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Setting up a VESA video mode

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This commit is contained in:
Thomas Oltmann 2025-07-16 04:45:32 +02:00
parent cdfef627fa
commit b8a175b78f
1 changed files with 113 additions and 0 deletions
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113
lboot.S
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@ -116,8 +116,13 @@ _start: cli
call read_file
mov %ebx, bb_ird_ptr
mov $msg_vbe, %si
call print
call vbe_setup
mov $msg_long, %si
call print
jmp hang // REMOVE ME
call long
jmp hang
@ -498,6 +503,112 @@ dump: push %eax
pop %eax
ret
vbe_setup:
push %ecx
push %esi
push %bp
mov %sp, %bp
call vbe_getinfo
mov vbe_info+14, %si
mov vbe_info+16, %cx
mov %cx, %fs
_vbenext: mov %fs:(%si), %cx
add $2, %si
cmp $0xFFFF, %cx
je _vbedone
call vbe_getmode
testw $0x80, tx_buf
jz _vbenext
mov %cx, %bx
and $0x0FFF, %bx
or $0x4000, %bx
call vbe_setmode
jmp _vbedone
_vbedone:
leave
pop %esi
pop %ecx
ret
vbe_getinfo:
push %eax
push %edi
push %bp
mov %sp, %bp
mov $0x4F00, %ax
mov $vbe_info, %di
int $0x10
cmp $0x4F, %ax
je 1f
mov $msg_vbeerr, %si
call print
jmp hang
1:
cmpl $0x41534556, vbe_info // "VESA"
je 1f
mov $msg_vbeerr, %si
call print
jmp hang
1: leave
pop %edi
pop %eax
ret
vbe_getmode:
push %eax
push %edi
push %bp
mov %sp, %bp
mov $0x4F01, %ax
mov $tx_buf, %di
int $0x10
cmp $0x4F, %ax
je 1f
mov $msg_vbeerr, %si
call print
jmp hang
1: leave
pop %edi
pop %eax
ret
vbe_setmode:
push %eax
push %bp
mov %sp, %bp
mov $0x4F02, %ax
int $0x10
cmp $0x4F, %ax
je 1f
mov $msg_vbeerr, %si
call print
jmp hang
1: leave
pop %eax
ret
vbe_info:
.ascii "VBE2"
.skip 512 - 4
// long: Enter long mode
long:
// Enable PAE
@ -594,9 +705,11 @@ msg_getmap: .asciz " * Memory Map\r\n"
msg_mkheap: .asciz " * Making Space\r\n"
msg_paging: .asciz " * Paging\r\n"
msg_read: .asciz " * Retrieving\r\n"
msg_vbe: .asciz " * Framebuffer\r\n"
msg_long: .asciz " * Long Mode\r\n"
msg_pserr: .asciz "panic: Missing !PXE structure.\r\n"
msg_pcerr: .asciz "panic: PXE call failed.\r\n"
msg_vbeerr: .asciz "panic: VBE call failed.\r\n"
msg_memerr: .asciz "panic: Out of heap space.\r\n"
msg_topen: .asciz "tftp_open\r\n"
msg_tclose: .asciz "tftp_close\r\n"