pkg/ipc: don't send program padding to executor

Currently we always send 2MB of data to executor in ipc_simple.go.
Send only what's consumed by the program, and don't send the trailing zeros.
Serialized programs usually take only few KBs.

3 files changed, 5 insertions, 4 deletions

diff --git a/pkg/csource/csource.go b/pkg/csource/csource.go
index 1bd818962..b0d44a94f 100644
--- a/pkg/csource/csource.go
+++ b/pkg/csource/csource.go
@@ -72,7 +72,7 @@ func Write(p *prog.Prog, opts Options) ([]byte, error) {
 		return nil, fmt.Errorf("csource: invalid opts: %v", err)
 	}
 	exec := make([]byte, prog.ExecBufferSize)
-	if err := p.SerializeForExec(exec, 0); err != nil {
+	if _, err := p.SerializeForExec(exec, 0); err != nil {
 		return nil, fmt.Errorf("failed to serialize program: %v", err)
 	}
 	w := new(bytes.Buffer)
diff --git a/pkg/ipc/ipc_linux.go b/pkg/ipc/ipc_linux.go
index 793611b91..0279b0ee8 100644
--- a/pkg/ipc/ipc_linux.go
+++ b/pkg/ipc/ipc_linux.go
@@ -128,7 +128,7 @@ func (env *Env) Close() error {
 func (env *Env) Exec(opts *ExecOpts, p *prog.Prog) (output []byte, info []CallInfo, failed, hanged bool, err0 error) {
 	if p != nil {
 		// Copy-in serialized program.
-		if err := p.SerializeForExec(env.in, env.pid); err != nil {
+		if _, err := p.SerializeForExec(env.in, env.pid); err != nil {
 			err0 = fmt.Errorf("executor %v: failed to serialize: %v", env.pid, err)
 			return
 		}
diff --git a/pkg/ipc/ipc_simple.go b/pkg/ipc/ipc_simple.go
index 4c2ac6925..50dcce661 100644
--- a/pkg/ipc/ipc_simple.go
+++ b/pkg/ipc/ipc_simple.go
@@ -70,7 +70,8 @@ func (env *Env) Exec(opts *ExecOpts, p *prog.Prog) (output []byte, info []CallIn
 	defer os.RemoveAll(dir)
 
 	data := make([]byte, prog.ExecBufferSize)
-	if err := p.SerializeForExec(data, env.pid); err != nil {
+	n, err := p.SerializeForExec(data, env.pid)
+	if err != nil {
 		err0 = err
 		return
 	}
@@ -78,7 +79,7 @@ func (env *Env) Exec(opts *ExecOpts, p *prog.Prog) (output []byte, info []CallIn
 	binary.Write(inbuf, binary.LittleEndian, uint64(env.config.Flags))
 	binary.Write(inbuf, binary.LittleEndian, uint64(opts.Flags))
 	binary.Write(inbuf, binary.LittleEndian, uint64(env.pid))
-	inbuf.Write(data)
+	inbuf.Write(data[:n])
 
 	cmd := exec.Command(env.bin[0], env.bin[1:]...)
 	cmd.Env = []string{}