X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?p=bootcensus;a=blobdiff_plain;f=src%2Fboot%2Fboot.s;h=4f0023a025b4c97d55cfda9e04914fe83e1c5f90;hp=22028005bf05bb09cbd62caf9af0e78e0539b119;hb=e253f9a0cad14f636a51f6211308491ab19dfbe5;hpb=7fe9b061ba7556ca9617cd061d16e2bc8e040f63 diff --git a/src/boot/boot.s b/src/boot/boot.s index 2202800..4f0023a 100644 --- a/src/boot/boot.s +++ b/src/boot/boot.s @@ -1,16 +1,35 @@ +# pcboot - bootable PC demo/game kernel +# Copyright (C) 2018-2019 John Tsiombikas +# +# This program is free software: you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation, either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY, without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see . + .code16 - .section .boot,"a" + .section .boot,"ax" + .set stack_top, 0x7be0 + .set read_retries, 0x7be8 + .set drive_number, 0x7bec + .set cursor_x, 0x7bee .set scratchbuf, 0x7bf0 .set scratchbuf_size, 16 boot: cli - cld # move stack to just below the code xor %ax, %ax mov %ax, %ss - mov $0x7bf0, %sp + mov $stack_top, %sp # use the code segment for data access mov %cs, %ax mov %ax, %ds @@ -18,7 +37,7 @@ boot: mov %dl, drive_number - call setup_serial + call get_drive_chs mov $loading_msg, %si call print_str @@ -26,9 +45,8 @@ boot: # load the second stage boot loader and jump to it mov $_boot2_size, %eax call print_num - mov $loading_msg2, %si - call print_str + mov $_boot2_size, %eax mov %eax, %ebx shr $9, %eax and $0x1ff, %ebx @@ -45,42 +63,64 @@ boot: call read_sectors jmp boot2_addr - .set SECT_PER_TRACK, 18 - - .set ARG_NSECT, 6 - .set ARG_SIDX, 4 - -loading_msg: .asciz "Loading " -loading_msg2: .asciz " bytes\n" +loading_msg: .asciz "\nLoad " +driveno_msg: .asciz "Drv:" + .global sect_per_track sect_per_track: .short 18 + .global num_cylinders num_cylinders: .short 80 + .global num_heads num_heads: .short 2 + .global heads_mask heads_mask: .byte 1 get_drive_chs: + mov $driveno_msg, %si + call print_str + xor %eax, %eax movb drive_number, %dl + mov %dl, %al + call print_num + mov $10, %al + call print_char + mov $8, %ah int $0x13 - jnc .Lok + jnc ok ret -.Lok: mov %ch, %al +ok: xor %eax, %eax + mov %ch, %al mov %cl, %ah rol $2, %ah + inc %ax and $0x3ff, %ax mov %ax, num_cylinders + and $0x3f, %cx mov %cx, sect_per_track - andw $0x3f, sect_per_track shr $8, %dx - mov %dx, num_heads - dec %dl mov %dl, heads_mask + inc %dx + mov %dx, num_heads + call print_num + mov $47, %al + call print_char + mov %dx, %ax + call print_num + mov $47, %al + call print_char + mov %cx, %ax + call print_num ret + + .set ARG_NSECT, 6 + .set ARG_SIDX, 4 + # read_sectors(first, num) read_sectors: push %bp @@ -101,19 +141,16 @@ read_sectors: pop %bp ret - .set VAR_ATTEMPTS, -2 - # read_sector(sidx) read_sector: push %bp mov %sp, %bp - sub $2, %sp push %cx push %dx - movw $3, VAR_ATTEMPTS(%bp) + movw $3, read_retries -.Lread_try: +read_try: # calculate the track (sidx / sectors_per_track) mov 4(%bp), %ax @@ -145,22 +182,22 @@ read_sector: mov $0x0201, %ax movb drive_number, %dl int $0x13 - jnc .Lread_ok + jnc read_ok # abort after 3 attempts - decw VAR_ATTEMPTS(%bp) - jz .Lread_fail + decw read_retries + jz read_fail # error detected, reset controller and retry xor %ah, %ah int $0x13 - jmp .Lread_try + jmp read_try -.Lread_fail: +read_fail: mov 4(%bp), %ax jmp abort_read -.Lread_ok: +read_ok: mov $46, %ax call print_char @@ -173,33 +210,19 @@ read_sector: 0: pop %dx pop %cx - add $2, %sp pop %bp ret -str_read_error: .asciz "read error, sector: " +str_read_error: .asciz "rderr:" abort_read: mov $str_read_error, %si - call print_str_num16 - hlt - - # prints a string (ds:si) followed by a number (eax) -print_str_num: - push %eax call print_str - pop %eax + and $0xffff, %eax call print_num mov $10, %al - call ser_putchar - ret - -print_str_num16: - push %eax - and $0xffff, %eax - call print_str_num - pop %eax - ret + call print_char + hlt # expects string pointer in ds:si print_str: @@ -207,18 +230,23 @@ print_str: 0: mov (%si), %al cmp $0, %al - jz .Lend + jz end call print_char inc %si jmp 0b -.Lend: popa +end: popa ret # expects character in al print_char: push %es - pushw $0xb800 + + cmp $10, %ax + jnz 0f + mov $32, %ax + +0: pushw $0xb800 pop %es movw cursor_x, %di shl $1, %di @@ -227,12 +255,9 @@ print_char: movb $7, %es:1(%di) incw cursor_x - call ser_putchar pop %es ret -cursor_x: .short 0 - # expects number in eax .global print_num print_num: @@ -242,14 +267,14 @@ print_num: movw $scratchbuf + scratchbuf_size, %si movb $0, (%si) mov $10, %ebx -.Lconvloop: +convloop: xor %edx, %edx div %ebx add $48, %dl dec %si mov %dl, (%si) cmp $0, %eax - jnz .Lconvloop + jnz convloop call print_str @@ -257,82 +282,7 @@ print_num: popa 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, 0x01 - .set FIFO_SEND_CLEAR, 0x04 - .set FIFO_RECV_CLEAR, 0x02 - .set MCTL_DTR, 0x01 - .set MCTL_RTS, 0x02 - .set MCTL_OUT2, 0x08 - .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, %al - or $FIFO_SEND_CLEAR, %al - or $FIFO_RECV_CLEAR, %al - mov $UART_FIFO, %dx - out %al, %dx - # assert RTS and DTR - mov $MCTL_DTR, %al - or $MCTL_RTS, %al - or $MCTL_OUT2, %al - mov $UART_MCTL, %dx - out %al, %dx - ret - - # expects a character in al - .global ser_putchar -ser_putchar: - push %dx - - cmp $10, %al - jnz 0f - push %ax - mov $13, %al - call ser_putchar - pop %ax - -0: mov %al, %ah - # wait until the transmit register is empty - mov $UART_LSTAT, %dx -.Lwait: in %dx, %al - and $LST_TREG_EMPTY, %al - jz .Lwait - mov $UART_DATA, %dx - mov %ah, %al - out %al, %dx - - pop %dx - ret - - -drive_number: .byte 0 .org 510 .byte 0x55 .byte 0xaa - boot2_addr: