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

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Message-ID: <20171110093459.w2pvo3ntkwbmgnha@gmail.com>
Date:   Fri, 10 Nov 2017 10:34:59 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Josef Bacik <josef@...icpanda.com>
Cc:     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,
        Josef Bacik <jbacik@...com>
Subject: Re: [PATCH 1/2] bpf: add a bpf_override_function helper


* Josef Bacik <josef@...icpanda.com> wrote:

> @@ -551,6 +578,10 @@ static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func
>  		return &bpf_get_stackid_proto;
>  	case BPF_FUNC_perf_event_read_value:
>  		return &bpf_perf_event_read_value_proto;
> +	case BPF_FUNC_override_return:
> +		pr_warn_ratelimited("%s[%d] is installing a program with bpf_override_return helper that may cause unexpected behavior!",
> +				    current->comm, task_pid_nr(current));
> +		return &bpf_override_return_proto;

So if this new functionality is used we'll always print this into the syslog?

The warning is also a bit passive aggressive about informing the user: what 
unexpected behavior can happen, what is the worst case?

Thanks,

	Ingo