new(cmd,pkg/driverbuilder): support env,src-dir and dkms build options in local builder.

Signed-off-by: Federico Di Pierro <nierro92@gmail.com>

Author: FedeDP

cmd/local.go

@@ -9,12 +9,20 @@ import (
 	"golang.org/x/sys/unix"
 	"log/slog"
 	"os"
+	"os/user"
 	"runtime"
 	"strings"
 )
 
+type localCmdOptions struct {
+	useDKMS bool
+	srcDir  string
+	envMap  map[string]string
+}
+
 // NewLocalCmd creates the `driverkit local` command.
 func NewLocalCmd(rootCommand *RootCmd, rootOpts *RootOptions, rootFlags *pflag.FlagSet) *cobra.Command {
+	opts := localCmdOptions{}
 	localCmd := &cobra.Command{
 		Use:               "local",
 		Short:             "Build Falco kernel modules and eBPF probes in local env with local kernel sources and gcc/clang.",
@@ -26,7 +34,18 @@ func NewLocalCmd(rootCommand *RootCmd, rootOpts *RootOptions, rootFlags *pflag.F
 				if !b.HasOutputs() {
 					return
 				}
-				if err := driverbuilder.NewLocalBuildProcessor(viper.GetInt("timeout")).Start(b); err != nil {
+				if opts.useDKMS {
+					currentUser, err := user.Current()
+					if err != nil {
+						slog.With("err", err.Error()).Error("Failed to retrieve user. Exiting.")
+						os.Exit(1)
+					}
+					if currentUser.Username != "root" {
+						slog.Error("Must be run as root for DKMS build.")
+						os.Exit(1)
+					}
+				}
+				if err := driverbuilder.NewLocalBuildProcessor(viper.GetInt("timeout"), opts.useDKMS, opts.srcDir, opts.envMap).Start(b); err != nil {
 					slog.With("err", err.Error()).Error("exiting")
 					os.Exit(1)
 				}
@@ -56,6 +75,9 @@ func NewLocalCmd(rootCommand *RootCmd, rootOpts *RootOptions, rootFlags *pflag.F
 			flagSet.AddFlag(flag)
 		}
 	})
+	flagSet.BoolVar(&opts.useDKMS, "dkms", false, "Enforce usage of DKMS to build the kernel module.")
+	flagSet.StringVar(&opts.srcDir, "src-dir", "", "Enforce usage of local source dir to build drivers.")
+	flagSet.StringToStringVar(&opts.envMap, "env", nil, "Env variables to be enforced during the driver build.")
 	localCmd.PersistentFlags().AddFlagSet(flagSet)
 	return localCmd
 }

pkg/driverbuilder/builder/local.go

@@ -15,6 +15,8 @@ var localTemplate string
 
 type LocalBuilder struct {
 	GccPath string
+	UseDKMS bool
+	SrcDir  string
 }
 
 func (l *LocalBuilder) Name() string {
@@ -25,7 +27,7 @@ func (l *LocalBuilder) TemplateScript() string {
 	return localTemplate
 }
 
-func (l *LocalBuilder) URLs(kr kernelrelease.KernelRelease) ([]string, error) {
+func (l *LocalBuilder) URLs(_ kernelrelease.KernelRelease) ([]string, error) {
 	return nil, nil
 }
 
@@ -36,18 +38,43 @@ func (l *LocalBuilder) MinimumURLs() int {
 
 type localTemplateData struct {
 	commonTemplateData
+	UseDKMS       bool
+	DownloadSrc   bool
+	DriverVersion string
+	KernelRelease string
 }
 
-func (l *LocalBuilder) TemplateData(c Config, _ kernelrelease.KernelRelease, _ []string) interface{} {
+func (l *LocalBuilder) TemplateData(c Config, kr kernelrelease.KernelRelease, _ []string) interface{} {
 	return localTemplateData{
 		commonTemplateData: commonTemplateData{
-			DriverBuildDir:    DriverDirectory,
+			DriverBuildDir:    l.GetDriverBuildDir(),
 			ModuleDownloadURL: fmt.Sprintf("%s/%s.tar.gz", c.DownloadBaseURL, c.DriverVersion),
 			ModuleDriverName:  c.DriverName,
-			ModuleFullPath:    ModuleFullPath,
+			ModuleFullPath:    l.GetModuleFullPath(c, kr),
 			BuildModule:       len(c.ModuleFilePath) > 0,
 			BuildProbe:        len(c.ProbeFilePath) > 0,
 			GCCVersion:        l.GccPath,
 		},
+		UseDKMS:       l.UseDKMS,
+		DownloadSrc:   len(l.SrcDir) == 0, // if no srcdir is provided, download src!
+		DriverVersion: c.DriverVersion,
+		KernelRelease: c.KernelRelease,
 	}
 }
+
+func (l *LocalBuilder) GetModuleFullPath(c Config, kr kernelrelease.KernelRelease) string {
+	moduleFullPath := ModuleFullPath
+	if l.UseDKMS {
+		// When using dkms, we will use a GLOB to match the pattern; ModuleFullPath won't be used in the templated script anyway.
+		moduleFullPath = fmt.Sprintf("/var/lib/dkms/%s/%s/%s/%s/module/%s.*", c.DriverName, c.DriverVersion, kr.String(), kr.Architecture.ToNonDeb(), c.DriverName)
+	}
+	return moduleFullPath
+}
+
+func (l *LocalBuilder) GetDriverBuildDir() string {
+	driverBuildDir := DriverDirectory
+	if len(l.SrcDir) > 0 {
+		driverBuildDir = l.SrcDir
+	}
+	return driverBuildDir
+}

pkg/driverbuilder/builder/templates/local.sh

@@ -22,6 +22,8 @@
 #
 set -xeuo pipefail
 
+{{ if .DownloadSrc }}
+echo "* Downloading driver sources"
 rm -Rf {{ .DriverBuildDir }}
 mkdir {{ .DriverBuildDir }}
 rm -Rf /tmp/module-download
@@ -32,8 +34,19 @@ mv /tmp/module-download/*/driver/* {{ .DriverBuildDir }}
 
 cp /tmp/module-Makefile {{ .DriverBuildDir }}/Makefile
 bash /tmp/fill-driver-config.sh {{ .DriverBuildDir }}
+{{ end }}
 
 {{ if .BuildModule }}
+{{ if .UseDKMS }}
+echo "* Building kmod with DKMS"
+# Build the module using DKMS
+echo "#!/usr/bin/env bash" > "/tmp/falco-dkms-make"
+echo "make CC={{ .GCCVersion }} \$@" >> "/tmp/falco-dkms-make"
+chmod +x "/tmp/falco-dkms-make"
+dkms install --directive="MAKE='/tmp/falco-dkms-make'" -m "{{ .ModuleDriverName }}" -v "{{ .DriverVersion }}" -k "{{ .KernelRelease }}"
+rm -Rf "/tmp/falco-dkms-make"
+{{ else }}
+echo "* Building kmod"
 # Build the module
 cd {{ .DriverBuildDir }}
 make CC={{ .GCCVersion }}
@@ -42,8 +55,10 @@ strip -g {{ .ModuleFullPath }}
 # Print results
 modinfo {{ .ModuleFullPath }}
 {{ end }}
+{{ end }}
 
 {{ if .BuildProbe }}
+echo "* Building eBPF probe"
 # Build the eBPF probe
 cd {{ .DriverBuildDir }}/bpf
 make

pkg/driverbuilder/local.go

@@ -7,9 +7,11 @@ import (
 	_ "embed"
 	"fmt"
 	"github.com/falcosecurity/driverkit/pkg/driverbuilder/builder"
+	"io"
 	"log/slog"
 	"os"
 	"os/exec"
+	"path"
 	"path/filepath"
 	"time"
 )
@@ -18,11 +20,17 @@ const LocalBuildProcessorName = "local"
 
 type LocalBuildProcessor struct {
 	timeout int
+	useDKMS bool
+	srcDir  string
+	envMap  map[string]string
 }
 
-func NewLocalBuildProcessor(timeout int) *LocalBuildProcessor {
+func NewLocalBuildProcessor(timeout int, useDKMS bool, srcDir string, envMap map[string]string) *LocalBuildProcessor {
 	return &LocalBuildProcessor{
 		timeout: timeout,
+		useDKMS: useDKMS,
+		srcDir:  srcDir,
+		envMap:  envMap,
 	}
 }
 
@@ -104,6 +112,11 @@ func (lbp *LocalBuildProcessor) Start(b *builder.Build) error {
 
 	// Cannot fail
 	vv, _ := v.(*builder.LocalBuilder)
+	vv.SrcDir = lbp.srcDir
+	vv.UseDKMS = lbp.useDKMS
+
+	modulePath := vv.GetModuleFullPath(c, kr)
+	probePath := path.Join(vv.GetDriverBuildDir(), "bpf", builder.ProbeFileName)
 	for _, gcc := range gccs {
 		vv.GccPath = gcc
 
@@ -115,6 +128,10 @@ func (lbp *LocalBuildProcessor) Start(b *builder.Build) error {
 		ctx, cancelFunc := context.WithTimeout(context.Background(), time.Duration(lbp.timeout)*time.Second)
 		defer cancelFunc()
 		cmd := exec.CommandContext(ctx, "/bin/bash", "-c", driverkitScript)
+		// Append requested env variables to the command env
+		for key, val := range lbp.envMap {
+			cmd.Env = append(cmd.Env, fmt.Sprintf("%s=%s", key, val))
+		}
 		stdout, err := cmd.StdoutPipe()
 		if err != nil {
 			slog.Warn("Failed to pipe output. Trying without piping.", "err", err)
@@ -139,28 +156,52 @@ func (lbp *LocalBuildProcessor) Start(b *builder.Build) error {
 		}
 		// If we received an error, perhaps we must just rebuilt the kmod.
 		// Check if we were able to build anything.
-		if _, err = os.Stat(builder.ModuleFullPath); !os.IsNotExist(err) {
-			// we built the kmod; there is no need to loop again.
+		koFiles, err := filepath.Glob(modulePath)
+		if err == nil && len(koFiles) > 0 {
 			break
 		}
-		if _, err = os.Stat(builder.ProbeFullPath); !os.IsNotExist(err) {
+		if _, err = os.Stat(probePath); !os.IsNotExist(err) {
 			c.ProbeFilePath = ""
 		}
 	}
 
 	if len(b.ModuleFilePath) > 0 {
-		if err = os.Rename(builder.ModuleFullPath, b.ModuleFilePath); err != nil {
+		// If we received an error, perhaps we must just rebuilt the kmod.
+		// Check if we were able to build anything.
+		koFiles, err := filepath.Glob(modulePath)
+		if err != nil || len(koFiles) == 0 {
+			return fmt.Errorf("failed to find kernel module .ko file: %s", modulePath)
+		}
+		if err = copyDataToLocalPath(koFiles[0], b.ModuleFilePath); err != nil {
 			return err
 		}
 		slog.With("path", b.ModuleFilePath).Info("kernel module available")
 	}
 
 	if len(b.ProbeFilePath) > 0 {
-		if err = os.Rename(builder.ProbeFullPath, b.ProbeFilePath); err != nil {
+		if err = copyDataToLocalPath(probePath, b.ProbeFilePath); err != nil {
 			return err
 		}
 		slog.With("path", b.ProbeFilePath).Info("eBPF probe available")
 	}
 
 	return nil
 }
+
+func copyDataToLocalPath(src, dest string) error {
+	in, err := os.Open(filepath.Clean(src))
+	if err != nil {
+		return err
+	}
+	defer in.Close()
+	err = os.MkdirAll(filepath.Dir(dest), 0o755)
+	if err != nil {
+		return err
+	}
+	out, err := os.OpenFile(filepath.Clean(dest), os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0o755)
+	if err == nil {
+		defer out.Close()
+		_, err = io.Copy(out, in)
+	}
+	return err
+}