Bug Index¶

All 23 bugs encountered during the MR18 OpenWrt JTAG flash project, from first power-on to successful failsafe boot.

Summary Table¶

Bug #	Title	Category	Related Doc	One-line Summary
1	Wrong Binary (ar71xx vs ath79)	Toolchain	address-map	ar71xx lzma-loader zeroes BSS before relocation, wiping LZMA data.
2	OpenOCD Startup Timing	JTAG/PRACC	script-reference	OpenOCD started before power-on; no live TAP during init scan.
3	Socket Buffer Contamination	JTAG/PRACC	script-reference	Hardcoded 0.5s socket timeout caused _drain() to return before load_image finished.
4	PRACC Write Bit Errors	JTAG/PRACC	mips-memory-model	PRACC handshake protocol errors caused 18 single-bit flips per 45 KB sample.
5	Hardware Watchdog	Boot/kernel	address-map	AR9344 hardware watchdog continues counting during JTAG halt.
6	Named Pipe EOF	Toolchain	script-reference	Named pipe "w" mode sends EOF on close, killing scpi-repl.
7	Flush Trampoline Timeout	Cache coherency	mips-memory-model	CACHE instruction exception when running from KSEG1 with Nandloader exception vectors.
8	Phantom Verify Errors	Verification	mips-memory-model	PRACC reads inherit the same bit-flip rate as writes, producing phantom corrections.
9	Trampoline Overlaps Binary	Verification	address-map	TRAMPOLINE_ADDR inside loaded binary range overwrote XOR program during chunk rewrite.
10	XOR Cancellation	Verification	mips-memory-model	Two corrupt words with matching XOR deltas cancelled, passing full-binary checksum.
11	D-Cache Stale Data	Cache coherency	mips-memory-model	D-cache held stale Cisco data; KSEG1 verification saw correct RAM, KSEG0 execution got stale bytes.
12	BEQ vs BNE Encoding	Verification	mips-memory-model	1-bit opcode error (op=4 vs op=5) caused flush loop to run once instead of 4096 times.
13	Flush Ordering	Cache coherency	mips-memory-model	Post-load flush evicted dirty Cisco D-cache lines back to DRAM, overwriting OpenWrt binary.
14	Ethernet Silent	Boot/kernel	script-reference	Meraki NAND overlay mounted over initramfs, running Cisco userspace instead of OpenWrt.
15	Meraki NAND Overlay	Failsafe	script-reference	OpenWrt preinit mounted Meraki NAND overlay; Meraki management frames appeared instead of OpenWrt.
16	Failsafe Timing	Failsafe	script-reference	GPIO17 asserted at t=30s, but failsafe window closed at t=18s.
17	Missing Resume	JTAG/PRACC	address-map	mdw halts CPU for PRACC read; CPU stayed halted through entire GPIO hammer loop.
18	mdw/mww Require Halt	JTAG/PRACC	address-map	After resume, mdw returns ERROR_TARGET_NOT_HALTED silently; GPIO reads returned nothing useful.
19	GPIO vs Pull-up	Hardware/electrical	address-map	External pull-ups (5 kohm effective) overpower AR934x GPIO drive strength.
20	Reset Supervisor IC	Hardware/electrical	prerequisites	Dedicated reset supervisor IC drives GPIO17 HIGH with strong CMOS output (10-50 mA).
21	Manual Prompt Too Late	Failsafe	script-reference	Useless JTAG hammer consumed 25s before printing prompt; failsafe window already closed.
22	Resistor Wrong Side	Hardware/electrical	prerequisites	100 ohm between GPIO17 net and EN transistor caused voltage drop on wrong side.
23	EN Before Boot	Failsafe	script-reference	EN assertion at t=12s released before kernel finished LZMA decompression at t=18-25s.

Bug Category Distribution¶

pie title Bug Categories
    "JTAG/PRACC" : 6
    "Cache coherency" : 3
    "Verification" : 4
    "Failsafe" : 4
    "Toolchain" : 2
    "Boot/kernel" : 2
    "Hardware/electrical" : 3

Category Breakdown¶

JTAG/PRACC (6): Bugs 2, 3, 4, 17, 18—protocol-level issues with EJTAG PRACC memory access and OpenOCD communication.
Verification (4): Bugs 8, 9, 10, 12—errors in the verify-and-correct pipeline (phantom reads, trampoline placement, XOR cancellation, instruction encoding).
Failsafe (4): Bugs 15, 16, 21, 23—timing and trigger issues getting OpenWrt into failsafe mode.
Cache coherency (3): Bugs 7, 11, 13—MIPS D-cache stale data and flush ordering relative to JTAG load.
Hardware/electrical (3): Bugs 19, 20, 22—physical signal contention between GPIO, pull-ups, reset supervisor IC, and EN wiring.
Toolchain (2): Bugs 1, 6—wrong firmware target and named pipe file mode.
Boot/kernel (2): Bugs 5, 14—hardware watchdog and NAND overlay issues during kernel boot.