On Friday, January 6, 2017 8:17:53 PM CEST Mark Wielaard wrote: > On Fri, Jan 06, 2017 at 11:28:25AM +0100, Milian Wolff wrote: > > On Wednesday, January 4, 2017 2:42:23 PM CET Mark Wielaard wrote: > > > Longer answer. An address pointing into the PLT does > > > really point to an ELF symbol. > > > > You mean: does _not_ > > Right? > > Yes, I meant "does not point". > > > > If we have such a backend function then we could even > > > do what BFD apparently does. Which is to then create a > > > "fake" symbol with as name real_function@plt. But I am > > > not sure such fake symbols are very useful (and will > > > quickly become confusing since they aren't real ELF > > > symbols). > > > > So the objdump command I used is leveraging BFD internally to give me the > > @plt names? I noticed that I also see @plt in perf, which is also > > probably using BFD internally. That at least clarifies why it works in > > some tools but not in when using dwfl. > > binutils objdump certainly does. > > > > Hope that helps. And maybe inspires someone (you?) to > > > write up such a backend function and corresponding > > > dwfl frontend function. > > > > It does help, thanks. I'm interested in contributing such functionality, > > but, sadly, I'm not sure when I'll get the time to actually do it. > > Thanks, wish I had spare time myself :)
I have now looked into this issue again and have found a way to workaround this limitation outside of elfutils, by manually resolving the address in a .plt section to a symbol. See: https://github.com/KDAB/perfparser/commit/ 885f88f3d66904cd94af65f802232f6c6dc339f4 This seems to work in my limited tests (only on X86_64). Beside the 32bit/ 64bit difference, it isn't really platform dependent, is it? Or was this what you had in mind when you said the elfutils code would be "architecture specific [and] we would need a backend function that translates an address pointing into the PLT into an actual function address"? If my code is roughly OK, then I'll try to put it into a patch for elfutils and submit it there. If it's fundamentally broken, please tell me. I still plan to get this functionality upstream into elfutils. Cheers -- Milian Wolff m...@milianw.de http://milianw.de
