Mazda Connect Reverse Engineering Tools
The CMU is an ARM Linux box. These are the tools used to unpack its firmware, take its binaries apart, build new ones for it, and read what it broadcasts. Each entry says what the tool is and, where it earned its place on this project, what it actually did. For curated community repos and forums, see Community.
Firmware unpacking and diffing
Section titled “Firmware unpacking and diffing”Mazda ships firmware as password-protected .up archives, and every teardown on this site starts by opening one. The v74 teardown unpacked three packages, 70.00.335C, 74.00.230A, and 74.00.324A, and compared them file by file.
Standard archive and diff tooling
Section titled “Standard archive and diff tooling”The packages unpack to a normal directory tree, and the comparison runs with ordinary diff tooling. The highest-signal artifact is the build registry the CMU carries at jci/version.ini: about 52 functional modules, each with its own version string, which turns “what changed” into a table instead of a guess. Binary sizes and checksums then separate a real behavior change from a plain recompile. That method confirmed the Bluetooth radio blob TIInit_10.6.15.bts is byte-for-byte identical across all three builds, and that the Android Auto engine is md5-identical between 230A and 324A. The full module-by-module account is at version differences.
Firmware extraction scripts and package-analysis notes. The community reference for how the .up format is laid out and what sits inside it.
Reverse engineering
Section titled “Reverse engineering”The primary tool for analyzing the ARM binaries pulled from CMU firmware. CMU binaries load under the Ghidra language spec ARM:LE:32:v7. Check the releases page for current versions.
On this project, Ghidra read the embedded strings and disassembly out of individual modules to prove what a size diff only hinted at. It confirmed the wireless-CarPlay API surface (EnableWirelessCarPlayConnection, WirelessSearchStatusChange) appearing in the v74 CarPlay engine blmjcicarplay.so, counted the 137 mode-swap control strings the Android Auto engine blmjciaapa.so gains at v74, and checked the location service svcjcilds.so for the u-blox receiver code absent on v70. Those findings drive version differences, and the service binaries themselves are mapped in Services.
MCP server for LLM-assisted reverse engineering inside Ghidra. Supports assistant mode and headless mode; requires Ghidra 11.3+ (recent releases target Ghidra 12). It layers onto the Ghidra work above; it is not required to reproduce any of it.
Cross-compilation
Section titled “Cross-compilation”ARM cross-compiler targeting the CMU. Built with crosstool-NG against musl libc. The CMU runs glibc 2.11.1, so static-linking against musl sidesteps glibc version conflicts.
This is the class of toolchain anything native needs. The CMU’s on-device C components, mfy-hotkeys, mfy-fastdata, and mfy-gpsdata (listed on what’s open source), are armv7le binaries that have to be built against the CMU’s old glibc to run on it. Cross-compiling for that target, without dragging in a newer libc the unit doesn’t have, is the exact problem this toolchain exists to solve.
On-device profiling and the bench
Section titled “On-device profiling and the bench”Static analysis tells you what changed in the firmware. It does not tell you how long the unit takes to boot or where its RAM goes. Those numbers came off a CMU running on the bench.
Custom boot profiler
Section titled “Custom boot profiler”A small profiler installs as the first startup task and stamps each milestone against /proc/uptime, the kernel’s own clock of seconds since power-on. It writes one log per boot, records each event the moment the process or network state actually appears, and runs under ~1% CPU so it doesn’t distort the thing it measures. It produced the stock-versus-tuned numbers in boot benchmarks: CarPlay 71 s down to 55 s, touch-ready 48 s down to 32 s, on one unit, back-to-back.
Bench rig
Section titled “Bench rig”A Mazda Connect CMU boots on the bench with a 12V supply and a handful of connectors, no vehicle harness and no CAN bus required. That rig is where the boot timings, the ~100-process idle landscape, and the RAM figures were measured. The parts list and connector pinouts are at bench setup, and the live process and memory measurements are at Runtime Analysis.
CAN bus
Section titled “CAN bus”For the CMU-side hardware these databases talk to, see Platform Specs.
Open-source CAN database for the ND MX-5. Standard DBC format, works with most CAN tooling. A DBC is the map that turns raw CAN IDs into named signals like lateral acceleration and yaw rate, the same signals behind the g-force gauge accuracy work.
HS-CAN and MS-CAN message database in KCD format, covering Skyactiv-generation Mazdas.
FORScan
Section titled “FORScan”OBD2 diagnostics and module configuration for Mazda SkyActiv vehicles. See the FORScan overview for Mazda-specific setup and the adapter buying guide for which interface to buy.
Hex editors
Section titled “Hex editors”For inspecting binaries and firmware blobs byte by byte. On this project, byte sizes and checksums were the evidence that separated a real change from a recompile: the CarPlay engine measured exactly 1,741,455 bytes on v70 and 2,744,432 bytes on v74, while TIInit_10.6.15.bts came back identical across all three builds.
- xxd — built into most Unix systems; fine for quick dumps.
- ImHex — pattern-based editor with structure highlighting.
- 010 Editor — commercial, with binary templates for structured formats.
Hardware and firmware references
Section titled “Hardware and firmware references”- silverchris/mazda-cmu-documentation — hardware specs, connector pinouts, and kernel configuration. The closest thing to a datasheet for the unit, and the cross-check behind much of the internals coverage.
- drone540/mazda-firmware-changelogs — compiled firmware version history and changelogs.
Full SoC and hardware detail lives in Platform Specs.