1 files changed, 127 insertions, 0 deletions
diff --git a/runsc/cmd/wait.go b/runsc/cmd/wait.go
new file mode 100644
index 000000000..a55a682f3
--- /dev/null
+++ b/runsc/cmd/wait.go
@@ -0,0 +1,127 @@
+// 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 cmd
+
+import (
+	"context"
+	"encoding/json"
+	"os"
+	"syscall"
+
+	"flag"
+	"github.com/google/subcommands"
+	"gvisor.googlesource.com/gvisor/runsc/boot"
+	"gvisor.googlesource.com/gvisor/runsc/container"
+)
+
+const (
+	unsetPID = -1
+)
+
+// Wait implements subcommands.Command for the "wait" command.
+type Wait struct {
+	rootPID int
+	pid     int
+}
+
+// Name implements subcommands.Command.Name.
+func (*Wait) Name() string {
+	return "wait"
+}
+
+// Synopsis implements subcommands.Command.Synopsis.
+func (*Wait) Synopsis() string {
+	return "wait on a process inside a container"
+}
+
+// Usage implements subcommands.Command.Usage.
+func (*Wait) Usage() string {
+	return `wait [flags] <container id>`
+}
+
+// SetFlags implements subcommands.Command.SetFlags.
+func (wt *Wait) SetFlags(f *flag.FlagSet) {
+	f.IntVar(&wt.rootPID, "rootpid", unsetPID, "select a PID in the sandbox root PID namespace to wait on instead of the container's root process")
+	f.IntVar(&wt.pid, "pid", unsetPID, "select a PID in the container's PID namespace to wait on instead of the container's root process")
+}
+
+// Execute implements subcommands.Command.Execute. It waits for a process in a
+// container to exit before returning.
+func (wt *Wait) Execute(_ context.Context, f *flag.FlagSet, args ...interface{}) subcommands.ExitStatus {
+	if f.NArg() != 1 {
+		f.Usage()
+		return subcommands.ExitUsageError
+	}
+	// You can't specify both -pid and -rootpid.
+	if wt.rootPID != unsetPID && wt.pid != unsetPID {
+		Fatalf("only one of -pid and -rootPid can be set")
+	}
+
+	id := f.Arg(0)
+	conf := args[0].(*boot.Config)
+
+	c, err := container.Load(conf.RootDir, id)
+	if err != nil {
+		Fatalf("loading container: %v", err)
+	}
+
+	var waitStatus syscall.WaitStatus
+	switch {
+	// Wait on the whole container.
+	case wt.rootPID == unsetPID && wt.pid == unsetPID:
+		ws, err := c.Wait()
+		if err != nil {
+			Fatalf("waiting on container %q: %v", c.ID, err)
+		}
+		waitStatus = ws
+	// Wait on a PID in the root PID namespace.
+	case wt.rootPID != unsetPID:
+		ws, err := c.WaitRootPID(int32(wt.rootPID), true /* clearStatus */)
+		if err != nil {
+			Fatalf("waiting on PID in root PID namespace %d in container %q: %v", wt.rootPID, c.ID, err)
+		}
+		waitStatus = ws
+	// Wait on a PID in the container's PID namespace.
+	case wt.pid != unsetPID:
+		ws, err := c.WaitPID(int32(wt.pid), true /* clearStatus */)
+		if err != nil {
+			Fatalf("waiting on PID %d in container %q: %v", wt.pid, c.ID, err)
+		}
+		waitStatus = ws
+	}
+	result := waitResult{
+		ID:         id,
+		ExitStatus: exitStatus(waitStatus),
+	}
+	// Write json-encoded wait result directly to stdout.
+	if err := json.NewEncoder(os.Stdout).Encode(result); err != nil {
+		Fatalf("marshaling wait result: %v", err)
+	}
+	return subcommands.ExitSuccess
+}
+
+type waitResult struct {
+	ID         string `json:"id"`
+	ExitStatus int    `json:"exitStatus"`
+}
+
+// exitStatus returns the correct exit status for a process based on if it
+// was signaled or exited cleanly.
+func exitStatus(status syscall.WaitStatus) int {
+	if status.Signaled() {
+		return 128 + int(status.Signal())
+	}
+	return status.ExitStatus()
+}