pkg/build: save kernel config early

Currently we don't capture kernel config for broken builds
because the config is saved as the last step.
Save it as early as possible.

2 files changed, 11 insertions, 4 deletions

diff --git a/pkg/build/build.go b/pkg/build/build.go
index 4d0489a63..615cc7ad7 100644
--- a/pkg/build/build.go
+++ b/pkg/build/build.go
@@ -33,6 +33,12 @@ func Image(targetOS, targetArch, vmType, kernelDir, outputDir, compiler, userspa
 	if err := osutil.MkdirAll(filepath.Join(outputDir, "obj")); err != nil {
 		return err
 	}
+	if len(config) != 0 {
+		// Write kernel config early, so that it's captured on build failures.
+		if err := osutil.WriteFile(filepath.Join(outputDir, "kernel.config"), config); err != nil {
+			return fmt.Errorf("failed to write config file: %v", err)
+		}
+	}
 	return builder.build(targetArch, vmType, kernelDir, outputDir, compiler, userspaceDir, cmdlineFile, sysctlFile, config)
 }
 
diff --git a/pkg/build/linux.go b/pkg/build/linux.go
index ccceeec82..f2bc4e0fe 100644
--- a/pkg/build/linux.go
+++ b/pkg/build/linux.go
@@ -54,6 +54,11 @@ func (linux) buildKernel(kernelDir, outputDir, compiler string, config []byte) e
 	if _, err := osutil.Run(10*time.Minute, cmd); err != nil {
 		return err
 	}
+	// Write updated kernel config early, so that it's captured on build failures.
+	outputConfig := filepath.Join(outputDir, "kernel.config")
+	if err := osutil.CopyFile(configFile, outputConfig); err != nil {
+		return err
+	}
 	// We build only bzImage as we currently don't use modules.
 	cpu := strconv.Itoa(runtime.NumCPU())
 	cmd = osutil.Command("make", "bzImage", "-j", cpu, "CC="+compiler)
@@ -64,10 +69,6 @@ func (linux) buildKernel(kernelDir, outputDir, compiler string, config []byte) e
 	if _, err := osutil.Run(time.Hour, cmd); err != nil {
 		return extractRootCause(err)
 	}
-	outputConfig := filepath.Join(outputDir, "kernel.config")
-	if err := osutil.CopyFile(configFile, outputConfig); err != nil {
-		return err
-	}
 	vmlinux := filepath.Join(kernelDir, "vmlinux")
 	outputVmlinux := filepath.Join(outputDir, "obj", "vmlinux")
 	if err := os.Rename(vmlinux, outputVmlinux); err != nil {