Update shim for exec

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

runtime/process.go

@@ -1,6 +1,8 @@
 package runtime
 
 import (
+	"encoding/json"
+	"io"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -10,6 +12,31 @@ import (
 	"github.com/opencontainers/specs"
 )
 
+type Process interface {
+	io.Closer
+
+	// ID of the process.
+	// This is either "init" when it is the container's init process or
+	// it is a user provided id for the process similar to the container id
+	ID() string
+	// Stdin returns the path the the processes stdin fifo
+	Stdin() string
+	// Stdout returns the path the the processes stdout fifo
+	Stdout() string
+	// Stderr returns the path the the processes stderr fifo
+	Stderr() string
+	// ExitFD returns the fd the provides an event when the process exits
+	ExitFD() int
+	// ExitStatus returns the exit status of the process or an error if it
+	// has not exited
+	ExitStatus() (int, error)
+	Spec() specs.Process
+	// Signal sends the provided signal to the process
+	Signal(os.Signal) error
+	// Container returns the container that the process belongs to
+	Container() Container
+}
+
 func newProcess(root, id string, c *container, s specs.Process) (*process, error) {
 	p := &process{
 		root:      root,
@@ -17,6 +44,14 @@ func newProcess(root, id string, c *container, s specs.Process) (*process, error
 		container: c,
 		spec:      s,
 	}
+	f, err := os.Create(filepath.Join(root, "process.json"))
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	if err := json.NewEncoder(f).Encode(s); err != nil {
+		return nil, err
+	}
 	// create fifo's for the process
 	for name, fd := range map[string]*string{
 		"stdin":  &p.stdin,
@@ -58,7 +93,7 @@ func loadProcess(root, id string, c *container, s specs.Process) (*process, erro
 		}
 		return nil, err
 	}
-	return nil, ErrProcessExited
+	return p, nil
 }
 
 func getExitPipe(path string) (*os.File, error) {