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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_table0:
.skip 4096
.section .multiboot.text, "a"
.global _start
.type _start, @function
_start:
movl $(boot_page_table0 - 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 $(0x000B8000 | 0x003), boot_page_table0 - 0xC0000000 + 1023 * 4
movl $(boot_page_table0 - 0xC0000000 + 0x003), boot_page_directory - 0xC0000000
movl $(boot_page_table0 - 0xC0000000 + 0x003), boot_page_directory - 0xC0000000 + 768 * 4
movl $(boot_page_directory - 0xC0000000), %ecx
movl %ecx, %cr3
movl %cr0, %ecx
orl $0x80000000, %ecx
movl %ecx, %cr0
lea 4f, %ecx
jmp *%ecx
.section .text
4: movl $0, boot_page_directory + 0
movl %cr3, %ecx
movl %ecx, %cr3
movl $stack_top, %esp
and $-16, %esp
pushl %ebx
pushl %eax
call i386_entry
cli
1: hlt
jmp 1b
.global load_page_dir
.type load_page_dir, @function
load_page_dir:
pushl %ebp
movl %esp, %ebp
movl 8(%ebp), %eax
movl %eax, %cr3
movl %ebp, %esp
popl %ebp
ret
.global enable_paging
.type enable_paging, @function
enable_paging:
pushl %ebp
movl %esp, %ebp
movl %cr0, %eax
orl $0x80000001, %eax
movl %eax, %cr0
movl %ebp, %esp
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
.global flush_tss
.type flush_tss, @function
flush_tss:
movw $0x28, %ax
ltr %ax
ret
.global jump_userspace
.type jump_userspace, @function
jump_userspace:
movw $0x23, %ax
movw %ax, %ds
movw %ax, %es
movw %ax, %fs
movw %ax, %gs
pushl $0x23
pushl %esp
pushf
orl $0x200, (%esp)
pushl $0x1B
pushl test_user_function
iret
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