netdev - Re: [PATCH 1/2] bpf: add a bpf_override

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Message-ID: <1b1ea1f7-14ff-9725-c481-6ca6059d6051@fb.com>
Date:   Wed, 1 Nov 2017 10:18:02 -0700
From:   Alexei Starovoitov <ast@...com>
To:     Josef Bacik <josef@...icpanda.com>, <rostedt@...dmis.org>,
        <mingo@...hat.com>, <davem@...emloft.net>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <ast@...nel.org>, <kernel-team@...com>
CC:     Josef Bacik <jbacik@...com>
Subject: Re: [PATCH 1/2] bpf: add a bpf_override_function helper

On 11/1/17 10:00 AM, Josef Bacik wrote:
> From: Josef Bacik <jbacik@...com>
>
> Error injection is sloppy and very ad-hoc.  BPF could fill this niche
> perfectly with it's kprobe functionality.  We could make sure errors are
> only triggered in specific call chains that we care about with very
> specific situations.  Accomplish this with the bpf_override_funciton
> helper.  This will modify the probe'd callers return value to the
> specified value and set the PC to an override function that simply
> returns, bypassing the originally probed function.  This gives us a nice
> clean way to implement systematic error injection for all of our code
> paths.
>
> Signed-off-by: Josef Bacik <jbacik@...com>

Both bpf and tracing bits look great to me.
Acked-by: Alexei Starovoitov <ast@...nel.org>