MON 231B (octal) - ExpandFile (EXPFI)¶
Expands the size of a file - increases the number of pages of contiguous and allocated files (indexed files created with 0 pages may also be expanded). EXPFI shares one code body with three sibling directory-allocation operations (SFACC, CRALN, CRALF) that enter at adjacent words and preset an SSK/SSM skip-flag pair to select the operation performed.
Status: GOTAB dispatch head byte-proven as fall-through (GOTAB[231B] = 000000,
no per-call stub); the EXPFI worker body is real SINTRAN L bytes and dispatches
(mode 2) to the MEXFI expand-file worker; the exact MON 231 -> worker link
crosses an uncarved kernel bridge (see Honest caveats). All
addresses/values are octal.
- Full disassembly:
231B-ExpandFile.ASM- the actual code (the EXPFI entry + shared create/allocate dispatcher body; there is no entry stub because the GOTAB slot is zero). - Bytes live once in the canonical segment layer:
../../segments-ref/.
Dispatch path¶
flowchart LR
A["User program<br/>MON 231B"] --> B["ENT14 level-14<br/>T = MON number"]
B --> C["GOTAB[231B] = 000000<br/>(byte-proven: fall-through)"]
C -.uncarved MFELL / CALLPROC.-> E["EXPFI expand-file entry<br/>006-S3FS :105555B"]
E --> F["mode 2 -> MEXFI worker<br/>006-S3FS :116623B"]
class A blue
class B,C blue
class E,F green
classDef blue fill:#E3F2FD,stroke:#0D47A1,color:#0D47A1
classDef teal fill:#E0F7FA,stroke:#00838F,color:#00838F
classDef green fill:#E8F5E9,stroke:#2E7D32,color:#2E7D32The GOTAB slot is zero, so there is no per-call entry stub. The dashed hop
(C -> E) is the resident MFELL/CALLPROC fall-through second-level dispatch -
it is not present in any carved segment, so it is the one link that cannot be
followed statically.
Code location (dispatch path)¶
Every row is a real region you can open. Byte offset = (addr - loadbase) in octal words x 2.
| Role | Segment (full disasm) | Addr range (octal) | Byte offset | Symbol | Verdict |
|---|---|---|---|---|---|
| GOTAB[231] dispatch word | commoncode.asm - .hex | 071464B (1 word) |
58984 | GOTAB+231 = 000000 |
VERIFIED (fall-through) |
| resident MFELL/CALLPROC bridge | - (uncarved) | - | - | CALLPROC |
UNVERIFIED |
| EXPFI entry + dispatcher body | 006-S3FS.asm - .hex | 105555B-106042B (body to 106036B) |
48858 | EXPFI |
real bytes; link MISATTRIBUTED |
| MEXFI mode-2 worker | 006-S3FS.asm - .hex | 116623B (link cell 106032) |
- | MEXFI |
link-cell VERIFIED; meaning inferred |
Verify by hand: grep '^105555 ' ../../segments-ref/006-S3FS/006-S3FS.hex -> byte offset 48858;
then dd if=../../../segments/006-S3FS.bin bs=1 skip=48858 count=8 | od -An -tx1 -> f8 b8 f8 10 a8 05 f8 90
(the stored words = octal 174270 174020 124005 174220 = BSET ONE SSM / BSET ZRO SSK / JMP 5 / BSET ONE SSK, the EXPFI entry + next sibling).
The GOTAB slot itself:
dd if=../../../resident/SINTRAN-DATA_commoncode.bin bs=1 skip=58984 count=2 | od -An -tx1 -> 00 00 (= 000000, fall-through).
Instruction walkthrough¶
Full listing: 231B-ExpandFile.ASM. The functional body is
the EXPFI dispatcher; there is no F16xx/F17xx stub because GOTAB[231] = 0. Calls
to shared file-system workers are indirect (JPL I / JMP I) through pointer
tables (link cells) at 105664-105677 and 106021-106042. nd100-dis renders those
pointer words as bogus instructions (STZ, MPY, FDV, STF, ...) - they are
data (link cells), not code; their contents are the real worker addresses
(resolved in the .ASM).
Sibling entries + mode fold (105552-105574) - four entries preset the
SSK/SSM pair and join at 105564: 105552 SFACC (SSM=1/SSK=1, mode 3),
105555 EXPFI (SSM=1/SSK=0, mode 2), 105560 CRALN (SSM=0/SSK=1, mode 1),
105562 CRALF (SSM=0/SSK=0, mode 0). The body stashes the caller's D
(105564 STD I 77), builds the frame B (105567 SAB 145), runs the prologue
worker (105570 JPL I 74 -> 003752), then folds SSM/SSK into a 0..3 mode:
105571 RADD CLD 0 DA (A = 0), 105572 SHA LIN 2 (shift left 2, M-bit fill),
105573 BSET BAC 0 DA (A bit0 = K), stored at B+123 (105574 STA ,B 123).
Parameter unpack + user context (105575-105720) - caller words are copied
into the frame (105575-105621); the user/context is established via
USCPS (031075) and USCPB (031067), and the directory object is read. Each
JPL I is followed by JMP -> 106010 (error, store status).
Second-phase mode dispatch (105721-105776) - a ladder of SAT n /
SKP IF DA EQL ST tests on B+123 selects the worker through a link cell:
| Mode | Worker (link cell) | Symbol | Operation (inferred) |
|------|--------------------|--------|----------------------|
| 3 | 106031 = 120752 | MSFLA | set file allocation |
| 2 | 106032 = 116623 | MEXFI | expand file (ExpandFile) |
| 1 | 106033/106034 = 115430/115433 | MCRFI / MCRNW | create / create-new |
| 0 | 106035/106036 = 116130/116133 | MALFI / MALNE | allocate / allocate-new |
For ExpandFile the mode is 2, so 105743 JPL I 67 -> 106032 = MEXFI runs.
Exit (105777-106042) - 105777 MIN ,B 4 bumps the status; 106000-106005
write the returned handles back through link cells; 106006 SAA -145,
106007 JMP I 33 -> 106042 (= 003776, resident return). The error path
106010 STA ,B 2 stores the status into the caller's slot then loops to 106000.
106021-106042 are the link cells.
Parameter / register contract¶
Contract from Developer/MON/calls/231B_ExpandFile.yaml.
| Reg / field | Dir | Meaning | Verdict |
|---|---|---|---|
| entry point | in | 105555B = EXPFI (expand, SSM=1/SSK=0); siblings 105552/105560/105562 = SFACC/CRALN/CRALF, shared body, SSK/SSM split |
VERIFIED (bytes) |
SSK,SSM |
internal | operation selector pair; preset at each entry, folded to a 0..3 mode at 105571-105574 |
VERIFIED (bytes) |
B+123 |
internal | operation mode (2 = expand) | VERIFIED (bytes); labels inferred |
B+143/144, B+135/136/137 |
internal | page/entry descriptors passed to the workers | VERIFIED (accesses); meaning inferred |
B+140/141/142 |
out | returned handles written back at exit (STA I 36/35/34) |
VERIFIED (bytes); meaning inferred |
B+2 |
out | returned status word (STA ,B 2 at 106010) |
VERIFIED (bytes) |
FileName (user X) |
in | address of file-name string (may be abbreviated) | inferred (manual/yaml) |
NoOfPages (user T) |
in | address of double word = additional pages | inferred (manual/yaml) |
| skip / error | out | normal return skips; error return has error number in A | inferred (manual/yaml) |
The mode-to-worker mapping (MSFLA/MEXFI/MCRFI/MCRNW/MALFI/MALNE) is
byte-proven at the link-cell level (the cell contents equal those FILSYS symbol
addresses); the meaning assigned to each is inferred from the symbol names.
The user-visible X/T convention lives in the caller-side MON 231 wrapper and
the uncarved MFELL/CALLPROC frame, so the X = file-name / T = NoOfPages
assignment is inferred from the manual, not byte-proven here.
Pseudo-code (for an emulator)¶
See 231B-ExpandFile.pseudo.c - a pseudo-C model
of the handler for emulator authors. Control flow + the SSK/SSM -> mode fold are
byte-verified; the worker semantics and error-number meanings are inferred from the
FILSYS symbol table and the call structure. Every instruction is translated per the
canonical ND100-INSTRUCTION-SEMANTICS.md
(note the RADD CLD COPY idiom, the SHA LIN M-bit fill, and BSET BAC K-source
used in the mode fold).
Honest caveats¶
What is byte-proven: GOTAB[231B] = 000000 (level-14 dispatch, a fall-through
with no per-call vector); the EXPFI entry at 105555B in 006-S3FS is real code
(entry bytes 174270 174020 124005 match the disassembly); EXPFI presets
SSM=1/SSK=0 and shares its body with the three sibling entries SFACC/CRALN/
CRALF; the mode fold yields mode 2; and the second-phase link cell 106032
contains the FILSYS worker address MEXFI = 116623.
What is NOT proven: the link from the zero GOTAB slot to the EXPFI worker.
Because the vector is zero there is no stub to disassemble and no pointer to
dereference; dispatch drops into the resident MFELL/CALLPROC second-level path,
which lives in an uncarved overlay. So the MON 231 -> EXPFI attribution rests
on the EXPFI symbol name + the matching MEXFI (expand-file) worker call, not a
followed pointer - hence MISATTRIBUTED in the strict sense. Confirming the link
needs a live trace: issue a real MON 231, single-step the level-14 fall-through
into the resident CALLPROC dispatch, and confirm P lands on EXPFI = 105555.
The prologue link cell 003752, the return cell 003776, and the cells 010500/
010506 (reached via 105713/105717) match no FILSYS-SYMBOLS entry; their low
addresses suggest resident-monitor routines outside the resolvable symbol set, and
are not resolved here.
Method: ../../../../../EXTRACTING-RESIDENT-CODE.md - dispatch reality: ../../TASK-05-mismatches.md - master map: ../../MON-CALL-INDEX.md.