Hello, World and build.zig

build.zig

@@ -4,113 +4,60 @@ const std = @import("std");
 // declaratively construct a build graph that will be executed by an external
 // runner.
 pub fn build(b: *std.Build) void {
-    // Standard target options allows the person running `zig build` to choose
-    // what target to build for. Here we do not override the defaults, which
-    // means any target is allowed, and the default is native. Other options
-    // for restricting supported target set are available.
-    const target = b.standardTargetOptions(.{});
-
-    // Standard optimization options allow the person running `zig build` to select
-    // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
-    // set a preferred release mode, allowing the user to decide how to optimize.
-    const optimize = b.standardOptimizeOption(.{});
-
-    // This creates a "module", which represents a collection of source files alongside
-    // some compilation options, such as optimization mode and linked system libraries.
-    // Every executable or library we compile will be based on one or more modules.
-    const lib_mod = b.createModule(.{
-        // `root_source_file` is the Zig "entry point" of the module. If a module
-        // only contains e.g. external object files, you can make this `null`.
-        // In this case the main source file is merely a path, however, in more
-        // complicated build scripts, this could be a generated file.
-        .root_source_file = b.path("src/root.zig"),
-        .target = target,
-        .optimize = optimize,
+    const initramfs = addNasmFiles(b, AddNasmFilesOptions{
+        .filename = "src/initramfs.asm",
+        .outputname = "initramfs.bin",
+        .addAsObjFile = false,
+        .flags = &.{"-f bin"},
     });
 
-    // We will also create a module for our other entry point, 'main.zig'.
-    const exe_mod = b.createModule(.{
-        // `root_source_file` is the Zig "entry point" of the module. If a module
-        // only contains e.g. external object files, you can make this `null`.
-        // In this case the main source file is merely a path, however, in more
-        // complicated build scripts, this could be a generated file.
-        .root_source_file = b.path("src/main.zig"),
-        .target = target,
-        .optimize = optimize,
-    });
+    const initramfs_install = b.addInstallBinFile(initramfs.obj, "initramfs.img");
+    initramfs_install.step.dependOn(&truncate(b, initramfs).step);
 
-    // Modules can depend on one another using the `std.Build.Module.addImport` function.
-    // This is what allows Zig source code to use `@import("foo")` where 'foo' is not a
-    // file path. In this case, we set up `exe_mod` to import `lib_mod`.
-    exe_mod.addImport("zos_lib", lib_mod);
+    b.getInstallStep().dependOn(&initramfs_install.step);
 
-    // Now, we will create a static library based on the module we created above.
-    // This creates a `std.Build.Step.Compile`, which is the build step responsible
-    // for actually invoking the compiler.
-    const lib = b.addLibrary(.{
-        .linkage = .static,
-        .name = "zos",
-        .root_module = lib_mod,
-    });
+    const run = b.addSystemCommand(&.{ "qemu-system-i386", "-fda" });
+    run.addFileArg(b.path("zig-out/bin/initramfs.img"));
 
-    // This declares intent for the library to be installed into the standard
-    // location when the user invokes the "install" step (the default step when
-    // running `zig build`).
-    b.installArtifact(lib);
-
-    // This creates another `std.Build.Step.Compile`, but this one builds an executable
-    // rather than a static library.
-    const exe = b.addExecutable(.{
-        .name = "zos",
-        .root_module = exe_mod,
-    });
-
-    // This declares intent for the executable to be installed into the
-    // standard location when the user invokes the "install" step (the default
-    // step when running `zig build`).
-    b.installArtifact(exe);
-
-    // This *creates* a Run step in the build graph, to be executed when another
-    // step is evaluated that depends on it. The next line below will establish
-    // such a dependency.
-    const run_cmd = b.addRunArtifact(exe);
-
-    // By making the run step depend on the install step, it will be run from the
-    // installation directory rather than directly from within the cache directory.
-    // This is not necessary, however, if the application depends on other installed
-    // files, this ensures they will be present and in the expected location.
-    run_cmd.step.dependOn(b.getInstallStep());
-
-    // This allows the user to pass arguments to the application in the build
-    // command itself, like this: `zig build run -- arg1 arg2 etc`
-    if (b.args) |args| {
-        run_cmd.addArgs(args);
-    }
-
-    // This creates a build step. It will be visible in the `zig build --help` menu,
-    // and can be selected like this: `zig build run`
-    // This will evaluate the `run` step rather than the default, which is "install".
-    const run_step = b.step("run", "Run the app");
-    run_step.dependOn(&run_cmd.step);
-
-    // Creates a step for unit testing. This only builds the test executable
-    // but does not run it.
-    const lib_unit_tests = b.addTest(.{
-        .root_module = lib_mod,
-    });
-
-    const run_lib_unit_tests = b.addRunArtifact(lib_unit_tests);
-
-    const exe_unit_tests = b.addTest(.{
-        .root_module = exe_mod,
-    });
-
-    const run_exe_unit_tests = b.addRunArtifact(exe_unit_tests);
-
-    // Similar to creating the run step earlier, this exposes a `test` step to
-    // the `zig build --help` menu, providing a way for the user to request
-    // running the unit tests.
-    const test_step = b.step("test", "Run unit tests");
-    test_step.dependOn(&run_lib_unit_tests.step);
-    test_step.dependOn(&run_exe_unit_tests.step);
+    const run_step = b.step("run", "run the os in qemu");
+    run_step.dependOn(&run.step);
+}
+
+const AddNasmFilesOptions = struct {
+    filename: []const u8,
+    outputname: ?[]const u8 = null,
+    addAsObjFile: bool = true,
+    flags: []const []const u8 = &.{},
+};
+
+const NasmFile = struct {
+    run: *std.Build.Step.Run,
+    obj: std.Build.LazyPath,
+};
+
+// adapted from https://codeberg.org/raddari/zig-nasm-lib.git
+fn addNasmFiles(b: *std.Build, options: AddNasmFilesOptions) NasmFile {
+    std.debug.assert(!std.fs.path.isAbsolute(options.filename));
+    const src_file = b.path(options.filename);
+    const output = options.outputname orelse b.fmt("{s}.o", .{std.mem.sliceTo(options.filename, '.')});
+
+    const nasm = b.addSystemCommand(&.{"nasm"});
+    nasm.addArgs(options.flags);
+    nasm.addPrefixedDirectoryArg("-i", b.path("src"));
+    const obj = nasm.addPrefixedOutputFileArg("-o", output);
+    nasm.addFileArg(src_file);
+
+    return .{
+        .run = nasm,
+        .obj = obj,
+    };
+}
+
+fn truncate(b: *std.Build, bin: NasmFile) *std.Build.Step.Run {
+    const exec = b.addSystemCommand(&.{"truncate"});
+    exec.addArgs(&.{ "-s", "1440k" });
+    exec.addFileArg(bin.obj);
+    exec.step.dependOn(&bin.run.step);
+
+    return exec;
 }