update README

README.md

@@ -13,13 +13,41 @@ aarch64. Install the following:
 * [Kraftkit](https://unikraft.org/docs/cli/install)
 
 Then run `zig build run` and everything will compile and run. The zig source
-code is all in the `ziggy` directory
+code is all in the `ziggy` directory. This is all prototype level code at this
+point.
 
+Reproducibility
+---------------
 
+This build is not reproducible at the moment. The problem is that we need v0.17.0
+or higher (this may be an issue with QEMU installed version, so YMMV). Kraftfile
+is designed to pin to a specific version, but as of this writing, versions of
+unikraft core post 0.16.1 are not listed in https://manifests.kraftkit.sh/unikraft.yaml,
+and as a result cannot be used, so we are forced to use "stable" as the version.
+
+undefined.c
+-----------
+
+This file aims to fill in all the undefined symbols that are referenced when
+a zig project links libC (necessary for unikraft kernel development). However,
+this is very incomplete. The `.config.hellowworld_qemu-x86_64` file, usually
+managed by the invocation of the TUI started by `kraft menu`, will add/remove
+features that result in various libc symbols being implemented. A few
+`#ifdef` statements exist currently, but even the few that are in there aren't
+quite right...this file is mostly a "hack around until it works" effort.
+
+Knowing that this is an initial effort, care was put into making sure that
+when a symbol is actually **used** at runtime, the unikernel will crash after
+posting a message indicating the specific function call that was involved. This
+is designed to either a) correct the configuration using `kraft menu` or
+b) provide an implementation directly in `undefined.c`. In some cases, I prefer
+the implementation in `undefined.c`, most specifically the `write` function,
+which will output stderr messages in red.
 
 Notes
 -----
 
+
 The build script basically runs these commands:
 
 ```sh

build.zig

@@ -74,7 +74,7 @@ pub fn build(b: *std.Build) void {
     const run_step = b.step("run", "Run the app");
     run_step.dependOn(&run_cmd.step);
 
-    const kraft_clean_cmd = b.addSystemCommand(&[_][]const u8{
+    var kraft_clean_cmd = b.addSystemCommand(&[_][]const u8{
         "kraft",
         "clean",
         "--plat",
@@ -82,6 +82,8 @@ pub fn build(b: *std.Build) void {
         "--arch",
         "x86_64",
     });
+    kraft_clean_cmd.stdio = .{ .check = .{} }; // kraft clean has some weird exit code behavior
+    kraft_clean_cmd.has_side_effects = true;
     const clean_step = b.step("clean", "Clean the unikraft build");
     clean_step.dependOn(&kraft_clean_cmd.step);
 
@@ -90,9 +92,17 @@ pub fn build(b: *std.Build) void {
         "-rf",
         ".unikraft",
     });
+
+    // rm -rf in this manner is leaving empty .unikraft/build, which is confusing
+    // let's whack it
+    const remove_empties_cmd = b.addSystemCommand(&[_][]const u8{
+        "find", ".unikraft", "-type", "d", "-empty", "-delete",
+    });
+    remove_empties_cmd.step.dependOn(&distclean_cmd.step);
+
     const distclean_step = b.step("distclean", "Deep clean the unikraft build");
     distclean_step.dependOn(clean_step);
-    distclean_step.dependOn(&distclean_cmd.step);
+    distclean_step.dependOn(&remove_empties_cmd.step);
 }
 
 const LazyPathEnvironmentVariable = struct {