🚀 go-pugleaf

Subject: Fix for APC floating point problem (part 1/2) IBM/4.3
Index: /sys/ca/{trap.c, ioim.h}

Description:	
	There is an unusual set of circumstances that could cause
	certain models of the IBM RT System (6150, 6151) and the IBM
	6152 Academic System to give inaccurate floating point arithmetic
	results.  Although the probability of its occurrence is
	extremely remote, we are informing our customers and
	providing a fix.

	These fixes are designed to detect the circumstances where
	a floating point error could potentially occur and to
	prevent the floating point error from occurring.

	The complete fix is comprised of 3 components: a patch
	to vmunix, a patch to the floating point library, and a
	new version of the Fortran compiler hf77.
 
		V1.27_kit.1 - Patch to the kernel (this file)
		V1.27_kit.2 - Patch to the floating point library

		hf77_12.1_tar.Z - Fortran hf77 with fix
		                  (628233 bytes, 20410 checksum) 
 
	The Fortran compiler can be copied (uucp) from the IBM support
	host ibmsupt from the directory /usr/spool/uucppublic/ibm43-fixes.
	(See V1.28 for details.)

Fix:	
	Following is a patch to the kernel.  Apply this patch to the
	Dec 88 release of IBM/4.3.  Make the kernel and install it.
	See "Building IBM/4.3 Systems with Config" in volume II
	of the manual.

	cd /sys/ca
	patch -p1 < V1.27_kit.1

*** trap.c	Thu Jan  4 17:50:06 1990
--- trap.c.fix	Mon Jan  8 16:40:57 1990
***************
*** 1,15 ****
  /*
!  * 5799-WZQ (C) COPYRIGHT IBM CORPORATION 1986,1987,1988
   * LICENSED MATERIALS - PROPERTY OF IBM
   * REFER TO COPYRIGHT INSTRUCTIONS FORM NUMBER G120-2083
   */
! /* $Header:trap.c 11.5$ */
! /* $ACIS:trap.c 11.5$ */
  /* $Source: /ibm/acis/usr/sys/ca/RCS/trap.c,v $ */
  
  #if !defined(lint) && !defined(NO_RCS_HDRS)
! static char *rcsid = "$Header:trap.c 11.5$";
  #endif
  #if defined(DEBUG) && !defined(SYSCALLTRACE)
  #define SYSCALLTRACE
  #endif
--- 1,16 ----
  /*
!  * 5799-CGZ (C) COPYRIGHT IBM CORPORATION 1986,1987,1988
   * LICENSED MATERIALS - PROPERTY OF IBM
   * REFER TO COPYRIGHT INSTRUCTIONS FORM NUMBER G120-2083
   */
! /* $Header: trap.c,v 12.2 89/06/07 13:48:42 cslater Exp $ */
! /* $ACIS:trap.c 9.0$ */
  /* $Source: /ibm/acis/usr/sys/ca/RCS/trap.c,v $ */
  
  #if !defined(lint) && !defined(NO_RCS_HDRS)
! static char *rcsid = "$Header: trap.c,v 12.2 89/06/07 13:48:42 cslater
Exp $";
  #endif
+ 
  #if defined(DEBUG) && !defined(SYSCALLTRACE)
  #define SYSCALLTRACE
  #endif
***************
*** 136,141 ****
--- 137,147 ----
  			goto grave;
  		}
  		if (locr0[ECR_COUNT] > 1)
+ 			if (check_apc_bug(locr0)) {
+ 				i = SIGBUS;
+ 				break;
+ 			}
+ 		if (locr0[ECR_COUNT] > 1)
  			info = apc_mux(locr0,info);	/* handle multiple exceptions */
  		info = (info&(NBPG-1)) | (locr0[EX1_ADDR] & (-NBPG));
  		/* fall thru for now */
***************
*** 142,147 ****
--- 148,158 ----
  #endif ROMPC
  	case DPAGE_FAULT + USER:	  /* data page fault */
  	case IPAGE_FAULT + USER:	  /* inst page fault */
+ 		if (locr0[ECR_COUNT] > 1)
+ 			if (check_apc_bug(locr0)) {
+ 				i = SIGBUS;
+ 				break;
+ 			}
  		if (info & MMU_EX_KEYS) {
  #ifdef SIM_CHG_BIT
  			if (GETSEG(info) == 0xf) {
***************
*** 1101,1103 ****
--- 1112,1137 ----
  }
  
  #endif ROMPC
+ 
+ static
+ check_apc_bug(locr0)
+ register int *locr0;
+ {
+ 	int addr2 = locr0[EX2_ADDR];
+ 	int ctl2 = locr0[EX2_CTL];
+ 	int addr1 = locr0[EX1_ADDR];
+ 	int ctl1 = locr0[EX1_CTL];
+ 
+ 	if (GETSEG(addr1) == 0xf && GETSEG(addr2) == 0xf &&
+ 		IS_FLOAT(addr1) && IS_FLOAT(addr2))
+ 		if (addr1 == addr2 && ctl1 == ctl2 &&
+ 				locr0[EX1_DATA] == locr0[EX2_DATA])
+ 			{
+ 			DEBUGF(1, printf("possible CPU fault:\n"));
+ 			DEBUGF(1, printf("addr1=addr2=%x\n",addr1));
+ 			DEBUGF(1, printf("ctl1=ctl2=%x\n",ctl1));
+ 			DEBUGF(1, printf("EX1_DATA=EX2_DATA=%x\n",locr0[EX1_DATA]));
+ 			return 1;
+ 			}
+ 	return 0;
+ }
*** ioim.h	Mon Jan  8 10:29:04 1990
--- ioim.h.fix	Mon Jan  8 10:31:47 1990
***************
*** 1,14 ****
  /*
!  * 5799-WZQ (C) COPYRIGHT IBM CORPORATION 1987
   * LICENSED MATERIALS - PROPERTY OF IBM
   * REFER TO COPYRIGHT INSTRUCTIONS FORM NUMBER G120-2083
   */
! /* $Header:ioim.h 12.0$ */
! /* $ACIS:ioim.h 12.0$ */
  /* $Source: /ibm/acis/usr/sys/ca/RCS/ioim.h,v $ */
  
  #if !defined(lint) && !defined(LOCORE) && defined(RCS_HDRS)
! static char *rcsidioim = "$Header:ioim.h 12.0$";
  #endif
  
  #ifdef ROMPC
--- 1,13 ----
  /*
!  * P_R_P_Q_# (C) COPYRIGHT IBM CORPORATION 1987
   * LICENSED MATERIALS - PROPERTY OF IBM
   * REFER TO COPYRIGHT INSTRUCTIONS FORM NUMBER G120-2083
   */
! /* $Header: ioim.h,v 12.1 89/05/12 11:44:14 triha Exp $ */
  /* $Source: /ibm/acis/usr/sys/ca/RCS/ioim.h,v $ */
  
  #if !defined(lint) && !defined(LOCORE) && defined(RCS_HDRS)
! static char *rcsidioim = "$Header: ioim.h,v 12.1 89/05/12 11:44:14
triha Exp $";
  #endif
  
  #ifdef ROMPC
***************
*** 157,162 ****
--- 156,163 ----
  		    /* GETSUBSEG() is defined in mmu.h */
  #define IS_IOCC(reg) (GETSUBSEG(reg) == 0 || GETSUBSEG(reg) == 4)
  #define IS_68881(reg) (GETSUBSEG(reg) == 0x0c || GETSUBSEG(reg) == 0x0d)
+ #define IS_FLOAT(reg) (GETSUBSEG(reg) >= 0x0c)
+ #define IS_FPA(reg) (GETSUBSEG(reg) == 0x0e || GETSUBSEG(reg) == 0x0f)
  #define IS_CANCELLED(reg) ((reg)&EX_CANCELLED)
  /**/
  /*


=====-----     Mark S. Lewis, IBM AWD Palo Alto    -----======
inet: mlewis%ibmsupt@uunet.uu.net		(415) 855-4486
uucp: uunet!ibmsupt!mlewis              IBM Tie Line: 465-4486