X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?a=blobdiff_plain;f=src%2Fboot%2Fboot.s;h=b976ec7f1c5f44554755d8bde61b67ff8b0a1b33;hb=eb934abaf0dcfa48589c6ac15f2a2ff235c5aea0;hp=499c38637e7936b7391df7cea937a9ed24ade657;hpb=ced643ce94dafd3d31e121435a40a967993e2be5;p=bootcensus diff --git a/src/boot/boot.s b/src/boot/boot.s index 499c386..b976ec7 100644 --- a/src/boot/boot.s +++ b/src/boot/boot.s @@ -1,12 +1,35 @@ +# pcboot - bootable PC demo/game kernel +# Copyright (C) 2018 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" + .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 the top of 512k - mov $0x7000, %ax + # move stack to just below the code + xor %ax, %ax mov %ax, %ss - xor %sp, %sp + mov $stack_top, %sp # use the code segment for data access mov %cs, %ax mov %ax, %ds @@ -14,18 +37,23 @@ mov %dl, drive_number - call clearscr + call setup_serial + + call get_drive_chs + mov $loading_msg, %si + call print_str + + # load the second stage boot loader and jump to it mov $_boot2_size, %eax call print_num - # load the second stage boot loader and jump to it mov $_boot2_size, %eax mov %eax, %ebx shr $9, %eax and $0x1ff, %ebx jz 0f - inc %eax + inc %ax 0: pushw %ax pushw $1 # set es to the start of the destination buffer to allow reading in @@ -34,29 +62,81 @@ shr $4, %bx mov %bx, %es xor %bx, %bx - call read_sect + call read_sectors jmp boot2_addr - cli - hlt +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 ok + ret + +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 + + shr $8, %dx + 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 SECT_PER_TRACK, 18 .set ARG_NSECT, 6 .set ARG_SIDX, 4 -# read_sect(first, num) -read_sect: +# read_sectors(first, num) +read_sectors: push %bp mov %sp, %bp mov ARG_SIDX(%bp), %ax - mov ARG_NSECT(%bp), %cx + xor %cx, %cx jmp 1f 0: push %ax call read_sector - add $2, %sp + pop %ax + inc %ax + inc %cx 1: cmp ARG_NSECT(%bp), %cx jnz 0b @@ -70,93 +150,207 @@ read_sector: push %cx push %dx + movw $3, read_retries + +read_try: # calculate the track (sidx / sectors_per_track) mov 4(%bp), %ax + xor %dx, %dx - mov $SECT_PER_TRACK, %cx + mov sect_per_track, %cx div %cx mov %ax, %cx - # save the remainder in ax - mov %dx, %ax + # save the remainder + push %dx # head in dh mov %cl, %dh - and $1, %dh - # cylinder (track/2) in ch [0-7] and cl[6,7]<-[8,9] - rol $7, %cx + and heads_mask, %dh + # cylinder (track/heads) in ch [0-7] and cl[6,7]<-[8,9] + push %dx + xor %dx, %dx + movw num_heads, %cx + div %cx + pop %dx + mov %ax, %cx + rol $8, %cx ror $2, %cl and $0xc0, %cl - # sector num cl[0-5] is sidx % sectors_per_track (saved in ax) + # sector num cl[0-5] is sidx % sectors_per_track + 1 + pop %ax inc %al - or %al, %cl + or %al, %cl + # ah = 2 (read), al = 1 sectors mov $0x0201, %ax movb drive_number, %dl int $0x13 + jnc read_ok + + # abort after 3 attempts + decw read_retries + jz read_fail + + # error detected, reset controller and retry + xor %ah, %ah + int $0x13 + jmp read_try + +read_fail: + mov 4(%bp), %ax + jmp abort_read + +read_ok: + mov $46, %ax + call print_char # increment es:bx accordingly (advance es if bx overflows) add $512, %bx - jno 0f + jnc 0f mov %es, %ax add $4096, %ax mov %ax, %es - pop %dx +0: pop %dx pop %cx pop %bp ret -clearscr: +str_read_error: .asciz "rderr:" + +abort_read: + mov $str_read_error, %si + call print_str + and $0xffff, %eax + call print_num + mov $10, %al + call print_char + hlt + + # expects string pointer in ds:si +print_str: + pusha + +0: mov (%si), %al + cmp $0, %al + jz end + call print_char + inc %si + jmp 0b + +end: popa + ret + + # expects character in al +print_char: push %es - pushw $0xb800 + + push %ax + cmp $10, %ax + jnz 0f + mov $32, %ax + +0: pushw $0xb800 pop %es - xor %eax, %eax - xor %di, %di - movl $500, %ecx - rep stosl + movw cursor_x, %di + shl $1, %di + + mov %al, %es:(%di) + movb $7, %es:1(%di) + incw cursor_x + + pop %ax + call ser_putchar pop %es ret -# expects number in eax + # expects number in eax + .global print_num print_num: - # save es - push %es + # save registers + pusha - xor %cx, %cx - movw $numbuf, %si + movw $scratchbuf + scratchbuf_size, %si + movb $0, (%si) mov $10, %ebx - -0: xor %edx, %edx +convloop: + xor %edx, %edx div %ebx add $48, %dl + dec %si mov %dl, (%si) - inc %si - inc %cx cmp $0, %eax - jnz 0b + jnz convloop - # print the backwards string - pushw $0xb800 - pop %es - xor %di, %di - -0: dec %si - mov (%si), %al - movb %al, %es:(%di) - inc %di - mov $7, %al - movb %al, %es:(%di) - inc %di - dec %cx - jnz 0b + call print_str - # restore es - pop %es + # restore regs + popa ret -drive_number: .byte 0 -numbuf: .space 10 + .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 + + # expects a character in al +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 +wait: in %dx, %al + and $LST_TREG_EMPTY, %al + jz wait + mov $UART_DATA, %dx + mov %ah, %al + out %al, %dx + + pop %dx + ret + .org 510 .byte 0x55 .byte 0xaa - boot2_addr: