basic-gcs has it's own make rule to handle the special compiler
invocation to build against nolibc. This rule does not respect the
$(CFLAGS) passed by the Makefile from the parent directory.
However these $(CFLAGS) set up the include path to include the UAPI
headers from the current kernel.
Due to this the asm/hwcap.h header is used from the toolchain instead of
the UAPI and the definition of HWCAP_GCS is not found.

Restructure the rule for basic-gcs to respect the $(CFLAGS).
Also drop those options which are already provided by $(CFLAGS).

Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Closes: https://lore.kernel.org/lkml/CA+G9fYv77X+kKz2YT6xw7=9UrrotTbQ6fgNac7oohOg8BgGvtw@mail.gmail.com/
Fixes: a985fe638344 ("kselftest/arm64/gcs: Use nolibc's getauxval()")
Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>

Add trivial assembly programs which give themselves the appropriate
permissions and then execute GCSPUSHM and GCSSTR, they will report errors
by generating signals on the non-permitted instructions. Not using libc
minimises the interaction with any policy set for the system but we skip on
failure to get the permissions in case the system is locked down to make
them inaccessible.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20241005-arm64-gcs-test-flags-v1-1-03cb9786c5cd@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Add a stress test which runs one more process than we have CPUs spinning
through a very recursive function with frequent syscalls immediately prior
to return and signals being injected every 100ms. The goal is to flag up
any scheduling related issues, for example failure to ensure that barriers
are inserted when moving a GCS using task to another CPU. The test runs for
a configurable amount of time, defaulting to 10 seconds.

Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Tested-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20241001-arm64-gcs-v13-38-222b78d87eee@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Verify that we can lock individual GCS mode bits, that other modes
aren't affected and as a side effect also that every combination of
modes can be enabled.

Normally the inability to reenable GCS after disabling it would be an
issue with testing but fortunately the kselftest_harness runs each test
within a fork()ed child.  This can be inconvenient for some kinds of
testing but here it means that each test is in a separate thread and
therefore won't be affected by other tests in the suite.

Once we get toolchains with support for enabling GCS by default we will
need to take care to not do that in the build system but there are no
such toolchains yet so it is not yet an issue.

Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Tested-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20241001-arm64-gcs-v13-36-222b78d87eee@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

There are things like threads which nolibc struggles with which we want
to add coverage for, and the ABI allows us to test most of these even if
libc itself does not understand GCS so add a test application built
using the system libc.

Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Tested-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20241001-arm64-gcs-v13-35-222b78d87eee@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

This test program just covers the basic GCS ABI, covering aspects of the
ABI as standalone features without attempting to integrate things.

Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Tested-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20241001-arm64-gcs-v13-34-222b78d87eee@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>