165 lines
4.2 KiB
Go
165 lines
4.2 KiB
Go
// Copyright 2018 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 kvm provides a kvm-based implementation of the platform interface.
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package kvm
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import (
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"fmt"
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"os"
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"syscall"
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"gvisor.dev/gvisor/pkg/sentry/platform"
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"gvisor.dev/gvisor/pkg/sentry/platform/ring0"
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"gvisor.dev/gvisor/pkg/sentry/platform/ring0/pagetables"
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"gvisor.dev/gvisor/pkg/sentry/usermem"
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"gvisor.dev/gvisor/pkg/sync"
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)
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// KVM represents a lightweight VM context.
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type KVM struct {
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platform.NoCPUPreemptionDetection
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// machine is the backing VM.
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machine *machine
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}
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var (
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globalOnce sync.Once
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globalErr error
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)
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// OpenDevice opens the KVM device at /dev/kvm and returns the File.
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func OpenDevice() (*os.File, error) {
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f, err := os.OpenFile("/dev/kvm", syscall.O_RDWR, 0)
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if err != nil {
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return nil, fmt.Errorf("error opening /dev/kvm: %v", err)
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}
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return f, nil
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}
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// New returns a new KVM-based implementation of the platform interface.
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func New(deviceFile *os.File) (*KVM, error) {
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fd := deviceFile.Fd()
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// Ensure global initialization is done.
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globalOnce.Do(func() {
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globalErr = updateGlobalOnce(int(fd))
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})
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if globalErr != nil {
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return nil, globalErr
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}
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// Create a new VM fd.
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var (
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vm uintptr
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errno syscall.Errno
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)
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for {
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vm, _, errno = syscall.Syscall(syscall.SYS_IOCTL, fd, _KVM_CREATE_VM, 0)
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if errno == syscall.EINTR {
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continue
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}
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if errno != 0 {
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return nil, fmt.Errorf("creating VM: %v", errno)
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}
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break
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}
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// We are done with the device file.
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deviceFile.Close()
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// Create a VM context.
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machine, err := newMachine(int(vm))
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if err != nil {
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return nil, err
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}
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// All set.
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return &KVM{
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machine: machine,
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}, nil
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}
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// SupportsAddressSpaceIO implements platform.Platform.SupportsAddressSpaceIO.
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func (*KVM) SupportsAddressSpaceIO() bool {
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return false
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}
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// CooperativelySchedulesAddressSpace implements platform.Platform.CooperativelySchedulesAddressSpace.
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func (*KVM) CooperativelySchedulesAddressSpace() bool {
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return false
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}
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// MapUnit implements platform.Platform.MapUnit.
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func (*KVM) MapUnit() uint64 {
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// We greedily creates PTEs in MapFile, so extremely large mappings can
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// be expensive. Not _that_ expensive since we allow super pages, but
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// even though can get out of hand if you're creating multi-terabyte
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// mappings. For this reason, we limit mappings to an arbitrary 16MB.
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return 16 << 20
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}
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// MinUserAddress returns the lowest available address.
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func (*KVM) MinUserAddress() usermem.Addr {
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return usermem.PageSize
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}
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// MaxUserAddress returns the first address that may not be used.
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func (*KVM) MaxUserAddress() usermem.Addr {
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return usermem.Addr(ring0.MaximumUserAddress)
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}
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// NewAddressSpace returns a new pagetable root.
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func (k *KVM) NewAddressSpace(_ interface{}) (platform.AddressSpace, <-chan struct{}, error) {
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// Allocate page tables and install system mappings.
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pageTables := pagetables.New(newAllocator())
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applyPhysicalRegions(func(pr physicalRegion) bool {
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// Map the kernel in the upper half.
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pageTables.Map(
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usermem.Addr(ring0.KernelStartAddress|pr.virtual),
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pr.length,
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pagetables.MapOpts{AccessType: usermem.AnyAccess},
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pr.physical)
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return true // Keep iterating.
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})
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// Return the new address space.
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return &addressSpace{
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machine: k.machine,
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pageTables: pageTables,
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dirtySet: k.machine.newDirtySet(),
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}, nil, nil
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}
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// NewContext returns an interruptible context.
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func (k *KVM) NewContext() platform.Context {
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return &context{
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machine: k.machine,
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}
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}
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type constructor struct{}
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func (*constructor) New(f *os.File) (platform.Platform, error) {
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return New(f)
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}
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func (*constructor) OpenDevice() (*os.File, error) {
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return OpenDevice()
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}
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func init() {
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platform.Register("kvm", &constructor{})
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}
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