X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?a=blobdiff_plain;ds=sidebyside;f=src%2Fboot%2Fboot.s;h=8ba4a11f18f786d11b557e98537d1ac635a37581;hb=60068d8dc031615c486e458d0426c659f72cb182;hp=499c38637e7936b7391df7cea937a9ed24ade657;hpb=ced643ce94dafd3d31e121435a40a967993e2be5;p=bootcensus

diff --git a/src/boot/boot.s b/src/boot/boot.s
index 499c386..8ba4a11 100644
--- a/src/boot/boot.s
+++ b/src/boot/boot.s
@@ -3,10 +3,10 @@
 
 	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 $0x7c00, %sp
 	# use the code segment for data access
 	mov %cs, %ax
 	mov %ax, %ds
@@ -14,7 +14,7 @@
 
 	mov %dl, drive_number
 
-	call clearscr
+	call setup_serial
 
 	mov $_boot2_size, %eax
 	call print_num
@@ -25,7 +25,7 @@
 	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
@@ -34,7 +34,7 @@
 	shr $4, %bx
 	mov %bx, %es
 	xor %bx, %bx
-	call read_sect
+	call read_sectors
 	jmp boot2_addr
 
 	cli
@@ -45,33 +45,48 @@
 	.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
 
 	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)
+
+.Lread_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
 	div %cx
@@ -87,12 +102,45 @@ read_sector:
 	and $0xc0, %cl
 	# sector num cl[0-5] is sidx % sectors_per_track (saved in ax)
 	inc %al
-	or %al, %cl 
+	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
+
+	# abort after 3 attempts
+	decw VAR_ATTEMPTS(%bp)
+	jz .Lread_fail
+
+	# error detected, reset controller and retry
+	xor %ah, %ah
+	int $0x13
+	jmp .Lread_try
+
+.Lread_fail:
+	mov 4(%bp), %ax
+	jmp abort_read
 
+.Lread_ok:
 	# increment es:bx accordingly (advance es if bx overflows)
 	add $512, %bx
 	jno 0f
@@ -100,26 +148,72 @@ read_sector:
 	add $4096, %ax
 	mov %ax, %es
 
-	pop %dx
+0:	pop %dx
 	pop %cx
+	add $2, %sp
 	pop %bp
 	ret
 
-clearscr:
+str_read_error: .asciz "err read sector: "
+
+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
+	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
+
+	# expects string pointer in ds:si
+print_str:
 	push %es
+	pusha
+
 	pushw $0xb800
 	pop %es
-	xor %eax, %eax
 	xor %di, %di
-	movl $500, %ecx
-	rep stosl
+	movb $0, cursor_x
+
+	push %si
+
+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
+
+	pop %si
+	call ser_putstr
+
+	popa
 	pop %es
 	ret
 
-# expects number in eax
+	# expects number in eax
 print_num:
-	# save es
+	# save registers
 	push %es
+	pusha
 
 	xor %cx, %cx
 	movw $numbuf, %si
@@ -137,11 +231,15 @@ print_num:
 	# print the backwards string
 	pushw $0xb800
 	pop %es
-	xor %di, %di
+	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)
@@ -149,12 +247,88 @@ print_num:
 	dec %cx
 	jnz 0b
 
-	# restore es
+	# 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 10
+numbuf: .space 8
 	.org 510
 	.byte 0x55
 	.byte 0xaa