§H.12 step 17: zuse_eligibility_list.h -- eligibility-list record format

Growable owner_pubkey[32]-list devblock type for the metadata fence,
one slot over from zuse_genesis_marker_t (§H.5 Phase 6). Type only,
no read/add/check logic yet.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QgooKd5hJNtTYqB6CyK5f9

include/starkernel/zuse_eligibility_list.h

@@ -0,0 +1,83 @@
+/*
+ * zuse_eligibility_list.h -- on-disk record format for Zuse's word/block
+ * elevation eligibility list (FABRIC-3.md §H.5/§H.12 Phase 6): a simple
+ * growable list of owner_pubkey[32] entries, no extra per-entry metadata
+ * ("simple list, no extra metadata, unless we find a reason this won't
+ * work"). Zuse checks this list before honoring any ELEVATE-REQUEST
+ * (§H.7/§H.8) -- gating layer on top of the message-based elevation
+ * trigger, not a replacement for it.
+ *
+ * Lives in the same top-of-device system-metadata fence as
+ * zuse_genesis_marker_t (block_subsystem.h's blk_meta_zone_read()/
+ * write(), Phase 8/§C), one slot over: the genesis marker owns
+ * devblock_from_top=0, this list starts at devblock_from_top=1. Growable
+ * across multiple devblocks via a singly-linked chain (each devblock's
+ * `next_devblock_from_top` points at the next one, ZULIST_NO_NEXT means
+ * "this is the last devblock in the chain") -- entries are appended by
+ * filling the current tail devblock, then chaining a fresh one out of the
+ * already-reserved BLK_META_FENCE_INIT budget once it's full. No fence
+ * growth logic is needed yet: only 2 of the 128 pre-reserved devblocks
+ * are spoken for (0 = genesis marker, 1 = this list's head) and the
+ * chain has 126 more slots to grow into before that budget itself would
+ * need extending.
+ *
+ * Raw, unpacked 4 KiB devblock -- same convention as
+ * zuse_genesis_marker_t/homeblocks_sig_t: real CRC from day one, this
+ * gates a real security check, not a placeholder.
+ */
+#ifndef STARKERNEL_ZUSE_ELIGIBILITY_LIST_H
+#define STARKERNEL_ZUSE_ELIGIBILITY_LIST_H
+
+#include <stdint.h>
+
+/* Packed via shifts, not a hand-computed hex literal -- see
+ * zuse_genesis_marker.h's own note on this project's standing
+ * numeric-constant convention. */
+#define ZUSE_ELIGIBILITY_LIST_MAGIC \
+    ((uint32_t)'Z' | ((uint32_t)'E' << 8) | ((uint32_t)'L' << 16) | ((uint32_t)'G' << 24))
+
+#define ZUSE_ELIGIBILITY_LIST_VERSION 1u
+
+/* devblock_from_top of this list's head devblock -- one past the genesis
+ * marker's devblock_from_top=0. */
+#define ZUSE_ELIGIBILITY_LIST_HEAD_DEVBLOCK 1u
+
+/* next_devblock_from_top value meaning "no further devblock -- this is
+ * the tail of the chain." 0xFFFFFFFF can never be a real
+ * devblock_from_top (BLK_META_FENCE_INIT is 128), so it is unambiguous. */
+#define ZUSE_ELIGIBILITY_LIST_NO_NEXT 0xFFFFFFFFu
+
+/* How many owner_pubkey[32] entries fit in one devblock alongside the
+ * header/crc/next-pointer overhead below. */
+#define ZUSE_ELIGIBILITY_ENTRIES_PER_DEVBLOCK 127u
+
+typedef struct {
+    uint32_t magic;       /* ZUSE_ELIGIBILITY_LIST_MAGIC; anything else on
+                            * the head devblock means "list not created
+                            * yet" (blank/foreign bytes), not a
+                            * format-corruption error. A non-head devblock
+                            * is only ever read by following a real
+                            * next_devblock_from_top link, so its own
+                            * magic is still checked the same way to catch
+                            * a corrupt/foreign devblock mid-chain. */
+    uint32_t version;     /* ZUSE_ELIGIBILITY_LIST_VERSION */
+    uint32_t count;        /* Number of valid entries in this devblock's
+                            * own entries[] (0..ZUSE_ELIGIBILITY_ENTRIES_
+                            * PER_DEVBLOCK), not a running total across the
+                            * whole chain. */
+    uint32_t next_devblock_from_top; /* Next devblock in the chain, or
+                            * ZUSE_ELIGIBILITY_LIST_NO_NEXT if this is the
+                            * tail. */
+    uint8_t  entries[ZUSE_ELIGIBILITY_ENTRIES_PER_DEVBLOCK][32]; /* Ed25519
+                            * public keys eligible for elevation. Only the
+                            * first `count` entries are meaningful. */
+    uint64_t crc;          /* CRC-64/ISO (block_subsystem.h's
+                            * compute_crc64()) over every byte of this
+                            * struct up to (not including) this field. */
+    uint8_t  _pad[4096 - (4 + 4 + 4 + 4 + (ZUSE_ELIGIBILITY_ENTRIES_PER_DEVBLOCK * 32) + 8)];
+} zuse_eligibility_devblock_t;
+
+_Static_assert(sizeof(zuse_eligibility_devblock_t) == 4096,
+               "zuse_eligibility_devblock_t must be exactly one 4 KiB devblock");
+
+#endif /* STARKERNEL_ZUSE_ELIGIBILITY_LIST_H */