Add exec APIs

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

linux/shim/exec.go

@@ -139,3 +139,7 @@ func (e *execProcess) Resize(ws console.WinSize) error {
 	}
 	return e.console.Resize(ws)
 }
+
+func (e *execProcess) Signal(sig int) error {
+	return syscall.Kill(e.pid, syscall.Signal(sig))
+}

linux/shim/init.go

@@ -169,3 +169,7 @@ func (p *initProcess) killAll(context context.Context) error {
 		All: true,
 	})
 }
+
+func (p *initProcess) Signal(sig int) error {
+	return syscall.Kill(p.pid, syscall.Signal(sig))
+}

linux/shim/process.go

@@ -15,5 +15,8 @@ type process interface {
 	Exited(status int)
 	// Status returns the exit status
 	Status() int
+	// Delete delets the process and its resourcess
 	Delete(context.Context) error
+	// Signal directly signals the process
+	Signal(int) error
 }

linux/shim/service.go

@@ -1,6 +1,7 @@
 package shim
 
 import (
+	"fmt"
 	"os"
 	"sync"
 	"syscall"
@@ -219,7 +220,17 @@ func (s *Service) Exit(ctx context.Context, r *shimapi.ExitRequest) (*google_pro
 }
 
 func (s *Service) Kill(ctx context.Context, r *shimapi.KillRequest) (*google_protobuf.Empty, error) {
-	if err := s.initProcess.Kill(ctx, r.Signal, r.All); err != nil {
+	if r.Pid == 0 {
+		if err := s.initProcess.Kill(ctx, r.Signal, r.All); err != nil {
+			return nil, err
+		}
+		return empty, nil
+	}
+	proc, ok := s.processes[int(r.Pid)]
+	if !ok {
+		return nil, fmt.Errorf("process does not exist %d", r.Pid)
+	}
+	if err := proc.Signal(int(r.Signal)); err != nil {
 		return nil, err
 	}
 	return empty, nil