ENTER-DIRECTORY error paths - complete carve¶

Closes the last two gaps in the @ENTER-DIRECTORY carves for SINTRAN III VSX/500 L07 (running system L-VSX-500, symbols L07):

PART 1 - the resource reserve/release family and PRSRV's uncarved jump target LEAV2 = 027417B.
PART 2 - the error-code / error-message emission paths the mount can hit.

Evidence grades. VERIFIED = re-read from the carved .bin with dd (byte offset in the .bin = (addr_oct - loadbase) * 2, decimal) and/or nd100-dis. INFERRED = reasoned from bytes + manual/symbols. OPEN = crosses into a foreign/low-resident overlay whose live mapping is a runtime fact. All addresses and values are octal.

Deliverables: - RESERVE-LEAV2-ERRORS-COMPLETE.ASM - RESERVE-LEAV2-ERRORS-COMPLETE.pseudo.c

Cross-links: ../PRSRV-124B/ (the PRSRV trampoline + block-0 reserve flow), ../ENTER-DIRECTORY/ (device-agnostic mount path), ../RCBLO/ (block-0 dispatch seam), ../../segments-ref/003-S3CP/003-S3CP.asm.

PART 1 - the reserve family and LEAV2¶

1.1 Dispatch (re-confirmed by dd on `044-S3IDPIT.bin`, MCTAB @ 005620B)¶

MON N -> ENT14 -> GOTAB[N]=MFELL -> CALLP -> MCTAB[N] -> worker. The four reserve/release slots land exactly on the L07 SYMBOL-1-LIST addresses:

MON	Symbol	worker	note
122B	`RESRV`	`037103B`	ReserveResource
123B	`RELES`	`037156B`	ReleaseResource
124B	`PRSRV`	`037076B`	ForceReserve (the mount's `MON 124`)
125B	`PRLS`	`037147B`	ForceRelease
070B	`COMSB`	`050673B`	@-command interpreter (called by EXECC)

Bodies are resident-monitor code, byte-identical in 071-S3SM, 070-S3SSM and 003-S3CP (all load base 30000B). dd re-reads (071-S3SM.bin): PRSRV[037076]=044322, const[037020]=000003, PRSRV ptr[037107]=027417, RESRV[037103]=036776, EXECC[037110]=045053 - all VERIFIED.

1.2 Two shapes in the family¶

PRSRV (124B) is a 2-word trampoline (LDA -56 -> A:=3 ; JMP I 10 -> 027417 = LEAV2). It never enters the reserve executor. (Carved in ../PRSRV-124B/; reproduced here as the entry to LEAV2.)
RESRV / PRLS / RELES funnel into the shared executor EXECC = 037110B, which builds a command line and runs it via MON 70B (COMSB) - i.e. a plain reserve/release is implemented as an internally-synthesised RESERVE .. / RELEASE .. command. Both MON 70B sites (037124, 037154) are VERIFIED. The only MON call the reserve family issues is MON 70B.

1.3 LEAV2 = 027417B - what it does, and what A=3 does¶

027417B is below the System Monitor's 30000B load base, so it is not in 071-S3SM. Using the skill's sibling-coherence discriminator on the monitor-leave family

3ENTE=027346  L3EAV=027371  LEAVX=027404  LEAV2=027417  3LEAV=027430

the only overlays where all five land on parallel entries are 013-S3SCP and 041-S3IMED (byte-identical, load base 26000B). In 006-S3FS/012-S3SFS those addresses land mid-instruction-stream (027417 there = 004007 STA 7); in 022-S3RFAC mid-loop - both rejected as incoherent. dd (013-S3SCP.bin byteoff 1566) = 030625 044662 172765 004662 - VERIFIED, and 041-S3IMED.bin identical.

LEAV2 is a "pop one context frame and leave" routine - one member of a parallel family. It: 1. saves the caller's F (027417 STF ,B -153), 2. loads the frame-stack pointer into A (027420 LDA ,B -116) - overwriting the A=3 that PRSRV passed in, 3. descends it by one 11-word (013B) frame (027421 AAA -13), 4. bounds-checks (027424 SUB 36 ; 027425 JAN -> 027452 underflow/refill), 5. joins the common tail (027437) that restores F/D from the popped frame, sets the return link L := frame[0] (027447), and EXITs (027451).

The family entries differ only in the SUB immediate (L3EAV 63, LEAVX 50, LEAV2 36, 3LEAV 25) = which frame level to leave to.

Does PRSRV reserve anything, or just return? Under this overlay: A=3 is discarded at 027420 and is not the value in A at the EXIT, so PRSRV = "set A=3, then monitor-leave/return" - it runs no reserve executor and raises no 147B. This is exactly what the live console shows on the failing SCSI mount: no 147B, and the mount proceeds past MON 124.

Honest caveat (OPEN). Whether 013-S3SCP is the overlay actually mapped at 027417 when the System Monitor runs PRSRV is a runtime fact not decidable from static bytes (the coherence test identifies the best-fit carve, not the live page mapping). So whether the 3 is a vestigial constant (this overlay) or a live resource-type selector consumed by a reserve primitive in a different co-resident overlay is OPEN. What is firmly anchored regardless: MON 124 PRSRV returns success on every device type, SCSI included (bytes + live console). A live nd100x/DAP break at 027417 with the monitor mapping in place would settle which overlay is live.

PART 2 - the ENTER-DIRECTORY error paths¶

Segment 006-S3FS (base 26000B), worker ENDIR = 140176B.

2.1 The FILSYS error-return convention (VERIFIED skeleton)¶

SINTRAN filesystem workers use a skip-return:

Success: the worker executes MIN ,B 4 (set the OK marker; seen at 140722 / 037666 / 037743) and returns through the resident epilogue SPOP = 003776, which takes the L+1 (skip) return - the caller's instruction after its "JMP I <err>" error return.
Error: the worker does SAA <code> ; JMP I <ptr> to a per-site error exit. The exit does STA ,B 2 (park the code in frame slot ,B 2), runs site cleanup, then joins the common tail (140723/140726) which returns through SPOP without the ,B 4 marker -> the L+0 (non-skip) error return, so the caller falls into its JMP I <err> and propagates the code upward (in A / ,B 2).

Cleanup on the way out: release the directory lock via UNLOC = 010506 ([140741]=010506, [141037]=010506, VERIFIED symbol), and - if the unit had been reserved - MON 125 ForceRelease at 141014 (VERIFIED 153125) to un-reserve it. SPUSH = 003752 / SPOP = 003776 are the resident frame push/pop; LOCK/XLOCK = 010500, UNLOC/XUNLO = 010506 the lock/unlock primitives (all named from L07 symbols).

2.2 The ENTER-DIRECTORY error-code table (VERIFIED codes + meanings)¶

Meanings from Reference-Manuals/ND-60.128.5 EN SINTRAN III Reference Manual.md.

Code	Meaning (manual text)	Raised at	Why in the mount	Evidence
147B (103)	Device unit reserved for special use - "Device must be reserved for special use to be accessed the way you tried."	`140254 SAA 147` after `MON 124` returns A<0	the unit ForceReserve was refused	VERIFIED dd (`f167`)
145B (101)	Illegal on tape device - "This function is not allowed on magnetic tape."	`140261 SAA 145` after a device-type-bit test	ENTER-DIRECTORY on a mag-tape unit	VERIFIED dd (`f165`); bit test INFERRED
42B (34)	Main directory not last one released - "Attempt to release the main directory while some other directory is still entered."	`140315 SAA 42`	main-directory ordering guard hit during the enter/release bookkeeping	VERIFIED dd (`f122`)
32B (26)	Directory entered - "Attempt to access a directory erroneously while it is entered."	`140370 SAA 32` (already-entered guard after the name match)	the directory is already entered on that unit	VERIFIED dd (`f11a`)
35B (29)	Master block transfer error - "Unable to read system information on the device."	`037747 SAA 35` in `WXDIR`	page-0 (master block) write-back failed	VERIFIED (`../ENTER-DIRECTORY`)

All five error exits funnel through STA ,B 2 -> cleanup -> common tail -> SPOP, delivering the code up to the @-command executor.

2.3 How an error code becomes a console message¶

The @-command executor receives the FILSYS error return and, on its error path, calls the resident error-message printer ERMSG = 016714B (ERMON = 114574B), which maps the numeric code to its text in the SINTRAN error-message table and writes it to the terminal as <message> (<code>B). ERMSG's body is in a lower resident overlay (016714 < 26000B) and is OPEN here; its role is named/known from the L07 symbols. The message texts live in the error-string segments 005-S3ERRS / 011-S3ERRL / 014-S3ERRP (not carved here).

2.4 Red herring - "APPROACHING END OF ACCOUNTING FILE" (243B)¶

Already established (see ../PRSRV-124B/ sec (e)): error 243B is set in exactly one place - RP-P2-ACCRT.NPL, the RT-accounting collector that runs at logout - and has no call edge from the ENTER-DIRECTORY mount path. Not raised by the mount. Documented here only so it is not re-hunted.

VERIFIED / INFERRED / OPEN¶

#	Claim	Verdict
1	`PRSRV[037076]=044322` (LDA -56 -> A=3), `[037020]=3`, `[037107]=027417`	VERIFIED (dd)
2	`027417 = LEAV2`; coherent overlay = `013-S3SCP` == `041-S3IMED` (dd `030625 044662 172765 004662`)	VERIFIED (dd + sibling coherence)
3	LEAV2 = pop-one-frame/leave; descends framePtr `,B -116` by 11 words, restores F/D, `L:=frame[0]`, EXIT	VERIFIED (dd)
4	A=3 overwritten at `027420`, unused; so PRSRV = leave/return, no reserve executor, no 147B	VERIFIED (bytes) + live console (no 147B)
5	Whether `013-S3SCP` is the live overlay at monitor time / whether A=3 is a live selector elsewhere	OPEN (runtime; DAP settles)
6	`RESRV`/`PRLS`/`RELES` funnel into `EXECC 037110`; issue `MON 70B` (COMSB) x2	VERIFIED (dd)
7	FILSYS convention: success `MIN ,B 4` -> SPOP L+1; error `STA ,B 2` -> cleanup -> common tail -> SPOP L+0	VERIFIED (bytes)
8	Error exits release dir lock via `UNLOC 010506` and `MON 125` ForceRelease if unit was reserved	VERIFIED (dd `153125` + symbols)
9	ENDIR codes 147/145/42/32 SAA immediates + manual meanings	VERIFIED (dd all four)
10	Code reaches console via `ERMSG 016714` (role); body + text tables in lower/error overlays	VERIFIED (symbol/role) / body OPEN
11	243B "approaching end of accounting file" not on mount path (RP-P2-ACCRT, logout)	VERIFIED

Provenance. 071-S3SM.bin (PRSRV/RESRV/EXECC family, base 30000B), 013-S3SCP.bin + 041-S3IMED.bin (LEAV2 family, base 26000B), 006-S3FS.bin (ENDIR error exits, base 26000B), 044-S3IDPIT.bin (MCTAB, base 4000B), all under tools/sintran-segment-carver/versions/L-VSX-500/segments/; symbols SINTRAN/NPL-SOURCE/SYMBOLS/L07/{SYMBOL-1-LIST,FILSYS-SYMBOLS}.SYMB.TXT; error meanings Reference-Manuals/ND-60.128.5 EN SINTRAN III Reference Manual.md; accounting SINTRAN/NPL-SOURCE/NPL/RP-P2-ACCRT.NPL. Disassembly via nd100-dis (WSL, little-endian input).