src/kernel/drivers/graphics.s (view raw)
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.section .text.realmode
.global realmode_int10h
.code32
realmode_int10h:
push %ebp
mov %esp, %ebp
pushf
cli
pusha
# preserve protected mode IDT
sidtl (pmode_IDT)
mov %esp, %eax
mov %eax, %esi
mov %ebp, %eax
mov %eax, %edi
# setup real mode stack
mov $0xF000, %eax
mov %eax, %esp
mov %eax, %ebp
push %esi
push %edi
mov +16(%edi), %eax
push %eax
mov +12(%edi), %eax
push %eax
mov +8(%edi), %eax
push %eax
push %ebp
mov %esp, %ebp
# disable paging
mov %cr3, %eax
push %eax
mov %cr0, %eax
and $0x3FFFFFFD, %eax
mov %eax, %cr0
xor %eax, %eax
mov %eax, %cr3
# switch to 16 bit protected mode
ljmp $0x8, $pmode16
.code16
pmode16:
# setup segments
movw $0x10, %ax
movw %ax, %ss
movw %ax, %ds
movw %ax, %es
movw %ax, %fs
# load real mode interrupt descriptor table
lidt (realmode_IDT)
# switch to real mode
mov %cr0, %eax
and $0xFFFFFFFE, %eax
mov %eax, %cr0
ljmp $0, $realmode
realmode:
# setup segments
movw $0x0000, %ax
movw %ax, %ss
movw %ax, %ds
movw %ax, %es
movw %ax, %fs
sti
# load arguments
movw +4(%bp), %ax
movw +8(%bp), %bx
movw +12(%bp), %cx
int $0x10
cli
lidtl (pmode_IDT)
mov %cr0, %eax
or $0x00000001, %eax
mov %eax, %cr0
ljmp $0x18, $pmode32
.code32
pmode32:
# set data segments
movw $0x20, %ax
movw %ax, %ss
movw %ax, %ds
movw %ax, %es
movw %ax, %fs
# restore paging
pop %eax
mov %eax, %cr3
mov %cr0, %eax
or $0x80000010, %eax
mov %eax, %cr0
# clean up argument buffer
pop %ebp
add $12, %esp
# restore original stack
pop %ebp
pop %eax
mov %eax, %esp
popa
popf
# return
pop %ebp
ret
realmode_IDT:
.word 0x3FF
.int 0
pmode_IDT:
.word 0
.int 0