| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
Step 5 of the 9P chain (docs/9p.typ 12.5, docs/registry.typ 9P-22, 9P-11, BOARD-1).
THE CLIENT. `Client` in src/9p.zig is the mirror of `Server` and the same shape:
sans-io, no allocator, no threads, no descriptor, caller-owned buffers, and it
builds freestanding. 152 bytes of struct against the server's 9,488, because a
client owns neither a fid table nor a park table -- the far end does.
The API is submit / push+output+wrote / take. Completion is a PULL: a callback
would fire inside push, inside the transport's read, inside the host's poll
dispatch, which is exactly where fs9_service says filesystem work must not
happen. `take()` returns the next completed operation or null, which is
`Server.next()`'s loop-until-null contract read from the other side. Tags are a
fixed 16-entry table indexed BY the tag, so an out-of-order reply -- which 9P
allows and both reference clients rely on -- costs one bounds check. The reply's
TYPE is checked against the request's op, because a tag is only as good as the
table behind it. A `Done` borrows the input buffer and is valid until the next
call; `take()` releases the previous frame on entry, so the rule is mechanical
rather than remembered, and read data and error strings are zero-copy.
And one real caller, so this is not a library with no user: the `9p` word takes
a dial and a path, walks another instance's tree, and opens the bytes in a pane
like any other `Look`.
THE BOARD. A SECOND image, not a second role: the console runtime keeps UART0
bidirectionally and is behaviourally untouched. On the new one the UART carries
9P AND NOTHING ELSE -- no ANSI, no vaxis, no allocator, no heap module. The loop
is uart.read -> push / retry+next -> handle -> reply / output -> writeSome ->
wrote. `writeSome` is new and additive: `write`'s bounded spin DROPS bytes on a
stalled transmitter, which on a protocol stream truncates a reply mid-message
and desynchronises for good, where a short count cannot. BOARD-1's one divider
write raises the line to 921600.
88,000 B text, 49,424 B bss, an 88,080-byte image -- 5.7% of the 1,536,000 B
partition, against the console image's 809,536 B.
THE COMPTIME BRIDGE, which is the part worth reading. `board9p.caps` is the ONLY
place the GPIO tree is described; node ids, parents, names, permissions,
handlers, buffer size and the per-pin directories are all derived from it, and
`fan.dirs` makes `gpio/<n>/value` one table entry serving eleven pins. Modes are
derived from which handlers a file has rather than declared. A second capability
is a table entry, not new tree code.
JP1 became a real table in the new leaf `src/board_pins.zig`, with the ASCII
drawing RENDERED from it at comptime and the pin list COLLECTED from it -- the
9P image links no core and so cannot import board_memory.zig, and copying the
table was not acceptable. A golden test pins the drawing byte for byte, the
console's own shape test still passes, and the identical bytes are present in
all three artifacts.
PROVED. Two daemons: B read A's `/1/body` through the `9p` word into a pane,
byte-identical to plan9port's `9p read` of the same path. Both board images
build. No hardware was attached, so nothing about the board is claimed beyond
what builds and what the host tests cover.
zig build unit-test 585/585. fs-bench unchanged and still zero allocations on
every read row.
---
REVIEW FIXES FOLDED IN. Steps 3, 4 and 5 were verified on the happy path and
then adversarially reviewed by three agents; eight defects, six fixed here, five
of them reproduced with measurements before and after. Full writeup in
docs/registry.typ `9P-27`. In brief:
* a remote crash of the WHOLE daemon: one `size[4]` of zero plus one byte hit
`unreachable` in `fs9_service.fill`. Also 99.7% of a core when the stuck
buffer made `room == 0` return without reading. Now `srv.dead` is a hangup,
checked before the room guard.
* the editor froze 177 s on a dial: `connect(2)` ran on a still-BLOCKING
socket before the deadline existed, and a full accept backlog waits forever.
Now non-blocking with the wait spent against the budget. After: 2.03 s.
* a 64 KiB pty read is exactly `queue_cap` and wiped every unread byte AND
dropped itself. `notePtyOutput` splits at half the cap. Deterministic.
* four silent sockets denied `--fs9` forever; connections now expire on the
same five-second rule the frontend transport already had.
* EMFILE spun a core; the listener pauses and leaves the poll set, as the
frontend listener does.
* `max_fids = 32` made `find` over `9pfuse` fail with 57 consecutive
`Rerror`s -- refuting this step's own acceptance clause. 256 for a host,
`board_fids` 32 for the microcontroller.
Found clean and worth recording: `sig` reaches the foreground process group; the
two-namespace pty lookup is right over both transports; `PaneFile`'s u4 wall is
guarded; reader counts release on every abrupt-death path; `fs_origin` routing
and the reply arithmetic hold under probing.
|
|
|
Step 4 of the 9P chain (docs/9p.typ 12.4, docs/registry.typ 9P-15/16/17/4/5).
src/9p.zig is a base 9P2000 codec and a SANS-IO server: it never touches a
descriptor, takes no allocator, starts no thread, and builds for
wasm32-freestanding and riscv32-freestanding. That is what lets the same code
serve a unix socket here and a UART on the board later.
Server(comptime fs: type) duck-typed on fs.Req/fs.Reply/fs.Reply.Attr, so it
never imports acmefs and acmefs never learns 9P
init{ in, out, root } the caller owns the buffers; msize is derived
retry/next/reply the three fs_service.Transport ops, by name
push/output/wrote/hangup bytes in, bytes out, partial writes supported
next() is a PUMP, not one-message-one-request: a 3-element Twalk is three
lookups, Topen|OTRUNC is a setattr then an open, Tversion is none at all.
Decisions that were open and are now taken, each recorded in the file:
* qid.version is ALWAYS 0, which makes Linux set P9L_DIRECT and skip its
cache -- the 9P equivalent of the FOPEN_DIRECT_IO fuse.zig relies on.
* Every Rread is clamped to the client's count. An over-long one is a hard
-EIO in Linux, not a truncation.
* Rerror carries Linux's exact strerror text (registry 9P-4 option A), so a
mount recovers the errno instead of ESERVERFAULT. Asserted as literals,
because a typo there is 'Unknown error 526' on every mount.
* `.` and `..` are resolved BY THE SERVER. Under FUSE the kernel does it
and acmefs says so; 9P has no kernel, and forwarding `..` as a lookup
would break every client that normalises a path.
* Topen checks the perm bits itself. Under FUSE the kernel enforced them;
over 9P nobody is above the server, and `errors` would have been readable.
* Tcreate and Tremove are Rerror: `new/` creates a pane on WALK, so the
capability exists and is not spelled Tcreate.
THE INTEGRATION BUG, which was not in the protocol: the daemon's push_fs_reply
sent every reply to the FUSE mount, whose park table has no 9P tag, so it
dropped it -- Tversion worked (no core involved) and Tattach hung forever. That
is exactly the 'no routing origin for the 9P descriptor' cell in the layering
table of docs/9p.typ. Session.fs_origin now carries the transport that asked.
Proved with plan9port against a live daemon serving BOTH transports at once:
9p ls / and /1, read index/ctl/tag, write /1/body, stat, a walk through
/1/../index, pane creation through `new/body`, and the two refusals arriving as
strings -- 'permission denied' and 'No such file or directory' -- confirmed on
the raw wire as Rerror text rather than numbers. A write over 9P reads back
through FUSE and a write through FUSE reads back over 9P.
msize 8192, 34,072 bytes per connection (Server 9,488 + in 8,192 + out 16,384,
out being two msize so that every reply is infallible), four connections.
zig build unit-test: 468 tests before, 503 after.
|
