selftests/powerpc/ptrace: Explain why tests are skipped

Many tests require specific hardware features/configurations that a
typical machine might not have. As a result, it's common to see a test
is skipped. But it is tedious to find out why a test is skipped
when all it gives is the file location of the skip macro.

Convert SKIP_IF() to SKIP_IF_MSG(), with appropriate descriptions of why
the test is being skipped. This gives a general idea of why a test is
skipped, which can be looked into further if it doesn't make sense.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230725005841.28854-3-bgray@linux.ibm.com

selftests/powerpc: ptrace-pkey: Don't update expected UAMOR value

With commit 4a4a5e5d2aad ("powerpc/pkeys: key allocation/deallocation
must not change pkey registers") we are not updating UAMOR on key
allocation. So don't update the expected uamor value in the test.

Fixes: 4a4a5e5d2aad ("powerpc/pkeys: key allocation/deallocation must not change pkey registers")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200709032946.881753-23-aneesh.kumar@linux.ibm.com

selftests/powerpc: ptrace-pkey: Update the test to mark an invalid pkey correctly

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200709032946.881753-22-aneesh.kumar@linux.ibm.com

selftests/powerpc: ptrace-pkey: Rename variables to make it easier to follow code

Rename variable to indicate that they are invalid values which we will
use to test ptrace update of pkeys.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200709032946.881753-21-aneesh.kumar@linux.ibm.com

selftests/powerpc: Fix pkey access right updates

The Power ISA mandates that all writes to the Authority
Mask Register (AMR) must always be preceded as well as
succeeded by a context synchronizing instruction.

This makes sure that the tests follow this requirement
when attempting to update a pkey's access rights.

Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200604125610.649668-2-sandipan@linux.ibm.com

selftests/powerpc: Fix ptrace-pkey for default execute permission change

The test case assumes execute-permissions of unallocated keys are
enabled by default, which is incorrect.

Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

selftests/powerpc: Add ptrace tests for Protection Key registers

This test exercises read and write access to the AMR, IAMR and UAMOR.

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
[mpe: Simplify make rule]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>