initial commit, asm operating system with the MikeOS bootloader

source/kernel.asm

@@ -0,0 +1,108 @@
+; ==================================================================
+; MikeOS -- The Mike Operating System kernel
+; Copyright (C) 2006 - 2022 MikeOS Developers -- see doc/LICENSE.TXT
+;
+; This is loaded from the drive by BOOTLOAD.BIN, as KERNEL.BIN.
+; First we have the system call vectors, which start at a static point
+; for programs to use. Following that is the main kernel code and
+; then additional system call code is included.
+; ==================================================================
+
+
+	BITS 16
+	CPU 386				; pusha offsets depends on a 386 or better
+					; FS and GS require a 386 or better
+
+	%DEFINE CRAWOS_VER '0.0.2'	; OS version number
+	%DEFINE CRAWOS_API_VER 1	; API version for programs to check
+
+
+	; This is the location in RAM for kernel disk operations, 24K
+	; after the point where the kernel has loaded; it's 8K in size,
+	; because external programs load after it at the 32K point:
+
+	disk_buffer	equ	24576
+
+
+; ------------------------------------------------------------------
+; OS CALL VECTORS -- Static locations for system call vectors
+; Note: these cannot be moved, or it'll break the calls!
+
+; The comments show exact locations of instructions in this section,
+; and are used in programs/mikedev.inc so that an external program can
+; use a CrawOS system call without having to know its exact position
+; in the kernel source code...
+
+os_call_vectors:
+	jmp os_main			; 0000h -- Called from bootloader
+	jmp os_print_string		; 0003h
+	jmp os_read_input
+	jmp os_display_input
+	jmp os_start_cli
+
+
+; ------------------------------------------------------------------
+; START OF MAIN KERNEL CODE
+
+os_main:
+	cli				; Clear interrupts
+	mov ax, 0
+	mov ss, ax			; Set stack segment and pointer
+	mov sp, 0FFFFh
+	sti				; Restore interrupts
+
+	cld				; The default direction for string operations
+					; will be 'up' - incrementing address in RAM
+
+	mov ax, 2000h			; Set all segments to match where kernel is loaded
+	mov ds, ax			; After this, we don't need to bother with
+	mov es, ax			; segments ever again, as MikeOS and its programs
+	mov fs, ax			; live entirely in 64K
+	mov gs, ax
+
+	cmp dl, 0
+	je no_change
+	mov [bootdev], dl		; Save boot device number
+	push es
+	mov ah, 8			; Get drive parameters
+	int 13h
+	pop es
+	and cx, 3Fh			; Maximum sector number
+	mov [SecsPerTrack], cx		; Sector numbers start at 1
+	movzx dx, dh			; Maximum head number
+	add dx, 1			; Head numbers start at 0 - add 1 for total
+	mov [Sides], dx
+
+no_change:
+	call os_clear_screen
+	call os_start_cli
+
+bootdev db 0
+SecsPerTrack dw 18
+Sides dw 2
+
+; ------------------------------------------------------------------
+; SYSTEM VARIABLES -- Settings for programs and system calls
+
+
+	; Time and date formatting
+
+	fmt_12_24	db 0		; Non-zero = 24-hr format
+
+	fmt_date	db 0, '/'	; 0, 1, 2 = M/D/Y, D/M/Y or Y/M/D
+					; Bit 7 = use name for months
+					; If bit 7 = 0, second byte = separator character
+
+
+; ------------------------------------------------------------------
+; FEATURES -- Code to pull into the kernel
+
+	%INCLUDE "features/screen.asm"
+	%INCLUDE "features/cli.asm"
+	%INCLUDE "features/power.asm"
+	%INCLUDE "features/strings.asm"
+
+; ==================================================================
+; END OF KERNEL
+; ==================================================================
+