Add build script

.gitignore

@@ -1,2 +1,2 @@
-hellos
-zig-cache
+zig-out
+.zig-cache

README.md

@@ -5,11 +5,11 @@ Bare bones "hello world" i386 kernel written in [Zig](https://ziglang.org/).
 ## Building
 
 ```
-zig build-exe hellos.zig -target i386-freestanding -T linker.ld
+zig build --release=small
 ```
 
 ## Testing with qemu
 
 ```
-qemu-system-i386 -kernel hellos
+qemu-system-i386 -kernel zig-out/bin/HellOs
 ```

build.zig

@@ -0,0 +1,25 @@
+const std = @import("std");
+
+pub fn build(b: *std.Build) void {
+    const target = b.standardTargetOptions(.{ .default_target = .{ .os_tag = .freestanding, .abi = .eabi, .ofmt = .elf, .cpu_arch = .x86 } });
+    const optimize = b.standardOptimizeOption(.{});
+
+    const kernel = b.addExecutable(.{
+        .name = "HellOS",
+        .root_source_file = b.path("src/main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+    kernel.setLinkerScriptPath(b.path("linker.ld"));
+
+    b.installArtifact(kernel);
+
+    const unit_tests = b.addTest(.{
+        .root_source_file = b.path("src/main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+    const run_unit_tests = b.addRunArtifact(unit_tests);
+    const test_step = b.step("test", "Run unit tests");
+    test_step.dependOn(&run_unit_tests.step);
+}

build.zig.zon

@@ -0,0 +1,12 @@
+.{
+    .name = "HellOS",
+    .version = "0.1.0",
+    .minimum_zig_version = "0.14.0",
+    .paths = .{
+        "build.zig",
+        "build.zig.zon",
+        "linker.ld",
+        "src",
+        "README.md",
+    },
+}

hellos.zig → src/main.zig

@@ -1,6 +1,9 @@
+const std = @import("std");
 const builtin = @import("builtin");
 
-const MultiBoot = packed struct {
+const StackTrace = std.builtin.StackTrace;
+
+const MultiBoot = extern struct {
     magic: i32,
     flags: i32,
     checksum: i32,
@@ -21,21 +24,28 @@ export var stack_bytes: [16 * 1024]u8 align(16) linksection(".bss") = undefined;
 const stack_bytes_slice = stack_bytes[0..];
 
 export fn _start() callconv(.Naked) noreturn {
-    @call(.{ .stack = stack_bytes_slice }, kmain, .{});
-
+    const stack = stack_bytes_slice;
+    asm volatile (
+        \\ movl %[stk], %esp
+        \\ movl %esp, %ebp
+        \\ jmp kmain
+        :
+        : [stk] "{ecx}" (@intFromPtr(&stack) + @sizeOf(@TypeOf(stack))),
+    );
     while (true) {}
 }
 
-pub fn panic(msg: []const u8, error_return_trace: ?*builtin.StackTrace) noreturn {
-    @setCold(true);
+pub fn panic(msg: []const u8, error_return_trace: ?*StackTrace) noreturn {
+    @branchHint(.cold);
+    _ = error_return_trace;
     terminal.write("KERNEL PANIC: ");
     terminal.write(msg);
     while (true) {}
 }
 
-fn kmain() void {
+export fn kmain() callconv(.C) void {
     terminal.initialize();
-    terminal.write("Hello, Kernel World from Zig 0.7.1!");
+    terminal.write("Hello, Kernel World from Zig 0.14.0!");
 }
 
 // Hardware text mode color constants
@@ -62,7 +72,7 @@ fn vga_entry_color(fg: VgaColor, bg: VgaColor) u8 {
 }
 
 fn vga_entry(uc: u8, color: u8) u16 {
-    var c: u16 = color;
+    const c: u16 = color;
 
     return uc | (c << 8);
 }
@@ -76,7 +86,7 @@ const terminal = struct {
 
     var color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
 
-    const buffer = @intToPtr([*]volatile u16, 0xB8000);
+    const buffer: [*]volatile u16 = @ptrFromInt(0xB8000);
 
     fn initialize() void {
         var y: usize = 0;