runsc: fix the local timezone support in logs

This patch fixes the local timezone support in logs by creating
etc/localtime in the rootfs of sandbox process and gofer process
based on the current /etc/localtime on host.

Before this patch, the timestamps in sandbox and gofer logs will
fallback to UTC timezone after execving "/proc/self/exe" which
may not be very convenient for users to analyse the logs:

I0708 15:37:43.825100       1 chroot.go:69] Setting up sandbox chroot in "/tmp"
I0708 15:37:43.825189       1 chroot.go:31] Mounting "proc" at "/tmp/proc"
......
I0708 15:37:43.850926       1 cmd.go:73] Execve "/proc/self/exe" again, bye!
I0708 07:37:43.856719       1 main.go:218] ***************************
I0708 07:37:43.856751       1 main.go:219] Args: [runsc-sandbox --root=/run/...]
I0708 07:37:43.856785       1 main.go:220] Version release-20210628.0-27-g02fec8dba5a6
I0708 07:37:43.856795       1 main.go:221] GOOS: linux
I0708 07:37:43.856803       1 main.go:222] GOARCH: amd64
......

Fixes #1984

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>

runsc/cmd/chroot.go

@@ -59,6 +59,23 @@ func pivotRoot(root string) error {
 	return nil
 }
 
+func copyFile(dst, src string) error {
+	in, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer in.Close()
+
+	out, err := os.Create(dst)
+	if err != nil {
+		return err
+	}
+	defer out.Close()
+
+	_, err = out.ReadFrom(in)
+	return err
+}
+
 // setUpChroot creates an empty directory with runsc mounted at /runsc and proc
 // mounted at /proc.
 func setUpChroot(pidns bool) error {
@@ -78,6 +95,14 @@ func setUpChroot(pidns bool) error {
 		return fmt.Errorf("error mounting tmpfs in choot: %v", err)
 	}
 
+	if err := os.Mkdir(filepath.Join(chroot, "etc"), 0755); err != nil {
+		return fmt.Errorf("error creating /etc in chroot: %v", err)
+	}
+
+	if err := copyFile(filepath.Join(chroot, "etc/localtime"), "/etc/localtime"); err != nil {
+		log.Warningf("Failed to copy /etc/localtime: %v. UTC timezone will be used.", err)
+	}
+
 	if pidns {
 		flags := uint32(unix.MS_NOSUID | unix.MS_NODEV | unix.MS_NOEXEC | unix.MS_RDONLY)
 		if err := mountInChroot(chroot, "proc", "/proc", "proc", flags); err != nil {

runsc/cmd/gofer.go

@@ -290,11 +290,17 @@ func setupRootFS(spec *specs.Spec, conf *config.Config) error {
 		if err := os.Mkdir("/proc/root", 0755); err != nil {
 			Fatalf("error creating /proc/root: %v", err)
 		}
+		if err := os.Mkdir("/proc/etc", 0755); err != nil {
+			Fatalf("error creating /proc/etc: %v", err)
+		}
 		// This cannot use SafeMount because there's no available procfs. But we
 		// know that /proc is an empty tmpfs mount, so this is safe.
 		if err := unix.Mount("runsc-proc", "/proc/proc", "proc", flags|unix.MS_RDONLY, ""); err != nil {
 			Fatalf("error mounting proc: %v", err)
 		}
+		if err := copyFile("/proc/etc/localtime", "/etc/localtime"); err != nil {
+			log.Warningf("Failed to copy /etc/localtime: %v. UTC timezone will be used.", err)
+		}
 		root = "/proc/root"
 		procPath = "/proc/proc"
 	}