Re: [PATCH update for 4.15 3/3] rseq: selftests: Provide self-tests (v4)

----- On Nov 22, 2017, at 10:23 AM, shuah shuah@kernel.org wrote:

On 11/21/2017 03:19 PM, Mathieu Desnoyers wrote:

quoted

Implements two basic tests of RSEQ functionality, and one more
exhaustive parameterizable test.

The first, "basic_test" only asserts that RSEQ works moderately
correctly. E.g. that the CPUID pointer works.

"basic_percpu_ops_test" is a slightly more "realistic" variant,
implementing a few simple per-cpu operations and testing their
correctness.

"param_test" is a parametrizable restartable sequences test. See
the "--help" output for usage.

A run_param_test.sh script runs many variants of the parametrizable
tests.

As part of those tests, a helper library "rseq" implements a user-space
API around restartable sequences. It uses the cpu_opv system call as
fallback when single-stepped by a debugger. It exposes the instruction
pointer addresses where the rseq assembly blocks begin and end, as well
as the associated abort instruction pointer, in the __rseq_table
section. This section allows debuggers may know where to place
breakpoints when single-stepping through assembly blocks which may be
aborted at any point by the kernel.

The rseq library expose APIs that present the fast-path operations.
The new from userspace is, e.g. for a counter increment:

    cpu = rseq_cpu_start();
    ret = rseq_addv(&data->c[cpu].count, 1, cpu);
    if (likely(!ret))
        return 0;        /* Success. */
    do {
        cpu = rseq_current_cpu();
        ret = cpu_op_addv(&data->c[cpu].count, 1, cpu);
        if (likely(!ret))
            return 0;    /* Success. */
    } while (ret > 0 || errno == EAGAIN);
    perror("cpu_op_addv");
    return -1;           /* Unexpected error. */

PowerPC tests have been implemented by Boqun Feng.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: Russell King <redacted>
CC: Catalin Marinas <catalin.marinas@arm.com>
CC: Will Deacon <redacted>
CC: Thomas Gleixner <redacted>
CC: Paul Turner <redacted>
CC: Andrew Hunter <redacted>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Andi Kleen <redacted>
CC: Dave Watson <redacted>
CC: Chris Lameter <redacted>
CC: Ingo Molnar <mingo@redhat.com>
CC: "H. Peter Anvin" <hpa@zytor.com>
CC: Ben Maurer <redacted>
CC: Steven Rostedt <rostedt@goodmis.org>
CC: "Paul E. McKenney" <redacted>
CC: Josh Triplett <josh@joshtriplett.org>
CC: Linus Torvalds <torvalds@linux-foundation.org>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Boqun Feng <redacted>
CC: Shuah Khan <shuah@kernel.org>
CC: linux-kselftest@vger.kernel.org
CC: linux-api@vger.kernel.org
---
Changes since v1:
- Provide abort-ip signature: The abort-ip signature is located just
  before the abort-ip target. It is currently hardcoded, but a
  user-space application could use the __rseq_table to iterate on all
  abort-ip targets and use a random value as signature if needed in the
  future.
- Add rseq_prepare_unload(): Libraries and JIT code using rseq critical
  sections need to issue rseq_prepare_unload() on each thread at least
  once before reclaim of struct rseq_cs.
- Use initial-exec TLS model, non-weak symbol: The initial-exec model is
  signal-safe, whereas the global-dynamic model is not.  Remove the
  "weak" symbol attribute from the __rseq_abi in rseq.c. The rseq.so
  library will have ownership of that symbol, and there is not reason for
  an application or user library to try to define that symbol.
  The expected use is to link against libreq.so, which owns and provide
  that symbol.
- Set cpu_id to -2 on register error
- Add rseq_len syscall parameter, rseq_cs version
- Ensure disassember-friendly signature: x86 32/64 disassembler have a
  hard time decoding the instruction stream after a bad instruction. Use
  a nopl instruction to encode the signature. Suggested by Andy Lutomirski.
- Exercise parametrized tests variants in a shell scripts.
- Restartable sequences selftests: Remove use of event counter.
- Use cpu_id_start field:  With the cpu_id_start field, the C
  preparation phase of the fast-path does not need to compare cpu_id < 0
  anymore.
- Signal-safe registration and refcounting: Allow libraries using
  librseq.so to register it from signal handlers.
- Use OVERRIDE_TARGETS in makefile.
- Use "m" constraints for rseq_cs field.

Changes since v2:
- Update based on Thomas Gleixner's comments.

Changes since v3:
- Generate param_test_skip_fastpath and param_test_benchmark with
  -DSKIP_FASTPATH and -DBENCHMARK (respectively). Add param_test_fastpath
  to run_param_test.sh.
---
 MAINTAINERS                                        |    1 +
 tools/testing/selftests/Makefile                   |    1 +
 tools/testing/selftests/rseq/.gitignore            |    4 +
 tools/testing/selftests/rseq/Makefile              |   33 +
 .../testing/selftests/rseq/basic_percpu_ops_test.c |  333 +++++
 tools/testing/selftests/rseq/basic_test.c          |   55 +
 tools/testing/selftests/rseq/param_test.c          | 1285 ++++++++++++++++++++
 tools/testing/selftests/rseq/rseq-arm.h            |  535 ++++++++
 tools/testing/selftests/rseq/rseq-ppc.h            |  567 +++++++++
 tools/testing/selftests/rseq/rseq-x86.h            |  898 ++++++++++++++
 tools/testing/selftests/rseq/rseq.c                |  116 ++
 tools/testing/selftests/rseq/rseq.h                |  154 +++
 tools/testing/selftests/rseq/run_param_test.sh     |  126 ++
 13 files changed, 4108 insertions(+)
 create mode 100644 tools/testing/selftests/rseq/.gitignore
 create mode 100644 tools/testing/selftests/rseq/Makefile
 create mode 100644 tools/testing/selftests/rseq/basic_percpu_ops_test.c
 create mode 100644 tools/testing/selftests/rseq/basic_test.c
 create mode 100644 tools/testing/selftests/rseq/param_test.c
 create mode 100644 tools/testing/selftests/rseq/rseq-arm.h
 create mode 100644 tools/testing/selftests/rseq/rseq-ppc.h
 create mode 100644 tools/testing/selftests/rseq/rseq-x86.h
 create mode 100644 tools/testing/selftests/rseq/rseq.c
 create mode 100644 tools/testing/selftests/rseq/rseq.h
 create mode 100755 tools/testing/selftests/rseq/run_param_test.sh

Looks good.

Acked-by: Shuah Khan <redacted>

Thanks the the reviews!

Mathieu

thanks,
-- Shuah

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com