From 9cc2436d33192e06ce2a227441f19f5a5e5ed2cb Mon Sep 17 00:00:00 2001
From: Josh Holtrop <jholtrop@gmail.com>
Date: Thu, 3 Mar 2022 11:24:05 -0500
Subject: [PATCH] Add D barebones sources and Makefile

---
 .gitignore    |  4 ++++
 Makefile      | 21 +++++++++++++++++++++
 boot.S        | 28 ++++++++++++++++++++++++++++
 kernel_main.d |  5 +++++
 link.ld       | 38 ++++++++++++++++++++++++++++++++++++++
 5 files changed, 96 insertions(+)
 create mode 100644 Makefile
 create mode 100644 boot.S
 create mode 100644 kernel_main.d
 create mode 100644 link.ld

diff --git a/.gitignore b/.gitignore
index 3f71dff..a3dc2ad 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,3 +3,7 @@
 /build-*/
 /gcc-*/
 /binutils-*/
+/*.o
+/*.elf
+/image/
+/image.img
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..40fda66
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,21 @@
+.PHONY: kernel
+kernel:
+	./i686-elf-gcc/bin/i686-elf-gcc -c -o boot.o -ffreestanding boot.S
+	ldc2 -march=x86 -mcpu=i686 --betterC -c -of=kernel_main.o kernel_main.d
+	./i686-elf-gcc/bin/i686-elf-gcc -o kernel.elf -ffreestanding -nostdlib -T link.ld boot.o kernel_main.o
+
+.PHONY: image
+image: kernel
+	rm -rf image
+	mkdir -p image/iso/boot/grub
+	echo 'set default="0"' >image/iso/boot/grub/grub.cfg
+	echo 'set timeout=1' >>image/iso/boot/grub/grub.cfg
+	echo 'menuentry "MyKernel" {' >>image/iso/boot/grub/grub.cfg
+	echo '  insmod multiboot' >>image/iso/boot/grub/grub.cfg
+	echo '  multiboot /kernel.elf' >>image/iso/boot/grub/grub.cfg
+	echo '}' >>image/iso/boot/grub/grub.cfg
+	cp kernel.elf image/iso
+	grub-mkrescue -o image.img image/iso
+
+run: image
+	qemu-system-x86_64 -hda image.img
diff --git a/boot.S b/boot.S
new file mode 100644
index 0000000..a24e6a5
--- /dev/null
+++ b/boot.S
@@ -0,0 +1,28 @@
+#define MAGIC 0x1BADB002
+#define FLAGS 0x3
+
+.section .multiboot
+MultiBootHeader:
+    .long MAGIC
+    .long FLAGS
+    .long -(MAGIC + FLAGS)
+
+.section .text
+.global mykernel_start
+.type mykernel_start, @function
+mykernel_start:
+    /* Set stack pointer. */
+    mov $_stack_end, %esp
+
+    /* Jump to C. */
+    push $0
+    push $0
+    push $0
+    push %ebx
+    call mykernel_main
+
+    cli
+1:  hlt
+    jmp 1b
+
+.size mykernel_start, . - mykernel_start
diff --git a/kernel_main.d b/kernel_main.d
new file mode 100644
index 0000000..9688603
--- /dev/null
+++ b/kernel_main.d
@@ -0,0 +1,5 @@
+extern (C) void mykernel_main() {
+    ubyte * vidmem = cast(ubyte *) 0xB8000u;
+    vidmem[0] = 'D';
+    vidmem[1] = 0x7u;
+}
diff --git a/link.ld b/link.ld
new file mode 100644
index 0000000..775fdaf
--- /dev/null
+++ b/link.ld
@@ -0,0 +1,38 @@
+ENTRY(mykernel_start)
+
+SECTIONS
+{
+    . = 1M;
+
+    .text BLOCK(4K) : ALIGN(4K)
+    {
+        *(.multiboot)
+        *(.text)
+    }
+
+    .rodata BLOCK(4K) : ALIGN(4K)
+    {
+        *(.rodata)
+    }
+
+    .data BLOCK(4K) : ALIGN(4K)
+    {
+        *(.data)
+    }
+
+    _stack_size = 16K;
+    .stack (NOLOAD) : ALIGN(4K)
+    {
+        _stack_start = .;
+        . = . + _stack_size;
+        _stack_end = .;
+    }
+
+    .bss BLOCK(4K) : ALIGN(4K)
+    {
+        *(COMMON)
+        *(.bss)
+    }
+
+    . = ALIGN(4K);
+}