BASH11M

	BASH11M IS A PROGRAM TO DYNAMICALLY PATCH THE IN MEMORY
RSX11M OR RSX11M PLUS EXECUTIVE (ASSEMBLY OPTION) TO PERMIT TASKS
TO BE RUN IN PREVIOUS KERNEL MODE MEMORY MAPPING.
	TASKS WILL ONLY RUN IN THIS MODE (AS OPPOSED TO THE
NORMAL PREVIOUS USER MODE) WHEN THEIR INITIAL PSW IS ZAPPED
ON DISK AFTER INSTALLATION OF THE TASK, OR WHEN THEY DECLARE
AN AST AND MODIFY THE STORED PSW ON THE STACK DURING AN AST
BY DOING A "BIC #30000,4(SP)" INSTRUCTION WITH THE STACK IN
THE NORMAL POSITION FOR AN ASTX$ CALL. OTHERWISE THEY RUN IN
CURRENT MODE USER, PREVIOUS MODE USER AS USUAL.
	THE BENEFITS OF PREVIOUS KERNEL MODE ARE GREAT. THIS
MODE ALLOWS THE MTPI/MFPI OR MTPD/MFPD INSTRUCTIONS TO HAVE
PEEK OR POKE ACCESS TO ANYWHERE IN KERNEL SPACE, WHICH
INCLUDES THE I/O PAGE AND HENCE ALL APRS, SO A TASK CAN
QUICKLY MAP A GLOBAL AREA ANYWHERE IN THE MACHINE, MODIFY
DATA THERE, AND RETURN TO NORMAL. IT SHOULD BE OBVIOUS TO
SYSTEM MANAGERS THAT THIS POWER CAN BE EXACTLY AS DANGEROUS
AS HAVING A COMMON IN THE I/O PAGE THAT NONPRIVILEGED TASKS
CAN MAP TO, SINCE IN EITHER CASE NONPRIVILEGED USERS CAN
MAKE THEMSELVES PRIVILEGED, MAP ANYWHERE, ETC.
	EVEN SO, WHERE MORE ADDRESS SPACE IS NEEDED, THIS SYSTEM
WILL ALLOW ONE TO HAVE IT WITH VERY LITTLE SPEED PENALTY.
	TO USE THE SYSTEM, BUILD BASH11M AND RUN IT ONCE.
THIS WILL PATCH RSX (BASH11M CAN BE BUILT TO UNPATCH RSX
AGAIN IF DESIRED; ERRORS WILL JUST BASH LOCATIONS 0 OR 2) SO
THE REST OF THE SYSTEM CAN BE USED. RSX CAN RUN NORMALLY IN THIS
STATE INDEFINITELY; ON OUR SYSTEM, STARTUP.CMD RUNS BASH11M FOR
US, WITHOUT DIFFICULTY.
	NOW YOU CAN ZAP THE DISK HEADERS OF YOUR TASK USING DDT,
ZAP, OR YOUR FAVORITE DISK PATCHER AFTER INSTALLING TASKS THAT
MUST USE PREVIOUS KERNEL MODE MAPPING. INSTALL SETS THE INITIAL
PSW TO BOTH CURRENT AND PREVIOUS MODES USER, SO YOU CANNOT JUST
RUN A TASK AND HAVE IT BE AUTO INSTALLED AND RUN PREVIOUS KERNEL
MODE. (THE FACT THAT INSTALL IS A PRIVILEGED OPERATION GIVES A
LITTLE PROTECTION). YOU DON'T REALLY NEED THE BASH11M PATCHES
IF YOUR TASK HAS NO ASTS; ON RSX11M, RSX11M+, AND IAS THE TASK
KEEPS ITS INITIAL PSW AS FOUND FROM DISK AND CAN BE RUN IN
PREVIOUS KERNEL TO YOUR HEART'S CONTENT. THE PATCHES MERELY
LET AST EXITS (AND SSTS) LEAVE THE TASK IN THAT MODE. THIS IS
TRUE FOR IAS V3.0, V3.1, RSX11M V3.2 AND EARLIER AND RSX11M+ V1
ANYWAY; IT MAY OR MAY NOT BE TRUE FOR LATER VERSIONS. (FOR THE
HACKERS, ALL YOU NEED TO DO IS USE THIS FACT TO DO THE PATCHES
IN RSX AND YOU CAN RUN IN PREVIOUS KERNEL EVEN IF BASH11M IS NOT
RUN...)
	THEN TO KEEP THE USE OF PREVIOUS KERNEL ORDERLY, I RECOMMEND
USING THE ALTWND ROUTINE TO HANDLE DATA "ANYWHERE". IT WILL
HANDLE THE MAPPING, CONTEXT SAVE/RESTORE, AND SO FORTH
WHILE ALLOWING USER SUBROUTINES ACCESS TO DATA AS THEY NEED IT.
(IT SHOULD BE NOTED THAT IN RSX11M ONE MAY RUN IN PREVIOUS SUPERVISOR
MODE AND ACCESS DATA STRUCTURES MAPPED BY SUPERVISOR APRS TOO.)
	I HAVE INCLUDED A LITLE ROUTINE THAT PUTS A TASK INTO
PREVIOUS KERNEL MODE (WORKS BY SETTING UP A MARKTIME AST AND
ZAPS THE PSW ON THE STACK INSIDE THE AST) SO TASKS NEED NOT
BE INSTALLED TO USE THE MAPPING MODE. NOTE IT WON'T WORK UNLESS
BASH11M HAS BEEN RUN (THOUGH IN RSX11M+ IT WILL PUT YOU INTO
PREVIOUS SUPERVISOR MODE - PROBABLY WITH PDRS ALL 0 THOUGH I HAVEN'T
INVESTIGATED). CALL THE ROUTINE WHEN YOU START UP. IT IS IN THE
ALTWND FILE.
	PREVIOUS-MODE MAPPING IS MAINLY FOR RELATIVELY
EXPERIENCED SYSTEM HACKERS. I RECOMMEND THAT ANYONE WRITING
FOR IT (EVEN WITH THE ALTWND ROUTINE) BE CAREFUL LEST HE
CRASH RSX. CHECK YOUR ALTWND SUBROUTINES ESPECIALLY TO BE
SURE THE STACK IS IN THE SAME PLACE AT EXIT AS AT ENTRY
SINCE YOU RUN ANYTHING THERE AT PRIORITY 7 AND IF THE OLD
PAR, PDR, AND PSW ARE GARBAGED, THE SYSTEM CAN GO BANANAS
VERY EASILY - AND NOBODY WILL SOLVE THE SYSTEM CRASH FOR
YOU; YOU'LL HAVE TO DO IT YOURSELF.
	FOR THOSE INTERESTED IN PERFORMING A REMAP QUICKLY
THAT CAN STAY AROUND AND NOT FORCE YOU TO USE PRIORITY 7 TO
AVOID CONTEXT SWITCHES, EXAMINE MXWDMG.MAC IN THE [312,315]
AREA OF THE DECUS RSX SIG TAPES. IT MAKES ASSUMPTIONS OF NO
CHECKPOINTING (AND MAYBE NO SHUFFLING) AND 4K PDRS, BUT
BASHES 1 WORD INSIDE THE RSX KERNEL SPACE FOR THE WINDOW
OFFSET AND THE APR TOGETHER, SO THE NEW MAPPING WILL REMAIN
IN EFFECT AFTER A CONTEXT SWITCH. IT SHOULD BE SEVERAL TIMES
FASTER THAN AN RSX MAP. IT ASSUMES I/O PAGE MAPPING TO SET UP
PREVIOUS KERNEL MAPPING, BUT IF PREVIOUS KERNEL MAPPING IS
ALREADY IN EFFECT, THE CODE TO SET IT UP VIA THE I/O PAGE
CAN BE OMITTED.