From c5ccb29b58f073e29148f08d82e970c4ea5147c8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maciej=20Krzy=C5=BCanowski?= <krzmaciek@gmail.com>
Date: Wed, 18 Sep 2024 20:30:35 +0200
Subject: [PATCH] Work on repairing multiboot with flat binary kernel

---
 build.zig     |  3 ++-
 src/boot.s    | 11 +++++++++++
 src/grub.cfg  |  2 +-
 src/linker.ld |  2 +-
 src/main.zig  | 17 -----------------
 5 files changed, 15 insertions(+), 20 deletions(-)
 create mode 100644 src/boot.s

diff --git a/build.zig b/build.zig
index d7549f3..8903f02 100644
--- a/build.zig
+++ b/build.zig
@@ -28,6 +28,7 @@ pub fn build(b: *std.Build) void {
         .code_model = .kernel,
     });
     kernel_elf.setLinkerScript(b.path("src/linker.ld"));
+    kernel_elf.addAssemblyFile(b.path("src/boot.s"));
 
     const kernel_elf_artifact = b.addInstallArtifact(kernel_elf, .{});
 
@@ -44,7 +45,7 @@ pub fn build(b: *std.Build) void {
     kernel_bin_copy.step.dependOn(&kernel_bin.step);
 
     const kernel_step_elf = b.step("elf", "Build the kernel ELF");
-    kernel_step_elf.dependOn(&kernel_elf.step);
+    kernel_step_elf.dependOn(&kernel_elf_artifact.step);
 
     const kernel_step_bin = b.step("bin", "Build the kernel BIN (with objcopy)");
     kernel_step_bin.dependOn(&kernel_bin_copy.step);
diff --git a/src/boot.s b/src/boot.s
new file mode 100644
index 0000000..2aa03f5
--- /dev/null
+++ b/src/boot.s
@@ -0,0 +1,11 @@
+.set ALIGN, 1<<0
+.set MEMINFO, 1<<1
+.set FLAGS, ALIGN
+.set MAGIC, 0x1BADB002
+.set CHECKSUM, -(MAGIC + FLAGS)
+
+.section .multiboot
+.align 4
+.long MAGIC
+.long FLAGS
+.long CHECKSUM
diff --git a/src/grub.cfg b/src/grub.cfg
index 7904bf7..ef006df 100644
--- a/src/grub.cfg
+++ b/src/grub.cfg
@@ -1,3 +1,3 @@
 menuentry "Zig Bare Bones" {
-	multiboot /boot/kernel.elf
+	multiboot /boot/kernel.bin
 }
diff --git a/src/linker.ld b/src/linker.ld
index d13c200..bd38da9 100644
--- a/src/linker.ld
+++ b/src/linker.ld
@@ -11,4 +11,4 @@ SECTIONS {
         *(COMMON)
         *(.bss)
     }
-}
\ No newline at end of file
+}
diff --git a/src/main.zig b/src/main.zig
index 11f024d..44b6d33 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -1,22 +1,5 @@
 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,
-    padding: u32 = 0,
-};
-
-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..];