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.set ALIGN, 1<<0
.set MEMINFO, 1<<1
.set FLAGS, ALIGN | MEMINFO
.set MAGIC, 0x1BADB002
.set CHECKSUM, -(MAGIC + FLAGS)
.section .multiboot.data, "aw"
.align 4
.long MAGIC
.long FLAGS
.long CHECKSUM
.section .bootstrap_stack, "aw", @nobits
stack_bottom:
.skip 16384
stack_top:
.section .bss, "aw", @nobits
.align 4096
boot_page_directory:
.skip 4096
boot_page_tables:
.skip 20480
.section .multiboot.text, "a"
.global _start
.type _start, @function
_start:
movl $(boot_page_tables - 0xC0000000), %edi
movl $0, %esi
movl $1023, %ecx
1: cmpl $_kernel_start, %esi
jl 2f
cmpl $(_kernel_end - 0xC0000000), %esi
jge 3f
movl %esi, %edx
orl $0x003, %edx
movl %edx, (%edi)
2: addl $4096, %esi
addl $4, %edi
loop 1b
3: movl $0xB8003, boot_page_tables - 0xC0000000 + 1023 * 4
movl $boot_page_tables, %ecx
subl $0xC0000000, %ecx
orl $0x003, %ecx
movl %ecx, boot_page_directory - 0xC0000000
movl %ecx, boot_page_directory - 0xC0000000 + 4 * 768
movl $boot_page_directory, %ecx
subl $0xC0000000, %ecx
movl %ecx, %cr3
movl %cr0, %ecx
orl $0x80000000, %ecx
movl %ecx, %cr0
lea 4f, %ecx
jmp *%ecx
.section .text
4: movl %cr3, %ecx
movl %ecx, %cr3
movl $stack_top, %esp
and $-16, %esp
pushl $boot_page_directory
pushl %ebx
pushl %eax
call i386_entry
cli
1: hlt
jmp 1b
.global enable_paging
.type enable_paging, @function
enable_paging:
pushl %ebp
movl %esp, %ebp
movl 8(%esp), %eax
movl %eax, %cr3
movl %cr0, %eax
orl $0x80000001, %eax
movl %eax, %cr0
movl $0, %eax
popl %ebp
ret
.global flush_gdt
.type flush_gdt, @function
flush_gdt:
cli
lgdt (gp)
movw $0x10, %ax
movw %ax, %ds
movw %ax, %es
movw %ax, %fs
movw %ax, %gs
movw %ax, %ss
jmp $0x08, $.flush
.flush:
ret
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