serial debugging in first stage loader

diff --git a/Makefile b/Makefile
index 9117c3f..500acb6 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -45,4 +45,4 @@ cleandep:
 
 .PHONY: run
 run: $(bin)
-       qemu-system-i386 -fda floppy.img
+       qemu-system-i386 -fda floppy.img -serial file:serial.log

diff --git a/src/boot/boot.s b/src/boot/boot.s
index ac4a424..8ba4a11 100644 (file)
--- a/src/boot/boot.s
+++ b/src/boot/boot.s
@@ -14,7 +14,7 @@
 
        mov %dl, drive_number
 
-       call clearscr
+       call setup_serial
 
        mov $_boot2_size, %eax
        call print_num
@@ -66,6 +66,10 @@ read_sectors:
        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:
@@ -80,6 +84,9 @@ read_sector:
 .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
@@ -95,7 +102,25 @@ 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
@@ -129,41 +154,45 @@ read_sector:
        pop %bp
        ret
 
-str_read_error: .asciz "Failed to read sector: "
+str_read_error: .asciz "err read sector: "
 
 abort_read:
-       push %ax
        mov $str_read_error, %si
-       call print_str
-
-       xor %eax, %eax
-       pop %ax
-       call print_num
-
+       call print_str_num16
        cli
        hlt
 
-clearscr:
-       push %es
-       pushw $0xb800
-       pop %es
-       xor %eax, %eax
-       xor %di, %di
-       movl $500, %ecx
-       rep stosl
-       pop %es
+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
 
-cursor_x: .byte 0
+print_str_num16:
+       push %eax
+       and $0xffff, %eax
+       call print_str_num
+       pop %eax
+       ret
 
-# expects string pointer in ds:si
+       # expects string pointer in ds:si
 print_str:
        push %es
+       pusha
+
        pushw $0xb800
        pop %es
        xor %di, %di
        movb $0, cursor_x
 
+       push %si
+
 0:     mov (%si), %al
        mov %al, %es:(%di)
        movb $7, %es:1(%di)
@@ -173,13 +202,18 @@ print_str:
        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
@@ -205,6 +239,7 @@ print_num:
 0:     dec %si
        mov (%si), %al
        movb %al, %es:(%di)
+       call ser_putchar
        inc %di
        mov $7, %al
        movb %al, %es:(%di)
@@ -212,12 +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