netdev - Re: [PATCH bpf-next v3 1/5] tracing/kprobe: bpf: Check error injectable event is on function entry

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Date:   Wed, 10 Jan 2018 10:21:39 -0500
From:   Josef Bacik <josef@...icpanda.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Alexei Starovoitov <ast@...com>, Josef Bacik <jbacik@...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, daniel@...earbox.net,
        linux-btrfs@...r.kernel.org, darrick.wong@...cle.com,
        Josef Bacik <josef@...icpanda.com>,
        Akinobu Mita <akinobu.mita@...il.com>
Subject: Re: [PATCH bpf-next v3 1/5] tracing/kprobe: bpf: Check error
 injectable event is on function entry

On Wed, Jan 10, 2018 at 07:17:06PM +0900, Masami Hiramatsu wrote:
> Check whether error injectable event is on function entry or not.
> Currently it checks the event is ftrace-based kprobes or not,
> but that is wrong. It should check if the event is on the entry
> of target function. Since error injection will override a function
> to just return with modified return value, that operation must
> be done before the target function starts making stackframe.
> 
> As a side effect, bpf error injection is no need to depend on
> function-tracer. It can work with sw-breakpoint based kprobe
> events too.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>

Reviewed-by: Josef Bacik <jbacik@...com>

Thanks,

Josef