pkg/build: add a new way of building linux images

Add a new, simpler procedure:
working bootable image is accepted as an input
and we only replace the kernel in it.
This just looks much saner and the right way to do it
(instead of assembling the image from bits and shelling out
to mkfs, fdisk, grub, etc). The new way also works inside of
containers much better.

1 files changed, 7 insertions, 7 deletions

diff --git a/pkg/build/linux.go b/pkg/build/linux.go
index f08455c39..be2341311 100644
--- a/pkg/build/linux.go
+++ b/pkg/build/linux.go
@@ -31,20 +31,20 @@ func (linux linux) build(params *Params) error {
 		return err
 	}
 	kernelPath := filepath.Join(params.KernelDir, filepath.FromSlash(kernelBin(params.TargetArch)))
-	if fileInfo, err := os.Stat(params.UserspaceDir); err == nil && !fileInfo.IsDir() && params.VMType == "qemu" {
+	if fileInfo, err := os.Stat(params.UserspaceDir); err == nil && fileInfo.IsDir() {
+		// The old way of assembling the image from userspace dir.
+		// It should be removed once all syzbot instances are switched.
+		return linux.createImage(params, kernelPath)
+	}
+	if params.VMType == "qemu" {
 		// If UserspaceDir is a file (image) and we use qemu, we just copy image and kernel to the output dir
 		// assuming that qemu will use injected kernel boot. In this mode we also assume password/key-less ssh.
-		// In future it would be good to switch to accepting complete disk image always and just replacing
-		// kernel in it for GCE VMs (assembling image from userspace files in createImage isn't reasonable).
 		if err := osutil.CopyFile(kernelPath, filepath.Join(params.OutputDir, "kernel")); err != nil {
 			return err
 		}
 		return osutil.CopyFile(params.UserspaceDir, filepath.Join(params.OutputDir, "image"))
 	}
-	if err := linux.createImage(params, kernelPath); err != nil {
-		return err
-	}
-	return nil
+	return embedLinuxKernel(params, kernelPath)
 }
 
 func (linux linux) sign(params *Params) (string, error) {