linux-kernel - Re: [PATCH x86/urgent] bpf: emulate push insns for uprobe on x86

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Message-ID: <f3babdc6-1018-7c48-86d6-b6b177885310@fb.com>
Date:   Wed, 8 Nov 2017 23:57:44 -0800
From:   Yonghong Song <yhs@...com>
To:     Thomas Gleixner <tglx@...utronix.de>
CC:     David Miller <davem@...emloft.net>, <mingo@...nel.org>,
        <oleg@...hat.com>, <peterz@...radead.org>,
        <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
        <netdev@...r.kernel.org>, <ast@...com>, <kernel-team@...com>
Subject: Re: [PATCH x86/urgent] bpf: emulate push insns for uprobe on x86



On 11/8/17 10:53 PM, Thomas Gleixner wrote:
> On Wed, 8 Nov 2017, Yonghong Song wrote:
>> On 11/8/17 4:06 PM, David Miller wrote:
>>> From: Yonghong Song <yhs@...com>
>>> Date: Wed, 8 Nov 2017 13:37:12 -0800
>>>
>>>> Uprobe is a tracing mechanism for userspace programs.
>>>> Typical uprobe will incur overhead of two traps.
>>>> First trap is caused by replaced trap insn, and
>>>> the second trap is to execute the original displaced
>>>> insn in user space.
>>>    ...
>>>
>>> I don't understand how this is bpf related, and if it is you don't
>>> explain it well in the commit message.
>>
>> Right. This is not related to bpf. Will remove the "bpf" from the subject line
>> in the next revision.
> 
> The proper subject is something like:
> 
>      [PATCH] uprobes/x86: .......

Thanks, Thomas,

I will fix the subject etc. Previously, I added x86/urgent as the branch
I did my test on top of it (similar to net-next). I will add that 
information in the comments and re-submit.

> 
> which you can figure out by looking at the subsystem prefixes via
> 
>      git log arch/x86/kernel/uprobes.c
> 
> Note, that it says [PATCH} and nothing else. That patch is a nice
> performance improvement, but certainly not x86/urgent material. x86/urgent
> is for bug and regression fixes.
> 
> Thanks,
> 
> 	tglx
>