linux-kernel - Re: [PATCH v2 3/4] perf annotate: configure objdump path at compile time

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Date:	Thu, 27 Sep 2012 10:52:14 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Irina Tirdea <irina.tirdea@...il.com>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Ingo Molnar <mingo@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	LKML <linux-kernel@...r.kernel.org>,
	Paul Mackerras <paulus@...ba.org>,
	David Ahern <dsahern@...il.com>,
	Pekka Enberg <penberg@...nel.org>,
	Jiri Olsa <jolsa@...hat.com>,
	Irina Tirdea <irina.tirdea@...el.com>
Subject: Re: [PATCH v2 3/4] perf annotate: configure objdump path at compile time

On Thu, 27 Sep 2012 03:51:07 +0300, Irina Tirdea wrote:
> On Tue, Sep 25, 2012 at 4:08 PM, Namhyung Kim <namhyung@...nel.org> wrote:
>> I thought about it twice and confused.
>>
>> For cross-compiling, the resulting perf binary will run on target - say
>> Android - but the toolchain runs on host, right?  So with this change
>> the cross-built perf will try to find the arm-eabi-objdump on Android.
>> Is it an intended behavior?  Is there an arm-eabi-objdump on Android?
>>
>
> Apparently I got confused about this as well...

:)

>
> There are two perf binaries built for Android: one for the target
> (that will run on Android) and the other one for the host (that can be
> used to analyse data recorded on the target).
>
> As you mentioned, the perf built to run on Android needs to use
> objdump as "objdump" (actually Android does not yet have objdump, but
> this is the naming convention). In this case, objdump should not have
> the CROSS_COMPILE prefix.

Ok.

>
> 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?

Thanks,
Namhyung
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