linux-kernel - Re: [PATCH v4 1/2] bpf: Add bpf_probe_write BPF helper to be called in tracers (kprobes)

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Message-ID: <20160723193510.GA23128@ast-mbp>
Date:	Sat, 23 Jul 2016 12:35:12 -0700
From:	Alexei Starovoitov <alexei.starovoitov@...il.com>
To:	Sargun Dhillon <sargun@...gun.me>
Cc:	Daniel Borkmann <daniel@...earbox.net>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v4 1/2] bpf: Add bpf_probe_write BPF helper to be called
 in tracers (kprobes)

On Fri, Jul 22, 2016 at 05:05:27PM -0700, Sargun Dhillon wrote:
> It was tested with the tracex7 program on x86-64.

it's my fault to start tracexN tradition that turned out to be
cumbersome, let's not continue it. Instead could you rename it
to something meaningful? Like test_probe_write_user ?
Right now it just prints client's peer address and human needs to
visually verify that probe_write_user actually happened, if you can
convert it into a test it will help a lot.
We were planning to convert all of the samples/bpf/ into tests,
so we can run them continuously.

btw, single patch re-submit will not be picked up. Please always
re-submit the whole patch set together.

> +static const struct bpf_func_proto *bpf_get_probe_write_proto(void) {
> +	pr_warn_once("*****************************************************\n");
> +	pr_warn_once("* bpf_probe_write_user: Experimental Feature in use *\n");
> +	pr_warn_once("* bpf_probe_write_user: Feature may corrupt memory  *\n");
> +	pr_warn_once("*****************************************************\n");
> +	pr_notice_ratelimited("bpf_probe_write_user: %s[%d] installing program with helper: it may corrupt user memory!",
> +	current->comm, task_pid_nr(current));

I thought we were argeeing on single pr_warn_ratelimited without banner ?

The rest looks good.
Thanks!