sys7.1-doc-wip/OS/FPUEmulation/FPSPMain.a

;
;	File:		FPSPMain.a
;
;	Contains:	Main entry point for the FPU Emulation Package
;
;	Originally Written by:	Motorola Inc.
;	Adapted to Apple/MPW:	Jon Okada
;
;	Copyright:	© 1990, 1991 by Apple Computer, Inc., all rights reserved.
;
;   This file is used in these builds:   Mac32
;
;	Change History (most recent first):
;
;		 <2>	 3/30/91	BG		Rolling in Jon Okada's latest changes.
;		 <1>	12/14/90	BG		First checked into TERROR/BBS.

;

;  fpspmain.a

;  Based upon Motorola file 'skeleton.sa'.

;  Main entry points to FPSP functionality:  ovfl, unfl, snan, operr, bsun, fline,
;    and unsupp.

;  CHANGE LOG:
;  03 Jan 91	JPO	Removed branches to emulator routines and moved entry point
;			  labels to appropriate emulator routines.  Removed dummy
;			  user exception routines 'real_XXX'.  Removed routine
;			  'fpsp_done' (RTE done in-line).  Modified and flattened
;			  structure of 'mem_write' function.  Removed 'mem_read'
;			  routine (to be done in-line).



*
*	skeleton.sa 3.1 12/10/90
*
*	This file contains code that is system dependent and will
*	need to be modified to install the FPSP.
*
*	Each entry point for exception 'xxxx' begins with a 'jmp fpsp_xxxx'.
*	Put any target system specific handling that must be done immediately
*	before the jump instruction.  If there no handling necessary, then
*	the 'fpsp_xxxx' handler entry point should be placed in the exception
*	table so that the 'jmp' can be eliminated. If the FPSP determines that the
*	exception is one that must be reported then there will be a
*	return from the package by a 'jmp real_xxxx'.  At that point
*	the machine state will be identical to the state before
*	the FPSP was entered.  In particular, whatever condition
*	that caused the exception will still be pending when the FPSP
*	package returns.  Thus, there will be system specific code
*	to handle the exception.
*
*	If the exception was completely handled by the package, then
*	the return will be via a 'jmp fpsp_done'.  Unless there is 
*	OS specific work to be done (such as handling a context switch or
*	interrupt) the user program can be resumed via 'rte'.
*
*	In the following skeleton code, some typical 'real_xxxx' handling
*	code is shown.  This code may need to be moved to an appropriate
*	place in the target system, or rewritten.
*	

*		Copyright (C) Motorola, Inc. 1990
*			All Rights Reserved
*
*	THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA 
*	The copyright notice above does not evidence any  
*	actual or intended publication of such source code.

* SKELETON	IDNT    2,1 Motorola 040 Floating Point Software Package

;	section 15
*
*	The following counters are used for standalone testing - DELETED <1/3/91, JPO>
*
;sigunimp	dc.l	0
;sigbsun	dc.l	0
;siginex	dc.l	0
;sigdz		dc.l	0
;sigunfl	dc.l	0
;sigovfl	dc.l	0
;sigoperr	dc.l	0
;sigsnan	dc.l	0
;sigunsupp	dc.l	0

;	section 8

;	include	fpsp.h

*
*	Divide by Zero exception - DELETED <1/3/91, JPO>
*
*	All dz exceptions are 'real', hence no fpsp_dz entry point.
*

;dz:
;real_dz:
;	link	a6,#-LOCAL_SIZE
;	fsave	-(sp)
;	bclr.b	#E1,E_BYTE(a6)
;	frestore (sp)+
;	unlk	a6
;
;	add.l	#1,sigdz		;for standalone testing
;
;	rte


*
*	Inexact exception - DELETED <1/3/91, JPO>
*
*	All inexact exceptions are real, but the 'real' handler
*	will probably want to clear the pending exception.
*	The provided code will clear the E3 exception (if pending), 
*	otherwise clear the E1 exception.  The frestore is not really
*	necessary for E1 exceptions.
*
* Code following the 'inex' label is to handle bug #1232.  In this
* bug, if an E1 snan, ovfl, or unfl occured, and the process was
* swapped out before taking the exception, the exception taken on
* return was inex, rather than the correct exception.  The snan, ovfl,
* and unfl exception to be taken must not have been enabled.  The
* fix is to check for E1, and the existence of one of snan, ovfl,
* or unfl bits set in the fpsr.  If any of these are set, branch
* to the appropriate  handler for the exception in the fpsr.  Note
* that this fix is only for d43b parts, and is skipped if the
* version number is not $40.
* 
*

;inex:
;	link	a6,#-LOCAL_SIZE
;	fsave	-(sp)
;	cmpi.b	#VER_40,(sp)		;test version number
;	bne.b	real_inex
;	fmove.l	fpsr,-(sp)
;	btst.b	#E1,E_BYTE(a6)		;test for E1 set
;	beq.b	not_b1232
;	btst.b	#snan_bit,2(sp) ;test for snan
;	beq	inex_ckofl
;	add.l	#4,sp
;	frestore (sp)+
;	unlk	a6
;	bra	snan
;inex_ckofl:
;	btst.b	#ovfl_bit,2(sp) ;test for ovfl
;	beq	inex_ckufl 
;	add.l	#4,sp
;	frestore (sp)+
;	unlk	a6
;	bra	ovfl
;inex_ckufl:
;	btst.b	#unfl_bit,2(sp) ;test for unfl
;	beq	not_b1232
;	add.l	#4,sp
;	frestore (sp)+
;	unlk	a6
;	bra	unfl

*
* We do not have the bug 1232 case.  Clean up the stack and call
* real_inex.
*
;not_b1232:
;	add.l	#4,sp
;	frestore (sp)+
;	unlk	a6

;real_inex:

;	add.l	#1,siginex		;for standalone testing

;	link	a6,#-LOCAL_SIZE
;	fsave	-(sp)
;	bclr.b	#E3,E_BYTE(a6)		;clear and test E3 flag
;	beq.b	inex_cke1
*
* Clear dirty bit on dest register in the frame before branching
* to b1238_fix.
*
;	movem.l	d0/d1,USER_DA(a6)
;	bfextu	CMDREG1B(a6){6:3},d0		;get dest reg no
;	bclr.b	d0,FPR_DIRTY_BITS(a6)	;clr dest dirty bit
;	bsr	b1238_fix				;test for bug1238 case
;	movem.l	USER_DA(a6),d0/d1
;	bra.b	inex_done
;inex_cke1:
;	bclr.b	#E1,E_BYTE(a6)
;inex_done:
;	frestore (sp)+
;	unlk	a6
;	rte
	
*
*	Overflow exception - DELETED <1/3/91, JPO>
*

;ovfl:
;	jmp	fpsp_ovfl
;real_ovfl:

;	add.l	#1,sigovfl		;for standalone testing

;	link	a6,#-LOCAL_SIZE
;	fsave	-(sp)
;	bclr.b	#E3,E_BYTE(a6)		;clear and test E3 flag
;	bne.b	ovfl_done
;	bclr.b	#E1,E_BYTE(a6)
;ovfl_done:
;	frestore (sp)+
;	unlk	a6
;	rte
	
*
*	Underflow exception - DELETED <1/3/91, JPO>
*

;unfl:
;	jmp	fpsp_unfl
;real_unfl:

;	add.l		#1,sigunfl		;for standalone testing

;	link		a6,#-LOCAL_SIZE
;	fsave		-(sp)
;	bclr.b		#E3,E_BYTE(a6)		;clear and test E3 flag
;	bne.b		unfl_done
;	bclr.b		#E1,E_BYTE(a6)
;unfl_done:
;	frestore	(sp)+
;	unlk		a6
;	rte
	
*
*	Signalling NAN exception - DELETED <1/3/91, JPO>
*

;snan:
;	jmp	fpsp_snan
;real_snan:
;	link	a6,#-LOCAL_SIZE
;	fsave	-(sp)
;	bclr.b	#E1,E_BYTE(a6)	;snan is always an E1 exception
;	frestore (sp)+
;	unlk	a6

;	add.l	#1,sigsnan		;for standalone testing
;	rte
	
*
*	Operand Error exception - DELETED <1/3/91, JPO>
*

;operr:
;	jmp	fpsp_operr
;real_operr:
;	link	a6,#-LOCAL_SIZE
;	fsave	-(sp)
;	bclr.b	#E1,E_BYTE(a6)	;operr is always an E1 exception
;	frestore (sp)+
;	unlk	a6

;	add.l	#1,sigoperr		;for standalone testing

;	rte
	
*
*	BSUN exception - DELETED <1/3/91, JPO>
*
*	This sample handler simply clears the nan bit in the FPSR.
*

;bsun:
;	jmp	fpsp_bsun
;real_bsun:
;	link	a6,#-LOCAL_SIZE
;	fsave	-(sp)
;	bclr.b	#E1,E_BYTE(a6)	;bsun is always an E1 exception
;	fmove.l	FPSR,-(sp)
;	bclr.b	#nan_bit,(sp)
;	fmove.l	(sp)+,FPSR
;	frestore (sp)+
;	unlk	a6

;	add.l	#1,sigbsun		;for standalone testing

;	rte

*
*	F-line exception - DELETED <1/3/91, JPO>
*
*	A 'real' F-line exception is one that the FPSP isn't supposed to 
*	handle. E.g. an instruction with a co-processor ID that is not 1.
*
*

;fline:
;	jmp	fpsp_fline
;real_fline:

;	add.l	#1,sigunimp		;for standalone testing

;	rte

*
*	Unsupported data type exception - DELETED <1/3/91, JPO>
*

;unsupp:
;	jmp	fpsp_unsupp
;real_unsupp:
;	link	a6,#-LOCAL_SIZE
;	fsave	-(sp)
;	bclr.b	#E1,E_BYTE(a6)	;unsupp is always an E1 exception
;	frestore (sp)+
;	unlk	a6

;	add.l	#1,sigunsupp		;for standalone testing

;	rte

*
*	Trace exception - DELETED <1/3/91, JPO>
*

;real_trace:
;	rte

*
*	fpsp_fmt_error --- exit point for frame format error
*
*	The fpu stack frame does not match the frames existing
*	or planned at the time of this writing.  The fpsp is
*	unable to handle frame sizes not in the following
*	version:size pairs:
*
*	{4060, 4160} - busy frame
*	{4028, 4130} - unimp frame
*	{4000, 4100} - idle frame
*
*	This entry point simply holds an f-line illegal value.  
*	Replace this with a call to your kernel panic code or
*	code to handle future revisions of the fpu.
*

fpsp_fmt_error:

	dc.l	$f27f0000	;f-line illegal 

*
*	fpsp_done --- FPSP exit point
*
*	The exception has been handled by the package and we are ready
*	to return to user mode, but there may be OS specific code
*	to execute before we do.  If there is, do it now.
*
*

;fpsp_done:
;	rte

*
*	mem_write --- write to user or supervisor address space - MODIFIED <1/3/91, JPO>
*
* Writes to memory while in supervisor mode.  copyout accomplishes
* this via a 'moves' instruction.  copyout is a UNIX SVR3 (and later) function.
* If you don't have copyout, use the local copy of the function below.
*
*	a0 - supervisor source address
*	a1 - user destination address
*	d0 - number of bytes to write (maximum count is 12)
*
* The supervisor source address is guaranteed to point into the supervisor
* stack.  The result is that a UNIX
* process is allowed to sleep as a consequence of a page fault during
* copyout.  The probability of a page fault is exceedingly small because
* the 68040 always reads the destination address and thus the page
* faults should have already been handled.
*
* If the EXC_SR shows that the exception was from supervisor space,
* then just do a dumb (and slow) memory move.  In a UNIX environment
* there shouldn't be any supervisor mode floating point exceptions.
*

mem_write:
;	btst.b	#5,EXC_SR(a6)	;check for supervisor state
;	beq.b	user_write
;super_write:
;moreout:
;	move.b	(a0)+,(a1)+
;	subq.l	#1,d0
;	bne.b	super_write

	sub.l	#1,d0		; dec count by 1 for 'dbf' below <1/3/91, JPO>
moreout:			; <1/3/91, JPO>
	move.b	(a0)+,(a1)+	; copy 1 byte <1/3/91, JPO>
	dbf	d0,moreout	; loop until done <1/3/91, JPO>

	rts

;user_write:
;	move.l	d1,-(sp)	;preserve d1 just in case
;	move.l	d0,-(sp)
;	move.l	a1,-(sp)
;	move.l	a0,-(sp)
;	jsr		copyout
;	add.w	#12,sp
;	move.l	(sp)+,d1
;	rts
*
*	mem_read --- read from user or supervisor address space - DELETED <1/3/91, JPO>
*
* Reads from memory while in supervisor mode.  copyin accomplishes
* this via a 'moves' instruction.  copyin is a UNIX SVR3 (and later) function.
* If you don't have copyin, use the local copy of the function below.
*
* The FPSP calls mem_read to read the original F-line instruction in order
* to extract the data register number when the 'Dn' addressing mode is
* used.
*
*Input:
*	a0 - user source address
*	a1 - supervisor destination address
*	d0 - number of bytes to read (maximum count is 12)
*
* Like mem_write, mem_read always reads with a supervisor 
* destination address on the supervisor stack.  Also like mem_write,
* the EXC_SR is checked and a simple memory copy is done if reading
* from supervisor space is indicated.
*

;mem_read:
;	btst.b	#5,EXC_SR(a6)	;check for supervisor state
;	beq.b	user_read
;super_read:
;	move.b	(a0)+,(a1)+
;	subq.l	#1,d0
;	bne.b	super_read
;	rts
;user_read:
;	move.l	d1,-(sp)	;preserve d1 just in case
;	move.l	d0,-(sp)
;	move.l	a1,-(sp)
;	move.l	a0,-(sp)
;	jsr		copyin
;	add.w	#12,sp
;	move.l	(sp)+,d1
;	rts

*
* Use these routines if your kernel doesn't have copyout/copyin equivalents.
* Assumes that D0/D1/A0/A1 are scratch registers. copyout overwrites DFC,
* and copyin overwrites SFC.
*
;copyout:			; DELETED <1/3/91, JPO>
;	move.l	4(sp),a0	; source
;	move.l	8(sp),a1	; destination
;	move.l	12(sp),d0	; count
;	sub.l	#1,d0		; dec count by 1 for dbra
;	move.l	#1,d1
;	movec	d1,DFC		; set dfc for user data space
;moreout:
;	move.b	(a0)+,d1	; fetch supervisor byte
;	moves.b	d1,(a1)+	; write user byte
;	dbf.w	d0,moreout
;	rts
;
;copyin:			; DELETED <1/3/91, JPO>
;	move.l	4(sp),a0	; source
;	move.l	8(sp),a1	; destination
;	move.l	12(sp),d0	; count
;	sub.l	#1,d0		; dec count by 1 for dbra
;	move.l	#1,d1
;	movec	d1,SFC		; set sfc for user space
;morein:
;	moves.b	(a0)+,d1	; fetch user byte
;	move.b	d1,(a1)+	; write supervisor byte
;	dbf.w	d0,morein
;	rts
;