[Crash-utility] Extensions: Dump log buffer of Intel Processor Trace

Hi Dave, The attached files are extension module to dump log buffer of Intel Processor Trace from vmcore. Please consider placing this in the extensions page. [Overview of PT] PT(Processor Trace) is a new feature of Intel CPU "Broadwell", it captures information about program execution flow.[1] Once Intel PT is enabled, the events which change program flow, like branch instructions, exceptions, interruptions, traps and so on are logged in the memory. This is very useful for debugging because we can know the detailed behavior of software. [About extension] This extension retrieves log buff of PT from vmcore and saves it as a file. 'ptdump' command can be used once this extension is loaded. crash> extend extensions/ptdump.so ./extensions/ptdump.so: shared object loaded crash> ptdump output_dir [0] buffer dump: dump.0 [0] packet decode: decode.0 [1] buffer dump: dump.1 [1] packet decode: decode.1 (snipped) In this case, output_dir directory is created, and then dump.N and decode.N files are created in the directory for each cpus(N is cpu number). dump.N: raw data of PT decode.N: result of PT packet decoder dump.N is binary data and it is not human readable. decode.N is generated by fastdecode[2], which is PT packet dumper created by Andi Kleen. It's useful for checking what kinds of packets are included in dump.N. I'll update extension using PT library(libipt[3]) to generate more useful file for investigation. [Build extension] To build the module from the top-level crash-<version> directory, enter: $ tar xvf ptdump-1.0.0.tar.gz $ mv ptdump-1.0.0/* extensions $ make extensions [1] https://software.intel.com/en-us/blogs/2013/09/18/processor-tracing [2] https://github.com/andikleen/simple-pt [3] https://github.com/01org/processor-trace Thanks, Takao Indoh