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

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Message-ID: <alpine.DEB.2.20.1711090749190.1962@nanos>
Date:   Thu, 9 Nov 2017 07:53:31 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Yonghong Song <yhs@...com>
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 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: .......

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