Messages in this thread | | | Date | Mon, 1 Oct 2012 09:21:54 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH v2 3/4] perf annotate: configure objdump path at compile time |
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* Namhyung Kim <namhyung@kernel.org> wrote:
> On Thu, 27 Sep 2012 14:25:10 +0300, Irina Tirdea wrote: > >>> The perf built to run on the host needs to use arm-eabi-objdump from > >>> the toolchain so that it can analyse data recorded on Android. This > >>> patch is targeting this scenario, not the previous one. In this case, > >>> the CROSS_COMPILE option would be different than arm-eabi- so using > >>> $(CROSS_COMPILE)objdump would be wrong. objdump should be overridden > >>> when running make since there is no connection between the toolchain > >>> used here and the path for objdump. I am always overriding objdump > >>> when calling make, so I did not catch this. > >>> > >>> I think that I should change DEFAULT_OBJDUMP_PATH=objdump in the > >>> Makefile to handle the first scenario. I'll also explain this in the > >>> commit message so that it is more clear and make the same change for > >>> the addr2line patch. > >>> > >>> What do you think? > >> > >> I think the right thing to do is finding a correct objdump at runtime in > >> some way. Why do you want to make it compile-time configurable? > >> > > > > The correct objdump path can be detected at runtime by setting the > > toolchain path. But since the name is arm-eabi-objdump and not > > objdump, it does not know to use it instead. > > > > The only way (I can think of) to change objdump at runtime would be to > > use the --objdump option for perf annotate (and provide a similar > > option for addr2line). The problem with this approach is that the user > > has to be aware that perf annotate uses the objdump tool and that he > > has to use the cross-compiler version instead. Since the user will > > have perf compiled for host as part of his Android tree, he will > > expect it to work without these further changes from his part. The > > path for objdump can be set in the Android Makefile at compile time so > > that the user doesn't need to be aware of it. > > What I'm thinking is that perf can try to find cross-built > binutils when it detects perf.data file is came from other > machine/architecture. Fortunately perf_session_env was added > recently and it has the arch information from the file so we > can use it to find the path. > > Following patch is a proof-of-concept patch and only build > tested. What do you think? Could you play with it for some > time? :)
This is a pretty clever idea - much better than hard-coding architecture details at build time.
Thanks,
Ingo
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