This change adds RSEQ support for platform/kvm. RSEQ is disabled by default.
To support RSEQ, the KVM platform must provide two key capabilities:
(1) A stable, unique CPU ID.
(2) A way to detect when a thread as been preempted.
This implementation provides the necessary support as follows:
CPU ID:
- platform/kvm now advertises the KVM vCPU ID as the cpu_id
Preemption Detection:
- Compares the last context the CPU ran against the current context being
scheduled.
- Compares the context's rseqCPU and CPU ID retrieved by the platform
To facilitate this, several new methods are introduced to the platform
interface and implemented by platform/kvm:
- HasCpuNumbers()
- NumCPUs()
- DetectsCPUPreemption()
- PreemptCpu()
- PreemptAllCpus()
A new user-facing KVM specific option, use_cpu_numbers, is introduced to
effectively feature guard RSEQ. When use_cpu_numbers is true, vCPU IDs are
exposed to the guest, enabling RSEQ support. Setting it to false reverts to
the previous behavior and effectively disables RSEQ for applications that
rely on it.
PiperOrigin-RevId: 844846226
Accept 128 + SIGNAL as well as SIGNAL as valid
returns for fork/exec tests.
Also, make changes so that test compiles in opensource. Test
had compile errors on latest Ubuntu 16.04 image with updated bazel to
3.4.0 (as well as base 2.0) used for Kokoro tests.
PiperOrigin-RevId: 327510310
Add a decent set of syscall tests for rseq(2). These are a bit awkward because
of issues with library integration. libc may register rseq on thread start
(including before main on the initial thread), precluding much testing. Thus we
run tests in a libc-free subprocess.
Support for rseq(2) in gVisor will come in a later commit.
PiperOrigin-RevId: 284595994
