Hi Milian, On Sat, Mar 17, 2018 at 02:14:48PM +0100, Milian Wolff wrote: > a recurring issue in the libdwfl integration of perf and perfparser are > supposedly overlapping modules. The perf data file contains the exact > mappings > for all files corresponding to the actual mmap events that occurred during > runtime, e.g.: > > ``` > $ perf script --show-mmap-events | grep MMAP | grep stdc > heaptrack_print 13962 87163.483450: PERF_RECORD_MMAP2 13962/13962: > [0x7fd0aea84000(0x387000) @ 0 08:03 413039 3864781083]: r-xp /usr/lib/libstdc+ > +.so.6.0.24 > heaptrack_print 13962 87163.483454: PERF_RECORD_MMAP2 13962/13962: > [0x7fd0aebfc000(0x1ff000) @ 0x178000 08:03 413039 3864781083]: ---p /usr/lib/ > libstdc++.so.6.0.24 > heaptrack_print 13962 87163.483458: PERF_RECORD_MMAP2 13962/13962: > [0x7fd0aedfb000(0xd000) @ 0x177000 08:03 413039 3864781083]: rw-p /usr/lib/ > libstdc++.so.6.0.24 > heaptrack_print 13962 87163.484860: PERF_RECORD_MMAP2 13962/13962: > [0x7fd0aedfb000(0xc000) @ 0x177000 08:03 413039 3864781083]: r--p /usr/lib/ > libstdc++.so.6.0.24 > ``` > So far, both perf and perfparser are using dwfl_report_elf to report the > file. > But that API is deducing the mapping addresses internally, which may or may > not be what we saw at runtime. I suspect that this is the reason for some > issues we are seeing, such as supposedly overlapping modules.
How exactly are you calling dwfl_report_elf? Specifically are you using false for the add_p_vaddr argument? And could you provide some example where the reported address is wrong/different from the start address of the Dwfl_Module? > Looking at the Dwfl API, I cannot figure out how to feed the mapping > directly. > There's dwfl_report_module, but how would I associate an Elf* and int fd with > it, as done by dwfl_report_elf? When using dwfl_report_module the find_elf callback will be called that you registered with dwfl_begin. That callback is called "lazily" the first time dwfl_module_getelf is called. The callback can then set the Elf*. But that does mean you have to keep track yourself (or immediately call dwfl_module_getelf). I would like to understand better what is really going wrong with dwfl_report_elf before diving into using dwfl_module_report. Cheers, Mark
