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Linux Developers Consider On-Screen QR Codes For Kernel Panics
An anonymous reader writes "Linux kernel developers are currently evaluating the possibility of using QR codes to display kernel oops/panic messages. Right now a lot of text is dumped to the screen when a kernel oops occurs, most of which isn't easily archivable by normal Linux end-users. With QR codes as Linux oops messages, a smart-phone could capture the display and either report the error string or redirect them to an error page on Kernel.org. The idea of using QR codes within the Linux kernel is still being discussed by upstream developers."
It might actually be more than that. Worst case, the screen in in 80x25 text mode (assuming a PC), which gives 2,000 binary bits, but if you start playing around with extended ASCII graphics characters you could probably encode a KB of data quite easily. Hardly a crash dump, but easily enough to get across the essentials.
UNIX? They're not even circumcised! Savages!
QR codes use Reed-Solomon error correction, so you don't get missing or corrupt data (in that the QR reader knows if it reconstructed all the data correctly or not). Readers will typically only "read" the code if they manage to reconstruct the entire thing. The error correction helps compensate for poor image quality, and the fact that the image is monochrome makes things like exposure less critical. There are four levels of error correction, which allow for the reconstruction of 7%, 15%,25%, or 30% of codewords respectively.
QR codes can store up to a bit under 3KB of data (the largest size with the lowest error correction), but I couldn't get my phone to read any v40 QR codes (the largest ones), and v25 took some effort. The plan for QR codes of kernel oopses will probably fail for that reason, if nothing else (that they need v40 codes to store an entire oops, and few phones will read v40 codes).
We are encoding the full Oops, i.e. from the "cut here" to the "end trace" marker. Classic won't ever go away, and we had already created a configuration option called CONFIG_QR_OOPS that can disable this at all. In case your distro or you had compiled it in and you don't want to have QR codes on your screen, I just added a new kernel parameter currently called 'qr_oops', which can as well disable it.
Cheers Levente Kurusa
Windows writes crash data to the swap file and even then it fails from time to time.