linux-kernel - Re: [PATCH 2/2 v2] perf tools: Enable bpf prologue for arm64

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Date:   Fri, 3 Feb 2017 19:08:53 +0800
From:   Hekuang <hekuang@...wei.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Will Deacon <will.deacon@....com>
CC:     Masami Hiramatsu <mhiramat@...nel.org>, <peterz@...radead.org>,
        <mingo@...hat.com>, <alexander.shishkin@...ux.intel.com>,
        <jolsa@...hat.com>, <wangnan0@...wei.com>,
        <bintian.wang@...wei.com>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/2 v2] perf tools: Enable bpf prologue for arm64

hi,

在 2017/1/27 3:31, Arnaldo Carvalho de Melo 写道:
> Em Thu, Jan 26, 2017 at 04:52:12PM +0000, Will Deacon escreveu:
>> On Thu, Jan 26, 2017 at 10:49:16AM +0900, Masami Hiramatsu wrote:
>>> On Wed, 25 Jan 2017 13:32:01 +0000
>>> Will Deacon <will.deacon@....com> wrote:
>>>
>>>> On Wed, Jan 25, 2017 at 07:23:11AM +0000, He Kuang wrote:
>>>>> Since HAVE_KPROBES can be enabled in arm64, this patch introduces
>>>>> regs_query_register_offset() to convert register name to offset for
>>>>> arm64, so the BPF prologue feature is ready to use.
>>>>>
>>>>> This patch also changes the 'dwarfnum' to 'offset' in register table,
>>>>> so the related functions are consistent with x86.
>>>> Wouldn't it be an awful lot simpler just to leave the code as-is, and
>>>> implement regs_query_register_offset in the same way that we implement
>>>> get_arch_regstr but return the dwarfnum?
>>> No, since the offset is not same as dwarfnum.
>>>
>>> With this style, the index of array becomes the dwarfnum (the index of
>>> each register defined by DWARF) and the "offset" member means the
>>> byte-offset of the register in (user_)pt_regs. Those should be different.
>> Ok, then do it as two patches then, rather than introduce functionality
>> along with the renaming.
>>
>>>> I don't really see the point of all the refactoring.
>>> Also, from the maintenance point of view, this rewrite work makes
>>> the code simply similar to x86 implementation, that will be easier to
>>> maintain :)
>> Right, apart from the two howling bugs in the version that was nearly merged
>> initially :p. I tend to err on the "if it ain't broke, don't fix it" side
>> of the argument but if you really want the refactoring lets keep it as a
>> separate change.
> So, He, can you do that? How do we proceed?
>
> - Arnaldo

I split the patch as Will suggested and resend them. Sorry for
late response, just back from Spring festival.