write linker script for MBR sector, as well as test MBR code

Makefile

@@ -1,11 +1,19 @@
 CC					=	gcc
+AS					=	as
+LD					=	ld
+OBJCOPY				=	objcopy
 CLFAGS				=	-g -Wall
+ASFLAGS				=
 LDFLAGS				=	-g
 
+SRC_DIR				=	src
+OBJ_DIR				=	obj
+BIN_DIR				=	bin
+
 UID					:=	$(shell id -u)
 GID					:=	$(shell id -g)
 
-DISK				=	bin/disk.img
+DISK				=	$(BIN_DIR)/disk.img
 DISK_SIZE			=	268435456
 DISK_LOOP			=	/dev/loop690
 
@@ -84,6 +92,19 @@ $(DISK): mnt
 	sudo losetup -d $(PART3_LOOP)
 	sudo losetup -d $(DISK_LOOP)
 
+$(OBJ_DIR)/%.o: $(SRC_DIR)/%.s
+	$(AS) $(ASFLAGS) -o $@ $<
+	$(OBJCOPY) --remove-section .note.gnu.property $@
+
+MBR_TEST_OBJ		=	obj/mbr_test.o
+
+mbr_test: $(MBR_TEST_OBJ) $(DISK)
+	$(LD) -T src/mbr_test.ld -o $(BIN_DIR)/mbr_test.bin $(MBR_TEST_OBJ)
+
+mbr_test_clean:
+	rm $(BIN_DIR)/mbr_test.bin
+	rm $(OBJ_DIR)/mbr_test.o
+
 clean:
 	rm -f bin/*
 	rm -f obj/*

src/mbr_test.ld

@@ -0,0 +1,31 @@
+MEMORY
+{
+    BOOTLOADER  (RWX)   :   ORIGIN = 0x7C00, LENGTH = 440
+    UNIQUE_ID   (R)     :   ORIGIN = 0x7DB8, LENGTH = 4
+    RESERVED    (R)     :   ORIGIN = 0x7DBC, LENGTH = 2
+    PTABLE      (R)     :   ORIGIN = 0x7DBE, LENGTH = 64
+    MBR_MAGIC   (R)     :   ORIGIN = 0x7DFE, LENGTH = 2
+}
+
+SECTIONS
+{
+    . = 0x7C00;
+    .text : {
+        *(.text)
+        *(.data)
+    } > BOOTLOADER
+
+    .unique_id : {
+        SHORT(0x1234)
+    } > UNIQUE_ID
+
+    .reserved : {
+        SHORT(0x0000)
+    } > RESERVED
+
+    .mbr_magic : {
+        SHORT(0xAA55)
+    } > MBR_MAGIC
+}
+
+OUTPUT_FORMAT(binary)

src/mbr_test.s

@@ -0,0 +1,21 @@
+.section .text
+.code16
+
+    mov $0x07C0, %ax
+    mov %ax, %dx
+
+    mov msg, %si
+.putc_loop:
+    lodsb
+    or %al, %al
+    jz .halt
+
+    mov $0x0E, %ah
+    mov $0, %al
+    int $0x10
+    jmp .putc_loop
+.halt:
+    hlt
+
+.section .data
+msg:    .asciz "Test MBR hello world\x0D\x0A" # len 22