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// Copyright 2020 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package linux
import (
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/errors/linuxerr"
"gvisor.dev/gvisor/pkg/sentry/arch"
"gvisor.dev/gvisor/pkg/sentry/kernel"
)
// Membarrier implements syscall membarrier(2).
func Membarrier(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
cmd := args[0].Int()
flags := args[1].Uint()
switch cmd {
case linux.MEMBARRIER_CMD_QUERY:
if flags != 0 {
return 0, nil, linuxerr.EINVAL
}
var supportedCommands uintptr
if t.Kernel().Platform.HaveGlobalMemoryBarrier() {
supportedCommands |= linux.MEMBARRIER_CMD_GLOBAL |
linux.MEMBARRIER_CMD_GLOBAL_EXPEDITED |
linux.MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED |
linux.MEMBARRIER_CMD_PRIVATE_EXPEDITED |
linux.MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED
}
if t.RSeqAvailable() {
supportedCommands |= linux.MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ |
linux.MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ
}
return supportedCommands, nil, nil
case linux.MEMBARRIER_CMD_GLOBAL, linux.MEMBARRIER_CMD_GLOBAL_EXPEDITED, linux.MEMBARRIER_CMD_PRIVATE_EXPEDITED:
if flags != 0 {
return 0, nil, linuxerr.EINVAL
}
if !t.Kernel().Platform.HaveGlobalMemoryBarrier() {
return 0, nil, linuxerr.EINVAL
}
if cmd == linux.MEMBARRIER_CMD_PRIVATE_EXPEDITED && !t.MemoryManager().IsMembarrierPrivateEnabled() {
return 0, nil, linuxerr.EPERM
}
return 0, nil, t.Kernel().Platform.GlobalMemoryBarrier()
case linux.MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED:
if flags != 0 {
return 0, nil, linuxerr.EINVAL
}
if !t.Kernel().Platform.HaveGlobalMemoryBarrier() {
return 0, nil, linuxerr.EINVAL
}
// no-op
return 0, nil, nil
case linux.MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED:
if flags != 0 {
return 0, nil, linuxerr.EINVAL
}
if !t.Kernel().Platform.HaveGlobalMemoryBarrier() {
return 0, nil, linuxerr.EINVAL
}
t.MemoryManager().EnableMembarrierPrivate()
return 0, nil, nil
case linux.MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ:
if flags&^linux.MEMBARRIER_CMD_FLAG_CPU != 0 {
return 0, nil, linuxerr.EINVAL
}
if !t.RSeqAvailable() {
return 0, nil, linuxerr.EINVAL
}
if !t.MemoryManager().IsMembarrierRSeqEnabled() {
return 0, nil, linuxerr.EPERM
}
// MEMBARRIER_CMD_FLAG_CPU and cpu_id are ignored since we don't have
// the ability to preempt specific CPUs.
return 0, nil, t.Kernel().Platform.PreemptAllCPUs()
case linux.MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ:
if flags != 0 {
return 0, nil, linuxerr.EINVAL
}
if !t.RSeqAvailable() {
return 0, nil, linuxerr.EINVAL
}
t.MemoryManager().EnableMembarrierRSeq()
return 0, nil, nil
default:
// Probably a command we don't implement.
t.Kernel().EmitUnimplementedEvent(t)
return 0, nil, linuxerr.EINVAL
}
}
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