🚀 go-pugleaf

Subject: 2.9 traps in exec
Index:	sys/sys1.c 2.9BSD

Description:
	The kernel panics with something akin to this in the stack.
		~panic
		~mapin
		~iupdat
		~iput
		~closef
		~setregs
		~exece
Repeat-By:
	It's different on every system, you find it when you raise
	MAXUSERS to the teens or above.
Fix:
	Apply the following diff to sys1.c.  The problem is that
	KDSA5 needs to be reset.

*** sys1.c.right	Tue Sep 17 14:16:07 1985
--- sys1.c.wrong	Mon Aug 19 23:59:28 1985
***************
*** 248,259
  	}
  	(void) suword((caddr_t) ap, 0);
  	(void) suword((caddr_t) (-NBPW), 0);
- 	if (bp) {
- 		mapout(bp);
- 		bp->b_flags |= B_AGE;
- 		brelse(bp);
- 		bp = 0;
- 	}
  	setregs();
  bad:
  	if (bp) {

--- 247,252 -----
  	}
  	(void) suword((caddr_t) ap, 0);
  	(void) suword((caddr_t) (-NBPW), 0);
  	setregs();
  bad:
  	if (bp) {