Roflin
30563b166d
Previous version launched the image it had just received, which is the one
thing that cannot be made safe: a broken build hangs the console and the
checks can only catch a truncated or non-DOL image, never a plausible but
broken one.
The flow is now receive -> write to SD -> boot /boot.dol:
- netboot_sd_write() mounts the card (auto-detecting SD2SP2, then SD Gecko
slot B, then slot A), writes the image to the path the host asked for,
and READS IT BACK AND COMPARES. A half-written .dol that still parses is
exactly the failure this design exists to avoid, and the card is the one
component here with no other integrity check.
- netboot_boot_file() then loads /boot.dol -- a known-good Swiss -- and
launches that instead.
So the only image this ever jumps into is one that was already known good. A
broken test build costs nothing: Swiss comes up and can load anything,
including the previous build. If the SD write or verify fails, nothing is
launched at all and the menu is still there.
The destination path travels in the DONE frame rather than being baked in, so
the host decides where the build lands (send-dol.py --dest, default
/gc_bba_test.dol).
libfat is unmounted before the jump: leaving the card mounted hands the next
image a filesystem libfat still thinks it owns, on an EXI channel it is about
to reinitialise.
Note the SD Gecko in memory-card slot A shares EXI channel 0 with the BBA
(channel 0, device 2). libogc arbitrates, but SD2SP2 is on its own channel
and avoids the question -- hence the detection order.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
152 lines
6.3 KiB
Markdown
152 lines
6.3 KiB
Markdown
# re-bba-rb — on-console test suite (GameCube)
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A `.dol` you run from Swiss that drives the adapter in Serial Port 1 and
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reports pass/fail per test on the TV.
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## Build
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Needs devkitPro's `gamecube-dev` group (devkitPPC + libogc). The devcontainer
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installs it — if `DEVKITPPC` is unset, **rebuild the container**, since the
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toolchain is added in `.devcontainer/Dockerfile`.
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```bash
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make # -> gc_bba_test.dol
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```
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Copy the `.dol` to your SD card (SD Gecko / SD2SP2) and launch it from Swiss.
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## Controls
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| Button | |
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| D-pad up/down | move |
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| A | open a suite / rerun the selected test |
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| X | run the selected suite |
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| START | run everything |
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| Y | clear all results |
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| B | back |
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## What it tests
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| Suite | Proves |
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| Identity | device enumerates: `04 02 02 00`, HIPR, NWAYS |
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| Registers | PAR0–5, IMR writable and read back; IR is write-1-clear |
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| Reset/control | NCRA RESET self-clears, SR holds |
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| EXI integrity | 200 reads with no bit errors; which EXI clock indices work |
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| Ethernet | MAC readback, 60-byte ARP transmit (TI), frame receive (RWP/RI) |
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| SPRAM/DMA | ring descriptor is well-formed; reads ≥ 0x100 stream until CS |
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## Things that will bite you
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**The device ID is a ONE-SHOT.** Address 0 returns `04 02 02 00` only until
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the first NCRA reset clears `id_phase` in the gateware; after that it reads
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back NCRA. That is correct — it matches the GC's own init order — but it means
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the Identity test can only pass once per *console power cycle*. Run it before
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the Reset suite. On a re-run the app reports SKIP with an explanation rather
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than a misleading failure.
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**TI is not proof of transmission.** It only means `TXFrameDrain` handed the
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frame to the W5100. A frame can set TI and never reach the wire. The TX test
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says so; to confirm the wire, capture on a PC or watch the RX test pick up a
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reply.
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**The RX test needs traffic.** It waits ~2 s for any frame. On an isolated
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link with nothing talking it will fail legitimately — give the PC an address on
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the same subnet (the ARP the TX test sends is aimed at `10.0.0.50`, so
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`sudo ip addr add 10.0.0.50/24 dev <nic>` makes the PC answer it and both tests
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pass together).
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**Never over-clock a register read.** Asking for N bytes and clocking more
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leaves stale prefetched bytes queued and desynchronises the *next* transaction
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— a deterministic every-Nth-read corruption that looks like a signal-integrity
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fault. `bba_read()` clocks exactly `len`; don't "round up" for convenience.
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**TXDATA takes one byte per transaction.** The register file's effective
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address auto-increments per data byte, so a 4-byte write to 0x48 would spill
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into 0x49–0x4B. `bba_tx_bytes()` does it correctly.
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## Build status
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Builds clean (no warnings) with devkitPPC 16.1.0 / GCC 16 in the devcontainer:
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`gc_bba_test.dol`, ~172 KB, entry `0x80003100`.
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`.gitignore` excludes the build products — run `make` to produce the `.dol`.
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## Self-update over the BBA (Z button)
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Press **Z**, then on the host:
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```bash
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sudo ./scripts/send-dol.py <iface> gc_bba_test/gc_bba_test.dol
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```
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The flow is deliberately **receive → write to SD → boot Swiss**:
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1. The new build arrives over the adapter into a staging buffer.
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2. It is written to the SD card (default `/gc_bba_test.dol`, override with
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`--dest`) and **read back and compared**.
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3. The app then boots **`/boot.dol`** — your known-good Swiss.
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**The received image is never launched.** The only thing this ever jumps into
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is Swiss, which was already known good. So a broken test build costs nothing:
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Swiss comes up, and you load whatever you like from there, including the
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previous build. That is what makes the update recoverable without a power
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cycle or digging the SD card out.
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If the SD write or the verify fails, nothing is launched at all — you stay in
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the menu with a working app.
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`sudo` is needed for `CAP_NET_RAW`. The GC's MAC is discovered from its first
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ACK, so neither side needs an address configured.
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### Why it is not IP
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Frames carry a private ethertype (`0x88B5`, IEEE 802 local experimental 1) and
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a 12-byte header: no ARP, no IP stack, no checksums, and no libogc network
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driver competing for the EXI channel. It reuses exactly the two paths the test
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suite already proves on hardware — `bba_tx_bytes()` for TX and the SPRAM ring
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at RRP for RX — so each update doubles as a few hundred round trips of soak
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testing through that path.
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### Stop-and-wait is load-bearing
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The gateware does not consume RRP, so `RXFrameAssembler` can overwrite ring
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pages the GC has not read yet — there is no overflow protection. One block in
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flight means the ring never holds more than one unread frame. Do **not** turn
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this into a sliding window without adding RBFI-style protection first.
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### SD interfaces
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`netboot_sd_write()` auto-detects, trying SD2SP2, then SD Gecko slot B, then
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slot A. Note the SD Gecko in **slot A shares EXI channel 0 with the BBA**
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(channel 0, device 2); libogc arbitrates, but SD2SP2 sits on its own channel
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and avoids the question.
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### Why the copier lives in assembly at the top of MEM1
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A DOL's sections load from 0x80003100 upward — exactly where this program's own
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`.text` sits. A copier compiled as an ordinary C function would **overwrite its
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own instructions partway through the copy** and hang. So:
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- `netboot_reserve()` carves the top of MEM1 and hands it to
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`SYS_SetArena1Hi()`, so neither libogc nor `malloc` will touch it.
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- `netboot_stub.S` is copied into that region and executed *there*. It must
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stay strictly position independent: no globals, no literal pool, no TOC
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references, no calls — otherwise it reads from the address it was *linked*
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at instead of the one it is *running* at.
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- `netboot_launch()` checks every section (and BSS) against the reserved
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region and **refuses** if any would land on it.
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### Failure behaviour
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- 30 s with no frames, or 5 s mid-transfer, aborts back to the menu.
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- A duplicate block is re-ACKed rather than ignored, so a lost ACK recovers.
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- `netboot_receive()` re-asserts the NCRA SR bit first: an earlier test may
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have left receive disabled, and it would otherwise wait forever for frames
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the gateware is not storing.
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- A failed SD write or verify launches nothing.
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- The residual risk is confined to booting `/boot.dol`. If that is a healthy
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Swiss, this is the safe part; if it is missing or corrupt, you get a message
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and stay in the menu — the new build is already on the card either way.
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