Working basics

arch/i386/boot.S

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+	# Constants for multiboot
+	.set ALIGN,	1<<0		 # align on page boundaries
+	.set MEMINFO,	1<<1		 # memory map
+	.set FLAGS,	ALIGN | MEMINFO	 # for multiboot 'flag' field
+	.set MAGIC,	0x1BADB002	 # magic number for bootloader
+	.set CHECKSUM,	-(MAGIC + FLAGS) # checksum to prove we're multiboot
+
+	# Declare header for multiboot
+	.section .multiboot
+	.align 4
+	.long MAGIC
+	.long FLAGS
+	.long CHECKSUM
+
+	# Reserve stack for initial thread
+	.section .bss
+	.align 16
+stack_bottom:
+	.skip 16384 # 16K
+stack_top:
+
+	# Kernel entry
+	.section .text
+	.global _start
+	.type _start, @function
+_start:
+	movl $stack_top, %esp
+
+	# Call global constructors
+	call _init
+
+	# Start kernel
+	call kern_main
+
+	# Hang if kernel returns
+	cli
+1:	hlt
+	jmp 1b
+	.size _start, . - _start

arch/i386/crti.S

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+	.section .init
+	.global _init
+	.type _init, @function
+_init:
+	push %ebp
+	movl %esp, %ebp
+
+	.section .fini
+	.global _fini
+	.type _fini, @function
+_fini:
+	push %ebp
+	movl %esp, %ebp

arch/i386/crtn.S

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+	.section .init
+	popl %ebp
+	ret
+
+	.section .fini
+	popl %ebp
+	ret