rdos/debug/run.asm

; Commands related to executing debugged code

cmd_g:	and word [reg_fl+1], 0xfe
	jmp return

cmd_t:	or word [reg_fl+1], 0x03
	jmp return

int3entry:
	; save DS and load bss segment from IVT
	push ds
	mov ds, [cs:zero]
	mov ds, [bssvec*4]
	; save AX so we can work with it
	mov [reg_ax], ax
	; pop DS, IP, CS and flags from stack
	pop ax
	mov [reg_ds], ax
	pop ax
	mov [reg_ip], ax
	pop ax
	mov [reg_cs], ax
	pop ax
	mov [reg_fl], ax
	; save the other registers
	mov [reg_cx], cx
	mov [reg_dx], dx
	mov [reg_bx], bx
	mov [reg_sp], sp
	mov [reg_bp], bp
	mov [reg_si], si
	mov [reg_di], di
	; save other segment registers we can access
	mov [reg_ss], ss
	mov [reg_es], es
	; initialize other segments and setup stack
	mov ax, ds
	mov es, ax
	mov ss, ax
	mov sp, stack
	call crlf
	call printregs
	push es
	mov es, [reg_cs]
	mov bx, [reg_ip]
	call disasm
	pop es

loop:	; show prompt
	mov al, '-'
	call putc
	; read data
	mov byte [inmin], 1
	mov byte [inmax], 16
	mov word [ingetc], getcu
	call gets
	pushf
	call crlf
	popf
	jc loop
	; execute
	call runcmd
	jmp loop

return:	; restore stack pointer
	mov ss, [reg_ss]
	mov sp, [reg_sp]
	; push flags, CS and IP
	mov ax, [reg_fl]
	push ax
	mov ax, [reg_cs]
	push ax
	mov ax, [reg_ip]
	push ax
	; restore GPR
	mov ax, [reg_ax]
	mov cx, [reg_cx]
	mov dx, [reg_dx]
	mov bx, [reg_bx]
	mov bp, [reg_bp]
	mov si, [reg_si]
	mov di, [reg_di]
	; restore segment registers
	; DS must be last
	mov es, [reg_es]
	mov ds, [reg_ds]
	; final jump back
	iret