From 7addcc4ca56f0a130e5acec88475fc78c76ce471 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maciej=20Krzy=C5=BCanowski?= <krzmaciek@gmail.com>
Date: Thu, 22 Aug 2024 23:57:22 +0200
Subject: [PATCH] Initial commit, not yet working

---
 .gitignore      |  2 ++
 build.zig       | 36 +++++++++++++++++++++
 src/console.zig | 84 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/grub.cfg    |  3 ++
 src/linker.ld   | 26 +++++++++++++++
 src/main.zig    | 32 +++++++++++++++++++
 6 files changed, 183 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 build.zig
 create mode 100644 src/console.zig
 create mode 100644 src/grub.cfg
 create mode 100644 src/linker.ld
 create mode 100644 src/main.zig

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..dca1103
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+zig-out/
+.zig-cache/
diff --git a/build.zig b/build.zig
new file mode 100644
index 0000000..24cff05
--- /dev/null
+++ b/build.zig
@@ -0,0 +1,36 @@
+const std = @import("std");
+
+pub fn build(b: *std.Build) void {
+    var disabled_features = std.Target.Cpu.Feature.Set.empty;
+    var enabled_features = std.Target.Cpu.Feature.Set.empty;
+
+    disabled_features.addFeature(@intFromEnum(std.Target.x86.Feature.mmx));
+    disabled_features.addFeature(@intFromEnum(std.Target.x86.Feature.sse));
+    disabled_features.addFeature(@intFromEnum(std.Target.x86.Feature.sse2));
+    disabled_features.addFeature(@intFromEnum(std.Target.x86.Feature.avx));
+    disabled_features.addFeature(@intFromEnum(std.Target.x86.Feature.avx2));
+    enabled_features.addFeature(@intFromEnum(std.Target.x86.Feature.soft_float));
+
+    const target_query = std.Target.Query{
+        .cpu_arch = std.Target.Cpu.Arch.x86,
+        .os_tag = std.Target.Os.Tag.freestanding,
+        .abi = std.Target.Abi.none,
+        .cpu_features_sub = disabled_features,
+        .cpu_features_add = enabled_features,
+    };
+    const optimize = b.standardOptimizeOption(.{});
+
+    const kernel = b.addExecutable(.{
+        .name = "kernel.elf",
+        .root_source_file = b.path("src/main.zig"),
+        .target = b.resolveTargetQuery(target_query),
+        .optimize = optimize,
+        .code_model = .kernel,
+    });
+
+    kernel.setLinkerScript(b.path("src/linker.ld"));
+    b.installArtifact(kernel);
+
+    const kernel_step = b.step("kernel", "Build the kernel");
+    kernel_step.dependOn(&kernel.step);
+}
diff --git a/src/console.zig b/src/console.zig
new file mode 100644
index 0000000..0b331ca
--- /dev/null
+++ b/src/console.zig
@@ -0,0 +1,84 @@
+const fmt = @import("std").fmt;
+const Writer = @import("std").io.Writer;
+
+const VGA_WIDTH = 80;
+const VGA_HEIGHT = 25;
+const VGA_SIZE = VGA_WIDTH * VGA_HEIGHT;
+
+pub const ConsoleColors = enum(u8) {
+    Black = 0,
+    Blue = 1,
+    Green = 2,
+    Cyan = 3,
+    Red = 4,
+    Magenta = 5,
+    Brown = 6,
+    LightGray = 7,
+    DarkGray = 8,
+    LightBlue = 9,
+    LightGreen = 10,
+    LightCyan = 11,
+    LightRed = 12,
+    LightMagenta = 13,
+    LightBrown = 14,
+    White = 15,
+};
+
+var row: usize = 0;
+var column: usize = 0;
+var color = vgaEntryColor(ConsoleColors.LightGray, ConsoleColors.Black);
+var buffer = @as([*]volatile u16, @ptrFromInt(0xB8000));
+
+fn vgaEntryColor(fg: ConsoleColors, bg: ConsoleColors) u8 {
+    return @intFromEnum(fg) | (@intFromEnum(bg) << 4);
+}
+
+fn vgaEntry(uc: u8, new_color: u8) u16 {
+    const c: u16 = new_color;
+
+    return uc | (c << 8);
+}
+
+pub fn initialize() void {
+    clear();
+}
+
+pub fn setColor(new_color: u8) void {
+    color = new_color;
+}
+
+pub fn clear() void {
+    @memset(buffer[0..VGA_SIZE], vgaEntry(' ', color));
+}
+
+pub fn putCharAt(c: u8, new_color: u8, x: usize, y: usize) void {
+    const index = y * VGA_WIDTH + x;
+    buffer[index] = vgaEntry(c, new_color);
+}
+
+pub fn putChar(c: u8) void {
+    putCharAt(c, color, column, row);
+    column += 1;
+    if (column == VGA_WIDTH) {
+        column = 0;
+        row += 1;
+        if (row == VGA_HEIGHT)
+            row = 0;
+    }
+}
+
+pub fn puts(data: []const u8) void {
+    for (data) |c|
+        putChar(c);
+}
+
+pub const writer = Writer(void, error{}, callback){ .context = {} };
+
+fn callback(_: void, string: []const u8) error{}!usize {
+    puts(string);
+    return string.len;
+}
+
+pub fn printf(comptime format: []const u8, args: anytype) void {
+    fmt.format(writer, format, args) catch unreachable;
+}
diff --git a/src/grub.cfg b/src/grub.cfg
new file mode 100644
index 0000000..2164e64
--- /dev/null
+++ b/src/grub.cfg
@@ -0,0 +1,3 @@
+menuentry "Zig Bare Bones" {
+	multiboot /boot/kernel.elf
+}
\ No newline at end of file
diff --git a/src/linker.ld b/src/linker.ld
new file mode 100644
index 0000000..ec475c8
--- /dev/null
+++ b/src/linker.ld
@@ -0,0 +1,26 @@
+ENTRY(_start)
+ 
+SECTIONS {
+    . = 1M;
+ 
+    .multiboot {
+        KEEP(*(.multiboot))
+    }
+
+    .text : ALIGN(4K) {
+        *(.text)
+    }
+ 
+    .rodata : ALIGN(4K) {
+        *(.rodata)
+    }
+ 
+    .data : ALIGN(4K) {
+        *(.data)
+    }
+ 
+    .bss : ALIGN(4K) {
+        *(COMMON)
+        *(.bss)
+    }
+}
diff --git a/src/main.zig b/src/main.zig
new file mode 100644
index 0000000..aa00104
--- /dev/null
+++ b/src/main.zig
@@ -0,0 +1,32 @@
+const console = @import("console.zig");
+
+const ALIGN = 1 << 0;
+const MEMINFO = 1 << 1;
+const MAGIC = 0x1BADB002;
+const FLAGS = ALIGN | MEMINFO;
+
+const MultibootHeader = packed struct {
+    magic: i32 = MAGIC,
+    flags: i32,
+    checksum: i32,
+};
+
+export var multiboot align(4) linksection(".multiboot") = MultibootHeader{
+    .flags = FLAGS,
+    .checksum = -(MAGIC + FLAGS),
+};
+
+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(.auto, kmain, .{});
+    //kmain();
+
+    while (true) {}
+}
+
+fn kmain() void {
+    console.initialize();
+    console.puts("Hello world!");
+}