Re: [PATCH 1/2] selftests/powerpc: Add ptrace tests for Protection Key registers

[Michael Ellerman <mpe@ellerman.id.au>]

Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> writes:

> This test exercises read and write access to the AMR, IAMR and UAMOR.
>
> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
> ---
>  tools/testing/selftests/powerpc/include/reg.h      |   1 +
>  tools/testing/selftests/powerpc/ptrace/Makefile    |   5 +-
>  tools/testing/selftests/powerpc/ptrace/child.h     | 130 ++++++++
>  .../testing/selftests/powerpc/ptrace/ptrace-pkey.c | 326 +++++++++++++++++++++

This is failing on machines without pkeys:

  test: ptrace_pkey
  tags: git_version:52e7d87
  [FAIL] Test FAILED on line 117
  [FAIL] Test FAILED on line 191
  failure: ptrace_pkey


I think the first fail is in the child here:

int ptrace_read_regs(pid_t child, unsigned long type, unsigned long regs[],
		     int n)
{
	struct iovec iov;
	long ret;

	FAIL_IF(start_trace(child));

	iov.iov_base = regs;
	iov.iov_len = n * sizeof(unsigned long);

	ret = ptrace(PTRACE_GETREGSET, child, type, &iov);
	FAIL_IF(ret != 0);


Which makes sense.

The test needs to skip if pkeys are not available/enabled. Using the
availability of the REGSET might actually be a nice way to detect that,
because it's read-only.

cheers