Hi, I work on Hotspot[1] an opensource linux perf aggregator and visualizer. For this we use perfparser[2], which in turn uses libdw for unwinding.
Recently, we found more and more perf trace-files to use the 'pgoff' field [3]. This happens especially on newer distros, (arch, opensuse tumbleweed). We suspect perf to offset its recording-addresses of mmapped dsos/executables starting with a specific section, such that they denote their pointers with this pg_offset parameter. (e.g. skipping a library's header and setting pgoff to the headersize). Although we are not 100% sure about this information. The Function I am using here is: extern Dwfl_Module *dwfl_report_elf (Dwfl *dwfl, const char *name, const char *file_name, int fd, GElf_Addr base, bool add_p_vaddr); in the specific call I am doing is: Dwfl_Module *ret = dwfl_report_elf( m_dwfl, info.originalFileName.constData(), info.localFile.absoluteFilePath().toLocal8Bit().constData(), -1, info.addr, false); and I am wondering how to include the pgoff here. Simply subtracting it from info.addr results in a lots of "address range overlaps an existing module" errors, where I guess I subtracted too much. I know pgoff is in bytes. Tried adding the offset, also overlap errors. Ignoring the offset results in errors where perfparser fails to find ELF for instruction pointer addresses. I would be happy to hear if anyone has experience unwinding with these offsets. Maybe there is a different function I should use reporting the elf. Maybe even someone unwinded/parsed perf data before. Thanks, Christoph [1] https://github.com/KDAB/hotspot [2] http://code.qt.io/cgit/qt-creator/perfparser.git/ [3] sparse info at http://man7.org/linux/man-pages/man2/perf_event_open.2.html -- Christoph Sterz | christoph.st...@kdab.com | Software Engineer KDAB (Deutschland) GmbH, a KDAB Group company Tel: +49-30-521325470 KDAB - The Qt, C++ and OpenGL Experts
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