internal/rosa/package: migrate system image

The overlay argument also enables migration of stage0.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/images.go

@@ -1,29 +0,0 @@
-package rosa
-
-import (
-	"hakurei.app/fhs"
-	"hakurei.app/internal/pkg"
-)
-
-func init() {
-	meta := Metadata{
-		Name:        "system-image",
-		Description: "Rosa OS system image",
-		Version:     Unversioned,
-	}
-	native.MustRegister(meta.Name, func(t Toolchain) (*Metadata, pkg.Artifact) {
-		return &meta, t.New("system.img", TNoToolchain, t.Append(nil,
-			H("squashfs-tools"),
-		), nil, nil, `
-mksquashfs /mnt/system /work/system.img
-`, pkg.Path(fhs.AbsRoot.Append("mnt"), false, t.Append(nil,
-			_musl,
-			_mksh,
-			_toybox,
-
-			H("kmod"),
-			H("kernel"),
-			H("firmware"),
-		)...))
-	})
-}

internal/rosa/package/images/package.az

@@ -19,3 +19,27 @@ package initramfs-image {
 		gen_init_cpio,
 	];
 }
+
+package system-image {
+	description = "Rosa OS system image";
+	version = unversioned;
+	exclude = true;
+
+	source = earlyinit;
+	extra = [
+		musl,
+		mksh,
+		toybox,
+
+		kmod,
+		kernel,
+		firmware,
+	];
+	overlay = "/mnt";
+
+	exec = generic {
+		build = "mksquashfs /mnt/system /work/system.img";
+	};
+
+	inputs = [ squashfs-tools ];
+}

internal/rosa/state.go

@@ -932,6 +932,7 @@ func (ctx *evalContext) pf(
 		output  pkg.Artifact
 		sourceA any
 		helper  Helper
+		overlay string
 
 		inputs, runtimes, extra azalea.Array
 	)
@@ -960,6 +961,7 @@ func (ctx *evalContext) pf(
 		k("inputs"):   &inputs,
 		k("runtime"):  &runtimes,
 		k("extra"):    &extra,
+		k("overlay"):  &overlay,
 	}); err != nil {
 		return
 	}
@@ -991,6 +993,7 @@ func (ctx *evalContext) pf(
 		})
 	}
 
+	if overlay == "" {
 		for _, h := range extraH {
 			_, a := ctx.t.MustLoad(h)
 			attr.Paths = append(attr.Paths, pkg.Path(
@@ -999,6 +1002,18 @@ func (ctx *evalContext) pf(
 				a,
 			))
 		}
+	} else {
+		var o pkg.ExecPath
+		if o.P, err = check.NewAbs(overlay); err != nil {
+			o.P = AbsUsrSrc.Append("extra", overlay)
+		}
+		o.A = make([]pkg.Artifact, len(extraH))
+		for i, h := range extraH {
+			_, a := ctx.t.MustLoad(h)
+			o.A[i] = a
+		}
+		attr.Paths = append(attr.Paths, o)
+	}
 
 	for _, pair := range files {
 		var pathname *check.Absolute