Hello, World and build.zig

This commit is contained in:
Dario48 2025-07-11 17:43:37 +02:00
parent c45514ce4f
commit b8c7fc5674
4 changed files with 113 additions and 163 deletions

155
build.zig
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@ -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;
}

62
src/initramfs.asm Normal file
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@ -0,0 +1,62 @@
; vim: ft=nasm
org 0x7C00
bits 16
%define ENDL 0x0D, 0x0A
start:
jmp main
;
; echo:
; print something to the screen
; - ds:si points to string
;
echo:
; save the registers we want to modify
push si
push ax
push bx
mov ah, 0xe
mov bh, 0
.loop:
lodsb ; load byte from ds:si to al
or al, al ; check if next char is null
jz .done
int 0x10
jmp .loop
.done:
pop bx
pop ax
pop si
ret
main:
; setup data segments
; use ax as and intermediary as we can't write to es/ds directly
mov ax, 0
mov ds, ax
mov es, ax
; setup stack
mov ss, ax
mov sp, 0x7C00 ; stack grows downward from where we are loaded in memory
; print the hello world
mov si, msg_hello
call echo
hlt
.halt:
jmp .halt
msg_hello: db 'Hello, world!', ENDL, 0
times 510-($-$$) db 0
dw 0AA55h

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@ -1,46 +0,0 @@
//! By convention, main.zig is where your main function lives in the case that
//! you are building an executable. If you are making a library, the convention
//! is to delete this file and start with root.zig instead.
pub fn main() !void {
// Prints to stderr (it's a shortcut based on `std.io.getStdErr()`)
std.debug.print("All your {s} are belong to us.\n", .{"codebase"});
// stdout is for the actual output of your application, for example if you
// are implementing gzip, then only the compressed bytes should be sent to
// stdout, not any debugging messages.
const stdout_file = std.io.getStdOut().writer();
var bw = std.io.bufferedWriter(stdout_file);
const stdout = bw.writer();
try stdout.print("Run `zig build test` to run the tests.\n", .{});
try bw.flush(); // Don't forget to flush!
}
test "simple test" {
var list = std.ArrayList(i32).init(std.testing.allocator);
defer list.deinit(); // Try commenting this out and see if zig detects the memory leak!
try list.append(42);
try std.testing.expectEqual(@as(i32, 42), list.pop());
}
test "use other module" {
try std.testing.expectEqual(@as(i32, 150), lib.add(100, 50));
}
test "fuzz example" {
const Context = struct {
fn testOne(context: @This(), input: []const u8) anyerror!void {
_ = context;
// Try passing `--fuzz` to `zig build test` and see if it manages to fail this test case!
try std.testing.expect(!std.mem.eql(u8, "canyoufindme", input));
}
};
try std.testing.fuzz(Context{}, Context.testOne, .{});
}
const std = @import("std");
/// This imports the separate module containing `root.zig`. Take a look in `build.zig` for details.
const lib = @import("zos_lib");

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@ -1,13 +0,0 @@
//! By convention, root.zig is the root source file when making a library. If
//! you are making an executable, the convention is to delete this file and
//! start with main.zig instead.
const std = @import("std");
const testing = std.testing;
pub export fn add(a: i32, b: i32) i32 {
return a + b;
}
test "basic add functionality" {
try testing.expect(add(3, 7) == 10);
}