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

[Shuah Khan]

On 11/21/2017 03:19 PM, Mathieu Desnoyers wrote:
> 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@xxxxxxxxxxxx>
> CC: Russell King <linux@xxxxxxxxxxxxxxxx>
> CC: Catalin Marinas <catalin.marinas@xxxxxxx>
> CC: Will Deacon <will.deacon@xxxxxxx>
> CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> CC: Paul Turner <pjt@xxxxxxxxxx>
> CC: Andrew Hunter <ahh@xxxxxxxxxx>
> CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> CC: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> CC: Andi Kleen <andi@xxxxxxxxxxxxxx>
> CC: Dave Watson <davejwatson@xxxxxx>
> CC: Chris Lameter <cl@xxxxxxxxx>
> CC: Ingo Molnar <mingo@xxxxxxxxxx>
> CC: "H. Peter Anvin" <hpa@xxxxxxxxx>
> CC: Ben Maurer <bmaurer@xxxxxx>
> CC: Steven Rostedt <rostedt@xxxxxxxxxxx>
> CC: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
> CC: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
> CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> CC: Boqun Feng <boqun.feng@xxxxxxxxx>
> CC: Shuah Khan <shuah@xxxxxxxxxx>
> CC: linux-kselftest@xxxxxxxxxxxxxxx
> CC: linux-api@xxxxxxxxxxxxxxx
> ---
> 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 <shuahkh@xxxxxxxxxxxxxxx>

thanks,
-- Shuah