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fw/ta_diff_all.py writes every meaningful same-branch consecutive-build diff to fw/diffs/, one file
per pair plus an INDEX.md.
Two correctness rules are baked in, both learned by getting them wrong first. The third version field
is a BRANCH, not a sequence -- ASD ships 33.0.0.x through 33.0.28.x in parallel -- so only same-branch
pairs are emitted; comparing across them made asd_dispatch oscillate 842/1306/1352 bytes, which is
branch identity misread as change over time. And the four noise sources measured earlier are
normalised away: tier annotations, address-derived tokens, long hex literals, local renumbering.
Each file leads with the size table from the index sidecars, which is the signal no decompiler
instability can fake: same function, different byte size means the code changed. Body hunks follow,
grouped per function, with local declarations dropped.
INDEX.md opens with four findings rather than making the reader hunt: the HDCP 23.0.0.52 -> .57
timing side-channel fix in the HDCP 2.x locality check, where L' verification moved from early-exit
memcmp_be to constant-time ct_memcmp; GCP's ASIC allowlist in cmdFE08 growing from 14 to 28 entries
across nine builds with 0xe backfilled out of order; the teardown sequence added to GCP's three
session-lifecycle handlers at 22.0.0.62; and a warning not to read ASD's dispatch case lists as
change, since the 48 labels that appear and vanish are Hex-Rays alternating between a switch and the
range check rpc_id - 384 <= 0x40.
The index marks `resized` as the trustworthy column and `new`/`gone` as leads, because a function
named in one build and not another shows up there without any firmware change behind it.
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