selftests/x86/amx: Add a ptrace test

Include a test case to validate the XTILEDATA injection to the target.

Also, it ensures the kernel's ability to copy states between different
XSAVE formats.

Refactor the memcmp() code to be usable for the state validation.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20230227210504.18520-3-chang.seok.bae%40intel.com

selftests/x86/amx: Use provided __cpuid_count() macro

kselftest.h makes the __cpuid_count() macro available
to conveniently call the CPUID instruction.

Remove the local CPUID wrapper and use __cpuid_count()
from kselftest.h instead.

__cpuid_count() from kselftest.h is used instead of the
macro provided by the compiler since gcc v4.4 (via cpuid.h)
because the selftest needs to be supported with gcc v3.2,
the minimal required version for stable kernels.

Cc: Chang S. Bae <chang.seok.bae@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

selftests/x86/amx: Update the ARCH_REQ_XCOMP_PERM test

Update the arch_prctl test to check the permission bitmap whether the
requested feature is added as expected or not.

Every non-dynamic feature that is enabled is permitted already for use.
TILECFG is not dynamic feature. Ensure the bit is always on from
ARCH_GET_XCOMP_PERM.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20220129173647.27981-3-chang.seok.bae@intel.com

selftests/x86/amx: Add context switch test

XSAVE state is thread-local. The kernel switches between thread
state at context switch time. Generally, running a selftest for
a while will naturally expose it to some context switching and
and will test the XSAVE code.

Instead of just hoping that the tests get context-switched at
random times, force context-switches on purpose. Spawn off a few
userspace threads and force context-switches between them.
Ensure that the kernel correctly context switches each thread's
unique AMX state.

[ dhansen: bunches of cleanups ]

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211026122525.6EFD5758@davehans-spike.ostc.intel.com

selftests/x86/amx: Add test cases for AMX state management

AMX TILEDATA is a very large XSAVE feature. It could have caused
nasty XSAVE buffer space waste in two places:

* Signal stacks
* Kernel task_struct->fpu buffers

To avoid this waste, neither of these buffers have AMX state by
default. The non-default features are called "dynamic" features.

There is an arch_prctl(ARCH_REQ_XCOMP_PERM) which allows a task
to declare that it wants to use AMX or other "dynamic" XSAVE
features. This arch_prctl() ensures that sufficient sigaltstack
space is available before it will succeed. It also expands the
task_struct buffer.

Functions of this test:
* Test arch_prctl(ARCH_REQ_XCOMP_PERM). Ensure that it checks for
proper sigaltstack sizing and that the sizing is enforced for
future sigaltstack calls.
* Ensure that ARCH_REQ_XCOMP_PERM is inherited across fork()
* Ensure that TILEDATA use before the prctl() is fatal
* Ensure that TILEDATA is cleared across fork()

Note: Generally, compiler support is needed to do something with
AMX. Instead, directly load AMX state from userspace with a
plain XSAVE. Do not depend on the compiler.

[ dhansen: bunches of cleanups ]

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211026122524.7BEDAA95@davehans-spike.ostc.intel.com