2 files changed, 209 insertions, 0 deletions
diff --git a/pkg/sentry/contexttest/BUILD b/pkg/sentry/contexttest/BUILD
new file mode 100644
index 000000000..6f4c86684
--- /dev/null
+++ b/pkg/sentry/contexttest/BUILD
@@ -0,0 +1,21 @@
+load("//tools:defs.bzl", "go_library")
+
+package(licenses = ["notice"])
+
+go_library(
+    name = "contexttest",
+    testonly = 1,
+    srcs = ["contexttest.go"],
+    visibility = ["//pkg/sentry:internal"],
+    deps = [
+        "//pkg/context",
+        "//pkg/memutil",
+        "//pkg/sentry/kernel/auth",
+        "//pkg/sentry/kernel/time",
+        "//pkg/sentry/limits",
+        "//pkg/sentry/pgalloc",
+        "//pkg/sentry/platform",
+        "//pkg/sentry/platform/ptrace",
+        "//pkg/sentry/uniqueid",
+    ],
+)
diff --git a/pkg/sentry/contexttest/contexttest.go b/pkg/sentry/contexttest/contexttest.go
new file mode 100644
index 000000000..031fc64ec
--- /dev/null
+++ b/pkg/sentry/contexttest/contexttest.go
@@ -0,0 +1,188 @@
+// Copyright 2018 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 contexttest builds a test context.Context.
+package contexttest
+
+import (
+	"os"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/memutil"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
+	"gvisor.dev/gvisor/pkg/sentry/limits"
+	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
+	"gvisor.dev/gvisor/pkg/sentry/platform"
+	"gvisor.dev/gvisor/pkg/sentry/platform/ptrace"
+	"gvisor.dev/gvisor/pkg/sentry/uniqueid"
+)
+
+// Context returns a Context that may be used in tests. Uses ptrace as the
+// platform.Platform.
+//
+// Note that some filesystems may require a minimal kernel for testing, which
+// this test context does not provide. For such tests, see kernel/contexttest.
+func Context(tb testing.TB) context.Context {
+	const memfileName = "contexttest-memory"
+	memfd, err := memutil.CreateMemFD(memfileName, 0)
+	if err != nil {
+		tb.Fatalf("error creating application memory file: %v", err)
+	}
+	memfile := os.NewFile(uintptr(memfd), memfileName)
+	mf, err := pgalloc.NewMemoryFile(memfile, pgalloc.MemoryFileOpts{})
+	if err != nil {
+		memfile.Close()
+		tb.Fatalf("error creating pgalloc.MemoryFile: %v", err)
+	}
+	p, err := ptrace.New()
+	if err != nil {
+		tb.Fatal(err)
+	}
+	// Test usage of context.Background is fine.
+	return &TestContext{
+		Context:     context.Background(),
+		l:           limits.NewLimitSet(),
+		mf:          mf,
+		platform:    p,
+		creds:       auth.NewAnonymousCredentials(),
+		otherValues: make(map[interface{}]interface{}),
+	}
+}
+
+// TestContext represents a context with minimal functionality suitable for
+// running tests.
+type TestContext struct {
+	context.Context
+	l           *limits.LimitSet
+	mf          *pgalloc.MemoryFile
+	platform    platform.Platform
+	creds       *auth.Credentials
+	otherValues map[interface{}]interface{}
+}
+
+// globalUniqueID tracks incremental unique identifiers for tests.
+var globalUniqueID uint64
+
+// globalUniqueIDProvider implements unix.UniqueIDProvider.
+type globalUniqueIDProvider struct{}
+
+// UniqueID implements unix.UniqueIDProvider.UniqueID.
+func (*globalUniqueIDProvider) UniqueID() uint64 {
+	return atomic.AddUint64(&globalUniqueID, 1)
+}
+
+// lastInotifyCookie is a monotonically increasing counter for generating unique
+// inotify cookies. Must be accessed using atomic ops.
+var lastInotifyCookie uint32
+
+// hostClock implements ktime.Clock.
+type hostClock struct {
+	ktime.WallRateClock
+	ktime.NoClockEvents
+}
+
+// Now implements ktime.Clock.Now.
+func (hostClock) Now() ktime.Time {
+	return ktime.FromNanoseconds(time.Now().UnixNano())
+}
+
+// RegisterValue registers additional values with this test context. Useful for
+// providing values from external packages that contexttest can't depend on.
+func (t *TestContext) RegisterValue(key, value interface{}) {
+	t.otherValues[key] = value
+}
+
+// Value implements context.Context.
+func (t *TestContext) Value(key interface{}) interface{} {
+	switch key {
+	case auth.CtxCredentials:
+		return t.creds
+	case limits.CtxLimits:
+		return t.l
+	case pgalloc.CtxMemoryFile:
+		return t.mf
+	case pgalloc.CtxMemoryFileProvider:
+		return t
+	case platform.CtxPlatform:
+		return t.platform
+	case uniqueid.CtxGlobalUniqueID:
+		return (*globalUniqueIDProvider).UniqueID(nil)
+	case uniqueid.CtxGlobalUniqueIDProvider:
+		return &globalUniqueIDProvider{}
+	case uniqueid.CtxInotifyCookie:
+		return atomic.AddUint32(&lastInotifyCookie, 1)
+	case ktime.CtxRealtimeClock:
+		return hostClock{}
+	default:
+		if val, ok := t.otherValues[key]; ok {
+			return val
+		}
+		return t.Context.Value(key)
+	}
+}
+
+// MemoryFile implements pgalloc.MemoryFileProvider.MemoryFile.
+func (t *TestContext) MemoryFile() *pgalloc.MemoryFile {
+	return t.mf
+}
+
+// RootContext returns a Context that may be used in tests that need root
+// credentials. Uses ptrace as the platform.Platform.
+func RootContext(tb testing.TB) context.Context {
+	return WithCreds(Context(tb), auth.NewRootCredentials(auth.NewRootUserNamespace()))
+}
+
+// WithCreds returns a copy of ctx carrying creds.
+func WithCreds(ctx context.Context, creds *auth.Credentials) context.Context {
+	return &authContext{ctx, creds}
+}
+
+type authContext struct {
+	context.Context
+	creds *auth.Credentials
+}
+
+// Value implements context.Context.
+func (ac *authContext) Value(key interface{}) interface{} {
+	switch key {
+	case auth.CtxCredentials:
+		return ac.creds
+	default:
+		return ac.Context.Value(key)
+	}
+}
+
+// WithLimitSet returns a copy of ctx carrying l.
+func WithLimitSet(ctx context.Context, l *limits.LimitSet) context.Context {
+	return limitContext{ctx, l}
+}
+
+type limitContext struct {
+	context.Context
+	l *limits.LimitSet
+}
+
+// Value implements context.Context.
+func (lc limitContext) Value(key interface{}) interface{} {
+	switch key {
+	case limits.CtxLimits:
+		return lc.l
+	default:
+		return lc.Context.Value(key)
+	}
+}