X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?p=bootcensus;a=blobdiff_plain;f=src%2Fboot%2Fboot.s;h=4f0023a025b4c97d55cfda9e04914fe83e1c5f90;hp=8ba4a11f18f786d11b557e98537d1ac635a37581;hb=e253f9a0cad14f636a51f6211308491ab19dfbe5;hpb=60068d8dc031615c486e458d0426c659f72cb182 diff --git a/src/boot/boot.s b/src/boot/boot.s index 8ba4a11..4f0023a 100644 --- a/src/boot/boot.s +++ b/src/boot/boot.s @@ -1,12 +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 $0x7c00, %sp + mov $stack_top, %sp # use the code segment for data access mov %cs, %ax mov %ax, %ds @@ -14,12 +37,15 @@ mov %dl, drive_number - 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 @@ -37,10 +63,60 @@ 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 @@ -65,272 +141,148 @@ read_sectors: pop %bp ret - .set VAR_ATTEMPTS, -2 -str_rdsec_msg: .asciz "rdsec: " -str_cyl_msg: .asciz " C " -str_head_msg: .asciz " H " -str_sec_msg: .asciz " S " - # 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 - mov $str_rdsec_msg, %si - call print_str_num16 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 - mov $str_cyl_msg, %si - mov %cx, %ax - rol $2, %al - and $3, %al - ror $8, %ax - call print_str_num16 - - mov $str_head_msg, %si - xor %ax, %ax - mov %dh, %al - call print_str_num16 - - mov $str_sec_msg, %si - mov %cl, %al - and $0x3f, %ax - call print_str_num16 - # ah = 2 (read), al = 1 sectors 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 + # 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 0: pop %dx pop %cx - add $2, %sp pop %bp ret -str_read_error: .asciz "err read sector: " +str_read_error: .asciz "rderr:" abort_read: mov $str_read_error, %si - call print_str_num16 - cli - hlt - -cursor_x: .byte 0 - - # 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: - push %es pusha - pushw $0xb800 - pop %es - xor %di, %di - movb $0, cursor_x +0: mov (%si), %al + cmp $0, %al + jz end + call print_char + inc %si + jmp 0b + +end: popa + ret - push %si + # expects character in al +print_char: + push %es + + cmp $10, %ax + jnz 0f + mov $32, %ax + +0: pushw $0xb800 + pop %es + movw cursor_x, %di + shl $1, %di -0: mov (%si), %al mov %al, %es:(%di) movb $7, %es:1(%di) - inc %si - add $2, %di - incb cursor_x - cmp $0, %al - jnz 0b + incw cursor_x - pop %si - call ser_putstr - - popa pop %es ret # expects number in eax + .global print_num print_num: # save registers - push %es 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 - movb cursor_x, %al - xor %ah, %ah - shl $1, %ax - mov %ax, %di - -0: dec %si - mov (%si), %al - movb %al, %es:(%di) - call ser_putchar - inc %di - mov $7, %al - movb %al, %es:(%di) - inc %di - dec %cx - jnz 0b + call print_str # restore regs popa - pop %es - 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 -ser_putchar: - push %dx - - mov %al, %ah - # wait until the transmit register is empty - mov $UART_LSTAT, %dx -0: in %dx, %al - and $LST_TREG_EMPTY, %al - jz 0b - mov $UART_DATA, %dx - mov %ah, %al - out %al, %dx - - pop %dx - ret - - # expects a string in ds:si -ser_putstr: - mov (%si), %al - cmp $0, %al - jz 0f - call ser_putchar - inc %si - jmp ser_putstr -0: ret - - -drive_number: .byte 0 -numbuf: .space 8 .org 510 .byte 0x55 .byte 0xaa - boot2_addr: