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https://github.com/hanzoai/visor.git
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Jimmy TranandgVisor bot
544a60277d
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
115 lines
3.7 KiB
Go
115 lines
3.7 KiB
Go
// Copyright 2020 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package linux
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import (
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"gvisor.dev/gvisor/pkg/abi/linux"
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"gvisor.dev/gvisor/pkg/errors/linuxerr"
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"gvisor.dev/gvisor/pkg/sentry/arch"
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"gvisor.dev/gvisor/pkg/sentry/kernel"
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)
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// Membarrier implements syscall membarrier(2).
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func Membarrier(t *kernel.Task, sysno uintptr, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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cmd := args[0].Int()
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flags := args[1].Uint()
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cpu := args[2].Int()
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switch cmd {
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case linux.MEMBARRIER_CMD_QUERY:
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if flags != 0 {
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return 0, nil, linuxerr.EINVAL
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}
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var supportedCommands uintptr
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if t.Kernel().Platform.HaveGlobalMemoryBarrier() {
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supportedCommands |= linux.MEMBARRIER_CMD_GLOBAL |
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linux.MEMBARRIER_CMD_GLOBAL_EXPEDITED |
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linux.MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED |
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linux.MEMBARRIER_CMD_PRIVATE_EXPEDITED |
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linux.MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED
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}
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if t.RSeqAvailable() {
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supportedCommands |= linux.MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ |
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linux.MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ
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}
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return supportedCommands, nil, nil
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case linux.MEMBARRIER_CMD_GLOBAL, linux.MEMBARRIER_CMD_GLOBAL_EXPEDITED, linux.MEMBARRIER_CMD_PRIVATE_EXPEDITED:
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if flags != 0 {
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return 0, nil, linuxerr.EINVAL
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}
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if !t.Kernel().Platform.HaveGlobalMemoryBarrier() {
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return 0, nil, linuxerr.EINVAL
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}
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if cmd == linux.MEMBARRIER_CMD_PRIVATE_EXPEDITED && !t.MemoryManager().IsMembarrierPrivateEnabled() {
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return 0, nil, linuxerr.EPERM
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}
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return 0, nil, t.Kernel().Platform.GlobalMemoryBarrier()
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case linux.MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED:
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if flags != 0 {
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return 0, nil, linuxerr.EINVAL
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}
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if !t.Kernel().Platform.HaveGlobalMemoryBarrier() {
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return 0, nil, linuxerr.EINVAL
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}
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// no-op
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return 0, nil, nil
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case linux.MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED:
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if flags != 0 {
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return 0, nil, linuxerr.EINVAL
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}
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if !t.Kernel().Platform.HaveGlobalMemoryBarrier() {
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return 0, nil, linuxerr.EINVAL
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}
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t.MemoryManager().EnableMembarrierPrivate()
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return 0, nil, nil
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case linux.MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ:
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if flags&^linux.MEMBARRIER_CMD_FLAG_CPU != 0 {
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return 0, nil, linuxerr.EINVAL
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}
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if !t.RSeqAvailable() {
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return 0, nil, linuxerr.EINVAL
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}
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if !t.MemoryManager().IsMembarrierRSeqEnabled() {
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return 0, nil, linuxerr.EPERM
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}
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platform := t.Kernel().Platform
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if flags&linux.MEMBARRIER_CMD_FLAG_CPU != 0 && cpu >= 0 && platform.HasCPUNumbers() {
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// Per membarrier(2), an out of range cpu# that is >= 0 is a no-op.
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if cpu >= int32(platform.NumCPUs()) {
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return 0, nil, nil
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}
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return 0, nil, platform.PreemptCPU(cpu)
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}
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// Preempt all CPUs if the platform does not support CPU numbers or cpu # is less than 0 -
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// this is the same behavior as Linux.
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return 0, nil, platform.PreemptAllCPUs()
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case linux.MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ:
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if flags != 0 {
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return 0, nil, linuxerr.EINVAL
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}
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if !t.RSeqAvailable() {
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return 0, nil, linuxerr.EINVAL
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}
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t.MemoryManager().EnableMembarrierRSeq()
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return 0, nil, nil
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default:
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// Probably a command we don't implement.
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t.Kernel().EmitUnimplementedEvent(t, sysno)
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return 0, nil, linuxerr.EINVAL
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}
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}
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