X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?p=bootcensus;a=blobdiff_plain;f=src%2Fboot%2Fboot2.s;h=894c7fa4cbaafa8d3bb5b487d586242df52c557f;hp=5aeebaa66a0e54dd2c043bbec8620a808d5c8c32;hb=e253f9a0cad14f636a51f6211308491ab19dfbe5;hpb=6ddbba6fc0185f6aaf64c661c303549eb088010f

diff --git a/src/boot/boot2.s b/src/boot/boot2.s
index 5aeebaa..894c7fa 100644
--- a/src/boot/boot2.s
+++ b/src/boot/boot2.s
@@ -1,5 +1,5 @@
 # pcboot - bootable PC demo/game kernel
-# Copyright (C) 2018  John Tsiombikas <nuclear@member.fsf.org>
+# Copyright (C) 2018-2019  John Tsiombikas <nuclear@member.fsf.org>
 # 
 # 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
@@ -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 $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
 
@@ -767,6 +811,8 @@ saved_eax: .long 0
 saved_es: .word 0
 saved_ds: .word 0
 saved_flags: .word 0
+saved_pic1_mask: .byte 0
+saved_pic2_mask: .byte 0
 
 	# drop back to unreal mode to call 16bit interrupt
 	.global int86
@@ -779,6 +825,16 @@ int86:
 	sidt (saved_idtr)
 	lidt (rmidt)
 
+	# save PIC masks
+	pushl $0
+	call get_pic_mask
+	add $4, %esp
+	mov %al, saved_pic1_mask
+	pushl $1
+	call get_pic_mask
+	add $4, %esp
+	mov %al, saved_pic2_mask
+
 	# modify the int instruction. do this here before the
 	# cs-load jumps, to let them flush the instruction cache
 	mov $int_op, %ebx
@@ -812,7 +868,6 @@ int86:
 	pop %es
 	pop %ds
 	# ignore fs and gs for now, don't think I'm going to need them
-	mov saved_esp, %esp
 
 	# move to the real-mode stack, accessible from ss=0
 	# just in case the BIOS call screws up our unreal mode
@@ -829,7 +884,7 @@ int_op:	int $0
 	mov %ds, saved_ds
 	mov %es, saved_es
 	pushfw
-	pop %ax
+	popw %ax
 	mov %ax, saved_flags
 
 	# re-enable protection
@@ -855,7 +910,11 @@ int_op:	int $0
 	pushw %ax
 	mov saved_es, %ax
 	pushw %ax
-	mov saved_flags, %ax
+	# grab the flags and replace the carry bit from the saved flags
+	pushfw
+	popw %ax
+	and $0xfffe, %ax
+	or saved_flags, %ax
 	pushw %ax
 	mov saved_eax, %eax
 	pushal
@@ -863,12 +922,43 @@ int_op:	int $0
 
 	# restore 32bit interrupt descriptor table
 	lidt (saved_idtr)
+
+	# restore PIC configuration
+	call init_pic
+
+	# restore IRQ masks
+	movzbl saved_pic1_mask, %eax
+	push %eax
+	pushl $0
+	call set_pic_mask
+	add $8, %esp
+
+	movzbl saved_pic2_mask, %eax
+	push %eax
+	pushl $1
+	call set_pic_mask
+	add $8, %esp
+
+	# keyboard voodoo: with some BIOS implementations, after returning from
+	# int13, there's (I guess) leftover data in the keyboard port and we
+	# can't receive any more keyboard interrupts afterwards. Reading from
+	# the keyboard data port (60h) once, seems to resolve this. And it's
+	# cheap enough, so why not... I give up.
+	push %eax
+	in $0x60, %al
+	pop %eax
+
 	sti
 	popal
 	pop %ebp
 	ret
 
 
+	.align 4
+	.global boot_drive_number
+boot_drive_number:
+	.long 0
+
 	# buffer used by the track loader ... to load tracks.
 	.align 16
 buffer: