Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 135 insertions, 0 deletions

diff --git a/pkg/sentry/kernel/context.go b/pkg/sentry/kernel/context.go
new file mode 100644
index 000000000..261ca6f7a
--- /dev/null
+++ b/pkg/sentry/kernel/context.go
@@ -0,0 +1,135 @@
+// 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
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/log"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+)
+
+// contextID is the kernel package's type for context.Context.Value keys.
+type contextID int
+
+const (
+	// CtxCanTrace is a Context.Value key for a function with the same
+	// signature and semantics as kernel.Task.CanTrace.
+	CtxCanTrace contextID = iota
+
+	// CtxKernel is a Context.Value key for a Kernel.
+	CtxKernel
+
+	// CtxPIDNamespace is a Context.Value key for a PIDNamespace.
+	CtxPIDNamespace
+
+	// CtxTask is a Context.Value key for a Task.
+	CtxTask
+
+	// CtxUTSNamespace is a Context.Value key for a UTSNamespace.
+	CtxUTSNamespace
+
+	// CtxIPCNamespace is a Context.Value key for a IPCNamespace.
+	CtxIPCNamespace
+)
+
+// ContextCanTrace returns true if ctx is permitted to trace t, in the same sense
+// as kernel.Task.CanTrace.
+func ContextCanTrace(ctx context.Context, t *Task, attach bool) bool {
+	if v := ctx.Value(CtxCanTrace); v != nil {
+		return v.(func(*Task, bool) bool)(t, attach)
+	}
+	return false
+}
+
+// KernelFromContext returns the Kernel in which ctx is executing, or nil if
+// there is no such Kernel.
+func KernelFromContext(ctx context.Context) *Kernel {
+	if v := ctx.Value(CtxKernel); v != nil {
+		return v.(*Kernel)
+	}
+	return nil
+}
+
+// PIDNamespaceFromContext returns the PID namespace in which ctx is executing,
+// or nil if there is no such PID namespace.
+func PIDNamespaceFromContext(ctx context.Context) *PIDNamespace {
+	if v := ctx.Value(CtxPIDNamespace); v != nil {
+		return v.(*PIDNamespace)
+	}
+	return nil
+}
+
+// UTSNamespaceFromContext returns the UTS namespace in which ctx is executing,
+// or nil if there is no such UTS namespace.
+func UTSNamespaceFromContext(ctx context.Context) *UTSNamespace {
+	if v := ctx.Value(CtxUTSNamespace); v != nil {
+		return v.(*UTSNamespace)
+	}
+	return nil
+}
+
+// IPCNamespaceFromContext returns the IPC namespace in which ctx is executing,
+// or nil if there is no such IPC namespace.
+func IPCNamespaceFromContext(ctx context.Context) *IPCNamespace {
+	if v := ctx.Value(CtxIPCNamespace); v != nil {
+		return v.(*IPCNamespace)
+	}
+	return nil
+}
+
+// TaskFromContext returns the Task associated with ctx, or nil if there is no
+// such Task.
+func TaskFromContext(ctx context.Context) *Task {
+	if v := ctx.Value(CtxTask); v != nil {
+		return v.(*Task)
+	}
+	return nil
+}
+
+// AsyncContext returns a context.Context that may be used by goroutines that
+// do work on behalf of t and therefore share its contextual values, but are
+// not t's task goroutine (e.g. asynchronous I/O).
+func (t *Task) AsyncContext() context.Context {
+	return taskAsyncContext{t: t}
+}
+
+type taskAsyncContext struct {
+	context.NoopSleeper
+	t *Task
+}
+
+// Debugf implements log.Logger.Debugf.
+func (ctx taskAsyncContext) Debugf(format string, v ...interface{}) {
+	ctx.t.Debugf(format, v...)
+}
+
+// Infof implements log.Logger.Infof.
+func (ctx taskAsyncContext) Infof(format string, v ...interface{}) {
+	ctx.t.Infof(format, v...)
+}
+
+// Warningf implements log.Logger.Warningf.
+func (ctx taskAsyncContext) Warningf(format string, v ...interface{}) {
+	ctx.t.Warningf(format, v...)
+}
+
+// IsLogging implements log.Logger.IsLogging.
+func (ctx taskAsyncContext) IsLogging(level log.Level) bool {
+	return ctx.t.IsLogging(level)
+}
+
+// Value implements context.Context.Value.
+func (ctx taskAsyncContext) Value(key interface{}) interface{} {
+	return ctx.t.Value(key)
+}