implement golang wrapper to replace shell scripts

Some platforms and Kubernetes distributions do not include a shell. This
patch replaces the shell wrapper scripts with a small Go program.

Signed-off-by: Jean-Francois Roy <jeroy@nvidia.com>

tools/container/wrapper/wrapper.go

@@ -0,0 +1,115 @@
+/**
+# Copyright (c) 2024, NVIDIA CORPORATION.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+*/
+
+package main
+
+import (
+	"bufio"
+	"errors"
+	"io/fs"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+
+	"golang.org/x/sys/unix"
+)
+
+func main() {
+	program, err := os.Executable()
+	if err != nil {
+		log.Fatalf("failed to get executable: %v", err)
+	}
+	if isRuntimeWrapper(program) && !isNvidiaModuleLoaded() {
+		log.Println("nvidia driver modules are not yet loaded, invoking runc directly")
+		program, err := exec.LookPath("runc")
+		if err != nil {
+			log.Fatalf("failed to find runc: %v", err)
+		}
+		argv := []string{"runc"}
+		argv = append(argv, os.Args[1:]...)
+		execve(program, argv, os.Environ())
+	}
+	argv := makeArgv(program)
+	envv := makeEnvv(program)
+	execve(program+".real", argv, envv)
+}
+
+func isRuntimeWrapper(program string) bool {
+	return filepath.Base(program) == "nvidia-container-runtime" ||
+		filepath.Base(program) == "nvidia-container-runtime.cdi" ||
+		filepath.Base(program) == "nvidia-container-runtime.legacy"
+}
+
+func isNvidiaModuleLoaded() bool {
+	_, err := os.Stat("/proc/driver/nvidia/version")
+	return err == nil
+}
+
+func makeArgv(program string) []string {
+	argv := []string{os.Args[0] + ".real"}
+	f, err := os.Open(program + ".argv")
+	if err != nil {
+		if !errors.Is(err, fs.ErrNotExist) {
+			log.Printf("failed to open argv file: %v", err)
+		}
+		return append(argv, os.Args[1:]...)
+	}
+	defer f.Close()
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		argv = append(argv, scanner.Text())
+	}
+	if err := scanner.Err(); err != nil {
+		log.Fatalf("failed to read argv file: %v", err)
+	}
+	return append(argv, os.Args[1:]...)
+}
+
+func makeEnvv(program string) []string {
+	f, err := os.Open(program + ".envv")
+	if err != nil {
+		if !errors.Is(err, fs.ErrNotExist) {
+			log.Printf("failed to open env file: %v", err)
+		}
+		return os.Environ()
+	}
+	defer f.Close()
+	var env []string
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		kv := strings.SplitN(scanner.Text(), "=", 2)
+		if strings.HasPrefix(kv[0], "<") {
+			kv[0] = kv[0][1:]
+			kv[1] = kv[1] + ":" + os.Getenv(kv[0])
+		} else if strings.HasPrefix(kv[0], ">") {
+			kv[0] = kv[0][1:]
+			kv[1] = os.Getenv(kv[0]) + ":" + kv[1]
+		}
+		env = append(env, kv[0]+"="+kv[1])
+	}
+	if err := scanner.Err(); err != nil {
+		log.Fatalf("failed to read argv file: %v", err)
+	}
+	return append(env, os.Environ()...)
+}
+
+func execve(program string, argv []string, envv []string) {
+	if err := unix.Exec(program, argv, envv); err != nil {
+		log.Fatalf("failed to exec %s: %v", program, err)
+	}
+}