AUSAM/sys106/defines.elec

/*
 ***********************************************************************
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 *                XX  XX  X    X  X    X  X			       *
 *                X XX X  X    X  X    X   XXXX			       *
 *                X    X  X    X  X    X       X		       *
 *                X    X  X    X  X    X  X    X		       *
 *                X    X   XXXX   XXXXX    XXXX			       *
 *                                                                     *
 *	The following defines represent certain improvements and       *
 *	enhancements to the unix 'op sys'. To negate the effect of     *
 *	these changes just delete the define by commenting it out.     *
 *	Corrections of obvious deficiencies and so on are not to be    *
 *	`ifdefed' since they will always be required. See FIXES below  *
 *                                                                     *
 *	For those who intend to alter the 'op sys' please bear the     *
 *	following points in mind:                                      *
 *                                                                     *
 *	1. please indicate   time - date - who                         *
 *                                                                     *
 *	2. why was mod needed.  what was done.  how it was done.       *
 *	   which source modules were altered.  etc . . .	       *
 *                                                                     *
 *	3. any other information which may be considered helpful       *
 *	     for a person following your alterations.                  *
 *                                                                     *
 *						Ian J.		       *
 *                                                                     *
 ***********************************************************************
								       */

/*
#define	_1170
       /*
	*	bio.c once.c m70.s l70.s trap.c user.h
	*	rdwri.c sys1.c
	*
	*	includes stuff specific to 70 cpu's.
	*	such as UNIBUS MAP etc...
	*	Use JNR m70.s which handles floating point properly,
	*	handles an 11/70 cpu as an 11/70 cpu - that is to
	*	say uses the ERROR registers properly etc...
	*	This entails altering 'trap' ,user.h and l.s
	*/

#ifdef	_1170
#define	UNIBUS_MAP
#endif	_1170
	/*
	 *	bio.c	powerf.s m70.s
	 *
	 *	enable code for Unibus Map.
	 *
	 *	note must define 'ubdmap' in m70.s if mapped.buffers
	 *
	 */
#define	_1145
       /*
	*	bio.c once.c m45.s l45.s trap.c user.h
	*	rdwri.c sys1.c
	*
	*	includes stuff specific to 45 cpu's.
	*	Use JNR m45.s which handles floating point properly,
	*	handles an 11/45 cpu as an 11/45 cpu - that is to
	*	say uses the ERROR registers properly etc...
	*	This entails altering 'trap' ,user.h and l.s
	*/

/* (not _1140)
#define	_1140
       /*
	*	clock.c param.h slp.c
	*
	*	includes stuff specific to 40 cpu's.
	*/

#define	FPU
       /*
	*	user.h	m70.s	m45.s
	*
	*	FP11-b or FP11-c installed 
	*/

/*
#define	RHSTART
       /*
	*	bio.c
	*
	*	include code for newer type controllers
	*	e.g. RJP04 on RH70 or RP04 on RH11
	*/

#define	DEVSTART
	/*
	 *	bio.c
	 *
	 *	rk type contollers on system !!
	*/

/* (not PROG_CLOCK)
#define	PROG_CLOCK
       /*
	*	clock.c once.c
	*
	*	if you have a programmable clock only
	*	saves some code ...
	*/

#define	SHARED_DATA
       /*
	*	Ian Johnstone	FEBRUARY '76	
	*
	*	sig.c slp.c sys4.c sysent.c trap.c user.h
	*	sys1.c	text.c	text.h  once.c param.h
	*
	*	New special a.out magic number 0412 signifies shared data
	*	segment (r/w text area).  Must be swapped out on last use
	*	not just abandoned.  Swap synchronization initially a problem,
	*	definitive solution made AUG 77 in conjunction with 
	*	LOWER_TEXT_SWAPS alteration.
	*	`x_spid' and word 6 of A.OUT header contain shared data
	*	identification field - inode pointer not good enough (not unique),
	*	since shared data segments are shared between any number
	*	of co-operating processes.
	*	Initially implemented to support UNSW batch system.
	*	P and V system calls implemented to allow process
	*	synchronization.  LKED does the linking needed for
	*	creation of 412 a.outs.
	*	db4.s needs to be altered to define text,data,stack size
	*	displacements in user.h. cdb,ddt too.
	*/

#define	ZOMBIE
       /*
	*	Chris Maltby	MARCH 77
	*
	*	sys1.c	proc.h	sys4.c	slp.c	clock.c
	*
	*	Several variables in the proc structure are used to store
	*	post-mortem information about processes.  This avoids the swap
	*	out & in of previous version for exit & wait.  Process
	*	terminations (exit&wait) go substantially faster.
	*	Alternative process structure pz_* contains definition of
	*	process area for dead processes.  A few of the scheduling
	*	routines have been altered so that no attempts are made
	*	to alter the process area of `dead'ns'.
	*/

#define	INIT_FIX
       /*
	*	Chris Maltby	MARCH 77
	*
	*	sys1.c
	*
	*	/etc/init (process one) only woken up when required.
	*	Previously every process termination in the system woke
	*	the init process. This is only necessary if the parent
	*	of the dying process is already dead. ``the whole piece
	*	of code that deals with this is still a mess''.
	*	PS needs to know of this alteration.
	*
	*	Piers Lauder	AUGUST 77
	*
	*	The whole thing re-written using a single scan of the
	*	proc array (up to 4 previously). MORE efficient. 
	*	Now the code is understandable.
	*
	*/

#define	TIME_LIMITS
       /*
	*	Chris Maltby	MARCH 77
	*
	*	clock.c	param.h	user.h sys4.c sysent.c sig.c proc.h
	*
	*	User area variables 'u.u_cpusec' and 'u.u_tix' contain
	*	seconds and clock ticks left before time limit expiry.
	*	A signal SIGCPULT is generated when
	*	cpusec becomes zero.  A process with a limit of zero is
	*	not restricted - this is normal state.
	*	Limit passed to children so that if `n' seconds
	*	to go before expiry before fork, after
	*	fork each process will have `n' seconds to go!!
	*
	*	Ian Johnstone	AUGUST 77
	*
	*	sys4.c sysent.c user.h
	*
	*	New system call "clktim" is implemented by these changes.
	*	Allows user to request a signal SIGTIMEOUT in `n' seconds(real)
	*	`n' is passed in r0. If p_rtl is non-zero then a real
	*	time limit has been set. When a limit has been set
	*	the clock interrupt routine decrements p_rtl once a second
	*	until zero when the signal is sent. This involves little extra
	*	cost to the system as the whole proc array is scanned each
	*	second anyway. Main cost is extra word in process table entry.
	*	Limit passed to children so that if 'n' seconds
	*	to go before expiry before fork, after fork each process
	*	will have 'n' seconds before being signalled.
	*/

#define	GPROCS
       /*
	*	received JUNE 77 second mailing (Rand)
	*
	*	sys1.c	sysent.c
	*
	*	Returns system proc array to user. Returns also the number of
	*	process slots.
	*	PS modified to use this - makes PS go faster
	*/

#ifndef	ZOMBIE
#define	BETTER_EXIT
       /*
	*	john lions class of '76
	*
	*	sys1.c
	*
	*	Shrink process to USIZE on entry to exit.
	*/
#endif	ZOMBIE

#define	BETTER_TIME
       /*
	*	Ian Johnstone & Andrew Hume SEPTEMBER 76
	*
	*	alloc.c
	*
	*	update() always updates on root file system super block.
	*	After booting time more likely to be correct.  Also allows
	*	knowledge of when a system crashed to within 30 seconds.
	*	Omitting to set date at BOOT of system less likley
	*	to cause havoc with incremental dumps.
	*/

#define EP_ADDRESS
       /*
	*	Craig McGregor	AUGUST 76
	*
	*	sys1.c	user.h
	*
	*	Implement entry point address as described in programmers
	*	manual.
	*
	*	db4.s needs to be altered to define text,data,stack size
	*	displacements in user.h. ps,cdb,ddt too.
	*/

#ifdef	_1140
#define	BIG_UNIX
#endif
       /*
	*	Jeff Rottman	jul 77
	*
	*	once.c m40.s user.h
	*
	*	This mod is a means of expanding the available addressing
	*	space for the resident operating system on pdp-11/40 style
	*	memory-management UNIX systems. A new linker `sysld' is
	*	used to generate such a system - A sysld command file specifies
	*	the division of the resident system into _s_e_g_m_e_n_t_s, one of
	*	which, the _r_o_o_t segment, is always addressable using
	*	segmentation pages 0 through 4. All the other segments
	*	share page 5, and are addressable only when running. Page
	*	6, as is usual, is reserved for the _U-table addressing, and
	*	page 7 for the I/O page.
	*
	*/

#define	VICAR
       /*
	*	Chris Maltby JUNE 77	Ian Johnstone AUGUST 77
	*
	*	systm.h user.h ( with side effects in tty.c )
	*
	*	Utilize `u.u_heap' as scratch area for erase and delete
	*	processing.  Eliminates canonb[] from systm.h.
	*	Saves space.
	*/

#define	NEW_TIMEOUT
       /*
	*	Piers Lauder	AUGUST 77
	*
	*	m40.s m45.s clock.c param.h systm.h
	*
	*	New timeout function utilises blocks off the clist
	*	for increased efficiency.
	*/

/* (not UN_TIMEOUT)
#ifdef	NEW_TIMEOUT
#define	UN_TIMEOUT
#endif
       /*
	*	Piers Lauder	AUGUST 77
	*
	*	clock.c
	*
	*	Allows cancellation of the effect of a previous call
	*	to timeout.
	*/

/* (not SETPSW)
#define	SETPSW
       /*
	*	clock.c sys4.c sysent.c trap.c m40.s m45.s
	*/

#define CBLOCK_16
       /*
	*	Piers Lauder   AUGUST 77
	*
	*	m70.s m40.s m45.s once.c tty.c
	*
	*	Allow larger cblocks. PUTC,GETC re-written to be 15% faster,
	*	as well as being parametric.
	*/

#define TTY_TRUE_RAW
       /*
	*	Piers Lauder	AUGUST 77
	*
	*	tty.c tty.h & all tty drivers
	*
	*	Allows the use of full 8 bit data
	*	on tty lines iff RAW flag set
	*	and other flags except HUPCL are reset.
	*/

#define	TTY_HISPEED
       /*
	*	Piers Lauder	AUGUST 77
	*
	*	tty.c tty.h & all tty drivers
	*
	*	Provides suitable water marks for high speed terminals.
	*/

/* (not TTY_FLOW_CONTROL)
#define	TTY_FLOW_CONTROL
       /*
	*	Piers Lauder	AUGUST 77
	*
	*	tty.c tty.h & getty stty
	*
	*	Allows tty.c to drive DIABLO type terminals
	*	at high baud rates ( >= 1200 )
	*/

/* George: I can't remember if you have this ... (kev)
#define	STACK_LIMIT
       /*
	*	Peter Hewitt & Dave Horsfall & Craig McGregor  	MAY 77
	*
	*	once.c param.h
	*
	*	Implement stack limit register.
	*/

#define	SMDATE
       /*
	*	UNIX version 6 with mod by Ian Johnstone AUGUST 77
	*
	*	sys4.c sysent.c
	*
	*	Enable smdate from level 6 system distribution.
	*	This call was originally commented out because of
	*	problems with incremental dumps - pseudo old
	*	files not dumped.  Smdate as implemented
	*	now only allows super-user to modify the access date
	*	hopefully super users know what they are doing.
	*/

#define	NEW_SLEEP
       /*
	*	Piers Lauder + Ian Johnstone	AUGUST 77
	*
	*	proc.h sys2.c clock.c systm.h param.h sys4.c
	*
	*	Sleep system calls now do unique sleeps
	*	( avoiding thrashing on wakeups of TOUT )
	*	
	*	Each proc entry has one additional word p_stl
	*	which when non-zero indicates that a sleep is in progress
	*	once a second the clock interrupt routine decrements this
	*	count, when reaches zero process woken up.  This involves
	*	little extra overhead as the proc array is already scanned
	*	once a second for other purposes.
	*/

#ifdef	 BIG_UNIX
#define	ONCE
#endif
       /*
	*	Ian Johnstone AUGUST 77
	*
	*	once.c(main.c) slp.c tty.c bio.c alloc.c c.c
	*
	*	Normally this change only in effect when BIG_UNIX is in effect
	*	however there exists no reason why ONCE can not be used without
	*	BIG_UNIX.  main.c renamed once.c.  The initialization routines
	*	cinit,binit,iinit are moved to once.c from tty.c,bio.c and
	*	alloc.c respectively by this change.  Also estabur,nseg,sureg
	*	are moved from once.c to slp.c.  Buffer allocation(declaration)
	*	is moved to c.c (in conf).
	*/

#ifdef	_1170
#define CRASH_TRACE
#endif

       /*
	*	Ian Johnstone AUGUST 77
	*
	*	trap.c param.h
	*
	*	When system panics print out contents
	*	of cpu error registers.
	*/

/* (not MALLOC_CHECK)
#define MALLOC_CHECK
       /*
	*	Ian Johnstone + Andrew Hume  AUGUST 77
	*
	*	malloc.c
	*
	*	Introduce means of gathering statistics of memory
	*	and swap space allocation under unix.
	*	Statistics gathered from this change instigated the
	*	LOWER_TEXT_SWAPS mod below.
	*/

#define	RAW_BUFFER_POOL
       /*
	*	Ian Johnstone	SEPTEMBER 77
	*
	*	once.c bio.c and others disk/tape raw i/o interfaces as reqd.
	*
	*	In order to improve system performance allocate 'NRAWBUFS'
	*	buffer headers - these headers to be used for swapping and
	*	general raw i/o. Instead if using 'swbuf' for all swap
	*	i/o in the system, allocate from the raw buffer pool.
	*	If 'physio' is passed a null buffer pointer then
	*	it will allocate a buffer for the i/o and free it on completion
	*	of the i/o.  Current raw i/o interfaces then do not have to be
	*	altered unless desired.  The main benefit to these interfaces
	*	will be that on multiple devices overlapped seeks will
	*	possible, also ordered queueing of raw
	*	i/o requests can also be done. (assuming a clever driver)
	*	Improves swapping.  'NRAWBUFS' should be 2 greater
	*	than the expected number of simultaneous raw i/o operations
	*	to prevent lockout of swap i/o.
	*
	*/

#define SLOSHED
       /*
	*	Chris Maltby	SEPTEMBER 77
	*
	*	tty.c
	*
	*	Change to canon to allow erases to delete kills
	*	In the process rewrote it to be more
	*	deterministic (and better).
	*	Handles \ erase-char properly. ie. doesnt assume '#' & '@'
	*	For penny-pinchers this change costs 44 bytes
	*
	*/

#define	LOWER_TEXT_SWAPS
       /*
	*	Chris Maltby	SEPTEMBER 77
	*
	*	slp.c text.c text.h
	*
	*	This alteration drastically reduces the number of swaps
	*	undertaken by UNIX. For example on Ian J's 11/70 swapping
	*	was reduced by about 85%. What more can I say !!
	*	When attaching to a shared text segment that was not
	*	already core resident the following procedure was
	*	followed:
	*		1. If in swap space goto 6
	*		2. Expand process size to enable read of
	*		   text from the a.out.
	*		3. Read text segment.
	*		4. Allocate swap space for text segment
	*		   and swap the segment out 
	*		5. Expand process size to USIZE.
	*		6. Swap out process!!
	*		7. Call sched.
	*	When the process is swapped back in to core
	*	all will magically be taken care of.
	*
	*	This is a little inefficient to say the least and
	*	47 % of all swaps counted were for 1024 bytes.
	*
	*	The new scheme:
	*		1. if in swap space goto 6
	*		2. Expand process size to enable read of
	*		   text from the a.out.
	*		3. Read text segment.
	*		4. Separate User Per Process area and text Segment
	*		   and install text segment in core. Mark it as not yet
	*		   swapped.
	*		5. Continue execution of process
	*		6. Swap in text segment.
	*		7. goto 5
	*	Note that only if required will the shared text segment now
	*	be swapped. It is now possible to run a shared
	*	text program that will cause no swapping if
	*	the program is not "sticky bit"ed.
	*
	*		AND all this only costs 98 bytes...
	*/

#define	BUFFER_AGING
       /*
	*	Jeff Rottman	Sep 77
	*
	*	buf.h bio.c
	*
	*	Allow proper handling of write behind blocks
	*	on freelist. Put at head of free queue those blocks
	*	that have to be written.
	*/

/* (not SLOW_CONSOLE)
#define SLOW_CONSOLE
       /*
	*	ian johnstone	oct 77
	*
	*	prf.c
	*
	*	enable the generation of filler characters
	*	by system putchar routine - if '\r' output
	*/

#define	LARGE_FILE_REFERENCES
	/*
	 *	Ian Johnstone	Nov '77
	 *
	 *	user.h fio.c sys1.c sys3.c
	 *
	 *	Allows > 127 references to a file structure,
	 *	up to maximum of 255 with ENREF error if exceeded.
	 *	Previously this condition would cause (catastrophic)
	 *	errors.
	 */

#define	ERROR_LOG
	/*
	 *	Piers Lauder	Nov '77
	 *
	 *	prf.c	c.c
	 *
	 *	change putchar to allow system program "errlogger"
	 *	to record "printf" messages instead of console.
	 *	Implements device "/dev/errlog".
	 *	see /usr/source/s1/errlog.c for error logger code.
	 */

#define	NICE_PUTCHAR
	/*
	 *	Piers Lauder	Nov '77
	 *
	 *	prf.c
	 *
	 *	change putchar to use tty driver for non-panic
	 *	messages only if cpu prty <= five
	 */

/* (not TTY_INVCASE)
#define	TTY_INVCASE
	/*
	 *	Piers Lauder	Nov '77
	 *
	 *	tty.h tty.c
	 *
	 *	handle inverted case terminals
	 *	yes - they exist.
	 */

#define	COOL_NO_SPACE
	/*
	 *	Piers Lauder	Nov '77
	 *
	 *	alloc.c
	 *
	 *	Since most programs ignore errors on write,
	 *	attempt to be a little less enthusiastic
	 *	with "no space" messages. The change is a
	 *	call to sleep on "lbolt", the effect is to
	 *	slow up programs doing repeated write calls
	 *	after no space error.
	 */

/* (not ILLEGAL_C)
#define	ILLEGAL_C
	/*
	 *	Piers Lauder	Nov '77
	 *
	 *	partab.c	bx.c
	 *
	 *	Enhance the table to know about communication
	 *	bytes which are illegal in a 7-bit + parity
	 *	protocol.
	 */

#define	UPRINTS
	/*
	 *	Piers Lauder	Jan '78
	 *
	 *	prf.c
	 *
	 *	This includes code implementing the routine "uprints"
	 *	which will print a system message on the tty
	 *	associated with the current process.
	 *	If caller is silly enough to use this routine when
	 *	cpu priority is greater than five then nothing happens.
	 */

#define	DELAY
	/*
	 *	Piers Lauder	Jan '78
	 *
	 *	clock.c
	 *
	 *	this includes code implementing the routine "delay"
	 *	which will delay the caller for a period using a
	 *	"timeout - sleep - wakeup" sequence.
	 */

#define	MAX_PROC
	/*
	 *	Ian Johnstone	Jan '78
	 *
	 *	clock.c	sig.c	slp.c	sys1.c	sys4.c	proc.h
	 *
	 *	Keep track of which slot in the proc table is the last one
	 *	in use, and when searching the proc table only go up to maxproc
	 *	rather than &proc[NPROC].  This does speed things up a little.
	 *	Ken Thompson is also supposed to have found that the
	 *	system spends most of its time scanning the proc array.
	 *	For example ps is now many times faster less to transfer less to scan.
	 *	For example consider a system with NPROC=200 and 5 active processes
	 *	ZOMBIE defined - WITHOUT MAX_PROC time for executing wait was 1.18ms
	 *	- WITH MAX_PROC time for executing wait was 0.34ms - thus the benefits
	 *	are obvious in those parts of the system that search the proc table.
	 *	NOTE:	time == elapsed time == user time + system time
	 *	These values obtained on AGSM's 11/70
	 */
#ifdef	MAX_PROC
/* (no HIGH_PROC )
#define	HIGH_PROC
	/*
	 *	Ian Johnstone	Jan '78
	 *
	 *	proc.h	slp.c
	 *
	 *	Enable code to keep proc high water mark in high_proc.
	 */
#endif

#define	LRU_INODE
	/*
	 *	UNKNOWN HACKER -- university of toronto
	 *	Improved debugged installed Ian Johnstone Jan 78
	 *
	 *	inode.h	iget.c	clock.c	sys3.c	sys4.c
	 *
	 *	Incore inode structures are allocated on an LRU basis, and
	 *	if a requested Inode is still in core, it is not read in
	 *	again.  This seems to dramatically speed up pathname
	 *	searches, which do an awful lot of iget's and iput's.
	 *	For example a stat of a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a
	 *	previously took 1.1 seconds (avg) per call this change
	 *	reduces this to 0.07 seconds (avg) !!!!
	 *	These tests carried out on AGSM 11/70 (1 RP04)
	 */

/* (not U_LOCK)
#define	U_LOCK
	/*
	 *	Pies Lauder	Feb '78
	 *
	 *	sys4.c	bio.c
	 *
	 *	provide code to implement system calls "slockon", "slockoff"
	 *	so that super users may lock themselves in memory.
	 */

/* (not IGNORE_SIGNALS)
#define	IGNORE_SIGNALS
	/*
	 *	Piers Lauder	Apr '78
	 *
	 *	proc.h	sig.c	slp.c	sys1.c	sys4.c
	 *
	 *	Introduce "p_ignsig" - a sixteen bit boolean array
	 *	in which "true" means that the correspondingly
	 *	numbered signal is being ignored. Basically this
	 *	stops swaps for ignored signals.
	 */

/*
#define	MEM_PAR_INTR
	/*
	 *	Piers Lauder	Apr '78
	 *	Ian Johnstone	May '78
	 *
	 *	once.c	trap.c
	 *
	 *	For 11/40s enable parity checking if it exists (once.c).
	 *	In trap.c report all memory parity errors, if user mode
	 *	then SIGMEMPAR the process.
	 */

/* (no POWER_FAIL)
#define	POWER_FAIL
	/*
	 *	Ian Johnstone	May '78
	 *
	 *	l70.s powerf.s m70.s
	 *	conf.h c.c dz.c dj.c hp.c rk.c msc.c kl.c lp.c cr.c
	 *	crd.c ht.c tm.c prf.c user.h
	 *
	 *	If defined all singing all dancing powerfail recovery.
	 *	If not defined just loop ....
	 */

/* (not U_DELAY)
#ifdef	DELAY
#define	U_DELAY
#endif
	/*
	 *	Piers Lauder	Apr '78
	 *
	 *	sys4.c	sysent.c
	 *
	 *	Implement new system call "sdelay" for sleeping for a number of ticks.
	 */

#define	AUSAM16
#define	AUSAML
	/*
	 *	Andrew Hume - Peter Ivanov - Ian Johnstone
	 *	Piers Lauder - John Lions - Chris Maltby
	 *	Greg Rose
	 *
	 *	bio.c dz.c rk.c tty.c inode.h
	 *	alloc.c clock.c debug.c fio.c iget.c
	 *	malloc.c nami.c once.c pipe.c rdwri.c
	 *	sig.c slp.c subr.c sys1.c sys2.c
	 *	sys3.c sys4.c sysent.c text.c trap.c
	 *	user.h proc.h pzomb.h systm.h
	 *
	 *	AUSAM16 - change to support 16 bit user id's
	 *	AUSAML  - Limit structures
	 *		limits system call (sys4)
	 *		proc limits (sys1)
	 *		modified wait (sys1)
	 *
	 */

#define LOCKING
	/*
	 *	Greg Rose	Mar 78
	 *
	 *	defines.h fio.c iget.c inode.h param.h rdwri.c
	 *	sys1.c sys2.c sys3.c sysent.c user.h
	 *
	 *	Enables the locking and unlocking of files to ensure safe
	 *	read/write accesses on a "n-reader, one writer" basis.
	 *	One new system call (no 56.) see man2/locking.2 for details.
	 */
#ifndef	AUSAM16 | LOCKING
#define	GROUP_ACCESS
#endif
       /*
	*	so well established no known author !!
	*
	*	fio.c	sysent.c	sys4.c
	*
	*	allow groups access checking etc.
	*	by defing this symbol will allow unix so
	*	generated to support groups as distributed
	*	by BELL - yuk.
	*/

#define	MANY_USERS
       /*
	*	C. Maltby			6/4/78
	*
	*	slp.c	clock.c
	*
	*	Really a fix to allow for more CPU bound
	*	in-core tasks. Where there are likely to be several
	* 	of these then original BELL 'SCHMAG' (clock.c) and
	*	the 'PRIORATE' in setpri could lead the scheduler
	*	to select a CPU-bound task first.
	*
	*	SCHMAG	 ==> clock ticks/second upper limit for I/O bound things
	*
	*	PRIORATE ==> rate at which cpu-bound priority is dropped
	*		minimum user priority is
	*		PUSER + 255 / PRIORATE + p_nice
	*/

#define	MORE_USER_PRIORITIES
       /*
	*	Chris	Maltby	May 78
	*
	*	param.h	sys4.c
	*
	*	Changes PUSER to 64, thus allowing a greater diversity
	*	of user priority levels. Coupled with MANY USERS mod
	*	it provides better scheduling on busy machines
	*/

/*
#define	SWITCH_DISPLAY
       /*
	*	Chris Maltby	APR 78
	*
	*	slp.c	m70.s
	*
	* 	make an interesting display in location 70
	*	count of swtch's in last 8 ticks
	*/

/* ( no DEBUG_SWAP )
#define	DEBUG_SWAP
       /*
	*	Peter Ivanov, John Lions, and Greg Rose	APR 78
	*
	*	slp.c	clock.c	bio.c	debug.c
	*
	*	certain debugging aids inserted to check
	*	for erroneous swaps. We used this to find
	*	the bug in LOWER_TEXT_SWAPS.
	*/

#define BETTER_PANIC
       /*
	*	slp.c	prf.c
	*
	*	Greg Rose and John Lions	APR 78
	*	Ian Johnstone			MAY 78
	*	
	*	Changes to "swtch" to make it refuse to
	* 	schedule processes during a panic.
	*	The first panic is the most important - remember
	*	its message string only.
	*/

#define	TTY_CONNECT
#define	TTY_SPECIAL_POWERS
       /*
	*
	*	user.h	tty.h	tty.c	c.c	conf.h	sysent.c
	*	param.h
	*
	*	Ian Johnstone	MAY 78
	*	Chris Maltby	APR 79
	*
	*	Support for the logical connection of two tty ports.
	*	(A great assistance for inter-machine communication!)
	*	NEW sys call:
	*		mov	master-fd,r0
	*		mov	slave-fd, r1
	*		sys	connect; type; cntrl-char
	*	where
	*		master-fd and slave-fd are files descriptors associated
	*		with terminal ports ( dj-dz-kl ).
	*	if type is
	*
	*	0	Then function is disconnect. Master and slave must
	*		be same tty.
	*
	*	1	Function is CONNECT (log)
	*
	*		ALL chars received from master or slave tty are
	*		re-directed to the output queue of the other.
#ifdef	TTY_SPECIAL_POWERS
	*
	*	2	Function is VIEW
	*		Master tty monitors receives a copy of all
	*		output (and input) sent to slave. Input at master
	*		is sent to master's input queue.
	*
	*	3	Function is GRAB
	*		Slave tty is disconnected from system, and
	*		master takes its place. The master appears to be
	*		the slave tty.
	*
	*	4	Function is SHARE
	*		Similar to VIEW, but input typed at master tty
	*		appears as if typed at slave tty.
#endif	TTY_SPECIAL_POWERS
	*
	*	If slave == master or if either slave or master is already
	*	redirected, no connection takes place.
	*
	*	IF the cntrl-char is received from the master tty
	*	then -
	*		1. the connect system call returns to caller.
	*		2. all re-direction of ttys stops.
	*/

/*
#define	TTY_SUSER
       /*
	*	Chris Maltby	MAY 78
	*	Ian Johnstone	JUN 78
	*
	*	tty.c
	*
	*	Non-super users restricted to 'TTY_MAXSPD' baud as max
	*	attainable speed !!
	*	ONLY super-users may 'stty/gtty' terminals that are
	*	not the controlling tty for the process.
	*/

/*
#define	SYS_TIME
	/*
	 *	Ian Johnstone	MAY 78
	 *
	 *	m70.s trap.c
	 *
	 *	Include code (optionally) in m70.s to return
	 *	the systems idea of the time (hh:mm).
	 *	Found to be useful for noting times of system crashes !!
	 *	call:	systime( timstr )
	 *		char timestr[6];
	 *
	 */

#define	QMOUNT
	/*
	 *	Ian Johnstone - Greg Rose - Chris Maltby	MAY 78
	 *
	 *	iinit.h	bio.c	alloc.c	sys3.c
	 *
	 *	Use buffers out of buffer pool for mounted
	 *	super-blocks mark these buffers with B_MOUNT flag
	 *	Main advantage is that when an update happens
	 *	buffers need not be allocated to copy super-blocks to
	 *	but can merely be written in-place !!
	 *	icheck -s, df ... should work better too
	 *	NOTE: MUST BE USED IF MAPPED_BUFFERS IN USE *******
	 */

/*
#define	MAPPED_BUFFERS
#ifndef	ZOMBIE
#define	ZOMBIE
#endif	ZOMBIE
#ifndef	QMOUNT
#define	QMOUNT
#endif	QMOUNT
	/*
	 *	Ian Johnstone - Greg Rose - Chris Maltby	MAY 78
	 *
	 *	alloc.c   binit.h   bio.c     buf.h
	 *	crd.c     defines.h iget.c    iinit.h
	 *	lp.c      nami.c    once.c    param.h
	 *	rdwri.c   subr.c    sys1.c    sys3.c
	 *	systm.h   user.h    
	 *
	 *	Use KDA5 to page buffers from the buffer pool.
	 *	In binit at system startup the buffer pool is
	 *	malloced and the buffer headers setup to addrees
	 *	them - if UNIBUS_MAP defined then b_xmem & b_addr
	 *	are set up so that unibus map will work - otherwise
	 *	b_xmem & b_addr contain full n-bit address.
	 *	This change costs 8Kb from kernal data space (loss of reg)
	 *	but does recover the data space previously occupied
	 *	by the buffers.
	 *	The only hassle is having to load KA5 prior to accessing
	 *	a buffers contents, bswtch (m70.s) will do this given 
	 *	address of buffer header.
	 */

/*
#define	MALLOC_UMAP
       /*
	*	Chris Maltby			Jun 78
	*
	*	param.h	systm.h	binit.c	bio.c
	*
	*	ONLY relevant if UNIBUS_MAP defined.
	*	Allows better allocation of UNIBUS-MAP via
	*	a call to malloc to allocate only as much as is
	*	required for this I/O. Avoids problem with previous 
	*	method when used with MAPPED_BUFFERS. This should
	*	allow multiple raw I/O's and swaps.
	*
	*	MUST BE USED WITH MAPPED_BUFFERS
	*/

#define	ACCESS
       /*
	*	bell labs ....	JUN 78
	*
	*	sys2.c sysent.c
	*
	*	implement access system call
	*	see sys2.c for details
	*/

/* (not	PROFILE)
#define PROFILE
	/*
	 *	Greg Rose	July 78.
	 *
	 *	once.c m70.s
	 *
	 *	Allows the taking of an arbitrarily detailed profile of the system.
	 *	The profile is kept in the supervisor mode data space, and hence
	 *	can be done in space-constrained systems (like ours) which previously
	 *	could not take it.
	 */

/*
#define	SWAP_CHECK
	/*
	 *	Piers Lauder				Nov '78
	 *
	 *	sys1.c
	 *
	 *	This is basically an attempt to limit panics - out of swap"
	 *	for systems with small swap areas. The method is to prevent
	 *	all process creation and process expansion unless there is
	 *	at least "maxmem" memory left in the swap-map.
	 *	'uprints' used to notify user of this - ian J
	 */

#ifndef	GPROCS
#define	GETTAB
#endif	GPROCS
	/*
	 *	Craig McGregor	..	77/09/02
	 *
	 *	sys4.c sysent.c
	 *
	 *	A system call for allowing user programs to
	 *	access executive tables.
	 *	This is similar to gprocs but more general
	 *	and has tighter checking of user's buffer.
	 *	Previously a user found the address of an
	 *	area from the symbol table in "/unix" and
	 *	read "/dev/kmem" to examint the table.
	 */

/*
#define	PROCESS_QUEUES
	/*
	 *	Chris Maltby (ala PWB-Unix)	Apr '79
	 *
	 *	slp.c text.c mch.s systm.h proc.h pzomb.h
	 *	sig.c ...
	 *
	 *	This change allows ready-to-run processes to
	 *	be linked together (via p_link proc entry).
	 *	Time spent in swtch is considerably smaller
	 *	if you have a large proc table. Also provides
	 *	an improved sched which ages 'easy' core, as
	 *	well as allowing separate swapping of text seg
	 *	and data. This results in less lost memory
	 *	due to holes being too small, and should therefore
	 *	reduce swapping.
	 *	The SWAIT state disappears; and a new function
	 *	'qswtch' appears, which must be used instead
	 *	of swtch if the current process is still in the
	 *	SRUN state.
	 */

/*
#ifdef	TTY_CONNECT
#define	TTY_MULTIPLEXED_PORTS
#endif	TTY_CONNECT
	/*
	 *	Piers Lauder	May '79
	 *
	 *	tty.h tty.c mx.c
	 *
	 *	implement indirect driver for multiplexing many tty ports
	 *	onto any real tty line.
	 */

/*
#define	HASHED_BUFFERS
	/*
	 *	Greg Rose.			May 79.
	 *
	 *	buf.h	bio.c	binit.h	conf.h	c.70.
	 *
	 *	This mod is used to (greatly) speed searching of the
	 *	device list for a particular buffer. The device
	 *	lists are coalesced into one large hash table.
	 *	The hashing function operates on both the dev and blkno.
	 */

#define NEWCOPYSEG
	/*
	 *	Greg Rose.			May 79.
	 *
	 *	m70.s
	 *
	 *	New copyseg and clearseg routines.
	 *	copyseg and clearseg changed to use kernel register
	 *	instead of user, hence 'mov' instructions instead
	 *	of (abortionately slow) m[ft]pi instructions.
	 *	Speed up (according to profiling) about 60-70%.
	 *
	 *	m70.s only (above define has no real meaning)
	 */

#define	CIRCULAR_PIPE
/* (no	READ_THEN_FREE)
#define	READ_THEN_FREE
	/*
	 *	Colin Webb.			May 79.
	 *
	 *	pipe.c (only)
	 *
	 *	Uses a circular buffering stategy for pipes. This has two
	 *	advantages.
	 *	1)  Pipes are more likely to be able to accept a write, and
	 *	    and thus a read call, giving higher transfer rates.
	 *	2)  The amount in the pipe is available to fstat, in the
	 *	    field i_size1. A process may now determine if there is
	 *	    stuff to read before reading it.
	 *	If READ_THEN_FREE is defined, then blocks are dissociated
	 *	from the pipe after they have been read, thus not requiring
	 *	a read later on when they are written again. This is most
	 *	useful if you have a small buffer pool, and thus little
	 *	chance of the buffer being present, and anyway it only is
	 *	really useful if the programs talking on the pipe are not
	 *	using 512 byte reads and writes.
	 */

/*
#define SYS_CALL_PROFILE
	/*
	**	Greg Rose 30th May 1980.
	**	Accumulate a histogram of system calls used. This is intended
	**	to highlight any deficiencies in the system interface.
	**
	**	trap.c only.
	*/

/*
 ***********************************************************************
 *                                                                     *
 *	        XXXXXX     X    X    X  XXXXXX   XXXX		       *
 *	        X          X     X  X   X       X		       *
 *	        XXXXX      X      XX    XXXXX    XXXX		       *
 *	        X          X      XX    X            X		       *
 *	        X          X     X  X   X       X    X		       *
 *	        X          X    X    X  XXXXXX   XXXX		       *
 *                                                                     *
 *	Please document all necessary fixes (fix obvious bugs) to the  *
 *	'op sys' here. no defines etc just documentation. Same plea    *
 *	with respect to documenting mods apply.			       *
 *	To indicate a fix in source code just put a comment on altered *
 *	lines referencing 'fixnnn' and document it here.	       *
 *                                                                     *
 ***********************************************************************
								       */
/*
 *	fix000
 *		Ian Johnstone	AUGUST 77
 *
 *		bio.c	file.h	filsys.h	ino.h	inode.h
 *		alloc.c	clock.c	fio.c	iget.c	nami.c	once.c
 *		pipe.c	rdwri.c	sig.c	subr.c	sys1.c	sys2.c
 *		sys4.c	text.c	proc.h	systm.h	user.h
 *
 *		These alterations mainly concerned with
 *		utilizing the facilities of the latest C compiler.
 *		All char * and int * which really were of unsigned type
 *		have been altered.
 *		Register arguments to procedures declared where noted
 *		Ian Johnstone	early 77
 *		All int [2] type whose purpose was to implement 32-bit
 *		arithmetic have been declared long - code altered as required
 *		to cope with new declarations.
 *		Ian Johnstone et al 77
 *		Correctly declare pointers. for example if a pointer
 *		is a pointer to an inode structure then declare it thus
 */
/*
 *	fix001
 *		Jeff Rottman	JUNE 77
 *
 *		bio.c	rdwri.c	
 *
 *		It has been suggested that `read ahead'
 *		may cause deadly embraces, so dmr/bio.c
 *		can be modded to stop read ahead if desired.
 *		The problem exists when ever the number of
 *		processes in "breada"  +  the number of processes
 *		in "exec"  +  the number of mounted file systems
 *		exceeds NBUF.
 */
/*
 *	fix002
 *		Dave Horsfall	APRIL 77
 *		Ian Johnstone	APRIL 78 (corrected)
 *
 *		bio.c
 *
 *		There appears to be a race condition in swap() whereby
 *		the same priority (PSWP) was used to wait for completion of
 *		i/o and for the buffer. A lower priority now used for
 *		buffer allocation sleep.  See bio.c
 */
/*
 *	fix003
 *		John Lions `op sys' class 76
 *
 *		sig.c
 *
 *		No limit to priority because of typo.
 *		See sig.c
 */
/*
 *	fix004
 *		UNSW
 *
 *		text.c
 *
 *		No swap error panic given ?
 */
/*
 *	fix005
 *		UNSW
 *
 *		trap.c
 *
 *		Partial fix to overlaying which signal is being
 *		processed.
 *			****** WITHDRAWN *****
 *
 */
/*
 *	fix006
 *
 *		George Goble purdue university JUNE 77
 *
 *		sys2.c
 *
 *		Chdir sys call could leave free "leaves"
 *			chdir /tmp
 *			mkdir a; chdir a
 *			rmdir /tmp
 *			cp /null orphan
 *			chdir /null
 *			****** WITHDRAWN *****
 *	Not a complete fix (could still mkdir and ln) - see fix044
 */
/*
 *	fix007
 *		Piers Lauder	AUGUST 77
 *
 *		tty.c
 *
 *		Get tty.c to echo nl to cr on half duplex terminals
 *		with CRMOD set.
 */
/*
 *	fix008
 *		Piers Lauder	AUGUST 77
 *
 *		tty.c
 *
 *		Fix tty.c not to call device start routine
 *		if timing out.
 */
/*
 *	fix009
 *		**************************
 *		fix made unnecessary by
 *		SLOSHED modification
 *	 	**************************
 *
 *		Piers Lauder AUGUST 77
 *
 *		Maptab.c changed to allow other escaped
 *		characters e.g.	'\b'.
 *
 */
/*
 *	fix010
 *
 *		Piers Lauder	AUGUST 77
 *
 *		Cret in m40.s & m45.s changed to allow long values
 *		to be returned.
 *			****** WITHDRAWN *****
 */
/*
 *	fix011
 *		Piers Lauder	AUGUST 77
 *
 *		once.c
 *
 *		Console start up printout "mem =" altered to give Kb.
 */
/*
 *	fix012
 *		1976
 *
 *		once.c(main.c)
 *
 *		Saves time at initialisation.
 *		The author hereby declares that no infringement
 *		of Western Electric copyrights is intended.
 */
/*
 *	fix013
 *		Chris Maltby	SEPTEMBER 77
 *
 *		fio.c
 *
 *		Super user can now change to zero
 *		mode directories.  (fio.c)
 */
/*
 *	fix014
 *		P A Hardie	uni of saskatchewan
 *
 *		tty.c
 *
 *		"lost characters fix"
 *		Ttwrite in tty.c - the mod stops ttstart being interrupted
 *		and losing the character it was about to output.
 */
/*
 *	fix015
 *		Greg Rose & Chris Maltby	UNSW
 *
 *		trap.c m40-45-70.s
 *
 *		make system do t bit tracing properly.
 *		Rti's are done from all traps except
 *		t or bpt traps.
 */
/*	fix016
 *		Piers Lauder	Nov '77
 *
 *		prf.c
 *
 *		always output panic messages
 *		even if switches down
 */
/*	fix017
 *		Piers Lauder	Nov '77
 *
 *		bio.c
 *
 *		ensure b-resid always zero - drivers may not always
 *		do this
 */
/*	fix018
 *		Piers Lauder	Apr '78
 *
 *		sig.c
 *
 *		Prevent SIGINS from overlaying other signals.
 *		( only if simulating floating point )
 */
/*	fix019
 *		Piers Lauder	Apr '78
 *		Chris Maltby	May '78
 *
 *		slp.c
 *
 *		Remove spl6() from "sched" while searching proc array.
 *		It is not clear why this was done in the first place,
 *		and its effect of locking out interrupts for several
 *		milliseconds was disastrous for high frequency interrupts.
 *		At sloop in sched protect runin from the clock !!
 *		also protect runout after spl6 removed.
 */
/*
 *	fix020
 *		Apr '78
 *
 *		bio.c
 *
 *		correct code that checks if physical i/o
 *		is wholly within data/stack spaces.
 *		the following should have worked but didn't !!
 *		 	mov	$fd,r0		/ fd is files descriptor
 *						/ for raw i/o
 *			sys	read ; 64 ; 64	/ this generated a segmentation
 *						/ error !!
 *		The correction is simplicity itself - merely subtract one
 *		from the sum of 'base+u.u_count'.
 */
/*	fix021
 *		APR 78
 *
 *		sig.c
 *
 *		Don't even create 'core' file if this is a setuid
 *		process!!. Just test earlier.
 */
/*
 *	fix022
 *		MAY 78
 *
 *		tty.c
 *
 *		A really triffic bug this one !!
 *		when tabs are being expanded in ttyoutput the
 *		assumption is made that the character queues never fill
 *		this assumption is FALSE hence infinite loops can occur !!
 *
 */
/*
 *	fix023
 *		MAY 78
 *
 *		m70.s powerf.s trap.c
 *
 *		instead of these routines magically knowing about
 *		certain displacements in the user structure define
 *		their addresses and use these indirectly to reference
 *		the desired location...
 */
/*
 *	fix024
 *		MAY78
 *
 *		slp.c
 *
 *		p_cpu not being initialized in newproc.
 *		causing new processes to inherit this value
 *		from last process to occupy the proc slot.
 *		APR79
 *		p_cpu & p_time are now inherited from parent
 *		process. This avoids abuse of fork call to
 *		achieve better priority
 */
/*
 *	fix025
 *		JUN 78
 *
 *		fixes etc from bell for level 6 - more docco to come
 *		see V6UNIX subdirectory for all details
 *		beware some mods do not work !!
 *		eg closef change in fio.c
 */
/*
 *	fix026
 *		JUN 78
 *
 *		alloc.c	sys3.c filsys.h
 *
 *		Avoid locking problems in ialloc & ifree.
 *		Improves search for free inodes (makes it faster).
 */
/*
 *	fix027
 *		JUN 78
 *
 *		once.c
 *
 *		Avoid parity errors at start up - use suiword
 *		instead of fuibyte.  Also free all of core in one
 *		hit not in zillions of little chunks.
 */
/*
 *	fix028
 *		JUN 78
 *
 *		trap.c
 *
 *		Remove special significance of system call 63.
 *		You may now use it for anything. Indirect calls
 *		of indir will now give SIGSYS.
 */
/*
 *	fix029
 *		jun 78
 *
 *		sys4.c
 *
 *		chmod system call does not alter modify time - only access time
 */
/*
 *	fix030
 *		JUN 78
 *
 *		bio.c buf.h fio.c sys3.c
 *
 *		Ian Johnstone & Chris Maltby
 *
 *		When a block device is closed ensure ALL blocks
 *		from the device are disposed of in a proper manner.
 *
 *		"binval(dev)" added to bio.c so that ALL blocks belonging
 *		to dev are marked with B_INVAL so that "getblk" and
 *		"incore" will not find them if dev re-opened.
 *		"binval" also sets B_AGE so that if block is
 *		later freed it will be place at the top of the free
 *		queue.
 *
 *		"closef" will only call device block close routine
 *		iff dev not currently mounted.
 *
 *		"closef" and "sumount" both call "binval" to invalidate
 *		the appropriate blocks.
 *
 *		NOTE:	after a dev has been umounted it is thus
 *			no longer possible on re-mounting the dev
 *			to get spurious results caused by finding
 *			blocks left over from before the umount.
 *			ditto for close and re-open
 *
 *		NOTE:	if you're wondering why this bug has not been
 *			noticed before then you may be comforted by
 *			the knowledge that it was first observed by
 *			us on a MAPPED_BUFFERS system with 128 buffers
 *			- so that natural wastage did not occur
 *			quick enough !!!!!!!
 */
/*
 *	fix031
 *		AUG 78
 *
 *		source code altered for ceates with correct modes
 *
 */
/*
 *	fix032
 *		AUG 78
 *
 *		user.h	dz.c dj.c lp.c
 *
 *		define 'EOPENFAIL' return this error when an open
 *		fails on a single use device.
 *
 */
/*
 *	fix033
 *		AUG 78
 *
 *		tty.c
 *
 *		by popular demand - if '\b' is erase character then
 *		echo '\b',' ','\b' to make it look pretty. persons
 *		normally use backspace as char erase on video terminals
 *		(by convention) - a slosh preceding a '\b' is not
 *		handled as nicely as it could be.
 */
/*
 *	fix034
 *		SEP 78
 *
 *		sys2.c
 *
 *		Tell system call to return the position in the file
 *		in R0, R1.
 */
/*
 *	fix035
 *		APR 79
 *
 *	swapdev to be opened just like rootdev.
 *	important if your disk driver needs an open to init the disks.
 */
/*
 *	fix036
 *		Jun 79
 *
 *	Provide routine fkword(addr) which checks for the existence
 *	of a word in kernel D space. The returned value is 1 if the
 *	word exists, otherwise it is 0.
 */
/*
 *	fix037
 *		Jun 79
 *
 *	fix routines 'fu' 'fui' 'su' 'sui' word & byte to set
 *	u.u_error to EFAULT on error, so that a value of -1
 *	can be detected.
 *	This fixes a bug in exec typified by the command "time cat ''".
 */
/*
 *	fix038
 *		Jun 79
 *
 *	inode.h pipe.c rdwri.c
 *
 *	A flag IPIPE is added to the inode, which is tested in writei
 *	to determine whether a bawrite or a bdwrite should be done.
 *	As the information in a pipe is quite transitory, and cannot be
 *	recovered in the event of a system crash, a bdwrite removes the
 *	unnecessary IO traffic, and doubles pipe transfer rates.
 */
/*
 *	fix039
 *		Jul '79
 *
 *	sys3.c
 *
 *	Check for super user in 'mount' and 'umount'. We don't want
 *	the masses mucking around with our disks. If this is what you
 *	really want, then /etc/mount can be made setuid to root.
 */
/*
 *	fix040
 *		Jul '79
 *
 *	nami.c
 *
 *	Check if a directory becomes greater than 4095 files and return
 *	new error code EDBIG. The fix is required because only i_size1 is
 *	used when searching directories. If the 4096'th entry is made then
 *	the directory appears to be zero length. A malicious program could
 *	really do damage this way.
 */
/*
 *	fix041
 *		Jul '79
 *
 *	tty.h	tty.c	param.h
 *
 *	The bug was that if exactly CANBSIZ-1 chars were typed at terminal
 *	and then a CR, Reading the tty would return CANBSIZ, and then 0 on
 *	the next read (often resulting in a log off). Given that TTYHOG and
 *	CANBSIZ are so intertwined, CANBSIZ is redefined to be TTYHOG, and
 *	TTYHOG is now TTYHOG-1. CANBSIZ declaration disappears, and the
 *	definition of TTYHOG moves from tty.h to param.h. Also the TTYHOG'th
 *	char is echoed.
 */
/*
 *	fix042
 *		Oct '79
 *
 *	sys4.c sig.c
 *
 *	as indicated in John Lions commentary,
 *	the signal number was not checked for being negative
 *	hence it was possible to use a negative signal no
 *	to cause certain areas (say uid) to be overwritten in
 *	the per process area.
 */
/*
 *	fix043
 *		Oct '79
 *
 *	sys1.c
 *
 *	Change to exec so that a process may only trace another
 *	if it owns it, or is the super-user.  This prevents
 *	misuse of tracing to read core images of programs,
 *	when the normal permissions may not allow this.
 *	It also prevents rewriting shared data areas.
 */
/*
 *	fix044
 *		March '80
 *
 *	iget.c
 *
 *	When i_nlink is zero (no directory entries), but i_count
 *	not about to become zero (file/dir still open/occupied),
 *	change mode to zero, owner to root.  This is to prevent
 *	mortals making orphan directories, and then creating files
 *	in them (possibly called . or ..). It is NOT sufficient
 *	to simply modify rmdir.
 */
/*
 *	fix045
 *
 *		March '80
 *
 *	sys4.c
 *
 *	Tightened up unlink system call - as well as needing write
 *	permission in the directory, you now also need to own either
 *	the file being unlinked, or the directory.  This solves the
 *	problem of mortals unlinking compiler temporaries in /tmp
 *	and substituting their own (presumably less interesting) ones.
 */
/*
 *	fix046
 *
 *		September '80
 *
 *	param.h sig.c
 *
 *	Altered SSIZE and SINCR from 20/20 to 15/16, to reduce probability
 *	of stack/data collisions. The stack can now approach to within
 *	64 bytes of the end of a 4Kw page, instead of a varying and
 *	significantly larger amount, before the next increment will take
 *	it over and into the next 4Kw page. Also fixed the test in
 *	grow(), which was incorrect on the boundary points.
 */