Re: [RFC PATCH for 4.15 14/14] Restartable sequences: Provide self-tests

[Michael Ellerman]

Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> writes:

> 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
> - Code infinitely looping within a critical section will eventually be
>   interrupted.
> - Critical sections are interrupted by signals.
>
> "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.
>
> 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 following rseq APIs are implemented in this helper library:
> - rseq_register_current_thread()/rseq_unregister_current_thread():
>     register/unregister current thread's use of rseq,
> - rseq_current_cpu_raw():
>     current CPU number,
> - rseq_start():
>     beginning of a restartable sequence,
> - rseq_cpu_at_start():
>     CPU number at start of restartable sequence,
> - rseq_finish():
>     End of restartable sequence made of zero or more loads, completed by
>     a word-sized store,
> - rseq_finish2():
>     End of restartable sequence made of zero or more loads, one
>     speculative word-sized store, completed by a word-sized store,
> - rseq_finish2_release():
>     End of restartable sequence made of zero or more loads, one
>     speculative word-sized store, completed by a word-sized store with
>     release semantic,
> - rseq_finish_memcpy():
>     End of restartable sequence made of zero or more loads, a
>     speculative copy of a variable length memory region, completed by a
>     word-sized store.
> - rseq_finish_memcpy_release():
>     End of restartable sequence made of zero or more loads, a
>     speculative copy of a variable length memory region, completed by a
>     word-sized store with release semantic.
>
> PowerPC tests have been implemented by Boqun Feng.

Hi Boqun,

I'm having trouble testing these, I get:

  ~/linus/tools/testing/selftests/cpu-opv$ ./basic_cpu_opv_test
  Testing test_compare_eq same
  Testing test_compare_eq different
  Testing test_compare_ne same
  Testing test_compare_ne different
  Testing test_2compare_eq index
  Testing test_2compare_ne index
  Testing test_memcpy
  Testing test_memcpy_u32
  Testing test_add
  Testing test_two_add
  Testing test_or
  Testing test_and
  Testing test_xor
  Testing test_lshift
  Testing test_rshift
  Testing test_cmpxchg success
  Testing test_cmpxchg fail
  
  ~/linus/tools/testing/selftests/rseq$ ./basic_test
  testing current cpu
  testing critical section
  testing critical section is interrupted by signal

  ~/linus/tools/testing/selftests/rseq$ ./basic_percpu_ops_test
  ./basic_percpu_ops_test: error while loading shared libraries: R_PPC64_ADDR16_HI re10d8f10a0 for symbol `' out of range
  ~/linus/tools/testing/selftests/rseq$ ./param_test
  ./param_test: error while loading shared libraries: R_PPC64_ADDR16_HI re136251b48 for symbol `' out of range


Any idea what's going on with the last two? I assume you don't see that
in your test setup :)

cheers