use string-concatenation instead of sprintf for simple cases

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

contrib/cmd/recvtty/recvtty.go

@@ -187,7 +187,7 @@ func main() {
 		v = append(v, version)
 	}
 	if gitCommit != "" {
-		v = append(v, fmt.Sprintf("commit: %s", gitCommit))
+		v = append(v, "commit: "+gitCommit)
 	}
 	app.Version = strings.Join(v, "\n")
 

libcontainer/apparmor/apparmor.go

@@ -23,9 +23,7 @@ func IsEnabled() bool {
 func setProcAttr(attr, value string) error {
 	// Under AppArmor you can only change your own attr, so use /proc/self/
 	// instead of /proc/<tid>/ like libapparmor does
-	path := fmt.Sprintf("/proc/self/attr/%s", attr)
-
-	f, err := os.OpenFile(path, os.O_WRONLY, 0)
+	f, err := os.OpenFile("/proc/self/attr/"+attr, os.O_WRONLY, 0)
 	if err != nil {
 		return err
 	}
@@ -35,14 +33,13 @@ func setProcAttr(attr, value string) error {
 		return err
 	}
 
-	_, err = fmt.Fprintf(f, "%s", value)
+	_, err = f.WriteString(value)
 	return err
 }
 
 // changeOnExec reimplements aa_change_onexec from libapparmor in Go
 func changeOnExec(name string) error {
-	value := "exec " + name
-	if err := setProcAttr("exec", value); err != nil {
+	if err := setProcAttr("exec", "exec "+name); err != nil {
 		return fmt.Errorf("apparmor failed to apply profile: %s", err)
 	}
 	return nil

libcontainer/cgroups/ebpf/devicefilter/devicefilter.go

@@ -7,8 +7,8 @@
 package devicefilter
 
 import (
-	"fmt"
 	"math"
+	"strconv"
 
 	"github.com/cilium/ebpf/asm"
 	"github.com/opencontainers/runc/libcontainer/configs"
@@ -114,9 +114,11 @@ func (p *program) appendDevice(dev *configs.DeviceRule) error {
 	// If the access is rwm, skip the check.
 	hasAccess := bpfAccess != (unix.BPF_DEVCG_ACC_READ | unix.BPF_DEVCG_ACC_WRITE | unix.BPF_DEVCG_ACC_MKNOD)
 
-	blockSym := fmt.Sprintf("block-%d", p.blockID)
-	nextBlockSym := fmt.Sprintf("block-%d", p.blockID+1)
-	prevBlockLastIdx := len(p.insts) - 1
+	var (
+		blockSym         = "block-" + strconv.Itoa(p.blockID)
+		nextBlockSym     = "block-" + strconv.Itoa(p.blockID+1)
+		prevBlockLastIdx = len(p.insts) - 1
+	)
 	if hasType {
 		p.insts = append(p.insts,
 			// if (R2 != bpfType) goto next
@@ -158,7 +160,7 @@ func (p *program) finalize() (asm.Instructions, error) {
 		// acceptBlock with asm.Return() is already inserted
 		return p.insts, nil
 	}
-	blockSym := fmt.Sprintf("block-%d", p.blockID)
+	blockSym := "block-" + strconv.Itoa(p.blockID)
 	p.insts = append(p.insts,
 		// R0 <- 0
 		asm.Mov.Imm32(asm.R0, 0).Sym(blockSym),

libcontainer/cgroups/systemd/common.go

@@ -307,7 +307,7 @@ func newProp(name string, units interface{}) systemdDbus.Property {
 func getUnitName(c *configs.Cgroup) string {
 	// by default, we create a scope unless the user explicitly asks for a slice.
 	if !strings.HasSuffix(c.Name, ".slice") {
-		return fmt.Sprintf("%s-%s.scope", c.ScopePrefix, c.Name)
+		return c.ScopePrefix + "-" + c.Name + ".scope"
 	}
 	return c.Name
 }

libcontainer/configs/namespaces_linux.go

@@ -56,7 +56,7 @@ func IsNamespaceSupported(ns NamespaceType) bool {
 	if nsFile == "" {
 		return false
 	}
-	_, err := os.Stat(fmt.Sprintf("/proc/self/ns/%s", nsFile))
+	_, err := os.Stat("/proc/self/ns/" + nsFile)
 	// a namespace is supported if it exists and we have permissions to read it
 	supported = err == nil
 	supportedNamespaces[ns] = supported

libcontainer/container_linux.go

@@ -14,6 +14,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"reflect"
+	"strconv"
 	"strings"
 	"sync"
 	"time"
@@ -453,7 +454,7 @@ func (c *linuxContainer) includeExecFifo(cmd *exec.Cmd) error {
 
 	cmd.ExtraFiles = append(cmd.ExtraFiles, os.NewFile(uintptr(fifoFd), fifoName))
 	cmd.Env = append(cmd.Env,
-		fmt.Sprintf("_LIBCONTAINER_FIFOFD=%d", stdioFdCount+len(cmd.ExtraFiles)-1))
+		"_LIBCONTAINER_FIFOFD="+strconv.Itoa(stdioFdCount+len(cmd.ExtraFiles)-1))
 	return nil
 }
 
@@ -496,24 +497,24 @@ func (c *linuxContainer) commandTemplate(p *Process, childInitPipe *os.File, chi
 	if cmd.SysProcAttr == nil {
 		cmd.SysProcAttr = &unix.SysProcAttr{}
 	}
-	cmd.Env = append(cmd.Env, fmt.Sprintf("GOMAXPROCS=%s", os.Getenv("GOMAXPROCS")))
+	cmd.Env = append(cmd.Env, "GOMAXPROCS="+os.Getenv("GOMAXPROCS"))
 	cmd.ExtraFiles = append(cmd.ExtraFiles, p.ExtraFiles...)
 	if p.ConsoleSocket != nil {
 		cmd.ExtraFiles = append(cmd.ExtraFiles, p.ConsoleSocket)
 		cmd.Env = append(cmd.Env,
-			fmt.Sprintf("_LIBCONTAINER_CONSOLE=%d", stdioFdCount+len(cmd.ExtraFiles)-1),
+			"_LIBCONTAINER_CONSOLE="+strconv.Itoa(stdioFdCount+len(cmd.ExtraFiles)-1),
 		)
 	}
 	cmd.ExtraFiles = append(cmd.ExtraFiles, childInitPipe)
 	cmd.Env = append(cmd.Env,
-		fmt.Sprintf("_LIBCONTAINER_INITPIPE=%d", stdioFdCount+len(cmd.ExtraFiles)-1),
-		fmt.Sprintf("_LIBCONTAINER_STATEDIR=%s", c.root),
+		"_LIBCONTAINER_INITPIPE="+strconv.Itoa(stdioFdCount+len(cmd.ExtraFiles)-1),
+		"_LIBCONTAINER_STATEDIR="+c.root,
 	)
 
 	cmd.ExtraFiles = append(cmd.ExtraFiles, childLogPipe)
 	cmd.Env = append(cmd.Env,
-		fmt.Sprintf("_LIBCONTAINER_LOGPIPE=%d", stdioFdCount+len(cmd.ExtraFiles)-1),
-		fmt.Sprintf("_LIBCONTAINER_LOGLEVEL=%s", p.LogLevel),
+		"_LIBCONTAINER_LOGPIPE="+strconv.Itoa(stdioFdCount+len(cmd.ExtraFiles)-1),
+		"_LIBCONTAINER_LOGLEVEL="+p.LogLevel,
 	)
 
 	// NOTE: when running a container with no PID namespace and the parent process spawning the container is
@@ -2033,7 +2034,7 @@ func (c *linuxContainer) bootstrapData(cloneFlags uintptr, nsMaps map[configs.Na
 		// write oom_score_adj
 		r.AddData(&Bytemsg{
 			Type:  OomScoreAdjAttr,
-			Value: []byte(fmt.Sprintf("%d", *c.config.OomScoreAdj)),
+			Value: []byte(strconv.Itoa(*c.config.OomScoreAdj)),
 		})
 	}
 

libcontainer/integration/exec_test.go

@@ -1244,7 +1244,7 @@ func TestHook(t *testing.T) {
 
 	config := newTemplateConfig(rootfs)
 	expectedBundle := bundle
-	config.Labels = append(config.Labels, fmt.Sprintf("bundle=%s", expectedBundle))
+	config.Labels = append(config.Labels, "bundle="+expectedBundle)
 
 	getRootfsFromBundle := func(bundle string) (string, error) {
 		f, err := os.Open(filepath.Join(bundle, "config.json"))

libcontainer/setns_init_linux.go

@@ -3,7 +3,6 @@
 package libcontainer
 
 import (
-	"fmt"
 	"os"
 	"runtime"
 
@@ -25,7 +24,7 @@ type linuxSetnsInit struct {
 }
 
 func (l *linuxSetnsInit) getSessionRingName() string {
-	return fmt.Sprintf("_ses.%s", l.config.ContainerId)
+	return "_ses." + l.config.ContainerId
 }
 
 func (l *linuxSetnsInit) Init() error {

libcontainer/specconv/spec_linux.go

@@ -224,14 +224,14 @@ func CreateLibcontainerConfig(opts *CreateOpts) (*configs.Config, error) {
 	}
 	labels := []string{}
 	for k, v := range spec.Annotations {
-		labels = append(labels, fmt.Sprintf("%s=%s", k, v))
+		labels = append(labels, k+"="+v)
 	}
 	config := &configs.Config{
 		Rootfs:          rootfsPath,
 		NoPivotRoot:     opts.NoPivotRoot,
 		Readonlyfs:      spec.Root.Readonly,
 		Hostname:        spec.Hostname,
-		Labels:          append(labels, fmt.Sprintf("bundle=%s", cwd)),
+		Labels:          append(labels, "bundle="+cwd),
 		NoNewKeyring:    opts.NoNewKeyring,
 		RootlessEUID:    opts.RootlessEUID,
 		RootlessCgroups: opts.RootlessCgroups,

libcontainer/standard_init_linux.go

@@ -3,10 +3,10 @@
 package libcontainer
 
 import (
-	"fmt"
 	"os"
 	"os/exec"
 	"runtime"
+	"strconv"
 
 	"github.com/opencontainers/runc/libcontainer/apparmor"
 	"github.com/opencontainers/runc/libcontainer/configs"
@@ -40,7 +40,7 @@ func (l *linuxStandardInit) getSessionRingParams() (string, uint32, uint32) {
 
 	// Create a unique per session container name that we can join in setns;
 	// However, other containers can also join it.
-	return fmt.Sprintf("_ses.%s", l.config.ContainerId), 0xffffffff, newperms
+	return "_ses." + l.config.ContainerId, 0xffffffff, newperms
 }
 
 func (l *linuxStandardInit) Init() error {
@@ -185,7 +185,7 @@ func (l *linuxStandardInit) Init() error {
 	// user process. We open it through /proc/self/fd/$fd, because the fd that
 	// was given to us was an O_PATH fd to the fifo itself. Linux allows us to
 	// re-open an O_PATH fd through /proc.
-	fd, err := unix.Open(fmt.Sprintf("/proc/self/fd/%d", l.fifoFd), unix.O_WRONLY|unix.O_CLOEXEC, 0)
+	fd, err := unix.Open("/proc/self/fd/"+strconv.Itoa(l.fifoFd), unix.O_WRONLY|unix.O_CLOEXEC, 0)
 	if err != nil {
 		return newSystemErrorWithCause(err, "open exec fifo")
 	}

libcontainer/system/proc.go

@@ -78,7 +78,7 @@ func GetProcessStartTime(pid int) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	return fmt.Sprintf("%d", stat.StartTime), nil
+	return strconv.FormatUint(stat.StartTime, 10), nil
 }
 
 func parseStat(data string) (stat Stat_t, err error) {

libcontainer/user/lookup_windows.go

@@ -3,8 +3,8 @@
 package user
 
 import (
-	"fmt"
 	"os/user"
+	"strconv"
 )
 
 func lookupUser(username string) (User, error) {
@@ -16,7 +16,7 @@ func lookupUser(username string) (User, error) {
 }
 
 func lookupUid(uid int) (User, error) {
-	u, err := user.LookupId(fmt.Sprintf("%d", uid))
+	u, err := user.LookupId(strconv.Itoa(uid))
 	if err != nil {
 		return User{}, err
 	}
@@ -32,7 +32,7 @@ func lookupGroup(groupname string) (Group, error) {
 }
 
 func lookupGid(gid int) (Group, error) {
-	g, err := user.LookupGroupId(fmt.Sprintf("%d", gid))
+	g, err := user.LookupGroupId(strconv.Itoa(gid))
 	if err != nil {
 		return Group{}, err
 	}

libcontainer/utils/utils_test.go

@@ -2,7 +2,6 @@ package utils
 
 import (
 	"bytes"
-	"fmt"
 	"os"
 	"path/filepath"
 	"testing"
@@ -44,7 +43,7 @@ func TestResolveRootfs(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if path != fmt.Sprintf("%s/%s", pwd, "rootfs") {
+	if path != pwd+"/rootfs" {
 		t.Errorf("expected rootfs to be abs and was %s", path)
 	}
 }

main.go

@@ -60,10 +60,10 @@ func main() {
 		v = append(v, version)
 	}
 	if gitCommit != "" {
-		v = append(v, fmt.Sprintf("commit: %s", gitCommit))
+		v = append(v, "commit: "+gitCommit)
 	}
-	v = append(v, fmt.Sprintf("spec: %s", specs.Version))
-	v = append(v, fmt.Sprintf("go: %s", runtime.Version()))
+	v = append(v, "spec: "+specs.Version)
+	v = append(v, "go: "+runtime.Version())
 	if seccomp.IsEnabled() {
 		major, minor, micro := seccomp.Version()
 		v = append(v, fmt.Sprintf("libseccomp: %d.%d.%d", major, minor, micro))

notify_socket.go

@@ -4,7 +4,6 @@ package main
 
 import (
 	"bytes"
-	"fmt"
 	"net"
 	"os"
 	"path"
@@ -54,7 +53,7 @@ func (s *notifySocket) setupSpec(context *cli.Context, spec *specs.Spec) error {
 		Options:     []string{"bind", "nosuid", "noexec", "nodev", "ro"},
 	}
 	spec.Mounts = append(spec.Mounts, mount)
-	spec.Process.Env = append(spec.Process.Env, fmt.Sprintf("NOTIFY_SOCKET=%s", pathInContainer))
+	spec.Process.Env = append(spec.Process.Env, "NOTIFY_SOCKET="+pathInContainer)
 	return nil
 }
 
@@ -162,8 +161,8 @@ func (n *notifySocket) run(pid1 int) error {
 			}
 
 			// now we can inform systemd to use pid1 as the pid to monitor
-			newPid := fmt.Sprintf("MAINPID=%d\n", pid1)
-			client.Write([]byte(newPid))
+			newPid := "MAINPID=" + strconv.Itoa(pid1)
+			client.Write([]byte(newPid + "\n"))
 			return nil
 		}
 	}

utils_linux.go

@@ -214,13 +214,13 @@ func createPidFile(path string, process *libcontainer.Process) error {
 	}
 	var (
 		tmpDir  = filepath.Dir(path)
-		tmpName = filepath.Join(tmpDir, fmt.Sprintf(".%s", filepath.Base(path)))
+		tmpName = filepath.Join(tmpDir, "."+filepath.Base(path))
 	)
 	f, err := os.OpenFile(tmpName, os.O_RDWR|os.O_CREATE|os.O_EXCL|os.O_SYNC, 0666)
 	if err != nil {
 		return err
 	}
-	_, err = fmt.Fprintf(f, "%d", pid)
+	_, err = f.WriteString(strconv.Itoa(pid))
 	f.Close()
 	if err != nil {
 		return err
@@ -284,12 +284,12 @@ func (r *runner) run(config *specs.Process) (int, error) {
 		return -1, err
 	}
 	if len(r.listenFDs) > 0 {
-		process.Env = append(process.Env, fmt.Sprintf("LISTEN_FDS=%d", len(r.listenFDs)), "LISTEN_PID=1")
+		process.Env = append(process.Env, "LISTEN_FDS="+strconv.Itoa(len(r.listenFDs)), "LISTEN_PID=1")
 		process.ExtraFiles = append(process.ExtraFiles, r.listenFDs...)
 	}
 	baseFd := 3 + len(process.ExtraFiles)
 	for i := baseFd; i < baseFd+r.preserveFDs; i++ {
-		_, err = os.Stat(fmt.Sprintf("/proc/self/fd/%d", i))
+		_, err = os.Stat("/proc/self/fd/" + strconv.Itoa(i))
 		if err != nil {
 			return -1, errors.Wrapf(err, "please check that preserved-fd %d (of %d) is present", i-baseFd, r.preserveFDs)
 		}