My bootloader works, but doesn't load my kernel into memory - c

Question

I've looked more into creating my own bootloader, rather than using grub. I soon came up with this: It takes care of switching to 32bit pm, it loads my kernel from the disk & it jumps to it to execute it.
I'm catting my kernel & my bootloader like this: cat boot.bin kernel > img.bin
I'm assembling my bootloader like this: nasm -f bin boot.s -o boot.bin
i686-elf-ld -o kernel -Ttext=0x1000 kernel_entry.bin kernel.bin --oformat binary
I'm compiling my kernel like this: i686-elf-gcc *.o -Ttext=0x1000 -o kernel.bin -ffreestanding -O2 -nostdlib -lgcc
(*.o are all compiled C files which I compile like this: i686-elf-gcc -c file.c -o file.o -std=gnu99 -ffreestanding -O2 -Wall -Wextra
[org 0x7c00]
[bits 16]
xor ax, ax
mov ds, ax
mov es, ax
mov ss, ax
mov sp, 0x7c00
jmp 0:skip ; far jump
skip:
; load kernel
mov bx, 0x1000
mov dh, 17 ; reading 20 sectors should be enough ._.
mov dl, [BOOT_DRIVE]
call dsk_load
call load_kernel
dsk_load:
mov [SECTORS], dh
mov ch, 0x00 ; C = 0
mov dh, 0x00 ; H = 0
mov cl, 0x02 ; S = 2
next_group:
mov di, 5 ; retry 5 times
again:
mov ah, 0x02
mov al, [SECTORS]
int 0x13
jc maybe_retry
sub [SECTORS], al ; set remaining sectors
jz done
mov cl, 0x01 ; read sector 1
xor dh, 1 ; next head
jnz next_group
inc ch ; next cylinder
jmp next_group
maybe_retry:
mov ah, 0x00 ; reset drive
int 0x13
dec di
jnz again
jmp dsk_err ; we've tried too many times, give up
dsk_err:
mov bx, BOOTLOADER_SIG
call print
mov bx, DISK_READ_FAIL
call print
jmp $
done:
ret
; print string
print:
; print loop
print_loop:
mov ah, 0x0e
mov al, [bx] ; load current character
cmp al, 0
je print_return ; return when finished
int 0x10 ; print character
inc bx ; next character
jmp print_loop
print_return:
ret
load_kernel:
; If all that went well, we can switch to protected mode
cli
lgdt [gdt_descriptor]
mov eax, cr0
or eax, 0x1
mov cr0 , eax
jmp CODE_SEG:init_32_pm ; make a far jump
[bits 32]
init_32_pm:
set_up_stack:
mov esp, stack_end
mov ax, DATA_SEG
mov ds, ax
mov ss, ax
mov es, ax
mov fs, ax
mov gs, ax
jmp 0x1000 ; jump to kernel_entry.s
; our beloved gdt
gdt_start:
gdt_null: ; null descriptor
dd 0x0
dd 0x0
gdt_code: ; code segment descriptor
dw 0xffff ; limit (bits 0-15)
dw 0x0 ; base (bits 0-15)
db 0x0 ; base (bits 16-23)
db 10011010b ; 1st flags, type flags
db 11001111b ; 2nd flags, Limit (bits 16-19)
db 0x0 ; base (bits 24 - 31)
gdt_data: ; data segment descriptor
dw 0xffff ; limit (bits 0-15)
dw 0x0 ; base (bits 0-15)
db 0x0 ; base (bits 16 -23)
db 10010010b ; 1st flags, type flags
db 11001111b ; 2nd flags, Limit (bits 16-19)
db 0x0 ; base (bits 24 - 31)
gdt_end:
gdt_descriptor:
dw gdt_end - gdt_start - 1 ; gdt size
dd gdt_start ; gdt start address
; some handy constants
CODE_SEG equ gdt_code - gdt_start
DATA_SEG equ gdt_data - gdt_start
BOOT_DRIVE db 0
SECTORS db 0
BOOTLOADER_SIG db "------ bootloader ------", 0x0d, 0xa, 0
DISK_READ_FAIL db "An error occurred while loading the kernel! Please restart your computer.", 0x0d, 0xa, 0
times 510-($-$$) db 0
dw 0xaa55
section .bss
stack_begin:
resb 4096 ; 4kib stack
stack_end:
; 9 sectors
The code that resides over at 0x1000 is this:
; kernel_entry.s
[bits 32]
[extern kmain]
call kmain
jmp $
times 510-($-$$) db 0
dw 0xaa55
; 1 sectors
My bootloader doesn't crash but it does not load my kernel, which should print some things to the screen.
This is the kmain function:
void kmain(void)
{
/* Initialize terminal */
tty_init();
tty_puts("Hello kernel!", VGA_COLOR_LIGHT_CYAN);
}
Assume the tty functions are working, since they were doing just fine when testing with grub instead of my own bootloader. Does anyone know what's going on? (Testing in bochs shows no errors)