saving more state on network crash

[Steven M. Schultz]

Subject: saving more state on network crash
Index:	sys/pdp/mch_dump.s 2.10BSD

Description:
	When a network crash occurs several key pieces of information
	(such as memory management registers) are not saved.

Repeat-By:
	You really don't want to, but if you must, then find a way
	to force the network to crash.  A good way is to (w/o installing
	a previous fix) do a "shutdown()" on a file descriptor that
	is not open.

Fix:
	Apply these patches to /sys/pdp/mch_dump.s and /sys/pdp/trap.c

*** mch_dump.s.old	Mon Aug 10 21:48:26 1987
--- mch_dump.s	Tue Aug  1 21:09:25 1989
***************
*** 28,33 ****
--- 28,73 ----
  	mov	KDSA5,(r0)+
  	rts	pc
  
+ #ifdef	UCB_NET
+ 
+ SPACE(GLOBAL, suprsav, 32)
+ 
+ /*
+  * Save ALL registers, KDSA[5,6], SDSA[5,6], SSR3.  Expressly for
+  * network crashes where the state at the time of initial trap is
+  * desired rather than after thrashing about on the way to a 'panic'.
+  * Also, this is extensible so that as much volatile information as
+  * required may be saved.  Currently 14 of the 16 words allocated are used.
+  * Multiple entries into this routine should be blocked by making the
+  * call to this routine conditional on 'netoff' being set and 
+  * setting 'netoff' on the first call.  Must be at splhigh upon entry.
+ */
+ 
+ ENTRY(savestate)
+ 	mov	r0,suprsav
+ 	mov	$suprsav+2,r0
+ 	mov	r1,(r0)+
+ 	mov	r2,(r0)+
+ 	mov	r3,(r0)+
+ 	mov	r4,(r0)+
+ 	mov	r5,(r0)+
+ 	mov	sp,(r0)+
+ 	mov	PS,-(sp)
+ 	mov	$010340,PS	/previous super, spl7
+ 	mfpd	sp		/fetch supervisor stack pointer
+ 	mov	(sp)+,(r0)+
+ 	mov	$030340,PS	/previous user, spl7
+ 	mfpd	sp		/fetch user stack pointer
+ 	mov	(sp)+,(r0)+
+ 	mov	(sp)+,PS
+ 	mov	KDSA5,(r0)+
+ 	mov	KDSA6,(r0)+
+ 	mov	SDSA5,(r0)+
+ 	mov	SDSA6,(r0)+
+ 	mov	SSR3,(r0)+
+ 	rts	pc
+ #endif
+ 
  #include "ht.h"
  #include "tm.h"
  #include "ts.h"
*** trap.c.old	Tue Jul  5 14:24:11 1988
--- trap.c	Tue Aug  1 20:41:41 1989
***************
*** 282,287 ****
--- 282,291 ----
  	case T_ZEROTRAP+SUPV:
  	case T_RANDOMTRAP+SUPV:
  		i = splhigh();
+ 		if (!netoff) {
+ 			netoff = 1;
+ 			savestate();
+ 		}
  		printf("Unexpected net code trap (%o)\n", dev-SUPV);
  		printf("ka6 = %o\n", *ka6);
  		printf("aps = %o\n", &ps);