X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?p=bootcensus;a=blobdiff_plain;f=src%2Fboot%2Fboot2.s;h=53dff6d218d37786870d0f34df567f8dd19162c5;hp=7470aef3aac5ca2d589039fab3d872c39f31f112;hb=81c11bdd80190ec319a82b0402173cfb65fcbf72;hpb=395502ec9dab0fda04bacb223f1fecdbbbdbe1b7 diff --git a/src/boot/boot2.s b/src/boot/boot2.s index 7470aef..53dff6d 100644 --- a/src/boot/boot2.s +++ b/src/boot/boot2.s @@ -1,4 +1,4 @@ -# pcboot - bootable PC demo/game kernel +# 256boss - bootable launcher for 256byte intros # Copyright (C) 2018 John Tsiombikas # # This program is free software: you can redistribute it and/or modify @@ -21,10 +21,17 @@ .section .boot2,"ax" .set main_load_addr, 0x100000 + .set drive_number, 0x7bec # make sure any BIOS call didn't re-enable interrupts cli + xor %eax, %eax + mov drive_number, %al + mov %eax, boot_drive_number + + call setup_serial + # enter unreal mode call unreal @@ -42,9 +49,6 @@ # load the whole program into memory starting at 1MB call load_main - #mov $0x13, %ax - #int $0x10 - # load initial GDT lgdt (gdt_lim) # load initial IDT @@ -227,11 +231,15 @@ ldloop: # the BIOS might have enabled interrupts cli - # just in case we were loaded from floppy, turn all floppy motors off + # if we were loaded from floppy, turn all floppy motors off + movb drive_number, %bl + and $0x80, %bl + jnz 0f mov $0x3f2, %dx in %dx, %al - and $0xf0, %al + and $0xf, %al out %al, %dx +0: mov $10, %ax call putchar @@ -248,7 +256,6 @@ rdfail_msg: .asciz "failed\n" read_retries: .short 0 - .set drive_number, 0x7bec read_track: # set es to the start of the destination buffer to allow reading in # full 64k chunks if necessary @@ -451,15 +458,52 @@ scrollup: clearscr: mov $0xb8000, %edi - xor %eax, %eax + # clear with white-on-black spaces + mov $0x07200720, %eax mov $1000, %ecx addr32 rep stosl ret .set UART_DATA, 0x3f8 + .set UART_DIVLO, 0x3f8 + .set UART_DIVHI, 0x3f9 + .set UART_FIFO, 0x3fa + .set UART_LCTL, 0x3fb + .set UART_MCTL, 0x3fc .set UART_LSTAT, 0x3fd + .set DIV_9600, 115200 / 9600 + .set LCTL_8N1, 0x03 + .set LCTL_DLAB, 0x80 + .set FIFO_ENABLE_CLEAR, 0x07 + .set MCTL_DTR_RTS_OUT2, 0x0b .set LST_TREG_EMPTY, 0x20 +setup_serial: + # set clock divisor + mov $LCTL_DLAB, %al + mov $UART_LCTL, %dx + out %al, %dx + mov $DIV_9600, %ax + mov $UART_DIVLO, %dx + out %al, %dx + shr $8, %ax + mov $UART_DIVHI, %dx + out %al, %dx + # set format 8n1 + mov $LCTL_8N1, %al + mov $UART_LCTL, %dx + out %al, %dx + # clear and enable fifo + mov $FIFO_ENABLE_CLEAR, %al + mov $UART_FIFO, %dx + out %al, %dx + # assert RTS and DTR + mov $MCTL_DTR_RTS_OUT2, %al + mov $UART_MCTL, %dx + out %al, %dx + ret + + ser_putchar: push %dx @@ -739,105 +783,18 @@ x88_fail: ret + # this part is placed at the very end of all low memory sections + .section .bootend,"ax" .global boot_mem_map_size boot_mem_map_size: .long 0 .global boot_mem_map boot_mem_map: .space 128 - -# this is not boot loader code. It's called later on by the main kernel -# code in 32bit protected mode. It's placed here because it needs to be -# located in base memory as it returns and runs in real mode. - .code32 .align 4 - # place to save the protected mode IDTR pseudo-descriptor - # with sidt, so that it can be restored before returning - .short 0 -saved_idtr: -idtlim: .short 0 -idtaddr:.long 0 - # real mode IDTR pseudo-descriptor pointing to the IVT at addr 0 - .short 0 -rmidt: .short 0x3ff + .global boot_drive_number +boot_drive_number: .long 0 -saved_esp: .long 0 -saved_ebp: .long 0 - - # drop back to unreal mode to call 16bit interrupt - .global int86 -int86: - push %ebp - mov %esp, %ebp - pushal - cli - # save protected mode IDTR and replace it with the real mode vectors - sidt (saved_idtr) - lidt (rmidt) - - # modify the int instruction do this here before the - # cs-load jumps, to let them flush the instruction cache - mov $int_op, %ebx - movb 8(%ebp), %al - movb %al, 1(%ebx) - - # long jump to load code selector for 16bit code (6) - ljmp $0x30,$0f -0: - .code16 - # disable protection - mov %cr0, %eax - and $0xfffe, %ax - mov %eax, %cr0 - # load cs <- 0 - ljmp $0,$0f -0: # zero data segments - xor %ax, %ax - mov %ax, %ds - mov %ax, %es - mov %ax, %ss - nop - - # load registers from the int86regs struct - mov %esp, saved_esp - mov %ebp, saved_ebp - mov 12(%ebp), %esp - popal - mov saved_esp, %esp - - # call 16bit interrupt -int_op: int $0 - - mov saved_ebp, %ebp - mov 12(%ebp), %esp - add $34, %esp - pushfw - pushal - mov saved_esp, %esp - - # re-enable protection - mov %cr0, %eax - or $1, %ax - mov %eax, %cr0 - # long jump to load code selector for 32bit code (1) - ljmp $0x8,$0f -0: - .code32 - # set data selector (2) to all segment regs - mov $0x10, %ax - mov %ax, %ds - mov %ax, %es - mov %ax, %ss - nop - - # restore 32bit interrupt descriptor table - lidt (saved_idtr) - sti - popal - pop %ebp - ret - - # buffer used by the track loader ... to load tracks. .align 16 buffer: