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: Convert to load/store doubles

Some of the ptrace tests check the contents of floating pointer
registers. Currently these use float, which is always 4 bytes, but the
ptrace API supports saving/restoring 8 bytes per register, so switch to
using doubles to exercise the code more fully.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220627140239.2464900-8-mpe@ellerman.id.au

selftests: Skip TM tests on synthetic TM implementations

Transactional Memory was removed from the architecture in ISA v3.1. For
threads running in P8/P9 compatibility mode on P10 a synthetic TM
implementation is provided. In this implementation, tbegin. always sets
cr0 eq meaning the abort handler is always called. This is not an issue
as users of TM are expected to have a fallback non transactional way to
make forward progress in the abort handler. The TEXASR indicates if a
transaction failure is due to a synthetic implementation.

Some of the TM self tests need a non-degenerate TM implementation for
their testing to be meaningful so check for a synthetic implementation
and skip the test if so.

Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210729041317.366612-2-jniethe5@gmail.com

selftests/powerpc: Add missing clobbered register to to ptrace TM tests

ISA v3.1 removes TM but includes a synthetic implementation for
backwards compatibility. With this implementation, the tests
ptrace-tm-spd-gpr and ptrace-tm-gpr should never be able to make any
forward progress and eventually should be killed by the timeout.
Instead on a P10 running in P9 mode, ptrace_tm_gpr fails like so:

test: ptrace_tm_gpr
tags: git_version:unknown
Starting the child
...
...
GPR[27]: 1 Expected: 2
GPR[28]: 1 Expected: 2
GPR[29]: 1 Expected: 2
GPR[30]: 1 Expected: 2
GPR[31]: 1 Expected: 2
[FAIL] Test FAILED on line 98
failure: ptrace_tm_gpr
selftests: ptrace-tm-gpr [FAIL]

The problem is in the inline assembly of the child. r0 is loaded with a
value in the child's transaction abort handler but this register is not
included in the clobbers list. This means it is possible that this
statement:
cptr[1] = 0;
which is meant to signal the parent to wait may actually use the value
placed into r0 by the inline assembly incorrectly signal the parent to
continue.

By inspection the same problem is present in ptrace-tm-spd-gpr.

Adding r0 to the clobbbers list makes the test fail correctly via a
timeout on a P10 running in P8/P9 compatibility mode.

Suggested-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210729041317.366612-1-jniethe5@gmail.com

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 3029 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

selftests/powerpc: Fix ptrace tm failure

Test ptrace-tm-spd-gpr fails on current kernel (4.19) due to a segmentation
fault that happens on the child process prior to setting cptr[2] = 1. This
causes the parent process to wait forever at 'while (!pptr[2])' and the test to
be killed by the test harness framework by timeout, thus, failing.

The segmentation fault happens because of a inline assembly being
generated as:

0x10000355c <tm_spd_gpr+492> lfs f0, 0(0)

This is reading memory position 0x0 and causing the segmentation fault.

This code is being generated by ASM_LOAD_FPR_SINGLE_PRECISION(flt_4), where
flt_4 is passed to the inline assembly block as:

[flt_4] "r" (&d)

Since the inline assembly 'r' constraint means any GPR, gpr0 is being
chosen, thus causing this issue when issuing a Load Floating-Point Single
instruction.

This patch simply changes the constraint to 'b', which specify that this
register will be used as base, and r0 is not allowed to be used, avoiding
this issue.

Other than that, removing flt_2 register from the input operands, since it
is not used by the inline assembly code at all.

Cc: stable@vger.kernel.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Acked-by: Segher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

selftests/powerpc: Add ptrace tests for GPR/FPR registers in suspended TM

This patch adds ptrace interface test for GPR/FPR registers
inside suspended TM context.

Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: Simon Guo <wei.guo.simon@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>