linux-kernel - Re: [PATCH perf 3/4] perf tools: Fix unused variables: x86_{32,64}_regoffset

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Date:	Thu, 21 Jan 2016 12:38:48 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	"Wangnan (F)" <wangnan0@...wei.com>
Cc:	Ben Hutchings <ben@...adent.org.uk>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	He Kuang <hekuang@...wei.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Jiri Olsa <jolsa@...nel.org>, Kaixu Xia <xiakaixu@...wei.com>,
	Zefan Li <lizefan@...wei.com>
Subject: Re: [PATCH perf 3/4] perf tools: Fix unused variables:
 x86_{32,64}_regoffset_table

Em Thu, Jan 21, 2016 at 12:43:04PM +0800, Wangnan (F) escreveu:
> I think this problem is not introduced by my patch. In fact
> there's a fundamental problem in get_arch_regstr() that it is
> impossible to switch sub ISA.

> Not only x86_64 and x86_32, I think on arm64 we also have this
> problem when we try to setup uprobes on arm32 code. For me the
> later problem is more important because there are many legacy arm32
> applications on Android platform (and I have already seen the buggy
> unwind result in this case. It is another problem though).

Humm, and possibly to do something with arm code on a x86 workstation,
even if just analysis, yeah, I think these functions should take as an
argument the desired architecture instead of assuming it is the one in
the machine issuing the commands.
 
> So I suggest us to solve this problem first before considering
> gcc 6 Werror. At least x86_32_regoffset_table and x86_64_regoffset_table
> should both be compiled no matter which ISA we select for perf.
> 
> Thank you.