From 4aad3cce1d22c39dfa9c0d360737fe6d92f38595 Mon Sep 17 00:00:00 2001
From: trimill <trimill@trimillxyz.org>
Date: Fri, 26 Jan 2024 22:29:49 -0500
Subject: [PATCH] added boilerplate (todo make it amd64)

---
 Makefile                 | 45 +++++++++++++++++++++++++
 grub.cfg                 |  7 ++++
 src/arch/amd64/boot.S    | 72 ++++++++++++++++++++++++++++++++++++++++
 src/arch/amd64/linker.ld | 25 ++++++++++++++
 src/kmain.c              |  5 +++
 5 files changed, 154 insertions(+)
 create mode 100644 grub.cfg
 create mode 100644 src/arch/amd64/linker.ld

diff --git a/Makefile b/Makefile
index e69de29..9e081c5 100644
--- a/Makefile
+++ b/Makefile
@@ -0,0 +1,45 @@
+CC=cc
+LD=ld
+
+CFLAGS=-ffreestanding -g -Wall -Wextra -pedantic -lgcc
+
+SRC_DIR=src
+INCLUDE_DIR=include
+BUILD_DIR=build
+
+K_BIN_NAME=kernel.bin
+ISO_NAME=os_image.iso
+
+C_SRC=$(shell find $(SRC_DIR) -type f -name "*.c")
+C_OBJ=$(patsubst %.c,$(BUILD_DIR)/%.o,$(C_SRC))
+
+H_SRC=$(shell find $(SRC_DIR) -type f -name "*.h") $(shell find $(INCLUDE_DIR) -type f -name "*.h")
+
+A_SRC=$(shell find $(SRC_DIR) -type f -name "*.S")
+A_OBJ=$(patsubst %.S,$(BUILD_DIR)/%.S.o,$(A_SRC))
+
+.PHONY: all clean
+
+all: $(BUILD_DIR)/$(ISO_NAME)
+
+clean:
+	rm -rf $(BUILD_DIR)/*
+
+$(A_OBJ): $(BUILD_DIR)/%.S.o : %.S
+	@mkdir -p $(@D)
+	nasm $< -f elf64 -o $@
+
+$(C_OBJ): $(BUILD_DIR)/%.o : %.c
+	@mkdir -p $(@D)
+	$(CC) -c $(CFLAGS) -o $@ $<
+
+$(BUILD_DIR)/$(K_BIN_NAME): $(SRC_DIR)/arch/amd64/linker.ld $(A_OBJ) $(C_OBJ) $(H_SRC)
+	@mkdir -p $(@D)
+	$(LD) -nmagic -o $(BUILD_DIR)/$(K_BIN_NAME) -T $(SRC_DIR)/arch/amd64/linker.ld $(A_OBJ) $(C_OBJ)
+
+$(BUILD_DIR)/$(ISO_NAME): $(BUILD_DIR)/$(K_BIN_NAME) grub.cfg
+	@mkdir -p $(@D)
+	@mkdir -p $(BUILD_DIR)/iso/boot/grub
+	cp grub.cfg $(BUILD_DIR)/iso/boot/grub
+	cp $(BUILD_DIR)/$(K_BIN_NAME) $(BUILD_DIR)/iso/boot
+	grub-mkrescue -o $(BUILD_DIR)/$(ISO_NAME) $(BUILD_DIR)/iso
diff --git a/grub.cfg b/grub.cfg
new file mode 100644
index 0000000..fedceac
--- /dev/null
+++ b/grub.cfg
@@ -0,0 +1,7 @@
+set timeout=1
+set default=0
+
+menuentry "corn" {
+    multiboot2 /boot/kernel.bin
+    boot
+}
diff --git a/src/arch/amd64/boot.S b/src/arch/amd64/boot.S
index e69de29..f7c24c4 100644
--- a/src/arch/amd64/boot.S
+++ b/src/arch/amd64/boot.S
@@ -0,0 +1,72 @@
+global start
+extern kmain
+bits 32
+
+; base, limit, access, flags
+%macro gdt_entry 4
+	db %2 & 0xff
+	db (%2 >> 8) & 0xff
+	db %1 & 0xff
+	db (%1 >> 8) & 0xff
+	db (%1 >> 16) & 0xff
+	db %3
+	db ((%2 >> 16) & 0x0f) | (%4 << 4)
+	db (%1 >> 24) & 0xff
+%endmacro
+
+section .multiboot
+align 8
+mb_start:
+; header
+dd 0xe85250d6
+dd 0
+dd mb_end - mb_start
+dd 0x100000000 - (0xe85250d6 + (mb_end - mb_start))
+; null tag
+dw 0
+dw 0
+dd 8
+;
+mb_end:
+
+section .bss
+align 16
+stack_start:
+	resb 16384
+stack_end:
+
+section .rodata
+align 16
+gdt_start:
+gdt_entry 0, 0, 0, 0
+gdt_entry 0, 0xFFFFF, 0x9A, 0xC
+gdt_entry 0, 0xFFFFF, 0x92, 0xC
+gdt_end:
+gdt_descriptor:
+	dw gdt_end - gdt_start - 1
+	dd gdt_start
+
+
+section .text
+align 8
+start:
+	cli
+	lgdt [gdt_descriptor]
+	jmp 0x08:after_lgdt
+after_lgdt:
+	mov ax, 0x10
+	mov ds, ax
+	mov ss, ax
+	mov es, ax
+	mov fs, ax
+	mov gs, ax
+	mov esp, stack_end
+	mov ebp, stack_end
+	sti
+	push ebx
+	call kmain
+	cli
+halt:
+	hlt
+	jmp halt
+
diff --git a/src/arch/amd64/linker.ld b/src/arch/amd64/linker.ld
new file mode 100644
index 0000000..4e796e2
--- /dev/null
+++ b/src/arch/amd64/linker.ld
@@ -0,0 +1,25 @@
+ENTRY(start)
+
+SECTIONS {
+    . = 1M;
+
+    .boot BLOCK(4K) : ALIGN(4K)
+    {
+        *(.multiboot)
+    }
+
+    .rodata BLOCK(4K) : ALIGN(4K)
+    {
+        *(.rodata)
+    }
+
+    .text BLOCK(4K) : ALIGN(4K)
+    {
+        *(.text)
+    }
+
+    .bss BLOCK(4K) : ALIGN(4K)
+    {
+        *(.bss)
+    }
+}
diff --git a/src/kmain.c b/src/kmain.c
index e69de29..6d45087 100644
--- a/src/kmain.c
+++ b/src/kmain.c
@@ -0,0 +1,5 @@
+void kmain(void *boot_info) {
+	while(1) {
+		asm("cli; hlt");
+	}
+}