From 56f9df5773b9f5c9c8a23c6b29e58185f17072df Mon Sep 17 00:00:00 2001 From: Ain <41307858+nero@users.noreply.github.com> Date: Sun, 29 Sep 2019 08:52:00 +0000 Subject: [PATCH] Throw DOS api away, re-layout memory to fit CP/M model --- boot/fat.asm | 60 +++++++++----------------------- kernel/chario.asm | 35 ------------------- kernel/drive.asm | 53 ---------------------------- kernel/intr.asm | 30 ---------------- kernel/main.asm | 89 ++++++++++++++++++++++------------------------- 5 files changed, 57 insertions(+), 210 deletions(-) delete mode 100644 kernel/chario.asm delete mode 100644 kernel/drive.asm delete mode 100644 kernel/intr.asm diff --git a/boot/fat.asm b/boot/fat.asm index 6966f59..6043a66 100644 --- a/boot/fat.asm +++ b/boot/fat.asm @@ -1,13 +1,15 @@ ; Memory layout: -%define self 0x00600 ; 1 sector -%define fattab 0x01000 ; variable size -%define rootdir 0x06000 ; variable size -%define config 0x07800 -%define prog 0x07C00 +%define segment 0x00100 + +%define self (0x7C00-(segment<<4)) ; 1 sector +%define fattab (self+0x200) ; variable size +%define rootdir 0x00100 ; variable size +%define prog 0x0F000 ; 4K at the end for OS org self jmp short init +dw self cluster_offset: dw 0 @@ -58,23 +60,16 @@ times (62 - ($-$$)) nop init: cli - - ; Stack grows down from 64k - xor ax, ax - mov ss, ax - mov sp, ax - - ; Relocate from [prog] to [self] - mov ds, ax - mov es, ax - mov si, prog - mov di, self - mov cx, 0x100 - rep movsw - - jmp 0:main + jmp segment:main main: + ; Stack grows down from 64k + mov ax, cs + mov ss, ax + mov sp, prog + mov ds, ax + mov es, ax + mov [fdc.drv], dl ; save drive number in fd sti @@ -110,31 +105,10 @@ main: mov bp, 0x3332 jc error - ; Load config file after kernel - push bx - mov ax, config_name - call load_file - pop bx - - ; Write a null byte after config file - mov BYTE [bx+di], 0 - - ; Setup registers for kernel - xor ax, ax - ; CX is size of config - mov cx, di - ; DL is drive number - xor dx, dx mov dl, [fdc.drv] - ; BX is offset of config - sub bx, prog - ; the pointers are 0 - xor bp, bp - xor si, si - xor di, di ; jump into kernel - jmp (prog>>4):0 + jmp segment:prog ; Load a file into memory ; IN AX pointer to 8.3 filename @@ -260,8 +234,6 @@ error: int 0x16 int 0x19 -config_name: - db "RCONFIG SYS" kernel_name: db "RDOS SYS" diff --git a/kernel/chario.asm b/kernel/chario.asm deleted file mode 100644 index 40788ce..0000000 --- a/kernel/chario.asm +++ /dev/null @@ -1,35 +0,0 @@ -; Reads a single character with echo -; out AL character -isr_getc_echo: - xor ax, ax - int 0x16 - test al, al - jz isr_getc_echo - call putc - iret - -; Reads a single character without echo -; out AL character -isr_getc: - xor ax, ax - int 0x16 - test al, al - jz isr_getc - iret - -; Prints a single character -; in DL character -isr_putc: - push ax - mov al, dl - call putc - pop ax - iret - -putc: - push bx - mov ah, 0x0e - mov bx, 0x0000 - int 0x10 - pop bx - ret diff --git a/kernel/drive.asm b/kernel/drive.asm deleted file mode 100644 index 31efa81..0000000 --- a/kernel/drive.asm +++ /dev/null @@ -1,53 +0,0 @@ -; drive table -%define drivetab_type 0x00 ; BYTE 0=unassigned, 1=BIOS/CHS, 2=BIOS/LBA -%define drivetab_num 0x01 ; BYTE DL number - -; CHS data for type=1 -; Might be reused for driver address -%define drivetab_heads 0x02 ; WORD CHS heads -%define drivetab_spt 0x04 ; WORD CHS sectors per track - -%define drivetab_sectors 0x06 ; DWORD total number of sectors -%define drivetab_offset 0x0A ; DWORD partition offset -%define drivetab_size 0x0E - -drive_table: - dw 0 -.count: - dw 4 - -; DI is incremented for the space taken -; IN ES:DI -drive_setup: - xor cx, cx - mov [drive_table], di - mov al, drivetab_size - mov ah, BYTE [drive_table.count] - mul ah - xchg cx, ax - ; this increments DI and also fills table with zeros - rep stosb - ret - -; Load a drive table entry -; IN DL drive number -; OUT DS:SI ptr to table item -drive_load: - ; bail out if number too high - cmp dl, [cs:drive_table.count] - jnc .err - - push cs - pop ds - mov si, [drive_table] - - push ax - mov al, drivetab_size - mul dl - add si, ax - pop ax - - ret -.err: - stc - ret diff --git a/kernel/intr.asm b/kernel/intr.asm deleted file mode 100644 index bca094e..0000000 --- a/kernel/intr.asm +++ /dev/null @@ -1,30 +0,0 @@ -; Register a interrupt handler (21h AH=25h) -; in: AL interrupt number -; DS:DX far ptr -isr_intr_register: - ; backup previous stos ptr - push es - push di - - ; DI = AL * 4 - mov ah, 4 - mul ah - mov di, ax - - ; ES = 0 - xor ax, ax - mov es, ax - - ; store offset - mov ax, dx - stosw - - ; store segment - mov ax, ds - stosw - - ; restore previous stos ptr - pop di - pop es - - iret diff --git a/kernel/main.asm b/kernel/main.asm index 0f5a06c..bff56aa 100644 --- a/kernel/main.asm +++ b/kernel/main.asm @@ -1,64 +1,57 @@ cpu 8086 -org 0x0 + +; Memory layout (starting from top) +%define self 0xF000 +%define diskbuf (self-0x200) +%define stack (diskbuf) ; end addr, grows down + +org self jmp init -isr_dos_main: - cmp ah, 0x01 - je isr_getc_echo - cmp ah, 0x02 - je isr_putc - cmp ah, 0x25 - je isr_intr_register - jmp isr_invalid +banner: + db "RDOS 2019-09", 0x0A, 0x0D, 0 -%include "intr.asm" -%include "chario.asm" - -; ISR for invalid subfunctions or unimplemented -isr_invalid: - mov bp, 0xFEFE - int3 -.hlt: - hlt - jmp .hlt -; ISR tail to set carry flag to signal error -isr_error: - push bp - mov bp, sp - ; set carry flag - or WORD [SS:BP+6], 1 - pop bp -isr_return: - iret - -%include "drive.asm" +print_banner: + mov cl, 2 + mov si, banner +.loop: + mov dl, BYTE [si] + test dl, dl + jz .end + call cpm_syscall + inc si + jmp .loop +.end: + ret init: - mov ax, cs - mov ds, ax - mov es, ax + mov sp, stack - call config_first_run - - mov di, kernel_end - call drive_setup - - mov dx, isr_dos_main - mov ax, 0x2521 - pushf - push cs - call isr_dos_main - - mov dl, 0x37 - mov ah, 0x02 - int 0x21 + call print_banner + int3 cli .halt: hlt jmp .halt +cpm_syscall: + cmp cl, 0x02 + je putc + stc + ret + +putc: + push ax + push bx + mov al, dl + mov ah, 0x0e + mov bx, 0x0000 + int 0x10 + pop bx + pop ax + ret + %include "string.asm" -%include "config.asm" kernel_end: