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.code32
.extern begin_long_mode
.section .boot32.text, "a"
.set STACK_TOP, 0x03008000
.global _start
_start:
cli
mov $STACK_TOP, %esp
pushl $0
pushl %eax
pushl $0
pushl %ebx
call setup_page_tables
call enable_paging
lgdt gdtp
ljmp $0x08, $begin_long_mode
setup_page_tables:
/* first 2mb */
mov $pt_lvl3, %eax
or $0x3, %eax
mov %eax, pt_lvl4
mov $pt_lvl2, %eax
or $0x3, %eax
mov %eax, pt_lvl3
xor %ecx, %ecx
1:
movl $0x00200000, %eax
mul %ecx
or $0b10000011, %eax
movl $pt_lvl2, %edx
leal (%edx, %ecx, 8), %edx
movl %eax, (%edx)
inc %ecx
cmp $25, %ecx
jne 1b
/* first 2mb in hh */
mov $pt_lvl3_hh, %eax
or $0x3, %eax
mov %eax, pt_lvl4 + 4096 - 8
mov $pt_lvl2_hh, %eax
or $0x3, %eax
mov %eax, pt_lvl3_hh + 4096 - 16
xor %ecx, %ecx
2:
movl $0x00200000, %eax
mul %ecx
or $0b10000011, %eax
movl $pt_lvl2_hh, %edx
leal (%edx, %ecx, 8), %edx
movl %eax, (%edx)
inc %ecx
cmp $25, %ecx
jne 2b
ret
.global enable_paging
enable_paging:
/* enable PAE */
mov %cr4, %edx
or $1<<5 ,%edx
mov %edx, %cr4
/* set LME (long mode enable) */
mov $0xC0000080, %ecx
rdmsr
or $1<<8, %eax
wrmsr
/* pt_lvl4 */
mov $pt_lvl4, %eax
mov %eax, %cr3
/* enable paging (+ protected mode if not already enabled) */
mov %cr0, %eax
or $1<<31 + 1<<0, %eax
mov %eax, %cr0
ret
.section .boot32.rodata
gdt:
gdt_null = . - gdt
.quad 0
gdt_code = . - gdt
.long 0xFFFF
.byte 0
.byte 0x9A
.byte 0xAF
.byte 0
gdt_data = . - gdt
.long 0xFFFF
.byte 0
.byte 0x92
.byte 0xAF
.byte 0
.global gdtp
gdtp:
.word . - gdt - 1
.quad gdt
.section .boot32.bss
.align 4096
pt_lvl4:
.skip 4096
pt_lvl3:
.skip 4096
pt_lvl3_hh:
.skip 4096
pt_lvl2:
.skip 4096
pt_lvl2_hh:
.skip 4096
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