From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C929B15E94; Fri, 13 Oct 2023 14:00:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=none Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3004EC433C7; Fri, 13 Oct 2023 14:00:25 +0000 (UTC) Date: Fri, 13 Oct 2023 10:00:23 -0400 From: Steven Rostedt To: Artem Savkov Cc: Andrii Nakryiko , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , bpf@vger.kernel.org, netdev@vger.kernel.org, Masami Hiramatsu , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Thomas Gleixner , linux-rt-users@vger.kernel.org, Jiri Olsa Subject: Re: [RFC PATCH bpf-next] bpf: change syscall_nr type to int in struct syscall_tp_t Message-ID: <20231013100023.5b0943ec@rorschach.local.home> In-Reply-To: References: <20231005123413.GA488417@alecto.usersys.redhat.com> <20231012114550.152846-1-asavkov@redhat.com> <20231012094444.0967fa79@gandalf.local.home> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 13 Oct 2023 08:01:34 +0200 Artem Savkov wrote: > > But looking at [0] and briefly reading some of the discussions you, > > Steven, had. I'm just wondering if it would be best to avoid > > increasing struct trace_entry altogether? It seems like preempt_count > > is actually a 4-bit field in trace context, so it doesn't seem like we > > really need to allocate an entire byte for both preempt_count and > > preempt_lazy_count. Why can't we just combine them and not waste 8 > > extra bytes for each trace event in a ring buffer? > > > > [0] https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/commit/?id=b1773eac3f29cbdcdfd16e0339f1a164066e9f71 > > I agree that avoiding increase in struct trace_entry size would be very > desirable, but I have no knowledge whether rt developers had reasons to > do it like this. > > Nevertheless I think the issue with verifier running against a wrong > struct still needs to be addressed. Correct. My Ack is based on the current way things are done upstream. It was just that linux-rt showed the issue, where the code was not as robust as it should have been. To me this was a correctness issue, not an issue that had to do with how things are done in linux-rt. As for the changes in linux-rt, they are not upstream yet. I'll have my comments on that code when that happens. -- Steve