netdev - Re: [PATCH 0/2][v5] Add the ability to do BPF directed error injection

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Date:   Sat, 11 Nov 2017 09:16:00 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     David Miller <davem@...emloft.net>
Cc:     josef@...icpanda.com, rostedt@...dmis.org, mingo@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        ast@...nel.org, kernel-team@...com, daniel@...earbox.net
Subject: Re: [PATCH 0/2][v5] Add the ability to do BPF directed error
 injection


* David Miller <davem@...emloft.net> wrote:

> From: Josef Bacik <josef@...icpanda.com>
> Date: Tue,  7 Nov 2017 15:28:41 -0500
> 
> > I'm sending this through Dave since it'll conflict with other BPF changes in his
> > tree, but since it touches tracing as well Dave would like a review from
> > somebody on the tracing side.
>  ...
> > A lot of our error paths are not well tested because we have no good way of
> > injecting errors generically.  Some subystems (block, memory) have ways to
> > inject errors, but they are random so it's hard to get reproduceable results.
> > 
> > With BPF we can add determinism to our error injection.  We can use kprobes and
> > other things to verify we are injecting errors at the exact case we are trying
> > to test.  This patch gives us the tool to actual do the error injection part.
> > It is very simple, we just set the return value of the pt_regs we're given to
> > whatever we provide, and then override the PC with a dummy function that simply
> > returns.
> > 
> > Right now this only works on x86, but it would be simple enough to expand to
> > other architectures.  Thanks,
> 
> Series applied, thanks Josef.

Please don't apply it yet as the series is still under active discussion - for now 
I'm NAK-ing the x86 bits because I have second thoughts about the whole premise of 
the feature being added here.

Thanks,

	Ingo