boot.s

# set magic number to 0x1BADB002 to indentified by bootloader
.set MAGIC,   0x1BADB002

# set flags to 0
.set FLAGS, 0

# set the checksum
.set CHECKSUM, -(MAGIC + FLAGS)

# set multiboot enabled
.section .multiboot

# define type to long for each data defined as above
.long MAGIC
.long FLAGS
.long CHECKSUM

# set the stack bottom
stackBottom:

# define the maximum size of stack to 1024 bytes
.skip 1024

# set the stack top which grows from higher to lower
stackTop:

.section .text
.global _start
.type _start, @function

_start:
  # assign current stack pointer location to stackTop
  mov $stackTop, %esp

  # call the kernel main source
  call kernel_entry
  cli

# put system in infinite loop
hltLoop:
  hlt
  jmp hltLoop

.size _start, . - _start