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@efficios.com CC: Russell King linux@arm.linux.org.uk CC: Catalin Marinas catalin.marinas@arm.com CC: Will Deacon will.deacon@arm.com CC: Thomas Gleixner tglx@linutronix.de CC: Paul Turner pjt@google.com CC: Andrew Hunter ahh@google.com CC: Peter Zijlstra peterz@infradead.org CC: Andy Lutomirski luto@amacapital.net CC: Andi Kleen andi@firstfloor.org CC: Dave Watson davejwatson@fb.com CC: Chris Lameter cl@linux.com CC: Ingo Molnar mingo@redhat.com CC: "H. Peter Anvin" hpa@zytor.com CC: Ben Maurer bmaurer@fb.com CC: Steven Rostedt rostedt@goodmis.org CC: "Paul E. McKenney" paulmck@linux.vnet.ibm.com CC: Josh Triplett josh@joshtriplett.org CC: Linus Torvalds torvalds@linux-foundation.org CC: Andrew Morton akpm@linux-foundation.org CC: Boqun Feng boqun.feng@gmail.com CC: Shuah Khan shuah@kernel.org CC: linux-kselftest@vger.kernel.org CC: linux-api@vger.kernel.org

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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.

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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@osg.samsung.com

thanks, -- Shuah -- To unsubscribe from this list: send the line "unsubscribe linux-kselftest" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html