Bootable multiboot2 kernel

.gitignore

@@ -1,3 +1,8 @@
 dist/
 build/
-sysroot/
+sysroot/
+
+*.d
+*.o
+
+src/kernel/kernel

Makefile

@@ -7,8 +7,18 @@ SYSROOT := $(BUILDROOT)/sysroot
 DIST := $(BUILDROOT)/dist/mittos.iso
 
 $(DIST):
+	setup-grub.sh
 	grub-mkrescue -o $@ $(SYSROOT)
 
+kernel:
+ifeq ($(shell make -sqC src/kernel || echo 1), 1)
+	$(MAKE) -C src/kernel install
+endif
+
 install: $(DIST)
 
+clean:
+	rm -rf $(DIST)
+	$(MAKE) -C src/kernel clean
+
 .PHONY: install

make

@@ -1,3 +1,3 @@
 #!/usr/bin/env bash
 
-docker-compose -f toolchain/docker-compose.yml run --rm make "$@"
+docker-compose -f toolchain/docker-compose.yml run --rm -u $(id -u):$(id -g) make make "$@"

src/kernel/Link.ld

@@ -0,0 +1,10 @@
+ENTRY(_start)
+
+SECTIONS
+{
+    .text :
+    {
+        *(.multiboot)
+        *(.text)
+    }
+}

src/kernel/Makefile

@@ -0,0 +1,33 @@
+
+CC := x86_64-elf-gcc
+
+SRC := $(wildcard **/*.[cS])
+OBJ := $(patsubst %, %.o, $(basename $(SRC)))
+
+CFLAGS := -Wall -Wextra -pedantic -ffreestanding
+CFLAGS += -ggdb -O0
+ASFLAGS += -ggdb
+CPPFLAGS += -I include
+LDFLAGS := -n -nostdlib -lgcc -T Link.ld
+
+kernel: $(OBJ)
+	$(LINK.c) $^ -o $@
+
+DEP := $(OBJ:.o=.d)
+DEPFLAGS = -MT $@ -MMD -MP -MF $*.d
+$(OBJ): CPPFLAGS += $(DEPFLAGS)
+%.d: ;
+
+DESTDIR ?= $(BUILDROOT)/sysroot
+
+$(DESTDIR)$(PREFIX)/kernel: kernel
+	install -D kernel $(DESTDIR)$(PREFIX)/kernel
+
+install: $(DESTDIR)$(PREFIX)/kernel
+
+clean:
+	rm -rf $(OBJ) $(DEP) kernel
+
+.PHONY: install
+
+include $(DEP)

src/kernel/boot/boot.S

@@ -0,0 +1,7 @@
+.intel_syntax noprefix
+.section .text
+.global _start
+.code32
+_start:
+cli
+jmp $

src/kernel/boot/multiboot_header.S

@@ -0,0 +1,15 @@
+#include <multiboot.h>
+.section .multiboot
+
+.align 0x8
+Multiboot2Header:
+.long MBOOT2_MAGIC
+.long MBOOT2_ARCH
+.long MBOOT2_LENGTH
+.long MBOOT2_CHECKSUM
+
+.short 0
+.short 0
+.long 8
+
+Multiboot2HeaderEnd:

src/kernel/include/multiboot.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#define MBOOT2_MAGIC 0xE85250D6
+#define MBOOT2_REPLY 0x36D76289
+#define MBOOT2_ARCH 0
+#define MBOOT2_LENGTH (Multiboot2HeaderEnd - Multiboot2Header)
+#define MBOOT2_CHECKSUM -(MBOOT2_MAGIC + MBOOT2_ARCH + MBOOT2_LENGTH)

toolchain/gdbinit

@@ -13,4 +13,9 @@ end
 
 define reset
 monitor system_reset
+end
+
+python
+import os
+gdb.execute('file ' + os.environ['BUILDROOT'] + '/sysroot/kernel')
 end

toolchain/setup-grub.sh

@@ -0,0 +1,13 @@
+#!/bin/sh
+
+mkdir -p ${BUILDROOT}/sysroot/boot/grub
+
+cat > ${BUILDROOT}/sysroot/boot/grub/grub.cfg << EOF
+set timeout=1
+set default=0
+
+menuentry "mittos64" {
+    multiboot2 /kernel
+}
+
+EOF