fix(pkg,cmd): eBPF probe must be symlinked under /root/.falco/falco-b…

…pf.o.

Signed-off-by: Federico Di Pierro <[email protected]>

cmd/driver/install/install.go

@@ -72,7 +72,7 @@ func NewDriverInstallCmd(ctx context.Context, opt *options.Common, driver *optio
 				// It is only useful for kmod, as it will try to
 				// modprobe a pre-existent version of the driver,
 				// hoping it will be compatible.
-				_ = driver.Type.Load(o.Printer, dest, err != nil)
+				_ = driver.Type.Load(o.Printer, dest, o.Driver.Name, err != nil)
 			}
 			return err
 		},
@@ -141,7 +141,7 @@ func (o *driverInstallOptions) RunDriverInstall(ctx context.Context) (string, er
 			return "", fmt.Errorf("detected an unsupported target system, please get in touch with the Falco community")
 		}
 	}
-	o.Printer.Logger.Info("found distro", o.Printer.Logger.Args("target", d))
+	o.Printer.Logger.Info("Found distro", o.Printer.Logger.Args("target", d))
 
 	var (
 		dest string
@@ -163,6 +163,7 @@ func (o *driverInstallOptions) RunDriverInstall(ctx context.Context) (string, er
 		// Print much more readable output as-is
 		o.Printer.DefaultText.Print(buf.String())
 	}
+	buf.Reset()
 	if err != nil {
 		return "", err
 	}

pkg/driver/type/bpf.go

@@ -17,9 +17,11 @@ package drivertype
 
 import (
 	"fmt"
+	"os"
 	"os/exec"
 	"path/filepath"
 
+	"github.com/docker/docker/pkg/homedir"
 	"github.com/falcosecurity/driverkit/pkg/kernelrelease"
 	"golang.org/x/net/context"
 	"k8s.io/utils/mount"
@@ -41,25 +43,23 @@ func (b *bpf) String() string {
 	return TypeBpf
 }
 
-func (b *bpf) Cleanup(printer *output.Printer, _ string) error {
-	// Mount /sys/kernel/debug that is needed on old (pre 4.17) kernel releases,
-	// since these releases still did not support raw tracepoints.
-	// BPF_PROG_TYPE_RAW_TRACEPOINT was introduced in 4.17 indeed:
-	// https://github.com/torvalds/linux/commit/c4f6699dfcb8558d138fe838f741b2c10f416cf9
-	exists, _ := utils.FileExists("/sys/kernel/debug/tracing")
-	if exists {
-		return nil
-	}
-	printer.Logger.Info("Mounting debugfs for bpf driver.")
-	mounter := mount.New("/bin/mount")
-	// We don't fail if this fails; let's try to build a probe anyway.
-	if err := mounter.Mount("debugfs", "/sys/kernel/debug", "debugfs", []string{"nodev"}); err != nil {
-		printer.Logger.Warn("Failed to mount debugfs.", printer.Logger.Args("err", err))
-	}
+func (b *bpf) Cleanup(_ *output.Printer, _ string) error {
 	return nil
 }
 
-func (b *bpf) Load(_ *output.Printer, _ string, _ bool) error {
+func (b *bpf) Load(printer *output.Printer, src, driverName string, fallback bool) error {
+	if !fallback {
+		symlinkPath := filepath.Join(homedir.Get(), ".falco", fmt.Sprintf("%s-bpf.o", driverName))
+		printer.Logger.Info("Symlinking eBPF probe", printer.Logger.Args("src", src, "dest", symlinkPath))
+		_ = os.Remove(symlinkPath)
+		err := os.Symlink(src, symlinkPath)
+		if err == nil {
+			printer.Logger.Info("eBPF probe symlinked")
+		} else {
+			printer.Logger.Info("Failed to symlink eBPF probe")
+		}
+		return err
+	}
 	return nil
 }
 
@@ -78,6 +78,8 @@ func (b *bpf) Build(ctx context.Context,
 	driverName, driverVersion string,
 	env map[string]string,
 ) (string, error) {
+	// We don't fail if this fails; let's try to build a probe anyway.
+	_ = mountKernelDebug(printer)
 	srcPath := fmt.Sprintf("/usr/src/%s-%s/bpf", driverName, driverVersion)
 
 	makeCmdArgs := fmt.Sprintf(`make -C %q`, filepath.Clean(srcPath))
@@ -93,3 +95,21 @@ func (b *bpf) Build(ctx context.Context,
 	outProbe := fmt.Sprintf("%s/probe.o", srcPath)
 	return outProbe, err
 }
+
+func mountKernelDebug(printer *output.Printer) error {
+	// Mount /sys/kernel/debug that is needed on old (pre 4.17) kernel releases,
+	// since these releases still did not support raw tracepoints.
+	// BPF_PROG_TYPE_RAW_TRACEPOINT was introduced in 4.17 indeed:
+	// https://github.com/torvalds/linux/commit/c4f6699dfcb8558d138fe838f741b2c10f416cf9
+	exists, _ := utils.FileExists("/sys/kernel/debug/tracing")
+	if exists {
+		return nil
+	}
+	printer.Logger.Info("Mounting debugfs for bpf driver.")
+	mounter := mount.New("/bin/mount")
+	err := mounter.Mount("debugfs", "/sys/kernel/debug", "debugfs", []string{"nodev"})
+	if err != nil {
+		printer.Logger.Warn("Failed to mount debugfs.", printer.Logger.Args("err", err))
+	}
+	return err
+}

pkg/driver/type/kmod.go

@@ -130,7 +130,7 @@ func (k *kmod) Cleanup(printer *output.Printer, driverName string) error {
 	return nil
 }
 
-func (k *kmod) Load(printer *output.Printer, driverName string, fallback bool) error {
+func (k *kmod) Load(printer *output.Printer, src, driverName string, fallback bool) error {
 	if fallback {
 		// Try to modprobe any existent version of the kmod; this is a fallback
 		// when both download and build of kmod fail.
@@ -144,15 +144,15 @@ func (k *kmod) Load(printer *output.Printer, driverName string, fallback bool) e
 		return err
 	}
 
-	chconCmdArgs := fmt.Sprintf(`chcon -t modules_object_t %q`, driverName)
+	chconCmdArgs := fmt.Sprintf(`chcon -t modules_object_t %q`, src)
 	// We don't want to catch any error from this call
 	// chcon(1): change file SELinux security context
 	_, _ = exec.Command("bash", "-c", chconCmdArgs).Output() //nolint:gosec // false positive
-	_, err := exec.Command("insmod", driverName).Output()
+	_, err := exec.Command("insmod", src).Output()
 	if err == nil {
-		printer.Logger.Info("Success: module found and loaded in dkms.", printer.Logger.Args("driver", driverName))
+		printer.Logger.Info("Success: module found and loaded in dkms.", printer.Logger.Args("driver", src))
 	} else {
-		printer.Logger.Warn("Unable to insmod module.", printer.Logger.Args("driver", driverName, "err", err))
+		printer.Logger.Warn("Unable to insmod module.", printer.Logger.Args("driver", src, "err", err))
 	}
 	return err
 }

pkg/driver/type/modernbpf.go

@@ -39,7 +39,7 @@ func (m *modernBpf) Cleanup(_ *output.Printer, _ string) error {
 	return nil
 }
 
-func (m *modernBpf) Load(_ *output.Printer, _ string, _ bool) error {
+func (m *modernBpf) Load(_ *output.Printer, _, _ string, _ bool) error {
 	return nil
 }
 

pkg/driver/type/type.go

@@ -34,7 +34,7 @@ var driverTypes = map[string]DriverType{}
 type DriverType interface {
 	fmt.Stringer
 	Cleanup(printer *output.Printer, driverName string) error
-	Load(printer *output.Printer, driverName string, fallback bool) error
+	Load(printer *output.Printer, src, driverName string, fallback bool) error
 	Extension() string
 	HasArtifacts() bool
 	Build(ctx context.Context, printer *output.Printer, kr kernelrelease.KernelRelease,