added README and license

[bootcensus] / src / boot / boot2.s

diff --git a/src/boot/boot2.s b/src/boot/boot2.s
index 86ee611..f27d940 100644 (file)
--- a/src/boot/boot2.s
+++ b/src/boot/boot2.s
@@ -1,13 +1,31 @@
+# pcboot - bootable PC demo/game kernel
+# Copyright (C) 2018  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
+# 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 <https://www.gnu.org/licenses/>.
+
 # this is the second-stage boot loader
        .code16
        .section .boot2,"a"
 
-       .extern print_num
        .extern ser_putchar
 
        mov $0x13, %ax
        int $0x10
 
+       movb $10, %al
+       call ser_putchar
+
        # copy palette
        mov $logo_pal, %si
        xor %cl, %cl
@@ -16,8 +34,8 @@
        mov $0x3c8, %dx
        movb %cl, %al
        outb %al, %dx
-       #DBG
-       call print_num
+       #### DBG
+       call ser_print_num
        mov $58, %al
        call ser_putchar
        mov $32, %al
@@ -30,8 +48,8 @@
        inc %si
        shr $2, %al
        outb %al, %dx
-       #DBG
-       call print_num
+       #### DBG
+       call ser_print_num
        mov $32, %al
        call ser_putchar
        xor %eax, %eax
@@ -41,8 +59,8 @@
        inc %si
        shr $2, %al
        outb %al, %dx
-       #DBG
-       call print_num
+       #### DBG
+       call ser_print_num
        mov $32, %al
        call ser_putchar
        xor %eax, %eax
@@ -52,12 +70,10 @@
        inc %si
        shr $2, %al
        outb %al, %dx
-       #DBG
-       call print_num
+       #### DBG
+       call ser_print_num
        mov $32, %al
        call ser_putchar
-       mov $13, %al
-       call ser_putchar
        mov $10, %al
        call ser_putchar
        xor %eax, %eax
@@ -79,6 +95,46 @@
        cli
        hlt
 
+       # expects string pointer in ds:si
+ser_print_str:
+       pusha
+
+0:     mov (%si), %al
+       cmp $0, %al
+       jz .Lend
+       call ser_putchar
+       inc %si
+       jmp 0b
+
+.Lend: popa
+       ret
+
+
+       # expects number in eax
+ser_print_num:
+       # save registers
+       pusha
+
+       movw $numbuf + 16, %si
+       movb $0, (%si)
+       mov $10, %ebx
+.Lconvloop:
+       xor %edx, %edx
+       div %ebx
+       add $48, %dl
+       dec %si
+       mov %dl, (%si)
+       cmp $0, %eax
+       jnz .Lconvloop
+
+       call ser_print_str
+
+       # restore regs
+       popa
+       ret
+
+numbuf: .space 16
+
 logo_pal:
        .incbin "logo.pal"