fix(transport): share one frame arena instead of a 12 KB stack frame - #344
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msg_write() encoded outbound frames into a MAX_FRAME_SIZE TrezorFrameBuffer declared as an automatic — a ~12.4 KB stack frame. With the Orchard engine linked in, static SRAM left an ~11 KB gap and the device hard-faulted on boot during RC7 bring-up. Inbound reassembly, outbound encode and the recovery-cipher wordlist scratch are mutually exclusive on a strictly cooperative single-threaded transport (there is no USB ISR; usbd_poll runs only from explicit usbPoll call sites), so they now share one static union. Acquiring the arena for TX or scratch drops any partially reassembled inbound frame; only a host that pipelines a second request before reading the first response can observe it, and it gets a Failure on its next continuation frame rather than silent corruption. The reassembly state moves to file scope so arena acquisition can invalidate it.
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Superseded by the smaller audit-ready 7.15 stack: #359 release foundation, #360 authenticated clear-signing, #361 recovery and entropy, #362 Zcash Orchard, #363 chain integrations, and #364 Bitcoin/release security. All release changes remain preserved in the replacement branches and preservation tags. The replacement aggregate was tree-verified against the prior release and passed the local CI-equivalent container suite (405 firmware, 2 board, 18 crypto, and 7 Pallas constant-time tests). GitHub-hosted checks have been explicitly dispatched and are currently queued. |
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7.15 review stack position 03/17.
This PR is intentionally one coherent commit, based on
feature/715-02-board-display-printf, for individual auditing.The full stack is linear from the clean fork
developat 1af2ffe.Review scope: fix(transport): share one frame arena instead of a 12 KB stack frame.
The preserved pre-restage candidate remains available at
preserve/alpha-2026-08-05.