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|
// Copyright 2018 Google Inc.
//
// 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 kernel provides an emulation of the Linux kernel.
//
// See README.md for a detailed overview.
//
// Lock order (outermost locks must be taken first):
//
// Kernel.extMu
// TaskSet.mu
// SignalHandlers.mu
// Task.mu
//
// Locking SignalHandlers.mu in multiple SignalHandlers requires locking
// TaskSet.mu exclusively first. Locking Task.mu in multiple Tasks at the same
// time requires locking all of their signal mutexes first.
package kernel
import (
"fmt"
"io"
"path/filepath"
"sync"
"sync/atomic"
"time"
"gvisor.googlesource.com/gvisor/pkg/abi/linux"
"gvisor.googlesource.com/gvisor/pkg/cpuid"
"gvisor.googlesource.com/gvisor/pkg/log"
"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
"gvisor.googlesource.com/gvisor/pkg/sentry/context"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs/timerfd"
"gvisor.googlesource.com/gvisor/pkg/sentry/hostcpu"
"gvisor.googlesource.com/gvisor/pkg/sentry/inet"
"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/auth"
"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/epoll"
"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/sched"
ktime "gvisor.googlesource.com/gvisor/pkg/sentry/kernel/time"
"gvisor.googlesource.com/gvisor/pkg/sentry/limits"
"gvisor.googlesource.com/gvisor/pkg/sentry/loader"
"gvisor.googlesource.com/gvisor/pkg/sentry/mm"
"gvisor.googlesource.com/gvisor/pkg/sentry/platform"
"gvisor.googlesource.com/gvisor/pkg/sentry/socket/netlink/port"
sentrytime "gvisor.googlesource.com/gvisor/pkg/sentry/time"
"gvisor.googlesource.com/gvisor/pkg/sentry/uniqueid"
"gvisor.googlesource.com/gvisor/pkg/state"
"gvisor.googlesource.com/gvisor/pkg/tcpip"
)
// Kernel represents an emulated Linux kernel. It must be initialized by calling
// Init() or LoadFrom().
type Kernel struct {
// extMu serializes external changes to the Kernel with calls to
// Kernel.SaveTo. (Kernel.SaveTo requires that the state of the Kernel
// remains frozen for the duration of the call; it requires that the Kernel
// is paused as a precondition, which ensures that none of the tasks
// running within the Kernel can affect its state, but extMu is required to
// ensure that concurrent users of the Kernel *outside* the Kernel's
// control cannot affect its state by calling e.g.
// Kernel.SendExternalSignal.)
extMu sync.Mutex `state:"nosave"`
// started is true if Start has been called. Unless otherwise specified,
// all Kernel fields become immutable once started becomes true.
started bool `state:"nosave"`
// All of the following fields are immutable unless otherwise specified.
// Platform is the platform that is used to execute tasks in the
// created Kernel. It is embedded so that Kernel can directly serve as
// Platform in mm logic and also serve as platform.MemoryProvider in
// filemem S/R logic.
platform.Platform `state:"nosave"`
// See InitKernelArgs for the meaning of these fields.
featureSet *cpuid.FeatureSet
timekeeper *Timekeeper
tasks *TaskSet
rootUserNamespace *auth.UserNamespace
networkStack inet.Stack `state:"nosave"`
applicationCores uint
useHostCores bool
extraAuxv []arch.AuxEntry
vdso *loader.VDSO
rootUTSNamespace *UTSNamespace
rootIPCNamespace *IPCNamespace
// mounts holds the state of the virtual filesystem. mounts is initially
// nil, and must be set by calling Kernel.SetRootMountNamespace before
// Kernel.CreateProcess can succeed.
mounts *fs.MountNamespace
// globalInit is the thread group whose leader has ID 1 in the root PID
// namespace. globalInit is stored separately so that it is accessible even
// after all tasks in the thread group have exited, such that ID 1 is no
// longer mapped.
//
// globalInit is mutable until it is assigned by the first successful call
// to CreateProcess, and is protected by extMu.
globalInit *ThreadGroup
// realtimeClock is a ktime.Clock based on timekeeper's Realtime.
realtimeClock *timekeeperClock
// monotonicClock is a ktime.Clock based on timekeeper's Monotonic.
monotonicClock *timekeeperClock
// syslog is the kernel log.
syslog syslog
// cpuClock is incremented every linux.ClockTick. cpuClock is used to
// measure task CPU usage, since sampling monotonicClock twice on every
// syscall turns out to be unreasonably expensive. This is similar to how
// Linux does task CPU accounting on x86 (CONFIG_IRQ_TIME_ACCOUNTING),
// although Linux also uses scheduler timing information to improve
// resolution (kernel/sched/cputime.c:cputime_adjust()), which we can't do
// since "preeemptive" scheduling is managed by the Go runtime, which
// doesn't provide this information.
//
// cpuClock is mutable, and is accessed using atomic memory operations.
cpuClock uint64
// cpuClockTicker increments cpuClock.
cpuClockTicker *ktime.Timer `state:"nosave"`
// fdMapUids is an ever-increasing counter for generating FDMap uids.
//
// fdMapUids is mutable, and is accessed using atomic memory operations.
fdMapUids uint64
// uniqueID is used to generate unique identifiers.
//
// uniqueID is mutable, and is accessed using atomic memory operations.
uniqueID uint64
// nextInotifyCookie is a monotonically increasing counter used for
// generating unique inotify event cookies.
//
// nextInotifyCookie is mutable, and is accesed using atomic memory
// operations.
nextInotifyCookie uint32
// netlinkPorts manages allocation of netlink socket port IDs.
netlinkPorts *port.Manager
// exitErr is the error causing the sandbox to exit, if any. It is
// protected by extMu.
exitErr error
// danglingEndpoints is used to save / restore tcpip.DanglingEndpoints.
danglingEndpoints struct{} `state:".([]tcpip.Endpoint)"`
}
// InitKernelArgs holds arguments to Init.
type InitKernelArgs struct {
// FeatureSet is the emulated CPU feature set.
FeatureSet *cpuid.FeatureSet
// Timekeeper manages time for all tasks in the system.
Timekeeper *Timekeeper
// RootUserNamespace is the root user namespace.
RootUserNamespace *auth.UserNamespace
// NetworkStack is the TCP/IP network stack. NetworkStack may be nil.
NetworkStack inet.Stack
// ApplicationCores is the number of logical CPUs visible to sandboxed
// applications. The set of logical CPU IDs is [0, ApplicationCores); thus
// ApplicationCores is analogous to Linux's nr_cpu_ids, the index of the
// most significant bit in cpu_possible_mask + 1.
ApplicationCores uint
// If UseHostCores is true, Task.CPU() returns the task goroutine's CPU
// instead of a virtualized CPU number, and Task.CopyToCPUMask() is a
// no-op. If ApplicationCores is less than hostcpu.MaxPossibleCPU(), it
// will be overridden.
UseHostCores bool
// ExtraAuxv contains additional auxiliary vector entries that are added to
// each process by the ELF loader.
ExtraAuxv []arch.AuxEntry
// Vdso holds the VDSO and its parameter page.
Vdso *loader.VDSO
// RootUTSNamespace is the root UTS namepsace.
RootUTSNamespace *UTSNamespace
// RootIPCNamespace is the root IPC namepsace.
RootIPCNamespace *IPCNamespace
}
// Init initialize the Kernel with no tasks.
//
// Callers must manually set Kernel.Platform before caling Init.
func (k *Kernel) Init(args InitKernelArgs) error {
if args.FeatureSet == nil {
return fmt.Errorf("FeatureSet is nil")
}
if args.Timekeeper == nil {
return fmt.Errorf("Timekeeper is nil")
}
if args.RootUserNamespace == nil {
return fmt.Errorf("RootUserNamespace is nil")
}
if args.ApplicationCores == 0 {
return fmt.Errorf("ApplicationCores is 0")
}
k.featureSet = args.FeatureSet
k.timekeeper = args.Timekeeper
k.tasks = newTaskSet()
k.rootUserNamespace = args.RootUserNamespace
k.rootUTSNamespace = args.RootUTSNamespace
k.rootIPCNamespace = args.RootIPCNamespace
k.networkStack = args.NetworkStack
k.applicationCores = args.ApplicationCores
if args.UseHostCores {
k.useHostCores = true
maxCPU, err := hostcpu.MaxPossibleCPU()
if err != nil {
return fmt.Errorf("Failed to get maximum CPU number: %v", err)
}
minAppCores := uint(maxCPU) + 1
if k.applicationCores < minAppCores {
log.Infof("UseHostCores enabled: increasing ApplicationCores from %d to %d", k.applicationCores, minAppCores)
k.applicationCores = minAppCores
}
}
k.extraAuxv = args.ExtraAuxv
k.vdso = args.Vdso
k.realtimeClock = &timekeeperClock{tk: args.Timekeeper, c: sentrytime.Realtime}
k.monotonicClock = &timekeeperClock{tk: args.Timekeeper, c: sentrytime.Monotonic}
k.netlinkPorts = port.New()
return nil
}
// SaveTo saves the state of k to w.
//
// Preconditions: The kernel must be paused throughout the call to SaveTo.
func (k *Kernel) SaveTo(w io.Writer) error {
saveStart := time.Now()
ctx := k.SupervisorContext()
// Do not allow other Kernel methods to affect it while it's being saved.
k.extMu.Lock()
defer k.extMu.Unlock()
// Stop time.
k.pauseTimeLocked()
defer k.resumeTimeLocked()
// Flush write operations on open files so data reaches backing storage.
if err := k.tasks.flushWritesToFiles(ctx); err != nil {
return err
}
// Remove all epoll waiter objects from underlying wait queues.
// NOTE: for programs to resume execution in future snapshot scenarios,
// we will need to re-establish these waiter objects after saving.
k.tasks.unregisterEpollWaiters()
// Clear the dirent cache before saving because Dirents must be Loaded in a
// particular order (parents before children), and Loading dirents from a cache
// breaks that order.
k.mounts.FlushMountSourceRefs()
// Ensure that all pending asynchronous work is complete:
// - inode and mount release
// - asynchronuous IO
fs.AsyncBarrier()
// Once all fs work has completed (flushed references have all been released),
// reset mount mappings. This allows individual mounts to save how inodes map
// to filesystem resources. Without this, fs.Inodes cannot be restored.
fs.SaveInodeMappings()
// Discard unsavable mappings, such as those for host file descriptors.
// This must be done after waiting for "asynchronous fs work", which
// includes async I/O that may touch application memory.
if err := k.invalidateUnsavableMappings(ctx); err != nil {
return fmt.Errorf("failed to invalidate unsavable mappings: %v", err)
}
// Save the kernel state.
kernelStart := time.Now()
var stats state.Stats
if err := state.Save(w, k, &stats); err != nil {
return err
}
log.Infof("Kernel save stats: %s", &stats)
log.Infof("Kernel save took [%s].", time.Since(kernelStart))
// Save the memory state.
//
// FIXME: In the future, this should not be dispatched via
// an abstract memory type. This should be dispatched to a single
// memory implementation that belongs to the kernel. (There is
// currently a single implementation anyways, it just needs to be
// "unabstracted" and reparented appropriately.)
memoryStart := time.Now()
if err := k.Platform.Memory().SaveTo(w); err != nil {
return err
}
log.Infof("Memory save took [%s].", time.Since(memoryStart))
log.Infof("Overall save took [%s].", time.Since(saveStart))
return nil
}
func (ts *TaskSet) flushWritesToFiles(ctx context.Context) error {
ts.mu.RLock()
defer ts.mu.RUnlock()
for t := range ts.Root.tids {
if fdmap := t.FDMap(); fdmap != nil {
for _, desc := range fdmap.files {
if flags := desc.file.Flags(); !flags.Write {
continue
}
if sattr := desc.file.Dirent.Inode.StableAttr; !fs.IsFile(sattr) && !fs.IsDir(sattr) {
continue
}
// Here we need all metadata synced.
syncErr := desc.file.Fsync(ctx, 0, fs.FileMaxOffset, fs.SyncAll)
if err := fs.SaveFileFsyncError(syncErr); err != nil {
name, _ := desc.file.Dirent.FullName(nil /* root */)
return fmt.Errorf("%q was not sufficiently synced: %v", name, err)
}
}
}
}
return nil
}
// Preconditions: The kernel must be paused.
func (k *Kernel) invalidateUnsavableMappings(ctx context.Context) error {
invalidated := make(map[*mm.MemoryManager]struct{})
k.tasks.mu.RLock()
defer k.tasks.mu.RUnlock()
for t := range k.tasks.Root.tids {
// We can skip locking Task.mu here since the kernel is paused.
if mm := t.tc.MemoryManager; mm != nil {
if _, ok := invalidated[mm]; !ok {
if err := mm.InvalidateUnsavable(ctx); err != nil {
return err
}
invalidated[mm] = struct{}{}
}
}
// I really wish we just had a sync.Map of all MMs...
if r, ok := t.runState.(*runSyscallAfterExecStop); ok {
if err := r.tc.MemoryManager.InvalidateUnsavable(ctx); err != nil {
return err
}
}
}
return nil
}
func (ts *TaskSet) unregisterEpollWaiters() {
ts.mu.RLock()
defer ts.mu.RUnlock()
for t := range ts.Root.tids {
if fdmap := t.FDMap(); fdmap != nil {
for _, desc := range fdmap.files {
if desc.file != nil {
if e, ok := desc.file.FileOperations.(*epoll.EventPoll); ok {
e.UnregisterEpollWaiters()
}
}
}
}
}
}
// LoadFrom returns a new Kernel loaded from args.
func (k *Kernel) LoadFrom(r io.Reader, p platform.Platform, net inet.Stack) error {
loadStart := time.Now()
if p == nil {
return fmt.Errorf("Platform is nil")
}
k.Platform = p
k.networkStack = net
initAppCores := k.applicationCores
// Load the kernel state.
kernelStart := time.Now()
var stats state.Stats
if err := state.Load(r, k, &stats); err != nil {
return err
}
log.Infof("Kernel load stats: %s", &stats)
log.Infof("Kernel load took [%s].", time.Since(kernelStart))
// Load the memory state.
//
// See the note in SaveTo.
memoryStart := time.Now()
if err := k.Platform.Memory().LoadFrom(r); err != nil {
return err
}
log.Infof("Memory load took [%s].", time.Since(memoryStart))
// Ensure that all pending asynchronous work is complete:
// - namedpipe opening
// - inode file opening
if err := fs.AsyncErrorBarrier(); err != nil {
return err
}
tcpip.AsyncLoading.Wait()
log.Infof("Overall load took [%s]", time.Since(loadStart))
// Applications may size per-cpu structures based on k.applicationCores, so
// it can't change across save/restore. When we are virtualizing CPU
// numbers, this isn't a problem. However, when we are exposing host CPU
// assignments, we can't tolerate an increase in the number of host CPUs,
// which could result in getcpu(2) returning CPUs that applications expect
// not to exist.
if k.useHostCores && initAppCores > k.applicationCores {
return fmt.Errorf("UseHostCores enabled: can't increase ApplicationCores from %d to %d after restore", k.applicationCores, initAppCores)
}
return nil
}
// Destroy releases resources owned by k.
//
// Preconditions: There must be no task goroutines running in k.
func (k *Kernel) Destroy() {
if k.mounts != nil {
k.mounts.DecRef()
k.mounts = nil
}
}
// UniqueID returns a unique identifier.
func (k *Kernel) UniqueID() uint64 {
id := atomic.AddUint64(&k.uniqueID, 1)
if id == 0 {
panic("unique identifier generator wrapped around")
}
return id
}
// CreateProcessArgs holds arguments to kernel.CreateProcess.
type CreateProcessArgs struct {
// Filename is the filename to load.
//
// If this is provided as "", then the file will be guessed via Argv[0].
Filename string
// Argvv is a list of arguments.
Argv []string
// Envv is a list of environment variables.
Envv []string
// WorkingDirectory is the initial working directory.
//
// This defaults to the root if empty.
WorkingDirectory string
// Credentials is the initial credentials.
Credentials *auth.Credentials
// FDMap is the initial set of file descriptors. If CreateProcess succeeds,
// it takes a reference on FDMap.
FDMap *FDMap
// Umask is the initial umask.
Umask uint
// Limits is the initial resource limits.
Limits *limits.LimitSet
// MaxSymlinkTraversals is the maximum number of symlinks to follow
// during resolution.
MaxSymlinkTraversals uint
// UTSNamespace is the initial UTS namespace.
UTSNamespace *UTSNamespace
// IPCNamespace is the initial IPC namespace.
IPCNamespace *IPCNamespace
}
// NewContext returns a context.Context that represents the task that will be
// created by args.NewContext(k).
func (args *CreateProcessArgs) NewContext(k *Kernel) *createProcessContext {
return &createProcessContext{
Logger: log.Log(),
k: k,
args: args,
}
}
// createProcessContext is a context.Context that represents the context
// associated with a task that is being created.
type createProcessContext struct {
context.NoopSleeper
log.Logger
k *Kernel
args *CreateProcessArgs
}
// Value implements context.Context.Value.
func (ctx *createProcessContext) Value(key interface{}) interface{} {
switch key {
case CtxKernel:
return ctx.k
case CtxPIDNamespace:
// "The new task ... is in the root PID namespace." -
// Kernel.CreateProcess
return ctx.k.tasks.Root
case CtxUTSNamespace:
return ctx.args.UTSNamespace
case CtxIPCNamespace:
return ctx.args.IPCNamespace
case auth.CtxCredentials:
return ctx.args.Credentials
case fs.CtxRoot:
if ctx.k.mounts == nil {
return nil
}
return ctx.k.mounts.Root()
case ktime.CtxRealtimeClock:
return ctx.k.RealtimeClock()
case limits.CtxLimits:
return ctx.args.Limits
case platform.CtxPlatform:
return ctx.k
case uniqueid.CtxGlobalUniqueID:
return ctx.k.UniqueID()
case uniqueid.CtxInotifyCookie:
return ctx.k.GenerateInotifyCookie()
default:
return nil
}
}
// CreateProcess creates a new task in a new thread group with the given
// options. The new task has no parent and is in the root PID namespace.
//
// If k.Start() has already been called, the created task will begin running
// immediately. Otherwise, it will be started when k.Start() is called.
//
// CreateProcess has no analogue in Linux; it is used to create the initial
// application task, as well as processes started by the control server.
func (k *Kernel) CreateProcess(args CreateProcessArgs) (*ThreadGroup, error) {
k.extMu.Lock()
defer k.extMu.Unlock()
log.Infof("EXEC: %v", args.Argv)
if k.mounts == nil {
return nil, fmt.Errorf("no kernel MountNamespace")
}
tg := NewThreadGroup(k.tasks.Root, NewSignalHandlers(), linux.SIGCHLD, args.Limits, k.monotonicClock)
ctx := args.NewContext(k)
// Grab the root directory.
root := fs.RootFromContext(ctx)
defer root.DecRef()
// Grab the working directory.
wd := root // Default.
if args.WorkingDirectory != "" {
var err error
wd, err = k.mounts.FindInode(ctx, root, nil, args.WorkingDirectory, args.MaxSymlinkTraversals)
if err != nil {
return nil, fmt.Errorf("failed to find initial working directory %q: %v", args.WorkingDirectory, err)
}
defer wd.DecRef()
}
if args.Filename == "" {
// Was anything provided?
if len(args.Argv) == 0 {
return nil, fmt.Errorf("no filename or command provided")
}
if !filepath.IsAbs(args.Argv[0]) {
return nil, fmt.Errorf("'%s' is not an absolute path", args.Argv[0])
}
args.Filename = args.Argv[0]
}
// Create a fresh task context.
tc, err := k.LoadTaskImage(ctx, k.mounts, root, wd, args.MaxSymlinkTraversals, args.Filename, args.Argv, args.Envv, k.featureSet)
if err != nil {
return nil, err
}
tr := newTaskResources(args.FDMap, newFSContext(root, wd, args.Umask))
// NewTask unconditionally takes ownership of tr, so we never have to call
// tr.release.
// Create the task.
config := &TaskConfig{
Kernel: k,
ThreadGroup: tg,
TaskContext: tc,
TaskResources: tr,
Credentials: args.Credentials,
UTSNamespace: args.UTSNamespace,
IPCNamespace: args.IPCNamespace,
AllowedCPUMask: sched.NewFullCPUSet(k.applicationCores),
}
t, err := k.tasks.NewTask(config)
if err != nil {
return nil, err
}
// Success.
if k.started {
tid := k.tasks.Root.IDOfTask(t)
t.Start(tid)
} else if k.globalInit == nil {
k.globalInit = tg
}
return tg, nil
}
// Start starts execution of all tasks in k.
//
// Preconditions: Start may be called exactly once.
func (k *Kernel) Start() error {
k.extMu.Lock()
defer k.extMu.Unlock()
if k.globalInit == nil {
return fmt.Errorf("kernel contains no tasks")
}
if k.started {
return fmt.Errorf("kernel already started")
}
k.started = true
k.cpuClockTicker = ktime.NewTimer(k.monotonicClock, kernelCPUClockListener{k})
k.cpuClockTicker.Swap(ktime.Setting{
Enabled: true,
Period: linux.ClockTick,
})
// If k was created by LoadKernelFrom, timers were stopped during
// Kernel.SaveTo and need to be resumed. If k was created by NewKernel,
// this is a no-op.
k.resumeTimeLocked()
// Start task goroutines.
k.tasks.mu.RLock()
defer k.tasks.mu.RUnlock()
for t, tid := range k.tasks.Root.tids {
t.Start(tid)
}
return nil
}
// pauseTimeLocked pauses all Timers and Timekeeper updates.
//
// Preconditions: Any task goroutines running in k must be stopped. k.extMu
// must be locked.
func (k *Kernel) pauseTimeLocked() {
// k.cpuClockTicker may be nil since Kernel.SaveTo() may be called before
// Kernel.Start().
if k.cpuClockTicker != nil {
k.cpuClockTicker.Pause()
}
// By precondition, nothing else can be interacting with PIDNamespace.tids
// or FDMap.files, so we can iterate them without synchronization. (We
// can't hold the TaskSet mutex when pausing thread group timers because
// thread group timers call ThreadGroup.SendSignal, which takes the TaskSet
// mutex, while holding the Timer mutex.)
for t := range k.tasks.Root.tids {
if t == t.tg.leader {
t.tg.tm.pause()
}
// This means we'll iterate FDMaps shared by multiple tasks repeatedly,
// but ktime.Timer.Pause is idempotent so this is harmless.
if fdm := t.tr.FDMap; fdm != nil {
for _, desc := range fdm.files {
if tfd, ok := desc.file.FileOperations.(*timerfd.TimerOperations); ok {
tfd.PauseTimer()
}
}
}
}
k.timekeeper.PauseUpdates()
}
// resumeTimeLocked resumes all Timers and Timekeeper updates. If
// pauseTimeLocked has not been previously called, resumeTimeLocked has no
// effect.
//
// Preconditions: Any task goroutines running in k must be stopped. k.extMu
// must be locked.
func (k *Kernel) resumeTimeLocked() {
if k.cpuClockTicker != nil {
k.cpuClockTicker.Resume()
}
k.timekeeper.ResumeUpdates()
for t := range k.tasks.Root.tids {
if t == t.tg.leader {
t.tg.tm.resume()
}
if fdm := t.tr.FDMap; fdm != nil {
for _, desc := range fdm.files {
if tfd, ok := desc.file.FileOperations.(*timerfd.TimerOperations); ok {
tfd.ResumeTimer()
}
}
}
}
}
// WaitExited blocks until all tasks in k have exited.
func (k *Kernel) WaitExited() {
k.tasks.liveGoroutines.Wait()
}
// Kill requests that all tasks in k immediately exit as if group exiting with
// status es. Kill does not wait for tasks to exit.
func (k *Kernel) Kill(es ExitStatus) {
k.extMu.Lock()
defer k.extMu.Unlock()
k.tasks.Kill(es)
}
// Pause requests that all tasks in k temporarily stop executing, and blocks
// until all tasks in k have stopped. Multiple calls to Pause nest and require
// an equal number of calls to Unpause to resume execution.
func (k *Kernel) Pause() {
k.extMu.Lock()
k.tasks.BeginExternalStop()
k.extMu.Unlock()
k.tasks.runningGoroutines.Wait()
}
// Unpause ends the effect of a previous call to Pause. If Unpause is called
// without a matching preceding call to Pause, Unpause may panic.
func (k *Kernel) Unpause() {
k.extMu.Lock()
defer k.extMu.Unlock()
k.tasks.EndExternalStop()
}
// SendExternalSignal injects a signal into the kernel.
//
// context is used only for debugging to describe how the signal was received.
//
// Preconditions: Kernel must have an init process.
func (k *Kernel) SendExternalSignal(info *arch.SignalInfo, context string) {
k.extMu.Lock()
defer k.extMu.Unlock()
k.sendExternalSignal(info, context)
}
// FeatureSet returns the FeatureSet.
func (k *Kernel) FeatureSet() *cpuid.FeatureSet {
return k.featureSet
}
// Timekeeper returns the Timekeeper.
func (k *Kernel) Timekeeper() *Timekeeper {
return k.timekeeper
}
// TaskSet returns the TaskSet.
func (k *Kernel) TaskSet() *TaskSet {
return k.tasks
}
// RootUserNamespace returns the root UserNamespace.
func (k *Kernel) RootUserNamespace() *auth.UserNamespace {
return k.rootUserNamespace
}
// RootUTSNamespace returns the root UTSNamespace.
func (k *Kernel) RootUTSNamespace() *UTSNamespace {
return k.rootUTSNamespace
}
// RootIPCNamespace returns the root IPCNamespace.
func (k *Kernel) RootIPCNamespace() *IPCNamespace {
return k.rootIPCNamespace
}
// RootMountNamespace returns the MountNamespace.
func (k *Kernel) RootMountNamespace() *fs.MountNamespace {
k.extMu.Lock()
defer k.extMu.Unlock()
return k.mounts
}
// SetRootMountNamespace sets the MountNamespace.
func (k *Kernel) SetRootMountNamespace(mounts *fs.MountNamespace) {
k.extMu.Lock()
defer k.extMu.Unlock()
k.mounts = mounts
}
// NetworkStack returns the network stack. NetworkStack may return nil if no
// network stack is available.
func (k *Kernel) NetworkStack() inet.Stack {
return k.networkStack
}
// GlobalInit returns the thread group with ID 1 in the root PID namespace, or
// nil if no such thread group exists. GlobalInit may return a thread group
// containing no tasks if the thread group has already exited.
func (k *Kernel) GlobalInit() *ThreadGroup {
k.extMu.Lock()
defer k.extMu.Unlock()
return k.globalInit
}
// ApplicationCores returns the number of CPUs visible to sandboxed
// applications.
func (k *Kernel) ApplicationCores() uint {
return k.applicationCores
}
// RealtimeClock returns the application CLOCK_REALTIME clock.
func (k *Kernel) RealtimeClock() ktime.Clock {
return k.realtimeClock
}
// MonotonicClock returns the application CLOCK_MONOTONIC clock.
func (k *Kernel) MonotonicClock() ktime.Clock {
return k.monotonicClock
}
// CPUClockNow returns the current value of k.cpuClock.
func (k *Kernel) CPUClockNow() uint64 {
return atomic.LoadUint64(&k.cpuClock)
}
// Syslog returns the syslog.
func (k *Kernel) Syslog() *syslog {
return &k.syslog
}
// GenerateInotifyCookie generates a unique inotify event cookie.
//
// Returned values may overlap with previously returned values if the value
// space is exhausted. 0 is not a valid cookie value, all other values
// representable in a uint32 are allowed.
func (k *Kernel) GenerateInotifyCookie() uint32 {
id := atomic.AddUint32(&k.nextInotifyCookie, 1)
// Wrap-around is explicitly allowed for inotify event cookies.
if id == 0 {
id = atomic.AddUint32(&k.nextInotifyCookie, 1)
}
return id
}
// NetlinkPorts returns the netlink port manager.
func (k *Kernel) NetlinkPorts() *port.Manager {
return k.netlinkPorts
}
// ExitError returns the sandbox error that caused the kernel to exit.
func (k *Kernel) ExitError() error {
k.extMu.Lock()
defer k.extMu.Unlock()
return k.exitErr
}
// SetExitError sets the sandbox error that caused the kernel to exit, if one is
// not already set.
func (k *Kernel) SetExitError(err error) {
k.extMu.Lock()
defer k.extMu.Unlock()
if k.exitErr == nil {
k.exitErr = err
}
}
// NowNanoseconds implements tcpip.Clock.NowNanoseconds.
func (k *Kernel) NowNanoseconds() int64 {
now, err := k.timekeeper.GetTime(sentrytime.Realtime)
if err != nil {
panic("Kernel.NowNanoseconds: " + err.Error())
}
return now
}
// SupervisorContext returns a Context with maximum privileges in k. It should
// only be used by goroutines outside the control of the emulated kernel
// defined by e.
//
// Callers are responsible for ensuring that the returned Context is not used
// concurrently with changes to the Kernel.
func (k *Kernel) SupervisorContext() context.Context {
return supervisorContext{
Logger: log.Log(),
k: k,
}
}
type supervisorContext struct {
context.NoopSleeper
log.Logger
k *Kernel
}
// Value implements context.Context.
func (ctx supervisorContext) Value(key interface{}) interface{} {
switch key {
case CtxCanTrace:
// The supervisor context can trace anything. (None of
// supervisorContext's users are expected to invoke ptrace, but ptrace
// permissions are required for certain file accesses.)
return func(*Task, bool) bool { return true }
case CtxKernel:
return ctx.k
case CtxPIDNamespace:
return ctx.k.tasks.Root
case CtxUTSNamespace:
return ctx.k.rootUTSNamespace
case CtxIPCNamespace:
return ctx.k.rootIPCNamespace
case auth.CtxCredentials:
// The supervisor context is global root.
return auth.NewRootCredentials(ctx.k.rootUserNamespace)
case fs.CtxRoot:
return ctx.k.mounts.Root()
case ktime.CtxRealtimeClock:
return ctx.k.RealtimeClock()
case limits.CtxLimits:
// No limits apply.
return limits.NewLimitSet()
case platform.CtxPlatform:
return ctx.k
case uniqueid.CtxGlobalUniqueID:
return ctx.k.UniqueID()
case uniqueid.CtxInotifyCookie:
return ctx.k.GenerateInotifyCookie()
default:
return nil
}
}
type kernelCPUClockListener struct {
k *Kernel
}
// Notify implements ktime.TimerListener.Notify.
func (l kernelCPUClockListener) Notify(exp uint64) {
// Only increment cpuClock by 1 regardless of the number of expirations.
// This approximately compensates for cases where thread throttling or bad
// Go runtime scheduling prevents the cpuClockTicker goroutine, and
// presumably task goroutines as well, from executing for a long period of
// time. It's also necessary to prevent CPU clocks from seeing large
// discontinuous jumps.
atomic.AddUint64(&l.k.cpuClock, 1)
}
// Destroy implements ktime.TimerListener.Destroy.
func (l kernelCPUClockListener) Destroy() {
}
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