicit test for the syscall ABI there is no need for
za-test to cover getpid() so just unconditionally do sched_yield() like we
do in fpsimd-test.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220829154452.824870-2-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

kselftest/arm64: Add stress test for SME ZA context switching

Add a stress test for context switching of the ZA register state based on
the similar tests Dave Martin wrote for FPSIMD and SVE registers. The test
loops indefinitely writing a data pattern to ZA then reading it back and
verifying that it's what was expected.

Unlike the other tests we manually assemble the SME instructions since at
present no released toolchain has SME support integrated.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20220419112247.711548-35-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>