nx_gdbstub_gate.nx

nx_gdbstub_gate.nx -- the VERDICT gate for NO1 (nx_gdbstub, watch symbol gdbstub_serve). NO mocks. THE ACCEPT RULE (nishios.plan NO1, verbatim): a STOCK gdb attaches to a running guest, breaks at an address the disassembler independently resolved, steps, reads a register whose value a separate path derived, and detaches leaving the guest running -- plus a NEG-CONTROL that a breakpoint at an address never executed does NOT stop. The oracle is a third-party debugger, so this rung cannot be self-graded. HOW EACH EXPECTATION IS DERIVED INDEPENDENTLY OF THE STUB (the stub is never its own oracle): bp address = the pc of the FIRST store-kind instruction the K-R0 boot image executes, found by running a SECOND, stub-free sim in this process and DECODING each fetched word with rv64im_min_decoder (nx_rv64im_decode_kind == NX_RV64IM_OP_STORE). register = that store's rs2 (decoded) read from the reference sim's regfile at that pc. next pc = bp + 4, after asserting the word is a 32-bit encoding ((w & 3) == 3) and a store never branches. memory words = the first two little-endian words of the IMAGE FILE, not of any sim. never-addr = the lowest 4-aligned RAM address at/after the image end that the reference run NEVER fetched (a bitmap of every executed pc over the WHOLE boot, not a guess). golden = <image>.gold, the transcript the boot rulers already certify. SESSIONS (each on a FRESH stub process, port 0 = kernel-chosen, read back from the stub's ready file): A stock gdb: attach, break *bp, continue, p/x $xN, stepi, x/2xw mem_base, detach -> T1..T7 B stock gdb: break *never-addr, continue -> the guest must run to EXIT, never a breakpoint stop -> T8 C sovereign RSP client (no gdb): a frame with a WRONG checksum must be NAK'd; a good '?' must be ACK'd and answered S05; 'D' must be answered OK; the stub must count the bad frame -> T9..T12 If no stock gdb is on this host, sessions A/B are a MISSING PRECONDITION (gv_need -> SKIP), never a pass and never a RED: the oracle leg is reported UNWITNESSED, C still runs. (NAS: no gdb; laptop WSL: gdb-multiarch 15.1 installed 2026-08-23 as a third-party ORACLE only.) Fixtures live in /tmp/nx_gdbstub_gate/ (created at setup; a crashed run cannot leave a fixture beside a production beat). Every tooth prints the values it compared, not only PASS/FAIL. license_tier: ORIGINAL (the debugger is an oracle; nothing of it ships)