Boot to 32-bit entry point

Set up 32-bit entry point via linker script.

Makefile

@@ -4,8 +4,8 @@
 all: loader.bin
 
 loader.bin: loader.elf
-	objcopy -O elf32-x86-64 $^ $@
+	objcopy -O elf32-i386 $^ $@
 
-loader.elf: loader.o
-	$(CXX) -o $@ $^
+loader.elf: arch/x64/boot.o arch/x64/loader.ld
+	$(CXX) -nostartfiles -static -nodefaultlibs -o $@ $^
 

arch/x64/boot.s

+
+.text
+.code32
+
+mb_magic = 0x1BADB002
+mb_flags = 0x00000001    # flags: 4k module alignment
+
+multiboot:
+    .long mb_magic
+    .long mb_flags
+    .long 0-mb_magic-mb_flags
+
+.globl start32
+start32:
+    jmp start32