From eedb54d946e0bac346e0b737ccbd7f224f0cd9a4 Mon Sep 17 00:00:00 2001 From: Eleni Maria Stea Date: Tue, 5 Jan 2021 15:41:53 +0200 Subject: [PATCH] disable/enable interrupts to stop the bios from reading the keyboard before we have the chance to do it... --- bb.asm | 48 +++++++++++++++++++++++++++++++++++++----------- 1 file changed, 37 insertions(+), 11 deletions(-) diff --git a/bb.asm b/bb.asm index 3f4bcd1..d9d1fe6 100644 --- a/bb.asm +++ b/bb.asm @@ -37,17 +37,6 @@ start: mov ax, 3 call clearscreen -; waiting for keypress -; x86 has 2 special instructions to read/write from I/O -; devices: in and out (because some processors have different -; address spaces for devices and for memory, arm not) -.key_wait: - in al, 64h ; 60h = keyb data port, 64h = keyb status port - and al, 1 ; 1 = OUTBUF_FULL = the keyb controller out buf is full - jz .key_wait - - in al, 60h ; reads the keyb that was pressed to reset the flag - ; load 2nd sector from boot device and jump to it ; bios helpers, 13h = disk io mov ax, 0 @@ -143,5 +132,42 @@ sector_2: test al, 3fh ; test with 3fh to keep the lowest 6 bits of al jnz .pal_loop +; disable all interrupts (for bios to not read the keyboard) + cli + +main_loop: + mov ax, 0a000h + mov ds, ax + xor bx, bx ; mov bx, 0 to clear the register +.static_loop: + call rand + and ax, 3fh ; last six bits of eax (see rand) + mov [bx], al + inc bx + cmp bx, 64000 ; num pixels + jnz .static_loop + + in al, 64h ; 60h = keyb data port, 64h = keyb status port + and al, 1 ; 1 = OUTBUF_FULL = the keyb controller out buf is full + jz main_loop ; no key pressed, loop back + in al, 60h ; reads the keyb that was pressed to reset the flag + +; re-enable all interrupts + sti + .inf_loop: jmp .inf_loop + +; random number generator +; by nuclear +rand: + mov eax, [randval] + mul dword [randmul] + add eax, 12345 + and eax, 0x7fffffff + mov [randval], eax + shr eax, 16 + ret + +randmul dd 1103515245 +randval dd 0ace1h -- 1.7.10.4